Distinct Kondo Screening Behaviors in Heavy Fermion Filled Skutterudites with 4f

CeOs_{4}Sb_{12} (COS) and PrOs_{4}Sb_{12} (POS) are two representative compounds that provide the ideal vantage point to systematically study the physics of multi-f-electron systems. COS with Ce 4f^{1}, and POS with Pr 4f^{2} configurations show distinct properties of Kondo insulating and heavy fermion superconductivity, respectively. We unveiled the underlying microscopic origin by angle-resolved photoemission spectroscopy studies. Their eV-scale band structure matches well, representing the common characters of conduction electrons in ROs_{4}Sb_{12} systems (R=rare earth). However, f electrons interact differently with conduction electrons in COS and POS. Strong hybridization between conduction electrons and f electrons is observed in COS with band dependent hybridization gaps, and the development of a Kondo insulating state is directly revealed. Although the ground state of POS is a singlet, finite but incoherent hybridization exists, which can be explained by the Kondo scattering with the thermally excited triplet crystalline electric field state. Our results help us to understand the intriguing properties in COS and POS, and provide a clean demonstration of the microscopic differences in heavy fermion systems with 4f^{1} and 4f^{2} configurations.

Mixed-Order Symmetry-Breaking Quantum Phase Transition Far from Equilibrium.

We study the current-carrying steady state of a transverse field Ising chain coupled to magnetic thermal reservoirs and obtain the nonequilibrium phase diagram as a function of the magnetization potential of the reservoirs. Upon increasing the magnetization bias we observe a discontinuous jump of the magnetic order parameter that coincides with a divergence of the correlation length. For steady states with a nonvanishing conductance, the entanglement entropy at zero temperature displays a bias dependent logarithmic correction that violates the area law and differs from the well-known equilibrium case. Our findings show that out-of-equilibrium conditions allow for novel critical phenomena not possible at equilibrium.

Band Dependent Interlayer f-Electron Hybridization in CeRhIn_{5}.

A key issue in heavy fermion research is how subtle changes in the hybridization between the 4f (5f) and conduction electrons can result in fundamentally different ground states. CeRhIn_{5} stands out as a particularly notable example: when replacing Rh with either Co or Ir, antiferromagnetism gives way to superconductivity. In this photoemission study of CeRhIn_{5}, we demonstrate that the use of resonant angle-resolved photoemission spectroscopy with polarized light allows us to extract detailed information on the 4f crystal field states and details on the 4f and conduction electron hybridization, which together determine the ground state. We directly observe weakly dispersive Kondo resonances of f electrons and identify two of the three Ce 4f_{5/2}^{1} crystal-electric-field levels and band-dependent hybridization, which signals that the hybridization occurs primarily between the Ce 4f states in the CeIn_{3} layer and two more three-dimensional bands composed of the Rh 4d and In 5p orbitals in the RhIn_{2} layer. Our results allow us to connect the properties observed at elevated temperatures with the unusual low-temperature properties of this enigmatic heavy fermion compound.

The effect of repeated testing vs repeated practice on skills learning in undergraduate dental education.

OBJECTIVES: Recent studies in undergraduate medical education have demonstrated the advantage of repeated testing over repeated practice with regard to knowledge and skills retention. The aim of this study was to investigate whether this "testing effect" also applies to skills retention in undergraduate dental education. METHODS: In this prospective, randomised controlled trial, fourth-year dental students at Göttingen University Medical Centre participated in a training session on surgical suturing in winter term 2014/2015. Following this, they were either assigned to two sessions of additional skills training (group A) or two sessions of skills assessment with feedback (group B). These sessions were spaced over a period of 4 weeks. Skills retention was assessed in a summative objective structured clinical examination (OSCE) at the end of term, that is 6 months after the initial teaching session. RESULTS: A total of 32 students completed the study. With regard to suturing, OSCE performance was significantly better in group B than group A (81.9±13.1% vs 63.0±15.4%; P=0.001; Cohen's d=1.33). There was no significant OSCE performance difference in the two groups with regard to other learning objectives that were addressed in the end-of-term examination. Thus, the group difference was specific to suturing skills. CONCLUSIONS: This is the first study to demonstrate that in dental education, repeated testing produces more favourable skills retention than repeated practice. Test-enhanced learning might be a viable concept for skills retention in undergraduate dentistry education.

