Growth of ZnO nanowire and its application as UV photodetector

Zinc Oxide (ZnO) nanostructures with their significant properties have various application in optoelectronics, sensor devices and energy conversion devices. This report includes deposition of ZnO film by rf reactive sputtering on glass substrate. Its analysis using XRD, FESEM and UV-VIS spectroscopy to study its morphology, crystal structure, band gap and transmittance. Further, the deposited film is taken as substrate for the growth of ZnO nanowires using Hydrothermal Method. Various parameters affecting the growth conditions like growth temperature, growth time, and precursor concentration have been studied and optimizations of reaction conditions are done. Analysis of the samples fabricated under different conditions is carried out using XRD and FESEM characterization techniques. Zinc oxide nanowires have their application as UV photodetector due to their wide band gap and high surface to volume ratio. To enhance the absorption ability, carrier concentration and photoresponse, Zinc Oxide nanowires surface is functionalized using Poly(vinyl alcohol) for the application of UV photodetector. Photoresponse and sensitivity is studied for both coated and uncoated, using I-V characterization. To analyse optical switching action under the illumination of UV light photoresponse of these nanowires is plotted with respect to the time

AMAZING ANTIMICROBIAL AND WOUND HEALING POTENTIAL OF ACACIA CATECHU BARK EXTRACTS- A REVIEW

Plants are not only the source of food, oxygen, and shelter, but the same are also a potential foundation of medicines. Many natural and plant-derived antimicrobial and wound healing compounds have been recognized. In the present review, we have studied the main bioactive components of Acacia catechu with their medicinal roles. Most of these bioactive components are secondary metabolites which are produced by plants as side products of certain physiological reactions and are of no use for the plant itself. These components have been reported for their medicinal properties. In this review, we have mentioned some antibacterial, antifungal, and wound healing properties of A. catechu with its known bioactive components. The aim of this review article is, to enlist the possible potent bioactive components of the plant, against pathogenic microbes that can replace the use of chemicals and synthetic antibiotics for the treatment of skin infections and other diseases

Cyanobacteria: The Wonderful Factories

Cyanobacteria are photosynthetic algae with outstanding endeavor to inhabit diverse habitats and are crowned with special metabolic acumen. Their morphological diversity is vivid and their ecological roles are magnificent and vital in nature ranging from nitrogen cycle to carbon dioxide mitigation. Their applications are now extensively explored and many novel compounds have been reported. The pigments, vitamins, lipids, proteins, polyketides, antioxidative enzymes, polysaccharides etc. derived from cyanobacteria are envisaged worldwide. Their diligent acumen makes them ideal tiny microbial factories for nutraceuticals, biofuels, cosmetics, pharmaceuticals, wastewater remediation and many more. Further investigations can aid in elucidating more cyanobacterial secondary metabolites and innovative approaches towards their wider applicability in plethora of avenues as sustainable reservoirs

Role of antioxidative enzymes in toxic bloom forming Cyanobacteria

The antioxidative enzymes catalase and ascorbate peroxidase in toxic bloom forming cyanobacteria play a pioneer role in scavenging free radicals, which are generated as an outcome of photosynthesis and respiration. Ten Bloom forming toxic cyanobacterial strains Synechococcus elongates, Synechocystis aquatalis, Merismopedia glauca, Microcystis aeruginosa, M. aeruginosa (O), Arthrospira (=Spirulina) platensis, Nostoc paludosum, Anabaena iyengarii, A. variabilis and Cylindrospermum muscicola were isolated from natural blooms and purified. The results depict the significant activity of antioxidative enzymes. In A. platensis the activity of catalase (28.7 ± 2.3 mM/min/ìg protein), and Ascorbate peroxidase (1.91±0.12 mM/min/ìg protein) enzyme was maximum. It was also observed that the activity of ascorbate perooxidase was very less compared to activity of catalase. The growth analysis and pigment profile were also studied. Growth measurements revealed that cells attain maximum growth nearly after 15-20 days of inoculation except S. aquatalis, A. platensis and N. paludosum maximum, where optimum growth was achieved after 25th day. Chlorophyll-a content of A.platensis showed maximum concentration (14.47 ± 1.17 mg/L) and minimum concentration in S. elongates (2.30 ± 0.138 mg/L). The concentration of phycobiliproteins was found maximum in A. platensis (2.09 mg/ml). The detection of antioxidative potential of cyanobacterial strains will help to broaden the knowledge about their survival and can pave path for their utilization in biotechnology

