Testing the neutrality of matter by acoustic means in a spherical resonator

New measurements to test the neutrality of matter by acoustic means are reported. The apparatus is based on a spherical capacitor filled with gaseous SF$_6$ excited by an oscillating electric field. The apparatus has been calibrated measuring the electric polarizability. Assuming charge conservation in the $\beta$ decay of the neutron, the experiment gives a limit of $\epsilon_\text{p-e}\lesssim1\cdot10^{-21}$ for the electron-proton charge difference, the same limit holding for the charge of the neutron. Previous measurements are critically reviewed and found incorrect: the present result is the best limit obtained with this technique

Reflectance anisotropy spectroscopy assessment of the MOVPE nucleation of GaInP on Germanium (100)

This work summarizes the observations made on the variation and time evolution of the reflectanceanisotropy signal during the MOVPE growth of GaInPnucleation layers on Germanium substrates. This in situ monitoring tool is used to assess the impact of different nucleation routines and reactor conditions on the quality of the layers grown. This comparison is carried out by establishing a correlation between reflectanceanisotropy signature at 2.1 eV and the morphology of the epilayers evaluated by atomic force microscopy (AFM). This paper outlines the potential of reflectanceanisotropy to predict, explore, and therefore optimize, the best growth conditions that lead to a high quality III–V epilayer on a Ge substrat

Resistance to colistin and production of extended-spectrum ß-lactamases and/or AmpC enzymes in Salmonella isolates collected from healthy pigs in Northwest Spain in two periods: 2008-2009 and 2018

Salmonellosis is a common subclinical infection in pigs and therefore apparently healthy animals may represent a reservoir of antibiotic-resistant Salmonella for humans. This study estimates and characterizes resistance to two classes of antimicrobials considered of the highest priority within the critically important antimicrobials for humans, i.e. colistin (CR) and 3rd generation cephalosporins (3GC), on a collection of Salmonella isolates from pigs from two periods: between 2008 and 09, when colistin was massively used; and in 2018, after three years under a National Plan against Antibiotic Resistance. Prevalence of CR was low (6 out of 625; 0.96%; 95%CI: 0.44–2.1) in 2008–09 and associated mostly to the mcr-1 gene, which was detected in four S. 4,5,12:i:- isolates. Polymorphisms in the pmrAB genes were detected in a S. 9,12:-:- isolate. No CR was detected in 2018 out of 59 isolates tested. Among 270 Salmonella isolates considered for the assessment of resistance to 3GC in the 2008–2009 sampling, only one Salmonella Bredeney (0.37%; 95%CI: 0.07–2.1) showed resistance to 3GC, which was associated with the blaCMY-2 gene (AmpC producer). In 2018, six isolates out of 59 (10.2%; 95%CI: 4.7–20.5) showed resistance to 3GC, but only two different strains were identified (S. 4,12:i:- and S. Rissen), both confirmed as extended-spectrum β-lactamases (ESBL) producers. The blaCTX-M-3 and blaTEM-1b genes in S. 4,12:i:- and the blaTEM-1b gene in S. Rissen seemed to be associated with this resistance. Overall, the prevalence of CR in Salmonella appeared to be very low in 2008–2009 despite the considerable use of colistin in pigs at that time, and seemed to remain so in 2018. Resistance to 3GC was even lower in 2008–2009 but somewhat higher in 2018. Resistance was mostly coded by genes associated with mobile genetic elements. Most serotypes involved in these antimicrobial resistances displayed a multidrug resistance pattern and were considered zoonotic

Heterogeneous Diffusion in Highly Supercooled Liquids

The diffusivity of tagged particles is demonstrated to be very heterogeneous on time scales comparable to or shorter than the $\alpha$ relaxation time $\tau_{\alpha}$ ($\cong$ the stress relaxation time) in a highly supercooled liquid via 3D molecular dynamics simulation. The particle motions in the relatively active regions dominantly contribute to the mean square displacement, giving rise to a diffusion constant systematically larger than the Einstein-Stokes value. The van Hove self-correlation function $G_s(r,t)$ is shown to have a long distance tail which can be scaled in terms of $r/t^{1/2}$ for t \ls 3\tau_{\alpha}. Its presence indicates heterogeneous diffusion in the active regions. However, the diffusion process eventually becomes homogeneous on time scales longer than the life time of the heterogeneity structure ($\sim 3 \tau_{\alpha}$).Comment: 4 pages, 5 figure

