Much of the algorithms used to calculate dose distributions for photon beams generated by clinical electron linacs (Zhou et al. 2010, Sikora and Alber 2009, Tillikainen 2009) consider three particle sources: a photon source corresponding to Bremsstrahlung in the target (primary source), a second photon source that takes into account those photons produced by scattering into the primary collimat...

We find and study a variety of the spectral-temporal behavior during the decay phase of the light curve of long and bright pulse structures in gamma-ray bursts (GRBs). Even though only a small fraction of observed bursts exhibit such pulses, these are of interest to study as they reflect individual emission episodes during the burst. We have previously found that for about half of these decays,...

The use of brachytherapy sources in radiation oncology requires their proper calibration to guarantee the correctness of the dose delivered to the treatment volume of a patient. One of the elements to take into account in the dose calculation formalism is the non-uniformity of the photon fluence due to the beam divergence that causes a steep dose gradient near the source. The correction factors...

Ultralow-threshold two-photon pumped amplified spontaneous emission (2ASE) and lasing in seeded CdSe/CdS nanodot/nanorod heterostructures is demonstrated for the first time. Such heterostructures allow the independent tunability of the two-photon absorption (2PA) cross-section (σ(2)) through varying the CdS rod size, and that of the emission wavelength through varying the CdSe dot size. With an...

The question of the appropriate extrapolation to low dose has long been a subject of controversy. A linear no-threshold model is favored by regulatory bodies as the basis of RBE assignments and estimates of radiation hazards to the general population. This model is largely supported by extensive application of the linear-quadratic survival formula "fitted" statistically to a wide variety of exp...

We have examined phytochrome regulated changes in transcript abundance for 11 different light regulated mRNAs in developing pea buds. Fluence-response curves were measured for changes in transcript abundance in response to red light pulses in both the low and very low fluence ranges. Most transcripts show only low fluence responses, with a threshold of approximately 10 micromoles per square met...

Imaging of the structure of single proteins or other biomolecules with atomic resolution would be enormously beneficial to structural biology. X-ray freeelectron lasers generate highly intense and ultrashort x-ray pulses, providing a route towards imaging of single molecules with atomic resolution. The information on molecular structure is encoded in the coherent x-ray scattering signal. In con...

We present a detailed investigation on the intensity dependent third-order nonlinear optical (NLO) properties of RF-sputtered WSe2 thin film using ultra short pulses. The employed single-beam Z-scan technique near-infrared (NIR) pulses centered at 1030 nm for ascertaining NLO response. results reveal reverse saturable absorption (RSA) signature, which is primarily due to contribution from two-p...

A three-dimensional (3D) intensity-modulated radiotherapy (IMRT) pretreatment verification procedure has been developed based on the measurement of two-dimensional (2D) primary fluence profiles using an amorphous silicon flat-panel electronic portal imaging device (EPID). As described in our previous work, fluence profiles are extracted from EPID images by deconvolution with kernels that repres...