Dispersion of plasmons in three-dimensional superconductors

We study the plasma branch of an homogeneous three-dimensional electron gas in an s-wave superconducting state. We focus on the regime where the plasma frequency ωp is comparable to the gap ∆, which is experimentally realized in cuprates. Although a sum rule guarantees that the departure of the plasma branch always coincides with the plasma frequency, the dispersion and lifetime of the plasmons is strongly affected by the presence of the pair condensate, especially at energies close to the pair-breaking threshold 2∆. When ωp is above 1.7∆, the level repulsion is strong enough to give the plasma branch an anomalous, negative dispersion with a minimum at finite wavelength. At non-zero temperature and at ωp > 2∆, we treat in a non-perturbative way the coupling of plasmons to the fermionic excitations, and show that a broadened plasma resonance inside the pair-breaking continuum coexists with an undamped solution in the band gap. This resonance splitting is associated with the presence of multiple poles in the analytic continuation of the propagator of the Cooper pairs

Elektromagnetischer Ultraschallwandler zur zerstoerungsfreien Pruefung von elektrisch leitfaehigen Werkstoffen

Zur zerstoerungsfreien Pruefung der Laufflaeche von Eisenbahnraedern ohne Ausbau der Radsaetze dienen Ultraschall-Oberflaechenwellen, die sich von in den Schienenkoepfen integrierten Pruefkoepfen ausgehend, beim Ueberrollen durch das Rad entlang dessen Laufflaeche ausbreiten und nach Durchlaufen des Radumfangs bzw. Reflexion auf dem Ausbreitungsweg, z.B. an einem Riss, von den Pruefkoepfen empfangen und anschliessend ausgewertet werden. Die Pruefkoepfe bestehen aus elektromagnetischen Ultraschallwandlern mit in Aussparungen der Schienenkoepfe untergebrachten Vormagnetisierungs- und Hochfrequenzwicklungen zur koppelmittelfreien Anregung der Oberflaechenwellen im ueberrollenden Rad und zum Empfang der umgelaufenen bzw. reflektierten Wellen. Zur Erzeugung der HF-Leistungsimpulse dienen mehrere jeweils in Gegentakt-B-Betrieb arbeitende Leistungstransistoren. Im Empfangsweg liegt ein logarithmischer Breitbandverstaerker, bei dem mehrere Logarithmierstufen ueber Begrenzer, Verstaerker und Da empfungsglieder gestuft angesteuert werden und ausgangsseitig ueber einen Summierer zusammengeschaltet sind

Dispersion of plasmons in three-dimensional superconductors

We study the plasma branch of an homogeneous three-dimensional electron gas in an s-wave superconducting state. We focus on the regime where the plasma frequency ωp is comparable to the gap ∆, which is experimentally realized in cuprates. Although a sum rule guarantees that the departure of the plasma branch always coincides with the plasma frequency, the dispersion and lifetime of the plasmons is strongly affected by the presence of the pair condensate, especially at energies close to the pair-breaking threshold 2∆. When ωp is above 1.7∆, the level repulsion is strong enough to give the plasma branch an anomalous, negative dispersion with a minimum at finite wavelength. At non-zero temperature and at ωp > 2∆, we treat in a non-perturbative way the coupling of plasmons to the fermionic excitations, and show that a broadened plasma resonance inside the pair-breaking continuum coexists with an undamped solution in the band gap. This resonance splitting is associated with the presence of multiple poles in the analytic continuation of the propagator of the Cooper pairs

Factors Affecting Family Presence During Fracture Reduction in the Pediatric Emergency Department

Introduction: Asking family members to leave during invasive procedures has historically been common practice; however, evidence-based recommendations have altered the trend of family presence during pediatric procedures. The aim of this study was to determine factors related to family members’ choice to be present or absent during fracture reductions in a pediatric emergency department (ED), and their satisfaction with that choice. Methods: We administered role-specific, anonymous surveys to a convenience sample of patients’ family members in the ED of a Level I pediatric trauma center. All family members were given a choice of where to be during the procedure. Results: Twenty-five family members of 18 patients completed surveys. Seventeen family members chose to stay in the room. Family member satisfaction with their decision to be inside or outside the room during the procedure (median = very satisfied) was almost uniformly high and not associated with any of the following variables: previous presence during a medical procedure; provider-reported procedure difficulty, or anxiety levels. Family member perception of procedure success (median = extremely well) was also high and not associated with other variables. Location during the procedure was associated with a desire to be in the same location in the future (Fisher’s exact test, p=0.001). Common themes found among family members’ reasons for their location decisions and satisfaction levels were a desire to support the patient, high staff competence, and their right as parents to choose their location. Conclusion: Family members self-select their location during their child’s fracture reduction to high levels of satisfaction, and they considered the ability to choose their location as important