1,129 research outputs found

    Hypothalamic neurons secreting vasopressin and neurophysin

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    Vasopressin is synthesized in the magnocellular system of the hypothalamus in clusters of cells which form the supraoptic nucleus and the paraventricular nucleus. The hormone is synthesized and packaged in neurosecretory granules with an intragpanular protein, neurophysin. The demonstration of axon flow of neurosecretory granules from the perikarya in the hypothalamus to the posterior lobe of the pituitary and subsequent release into the blood has been an important historical chapter in our understanding of neurosecretion. Isolation of neurophysins from several species and development of antisera to these peptides as well as antibodies to vasopressin have provided new tools to re-examine this system. In several species, the data indicate a specific neurophysin for vasopressin and a different neurophysin for oxytocin. It is now well established that neurophysins are secreted with hormones and this has provided a cogent argument that exocytosis is a major form of neurosecretion of vasopressin. Assay of neurophysin in plasma can be used to study vasopressin release. Immunohistochemical studies using antibodies to vasopressin and neurophysin demonstrated that the magnocellular system is more diffusely distributed throughout the hypothalamus than was previously appreciated. In addition, vasopressin and neurophysin are formed in both the supraoptic and paraventricular neurons and there are three pathways of secretion. The major pathway is the supraoptico-hypophyseal tract to the posterior lobe. The second pathway is to the external zone of the median eminence for secretion into the hypophyseal portal blood. The third pathway is to the third ventricle for secretion into cerebral spinal fluid. Vasopressin in the external zone is greatly increased by the absence of adrenal cortical steroids which suggests that vasopressin may play a role in the hypothalamic anterior pituitary adrenal axis. The cerebral spinal fluid pathway may be important in man if vasopressin is found to have the memory consolidating effects which have been investigated in other animals

    The orientation-preserving diffeomorphism group of S^2 deforms to SO(3) smoothly

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    Smale proved that the orientation-preserving diffeomorphism group of S^2 has a continuous strong deformation retraction to SO(3). In this paper, we construct such a strong deformation retraction which is diffeologically smooth.Comment: 16 page

    Acid Polishing of Lead Crystal Glass

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    The industrial partner manufactures high quality lead crystal glassware. The cutting of decorative features in the glass damages the surface and the cuts are optically opaque; to restore transparency, the glass is polished in a solution of hydrofluoric (HF) and sulphuric acid (H2 SO4 .) The polishing process comprises three stages: 1. immersion in a polishing tank containing acid; 2. rinsing in a tank containing water; and 3. settlement of the solid reaction products in a settlement tank. The manufacturer hopes to optimise its polishing process to • minimise the health/environmental impact of the process; • maximise throughput; • maintain the sharpness of the cut edges while still polishing to an acceptable level of transparency. The study group was asked to focus on modelling three aspects of the process: • the chemical reactions involved in the etching at the glass-acid solution interface; • the removal of reaction products in the settlement tank; • flow within the polishing tank

    Spin-on-carbon hard masks utilising fullerene derivatives

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    Spin-on-Carbon (SoC) hardmasks are an increasingly key component of the microchip fabrication process. Progress in lithographic resolution has made the adoption of extremely thin photoresist films necessary for the fabrication of “1x nanometre” linewidth structures to prevent issues such as resist collapse during development. While there are resists with high etch durability [1], ultimately etch depth is limited by resist thickness. A possible solution is the use of a multilayer etch stack. This allows for considerable increase in aspect ratio. For the organic hard mask base layer, a carbon-rich material is preferred as carbon possesses a high etch resistance in silicon plasma etch processes. A thin silicon topcoat deposited on the carbon film can be patterned with a thin photoresist film without feature collapse, and the pattern transferred to the underlying carbon film by oxygen plasma. This produces high aspect ratio carbon structures suitable for substrate etching. In terms of manufacturability it is beneficial to spin coat the carbon layer instead of using chemical vapor deposition [2], but the presence of carbon-hydrogen bonds in typical spin-on-carbon leads to line wiggling during the etch (a significant problem at smaller feature sizes). We have previously introduced a fullerene based SoC and reported on material characterization [3,4,5]. The materials low Ohnishi number provides high etch durability and the low hydrogen level allows for high resolution etching without wiggling. The use of the materials in such etch stacks is demonstrated (figures 1-3). A 20nm thin silicon film was sputtered on top of the carbon layers. Resist patterns are defined by e-beam, and in the case of figure 2, EUV lithography and transferred to the silicon thin film using SF6/CHF3 etch chemistry. The carbon layer was then etched by O2 plasma using the silicon mask and finally the pattern was transferred into the silicon substrate using the same process used to etch the topcoat. Recent advances in material development and work towards commercialization of the materials will be reported. Some results from external evaluations of the original 100 series will be presented, together with recent developments with the newer 200 and 300 series formulations (offering improved thermal stability and etch durability). [1] J. Manyam, M. Manickam, J.A. Preece, R.E. Palmer, and A.P.G. Robinson, Proc. SPIE 7972 (2011) 79722N. [2] C.Y. Ho, X.J. Lin, H.R. Chien, C. Lien, Thin Solid Films 518 (2010) 6076 [3] A. Frommhold, J. Manyam, R.E. Palmer, and A.P.G. Robinson, Proc. SPIE 8328 (2012) 83280U [4] A. Frommhold, R.E. Palmer, and A.P.G. Robinson, J. Micro/Nanolith. MEMS MOEMS. 12 (3), 033003 (2013) [5] A Frommhold, A G. Brown, T Lada, A P. G. Robinson, Proc SPIE 9421-21 (2015

    Ultra-high carbon fullerene-based spin-on-carbon hardmasks

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    Fullerene-based spin-on-carbon enables very high carbon content, and shows very high thermal stability, and etch resistance approaching amorphous carbon. Here we describe the performance of the HM1300 fullerene SOC, including results using high temperature inert atmosphere curing. Ohnishi numbers below 1.44 are achieved (measured by elemental analysis) and etch performance improved over the standard bake. A new high carbon crosslinker, designed to link directly to the fullerene cage, and with a carbon content comparable to the fullerene (significantly higher than the previous crosslinker) is also introduced. The new crosslinker is designed to enhance both etch and thermal stability performance

    Prevalent But Moderate Variation Across Small Geographic Regions in Patient Nonadherence to Evidence-based Preventive Therapies in Older Adults After Acute Myocardial Infarction

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    Patient long-term adherence to β-blockers, HMG-CoA reductase inhibitors (statins), and angiotensin-converting-enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) after acute myocardial infarction (AMI) is alarmingly low. It is unclear how prevalent patient adherence may be across small geographic areas and whether this geographic prevalence may vary
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