469 research outputs found

    Ansel B. Sterling Correspondence

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    Entry is the fanciful, handwritten biographical sketch of a Maine artist readying his book of poetry Weavings and Meanderings for publication

    Method of providing a lunar habitat from an external tank

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    A lunar habitat is provided by placing an external tank of an orbiter in a low Earth orbit where the hydrogen tank is separated from the intertank and oxygen tank which form a base structure. The base structure is then outfitted with an air lock, living quarters, a thermal control system, an environmental control and life support system, and a propulsion system. After the mounting of an outer sheath about the base structure to act as a micrometeoroid shield, the base structure is propelled to a soft landing on the moon. The sheath is mounted at a distance from the base structure to provide a space therebetween which is filled with regolith after landing. Conveniently, a space station is used to outfit the base structure. Various elements of the oxygen tank and intertank are used in outfitting

    Cathode & Electromagnet Qualification Status and Power Processing Unit Development Update for the Ascendant Sub-kW Transcelestial Electric Propulsion System

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    A review of the component-level flight qualification efforts and power processing unit development status of the Ascendant Sub-kW Transcelestial Electric Propulsion System (ASTRAEUS) program is presented. Component-level qualification efforts were undertaken for the system’s ultra-compact heaterless LaB6 hollow cathode and electromagnets, both of which employ designs bespoke to ASTRAEUS, as they represent the highest failure risks for the thruster. Through parallel long-duration wear and ignition tests, the ASTRAEUS cathode demonstrated invariant discharge performance over more than 5000 h of operation at its maximum operating current of 4 A and demonstrated more than 25,000 ignition cycles. The ASTRAEUS electromagnets completed their environmental qualification through a demonstration of more than 1200 deep thermal cycles with no indication of coil degradation (the test articles previously completed qualification-level vibration and shock testing). ASTRAEUS’s prototype power processing unit has demonstrated more than 92% total power conversion efficiency and class-leading power density & specific power density of 4.5 W/cm3 & 1670 W/kg, respectively. The various power converters found in the ASTRAEUS power processing unit are reviewed with a focus on the methods by which such high performance was achieved

    The Pentose Phosphate Pathway Regulates the Circadian Clock

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    The circadian clock is a ubiquitous timekeeping system that organizes the behavior and physiology of organisms over the day and night. Current models rely on transcriptional networks that coordinate circadian gene expression of thousands of transcripts. However, recent studies have uncovered phylogenetically conserved redox rhythms that can occur independently of transcriptional cycles. Here we identify the pentose phosphate pathway (PPP), a critical source of the redox cofactor NADPH, as an important regulator of redox and transcriptional oscillations. Our results show that genetic and pharmacological inhibition of the PPP prolongs the period of circadian rhythms in human cells, mouse tissues, and fruit flies. These metabolic manipulations also cause a remodeling of circadian gene expression programs that involves the circadian transcription factors BMAL1 and CLOCK, and the redox-sensitive transcription factor NRF2. Thus, the PPP regulates circadian rhythms via NADPH metabolism, suggesting a pivotal role for NADPH availability in circadian timekeeping.Peer reviewe

