Recent Research Highlights



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https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 A new species of stone loach

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Analysing indoor power lines

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Key lime oils on Aedes aegypti

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Gold mineralisation in Bhukia deposit

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Fractal nature of ZnO nanoparticles

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Vermicomposting citronella waste

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Powerline communication

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Emission based pH sensors

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Re-awakening of an X-Ray binary

https://sites.google.com/a/gauhati.ac.in/research/#ds11092019 Embryonic development of pipefish

https://sites.google.com/a/gauhati.ac.in/research/#rdc30082019 Classifying the soil with image processing

https://sites.google.com/a/gauhati.ac.in/research/#ps30082019 Solar hydrogen generation

https://sites.google.com/a/gauhati.ac.in/research/#rt21082019 A pick on mechanochemistry

https://sites.google.com/a/gauhati.ac.in/research/#bk01072019 Killing the killers

https://sites.google.com/a/gauhati.ac.in/research/#ds13062019 CDs-porous silicon photo sensor

https://sites.google.com/a/gauhati.ac.in/research/#udb03062019 A changing coastline

https://sites.google.com/a/gauhati.ac.in/research/#th23052019 Indian Research Articles in PLoS Journals

https://sites.google.com/a/gauhati.ac.in/research/#nn06052019 Pigments from the deep sea

https://sites.google.com/a/gauhati.ac.in/research/#hps08052019 Heavy metals in freshwater wetlands

https://sites.google.com/a/gauhati.ac.in/research/#ac04052019 Bayesian inference for queuing model

https://sites.google.com/a/gauhati.ac.in/research/#ph03052019 Xenotime dating of Meghalayan rocks

https://sites.google.com/a/gauhati.ac.in/research/#nn26042019 How plankton shaped our ecosystem

https://sites.google.com/a/gauhati.ac.in/research/#mpb12042019 Driving the electrons unstable

https://sites.google.com/a/gauhati.ac.in/research/#us04042019 Microwave safe!

https://sites.google.com/a/gauhati.ac.in/research/#sb14032019 A new plant species from Assam

https://sites.google.com/a/gauhati.ac.in/research/#rt08032019 Cocrystal dissociation - a case study

https://sites.google.com/a/gauhati.ac.in/research/#sm06032019 Treating oral cancer

https://sites.google.com/a/gauhati.ac.in/research/#bb05032019 Probing protons at LHC

https://sites.google.com/a/gauhati.ac.in/research/#bks23022019 AZO transparent conductors

https://sites.google.com/a/gauhati.ac.in/research/#kk20022019 Targets for nuclear reaction experiments

https://sites.google.com/a/gauhati.ac.in/research/#us20022019 Measuring soil moisture

https://sites.google.com/a/gauhati.ac.in/research/#ds19022019 Properties of PANI-SA composites

https://sites.google.com/a/gauhati.ac.in/research/#rt12022019 A perspective on π-π stacking

https://sites.google.com/a/gauhati.ac.in/research/#kb11022019 One more neutrino

https://sites.google.com/a/gauhati.ac.in/research/#hc01022019 Schistura rebuw - a new species of fish

https://sites.google.com/a/gauhati.ac.in/research/#kt09012019 Modeling magnetospheric oscillations

https://sites.google.com/a/gauhati.ac.in/research/#tkg08122018 Killing cancer cells

https://sites.google.com/a/gauhati.ac.in/research/#sh30112018 Detection of arsenic in water

https://sites.google.com/a/gauhati.ac.in/research/#kt21112018 Funiculosone - an antimicrobial metabolites
Schistura syngkai - a new species of stone loach

Hrishikesh Choudhury and coworkers report about the discovery of a new fish species of stone loach from Meghalaya. This discovery is published in the journal Zootaxa.


Authors
Hrishikesh Choudhury, D Khlur B Mukhim1, Abhinit Dey, Deisakee P Warbah1, and Dandadhar Sarma
from other institution

Abstract
Schistura syngkai, a new stone loach, is described from the Twahdidoh Stream of Wahblei River (Surma-Meghna drainage) in Meghalaya, northeast India. It is unique among its Indian congeners in having a prominent dark-brown to blackish mid- lateral stripe about an eye diameter or more in width, overlain on 12–18 vertically-elongate black blotches on a golden-brown to amber body. Additionally, the species possesses an incomplete lateral line and a slightly emarginate caudal fin, and exhibits no apparent sexual dimorphism.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Analysing indoor power lines

Banty Tiru and her collaborators analyse the aspects of indoor power lines. This is an emerging technology which looks at using the power lines (the electrical wirings which supplies electricity to our houses) as a means of communication which will effectively remove the need for other media for communication. This work is published in the journal Arabian Journal for Science and Engineering (Springer).


Authors
Abstract
One of the challenges faced by indoor power line communication systems is the frequency-selective channels that are time varying and dependent on a large number of variabilities. A probable solution is to extract as much determinism as possible through prediction and statistical analysis of the frequency-selective notches. However, such deterministic tools are available only for simple open- and short-circuit branches and not for complex loads and topologies. This paper proposes an alternate method to predict and analyze notches using a minimum of four parameters without evaluating the transfer function. Termed as the load frequency mapping, the method is applicable for any frequency-dependent time-invariant loads and topologies and also capable of performing statistical analysis of random channels. A high decrease in prediction error (99.46–93.63%) is found for all the channels analyzed. Statistical analysis of 26 power line cables using random loads shows that some cables and loads offer more variations in frequency selectivity than others. For capacitive loads, the variation is more for the low-frequency notches and for those modeled as parallel resonant circuits at the frequencies near the resonance. Maximum variation is found for cables with high characteristic impedance with loads having high resonant frequencies and low quality factor and least for inductive loads. The power line therefore has considerable amount of determinism, and this can be incorporated to complement for fading channels or analysis of variability optimized for dual purpose of power delivery and data transfer.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Key lime oils on Aedes aegypti

Bulbuli Khanikor and co-workers report about the insecticidal activities of Key lime (Assamese : Sokola Tenga) oils on Aedes aegypti, the mosquito that causes dengue fever. This work is published in the journal Toxicology Reports.


Authors
Riju Sarma, Kamal Adhikari, Sudarshana Mahanta, and Bulbuli Khanikor

Abstract
In the recent time, global attention for the control of vectors has shifted from chemical insecticides to botanicals. In the present investigation, authors attempted to evaluate the efficacy of peel and leaf essential oil (EO) of Citrus aurantifolia (Assamese : Sokola Tenga) against Aedes aegypti. The results revealed that both the oils possess more ovicidal activity (LC50 value of 5.26 ppm and 17.71 ppm for leaf and peel oil respectively at 72 h) than larvicidal activity. As larvicide, the essential oil from the peel of Citrus aurantifolia showed rapid effect with LC50 value of 128.81 ppm at 24 h which reduced to 106.77 ppm at 72 h while the leaf oil showed slow effect with LC50 value of 188.59 ppm, 107.37 ppm and 104.59 ppm at 24 h, 48 h and 72 h respectively. Again, the two essential oils did not show significant adulticidal activity. GC–MS analysis of both the oils recorded presence of different compounds. As a major constituent compound of the leaf EO of Citrus aurantifolia, citral was tested for their ovicidal, larvicidal and adulticidal activities against Aedes aegypti. The result showed highest ovicidal activities (LC50 value of 4.84 ppm at 72 h) of citral followed by larvicidal (LC50 value of 87.02 ppm at 24 h) and adulticidal (LC50 value of 103.88 ppm at 24 h) activities. From this study, it can be concluded that the essential oil extracted from the leaf and peel of Citrus aurantifolia and one of its major constituent compound citral can be included in the mosquito control programme of Aedes aegypti.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Looking for Bhukia's gold!

