Tests of Spurious Transport in Smoothed Particle Hydrodynamics

We have performed a series of systematic tests to evaluate the effects of spurious transport in three-dimensional smoothed particle hydrodynamics (SPH) calculations. Our tests investigate (i) particle diffusion, (ii) shock heating, (iii) numerical viscosity, and (iv) angular momentum transport. The results are useful for quantifying the accuracy of the SPH scheme, especially for problems where shear flows or shocks are present, as well as for problems where true hydrodynamic mixing is relevant. We examine the different forms of artificial viscosity (AV) which have been proposed by Monaghan, by Hernquist & Katz, and by Balsara. For each form, our tests suggest a single set of values for the AV parameters $\alpha$ and $\beta$ (coefficients of the linear and quadratic terms) which are appropriate in a large number of situations. We also discuss how these parameters should be adjusted depending on the goals of the particular application. We find that both the Hernquist & Katz and Balsara forms introduce relatively small amounts of numerical viscosity. Furthermore, both Monaghan's and Balsara's AV do well at treating shocks and at limiting the amount of spurious mixing. For these reasons, we endorse the Balsara AV for use in a broad range of applications.Comment: 49 pages, 26 figures as 30 postscript files, submitted to The Journal of Computational Physic

Ambient pH and the response to chemical alarm cues in juvenile Atlantic salmon (Salmo salar): mechanisms of reduced behavioral responses.

Even at sublethal concentrations, various anthropogenic pollutants may disrupt the transfer of chemosensory information, often inducing maladaptive behavioral responses. Recent studies of freshwater prey fishes have shown impaired abilities to respond to damage-released chemical alarm cues from conspecifics under weakly acidic conditions (pH ; 6.0). Several factors acting individually or collectively may account for such chemosensory impairment. By itself, acidification may chemically disrupt the alarm cues and affect fish olfactory functions. Alternatively, differences in local environmental conditions may affect biochemical composition, quantity of chemical alarm cues produced by epidermal tissue, or both, leading to variations in alarm response. Our goal was to assess whether the ability to produce and detect onspecific chemical alarm cues is similar in individuals reared under neutral versus acidic conditions. We conducted two experiments in which we measured the behavioral response of wild juvenile Atlantic salmon Salmo salar exposed to chemical alarm cues. In particular, we looked for differences in the ability of individual fish to (1) produce alarm cues capable of eliciting consistent antipredator behavior in conspecifics and (2) detect alarm cues upon the fish’s introduction into a stream with a pH differing from that of the stream of origin; the latter experiment involved reciprocal transplant of fish between neutral (pH range ; 7.0–7.3) and acidic (pH range ; 5.9–6.3) sites. Our results demonstrate that the ability to produce and respond to chemical alarm cues is maintained in Atlantic salmon reared under acidic conditions and did not differ from that of fish reared under neutral conditions. Overall, these data suggest that no permanent olfactory damage occurred under reduced pH and, likewise, no significant difference in functional alarm cue production existed between Atlantic salmon reared under neutral and acidic conditions. Short-term reduction in olfactory sensitivity and degradation of the chemical alarm cues under acidic conditions are the likely mechanisms affecting detection of these important chemicals by prey fish

The CHEOPS mission

The CHaracterising ExOPlanet Satellite (CHEOPS) was selected in 2012, as the first small mission in the ESA Science Programme and successfully launched in December 2019. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys and to following phase curves. CHEOPS will provide prime targets for future spectroscopic atmospheric characterisation. Requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars in the magnitude range between 6 and 9 by achieving a photometric precision of 20 ppm in 6 hours of integration. For K stars in the magnitude range between 9 and 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration. This is achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter telescope. The 280 kg spacecraft has a pointing accuracy of about 1 arcsec rms and orbits on a sun-synchronous dusk-dawn orbit at 700 km altitude. The nominal mission lifetime is 3.5 years. During this period, 20% of the observing time is available to the community through a yearly call and a discretionary time programme managed by ESA.Comment: Submitted to Experimental Astronom

Rice imports in West Africa: trade regime and food policy formulation.

West African agriculture rice production represents only 50% of consumers' needs in the sub-region. The on-going negotiation on the Agreement on Agriculture and the establishment of a custom union within the ECOWAS offer an opportunity to reopen the discussion on the possible impact of appropriate trade regulation to stimulate the development of the domestic rice value chain. Based on the review of the outcome of recent studies and national statistics, comparing the rice sector history across different West African countries, the poster underlines that the competitiveness of domestic rice production does not depend only upon the cost efficiency of rice producer. It is adversely affected by the performance of the post-harvest operations which does not allow domestic product to match the quality of imported rice in terms of homogeneity and cleanliness. Consumers are ready to pay for a higher price for imported clean and well packed rice. Therefore the design of appropriate trade regulation cannot be limited to a discussion on the level of tariff to be applied by the ECOWAS custom union. Trade regulation could be used as buffer mechanisms to mitigate the negative impact of unpredictable world rice market trends on the willingness of private entrepreneur to invest in rice marketing and processing improvement

Rice imports in West Africa: trade regime and food policy formulation.

