Coherence properties of individual femtosecond pulses of an x-ray free-electron laser

Measurements of the spatial and temporal coherence of single, femtosecond x-ray pulses generated by the first hard x-ray free-electron laser, the Linac Coherent Light Source, are presented. Single-shot measurements were performed at 780 eV x-ray photon energy using apertures containing double pinholes in "diffract-and-destroy" mode. We determined a coherence length of 17  μm in the vertical direction, which is approximately the size of the focused Linac Coherent Light Source beam in the same direction. The analysis of the diffraction patterns produced by the pinholes with the largest separation yields an estimate of the temporal coherence time of 0.55 fs. We find that the total degree of transverse coherence is 56% and that the x-ray pulses are adequately described by two transverse coherent modes in each direction. This leads us to the conclusion that 78% of the total power is contained in the dominant mode.

Efficacy of statin pretreatment for the prevention of contrast-induced nephropathy: a meta-analysis of randomised controlled trials

Contrast-induced nephropathy (CIN) is a common cause of acute kidney injury. Whether additional benefits can be achieved with the use of statin in decreasing the risk of CIN remains undetermined. The purpose of this meta-analysis is to evaluate the effects of statin pretreatment for the prevention of CIN. PubMed, MEDLINE, Web of Science, EMBASE and EBM Reviews databases were searched for randomised controlled trials comparing statin pretreatment with non-statin pretreatment for the prevention of CIN. Two reviewers independently assessed studies and performed data extraction. Risk ratio (RR) or weighted mean differences (WMD) with 95% confidence intervals (CI) were calculated using random-effects models. Four trials with 751 subjects were included. Pooled analyses showed that the incidence of CIN was not significantly lower in statin pretreatment group, as compared with control group (RR = 0.76, 95% CI 0.44-1.29, p = 0.30). Similarly, none of 276 patients in statin pretreatment group needed renal replacement therapy (RRT), which was not significantly less than 2 of 275 patients assigned to control group during 1-month follow up (RR = 0.33, 95% CI 0.03-3.17, p = 0.34). Moreover, statin pretreatment was associated with mild reduction of serum creatinine (SCr) (WMD = -0.06 mg/dl, 95% CI -0.12 to 0.00 mg/dl, p = 0.05). The current cumulative evidence suggests that statin pretreatment may neither prevent CIN nor reduce the need for RRT. However, it may slightly decrease the level of SCr.

Nuclear physics: quantitative single-cell approaches to nuclear organization and gene expression

The internal workings of the nucleus remain a mystery. A list of component parts exists, and in many cases their functional roles are known for events such as transcription, RNA processing, or nuclear export. Some of these components exhibit structural features in the nucleus, regions of concentration or bodies that have given rise to the concept of functional compartmentalization--that there are underlying organizational principles to be described. In contrast, a picture is emerging in which transcription appears to drive the assembly of the functional components required for gene expression, drawing from pools of excess factors. Unifying this seemingly dual nature requires a more rigorous approach, one in which components are tracked in time and space and correlated with onset of specific nuclear functions. In this chapter, we anticipate tools that will address these questions and provide the missing kinetics of nuclear function. These tools are based on analyzing the fluctuations inherent in the weak signals of endogenous nuclear processes and determining values for them. In this way, it will be possible eventually to provide a computational model describing the functional relationships of essential components.

The potential of shape-based treatment plan optimization for pancreatic IMRT treatments to spare organs at risk and allow for dose escalation to the tumor PTV

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Background: Due to the low dose tolerance of the organs at risk (OARs) in the abdomen the tumor dose for pancreatic cancer patient is restricted to 50-60 Gy in 1.8-2.0 Gy fractions when combined with chemotherapy. The goal of this study was to develop a system that can determine the minimal radiation dose to the OARs of each individual patient that is achievable while maintaining adequate tumor coverage. This could guide treatment planners to spare the OARs to the fullest extent. When the minimal doses to the OAR are achieved, the total plan can be upscaled until the normal tissue dose constraints are met, allowing for an increase in tumor dose without increased normal tissue toxicity.

Methods: The minimal achievable dose to the OARs depends on its proximity to the planning target volume (PTV). The overlap volume histogram (OVH) was used to describe the spatial relation of each OAR to the PTV. A database of 33 patients, treated with IMRT, was queried to find the lowest achieved dose to an organ for any of the prior patients with less favorable PTV-OAR configurations than the current patient. This minimal dose must also be achievable for the OAR of the new patient. For 25 randomly chosen patients the lowest achievable dose to the liver and kidneys was predicted this way. Then the patients were replanned to verify if this dose could be achieved. The new plans were compared to the original clinical plans.

