Numerical modeling of elastic-wave scattering by near-surface heterogeneities

In land seismic data, scattering from surface and near-surface heterogeneities adds complexity to the recorded signal and masks weak primary reflections. To understand the effects of near-surface heterogeneities on seismic reflections, we simulated seismic-wave scattering from arbitrary-shaped, shallow, subsurface heterogeneities through the use of a perturbation method for elastic waves and finite-difference forward modeling. The near-surface scattered wavefield was modeled by looking at the difference between the calculated incident (i.e., in the absence of scatterers) and the total wavefields. Wave propagation was simulated for several earth models with different near-surface characteristics to isolate and quantify the influence of scattering on the quality of the seismic signal. The results indicated that the direct surface waves and the upgoing reflections were scattered by the near-surface heterogeneities. The scattering took place from body waves to surface waves and from surface waves to body waves. The scattered waves consisted mostly of body waves scattered to surface waves and were, generally, as large as, or larger than, the reflections. They often obscured weak primary reflections and could severely degrade the image quality. The results indicated that the scattered energy depended strongly on the properties of the shallow scatterers and increased with increasing impedance contrast, increasing size of the scatterers relative to the incident wavelength, decreasing depth of the scatterers, and increasing attenuation factor of the background medium. Also, sources deployed at depth generated weak surface waves, whereas deep receivers recorded weak surface and scattered body-to-surface waves. The analysis and quantified results helped in the understanding of the scattering mechanisms and, therefore, could lead to developing new acquisition and processing techniques to reduce the scattered surface wave and enhance the quality of the seismic image.Saudi AramcoMassachusetts Institute of Technology. Earth Resources Laborator

Suppression of Sproutys Has a Therapeutic Effect for a Mouse Model of Ischemia by Enhancing Angiogenesis

Sprouty proteins (Sproutys) inhibit receptor tyrosine kinase signaling and control various aspects of branching morphogenesis. In this study, we examined the physiological function of Sproutys in angiogenesis, using gene targeting and short-hairpin RNA (shRNA) knockdown strategies. Sprouty2 and Sprouty4 double knockout (KO) (DKO) mice were embryonic-lethal around E12.5 due to cardiovascular defects. The number of peripheral blood vessels, but not that of lymphatic vessels, was increased in Sprouty4 KO mice compared with wild-type (WT) mice. Sprouty4 KO mice were more resistant to hind limb ischemia and soft tissue ischemia than WT mice were, because Sprouty4 deficiency causes accelerated neovascularization. Moreover, suppression of Sprouty2 and Sprouty4 expression in vivo by shRNA targeting accelerated angiogenesis and has a therapeutic effect in a mouse model of hind limb ischemia. These data suggest that Sproutys are physiologically important negative regulators of angiogenesis in vivo and novel therapeutic targets for treating peripheral ischemic diseases

Hepatitis C Virus Infection Suppresses the Interferon Response in the Liver of the Human Hepatocyte Chimeric Mouse

BACKGROUND AND AIMS: Recent studies indicate that hepatitis C virus (HCV) can modulate the expression of various genes including those involved in interferon signaling, and up-regulation of interferon-stimulated genes by HCV was reported to be strongly associated with treatment outcome. To expand our understanding of the molecular mechanism underlying treatment resistance, we analyzed the direct effects of interferon and/or HCV infection under immunodeficient conditions using cDNA microarray analysis of human hepatocyte chimeric mice. METHODS: Human serum containing HCV genotype 1b was injected into human hepatocyte chimeric mice. IFN-α was administered 8 weeks after inoculation, and 6 hours later human hepatocytes in the mouse livers were collected for microarray analysis. RESULTS: HCV infection induced a more than 3-fold change in the expression of 181 genes, especially genes related to Organismal Injury and Abnormalities, such as fibrosis or injury of the liver (P = 5.90E-16∼3.66E-03). IFN administration induced more than 3-fold up-regulation in the expression of 152 genes. Marked induction was observed in the anti-fibrotic chemokines such as CXCL9, suggesting that IFN treatment might lead not only to HCV eradication but also prevention and repair of liver fibrosis. HCV infection appeared to suppress interferon signaling via significant reduction in interferon-induced gene expression in several genes of the IFN signaling pathway, including Mx1, STAT1, and several members of the CXCL and IFI families (P = 6.0E-12). Genes associated with Antimicrobial Response and Inflammatory Response were also significantly repressed (P = 5.22×10(-10)∼1.95×10(-2)). CONCLUSIONS: These results provide molecular insights into possible mechanisms used by HCV to evade innate immune responses, as well as novel therapeutic targets and a potential new indication for interferon therapy

Yoga jam: remixing Kirtan in the Art of Living

Yoga Jam are a group of musicians in the United Kingdom who are active members of the Art of Living, a transnational Hindu-derived meditation group. Yoga Jam organize events—also referred to as yoga raves and yoga remixes—that combine Hindu devotional songs (bhajans) and chants (mantras) with modern Western popular musical genres, such as soul, rock, and particularly electronic dance music. This hybrid music is often played in a clublike setting, and dancing is interspersed with yoga and meditation. Yoga jams are creative fusions of what at first sight seem to be two incompatible phenomena—modern electronic dance music culture and ancient yogic traditions. However, yoga jams make sense if the Durkheimian distinction between the sacred and the profane is challenged, and if tradition and modernity are not understood as existing in a sort of inverse relationship. This paper argues that yoga raves are authenticated through the somatic experience of the modern popular cultural phenomenon of clubbing combined with therapeutic yoga practices and validated by identifying this experience with a reimagined Vedic tradition

GaSbBi alloys and heterostructures: fabrication and properties

International audienceDilute bismuth (Bi) III-V alloys have recently attracted great attention, due to their properties of band-gap reduction and spin-orbit splitting. The incorporation of Bi into antimonide based III-V semiconductors is very attractive for the development of new optoelectronic devices working in the mid-infrared range (2-5 µm). However, due to its large size, Bi does not readily incorporate into III-V alloys and the epitaxy of III-V dilute bismides is thus very challenging. This book chapter presents the most recent developments in the epitaxy and characterization of GaSbBi alloys and heterostructures

Annual output estimation of concentrator photovoltaic systems using high-efficiency InGaP/InGaAs/Ge triple-junction solar cells based on experimental solar cell's characteristics and field-test meteorological data

The temperature dependences of the electrical characteristics of InGaP/InGaAs/Ge triple-junction solar cells under concentration were evaluated. For these solar cells, conversion efficiency (η) decreased with increasing temperature, and increased with increasing concentration ratio owing to an increase in open-circuit voltage. The decrease in ηwith increasing temperature decreases with increasing concentration ratio. Moreover, the annual output of a concentrator system with a high-efficiency triple-junction cell is estimated utilizing the experimental solar cell’s characteristics obtained in this study and field-test meteorological data collected for one year at the Nara Institute of Science and Technology, and compared with that of a nonconcentration flat-plate system

Evaluation of InGaP/InGaAs/Ge triple-junction solar cell and optimization of solar cell's structure focusing on series resistance for high-efficiency concentrator photovoltaic systems

The series resistance of an InGaP/InGaAs/Ge triple-junction solar cell was evaluated in detail. Series resistance components such as electrode resistance, tunnel junction resistance and lateral resistance between electrodes were estimated separately. The characteristics of the triple-junction solar cell under concentrated light were evaluated by equivalent circuit calculation with a simulation program with integrated circuit emphasis (SPICE). By equivalent circuit calculation, the optimization of cell designs was performed, focusing on series resistance and cell current in order to realize high-efficiency concentrator cells