10,612 research outputs found
Optimal error bound and Fourier regularization for identifying an unknown source in the heat equation
AbstractIn this paper we investigate a problem of the identification of an unknown source from one supplementary temperature measurement at a given instant of time for the transient heat equation. Under an a priori condition we answer the question concerning the best possible accuracy for the problem. The Fourier regularization method is utilized for solving the problem, and its convergent rate is analyzed. Numerical results are presented to illustrate the accuracy and efficiency of the method
A statistical method (cross-validation) for bone loss region detection after spaceflight.
Astronauts experience bone loss after the long spaceflight missions. Identifying specific regions that undergo the greatest losses (e.g. the proximal femur) could reveal information about the processes of bone loss in disuse and disease. Methods for detecting such regions, however, remains an open problem. This paper focuses on statistical methods to detect such regions. We perform statistical parametric mapping to get t-maps of changes in images, and propose a new cross-validation method to select an optimum suprathreshold for forming clusters of pixels. Once these candidate clusters are formed, we use permutation testing of longitudinal labels to derive significant changes
Spatial Locality of Galaxy Correlation Function in Phase Space: Samples from the 2MASS Extended Source Catalog
We analyze the statistical properties and dynamical implications of galaxy
distributions in phase space for samples selected from the 2MASS Extended
Source Catalog. The galaxy distribution is decomposed into modes which describe the number density perturbations of galaxies in phase
space cell given by scale band to and spatial
range to . In the nonlinear regime,
is highly non-Gaussian. We find, however, that the
correlations between and are always
very weak if the spatial ranges (, ) and
(, ) don't overlap. This feature is due to
the fact that the spatial locality of the initial perturbations is memorized
during hierarchical clustering. The highly spatial locality of the 2MASS galaxy
correlations is a strong evidence for the initial perturbations of the cosmic
mass field being spatially localized, and therefore, consistent with a Gaussian
initial perturbations on scales as small as about 0.1 h Mpc. Moreover,
the 2MASS galaxy spatial locality indicates that the relationship between
density perturbations of galaxies and the underlying dark matter should be
localized in phase space. That is, for a structure consisting of perturbations
on scales from to , the nonlocal range in the relation
between galaxies and dark matter should {\it not} be larger than . The stochasticity and nonlocality of the bias
relation between galaxies and dark matter fields should be no more than the
allowed range given by the uncertainty relation .Comment: 27 pages, 9 figures, accepted by Ap
Blimp1 Expression Predicts Embryonic Stem Cell Development InĀ Vitro
SummaryDespite recent critical insights into the pluripotent state of embryonic stem cells (ESCs), there is little agreement over the inaugural and subsequent steps leading to its generation [1ā4]. Here we show that inner cell mass (ICM)-generated cells expressing Blimp1, a key transcriptional repressor of the somatic program during germ cell specification [5, 6], emerge on day 2 of blastocyst culture. Single-cell gene expression profiling indicated that many of these Blimp1-positive cells coexpress other genes typically associated with early germ cell specification. When genetically traced inĀ vitro, these cells acquired properties normally associated with primordial germ cells. Importantly, fate-mapping experiments revealed that ESCs commonly arise from Blimp1-positive precursors; indeed, prospective sorting of such cells from ICM outgrowths increased the rate of ESC derivation more than 9-fold. Finally, using genetic ablation or distinct small molecules [7, 8], we show that epiblast cells can become ESCs without first acquiring Blimp1 positivity. Our findings suggest that the germ cell-like state is facultative for the stabilization of pluripotency inĀ vitro. Thus, the association of Blimp1 expression with ESC development furthers understanding of how the pluripotent state of these cells is established inĀ vitro and suggests a means to enhance the generation of new stem cell lines from blastocysts
Potential protective role of hydrogen against cisplatininduced side effects during chemotherapy: A mini-review of a novel hypothesis for antagonism of hydrogen