Biofuels from Microalgae

Biofuels are the most awaited products of scientific research. The fossil fuels are being exhausted, and pollution is increasing globally. Algal biofuels are one of the promising options. They are wonderful tiny factories that yield a variety of substances that have the property to act as sources of ecofriendly fuels. More attention has been focused on microalgae-derived biomass for generating diverse renewable energy sources. The distinct features that microalgae possess include high biomass yield, abundant oil content, no requirement for land and easy cultivation in wastewaters coupled with carbon dioxide mitigation. Microalgae are tiny reservoirs of a plethora of biofuels. The diverse algal biofuels range from biodiesel, straight vegetable oil (SVO), lipids, ethanol and hydrogen. Biofuels are the need of today, and researchers around the globe are exploring the options for biological fuel production

Impact of Environmental Degradation on Human Health

Degradation of environment is one of the most serious challenges before the mankind in today's world. Mankind has been facing a wide range of problem arising out of the degradation of environment. Not only the areas under human inhabitation, but the areas of the planet without human population have also been suffering from these problems. As the population increase day by day, the amenities are not improved simultaneously. With the advancement of science and technologies the needs of human beings has been changing rapidly. As a result different types of environmental problems have been rising. Environmental degradation is a wide- reaching problem and it is likely to influence the health of human population is great. It may be defined the deterioration of the environment through depletion of resources such as air, water, and soil. The destruction of ecosystem and extinction of wildlife. Environmental degradation has occurred due to the recent activities in the field of socio-economic, institute and technology. Poverty still remains a problem as the root of several environmental problems to create awareness among the people about the ill effect of environmental pollution. In the whole research it is clear that all factors of environmental degradation may be reduced through- Framing the new laws on environmental degradation, Environment friend policy, Controlling all the ways and means of noise, air, soil and water pollution, Through growing more and more trees and by adapting the proper sanitation policy.&nbsp

Magnetotransport in Transition Metal Dichalcogenide Semimetals

In this thesis, we study the large magnetoresistance in MoTe2, and non-linear anomalous Hall effect in MoTe2 and WTe2. Thin flakes cleaved from layered single crystals exhibit high mobility, and semimetals show nearly compensated electron and hole density. The two combined in a layered semimetallic TMDC show a large and unsaturated magnetoresistance. However, thinning down the sample to a few atomic layers results in a charge imbalance and a decreased mobility, suppressing the overall magnetoresistance. As large magnetoresistance is an important component of various applications, it is important to determine which of these factors are prominent in affecting the magnetoreistance in the thin materials, and potentially modify that factor for 2D XMR applications. To study this, we use thickness tuned magnetotransport measurements on a semimetallic layered TMDC, MoTe2. We use a two-band model to extract mobility and electron-hole ratio from the magnetoresistance measurements. Upon analysing the data over various thicknesses, we conclude that the suppression of magnetoresistance in thin layers is prominently impacted by the mobility. A high mobility in thin layers can be achieved by using a high quality single crystals and providing an atomically at substrate of boron nitride for device fabrication. We also measure Shubnikov de-Haas (SdH) oscillations in the resistivity of MoTe2 at high magnetic field. We analysed the frequency of these oscillations in the inverse of magnetic field to find corresponding signatures of electron and hole pockets on the Fermi surface. The other phenomena we try to explore is the anomalous Hall effect(AHE) in a time reversal invariant system. AHE originates both from the Berry curvature mechanism intrinsic to the material, and spin-orbit coupled impurity scattering processes. A non-zero Berry curvature requires the system to be breaking either of the time-reversal(TRS) or inversion symmetries. While the AHE in TRS breaking ferromagnetic materials has been elaborated upon in literature, a general theory of AHE in IS breaking materials was only recently provided. For inversion symmetry breaking systems, the Hall effects appears as a DC and second harmonic response to the applied current, giving a non-linear anomalous Hall effect (NLAHE). Three dimensional TMDCs, MoTe2 and WTe2, are non-centrosymmetric crystals, where application of in-plane electric field gives a finite NLAHE along the c-axis. For measurements, we designed a device with both in-plane and vertical contacts to measure the first and second harmonic responses. To parse different contributions to the NLAHE, we rely on the scaling relation between the NLAHE strength and longitudinal conductivity. We provide a scaling with conductivity by changing the thickness and temperature. Our scaling relation shows that the NLAHE is dominated by skew scattering contribution along with a new exponential dependence on conductivity at low temperatures. Finally, to put this work in context with the existing AHE results, we measure the Hall ratio and Hall conductivity