Effect of different scoring approaches upon credit assignment when using Multiple True-False items in dental undergraduate examinations.

INTRODUCTION: Various scoring approaches for Multiple True-False (MTF) items exist. This study aimed at comparing scoring results obtained with different scoring approaches and to assess the effect of item cues on each scoring approaches' result. MATERIALS AND METHODS: Different scoring approaches (MTF, Count-2, Count-3, "Vorkauf-Method," PS50 , Dichotomized MTF, "Blasberg-Method," Multiple response (MR), Correction for Guessing, "Ripkey-Method," Morgan-Method, Balanced Scoring Method) were retrospectively applied to all MTF items used within electronic examinations of undergraduate dental students at the University Medical Center Göttingen in the winter term 2016/2017 (1297 marking events). Item quality was evaluated regarding formal parameters such as presence of cues and correctness of content. Differences between scoring results of all scoring approaches and the differences between each methods' scoring results of items with and without cues were calculated by Wilcoxon rank sum tests (P < .05). RESULTS: Average scoring results per item highly differed between the scoring approaches and ranged from 0.46 (MR) to 0.92 (Dichotomized MTF). Presence of cues leads to significantly higher scoring in case of all scoring approaches (P < .001; +0.14 on average). However, effect of cues differed amongst scoring approaches and ranged from +0.04 (Dichotomized MTF) to +0.20 (MR). CONCLUSION: Scoring of MTF items is complex. The data presented in this manuscript may help educators make informed choices about scoring algorithms.

Impact of Atomic-Scale Contact Geometry on Andreev Reflection.

Charge transport has been examined in junctions comprising the normal-metal tip of a low-temperature scanning tunneling microscope, the surface of a conventional superconductor, and adsorbed C_{60} molecules. The Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak with decreasing electrode separation. The peak is assigned to the spectroscopic signature of Andreev reflection. The conductance due to Andreev reflection is determined by the atomic termination of the tip apex and the molecular adsorption orientation. Transport calculations unveil the finite temperature and the strong molecule-electrode hybridization as the origin to the surprisingly good agreement between spectroscopic data and the Blonder-Tinkham-Klapwijk model that was conceived for macroscopic point contacts.

Emerging local Kondo screening and spatial coherence in the heavy-fermion metal YbRh2Si2.

The entanglement of quantum states is both a central concept in fundamental physics and a potential tool for realizing advanced materials and applications. The quantum superpositions underlying entanglement are at the heart of the intricate interplay of localized spin states and itinerant electronic states that gives rise to the Kondo effect in certain dilute magnetic alloys. In systems where the density of localized spin states is sufficiently high, they can no longer be treated as non-interacting; if they form a dense periodic array, a Kondo lattice may be established. Such a Kondo lattice gives rise to the emergence of charge carriers with enhanced effective masses, but the precise nature of the coherent Kondo state responsible for the generation of these heavy fermions remains highly debated. Here we use atomic-resolution tunnelling spectroscopy to investigate the low-energy excitations of a generic Kondo lattice system, YbRh(2)Si(2). We find that the hybridization of the conduction electrons with the localized 4f electrons results in a decrease in the tunnelling conductance at the Fermi energy. In addition, we observe unambiguously the crystal-field excitations of the Yb(3+) ions. A strongly temperature-dependent peak in the tunnelling conductance is attributed to the Fano resonance resulting from tunnelling into the coherent heavy-fermion states that emerge at low temperature. Taken together, these features reveal how quantum coherence develops in heavy 4f-electron Kondo lattices. Our results demonstrate the efficiency of real-space electronic structure imaging for the investigation of strong electronic correlations, specifically with respect to coherence phenomena, phase coexistence and quantum criticality.

Perceived indoor air quality and its relationship to air pollutants in French dwellings.

