Beam-pointing verification using x-ray pinhole cameras on the 60-beam OMEGA laser.

On the OMEGA laser system, the beam-pointing accuracy is verified by irradiating a 4 mm diameter Au-coated spherical target with ∼23 kJ of laser energy. Up to ten x-ray pinhole cameras record the x-ray emission from all 60-beam spots. A new set of algorithms has been developed to improve the accuracy of the pointing evaluation. An updated edge-finding procedure allows one to infer the center of the sphere with subpixel accuracy. A new approach was introduced to back-propagate the pixel locations on the 2D image to the 3D surface of the sphere. A fast Fourier transform-based de-noising method significantly improves the signal-to-noise of the data. Based on the beam-pointing analysis, hard-sphere calculations of the laser-drive illumination uniformity on the target surface and the decomposition of the illumination distribution into lower order modes (1-10) are evaluated.

3D Simulations Capture the Persistent Low-Mode Asymmetries Evident in Laser-Direct-Drive Implosions on OMEGA.

Spherical implosions in inertial confinement fusion are inherently sensitive to perturbations that may arise from experimental constraints and errors. Control and mitigation of low-mode (long wavelength) perturbations is a key milestone to improving implosion performances. We present the first 3D radiation-hydrodynamic simulations of directly driven inertial confinement fusion implosions with an inline package for polarized crossed-beam energy transfer. Simulations match bang times, yields (separately accounting for laser-induced high modes and fuel age), hot spot flow velocities and direction, for which polarized crossed-beam energy transfer contributes to the systematic flow orientation evident in the OMEGA implosion database. Current levels of beam mispointing, imbalance, target offset, and asymmetry from polarized crossed-beam energy transfer degrade yields by more than 40%. The effectiveness of two mitigation strategies for low modes is explored.

Optical characterization of the on-target OMEGA focal spot at high energy using the full-beam in-tank diagnostic.

The full-beam in-tank (FBIT) diagnostic has been deployed to directly measure the target-plane beam fluence profile, when operated at high energy, of the OMEGA Laser System at the University of Rochester's Laboratory for Laser Energetics. This paper presents the results of early measurements taken with this diagnostic and discusses an improvement that has overcome performance limitations discovered during the initial testing. The diagnostic gives new insight into the ability of the OMEGA Laser System to provide uniform fluence profiles that are consistent across all 60 beams in the laser. The ultimate goal of the FBIT diagnostic is to allow accurate assessment of the fluence uniformity on a spherical target in 60-beam implosion experiments.

Inferred UV fluence focal-spot profiles from soft x-ray pinhole-camera measurements on OMEGA.

A method was developed with laser-irradiated Au planar foils to characterize the focal spot of UV laser beams on a target at full energy from soft x-ray emission. A pinhole camera with a back-thinned charge-coupled device detector and filtration with thin Be and Al foil filters provides images of the x-ray emission at photon energies <2 keV. This method requires a careful measurement of the relationship between the applied UV fluence and the x-ray signal, which can be described by a power-law dependence. The measured exponent γ ∼ 2 provides a dynamic range of ∼25 for the inferred UV fluence. UV fluence profiles of selected beams were measured for 100-ps and 1-ns laser pulses and were compared to directly measured profiles from an UV equivalent-target-plane diagnostic. The inferred spot size and super-Gaussian order from the x-ray technique agree within several percent with the values measured with the direct UV measurements.

Power balancing the multibeam OMEGA laser.

Multibeam lasers often require an output beam balance that specifies the degree of simultaneity of the laser output energy, instantaneous power, or instantaneous irradiance (power per unit area). This work describes the general problem of balancing a multibeam laser. Specific techniques used to balance the output power of the 60-beam pulsed OMEGA Laser System are discussed along with a measured reduction of beam-to-beam imbalance. In particular, the square-pulse distortion induced by a simple saturating amplifier operating with its output at some fraction of its saturation fluence is derived, and a method to exchange gain between saturated amplifiers in a single beam that have different saturation fluences to adjust balance is described.

The influence of enteral obestatin administration to suckling rats on intestinal contractility.

