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In order to smooth the focal spot of high-power energetic lasers, pulses are phase-modulated. However, due to propagation impairments, phase modulation is partly converted into power modulation. This is called frequency modulation to amplitude modulation (FM-to-AM conversion). This effect may increase laser damage and thus increase operating costs. For the first time, to the best of our knowledge, we have studied the impact of the Kerr effect in this process. We have shown that when the Kerr effect is followed by a dispersive transfer function, a dramatic increase of FM-to-AM conversion may occur for a particular kind of FM-to-AM conversion that we have named “anomalous.” Hence, we should remove or compensate for one of the items of the sequence: phase modulation, anomalous FM-to-AM conversion, Kerr effect, or the dispersive function. We have assessed all these solutions, and we have found an efficient inspection method to avoid anomalous FM-to-AM conversion.

Development of appropriate water management strategies in the context of projected air temperature increases under a changing climate necessitates assessing how increases in atmospheric dem...

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5 % N d : 5 % L u : C a F 2 . We observed that depending on the material, wavefront distortions’ profile can vary from a circular lens-like distortion to a complex astigmatic distortion. We showed that this difference comes from the relative sign of piezo-optic tensor coefficients.

High-power nanosecond laser pulses are usually spectrally broadened via temporal phase modulations to tackle the issue of stimulated Brillouin scattering and to achieve optical smoothing of the focal spot. While propagating along the beamline, such pulses can undergo frequency modulation to amplitude modulation (FM-to-AM) conversion. This phenomenon induces modulations of the optical power that can have a strong impact on laser performance. Interference filters are specific FM-to-AM conversion contributors that lead to high-frequency modulations that cannot be measured using conventional means. We propose an indirect method to investigate for such FM-to-AM contributors using spectral measurements. Further analysis of the collected data makes the quantification of the defining parameters of interference filters possible. In turn, we show that it is possible to estimate the range of power modulations induced by interference filters.

We report on the implications that the temporal and spatial beam metrologies have on the accuracy of temporal scaling laws of Laser Induced Damage Threshold (LIDT) for dielectric materials in the picosecond regime. Thanks to a specific diagnostic able to measure the temporal pulse shape of subpicosecond and picosecond pulses, we highlight through simulations and experiments how the temporal shape has to be taken into account first in order to correctly understand the temporal dependency of dielectrics LIDT. This directly eases the interpretation of experimental temporal scaling laws of LIDT and improves their accuracy as a prediction means. We also give numerically determined benchmark temporal scaling laws of intrinsic LIDT for SiO2 (thin film) based on the model developed for this work. Finally, we show as well what kind of spatial metrology is needed during any temporal scaling law determination to take into account potential variations of the spatial profile.

We report on the impact the pulse duration has on the Laser Induced Damage Threshold (LIDT) and on defects initiated damage for dielectric mirrors irradiated by picosecond pulses.

Seeded nanosecond Q-switched Nd:YAG lasers working with an unstable resonator and a variable reflectivity mirror are widely used, for they represent useful sources for stable and repeatable light–matter interaction experiments. Moreover, in most setups, the fundamental wavelength is converted to higher harmonics. When the injection seeder is turned off, random longitudinal mode beating occurs in the cavity, resulting in strong variations of the temporal profile of the pulses. The generated spikes can then be ten times higher than the maximum of equivalent seeded pulses. This strong temporal incoherence is shown to engender spatial incoherence in the focal plane of such unseeded pulses leading to an instantaneous angular displacement of tens of µrad. This effect is even more pronounced after frequency conversion.

This study proposed a natural-rule-based-connection (NRBC) method to connect river segments after water body detection from remotely sensed imagery. A complete river network is important for many hydrological applications. While water body detection methods using remote sensing are well-developed, less attention has been paid to connect discontinuous river segments and form a complete river network. This study designed an automated NRBC method to extract a complete river network by connecting river segments at polygon level. With the assistance of an image pyramid, neighbouring river segments are connected based on four criteria: gap width (Tg), river direction consistency (Tθ), river width consistency (Tw), and minimum river segment length (Tl). The sensitivity of these four criteria were tested, analyzed, and proper criteria values were suggested using image scenes from two diverse river cases. The comparison of NRBC and the alternative morphological method demonstrated NRBC’s advantage of natural rule based selective connection. We refined a river centerline extraction method and show how it outperformed three other existing centerline extraction methods on the test sites. The extracted river polygons and centerlines have a multitude of end uses including rapidly mapping flood extents, monitoring surface water supply, and the provision of validation data for simulation models required for water quantity, quality and aquatic biota assessments. The code for the NRBC is available on GitHub.