Pranjit Hazarika and his colleagues try to explain the origin of the gold mineralisation in the newly discovered Bhukia deposit in the Aravalli-Delhi belt. This work is published in the journal Lithos.


Authors
Pranjit Hazarika, Niraj Bhuyan, Dewashish Upadhyay1, Kumar Abhinay1, and N N Singh1
from other institution

Abstract
Gold mineralisation in the newly discovered Bhukia deposit in northwestern India is hosted in Proterozoic metamorphosed volcano-sedimentary rocks of the Aravalli-Delhi Belt. Three generations of tourmaline occurring in different textural settings are recognised in the host rocks of the deposit. Fine-grained texturally early tourmalines (Tur-I) precipitated during the gold-sulfide mineralization stage. They are dravitic in composition and occur parallel to the S1 tectonic foliation as fine-grained crystals in tourmaline-albite layers within quartz-albite rock and as scattered grains in calc-silicate rocks. Coarse-grained texturally later schorls (Tur-II) are also restricted to calc-silicate and quartz-albite rocks and characterised by sector zoning. Late-stage type III tourmaline (Tur-III), also of schorl composition, replaces Tur-II along fractures and margins. They are interpreted to have formed during a phase of ore remobilisation. All tourmalines, especially the schorls, are strongly enriched in Li, Ga, Mn and Zn with Ga concentrations being the highest ever reported in natural tourmalines (up to 1380 ppm). The boron isotope composition is similar in all three tourmaline types with the consistently light δ 11Β (-10.4‰ to -7.2‰) indicative of a continental source for B. The chemical and B-isotopic composition of tourmaline is suggestive of the involvement of two fluids, a granitic-derived hydrothermal fluid and metapelite-derived metamorphic fluid. The δ 11Β variations in the tourmalines can be explained by mixing between 11B-poor granitic-derived hydrothermal fluid and 11B-rich metamorphic-hydrothermal fluid. While high V (2110-4247, avg. 3339 ppm) in the early dravitic tourmalines indicate mixing of granitic-derived hydrothermal fluid with pelite-derived metamorphic hydrothermal fluids during gold-sulfide mineraliσation, the enrichment of Li, Mn, Zn and Ta, and depletion of V in the later schorlitic tourmalines suggest increasing influence of granitic-derived hydrothermal fluids during ore remobiliσation.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Fractal nature of nanoparticles

Eeshankur Saikia and co-workers have reported multifractal nature in ZnO nanoparticles. This work is published in the journal Material Science and Engineering C.


Authors
Rajat K Saha, Mrinal K Debanath, and Eeshankur Saikia

Abstract
ZnO nanoparticles (NPs) have variety of applications in different fields due to its size, structure, as well as physical and chemical properties. One of its prominent characteristics is its antibacterial behaviour. Nonlinear Dynamical Theory (NLD) has a vast scope in the field of material science, especially when subtle correlations are searched for to extract hidden information. Since nano-ZnO materials may be used in inhibiting pathogens, its nonlinear features can be quantified and calibrated with the help of NLD tools. Multi-fractal Analysis (MFA) is an important diagnostic tool of NLD for not only analysing nonlinear signal or images, but also predicting any spurious events likely to occur in the system under study. Thus, the analysis of the surface texture of the ZnO nano particles formed, using the TEM images and relate it with the variations of the XRD signal using NLD tools, is our first attempt reported here. Further, tools of MFA are used, for the first time, to see if there exists any correlation between the texture of the nano particles formed and the Zone of Inhibition (ZoI) we obtain as an output after allowing certain pathogens inhibit in the presence of the same nano particles. Analysis of TEM images guide us to predict the texture and structure of crystallites of ZnO:Cu samples which are responsible for overall behaviour of inhibiting pathogens. In this paper, MFA of ZoI images, TEM images, and signal of four different Cu-doped ZnO nanoparticles are carried out and their outcomes are calibrated for estimating the size and pattern of unknown NPs synthesised under similar physical and chemical condition. Moreover, that MFA can be used reliably to predict spurious or abnormal surface structure or bacterial inhibition is also established.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Vermicomposting citronella waste and a mixture of sludge

Hemen Deka and coworkers report about vermicomposting of citronella bagasse and mixture of paper-mill sludge. This work is published in the journal Bioresource Technology.



Authors
T Boruah, A Barman, P Kalita, J Lahkar1, and H Deka
from other institution

Abstract
The vermicomposting potential of Eisenia fetida on citronella bagasse and paper mill sludge mixture was studied. The experiment was carried out in pots by taking a mixture of citronella bagasse and paper mill sludge in 3:2 ratios. The physico-chemical properties such as pH, conductivity, total organic carbon, nitrogen, phosphorus, potassium, calcium, trace elements and heavy metals were studied in the end products. The ash content, humification index, C/N ratio and scanning electron microscopic analysis were done to understand the maturity of the vermicompost. Results revealed that bioconversion of citronella bagasse and paper mill sludge mixture is accompanied with reduction of C/N ratio and humification index; enhancement of nutrients profile, nitrogen fixing, phosphate and potassium solubilising bacterial population. SEM analysis showed that there was more disintegration in vermicompost samples than the initial raw materials and compost. Further, earthworm population and biomass has significantly increased by the end of the experimental trials.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Powerline communication

Banty Tiru, her graduate student, and collaborator explores if the powerlines (supplying electricity to our homes) can be used as a medium of communication. This research work is published in the Journal of Circuits, Systems and Computers.


Authors
Abstract
This paper deals with the development of a realistic power line channel simulator wherein power line communication devices can be tested before implementation to meet the massive need of data transfer. The statistics of the noise follow the experimentally observed in different sites, namely the time-varying non-white power spectral densities (PSDs) of the background noise and a target non Gaussian amplitude distribution. The procedure based on the inverse cumulative distribution function method of generation of random numbers and iteratively updating a target spectrum necessitates knowledge of a maximum of 17 parameters for successful implementation and has been validated for three sites in the low-frequency (< 500kHz) and high-frequency (1–30MHz) bands. The average percentage errors in prediction of the mean of the channel capacity (CC) are 12.68% and 10.66% in the two bands, respectively. The minimum correlations of the distribution of BER of OFDM in a channel corrupted by the simulated and observed noises are is 0.883 and 0.801 in the two bands which are high compared to 0.422 and 0.355, respectively, when the requirement of a target amplitude distribution is neglected. With low-frequency noise emulated by a data acquisition card, an average percentage error of 11.82% in the CC and a correlation of 0.867 (against 0.498) in BER are obtained. The noise thus generated can be used as a testbed for system testing, instead of the conventional static models (additive white Gaussian noise or with time-invariant coloured PSD), leading to better optimisation of the implemented devices.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Emission based pH sensors

Ranjit Thakuria and coworkers explore the possibility of finding materials with strong solid-state fluorescence which can be used as pH sensors. This research work is published in Acta Crystallograohica B.



Authors
P Sarma, K. Patir, K K Sarmah, S K Gogoi, R Thakuria, and P J Das

Abstract
A series of three biphenyl‐based Knoevenagel products (denoted 1a, 1b, 1c) with active methylene groups has been synthesized. Compounds 1a and 1b show strong solid‐state fluorescence, whereas 1c displays low emission. Effects of substituent groups in condensed phase packing of the molecules have been investigated and correlated with their photophysical properties. Interestingly, compound 1a exhibits mechanofluorochromism with emission color changes from yellow to green (wavelength shift of 40 nm) after mechanical grinding. Furthermore, fluorescence of 1a and 1b is turned off under alkaline conditions, making them potential candidates for aggregation‐enhanced emission‐based pH sensors.

