Effect of target material on fast-electron transport and resistive collimation

The effect of target material on fast-electron transport is investigated using a high-intensity (0.7 ps, 10(20)  W/cm2) laser pulse irradiated on multilayered solid Al targets with embedded transport (Au, Mo, Al) and tracer (Cu) layers, backed with millimeter-thick carbon foils to minimize refluxing. We consistently observed a more collimated electron beam (36% average reduction in fast-electron induced Cu Kα spot size) using a high- or mid-Z (Au or Mo) layer compared to Al. All targets showed a similar electron flux level in the central spot of the beam. Two-dimensional collisional particle-in-cell simulations showed formation of strong self-generated resistive magnetic fields in targets with a high-Z transport layer that suppressed the fast-electron beam divergence; the consequent magnetic channels guided the fast electrons to a smaller spot, in good agreement with experiments. These findings indicate that fast-electron transport can be controlled by self-generated resistive magnetic fields and may have important implications to fast ignition.

Validation of MIMGO: a method to identify differentially expressed GO terms in a microarray dataset

BACKGROUND

We previously proposed an algorithm for the identification of GO terms that commonly annotate genes whose expression is upregulated or downregulated in some microarray data compared with in other microarray data. We call these "differentially expressed GO terms" and have named the algorithm "matrix-assisted identification method of differentially expressed GO terms" (MIMGO). MIMGO can also identify microarray data in which genes annotated with a differentially expressed GO term are upregulated or downregulated. However, MIMGO has not yet been validated on a real microarray dataset using all available GO terms.

FINDINGS

We combined Gene Set Enrichment Analysis (GSEA) with MIMGO to identify differentially expressed GO terms in a yeast cell cycle microarray dataset. GSEA followed by MIMGO (GSEA + MIMGO) correctly identified (p < 0.05) microarray data in which genes annotated to differentially expressed GO terms are upregulated. We found that GSEA + MIMGO was slightly less effective than, or comparable to, GSEA (Pearson), a method that uses Pearson's correlation as a metric, at detecting true differentially expressed GO terms. However, unlike other methods including GSEA (Pearson), GSEA + MIMGO can comprehensively identify the microarray data in which genes annotated with a differentially expressed GO term are upregulated or downregulated.

CONCLUSIONS

MIMGO is a reliable method to identify differentially expressed GO terms comprehensively.

Emission of energetic protons from relativistic intensity laser interaction with a cone-wire target

Emission of energetic protons (maximum energy ∼18 MeV) from the interaction of relativistic intensity laser with a cone-wire target is experimentally measured and numerically simulated with hybrid particle-in-cell code, lsp [D. R. Welch et al., Phys. Plasmas 13, 063105 (2006)]. The protons originate from the wire attached to the cone after the OMEGA EP laser (670 J, 10 ps, 5 × 10^{18} W/cm^{2}) deposits its energy inside the cone. These protons are accelerated from the contaminant layer on the wire surface, and are measured in the radial direction, i.e., in a direction transverse to the wire length. Simulations show that the radial electric field, responsible for the proton acceleration, is excited by three factors, viz., (i) transverse momentum of the relativistic fast electrons beam entering into the wire, (ii) scattering of electrons inside the wire, and (iii) refluxing of escaped electrons by "fountain effect" at the end of the wire. The underlying physics of radial electric field and acceleration of protons is discussed.

Dynamics of relativistic laser-plasma interaction on solid targets

A novel time-resolved diagnostic is used to record the critical surface motion during picosecond-scale relativistic laser interaction with a solid target. Single-shot measurements of the specular light show a redshift decreasing with time during the interaction, corresponding to a slowing-down of the hole boring process into overdense plasma. On-shot full characterization of the laser pulse enables simulations of the experiment without any free parameters. Two-dimensional particle-in-cell simulations yield redshifts that agree with the data, and support a simple explanation of the slowing-down of the critical surface based on momentum conservation between ions and reflected laser light.

An evaluation of high energy bremsstrahlung background in point-projection x-ray radiography experiments

Backlit pinhole x-ray radiography has provided high-resolution images in many recent high-energy-density laser experiments. Its aim is to image the object of interest with a roughly monochromatic Kα source. However, despite the high intrinsic brightness achieved by the technique, data on x-ray film have shown a signal to background ratio near one, with data on image plates producing a higher background. This has been attributed, without direct evidence, to the interaction of suprathermal electrons with the (high Z) pinhole substrate. We present here the first direct measurement of the hard x-rays produced by such a backlighter target and a test of an approach to reducing the background. Specifically, a thick, low-Z layer was added on the side of the substrate toward the detector, intended to stop the energetic electrons and produce smaller emissions. Results from the Omega-60 laser experiment showed that the oft-seen background signal is in the range of 60-80 keV, a plausible energy range for energetic electrons produced in the laser-irradiated plasma. It also showed a comparable level of background signal in both types of targets. The work presented here includes target design and motivating theory, as well as the unexpected findings about x-ray background production.