West African agriculture rice production represents only 50% of consumers' needs in the sub-region. The on-going negotiation on the Agreement on Agriculture and the establishment of a custom union within the ECOWAS offer an opportunity to reopen the discussion on the possible impact of appropriate trade regulation to stimulate the development of the domestic rice value chain. Based on the review of the outcome of recent studies and national statistics, comparing the rice sector history across different West African countries, the poster underlines that the competitiveness of domestic rice production does not depend only upon the cost efficiency of rice producer. It is adversely affected by the performance of the post-harvest operations which does not allow domestic product to match the quality of imported rice in terms of homogeneity and cleanliness. Consumers are ready to pay for a higher price for imported clean and well packed rice. Therefore the design of appropriate trade regulation cannot be limited to a discussion on the level of tariff to be applied by the ECOWAS custom union. Trade regulation could be used as buffer mechanisms to mitigate the negative impact of unpredictable world rice market trends on the willingness of private entrepreneur to invest in rice marketing and processing improvement.Agricultural and Food Policy, International Relations/Trade,

An Approach to a Trustworthy System Architecture Using Virtualization

Abstract. We present a system architecture for trusted transactions in highly sensitive environments. This architecture takes advantage of techniques provided by the Trusted Computing Group (TCG) to attest the system state of the communication partners, to guarantee that the system is free of malware and that its software has not been tampered with. To achieve meaningful attestation, virtualization is used to establish several different execution environments. The attestation process is limited to a fragment of the software running on the platform, more specifically, to the part requesting access to sensitive data. The Trusted Platform Module (TPM) is virtualized, in order to make it accessible for an execution environment with a higher trust level.

Sarcopenia and Sarcopenic Obesity and Mortality Among Older People

Importance: Sarcopenia and obesity are 2 global concerns associated with adverse health outcomes in older people. Evidence on the population-based prevalence of the combination of sarcopenia with obesity (sarcopenic obesity [SO]) and its association with mortality are still limited. Objective: To investigate the prevalence of sarcopenia and SO and their association with all-cause mortality. Design, Setting, and Participants: This large-scale, population-based cohort study assessed participants from the Rotterdam Study from March 1, 2009, to June 1, 2014. Associations of sarcopenia and SO with all-cause mortality were studied using Kaplan-Meier curves, Cox proportional hazards regression, and accelerated failure time models fitted for sex, age, and body mass index (BMI). Data analysis was performed from January 1 to April 1, 2023. Exposures: The prevalence of sarcopenia and SO, measured based on handgrip strength and body composition (BC) (dual-energy x-ray absorptiometry) as recommended by current consensus criteria, with probable sarcopenia defined as having low handgrip strength and confirmed sarcopenia and SO defined as altered BC (high fat percentage and/or low appendicular skeletal muscle index) in addition to low handgrip strength. Main Outcome and Measure: The primary outcome was all-cause mortality, collected using linked mortality data from general practitioners and the central municipal records, until October 2022. Results: In the total population of 5888 participants (mean [SD] age, 69.5 [9.1] years; mean [SD] BMI, 27.5 [4.3]; 3343 [56.8%] female), 653 (11.1%; 95% CI, 10.3%-11.9%) had probable sarcopenia and 127 (2.2%; 95% CI, 1.8%-2.6%) had confirmed sarcopenia. Sarcopenic obesity with 1 altered component of BC was present in 295 participants (5.0%; 95% CI, 4.4%-5.6%) and with 2 altered components in 44 participants (0.8%; 95% CI, 0.6%-1.0%). An increased risk of all-cause mortality was observed in participants with probable sarcopenia (hazard ratio [HR], 1.29; 95% CI, 1.14-1.47) and confirmed sarcopenia (HR, 1.93; 95% CI, 1.53-2.43). Participants with SO plus 1 altered component of BC (HR, 1.94; 95% CI, 1.60-2.33]) or 2 altered components of BC (HR, 2.84; 95% CI, 1.97-4.11) had a higher risk of mortality than those without SO. Similar results for SO were obtained for participants with a BMI of 27 or greater. Conclusions and Relevance: In this study, sarcopenia and SO were found to be prevalent phenotypes in older people and were associated with all-cause mortality. Additional alterations of BC amplified this risk independently of age, sex, and BMI. The use of low muscle strength as a first step of both diagnoses may allow for early identification of individuals at risk for premature mortality.</p

Constant replenishment from circulating monocytes maintains the macrophage pool in the intestine of adult mice

The paradigm that macrophages that reside in steady-state tissues are derived from embryonic precursors has never been investigated in the intestine, which contains the largest pool of macrophages. Using fate-mapping models and monocytopenic mice, together with bone marrow chimera and parabiotic models, we found that embryonic precursor cells seeded the intestinal mucosa and demonstrated extensive in situ proliferation during the neonatal period. However, these cells did not persist in the intestine of adult mice. Instead, they were replaced around the time of weaning by the chemokine receptor CCR2–dependent influx of Ly6Chi monocytes that differentiated locally into mature, anti-inflammatory macrophages. This process was driven largely by the microbiota and had to be continued throughout adult life to maintain a normal intestinal macrophage pool