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Review on the phosphate-based conversion coatings of magnesium and its alloys

International Journal of Minerals,Metallurgy and Materials 2022年第7期29卷 1435-1452页

作者： Debasis Saran atul kumar Sivaiah Bathula David Klaumünzer Kisor K Sahu School of Minerals Metallurgical and Materials EngineeringIndian Institute of Technology BhubaneswarBhubaneswar 752050India Group Innovation(COI Battery-Metals) Volkswagen AGWolfsburg 38440Germany Virtual and Augmented Reality Centre of Excellence(VARCOE) Indian Institute of Technology BhubaneswarBhubaneswar 752050India

Magnesium(Mg)and its alloys are lightweight as well as biocompatible and possess a high strength-to-weight ratio,making them suitable for many industries,including aerospace,automobile,and medical.The major challenge is their high susceptibility to corrosion,thereby limiting their usability.The considerably lower reduction potential of Mg compared to other metals makes it vulnerable to galvanic coupling.The oxide layer on Mg offers little corrosion resistance because of its high porosity,inhomogeneity,and fragility.Chemical conversion coatings(CCs)belong to a distinct class because of underlying chemical reactions,which are fundamentally different from other types of coating.Typically,a CC acts as an intermediate sandwich layer between the base metal and an aesthetic paint.Although chromate CCs offer superior performance compared to phosphate CCs,yet still they release carcinogenic hexavalent chromium ions(Cr^(6+));therefore,their use is prohibited in most European nations under the Registration,Evaluation,Authorization and Restriction of Chemicals legislation framework.Phosphate-based CCs are a cost-effective and environment-friendly alternative.Accordingly,this review primarily focuses on different types of phosphate-based CCs,such as zinc,calcium,Mg,vanadium,manganese,and permanganate.It discusses their mechanisms,current status,pretreatment practices,and the influence of various parameters-such as pH,temperature,immersion time,and bath composition-on the coating performance.Some challenges associated with phosphate CCs and future research directions are also elaborated.

关键词： phosphate conversion coatings magnesium alloys corrosion zinc phosphate conversion coatings calcium phosphate conversion coatings magnesium phosphate conversion coatings

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First contact investigations and compliance to treatment in patients with uveitis

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International Journal of Ophthalmology(English edition) 2023年第11期16卷 1820-1826页

作者： Anuja Patil Sanjeev Gupta Pradeep Venkatesh Mousumi Banerjee Vinod kumar Rohan Chawla Shorya Vardhan Azad atul kumar Dr.Rajendra Prasad Centre for Ophthalmic Sciences All India Institute of Medical SciencesNew Delhi 110029India

AIM:To ascertain the pattern of investigations at first contact in uveitic patients and evaluate compliance to treatment.METHODS:An observational study comprised of 201 uveitic patients presenting for the first time to our centre from January 2019 to June 2020.Detailed information regarding systemic investigations undertaken by specialists at the time of first contact and the cost of these investigations were reviewed on the first visit to our centre.Compliance with the treatment was determined and reasons behind non-compliance were evaluated on the first follow-up in patients who had no improvement in clinical signs and symptoms.RESULTS:The mean age of the study group was 35.35±14.1y and gender composition was 59.7%males and 40.3%females.Anterior uveitis was observed in 45.3%of patients,intermediate uveitis in 31.8%of patients,posterior uveitis in 14.9%of patients and panuveitis in 8.0%of patients.Association with a systemic disease was evident in 17.9%of patients.When compared with standard guidelines and uveitis patterns,systemic investigations were identified to be relevant only in 38.3%of patients.Non-compliance to treatment was documented in 22.4%of patients.Common reasons for non-compliance were inadequate counselling by the treating physician about treatment in 26.7%of patients and a busy schedule at work/school in 22.2%of patients.CONCLUSION:Significant number of investigations performed at first contact is found to be contrary to standard guidelines and are not contributory to the care.About a quarter of patients in this study are found to be non-compliant with the treatment.Compliance is more challenging to achieve in school-going children and working adults.The availability of comprehensive,periodically updated,evidence-based guidelines on the role of investigations and the use of trained counsellors may help to channelize proper evaluation and improve compliance to treatment,respectively,in patients with uveitis.

