A simplified model of the source channel of the Leksell Gamma Knife(R)^(R): testing multisource configurations with PENELOPE

A simplification of the source channel geometry of the Leksell Gamma Knife$^{\circledR}$, recently proposed by the authors and checked for a single source configuration (Al-Dweri et al 2004), has been used to calculate the dose distributions along the $x$, $y$ and $z$ axes in a water phantom with a diameter of 160~mm, for different configurations of the Gamma Knife including 201, 150 and 102 unplugged sources. The code PENELOPE (v. 2001) has been used to perform the Monte Carlo simulations. In addition, the output factors for the 14, 8 and 4~mm helmets have been calculated. The results found for the dose profiles show a qualitatively good agreement with previous ones obtained with EGS4 and PENELOPE (v. 2000) codes and with the predictions of GammaPlan$^{\circledR}$. The output factors obtained with our model agree within the statistical uncertainties with those calculated with the same Monte Carlo codes and with those measured with different techniques. Owing to the accuracy of the results obtained and to the reduction in the computational time with respect to full geometry simulations (larger than a factor 15), this simplified model opens the possibility to use Monte Carlo tools for planning purposes in the Gamma Knife$^{\circledR}$.Comment: 13 pages, 8 figures, 5 table

A reconfigurable wideband and multiband antenna using dual-patch elements for compact wireless devices

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 IEEEA reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied

Recursive methods for a multi-dimensional risk process with common shocks

In this paper, a multi-dimensional risk model with common shocks is studied. Using a simple probabilistic approach via observing the risk processes at claim instants, recursive integral formulas are developed for the survival probabilities as well as for a class of Gerber-Shiu expected discounted penalty functions that include the surplus levels at ruin. Under the assumption of exponential or mixed Erlang claims, the recursive integrals can be simplified to give recursive sums which are computationally more tractable. Numerical examples including an optimal capital allocation problem are also given towards the end. © 2011 Elsevier B.V.postprin

Rotational and hyperfine analysis of the near infrared 3Φ4-X3Φ4 transitions of CoCl and Col

A rotational and hyperfine analysis of the 3φ 4- 3φ 4 transition of CoCl and CoI in the near infrared region was reported. Six and eight vibronic transition band soft CoCl and CoI, respectively, were recorded and analyzed. Accurate molecular parameters for both the upper and the ground 3φ 4 states were determined by least squares fitting of line positions of observed bands simultaneously for each molecule, which yielded accurate molecular parameters for both the upper and lower 3φ 4 states.published_or_final_versio

On a generalization of the risk model with Markovian claim arrivals

The class of risk models with Markovian arrival process (MAP) (see e.g., Neuts[15]) is generalized by allowing the waiting times between two successive events (which can be a change in the environmental state and/or a claim arrival) to have an arbitrary distribution. Using a probabilistic approach, we determine the solution for a class of Gerber-Shiu functions apart from some unknown constants when claim sizes have a mixed exponential distribution. Such constants are later determined using the more classic ruin-analytic approach. A numerical example is later considered to illustrate the tractability of the suggested methodology in the study of Gerber-Shiu functions. Copyright © 2011 Taylor &Francis Group, LLC.postprin

„Kitalált történetek”. ,A látogató’ és az ,Útvesztõ’

Andrographolide (Andro) has emerged recently as a potential and effective anticancer agent with induction of apoptosis in some cancer cell lines while induction of G2/M arrest with weak apoptosis in others. Few studies have proved that Andro is also effective in combination therapy. The flavonoid Taxifolin (Taxi) has showed anti-oxidant and antiproliferative effects against different cancer cells. Therefore, the present study investigated the cytotoxic effects of Andro alone or in combination with Taxi on HeLa cells. The combination of Andro with Taxi was synergistic at all tested concentrations and combination ratios. Andro alone induced caspase-dependent apoptosis which was enhanced by the combination with Taxi and attenuated partly by using Z-Vad-Fmk. Andro induced a protective reactive oxygen species (ROS)-dependent autophagy which was attenuated by Taxi. The activation of p53 was involved in Andro-induced autophagy where the use of Taxi or pifithrin-α (PFT-α) decreased it while the activation of JNK was involved in the cell death of HeLa cells but not in the induction of autophagy. The mitochondrial outer-membrane permeabilization (MOMP) plays an important role in Andro-induced cell death in HeLa cells. Andro alone increased the MOMP which was further increased in the case of combination. This led to the increase in AIF and cytochrome c release from mitochondria which consequently increased caspase-dependent and independent cell death. In conclusion, Andro induced a protective autophagy in HeLa cells which was reduced by Taxi and the cell death was increased by increasing the MOMP and subsequently the

Measurement-Adaptive Cellular Random Access Protocols

This work considers a single-cell random access channel (RACH) in cellular wireless networks. Communications over RACH take place when users try to connect to a base station during a handover or when establishing a new connection. Within the framework of Self-Organizing Networks (SONs), the system should self- adapt to dynamically changing environments (channel fading, mobility, etc.) without human intervention. For the performance improvement of the RACH procedure, we aim here at maximizing throughput or alternatively minimizing the user dropping rate. In the context of SON, we propose protocols which exploit information from measurements and user reports in order to estimate current values of the system unknowns and broadcast global action-related values to all users. The protocols suggest an optimal pair of user actions (transmission power and back-off probability) found by minimizing the drift of a certain function. Numerical results illustrate considerable benefits of the dropping rate, at a very low or even zero cost in power expenditure and delay, as well as the fast adaptability of the protocols to environment changes. Although the proposed protocol is designed to minimize primarily the amount of discarded users per cell, our framework allows for other variations (power or delay minimization) as well.Comment: 31 pages, 13 figures, 3 tables. Springer Wireless Networks 201

Form factors for B−−>πlνB-->\pi l\nu decay in a model constrained by chiral symmetry and quark model

The form factors for the $B-->\pi$ transition are evaluated in the entire momentum transfer range by using the constraints obtained in the framework combining the heavy quark expansion and chiral symmetry for light quarks and the quark model. In particular, we calculate the valence quark contributions and show that it together with the equal time commutator contribution simulate a B-meson pole q^2-dependence of form factors in addition to the usual vector meson B^{*}-pole diagram for $B --> \pi l\nu$ in the above framework. We discuss the predictions in our model, which provide an estimate of |V_{ub}|^2.Comment: 7 pages, Revtex, 5 figure, fig 3 is replaced and some text is adde