Results: After replanning the predicted achievable dose to the liver was realized within 1 and 2 Gy for more than 86% and 96% of the patients respectively. For the kidneys these numbers were 83% and 96%. The average improvement in terms of mean dose was 1.4 Gy (range 0 – 4.6 Gy) for the liver and 1.7 Gy (range 0 – 6.3 Gy) for the kidneys. This would have allowed an increase in PTV dose of on average 5 Gy (range 0-13 Gy) based on the liver and 8.5 Gy (range 0-38 Gy) based on the kidneys compared to the original plan, without an increase in dose to the bowel, cord, and stomach.

Conclusions: The lowest achievable dose to the OARs could accurately be predicted for pancreatic cancer patients within seconds. This can guide dosimetrists to spare the OARs or increase the PTV dose by 5 Gy without increased toxicity.

[Table: see text]

Low rainfall-induced shift in leaf trait relationship within species along a semi-arid sandy land transect in northern China

It is unclear whether the shift in leaf traits between species of high- and low-rainfall sites is caused by low rainfall or by species replacement, because leaf traits vary substantially among species and sites. Our objective was to test if the within-species relationship between specific leaf area (SLA) and leaf N concentration (N(mass) ) shifts across a rainfall gradient in the semi-arid sandy lands of northern China. Data for SLA and N(mass) of dominant species and related canopy and soil variables were collected from 33 plots along a rainfall transect (270-390 mm) having similar temperatures in the Mu Us, Inner Mongolia. We further investigated the generality of Mu Us data using 12 additional plots in the southeastern Qaidam Basin, Qinghai. Artemisia ordosica is a widespread species in both regions. Across and within species, the positive SLA-N(mass) relationship shifted between two plant groups in the lowest rainfall plots (270 mm) and other higher rainfall plots (320-390 mm), which was confirmed by additional data from Qinghai. For A. ordosica populations, leaf area index (LAI) decreased and N(mass) increased with decreasing rainfall, while the foliage N pool and SLA varied little. Rainfall was the limiting factor that determined variations in N(mass) and LAI. Accordingly, N(mass) /SLA ratios continually increased with decreasing LAI along the rainfall gradient (r = -0.76, P < 0.001). Results indicate a low rainfall-induced shift in the SLA-N(mass) relationship associated with changes in LAI and foliage N pool, suggesting a link between leaf characteristics and ecosystem function.

Review of photokeratitis: Corneal response to ultraviolet radiation (UVR) exposure*

The development of photokeratitis in response to natural solar ultraviolet radiation (UVR) is prevalent in individuals participating in outdoor recreational activities in environments with high reflective surfaces, such as beach activities, water sports and snow skiing. Eye care practitioners (ECPs) are frequently encouraged by manufacturers and researchers to recommend UVR-blocking eyewear in the form of sunglasses and contact lenses. However, little is known about the precise nature of the corneal tissue response in the development of photokeratitis. This paper reviews the mechanisms responsible for the development of photokeratitis. Clinical signs and symptoms of photokeratitis, UVR corneal threshold and action spectra, corneal cellular changes and ocular protection from corneal UVR exposure are discussed. The content of this article will be useful to ECPs in making appropriate recommendations when prescribing UVR-protec-tive eyewear. (S Afr Optom 2010 69(3) 123-131)

Influence of 8DSS Peptide on Nano-mechanical Behavior of Human Enamel

Aspartate-serine-serine (DSS) repeats are abundant in naturally occurring proteins that are critical for tooth formation. We recently developed octuplet repeats of aspartate-serine-serine (8DSS) peptides to promote the nucleation of calcium phosphate carbonate from free ions. In this paper, we report a possible role of 8DSS in promoting mineral deposition onto human enamel. Human enamel specimens were demineralized, exposed briefly to 8DSS solution, and then exposed to simulated body fluid that favors mineral deposition. At various stages of treatment, nano-mechanical behaviors, namely, hardness and elastic modulus, were determined by nano-indentation. Nano-indentation results showed that 8DSS treatment effectively improved the mechanical and elastic properties of demineralized enamel. The values of hardness and elastic modulus for the 8DSS-treated enamel were significantly higher than those of surfaces without 8DSS treatment. Furthermore, 8DSS peptides promoted the uniform deposition of nano-crystalline calcium phosphate carbonate over demineralized enamel surfaces and reduced surface roughness of demineralized enamel.

