46,840 research outputs found
Tropospheric HO2 determination by FAGE
The detection efficiency is greatest at low pressures, where the subsequent removal of the HO product by the NO reagent (via HO + NO + M yields HONO + M) is relatively slow. Moreover, nozzle expansion of the air from ambient to low pressures produces a turbulent zone that assists in mixing the reagent with the sample. If the HO product is observed by laser-excited fluorescence, then the other advantages of low-pressure detection by FAGE (Fluorescence Assay with Gas Expansion) also apply. The FAGE instrumental response was calibrated to external HO2 by observing NO decay in the photolysis of HO-CH2O mixtures and by choosing conditions in which HO2 + NO is the only significant NO destruction path. HO2 was determined in urban air
Stabilization of the p-wave superfluid state in an optical lattice
It is hard to stabilize the p-wave superfluid state of cold atomic gas in
free space due to inelastic collisional losses. We consider the p-wave Feshbach
resonance in an optical lattice, and show that it is possible to have a stable
p-wave superfluid state where the multi-atom collisional loss is suppressed
through the quantum Zeno effect. We derive the effective Hamiltonian for this
system, and calculate its phase diagram in a one-dimensional optical lattice.
The results show rich phase transitions between the p-wave superfluid state and
different types of insulator states induced either by interaction or by
dissipation.Comment: 5 pages, 5 figure
Structural and Physical Properties of CaFe4As3 Single Crystals
We report the synthesis, and structural and physical properties of CaFe4As3
single crystals. Needle-like single crystals of CaFe4As3 were grown out of Sn
flux and the compound adopts an orthorhombic structure as determined by X-ray
diffraction measurements. Electrical, magnetic, and thermal properties indicate
that the system undergoes two successive phase transitions occurring at TN1 ~
90 K and TN2 ~ 26 K. At TN1, electrical resistivities (\rho(b) and \rho(ac))
are enhanced while magnetic susceptibilities (\chi(b) and \chi(ac)) are reduced
in both directions parallel and perpendicular to the b-axis, consistent with
the scenario of antiferromagnetic spin-density-wave formation. At TN2, specific
heat reveals a slope change, and \chi(ac) decreases sharply but \chi(b) has a
clear jump before it decreases again with decreasing temperature. Remarkably,
both \rho(b) and \rho(ac) decrease sharply with thermal hysteresis, indicating
the first-order nature of the phase transition at TN2. At low temperatures,
\rho(b) and \rho(ac) can be described by {\rho} = {\rho}0 + AT^\alpha ({\rho}0,
A, and {\alpha} are constants). Interestingly, these constants vary with
applied magnetic field. The ground state of CaFe4As3 is discussed.Comment: 15 pages, 8 figures, Submitted to Physical Review
MOLECULAR ANALYSIS OF THE CAMP- RESPONSE ELEMENT [CRE] ELEMENTS IN THE PROMOTER REGION AND EXON 1 OF THE SURVIVAL OF MOTOR NEURON 2 [SMN2] GENE IN MALAYSIAN SPINAL MUSCULAR ATROPHY PATIENTS; TO ELUCIDATE THEIR ROLE IN CIRCUMSCRIBING THE CLINICAL SEVERITY
Objective: In the Spinal muscular atrophy [SMA] genes [SMN1 and SMN2 genes]; the CRE-II elements at -400 bp in the promoter region of the SMN genes and CRE-I element at +108 bp in the exon 1 of the SMN genes, are reported to have a role in c-AMP induce expression of the SMN genes through its binding affinity to CREB-1. This study was designed to determine the role of CRE sites in the circumscribing the clinical severity of SMA.
Methods: Direct sequencing was performed for the PCR products of the promoter regions of the SMA patients with homozygous deletion of SMN1, different copy number of SMN2 and NAIP non deletion.
Results: No variation among the CRE-I and CRE-II sites was found in all the clinical types as compare to normal healthy control showing no role of CRE sites in circumscribing the clinical severity of SMA.
