Structure and Dynamics of amorphous Silica Surfaces

We use molecular dynamics computer simulations to study the equilibrium properties of the surface of amorphous silica. Two types of geometries are investigated: i) clusters with different diameters (13.5\AA, 19\AA, and 26.5\AA) and ii) a thin film with thickness 29\AA. We find that the shape of the clusters is independent of temperature and that it becomes more spherical with increasing size. The surface energy is in qualitative agreement with the experimental value for the surface tension. The density distribution function shows a small peak just below the surface, the origin of which is traced back to a local chemical ordering at the surface. Close to the surface the partial radial distribution functions as well as the distributions of the bond-bond angles show features which are not observed in the interior of the systems. By calculating the distribution of the length of the Si-O rings we can show that these additional features are related to the presence of two-membered rings at the surface. The surface density of these structures is around 0.6/nm^2 in good agreement with experimental estimates. From the behavior of the mean-squared displacement at low temperatures we conclude that at the surface the cage of the particles is larger than the one in the bulk. Close to the surface the diffusion constant is somewhat larger than the one in the bulk and with decreasing temperature the relative difference grows. The total vibrational density of states at the surface is similar to the one in the bulk. However, if only the one for the silicon atoms is considered, significant differences are found.Comment: 30 pages of Latex, 16 figure

Characteristics of patients with haematological and breast cancer (1996–2009) who died of heart failure-related causes after cancer therapy

Aims: To describe the characteristics and time to death of patients with breast or haematological cancer who died of heart failure (HF) after cancer therapy. Patients with an index admission for HF who died of HF-related causes (IAHF) and those with no index admission for HF who died of HF-related causes (NIAHF) were compared. Methods and results: We performed a linked data analysis of cancer registry, death registry, and hospital administration records (n = 15 987). Index HF admission must have occurred after cancer diagnosis. Of the 4894 patients who were deceased (30.6% of cohort), 734 died of HF-related causes (50.1% female) of which 279 (38.0%) had at least one IAHF (41.9% female) post-cancer diagnosis. Median age was 71 years [interquartile range (IQR) 62–78] for IAHF and 66 years (IQR 56–74) for NIAHF. There were fewer chemotherapy separations for IAHF patients (median = 4, IQR 2–9) compared with NIAHF patients (median = 6, IQR 2–12). Of the IAHF patients, 71% had died within 1 year of the index HF admission. There was no significant difference in HF-related mortality in IAHF patients compared with NIAHF (HR, 1.10, 95% CI, 0.94–1.29, P = 0.225). Conclusions: The profile of IAHF patients who died of HF-related causes after cancer treatment matched the current profile of HF in the general population (over half were aged ≥70 years). However, NIAHF were younger (62% were aged ≤69 years), female patients with breast cancer that died of HF-related causes before hospital admission for HF-related causes—a group that may have been undiagnosed or undertreated until death

High-Temperature Series Analysis of the Free Energy and Susceptibility of the 2D Random-Bond Ising Model

We derive high-temperature series expansions for the free energy and susceptibility of the two-dimensional random-bond Ising model with a symmetric bimodal distribution of two positive coupling strengths J_1 and J_2 and study the influence of the quenched, random bond-disorder on the critical behavior of the model. By analysing the series expansions over a wide range of coupling ratios J_2/J_1, covering the crossover from weak to strong disorder, we obtain for the susceptibility with two different methods compelling evidence for a singularity of the form $\chi \sim t^{-7/4} |\ln t|^{7/8}$, as predicted theoretically by Shalaev, Shankar, and Ludwig. For the specific heat our results are less convincing, but still compatible with the theoretically predicted log-log singularity.Comment: 19 pages, 6 Postscript figure

Heart failure following blood cancer therapy in pediatric and adult populations

Aim: The link between chemotherapy treatment and cardiotoxicity is well established, particularly for adults with blood cancers. However, it is less clear for children. This analysis aimed to compare the trajectory and mortality of children and adults who received chemotherapy for blood cancers and were subsequently hospitalised for heart failure. Methods: Linked data from the Queensland Cancer Registry, Death Registry and Hospital Administration records for initial chemotherapy and later heart failure were reviewed (1996-2009). Of all identified blood cancer patients (N=23,434); 8,339 received chemotherapy, including 817 children (aged ≤18 years at time of cancer diagnosis) and 7,522 adults. Time-varying Cox proportional hazards regression models were used to compare the characteristics and survival between the two groups. Results: Of those who were subsequently hospitalised for heart failure, 70% of children and 46% of adults had the index admission within 12 months of their cancer diagnosis. Of these, 53% of the pediatric heart failure population and 71% of the adult heart failure population died within the study period. Following adjustment for age, sex and chemotherapy admissions, children with heart failure had an increased mortality risk compared to their non-heart failure counterparts, a difference which was much greater than that between the adult groups. Conclusion: The impact of heart failure on children previously treated for blood cancer is more severe than for adults, with earlier morbidity and greater mortality. Improved strategies are needed for the prevention and management of cardiotoxicity in this population

