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A kinetic model of the transformation of a micropatterned amorphous precursor into a porous single crystal
Biogenic single crystals with complex shapes are believed to be generated by the crystallisation of an amorphous precursor. Recent biomimetic experiments on the crystallisation of calcite via amorphous-to-crystalline transition point to the fact that the transformation kinetics may be controlled by the micropattern and the macroscopic shape of the amorphous precursor phase. Here we analyse a simple kinetic model, based on thermodynamic considerations, showing that the presence of cavities in the micropatterned precursor phase might interfere with the transformation process and control its kinetics. The size of the cavities couples to the total surface energy and, hence, to crystal nucleation and growth, while the spacing of the cavities, as compared to the typical diffusion path, controls the possible nucleation of competing crystals.Chemistry and Chemical Biolog
Mechanical model for a collagen fibril pair in extracellular matrix
In this paper, we model the mechanics of a collagen pair in the connective
tissue extracellular matrix that exists in abundance throughout animals,
including the human body. This connective tissue comprises repeated units of
two main structures, namely collagens as well as axial, parallel and regular
anionic glycosaminoglycan between collagens. The collagen fibril can be modeled
by Hooke's law whereas anionic glycosaminoglycan behaves more like a
rubber-band rod and as such can be better modeled by the worm-like chain model.
While both computer simulations and continuum mechanics models have been
investigated the behavior of this connective tissue typically, authors either
assume a simple form of the molecular potential energy or entirely ignore the
microscopic structure of the connective tissue. Here, we apply basic physical
methodologies and simple applied mathematical modeling techniques to describe
the collagen pair quantitatively. We find that the growth of fibrils is
intimately related to the maximum length of the anionic glycosaminoglycan and
the relative displacement of two adjacent fibrils, which in return is closely
related to the effectiveness of anionic glycosaminoglycan in transmitting
forces between fibrils. These reveal the importance of the anionic
glycosaminoglycan in maintaining the structural shape of the connective tissue
extracellular matrix and eventually the shape modulus of human tissues. We also
find that some macroscopic properties, like the maximum molecular energy and
the breaking fraction of the collagen, are also related to the microscopic
characteristics of the anionic glycosaminoglycan
Measurement of the Neutron Cross Section on Argon Between 95 and 720 MeV
We report an extended measurement of the neutron cross section on argon in
the energy range of 95-720 MeV. The measurement was obtained with a 4.3-hour
exposure of the Mini-CAPTAIN detector to the WNR/LANSCE beam at LANL. Compared
to an earlier analysis of the same data, this extended analysis includes a
reassessment of systematic uncertainties, in particular related to unused wires
in the upstream part of the detector. Using this information we doubled the
fiducial volume in the experiment and increased the statistics by a factor of
2.4. We also shifted the analysis from energy bins to time-of-flight bins. This
change reduced the overall considered energy range, but improved the
understanding of the energy spectrum of incoming neutrons in each bin. Overall,
the new measurements are extracted from a fit to the attenuation of the neutron
flux in five time-of-flight regions: 140 ns - 180 ns, 120 ns - 140 ns, 112 ns -
120 ns, 104 ns - 112 ns, 96 ns - 104 ns. The final cross sections are given for
the flux-averaged energy in each time-of-flight bin:
(syst) b,
(syst) b,
(syst) b,
(syst) b,
(syst) b.Comment: 15 pages, 7 tables, 11 figures. Prepared for submission to PR
First Measurement of the Total Neutron Cross Section on Argon Between 100 and 800 MeV
We report the first measurement of the neutron cross section on argon in the
energy range of 100-800 MeV. The measurement was obtained with a 4.3-hour
exposure of the Mini-CAPTAIN detector to the WNR/LANSCE beam at LANL. The total
cross section is measured from the attenuation coefficient of the neutron flux
as it traverses the liquid argon volume. A set of 2,631 candidate interactions
is divided in bins of the neutron kinetic energy calculated from time-of-flight
measurements. These interactions are reconstructed with custom-made algorithms
specifically designed for the data in a time projection chamber the size of the
Mini-CAPTAIN detector. The energy averaged cross section is . A comparison
of the measured cross section is made to the GEANT4 and FLUKA event generator
packages.Comment: 5 pages, 1 table, 3 figures, submitted to Physical Review Letter
The Mini-CAPTAIN Liquid Argon Time Projection Chamber
This manuscript describes the commissioning of the Mini-CAPTAIN liquid argon
detector in a neutron beam at the Los Alamos Neutron Science Center (LANSCE),
which led to a first measurement of high-energy neutron interactions in argon.
