4,956 research outputs found
Image Reconstruction with a LaBr3-based Rotational Modulator
A rotational modulator (RM) gamma-ray imager is capable of obtaining
significantly better angular resolution than the fundamental geometric
resolution defined by the ratio of detector diameter to mask-detector
separation. An RM imager consisting of a single grid of absorbing slats
rotating ahead of an array of a small number of position-insensitive detectors
has the advantage of fewer detector elements (i.e., detector plane pixels) than
required by a coded aperture imaging system with comparable angular resolution.
The RM therefore offers the possibility of a major reduction in instrument
complexity, cost, and power. A novel image reconstruction technique makes it
possible to deconvolve the raw images, remove sidelobes, reduce the effects of
noise, and provide resolving power a factor of 6 - 8 times better than the
geometric resolution. A 19-channel prototype RM developed in our laboratory at
Louisiana State University features 13.8 deg full-angle field of view, 1.9 deg
geometric angular resolution, and the capability of resolving sources to within
35' separation. We describe the technique, demonstrate the measured performance
of the prototype instrument, and describe the prospects for applying the
technique to either a high-sensitivity standoff gamma-ray imaging detector or a
satellite- or balloon-borne gamma-ray astronomy telescope.Comment: submitted to Nuclear Instrument & Methods, special edition: SORMA
2010 on June 16, 201
Augmenting graphs to minimize the diameter
We study the problem of augmenting a weighted graph by inserting edges of
bounded total cost while minimizing the diameter of the augmented graph. Our
main result is an FPT 4-approximation algorithm for the problem.Comment: 15 pages, 3 figure
Mechanical Properties of Bulk Metallic Glasses and Composites
We have studied the mechanical properties of monolithic bulk metallic glasses and composite in the La based alloys. La₈₆₋yAl₁₄(Cu, Ni)y (y=24 to 32) alloy systems was used to cast the in-situ structure and subsequently tested under compression. We found that the ductility of the monolithic is actually poorer than that of the fully crystalline composite.Singapore-MIT Alliance (SMA
Identification of Critical Molecular Determinants of West Nile Virus PrM Protein: A Potential Site for Antiviral Targeting
Digitalitzat per Artypla
Paclitaxel-octreotide conjugates inhibit growth of human non-small cell lung cancer cells in vitro
Aim: To evaluate the effects of paclitaxel-octreotide conjugates on the growth of cultured non-small cell lung cancer cells. Methods: RT-PCR was performed to detect mRNA for the subtypes of the human somatostatin receptor (SSTR) using specific primers. MTT-based cytotoxicity assay was used to evaluate the cell viability after treatment with paclitaxel and the conjugates. Cell cycle perturbations were determined using a Fluorescence-Activated Cell Sorter. Results: Non-small cell lung cancer A549 and Calu-6 cells expressed mRNA for SSTR2 and SSTR5. Paclitaxel and the conjugates effectively inhibited the growth of A549 and Calu-6 cells in a concentration- and time-dependent manner. In SSTR-negative fibroblasts, the conjugates were less cytotoxic than paclitaxel. The conjugates and paclitaxel could induce the increase of G2/M phase ratio in A549 cells. Conclusion: The paclitaxel-octreotide conjugates can be used as selective-targeted chemotherapeutic agents for treating non-small cell lung cancer.Цель: оценить эффект конъюгатов паклитаксела-октреотида на рост культивированных клеток немелкоклеточного рака
легкого человека. Методы: для определения мРНК подтипов рецептора соматостатина человека (SSTR) применяли ОT-ПЦР.
Анализ цитотоксичности в МТТ-тесте применяли для оценки выживаемости клеток после их инкубации с паклитакселом
и конъюгатами. Нарушения клеточного цикла определяли с применением FACS — клеточного сортера. Результаты:
установлено, что клеточные линии немелкоклеточного рака легкого A549 и Calu-6 экспрессируют SSTR2 и SSTR5 мРНК.
Отмечено эффективное дозо- и времязависимое угнетение роста клеток A549 и Calu-6 паклитакселом и конъюгатами.
Для SSTR-негативных фибробластов конъюгаты менее цитотоксичны, чем паклитаксел. Конъюгаты и паклитаксел могут
индуцировать повышение соотношения фаз G2
/M в клетках A549. Выводы: конъюгаты паклитаксел-октреотида могут быть
использованы как селективные химиотерапевтические агенты для воздействия на немелкоклеточный рак легкого
A simpler and more efficient algorithm for the next-to-shortest path problem
Given an undirected graph with positive edge lengths and two
vertices and , the next-to-shortest path problem is to find an -path
which length is minimum amongst all -paths strictly longer than the
shortest path length. In this paper we show that the problem can be solved in
linear time if the distances from and to all other vertices are given.
Particularly our new algorithm runs in time for general
graphs, which improves the previous result of time for sparse
graphs, and takes only linear time for unweighted graphs, planar graphs, and
graphs with positive integer edge lengths.Comment: Partial result appeared in COCOA201
Negative-coupling resonances in pump-coupled lasers
We consider coupled lasers, where the intensity deviations from the steady
state, modulate the pump of the other lasers. Most of our results are for two
lasers where the coupling constants are of opposite sign. This leads to a Hopf
bifurcation to periodic output for weak coupling. As the magnitude of the
coupling constants is increased (negatively) we observe novel amplitude effects
such as a weak coupling resonance peak and, strong coupling subharmonic
resonances and chaos. In the weak coupling regime the output is predicted by a
set of slow evolution amplitude equations. Pulsating solutions in the strong
coupling limit are described by discrete map derived from the original model.Comment: 29 pages with 8 figures Physica D, in pres
Adhesion mechanics of graphene membranes
The interaction of graphene with neighboring materials and structures plays
an important role in its behavior, both scientifically and technologically. The
interactions are complicated due to the interplay between surface forces and
possibly nonlinear elastic behavior. Here we review recent experimental and
theoretical advances in the understanding of graphene adhesion. We organize our
discussion into experimental and theoretical efforts directed toward: graphene
conformation to a substrate, determination of adhesion energy, and applications
where graphene adhesion plays an important role. We conclude with a brief
prospectus outlining open issues.Comment: Review article to appear in special issue on graphene in Solid State
Communication
State transfer in dissipative and dephasing environments
By diagonalization of a generalized superoperator for solving the master
equation, we investigated effects of dissipative and dephasing environments on
quantum state transfer, as well as entanglement distribution and creation in
spin networks. Our results revealed that under the condition of the same
decoherence rate , the detrimental effects of the dissipative
environment are more severe than that of the dephasing environment. Beside
this, the critical time at which the transfer fidelity and the
concurrence attain their maxima arrives at the asymptotic value
quickly as the spin chain length increases. The transfer
fidelity of an excitation at time is independent of when the system
subjects to dissipative environment, while it decreases as increases when
the system subjects to dephasing environment. The average fidelity displays
three different patterns corresponding to , and . For
each pattern, the average fidelity at time is independent of when the
system subjects to dissipative environment, and decreases as increases when
the system subjects to dephasing environment. The maximum concurrence also
decreases as increases, and when , it arrives at an
asymptotic value determined by the decoherence rate and the structure
of the spin network.Comment: 12 pages, 6 figure
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