Perception of indoor air quality (PIAQ) was evaluated in a nationwide survey of 567 French dwellings, and this survey was combined with measurements of gaseous and particulate matter (PM10 and PM2.5 ) indoor air pollutants and indoor climate parameters. The perception was assessed on a nine-grade scale by both the occupants of the dwellings and the inspectors who performed the measurements. The occupants perceived the air quality in their homes as more pleasant than the inspectors. The inspectors perceived the air quality as more unpleasant in dwellings in which the residents smoked indoors. Significant associations between PIAQ and indoor air pollutant concentrations were observed for both the inspectors and, to a lesser extent, the occupants. Introducing confounding parameters, such as building and personal characteristics, into a multivariate model suppressed most of the observed bivariate correlations and identified the tenure status of the occupants and their occupation as the parameters that most influenced their PIAQ. For the inspectors, perceived air quality was affected by the presence of smokers, the season, the type of ventilation, retrofitting, and the concentrations of acetaldehyde and acrolein.

Two-Channel Kondo Physics due to As Vacancies in the Layered Compound ZrAs_{1.58}Se_{0.39}.

We address the origin of the magnetic-field-independent -|A|T^{1/2} term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs_{1.58}Se_{0.39}, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the nonmagnetic version of the two-channel Kondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a C_{4} symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the low superconducting transition temperature T_{c}≈0.14 K of ZrAs_{1.58}Se_{0.39} compared to the free-of-vacancies homologue ZrP_{1.54}S_{0.46} (T_{c}≈3.7 K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.

Relaxed selective constraints drove functional modifications in peripheral photoreception of the cavefish P. andruzzii and provide insight into the time of cave colonization.

The genetic basis of phenotypic changes in extreme environments is a key but rather unexplored topic in animal evolution. Here we provide an exemplar case of evolution by relaxed selection in the Somalian cavefish Phreatichthys andruzzii that has evolved in the complete absence of light for at least 2.8 million years. This has resulted in extreme degenerative phenotypes, including complete eye loss and partial degeneration of the circadian clock. We have investigated the molecular evolution of the nonvisual photoreceptor melanopsin opn4m2, whose mutation contributes to the inability of peripheral clocks to respond to light. Our intra- and inter-species analyses suggest that the 'blind' clock in P. andruzzii evolved because of the loss of selective constraints on a trait that was no longer adaptive. Based on this change in selective regime, we estimate that the functional constraint on cavefish opn4m2 was relaxed at ∼5.3 Myr. This implies a long subterranean history, about half in complete isolation from the surface. The visual photoreceptor rhodopsin, expressed in the brain and implicated in photophobic behavior, shows similar evolutionary patterns, suggesting that extreme isolation in darkness led to a general weakening of evolutionary constraints on light-responsive mechanisms. Conversely, the same genes are still conserved in Garra barreimiae, a cavefish from Oman, that independently and more recently colonized subterranean waters and evolved troglomorphic traits. Our results contribute substantially to the open debate on the genetic bases of regressive evolution.

Steady-State Dynamics and Effective Temperature for a Model of Quantum Criticality in an Open System.

We study the thermal and nonthermal steady-state scaling functions and the steady-state dynamics of a model of local quantum criticality. The model we consider, i.e., the pseudogap Kondo model, allows us to study the concept of effective temperatures near fully interacting as well as weak-coupling fixed points. In the vicinity of each fixed point we establish the existence of an effective temperature-different at each fixed point-such that the equilibrium fluctuation-dissipation theorem is recovered. Most notably, steady-state scaling functions in terms of the effective temperatures coincide with the equilibrium scaling functions. This result extends to higher correlation functions as is explicitly demonstrated for the Kondo singlet strength. The nonlinear charge transport is also studied and analyzed in terms of the effective temperature.

Second primary malignancies in head and neck cancer patients: high prevalence of curable-stage disease.

