Utility of Lamb Waves for Near Surface Crack Detection

Ultrasonic waves have a long history in detection of surface breaking cracks. Attempts are being made to use guided waves as a defect detection tool in aging skin structures in aircrafts and in the power generation industries as these waves offer a great advantage over conventional bulks waves. Guided waves can be excited at one position and allowed to propagate considerable distances before attenuating. Depending on the configuration employed for defect detection, reflected or received waveforms give information regarding the integrity of the structure along the line of sight. This description makes the technique look rather simple. Particularly, NDT utilizing Lamb waves is more complex due to the existence of two or more modes at any given frequency. Success was reported by several authors on defect detection using Lamb waves. Brief or no explanation was given on the reasons behind the choice of specific excitation frequencies and incident angles. The emphasis was solely on the defect detection aspects

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ∼90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 10$^8$, a sub-threshold slope of 0.55 V dec$^{-1}$, and a field effect mobility of 15 cm$^2$ V$^{-1}$ s$^{-1}$, which is a sharp increase from 0.8 cm$^2$ V$^{-1}$ s$^{-1}$ obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm$^2$ V$^{-1}$ s$^{-1}$, but the sub-threshold slope is slightly deteriorated to 0.65 V dec$^{-1}$. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn$_2$SnO$_4$ and ZnSnO$_3$ phases.Engineering and Physical Sciences Research Council (Grant ID: EP/M013650/1

Transient intraluminal diverticulum of the esophagus: A significant flow artifact

Esophagography in 12 patients showed a characteristic oval-to oblong-shaped barium collection surrounded by a thin radiolucent margin. The collection closely resembled an intraluminal diverticulum. Twelve patients demonstrated these findings, 6 on single-contrast and 6 on double-contrast examinations. These findings were not reproducible on repeat barium swallows, and endoscopy failed to demonstrate an intraluminal diverticulum. Nine of the patients underwent esophagectomy and esophageal substitution. Pathologic examination of the gross specimen did not reveal evidence of intraluminal diverticula. The association of this radiologic appearance in patients with moderately severe motility disorder of the esophagus is emphasized.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48158/1/261_2005_Article_BF01887813.pd

Controlling Curie temperature in (Ga,Ms)As through location of the Fermi level within the impurity band

The ferromagnetic semiconductor (Ga,Mn)As has emerged as the most studied material for prototype applications in semiconductor spintronics. Because ferromagnetism in (Ga,Mn)As is hole-mediated, the nature of the hole states has direct and crucial bearing on its Curie temperature TC. It is vigorously debated, however, whether holes in (Ga,Mn)As reside in the valence band or in an impurity band. In this paper we combine results of channeling experiments, which measure the concentrations both of Mn ions and of holes relevant to the ferromagnetic order, with magnetization, transport, and magneto-optical data to address this issue. Taken together, these measurements provide strong evidence that it is the location of the Fermi level within the impurity band that determines TC through determining the degree of hole localization. This finding differs drastically from the often accepted view that TC is controlled by valence band holes, thus opening new avenues for achieving higher values of TC.Comment: 5 figures, supplementary material include

The Role of Parvalbumin-positive Interneurons in Auditory Steady-State Response Deficits in Schizophrenia

© The Author(s) 2019. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.Despite an increasing body of evidence demonstrating subcellular alterations in parvalbumin-positive (PV+) interneurons in schizophrenia, their functional consequences remain elusive. Since PV+ interneurons are involved in the generation of fast cortical rhythms, these changes have been hypothesized to contribute to well-established alterations of beta and gamma range oscillations in patients suffering from schizophrenia. However, the precise role of these alterations and the role of different subtypes of PV+ interneurons is still unclear. Here we used a computational model of auditory steady-state response (ASSR) deficits in schizophrenia. We investigated the differential effects of decelerated synaptic dynamics, caused by subcellular alterations at two subtypes of PV+ interneurons: basket cells and chandelier cells. Our simulations suggest that subcellular alterations at basket cell synapses rather than chandelier cell synapses are the main contributor to these deficits. Particularly, basket cells might serve as target for innovative therapeutic interventions aiming at reversing the oscillatory deficits.Peer reviewe

Zinc tin oxide thin film transistors produced by a high rate reactive sputtering: Effect of tin composition and annealing temperatures

