Cryogenic Thermometer Calibration Facility at CERN

A cryogenic thermometer calibration facility has been designed and is being commissioned in preparation for the very stringent requirements on the temperature control of the LHC superconducting magnets. The temperature is traceable in the 1.5 to 30 K range to standards maintained in a national metrological laboratory by using a set of Rhodium-Iron temperature sensors of metrological quality. The calibration facility is designed for calibrating simultaneously 60 industrial cryogenic thermometers in the 1.5 K to 300 K temperature range, a thermometer being a device that includes both a temperature sensor and the wires heat-intercept. The thermometers can be calibrated in good and degraded vacuum or immersed in the surrounding fluid and at different Joule self-heating conditions that match those imposed by signal conditioners used in large cryogenic machinery. The calibration facility can be operated in an automatic mode and all the control and safety routines are handled by a Programmable Logic Controller (PLC). LabVIEW is used both as the PLC operator interface and for configuring and reading the thermometric data sampled by the higher accuracy laboratory equipment. The isothermal support onto which the thermometers are mounted is thermally anchored through the wiring to a helium bath. The calibration procedure begins once the temperature of the support is stabilized. Measured data is presented and it is possible to infer that the absolute accuracy that can be obtained is better than ± 5 mK for the full temperature range

Test Station for a 30 m long Superconducting Link

The Large Hadron Collider (LHC) requires distribution of high electrical currents in the limited space of LHC tunnel. Four superconducting links of about 76 m length and one of 510 m will be installed in the tunnel to carry 6 kA and 600 A. For validation of the longest link a test station was designed which is presently under construction. The design will permit the test station to be adapted for other links and/or cables as well. It will operate either in pool boiling mode, in order to measure thermal loads, or in forced super-critical helium flow mode to simulate real operation. Inlet pressure is 1.2 bar to 3 bar. Inlet temperature is adjustable from 4.4 K up to about 20 K. The station is being prepared to validate the LHC model link, consisting of 48 superconducting cables, each operating at 600 A between 4.5 K and 5.4 K. This article describes features of the equipment

The Fossil Phase in the Life of a Galaxy Group

We investigate the origin and evolution of fossil groups in a concordance LCDM cosmological simulation. We consider haloes with masses between (1-5)\times10^{13} \hMsun and study the physical mechanisms that lead to the formation of the large gap in magnitude between the brightest and the second most bright group member, which is typical for these fossil systems. Fossil groups are found to have high dark matter concentrations, which we can relate to their early formation time. The large magnitude-gaps arise after the groups have build up half of their final mass, due to merging of massive group members. We show that the existence of fossil systems is primarily driven by the relatively early infall of massive satellites, and that we do not find a strong environmental dependence for these systems. In addition, we find tentative evidence for fossil group satellites falling in on orbits with typically lower angular momentum, which might lead to a more efficient merger onto the host. We find a population of groups at higher redshifts that go through a ``fossil phase'': a stage where they show a large magnitude-gap, which is terminated by renewed infall from their environment.Comment: 9 pages and 8 figures, submitted to MNRA

Analytic evaluation of non-adiabatic couplings within the complex absorbing potential equation-of-motion coupled-cluster method

We present the theory for the evaluation of non-adiabatic couplings (NACs) involving resonance states within the complex absorbing potential equation-of-motion coupled-cluster (CAP-EOM-CC) framework implemented within the singles and doubles approximation. Resonance states are embedded in the continuum and undergo rapid decay through autodetachment. In addition, nuclear motions can facilitate transitions between different resonances and between resonances and bound states. These non-adiabatic transitions affect the chemical fate of resonances and have distinct spectroscopic signatures. The NAC vector is a central quantity needed to model such effects. In the CAP-EOM-CC framework, resonance states are treated on the same footing as bound states. Using the example of fumaronitrile, which supports a bound radical anion and several anionic resonances, we analyze the non-adiabatic coupling between bound states and pseudocontinuum states, between bound states and resonances and between two resonances. We find that the NAC between a bound state and a resonance is nearly independent of the CAP strength and thus straightforward to evaluate whereas the NAC between two resonance states or between a bound state and a pseudocontinuum state is more difficult to evaluate

A logic road from special relativity to general relativity

We present a streamlined axiom system of special relativity in first-order logic. From this axiom system we "derive" an axiom system of general relativity in two natural steps. We will also see how the axioms of special relativity transform into those of general relativity. This way we hope to make general relativity more accessible for the non-specialist

Molecular Screening for Terahertz Detection with Machine-Learning-Based Methods

The molecular requirements are explored for achieving efficient signal up-conversion in a recently developed technique for terahertz (THz) detection based on molecular optomechanics. We discuss which molecular and spectroscopic properties are most important for predicting efficient THz detection and outline a computational approach based on quantum-chemistry and machine-learning methods for calculating these properties. We validate this approach by bulk and surface-enhanced Raman scattering and infrared absorption measurements. We develop a virtual screening methodology performed on databases of millions of commercially available compounds. Quantum-chemistry calculations for about 3000 compounds are complemented by machine-learning methods to predict applicability of 93 000 organic molecules for detection. Training is performed on vibrational spectroscopic properties based on absorption and Raman scattering intensities. Our top molecules have conversion intensity two orders of magnitude higher than an average molecule from the database. We also discuss how other properties like molecular shape and self-assembling properties influence the detection efficiency. We identify molecular moieties whose presence in the molecules indicates high activity for THz detection and show an example where a simple modification of a frequently used self-assembling compound can enhance activity 85-fold. The capabilities of our screening method are demonstrated on narrow-band and broadband detection examples, and its possible applications in surface-enhanced spectroscopy are also discussed

Structure of the RBM7-ZCCHC8 core of the NEXT complex reveals connections to splicing factors

The eukaryotic RNA exosome participates extensively in RNA processing and degradation. In human cells, three accessory factors (RBM7, ZCCHC8 and hMTR4) interact to form the nuclear exosome targeting (NEXT) complex, which directs a subset of non-coding RNAs for exosomal degradation. Here we elucidate how RBM7 is incorporated in the NEXT complex. We identify a proline-rich segment of ZCCHC8 as the interaction site for the RNA-recognition motif (RRM) of RBM7 and present the crystal structure of the corresponding complex at 2.0 resolution. On the basis of the structure, we identify a proline-rich segment within the splicing factor SAP145 with strong similarity to ZCCHC8. We show that this segment of SAP145 not only binds the RRM region of another splicing factor SAP49 but also the RRM of RBM7. These dual interactions of RBM7 with the exosome and the spliceosome suggest a model whereby NEXT might recruit the exosome to degrade intronic RNAs

Recentering responsible and explainable artificial intelligence research on patients: implications in perinatal psychiatry

In the setting of underdiagnosed and undertreated perinatal depression (PD), Artificial intelligence (AI) solutions are poised to help predict and treat PD. In the near future, perinatal patients may interact with AI during clinical decision-making, in their patient portals, or through AI-powered chatbots delivering psychotherapy. The increase in potential AI applications has led to discussions regarding responsible AI and explainable AI (XAI). Current discussions of RAI, however, are limited in their consideration of the patient as an active participant with AI. Therefore, we propose a patient-centered, rather than a patient-adjacent, approach to RAI and XAI, that identifies autonomy, beneficence, justice, trust, privacy, and transparency as core concepts to uphold for health professionals and patients. We present empirical evidence that these principles are strongly valued by patients. We further suggest possible design solutions that uphold these principles and acknowledge the pressing need for further research about practical applications to uphold these principles