796 research outputs found
Dual effect of CTCF loss on neuroprogenitor differentiation and survival
An increasing number of proteins involved in genome organization have been implicated in neurodevelopmental disorders, highlighting the importance of chromatin architecture in the developing CNS. The CCCTC-binding factor (CTCF) is a zinc finger DNA binding protein involved in higher-order chromatin organization, and mutations in the human CTCF gene cause an intellectual disability syndrome associated with microcephaly. However, information on CTCF function in vivo in the developing brain is lacking. To address this gap, we conditionally inactivated the Ctcf gene at early stages of mouse brain development. Cre-mediated Ctcf deletion in the telencephalon and anterior retina at embryonic day 8.5 triggered upregulation of the p53 effector PUMA (p53 upregulated modulator of apoptosis), resulting in massive apoptosis and profound ablation of telencephalic structures. Inactivation of Ctcf several days later at E11 also resulted in PUMA upregulation and increased apoptotic cell death, and the Ctcf-null forebrain was hypocellular and disorganized at birth. Although deletion of both Ctcf and Puma in the embryonic brain efficiently rescued Ctcf-null progenitor cell apoptosis, it failed to improve neonatal hypocellularity due to decreased proliferative capacity of rescued apical and outer radial glia progenitor cells. This was exacerbated by an independent effect of CTCF loss that resulted in depletion of the progenitor pool due to premature neurogenesis earlier in development. Our findings demonstrate that CTCF activities are required for two distinct events in early cortex formation: first, to correctly regulate the balance between neuroprogenitor cell proliferation and differentiation, and second, for the survival of neuroprogenitor cells, providing new clues regarding the contributions of CTCF in microcephaly/intellectual disability syndrome pathologies
AMBIVALENT IMPLICATIONS OF HEALTH CARE INFORMATION SYSTEMS: A STUDY IN THE BRAZILIAN PUBLIC HEALTH CARE SYSTEM
This article evaluates social implications of the ""SIGA"" Health Care Information System (HIS) in a public health care organization in the city of Sao Paulo. The evaluation was performed by means of an in-depth case study with patients and staff of a public health care organization, using qualitative and quantitative data. On the one hand, the system had consequences perceived as positive such as improved convenience and democratization of specialized treatment for patients and improvements in work organization. On the other hand, negative outcomes were reported, like difficulties faced by employees due to little familiarity with IT and an increase in the time needed to schedule appointments. Results show the ambiguity of the implications of HIS in developing countries, emphasizing the need for a more nuanced view of the evaluation of failures and successes and the importance of social contextual factors
Dynamic screening and collective excitation of an electron gas under intense terahertz radiation
A limit model for thermoelectric equations
We analyze the asymptotic behavior corresponding to the arbitrary high
conductivity of the heat in the thermoelectric devices. This work deals with a
steady-state multidimensional thermistor problem, considering the Joule effect
and both spatial and temperature dependent transport coefficients under some
real boundary conditions in accordance with the Seebeck-Peltier-Thomson
cross-effects. Our first purpose is that the existence of a weak solution holds
true under minimal assumptions on the data, as in particular nonsmooth domains.
Two existence results are studied under different assumptions on the electrical
conductivity. Their proofs are based on a fixed point argument, compactness
methods, and existence and regularity theory for elliptic scalar equations. The
second purpose is to show the existence of a limit model illustrating the
asymptotic situation.Comment: 20 page
Doping effect on the anomalous behavior of the Hall effect in electron-doped superconductor NdCeCuO
Transport properties of NdCeCuO single crystal films
are investigated in magnetic fields up to 9T at =(0.4-4.2)K. An analysis
of normal state (at ) Hall coefficient dependence on Ce
doping takes us to a conclusion about the existence both of electron-like and
hole-like contributions to transport in nominally electron-doped system. In
accordance with (x) analysis an anomalous sign reversal of Hall effect
in mixed state at may be ascribed to a flux-flow regime for two
types of carriers with opposite charges.Comment: 14 pages, 5 figure
Study of Bs-> \phi l^+ l^-$ Decay in a Single Universal Extra Dimension
Utilizing form factors calculated within the light-cone sum rules, we have
evaluated the decay branching ratios of and in a single universal extra dimension model (UED), which is
viewed as one of the alternative theories beyond the standard model (SM). For
the decay , the dilepton invariant mass spectra, the
forward-backward asymmetry, and double lepton polarization are also calculated.
