Ohmic contacts to p-type Hg0.3Cd0.7Te by metalorganic chemical vapour deposition of HgTe

Ohmic contacts were obtained to p-type Hg_0.3Cd_0.7Te crystals by metalorganic chemical vapour deposition (MOCVD) of HgTe as an interface material between the crystals and the contacting metal. Deposition at a reduced temperature of 350C did not lead to an obvious change in the material performance. Electronic-transport data are given. Two acceptor levels, at 4.8 and 60 meV above the valence-band edge, were found.     

Combined infra-red and X-ray studies of β-silicon nitride and β′-sialons

Previous investigations of the replacement of silicon by aluminium and nitrogen by oxygen in -silicon nitride have been based primarily on X-ray powder diffraction studies. In the present work this technique is coupled with parallel infra-red studies. X-ray analyses of sialons over a wide composition range confirm previous observations that increasing substitution of aluminium for silicon and nitrogen for oxygen in -silicon nitride is accompanied by an increase in cell size, with no evidence of any other structural modification. Parallel infra-red analyses show shifts in certain of the infra-red absorption bands to lower wavenumbers as the degree of substitution increases. Changes in the infrared spectra at the composition Si₂Al₄N₄O₄ indicate structural modifications which are not apparent from the X-ray investigations. It is suggested that these changes are a result of the ordering of the different atom types at this composition.     

Very low-temperature search for superconductivity in semiconducting KTaO3

A series of attempts have been made to detect the presence of superconductivity in semiconducting potassium tantalate (KTaO₃) single crystals. Semiconducting potassium tantalate has a number of properties in common with semiconducting SrTiO₃, which is superconducting below 0.3 K, with a critical temperatureT _c that varies as a function of the carrier concentration. Both KTaO₃ and SrTiO₃ are perovskite-structure oxides and both materials are so-called incipient ferroelectrics that are characterized by high dielectric constants at low temperature. These common properties suggest that superconductivity might also be observed in semiconducting potassium tantalate. In the temperature ange from 0.01 to 4.0 K, however, no evidence was found for superconductivity in KTaO₃ in the presence of magnetic fields of 10^–5–10^–4 T (i.e., 0.1–1 Oe). Below 1.5 K, the search for superconductivity in KTaO₃ was carried out using a³He-⁴He dilution refrigerator equipped with a SQUID magnetometer and an ac magnetometer. The system response was verified by measuring the paramagnetic susceptibility of Dy₂O₃-doped KTaO₃. The failure to observe superconductivity in KTaO₃, while SrTiO₃ is an established superconducting material, may be related to the fact that the latter substance assumes a tetragonal symmetry phase at 105 K, while KTaO₃ remains cubic to low temperatures.Operated by Union Carbide Corporation for the U.S. Department of Energy under contract w-7405-eng-26.     

Histochemical light microscopic study of catecholamine containing paraganglia in the human pelvis

Histological and histochemical techniques have been employed to determine the structure and autonomic innervation of paraganglia located in the human pelvis. In foetal and early postnatal tissues, paraganglia formed rounded cellular masses which were frequently in company with the autonomic nerves and ganglia of the urinary bladder and other pelvic viscera. The constituent cells contained only small amounts of cholinesterase and were unrelated to enzyme positive autonomic nerves; acetylcholinesterase containing nerves were occasionally observed in the capsule and the fibrous septa of the pelvic paraganglia. In early postnatal specimens, pelvic paraganglia frequently contained single or multiple "pacinian-like" corpuscles, each possessing a central region which was rich in both acetyl and pseudocholinesterase. These structures were rarely observed within autonomic ganglia and were absent 4 1/2 years post partum. By means of a histochemical technique, pelvic paraganglia were found to contain catecholamine which was attributed to the presence of relatively large quantities of noradrenaline. These observations have been discussed with particular reference to the results of other studies on the autonomic innervation of paraganglia.     

Why security testing is hard

Software testing fairly readily detects a program's failure to do what it is designed to do, but does not detect all of the other things that it may do in the process. Some of these may compromise security. The article discusses the development of methods and software tools to deal with these bugs.     

miR-486-5p and miR-22-3p Enable Megakaryocytic Differentiation of Hematopoietic Stem and Progenitor Cells without Thrombopoietin

Megakaryocytes release submicron size microparticles (MkMPs) in circulation. We have shown that MkMPs target CD34+ hematopoietic stem/progenitor cells (HSPCs) to induce megakaryocytic differentiation, and that small RNAs in MkMPs play an important role in the development of this phenotype. Here, using single-molecule real-time (SMRT) RNA sequencing (RNAseq), we identify the synergetic effect of two microRNAs (miRs), miR-486-5p and miR-22-3p (highly enriched in MkMPs), in driving the Mk differentiation of HSPCs in the absence of thrombopoietin (TPO). Separately, our data suggest that the MkMP-induced Mk differentiation of HSPCs is enabled through JNK and PI3K/Akt/mTOR signaling. The interaction between the two signaling pathways is likely mediated by a direct target of miR-486-5p and a negative regulator of PI3K/Akt signaling, the phosphatase and tensin homologue (PTEN) protein. Our data provide a possible mechanistic explanation of the biological effect of MkMPs in inducing megakaryocytic differentiation of HSPCs, a phenotype of potential physiological significance in stress megakaryopoiesis.     

Release of cholesteryl esters by the mammary gland of the pre-partum cow

In five cows that were regularly milked before parturition, cholesteryl esters were continuously released into the mammary fluid; their concentration in the fluid was initially high, but decreased a few days before parturition when mammary secretion of fluid and triglyceride was increasing. The composition of fatty acids in the cholesteryl esters of mammary fluid and in blood plasma was different, suggesting mammary synthesis of cholesteryl esters.     

Surface-constrained volumetric brain registration using harmonic mappings

In order to compare anatomical and functional brain imaging data across subjects, the images must first be registered to a common coordinate system in which anatomical features are aligned. Intensity-based volume registration methods can align subcortical structures well, but the variability in sulcal folding patterns typically results in misalignment of the cortical surface. Conversely, surface-based registration using sulcal features can produce excellent cortical alignment but the mapping between brains is restricted to the cortical surface. Here we describe a method for volumetric registration that also produces an accurate one-to-one point correspondence between cortical surfaces. This is achieved by first parameterizing and aligning the cortical surfaces using sulcal landmarks. We then use a constrained harmonic mapping to extend this surface correspondence to the entire cortical volume. Finally, this mapping is refined using an intensity-based warp. We demonstrate the utility of the method by applying it to T1-weighted magnetic resonance images (MRIs). We evaluate the performance of our proposed method relative to existing methods that use only intensity information; for this comparison we compute the intersubject alignment of expert-labeled subcortical structures after registration.