Purpose: To evaluate the use of a Fast Fourier Transform (FFT) based pattern‐matching algorithm for two‐dimensional translational and rotational medical image registration.Methods: The FFT pattern matching algorithm is based on the Fourier shift theorem. Briefly, image registration is accomplished by obtaining the Fourier Transform (FT) of two images, taking the normalized cross‐correlation of the two FT, and performing an inverse FT on this correlation matrix. This results in a Dirchlet delta function that has a maximum value at a location corresponding to the translational shift between the two images. Rotational registration can also be achieved by performing this algorithm on the polar transformation of the FT images. The FT registration method was evaluated through the use of clinical images with induced translational and rotational shifts. Results: Over a range of induced shifts of +/−10 mm in both the x and y directions, and induced rotations of +/−10 degrees, all recovered rotations were within 0.1 degree of the induced rotation, and all recovered translations were within 0.5 mm of the induced translation. The computational time of the FT registration on a 1024×1024 image was approximately 2.23 sec. Conclusions: An FFT based image registration algorithm is computationally efficient and provides a high degree of accuracy for two dimensional image registrations. The FFT registration approach provides a distinct analytical solution and does not rely on iterative methods to converge on a solution. In addition, the discrete nature of the FFT means that the accuracy of the solution is directly related to the size of the pixels in the images. The equivalent of sub‐pixel registration can be achieved by simply resizing the image to a larger matrix (i.e. 512×512 to 1024×1024).

Purpose: To evaluate the efficiency gains obtained from using a Graphics Processing Unit (GPU) to perform a Fourier Transform (FT) based image registration.Methods: Fourier‐based image registration involves obtaining the FT of the component images, and analyzing them in Fourier space to determine the translations and rotations of one image set relative to another. An important property of FT registration is that by enlarging the images (adding additional pixels), one can obtain translations and rotations with sub‐pixel resolution. The expense, however, is an increased computational time. GPUs may decrease the computational time associated with FT image registration by taking advantage of their parallel architecture to perform matrix computations much more efficiently than a Central Processor Unit (CPU). In order to evaluate the computational gains produced by a GPU, images with known translational shifts were utilized. A program was written in the Interactive Data Language (IDL; Exelis, Boulder, CO) to performCPU‐based calculations. Subsequently, the program was modified using GPU bindings (Tech‐X, Boulder, CO) to perform GPU‐based computation on the same system. Multiple image sizes were used, ranging from 256×256 to 2304×2304. The time required to complete the full algorithm by the CPU and GPU were benchmarked and the speed increase was defined as the ratio of the CPU‐to‐GPU computational time. Results: The ratio of the CPU‐to‐ GPU time was greater than 1.0 for all images, which indicates the GPU is performing the algorithm faster than the CPU. The smallest improvement, a 1.21 ratio, was found with the smallest image size of 256×256, and the largest speedup, a 4.25 ratio, was observed with the largest image size of 2304×2304. Conclusions: GPU programming resulted in a significant decrease in computational time associated with a FT image registration algorithm. The inclusion of the GPU may provide near real‐time, sub‐pixel registration capability.

PETAL is an additional PW beamline to the LMJ. The kJ shots in the amplifier section, the compressor alignment and the 1.15 PW @ 850 J operations are detailed. Damage issues encountered are also addressed.

A Fourier Transform (FT) based pattern-matching algorithm was adapted for use in medical image registration. This algorithm obtained the FT of two images, determined the normalized cross-power spectrum of the transformed images, and then applied an inverse FT. The result was a delta function with a maximum value at the location corresponding to the distance between the two images; a similar method was used to recover rotations. This algorithm was first tested using a simple two-dimensional image, with induced shifts of ±20 pixels and ±10 degrees. All translations were recovered with no error and all rotations were recovered within 0.18 degrees. Subsequently, this algorithm was tested on eight clinical kV images drawn from four different body sites. Twenty-five random shifts and rotations were applied to each image. The average mean error of the registration solution was -0.002 ± 0.077 mm in the x direction, 0.002 ± 0.075 mm in the y direction, and -0.012 ± 0.099 degrees. These initial results suggest that a FT algorithm has a high degree of accuracy when registering clinical kV images.