This study investigated the effect of enteral administration of obestatin on the contractility of whole-thickness preparations of duodenum and middle jejunum, as well as on the morphology of the enteric nervous system (ENS). Suckling rats were assigned to 3 groups (n=12) treated with: C-saline solution; LO-obestatin (125nmol/kgb.wt); HO-obestatin (250nmol/kgb.wt). Saline solution or obestatin were administered twice daily, from the 14th to the 21st day of life. Sections were studied in an organ bath, for isometric recording in the presence of acetylocholine (ACh), atropine (ATR) and tetradotoxin (TTX). Thickness of intestinal muscularis layer, the number of interstitial cells of Cajal (ICC) were measured in the paraffin sections. The immunodetection of Muscarinic Acetylocholine Receptor 2 (M2 receptor) was performed in the intestinal segments. In both intestinal segments HO treatment decreased the amplitude of spontaneous contraction compared to that observed in the C group. In the middle jejunum, the LO treatment also decreased the amplitude. TTX and ATR had no effect on amplitude of spontaneous contraction in the jejunum of LO and HO-treated animals. Compared to the C group, duodenal sections from HO animals and middle jejunum sections from LO and HO groups displayed a lower amplitude in response to ACh and EFS evoked contraction. An increase in the thickness of the muscularis layer was observed in the duodenum of LO and HO groups whereas the number ICC did not change significantly after treatment with obestatin. Moreover, the enteral administration of obestatin did not effect significantly on the cytoplasmic expression of M2 receptor in the jejunum. Our study demonstrated that enteral administration of obestatin to suckling rats influences small intestine contractility in the segment specific manner.

A picosecond beam-timing system for the OMEGA laser.

A timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the ultraviolet light from each beam into a single photodetector.

250 mJ, self-adaptive, diode-side-pumped Nd:YAG slab laser.

A scheme of self-adaptive, closed-loop, diode-side-pumped Nd:YAG slab laser was presented. As a result of four-wave mixing of standing waves intersecting at a small angle in a closed-loop cavity, the self-adaptive process of beam cleaning leading to fundamental mode operation despite severe asymmetry of the inversion profile and thermal-optical distortion was achieved. The output beam was extracted from the cavity as the first- order diffraction beam on the dynamic gain gratings created in an active medium. The near-diffraction-limited (parameter M(2)<1.4, divergence of 1 mrad) output beam of 250 mJ energy and the optical slope efficiency of 30% at a repetition rate of up to 25 Hz in a free-running regime were demonstrated.

Increasing hydrodynamic efficiency by reducing cross-beam energy transfer in direct-drive-implosion experiments.

A series of experiments to determine the optimum laser-beam radius by balancing the reduction of cross-beam energy transfer (CBET) with increased illumination nonuniformities shows that the hydrodynamic efficiency is increased by ∼35%, which leads to a factor of 2.6 increase in the neutron yield when the laser-spot size is reduced by 20%. Over this range, the absorption is measured to increase by 15%, resulting in a 17% increase in the implosion velocity and a 10% earlier bang time. When reducing the ratio of laser-spot size to a target radius below 0.8, the rms amplitudes of the nonuniformities imposed by the smaller laser spots are measured at a convergence ratio of 2.5 to exceed 8 µm and the neutron yield saturates despite increasing absorbed energy, implosion velocity, and decreasing bang time. The results agree well with hydrodynamic simulations that include both nonlocal and CBET models.

Association of pulsatility index in the middle cerebral artery with intelligence quotient in children with sickle cell disease.

The aim of this study was to explore whether intellectual performance in children with Sickle Cell Disease and with low risk of stroke as determined with conventional transcranial Doppler ultrasonography (TCD) criteria was associated with hemodynamic parameters in imaging TCD, when controlling for hematological and socio-economical variables and presence of silent infarcts. We performed neuropsychological testing with Kaufman Brief Intelligence Test (K-BIT-IQ) and imaging TCD examinations to measure blood flow velocities and pulsatility indexes (PI) in the middle cerebral arteries (MCA) In 46 children with homozygous HbSS (mean age 108±34 months, range limits: 47-166 months; 24 females), without a history of stroke or transient ischemic attack, with no stenosis on magnetic resonance angiography and with velocities below 170 cm/s in screening conventional TCD. Mean K-BIT IQ Composite and Vocabulary scores (91±13 and 86±14 respectively) were significantly below the average scores of 100 for the age-matched population (one sample t-test=5.21, p<0.001). Using univariate and multivariate regression models, we found that lower PI in the right MCA was associated with lower K-BIT-IQ Composite and Vocabulary scores. Furthermore, we found that interhemispheric differences in PIs were even more strongly associated with neuropsychological performance, whereas flow velocities were not associated with the K-BIT-IQ score. Using a model of chronic anemia, we found that cognitive functioning was associated with cerebral hemodynamics.

