1,500 research outputs found
Long-term orbital lifetime predictions
Long-term orbital lifetime predictions are analyzed. Predictions were made for three satellites: the Solar Max Mission (SMM), the Long Duration Exposure Facility (LDEF), and the Pegasus Boiler Plate (BP). A technique is discussed for determining an appropriate ballistic coefficient to use in the lifetime prediction. The orbital decay rate should be monitored regularly. Ballistic coefficient updates should be done whenever there is a significant change in the actual decay rate or in the solar activity prediction
Umbilical endometriosis
We report two women who presented with a recurrent, mildly painful, bluish nodule in the umbilicus. Both patients complained of local tenderness and occasional bleeding that increased during menstruation. Neither patient had had previous pelvic surgery. Excision of the lesions revealed a primary umbilical endometriosis; in one case, a simultaneous laparoscopy showed a pelvic endometriosis. We review the current literature and discuss the possible etiopathogenesis and when a laparoscopy is indicated to diagnose a concomitant pelvic endometriosis. Umbilical endometriosis is a very rare disease but should be considered in the differential diagnosis of umbilical lesion
Physicochemical analysis of rotavirus segment 11 supports a 'modified panhandle' structure and not the predicted alternative tRNA-like structure (TRLS)
.Rotaviruses are a major cause of acute gastroenteritis, which is often fatal in infants. The viral genome consists of 11 double-stranded RNA segments, but little is known about their cis-acting sequences and structural elements. Covariation studies and phylogenetic analysis exploring the potential structure of RNA11 of rotaviruses suggested that, besides the previously predicted "modified panhandle" structure, the 5' and 3' termini of one of the isoforms of the bovine rotavirus UKtc strain may interact to form a tRNA-like structure (TRLS). Such TRLSs have been identified in RNAs of plant viruses, where they are important for enhancing replication and packaging. However, using tRNA mimicry assays (in vitro aminoacylation and 3'- adenylation), we found no biochemical evidence for tRNA-like functions of RNA11. Capping, synthetic 3' adenylation and manipulation of divalent cation concentrations did not change this finding. NMR studies on a 5'- and 3'-deletion construct of RNA11 containing the putative intra-strand complementary sequences supported a predominant panhandle structure and did not conform to a cloverleaf fold despite the strong evidence for a predicted structure in this conserved region of the viral RNA. Additional viral or cellular factors may be needed to stabilise it into a form with tRNA-like properties
Structure and conductance histogram of atomic-sized Au contacts
Many experiments have shown that the conductance histograms of metallic
atomic-sized contacts exhibit a peak structure, which is characteristic of the
corresponding material. The origin of these peaks still remains as an open
problem. In order to shed some light on this issue, we present a theoretical
analysis of the conductance histograms of Au atomic contacts. We have combined
classical molecular dynamics simulations of the breaking of nanocontacts with
conductance calculations based on a tight-binding model. This combination gives
us access to crucial information such as contact geometries, forces, minimum
cross-section, total conductance and transmission coefficients of the
individual conduction channels. The ensemble of our results suggests that the
low temperature Au conductance histograms are a consequence of a subtle
interplay between mechanical and electrical properties of these nanocontacts.
At variance with other suggestions in the literature, our results indicate that
the peaks in the Au conductance histograms are not a simple consequence of
conductance quantization or the existence of exceptionally stable radii. We
show that the main peak in the histogram close to one quantum of conductance is
due to the formation of single-atom contacts and chains of gold atoms.