BACKGROUND AND PURPOSE: Patients treated for squamous cell carcinoma of the head and neck (HNSCC) carry a high risk of second primary malignancies (SPM). Recently, computed tomography (CT) of the chest was shown to significantly decrease the risk of death due to bronchial carcinoma (BC) in a cohort of smokers whose risk of BC is increased but might be lower than that of patients previously treated for HNSCC. Thus, the present study evaluated the potential benefit of CT and other examinations in the detection of SPM in HNSCC patients. PATIENTS AND METHODS: Between July 2008 and November 2011, 118 participants underwent a prospective, systematic examination for SPM (13 women, 105 men, median age 62 years). All patients had been previously treated for HNSCC and showed no recurrence or distant metastases at the time of the study start. CT scans, ear-nose-throat endoscopy, and endoscopy of the esophagus and stomach were performed. RESULTS: Overall, 33 suspicious findings were clarified by additional investigations. In all, 26 SPM were confirmed in 21 of 118 patients (18%; 10 lung, 7 HNSCC, 3 gastrointestinal, 1 renal). Eighteen of these 21 patients (86%) underwent therapy with curative intent. CONCLUSION: The examinations revealed a high prevalence of curable stage SPM in HNSCC patients. Adapting a surveillance scheme including a chest CT is recommended.

Necrotizing endometritis and isolation of an alpha-toxin producing strain of Clostridium septicum in a wild sooty mangabey from Côte d'Ivoire.

Few lethal pathogens in wild-living primates have been described, and little is known about infectious diseases of the reproductive tract and their possible impact on health and reproduction. This report describes the pathology and isolation of an alpha-toxin producing strain of Clostridium septicum in a case of necrotizing endometritis in a wild sooty mangabey found dead in a tropical rainforest of West Africa.

Extracellular factors and immunosuppressive drugs influencing insulin secretion of murine islets.

Approximately 60% of transplanted islets undergo apoptosis within the first week post-transplantation into the liver attributed to poor engraftment, immune rejection and toxicity of immunosuppressive drugs. Understanding how extracellular matrix (ECM) components, immunosuppressive drugs and proinflammatory cytokines affect insulin secretion will contribute to an improved clinical outcome of islet transplantations. In this study, functional activity of isolated murine islets was measured by glucose-stimulated insulin secretion (GSIS) and by electrophysiological measurements using patch-clamp. Cultivating islets with soluble fibronectin or laminin, as opposed to with coated laminin, markedly increased GSIS. Addition of cyclosporin A reduced GSIS and suppressed glucose-induced spike activity. Tacrolimus affected neither GSIS nor spike activity, indicating a different mechanism. To evaluate the influence of proinflammatory cytokines, islets were incubated with interleukin (IL)-1ß, tumour necrosis factor (TNF)-α or with supernatants from cultured Kupffer cells, the main mediators of inflammation in the hepatic sinusoids. IL-1ß exerted a bimodal effect on insulin secretion, stimulating below 2 ng/ml and suppressing above 10 ng/ml. Soluble laminin in combination with a stimulatory IL-1ß concentration further increased insulin secretion by 20% compared to IL-1ß alone, while with high IL-1ß concentrations soluble laminin slightly attenuated GSIS inhibition. TNF-α alone did not affect GSIS, but with stimulatory IL-1ß concentrations completely abolished it. Similarly, supernatants derived from Kupffer cells exerted a bimodal effect on GSIS. Our data suggest that improved insulin secretion of transplanted islets could be achieved by including soluble laminin and low IL-1ß concentrations in the islet cultivation medium, and by a simultaneous inhibition of cytokine secretion from Kupffer cells.

Charge-doping-driven evolution of magnetism and non-Fermi-liquid behavior in the filled skutterudite CePt4Ge(12-x)Sb(x).

The filled skutterudite compound CePt(4)Ge(12) is situated close to the border between the intermediate valence of Ce and heavy-fermion behavior. Substitution of Ge by Sb drives the system into a strongly correlated and, ultimately, upon further increasing the Sb concentration, an antiferromagnetically ordered state. Our experiments evidence a delicate interplay of emerging Kondo physics and the formation of a local 4f moment. An extended non-Fermi-liquid region, which can be understood in the framework of a Kondo-disorder model, is observed. Band-structure calculations support the conclusion that the physical properties are governed by the interplay of electron supply via Sb substitution and the concomitant volume effects.