Homotopy Theory for CW-Complexes

In this review work we have studied on homotopy properties of CW-complexes with an emphasis on finite dimensional CW-complexes. We have first given a brief introduction on basic definitions from the general topology and then have discussed the homotopy theory for general topological spaces. Basic definitions and constructions of homotopy and CW-complexes have been discussed exhaustively. Then certain theorems and definitions on homotopy theory of CW-complexes have been discussed briefly. Finally, we have studied Whitehead Theore

Importance of Routine Histopathological Examination of Gallbladder Specimen in Detecting Incidental Malignancies

Introduction: Gallbladder carcinoma is the most common cancer of biliary tree and the 5th most common gastrointestinal malignancy.  An early diagnosis is essential as this malignancy progresses silently with a late diagnosis and poor prognosis. Epidemiological studies have identified striking geographic and ethnic variation with high occurrence in Southeast Asia, yet low elsewhere in the world. Gallbladder carcinoma, in 15-30% of patients, show  no preoperative  or intraoperative evidence and are detected only on histopathological examination. They are called as incidental gallbladder cancer (IGBC). The objective of this study was to find out the occurrence of IGBC in cholecystectomy specimens received in our histopathology laboratory and to analyze their clinico-pathological features. Methods: This was a prospective study carried out in the Department of Histopathology, Lumbini Medical College Teaching Hospital during a period of two years from May 2014 to April 2016. The study included 800 cases of cholecystectomized Gall bladder specimens. Result: Ninety seven percent of the specimens (n=776) revealed benign pathology. Malignancy was detected incidentally in 8 cases (1.25%). The mean age of patients with incidental Gall bladder carcinoma was 69 years (SD=4.1) and F:M ratio was 9:1. Out of 10 incidental malignancies, cholelithiesis was found in 8 (80%) cases. Fundus was the most common location (n=5, 50%) and focal fragile necrotic area was most common (n=3, 30%) gross morphology. On pathological staging, all the incidentally detected malignancies (n=10) were found to be in surgically resectable stages. Conclusion: IGBC was found in 1.25% of the gallbladder specimen. Detailed gross and histopathological examination of gallbladder specimen is mandatory for every cholecystectomy specimen, even for benign diseases, to detect incidental carcinoma at potentially curable stage

Fine Needle Aspiration versus Fine Needle Capillary Sampling Technique in Cyto-diagnosis of Thyroid Lesions

Introduction: In diagnosis of thyroid lesions, the negative pressure applied during fine needle aspirationcytology (FNAC) frequently produces bloody smears. This results in a compromise in cellular concentrationand architecture which may lead to improper interpretation. Fine needle capillary sampling cytology(FNCC), on the other hand, avoids active aspiration as it depends on capillary tension to collect tissuesamples in the needle bore. This study evaluated the diagnostic performance of FNAC and FNCC in thyroidlesions. Methods: A total of 120 patients were included in this study conducted over a duration of 19months. All thyroid swellings advised for cyto-diagnosis were sampled by both fine-needle aspiration(FNAC) and non-aspiration (FNCC) techniques. The slides were assessed according to the Mair et al.scoring system. Results: In the FNCC group, 72 (60%) smears were diagnostically superior while 54 (45%)smears were diagnostically superior in the FNAC group. Blood contamination (p=0.003), cellular trauma(p=0.019), and degree of cellular degeneration (p=0.026) were less and cellular architecture (p=0.047) waspreserved more in FNCC in comparison to FNAC groups. Conclusion: This study showed the superiority ofFNCC for the interpretation and diagnosis of thyroid lesions. However, the combination of both FNAC andFNCC could maximize the diagnostic yield