Development of a Model for the Small-Particle Orbital Debris Population Based on the STS Impact Record

In preparation for the release of the Orbital Debris Engineering Model (ORDEM) version 3.1, the NASA Orbital Debris Program Office (ODPO) revisited how orbiting debris populations of characteristic sizes smaller than 1 cm were modeled. The primary contributor to the population of sub-centimeter debris particles is the surface deterioration or erosion of spacecraft materials exposed to the outer-space environment. Because small particulates are not directly trackable by remote sensing, the primary means of detection is via historical counts of small impact features on flown radiator and window surfaces of the U.S. Space Transportation System (STS, also known as the Space Shuttle) from 1995-2011. Historic NASA studies of high-velocity impact tests have related impact-feature size to particle mass and velocity for certain STS surfaces, so that a corresponding particle size may be inferred from each small-impact feature observed. Micro-debris populations are then estimated by modeling the path and orientation of an STS mission through a simulated debris environment, and the densities of this simulated environment are rescaled to approximate the number of observed STS impact features. Monte-Carlo methods are further employed to gauge the estimation uncertainty of the rescaled environment. A description of the chosen methodologies for estimating and adjusting the micro-debris population model, and the results, are presented

Benchmarking leakage from water reticulation systems in South Africa

A project to assess the levels of leakage in 30 water utilities throughout South Africa was initiated by the Water Research Commission. The BENCHLEAK software was used to evaluate the water utilities and performance indicators calculated by the model were used to compare levels of non-revenue water. Results showed that utilities ranked differently according to the different indicators, and that the South African results are similar to world norms. Feed back from the water utilities showed that some of the data requested were confusing and required clarity. The number of service connections, apparent losses and length of pipe between the street edge and the meter were looked at in more detail. Standard drawings were developed to assist water utilities in determining their number of service connections. A table is presented to assess the apparent losses of each water utility in a more pragmatic way. Water SA Vol. 30 (5) 2005: pp.25-3

The NASA Orbital Debris Engineering Model 3.1: Development, Verification, and Validation

The NASA Orbital Debris Program Office has developed the Orbital Debris Engineering Model (ORDEM) primarily as a tool for spacecraft designers and other users to understand the long-term risk of collisions with orbital debris. The newest version, ORDEM 3.1, incorporates the latest and highest fidelity datasets available to build and validate representative orbital debris populations encompassing low Earth orbit (LEO) to geosynchronous orbit (GEO) altitudes for the years 2016-2050. ORDEM 3.1 models fluxes for object sizes > 10 m within or transiting LEO and > 10 cm in GEO. The deterministic portion of the populations in ORDEM 3.1 is based on the U.S. Space Surveillance Network (SSN) catalog, which provides coverage down to approximately 10 cm in LEO and 1 m in GEO. Observational datasets from radar, in situ, and optical sources provide a foundation from which the model populations are statistically extrapolated to smaller sizes and orbit regions that are not well-covered by the SSN catalog, yet may pose the greatest threat to operational spacecraft. Objects in LEO ranging from approximately 5 mm to 10 cm are modeled using observational data from ground-based radar, namely the Haystack Ultrawideband Satellite Imaging Radar (HUSIR formerly known as Haystack). The LEO population smaller than approximately 3 mm in size is characterized based on a reanalysis of in situ data from impacts to the windows and radiators of the U.S. Space Transportation System orbiter vehicle, i.e., the Space Shuttle. Data from impacts on the Hubble Space Telescope are also used to validate the sub-millimeter model populations in LEO. Debris in GEO with sizes ranging from 10 cm to 1 m is modeled using optical measurement data from the Michigan Orbital DEbris Survey Telescope (MODEST). Specific, major debris-producing events, including the Fengyun-1C, Iridium 33, and Cosmos 2251 debris clouds, and unique populations, such as sodium-potassium droplets, have been re-examined and are modeled and added to the ORDEM environment separately. The debris environment greater than 1 mm is forecast using NASAs LEO-to- GEO ENvironment Debris model (LEGEND). Future explosions of intact objects and collisions involving objects greater than 10 cm are assessed statistically, and the NASA Standard Satellite Breakup Model is used to generate fragments from these events. Fragments smaller than 10 cm are further differentiated based on material density categories, i.e., high-, medium-, and low-density, to better characterize the potential debris risk posed to spacecraft. The future projection of the sub-millimeter environment is computed using a special small-particle degradation model where small particles are created from intact spacecraft and rocket bodies. This work discusses the development, features, and capabilities of the ORDEM 3.1 model; the ne new data analyses used to build the model populations; and sample verification and validation results