Amorphous zinc tin oxides (a-ZTO), which are stoichiometrically close to the Zn$_2$SnO$_4$ and ZnSnO$_3$ phases, have been deposited using remote-plasma reactive sputtering, and incorporated as the channel layers in thin film transistors (TFTs). The influence of tin composition and annealing temperatures on the structural and phase evolutions of the thin films, and the electrical performances of the TFTs are investigated. Zn$_2$SnO$_4$ exhibited randomly oriented polycrystalline peaks at annealing temperatures ≥700 °C, while ZnSnO$_3$ decomposed into Zn$_2$SnO$_4$ and SnO$_2$ at 950 °C. TFTs employing a Zn$_2$SnO$_4$ channel, after a post-deposition annealing at 500 °C, exhibited a field effect mobility ~14 cm$^2$ V$^{−1}$ s$^{−1}$ and a sub-threshold slope ~0.6 V dec$^{−1}$. When the tin content was increased in the channel, as in ZnSnO$_3$, TFTs exhibited an increase in field effect mobility ~20 cm$^2$ V$^{−1}$ s$^{−1}$, but with a slight deterioration of sub-threshold slope to ~0.8 V dec$^{−1}$. When the post-deposition annealing temperature was reduced to 300 °C, a mobility as high as ~10 cm$^2$ V$^{−1}$ s$^{−1}$ was still achieved, however, a significant shoulder in the IDS–VGS curve, together with a higher off-state current was observed. TFT characteristics are explained by the sub-bandgap defect states measured by photothermal deflection spectroscopy and the extracted Urbach energies.The support of this work by the Engineering and Physical Sciences Research Council (EPSRC) through project EP/M013650/1 is acknowledged. A.S. and R.H.F. would like to acknowledge funding and active support from EPSRC and India-UK APEX project. K.M.N. thanks Dr. S. Thornley of PlasmaQuest for providing the metallic tin target

Spread of Mutant Middle East Respiratory Syndrome Coronavirus with Reduced Affinity to Human CD26 during the South Korean Outbreak

The newly emerging Middle East respiratory syndrome coronavirus (MERS-CoV) causes a severe respiratory infection with a high mortality rate (similar to 35%). MERS-CoV has been a global threat due to continuous outbreaks in the Arabian peninsula and international spread by infected travelers since 2012. From May to July 2015, a large outbreak initiated by an infected traveler from the Arabian peninsula swept South Korea and resulted in 186 confirmed cases with 38 deaths (case fatality rate, 20.4%). Here, we show the rapid emergence and spread of a mutant MERS-CoV with reduced affinity to the human CD26 receptor during the South Korean outbreak. We isolated 13 new viral genomes from 14 infected patients treated at a hospital and found that 12 of these genomes possess a point mutation in the receptor-binding domain (RBD) of viral spike (S) protein. Specifically, 11 of these genomes have an I529T mutation in RBD, and 1 has a D510G mutation. Strikingly, both mutations result in reduced affinity of RBD to human CD26 compared to wild-type RBD, as measured by surface plasmon resonance analysis and cellular binding assay. Additionally, pseudotyped virus bearing an I529T mutation in S protein showed reduced entry into host cells compared to virus with wild-type S protein. These unexpected findings suggest that MERS-CoV adaptation during human-to-human spread may be driven by host immunological pressure such as neutralizing antibodies, resulting in reduced affinity to host receptor, and thereby impairs viral fitness and virulence, rather than positive selection for a better affinity to CD26. IMPORTANCE Recently, a large outbreak initiated by an MERS-CoV-infected traveler from the Middle East swept South Korea and resulted in 186 confirmed cases with 38 deaths. This is the largest outbreak outside the Middle East, and it raised strong concerns about the possible emergence of MERS-CoV mutations. Here, we isolated 13 new viral genomes and found that 12 of them possess a point mutation in the receptor-binding domain of viral spike protein, resulting in reduced affinity to the human cognate receptor, CD26, compared to the wild-type virus. These unexpected findings suggest that MERS-CoV adaptation in humans may be driven by host immunological pressure.111819Ysciescopu

Preferences and skills of Indian public sector teachers

With a sample of 700 future public sector primary teachers in India, a Discrete Choice Experiment is used to measure job preferences, particularly regarding location. General skills are also tested. Urban origin teachers and women are more averse to remote locations than rural origin teachers and men respectively. Women would require a 26-73 percent increase in salary for moving to a remote location. The results suggest that existing caste and gender quotas can be detrimental for hiring skilled teachers willing to work in remote locations. The most preferred location is home, which supports decentralised hiring, although this could compromise skills