We report an effect potentially harmful occurring in regenerative amplifiers due to stimulated Brillouin scattering (SBS). Most high energy laser facilities use phase-modulated pulses to prevent the transverse SBS effect in large optical components and to smooth the focal spot on target. However, this kind of pulse format may undergo a detrimental effect known as frequency modulation to amplitude modulation (FM-AM) conversion in the presence of spectral distortions. In the present letter, we show experimentally and numerically, that SBS can also potentially be created in the regenerative amplifier located in the front-end. In this scenario, some of the side bands of the pulse reflected by regen end-cavity mirror may act as a seed for SBS in an optical component, if the pulse spectrum contains frequency components exactly separated by the Brillouin frequency shift. This self-seeded SBS induces amplitude modulation with a nonlinear dependence that may be detrimental during down-stream propagation. However, we show that a careful choice of the modulation frequencies can mitigate this effect.

Dual energy (DE) imaging consists of obtaining kilovoltage (kV) x-ray images at two different diagnostic energies and performing a weighted subtraction of these images. A third image is then produced that highlights soft tissue. DE imaging has been used by radiologists to aid in the detection of lung malignancies. However, it has not been used clinically in radiotherapy. The goal of this study is to assess the feasibility of performing DE imaging using a commercial on-board imaging system. Both a simple and an anthropomorphic phantom were constructed for this analysis. Planar kV images of the phantoms were obtained using varied imaging energies and mAs. Software was written to perform DE subtraction using empirically determined weighting factors. Tumor detectability was assessed quantitatively using the signal-difference-to-noise ratio (SDNR). Overall DE subtraction suppressed high density objects in both phantoms. The optimal imaging technique, providing the largest SDNR with a dose less than our reference technique was 140 kVp, 1.0 mAs and 60 kVp, 3.2 mAs. Based on this analysis, DE subtraction imaging is feasible using a commercial on-board imaging system and may improve the visualization of tumors in lung cancer patients undergoing image-guided radiotherapy.

Background Ankyrin 3 ( ANK3 ) has been strongly implicated as a risk gene for bipolar disorder (BD) by recent genome-wide association studies of patient populations. However, the genetic variants of ANK3 contributing to BD risk and their pathological function are unknown. Methods To gain insight into the potential disease relevance of ANK3 , we examined the function of mouse Ank3 in the regulation of psychiatric-related behaviors using genetic, neurobiological, pharmacological, and gene-environment interaction (G×E) approaches. Ank3 expression was reduced in mouse brain either by viral-mediated RNA interference or through disruption of brain-specific Ank3 in a heterozygous knockout mouse. Results RNA interference of Ank3 in hippocampus dentate gyrus induced a highly specific and consistent phenotype marked by decreased anxiety-related behaviors and increased activity during the light phase, which were attenuated by chronic treatment with the mood stabilizer lithium. Similar behavioral alterations of reduced anxiety and increased motivation for reward were also exhibited by Ank3+/– heterozygous mice compared with wild-type Ank3+/+ mice. Remarkably, the behavioral traits of Ank3 +/– mice transitioned to depression-related features after chronic stress, a trigger of mood episodes in BD. Ank3 +/– mice also exhibited elevated serum corticosterone, suggesting that reduced Ank3 expression is associated with elevated stress reactivity. Conclusions This study defines a new role for Ank3 in the regulation of psychiatric-related behaviors and stress reactivity that lends support for its involvement in BD and establishes a general framework for determining the disease relevance of genes implicated by patient genome-wide association studies.

Some silica plates of high power nanosecond lasers may be a few centimeter thick for instance because they should sustain vacuum. Measuring laser-induced damage thresholds at the output surface of these thick silica plates is a complex task because non-linear laser propagation effects may occur inside the plate which prevents knowing accurately the fluence at the output. Two non-linear effects have to be considered: stimulated Brillouin scattering (SBS) and Kerr effect. SBS is mainly driven by the spectral power density of the pulses: if the spectral power density is below a threshold, SBS is negligible. Thus, spectral broadening is required. Kerr effect depends on the instantaneous intensity. Hence, a smooth temporal shape without overshoots is required. However, both conditions (wide spectrum and no overshoots) are impossible to fulfill with standard lasers. As a matter of fact, an injected laser has a smooth temporal profile but is spectrally narrow. Without injection, the laser is multimode yielding a wide spectrum but a chaotic temporal profile. We solved the problem by phase-modulating a continuous-wave seeder of our laser (patent pending). The phasemodulation frequency is adjusted to a multiple of the inverse of the round-trip time of the laser cavity. The laser pulses have a wide spectrum to suppress SBS and do not exhibit temporal overshoots to reduce Kerr effects. During the presentation, we will show the features of the laser pulses and laser-induced damage measurements of thick silica plates using this scheme.