Effects of Metallicity on the Rotation Rates of Massive Stars

Recent theoretical predictions for low metallicity massive stars predict that these stars should have drastically reduced equatorial winds (mass loss) while on the main sequence, and as such should retain most of their angular momentum. Observations of both the Be/(B+Be) ratio and the blue-to-red supergiant ratio appear to have a metallicity dependence that may be caused by high rotational velocities. We have analyzed 39 archival Hubble Space Telescope Imaging Spectrograph (STIS), high resolution, ultraviolet spectra of O-type stars in the Magellanic Clouds to determine their projected rotational velocities V sin i. Our methodology is based on a previous study of the projected rotational velocities of Galactic O-type stars using International Ultraviolet Explorer (IUE) Short Wavelength Prime (SWP) Camera high dispersion spectra, which resulted in a catalog of V sin i values for 177 O stars. Here we present complementary V sin i values for 21 Large Magellanic Cloud and 22 Small Magellanic Cloud O-type stars based on STIS and IUE UV spectroscopy. The distribution of V sin i values for O type stars in the Magellanic Clouds is compared to that of Galactic O type stars. Despite the theoretical predictions and indirect observational evidence for high rotation, the O type stars in the Magellanic Clouds do not appear to rotate faster than their Galactic counterparts.Comment: accepted by ApJ, to appear 20 December 2004 editio

Classical swine fever virus Npro antagonises IRF3 to prevent IFN-independent TLR3 and RIG-I-mediated apoptosis

Classical swine fever virus (CSFV) is the causative agent of classical swine fever,a notifiable disease of economic importance that causes severe leukopenia, fever and haemorrhagic disease in domesticated pigs and wild boar across the globe. CSFV has been shown to antagonise the induction of type I IFN, partly through a function of its N-terminal protease (Npro) which binds IRF3 and targets it for proteasomal degradation. Additionally, Npro has been shown to antagonise apoptosis triggered by the dsRNA-homologpoly (I:C), however the exact mechanism by which this is achieved has not been fully elucidated. In this study we confirm the ability of Npro to inhibit dsRNA-mediated apoptosis and show that Npro is also able to antagonise Sendai virus-mediated apoptosis in PK-15 cells. Gene editedPK-15 cell lines were used to show the dsRNA-sensing pathogen recognition receptors (PRRs) TLR3 and RIG-I specifically respond to poly(I:C) and SeV respectively, subsequently triggering apoptosis through pathways that convergeon IRF3 and culminate in the cleavage of caspase-3.Importantly, this IRF3-mediated apoptosis was found to be dependent on transcription-independent functions of IRF3 and also on Bax, a pro-apoptotic Bcl-2 family protein, through a direct interaction between the two proteins. Deletion of IRF3, stable expression of Npro and infection with wild-type CSFV were found to antagonise the mitochondrial localisation of Bax, a key hallmark of the intrinsic, mitochondrial pathway of apoptosis. Together, these findings show that Npro’s putative interaction with IRF3 is involved not only in its antagonism of type I IFN, but also dsRNA-mediated mitochondrial apoptosis

Water Exchange Rate across the Blood-Brain Barrier Is Associated with CSF Amyloid-β 42 in Healthy Older Adults

