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Due to the periodicity and rhythmicity of sedimentation, short-term cycles are commonly developed in sedimentary strata. Under the assumption of a long seismic wavelength, such strata can be regarded as a seismic single thin bed with vertical transversely isotropic (VTI) characteristics. A thin interbed can be formed by the stacking of a series of isotropic and VTI single thin beds. In seismic inversion, the interference of multiples and mode-converted waves generated within and between thin beds and transmission losses are ignored. These interferences are hardly addressed in seismic data processing due to being submerged in first arrivals. In this work, to thin interbeds of isotropic and VTI single thin beds, we propose second-order approximations of Kennett reflection coefficients for PP-, SP-, PS-, and SS-waves, which consider the internal and interlayer wave propagation effects. The numerical analyses show that the proposed approximations are of high accuracy when the P-wave impedance difference in the VTI single thin bed is from − 40 to 100% and of strong anisotropy. The proposed approximations can be used for the efficient and accurate simulation of the wavefields of media with thin interbedding, bringing great potential for the studies of the inversion methods for the internal property parameters of thin interbeds. [ABSTRACT FROM AUTHOR]

This study attempted a rock physics template (RPT) based approach to model the impact of mechanical compaction and chemical diagenesis on overall porosity reduction of the Barail Sandstone across the Assam Shelf and Schuppen Belt area. Then, a sensitivity analysis was carried out based on the probabilistic amplitude variation with angle (AVA) approach to study the impact of diagenesis, rock frame constituents, and pore fluids on seismic amplitude response. The RPT depth trend suggests a significant upliftment (~ 2500 m) within the supra-thrust region, while the Assam Shelf and sub-thrust part of the Schuppen Belt were normally compacted throughout the geologic time. The geologically constrained RPT was used to (i) identify the primary process for chemical diagenesis as feldspar dissolution and (ii) estimate total cement, non-contact cement (NCC), and contact cement (CC) values. Laboratory-based analysis of rock samples validated the modeled cement volumes. The RPT-based CC (mode value) estimates were observed as 3%, 5%, and 7%, whereas the NCC varied as 6%, 8.5%, and 11% sequentially from extensional through supra-thrust to sub-thrust regions. The extensional and supra-thrust regions dominantly exhibited class IV AVA for oil and gas saturated rocks mainly due to the presence of coal and the relatively under compacted nature of the Barail Sandstones. A change in AVA class was observed to class II and IIP within the sub-thrust region due to enhanced cementation. The forward modeling revealed that a small amount (2%) of coal presence could potentially change the AVA class from II to IV, and an increase in CC from 5 to 7% could cause the AVA class to change from IV to II. This study efficiently modeled the digenetic effects and seismic amplitude in this tectonically complex region. [ABSTRACT FROM AUTHOR]

Recently, with the faster pace of development on the sophisticated detection and stealth technology, extensive attention is being paid to the reduction of Radar Cross Section (RCS) as it emerges in security and commercial applications. The Vivaldi antennas are one of the best choices for wide impedance bandwidth, planar configuration, and low profile as well. However, RCS reduction affects the antenna gain due to the complexity of radiation property. This paper intends to design an optimized vivaldi antenna to enhance gain performance. More particularly, the antenna is designed with the fine-tuning of antenna parameters like taper length l t , aperture width w ap , opening rate, slot line width w s , cavity diameter d , cavity to taper spacing s , ground plane length l and ground plane width w , respectively. More particularly, optimization algorithms play a vital role in fine-tuning of the parameter, and hence this paper intends to propose a new Improved Grey Wolf Optimization Algorithm with Fitness based Update evaluation (IGWO-FU), which is the enhanced version of traditional GWO. Finally, the performance of the proposed IGWO-FU model is compared over other traditional algorithms with respect to gain, VSWR, directivity, charge and current distribution, return loss as well. [ABSTRACT FROM AUTHOR]

Anthrax has been a major cause of death in grazing animals and an occasional cause of death in humans for thousands of years. Since the late 1800s there has been an exceptional international history of anthrax vaccine development. Due to animal vaccinations, the rate of infection has dropped dramatically. Anthrax vaccines have progressed from uncharacterized whole-cell vaccines in 1881, to pXO2-negative spores in the 1930s, to culture filtrates absorbed to aluminum hydroxide in 1970, and likely to recombinant protective antigen in the near future. Each of these refinements has increased safety without significant loss of efficacy. The threat of genetically engineered, antibiotic and vaccine resistant strains of Bacillus anthracis is fueling hypothesis-driven research and global techniques – including genomics, proteomics and transposon site hybridization – to facilitate the discovery of novel vaccine targets. This review highlights historical achievements and new developments in anthrax vaccine research. [ABSTRACT FROM AUTHOR]

Arteriovenous anastomosis (AVA) in nasal respiratory mucosa of humans and guinea pigs were studied with scanning electron microscopy (SEM) after removal of extracellular connective tissues by tryptic digestion and HCl hydrolysis. The shape of AVA in humans is different from that in guinea pigs. In guinea pigs, it is simple with no specific structure observed on the vessels. In humans, it is characterized by a spherical swelling at the intermediate segment. The Tunica media of the spherical body is formed by the aggregation of spindle-shaped cells and receives a rich nerve supply. These findings suggest powerful contractility of human AVA compared with guinea pigs. Arteriovenous anastomosis in human nasal respiratory mucosa may strongly influence arterial blood flow into the cavernosus sinusoid and determine the characteristic microcirculatory pattern in human nasal mucosa. [ABSTRACT FROM AUTHOR]