Thanks to a phase-modulated injection seeder, we report the operation of a nanosecond Nd:YAG Q-switched laser with pulses having both a large spectral bandwidth and a smooth temporal waveform. Because of the smooth temporal waveform, such pulses allow, for instance, reducing the impact of the Kerr effect and, because of the large spectral bandwidth, suppressing stimulated Brillouin scattering. We conducted a parametric study of the features of the generated pulses versus the injection conditions. We show that, as opposed to the central frequency (wavelength) of the seeder, the phase modulation frequency has to be carefully chosen, but it is not a critical parameter and does not require any particular feedback.

Periphytic algae are a rich food resource that sustains the upper trophic levels of stream ecosystems. These algae are susceptible to loss through hydraulic shear and abrasion by mobile sediments, but there are few documented linkages between periphyton biomass and sediment transport regimes. In this study, we use both a large set of field observations and an in situ experiment to document the relationship between periphyton biomass and sand transport rate. The in situ experimental design investigates the response of diatom-dominated periphyton biomass to abrasion from fine and coarse sand in transport over low-lying and higher protruding host rocks. Our results showed that periphyton biomass decreased with increasing transport rates in a threshold-type response (transport rates > 0·04–1·8 g m−1 s−1) quantified using classification and regression trees. The in situ experiment revealed that low-lying rocks lost more biomass for a given transport rate than the higher, protruding ones. Saltating coarse sand abraded surfaces more effectively than fine sand travelling primarily in suspension. The observed pattern of biomass loss was similar to that reported in flume studies of the effects of suspended sediment on periphyton. The negative relationship between sand transport rate and post-flow event biomass was nearly identical to that found on the Skona River, Norway, for larger flow events. Sand constitutes a large percentage of the bedload of gravel-bed rivers and is susceptible to transport during frequent flow events. Even small increases in sand loadings to the gravel-cobble river bed can cause large increases in streambed abrasion. Copyright © 2012 John Wiley & Sons, Ltd.

Several genome-wide association studies (GWAS) for bipolar disorder (BD) have found a strong association of the Ankyrin3 (ANK3) gene. This association spans numerous linked single nucleotide polymorphisms (SNPs) in a ~250 kb genomic region overlapping ANK3. The associated region encompasses predicted regulatory elements as well as two of six validated alternative first exons, which encode distinct protein domains at the N-terminus of the protein also known as ankyrin-G (AnkG). Using RNA Ligase-Mediated Rapid Amplification of cDNA Ends (RLM-RACE) to identify novel transcripts in conjunction with a highly sensitive, exon-specific multiplexed mRNA expression assay, we detected differential regulation of distinct ANK3 transcription start sites (TSSs) and coupling of specific 5’ ends with 3’ mRNA splicing events in post-mortem human brain and human stem cell-derived neural progenitors and neurons. Furthermore, allelic variation at the BD–associated SNP rs1938526 correlated with a significant difference in cerebellar expression of a brain-specific ANK3 transcript. These findings suggest a brain-specific cis-regulatory transcriptional effect of ANK3 may be relevant to BD pathophysiology.

Frequency modulation to amplitude modulation (FM-to-AM) conversion is an important issue that can prevent fusion ignition with high power lasers such as with the Laser Megajoule (LMJ). A way to reduce FM-to-AM conversion is to change the phase modulation (currently sinusoidal). In this paper, we study the case of random phase modulation. We show, with numerical simulation modeling, FM-to-AM conversion induced by different transfer functions, in which such a modulation format, in some cases, may significantly reduce FM-to-AM conversion, particularly in the case of amplitude filtering. Phase filtering may create high overshoots, but the occurence probability is low, and, on average, random phase modulation is advantageous compared with sinusoidal modulation. We also demonstrate an equivalent smoothing efficiency with the LMJ facility with an important reduction of FM-to-AM conversion compared with the current solution. Taking particular random draws (pseudo-random modulation), we exhibit optimal performance.

