5,390 research outputs found
Ultrasound propagation and binding in solids
Measurement of sound wave velocity and attenuation by the ultrasonic pulse-echo technique are used to obtain insight into the nature of weak interatomic binding forces which are present or develop in certain materials. In particular, anomalies are found in both the elastic and anelastic properties in the vicinity of the martensitic phase transformations which occur in TiNi andIndium-thallium alloys. Considerable differences found between the elastic moduli of the two phases of TiNi are shown to arise Mainly from a variation in the free carrier density. Previously reported elastic constant data of some fcc indium-thallium alloysAre complemented by the present results and an overall picture of the compositional dependence of the elastic properties of theseAlloys in both the tetragonal and cubic phases are provided. Zirconia can be forced into a cubic structure by the addition of more than 7 mole % yttria: elastic constant data of two zirconia-yttria solid solutions, technologically important materials, provides a basis for the discussion of the stability of the cubic phase. Finally, on the basis of an evaluation of the elastic moduliof arsenic, a pronounced layer-type crystal, the ultrasonic wave propagation characteristics in this material are extensively compared and contrasted with those of the other two rhombohedral elemental semimetals antimony and bismuth, neither of which are themselves layer-like. The elastic wave propagation in antimony and bismuth is shown to differ not only in degree but also in kind from that in arsenic which exhibits the characteristics expected for a layer-like crystal. The weak binding forces in each of the materials studied are shown to play a dominant role in their elastic behaviour
The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds
Given the rarity of young O star candidates, compact HII regions embedded in
dense molecular cores continue to serve as potential sites to peer into the
details of high-mass star formation. To uncover the ionizing sources of the
most luminous and compact HII regions embedded in the RCW106 and RCW122 giant
molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus
providing an opportunity to examine spatial scales of a few hundred to a
thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra
(R=350), including the fine structure lines [ArIII] and [NeII], were obtained
for four luminous compact HII regions, embedded inside the dense cores within
the RCW106 and RCW122 molecular cloud complexes. At this resolution, these
targets reveal point-like sources surrounded by nebulosity of different
morphologies, uncovering details at spatial dimensions of <1000AU. The
point-like sources display [ArIII] and [NeII] lines - the ratios of which are
used to estimate the temperature of the embedded sources. The derived
temperatures are indicative of mid-late O type objects for all the sources with
[ArIII] emission. Previously known characteristics of these targets from the
literature, including evidence of disk or accretion suggest that the identified
sources may grow more to become early-type O stars by the end of the star
formation process
A perturbation density functional theory for the competition between inter and intramolecular association
Using the framework of Wertheim's thermodynamic perturbation theory we
develop the first density functional theory which accounts for intramolecular
association in chain molecules. To test the theory new Monte Carlo simulations
are performed at a fluid solid interface for a 4 segment chain which can both
intra and intermolecularly associate. The theory and simulation results are
found to be in excellent agreement. It is shown that the inclusion of
intramolecular association can have profound effects on interfacial properties
such as interfacial tension and the partition coefficient
Effects of the Cosmos 1129 Soviet paste diet on body composition in the growing rat
Six Simonsen albino rats (45 days of age) were placed on a regimen of 40 g/day the semipurified Soviet paste diet used in the 18.5 day Cosmos 1129 spacecraft was to support the rats for various experiments on the physiological effects of weightlessness. The animals were maintained on the Soviet paste diet for 35 days, metabolic rate was measured and body composition was determined by direct analysis. The results were compared with a control group of rates of the same age, which had been kept on a standard commercial grain diet during the same period of time
3-Nets realizing a group in a projective plane
In a projective plane PG(2,K) defined over an algebraically closed field
K of characteristic 0, we give a complete classification of 3-nets realizing a finite
group. An infinite family, due to Yuzvinsky (Compos. Math. 140:1614–1624, 2004),
arises from plane cubics and comprises 3-nets realizing cyclic and direct products of
two cyclic groups. Another known infinite family, due to Pereira and Yuzvinsky (Adv.
