Size-dependent molecular interaction of nontraditional 2D antibiotics withStaphylococcus aureus.

The application of nanomaterials for their antibacterial properties is the subject of many studies due to antibiotic resistance of pathogen bacteria and the necessity of omitting them from food and water resources. Graphene oxide (GO) is one of the most popular candidates for antibacterial application. However, the optimum condition for such an effect is not yet clear for practical purposes. To shed light on how GO and bacteria interaction depends on size, a wide range of GO flake sizes from hundreds of µm2going down to nano-scale as low as 10 N m2was produced. In anin-vitrosystematic study to inhibitStaphylococcus aureusgrowth, the correlation between GO flake size, thickness, functional group density, and antibacterial activity was investigated. The GO suspension with the average size of 0.05 µm2, in the order of the size of the bacteria itself, had the best bacteriostatic effect onS. aureuswith the minimum inhibitory concentration value of 8 µg ml-1, well within the acceptable range for practical use. The bacteriostatic effect was measured to be a 76.2% reduction of the colony count over 2 h of incubation and the mechanism of action was the wrapping and isolation of cells from the growth environment. Furthermore,in-vivoanimal studies revealed that 16 µg ml-1of the optimum GO has efficient antibacterial performance against the methicillin-resistant strains of the bacteria with an enhanced wound healing rate and tensiometrial parameters which is important for realized targets.

Electron energization dynamics in interaction of self-generated magnetic vortices in upstream of collisionless electron/ion shocks.

Relativistic collisionless shocks are considered responsible for particle energization mechanisms leading to particle acceleration. While electron energization in shock front region of electron/ion collisionless shocks are the most studied, the mechanism of electron energization in interaction with self-generated magnetic vortices (MVs) in the upstream region is still unclear. We investigate electron energization mechanism in the upstream region of electron/ion relativistic collisionless shocks, using two dimensional particle-in-cell (PIC) simulations. We discuss mechanism of electron energization which takes place in the upstream region of the shock, where the counter stream particles interact with incoming flow. The energy gain of electrons happens during their interaction with evolving fields of self-generated magnetic vortices in this region. Three Fermi-like electron energization scenarios are discussed. Stochastic acceleration of electrons in interaction with fields of MV leads to anisotropic heating of fast electrons due to diffusion in the momentum space of electrons and, finally, synergetic effect of evolving fields of MVs leads to the formation of a power-law tail of supra-thermal particles.

Mechanism of laser induced filamentation in dielectrics.

Femtosecond laser filamentation in transparent media has a wide range of applications, from three dimensional manufacturing to biological technologies to supercontinuum generation. While there has been extensive investigations over the last two decades, there remain aspects that are not understood, owing to the complexity of the interaction. We revisit intense femtosecond laser interaction with dielectric materials at 800nm under tight focusing via high resolution three dimensional simulations, where the complete set of Maxwell's equations is solved. We simulate filament formation for a range of tight focusing conditions and laser energies, and through this are able to shed new insight on the dynamics. We find that the role of the Kerr effect is very different depending upon the degree of tight focusing. We are also able to observe the formation of two distinct damage zones for intermediate tight focusing, similar to what was seen but not fully understood almost two decades ago.

Assessment of the changes in quality of life of patients with class II and III deformities during and after orthodontic-surgical treatment.

The aim of this longitudinal study was to assess and compare the oral health-related quality of life (OHRQoL) of patients with class II and III deformities during and after orthodontic-surgical treatment. Thirty class III and 28 class II patients were evaluated at baseline (T0), just prior to surgery (T1), at 6 months after surgery (T2), and at 12 months after debonding (T3). OHRQoL was assessed using the Oral Health Impact Profile (OHIP-14). Friedman two-way analysis of variance and the Wilcoxon signed-rank test were performed to compare the relative changes in OHRQoL during treatment. Significant changes in the overall OHIP-14 scores were observed during and after orthodontic-surgical treatment in both groups. During the pre-surgical stage, psychological discomfort and psychological disability decreased in class III patients, and class II patients experienced a significant deterioration in psychological discomfort during the same period. Six months after surgery, patients in both groups showed improvements in psychological discomfort, social disability, and handicap. Physical disability and functional limitation showed further improvement at 12 months after debonding in class II patients. This study reaffirms that orthodontic-surgical treatment has a significant effect on the OHRQoL of class III and class II patients.

Channeling of relativistic laser pulses, surface waves, and electron acceleration.

The interaction of a high-energy relativistic laser pulse with an underdense plasma is studied by means of 3-dimensional particle in cell simulations and theoretical analysis. For powers above the threshold for channeling, the laser pulse propagates as a single mode in an electron-free channel during a time of the order of 1 picosecond. The steep laser front gives rise to the excitation of a surface wave along the sharp boundaries of the ion channel. The surface wave first traps electrons at the channel wall and preaccelerates them to relativistic energies. These particles then have enough energy to be further accelerated in a second stage through an interplay between the acceleration due to the betatron resonance and the acceleration caused by the longitudinal part of the surface wave electric field. It is necessary to introduce this two-stage process to explain the large number of high-energy electrons observed in the simulations.

The lived experiences of parents of children diagnosed with cancer in Iran.

Threatening nature of childhood cancer and the aggressiveness of prescribed treatments place enormous stress on the family of children suffering from cancer. This study was conducted to better understand the lived experiences of parents of children suffering from cancer and to document their account of such experiences. The aim of this research was to describe the lived experiences of parents of children diagnosed with cancer in Iran. This hermeneutic phenomenological study was conducted between June 2008 and May 2009. Data were generated from 15 parents using in-depth interviews to capture their experiences of having children with cancer. Analysis is based on the framework of Diekelmann enabled data interpretation and elaboration of shared themes. One constitutive pattern 'Feeling trapped in the cancer dead end' and four related themes, namely 'Contradiction in reconciliation with situation', 'Doomed to accept', 'Isolation from others' and 'Devastated life', were identified. The results of this study showed that parents feel as if they are trapped by their child's disease. They are affected by several mental, social and familial issues while trying to tolerate their child's illness and conform to the new order of life.

The first study on enhanced photoresponsivity of ZnO-TiO2 nanocomposite thin films by anodic polarization.

The physical and photoelectrochemical properties of the anodized ZnO-TiO(2) thin films were investigated in this study. Impedance spectroscopy revealed a decrease in charge transfer resistance and Tafel plots determined enhancement of about 200 times in the exchange current (i(0)) after anodization at high positive potential. It was found from XPS analysis that after applying the potential of 5 V to the ZnO-TiO(2) photoelectrode, the lattice oxygen (O(2-)) in the thin film is oxidized to molecular oxygen and then, cations such as Zn(2+) can be solved in the basic electrolyte and passed to the solution. Moreover, according to AFM analysis it was observed that the surface of the samples has been grooved by applying anodic voltage resulting in an increase of effective surface of the film. A mechanism for describing the significant enhancement in the photoresponse of the anodized layer is proposed.

Ion response to relativistic electron bunches in the blowout regime of laser-plasma accelerators.

The ion response to relativistic electron bunches in the so called bubble or blowout regime of a laser-plasma accelerator is discussed. In response to the strong fields of the accelerated electrons the ions form a central filament along the laser axis that can be compressed to densities 2 orders of magnitude higher than the initial particle density. A theory of the filament formation and a model of ion self-compression are proposed. It is also shown that in the case of a sharp rear plasma-vacuum interface the ions can be accelerated by a combination of three basic mechanisms. The long time ion evolution that results from the strong electrostatic fields of an electron bunch provides a unique diagnostic of laser-plasma accelerators.