Maximum occupation number for composite boson states

One of the major differences between fermions and bosons is that fermionic states have a maximum occupation number of one, whereas the occupation number for bosonic states is in principle unlimited. For bosons that are made up of fermions, one could ask the question to what extent the Pauli principle for the constituent fermions would limit the boson occupation number. Intuitively one can expect the maximum occupation number to be proportional to the available volume for the bosons divided by the volume occupied by the fermions inside one boson, though a rigorous derivation of this result has not been given before. In this letter we show how the maximum occupation number can be calculated from the ground-state energy of a fermionic generalized pairing problem. A very accurate analytical estimate of this eigenvalue is derived. From that a general expression is obtained for the maximum occupation number of a composite boson state, based solely on the intrinsic fermionic structure of the bosons. The consequences for Bose-Einstein condensates of excitons in semiconductors and ultra cold trapped atoms are discussed.Comment: 4 pages, Revte

Prewetting transition on a weakly disordered substrate : evidence for a creeping film dynamics

We present the first microscopic images of the prewetting transition of a liquid film on a solid surface. Pictures of the local coverage map of a helium film on a cesium metal surface are taken while the temperature is raised through the transition. The film edge is found to advance at constant temperature by successive avalanches in a creep motion with a macroscopic correlation length. The creep velocity varies strongly in a narrow temperature range. The retreat motion is obtained only at much lower temperature, conforming to the strong hysteresis observed for prewetting transition on a disordered surface. Prewetting transition on such disordered surfaces appears to give rise to dynamical phenomena similar to what is observed for domain wall motions in 2D magnets.Comment: 7 pages, 3 figures, to be published in Euro.Phys.Let

ANALYSIS OF VENTING OF A RESIN SLURRY

A resin slurry venting analysis was conducted to address safety issues associated with overpressurization of ion exchange columns used in the Purex process at the Savannah River Site (SRS). If flow to these columns were inadvertently interrupted, an exothermic runaway reaction could occur between the ion exchange resin and the nitric acid used in the feed stream. The nitric acid-resin reaction generates significant quantities of noncondensable gases, which would pressurize the column. To prevent the column from rupturing during such events, rupture disks are installed on the column vent lines. The venting analysis models accelerating rate calorimeter (ARC) tests and data from tests that were performed in a vented test vessel with a rupture disk. The tests showed that the pressure inside the test vessel continued to increase after the rupture disk opened, though at a slower rate than prior to the rupture. Calculated maximum discharge rates for the resin venting tests exceeded the measured rates of gas generation, so the vent size was sufficient to relieve the pressure in the test vessel if the vent flow rate was constant. The increase in the vessel pressure is modeled as a transient phenomenon associated with expansion of the resin slurry/gas mixture upon rupture of the disk. It is postulated that the maximum pressure at the end of this expansion is limited by energy minimization to approximately 1.5 times the rupture disk burst pressure. The magnitude of this pressure increase is consistent with the measured pressure transients. The results of this analysis demonstrate the need to allow for a margin between the design pressure and the rupture disk burst pressure in similar applications

Std fimbriae-fucose interaction increases Salmonella-induced intestinal inflammation and prolongs colonization

Author summary The intestinal epithelium is a crucial biological interface, interacting with both commensal and pathogenic microorganisms. It’s lined with heavily glycosylated proteins and glycolipids which can act as both attachment sites and energy sources for intestinal bacteria. Fut2, the enzyme governing epithelial α1,2-fucosylation, has been implicated in the interaction between microbes and intestinal epithelial cells. Salmonella is one of the most important bacterial gastrointestinal pathogens affecting millions of people worldwide. Salmonella possesses fimbrial and non-fimbrial adhesins which can be used to adhere to host cells. Here we show that Salmonella expresses Std fimbriae in the gastrointestinal tract in vivo and exploit Std fimbriae to bind fucosylated structures in the mucus and on the intestinal epithelium. Furthermore, we demonstrate that the Std fimbriae-fucose interaction is necessary for bacterial colonization of the intestine and for triggering intestinal inflammation. These data lend new insights into bacterial adhesion-epithelial interactions which are essential for bacterial pathogenesis and key factors in determining tissue tropism and host susceptibility to infectious disease

Thermal Modeling Analysis of SRS 70 Ton Cask

The primary objective of this work was to perform the thermal calculations to evaluate the Material Test Reactor (MTR) fuel assembly temperatures inside the SRS 70-Ton Cask loaded with various bundle powers. MTR fuel consists of HFBR, MURR, MIT, and NIST. The MURR fuel was used to develop a bounding case since it is the fuel with the highest heat load. The results will be provided for technical input for the SRS 70 Ton Cask Onsite Safety Assessment. The calculation results show that for the SRS 70 ton dry cask with 2750 watts total heat source with a maximum bundle heat of 670 watts and 9 bundles of MURR bounding fuel, the highest fuel assembly temperatures are below about 263 C. Maximum top surface temperature of the plastic cover is about 112 C, much lower than its melting temperature 260 C. For 12 bundles of MURR bounding fuel with 2750 watts total heat and a maximum fuel bundle of 482 watts, the highest fuel assembly temperatures are bounded by the 9 bundle case. The component temperatures of the cask were calculated by a three-dimensional computational fluid dynamics approach. The modeling calculations were performed by considering daily-averaged solar heat flux