Math. 219:672–688, 2008), comprises 3-nets realizing dihedral groups.We prove that
there is no further infinite family. Urzúa’s 3-nets (Adv. Geom. 10:287–310, 2010)
realizing the quaternion group of order 8 are the unique sporadic examples.
If p is larger than the order of the group, the above classification holds in characteristic
p >0 apart from three possible exceptions Alt4, Sym4, and Alt5.
Motivation for the study of finite 3-nets in the complex plane comes from the study
of complex line arrangements and from resonance theory; see (Falk and Yuzvinsky
in Compos. Math. 143:1069–1088, 2007; Miguel and Buzunáriz in Graphs Comb.
25:469–488, 2009; Pereira and Yuzvinsky in Adv. Math. 219:672–688, 2008; Yuzvinsky in Compos. Math. 140:1614–1624, 2004; Yuzvinsky in Proc. Am. Math. Soc.
137:1641–1648, 2009
Glitches in Southern Pulsars
Timing observations of 40 mostly young pulsars using the ATNF Parkes radio
telescope between 1990 January and 1998 December are reported. In total, 20
previously unreported glitches and ten other glitches were detected in 11
pulsars. These included 12 glitches in PSR J13416220, corresponding to a
glitch rate of 1.5 glitches per year. We also detected the largest known
glitch, in PSR J16145047, with
where is the pulse frequency. Glitch parameters were determined
both by extrapolating timing solutions to inter-glitch intervals and by
phase-coherent timing fits across the glitch(es). Analysis of glitch
parameters, both from this work and from previously published results, shows
that most glitches have a fractional amplitude of between
and . There is no consistent relationship between glitch
amplitude and the time since the previous glitch or the time to the following
glitch, either for the ensemble or for individual pulsars. As previously
recognised, the largest glitch activity is seen in pulsars with ages of order
10 years, but for about 30 per cent of such pulsars, no glitches were
detected in the 8-year data span. There is some evidence for a new type of
timing irregularity in which there is a significant increase in pulse frequency
over a few days, accompanied by a decrease in the magnitude of the slowdown
rate. Fits of an exponential recovery to post-glitch data show that for most
older pulsars, only a small fraction of the glitch decays. In some younger
pulsars, a large fraction of the glitch decays, but in others, there is very
little decay.Comment: 19 pages, 20 figures. Accepted for publication in MNRA
Body composition data from the rat subjects of Cosmos 1129 experiment K-316
The effects of 18.5 days of weightlessness on the body composition of young, growing, male laboratory rats were examined. Three groups of 5 rats each were examined. It is indicated that exposure of young, growing, male rats to 18.5 days of weightlessness produces: (1) no effect on the quantity of fat stored by the body; (2) a slight reduction in the quantity of fat free tissue laid down by the body; (3) a small reduction in the fraction of water contained by the fat free body mass; (4) a similar reduction in the fraction of water contained by the fat free skin and fat free carcass; (5) a shift in relative distribution of the total body water from skin to viscera; (6) a diminution in the fraction of extracellular water contained by the fat free body; (7) no effect on the fraction of total skeletal musculature contained by the fat free body, as indicated by body creatine content; (8) a sizeable reduction in the fraction of bone mineral contained by the fat free body, as calculated from body calcium content. The nature of the physiological changes induced by unloading from Earth gravity in the mammalian organism are illustrated
Strengthening coherence between social protection and productive interventions – The case of Lesotho
Social protection has been recognized as a key strategy to address poverty, vulnerability and social exclusion in Lesotho. As a result, the Government, with support from UNICEF and the European Union, developed the Child Grants Programme (CGP), which provides unconditional cash transfers to poor and vulnerable households registered in the National Information System for Social Assistance (NISSA). The quantitative impact evaluation presented in this report seeks to document the welfare and economic impacts of CGP and SPRINGS on direct beneficiaries and assess whether combining the cash transfers with a package of rural development interventions can create positive synergies at both individual and household level, especially in relation to income generating activities and nutrition. This paper is being published in the context of a partnership between FAO, IFAD and the Universidad de los Andes (UNIANDES) and its Centro de Estudios en Desarrollo Económico (CEDE) based in Bogotá, Colombia
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