Hot electron temperature and coupling efficiency scaling with prepulse for cone-guided fast ignition

The effect of increasing prepulse energy levels on the energy spectrum and coupling into forward-going electrons is evaluated in a cone-guided fast-ignition relevant geometry using cone-wire targets irradiated with a high intensity (10(20) W/cm(2)) laser pulse. Hot electron temperature and flux are inferred from Kα images and yields using hybrid particle-in-cell simulations. A two-temperature distribution of hot electrons was required to fit the full profile, with the ratio of energy in a higher energy (MeV) component increasing with a larger prepulse. As prepulse energies were increased from 8 mJ to 1 J, overall coupling from laser to all hot electrons entering the wire was found to fall from 8.4% to 2.5% while coupling into only the 1-3 MeV electrons dropped from 0.57% to 0.03%.

Classification of lymphoscintigraphy and relevance to surgical indication for lymphaticovenous anastomosis in upper limb lymphedema

Upper limb lymphedema that develops after breast cancer surgery causes physical discomfort and psychological distress, and it can require both conservative and surgical treatment. Lymphaticovenous anastomosis has been reported to be an effective treatment; however the disease severity criteria that define indications for this treatment remain unclear. Here, we examined lymphoscintigraphic findings in 78 patients with secondary upper limb lymphedema and classified them into 5 major types (Type I-V) and 3 subtypes (Subtype E, L, and 0). Results revealed that this classification is related to the clinical stage scale of the International Society of Lymphology. Based on intraoperative examination findings in 20 of the 78 patients, lymphatic pressure is likely to be further elevated in Type II-V cases which are characterized by the presence of dermal back flow. Therefore, lymphaticovenous anastomosis should be considered as a treatment option for lymphedema in Type II-V cases. Furthermore, there are only limited lymph vessel sites usable for lymphaticovenous anastomosis in more severe lymphedema types [Types IV and Type V (which is characterized by dermal backflow only in the hand)]. The findings in Type IV-V cases suggest that therapeutic strategies for severe upper limb lymphedema need further consideration.

Microbial Production of Ursodeoxycholic Acid from Lithocholic Acid by Fusarium equiseti M41

A fungus identified as Fusarium equiseti was isolated from soil and found to carry out 7beta-hydroxylation of lithocholic acid to ursodeoxycholic acid (35% yield; 350 mg/liter) in 112 h.

Differential ozone sensitivity of rice cultivars as indicated by visible injury and grain yield

Surface ozone pollution may cause reductions in rice (Oryza sativa L.) yield. Ozone sensitivity in rice cultivars is often evaluated based on visible leaf injury at an early growth stage. However, it is not clear whether reduction in grain yield is related to visible injury. Therefore, visible damage and grain yield reduction were examined in Japanese and Asian rice cultivars exposed to ozone. In experiment 1, 3-week-old rice seedlings were exposed to ozone (min.: 20 nl.l(-1), max.:120 nl.l(-1)) for 12 h in open-top chambers (OTCs). Visible leaf injury was quantified according to a leaf bronzing score. In experiment 2, rice plants were exposed to ozone in OTCs throughout the cropping season until grain harvest. Daily mean ozone concentrations were maintained at 2, 23, 28, 42, and 57 nl.l(-1) with a regular diurnal pattern of exposure. After harvest, grain yield was determined. Based on visible injury to the uppermost fully expanded leaf, the indica cultivar 'Kasalath' was most tolerant, and the japonica cultivar 'Kirara 397' was most sensitive to ozone. However, grain yields for both 'Kasalath' and 'Kirara 397' were significantly decreased after ozone exposure. The indica cultivar 'Jothi' suffered severe injury after ozone exposure but had no reduction in grain yield. Therefore, ozone sensitivity of rice cultivars evaluated by visible injury did not coincide with that evaluated by the reductions in grain yield. These results suggest that mechanisms that induce acute leaf injury do not relate to chronic ozone toxicity that reduces yield.

Tie2-mediated loss of peroxisome proliferator-activated receptor-gamma in mice causes PDGF receptor-beta-dependent pulmonary arterial muscularization

