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Tuning copper sulfide nanosheets by cation exchange reactions to realize two-dimensional CZTS dielectric layers
No full textDesign of two-dimensional (2D) quaternary copper-zinc-tin-sulfide (Cu2ZnSnS4, CZTS) nanosheets (NSs) consisting of purely earth abundant elements with desired morphologies, compositions and phases is challenging by conventional colloidal synthesis routes. Here we report the colloidal synthesis of ultra-thin (approximate to 2 nm) phase-pure 2D wurtzite CZTS NSs using 2D copper sulfide (Cu2S) NSs as a template. We incorporated Zn(ii) and Sn(iv) ions into the crystal lattice of Cu2S NSs retaining the 2D shape via controlled cation exchange reactions. The reaction protocol allows the achievement of the desired elemental composition of the NSs by varying the composition of the precursors. CZTS NSs with a large planar area exhibit a nearly temperature and frequency independent dielectric constant (>6.1) with a low dielectric loss over broad temperature and frequency ranges which makes the system an effective 2D dielectric material. The template based cation exchange reaction protocol provides a guideline to obtain phase-pure CZTS by avoiding the secondary phases often associated with the colloidal synthesis routes. This work demonstrates the realization of 2D quaternary dielectric non-oxide semiconductors composed of purely earth abundant elements for miniaturized energy storage devices using flexible solution processed routes
Combinations of single-top-quark production cross-section measurements and |fLVVtb| determinations at √s = 7 and 8 TeV with the ATLAS and CMS experiments
No full textThis paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at s√ = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb−1 at s√ = 7 TeV and 12.2 to 20.3 fb−1 at s√ = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at s√ = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at s√ = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at s√ = 8 TeV. The square of the magnitude of the CKM matrix element Vtb multiplied by a form factor fLV is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |Vtd|, |Vts| ≪ |Vtb|. All the |fLVVtb|2 determinations, extracted from individual ratios at s√ = 7 and 8 TeV, are combined, resulting in |fLVVtb| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model prediction
Multi-layered stack consisting of PVDF nanocomposites with flow-induced oriented MWCNT structure can supress electromagnetic radiation
No full textPolymeric nanocomposites have emerged as a potential material in the electronic world owing to its numerous advantages like ease of processing, design flexibility, light-weight, ease of embedding and integrating with the existing production line. Given the surge in electronic components, electromagnetic interference, which severely impairs the reliability of precise electronic devices, has emerged as a new challenge. Hence, technologically, viable design is the need of the day. However, the high concentration of fillers required to achieve the desired properties still remains a challenge with respect to the design of functional polymeric nanocomposites. In this context herein, we report as to how flow induced distribution of multi-walled carbon nanotubes (MWCNT) in poly-vinylidene (PVDF) matrix during mechanical rolling influence the texture, polymorphism and electromagnetic shielding properties. We demonstrate the flow induced orientation of MWCNT, polymorphism in PVDF and composites shielding performance by TEM, crystallographic texture and shielding effectiveness measurements, respectively. Further, mechanical and thermal properties of as pressed and mechanically rolled samples were investigated by DMA and DSC. TEM analysis revealed that MWCNT form small aggregate, however were aligned along the rolling direction. This observation is in sharp contrast to the random distribution for as pressed samples. Quantitatively, a strong texture was observed for rolled samples as compared to as pressed samples. Absorption of EM waves is the major shielding mechanism which is mechanistically discussed here through associated dielectric loss parameters. Interactions, alignment of MWCNTs, and polymorphism influence the shielding efficiency in these composites. In addition, stacking of such nanocomposite layers further enhances the overall shielding efficiency by absorption (up to 72%) due to the polarization, multiple internal reflections and interlayer charge storing capacity. A Bluetooth module was employed to successfully demonstrate the efficacy of this approach in supressing unwanted EM interference. This study comprehensively guides researchers as to how processing or flow-induced changes alter the distribution of MWCNTs in polymer composites and how this influences the overall shielding behaviour
Pyroxenite dykes with petrological and geochemical affinities to the Alaskan-type ultramafics at the northwestern margin of the Cuddapah basin, Dharwar craton, southern India: Tectonomagmatic implications
No full textTwo previously reported lamprophyre dykes from the Kalwakurthy area, at the northwestern margin of the Cuddapah basin, Dharwar craton, southern India, are reinvestigated. Petrography reveals that they have an overall cumulate texture and comprise clinopyroxene (dominant phase), amphibole (mostly secondary), magnetite, ilmenite and chromite and are reclassified as clinopyroxenites. The chemistry of clinopyroxene and chromite, bulk-rock major and trace element composition and the Sr-Nd isotopic systematics of the Kalwakurthy dykes strongly favour the involvement of subduction-related processes in their genesis and are strikingly similar to those of the continental arc-cumulates and Alaskan-type ultramafics reported from the supra-subduction type of tectonic settings. Incompatible trace element ratios, involving high field strength elements, of these clinopyroxenites are also suggestive of the fluid-related metasomatism influencing their source regions. Petrogenetic modelling reveals that 10-20% partial melting of the fertile lithospheric mantle source was involved in their genesis. The tectonomagmatic significance of the studied clinopyroxenites is evaluated in light of the existing models invoking a Neoarchaean subduction in the evolution of the Dharwar craton
Does resource availability help determine the evolutionary route to multicellularity?
