Feshbach resonances with large background scattering length: interplay with open-channel resonances

Feshbach resonances are commonly described by a single-resonance Feshbach model, and open-channel resonances are not taken into account explicitly. However, an open-channel resonance near threshold limits the range of validity of this model. Such a situation exists when the background scattering length is much larger than the range of the interatomic potential. The open-channel resonance introduces strong threshold effects not included in the single-resonance description. We derive an easy-to-use analytical model that takes into account both the Feshbach resonance and the open-channel resonance. We apply our model to $^{85}$Rb, which has a large background scattering length, and show that the agreement with coupled-channels calculations is excellent. The model can be readily applied to other atomic systems with a large background scattering length, such as $^6$Li and $^{133}$Cs. Our approach provides full insight into the underlying physics of the interplay between open-channel (or potential) resonances and Feshbach resonances.Comment: 16 pages, 12 figures, accepted for publication in Phys. Rev. A; v2: added reference

Advancing interoperable soil data exchange for global soil data information systems

In order to be able to address local, regional and global issues such as sustainable land management, food security, climate change mitigation and soil-related indicators of the UN Agenda for Sustainable Development the need for reliable, relevant and accurate soil information and data is increasing. Currently, ..

Polyhedral restrictions of feasibility regions in optimal power flow for distribution networks

The optimal power flow (OPF) problem is one of the most fundamental problems in power system operations. The non-linear alternating current (AC) power flow equations that model different physical laws (together with operational constraints) lay the foundation for the feasibility region of the OPF problem. While significant research has focused on convex relaxations, which are approaches to solve an OPF problem by enlarging the true feasibility region, the opposite approach of convex restrictions offers valuable insights as well. Convex restrictions, including polyhedral restrictions, reduce the true feasible region to a convex region, ensuring that it contains only feasible points. In this work, we develop a sequential optimization method that offers a scalable way to obtain (bounds on) solutions to OPF problems for distribution networks. To do so, we first develop sufficient conditions for the existence of feasible power flow solutions in the neighborhood of a specific (feasible) operating point in distribution networks, and second, based on these conditions, we construct a polyhedral restriction of the feasibility region. Our numerical results demonstrate the efficacy of the sequential optimization method as an alternative to existing approaches to obtain (bounds on) solutions to OPF problems for distribution networks. By construction, the optimization problems can be solved in polynomial time and are guaranteed to have feasible solutions

Predicting scattering properties of ultracold atoms: adiabatic accumulated phase method and mass scaling

Ultracold atoms are increasingly used for high precision experiments that can be utilized to extract accurate scattering properties. This calls for a stronger need to improve on the accuracy of interatomic potentials, and in particular the usually rather inaccurate inner-range potentials. A boundary condition for this inner range can be conveniently given via the accumulated phase method. However, in this approach one should satisfy two conditions, which are in principle conflicting, and the validity of these approximations comes under stress when higher precision is required. We show that a better compromise between the two is possible by allowing for an adiabatic change of the hyperfine mixing of singlet and triplet states for interatomic distances smaller than the separation radius. A mass scaling approach to relate accumulated phase parameters in a combined analysis of isotopically related atom pairs is described in detail and its accuracy is estimated, taking into account both Born-Oppenheimer and WKB breakdown. We demonstrate how numbers of singlet and triplet bound states follow from the mass scaling.Comment: 14 pages, 9 figure

Validatie van het nutriënten-emissiemodel STONE met meetgegevens uit het Landelijk Meetnet effecten Mestbeleid (LMM) en de Landelijke Steekproef Kaarteenheden (LSK)

De uitkomsten van het model STONE zijn gevalideerd op gemeten concentraties in drains en grondwater uit LMM (Landelijk Meetnet effecten Mestbeleid) en gemeten fosfaatophoping volgens LSK (Landelijke Steekproef Kaarteenheden). Voor de validatie is gebruik gemaakt van een in 2008 ontwikkeld protocol. Uit de validatie komt naar voren dat op nationale schaal de gemiddelde door STONE gesimuleerde nitraatconcentraties in grondwater en drainwater goed overeenkomen met de metingen. De gesimuleerde DOC-concentraties in grondwater en drainwater en de fosfaatconcentraties in het grondwater wijken sterker af van de metingen. Tevens bleek uit de validatie op LSK dat de verdeling van P over boven- en ondergrond afwijkt van de metingen. Voor deze stoffen is dus een verdere verbetering van het model en/of de parameterisatie gewenst