Journal References
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Re-awakening of an X-Ray binary

Kalyanee Boruah and collaborators report about a surprise outburst from the low-mass X-Ray binary GRS 1716-249. The last time an outburst was observed was 23 years ago! This work and another related works are published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).


Authors
Priya Bharali, Sunil Chandra1, Jaiverdhan Chauhan1, Javier A García1, Jayashree Roy1, Markus Boettcher1, and Kalyanee Boruah
from other institutions

Abstract
In this work, the author present a spectral and temporal analysis of Swift/XRT and NuSTAR observations of GRS 1716–249 during its recent 2016–2017 outburst. This low-mass X-ray binary underwent an extraordinary outburst after a long quiescence of 23 years, since its last major outburst in 1993. The source was observed over two different epochs during 2017 April 7 and 10. The best-fitting joint spectral fitting in the energy range 0.5–79.0 keV indicates that the spectrum is best described by relatively cold, weak disc blackbody emission, dominant thermal Comptonisation emission, and a relativistically broadened fluorescent iron Kα emission line. The authors observed a clear indication of a Compton hump around 30 keV. They also detected an excess feature of 1.3 keV. Assuming a lamp-post geometry of the corona, we constrained the inner disc radius for both observations to 11.92+8.62−11.92 RISCO (i.e. an upper limit) and 10.39+9.51−3.02 RISCO (where RISCO is the radius of the innermost stable circular orbit) for the first epoch (E1) and second epoch (E2), respectively. A significant (5σ) type C quasi-periodic oscillation (QPO) at 1.20 ± 0.04 Hz is detected for the first time for GRS 1716–249, which drifts to 1.55 ± 0.04 Hz (6σ) at the end of the second observation. The derived spectral and temporal properties show a positive correlation between the QPO frequency and the photon index.

In a subsequent report, the authors also report about the observation of a newly discovered X-Ray transient.

Embryonic development of a pipefish

Dandadhar Sarma and collaborators report about a first comprehensive embryonic development of an endangered freshwater pipefish endemic to the region, which may help conserve such species. This work is published in the Journal of Applied Ichthyology.



Authors
Anu Saikia, Minakshi Kalita, Hrishikesh Choudhury, Lalit K Tyagi1, Dandadhar Sarma, and Kuldeep K Lal1
from other institutions

Abstract
The present study provides the first comprehensive embryonic development of the freshwater Syngnathid fish species, Microphis deocata (Hamilton), a Near Threatened pipefish endemic to the Brahmaputra River drainage in Northeast India and Bangladesh. Microphis deocata is a Gastrophori species as the males develop an abdominal brood pouch. Mature individuals were collected and maintained in well‐aerated aquaria under controlled conditions to induce natural spawning. The number of eggs within the males' brood pouch ranged from 17 to 22 (for n = 10), measuring 0.7–1.0 mm in diameter. A total of 10 developmental stages could be recognised under four developmental periods namely, early embryogenesis, eye development, snout formation and juvenile. However, sensitivity, and therefore mortality, while handling of this species restricted the study from reporting the exact time intervals for stages following the blastodisc formation ~48 hr post fertilisation. A newborn larvae measures ~14 mm and is free‐swimming with distinct dorsal fin (with 31–32 rays) and a sector‐shaped caudal fin (with 8–9 rays). The study aims to provide baseline information on the embryology of M. deocata in culture condition which will be helpful for future studies on conservation biology, population status and management of this species.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Classifying soil through image processing

Ridip Dev Choudhury and Utpal Barman show how a low-cost imaging method can provide valuable information to the rural farmer in the agriculture sector. This research work is published in Information Processing in Agriculture.


Authors
Abstract
The objective of this study is to process the soil images to generate a digital soil classification system for rural farmers at low cost. Soil texture is the main factor to be considered before doing cultivation. It affects the crop selection and regulates the water transmission property. The conventional hydrometer method determines the percentage of sand, silt, and clay present in a soil sample. This method is very cost and time-consuming process. In this approach, the authors collect 50 soil samples from the different region of west Guwahati, Assam, India. The samples are photographed under a constant light condition using an Android mobile of 13 MP camera. The fraction of sand, silt, and clay of the soil samples are determined using the hydrometer test. The result of the hydrometer test is processed with the United State Department of Agriculture soil classification triangle for the final soil classification. Soil images are processed through the different stages like pre-processing of soil images for image enhancement, extracting the region of interest for segmentation and the texture analysis for feature vector. The feature vector is calculated from the Hue, Saturation, and Value (HSV) histogram, colour moments, colour auto Correlogram, Gabor wavelets, and discrete wavelet transform. Finally, Support Vector Machine classifier is used to classify the soil images using linear kernel. The proposed method gives an average of 91.37% accuracy for all the soil samples and the result is nearly the same with the United State Department of Agriculture soil classification.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Generating hydrogen in the sunlight

Pranjal Saikia and co-workers report about solar hydrogen generation. This work is published in the journal ACS Applied Materials and Interface.


Authors
Bijoy Tudu, Naresh Nalajala1, Kasala P Reddy1, Pranjal Saikia, and Chinnakonda S Gopinath1
from other institution

Abstract
The authors have synthesised noble bimetallic nanoparticles (Au−Pd NPs) on a carbon-based support and integrated with titania to obtain Au−Pd/C/TiO2 and Au−Pd/rGO/TiO2 nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au−Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m2g−1 ) activated carbon (Au−Pd/C), prepared from a locally available plant source (in Assam, India), and (b) reduced graphene oxide (rGO) (Au−Pd/rGO); subsequently, they were integrated with TiO2. The shift observed in Raman spectroscopy demonstrates the electronic integration of the bimetal with titania. The photocatalytic activity of the above materials for the hydrogen evolution reaction was studied under 1 sun conditions using methanol as a sacrificial agent in a powder form. The photocatalysts were also employed to prepare a thin film by the drop-casting method. Au−Pd/rGO/TiO2 exhibits 43 times higher hydrogen (H2) yield in the thin film form (21.50 mmol h−1g−1) compared to the powder form (0.50 mmol h−1g−1). On the other hand, Au−Pd/C/TiO2 shows 13 times higher hydrogen (H2) yield in the thin film form (6.42 mmol h−1g−1) compared to the powder form (0.48 mmol h−1g−1). While powder forms of both catalysts show comparable activity, the Au− Pd/rGO/TiO2 thin film shows 3.4 times higher activity than that of Au−Pd/C/TiO2. This can be ascribed to (a) an effective separation of photogenerated electron−hole pairs at the interface of Au−Pd/rGO/TiO2 and (b) the better field effect due to plasmon resonance of the bimetal in the thin film form. The catalytic influence of the carbon-based support is highly pronounced due to synergistic binding interaction of bimetallic nanoparticles. Further, a large amount of hydrogen evolution in the film form with both catalysts (Au−Pd/C/TiO2 and Au−Pd/rGO/TiO2) reiterates that charge utilisation should be better compared to that in powder catalysts.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Solvent polarity and mechanochemistry

Ranjit Thakuria and coworkers study the effect of solvent polarity on mechanochemistry. Mechanochemistry is the coupling of mechanical and chemical phenomena on a molecular scale and open doors to the emerging field of molecular machines (from Wikipedia). This research work is published in the journal Chemical Communications.