No full textGenetic heterogeneity and homogeneity are associated with distinct sets of adaptive advantages and bottlenecks, both in developmental biology and population genetics. Whereas populations of individuals are usually genetically heterogeneous, most multicellular metazoans are genetically homogeneous. Observing that resource scarcity fuels genetic heterogeneity in populations, we propose that monoclonal development is compatible with the resource-rich and stable internal environments that complex multicellular bodies offer. In turn, polyclonal development persists in tumors and in certain metazoans, both exhibiting a closer dependence on external resources. This eco-evo-devo approach also suggests that multicellularity may originally have emerged through polyclonal development in early metazoans, because of their reduced shielding from environmental fluctuations
Random lattice strain and its relaxation towards the morphotropic phase boundary of Na0.5Bi0.5TiO3-based piezoelectrics: Impact on the structural and ferroelectric properties
No full textWe demonstrate that the lead-free piezoelectric compound Na0.5Bi0.5TiO3 (NBT) exhibits random lattice strain in the ferroelectric phase, and that this feature primarily dictates the way the system evolves towards the morphotropic phase boundary in the unpoled state of NBT-based piezoelectrics. Investigations on two different morphotropic phase boundary (MPB) systems, namely Na0.5Bi0.5TiO3 - K0.5Bi0.5TiO3 (NBT-KBT) and Na0.5Bi0.5TiO3 - BaTiO3 (NBT-BT), revealed that the coupled structural-polar evolution towards the MPB is primarily driven by the necessity to minimize this strain. Our study suggests that the random lattice strain originates in the random stacking of the in-phase tilt and antiphase octahedral tilted regions, and that the system is able to minimize it by adopting a sequential stacking of the two tilt types, leading to a long-period modulation in the octahedral tilt configuration over large parts of the sample volume. This hinders the development of long-range ferroelectric order as the MPB is approached. We also demonstrate that the composition showing the maximum piezoelectric coefficient corresponds to a structural state wherein considerable polar-structural disorder coexists with the field-stabilized long-range rhombohedral ferroelectric order after poling, and not coexistence of two ferroelectric phases (tetragonal and rhombohedral), generally believed
Electrical conduction mechanism for the investigation of charge ordering in Pr0.5Ca0.5MnO3 manganite system
No full textIn the present work, a systematic investigation of electrical transport mechanism has been used as a tool to investigate the charge-order suppression and its crossover in Pr0.5Ca0.5MnO3 (PCMO) manganite system with varying particle size and applied magnetic field. The samples with different particle sizes were synthesized by adopting sol-gel method and sintering at different temperatures. The prepared samples were thoroughly characterized by various physicochemical techniques. The activation energy and density of states at Fermi level obtained from the temperature-dependent electrical resistivity data clearly show the charge order crossover signatures and its suppression in the samples below 70 nm particle size and applied magnetic fields above 4 T. The significant change in various electrical transport parameters with the particle size around 70 nm could be attributed to the melting of long-range charge ordering behavior due to surface spin disorder and induced lattice-strain effects in PCMO manganite system
A multifunctional therapeutic approach: Synthesis, biological evaluation, crystal structure and molecular docking of diversified 1H-pyrazolo3,4-b]pyridine derivatives against Alzheimer's disease
No full text2-(piperazin-1-yl)-N-(1H-pyrazolo3,4-b]pyridin-3-yl)acetamides are described as a new class of selective and potent acetylcholinesterase (AChE) inhibitors and amyloid beta aggregation inhibitors. Formation of synthesized compounds (P1-P9) was justified via H-1 NMR, C-13 NMR, mass spectra and single crystal X-Ray diffraction study. All compounds were evaluated for their acetylcholinesterase and butyrylcholinesterase inhibitory activity, inhibition of self-mediated A beta aggregation and Cu(II)-mediated A beta aggregation. Also, docking study carried out was in concordance with in vitro results. The most potent molecule amongst the derivatives exhibited excellent anti-AChE activity (IC50=4.8 nM). Kinetic study of P3 suggested it to be a mixed type inhibitor. In vitro study revealed that all the compounds are capable of inhibiting self-induced beta-amyloid (A beta) aggregation with the highest inhibition percentage to be 81.65%. Potency of P1 and P3 to inhibit self-induced A beta(1-)(42) aggregation was ascertained by TEM analysis. Compounds were also evaluated for their A beta disaggregation, antioxidation, metal-chelation activity
Structure and Deformation of Gradient Metal Foams Produced by Machining
No full textThe effects of surface structure on mechanical performance for open-cell aluminum foam specimens were investigated in the present study. A surface gradient for pore structure and diameter was introduced into open-cell aluminum foams by machining-based processing. The structure changes in the strut and pore network were evaluated by computed tomography characterization. The role of structure gradients in affecting mechanical performance was determined using digital volume correlation and in situ compression within the computed tomographic scanner. These preliminary results show that the strength of these materials may be enhanced through surface structural gradients
Oxo-bridged trinuclear and tetranuclear manganese complexes supported with nitrogen donor ligands: syntheses, structures and properties
No full textIn this work, we present the syntheses of two mu(3)-oxo bridged mixed-valent trinuclear (MnMnIII)-Mn-II complexes (1 and 2) and a mu(4)-oxo bridged tetranuclear Mn-4(II) complex (3). All the three manganese complexes have been characterized crystallographically and by using different analytical techniques. Both mixed-valent trinuclear complexes 1 and 2 exhibited Jahn-Teller distortion for the Mn(III) ion. Variable temperature magnetic susceptibility studies of all three complexes revealed antiferromagnetic coupling between the closely placed paramagnetic manganese ions mediated via a mu-oxo bridge. Cyclic voltammetry studies displayed both Mn(III)/Mn(II) and Mn(IV) Mn(III) redox couples in 1 whereas only the Mn(III) Mn(II) couple was observed for complexes 2 and 3. Importantly, complexes 2 and 3 were found to disproportionate H2O2, and the catalase activity has been related to their structural features and redox properties