Conclusion: There was no sequence variation found in the CRE binding sites in the three different clinical types of SMA reflecting no role of CRE binding sites in circumscribing the clinical severity of SMA
Chiral Symmetry Breaking with Scalar Confinement
Spontaneous chiral symmetry breaking is accepted to occur in low energy
hadronic physics, resulting in the several successful theorems of PCAC. On the
other hand scalar confinement is suggested both by the spectroscopy of hadrons
and by the string picture of confinement. However these two evidences are
apparently conflicting, because chiral symmetry breaking requires a chiral
invariant coupling to the quarks, say a vector coupling like in QCD. Here we
reformulate the coupling of the quarks to the string, and we are able to comply
with chiral symmetry breaking, using scalar confinement. The results are quite
encouraging.Comment: 4 pages, 5 figures, contribution to the XXXVIIIth Rencontres de
Moriond QCD and High Energy Hadronic Interaction
Newtonian flow inside carbon nanotube with permeable boundary taking into account van der Waals forces
Here, water flow inside large radii semi-infinite carbon nanotubes is investigated. Permeable wall taking into account the molecular interactions between water and a nanotube, and the slip boundary condition will be considered. Furthermore, interactions among molecules are approximated by the continuum approximation. Incompressible and Newtonian fluid is assumed, and the Navier-Stokes equations, after certain assumptions, transformations and derivations, can be reduced into two first integral equations. In conjunction with the asymptotic expansion technique, we are able to derive the radial and axial velocities analytically, capturing the effect of the water leakage, where both mild and exceptionally large leakages will be considered. The radial velocity obeys the prescribed boundary condition at the (im)permeable wall. Through the mean of the radial forces, the sufficiently large leakages will enhance the radial velocity at the center of the tube. On the other hand, unlike the classical laminar flow, the axial velocity attains its maximum at the wall due to the coupling effect with the radial forces as water is being pushed into the proximity of the inner wall. In addition, the axial velocity and the flux with the consideration of the suck-in forces, induced by the tubes’ entry turn out to be one order higher than that without the suck-in forces. All the aforementioned considerations might partially resolve the mysteriously high water penetration through nanotubes. Axial velocity also drops with the tube’s length when the water leakage is permitted and the suck-in forces will ease the decline rate of the axial velocity. The present mathematical framework can be directly employed into the water flow inside other porous nano-materials, where large water leakage is permitted and therefore are of huge practical impact on ultra-filtration and environmental protection
Entropy for Asymptotically AdS_3 Black Holes
We propose that Strominger's method to derive the BTZ black hole entropy is
in fact applicable to other asymptotically AdS_3 black holes and gives the
correct functional form of entropies. We discuss various solutions in the
Einstein-Maxwell theory, dilaton gravity, Einstein-scalar theories, and
Einstein-Maxwell-dilaton theory. In some cases, solutions approach AdS_3
asymptotically, but their entropies do not have the form of Cardy's formula.
However, it turns out that they are actually not "asymptotically "
solutions. On the other hand, for truly asymptotically AdS_3 solutions, their
entropies have the form of Cardy's formula. In this sense, all known solutions
are consistent with our proposal.Comment: 21 pages, LaTeX; v2: added discussion for section 3.
Unique gap structure and symmetry of the charge density wave in single-layer VSe
Single layers of transition metal dichalcogenides (TMDCs) are excellent
candidates for electronic applications beyond the graphene platform; many of
them exhibit novel properties including charge density waves (CDWs) and
magnetic ordering. CDWs in these single layers are generally a planar
projection of the corresponding bulk CDWs because of the quasi-two-dimensional
nature of TMDCs; a different CDW symmetry is unexpected. We report herein the
successful creation of pristine single-layer VSe, which shows a () CDW in contrast to the (4 4) CDW for the layers in
bulk VSe. Angle-resolved photoemission spectroscopy (ARPES) from the single
layer shows a sizable () CDW gap of 100 meV at the
zone boundary, a 220 K CDW transition temperature twice the bulk value, and no
ferromagnetic exchange splitting as predicted by theory. This robust CDW with
an exotic broken symmetry as the ground state is explained via a
first-principles analysis. The results illustrate a unique CDW phenomenon in
the two-dimensional limit
Decreasing time consumption of microscopy image segmentation through parallel processing on the GPU
The computational performance of graphical processing units (GPUs) has improved significantly. Achieving speedup factors of more than 50x compared to single-threaded CPU execution are not uncommon due to parallel processing. This makes their use for high throughput microscopy image analysis very appealing. Unfortunately, GPU programming is not straightforward and requires a lot of programming skills and effort. Additionally, the attainable speedup factor is hard to predict, since it depends on the type of algorithm, input data and the way in which the algorithm is implemented. In this paper, we identify the characteristic algorithm and data-dependent properties that significantly relate to the achievable GPU speedup. We find that the overall GPU speedup depends on three major factors: (1) the coarse-grained parallelism of the algorithm, (2) the size of the data and (3) the computation/memory transfer ratio. This is illustrated on two types of well-known segmentation methods that are extensively used in microscopy image analysis: SLIC superpixels and high-level geometric active contours. In particular, we find that our used geometric active contour segmentation algorithm is very suitable for parallel processing, resulting in acceleration factors of 50x for 0.1 megapixel images and 100x for 10 megapixel images
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