The patchy spatial distribution of benthic algae (periphyton) on gravel-bed rivers might be caused by physical disturbances during small frequent flow spates. During such spates, the gravel–cobble river bed is stable, but flows are often strong enough to transport large quantities of sand by a hopping motion called saltation. We tested the hypothesis that a spate-related refuge habitat exists in a transition zone (TZ) between the edge of the varial zone and the thalweg of the river channel where high hydraulic stress and saltating sand reduce biomass. We documented physical disturbance and periphyton biomass across 15 riffles after 3 summer spate periods in an oligomesotrophic river in Quebec. Periphyton perturbation thresholds were identified for near-bed water velocity during prespate growth (0.25 m/s) and for sand transport (64–180 g m−1event−1) and flow shear stress (15 Pa) during spates. Generalized linear models were used to examine cross-riffle trends in these 3 disturbance variables and in...

The magnitude and frequency of discharge and fine sediment delivery to rivers can influence riverine food webs through the frequency of scour of algae from the streambed. Models that simulate changes in algal biomass are not very accurate for long periods with frequent low-magnitude flow events. During these periods, sand is mobilized over a stable gravel bed and periphyton losses are patchy at the reach scale. At the patch scale, we examine if an established threshold for rapid sand transport ( W s a * = 0.002 ) is also a periphyton perturbation threshold. We also develop and validate a statistical rock scale periphyton saltation abrasion model (PSAM) to simulate the abrasive effects of sand, transported by a hopping motion called saltation, on post-flow event biomass. Data were collected from 15 riffles of a Canadian Atlantic salmon river. The W s a * = 0.002 threshold clearly divided bed patches with high biomass and low transport rates, from those patches with low biomass and high transport rates. A dimensionally balanced PSAM regression model including W s a * explained 57% of the variance in post-flow event biomass. The validated model indicates that periphyton biomass decreases with increasing sand transport rates ( W s a * ) . Biomass was higher if the microscopic algae were protected from abrasion by growing either above the near-bed layer of saltating sand or within a mat containing more resistant macroalgae (e.g. Nostoc). The use of W s a * in our models facilitates testing of our findings in other hydro-sedimentary environments because W* is a dimensionless scaling parameter that is well established in sediment transport literature. New insight is provided regarding modelling local heterogeneity in post-flow event biomass. These developments are essential to enable more accurate assessments of how periphyton biomass will change with the increase in the recurrence frequency of small flow events (and sand supply) associated with urbanization and climate change.

This paper proposes an automated water body detection method to delineate detailed water bodies from high-resolution satellite images. It consists of three steps: a) coarse water mask detection from optical imagery using unsupervised classification; b) water mask refinement using backscatter value from synthetic aperture radar (SAR) images; and c) advanced morphological filtering to produce a final water mask. The experiments over Calgary Alberta demonstrate the importance of each step and show the advantages of this method relative to traditional methods, namely, its high degree of accuracy, ability to be full-automated, stability and potential for transferability. It is designed for water mask detection at sub-meter accuracy for industrial and governmental users undertaking hydraulic modeling in an urban environment.

G-quadruplexes (G4) are tetrahelical structures formed from planar arrangement of guanines in nucleic acids. A simple, regular motif was originally proposed to describe G4-forming sequences. More recently, however, formation of G4 was discovered to depend, at least in part, on the contextual backdrop of neighboring sequences. Prediction of G4 folding is thus becoming more challenging as G4 outlier structures, not described by the originally proposed motif, are increasingly reported. Recent observations thus call for a comprehensive tool, capable of consolidating the expanding information on tested G4s, in order to conduct systematic comparative analyses of G4-promoting sequences. The G4RNA Database we propose was designed to help meet the need for easily-retrievable data on known RNA G4s. A user-friendly, flexible query system allows for data retrieval on experimentally tested sequences, from many separate genes, to assess G4-folding potential. Query output sorts data according to sequence position, G4 likelihood, experimental outcomes and associated bibliographical references. G4RNA also provides an ideal foundation to collect and store additional sequence and experimental data, considering the growing interest G4s currently generate. Database URL: scottgroup.med.usherbrooke.ca/G4RNA

Seeded nanosecond Q-switched Nd:YAG lasers working with an unstable resonator and a variable-reflectivity-mirror are widely used for they represent useful sources for stable and repeatable light-matter-interaction experiments. Moreover, in most setups, the fundamental wavelength is converted to higher harmonics. When the injection seeder is turned off, random longitudinal mode beating occurs in the cavity, resulting in strong variations of the temporal profile of the pulses. The generated spikes can then be ten times higher than the maximum of equivalent seeded pulses. This strong temporal incoherence is shown to engender spatial incoherence in the focal plane of such unseeded pulses leading to an instantaneous angular displacement of tens of µrad. This effect is even more pronounced after frequency conversion.