关键词： uveitis compliance investigations first contact

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Evolution of tectonic landscapes and deformation in the southeast Kumaun and western Nepal Himalaya

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Journal of Mountain Science 2024年第8期 2592-2617页

作者： Khayingshing LUIREI Girish Ch.KOTHYARI Param K GAUTAM Ambar SOLANKI atul kumar PATIDAR Sentisenla JAMIR Anirudh DATTA Tanupriya CHOUDHURY Wadia Institute of Himalayan Geology Department of Petroleum Engineering and Earth Sciences University of Petroleum and Energy Studies Department of Geology Nagaland University Academy of Scientific and Innovative Research CSE Department Graphic Era deemed to be University CSE Department Symbiosis Institute of Technology Symbiosis International (Deemed University)

The area of the present investigation's expanse constitutes the southernmost extent of the southeast Kumaun Himalaya and western Nepal Himalaya. Multidisciplinary approaches have been employed to understand the landforms associated with tectonic deformation, through detailed field investigation supplemented by the geodetic, chronological, and morphometric database. The morphogenic expressions of the Main Boundary Thrust(MBT) are reflected in the form of ～25 km long E-W trending north dipping fault scarp. The deformation along the strike length of the Himalayan Frontal Thrust(HFT) is noticed in the form of uplifted and incised fill terraces, and strath terraces. The deformation within the fluvial sequences in the study area can be visualized in the form of sheared boulders and pebbles, tilted and faulted terrace deposits. Furthermore, the chronological data of fluvial landforms in the study area suggests two major phases of tectonic deformations that have occurred around 58.7±10.8 ka and 3.88±0.4 ka. The chronology of lateQuaternary landforms advocates that the initial stage of aggradations in the Himalayan foothills commenced around 75.1±0.58 ka. The aggradational landforms resulted from the diverse depositional regime as evident from the nature of the sediment sequences from clasts dominated to thick mud sequences. The rate of deformation in the southeastern Kumaun and western Nepal Himalaya is ± 7 mm/yr, as per the data obtained from the Persistent Scatterer Interferometric Synthetic Aperture Radar(PSIn SAR). The landform deformation pattern, phase of incision and aggradation, frequent occurrence of landslides, and recent past earthquake activity within the wide zone of the HFT, the MBT, and Ramgarh Thrust suggests that the southernmost front of the Kumaun Himalaya is active and has potential for future geohazard. The foothill zone of Himalayan towns are actively growing in terms of population and infrastructural development. Therefore, such intradisciplinary studies for tectonically active regions are needed f

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Cameron ulcers:An atypical source for a massive upper gastrointestinal bleed

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World Journal of Gastroenterology 2012年第35期18卷 4959-4961页

作者： Samir Kapadia Sophia Jagroop atul kumar Department of Medicine Stony Book Univer sity School of MedicineStony BrookNY 11794United States Gastroenterology and Hepatol ogy Northport VA Medical CenterNorthportNY 11768United States

Cameron lesions represent linear gastric erosions and ulcers on the crests of mucosal folds in the distal neck of a hiatal hernia(HH).Such lesions may be found in upto 50% of endoscopies performed for another indication.Though typically asymptomatic,these may rarely present as acute,severe upper gastrointestinal bleed(GIB).The aim is to report a case of a non-anemic 87-year-old female with history of HH and atrial fibrillation who presented with hematemesis and melena resulting in hypovolemic shock.Repeat esophagogastroduodenoscopy was required to identify multiple Cameron ulcers as the source.Endoscopy in a patient with HH should involve meticulous visualization of hernia neck and surrounding mucosa.Cameron ulcers should be considered in all patients with severe,acute GIB and especially in those with known HH with or without chronic anemia.

关键词：上消化道出血溃疡非典型梅 GIB 血容量源识别可视化

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Evaluating role of bone marrow-derived stem cells in dry age-related macular degeneration using multifocal electroretinogram and fundus autofluorescence imaging

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International Journal of Ophthalmology(English edition) 2017年第10期10卷 1552-1558页

作者： atul kumar Neha Midha Sujata Mohanty Annu Chohan Tulika Seth Varun Gogia Shikha Gupta Dr.Rajendra Prasad Centre for Ophthalmic Sciences All India Institute of Medical Sciences Stem Cell Facility All India Institute of Medical Sciences Department of Hematology All India Institute of Medical Sciences

