1,227 research outputs found
Penrose-Onsager Criterion Validation in a One-Dimensional Polariton Condensate
We perform quantum tomography on one-dimensional polariton condensates,
spontaneously occurring in linear disorder valleys in a CdTe planar microcavity
sample. By the use of optical interferometric techniques, we determine the
first-order coherence function and the amplitude and phase of the order
parameter of the condensate, providing a full reconstruction of the single
particle density matrix for the polariton system. The experimental data are
used as input to theoretically test the consistency of Penrose-Onsager
criterion for Bose-Einstein condensation in the framework of nonequilibrium
polariton condensates. The results confirm the pertinence and validity of the
criterion for a non equilibrium condensed gas.Comment: 5 pages, 4 figure
Relevance of the Heisenberg-Kitaev model for the honeycomb lattice iridates A_2IrO_3
Combining thermodynamic measurements with theoretical density functional and
thermodynamic calculations we demonstrate that the honeycomb lattice iridates
A2IrO3 (A = Na, Li) are magnetically ordered Mott insulators where the
magnetism of the effective spin-orbital S = 1/2 moments can be captured by a
Heisenberg-Kitaev (HK) model with Heisenberg interactions beyond
nearest-neighbor exchange. Experimentally, we observe an increase of the
Curie-Weiss temperature from \theta = -125 K for Na2IrO3 to \theta = -33 K for
Li2IrO3, while the antiferromagnetic ordering temperature remains roughly the
same T_N = 15 K for both materials. Using finite-temperature functional
renormalization group calculations we show that this evolution of \theta, T_N,
the frustration parameter f = \theta/T_N, and the zig-zag magnetic ordering
structure suggested for both materials by density functional theory can be
captured within this extended HK model. Combining our experimental and
theoretical results, we estimate that Na2IrO3 is deep in the magnetically
ordered regime of the HK model (\alpha \approx 0.25), while Li2IrO3 appears to
be close to a spin-liquid regime (0.6 < \alpha < 0.7).Comment: Version accepted for publication in PRL. Additional DFT and
thermodynamic calculations have been included. 6 pages of supplementary
material include
Synchronous bilateral epithelial-myoepithelial carcinoma of the parotid gland: case report and review of the literature
Metastasis of hormone-independent breast cancer to lung and bone is decreased by α-difluoromethylornithine treatment
INTRODUCTION: Polyamines affect proliferation, differentiation, migration and apoptosis of cells, indicating their potential as a target for cancer chemotherapy. Ornithine decarboxylase converts ornithine to putrescine and is the rate-limiting step in polyamine synthesis. α-Difluoromethylornithine (DFMO) irreversibly inhibits ornithine decarboxylase and MDA-MB-435 human breast cancer metastasis to the lung without blocking orthotopic tumor growth. This study tested the effects of DFMO on orthotopic tumor growth and lung colonization of another breast cancer cell line (MDA-MB-231) and the effects on bone metastasis of MDA-MB-435 cells. METHODS: MDA-MB-231 cells were injected into the mammary fat pad of athymic mice. DFMO treatment (2% per orally) began at the day of tumor cell injection or 21 days post injection. Tumor growth was measured weekly. MDA-MB-231 cells were injected into the tail vein of athymic mice. DFMO treatment began 7 days prior to injection, or 7 or 14 days post injection. The number and incidence of lung metastases were determined. Green fluorescent protein-tagged MDA-MB-435 cells were injected into the left cardiac ventricle in order to assess the incidence and extent of metastasis to the femur. DFMO treatment began 7 days prior to injection. RESULTS: DFMO treatment delayed MDA-MB-231 orthotopic tumor growth to a greater extent than growth of MDA-MB-435 tumors. The most substantial effect on lung colonization by MDA-MB-231 cells occurred when DFMO treatment began 7 days before intravenous injection of tumor cells (incidence decreased 28% and number of metastases per lung decreased 35–40%). When DFMO treatment began 7 days post injection, the incidence and number of metastases decreased less than 10%. Surprisingly, treatment initiated 14 days after tumor cell inoculation resulted in a nearly 50% reduction in the number of lung metastases without diminishing the incidence. After intracardiac injection, DFMO treatment decreased the incidence of bone metastases (55% vs 87%) and the area occupied by the tumor (1.66 mm(2 )vs 4.51 mm(2), P < 0.05). CONCLUSION: Taken together, these data demonstrate that DFMO exerts an anti-metastatic effect in more than one hormone-independent breast cancer, for which no standard form of biologically-based treatment exists. Importantly, the data show that DFMO is effective against metastasis to multiple sites and that treatment is generally more effective when administered early
A Tchebycheffian extension of multi-degree B-splines: Algorithmic computation and properties
In this paper we present an efficient and robust approach to compute a
normalized B-spline-like basis for spline spaces with pieces drawn from
extended Tchebycheff spaces. The extended Tchebycheff spaces and their
dimensions are allowed to change from interval to interval. The approach works
by constructing a matrix that maps a generalized Bernstein-like basis to the
B-spline-like basis of interest. The B-spline-like basis shares many
characterizing properties with classical univariate B-splines and may easily be
incorporated in existing spline codes. This may contribute to the full
exploitation of Tchebycheffian splines in applications, freeing them from the
restricted role of an elegant theoretical extension of polynomial splines.