Coronakrisens betydning for kirkegårdene

Intet resumé

Experimental search for radiative decays of the pentaquark baryon \Theta^+(1540)

The data on the reactions K^+Xe --> K^0 \gamma X and K^+Xe --> K^+ \gamma X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the \Theta^+(1540) baryon: \Theta^+ --> K^0 p \gamma and \Theta^+ --> K^+ n \gamma. No signals have been observed, and we derive the upper limits \Gamma(\Theta^+ --> K^0 p \gamma) / \Gamma(\Theta^+ --> K^0 p) < 0.032 and \Gamma(\Theta^+ --> K^+ n \gamma) / \Gamma(\Theta^+ --> K^+ n) < 0.041 which, using our previous measurement of \Gamma(\Theta^+ --> KN) = (0.39+-0.10) MeV, translate to \Gamma(\Theta^+ --> K^0 p \gamma) < 8 keV and \Gamma(\Theta^+ --> K^+ n \gamma) < 11 keV at 90% confidence level. We have also measured the cross sections of K^+ -induced reactions involving emission of a neutral pion: \sigma(K^+n --> K^0 p \pi^0) = (68+-18) \mub and \sigma(K^+N --> K^+ N \pi^0) = (30+-8) \mub for incident K^+ momentum of 640 MeV.Comment: 8 page

Search for Millicharged Particles at SLAC

Particles with electric charge q < 10^(-3)e and masses in the range 1--100 MeV/c^2 are not excluded by present experiments. An experiment uniquely suited to the production and detection of such "millicharged" particles has been carried out at SLAC. This experiment is sensitive to the infrequent excitation and ionization of matter expected from the passage of such a particle. Analysis of the data rules out a region of mass and charge, establishing, for example, a 95%-confidence upper limit on electric charge of 4.1X10^(-5)e for millicharged particles of mass 1 MeV/c^2 and 5.8X10^(-4)e for mass 100 MeV/c^2.Comment: 4 pages, REVTeX, multicol, 3 figures. Minor typo corrected. Submitted to Physical Review Letter

Dielectric and thermal relaxation in the energy landscape

We derive an energy landscape interpretation of dielectric relaxation times in undercooled liquids, comparing it to the traditional Debye and Gemant-DiMarzio-Bishop pictures. The interaction between different local structural rearrangements in the energy landscape explains qualitatively the recently observed splitting of the flow process into an initial and a final stage. The initial mechanical relaxation stage is attributed to hopping processes, the final thermal or structural relaxation stage to the decay of the local double-well potentials. The energy landscape concept provides an explanation for the equality of thermal and dielectric relaxation times. The equality itself is once more demonstrated on the basis of literature data for salol.Comment: 7 pages, 3 figures, 41 references, Workshop Disordered Systems, Molveno 2006, submitted to Philosophical Magazin

Meervoudige stress door herhaaldelijk gebruik van gewasbeschermingsmiddelen in landbouwgebieden

