Assessment of geodetic velocities using GPS campaign measurements over long baseline lengths

GPS campaign measurements are frequently used in order to determine geophysical phenomena such as tectonic motion, fault zones, landslides, and volcanoes. When observation duration is shorter, the accuracy of coordinates are degraded and the accuracy of point velocities are affected. The accuracies of the geodetic site velocities from a global network of International GNSS Service (IGS) stations were previously investigated using only PPP. In this study, we extend which site velocities will also be assessed, including fundamental relative positioning. PPP-derived results will also be evaluated to see the effect of reprocessed JPL products, single-receiver ambiguity resolution, repeating survey campaigns minimum 3 days at the site, and eliminating noisier solutions prior to the year 2000. To create synthetic GPS campaigns, 18 globally distributed, continuously operating IGS stations were chosen. GPS data were processed comparatively using GAMIT/GLOBK v10.6 and GIPSY-OASIS II v6.3. The data of synthetic campaign GPS time series were processed using a regression model accounting for the linear and seasonal variation of the ground motion. Once the velocities derived from 24&thinsp;h sessions were accepted as the truth, the results from sub-sessions were compared with the results of 24&thinsp;h and hypothesis testing was applied for the significance of the differences. The major outcome of this study is that on global scales (i.e. over long distances) with short observation sessions, the fundamental relative positioning produces results similar to PPP. The reliability of the velocity estimation for GPS horizontal baseline components has now been improved to about 85&thinsp;% of the average for observation durations of 12&thinsp;h.</p

Observation of multifractality in Anderson localization of ultrasound

We report the first experimental observation of strong multifractality in wave functions at the Anderson localization transition in open three-dimensional elastic networks. Our results confirm the recently predicted symmetry of the multifractal exponents. We have discovered that the result of multifractal analysis of the real data depends on the excitation scheme used in the experiment.Comment: 4 pages, 3 figure

Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology.

Abstract-This paper introduces a new method for fabricating capacitive micromachined ultrasonic transducers (CMUTs) that uses a wafer bonding technique. The transducer membrane and cavity are defined on an SOI (silicon-on-insulator) wafer and on a prime wafer, respectively. Then, using silicon direct bonding in a vacuum environment, the two wafers are bonded together to form a transducer. This new technique, capable of fabricating large CMUTs, offers advantages over the traditionally micromachined CMUTs. First, forming a vacuum-sealed cavity is relatively easy since the wafer bonding is performed in a vacuum chamber. Second, this process enables better control over the gap height, making it possible to fabricate very small gaps (less than 0.1 m). Third, since the membrane is made of single crystal silicon, it is possible to predict and control the mechanical properties of the membrane to within 5%. Finally, the number of process steps involved in making a CMUT has been reduced from 22 to 15, shortening the device turn-around time. All of these advantages provide repeatable fabrication of CMUTs featuring predictable center frequency, bandwidth, and collapse voltage. Using this new technique, we have fabricated CMUTs that have membrane sizes between 12 m and 750 m, and thicknesses between 0.34 m and 4.5 m. This paper presents the fabrication process and some experimental results obtained from the wafer-bonded devices. [929] Index Terms-Capacitive micromachined ultrasonic transducers (CMUT), silicon-on-insulator (SOI) wafer, ultrasonic transducer, wafer bonding

Sestrin2 Modulates AMPK Subunit Expression and Its Response to Ionizing Radiation in Breast Cancer Cells

Background: The sestrin family of stress-responsive genes (SESN1-3) are suggested to be involved in regulation of metabolism and aging through modulation of the AMPK-mTOR pathway. AMP-activated protein kinase (AMPK) is an effector of the tumour suppressor LKB1, which regulates energy homeostasis, cell polarity, and the cell cycle. SESN1/2 can interact directly with AMPK in response to stress to maintain genomic integrity and suppress tumorigenesis. Ionizing radiation (IR), a widely used cancer therapy, is known to increase sestrin expression, and acutely activate AMPK. However, the regulation of AMPK expression by sestrins in response to IR has not been studied in depth. Methods and Findings: Through immunoprecipitation we observed that SESN2 directly interacted with the AMPKa1b1c1 trimer and its upstream regulator LKB1 in MCF7 breast cancer cells. SESN2 overexpression was achieved using a Flag-tagged SESN2 expression vector or a stably-integrated tetracycline-inducible system, which also increased AMPKa1 and AMPKb1 subunit phosphorylation, and co-localized with phosphorylated AMPKa-Thr127 in the cytoplasm. Furthermore, enhanced SESN2 expression increased protein levels of LKB1 and AMPKa1b1c1, as well as mRNA levels of LKB1, AMPKa1, and AMPKb1. Treatment of MCF7 cells with IR elevated AMPK expression and activity, but this effect was attenuated in the presence of SESN2 siRNA. In addition, elevated SESN2 inhibited IR-induced mTOR signalling and sensitized MCF7 cells to IR through an AMPK-dependent mechanism

