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Investigations on Magnetization and Electron Magnetic Resonance Properties of Nd0.65Ca0.35Mn1-xZnxO3(x =0, 0.1, 0.3) Nanomanganite
No full textZinc substitution effects on the magnetic ordering of nanosized Nd0.65Ca0.35MnO3 particles prepared by sol-gel method have been investigated by electron magnetic resonance (EMR) technique complimented by magnetization measurements. Bulk Nd0.65Ca0.35 MnO3 exhibits a charge ordering transition at 240 K and an antiferromagnetic transition at 150 K followed by a transition to a ferromagnetic (FM) phase below 50 K. In contrast, the nano Nd0.65Ca0.35MnO3 exhibits only a single transition from paramagnetic to ferromagnetic phase at 102 K which supports the general phenomenon of vanishing phase complexities in nano materials. In this paper, we discuss the effect of 10% and 30% zinc doping on the nano sized Nd0.65Ca0.35Mn1-x ZnxO3. Magnetization and EMR studies confirm the existence of ferromagnetism in all the samples which weakens with increasing doping of zinc. Though magnetization measurements do not show the charge order fluctuations and short range antiferromagnetic (AFM) order in the zinc-doped samples, EMR measurements evidence it. Electron magnetic resonance line width increases with zinc doping over a wide range of temperature due to the destruction of motional narrowing
Tunable CoNi microstructures in flexible multilayered polymer films can shield electromagnetic radiation
No full textThis paper highlights the outstanding electromagnetic shielding efficiency achieved by constructing layer-wise assembly of polymer films containing CoNi (cobalt-nickel) micro flowers, rods, and microspheres. Following a hydrothermal approach, various CoNi microstructures were synthesized from their metal salt precursors using wet chemistry followed by dispersing them in a PVDF matrix along with conducting multiwalled carbon nanotubes (MWNT) and subsequently hot-compressing them into thin flexible films (of thickness less than 1 mm). Few films were also prepared by dispersing only MWNTs in PVDF to construct a layer-wise assembly following an approach wherein a reflector spacer (PVDF/MWNT composites) is sandwiched between n (n = 0,1,2,3) absorbers (PVDF/CoNi/MWNT composites). The film thickness was adjusted in such a way that the total thickness of each assembly is ca. 0.9 mm. This strategy wherein a reflecting layer is sandwiched between the absorbing layers resulted in an excellent total shielding efficiency (SET) of -41 dB. By careful control of different layers in this layer-wise assembly, we managed to facilitate significant magnetic losses coupled with conducting losses. Therefore, this paper offers a replacement of conventional metallic shields with unique CoNi-based polymer composites for suppressing EM radiation
Shuffle-induced modulated structure and heating-induced ordering in the metastable beta-titanium alloy, Ti-5Al-5Mo-5V-3Cr
No full textA nano-scaled shuffle-induced modulated structure and heating-induced ordering have been characterized in a metastable beta-titanium alloy, Ti-5Al-5Mo-5V-3Cr, and their inter-relationship was investigated through in-situ and ex-situ conventional and aberration-corrected scanning/transmission electron microscopy and atom probe tomography. The nano-scaled O' phase with a disordered orthorhombicmodulated structure formed by the {O11} < 01 <(1)over bar>>beta transverse phonon was characterized for the first time to be stable from room temperature to similar to 200 degrees C. The O `' phase with an ordered orthorhombic structure formed from the beta phase during aging above the O' phase solvus temperature, where Al segregation in nano-scaled regions led to ordering of every third {011} planes
Bounds on slow roll and the de Sitter Swampland
No full textThe recently introduced swampland criterion for de Sitter 17] can be viewed as a (hierarchically large) bound on the smallness of the slow roll parameter epsilon(V). This leads us to consider the other slow roll parameter eta(V) more closely, and we are lead to conjecture that the bound is not necessarily on epsilon(V), but on slow roll itself. A natural refinement of the de Sitter swampland conjecture is therefore that slow roll is violated at O(1) in Planck units in any UV complete theory. A corollary is that epsilon(V) need not necesarily be O(1), if eta(V) less than or similar to -O(1) holds. We consider various tachyonic tree level constructions of de Sitter in IIA/IIB string theory (as well as closely related models of inflation), which superficially violate 17], and show that they are consistent with this refined version of the bound. The phrasing in terms of slow roll makes it plausible why both versions of the conjecture run into trouble when the number of e-folds during inflation is high. We speculate that one way to evade the bound could be to have a large number of fields, like in N-flation
