Coexistence of surface oxygen vacancy and interface conducting states in LaAlO3/SrTiO3 revealed by low-angle resonant soft X-ray scattering

Oxide heterostructures have shown rich physics phenomena, particularly in the conjunction of exotic insulator-metal transition (IMT) at the interface between polar insulator LaAlO3 and non-polar insulator SrTiO3 (LaAlO3/SrTiO3). Polarization catastrophe model has suggested an electronic reconstruction yielding to metallicity at both the interface and surface. Another scenario is the occurrence of surface oxygen vacancy at LaAlO3 (surface-Ov), which has predicted surface-to-interface charge transfer yielding metallic interface but insulating surface. To clarify the origin of IMT, one should probe surface-Ov and the associated electronic structures at both the surface and the buried interface simultaneously. Here, using low-angle resonant soft X-ray scattering (LA-RSXS) supported with first-principles calculations, we reveal the co-existence of the surface-Ov state and the interface conducting state only in conducting LaAlO3/SrTiO3 (001) films. Interestingly, both the surface-Ov state and the interface conducting state are absent for the insulating film. As a function of Ov density, while the surface-Ov state is responsible for the IMT, the spatial charge distribution is found responsible for a transition from two-dimensional-like to three-dimensional-like conducting accompanied by spectral weight transfer, revealing the importance of electronic correlation. Our results show the importance of surface-Ov in determining interface properties and provides a new strategy in utilizing LA-RSXS to directly probe the surface and buried interface electronic properties in complex oxide heterostructures

High performance building design strategy to achieve resilience towards climate change

10th International Conference on Healthy Buildings 20122919-92

Giant dielectric macroporous graphene oxide foams with aqueous salt solutions: Impedance spectroscopy

Ultralight and ultrathin dielectric materials with high dielectric permittivity and power densities are required to meet the ever-increasing demands of microelectronic and energy storage devices. In the present study, we demonstrate the feasibility of achieving giant dielectric performance of light weight, highly porous three-dimensional architectures of insulating graphene oxide (GO) foams by saturating the pores with liquid containing mobile ions. Dielectric behavior of GO foam is investigated over a range of frequencies (1 kHz-10 kHz) by employing electrochemical impedance spectroscopy. The relative permittivity of pristine GO foam is shown to improve by five orders upon saturating the pores with different concentrations of aqueous NaCl solutions. Dielectric constants of foams saturated with aqueous NaCl solutions are measured to be of the order of 10(6) at high frequencies (1 kHze10 kHz) and are observed to enhance to 10(8) at lower frequencies down to 0.01 Hz. Various contributions to the measured capacitance are deciphered by modelling the impedance data to an equivalent circuit in order to evaluate the exact contribution from dipole orientation. The plausible reasons for the enhanced dielectric behavior are emphasized. (C) 2019 Elsevier Ltd. All rights reserved

Finite Element Method-Based Spherical Indentation Analysis of Jute/Sisal/Banana-Polypropylene Fiber-Reinforced Composites

Material hardness of natural fiber composites depends upon the orientation of fibers, ratio of fiber to matrix, and their mechanical and physical properties. Experimentally finding the material hardness of composites is an involved task. The present work attempts to explore the deformation mechanism of natural fiber composites subjected to post-yield indentation by a spherical indenter through a two-dimensional finite element analysis. In the present work, jute-polypropylene, sisal-polypropylene, and banana-polypropylene composites are considered. The analysis is attempted by varying the properties of Young’s modulus of fiber and matrix, diameter of fiber, and horizontal and vertical center distance between the fibers. The analyses results showed that as the distance between the fiber’s center increases, the bearing load capacity of all composite increases nonlinearly. The jute fiber composite shows predominate load-carrying capacity compared to other composites at all L/D ratios and interference ratios. The influence of subsurface stress in lateral direction is minimal and gets reduced as the distance between the fiber centers increases. The variation in diameter of fiber influences significantly, i.e., beyond the L/D ratio of 1.0; for the same contact load ratio, the bearing area support is double for jute-polypropylene composite compared to sisal-polypropylene composite. Compared to the sisal-polypropylene composite, for the same interference ratio, the load-carrying capacity is two times high for banana-polypropylene composite, whereas four times high for jute-polypropylene composite, but this effect decreases as the L/D ratio decreases. In all the composites, the subsurface stress gets distributed as the L/D ratio increases. The ratio of fibers center distance to diameter of fiber influences marginally on the contact load and contact area and significantly on the contact stress for all the fiber-reinforced composites

Poly propyl ether imine (PETIM) dendrimer: A novel non-toxic dendrimer for sustained drug delivery

In the present study, an attempt was made to study the acute and sub-acute toxicity profile of G3-COOH Poly (propyl ether imine) PETIM] dendrimer and its use as a carrier for sustained delivery of model drug ketoprofen. Drug-dendrimer complex was prepared and characterized by FTIR, solubility and in vitro drug release study. PETIM dendrimer was found to have significantly less toxicity in A541 cells compared to Poly amido amine (PAMAM) dendrimer. Further, acute and 28 days sub-acute toxicity measurement in mice showed no mortality, hematological, biochemical or histopathological changes up to 80 mg/kg dose of PETIM dendrimer. The results of study demonstrated that G3-COOH PETIM dendrimer can be used as a safe and efficient vehicle for sustained drug delivery. (C) 2010 Elsevier Masson SAS. All rights reserved

Preperitoneal packing for pelvic fracture-associated hemorrhage: A systematic review, meta-analysis, and practice management guideline from the Eastern Association for the Surgery of Trauma

•Availability of institutional resources dictate initial usage of PPP versus AE.•PPP should be used over resuscitation alone while waiting for pelvic angiography.•No recommendations for or against initial use of PPP versus initial pelvic external fixation can be made.•Post-PPP hemodynamic instability is an indication for post-PPP pelvic angiography