Point defect segregation and its role in the detrimental nature of Frank partials in Cu(In,Ga)Se2 thin-film absorbers

The interaction of point defects with extrinsic Frank loops in the photovoltaic absorber material Cu(In,Ga)Se₂ was studied by aberration-corrected scanning transmission electron microscopy in combination with electron energy-loss spectroscopy and calculations based on density-functional theory. We find that Cu accumulation occurs outside of the dislocation cores bounding the stacking fault due to strain-induced preferential formation of Cu‾²In, which can be considered a harmful hole trap in Cu(In,Ga)Se₂. In the core region of the cation-containing α-core, Cu is found in excess. The calculations reveal that this is because Cu on In-sites is lowering the energy of this dislocation core. Within the Se-containing β-core, in contrast, only a small excess of Cu is observed, which is explained by the fact that Cu¡ⁿ and Cu¡ are the preferred defects inside this core, but their formation energies are positive. The decoration of both cores induces deep defect states, which enhance nonradiative recombination. Thus, the annihilation of Frank loops during the Cu(In,Ga)Se₂ growth is essential in order to obtain absorbers with high conversion efficiencies

Optoelectronic Inactivity of Dislocations in Cu In,Ga Se2 Thin Films

High efficiency Cu In,Ga Se2 CIGS thin film solar cells are based on poly crystalline CIGS absorber layers, which contain grain boundaries, stacking faults, and dislocations. While planar defects in CIGS layers have been investigated extensively, little is still known about the impact of dislocations on optoelectronic properties of CIGS absorbers. Herein, evidence for an optoelectronic inactivity of dislocations in these thin films is given, in contrast to the situation at grain boundaries. This unique behavior is explained by the extensive elemental redis tribution detected around dislocation cores, which is connected with the dislocation strain field, probably leading to a shift of defect states toward the band edge

Effects of retinoic acid on compensatory lung growth

<p>Abstract</p> <p>Background</p> <p>We investigated the effect of Retinoic acid in the growth of contralateral lung after pneumonectomy.</p> <p>Methods</p> <p>Twentyone adult male Wistar albino rats from the same colony were used. They were divided into three groups (Group A, B and C). Group A undergone only left posterolateral thoracotomy. In Group B and C, the rats were subjected to left posterolateral thoracotomy and left pneumonectomy. In Group C, rats were given intraperitoneal Retinoic acid during the operation and continued to be given everyday postoperatively. Rats were sacrificed on the 10^thday and their total body, right lung weights and right lung volumes were measured.</p> <p>Results</p> <p>The volume and weight indices of the lung were found to be higher in Group C. In histopathological examination, there was a reduction in the mean number of alveoli in Group B and C. A significant rise in the mean dimension and average wall thickness of the alveolar structure were determined in Group C.</p> <p>Conclusion</p> <p>Retinoic acid contributes to the compensatory growth of the residual lung tissue.</p

Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina

Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting

Elemental redistributions at structural defects in Cu(In,Ga)Se₂ thin films for solar cells

The microstructural evolution of Cu(In,Ga)Se2 absorber layers during a three-stage-type co-evaporation process was studied to elucidate the effect of a Cu-rich stage on the formation of extended structural defects. Defect densities for two Cu-poor samples, one interrupted before and one after this crucial Cu-rich composition stage, were investigated by scanning transmission electron microscopy (STEM) imaging. The structure and chemical nature of individual defects were investigated by aberration-corrected high-resolution STEM in combination with electron energy-loss spectroscopy on the atomic-scale. In spite of the different defect densities between the two samples, most of the individual defects exhibited similar chemistry. In particular, the elemental distributions of atomic columns at {112} twin planes, which are very frequent in Cu(In,Ga)Se2 thin films, were found to be the same as in the defect-free grain interiors. In contrast, within grain boundaries, dislocation cores, and other structurally more complex defects, elemental redistributions of Cu and In were observed