3,286 research outputs found
Spacecraft Systems Working Group report
Issues addressed include: definition of user/commercial/government needs by function; criteria for prioritization of needs; overall criteria for technology assessment; system configuration drivers (key trade studies); space infrastructure interface; and cost drivers (pros and cons of standardization, manufacturing, test, serviceability, and supportability)
Control system designs for the shuttle infrared telescope facility
The Shuttle Infrared Telescope Facility (SIRTF) image motion compensation system is described in detail and performance is analyzed with respect to system noise inputs, environmental disturbances, and error sources such as bending and feedforward scale factor. It is concluded that the SIRTF accuracy and stability requirements can be met with this design
Swelling of acetylated wood in organic liquids
To investigate the affinity of acetylated wood for organic liquids, Yezo
spruce wood specimens were acetylated with acetic anhydride, and their swelling
in various liquids were compared to those of untreated specimens. The
acetylated wood was rapidly and remarkably swollen in aprotic organic liquids
such as benzene and toluene in which the untreated wood was swollen only
slightly and/or very slowly. On the other hand, the swelling of wood in water,
ethylene glycol and alcohols remained unchanged or decreased by the
acetylation. Consequently the maximum volume of wood swollen in organic liquids
was always larger than that in water. The effect of acetylation on the maximum
swollen volume of wood was greater in liquids having smaller solubility
parameters. The easier penetration of aprotic organic liquids into the
acetylated wood was considered to be due to the scission of hydrogen bonds
among the amorphous wood constituents by the substitution of hydroxyl groups
with hydrophobic acetyl groups.Comment: to be published in J Wood Science (Japanese wood research society
Chandra observations of the HII complex G5.89-0.39 and TeV gamma-ray source HESSJ1800-240B
We present the results of our investigation, using a Chandra X-ray
observation, into the stellar population of the massive star formation region
G5.89-0.39, and its potential connection to the coincident TeV gamma-ray source
HESSJ1800-240B. G5.89-0.39 comprises two separate HII regions G5.89-0.39A and
G5.89-0.39B (an ultra-compact HII region). We identified 159 individual X-ray
point sources in our observation using the source detection algorithm
\texttt{wavdetect}. 35 X-ray sources are associated with the HII complex
G5.89-0.39. The 35 X-ray sources represent an average unabsorbed luminosity
(0.3-10\,keV) of \,erg/s, typical of B7-B5 type stars. The
potential ionising source of G5.89-0.39B known as Feldt's star is possibly
identified in our observation with an unabsorbed X-ray luminosity suggestive of
a B7-B5 star. The stacked energy spectra of these sources is well-fitted with a
single thermal plasma APEC model with kT5\,keV, and column density
N\,cm (A). The residual
(source-subtracted) X-ray emission towards G5.89-0.39A and B is about 30\% and
25\% larger than their respective stacked source luminosities. Assuming this
residual emission is from unresolved stellar sources, the total
B-type-equivalent stellar content in G5.89-0.39A and B would be 75 stars,
consistent with an earlier estimate of the total stellar mass of hot stars in
G5.89-0.39. We have also looked at the variability of the 35 X-ray sources in
G5.89-0.39. Ten of these sources are flagged as being variable. Further studies
are needed to determine the exact causes of the variability, however the
variability could point towards pre-main sequence stars. Such a stellar
population could provide sufficient kinetic energy to account for a part of the
GeV to TeV gamma-ray emission in the source HESSJ1800-240B.Comment: 34 pages, 9 figure
Financing Education in Nigeria: Implications and Options for National Development
The future of any country lies in the quality of its education. Education remains the major tool for national socio-economic development, individual socio-economic empowerment and poverty reduction. Unfortunately, one of major problem now facing education in Nigeria is the issue of underfunding. We have, in the last decades, witnessed a gradual degradation in infrastructure, in manpower development and access to qualitative education. Precisely, the federal government spending on education is below 10 percent of its overall budget. This is largely due to the fall of the oil market, and the need to reduce the huge and raising debt service obligations. This study critically examined the past and present situation of financing education in Nigeria, the implications of inadequate funding and possible strategies of funding education. Thus, it was suggested among others that all stakeholders, parents and guardians, the society in general, the private sector and non-governmental agencies must become involved in the financing of education in Nigeria
