Graphs related to Held's simple group

AbstractWe analyze the permutation representations of low degree of Held's simple group He. We also determine its primitive multiplicity free permutation representations and show that there is no graph on which it or its automorphism group acts as a distance transitive group of automorphisms. In doing so, we supply a computer-free construction of He

An ASCA Study of the W51 Complex

We present the analysis of ASCA archival data from the Galactic source W51. The ASCA spectra show that the soft (kT<= 2.5 keV) X-rays are of thermal origin and are compatible with W51C being a single, isothermal (kT~0.3 keV) supernova remnant at the far-side of the Sagittarius arm. The ASCA images reveal hard (kT>=2.5 keV) X-ray sources which were not seen in previous X-ray observations. Some of these sources are coincident with massive star-forming regions and the spectra are used to derive X-ray parameters. By comparing the X-ray absorbing column density with atomic hydrogen column density, we infer the location of star-forming regions relative to molecular clouds. There are unidentified hard X-ray sources superposed on the supernova remnant and we discuss the possibility of their association.Comment: 13 pages, 11 figures, to be published in Astronomical Journa

Hole-Hole Contact Interaction in the t-J Model

Using an analytical variational approach we calculate the hole-hole contact interaction on the N\'{e}el background. Solution of the Bethe-Salpeter equation with this interaction gives bound states in $d$- and p-waves with binding energies close to those obtained by numerical methods. At $t/J \ge 2-3$ the bound state disappears. In conclusion we discuss the relation between short range and long range interactions and analogy with the problem of pion condensation in nuclear matter.Comment: 11 pp. (LATEX), 7 figures (PostScript) appended, report N

Inhibition of p85, the non-catalytic subunit of phosphatidylinositol 3-kinase, exerts potent antitumor activity in human breast cancer cells

: The phosphoinositide 3-kinases (PI3Ks) are heterodimers consisting of the catalytic subunit p110 and the regulatory subunit p85. The PI3K/Akt pathway is strongly deregulated in breast cancer (BC) representing one of the mechanisms of resistance to therapies. Therefore, the identification of inhibitors of PI3K components represents one of the main goals to produce therapeutic agents. Here, we evaluated the efficacy of a phosphopeptide 1257 (P-1257) that targeting p85 strongly inhibits PI3K activity. We tested the effects of P-1257 administration in vitro and in vivo using BC cells expressing different levels of ErbB-2 and resistant or responsive to Trastuzumab. We demonstrated that inhibition of p85 activity by P-1257 induces cell death and sensitizes JIMT-1 and KPL-4 ErbB-2-overexpressing BC cells to Trastuzumab treatment. It is noteworthy that P-1257 delivery in vivo by electroporation or liposomes significantly inhibits the proliferation of tumor cells engrafted at subcutaneous and visceral sites. Overall, our data indicate that the p85 subunit is a valid target for therapeutic approaches and suggest that the structure of the peptide used in our study could be utilized for the development of novel drugs to apply in combination with therapies that fail to cure BCs with high PI3K activity

Measurement of the conductance of a hydrogen molecule

Recent years have shown steady progress in research towards molecular electronics [1,2], where molecules have been investigated as switches [3-5], diodes [6], and electronic mixers [7]. In much of the previous work a Scanning Tunnelling Microscope was employed to address an individual molecule. As this arrangement does not provide long-term stability, more recently metal-molecule-metal links have been made using break junction devices [8-10]. However, it has been difficult to establish unambiguously that a single molecule forms the contact [11]. Here, we show that a single H2 molecule can form a stable bridge between Pt electrodes. In contrast to results for other organic molecules, the bridge has a nearly perfect conductance of one quantum unit, carried by a single channel. The H2-bridge provides a simple test system and a fundamental step towards understanding transport properties of single-molecule devices.Comment: 6 pages, 4 figure

SURGERY OF BRAIN STEM CAVERNOUSES MALFORMATION

Cavernous malformations (CM), also known as cavernous angiomas or cavernomas, are benign vascular hamartomas having a sinusoidal type of wall structure.CM occurs in the brain stem with a frequency of 9–35 % of cases. They are most often localized in the brain stem, have a higher risk of hemorrhage compared to supratentorial. After the primary hemorrhage, the risks of recurrent hemorrhages are very high. CM located in the brain stem has not always been subjected to surgical treatment. Conservative treatment was recommended for most patients. At the same time, according to the literature data, mortality reached 20 %, and during radiosurgery up to 8.3 % with recurrence of hemorrhage up to 59 %. The aim of the study was to evaluate the results of surgical treatment of patients with cavernomas of the brain stem. Materials and methods. the study included 16 patients who had hemorrhages in different parts of the brain stem. There were 12 males (75 %) and 4 females (25 %). Indications for surgical treatment were: presence of subacute hematoma, recurrent hemorrhage and progressive symptoms of brain stem damage. All patients were operated using modern methods of microsurgery. Neurophysiological monitoring was performed intraoperatively. Statistical processing was carried out with the program Statistica (version 10). Results. There was no operational mortality. At discharge, patients were assessed on the Rankin scale. Good functional outcomes were achieved in 87.8 % of cases (Rankin 1 – 43.8 %, Rankin 2 – 31.5 %, Rankin 3 – 12.5 %). Summary. Symptomatic malformations of the brain stem are subject to surgical removal when they are anatomically accessible. The use of modern methods of neuroimaging, adequate, sparing surgical approaches, microsurgical techniques for removing the cavernous brain stem, allows us to achieve goodfunctional results in the operated patients, in the absence of postoperative mortality

Morphological disturbances of rat parietal cortex and hippocampus neurons in the dynamics steady subtotal ischemia of the brain

The purpose of the work is to analyze changes in the morphological characteristics of neurons of phylogenetical different parts of the cerebral cortex (parietal cortex and hippocampus) of rats at different periods in the dynamics of stepwise subtotal experimental cerebral ischemia. Methods. The experiments were performed on 42 males of outbred white rats. Step subtotal cerebral ischemia was performed as follows: first, one common carotid artery was ligated, simulating partial ischemia. Then, with an interval of 1 day (subgroup 1), 3 days (subgroup 2) or 7 days (subgroup 3), the second common carotid artery was ligated. Results. A microscopic study of the size, shape, degree of chromatophilia of the cytoplasm and the content of ribonucleoproteins in pyramidal neurons of phylogenetically different parts of the cerebral cortex have shown the dependence of the severity of brain damage on the interval between the cessation of blood flow in both carotid artery. Adaptation was better with a 7-day interval between dressings, while the ligation with an interval of 1 day, the degree of morphological changes was maximum indicating a lack of resources for the implementation of adaptation mechanisms