Numerical examples are provided that illustrate the procedure described
A new geometric description for Igusa's modular form
The modular form notably appears in one of Igusa's classic
structure theorems as a generator of the ring of full modular forms in genus 2,
being exhibited by means of a complicated algebraic expression. In this work a
different description for this modular form is provided by resorting to a
peculiar geometrical approach.Comment: 10 page
Crystal field splitting and correlation effect on the electronic structure of A2IrO3
The electronic structure of the honeycomb lattice iridates Na2IrO3 and
Li2IrO3 has been investigated using resonant inelastic x-ray scattering (RIXS).
Crystal-field split d-d excitations are resolved in the high-resolution RIXS
spectra. In particular, the splitting due to non-cubic crystal fields, derived
from the splitting of j_eff=3/2 states, is much smaller than the typical
spin-orbit energy scale in iridates, validating the applicability of j_eff
physics in A2IrO3. We also find excitonic enhancement of the particle-hole
excitation gap around 0.4 eV, indicating that the nearest-neighbor Coulomb
interaction could be large. These findings suggest that both Na2IrO3 and
Li2IrO3 can be described as spin-orbit Mott insulators, similar to the square
lattice iridate Sr2IrO4
THE EIGHTH COMPONENT OF HUMAN COMPLEMENT (C8): ISOLATION, CHARACTERIZATION, AND HEMOLYTIC EFFICIENCY
Promoter methylation and downregulated expression of the TBX15 gene in ovarian carcinoma.
TBX15 is a gene involved in the development of mesodermal derivatives. As the ovaries and the female reproductive system are of mesodermal origin, the aim of the present study was to determine the methylation status of the TBX15 gene promoter and the expression levels of TBX15 in ovarian carcinoma, which is the most lethal and aggressive type of gynecological tumor, in order to determine the role of TBX15 in the pathogenesis of ovarian carcinoma. This alteration could be used to predict tumor development, progression, recurrence and therapeutic effects. The study was conducted on 80 epithelial ovarian carcinoma and 17 control cases (normal ovarian and tubal tissues). TBX15 promoter methylation was first determined by pyrosequencing following bisulfite modification, then by cloning and sequencing, in order to obtain information about the epigenetic haplotype. Immunohistochemical analysis was performed to evaluate the correlation between the methylation and protein expression levels. Data revealed a statistically significant increase of the TBX15 promoter region methylation in 82% of the tumor samples and in various histological subtypes. Immunohistochemistry showed an inverse correlation between methylation levels and the expression of the TBX15 protein. Furthermore, numerous tumor samples displayed varying degrees of intratumor heterogeneity. Thus, the present study determined that ovarian carcinoma typically expresses low levels of TBX15 protein, predominantly due to an epigenetic mechanism. This may have a role in the pathogenesis of ovarian carcinoma independent of the histological subtype
Transcriptional variation of sensory-related genes in natural populations of Aedes albopictus
BACKGROUND: The Asian tiger mosquito, Aedes albopictus, is a highly dangerous invasive vector of numerous medically important arboviruses including dengue, chikungunya and Zika. In four decades it has spread from tropical Southeast Asia to many parts of the world in both tropical and temperate climes. The rapid invasion process of this mosquito is supported by its high ecological and genetic plasticity across different life history traits. Our aim was to investigate whether wild populations, both native and adventive, also display transcriptional genetic variability for functions that may impact their biology, behaviour and ability to transmit arboviruses, such as sensory perception. RESULTS: Antennal transcriptome data were derived from mosquitoes from a native population from Ban Rai, Thailand and from three adventive Mediterranean populations: Athens, Greece and Arco and Trento from Italy. Clear inter-population differential transcriptional activity was observed in different gene categories related to sound perception, olfaction and viral infection. The greatest differences were detected between the native Thai and the Mediterranean populations. The two Italian populations were the most similar. Nearly one million quality filtered SNP loci were identified. CONCLUSION: The ability to express this great inter-population transcriptional variability highlights, at the functional level, the remarkable genetic flexibility of this mosquito species. We can hypothesize that the differential expression of genes, including those involved in sensory perception, in different populations may enable Ae. albopictus to exploit different environments and hosts, thus contributing to its status as a global vector of arboviruses of public health importance. The large number of SNP loci present in these transcripts represents a useful addition to the arsenal of high-resolution molecular markers and a resource that can be used to detect selective pressure and adaptive changes that may have occurred during the colonization process
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