Dissociative charge exchange and ionization of O-2 by fast H+ and O+ ions: Energetic ion interactions in Europa's oxygen atmosphere and neutral torus

Measurements of electron capture and ionization of O-2 molecules in collisions with H+ and O+ ions have been made over an energy range 10 - 100 keV. Cross sections for dissociative and nondissociative interactions have been separately determined using coincidence techniques. Nondissociative channels leading to O-2(+) product formation are shown to be dominant for both the H+ and the O+ projectiles in the capture collisions and only for the H+ projectiles in the ionization collisions. Dissociative channels are dominant for ionizing collisions involving O+ projectiles. The energy distributions of the O+ fragment products from collisions involving H+ and O+ have also been measured for the first time using time-of-flight methods, and the results are compared with those from other related studies. These measurements have been used to describe the interaction of the energetic ions trapped in Jupiter's magnetosphere with the very thin oxygen atmosphere of the icy satellite Europa. It is shown that the ionization of oxygen molecules is dominated by charge exchange plus ion impact ionization processes rather than photoionization. In addition, dissociation is predominately induced through excitation of electrons into high-lying repulsive energy states ( electronically) rather than arising from momentum transfer from knock-on collisions between colliding nuclei, which are the only processes included in current models. Future modeling will need to include both these processes.

Distribution of the Receptor for Advanced Glycation End Products (RAGE) in the Human Male Reproductive Tract. Prevalence in Men with Diabetes Mellitus.

BACKGROUND: Diabetics have a significantly higher percentage of sperm with nuclear DNA (nDNA) fragmentation and increased levels of advanced glycation end products (AGEs), in their testis, epididymis and sperm. As the receptor for AGEs (RAGE) is important to oxidative stress and cell dysfunction, we hypothesise, that it may be involved in sperm nDNA damage. METHODS: Immunohistochemistry was performed to determine the presence of RAGE in the human testis and epididymis. A comparison of the receptor's incidence and localisation on sperm from 10 diabetic and 11 non-diabetic men was conducted by blind semi-quantitative assessment of the immunostaining. ELISA analysis ascertained RAGE levels in seminal plasma and sperm from 21 diabetic and 31 non-diabetic subjects. Dual labelling immunolocalisation was employed to evaluate RAGE's precise location on the sperm head. RESULTS: RAGE was found throughout the testis, caput epididymis, particularly the principle cells apical region, and on sperm acrosomes. The number of sperm displaying RAGE and the overall protein amount found in sperm and seminal plasma were significantly higher in samples from diabetic men (p

Impaired retinal angiogenesis in diabetes: role of advanced glycation end products and galectin-3

Suppression of angiogenesis during diabetes is a recognized phenomenon but is less appreciated within the context of diabetic retinopathy. The current study has investigated regulation of retinal angiogenesis by diabetic serum and determined if advanced glycation end products (AGEs) could modulate this response, possibly via AGE-receptor interactions. A novel in vitro model of retinal angiogenesis was developed and the ability of diabetic sera to regulate this process was quantified. AGE-modified serum albumin was prepared according to a range of protocols, and these were also analyzed along with neutralization of the AGE receptors galectin-3 and RAGE. Retinal ischemia and neovascularization were also studied in a murine model of oxygen-induced proliferative retinopathy (OIR) in wild-type and galectin-3 knockout mice (gal3(-/-)) after perfusion of preformed AGEs. Serum from nondiabetic patients showed significantly more angiogenic potential than diabetic serum (P <0.0001) and within the diabetic group, poor glycemic control resulted in more AGEs but less angiogenic potential than tight control (P <0.01). AGE-modified albumin caused a dose-dependent inhibition of angiogenesis (P <0.001), and AGE receptor neutralization significantly reversed the AGE-mediated suppression of angiogenesis (P <0.01). AGE-treated wild-type mice showed a significant increase in inner retinal ischemia and a reduction in neovascularization compared with non-AGE controls (P <0.001). However, ablation of galectin-3 abolished the AGE-mediated increase in retinal ischemia and restored the neovascular response to that seen in controls. The data suggest a significant suppression of angiogenesis by the retinal microvasculature during diabetes and implicate AGEs and AGE-receptor interactions in its causation.

