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Observation of~100%valley-coherent excitons in monolayer MoS_(2) through giant enhancement of valley coherence time

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光:科学与应用(英文版) 2023年第8期12卷 1644-1650页

作者： Garima Gupta Kenji Watanabe Takashi Taniguchi Kausik Majumdar Department of Electrical Communication Engineering Indian Institute of ScienceBangaloreIndia Research Center for Functional Materials National Institute for Materials ScienceTsukubaJapan international Center for Materials Nanoarchitectonics National Institute for Materials ScienceTsukubaJapan

In monolayer transition metal dichalcogenide semiconductors,valley coherence degrades rapidly due to a combination of fast scattering and inter-valley exchange *** leads to a sub-picosecond valley coherence time,making coherent manipulation of exciton a highly challenging task Using monolayer MoS_(2) sandwiched between top and bottom graphene,here we demonstrate fully valley-coherent excitons by observing~100%degree of linear polarization in steady state *** is achieved in this unique design through a combined effect of(a)suppression in exchange interaction due to enhanced dielectric screening,(b)reduction in exciton lifetime due to a fast inter-layer transfer to graphene,and(c)operating in the motional narrowing *** disentangle the role of the key parameters affecting valley coherence by using a combination of calculation(solutions of Bethe-Salpeter and Maiallle-Silva-Sham equations)and a careful choice of design of experiments using four different stacks with systematic variation of screening and exciton *** the best of our knowledge,this is the first report in which the excitons are found to be valley coherent in the entire lifetime in monolayer semiconductors,allowing optical readout of valley coherence possible.

关键词： coherent monolayer lifetime

Metallurgical behavior and variation of vibro-acoustic signal during preheating assisted friction stir welding between AA6061-T6 and AA7075-T651 alloys

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Transactions of Nonferrous Metals Society of China 2019年第8期29卷 1610-1620页

作者： Ashu GARG Madhav RATURI Anirban BHATTACHARYA Department of Mechanical Engineering Indian Institute of Technology Patna

The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acoustic signal pattern and joint strength during friction stir welding(FSW)between AA6061-T6 and AA7075-T651 *** eccentric tool pins were observed to provide good flowability and intermixing between dissimilar metals,increased the size of stir zone,and the grains in stir zone were sufficiently finer with eccentric tool pin than concentric *** magnitude of vibro-acoustic signal increased when shoulder plunging started and drop in signal was noted when the tool shoulder reached its desired *** signal magnitude was noted to be higher in welding stage compared to tool plunging stage as the tool took in fresh material during tool movement along the weld *** the workpiece prior to pin plunging and during welding notably influenced the flow behavior and mixing pattern,and the grains in stir zone were slightly coarser than those in specimen without *** reduction in the magnitude of the signal was also observed after *** and flexural strength of joints were also improved slightly when additional heating was employed.

关键词： friction stir welding tool pin profile eccentricity preheating vibro-acoustic signal microstructure strength

Selective inhibition of resistant bacterial pathogens using a β-lactamase-activatable antimicrobial peptide with significantly reduced cytotoxicity

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Chinese Chemical Letters 2023年第5期34卷 241-245页

作者： Weipan Xu Zheng Ma Geetika Dhanda Jayanta Haldar Hexin Xie State Key Laboratory of Bioreactor Engineering Shanghai Key Laboratory of New Drug DesignFrontiers Science Center for Materiobiology and Dynamic ChemistryShanghai Frontier Science Research Base of Optogenetic Techniques for Cell MetabolismSchool of PharmacyEast China University of Science and TechnologyShanghai 200237China Antimicrobial Research Laboratory New Chemistry UnitJawaharlal Nehru Centre for Advanced Scientific Research(JNCASR)JakkurBengaluru 560064India School of Advanced Materials Jawaharlal Nehru Centre for Advanced Scientific Research(JNCASR)JakkurBengaluru 560064India

The expression ofβ-lactamase,particularly metallo-β-lactamase(MBL)in bacteria has caused significant resistance to clinically importantβ-lactam antibiotics,including life-saving *** peptides(AMPs)have emerged as promising therapeutic agents to combat antibiotic ***,the cytotoxic AMPs has been one of the major concerns for their applications in clinical ***,we report a novel cephalosporin-caged AMP,which shows significantly reduced cytotoxicity,hemolytic activity,and antibacterial activity but turns highly active against bacteria upon specific hydrolysis by the antimicrobial resistance-causativeβ-*** investigations demonstrate thisβ-lactamaseactivatable AMP selectively inactivates resistant bacterial pathogens over susceptible *** strategy should be applicable to other AMPs as a potential solution for the treatment of infectious diseases caused byβ-lactamase-expressing pathogenic bacteria.

