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Enhanced dynamics in fusion of neutron-rich oxygen nuclei at above-barrier energies
No full textAbove-barrier fusion cross-sections for an isotopic chain of oxygen isotopes with A=16-19 incident on a C target are presented. Experimental data are compared with both static and dynamical microscopic calculations. These calculations are unable to explain the ∼37% increase in the average above-barrier fusion cross-section observed for O as compared to β-stable oxygen isotopes. This result suggests that for neutron-rich nuclei existing time-dependent Hartree-Fock calculations underpredict the role of dynamics at near-barrier energies. High-quality measurement of above-barrier fusion for an isotopic chain of increasingly neutron-rich nuclei provides an effective means to probe this fusion dynamics
Highlights of the mini-symposium on extracellular vesicles in inter-organismal communication, held in Munich, Germany, August 2018
No full textAll living organisms secrete molecules for intercellular communication. Recent research has revealed that extracellular vesicles (EVs) play an important role in inter-organismal cell-to-cell communication by transporting diverse messenger molecules, including RNA, DNA, lipids and proteins. These discoveries have raised fundamental questions regarding EV biology. How are EVs biosynthesized and loaded with messenger/cargo molecules? How are EVs secreted into the extracellular matrix? What are the EV uptake mechanisms of recipient cells? As EVs are produced by all kind of organisms, from unicellular bacteria and protists, filamentous fungi and oomycetes, to complex multicellular life forms such as plants and animals, basic research in diverse model systems is urgently needed to shed light on the multifaceted biology of EVs and their role in inter-organismal communications. To help catalyse progress in this emerging field, a mini-symposium was held in Munich, Germany in August 2018. This report highlights recent progress and major questions being pursued across a very diverse group of model systems, all united by the question of how EVs contribute to inter-organismal communication
A Phytophthora Effector Suppresses Trans-Kingdom RNAi to Promote Disease Susceptibility
No full textRNA silencing (RNAi) has a well-established role in anti-viral immunity in plants. The destructive eukaryotic pathogen Phytophthora encodes suppressors of RNAi (PSRs), which enhance plant susceptibility. However, the role of small RNAs in defense against eukaryotic pathogens is unclear. Here, we show that Phytophthora infection of Arabidopsis leads to increased production of a diverse pool of secondary small interfering RNAs (siRNAs). Instead of regulating endogenous plant genes, these siRNAs are found in extracellular vesicles and likely silence target genes in Phytophthora during natural infection. Introduction of a plant siRNA in Phytophthora leads to developmental deficiency and abolishes virulence, while Arabidopsis mutants defective in secondary siRNA biogenesis are hypersusceptible. Notably, Phytophthora effector PSR2 specifically inhibits secondary siRNA biogenesis in Arabidopsis and promotes infection. These findings uncover the role of siRNAs as antimicrobial agents against eukaryotic pathogens and highlight a defense/counter-defense arms race centered on trans-kingdom gene silencing between hosts and pathogens
Rheological properties of liquids under conditions of elastohydrodynamic lubrication
No full textThere is an ongoing debate concerning the best rheological model for liquid flows in elastohydrodynamic lubrication (EHL). Due to the small contact area and high relative velocities of bounding solids, the lubricant experiences pressures in excess of 500 MPa and strain rates that are typically 105−107s−1. The high pressures lead to a dramatic rise in Newtonian viscosity and the high rates lead to large shear stresses and pronounced shear thinning. This paper presents detailed simulations of a model EHL fluid, squalane, using nonequilibrium molecular dynamics methods to extract the scaling of its viscosity with shear rate (105−1010s−1) over a wide range of pressure P (0.1 MPa to 1.2 GPa), and temperature T (150−373 K). Simulation results are consistent with a broad range of equilibrium and nonequilibrium experiments. At high T and low P, where is low, the response can be fit to a power law, as in the common Carreau model. Shear thinning becomes steeper as increases, and for ≳1 Pa s, shear thinning is consistent with the thermally activated flow assumed by another common model, Eyring theory. Simulations for a bi-disperse Lennard–Jones (LJ) system show that the transition from Carreau to Eyring is generic. For both squalane and the LJ system, the viscosity decreases by only about a decade in the Carreau regime, but may fall by many orders of magnitude in the Eyring regime. Shear thinning is often assumed to reflect changing molecular alignment, but the alignment of squalane molecules saturates after the viscosity has dropped by only about a factor of three. In contrast, thermal activation describes shear thinning by six or more decades in viscosity. Changes in the diagonal elements of the stress tensor with rate and shear stress are also studied