Moreover, we present a detailed comparison with experimental results on Au
atomic contacts where the individual channel transmissions have been
determined.Comment: 11 pages, 10 figures, version to be published in Phys. Rev. B. The
paper has been thoroughly revised and several figures have been replaced by
new one
Mechanism of active targeting in solid tumors with transferrin-containing gold nanoparticles
PEGylated gold nanoparticles are decorated with various amounts of human transferrin (Tf) to give a series of Tf-targeted particles with near-constant size and electrokinetic potential. The effects of Tf content on nanoparticle tumor targeting were investigated in mice bearing s.c. Neuro2A tumors. Quantitative biodistributions of the nanoparticles 24 h after i.v. tail-vein injections show that the nanoparticle accumulations in the tumors and other organs are independent of Tf. However, the nanoparticle localizations within a particular organ are influenced by the Tf content. In tumor tissue, the content of targeting ligands significantly influences the number of nanoparticles localized within the cancer cells. In liver tissue, high Tf content leads to small amounts of the nanoparticles residing in hepatocytes, whereas most nanoparticles remain in nonparenchymal cells. These results suggest that targeted nanoparticles can provide greater intracellular delivery of therapeutic agents to the cancer cells within solid tumors than their nontargeted analogs
Numerical modeling of quasiplanar giant water waves
In this work we present a further analytical development and a numerical
implementation of the recently suggested theoretical model for highly nonlinear
potential long-crested water waves, where weak three-dimensional effects are
included as small corrections to exact two-dimensional equations written in the
conformal variables [V.P. Ruban, Phys. Rev. E 71, 055303(R) (2005)]. Numerical
experiments based on this theory describe the spontaneous formation of a single
weakly three-dimensional large-amplitude wave (alternatively called freak,
killer, rogue or giant wave) on the deep water.Comment: revtex4, 8 pages, 7 figure
The determinants of election to the United Nations Security Council
This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11127-013-0096-4.The United Nations Security Council (UNSC) is the foremost international body responsible for the maintenance of international peace and security. Members vote on issues of global importance and consequently receive perks—election to the UNSC predicts, for instance, World Bank and IMF loans. But who gets elected to the UNSC? Addressing this question empirically is not straightforward as it requires a model that allows for discrete choices at the regional and international levels; the former nominates candidates while the latter ratifies them. Using an original multiple discrete choice model to analyze a dataset of 180 elections from 1970 to 2005, we find that UNSC election appears to derive from a compromise between the demands of populous countries to win election more frequently and a norm of giving each country its turn. We also find evidence that richer countries from the developing world win election more often, while involvement in warfare lowers election probability. By contrast, development aid does not predict election
Impact of tumor burden on normal organ distribution in patients imaged with CXCR4-targeted [68Ga]Ga-PentixaFor PET/CT
BACKGROUND: CXCR4-directed positron emission tomography/computed tomography (PET/CT) has been used as a diagnostic tool in patients with solid tumors. We aimed to determine a potential correlation between tumor burden and radiotracer accumulation in normal organs. METHODS: Ninety patients with histologically proven solid cancers underwent CXCR4-targeted [(68)Ga]Ga-PentixaFor PET/CT. Volumes of interest (VOIs) were placed in normal organs (heart, liver, spleen, bone marrow, and kidneys) and tumor lesions. Mean standardized uptake values (SUV(mean)) for normal organs were determined. For CXCR4-positive tumor burden, maximum SUV (SUV(max)), tumor volume (TV), and fractional tumor activity (FTA, defined as SUV(mean) x TV), were calculated. We used a Spearman's rank correlation coefficient (ρ) to derive correlative indices between normal organ uptake and tumor burden. RESULTS: Median SUV(mean) in unaffected organs was 5.2 for the spleen (range, 2.44 – 10.55), 3.27 for the kidneys (range, 1.52 – 17.4), followed by bone marrow (1.76, range, 0.84 – 3.98), heart (1.66, range, 0.88 – 2.89), and liver (1.28, range, 0.73 – 2.45). No significant correlation between SUV(max) in tumor lesions (ρ ≤ 0.189, P ≥ 0.07), TV (ρ ≥ -0.204, P ≥ 0.06) or FTA (ρ ≥ -0.142, P ≥ 0.18) with the investigated organs was found. CONCLUSIONS: In patients with solid tumors imaged with [(68)Ga]Ga-PentixaFor PET/CT, no relevant tumor sink effect was noted. This observation may be of relevance for therapies with radioactive and non-radioactive CXCR4-directed drugs, as with increasing tumor burden, the dose to normal organs may remain unchanged
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