Authors
Kashyap Kumar Sarmah, Trishna Rajbongshi, Achyut Bhuyana,  and Ranjit Thakuria

Abstract
Cocrystallization of racemic DL-tartaric acid (DL-ta) and achiral isoniazid (ISN) was investigated using mechanochemistry. Neat grinding (NG) and liquid-assisted grinding (LAG) in the presence of non-polar liquids result in the formation of a conglomerate (ISN·D-ta/ISN·L-ta); whereas LAG with polar liquids yields racemic salt ISN·DL-ta. The effect of solvent polarity and dipole moment in mechanochemistry is discussed.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



A concoction of oils for the killer mosquitoes 

Bulbuli Khanikor and her scholars test a concoction of plant-based oils to target the Aedes aegypti mosquitoes, which is the primary cause of diseases like dengue fever, chikungunya, etc. This research work is published in Nature Scientific Reports.


Authors
Riju Sarma, Kamal Adhikari, Sudarshana Mahanta, and Bulbuli Khanikor

Abstract
Twenty-eight combinations of plant essential oil-based terpene compounds were prepared and tested against larval and adult stages of Aedes aegypti. Initially five plant essential oils (EOs) were assessed for their larvicidal and adulticidal efficacy and two of their major compounds from each EO were identified from GC-MS results. Identified major compounds namely Diallyldisulfide, Diallyltrisulfide, Carvone, Limonene, Eugenol, Methyl Eugenol, Eucalyptol, Eudesmol and α-pinene were purchased and tested individually against Aedes aegypti. Binary combinations of these compounds were then prepared using sub-lethal doses, tested and their synergistic and antagonistic effects were determined. The best larvicidal compositions and the best adulticidal composition of terpene compounds and terpene plus commercial mosquitocidal compounds were highlighted based on small scale and large scale treatments on Aedes aegypti.

CDs-porous silicon nanostructured photo sensor

Deepali Sarkar and her coworkers are studying the photo sensing properties of CDs-proous silicon based metal-semiconductor-metal (MSM) hetero-structure. This work is published in Journal of Materials Science: Materials in Electronics.


Authors
Abstract
Present work reports light sensing property of metal–semiconductor–metal device based on nanostructured CdS-PS:p-Si hetero-structure. PS with thickness of ~ 1500 nm is prepared on p-Si (100) oriented wafer using electrochemical anodization method. Thin nanostructured n-CdS layer of ~ 170 nm is deposited on PS:p-Si substrate by vacuum evaporation. FESEM observation confirms growth of hierarchical flower like CdS nanostructure on PS:p-Si substrate. UV–Vis absorption spectrum gives bandgap of CdS nanostructure to be 2.6 eV. Reflectance measurement of CdS-PS:p-Si hetero-structure shows multiple interference pattern within the spectral range of 200–800 nm, with remarkable blue shift of the pattern compared to that of PS:p-Si structure. Photoluminescence study of the hetero-structure reveals presence of various luminescence bands peaked at ~ 450, 460, 468, 482, 560, and 590 nm. Dark current (Id) analysis shows low leakage current ~ 32 nA at − 2 V with ideality factor (n) and reverse saturation current (Is) values of 1.57 and 0.2 nA respectively. Spectral response of the hetero-structure at a bias voltage of − 2 V and irradiation wavelength of 400 nm shows maximum responsivity (Rλ) value of ~ 0.6 AW−1 and external quantum efficiency of ~ 180%. Response and recovery times of the device are ~ 160 and ~ 350 ms respectively. The prepared hetero-structure has been compared with other silicon based optoelectronic switching devices to find suitability of an alternate choice.

How are we changing a coastline?

Ujjal Deka Baruah and his fellow researchers report the long & short time changes of the Puri Coastline due to natural and anthropogenic (human) causes using satellite imagery. This research is published in Environmental Earth Sciences.


Authors
from other institutions

Abstract
The coastal regions of India are densely populated and most biological productive ecosystems which are threatened by erosion, natural disaster, and anthropogenic interferences. These threats have made priority in appraisal of shoreline dynamicity as part of sustainable management of coastal zones. The present study assessed the long- to short-term dynamicity of shoreline positions along the coast of Puri district, Odisha, India, during the past 25 years (1990–2015) using open-source multi-temporal satellite images (Landsat TM, ETM+, and OLI) and statistical-based methods (endpoint rate, linear regression rate and weighted linear regression). The long-term assessment during 1990–2015 shows that shoreline accredited at the rate of 0.3 m a−1 with estimated mean accretion and erosional rate of 1.18 m a−1 and 0.64 m a−1, respectively. A significant trend of coastal erosion is primarily observed on the northern side of Puri district coast. A cyclic pattern of accretion (during 1990–1995 and 2000–2004) and erosion (during 1995–2000 and 2009–2015) was observed during the assessment of short-term shoreline change. It exhibited significant correlation with the landfall of severe cyclones and identified cyclic phases after severe cyclonic storms, i.e., phase of erosion, phase of accretion and phase of stabilisation. Overall, the natural processes specifically the landfall of tropical cyclones and anthropogenic activities such as the construction of coastal structures, encroachment and recent construction in the coastal regulatory zone, and construction of dams in upper catchment areas are the major factors accountable for shoreline changes. The output of the research undertaken is not only crucial for monitoring the dynamism of coastal ecosystem boundaries but to enable long- to short-term coastal zone management planning in response to recently reported high erosion along the Puri coast. Moreover, the usage of open-source satellite imageries and statistical-based method provides an opportunity in developing cost-effective spatial data infrastructure for shoreline monitoring and vulnerability mapping along the coastal region.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Influence in the citation growth of Indian Research Articles in PLoS Journals

Tilak Hazarika and his colleagues put forward a study to show how the citation profile of Indian Research Articles in PLoS Journals are affected. This work is published in the journal Journal of Scientometric Research.


Authors
Abstract
The general approach of research impact evaluation is entirely based upon citations. But in the current Web2.0 era, this citation based evaluation process often do not include the generic discussions people make in social media, blogs, online scholarly discussion forums or even the online readership of the article. Altmetrics, often referred as the article level metrics is a tool that have emerged, which crowd source all the non-citation based discussions from various web2.0 platforms and tries to reflect the overhaul attention that an article gets. Since its introduction, altmetrics have been able to gather a good attention from the scientific community, and researchers are trying to evaluate if it does have scholarly value to complement the citation based impact measure process. The current study tries to evaluate altmetrics penetration in Indian research articles and the influence of altmetrics in the citation growth process. The problem was addressed taking the example of Indian research articles published in PLoS journals. Two hypothesis were set for the study and PLoS altmetrics data were taken to run the t-test for paired sample mean to test the hypothesis. Findings from the t-test estimated a low significant p value, hence rejecting the null hypothesis and accepting the alternate hypothesis proving the positive influence of altmetrics in the citation growth process for the Indian research articles in PLoS journals. Also the presence of altmetrics data in the Indian research articles of PLoS journals is evaluated in the study.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Scouring the deep sea to find pigments

Nilamoni Nath and coworkers find five new water soluble pigments from the deep sea off the coast of Japan. This work is published in the Journal of Natural Products.