The Mini-CAPTAIN detector consists of a Time Projection Chamber (TPC) with an
accompanying photomultiplier tube (PMT) array sealed inside a
liquid-argon-filled cryostat. The liquid argon is constantly purified and
recirculated in a closed-loop cycle during operation. The specifications and
assembly of the detector subsystems and an overview of their performance in a
neutron beam are reported.Comment: 21 pages, 27 figure
Molecular classification of selective oestrogen receptor modulators on the basis of gene expression profiles of breast cancer cells expressing oestrogen receptor α
The purpose of this study was to classify selective oestrogen receptor modulators based on gene expression profiles produced in breast cancer cells expressing either wtERα or mutant351ERα. In total, 54 microarray experiments were carried out by using a commercially available Atlas cDNA Expression Arrays (Clontech), containing 588 cancer-related genes. Nine sets of data were generated for each cell line following 24âh of treatment: expression data were obtained for cells treated with vehicle EtOH (Control); with 10â9 or 10â8âM oestradiol; with 10â6âM 4-hydroxytamoxifen; with 10â6âM raloxifene; with 10â6âM idoxifene, with 10â6âM EM 652, with 10â6âM GW 7604; with 5Ă10â5âM resveratrol and with 10â6âM ICI 182,780. We developed a new algorithm âExpression Signaturesâ to classify compounds on the basis of differential gene expression profiles. We created dendrograms for each cell line, in which branches represent relationships between compounds. Additionally, clustering analysis was performed using different subsets of genes to assess the robustness of the analysis. In general, only small differences between gene expression profiles treated with compounds were observed with correlation coefficients ranged from 0.83 to 0.98. This observation may be explained by the use of the same cell context for treatments with compounds that essentially belong to the same class of drugs with oestrogen receptors related mechanisms. The most surprising observation was that ICI 182,780 clustered together with oestrodiol and raloxifene for cells expressing wtERα and clustered together with EM 652 for cells expressing mutant351ERα. These data provide a rationale for a more precise and elaborate study in which custom made oligonucleotide arrays can be used with comprehensive sets of genes known to have consensus and putative oestrogen response elements in their promoter regions
The peroxisome: still a mysterious organelle
More than half a century of research on peroxisomes has revealed unique features of this ubiquitous subcellular organelle, which have often been in disagreement with existing dogmas in cell biology. About 50 peroxisomal enzymes have so far been identified, which contribute to several crucial metabolic processes such as ÎČ-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, and render peroxisomes indispensable for human health and development. It became obvious that peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. However, many aspects of peroxisome biology are still mysterious. This review addresses recent exciting discoveries on the biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross talk of peroxisomes with other subcellular compartments. Furthermore, recent advances on the role of peroxisomes in medicine and in the identification of novel peroxisomal proteins are discussed
Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment
The Deep Underground Neutrino Experiment (DUNE) will produce world-leading
neutrino oscillation measurements over the lifetime of the experiment. In this
work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in
the neutrino sector, and to resolve the mass ordering, for exposures of up to
100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed
uncertainties on the flux prediction, the neutrino interaction model, and
detector effects. We demonstrate that DUNE will be able to unambiguously
resolve the neutrino mass ordering at a 3 (5) level, with a 66
(100) kt-MW-yr far detector exposure, and has the ability to make strong
statements at significantly shorter exposures depending on the true value of
other oscillation parameters. We also show that DUNE has the potential to make
a robust measurement of CPV at a 3 level with a 100 kt-MW-yr exposure
for the maximally CP-violating values \delta_{\rm CP}} = \pm\pi/2.
Additionally, the dependence of DUNE's sensitivity on the exposure taken in
neutrino-enhanced and antineutrino-enhanced running is discussed. An equal
fraction of exposure taken in each beam mode is found to be close to optimal
when considered over the entire space of interest
Identification and reconstruction of low-energy electrons in the ProtoDUNE-SP detector
Measurements of electrons from interactions are crucial for the Deep
Underground Neutrino Experiment (DUNE) neutrino oscillation program, as well as
searches for physics beyond the standard model, supernova neutrino detection,
and solar neutrino measurements. This article describes the selection and
reconstruction of low-energy (Michel) electrons in the ProtoDUNE-SP detector.
ProtoDUNE-SP is one of the prototypes for the DUNE far detector, built and
operated at CERN as a charged particle test beam experiment. A sample of
low-energy electrons produced by the decay of cosmic muons is selected with a
purity of 95%. This sample is used to calibrate the low-energy electron energy
scale with two techniques. An electron energy calibration based on a cosmic ray
muon sample uses calibration constants derived from measured and simulated
cosmic ray muon events. Another calibration technique makes use of the
theoretically well-understood Michel electron energy spectrum to convert
reconstructed charge to electron energy. In addition, the effects of detector
response to low-energy electron energy scale and its resolution including
readout electronics threshold effects are quantified. Finally, the relation
between the theoretical and reconstructed low-energy electron energy spectrum
is derived and the energy resolution is characterized. The low-energy electron
selection presented here accounts for about 75% of the total electron deposited
energy. After the addition of lost energy using a Monte Carlo simulation, the
energy resolution improves from about 40% to 25% at 50~MeV. These results are
used to validate the expected capabilities of the DUNE far detector to
reconstruct low-energy electrons.Comment: 19 pages, 10 figure
A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE
This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model
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