37,859 research outputs found
Real photons produced from photoproduction in collisions
We calculate the production of real photons originating from the
photoproduction in relativistic collisions. The
Weizscker-Williams approximation in the photoproduction is
considered. Numerical results agree with the experimental data from
Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC). We find
that the modification of the photoproduction is more prominent in large
transverse momentum region.Comment: 2 figure
Calibration of the Pulsed Electroacoustic Technique in the Presence of Trapped Charge
The influence of pulse voltage on the accuracy of charge density distribution in the pulsed electroacoustic technique (PEA) is discussed. It is shown that significant error can be introduced if a low dc voltage and high pulse voltage are used to calibrate charge density. However, our main focus in the present paper is to deal with one of the practical situations where space charge exists in the material prior to any measurements. The conventional calibration method can no longer be used to calibrate charge density due to the interference by the charge on the electrode induced by space charge. A method has been proposed which is based on two measurements. Firstly, the sample containing charge is measured without any applied voltage. The second measurement is carried out with a small external applied voltage. The applied voltage should be small enough so there is no disturbance of the existing charge in the sample. The difference of the two measurements can be used for calibration. An additional advantage of the proposed method avoids the influence of the pulse voltage on calibration and therefore gives a more accurate representation of space charge. The proposed method has been validated
Spherical to deformed shape transition in the nucleon-pair shell model
A study of the shape transition from spherical to axially deformed nuclei in
the even Ce isotopes using the nucleon-pair approximation of the shell model is
reported. As long as the structure of the dominant collective pairs is
determined using a microscopic framework appropriate to deformed nuclei, the
model is able to produce a shape transition. However, the resulting transition
is too rapid, with nuclei that should be transitional being fairly well
deformed, perhaps reflecting the need to maintain several pairs with each
angular momentum.Comment: 7 pages, 5 figure
Residual proton-neutron interactions and the scheme
We investigate the correlation between integrated proton-neutron interactions
obtained by using the up-to-date experimental data of binding energies and the
, the product of valence proton number and valence neutron
number with respect to the nearest doubly closed nucleus. We make corrections
on a previously suggested formula for the integrated proton-neutron
interaction. Our results demonstrate a nice, nearly linear, correlation between
the integrated p-n interaction and , which provides us
with a firm foundation of the applicability of the scheme
to nuclei far from the stability line.Comment: four pages, three figures, Physical Review C, in pres
Structure propagation for zero-shot learning
The key of zero-shot learning (ZSL) is how to find the information transfer
model for bridging the gap between images and semantic information (texts or
attributes). Existing ZSL methods usually construct the compatibility function
between images and class labels with the consideration of the relevance on the
semantic classes (the manifold structure of semantic classes). However, the
relationship of image classes (the manifold structure of image classes) is also
very important for the compatibility model construction. It is difficult to
capture the relationship among image classes due to unseen classes, so that the
manifold structure of image classes often is ignored in ZSL. To complement each
other between the manifold structure of image classes and that of semantic
classes information, we propose structure propagation (SP) for improving the
performance of ZSL for classification. SP can jointly consider the manifold
structure of image classes and that of semantic classes for approximating to
the intrinsic structure of object classes. Moreover, the SP can describe the
constrain condition between the compatibility function and these manifold
structures for balancing the influence of the structure propagation iteration.
The SP solution provides not only unseen class labels but also the relationship
of two manifold structures that encode the positive transfer in structure
propagation. Experimental results demonstrate that SP can attain the promising
results on the AwA, CUB, Dogs and SUN databases
The effect of pre-processing and grain structure on the bio-corrosion and fatigue resistance of magnesium alloy AZ31
Magnesium alloys are broadly used for structural applications in the aerospace and automotive industries as well as in consumer electronics. While a high specific strength is the forte of magnesium alloys, one serious limitation for Mg alloys is their corrosion performance. Unlike aluminium, it does not form a stable passive film to provide long-term protection from further corrosion. The poor corrosion resistance of magnesium and magnesium alloys is regarded as a major drawback, and significant effort has been focused on improving this.[1-3] However, the high reactivity of magnesium alloys in corrosive media can be used to advantage in biomedical applications, particularly in temporary implants where the capacity of a material for bio-degradation is one of the most sought after properties. Indeed, permanent implant materials, such as stainless steel, titanium alloys or Nitinol (55Ni-45Ti), are the only choices currently available for hard tissue implantation. They can cause permanent physical irritation, long-term endothelial dysfunction and chronic inflammatory local reaction. Sometimes a second operation is needed for the implant to be removed. Given the ability of the human body to gradually recover and regenerate damaged tissue, the ideal solution would thus be a degradable implant, which would offer a physiologically less invasive repair and temporary support during tissue recovery. After fulfilling its function, this implant would be obliterated, being absorbed by the body. This philosophy of implant surgery would also be of particular interest for endovascular stent
Surface States of the Topological Insulator Bi_{1-x}Sb_x
We study the electronic surface states of the semiconducting alloy BiSb.
Using a phenomenological tight binding model we show that the Fermi surface of
the 111 surface states encloses an odd number of time reversal invariant
momenta (TRIM) in the surface Brillouin zone confirming that the alloy is a
strong topological insulator. We then develop general arguments which show that
spatial symmetries lead to additional topological structure, and further
constrain the surface band structure. Inversion symmetric crystals have 8 Z_2
"parity invariants", which include the 4 Z_2 invariants due to time reversal.
The extra invariants determine the "surface fermion parity", which specifies
which surface TRIM are enclosed by an odd number of electron or hole pockets.
We provide a simple proof of this result, which provides a direct link between
the surface states and the bulk parity eigenvalues. We then make specific
predictions for the surface state structure for several faces of BiSb. We next
show that mirror invariant band structures are characterized by an integer
"mirror Chern number", n_M. The sign of n_M in the topological insulator phase
of BiSb is related to a previously unexplored Z_2 parameter in the L point k.p
theory of pure Bi, which we refer to as the "mirror chirality", \eta. The value
of \eta predicted by the tight binding model for Bi disagrees with the value
predicted by a more fundamental pseudopotential calculation. This explains a
subtle disagreement between our tight binding surface state calculation and
previous first principles calculations on Bi. This suggests that the tight
binding parameters in the Liu Allen model of Bi need to be reconsidered.
Implications for existing and future ARPES experiments and spin polarized ARPES
experiments will be discussed.Comment: 15 pages, 7 figure
The spinal precerebellar nuclei: Calcium binding proteins and gene expression profile in the mouse
We have localized the spinocerebellar neuron groups in C57BL/6J mice by injecting the retrograde neuronal tracer Fluoro-Gold into the cerebellum and examined the distribution of SMI 32 and the calcium-binding proteins (CBPs), calbindin-D-28K (Cb), calretinin (Cr), and parvalbumin (Pv) in the spinal precerebellar nuclei. The spinal precerebellar neuron clusters identified were the dorsal nucleus, central cervical nucleus, lumbar border precerebellar nucleus, lumbar precerebellar nucleus, and sacral precerebellar nucleus. Some dispersed neurons in the deep dorsal horn and spinal laminae 6–8 also projected to the cerebellum. Cb, Cr, Pv, and SMI 32 were present in all major spinal precerebellar nuclei and Pv was the most commonly observed CBP. A number of genes expressed in hindbrain precerebellar nuclei are also expressed in spinal precerebellar groups, but there were some differences in gene expression profile between the different spinal precerebellar nuclei, pointing to functional diversity amongst them
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