For each case, we compared the obtained results with predictions of the SM. In
lower values of the compactification factor 1/R, the only parameter in this
model, we see the considerable discrepancy between the UED and SM models.
However, when 1/R increases, the results of UED tend to diminish and at , two models have approximately the same predictions.
Compared with data from CDF of , the 1/R tends to be
larger than . We also note that the zero crossing point of
the forward-backward asymmetry is become smaller, which will be an important
plat to prob the contribution from the extra dimension model. The results
obtained in this work will be very useful in searching new physics beyond SM.
Moreover, the order of magnitude for branching ratios shows a possibility to
study these channels at the Large Hadron Collider (LHC), CDF and the future
super-B factory.Comment: 13 pages, 16 figure
Charmless Exclusive Baryonic B Decays
We present a systematical study of two-body and three-body charmless baryonic
B decays. Branching ratios for two-body modes are in general very small,
typically less than , except that \B(B^-\to p \bar\Delta^{--})\sim
1\times 10^{-6}. In general, due to
the large coupling constant for . For three-body modes we
focus on octet baryon final states. The leading three-dominated modes are with a branching ratio of
order for and
for . The penguin-dominated decays with strangeness
in the meson, e.g., and , have appreciable rates and the mass
spectrum peaks at low mass. The penguin-dominated modes containing a strange
baryon, e.g., , have
branching ratios of order . In contrast, the decay
rate of is smaller. We explain why some of
charmless three-body final states in which baryon-antibaryon pair production is
accompanied by a meson have a larger rate than their two-body counterparts:
either the pole diagrams for the former have an anti-triplet bottom baryon
intermediate state, which has a large coupling to the meson and the
nucleon, or they are dominated by the factorizable external -emission
process.Comment: 46 pages and 3 figures, to appear in Phys. Rev. D. Major changes are:
(i) Calculations of two-body baryonic B decays involving a Delta resonance
are modified, and (ii) Penguin-dominated modes B-> Sigma+N(bar)+p are
discusse
Markov Properties of Electrical Discharge Current Fluctuations in Plasma
Using the Markovian method, we study the stochastic nature of electrical
discharge current fluctuations in the Helium plasma. Sinusoidal trends are
extracted from the data set by the Fourier-Detrended Fluctuation analysis and
consequently cleaned data is retrieved. We determine the Markov time scale of
the detrended data set by using likelihood analysis. We also estimate the
Kramers-Moyal's coefficients of the discharge current fluctuations and derive
the corresponding Fokker-Planck equation. In addition, the obtained Langevin
equation enables us to reconstruct discharge time series with similar
statistical properties compared with the observed in the experiment. We also
provide an exact decomposition of temporal correlation function by using
Kramers-Moyal's coefficients. We show that for the stationary time series, the
two point temporal correlation function has an exponential decaying behavior
with a characteristic correlation time scale. Our results confirm that, there
is no definite relation between correlation and Markov time scales. However
both of them behave as monotonic increasing function of discharge current
intensity. Finally to complete our analysis, the multifractal behavior of
reconstructed time series using its Keramers-Moyal's coefficients and original
data set are investigated. Extended self similarity analysis demonstrates that
fluctuations in our experimental setup deviates from Kolmogorov (K41) theory
for fully developed turbulence regime.Comment: 25 pages, 9 figures and 4 tables. V3: Added comments, references,
figures and major correction
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Global variation in the fraction of leaf nitrogen allocated to photosynthesis
Plants invest a considerable amount of leaf nitrogen in the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), forming a strong coupling of nitrogen and photosynthetic capacity. Variability in the nitrogen-photosynthesis relationship indicates different nitrogen use strategies of plants (i.e., the fraction nitrogen allocated to RuBisCO; fLNR), however, the reason for this remains unclear as widely different nitrogen use strategies are adopted in photosynthesis models. Here, we use a comprehensive database of in situ observations, a remote sensing product of leaf chlorophyll and ancillary climate and soil data, to examine the global distribution in fLNR using a random forest model. We find global fLNR is 18.2 ± 6.2%, with its variation largely driven by negative dependence on leaf mass per area and positive dependence on leaf phosphorus. Some climate and soil factors (i.e., light, atmospheric dryness, soil pH, and sand) have considerable positive influences on fLNR regionally. This study provides insight into the nitrogen-photosynthesis relationship of plants globally and an improved understanding of the global distribution of photosynthetic potential
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