[Schools, office buildings, leisure settings: diversity of indoor air quality issues. Global review on indoor air quality in these settings]. / Écoles, bureaux, espaces de loisirs : des lieux de vie variés, des pollutions intérieures contrastées. Revue générale des connaissances disponibles sur la qualité de l'air dans ces espaces.

This review provides a global overview of indoor air quality issues in schools, office buildings and recreational settings. It presents the most recent scientific publications and the on-going work conducted in France in the frame of the indoor air quality Observatory. Monitoring campaigns on indoor air quality in schools have been carried out in the recent years in Europe. However, few studies have specifically addressed the role of exposure in these buildings on children's health. Indoor air quality in office buildings has been little studied so far. However, some specificities, such as emissions from electronic devices, frequent cleaning, impossibility to open windows in high-rise buildings, for example, should be examined and their role on the health and comfort studied. Finally, even if the time spent in recreational settings is short, the quality of indoor air should also be considered because of specific pollution. This is the case of indoor swimming pools (exposure to chlorination byproducts) and ice-rinks (exposure to exhaust from machines used to smooth the ice).

Mental health over nine months during the SARS-CoV2 pandemic: Representative cross-sectional survey in twelve waves between April and December 2020 in Austria.

BACKGROUND: There is accumulating evidence about detrimental impacts of the pandemic on population mental health, but knowledge on risk of groups specifically affected by the pandemic and variations across time is still limited. METHODS: We surveyed approximately n=1,000 Austrian residents in 12 waves between April and December 2020 (n=12,029). Outcomes were suicidal ideation (Beck Suicidal Ideation Scale), depressive symptoms (Patient Health Questionnaire-9), anxiety (Hospital Anxiety Depression Scale), and domestic violence. We also assessed the perceived burden from the pandemic. Demographic and Covid-19 specific occupational and morbidity-related variables were used to explain outcomes in multivariable regression analyses, controlling for well-established risk factors of mental ill-health, and variations over time were analyzed. RESULTS: Young age, working in healthcare or from home, and own Covid-19 illness were consistent risk factors controlling for a wide range of known mental health risk factors. Time patterns in the perceived burden from Covid-19-related measures were consistent with the time sequence of restrictions and relaxations of governmental measures. Depressive and anxiety symptoms were relatively stable over time, with some increase of depression during the second phase of lockdowns. Domestic violence increased immediately after both hard lockdowns. Suicidal ideation decreased slightly over time, with a low during the second hard lockdown. Mental health indicators for women and young people showed some deterioration over time, whereas those reporting own Covid-19 illness improved. LIMITATIONS: Data from before the pandemic were not available. CONCLUSIONS: Among mental health outcomes, increases in domestic violence and, to some smaller extent, depressive symptoms, appeared most closely related to the timing of hard lockdowns. Healthcare staff, individuals working from home, those with Covid-19, as well as young people and women are non-traditional risk groups who warrant heightened attention in prevention during and in the aftermath of the pandemic.

Salzburg Skiing for the Elderly Study: influence of alpine skiing on aerobic capacity, strength, power, and balance.

Alpine skiing is a recreational sport with high demands on the cardiovascular and neuromuscular systems. It is assumed that skiing could have positive effects on the decline in aerobic capacity, strength, and balance ability of older individuals. In a 12-week intervention study, 47 elderly subjects (age 60-76 years) were randomized into an intervention group (IG) and a control group (CG). The IG averaged 28.5 days of guided skiing during 12 weeks. Aerobic capacity, leg power, and strength as well as postural stability were tested before, immediately after, and 10 weeks after the intervention phase. VO(2 max) improved by 7.2% from Pre to Post for the IG, without any change in the CG. Jump height increased on average by 6% over the 12 weeks for the IG, while jump height for the CG deteriorated by -11.7%. Dynamic maximal strength measured in both legs increased by 16% in the IG during the 12 weeks of skiing. In the CG, it increased by 7%, without being significant. In postural ability, no differences between groups or over time were noted. It appears that, in older individuals, 12 weeks of skiing leads to a significant increase in aerobic capacity, leg muscle power, and strength.