Heart Failure Following Cancer Therapy in Patients with Hematological Malignancies Aged 18 Years and Under: A Linked Health Data Analysis (1996-2009)

Made available in accordance with Publisher's Open Access policyntroduction: The causal link between chemotherapy treatments and subsequent cardiotoxicity is well established, particularly for children with hematological malignancies. Little information exists on the characteristics and outcomes for patients with heart failure (HF) after chemotherapy. This study aimed to describe the characteristics, survival and mortality of patients who received chemotherapy for hematological cancer (leukemias, lymphomas and related disorders) before 18 years old and subsequently developed HF compared to those who did not. Methods: Linked health data (1996-2009) from the Queensland Cancer Registry, Death Registry and Hospital Administration records for HF and chemotherapy admissions were reviewed. From all breast and hematological cancers patients (n=73,158), 15,987 received chemotherapy, including 819 patients aged ≤18 years at time of cancer diagnosis. Patients were categorized as those with an index HF admission (occurred after cancer diagnosis) and those without an index HF admission (non HF). Results: Of the 819 patients, 3.7% (n=30) had an index HF admission. Median age of HF patients at time of cancer diagnosis was 5 years (IQR 3-12) compared to 7 years (IQR 3-14) in the non HF group (p=0.503). Median follow up from cancer diagnosis was 2.5 years in the HF group compared to 5.42 years in the non HF group (p<0.01). Of those who developed HF, 70% (n=21) had the index admission within 12 months of their cancer diagnosis. Of those with HF, 53.3% (n=16) died (all cause) compared to 14.6% (n=115) with no HF. On adjustment for age, sex and chemotherapy admissions, HF patients had an almost 5 fold increased mortality risk compared to non HF patients (HR 4.91 [95% CI, 2.88-8.36]) Conclusions: This study demonstrated that in children with hematological cancers the onset of HF occurred soon after chemotherapy and mortality risk is almost 5 times that of children who do not develop HF. Innovative strategies are still needed for the prevention and management of cardiotoxicity in this populatio

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Influence of Xenorhabdus Symbionts on Gonad Development and Pheromone Production of First-Generation Adult Steinernema Nematodes (Nematoda: Steinernematidae)

Entomopathogenic Steinernema nematodes (Nematoda: Steinernematidae) have a mutualistic relationship with Xenorhabdus bacteria (Gamma-Proteobacteria Enterobacteriaceae). The two partners form an insecticidal alliance that is successful in killing a wide range of insects. A few studies have shown that Steinernema IJs have an enhanced virulence and reproductive fitness when they associate with their cognate symbionts. However, there are unanswered questions regarding the physiological interactions that govern and perpetuate the interactions between different nematode developmental stages and their bacterial partners. In this study, we evaluated gonad development and maturation time of first-generation adults of S. carpocapsae and S. feltiae adults when reared under four bacterial scenarios: a) cognate symbiotic, b) non-cognate symbiotic bacterial strain, c) non-cognate symbiotic bacterial species and d) non-symbiotic bacteria (Serratia proteamaculans). For comparative purposes, we also considered adult nematodes reared in vivo in Galleria mellonella larvae to assess nematode development under natural conditions. Furthermore, in this study we also measured production of nematode pheromones (ascarosides), which play a key role in mating and reproduction. For this purpose, we considered in vitro rearing methods (with cognate and non-cognate Xenorhabdus symbionts) to qualitatively and quantitatively characterize ascarosides produced by first-generation adults. Our data showed that for both Steinernema spp. tested, time to adult maturation and gonad development was tightly dependent on the bacterial conditions under which juveniles were reared. However, contrasting results were observed when assessing total body length and gonad size. S. feltiae males and females size (body length and width) and respective gonad length were smaller when reared with a non-cognate symbiotic species. Additionally, non-symbiotic bacteria did not sustain S. feltiae maturation to adult stages. Contrarily, S. carpocapsae juveniles developed to adults when reared with any of the bacterial conditions tested, including with non-symbiotic Serratia proteamaculans. Additionally, S. carpocapsae adults, unlike S. feltiae, did not exhibit enhanced body and gonad size when reared with their cognate symbiont. In fact, S. carpocapsae males and females had larger gonad lengths when reared with a non-cognate symbiotic strain, XnAna (X. nematophila associated with S. anatoliense). S. carpocapsae males and females had significantly underdeveloped gonads when reared with non-symbiotic bacteria. In both Steinernema spp., sex ratio was not impacted by the bacterial condition. However, sex ratio (female:male) S. carpocapsae, decreased from 2:1 to 1:1 when reared with non-symbiotic bacteria. The body and gonad sizes of Steinernema spp. reared in vitro with their cognate symbiont were significantly smaller than those grown in vivo. Ascaroside production in either Steinernema spp. was not significantly impacted by the rearing conditions. In S. carpocapsae, a significant increase in glucoside-1 was observed when the nematodes were reared with cognate or non-cognate bacteria. No detectable quantities of asc-C11 were produced by S. feltiae nematodes when reared with a non-cognate symbiotic bacterial species. We conclude that bacterial symbionts influenced maturation and development of first-generation adults’ in both Steinernema spp. tested in this study. However, response to the bacterial symbionts was species specific. Additionally, this study showed that Xenorhabdus as a food source plays an important role in the type and amount of ascarosides produced by Steinernema spp.Release after 19-Dec-201