Changing associations between socioeconomic status and self-reported discrimination from the 1990s to the 2010s in the United States
We examined whether prevalence of social class discrimination-and its association with psychological distress-has changed between 1990s and 2010s in the United States. Data were from the original Midlife in the United States (MIDUS) study with data collections in 1995-1996 (n = 2931) and 2004-2005 (n = 1708), and the new MIDUS Refresher sample from 2011 to 2014 (n = 2543). Socioeconomic status (SES) became more strongly associated with self-rated discrimination over time, with individuals with the lowest SES experiencing more discrimination (B = 0.75, p < .001) and those with the highest SES less discrimination (B = 0.36, p < .001) over time: at baseline, the difference in self-rated discrimination between the highest and lowest SES groups was 15.3% versus 10.8% (4.7% point difference). This difference increased to 20.0% versus 7.4% in the last study wave (12.6% point difference). Association between self-reported discrimination and psychological distress strengthened over time, but the associations between socioeconomic indicators and distress did not change. The results suggest that people with low SES had higher risk of encountering unfair and disrespectful treatment in the 2010s compared to the 1990s.Peer reviewe
Progesterone during the breeding season and pregnancy in female muskoxen on different dietary regimens
Previously, we documented lowered calving success in captive muskoxen raised for 6 years on a low nutritional plane. In an effort to identify causes of lowered calf production, we looked at serum progesterone during the breeding season in muskoxen raised on either a high (HP) or low (LP) nutritional plane. Complete cessation of estrous cycli-city in 2 parous cows was the only irregularity identified. Abortion and/or embryonic loss occurred in both HP and LP cows. We also compared progesterone during pregnancy between the 2 nutritional planes and lactating and non-lacta-ting cows. The timing of the rise and fall of the mid-pregnant progesterone peak was consistent with stage of gestation and apparently independent of time of breeding, diet or lactational status
Discovery of very high energy gamma-ray emission in the W 28 (G6.4-0.1) region, and multiwavelength comparisons
H.E.S.S. observations of the old-age (>10^4yr; ~0.5deg diameter) composite
supernova remnant (SNR) W 28 reveal very high energy (VHE) gamma-ray emission
situated at its northeastern and southern boundaries. The northeastern VHE
source (HESS J1801-233) is in an area where W 28 is interacting with a dense
molecular cloud, containing OH masers, local radio and X-ray peaks. The
southern VHE sources (HESS J1800-240 with components labelled A, B and C) are
found in a region occupied by several HII regions, including the ultracompact
HII region W 28A2. Our analysis of NANTEN CO data reveals a dense molecular
cloud enveloping this southern region, and our reanalysis of EGRET data reveals
MeV/GeV emission centred on HESS J1801-233 and the northeastern interaction
region.Comment: 4 pages, 3 figures, proceedings of the 30th ICRC, Merida, Mexico,
200
Strength of forelimb lateralization predicts motor errors in an insect
Lateralized behaviours are widespread in both vertebrates and invertebrates, suggesting that lateralization is advantageous. Yet evidence demonstrating proximate or ultimate advantages remains scarce, particularly in invertebrates or in species with individual-level lateralization. Desert locusts (Schistocerca gregaria) are biased in the forelimb they use to perform targeted reaching across a gap. The forelimb and strength of this bias differed among individuals, indicative of individual-level lateralization. Here we show that strongly biased locusts perform better during gap-crossing, making fewer errors with their preferred forelimb. The number of targeting errors locusts make negatively correlates with the strength of forelimb lateralization. This provides evidence that stronger lateralization confers an advantage in terms of improved motor control in an invertebrate with individual-level lateralization
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