Low socioeconomic status has been reported to be associated with head and neck cancer risk. However, previous studies have been too small to examine the associations by cancer subsite, age, sex, global region and calendar time and to explain the association in terms of behavioral risk factors. Individual participant data of 23,964 cases with head and neck cancer and 31,954 controls from 31 studies in 27 countries pooled with random effects models. Overall, low education was associated with an increased risk of head and neck cancer (OR 5 2.50; 95% CI 5 2.02-3.09). Overall one-third of the increased risk was not explained by differences in the distribution of cigarette smoking and alcohol behaviors; and it remained elevated among never users of tobacco and nondrinkers (OR 5 1.61; 95% CI 5 1.13-2.31). More of the estimated education effect was not explained by cigarette smoking and alcohol behaviors: in women than in men, in older than younger groups, in the oropharynx than in other sites, in South/Central America than in Europe/North America and was strongest in countries with greater income inequality. Similar findings were observed for the estimated effect of low versus high household income. The lowest levels of income and educational attainment were associated with more than 2-fold increased risk of head and neck cancer, which is not entirely explained by differences in the distributions of behavioral risk factors for these cancers and which varies across cancer sites, sexes, countries and country income inequality levels. © 2014 UICC.

Because the piglet is frequently used as a model for developmental disorders of the medullary serotonergic (5-HT) system in the human infant, this review compares the topography and developmental profile of selected 5-HT markers between humans in the first year of life and piglets in the first 60 days of life. The distribution of tryptophan hydroxylase-immunoreactive 5-HT neurons in the human infant medulla is very similar, but not identical, to that in the piglet. One notable difference is the presence of compact clusters of 5-HT neurons at the ventral surface of the piglet medulla. While it lacks these distinctive clusters, the human infant medulla contains potentially homologous 5-HT neurons scattered along the ventral surface embedded in the arcuate nucleus. Each species shows evidence of age-related changes in the 5-HT system, but the changes are different in nature; in the human infant, statistically significant age-related changes are observed in the proportional distribution of medullary 5-HT cells, while in the piglet, statistically significant age-related changes are observed in the levels of 5-HT receptor binding in certain medullary nuclei. Analyses of 5-HT receptor binding profiles in selected nuclei in the two species suggest that the equivalent postnatal ages for 5-HT development in piglets and human infants are, respectively, 4 days and 1 month, 12 days and 4 months, 30 days and 6 months, and 60 days and 12 months. Collectively, when certain species differences are considered, these data support the use of the piglet as a model for the human infant medullary 5-HT system.

The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline. The first kJ shots in the amplifier section with a large spectrum front end, the alignment of the synthetic aperture compression stage and the initial demonstration of the 1.15 PW @ 850 J operations in the compression stage are detailed. Issues encountered relating to damage to optics are also addressed.

Purpose To retrospectively estimate the cumulative absorbed dose (at the skin) from kilovoltage planar x-rays received by 90 patients treated on a Varian iX and to determine if that dose could be reduced without sacrificing image quality. Methods and materials To estimate surface dose, measurements were obtained using the “in-air” method by varying the source-to-detector distance from 80 to 100 cm in steps of 5 cm. Energy was varied from 70 to 120 kVp. Using these data, a global equation was developed to estimate the cumulative skin dose by applying the imaging settings (kVp, mAs), patient-specific source-to-skin distance, and total number of images. To reduce the imaging dose, anterior and lateral images of RANDO phantoms were obtained using the same kVp; however, the mAs settings were systematically reduced. Contrast-to-noise ratios (CNRs) were calculated for both the standard phantom images and reduced mAs images. The mAs values were chosen to minimize skin dose while maintaining a similar CNR. Last, daily kV anterior and lateral images were obtained using these reduced mAs settings for 7 patients currently being treated with image guided radiation therapy. CNR was determined and compared with the values obtained on images taken 1 day before this change. Results Average cumulative kV imaging dose was as large as 162.2 cGy for pelvic cases with standard kVp, mAs. Other doses varied by site and technique. By lowering mAs, this dose could be reduced by 49% with only a 0.9% decrease in CNR. For the 7 patients currently being treated with image guided radiation therapy, CNR values were not statistically different ( P = .79), whereas the skin dose was reduced by an average of approximately 50%. Conclusions kV planar imaging dose reduction should be considered, given the large cumulative skin dose for certain disease sites. When mAs are reduced, planar dose reduction is clinically feasible without sacrificing image quality.