    Razvoj i vrednovanje dvoslojnih tableta propranolol hidroklorida

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    The objective of the present research was to develop a bilayer tablet of propranolol hydrochloride using superdisintegrant sodium starch glycolate for the fast release layer and water immiscible polymers such as ethyl cellulose, Eudragit RLPO and Eudragit RSPO for the sustaining layer. In vitro dissolution studies were carried out in a USP 24 apparatus I. The formulations gave an initial burst effect to provide the loading dose of the drug followed by sustained release for 12 hrs from the sustaining layer of matrix embedded tablets. In vitro dissolution kinetics followed the Higuchi model via a non-Fickian diffusion controlled release mechanism after the initial burst release. FT-IR studies revealed that there was no interaction between the drug and polymers used in the study. Statistical analysis (ANOVA) showed no significant difference in the cumulative amount of drug release after 15 min, but significant difference (p 0.005) in the amount of drug released after 12 h from optimized formulations was observed.U radu je opisan razvoj dvoslojnih tableta propranolol hidroklorida, koristeći superdezintegrator škrob glikolat natrij u sloju za brzo oslobađanje i polimere koji se ne miješaju s vodom (etil celuloza, Eudragit RLPO i Eudragit RSPO) u sloju za usporeno oslobađanje. In vitro oslobađanje praćeno je u USP aparatu I te je uočeno početno naglo oslobađanje ljekovite tvari iza kojeg slijedi polagano oslobađanje tijekom 12 sati. In vitro kinetika oslobađanja prati Higouchijev model, dok mehanizam kontroliranog oslobađanja ne slijedi Fickov zakon poslije početnog naglog oslobađanja. FT-IR studije ukazuju da nema interakcije između ljekovite tvari i polimera upotrebljenih u oblikovanju. Statistička analiza (ANOVA) nije pokazala značajne razlike u kumulativnoj količini oslobođenog lijeka iz optimiranih formulacija poslije 15 minuta i polije 12 h

    Endovascular baroreflex amplification for resistant hypertension: a safety and proof-of-principle clinical study

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    Summary Background Carotid baroreflex activation lowers blood pressure and might have potential application for the treatment of resistant hypertension. We did a proof-of-principle trial with a novel endovascular baroreceptor amplification device, MobiusHD (Vascular Dynamics, Mountain View, CA, USA), in patients with resistant hypertension. Methods CALM-FIM_EUR was a prospective, first-in-human, open-label study done at six European centres. Eligible patients were adults with resistant hypertension (office systolic blood pressure ≥160 mm Hg despite taking at least three antihypertensive agents, including a diuretic). MobiusHD devices were implanted unilaterally in the internal carotid artery. The primary endpoint was the incidence of serious adverse events at 6 months. Secondary endpoints included changes in office and 24 h ambulatory blood pressure. This trial is registered with ClinicalTrials.gov, number NCT01911897. Findings Between December, 2013, and February, 2016, 30 patients were enrolled and underwent successful implantation. Mean age was 52 years (SD 12), 15 patients (50%) were men, and mean antihypertensive use was 4·4 drugs (1·4). Mean office blood pressure was 184/109 mm Hg (18/14) at baseline and was reduced by 24/12 mm Hg (13–34/6–18) at 6 months (p=0·0003 for systolic and p=0·0001 diastolic blood pressure). Mean baseline 24 h ambulatory blood pressure was 166/100 mm Hg (17/14) at baseline and was reduced by 21/12 mm Hg (14–29/7–16) at 6 months (p<0·0001 for systolic and diastolic blood pressure). Five serious adverse events had occurred in four patients (13%) at 6 months: hypotension (n=2), worsening hypertension (n=1), intermittent claudication (n=1) and wound infection (n=1). Interpretation In patients with resistant hypertension, endovascular baroreceptor amplification with the MobiusHD device substantially lowered blood pressure with an acceptable safety profile. Randomised, double-blind, sham-controlled trials are warranted to investigate the use of this treatment further. Funding Vascular Dynamics

    A Genetic Lesion that Arrests Plasma Cell Homing to the Bone Marrow

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    The coordinated regulation of chemokine responsiveness plays a critical role in the development of humoral immunity. After antigen challenge and B cell activation, the emerging plasma cells (PCs) undergo CXCL12-induced chemotaxis to the bone marrow, where they produce Ab and persist. Here we show that PCs, but not B cells or T cells from lupus-prone NZM mice, are deficient in CXCL12-induced migration. PC unresponsiveness to CXCL12 results in a marked accumulation of PCs in the spleen of mice, and a concordant decrease in bone marrow PCs. Unlike normal mice, in NZM mice, a majority of the splenic PCs are long-lived. This deficiency is a consequence of the genetic interactions of multiple systemic lupus erythematosus susceptibility loci
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