Sickle cell disease in children: accuracy of imaging transcranial Doppler ultrasonography in detection of intracranial arterial stenosis.

This study aimed to determine the accuracy of imaging transcranial Doppler sonography in detection of intracranial arterial stenosis in children with sickle cell disease using three-dimensional MR angiography as a reference standard. Sixty-one children (mean age 102±39 months, 30 males), who had no history of overt stroke, and were classified as at lowest risk of stroke by mean flow velocity criterion <170 cm/s, underwent conventional and imaging transcranial Doppler ultrasonographic examinations. We employed the area under the receiver operating characteristic curve (AUC) to determine the accuracy of flow velocity measurements obtained with imaging ultrasonography with and without correction for the angle of insonation as well as with conventional ultrasonography. We also established the most efficacious velocity thresholds for detection of the stenosis. We found ten intracranial stenoses in six patients on MR angiography, but we calculated AUC only for detection of stenosis (n=6) of the left intracranial internal carotid artery. The accuracy of flow velocity with angle correction was lower than the accuracy of velocity without angle correction (AUC=0.73, 95% CI, 0.53-0.93 versus AUC=0.87, 95% CI, 0.74-1.00; p=0.017). The accuracy of flow velocity obtained with conventional ultrasonography (AUC=0.82, 95% CI, 0.67-0.97) was not different from the accuracy of flow velocities obtained with imaging ultrasonography. We found that the threshold of 165 cm/s of mean velocity without angle correction is associated with highest efficiency for imaging (92%) and conventional ultrasonography (90%). Velocity measurements without angle-correction provide good accuracy in detection of stenosis of the terminal internal carotid artery, whereas angle-corrected velocities have lower accuracy.

Sickle cell disease: reference values and interhemispheric differences of nonimaging transcranial Doppler blood flow parameters.

BACKGROUND AND PURPOSE: TCD screening is widely used to identify children with SCD at high risk of stroke. Those with high mean flow velocities in major brain arteries have increased risk of stroke. Thus, our aim was to establish reference values of interhemispheric differences and ratios of blood flow Doppler parameters in the tICA, MCA, and ACA as determined by conventional TCD in children with sickle cell anemia. MATERIALS AND METHODS: Reference limits of blood flow parameters were established on the basis of a consecutive cohort of 56 children (mean age, 100 ± 40 months; range, 29-180 months; 30 females) free of neurologic deficits and intracranial stenosis detectable by MRA, with blood flow velocities <170 cm/s by conventional TCD. Reference limits were estimated by using tolerance intervals, within which are included with a probability of .90 of all possible data values from 95% of a population. RESULTS: Average peak systolic velocities were significantly higher in the right hemisphere in the MCA and ACA (185 ± 28 cm/s versus 179 ± 27 and 152 ± 30 cm/s versus 143 ± 34 cm/s respectively). Reference limits for left-to-right differences in the mean flow velocities were the following: -43 to 33 cm/s for the MCA; -49 to 38 cm/s for the ACA, and -38 to 34 cm/s for the tICA, respectively. Respective reference limits for left-to-right velocity ratios were the following: 0.72 to 1.25 cm/s for the MCA; 0.62 to 1.39 cm/s for the ACA, and 0.69 to 1.27 cm/s for the tICA. Flow velocities in major arteries were inversely related to age and Hct or Hgb. CONCLUSIONS: The study provides reference intervals of TCD flow velocities and their interhemispheric differences and ratios that may be helpful in identification of intracranial arterial stenosis in children with SCD undergoing sonographic screening for stroke prevention.

Quality of life in thalassemia: a comparison of SF-36 results from the thalassemia longitudinal cohort to reported literature and the US norms.

Thalassemia is a chronic, inherited blood disorder, which, in its most severe form, causes life-threatening anemia. Advances in treatment have led to increased life expectancy however the need for chronic blood transfusions and chelation therapy remains a significant burden for patients. Our study compared health related quality of life (HRQOL) from the Thalassemia Clinical Research Network's (TCRNs) Thalassemia Longitudinal Cohort (TLC) study to US norms and assessed association with clinical variables. There were 264 patients over age 14 who completed the Medical Outcomes Study 36-Item Short Form Health Survey version 2 (SF36v2) baseline assessment. When compared to US norms, TLC patients had statistically significant (P < 0.05) worse HRQOL on five of the eight subscales (physical functioning, role-physical, general health, social functioning, and role-emotional) and on both summary scales (physical component summary and mental component summary). Women, older patients, and those with more disease complications and side effects from chelation reported lower HRQOL. In general, adolescents and adults with thalassemia report worse HRQOL than the US population, despite contemporary therapy. The SF-36 should become a standard instrument for assessing HRQOL in thalassemia to determine predictors of low HRQOL which may be better addressed by a multidisciplinary team.