关键词： Antibiotic resistance β-Lactamase Antimicrobial peptide Cytotoxicity

NONLINEAR WAVE INTERACTIONS IN A MACROSCOPIC PRODUCTION MODEL

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Acta Mathematica Scientia 2021年第3期41卷 764-780页

作者： MINHAJUL T RAJA SEKHAR Center for Applicable Mathematics Tata Institute of Fundamental ResearchBangaloreKarnataka-560065India Department of Mathematics Indian Institute of Technology KharagpurKharagpur-2India

In this article,we study the exhaustive analysis of nonlinear wave interactions for a 2×2 homogeneous system of quasilinear hyperbolic partial differential equations(PDEs)governing the macroscopic *** use the hodograph transformation and differential constraints technique to obtain the exact solution of governing ***,we study the interaction between simple waves in detail through exact solution of general initial value ***,we discuss the all possible interaction of elementary waves using the solution of Riemann problem.

关键词： Elementary waves wave interactions Riemann problem simple wave differential constraints Hodograph transformation

Spectroscopic study of strangeness=-3Ω^(-)baryon

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Chinese Physics C 2022年第10期46卷 43-51页

作者： Chandni Menapara Ajay Kumar Rai Department of Physics Sardar Vallabhbhai National Institute of TechnologySurat-395007GujaratIndia

Ω^(-)baryon with sss quarks has been investigated through many theoretical studies so far but scarcely observed in ***,an attempt has been made to explore properties of Ω with hypercentral Constituent Quark Model(hCQM)with a linear confining *** resonance mass spectra have been obtained for 1S-4S,1P-4P,1D-3D,and *** Regge trajectory has been investigated for the linear nature based on calculated data along with the magnetic *** present work has been compared with various approaches and known experimental findings.

关键词： mass spectra strange baryon Regge trajectory magnetic moment

Palaeogeography, palaeohydraulics and palaeoclimate of the Mio-Pliocene Siwalik Group, eastern India

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Journal of Palaeogeography 2014年第3期3卷 270-296页

作者： Sunipa Mandal Subir Sarkar Nivedita Chakraborty Pradip K.Bose Department of Geology Asutosh College Department of Geological Sciences Jadavpur University

South-southwestward palaeocurrent swerved to east-southeast and then broadly to southeast over the transition from alluvial fan to axial channel and then to the flood plain in the Mio-Pliocene foreland system within which the Siwalik Group depositd in Darjeel- ing-Jalpaiguri Districts, eastern India. Palaeocurrent pattern is found to be multi-modal on the fans, virtually unimodal on the axial channel zone and again multi-modal, more profoundly, on the flood plain. Coarse siliciclastic mass-flows were progressively eliminated and gave way to predominant bed-load transport downfan and the axial river, and then to suspensionload dominance in fine siliciclastics on the flood plain. Distal flood plain lacustrine sediment included most of the coals and the entire bulk of the dolomitic limestone. Further resolution in palaeogeography within the frame of aforementioned foursome facies associations is elicited in twenty-six distinctive facies altogether. Critical evaluation of chemical indices （CIA, CIW, ICV, PIA, as well as Rb/Sr ratio） for weathering and depleted （3180 values indicate a high precipitation rate. The contention is further corroborated by the high discharge rate calculated from cross-set thicknesses within the main channel deposits. Reconciliation of various relevant data sets collected or calculated from all known worksites along the entire 2000 km-Iong exposure belt of the Siwaliks along the Himalayan foothills reveal confluence of two tributaries, one from the west and the other from the east, close to the present study area before escaping onto the Indian plains. Channel parameters, channel-belt width and discharge thus attained maxima in the present study area. The precipitation rate and temperature increased eastward overall as a prelude to the modern trend in this regard. 13C enrichment indicates that the transition from C3 to C4 vegetation had already set in.

关键词： Mio-Pliocene Siwalik Group Darjeeling Himalayas spatial variation axialriver reconstruction vegetation

Trap analysis on Pt-AlGaN/GaN Schottky barrier diode through deep level transient spectroscopy

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Journal of Semiconductors 2023年第4期44卷 92-97页

作者： Ashish Kumar Jayjit Mukherjee D.S.Rawal K.Asokan D.Kanjilal Department of Physics School of Natural ScienceUniversity of Petroleum and Energy StudiesBidholiDehradun-248007India Inter University Accelerator Centre Aruna Asaf Ali RoadVasantkunjNew Delhi-110067India Solid State Physics Laboratory DRDOTimarpurNew Delhi-110054India

Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap signatures at similar temperature *** traps are found to be within the values:0.05–1.2 eV from the conduction band edge whereas the hole traps 1.37–2.66 eV from the valence band edge on the *** the lower temperature regime,the deeper electron traps contribute to the capacitance transients with increasing r values,whereas at the higher temperatures>300 K,a slow variation of the trap levels(both electrons and holes)is observed when r is *** traps are found to be mainly contributed to dislocations,interfaces,and vacancies within the structure.