AIM：To evaluate the role of bone marrow-derived stem cells in the treatment of advanced dry age-related macular degeneration（AMD）using multifocal electroretinogram（mf-ERG）and fundus autofluorescence imaging.METHODS：Thirty patients（60 eyes）with bilateral central geographic atrophy（GA）were recruited.Worse eye of each patient received autologous bone marrow-derived hematopoietic stem cells（BM-HSCs）（group 1）and the fellow eye with better visual acuity served as control（group2）.The effect of stem cell therapy was determined in terms of visual acuity,amplitude and implicit time in mf-ERG and size of GA on fundus autofluorescence imaging.These tests were performed at presentation and first,third and sixth month follow up.Adverse events（if any）were also monitored.RESULTS：At 6mo follow-up there was no statistically significant improvement in median log MAR best corrected visual acuity（BCVA）in either group.Mf-ERG revealed significant improvement in amplitude and implicit time in the intervention group.A significant decrease was also noted in greatest linear dimension（GLD）of GA in the eyes receiving stem cells[6.78±2.60 mm at baseline to 6.56±2.59 mm at 6mo（P=0.021）].However,no such improvement was noted in the control group.CONCLUSION：Electrophysiological and anatomical improvement in the intervention group sheds light on the therapeutic role of BM-HSCs.Further studies are required to determine the stage of disease at which the maximal benefit can be achieved and to standardize the dose andfrequency of stem cell injection.

关键词： dry age-related macular degeneration multifocal electroretinogram stem cells fimdus autofluorescence imaging

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Geochemical signatures of potassium metasomatism in anthracite from the Himalayan fold‑thrust belts of Sikkim,India

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International Journal of Coal Science & Technology 2022年第2期9卷 48-69页

作者： Santanu Ghosh Anwita Ojha atul kumar Varma Coal Geology and Organic Petrology Laboratory Department of Applied GeologyIndian Institute of Technology(Indian School of Mines)DhanbadJharkhand 826004India Department of Earth Sciences Indian Institute of Technology BombayPowaiMumbaiMaharashtra 400076India

The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basins,as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim,India.The SiO_(2)content(48.05 wt%to 65.09 wt%and 35.92 wt%to 50.11 wt%in the bituminous and anthracite samples,respectively)and the ratio of Al_(2)O_(3)/TiO_(2)(6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples)reveal the intermediate igneous source rock composition of the minerals.The ratio of the K_(2)O/Al_(2)O_(3)in the ash yield of the bituminous coal samples(0.03 to 0.09)may suggest the presence of kaolinite mixed with montmorillonite,while its range in the ash yield of the anthracite samples(0.16 to 0.27)may imply the presence of illite mixed with kaolinite.The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions.The plot of the bituminous coal samples in the A–CN–K diagram depicts the traditional weathering trend of parent rocks,but the anthracite samples plot near the illite feld and are a bit ofset from the weathering trend.This may imply the plausible infuences of the potassium-metasomatism at post coalifcation stages,which is further supported by high K_(2)O/Na_(2)O ratio(29.88–80.13).The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the efect of the epigenetic potassium-metasomatism.The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.

关键词： Himalayan fold-thrust belts Anthracite Potassium metasomatism Kaolinite to quartz-feldspar intensity ratio Montmorillonite stretching and bending intensities Illite-stretching frequency

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Journal of Ocean Engineering and Science 2023年第2期8卷 111-123页

作者： Raj kumar Ravi Shankar Verma atul kumar Tiwari Department of Mathematics Faculty of Engineering&TechnologyVeer Bahadur Singh Purvanchal UniversityJaunpur222003India Department of Mathematics Motihari College of EngineeringMotihari845401BiharIndia

This work is devoted to get a new family of analytical solutions of the(2+1)-coupled dispersive long wave equations propagating in an infinitely long channel with constant depth,and can be observed in an open sea or in wide channels.The solutions are obtained by using the invariance property of the similarity transformations method via one-parameter Lie group theory.The repeated use of the similarity transformations method can transform the system of PDEs into system of ODEs.Under adequate restrictions,the reduced system of ODEs is solved.Numerical simulation is performed to describe the solutions in a physically meaningful way.The profiles of the solutions are simulated by taking an appropriate choice of functions and constants involved therein.In each animation,a frame for dominated behavior is captured.They exhibit elastic multisolitons,single soliton,doubly solitons,stationary,kink and parabolic nature.The results are significant since these have confirmed some of the established results of S.kumar et al.(2020)and K.Sharma et al.(2020).Some of their solutions can be deduced from the results derived in this work.Other results in the existing literature are different from those in this work.

