769 research outputs found
Optical properties of small polarons from dynamical mean-field theory
The optical properties of polarons are studied in the framework of the
Holstein model by applying the dynamical mean-field theory. This approach
allows to enlighten important quantitative and qualitative deviations from the
limiting treatments of small polaron theory, that should be considered when
interpreting experimental data. In the antiadiabatic regime, accounting on the
same footing for a finite phonon frequency and a finite electron bandwidth
allows to address the evolution of the optical absorption away from the
well-understood molecular limit. It is shown that the width of the multiphonon
peaks in the optical spectra depends on the temperature and on the frequency in
a way that contradicts the commonly accepted results, most notably in the
strong coupling case. In the adiabatic regime, on the other hand, the present
method allows to identify a wide range of parameters of experimental interest,
where the electron bandwidth is comparable or larger than the broadening of the
Franck-Condon line, leading to a strong modification of both the position and
the shape of the polaronic absorption. An analytical expression is derived in
the limit of vanishing broadening, which improves over the existing formulas
and whose validity extends to any finite-dimensional lattice. In the same
adiabatic regime, at intermediate values of the interaction strength, the
optical absorption exhibits a characteristic reentrant behavior, with the
emergence of sharp features upon increasing the temperature -- polaron
interband transitions -- which are peculiar of the polaron crossover, and for
which analytical expressions are provided.Comment: 16 pages, 6 figure
The behavior limestone under explosive load
Limestone behavior under explosive loading was investigated. The behavior of the limestone by the action of the three types of explosives, including granular, ammonite and emulsion explosives was studied in detail. The shape and diameter of the explosion craters were obtained. The observed fragments after the blast have been classified as large, medium and small fragments. Three full-scale experiments were carried out. The research results can be used as a qualitative test for the approbation of numerical methods
Diffusion and Transport Coefficients in Synthetic Opals
Opals are structures composed of the closed packing of spheres in the size
range of nano-to-micro meter. They are sintered to create small necks at the
points of contact. We have solved the diffusion problem in such structures. The
relation between the diffusion coefficient and the termal and electrical
conductivity makes possible to estimate the transport coefficients of opal
structures. We estimate this changes as function of the neck size and the
mean-free path of the carriers. The theory presented is also applicable to the
diffusion problem in other periodic structures.Comment: Submitted to PR
Towards Personalized Prostate Cancer Therapy Using Delta-Reachability Analysis
Recent clinical studies suggest that the efficacy of hormone therapy for
prostate cancer depends on the characteristics of individual patients. In this
paper, we develop a computational framework for identifying patient-specific
androgen ablation therapy schedules for postponing the potential cancer
relapse. We model the population dynamics of heterogeneous prostate cancer
cells in response to androgen suppression as a nonlinear hybrid automaton. We
estimate personalized kinetic parameters to characterize patients and employ
-reachability analysis to predict patient-specific therapeutic
strategies. The results show that our methods are promising and may lead to a
prognostic tool for personalized cancer therapy.Comment: HSCC 201
Metallic Xenon, Molecular Condensates, and Superconductivity
A possibility of explaining the light absorption observed to occur under
pressure-induced xenon metallization as due to the transition to the
superconducting state is analyzed. The mechanism of the van der Waals bonding
is discussed.Comment: LaTeX 2.09 (RevTeX), 4 pages, 4 PostScript figures included in tex
Relief and geology of the north polar region of the planet Venus
Description of topographic features is given for the North polar region of the planet Venus. Principal geomorphic types of terrain are characterized as well as their geologic relations. Relative ages of geologic units in Venus North polar region are discussed
Feasibility of a Small, Rapid Optical-to-IR Response, Next Generation Gamma Ray Burst Mission
We present motivations for and study feasibility of a small, rapid optical to
IR response gamma ray burst (GRB) space observatory. By analyzing existing GRB
data, we give realistic detection rates for X-ray and optical/IR instruments of
modest size under actual flight conditions. Given new capabilities of fast
optical/IR response (about 1 s to target) and simultaneous multi-band imaging,
such an observatory can have a reasonable event rate, likely leading to new
science. Requiring a Swift-like orbit, duty cycle, and observing constraints, a
Swift-BAT scaled down to 190 square cm of detector area would still detect and
locate about 27 GRB per yr. for a trigger threshold of 6.5 sigma. About 23
percent of X-ray located GRB would be detected optically for a 10 cm diameter
instrument (about 6 per yr. for the 6.5 sigma X-ray trigger).Comment: Elaborated text version of a poster presented at 2012 Malaga/Marbella
symposiu
HugeNon-Organ Retroperitoneal Tumor inCombination with aCystoma of Uterine Appendages
The article describes the experience of successful diagnostics and treatment of giant non-organ extraperitoneal tumor combined with a cystoma of uterine appendages.Patient P., 43 years old, was hospitalized in the oncology department, diagnosed with “Abdominal tumor, right ovary?” The state was satisfactory, after palpation of the abdomen, a lumpy formation of a densely elastic consistency, from the womb to the epigastric region, was found. An ultrasound revealed a homogeneous tumor formation 30×28 cm from the border of the uterus to the liver. When performing median laparotomy, a dumbbell-shaped tumor (36×26×20 cm) was found in the retroperitoneal space with involvement of the mesentery of the small intestine, lower horizontal portion of the duodenum, mesentery of the transverse colon, superior mesenteric vessels, aorta and jejunum. In the right appendages, a cystoma 12–15 cm in diameter was found, with inversion and necrosis. Adnexectomy was performed. An express lymph node biopsy revealed cells suspicious for malignancy. The tumor was mobilized and removed as a single unit with retroperitoneal tissue, lymph nodes in combination with resection of 70 cm of the jejunum and fenestrated resection of the duodenum. The resulting gut defect 9×7 cm was sutured with a precision single-row suture. Inter-intestinal anastomosis “endto-end” was formed. Nasointestinal intubation was performed. The abdominal cavity was sutured, and two tubular drainages were installed. The postoperative period was uneventful. The histological conclusion: fibrous histiocytoma of the mesentery of the intestine with malignancy in the center of the node, in the ovary – total hemorrhagic infiltration of all layers, edema. The tumor conference consultation was recommended. After 1.5 years, the patient was admitted with the same clinical picture. During laparotomy, a tumor recurrence was discovered, the nodes of which were located in the retroperitoneal space, in the abdominal cavity with invasion to organs and large vessels. The case was recognized as inoperable, the laparotomic wound was closed completely. Sixteen days after surgery the patient was discharged
Melting Point and Lattice Parameter Shifts in Supported Metal Nanoclusters
The dependencies of the melting point and the lattice parameter of supported
metal nanoclusters as functions of clusters height are theoretically
investigated in the framework of the uniform approach. The vacancy mechanism
describing the melting point and the lattice parameter shifts in nanoclusters
with decrease of their size is proposed. It is shown that under the high vacuum
conditions (p<10^-7 torr) the essential role in clusters melting point and
lattice parameter shifts is played by the van der Waals forces of
cluster-substrate interation. The proposed model satisfactorily accounts for
the experimental data.Comment: 6 pages, 3 figures, 1 tabl
- …