关键词： deep traps Pt-SBD DLTS rate window defects

Enhanced dielectric and ferroelectric properties of surface hydroxylated Na_(0.5)Bi_(0.5)TiO_(3)(NBT)-poly(vinylidene fluoride)(PVDF)composites

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Journal of Advanced Dielectrics 2018年第3期8卷 34-43页

作者： Srikanta Moharana Shraddhakara Sai Ram Naresh Mahaling Laboratory of Polymeric and Materials Chemistry School of Chemistry Sambalpur University Jyoti ViharBurla 768019OdishaIndia Nano Research Centre Sambalpur University Jyoti ViharBurla 768019OdishaIndia

The surface hydroxylation treatment has been carried out by using hydrogen peroxide(H_(2)O_(2))to modify the surface of Na_(0.5)Bi_(0.5)TiO_(3)(NBT)particles in a ferroelectric polymer(PVDF)via solution casting *** FTIR study confirms the presence of hydroxyl groups on the surface of *** FE-SEM analysis reveals that h-NBT particles are dispersed homogeneously within the polymer *** surface hydroxylation treatment plays an important role in high dielectric constant and also reduced loss by conducting the material surface withOH functional *** prepared composite with 40 wt.%of h-NBT showed enhanced dielectric constant(≈114),negligible loss(0.22)and high AC conductivity as compared to that of the unmodified *** significant enhancement in dielectric properties may be due to the strong interaction between h-NBT particles and PVDF matrix at the *** percolation theory is used to explain the dielectric properties of h-NBT-PVDF ***,the remnant polarization of the un-poled h-NBT-PVDF composites(2 Pr–1.19C/cm^(2) for 40 wt.%of h-NBT)is also *** present findings give an idea of high dielectric constant and relatively low loss composite materials as a promising candidate for electronic and energy storage devices.

关键词： Poly(vinylidene fluoride) dielectric properties surface hydroxylation

Petrology,genesis and geodynamic implication of the Mesoproterozoic-Late Cretaceous Timmasamudram kimberlite cluster,Wajrakarur field,Eastern Dharwar Craton,southern India

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Geoscience Frontiers 2017年第3期8卷 541-553页

作者： Ashish Dongre N.V.Chalapathi Rao K.S.Viljoen B.Lehmann Department of Geology University of Johannesburg Department of Geology Centre of Advanced StudyBanaras Hindu University Mineral Resources Technical University of Clausthal

New mineralogical and bulk-rock geochemical data for the recently recognised Mesoproterozoic （ca. 1100 Ma） and late Cretaceous （ca. 90 Ma） kimberlites in the Timmasamudram cluster （TKC） of the Wajrakarur kimberlite field （WKF）, Eastern Dbarwar Craton, southern India, are presented. On the basis of groundmass mineral chemistry （phlogopite, spinel, perovskite and clinopyroxene）, bulk-rock chem- istry （SiO2, K20, low TiO2, Ba/Nb and La/Sm）, and perovskite Nd isotopic compositions, the TI（-1 （mac- rocrystic variety） and TI（-4 （Macrocrystic variety） kimberlites in this cluster are here classified as orangeites （i.e. Group II kimberlites）, with geochemical characteristics that are very similar to orangeites previously described from the Bastar Craton in central India, as well as the Kaapvaal Craton in South Africa. The remaining kimberlites （e.g., TK-2, TK-3 and the TK-1 microcrystic variant）, are more similar to other 1100 Ma, Group l-type kimberlites of the Eastern Dharwar Craton, as well as the typical Group I kimberlites of the Kaapvaal Craton. Through the application of geochemical modelling, based on pub- lished carbonated peridotite/melt trace element partition coefficients, we show that the generation of the TI（C kimberlites and the orangeites results from low degrees of partial melting of a metasomatised, carbonated peridotite. Depleted mantle （TDM） Nd perovskite model ages of the 1100 Ma Timmasamudram kimberlites show that the metasomatic enrichment of their source regions are broadly similar to that of the Meso- proterozoic kimberlites of the EDC. The younger, late Cretaceous （ca. 90 Ma） TI（-1 （macrocrystic variant） and TK-4 kimberlites, as well as the orangeites from the 8astar Craton, share similar Nd model ages of 1100 Ma, consistent with a similarity in the timing of source enrichment during the amalgamation of Rodinia supercontinent. The presence of late Cretaceous diamondiferous orangeite activity, presumably related to the location of the Marion hotspot

关键词： Kimberlite Orangeite Diamond Timmasamudram Wajrakarur India