INTRODUCTION: We tested if water exchange across the blood-brain barrier (BBB), estimated with a noninvasive magnetic resonance imaging (MRI) technique, is associated with cerebrospinal fluid (CSF) biomarkers of Alzheimer\u27s disease (AD) and neuropsychological function. METHODS: Forty cognitively normal older adults (67–86 years old) were scanned with diffusion‐prepared, arterial spin labeling (DP‐ASL), which estimates water exchange rate across the BBB (kw). Participants also underwent CSF draw and neuropsychological testing. Multiple linear regression models were run with kw as a predictor of CSF concentrations and neuropsychological scores. RESULTS: In multiple brain regions, BBB kw was positively associated with CSF amyloid beta (Aβ)42 concentration levels. BBB kw was only moderately associated with neuropsychological performance. DISCUSSION: Our results suggest that low water exchange rate across the BBB is associated with low CSF Aβ42 concentration. These findings suggest that kw may be a promising noninvasive indicator of BBB Aβ clearance functions, a possibility which should be further tested in future research

Inducible nitric oxide synthase and guinea-pig ileitis induced by adjuvant

We sought to establish a model of inflammatory bowel disease by augmenting the activity of the local immune system with Freund's complete adjuvant, and to determine if inducible nitric oxide synthase (iNOS) expression and peroxynitrite formation accompanied the inflammatory condition. In anaesthetized guinea-pigs, a loop of distal ileum received intraluminal 50% ethanol followed by Freund's complete adjuvant. Control animals were sham operated. When the animals were killed 7 or 14 days later, loop lavage fluid was examined for nitrite and PGE2 levels; mucosal levels of granulocyte and macrophages were estimated by myeloperoxidase (MPO) and N-acetyl-D-glucosaminidase (NAG) activity, respectively. Cellular localization if iNOS and peroxynitrite formation were determined by immunohistochemistry with polyclonal antibodies directed against peptide epitopes of mouse iNOS and nitrotyrosine, respectfully. Adjuvant administration resulted in a persistent ileitis, featuring gut thickening, crypt hyperplasia, villus tip swelling and disruption, and cellular infiltration. Lavage levels of PGE2 and nitrite were markedly elevated by adjuvant treatment. Immunoreactive iNOS and nitrotyrosine bordered on detectability in normal animals but were markedly evident with adjuvant treatment at day 7 and particularly day 14. Immunohistochemistry suggested that enteric neurons and epithelia were major sites of iNOS activity and peroxynitrite formation. We conclude that local administration of adjuvant establishes a chronic ileitis. Inducible nitric oxide synthase may contribute to the inflammatory process

Older adult experience of care and staffing on hospital and community wards: a cross-sectional study

BACKGROUND: Recent major concerns about the quality of healthcare delivered to older adults have been linked to inadequate staffing and a lack of patient-centred care. Patient experience is a key component of quality care - yet there has been little research on whether and how staffing levels and staffing types affect satisfaction amongst older adult hospital inpatients. This study aimed to evaluate the association between registered nurse and healthcare assistant staffing levels and satisfaction with care amongst older adult hospital inpatients, and to test whether any positive effect of higher staffing levels is mediated by staff feeling they have more time to care for patients. METHODS: Survey data from 4928 inpatients aged 65 years and older and 2237 medical and nursing staff from 123 acute and community medical wards in England, United Kingdom (UK) was collected through the Royal College of Psychiatrist's Elder Care Quality Mark. The cross-sectional association between staffing ratios and older adult patient satisfaction, and mediation by staff perceived time to care, was evaluated using multi-level modelling, adjusted for ward type and with a random effect for ward identity. RESULTS: Higher numbers of patients per healthcare assistant were associated with poorer patient satisfaction (adjusted β = - 0.32, 95% CI - 0.55 to 0.10, p < 0.01), and this was found to be partially mediated by all ward staff reporting less time to care for patients (adjusted β = - 0.10, bias-corrected 95% CI - 1.16 to - 0.02). By contrast, in both unadjusted and adjusted models, the number of patients per registered nurse was not associated with patient satisfaction. CONCLUSIONS: Older adult hospital patients may particularly value the type of care provided by healthcare assistants, such as basic personal care and supportive communication. Additionally, higher availability of healthcare assistants may contribute to all ward staff feeling more able to spend time with patients. However, high availability of registered nurses has been shown in other research to be vital for ensuring quality and safety of patient care. Future research should seek to identify the ideal balance of registered nurses and healthcare assistants for optimising a range of outcomes amongst older adult patients