Molekulardynamik-Simulationen zu Oberflächeneigenschaften von Siliziumdioxid-Schmelzen

Molekulardynamik-Simulationen zu OberflächeneigenschaftenvonSiliziumdioxid-Schmelzen In der vorliegenden Arbeit werdenMolekulardynamik-Computersimulationenzur Untersuchung der statischen und dynamischenOberflächeneigenschafteneiner Siliziumdioxid (SiO$_2$)-Schmelze durchgeführt.Als Modellpotential verwenden wirein in der Literatur als BKS-Potential bezeichnetesPaarpotential.Wir betrachten in dieser Arbeit zwei Systemgeometrien: zumeinenSysteme aus 432, 1536 und 4608 Atomen ohne periodischeRandbedingungen(Tropfen), zum anderen ein System aus 1152 Atomen mitperiodischen Randbedingungen in zwei Richtungen (dünnerFilm).Für beide Geometrien finden wir im Inneren der Systemekonstante Dichten.Direktan der Oberfläche halten sich ausschließlich Sauerstoffatomeauf.Die Strukturan der Oberfläche erscheint weniger ausgeprägt mit mehrDefekten, als im Inneren des Systems.Es erweist sich,daß viele Eigenschaften statischer Größen, die wir an derOberfläche im Vergleich zum Inneren finden, aufdas Vorhandensein von Zweierringen zurückzuführen sind.Bei der Betrachtung der dynamischen Größen finden wir eineerhöhteBeweglichkeit der Atome an der Oberfläche gegenüber demSysteminneren.A analysis of the surface of a silica melt via moleculardynamics computersimulation Molecular dynamics computer simulations were used to studythe staticand dynamic properties of the surface of a silica melt.The potential used here was that proposed by van Beest etal. (BKS).We studied two different system geometries: one without anyperiodicboundary conditions (drop) and one with periodic boundaryconditionsin two dimensions (thin slab). In both cases we founda constant density inside the systems and a predominance ofoxygen atoms at the surface.There is a less pronounced structure with more defects atthe surfacecompared to the interior.Many local structural differences between atoms in theinterior andatoms near the surface are due to two-membered rings.By looking at dynamic properties we found a highermobility of the atoms at the surface

Influence of symbiotic and non-symbiotic bacteria on pheromone production in nematodes (Nematoda, Steinernematidae)

In this study, we assessed the effect of symbiotic (cognate and non-cognate) and non-symbiotic bacteria on ascaroside production of first-generation adults in two Steinernema spp.: S. carpocapsae All strain and S. feltiae SN strain. Each nematode species was reared under three bacterial scenarios: (1) cognate symbiotic, (2) non-cognate symbiotic strain and (3) non-cognate symbiotic species. Our results showed S. carpocapsae produced four quantifiable ascaroside molecules: asc-C5, asc-C6, asc-C7 and asc-C11, whereas in S. feltiae only three molecules were detected: asc-C5, asc-C7 and asc-C11. Bacterial conditions did not significantly affect the quantity of the secreted ascarosides in first-generation adults of S. carpocapsae However, in S. feltiae, Xenorhabdus nematophila All strain influenced the production of two ascaroside molecules: asc-C5 and asc-C11.US Department of Agriculture, NIFA Program [2015-67013-23086]; University of Arizona Graduate and Professional Student Council grant12 month embargo; published online: 25 September 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]