Current risk assessment of plant protection products is performed on a formulated-product-by-formulated-product basis and does not take into account the fact that products may be mixed and/or that different products are used sequentially within a growing season. This report evaluates three possibilities for taking these aspects into account in the future that target the risks for surface water. The investigated methods have been shown to be able to take 'multiple stresses' into consideration. Further investigation is needed to check if these methods are sufficient. In this report, three different methods were used to assess the multiple stresses caused by parallel and sequential applications of plant protection products according to realistic application scenarios during the growing season of a tuber crop and an orchard crop. The methods show the effects of the different products on the organisms living in a ditch at the edge of a field. The first method used is the so-called Toxic Unit method, in which the contributions of the individual substances to the overall toxicity are summed and the maximum in time is calculated. The second method, the mixture toxic pressure method (msPAF), calculates the potentially affected fraction of aquatic organisms, taking into account differences in the sensitivity of the organisms to the various substances. The third method, the MASTEP population model, calculates the time necessary for a sensitive aquatic organism (an aquatic isopod) to recover from its exposure to the various substances. The Toxic Unit method (TU) is the one most comparable to the current authorization assessment. All three methods show that a few substances determine a large part of the calculated total effect. The TU-method and the mixture toxic pressure (msPAF) method are useful in identifying these active substances. These selected substances were then used in the MASTEP calculations. The MASTEP method, using Asellus aquaticus as indicator species, did indicate no or hardly any longer recovery times for the multiple applications in comparison with those calculated for the individual pesticide applications. This result applies to species with a high number of offspring. It is recommended that the MASTEP method is used with water organisms that have other survival strategies. At the moment, EFSA (European Food Safety Authority) undertakes activities to develop tools and guidance to assess the human and ecological risks of combined exposure to multiple active substances. This report can contribute to these activities.In de huidige toelatingsbeoordeling van gewasbeschermingsmiddelen worden effecten beoordeeld op basis van de werkzame stoffen die er in zitten. Er wordt daarbij geen rekening mee gehouden dat er meerdere gewasbeschermingsmiddelen, met andere werkzame stoffen, bij dezelfde teelt worden gebruikt. Dit onderzoek verkent drie mogelijkheden om hier in de toekomst wel rekening mee te houden, gericht op de risico's voor oppervlaktewater. De onderzochte methoden blijken deze 'meervoudige stress' te kunnen meenemen. Wel is meer onderzoek nodig om na te gaan of deze methoden toereikend zijn. Voor dit onderzoek zijn met de drie methoden realistische scenario's van het gebruik van gewasbeschermingsmiddelen binnen een groeiseizoen voor een knolgewas en een fruitteeltgewas doorgerekend. De methoden nemen de effecten mee die de verschillende middelen hebben op de organismen in de nabijgelegen sloot. Een van de methoden telt toxiciteitsindexen bij elkaar op (de Toxic Unit-methode, TU), een andere houdt rekening met verschillen in gevoeligheid van soorten organismen voor het bestrijdingsmiddel (de toxisch druk-methode, msPAF) en de derde methode berekent effecten op en het herstel van een gevoelig waterorganisme (het MASTEP-populatiemodel voor de waterpissebed). De TU-methode is het meest vergelijkbaar met de huidige toelatingsbeoordeling. Bij alle drie de methoden blijkt dat enkele stoffen een groot deel van het totaal berekende effect bepalen. De TU-methode en de toxische druk- methode (msPAF) blijken nuttig om deze werkzame stoffen te bepalen. Met deze werkzame stoffen zijn vervolgens de MASTEP-berekeningen uitgevoerd. Uit de MASTEP-berekeningen blijkt dat de periode die de waterpissebed nodig heeft om te herstellen van het effect van de middelen niet of nauwelijks langer duurt als meerdere middelen tegelijk worden gebruikt. Dit resultaat geldt voor waterorganismen die als overlevingsstrategie hebben dat ze veel nakomelingen produceren. Het verdient aanbeveling de MASTEP- berekeningen ook uit te voeren voor organismen met andere overlevingsstrategieën. EFSA (European Food Safety Authority) zoekt momenteel naar mogelijkheden om richtlijnen en instrumenten te ontwikkelen voor het beoordelen van de risico's van gecombineerde blootstelling van mens en milieu aan meerdere werkzame stoffen. Dit rapport kan hieraan bijdragen.Ministerie van I&

High resolution study of the Lambda p final state interaction in the reaction p + p -> K+ + (Lambda p)

The reaction pp -> K+ + (Lambda p) was measured at Tp=1.953 GeV and Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. The large final state enhancement near the Lambda p threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Lambda p invariant mass spectrum and the total cross section data of the free Lambda p scattering.Comment: submitted to Physics Letters B, 10 pages, 3 figure