Obesity Perception Survey Among Youth in Turkey: Instrument Development and Test-Retest Reliability
No full textBackground/aim: We aimed to develop an instrument that can assess the perceptions and opinions of young people regarding the causes and consequences of obesity and the role of individuals, families, communities, and government in addressing obesity. Materials and methods: A 36-question (101-item) survey was developed by adopting, translating, and revising multiple-choice or Likertscale questions from existing surveys to assure construct cross-cultural validity. A two-factor mixed-effects model estimated the intraclass correlation coefficient (ICC) to measure the test-retest reliability of questions administered 2 weeks apart to a convenient sample of İstanbul high school and university students, aged 15–25 years (n = 122). Results: The mean ICC for university and high school was 0.70 and 0.63, respectively. University students were more consistent in relating the problem to society and public policy preferences. High school students were more consistent in relating the problem and solution to themselves and their immediate environments. Using a 0.5 cutoff for the ICC’s lower 95% confidence limit, followed by reevaluation of the question flow, a 19-question (36-item) survey was retained for adolescents and a 26-question (52-item) survey for young adults. Conclusion: While the survey items have moderate to excellent reliability for high school and university students, it can be administered longitudinally to suggest changes to policies and interventions, and after cross-cultural validation, it can be utilized to compare obesity perceptions across different populations
Effect of Alcohol Intoxication on Bystander Intervention in a Vignette Depiction of Sexual Assault
No full textObjective: Alcohol-related sexual violence remains a public health problem. Despite the popularity of sexual assault bystander intervention programs, these may be limited in addressing bystander intoxication because the effects of intoxication on intervening in a sexual assault are unknown. Therefore, we tested the effects of alcohol intoxication on the five steps of bystander intervention in a sexual assault vignette. Method: Young adults (N = 128; 50% women) were randomly assigned to consume alcohol (target blood alcohol concentration = 0.08%; n = 64) or a nonalcoholic control beverage (n = 64) in a bar-laboratory. Next, participants were presented with a vignette describing events occurring in a convivial drinking context that ends with nonconsensual sexual behavior. Latané and Darley’s bystander intervention model steps were assessed in a semistructured interview. Results: Participants in the control condition recalled the story more accurately (Step 1: notice the event) and reported greater risk/need for intervention (Step 2), but they did not differ on the latter three steps of bystander intervention compared with alcohol-condition participants. Intoxication effects were similar for men and women. Furthermore, risk/need for intervention (Step 2) partially mediated the effect of alcohol condition on personal responsibility (Step 3) and relative benefits versus costs from intervening (Step 4). Conclusions: Prevention programs should consider the effects of alcohol on detecting a sexual assault and the need to intervene. If intoxicated bystanders do not detect a sexual assault, then bystanders will not reach the crucial steps (i.e., taking responsibility for intervening; willingness and ability to intervene) required to intervene successfully
Thyroid hormones and neurobehavioral functions among adolescents chronically exposed to groundwaterwith geogenic arsenic in Bangladesh