Peroxisome proliferator-activated receptor (PPAR)-gamma is reduced in pulmonary arteries (PAs) of patients with PA hypertension (PAH), and we reported that deletion of PPARgamma in smooth muscle cells (SMCs) of transgenic mice results in PAH. However, the sequelae of loss of PPARgamma in PA endothelial cells (ECs) are unknown. Therefore, we bred Tie2-Cre mice with PPARgamma(flox/flox) mice to induce EC loss of PPARgamma (Tie2 PPARgamma(-/-)), and we assessed PAH by right ventricular systolic pressure (RVSP), RV hypertrophy (RVH), and muscularized distal PAs in room air (RA), after chronic hypoxia (CH), and after 4 wk of recovery in RA (Rec-RA). The Tie2 PPARgamma(-/-) mice developed spontaneous PAH in RA with increased RVSP, RVH, and muscularized PAs vs. wild type (WT); both genotypes exhibited a similar degree of PAH following chronic hypoxia, but Tie2 PPARgamma(-/-) mice had more residual PAH compared with WT mice after Rec-RA. The Tie2 PPARgamma(-/-) vs. WT mice in RA had increased platelet-derived growth factor receptor-beta (PDGF-Rbeta) expression and signaling, despite an elevation in the PPARgamma target apolipoprotein E, an inhibitor of PDGF signaling. Inhibition of PDGF-Rbeta signaling with imatinib, however, was sufficient to reverse the PAH observed in the Tie2 PPARgamma(-/-) mice. Thus the disruption of PPARgamma signaling in EC is sufficient to cause mild PAH and to impair recovery from CH-induced PAH. Inhibition of heightened PDGF-Rbeta signaling is sufficient to reverse PAH in this genetic model.

Optimal tilt magnitude determination for aberration-corrected super resolution exit wave function reconstruction

Transmission electron microscope (TEM) images recorded under tilted illumination conditions transfer higher spatial frequencies than axial images. This super resolution information transfer is highly directional in a single image, but can be extended in all directions through the use of complementary beam tilts during exit wave function reconstruction. We have determined the optimal experimental tilt magnitude for aperture synthesis in an aberration-corrected TEM. It is shown that electron-optical aberration correction allows the use of larger tilt angles and reduces the constraints that are imposed on experimental data acquisition in an uncorrected microscope. We demonstrate that, in many cases, the resolution improvement achievable is now limited by the sample and not by instrumental parameters. An exit wave function is presented that has been successfully reconstructed from a dataset of aberration-corrected images, including images acquired at a beam tilt of 18 mrad, which clearly demonstrates a resolution improvement from 0.11 nm to better than 0.08 nm at 200 kV.

Diagnostic accuracy of cardiac metaiodobenzylguanidine scintigraphy in Parkinson disease

BACKGROUND AND PURPOSE

To estimate the diagnostic accuracy of cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigram for detection of Parkinson disease.

METHODS

A cross-sectional study with index test of MIBG scintigram and reference standard of U.K. Parkinson's Disease Brain Bank Criteria was performed in 403 patients. Ratio of cardiac-to-mediastinum MIBG accumulation was determined at 20 min (early H/M) and 4 h (late H/M). Area under the receiver-operator characteristic (ROC) curve, sensitivity and specificity in detecting Parkinson disease were analyzed. Accuracy was analyzed in a subgroup of patients with disease duration of 3 years or less.

RESULTS

Area under the ROC curve was 0.89 using either early or late H/M as a diagnostic marker (95% CI 0.85-0.92 for early H/M and 0.86-0.93 for late H/M). Sensitivity and specificity were 81.3% (76.1-85.8%) and 85.0% (77.7-90.6%) for early H/M and 84.3% (79.3-88.4%) and 89.5% (83.01-94.1%) for late H/M. In the subgroup with duration of 3 years or less, the ROC curve area, sensitivity, and specificity were 0.86 (0.79-0.92), 76.0% (64.8-85.1%), and 83.9% (71.7-92.4%) for early H/M and 0.85 (0.78-0.92), 73.3% (61.9-82.9%), and 87.5% (75.9-94.8%) for late H/M.

CONCLUSION

Although diagnostic accuracy of cardiac MIBG scintigram is high, it is limited because of insufficient sensitivity in patients with short duration.

Effects of dietary energy intake and cold exposure on kinetics of plasma glucose metabolism in sheep

An isotope dilution method using [U-(13)C]glucose injection was applied to determine the effects of dietary energy intake and cold exposure on plasma glucose metabolism in sheep. The sheep were assigned to two dietary treatments and were fed on diets containing either 100% or 160% of ME and both containing 150% of dietary crude protein intake for maintenance. The sheep were exposed from a thermoneutral environment (23 degrees C) to a cold environment (2-4 degrees C) for 5 days. The isotope dilution method was performed on the 18th day in the thermoneutral environment and on the fifth day of cold exposure. Plasma concentrations of glucose and NEFA increased (p < 0.05) during cold exposure for both diets. Plasma glucose pool size remained unchanged (p = 0.67), but plasma glucose turnover rate tended to increase (p = 0.07) with increased energy intake. Both pool size and turnover rate of plasma glucose increased (p = 0.01 and p = 0.0001, respectively) during cold exposure. No significant diet x environment interaction was detected. It is concluded that plasma glucose metabolism was influenced by both dietary energy intake and cold exposure, and plasma glucose metabolism in response to cold exposure was not modified by energy intake in sheep under the conditions (2-4 degrees C on the fifth day) of the present experiment.