Biomonitoring of essential and toxic metals in single hair using on-line solution-based calibration in laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful and sensitive surface analytical technique for the determination of concentration and distribution of trace metals within biological systems at micrometer spatial resolution. LA-ICP-MS allows easy quantification procedures if suitable standard references materials (SRM) are available. In this work a new SRM-free approach of solution-based calibration method in LA-ICP-MS for element quantification in hair is described. A dual argon flow of the carrier gas and nebulizer gas is used. A dry aerosol produced by laser ablation (LA) of biological sample and a desolvated aerosol generated by pneumatic nebulization (PN) of standard solutions are carried by two different flows of argon as carrier or nebulizer gas, respectively and introduced separately in the injector tube of a special ICP torch, through two separated apertures. Both argon flows are mixed directly in the ICP torch. External calibration via defined standard solutions before analysis of single hair was employed as calibration strategy. A correction factor, calculated using hair with known analyte concentration (measured by ICP-MS), is applied to correct the different elemental sensitivities of ICP-MS and LA-ICP-MS. Calibration curves are obtained by plotting the ratio of analyte ion M(+)/(34)S(+) ion intensities measured using LA-ICP-MS in dependence of analyte concentration in calibration solutions. Matrix-matched on-line calibration in LA-ICP-MS is carried out by ablating of human hair strands (mounted on a sticky tape in the LA chamber) using a focused laser beam in parallel with conventional nebulization of calibration solutions. Calibrations curves of Li, Na, Mg, Al, K, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Sr, Mo, Ag, Cd, I, Hg, Pb, Tl, Bi and U are presented. The linear correlation coefficients (R) of calibration curves for analytes were typically between 0.97 and 0.999. The limits of detection (LODs) of Li, V, Mn, Ni, Co, Cu, Sr, Mo, Ag, Ba, Cd, I, Hg, Pb, Bi and U in a single hair strand were in the range of 0.001-0.90 μg g(-1), whereas those of Cr and Zn were 3.4 and 5.1 μg g(-1), respectively. The proposed quantification strategy using on-line solution-based calibration in LA-ICP-MS was applied for biomonitoring (the spatial resolved distribution analysis) of essential and toxic metals and iodine in human hair and mouse hair.

Transporters in the brain endothelial barrier

The blood-brain barrier (BBB) not only impedes the influx of intravascular substances from blood to brain, but also promotes transport of substances from blood to brain or from brain to blood through several transport systems such as carrier-mediated transport, active efflux transport, and receptor-mediated transport systems. The multidrug resistance transporter P-glycoprotein (P-gp) is an ATP-dependent efflux pump and contributes to efflux of undesirable substances such as amyloid-beta:(Abeta) proteins from the brain into the blood as well as many drugs such as anti-cancer drugs. The inhibition of P-gp has favorable and unfavorable effects on living bodies. P-gp deficiency at the BBB induces the increase of Abeta:deposition in the brain of an Alzheimer disease mouse model. It is also known that the Abeta:deposition is inversely correlated with P-gp expression in the brains of elderly non-demented humans. However, the transient inhibition of P-gp by antidepressants enables medicines such as anti-cancer drugs to enter the brain. Concerning Abeta:clearance in the brain, the low-density lipoprotein receptor-related protein 1 (LRP1) is a major efflux transporter for Abeta, while the receptor for advanced glycation end products (RAGE) is a major influx transporter for Abeta:across the BBB. Dysfunction of the BBB with efflux and influx transporters may contribute to the pathogenesis of some degenerative neuronal disorders. This review will focus on several transporters and discuss how medicines pass the BBB to reach the brain parenchyma.

Induction of pancreatic phenotypes in central nervous system derived pluripotential progenitor cells

Fetal rat brain stem cells (RSCs) have been induced to express pituitary properties when exposed to pituitary cells (U et al., 2002). In this study, we explored whether these RSCs could also be influenced to acquire properties characteristic of the pancreas. To this end, RSCs in culture were exposed to media conditioned by rat islet tumor cells and media containing Exendin-4 and nicotinamide since both have been shown to induce pancreatic phenotypes in embryonic stem cells. Lastly, an expression construct for pdx-1 was introduced into RSCs. The expression of pancreatic markers was analyzed using RT-PRC and immunocytochemistry. When RSCs were exposed to rat islet tumor cell conditioned media and media containing Exendin-4 and nicotinamide, the expression of pdx-1, insulin and somatostatin were observed. They also acquired a spherical shape typical of pancreatic cells in culture. Under these varied conditions, transcriptional factors essential to pancreatic development such as pdx-1 and Isl-1 were induced. The critical role of pdx-1 in stimulating certain endocrine pancreatic properties in RSCs was further confirmed upon the introduction of an expression construct for pdx-1 which markedly induced insulin and somatostatin. Taken together, these findings suggests that fetal brain stem cells are pluripotent and can be reprogrammed to acquire pancreatic properties through pathways which involved the transcription factor Pdx1.