Authors
Klaus Wolkenstein1, Juan Carlos Fuentes-Monteverde1, Nilamoni Nath, Tatsuo Oji1, and Christian Griesinger1
from other institutions

Abstract
Five new water-soluble amido- and aminoanthraquinone pigments, hypalocrinins A–E (1–5), the new amidoanthraquinone biaryls hypalocrinin F (6) and hypalocrinin G (7), and the known compounds 6-bromoemodic acid (8), crinemodin (9), and crinemodin sulfate (10) were isolated from the deep sea crinoid Hypalocrinus naresianus collected off Japan. The structures of the compounds were elucidated by NMR spectroscopy and mass spectrometry. Amido- and aminoquinones are quite unusual among natural products. The hypalocrinins are the first naturally occurring anthraquinones and anthraquinone biaryls conjugated with taurine.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Heavy metals in freshwater wetlands

Hari Prasad Sarma and coworkers investigate the heavy metal pollution in freshwater wetlands such as Deepor Beel (near Guwahati, Assam, India, Location : 26.1196, 91.6475). This research work is published in the journal Environmental Pollution.


Authors
Suravi Kalita1, Hari Prasad Sarma, and Arundhuti Devi1
from other institutions

Abstract
The sediment characterisation of wetlands belonging to the Northeastern Region of India particularly regarding the assessment of sediment carbon stock is very scanty. The presently available literature on the wetlands cannot be employed as a common model for managing the wetlands of the Northeastern Region of India as wetlands are a sensitive ecosystem with a different origin or endogenous interventions. Thereby, this research was conducted on Deepor Beel for investigating the spatial and seasonal variation of sediment parameters, the relationship between the parameters and pollution status of the wetland. Results revealed that the study area is of an acidic nature with a sandy clay loam type texture. Organic carbon, total nitrogen and available nitrogen were higher in sediments in the monsoon period. The mean stock of the sediment carbon pool of Deepor Beel is estimated to be 2.5 ± 0.7 kg m−2. The average non-residual fraction percentage (63.2%) of Pb was higher than the residual fraction. Zn content ~490 mg kg−1 exceeding its effect range medium (ERM) was determined to suggest frequent biological adverse effects. Highest metal enrichment factor (EF) values were shown by Zn and Pb, which ranged between 78 and 255. Risk assessment code (RAC) values of Pb between 21 and 29% indicated its high bio-accessibility risk. Pearson's coefficient matrix revealed a low degree of positive correlation between organic carbon content and metal concentration. Principal component analysis revealed that the first component comprising of EC, basic cations and metals accounted for 62.3% of variance while the second component (OM, OC, TN, AN, AP) and the third component (pH) accounted for 21.8% and 7.0% of the variance, respectively. The present study revealed the adverse impact of human inputs on the Deepor Beel quality status.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Bayesian inference & prediction for queuing model

Amit Choudhury and his collaborator estimate traffic intensity for single server queuing model using Bayesian inference. Bayesian inference is an important technique in mathematical statistics, which uses Bayes' theorem to update the probability for a hypothesis as more evidence or information becomes available. This research works is published in the journal Communications in Statistics - Simulation and Computation.

Figure used under Creative Commons 
https://en.wikipedia.org/wiki/Creative_Commons 
license


Authors

Abstract
This paper is concerned with the problem of estimating traffic intensity, ρ for single server queuing model in which inter-arrival and service times are exponentially distributed (Markovian) using data on queue size (number of customers present in the queue) observed at any random point of time. Here, it is assumed that ρ is unknown but random quantity. Bayes estimator of ρ are derived under squared error loss function assuming two forms of prior information on ρ. The performance of the proposed Bayes estimators is compared with that of the corresponding classical version estimator based on max- imum likelihood principle. The model comparison criterion based on Bayes factor is used to select a suitable prior for Bayesian analysis.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Xenotime chemical dating of Meghalayan metamorphic rocks

Pranjit Hazarika and his collaborators validate xenotime (a rare-earth phosphate mineral) chemical dating for metamorphic rocks in the Meghalaya-region. This research work is published in Journal of Earth System Science.


Authors
Pritom Borah, Pranjit Hazarika, Amulya Chandra Mazumdar, and Mridul Rabha1
1from other institution

Abstract
Monazite and xenotime are the two most useful and commonly used geochronometers for deciphering ages from metamorphic rocks. The low analytical cost involved in electron probe micro-analyser chemical dating, ease of sample preparation and abundance in metamorphic rocks of wide P–T conditions make monazite and xenotime dating most widely used technique for age determination amongst metamorphic petrologists. This contribution presents age comparisons between coexisting monazite and xenotime in the basement metapelitic rocks of the central part of the Shillong–Meghalaya Gneissic Complex (SMGC). Thermobarometric estimates in the studied samples indicate granulite facies conditions of metamorphism with peak P–T conditions of ~ 6.5 kbar and -750 ºC. Results indicate that xenotime in the basement rocks in the central SMGC formed in four discrete geological events while monazite either formed only in the latest Pan-African granulite grade metamorphic event or recrystallised during this event. Monazite in the studied samples yielded a single ubiquitous age of ca. 500 Ma. Xenotime in the study area, although found in only one sample, preserves four distinct ages at 1153±29, 930±36, 823±41,and 490±11 Ma. Preservation of Grenvillian ages in xenotime from central SMGC marks the eastward extension of Rodinia amalgamation front in the Indian Shield. The Neoproterozoic ages in xenotime from central SMGC suggest that the ca. 820 Ma high-grade metamorphism in the Eastern Indian Tectonic Zone had a wider impact in the SMGC than perceived previously.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



How predatory plankton created modern ecosystems!

Nilamoni Nath and his collaborators shed light on the great zigsaw puzzle involving intricacies how our modern ecosystem has come to this stage. This research work is published in Nature Communications.
This highlight is also featured in GU Homepage.


Authors

Abstract
Eukaryotic algae rose to ecological relevance after the Neoproterozoic Snowball Earth glaciations, but the causes for this consequential evolutionary transition remain enigmatic. Cap carbonates were globally deposited directly after these glaciations, but they are usually organic barren or thermally overprinted. Here we show that uniquely-preserved cap dolos- tones of the Araras Group contain exceptional abundances of a newly identified biomarker: 25,28-bisnorgammacerane. Its secular occurrence, carbon isotope systematics and co- occurrence with other demethylated terpenoids suggest a mechanistic connection to extensive microbial degradation of ciliate-derived biomass in bacterially dominated ecosys- tems. Declining 25,28-bisnorgammacerane concentrations, and a parallel rise of steranes over hopanes, indicate the transition from a bacterial to eukaryotic dominated ecosystem after the Marinoan deglaciation. Nutrient levels already increased during the Cryogenian and were a prerequisite, but not the ultimate driver for the algal rise. Intense predatory pressure by bacterivorous protists may have irrevocably cleared self-sustaining cyanobacterial eco- systems, thereby creating the ecological opportunity that allowed for the persistent rise of eukaryotic algae to global importance.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Driving the electrons unstable - a numerical simulation

Madhurjya P Bora and graduate student Suniti Changmai show how the photoemission in a plasma can drive the electron two-stream instability (ETSI) and can modify a plasma sheath. This research work is published in the journal Physics of Plasmas.



Authors

Abstract
Analysis related to the onset and evolution of the electron two-stream instability (ETSI) near a surface with a continuous photoemission flux is presented. With the help of a particle-in-cell simulation code, it is shown that when a surface emits photoelectrons due to exposure to ultraviolet photons (or due to similar mechanisms), it may lead to the onset of the ETSI due to the relative bulk velocity difference between the photoelectrons and the plasma electrons. It is shown that the ETSI thus developed is sustained through the lifetime of the plasma and prevents thermalisation of the electrons, which leads to a distortion in the electron velocity distribution function (EVDF) resulting a high energy tail, at least near the surface. We have shown that the resultant EVDF can be highly Lorentzian with a spectral index of ~1.5. The simulation results are supported with the corresponding theory, which are found to be in good agreement.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Microwave safe!

