Surface charging of thick porous water ice layers relevant for ion sputtering experiments

We use a laboratory facility to study the sputtering properties of centimeter-thick porous water ice subjected to the bombardment of ions and electrons to better understand the formation of exospheres of the icy moons of Jupiter. Our ice samples are as similar as possible to the expected moon surfaces but surface charging of the samples during ion irradiation may distort the experimental results. We therefore monitor the time scales for charging and dis- charging of the samples when subjected to a beam of ions. These experiments allow us to derive an electric conductivity of deep porous ice layers. The results imply that electron irradiation and sputtering play a non-negligible role for certain plasma conditions at the icy moons of Jupiter. The observed ion sputtering yields from our ice samples are similar to previous experiments where compact ice films were sputtered off a micro-balance.Comment: arXiv admin note: text overlap with arXiv:1509.0400

Aphid genotypes vary in their response to the presence of fungal endosymbionts in host plants

Genetic variation for fitness-relevant traits may be maintained in natural populations by fitness differences that depend on environmental conditions. For herbivores, plant quality and variation in chemical plant defences can maintain genetic variation in performance. Apart from plant secondary compounds, symbiosis between plants and endosymbiotic fungi (endophytes) can produce herbivore-toxic compounds. We show that there is significant variation among aphid genotypes in response to endophytes by comparing life-history traits of 37 clones of the bird cherry-oat aphid Rhopalosiphum padi feeding on endophyte-free and endophyte-infected tall fescue Lolium arundinaceum. Clonal variation for life-history traits was large, and most clones performed better on endophyte-free plants. However, the clones differed in the relative performance across the two environments, resulting in significant genotype · environment interactions for all reproductive traits. These findings suggest that natural variation in prevalence of endophyte infection can contribute to the maintenance of genetic diversity in aphid populations

Three-dimensional vision enhances task performance independently of the surgical method

Background: Within the next few years, the medical industry will launch increasingly affordable three-dimensional (3D) vision systems for the operating room (OR). This study aimed to evaluate the effect of two-dimensional (2D) and 3D visualization on surgical skills and task performance. Methods: In this study, 34 individuals with varying laparoscopic experience (18 inexperienced individuals) performed three tasks to test spatial relationships, grasping and positioning, dexterity, precision, and hand-eye and hand-hand coordination. Each task was performed in 3D using binocular vision for open performance, the Viking 3Di Vision System for laparoscopic performance, and the DaVinci robotic system. The same tasks were repeated in 2D using an eye patch for monocular vision, conventional laparoscopy, and the DaVinci robotic system. Results: Loss of 3D vision significantly increased the perceived difficulty of a task and the time required to perform it, independently of the approach (P<0.0001-0.02). Simple tasks took 25% to 30% longer to complete and more complex tasks took 75% longer with 2D than with 3D vision. Only the difficult task was performed faster with the robot than with laparoscopy (P=0.005). In every case, 3D robotic performance was superior to conventional laparoscopy (2D) (P<0.001-0.015). Conclusions: The more complex the task, the more 3D vision accelerates task completion compared with 2D vision. The gain in task performance is independent of the surgical metho

Direkter Nachweis der renalen Hyperämie nach intravenöser Injektion von Fursemid beim Hund