Engineering approaches for characterizing soft tissue mechanical properties: A review
No full textFrom cancer diagnosis to detailed characterization of arterial wall biomechanics, the elastic property of tissues is widely studied as an early sign of disease onset. The fibrous structural features of tissues are a direct measure of its health and functionality. Alterations in the structural features of tissues are often manifested as local stiffening and are early signs for diagnosing a disease. These elastic properties are measured ex vivo in conventional mechanical testing regimes, however, the heterogeneous microstructure of tissues can be accurately resolved over relatively smaller length scales with enhanced spatial resolution using techniques such as micro-indentation, microelectromechanical (MEMS) based cantilever sensors and optical catheters which also facilitate in vivo assessment of mechanical properties. In this review, we describe several probing strategies (qualitative and quantitative) based on the spatial scale of mechanical assessment and also discuss the potential use of machine learning techniques to compute the mechanical properties of soft tissues. This work details state of the art advancement in probing strategies, associated challenges toward quantitative characterization of tissue biomechanics both from an engineering and clinical standpoint
Semi-regular Tilings of the Hyperbolic Plane
No full textA semi-regular tiling of the hyperbolic plane is a tessellation by regular geodesic polygons with the property that each vertex has the same vertex-type, which is a cyclic tuple of integers that determine the number of sides of the polygons surrounding the vertex. We determine combinatorial criteria for the existence, and uniqueness, of a semi-regular tiling with a given vertex-type, and pose some open questions
Highly Sensitive, Fast Graphene Photodetector with Responsivity >10(6) A/W Using a Floating Quantum Well Gate
No full textGraphene, owing to its zero-band-gap electronic structure, is promising as an absorption material for ultrawideband photodetection applications. However, graphene-absorption-based detectors inherently suffer from poor responsivity because of weak absorption and fast photocarrier recombination, limiting their viability for low-intensity light detection. Here, we use a graphene/WS2/MoS2 vertical heterojunction to demonstrate a highly sensitive photodetector, where the graphene layer serves dual purposes, namely, as the light absorption layer and also as the carrier conduction channel, thus maintaining the broadband nature of the photodetector. A fraction of the photoelectrons in graphene encounter ultrafast interlayer transfer to a floating monolayer MoS2 quantum well, providing a strong quantum-confined photogating effect. The photodetector shows a responsivity of 4.4 X 10(6) A/W at 30 1W incident power, outperforming photodetectors reported till date where graphene is used as a light absorption material by several orders. In addition, the proposed photodetector exhibits an extremely low noise equivalent power of <4 fW/root Hz. and a fast response (similar to milliseconds) with zero reminiscent photocurrent. The findings are attractive toward the demonstration of a graphene-based highly sensitive, fast, broadband photodetection technology
Visible light-induced cytotoxicity studies on Co(ii) complexes having an anthracene-based curcuminoid ligand
No full textHerein, two ternary cobalt(ii) complexes, namely Co(9-accm)(phen)(2)](OAc) (1) and Co(9-accm)(dppz)(2)](OAc) (2), where 9-accmH is 1,7-(di-9-anthracene-1,6-heptadiene-3,5-dione), phen is 1,10-phenanthroline and dppz is dipyrido3,2-a:2 `,3 `-c]phenazine, having an anthracene-based curcuminoid and phenanthroline bases were synthesized and fully characterized, and their in vitro photocytotoxicities were studied in cancer cells. To understand the role of the curcuminoid ligand 9-accm in photo-activated cytotoxicity, two control complexes, viz. Co(dbm)(phen)(2)](OAc) (3) and Co(dbm)(dppz)(2)](OAc) (4), where dbmH is 1,3-diphenyl-1,3-propanedione (dibenzoylmethane), were prepared and used for the control experiments. Complex 3 was structurally characterized by X-ray crystallography. The complexes displayed a quasi-reversible Co(i)/Co(ii) redox couple at similar to-1.1 V and an irreversible Co(ii)/Co(iii) couple at similar to 1.3 V vs. Ag/AgCl in DMF-0.1 M (Bu4N)-N-n](ClO4). Highly intense 9-accm ligand-centred bands were observed