2,759 research outputs found
A zinc transporter gene required for development of the nervous system.
The essentiality of zinc for normal brain development is well established. It has been suggested that primary and secondary zinc deficiencies can contribute to the occurrence of numerous human birth defects, including many involving the central nervous system. In a recent study, we searched for zinc transporter genes that were critical for neurodevelopment. We confirmed that ZIP12 is a zinc transporter encoded by the gene slc39a12 that is highly expressed in the central nervous systems of human, mouse, and frog (Xenopus tropicalis).Using loss-of-function methods, we determined that ZIP12 is required for neuronal differentiation and neurite outgrowth and necessary for neurulation and embryonic viability. These results highlight an essential need for zinc regulation during embryogenesis and nervous system development. We suggest that slc39a12 is a candidate gene for inherited neurodevelopmental defects in humans
The relation between the clay content of certain physical properties of a soil
A simple experimental method has been described for measuring certain physical constants of soil, using small brass boxes into which soil passing a sieve of 100 meshes to the inch has been packed by hand. The quantities determined are:
(1) The weight of unit volume (100 c.c.s.) of air-dry soil, or the apparent specific gravity.
(2) Amount of water taken up by unit weight of soil.
(3) Pore space.
(4) Specific gravity of the soil.
(5) The volume expansion of unit volume (100 c.c.) of soil when saturated.
The results for one soil only are given, and discussed, to illustrate the method. With the co-operation of the Science Masters Association it is being applied to a number of soils by various schools.
The particular soil used was obtained in six depths as follows: 0–6–12″, 12–18″, 18–24″, 2–3′, 3–4′, and the above constants were determined on each depth. It was shown that (1) and (4) varied inversely with the percentage of clay in the soil, while (2), (3), and (5) varied directly with the clay percentage. The effect on the constants of the larger quantities of organic, matter present in the top two layers of soil was, weight for weight, approximately equal to that of the clay, except in the volume expansion results where the effect if any was within experimental error.
It is possible that the fraction fine silt II, whose upper limit of diameter is ·005 mm., has similar effects to the clay fraction
Radiation of Neutron Stars Produced by Superfluid Core
We find that neutron star interior is transparent for collisionless electron
sound, the same way as it is transparent for neutrinos. In the presence of
magnetic field the electron sound is coupled with electromagnetic radiation and
form the fast magnetosonic wave. We find that electron sound is generated by
superfluid vortices in the stellar core. Thermally excited helical vortex waves
produce fast magnetosonic waves in the stellar crust which propagate toward the
surface and transform into outgoing electromagnetic radiation. The vortex
radiation has the spectral index -0.45 and can explain nonthermal radiation of
middle-aged pulsars observed in the infrared, optical and hard X-ray bands. The
radiation is produced in the stellar interior which allows direct determination
of the core temperature. Comparing the theory with available spectra
observations we find that the core temperature of the Vela pulsar is T=8*10^8K,
while the core temperature of PSR B0656+14 and Geminga exceeds 2*10^8K. This is
the first measurement of the temperature of a neutron star core. The
temperature estimate rules out equation of states incorporating Bose
condensations of pions or kaons and quark matter in these objects. Based on the
temperature estimate and cooling models we determine the critical temperature
of triplet neutron superfluidity in the Vela core Tc=(7.5\pm 1.5)*10^9K which
agrees well with recent data on behavior of nucleon interactions at high
energies. Another finding is that in the middle aged neutron stars the vortex
radiation, rather then thermal conductivity, is the main mechanism of heat
transfer from the stellar core to the surface. Electron sound opens a
perspective of direct spectroscopic study of superdense matter in the neutron
star interiors.Comment: 43 pages, 7 figures, to appear in Astrophysical Journa
Evidence for the Gompertz Curve in the Income Distribution of Brazil 1978-2005
This work presents an empirical study of the evolution of the personal income
distribution in Brazil. Yearly samples available from 1978 to 2005 were studied
and evidence was found that the complementary cumulative distribution of
personal income for 99% of the economically less favorable population is well
represented by a Gompertz curve of the form , where
is the normalized individual income. The complementary cumulative
distribution of the remaining 1% richest part of the population is well
represented by a Pareto power law distribution . This
result means that similarly to other countries, Brazil's income distribution is
characterized by a well defined two class system. The parameters , ,
, were determined by a mixture of boundary conditions,
normalization and fitting methods for every year in the time span of this
study. Since the Gompertz curve is characteristic of growth models, its
presence here suggests that these patterns in income distribution could be a
consequence of the growth dynamics of the underlying economic system. In
addition, we found out that the percentage share of both the Gompertzian and
Paretian components relative to the total income shows an approximate cycling
pattern with periods of about 4 years and whose maximum and minimum peaks in
each component alternate at about every 2 years. This finding suggests that the
growth dynamics of Brazil's economic system might possibly follow a
Goodwin-type class model dynamics based on the application of the
Lotka-Volterra equation to economic growth and cycle.Comment: 22 pages, 15 figures, 4 tables. LaTeX. Accepted for publication in
"The European Physical Journal B
Trust, Familiarity, Optimism, and Pleasure: Australian Gay Men Accounting for Inconsistent HIV Prevention Practices in the PrEP Era
Despite an increase in the range of effective HIV risk reduction strategies that are available, some gay and bisexual men (GBM) do not use any of them consistently. Understanding why GBM do not always use a protective strategy may help develop more effective responses. Semi-structured interviews with 24 sexually active GBM in Sydney, Australia were conducted and analyzed using thematic analysis. The main characteristics of encounters featuring little or no use of HIV risk reduction strategies were familiarity and trust with partners, pleasure and intoxication, expectations that partners were using HIV pre-exposure prophylaxis or treatment as prevention, and in some cases feelings of inevitability about acquiring HIV. An increase in pleasure and a reduction in anxiety about sex were noted by some GBM who had commenced PrEP. Encouraging GBM to adopt a strategy such as PrEP and to use it consistently may be easier by emphasizing benefits to mental health and the quality of sex and intimacy it can offer. However, even with the increased availability of effective biomedical HIV risk reduction strategies, not all GBM are able to consistently manage HIV risk and some continue to hold optimistic and potentially inaccurate beliefs about sexual partners that may increase HIV risk
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