Your kitchen microwave can probably make you eat better Rajmas! Utpal Sarma and his collaborators report that high power microwave can effectively disinfect the red kidney beans (Indian Rajma) while keeping the nutritional values intact. This research is published in the journal IEEE Access.


Authors
Chitra Gautam1, Sk Masiul Islam1, Shashikant Sadistap1, and Utpal Sarma
1 from other institutions

Abstract
In this work, the effect of microwave heat on the nutritional characteristics of affected red kidney beans, i.e., Rajma is studied. Evaluation of crude protein content in microwave heated red kidney beans are carried out using standard Kjeldahl method and Fourier transform infra-red (FTIR) spectroscopy. Red kidney beans affected by Pulse Beetle (Callosobruchus chinensis) have been analysed throughout the experiments. The heat treatment of the samples is undertaken using a domestic microwave oven at 2.45 GHz. The samples are heated at different microwave powers, such as 90, 270, 450, 750, and 900 W, while the exposure time is varied from 30-90 s. The effective microwave power for maximum disinfestation is found to be 270-450 W at 30-60 s. Most of the red kidney beans are damaged at 900 W for 60 s. Using Kjeldahl method, a constant crude protein level of 22.5% is obtained for untreated and treated samples at 90-450 W. Crude protein level of red kidney beans is changed at 750-900 W. From FTIR analysis, the absorbance spectrum of carbohydrate peaks is found at 900-1250 cm -1 , a moisture peak at 1650 cm -1 , and a protein peaks at 2800-3000 cm -1 . Statistical analysis of the treated and untreated samples represents the lowest error of 0.0016 at 450 W power level for 60 s. Variances are determined to be the lowest with a value of 270 W and 450 W at 90 s and 60 s. These findings indicate the optimum microwave heat treatment for red kidney beans to retain its protein content.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Impatiens kamrupana - a new plant species from Assam

Souravjyoti Borah and fellow researchers report about discovery of a new plant species Impatiens kamrupana (Balsaminaceae) from Assam. This is now listed and published in the journal Phytotaxa.


Authors
Souravjyoti Borah, Jatindra Sarma, and Rajib Gogoi

Abstract
Impatiens Kamrupana - a new species is discovered from Kamrup district (rural) of Assam, bordering the adjoining state of Meghalaya. The new species is easily distinguished from its allied taxa by its bicoloured, white and purple flowers and sub-bucciniform lower sepal with straight to slightly curved spur.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Cocrystal dissociation under controlled humidity

Ranjit Thakuria and collaborators report a case study of cocrystal dissociation under a controlled environment. Cocrystals can be defined to be consisted of two or more components that form a unique crystalline structures having unique properties. This research work is published in Organic Process Research and Development.


Authors
Ranjit Thakuria1, Mihails Arhangelskis2, Mark D Eddleston2, Ernest H H Chow2, Kashyap Kumar Sarmah, Barry J Aldous2, Joseph F Krzyzaniak2, and William Jones2
1 Department of Chemistry, University of Cambridge
2 from other institutions

Abstract
Caffeine-glutaric acid cocrystal polymorphs, Form I and Form II, are presented as a model system to study cocrystal dissociation under controlled humidity. On the basis of relative humidity (RH) data, it is observed that Form I transforms to Form II at high RH and that the rate of the polymorphic phase transformation increases with increasing RH, with the relative stability of the cocrystal following a trend similar to that of the coformer deliquescence point for other caffeine dicarboxylic acid cocrystals. In addition, reduction in particle size, change in crystal morphology with greater number of crystal faces exposed to surrounding atmosphere, and internal arrangement of molecules in the crystal structure are shown to influence cocrystal instability and favour dissociation under increased humidity.

Treating oral cancer

Subhash Medhi and his collaborators explore the way an oral carcinoma (cancer) can be effectively treated. This research is published in the journal Artificial Cells, Nanomedicine, and Biotechnology.


Authors
Rituraj Bharadwaj, Bhanu P Sahu1, Jayanta Haloi, Damiki Laloo1, Prajjalendra Barooah, Chenole Keppen, Manab Deka, and Subhash Medhi
1 from other institution

Abstract
High recurrence rates are found in patients undergoing the standard treatment, and delay in initiation of treatment is considered as the most prominent cause for no relevant improvement in the survival rate . Moreover, conventional chemotherapy suffers from numerous drawbacks including poor drug specificity , undesired side effects and resistance towards the treatment. SLN have been chosen to be the best mode of anticancer drug delivery since they are generally made up of physiological lipids thus they are well accepted by our physiological system. The present research study includes preparation of PTX, 5- FU and AA entrapped SLN to ensure a sustained release of drug at the desired concentration and at a specific site for the treatment of oral cancer. The study involves evaluation of each of these SLN and their combination for the effective treatment of oral cancer. Entrapment of PTX, 5-FU, and AA d within the SLN by using high-speed homogenisation and ultrasonication method were evaluated both in-vitro and in-vivo to get the best combination for the effective therapeutic efficacy.

Probing the protons at Large Hadron Collider (LHC)

Buddhadeb Bhattacharjee and graduate student Pranjal Sarma explore a possible mechanism of intermittency during p-p collisions at Large Hadron Collider (LHC) in CERN. This work is published in Physical Review C.


Authors

Abstract
Nonstatistical fluctuation in pseudorapidity (η), azimuthal (φ), and pseudorapidity-azimuthal (η – φ) distribution spectra of primary particles of PYTHIA Monash (default) generated pp events at √s = 2.76, 7, and 13 TeV have been studied using the scaled factorial moment technique. A weak intermittent type of emission could be realised for minimum-bias (MB) pp events in χ(η – φ) space and a much stronger intermittency could be observed in high-multiplicity (HM) pp events in all χ(η), χ(φ), and χ(η – φ) spaces at all the studied energies. For HM pp events, at a particular energy, the intermittency index αq is found to be largest in two-dimensional χ(η – φ) space and least in χ(η) space, and no centre of mass energy dependence of αq could be observed. The anomalous dimensions dq are observed to be increased with the order of the moment q, suggesting a multifractal nature of the emission spectra of various studied events. While, the coefficient λq is found to decrease monotonically with the order of the moment q for two-dimensional analysis of MB pp events as well as for one-dimensional analysis of HM pp events, a clear minimum in λq values could be observed from the two-dimensional HM pp data analysis. For PYTHIA Monash generated sets of data, the strength of the intermittency is found to vary significantly with the variation of the strength of the colour reconnection (CR) parameter, i.e. reconnection range RR, for RR = 0.0, 1.8 and 3.0, thereby, establishing a strong connection between the CR mechanism and the observed intermittent type of emission of primary charged particles of the studied high-multiplicity pp events.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



The physics of transparent conductors

Bimal Kumar Sarma and his graduate students come up with an AZO transparent conductor with high figure of merit for possible optoelectronic applications. This research is published in the journal Applied Surface Science.