The role of advanced glycation end products in retinal microvascular leukostasis

PURPOSE: A critical event in the pathogenesis of diabetic retinopathy is the inappropriate adherence of leukocytes to the retinal capillaries. Advanced glycation end-products (AGEs) are known to play a role in chronic inflammatory processes, and the authors postulated that these adducts may play a role in promoting pathogenic increases in proinflammatory pathways within the retinal microvasculature. METHODS: Retinal microvascular endothelial cells (RMECs) were treated with glycoaldehyde-modified albumin (AGE-Alb) or unmodified albumin (Alb). NFkappaB DNA binding was measured by electromobility shift assay (EMSA) and quantified with an ELISA: In addition, the effect of AGEs on leukocyte adhesion to endothelial cell monolayers was investigated. Further studies were performed in an attempt to confirm that this was AGE-induced adhesion by co-incubation of AGE-treated cells with soluble receptor for AGE (sRAGE). Parallel in vivo studies of nondiabetic mice assessed the effect of intraperitoneal delivery of AGE-Alb on ICAM-1 mRNA expression, NFkappaB DNA-binding activity, leukostasis, and blood-retinal barrier breakdown. RESULTS: Treatment with AGE-Alb significantly enhanced the DNA-binding activity of NFkappaB (P = 0.0045) in retinal endothelial cells (RMECs) and increased the adhesion of leukocytes to RMEC monolayers (P = 0.04). The latter was significantly reduced by co-incubation with sRAGE (P <0.01). Mice infused with AGE-Alb demonstrated a 1.8-fold increase in ICAM-1 mRNA when compared with control animals (P <0.001, n = 20) as early as 48 hours, and this response remained for 7 days of treatment. Quantification of retinal NFkappaB demonstrated a threefold increase with AGE-Alb infusion in comparison to control levels (AGE Alb versus Alb, 0.23 vs. 0.076, P <0.001, n = 10 mice). AGE-Alb treatment of mice also caused a significant increase in leukostasis in the retina (AGE-Alb versus Alb, 6.89 vs. 2.53, n = 12, P <0.05) and a statistically significant increase in breakdown of the blood-retinal barrier (AGE Alb versus Alb, 8.2 vs. 1.6 n = 10, P <0.001). CONCLUSIONS: AGEs caused upregulation of NFkappaB in the retinal microvascular endothelium and an AGE-specific increase in leukocyte adhesion in vitro was also observed. In addition, increased leukocyte adherence in vivo was demonstrated that was accompanied by blood-retinal barrier dysfunction. These findings add further evidence to the thinking that AGEs may play an important role in the pathogenesis of diabetic retinopathy.

Advanced Glycation End Products (AGEs) accumulate in the Reproductive Tract of Men with Diabetes.

Light microscopic studies comparing sperm parameters show little association between diabetes and male fertility. However, with the introduction of new analytical techniques, evidence is now emerging of previously undetectable affects of diabetes on sperm function. Specifically, a recent study has found significantly higher sperm nuclear DNA (nDNA) fragmentation in diabetic men. As advanced glycation end products (AGEs) are important instigators of oxidative stress and cell dysfunction in numerous diabetic complications, we hypothesized that these compounds could also be present in the male reproductive tract. The presence and localization of the most prominent AGE, carboxymethyl-lysine (CML), in the human testis, epididymis and sperm was determined by immunohistochemistry. Parallel ELISA and Western blot analyses were performed to ascertain the amount of CML in seminal plasma and sperm from 13 diabetic and 9 non-diabetic subjects. CML immunoreactivity was found through out the seminiferous epithelium, the nuclei of spermatogonia and spermatocytes, in the basal and principle cells (cytoplasm and nuclei) of the caput epididymis and on most sperm tails, mid pieces and all cytoplasmic droplets. The acrosomal cap, especially the equatorial band, was prominently stained in diabetic samples only. The amount of CML was significantly higher (p = 0.004) in sperm from non diabetic men. Considering the known detrimental actions of AGEs in other organs, the presence, location and quantity of CML, particularly the increased expression found in diabetic men, suggests that these compounds may play a hitherto unrecognized role in male infertility.

The role of plug design in determining wall thickness distribution in thermoforming

An experimental investigation has been carried out into the effects of changes in plug design on the wall thickness distribution of thermoformed products. Plugs were machined with a series of geometrical variations and their effects on the process were measured. The overall results show that the plug has a crucial role in controlling the wall thickness distribution in thermoforming. Larger plugs tend to distribute more material to the base of the product, but the introduction of a small sidewall taper, base radius, or a reduction in plug diameter tend to lead to more balanced distributions. However, larger changes in any of the variables tend to destroy these benefits. It has also been demonstrated that the frictional and thermal properties of the plug are important in determining the deformation response of the sheet material. There is a clear evidence of slip in the sheet during plug contact and, although the cooling effect of the plug appears to be minimal, cooling in the highly deformed regions away from the plug appears to be a significant factor.

Spatially Correlated Multiple-Ananna Channel Capacity Distributions

In this paper, we investigate the capacity of multiple-input multiple-output (MIMO) wireless communication systems over spatially correlated Rayleigh distributed flat fading channels with complex Gaussian additive noise. Specifically, we derive the probability density function of the mutual information between transmitted and received complex signals of MIMO systems. Using this density we derive the closed-form ergodic capacity (mean), delay-limited capacity, capacity variance and outage capacity formulas for spatially correlated channels and then evaluate these formulas numerically. Numerical results show how the channel correlation degrades the capacity of MIMO communication systems. We also show that the density of mutual information of correlated/uncorrelated MIMO systems can be approximated by a Gaussian density with derived mean and variance, even for a finite number of inputs and outputs.

Fast-beam study of H2+ ions in an intense femtosecond laser field

A fast beam of H-2(+) ions, produced from a low energy ion accelerator, has been used for the first time in intense laser field experiments. The technique has enabled neutral dissociation products to be analysed and detected for the first time in such studies. Energy spectra of neutral and ionized fragments, product yields as a function of focused laser intensity and angular distributions of neutral dissociation products have been measured. Significant differences are observed between the present results and those obtained from experiments involving neutral H-2 molecules. These differences are indicative of the precursor H-2 molecule playing an important and hitherto neglected formative role in the laser-induced fragmentation processes.