Some properties of meromorphic alpha-convex functions and its applications

The aim of the present paper is to obtain sufficient condition for the class of meromorphic alpha convex functions of order ζ and then to study mapping properties of an integral operator. Many known results apear as special consequences ofour wor

Novel VPS13B Mutations in Three Large Pakistani Cohen Syndrome Families Suggests a Baloch Variant with Autistic-Like Features.

BackgroundCohen Syndrome (COH1) is a rare autosomal recessive disorder, principally identified by ocular, neural and muscular deficits. We identified three large consanguineous Pakistani families with intellectual disability and in some cases with autistic traits.MethodsClinical assessments were performed in order to allow comparison of clinical features with other VPS13B mutations. Homozygosity mapping followed by whole exome sequencing and Sanger sequencing strategies were used to identify disease-related mutations.ResultsWe identified two novel homozygous deletion mutations in VPS13B, firstly a 1 bp deletion, NM_017890.4:c.6879delT; p.Phe2293Leufs*24, and secondly a deletion of exons 37-40, which co-segregate with affected status. In addition to COH1-related traits, autistic features were reported in a number of family members, contrasting with the "friendly" demeanour often associated with COH1. The c.6879delT mutation is present in two families from different regions of the country, but both from the Baloch sub-ethnic group, and with a shared haplotype, indicating a founder effect among the Baloch population.ConclusionWe suspect that the c.6879delT mutation may be a common cause of COH1 and similar phenotypes among the Baloch population. Additionally, most of the individuals with the c.6879delT mutation in these two families also present with autistic like traits, and suggests that this variant may lead to a distinct autistic-like COH1 subgroup

Dielectric reliability and spin dependent transport in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions

Khan AA. Dielectric reliability and spin dependent transport in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions. Bielefeld (Germany): Bielefeld University; 2011.The experiments described in this thesis relate to the recently emerging and rapidly growing field of spin electronics or spintronics. This area of study allies electronics and magnetism. It uses the spin of the electron to obtain new proporties or functions. These developments concern a new type of non-volatile memories. In contrast, conventional electronics is based on the use of an electric field to act on the charge of electrons. The electronic spin gives rise to the magnetism of solids, but also provides a means to influence the electrons by a magnetic field. Thus, in ferromagnetic (FM) materials, the motion of an electron depends on its spin orientation with respect to local magnetization. This gives rise to interesting new effects to the field of spintronics. Spintronic effects occur on a length scale in which spin is conserved, called the spin diffusion length, which is of the order of a few nanometers. Another milestone in the spintronic was the observation of the tunnel magnetoresistance effect in magnetic tunnel junctions which have a thin layer of an insulating material sandwich between two FM materials. The dielectric reliability of the insulating layer is a major reliability concern in spintronic devices. Currently, the understanding of materials, physics, and reliability at the ano, or atomic, level is vital to the proper design and manufacturing of these devices

Analysis of dielectric breakdown in CoFeB/MgO/CoFeB magnetic tunnel junction

Khan AA. Analysis of dielectric breakdown in CoFeB/MgO/CoFeB magnetic tunnel junction. Microelectronics Reliability. 2015;55(6):894-902.The time-dependent dielectric breakdown has been investigated in a series of nominally identical Co-Fe-B/MgO/Co-Fe-B junctions by voltage ramp experiments. The results divulge that the breakdown voltage strongly depends on the polarity of the applied voltage, junction area, ramp speed and the annealing temperature. Magnetic tunnel junctions (MTJs) with positive bias on the top electrode show higher breakdown voltage than MTJs with negative bias. We found that there is a significant decrease in the breakdown voltage when the annealing temperature is increased above 350 degrees C. The experimental data can be described by different specific forms of breakdown probability functions which lead to different extrapolation of life time of junctions. (C) 2015 Elsevier Ltd. All rights reserved

1-6Improved Optical Properties of Tin Antimony Sulphide Thin Films for Photovoltaics

Abstract Tin antimony sulphide thin films have been synthesized as an absorber layer for solar cells. These films are deposited by vacuum thermal evaporation on glass substrate at a pressure of 10 -5 torr. The films are then annealed at different temperatures in argon atmosphere. XRD analysis reveals that both as deposited and annealed films are found to be in polycrystalline phase. The crystallinity of the films is significantly enhanced with increasing annealing temperatures. The quantum efficiency is higher in the visible and near infrared region for the annealed films whereas the quantum efficiency of as deposited film is comparatively lower. The transmittance of the annealed films is found to be decreasing with increasing temperatures. The thickness and band gap of the films are measured by ellipsometric data. The absorption coefficient of the films is significantly higher (~10 5 cm -1 ), which is very important factor regarding solar conversion efficiency. Hot point probe measurements show that the films possess ntype electrical conductivity

Dielectric breakdown and inelastic electron tunneling spectroscopy of top and bottom pinned Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions

Khan AA, Schmalhorst J-M, Thomas A, Drewello V, Reiss G. Dielectric breakdown and inelastic electron tunneling spectroscopy of top and bottom pinned Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions. Journal of Applied Physics. 2009;105(8):083723.The time dependent dielectric breakdown in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions was investigated by voltage ramp experiments. The measurements were done for two types of junctions: one set of junctions had exchange biased (pinned) bottom electrodes and one set had exchange biased (pinned) top electrodes with an additional artificial ferrimagnet. We found a significant polarity dependence in the dielectric breakdown: top as well as bottom pinned tunnel junctions showed higher breakdown voltage when the top electrode was biased positively compared to negative bias. In contrast to this the differential resistance (dV/dI)-V spectra revealed an asymmetry for the top pinned junctions which was reversed in comparison to the bottom pinned system. This indicates that both asymmetries have different origins. Additionally the bottom pinned junctions showed in general slightly lower breakdown voltages and stronger magnon excitation in the inelastic electron tunneling (d(2)I/dV(2))-V spectra than the top pinned junctions. Possible reasons for these correlations are discussed