Authors
Bikash Sarma, Dipak Barman, and Bimal K Sarma

Abstract
This work presents a broad study of transparent and conducting Al-doped ZnO (AZO) thin films that could replace indium tin oxide (ITO) as transparent electrode in optoelectronic devices. AZO thin films are deposited by pulsed DC magnetron sputtering at a sputtering power of 80 W with different pulse frequencies in the range 50-100 kHz. Diffraction data confirm formation of doped ZnO and AZO thin films exhibit preferred orientation in the c-direction. The crystallite sizes of Al:ZnO are in the range 16–21 nm. The field emission scanning electron microscopy and atomic force microscopy of AZO thin films reveal nucleation and growth of uniform and dense films with better quality films deposited at a pulse frequency 75 kHz. A simple and non-destructive optical method is adopted to determine thickness and dispersion parameters such as dispersion energy, carrier concentration to effective mass ratio, and plasma frequency. AZO thin films offer excellent visible light transparency and limited transparency in the near-infrared region due to free carrier absorption. The sheet resistance of AZO thin films is recorded in the range 9-45 Ω/sq making these transparent conducting oxides (TCOs) suitable for optoelectronic applications. The figure of merit as high as 1.99 × 10−2 Ω−1 is achieved for AZO thin film deposited at a pulse frequency of 75 kHz. AZO thin film sputtered with a pulse frequency of 75 kHz is quite stable in ambient oxidising environment and surface adsorption sites might govern the initial oxidation of films when exposed to atmosphere. Excellent figure of merit and good stability of sputtered AZO thin films as TCO fulfil the requirements of a transparent electrode in photovoltaics.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Fabricating targets for nuclear reaction experiments

Kushal Kalita, graduate student Nabendu Kumar Deb, and their collaborators report about fabrication of thin nickel targets for present and future nuclear reaction experiments. This research work is published in the journal Vacuum.


Authors
Nabendu Kumar Deb, Kushal Kalita, S R Abhilash1, Pankaj K Giri1, Rohan Biswas1, G R Umapathy1, D Kabiraj1, and S Chopra1
1from other institutions

Abstract
To perform nuclear reaction experiments at HIRA, IUAC, New Delhi, thin (100–150 ) and pure 61,62Ni targets of uniform thickness are required. Self supporting targets are preferable for such case but, instead, carbon-backed isotopic targets are fabricated by adapting physical vapour deposition technique as it was comparatively more stable and consistent. Around 25 thin targets of both 61,62Ni isotopes are prepared using the limited amount of available enriched target material (less than 100 mg). The carbon-backed slides along with the parting agents are prepared using a diffusion pump based coating unit and the target material is deposited over the carbon-backed slides in the turbo pump based coating unit. To obtain consistent and intact targets, some trials were done with deposited slides and was found that the material degrades in any of the slides when kept idle for few days. The thicknesses of the targets are verified using profilometer, α energy loss technique, and RBS technique. They were found to be in good agreement with each other using the three techniques. The purity and the uniformity of the fabricated targets are further confirmed after verification using the RBS, the EDS and the XRD techniques.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Measuring soil moisture

Utpal Sarma, Manash Protim Goswami, and graduate student Babak Montazer report a novel method to measure soil moisture. This work is published in the IEEE Transactions on Instrumentation and Measurement.


Authors

Abstract
This paper addresses the optimisation and implementation of a fringing field capacitive soil moisture sensor using the printed circuit board technology. It includes the analysis of a novel configuration of an interdigital sensor for measuring soil moisture with two existing configurations. The optimised designs were simulated by using a 3-D finite-element method and fabricated by using a copper clad board. The performance of the fabricated sensors was evaluated using four soil samples collected from different locations. The observations were compared with the standard gravimetric method to evaluate the soil water content of the samples. The characterisation method and the results of the whole sensing system are discussed in terms of calibration, dynamic test, and repeatability.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Studying dielectric properties of PANI-SA composites

Deepali Sarkar and her graduate students study the dielectric properties of polyaniline (PANI) sulphonic acid (SA) composites. This work is published in the journal Synthetic Metals.


Authors
Mausumi Das, Ali Akbar, and D Sarkar

Abstract
Present work is primarily emphasised on the study of dielectric properties of sulphonic acids (SA) incorporated polyaniline (PANI). SA's function as dopants as well as surfactants for PANI. The PANI and PANI-SA samples are prepared by interfacial technique. The three composites prepared with three SA's [camphor sulphonic acid (CSA), dodecylbenzene sulphonic acid (DBSA) and polystyrene sulfonic acid (PSSA)] are characterised by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field effect scanning electron microscopy (FESEM) and thermogravimetric analysis (TGA) and differential thermogram (DTG) prior to dielectric studies. The results of PANI not incorporated with SA are also shown for comparison. XRD shows enhancement of crystallinity on SA doping. FTIR confirms the molecular structure with enhanced oxidation states on SA doping. FESEM shows fibrillar morphology with reduced fibre diameter from 86 nm in pure PANI to minimum of 50 nm in one of the composites. TGA and DTG results show better thermal stability on SA doping. The dielectric and AC conductivity measurements of the undoped and dopedPANI are studied in the frequency range of 42 kHz - 2 MHz and in the temperature range of 300 K–330 K. The dielectric constant for all the PANI composites increases with increase in temperature which indicates increase in mobility of the electric dipoles in the polymers. The dielectric constant for DBSA doped PANI is nearly 5000 which is much higher in context to interfacially polymerised nanofibres compared to that of undoped PANI where this value is about 800. Electric modulus studies show relaxation peaks in imaginary modulus spectra which ascertains about the type of relaxation process. The AC conductivity of the composites is found to be much higher than that of undoped PANI. The electrical conductivity increases with increase of temperature. This is suggested to be caused due to the activated trapped charge carriers.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Stacking - in the chemical way

Ranjit Thakuria and his collaborators elaborate on the nature and applications of π-π interactions. This work is published in the journal Crystal Growth & Design.


Authors
Ranjit Thakuria, Naba K Nath1, and Binoy K Saha1
1from other institutions

Abstract
This research article is a perspective published by the Guest Editors Ranjit Thakuria, Naba K Nath and Binoy K Saha for the Virtual Special Issue of Crystal Growth & Design on π−π Stacking in Crystal Engineering: Fundamentals and Applications. It highlights the nature of π−π interactions and their uses in various fields ranging from crystal engineering to material science to biochemistry and discusses about the articles published in the special issue.

https://sites.google.com/a/gauhati.ac.in/research/#top 
 



One more neutrino!

Kalpana Bora and her collaborators ask whether the sterile neutrino can fit into the existing neutrino hierarchy. Sterile neutrino is a possible dark matter candidate. This research is published in The European Physical Journal C.


Authors
Neelakshi Sarma, Kalpana Bora, and Debasish Borah1
1from other institution

Abstract
Motivated by the recent resurrection of the evidence for an eV scale sterile neutrino from the MiniBooNE experiment, the authors revisit one of the most minimal seesaw model known as the minimal extended seesaw that gives rise to a 3 + 1 light neutrino mass matrix. The authors consider the presence of A4 flavour symmetry which plays a nontrivial role in generating the structure of the neutrino mass matrix. Considering a diagonal charged lepton mass matrix and generic vacuum alignments of A4 triplet flavons, we classify the resulting mass matrices based on their textures. Keeping aside the disallowed texture zeros based on earlier studies of 3 + 1 neutrino textures, we categorise the remaining ones based on texture zeros, μ-τ symmetry in the 3 × 3 block and hybrid textures. After pointing out the origin of such 3 + 1 neutrino textures to A4 vacuum alignments, the authors use the latest 3 + 1 neutrino oscillation data and numerically analyse the texture zeros and μ–τ symmetric cases. The authors find that a few of them are allowed from each category predicting interesting cor- relations between neutrino parameters. They also find that all of these allowed cases prefer normal hierarchical pattern of light neutrino masses over inverted hierarchy.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Schistura rebuw - a new species of stone loach