关键词： Dispersive long wave equations Solitons Invariants Lie-group Similarity solutions

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Spectral narratives of microstructural restyling and their controls on hydrocarbon generation potential from coal

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International Journal of Coal Science & Technology 2023年第3期10卷 167-189页

作者： Tushar Adsul Santanu Ghosh Anwita Ojha Sudip Bhattacharyya atul kumar Varma Coal Geology and Organic Petrology Laboratory Department of Applied GeologyIndian Institute of Technology(Indian School of Mines)DhanbadJharkhand 826004India Department of Geology Mizoram UniversityAizawlMizoram 796004India Specialized Coal Petrography Laboratory Natural Energy ResourcesMission II-BGeological Survey of IndiaDK-6Sector-IlSalt Lake CityKolkataWest Bengal 700091India

The low to medium-rank Tertiary coals from Meghalaya,India,are explored for the first time for their comprehensive micro-structural characterization using the FTIR and Raman spectroscopy.Further,results from these coals are compared with the Permian medium and high-rank coals to understand the microstructural restyling during coalification and its controls on hydrocarbon generation.The coal samples are grouped based on the mean random vitrinite reflectance values to record the transformations in spectral attributes with increasing coal rank.The aliphatic carbon and the apparent aromaticity respond sharply to the first coalification jump(R:0.50%)during low to medium-rank transition and anchizonal metamorphism of the high-rank coals.Moreover,the Raman band intensity ratio changes during the first coalification jump but remains invari-able in the medium-rank coals and turns subtle again during the onset of pregraphitization in high-rank coals,revealing a polynomial trend with the coal metamorphism.The Rock-Eval hydrogen index and genetic potential also decline sharply at the first coalification jump.Besides,an attempt to comprehend the coal microstructural controls on the hydrocarbon poten-tial reveals that the Tertiary coals comprise highly reactive aliphatic functionalities in the type I-S kerogen,along with the low paleotemperature(74.59-112.28℃)may signify their potential to generate early-mature hydrocarbons.However,the presence of type II-II admixed kerogen,a lesser abundance of reactive moieties,and overall moderate paleotemperature(91.93-142.52℃)of the Permian medium-rank coals may imply their mixed hydrocarbon potential.Meanwhile,anchizonal metamorphism,polycondensed aromatic microstructure,and high values of paleotemperature(~334.25 to~366.79℃)of the high-rank coals indicate a negligible potential of producing any hydrocarbons.

关键词： Early mature oil generation Meghalaya high-sulfur coal Type II-S kerogen Microstructural ordering Coalification jump Hydrocarbon generation potential

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Analytical Solution to the One-Dimensional Advection-Diffusion Equation with Temporally Dependent Coefficients

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Journal of Water Resource and Protection 2011年第1期3卷 76-84页

作者： Dilip kumar Jaiswal atul kumar Raja Ram Yadav 不详

In a one-dimensional advection-diffusion equation with temporally dependent coefficients three cases may arise: solute dispersion parameter is time dependent while the flow domain transporting the solutes is uniform, the former is uniform and the latter is time dependent and lastly the both parameters are time dependent. In the present work analytical solutions are obtained for the last case, studying the dispersion of continuous input point sources of uniform and increasing nature in an initially solute free semi-infinite domain. The solutions for the first two cases and for uniform dispersion along uniform flow are derived as particular cases. The dispersion parameter is not proportional to the velocity of the flow. The Laplace transformation technique is used. New space and time variables are introduced to get the solutions. The solutions in all possible combinations of increasing/decreasing temporal dependence are compared with each other with the help of graphs. It has been observed that the concentration attenuation with position and time is the fastest in case of decreasing dispersion in accelerating flow field.

关键词： Advection Diffusion Dispersion Continuous Input Flux Type Condition

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STRATEGIES FOR CONTROLLING LATE BLIGHT OF POTATO IN DEVELOPING COUNTRIES

STRATEGIES FOR CONTROLLING LATE BLIGHT OF POTATO IN DEVELOPI...

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The ⅩⅤth International Plant Protection Congress

作者： Vandana a.kumar atul kumar Dept.of Basic Sciences College of Forestry and Hill Agriculture （GBPUA＆T） Hill Campus Ranichauri-249 199 Tehri Garhwal Uttaranchal India Dept.of Basic Sciences College of Forestry and Hill Agriculture （GBPUA＆T） Hill Campus Ranichauri-249 199 Tehri Garhwal Uttaranchal India

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