In lasers used for inertial confinement fusion (ICF) both temporal and spectral performances have to be controlled with accuracy. As commercial systems do not allow accurate enough measurements, we developed new diagnostics. For spectral measurements, we developed an innovative highly resolving spectrometer. This system allows a 1GHz resolution measure of spectrum in single-shot operation. For temporal shape measurement, we implemented upgrades and go on with the pre-industrial integration of our previous early design1, in an all-in-one box system. This system enables real-time analysis of optical pulse shapes for wavelengths from 300nm up to 2μm. Thanks to an innovative optical-electro-optical (OEO) sub-converter, it is also possible to measure electrical pulses, with 60GHz bandwidth at 500Gs/s and up to 3Ts/s sampling rate and more than 8-bit dynamics range. We developed an all fibered system that allows direct measurement of temporal Dynamic Extinction Ration (DER) 3 for pulsed laser in single shot operation. This device could be adapted to several wavelengths and allows achieving a measurement up to 60dB of DER with 1dB accuracy. In brief, we will give an up-to-date description of some recent development in high precision diagnostics applied to LMJ front-end.

With the purpose of understanding nanosecond laser induced damage mechanisms when working with multiple longitudinal mode pulses, an accurate measurement of the temporal profiles is required. In this study, the use of a streak camera with a wide bandwidth is justified through the knowledge of the Nd:YAG spectral characteristics. A statistical and phenomenological analysis of multiple longitudinal modes intensity profiles is then performed through experiments and modeling. The resolution limitation of our photodiodes is also discussed.

NELL1 and NELL2 (neural epidermal growth factor-like 1 and 2) are recently described members of the epidermal growth factor gene family that have previously been shown to be expressed almost exclusively in brain tissue. Here we demonstrate regulated expression of NELL1 and NELL2 in human hematopoietic cells. Mature NELL1 mRNA is not detected in any normal hemopoietic cell type, although the gene is transcribed during a narrow window of pre-B cell development, and cell lines at the same developmental stage express the NELL1 mRNA. The related NELL2 gene is expressed by all nucleated peripheral blood cells examined (B, T, monocyte, and natural killer cells), but not in any of the bone marrow B lineage cells at earlier stages of development. However, leukemic cell lines corresponding to the same early differentiation stages express abundant NELL2 mRNA. These results suggest normal and possible oncogenic roles for the NELL proteins in hemopoietic cells.

A multi-Petawatt high-energy laser PETAL coupled to the Ligne d’Int´ Laser (LIL) is under construction in the Aquitaine Region in France. This Petawatt laser will be dedicated to academic experiments in the fields of high energy density physics and ultra high intensity. Nd : glass laser chain coupled with the chirped pulse amplification (CPA technique allows delivery of high energy. Optical parametric CPA for pre-amplification and a new compression scheme will be implemented. PETAL is designed to deliver 3.6 kJ of energy in 500 fs on a target corresponding to 7.2 PW. The PETAL beam linked to the up to 60 kJ ns UV beams from the LIL will present new scientific research opportunities. (Some figures in this article are in colour only in the electronic version)

We report on an experimental demonstration of linear precompensation of nonlinear phase and amplitude transfer functions. We show the effective compensation with a linear all-fiber system of phase-to-amplitude modulation conversion due to a frequency conversion system including plane gratings and a nonlinear crystal.

A prospective feasibility study was conducted to investigate the utility of dual-energy (DE) imaging compared to conventional x-ray imaging for patients undergoing kV-based image guided radiation therapy (IGRT) for lung cancer.An institutional review board-approved feasibility study enrolled patients with lung cancer undergoing IGRT and was initiated in September 2011. During daily setup, 2 sequential respiration-gated x-ray images were obtained using an on-board imager. Imaging was composed of 1 standard x-ray image at 120 kVp (1 mAs) and a second image obtained at 60 kVp (4 mAs). Weighted logarithmic subtraction of the 2 images was performed offline to create a soft tissue-selective DE image. Conventional and DE images were evaluated by measuring relative contrast and contrast-to-noise ratios (CNR) and also by comparing spatial localization, using both approaches. Imaging dose was assessed using a calibrated ion chamber.To date, 10 patients with stage IA to IIIA lung cancer were enrolled and 57 DE images were analyzed. DE subtraction resulted in complete suppression of overlying bone in all 57 DE images, with an average improvement in relative contrast of 4.7 ± 3.3 over that of 120 kVp x-ray images (P.0002). The improvement in relative contrast with DE imaging was seen for both smaller (gross tumor volume [GTV] ≤5 cc) and larger tumors (GTV5 cc), with average relative contrast improvement ratios of 3.4 ± 4.1 and 5.4 ± 3.6, respectively. Moreover, the GTV was reliably localized in 95% of the DE images versus 74% of the single energy (SE images, (P=.004). Mean skin dose per DE image set was 0.44 ± 0.03 mGy versus 0.43 ± 0.03 mGy, using conventional kV imaging parameters.Initial results of this feasibility study suggest that DE thoracic imaging may enhance tumor localization in lung cancer patients receiving kV-based IGRT without increasing imaging dose.