The effect of intravenous furosemide (1 mg/kg) body weight on the clearance of sodium-para-aminohippurate ( C PAH ) and on renal blood flow (electromagnetic flowmeter) was investigated under Nembutal anesthesia in 6 mongrel dogs. Renal blood flow, after a slight decrease, 20–30 sec after the Furosemide injection, increased rapidly and attained a mean value of +30.0% ( p <0.001) within the first 10 min. During the second 10 min, the increase averaged +23.1% ( p <0.0025) and dropped to +10.6% ( p <0.05) in the third 10 min period. The C PAH showed a similar pattern with mean increases of 24.8% ( p <0.05), 13.0% ( p <0.05) and +6.9% respectively. In 2 dogs, electromagnetic flowmeters were implanted on the renal artery and the same studies peformed without anesthesia. Again renal blood flow and C PAH increased in a similar way to that seen in the previous study, although the increase was slightly more pronounced. We conclude that the observed increase of C PAH in dogs after furosemide reflects a real increase of renal plasma flow and is not merely due to a washout effect. Bei 6 Bastard-Hunden wurde unter Nembutal-Narkose die Wirkung von Fursemid (1,0 mg/kg) Körpergewicht, i.v. injiziert auf die Natrium-Paraaminohippurat-Clearance ( C PAH ) und auf die renale Durchblutung, gemessen mit einem elektromagnetischen Durchflußmesser, untersucht. Die Nierendurchblutung nahm, nach einer wenige Sekunden dauernden leichten Abnahme, regelmäßig zu. Die größte Zunahme, im Mittel +30% ( p <0,001) trat innerhalb der ersten 10 min nach Fursemid auf. In den zweiten 10 min sank die mittlere Zunahme auf +23,1% ( p <0,0025), in den folgenden 10 min auf +10,6% ( p <0,05) ab. Die entsprechenden Werte für die C PAH lauten +24,8% ( p <0,05), +13,0% ( p <0,05) und +6,9% ( p <0,05). Um die Wirkung der Barbiturat-Narkose auszuschalten, wurden bei 2 Hunden mit implantierten elektromagnetischen Druckmessern dieselben Meßgrößen nach Fursemid in derselben Dosierung untersucht. Die Zunahme der Nierendurchblutung und der C PAH tritt auch unter diesen Bedingungen, sogar noch etwas ausgesprochener, auf. Wir schließen aus unseren Befunden daß die nach Fursemid beim Hund auftretende Zunahme der C PAH einer Zunahme der renalen Plasmadurchströmung, resp. der Nierendurchblutung entspricht und nicht auf einem „Auswasch“-Effekt beruht.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46305/1/210_2004_Article_BF00537179.pd

Inhibition of SIRT1 Impairs the Accumulation and Transcriptional Activity of HIF-1α Protein under Hypoxic Conditions

Sirtuins and hypoxia-inducible transcription factors (HIF) have well-established roles in regulating cellular responses to metabolic and oxidative stress. Recent reports have linked these two protein families by demonstrating that sirtuins can regulate the activity of HIF-1 and HIF-2. Here we investigated the role of SIRT1, a NAD+-dependent deacetylase, in the regulation of HIF-1 activity in hypoxic conditions. Our results show that in hepatocellular carcinoma (HCC) cell lines, hypoxia did not alter SIRT1 mRNA or protein expression, whereas it predictably led to the accumulation of HIF-1α and the up-regulation of its target genes. In hypoxic models in vitro and in in vivo models of systemic hypoxia and xenograft tumor growth, knockdown of SIRT1 protein with shRNA or inhibition of its activity with small molecule inhibitors impaired the accumulation of HIF-1α protein and the transcriptional increase of its target genes. In addition, endogenous SIRT1 and HIF-1α proteins co-immunoprecipitated and loss of SIRT1 activity led to a hyperacetylation of HIF-1α. Taken together, our data suggest that HIF-1α and SIRT1 proteins interact in HCC cells and that HIF-1α is a target of SIRT1 deacetylase activity. Moreover, SIRT1 is necessary for HIF-1α protein accumulation and activation of HIF-1 target genes under hypoxic conditions

Heterogeneous Distribution of Chromium on Mercury

Measurements made with geochemical instruments on the MESSENGER spacecraft revealed that Mercury's crust is surprisingly rich in volatile elements, including S, Na, K, Cl, and C, and that it is enriched in Mg and depleted in Al, Ca, and Fe, relative to other terrestrial planets. Geochemical maps also indicated the presence of a number of distinct geochemical terranes. The MESSENGER X-ray Spectrometer (XRS) detected X-ray fluorescence, induced by incident solar X-rays, from the top approx. 10s of micrometers of Mercury's surface. Like Fe, Cr was only detectable by XRS during large solar flares. However, accurate Cr measurements are more susceptible to systematic errors than other elements measured by the XRS. Therefore, to date, Cr data have been published for only 11 XRS measurements, but we have recently derived a map of Cr/Si across Mercury's surface. This map is based on data acquired through the complete MESSENGER mission and reveals clear spatial heterogeneity in Cr

Particles and Photons as Drivers for Particle Release from the Surfaces of the Moon and Mercury

The Moon and Mercury are airless bodies, thus they are directly exposed to the ambient plasma (ions and electrons), to photons mostly from the Sun from infrared range all the way to X-rays, and to meteoroid fluxes. Direct exposure to these exogenic sources has important consequences for the formation and evolution of planetary surfaces, including altering their chemical makeup and optical properties, and generating neutral gas exosphere. The formation of a thin atmosphere, more specifically a surface bound exosphere, the relevant physical processes for the particle release, particle loss, and the drivers behind these processes are discussed in this review