220 research outputs found
Disorder raises the critical temperature of a cuprate superconductor
With the discovery of charge density waves (CDW) in most members of the
cuprate high temperature superconductors, the interplay between
superconductivity and CDW has become a key point in the debate on the origin of
high temperature superconductivity. Some experiments in cuprates point toward a
CDW state competing with superconductivity, but others raise the possibility of
a CDW-superconductivity intertwined order, or more elusive pair-density wave
(PDW). Here we have used proton irradiation to induce disorder in crystals of
LaBaCuO and observed a striking 50% increase of
accompanied by a suppression of the CDW. This is in clear
contradiction with the behaviour expected of a d-wave superconductor for which
both magnetic and non-magnetic defects should suppress . Our
results thus make an unambiguous case for the strong detrimental effect of the
CDW on bulk superconductivity in LaBaCuO. Using tunnel
diode oscillator (TDO) measurements, we find evidence for dynamic layer
decoupling in PDW phase. Our results establish irradiation-induced disorder as
a particularly relevant tuning parameter for the many families of
superconductors with coexisting density waves, which we demonstrate on
superconductors such as the dichalcogenides and LuIrSi.Comment: 10 pages, 7 figure
Geophysical studies with laser-beam detectors of gravitational waves
The existing high technology laser-beam detectors of gravitational waves may
find very useful applications in an unexpected area - geophysics. To make
possible the detection of weak gravitational waves in the region of high
frequencies of astrophysical interest, ~ 30 - 10^3 Hz, control systems of laser
interferometers must permanently monitor, record and compensate much larger
external interventions that take place in the region of low frequencies of
geophysical interest, ~ 10^{-5} - 3 X 10^{-3} Hz. Such phenomena as tidal
perturbations of land and gravity, normal mode oscillations of Earth,
oscillations of the inner core of Earth, etc. will inevitably affect the
performance of the interferometers and, therefore, the information about them
will be stored in the data of control systems. We specifically identify the
low-frequency information contained in distances between the interferometer
mirrors (deformation of Earth) and angles between the mirrors' suspensions
(deviations of local gravity vectors and plumb lines). We show that the access
to the angular information may require some modest amendments to the optical
scheme of the interferometers, and we suggest the ways of doing that. The
detailed evaluation of environmental and instrumental noises indicates that
they will not prevent, even if only marginally, the detection of interesting
geophysical phenomena. Gravitational-wave instruments seem to be capable of
reaching, as a by-product of their continuous operation, very ambitious
geophysical goals, such as observation of the Earth's inner core oscillations.Comment: 29 pages including 8 figures, modifications and clarifications in
response to referees' comments, to be published in Class. Quant. Gra
The relationship between the perception of distributed leadership in secondary schools and teachers' and teacher leaders' job satisfaction and organizational commitment
This study investigates the relation between distributed leadership, the cohesion of the leadership team, participative decision-making, context variables, and the organizational commitment and job satisfaction of teachers and teacher leaders. A questionnaire was administered to teachers and teacher leaders (n=1770) from 46 large secondary schools. Multiple regression analyses and path analyses revealed that the study variables explained significant variance in organizational commitment. The degree of explained variance for job satisfaction was considerably lower compared to organizational commitment. Most striking was that the cohesion of the leadership team and the amount of leadership support was strongly related to organizational commitment, and indirectly to job satisfaction. Decentralization of leadership functions was weakly related to organizational commitment and job satisfaction
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