The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL

NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8 Msun) protostar located at a distance of 1250 pc. High spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218200 MHz to 221800 MHz carried out with the IRAM Plateau de Bure Interferometer. These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30m telescope. We used a Local Thermodynamic Equilibrium (LTE) single temperature code to model the whole dataset. The interferometric spectrum is crowded with a total of ~300 lines from which a few dozens remain unidentified yet. The spectrum has been modeled with a total of 20 species and their isomers, isotopologues and deuterated compounds. Complex molecules like methyl formate (CH3OCHO), ethanol (CH3CH2OH), glycolaldehyde (CH2OHCHO), acetone (CH3COCH3), dimethyl ether (CH3OCH3), ethyl cyanide (CH3CH2CN) and the aGg' conformer of ethylene glycol (aGg'-(CH2OH)_2) are among the detected species. The detection of vibrationally excited lines of CH3CN, CH3OCHO, CH3OH, OCS, HC3N and CH3CHO proves the existence of gas and dust at high temperatures. In fact, the gas kinetic temperature estimated from the vibrational lines of CH3CN, ~405 K, is similar to that measured in massive hot cores. Our data allow an extensive comparison of the chemistry in FIRS~2 and the Orion hot core. We find a quite similar chemistry in FIRS 2 and Orion. Most of the studied fractional molecular abundances agree within a factor of 5. Larger differences are only found for the deuterated compounds D2CO and CH2DOH and a few molecules (CH3CH2CN, SO2, HNCO and CH3CHO). Since the physical conditions are similar in both hot cores, only different initial conditions (warmer pre-collapse phase in the case of Orion) and/or different crossing time of the gas in the hot core can explain this behavior.Comment: 30 pages, 9 figure

Dust, Ice and Gas in Time (DIGIT) Herschel program first results: A full PACS-SED scan of the gas line emission in protostar DK Cha

DK Cha is an intermediate-mass star in transition from an embedded configuration to a star plus disk stage. We aim to study the composition and energetics of the circumstellar material during this pivotal stage. Using the Range Scan mode of PACS on the Herschel Space Observatory, we obtained a spectrum of DK Cha from 55 to 210 micron as part of the DIGIT Key Program. Almost 50 molecular and atomic lines were detected, many more than the 7 lines detected in ISO-LWS. Nearly the entire ladder of CO from J=14-13 to 38-37 (E_u/k = 4080 K), water from levels as excited as E_u/k = 843 K, and OH lines up to E_u/k = 290 K were detected. The continuum emission in our PACS SED scan matches the flux expected from a model consisting of a star, a surrounding disk of 0.03 Solar mass, and an envelope of a similar mass, supporting the suggestion that the object is emerging from its main accretion stage. Molecular, atomic, and ionic emission lines in the far-infrared reveal the outflow's influence on the envelope. The inferred hot gas can be photon-heated, but some emission could be due to C-shocks in the walls of the outflow cavity.Comment: 4 Page letter, To appear in A&A special issue on Hersche

Radio-Frequency Spectroscopy of Ultracold Fermions

Radio-frequency techniques were used to study ultracold fermions. We observed the absence of mean-field "clock" shifts, the dominant source of systematic error in current atomic clocks based on bosonic atoms. This is a direct consequence of fermionic antisymmetry. Resonance shifts proportional to interaction strengths were observed in a three-level system. However, in the strongly interacting regime, these shifts became very small, reflecting the quantum unitarity limit and many-body effects. This insight into an interacting Fermi gas is relevant for the quest to observe superfluidity in this system.Comment: 6 pages, 6 figure

Producing Crack-Free, High Density M2 HSS Parts by Selective Laser Melting: Pre-Heating the Baseplate

Cracks and delamination, resulting from residual stresses are a barrier in the world of Additive Manufacturing and Selective Laser Melting (SLM) that prohibits the use of many metals in this field. By preheating the baseplate, thermal gradients are lowered and stresses can be reduced. In this work, some initial tests were performed with M2 Tool Steel. Results show that pre-heating enables the production of dense M2 parts. The influence of pre-heating on density and mechanical and physical properties is investigated. The paper shows many promising results for the production of SLM parts in materials that are very sensitive to crack formation and delamination. When using a pre-heating of 200°C, crack-free parts were produced with a relative density of 99.8%.Mechanical Engineerin

Connexin expression in cultured neonatal rat myocytes reflects the pattern of the intact ventricle

Objective: Primary cultures of neonatal rat ventricular myocytes have become a widely used model to examine a variety of functional, physiological and biochemical cardiac properties. In the adult rat, connexin43 (Cx43) is the major gap junction protein present in the working myocardium. In situ hybridization studies on developing rats, however, showed that Cx40 mRNA displays a dynamic and heterogeneous pattern of expression in the ventricular myocardium around birth. The present studies were performed to examine the expression pattern of the Cx40 protein in neonatal rat heart, and to examine the connexins present in cultures of ventricular myocytes obtained from those hearts. Methods: Cryosections were made of hearts of 1-day-old Wistar rats. Cultures of ventricular myocytes obtained from these hearts by enzymatic dissociation were seeded at various densities (to obtain >75, ∼50%, and 75% confluency) Cx43 and Cx40 immunoreactivity could be detected. In contrast to Cx43 immunolabeling which showed a homogeneous distribution pattern, Cx40 staining was heterogeneous, i.e. in some clusters of cells abundant labeling was present whereas in others no Cx40 staining could be detected. The pattern of Cx43 immunoreactivity was not altered by the culture density. In contrast, in isolated ventricular myocytes cultured at low density (<25% confluency) the relative number of cell—cell interfaces that were Cx40-immunopositive decreased as compared to high density cultures (35 vs. 70%). Western blots did not reveal significant differences in the level of Cx40 and Cx43 expression at different culture densities. Conclusions: These results show that cultured ventricular myocytes retained typical features of the native neonatal rat ventricular myocardium with regard to their composition of gap junctions. This implicates that these cultures may serve as a good model for studying short-term and long-term regulation of cardiac gap junction channel expression and functio