Dielectric breakdown in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junction

Khan AA, Schmalhorst J-M, Thomas A, Schebaum O, Reiss G. Dielectric breakdown in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junction. JOURNAL OF APPLIED PHYSICS. 2008;103(12): 123705.The time-dependent dielectric breakdown has been investigated in Co-Fe-B/MgO/Co-Fe-B junctions by voltage ramp experiments and focused on its dependence on the barrier thickness, junction area, polarity of the applied voltage, ramp speed, and annealing temperature. The results suggest that the breakdown voltage strongly depends both on the polarity of the applied voltage and the annealing temperature. Magnetic tunnel junctions (MTJs) with positive bias on the top electrode show higher breakdown voltage than MTJs with negative bias. We found that there is a significant decrease in the breakdown voltage when the annealing temperature is increased above 350 degrees C. (C) 2008 American Institute of Physics

Damages to Himalayan White Pine (Pinus wallichiana) by Asiatic Black Bear (Ursus thibetanus) in Kaghan Valley, Pakistan

Tree damage is one of the destructive behaviors of the Asiatic black bear (Ursus thibetanus G. (Baron) Cuvier, 1823), and this type of damage causes great economic loss to the forest. A survey about Himalayan white pine (Pinus wallichiana (A. B) Jacks, 1836) damages was conducted at Kaghan Valley, District Mansehra, Khyber Pakhtunkhwa, Pakistan. Field surveys were carried out within five major sites of Kaghan Valley, including Manshi reserve forest, Kamal Bann reserve forest, Malkandi reserve forest, Noori Bichla reserve forest, and some Guzara forests. Line transects and diameter at breast height (DBH) methods were selected for data collection. Eighteen transects were placed in different sites of the valley. A total of (n = 201) affected trees were observed from eighteen transects, along with a total population of 1081 trees with the encounter rate (ER: 0.657) and the mean DBH is x¯ = 71.97 cm. Among total damages, the most severe (n = 39: 19.4%) were fully damaged with a greater encounter rate. Bark stripping was made during the late winter season and used as foodstuff when natural food is limited in the area. In severe cases, the bear-stripped bark encircles from the entire tree trunk, which results in the drying of trees and, finally, falls. Among all five sites, Manshi reserve forest was greatly affected, where the highest number (n = 76) of tree damage, and (n = 21) the entire diameter of trunks were damaged. People of the study area claimed that the black bear causes great forest damage, as well as crop destruction that leads to high economic loss

Elastic and inelastic conductance in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions

Khan AA, Schmalhorst J-M, Reiss G, et al. Elastic and inelastic conductance in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions. PHYSICAL REVIEW B. 2010;82(6): 064416.A systematic analysis of the bias voltage and temperature dependence of the tunneling magnetoresistance (TMR) in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions with barrier thickness t(B) between 1.8 and 4.0 nm has been performed. The resistance measured at low temperature in the parallel state shows the expected exponential increase with increasing barrier thickness. The low-temperature TMR amplitude of about 300% is quite similar for all MgO thicknesses. This is in accordance with microstructural investigations by transmission electron microscopy, which do not give hints to a reduction in the barrier quality with increasing MgO thickness. Both the junction resistance and TMR decrease with increasing temperature and bias voltage. In general, the decrease is much stronger for thicker barriers, e. g., a decrease in the TMR by a factor of 13.4 from 293% at 15 K to 21.9% at 300 K was observed for t(B) = 4.0 nm compared to a reduction by only a factor of 1.6 for t(B) = 1.8 nm. This behavior can be described self-consistently for all barrier thicknesses within a model that extends the magnon-assisted tunneling model by adding an inelastic, unpolarized tunneling contribution. Furthermore we discuss our results in the framework of a recent model by Lu et al. [Phys. Rev. Lett. 102, 176801 (2009)] claiming that polarized hopping conductance becomes important for larger MgO thickness

Inelastic electron tunneling spectra of MgO-based magnetic tunnel junctions with different electrode designs

Drewello V, Schäfers M, Schebaum O, et al. Inelastic electron tunneling spectra of MgO-based magnetic tunnel junctions with different electrode designs. PHYSICAL REVIEW B. 2009;79(17): 174417.MgO-based magnetic tunnel junctions with up to 230% tunnel magnetoresistance ratio at room temperature and up to 345% at 13 K are prepared. The lower electrode is either exchange-biased or free, while the top electrode is free or an exchanged-biased artificial ferrimagnet, respectively. Additionally, a pseudo-spin-valve (hard-soft switching) design with two unpinned electrodes is used. Inelastic electron-tunneling spectra for each of these systems show a strong variation in the zero-bias anomaly with a reduced peak for some of the junctions. At voltages around 200 mV additional structures are found, which are not known from junctions with lower magneto resistance, such as alumina-based junctions. We discuss the spectra for the different electrode types and compare our findings with respect to barrier material and magnetoresistance ratio