No full textGroundwater, the major source of drinking water in Bengal Delta Plain, is contaminated with geogenic arsenic (As) enrichment affecting millions of people. Children exposed to tubewell water containing As may be associated with thyroid dysfunction, which in turn may impact neurodevelopmental outcomes. However, data to support such relationship is sparse. The purpose of this study was to examine if chronic water As (WAs) from Holocene alluvial aquifers in this region was associated with serum thyroid hormone (TH) and if TH biomarkers were related to neurobehavioral (NB) performance in a group of adolescents. A sample of 32 healthy adolescents were randomly drawn from a child cohort in the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh. Half of these participants were consistently exposed to low WAs (<10 μg/L) and the remaining half had high WAs exposure (≥10 μg/L) since birth. Measurements included serum total triiodothyronine (tT3), free thyroxine (fT4), thyrotropin (TSH) and thyroperoxidase antibodies (TPOAb); concurrent WAs and urinary arsenic (UAs); and adolescents' NB performance. WAs and UAs were positively and significantly correlated with TPOAb but were not correlated with TSH, tT3 and fT4. After accounting for covariates, both WAs and UAs demonstrated positive but non-significant relationships with TSH and TPOAb and negative but non-significant relationships with tT3 and fT4. TPOAb was significantly associated with reduced NB performance indicated by positive associations with latencies in simple reaction time (b = 82.58; p < 0.001) and symbol digit (b = 276.85; p = 0.005) tests. TSH was significantly and negatively associated with match-to-sample correct count (b = −0.95; p = 0.05). Overall, we did not observe significant associations between arsenic exposure and TH biomarkers although the relationships were in the expected directions. We observed TH biomarkers to be related to reduced NB performance as hypothesized. Our study indicated a possible mechanism of As-induced neurotoxicity, which requires further investigations for confirmatory findings
A toxicogenomic approach for the risk assessment of the food contaminant acetamide
No full textAcetamide (CAS 60-35-5) is detected in common foods. Chronic rodent bioassays led to its classification as a group 2B possible human carcinogen due to the induction of liver tumors in rats. We used a toxicogenomics approach in Wistar rats gavaged daily for 7 or 28 days at doses of 300 to 1500 mg/kg/day (mkd) to determine a point of departure (POD) and investigate its mode of action (MoA). Ki67 labeling was increased at doses ≥750 mkd up to 3.3-fold representing the most sensitive apical endpoint. Differential gene expression analysis by RNA-Seq identified 1110 and 1814 differentially expressed genes in male and female rats, respectively, following 28 days of treatment. Down-regulated genes were associated with lipid metabolism while up-regulated genes included cell signaling, immune response, and cell cycle functions. Benchmark dose (BMD) modeling of the Ki67 labeling index determined the BMD10 lower confidence limit (BMDL10) as 190 mkd. Transcriptional BMD modeling revealed excellent concordance between transcriptional POD and apical endpoints. Collectively, these results indicate that acetamide is most likely acting through a mitogenic MoA, though specific key initiating molecular events could not be elucidated. A POD value of 190 mkd determined for cell proliferation is suggested for risk assessment purposes
A critique of the objective function utilized in calculating the Thrifty Food Plan
No full textThe Thrifty Food Plan (TFP) is the basis of benefit allocations within the USDA’s Supplemental Nutrition Assistance Program (SNAP), which administers nearly $70 billion in benefits to over 42 million people annually. To produce the allocation of food within the TFP, the USDA uses a mathematical optimization model that solves for the daily apportionment across various food groups. The model is constrained by nutritional and consumption requirements to produce an “optimal” allocation. Despite the importance of the TFP, the computational solution developed by the USDA has received insufficient attention, with only a handful of articles written on the TFP optimization model. Here, we run three alternative objective functions that are simpler than the one used by USDA. Our first alternative objective function minimizes the sum of squared errors between the consumed market basket of goods and an allocated market basket of goods, the second alternative objective function minimizes the sum of the absolute value of the difference between the consumed market basket of goods and an allocated market basket of goods, and the third alternative objective function minimizes the weighted absolute deviation of allocations and actual consumption expressed as a proportion of observed consumption. A clear theoretical advantage of either of our methods is that they eliminate the need to arbitrarily set allocated consumption to nonzero values, as is the case for the logarithmic objective function used by USDA. In an operational sense, we find that our model formulations produce an allocation that fits actual consumption better than the objective function employed by the USDA