Purpose: To review the potential protective role of hydrogen against cisplatin-induced side effects during chemotherapy.Methods: We searched PubMed and SCOPUS using the following keywords and combinations in titles, keywords, abstracts and full texts: cisplatin; side effects; chemotherapy; tumor; toxicity; hydrogen; reactive oxidative species; and ischemic reperfusion.Results: The pathogenesis of cisplatin-induced side effects is suggested based on the increased level of reactive oxidative species (ROS). Cisplatin induces ROS-dependent platelet apoptosis via the extracellular signal-regulated kinase (ERK) signaling pathway, which might have contributed to cisplatininduced hematotoxicity, and in particular, thrombocytopenia. Molecular hydrogen has been shown to have therapeutic effects against damage to various organs (especially kidney, brain and liver) caused by ischemic reperfusion (IR) through selective elimination of the most cytotoxic ROS hydrogen radicals without affecting other types of ROS involved in signal transduction in vitro and in vivo.Conclusion: Hydrogen may not only alleviate hematotoxicity in patients with hemorrhagic tendencies during cisplatin-based chemotherapy, but also has a potential protective effect against other side effects induced by cisplatin.Keywords: Reactive oxygen species, Hydrogen radicals, Cisplatin, Hepatotoxicity, Chemotherapy, Side effects, Antagonis
Log-Poisson Hierarchical Clustering of Cosmic Neutral Hydrogen and Ly-alpha Transmitted Flux of QSO Absorption Spectrum
we study, in this paper, the non-Gaussian features of the mass density field
of neutral hydrogen fluid and the Ly-alpha transmitted flux of QSO absorption
spectrum from the point-of-view of self-similar log-Poisson hierarchy. It has
been shown recently that, in the scale range from the onset of nonlinear
evolution to dissipation, the velocity and mass density fields of cosmic baryon
fluid are extremely well described by the She-Leveque's scaling formula, which
is due to the log-Poisson hierarchical cascade. Since the mass density ratio
between ionized hydrogen to total hydrogen is not uniform in space, the mass
density field of neutral hydrogen component is not given by a similar mapping
of total baryon fluid. Nevertheless, we show, with hydrodynamic simulation
samples of the concordance CDM universe, that the mass density field
of neutral hydrogen, is also well described by the log-Poisson hierarchy. We
then investigate the field of Ly transmitted flux of QSO absorption
spectrum. Due to redshift distortion, Ly transmitted flux fluctuations
are no longer to show all features of the log-Poisson hierarchy. However, some
non-Gaussian features predicted by the log-Poisson hierarchy are not affected
by the redshift distortion. We test these predictions with the high resolution
and high S/N data of quasars Ly absorption spectra. All results given
by real data, including -hierarchy, high order moments and scale-scale
correlation, are found to be well consistent with the log-Poisson hierarchy. We
compare the log-Poisson hierarchy with the popular log-normal model of the
Ly transmitted flux. The later is found to yield too strong
non-Gaussianity at high orders, while the log-Poisson hierarchy is in agreement
with observed data.Comment: 24 pages, 9 figures, accepted by Ap
Time-Selective RNN for Device-Free Multi-Room Human Presence Detection Using WiFi CSI
Human presence detection is a crucial technology for various applications,
including home automation, security, and healthcare. While camera-based systems
have traditionally been used for this purpose, they raise privacy concerns. To
address this issue, recent research has explored the use of channel state
information (CSI) approaches that can be extracted from commercial WiFi access
points (APs) and provide detailed channel characteristics. In this thesis, we
propose a device-free human presence detection system for multi-room scenarios
using a time-selective conditional dual feature extract recurrent Network
(TCD-FERN). Our system is designed to capture significant time features with
the condition on current human features using a dynamic and static (DaS) data
preprocessing technique to extract moving and spatial features of people and
differentiate between line-of-sight (LoS) path blocking and non-blocking cases.
To mitigate the feature attenuation problem caused by room partitions, we
employ a voting scheme. We conduct evaluation and real-time experiments to
demonstrate that our proposed TCD-FERN system can achieve human presence
detection for multi-room scenarios using fewer commodity WiFi APs
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