Effects of fibroblast extracellular matrix calcification on platelet adhesion in vitro.

Calcified atherosclerotic lesions are more prone to rupture during angioplasty than non-calcified lesions and are associated with an increased risk of thrombotic complications following angioplasty. This study investigates the possible role of extracellular matrix (ECM) calcification for platelet adhesion. Human cultured fibroblasts (CRL-1635) were subjected to beta-glycerophosphate (10 mM) for 10 to 16 days. Calcification was visualized by von Kossa staining and quantified by the O-cresolphthalein complexone method. Adhesion of calcein-labelled platelets was measured by fluorescence microscopy at static conditions and in a parallel-flow chamber at a shear rate of 1000 s(-1). beta-glycerophosphate treatment resulted in a marked calcification of the ECM. In parallel, a small, albeit significant increase in platelet adhesion under static conditions was observed. In contrast, at flow conditions, the area covered by thrombi was significantly lower when calcified ECM was used. The number of thrombi was not significantly different which is compatible with a smaller thrombus size. Taken together, it appears unlikely that calcification of atherosclerotic lesions contributes to thrombotic complications by an increased platelet adhesion.

A focal-spot diagnostic for on-shot characterization of high-energy petawatt lasers.

An on-shot focal-spot diagnostic for characterizing high-energy, petawatt-class laser systems is presented. Accurate measurements at full energy are demonstrated using high-resolution wavefront sensing in combination with techniques to calibrate on-shot measurements with low-power sample beams. Results are shown for full-energy activation shots of the OMEGA EP Laser System.

Simulating charge transport in tris(8-hydroxyquinoline) aluminium (Alq(3)).

We present a model of charge transport in organic solids which explicitly considers the packing and electronic structure of individual molecules. We simulate the time-of-flight mobility measurement in crystalline and disordered films of tris(8-hydroxyquinoline) aluminium (Alq(3)). The morphology of disordered Alq(3) is modelled on a molecular scale, and density functional theory is used to determine the electronic couplings between molecules. Without any fitting parameters we predict electron mobilities in the crystalline and disordered phases of approximately 1 and approximately 10(-4) cm(2) V(-1) s(-1), respectively. In good agreement with experiment we find that electron mobilities are two orders of magnitude greater than those of holes. We explain this difference in terms of the spatial extent of the frontier orbitals. Our results suggest that charge transport in disordered Alq(3) is dominated by a few highly conducting pathways.

Angle-corrected imaging transcranial doppler sonography versus imaging and nonimaging transcranial doppler sonography in children with sickle cell disease.

BACKGROUND AND PURPOSE: Nonimaging transcranial Doppler sonography (TCD) and imaging TCD (TCDI) are used for determination of the risk of stroke in children with sickle cell disease (SCD). The purpose was to compare angle-corrected, uncorrected TCDI, and TCD blood flow velocities in children with SCD. MATERIALS AND METHODS: A total of 37 children (mean age, 7.8 +/- 3.0 years) without intracranial arterial narrowing determined with MR angiography, were studied with use of TCD and TCDI at the same session. Depth of insonation and TCDI mean velocities with and without correction for the angle of insonation in the terminal internal carotid artery (ICA) and middle (MCA), anterior (ACA), and posterior (PCA) cerebral arteries were compared with TCD velocities with use of a paired t test. RESULTS: Two arteries were not found on TCDI compared with 15 not found on TCD. Average angle of insonation in the MCA, ACA, ICA, and PCA was 31 degrees , 44 degrees , 25 degrees , and 29 degrees , respectively. TCDI and TCD mean depth of insonation for all arteries did not differ significantly; however, individual differences varied substantially. TCDI velocities were significantly lower than TCD velocities, respectively, for the right and left sides (mean +/- SD): MCA, 106 +/- 22 cm/s and 111 +/- 33 cm/s versus 130 +/- 19 cm/s and 134 +/- 26 cm/s; ICA, 90 +/- 14 cm/s and 98 +/- 27 cm/s versus 117 +/- 18 cm/s and 119 +/- 23 cm/s; ACA, 74 +/- 24 cm/s and 88 +/- 25 cm/s versus 105 +/- 23 cm/s and 105 +/- 31 cm/s; and PCA, 84 +/- 27 cm/s and 82 +/- 21 cm/s versus 95 +/- 23 cm/s and 94 +/- 20 cm/s. TCD and angle-corrected TCDI velocities were not statistically different except for higher angle-corrected TCDI values in the left ACA and right PCA. CONCLUSION: TCD velocities are significantly higher than TCDI velocities but are not different from the angle-corrected TCDI velocities. TCDI identifies the major intracranial arteries more effectively than TCD.