In order to avoid propagation nonlinearities (Kerr effect, Raman and Brillouin scattering) and optical damage, nanosecond high power lasers such as the Laser MegaJoule (LMJ) amplify quasi-monochromatic pulses. But they generate a static speckle pattern in the focal spot. This speckle pattern needs to be smoothed in order to lower high intensity peaks which are detrimental during the propagation and the interaction with the plasma in the target. Different techniques are implemented to smooth the intensity nevertheless all high power lasers carry at least smoothing by spectral dispersion. It consists in broadening the spectrum through a phase modulator and focusing the different wavelengths at slightly different positions using a diffractive element such as a grating. In the temporal domain, it has been theoretically shown that the pulse power is thus filtered between near field and far field [1, 2]. The filtering allows techniques such as “picket fence” to increase conversion efficiency [1] and reduces detrimental effects of unwanted intensity distortions called FM-AM conversion [2, 3]. Here, to the best of our knowledge we show the first experimental measurement of the frequency transfer function of this filtering. Measurements are in perfect agreement with the numerical calculations.

We have identified DNA sequence polymorphisms in the C gamma 3 genes of BALB/c and C57BL/6 mice. One of these results in a Ser-->Gly amino acid difference in CH1 at position 129 according to the Wu and Kabat numbering system. There are three additional silent substitutions in the coding region and two polymorphic nucleotides in the 3' untranslated region. According to standard nomenclature in which alleles are numbered according to the order of their identification, these C gamma 3 alleles are designated Igh-8a and Igh-8b respectively. We also describe two polymerase chain reaction-based assays that identify the allelic differences.

It is known that a linear filter may be easily compensated with its inverse transfer function. However, it was shown that this approach could also be valid even for such a complex nonlinear system as frequency conversion. As a matter of fact, it is possible to at least partly precompensate for distortions occurring within, or even downstream from, frequency conversion crystals with a simple linear optical filter set upstream. In this paper, we give the theoretical background and derive the optimum precompensation filter from simple analytical formulas even in the case of saturation. We first show the relevance of our approach for Gaussian pulses: the pulse may be short or not and chirped or not, and the same linear precompensation filter may be used as long as saturation is not reached. We then study the case of phase-modulated pulses, as can be found on high power lasers such as lasers for fusion. We show that previous experimental results are in perfect agreement with these calculations. Finally, justified by our simple analytical formulas, we present a rigorous parametrical study giving the distortion reduction for any second and third harmonic generation system in the case of phase-modulated pulses.

The LMJ (Laser MegaJoule) is dedicated to inertial confinement fusion. To perform this type of experiment, 160 square beams are frequency converted and focused onto a target filled with a deuterium tritium mixture. We propose to review how these beams are shaped along their propagation through the LMJ. Going upstream from the target to the laser source, specific optics has been designed to meet the beam shaping requirement. A focusing grating and a pseudorandom phase plate concentrate the energy onto the target. A deformable mirror controls and compensates the spatial phase defect occurring during the propagation through the main slab amplifiers. A liquid crystal cell shapes the beam in order to compensate the gain profile of the main amplifiers. It also protects the growth of damages that take place in the final optics of the chain. At last, a phase mirror generates a square flat top mode from a gaussian beam within a regenerative amplifier. All these optical components have one common principle: they control the phase of the spatial laser field.

We report on an experimental demonstration of linear precompensation of nonlinear phase and amplitude transfer functions. We show the effective compensation with a linear all-fiber system of phase-to-amplitude modulation conversion due to a complete frequency conversion system including plane gratings and a nonlinear crystal.

The first experimental demonstration of linear precompensation of a non-linear transfer function due to frequency conversion is reported. We show the effective precompensation with an interferometric filter of phase-to-amplitude modulations conversion due to second-harmonic generation.