700 research outputs found
Surface treatment of glass vials for lyophilization: Implications for vacuum-induced surface freezing
Freeze-drying is commonly used to increase the shelf-life of pharmaceuticals and biopharmaceuticals. Freezing represents a crucial phase in the freeze-drying process, as it determines both cycle efficiency and product quality. For this reason, different strategies have been developed to allow for a better control of freezing, among them, the so-called vacuum-induced surface freezing (VISF), which makes it possible to trigger nucleation at the same time in all the vials being processed. We studied the effect of different vial types, characterized by the presence of hydrophilic (sulfate treatment) or hydrophobic (siliconization and TopLyo Si–O–C–H layer) inner coatings, on the application of VISF. We observed that hydrophobic coatings promoted boiling and blow-up phenomena, resulting in unacceptable aesthetic defects in the final product. In contrast, hydrophilic coatings increased the risk of fogging (i.e., the undesired creeping of the product upward along the inner vial surface). We also found that the addition of a surfactant (Tween 80) to the formulation suppressed boiling in hydrophobic-coated vials, but it enhanced the formation of bubbles. This undesired bubbling events induced by the surfactant could, however, be eliminated by a degassing step prior to the application of VISF. Overall, the combination of degasification and surfactant addition seems to be a promising strategy for the successful induction of nucleation by VISF in hydrophobic vials
The Isotropic Radio Background and Annihilating Dark Matter
Observations by ARCADE-2 and other telescopes sensitive to low frequency
radiation have revealed the presence of an isotropic radio background with a
hard spectral index. The intensity of this observed background is found to
exceed the flux predicted from astrophysical sources by a factor of
approximately 5-6. In this article, we consider the possibility that
annihilating dark matter particles provide the primary contribution to the
observed isotropic radio background through the emission of synchrotron
radiation from electron and positron annihilation products. For reasonable
estimates of the magnetic fields present in clusters and galaxies, we find that
dark matter could potentially account for the observed radio excess, but only
if it annihilates mostly to electrons and/or muons, and only if it possesses a
mass in the range of approximately 5-50 GeV. For such models, the annihilation
cross section required to normalize the synchrotron signal to the observed
excess is sigma v ~ (0.4-30) x 10^-26 cm^3/s, similar to the value predicted
for a simple thermal relic (sigma v ~ 3 x 10^-26 cm^3/s). We find that in any
scenario in which dark matter annihilations are responsible for the observed
excess radio emission, a significant fraction of the isotropic gamma ray
background observed by Fermi must result from dark matter as well.Comment: 11 pages, 6 figure
A Vicious Cycle of Fear of Falling Avoidance Behavior in Parkinson’s Disease: A Path Analysis
Background: Postural instability (PI) in Parkinson\u27s disease (PD) is associated with several negative downstream consequences. Objective: The purpose was to explore the validity of a theoretical model of these downstream consequences arranged in a vicious cycle wherein PI leads to decreased balance confidence, which in turn leads to increased fear of falling (FOF) avoidance behavior, which in turn leads to decreased physical conditioning, which then feeds back and negatively affects PI. Methods: A path analysis of cross-sectional data from 55 participants with PD was conducted. The four constructs in the model connected in succession were: 1. PI (principal components analysis (PCA) composite of the Unified Parkinson\u27s Disease Rating Scale PI and Gait Difficulty score, Timed Up and Go test, and Berg Balance Scale); 2. balance confidence (Activities-Specific Balance Confidence Scale); 3. FOF avoidance behavior (PCA composite of the FOF Avoidance Behavior Questionnaire and average number of steps per day); and, 4. physical conditioning (2-Minute Step Test). Results: The path model was an excellent fit to the data, χ2 (7) = 7.910, p =.341, CFI = 0.985, TLI = 0.968, RMSEA = 0.049 (90% CI: 0.000 to 0.179). The moderate to strong and uniformly significant parameter estimates were −0.519, −0.651, −0.653, and −0.570, respectively (ps \u3c 0.01). Conclusions: PI directly and inversely predicted balance confidence, which in turn directly and inversely predicted FOF avoidance behavior. Furthermore, FOF avoidance behavior directly and inversely predicted physical conditioning, which directly and inversely predicted PI, thereby closing the cycle. These findings highlight the downstream consequences of PI in PD and support the notion of a vicious cycle of FOF avoidance behavior
Study of damage control systems for space station
Damage control systems for detecting and locating overboard and onboard leak and damage modes on space station
Optical Instrument Thermal Control on the Large Ultraviolet/Optical/Infrared Surveyor
The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a multi-wavelength observatory commissioned by NASA as one of four large mission concept studies for the Astro2020 Decadal Survey. Two concepts are under study which bound a range of cost, risk, and scientific return: an 8-meter diameter unobscured segmented aperture primary mirror and a 15-meter segmented aperture primary mirror. Each concept carries with it an accompanying suite of instruments. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is a near-ultraviolet (NUV) / optical / near-infrared (NIR) coronagraph; the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS) provides multi-object imaging spectroscopy in the 100-400 nanometer ultraviolet (UV) range; and the High Definition Imager (HDI) is a wide field-of-view near-UV / optical / near-IR camera that can also perform astrometry. The 15-meter concept also contains an additional instrument, Pollux, which is a high-resolution UV spectro-polarimeter. While the observatory is nominally at a 270 Kelvin operational temperature, the requirements of imaging in both IR and UV require separate detectors operating at different temperature regimes, each with stringent thermal stability requirements. The change in observatory size requires two distinct thermal designs per instrument. In this current work, the thermal architecture is presented for each instrument suite. We describe here the efforts made to achieve the target operational temperatures and stabilities with passive thermal control methods. Additional discussion will focus on how these instrument thermal designs impact the overall system-level architecture of the observatory and indicate the thermal challenges for hardware implementation
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