Prevalence of fractures among the Thalassemia syndromes in North America.

Historically, fractures are cited as a frequent problem in patients with Thalassemia prior to optimization of transfusion and chelation regimens. The aim of this study was to determine the prevalence of fractures in a contemporary sample of North American patients with Thalassemia. The North American Thalassemia Clinical Research Network (TCRN) database registry was used to gather historical data on 702 patients with common alpha and beta-Thalassemia diagnoses including Thalassemia Major (TM), Intermedia (TI), E/Beta, homozygous alpha Thalassemia (AT), Hemoglobin H disease (HbH) and HbH with Constant Spring (HbH/CS), who consented to a medical record chart review. Bone mineral density (BMD) measurements by DXA were available for review in a subgroup of patients (n = 312). The overall fracture prevalence among all Thalassemia syndromes was 12.1%, equally distributed between females (11.5%) and males (12.7%). Fractures occurred more frequently in TM (16.6%) and TI (12.2%) compared to E/Beta (7.4%) and alpha (2.3%). Prevalence increased with age (2.5% ages 0-10 years, 7.4% ages 11-19 years, 23.2% ages >20 years) and with use of sex hormone replacement therapy (SHRT) (P < 0.01). On average, BMD Z and T scores were 0.85 SD lower among patients with a history of fractures (mean Z/T score -2.78 vs. -1.93, 95% CI for the difference -0.49 to -1.22 SD, P = 0.02). Presence of other endocrinopathies (i.e. hypothyroidism, hypoparathyroidism and diabetes mellitus), anthropometric parameters, heart disease or hepatitis C were not significant independent predictors of fractures. These data indicate that fractures remain a frequent complication among the aging patients with both TM and TI beta-Thalassemia. However, the fracture prevalence has improved compared to published reports from the 1960s to 1970s. In addition, children with Thalassemia appear to have low fracture rates compared to the general population.

DFT studies of the structure and vibrational spectra of 8-hydroxyquinoline N-oxide.

The geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline N-oxide (8-HQNO) and its deuterated derivative (8-DQNO) were obtained by the density functional theory (DFT) with the BLYP and B3LYP functionals and 6-31G(d,p) basis set. The optimized bond lengths and bond angles are in good agreement with the X-ray data. The IR and INS spectra of 8-HQNO and 8-DQNO computed at the DFT level reproduce the vibrational wavenumbers and intensities with an accuracy, which allows reliable vibrational assignments.

Auxin herbicides induce H(2)O(2) overproduction and tissue damage in cleavers (Galium aparine L.).

The phytotoxic effects of auxin herbicides, including the quinoline carboxylic acids quinmerac and quinclorac, the benzoic acid dicamba and the pyridine carboxylic acid picloram, were studied in relation to changes in phytohormonal ethylene and abscisic acid (ABA) levels and the production of H(2)O(2) in cleavers (Galium aparine). When plants were root-treated with 10 microM quinmerac, ethylene synthesis was stimulated in the shoot tissue, accompanied by increases in immunoreactive levels of ABA and its precursor xanthoxal. It has been demonstrated that auxin herbicide-stimulated ethylene triggers ABA biosynthesis. The time-course and dose-response of ABA accumulation closely correlated with reductions in stomatal aperture and CO(2) assimilation and increased levels of hydrogen peroxide (H(2)O(2)), deoxyribonuclease (DNase) activity and chlorophyll loss. The latter parameters were used as sensitive indicators for the progression of tissue damage. On a shoot dry weight basis, DNase activity and H(2)O(2) levels increased up to 3-fold, relative to the control. Corresponding effects were obtained using auxin herbicides from the other chemical classes or when ABA was applied exogenously. It is hypothesized, that auxin herbicides stimulate H(2)O(2) generation which contributes to the induction of cell death in Galium leaves. This overproduction of H(2)O(2) could be triggered by the decline of photosynthetic activity, due to ABA-mediated stomatal closure.