3,348 research outputs found
Evaporation of a packet of quantized vorticity
A recent experiment has confirmed the existence of quantized turbulence in
superfluid He3-B and suggested that turbulence is inhomogenous and spreads away
from the region around the vibrating wire where it is created. To interpret the
experiment we study numerically the diffusion of a packet of quantized vortex
lines which is initially confined inside a small region of space. We find that
reconnections fragment the packet into a gas of small vortex loops which fly
away. We determine the time scale of the process and find that it is in order
of magnitude agreement with the experiment.Comment: figure 1a,b,c and d, figure2, figure
Reconnection of superfluid vortex bundles
Using the vortex filament model and the Gross Pitaevskii nonlinear
Schroedinger equation, we show that bundles of quantised vortex lines in helium
II are structurally robust and can reconnect with each other maintaining their
identity. We discuss vortex stretching in superfluid turbulence and show that,
during the bundle reconnection process, Kelvin waves of large amplitude are
generated, in agreement with the finding that helicity is produced by nearly
singular vortex interactions in classical Euler flows.Comment: 10 pages, 7 figure
Polarization of superfluid turbulence
We show that normal fluid eddies in turbulent helium II polarize the tangle
of quantized vortex lines present in the flow, thus inducing superfluid
vorticity patterns similar to the driving normal fluid eddies. We also show
that the polarization is effective over the entire inertial range. The results
help explain the surprising analogies between classical and superfluid
turbulence which have been observed recently.Comment: 3 figure
Specific heat of the Kelvin modes in low temperature superfluid turbulence
It is pointed out that the specific heat of helical vortex line excitations,
in low temperature superfluid turbulence experiments carried out in helium II,
can be of the same order as the specific heat of the phononic quasiparticles.
The ratio of Kelvin mode and phonon specific heats scales with L_0 T^{-5/2},
where L_0 represents the smoothed line length per volume within the vortex
tangle, such that the contribution of the vortex mode specific heat should be
observable for L_0 = 10^6-10^8 cm^{-2}, and at temperatures which are of order
1-10 mK.Comment: 3 pages, 1 figur
Recommended from our members
Emergency Department Clinicians’ Attitudes Toward Opioid Use Disorder and Emergency Department-initiated Buprenorphine Treatment: A Mixed-Methods Study
Introduction: Emergency department (ED) visits related to opioid use disorder (OUD) have increased nearly twofold over the last decade. Treatment with buprenorphine has been demonstrated to decrease opioid-related overdose deaths. In this study, we aimed to better understand ED clinicians’ attitudes toward the initiation of buprenorphine treatment in the ED.Methods: We performed a mixed-methods study consisting of a survey of 174 ED clinicians (attending physicians, residents, and physician assistants) and semi-structured interviews with 17 attending emergency physicians at a tertiary-care academic hospital.Results: A total of 93 ED clinicians (53% of those contacted) completed the survey. While 80% of respondents agreed that buprenorphine should be administered in the ED for patients requesting treatment, only 44% felt that they were prepared to discuss medication for addiction treatment. Compared to clinicians with fewer than five years of practice, those with greater experience were less likely to approve of ED-initiated buprenorphine. In our qualitative analysis, physicians had differing perspectives on the role that the ED should play in treating OUD. Most physicians felt that a buprenorphine-based intervention in the ED would be feasible with institutional support, including training opportunities, protocol support within the electronic health record, counseling and support staff, and a robust referral system for outpatient follow-up.Conclusion: ED clinicians’ perception of buprenorphine varied by years of practice and training level. Most ED clinicians did not feel prepared to initiate buprenorphine in the ED. Qualitative interviews identified several addressable barriers to ED-initiated buprenorphine
Decay of quantised vorticity by sound emission
It is thought that in a quantum fluid sound generation is the ultimate sink
of turbulent kinetic energy in the absence of any other dissipation mechanism
near absolute zero. We show that a suitably trapped Bose-Einstein condensate
provides a model system to study the sound emitted by accelerating vortices in
a controlled way.Comment: 6 pages, 3 figure
Dissipative dynamics of vortex lines in superfluid He
We propose a Hamiltonian model that describes the interaction between a
vortex line in superfluid He and the gas of elementary excitations. An
equation of irreversible motion for the density operator of the vortex,
regarded as a macroscopic quantum particle with a finite mass, is derived in
the frame of Generalized Master Equations. This enables us to cast the effect
of the coupling as a drag force with one reactive and one dissipative
component, in agreement with the assumption of the phenomenological theories of
vortex mutual friction in the two fluid model.Comment: 16 pages, no figures, to be published in PR
Whole-genome association analysis of treatment response in obsessive-compulsive disorder.
Up to 30% of patients with obsessive-compulsive disorder (OCD) exhibit an inadequate response to serotonin reuptake inhibitors (SRIs). To date, genetic predictors of OCD treatment response have not been systematically investigated using genome-wide association study (GWAS). To identify specific genetic variations potentially influencing SRI response, we conducted a GWAS study in 804 OCD patients with information on SRI response. SRI response was classified as 'response' (n=514) or 'non-response' (n=290), based on self-report. We used the more powerful Quasi-Likelihood Score Test (the MQLS test) to conduct a genome-wide association test correcting for relatedness, and then used an adjusted logistic model to evaluate the effect size of the variants in probands. The top single-nucleotide polymorphism (SNP) was rs17162912 (P=1.76 × 10(-8)), which is near the DISP1 gene on 1q41-q42, a microdeletion region implicated in neurological development. The other six SNPs showing suggestive evidence of association (P<10(-5)) were rs9303380, rs12437601, rs16988159, rs7676822, rs1911877 and rs723815. Among them, two SNPs in strong linkage disequilibrium, rs7676822 and rs1911877, located near the PCDH10 gene, gave P-values of 2.86 × 10(-6) and 8.41 × 10(-6), respectively. The other 35 variations with signals of potential significance (P<10(-4)) involve multiple genes expressed in the brain, including GRIN2B, PCDH10 and GPC6. Our enrichment analysis indicated suggestive roles of genes in the glutamatergic neurotransmission system (false discovery rate (FDR)=0.0097) and the serotonergic system (FDR=0.0213). Although the results presented may provide new insights into genetic mechanisms underlying treatment response in OCD, studies with larger sample sizes and detailed information on drug dosage and treatment duration are needed
- …