Hrishikesh Choudhury and his colleagues have reported the finding of a new fish species from the Kameng River of lower Arunachal Pradesh. This finding is published in the journal Zootaxa


Authors
Hrishikesh Choudhury, Abhinit Dey, Ratul Ch Bharali1, Dandadhar Sarma, and Waikhom Vishwanath1
1 from other institutions

Abstract
Schistura rebuw, new species, is described from the Kameng River, a north-bank tributary of the Brahmaputra, Arunachal Pradesh, India. The new species is easily distinguished from all known congeners in the Brahmaputra basin by its unique sexual dimorphism, specifically a suborbital slit in adult females, and a suborbital flap in adult males; and a colour pattern of 10–11 blackish bars on a greyish-beige body, the pre-dorsal bars mostly broken or incomplete, coalescing dorsally in a more or less alternate fashion.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



Modeling aperiodic magnetospheric oscillations

Graduate Student Murchana Khusroo and Madhurjya P Bora explain why the magnetic oscillations in earth's magnetosphere are always almost aperiodic. This research work is published in Physical Review E


(Featured in the Kaleidoscope of Phys Rev E for the Month of Jan 2019)

Authors

Abstract
The authors present an analysis of a Hall-magnetohydrodynamics model of the magnetospheric plasma with finite Larmor radius effect. Through a bifurcation analysis of the resultant nonlinear system, they show that this nonlinear model does not possess a limit cycle, which rules out regular periodic oscillations with constant amplitude. However, it does result in a train of magnetosonic solitons, localised in space, with amplitudes increasing in time, which are largely in agreement with what is usually observed in the magnetopause region. We call these oscillations aperiodic magnetospheric oscillations. The authors emphasise that most of the train of solitary oscillations observed by the Cluster fleet and other spacecrafts do not have constant amplitudes: they either continuously increase or decrease. These train of solitons with non-constant amplitudes is a primary solution of their mathematical model.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 
 



What it takes to take on cancer

Tridib Kumar Goswami and his collaborators synthesise complexes which are found to kill cancer cells through generation of reactive oxygen species (ROS). This research work is published in Journal of Inorganic Biochemistry.


Authors
Atrayee Banaspati, Dhananjay Das, Chandan J Choudhury, Arnab Bhattacharyya1, and Tridib K Goswami
1 from other institution

Abstract
Four ternary copper(II) complexes of N-salicylyl-L-Tryptophan (Sal-TrpH) and phenanthroline bases of general formula [Cu(Sal-Trp)(L)], where L is 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq, 2), dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 3) and 2-(anthracen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (aip, 4), are synthesised and fully characterised. The complexes are evaluated for their affinity for biomolecules and photocytotoxic activities. Single crystal X-ray diffraction studies of complex 1 reveals that it has a square pyramidal CuN3O2 core with the phenolate oxygen of salicylaldehyde occupying the axial coordination site in the solid state. Complexes 1–4 display the Cu(II)-Cu(I) redox couples at ~ −0.3 V vs Ag/AgCl reference electrode in DMF-0.1 M [BunN4](ClO4). A Cu(II)-based weak d-d band ~650 nm and a moderately strong ligand to metal charge transfer band at ~430 nm are observed in DMF-Tris-HCl buffer (pH 7.2) (1:4 v/v). The complexes are efficient binders to calf thymus DNA and model proteins such as bovine serum albumin and lysozyme. They cleave supercoiled plasmid DNA efficiently when exposed to 446 and 660 nm laser radiation. They are cytotoxic to HeLa (human cervical cancer) and MCF-7 (human breast cancer) cells showing significant enhancement of cytotoxicity upon photo-excitation with low energy visible light. The complexes are found to kill cancer cells through generation of reactive oxygen species (ROS) as confirmed by DCFDA (2′,7′-dichlorofluorescin diacetate) assay. The apoptotic cell death induced by complex 4 is confirmed by Annexin V-Fluorescein isothiocyanate-Propidium iodide assay. Confocal microscopic images using 4 shows its primary cytosolic localisation in the HeLa and MCF-7 cells.

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Detection of arsenic in water

Simanta Hazarika and graduate student Chiranjib Rajkonwar describe a method which has the potential for being an in-situ method for detection of groundwater arsenic. This research is published in the journal Laser Physics.





Authors

Abstract
Ingestion of arsenic by the human body through drinking water induces numerous diseases. Therefore, detection and estimation of arsenic concentration in water, especially in groundwater, is important to protect the human world from its toxicity. In this work we demonstrate a laser induced fluorescence resonance energy transfer (LIFRET) method for the determination of the arsenic concentration in water. The fluorescence resonance energy transfer (FRET) is observed in an aqueous solution of 1, 8-naphthalimide and rhodamine-B by exciting it with a laser radiation of wavelength 405 nm. It is observed that if arsenic contaminated water is added to the pure solution of 1, 8-naphthalimide and rhodamine-B the wavelength of the peak in its FRET spectrum shifts from its pure value at 632.45 nm (peak position of the FRET spectrum of a pure solution of 1, 8-naphthalimide and rhodamine-B). These shifts of wavelengths are towards the lower wavelength side, corresponding to an increase in the concentration of arsenic added to the solution. In the present work, based on the shifting of the peak wavelength value of the FRET spectra corresponding to different concentrations of arsenic, we have described a method for the estimation of arsenic in water up to a lowest limit of 0.00001 gm l−1 (the maximum permissible limit of arsenic in water according to the World Health Organisation). The LIFRET method described in this work is portable, relatively cost effective, more convenient and has the potential for any in situ measurement of arsenic in the ground water of arsenic contaminated areas.

Journal Reference
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Funiculosone - a new antimicrobial metabolites

Kumanand Tayung and his collaborators have isolated a new antimicrobial metabolites which also shows anticandidal activity against Candida albicans Berkhout. This research is published in the journal Phytochemistry.



Authors
Srichanadan Padhi1, Marco Masi1, Alessio Cimmino1, Angela Tuzi1, Subhrakanta Jena1, Kumananda Tayung, and Antonio Evidente1
1 from other institutions

Abstract
An undescribed substituted dihydroxanthene-1,9-dione, named funiculosone, was isolated together with its two analogues identified as mangrovamide J and ravenelin, from the culture filtrates of Talaromyces funiculosus (Thom) Samson, Yilmaz, Frisvad & Seifert (Trichocomaceae), an endolichenic fungus isolated from lichen thallus of Diorygma hieroglyphicum (Pers.) Staiger & Kalb (Graphidaceae), in India. Funiculosone was characterised, essentially by spectroscopic methods, as 4,8,9a-trihydroxy-3,4a-dimethyl-4a,9a-dihydro-4H-xanthene-1,9-dione. Its relative stereochemistry was deduced by single crystal X-ray analysis while the absolute configuration was assigned as 4S,4aS,9aS by ECD spectra in comparison to that of the closely related mangrovamide J. This latter, to which, not being an amide, an inappropriate common name was given, was only recently isolated, together with undescribed and known prenylatedindole alkaloids and chromone derivatives from an unidentified Penicillium sp. X-ray structural analysis of the isolated mangrovamide J, for which no biological activity was previously reported, revealed polymorphism and a new crystalline phase is described. All the compounds displayed antibacterial activity with an IC50 range 23–104 μg/mL when assayed against Escherichia coli Escherich and Staphylococcus aureus Ogston. Funiculosone also showed anticandidal activity against Candida albicans Berkhout with an IC50 35 μg/mL.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top