2,735 research outputs found

### Nesting, spin-fluctuations, and odd-gap superconductivity in NaxCoO2 yH2O

We have calculated the one-electron susceptibility of hydrated NaxCoO2 and
find strong nesting nearly commensurate with a 2X2 superstructure. The nesting
involves about 70% of all electrons at the Fermi level and is robust with
respect to doping. This nesting creates a tendency to a charge density wave
compatible with the charge order often seen at x approx 0.5, which is usually
ascribed to electrostatic repulsion of Na ions. In the spin channel, it gives
rise to strong spin-fluctuations, which should be important for
superconductivity. The superconducting state most compatible with this nesting
structure is an odd-gap triplet s-wave state.Comment: 4 figure

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### Supervisors, Trainees, and Client Outcomes in the Training Clinic: Toward an Understanding of Relational Factors

Estimates of healthy years of life lost due to mental illness are increasing, calling greater attention to the provision of effective psychotherapy services. Hypothesized to be the key mechanism through which competencies are developed in trainee clinicians and subsequent client outcomes, clinical supervision is deserving of greater attention. Drawing on a sample of supervisors, trainees, and clients from a training clinic, the present study sought to clarify the relational factors that could facilitate the asserted supervisor-client outcome link and to better understand if, and how, clinical supervisors influence client outcomes. With the exception of supervisor openness to experience, supervisor factors did not predict meaningful variance in client outcomes. Trainee extraversion and openness to experience predicted significant variance in leader-member exchange and supervisory working alliance. Dispositional trainee factors (e.g., personality) appear to impact trainee perceptions of the supervisory relationship. Implications for training and development are discussed, in addition to directions for future research

### Connected Coordinated Motion Planning with Bounded Stretch

We consider the problem of connected coordinated motion planning for a large
collective of simple, identical robots: From a given start grid configuration
of robots, we need to reach a desired target configuration via a sequence of
parallel, collision-free robot motions, such that the set of robots induces a
connected grid graph at all integer times. The objective is to minimize the
makespan of the motion schedule, i.e., to reach the new configuration in a
minimum amount of time. We show that this problem is NP-complete, even for
deciding whether a makespan of 2 can be achieved, while it is possible to check
in polynomial time whether a makespan of 1 can be achieved. On the algorithmic
side, we establish simultaneous constant-factor approximation for two
fundamental parameters, by achieving constant stretch for constant scale.
Scaled shapes (which arise by increasing all dimensions of a given object by
the same multiplicative factor) have been considered in previous seminal work
on self-assembly, often with unbounded or logarithmic scale factors; we provide
methods for a generalized scale factor, bounded by a constant. Moreover, our
algorithm achieves a constant stretch factor: If mapping the start
configuration to the target configuration requires a maximum Manhattan distance
of $d$, then the total duration of our overall schedule is $\mathcal{O}(d)$,
which is optimal up to constant factors.Comment: 28 pages, 18 figures, full version of an extended abstract that
appeared in the proceedings of the 32nd International Symposium on Algorithms
and Computation (ISAAC 2021); revised version (more details added, and typing
errors corrected

### Efficiently Reconfiguring a Connected Swarm of Labeled Robots

When considering motion planning for a swarm of $n$ labeled robots, we need
to rearrange a given start configuration into a desired target configuration
via a sequence of parallel, continuous, collision-free robot motions. The
objective is to reach the new configuration in a minimum amount of time; an
important constraint is to keep the swarm connected at all times. Problems of
this type have been considered before, with recent notable results achieving
constant stretch for not necessarily connected reconfiguration: If mapping the
start configuration to the target configuration requires a maximum Manhattan
distance of $d$, the total duration of an overall schedule can be bounded to
$\mathcal{O}(d)$, which is optimal up to constant factors. However, constant
stretch could only be achieved if disconnected reconfiguration is allowed, or
for scaled configurations (which arise by increasing all dimensions of a given
object by the same multiplicative factor) of unlabeled robots.
We resolve these major open problems by (1) establishing a lower bound of
$\Omega(\sqrt{n})$ for connected, labeled reconfiguration and, most
importantly, by (2) proving that for scaled arrangements, constant stretch for
connected reconfiguration can be achieved. In addition, we show that (3) it is
NP-hard to decide whether a makespan of 2 can be achieved, while it is possible
to check in polynomial time whether a makespan of 1 can be achieved.Comment: 26 pages, 17 figures, full version of an extended abstract accepted
for publication in the proceedings of the 33rd International Symposium on
Algorithms and Computation (ISAAC 2022

### Estimation of energy efficiency of residential buildings

Increasing energy performance of the residential buildings by means of reducing heat consumption on the heating and ventilation is the last segment in the system of energy resources saving. The first segments in the energy saving process are heat producing and transportation over the main lines and outside distribution networks. In the period from 2006 to 2013. by means of the heat-supply schemes optimization and modernization of the heating systems. using expensive (200-30

### A Two-dimensional Superconductor in a Tilted Magnetic Field - new states with finite Cooper-pair momentum

Varying the angle Theta between applied field and the conducting planes of a
layered superconductor in a small interval close to the plane-parallel field
direction, a large number of superconducting states with unusual properties may
be produced. For these states, the pair breaking effect of the magnetic field
affects both the orbital and the spin degree of freedom. This leads to pair
wave functions with finite momentum, which are labeled by Landau quantum
numbers 0<n<\infty. The stable order parameter structure and magnetic field
distribution for these states is found by minimizing the quasiclassical free
energy near H_{c2} including nonlinear terms. One finds states with coexisting
line-like and point-like order parameter zeros and states with coexisting
vortices and antivortices. The magnetic response may be diamagnetic or
paramagnetic depending on the position within the unit cell. The structure of
the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states at Theta=0 is reconsidered.
The transition n->\infty of the paramagnetic vortex states to the FFLO-limit is
analyzed and the physical reason for the occupation of higher Landau levels is
pointed out.Comment: 24 pages, 11 figure

### Superconducting gap anisotropy of LuNi2B2C thin films from microwave surface impedance measurements

Surface impedance measurements of LuNi2B2C superconducting thin films as a
function of temperature have been performed down to 1.5 K and at 20 GHz using a
dielectric resonator technique. The magnetic penetration depth closely
reproduces the standard B.C.S. result, but with a reduced value of the energy
gap at low temperature. These data provide evidence for an anisotropic s-wave
character of the order parameter symmetry in LuNi2B2C. From the evaluation of
the real part of complex conductivity, we have observed constructive (type II)
coherence effects in the electromagnetic absorption below Tc.Comment: 15 pages, 4 figure

### Anisotropy of the upper critical field in superconductors with anisotropic gaps. Anisotropy parameters of MgB2

The upper critical field Hc2 is evaluated for weakly-coupled two-band
superconductors. By modeling the actual bands and the gap distribution of MgB2
by two Fermi surface spheroids with average parameters of the real material, we
show that H_{c2,ab}/H_{c2,c} increases with decreasing temperature in agreement
with available data.Comment: 4 pages, 2 figure

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