A novel patch micro electrode array for sensing ionic membrane currents

Ionic membrane currents play an important role during regeneration of nerve cells, embryonic development and wound healing processes. Measuring the intracellular ion currents across the cell membrane is important in understanding the cellular functions related to the ion activities. A novel patch micro electrode array (p-MEA) for measuring the ionic membrane currents without poisoning the cells due to emitting metal ions is described in this paper. Results on biocompatibility of the device are presented. We discuss the fabrication and working principle of p-MEA

Plutonium storage thermal analysis (U)

Thermal modeling of plutonium metal ingots stored in food pack cans provides information useful for performing stored material safety evaluations. Four storage can geometries were modeled, and several conclusions can be made from the 14 cases analyzed. The ingot temperature increased from 7 degrees F to 12 degrees F (depending on can configuration) per additional watt of power. Including internal convection lowers computed ingot temperatures by 70 degrees F. Accounting for the heat flow through the bottom of the cans to the storage rack lowered computed ingot temperatures by an additional 70 degrees F to 80 degrees F. In the rimmed can systems storing ingots with a power of 10.35 watts, the ingot temperature varies from 190 degrees F to 213 degrees F. Including a plastic bag between the inner and outer can increases the ingot temperature by 15 degrees F. Adding a label to the outer can side reduces the outer can side temperature by 13 degrees F. Changes in ambient temperature affect the outer can temperatures more than the ingot temperature by a factor of 3. Similarly, a 5 degrees F drop in outer can temperature due to increased convection lowered the ingot temperature by only 2 degrees

Packaging and Transportation of Additional Neptunium Oxide

The Savannah River Site's HB-Line Facility completed a second neptunium oxide production campaign in which nine (9) additional cans of neptunium oxide were produced and shipped to the Idaho National Laboratory and Oak Ridge National Laboratory in the 9975 shipping container. These additional cans were from a different feed solution than the first fifty (50) cans of neptunium oxide that were previously produced and shipped via a Letter of Amendment to the 9975 Safety Analysis Report for Packaging (SARP) content table. This paper will address the challenges associated with demonstrating the neptunium oxide produced from the additional feed solution was equivalent to the original neptunium oxide and within the content description of the Letter of Amendment

Extreme event ecology needs proactive funding

Commentary: Extreme events such as wildfires, hurricanes, and floods have increased in frequency and intensity. It is no longer a question of if, but rather when and where these events will occur (Stott 2016), with adverse impacts on essential ecosystemservices including clean water, harvestable materials, and carbon sequestration. In some cases, extreme events such as wildfires may have positive impacts on populations and ecosystems. Managing these impacts requires understanding how environmental context as well as ecosystem and disturbance characteristics drive system responses (Hogan et al. 2020). However, funding for ecological extreme events research, such as through the US National Science Foundation’s (NSF’s) RAPID program, is typically reactive. Pre-event data, a RAPID prerequisite, aretypically lacking or only sporadically available, and case studies of extreme events often arise from chance disturbances at existing long-term research sites. This reactive stochastic approach has seeded the literature with unplanned case studies describing individual events. While useful for meta-analyses (eg Patrick et al. 2022), such studies provide limited spatiotemporal inference and predictive capacity. Prioritizing the study of extreme events and empirically testing fundamental concepts in disturbance ecology is paramount (Aoki et al. 2022). (...

Only Yes Means Yes: Sexual Coercion in Rural Adolescent Relationships

Purpose Sexual consent is important to healthy relationships; however, sexual coercion is common. We examine modifiable risk and protective factors for sexual coercion among high school students in a rural community. Methods We surveyed 10th graders (N = 442) in a rural, Midwestern, low-to-middle income county before receiving an evidence-based sex education program. Sexual coercion was a single item, “has anyone you were dating or going out with forced you to do sexual things that you did not want to do?” We examined associations between sexual coercion and demographics, risk behaviors, sexual self-efficacy, controlling relationship behaviors, parent communication, and adverse childhood experiences. Results Approximately 22% of females and 8% of males reported experiencing sexual coercion at least once in their lifetime. Gender differences emerged in associated risk and protective factors, including sexual sex efficacy, controlling relationship behaviors, parent–adolescent communication about sex, and adverse childhood experiences. Conclusions Sexual coercion is common among adolescents in rural communities. Prevention interventions should target modifiable risk and protective factors