at similar to 250-450 nm, which masked the Co(ii)-based weak d-d bands in the DMF-Tris-HCl buffer (1 : 9 v/v). The complexes displayed a significant binding propensity for calf-thymus (ct) DNA with binding constants in the range from (2.42 +/- 0.10) x 10(5) to (3.24 +/- 0.13) x 10(6) M-1. They also showed a moderate binding affinity for human serum albumin (HSA), displaying K-b values in the order of similar to 10(4)-10(5) M-1. The complexes 1 and 2 showed prodigious photoenhanced cytotoxicity in human cervical cancer (HeLa) and breast cancer (MCF-7 and MDA-MB-231) cells with low dark toxicity, whereas they were non-toxic to immortalized lung epithelial normal cells (HPL1D). Flow cytometric studies showed a time-dependent uptake of the complexes 1 and 2 in HeLa cells. The complexes generated reactive oxygen species (ROS) upon excitation with low energy visible light, thereby killing the cancer cells. The results from DAPI staining, AO/EB dual staining and Annexin-V-FITC experiments suggested that the complexes induce cell death primarily via an apoptotic mechanism in HeLa cells
High vapour pressure nanofuel droplet combustion and heat transfer: Insights into droplet burning time scale, secondary atomisation and coupling of droplet deformations and heat release
No full textCombustion characteristics of ethanol-water (EW) droplets laden with ceria nanoparticles are investigated. The present experimental study focuses on three facets of droplet combustion (i) burning time scale of droplets with and without NPs, (ii) pathways of secondary atomisation due to interface deformations and (iii) coupling of droplet shape deformations and flame heat release. A theoretical vaporisation timescale is advocated which considers natural convection-based evaporation, mass loss due to daughter droplet ejections, and flow through porous media. Droplets seeded with ceria nanoparticles, exhibit arrested surface undulations although internal ebullition is discernibly enhanced as compared to EW droplets without NPs. Deformations and formation of surface craters in EW droplets are traced to the imbalance between local vapour recoil (due to rapid ethanol vaporisation) and surface tension. Such craters collapse and form high-speed ligaments which eventually break at the tip through Rayleigh Plateau mechanism. This pathway of secondary atomisation of EW droplets has been elucidated using a modified local weber number. On the contrary, for nanofuels, bubble rupture is the mechanism behind the surface crater formation. Proper orthogonal decomposition (POD) technique is utilised for investigating the droplet shape and flame heat release coupling. EW droplet shape and HR are found to be a synced system with a phase lag arising from the flame response timescale. However, a weak coupling is detected for nanofuel droplets
The Structural and Functional Diversity of Intrinsically Disordered Regions in Transmembrane Proteins
No full textThe intrinsically disordered proteins and protein regions (IDPs/IDPRs) do not have unique structures, but are known to be functionally important and their conformational flexibility and structural plasticity have engendered a paradigmatic shift in the classical sequence-structure-function maxim. Fundamental understanding in this field has significantly evolved since the discovery of this class of proteins about 25 years ago. Though the IDPRs of transmembrane proteins (TMP-IDPRs) comply with the broad definition of typical IDPs and IDPRs found in water-soluble globular proteins, much less is explored and known about them. In this review, we assimilate the key emerging biophysical principles from the limited studies on TMP-IDPRs and provide several context-specific biological examples to highlight the ubiquitous nature of TMP-IDPRs and their functional importance in cellular functions. Besides providing a spectrum of insights from sequence to structural disorder and functions, we also review the challenges and methodological advances in studying the structure-function relationship of TMP-IDPRs. We also lay stress upon the importance of an integrative framework, where ensemble-averaged (and mostly low-resolution) data from multiple experiments can be faithfully integrated with modelling techniques such as advanced sampling, coarse-graining, and free energy minimization methods for a high-fidelity characterization of TMP-IDPRs. We close the review by providing futuristic perspective with suggestions on how we could use the ideas and methods from the exciting field of protein engineering in conjunction with integrative modelling framework to advance the IDPR field and harness the sequence-disorder-function paradigm towards functional design of proteins