Transition to superfluid turbulence governed by an intrinsic parameter

Hydrodynamic flow in both classical and quantum fluids can be either laminar or turbulent. To describe the latter, vortices in turbulent flow are modelled with stable vortex filaments. While this is an idealization in classical fluids, vortices are real topologically stable quantized objects in superfluids. Thus superfluid turbulence is thought to hold the key to new understanding on turbulence in general. The fermion superfluid 3He offers further possibilities owing to a large variation in its hydrodynamic characteristics over the experimentally accessible temperatures. While studying the hydrodynamics of the B phase of superfluid 3He, we discovered a sharp transition at 0.60Tc between two regimes, with regular behaviour at high-temperatures and turbulence at low-temperatures. Unlike in classical fluids, this transition is insensitive to velocity and occurs at a temperature where the dissipative vortex damping drops below a critical limit. This discovery resolves the conflict between existing high- and low-temperature measurements in 3He-B: At high temperatures in rotating flow a vortex loop injected into superflow has been observed to expand monotonically to a single rectilinear vortex line, while at very low temperatures a tangled network of quantized vortex lines can be generated in a quiescent bath with a vibrating wire. The solution of this conflict reveals a new intrinsic criterion for the existence of superfluid turbulence.Comment: Revtex file; 5 pages, 2 figure

A note on the propagation of quantized vortex rings through a quantum turbulence tangle:energy transport or energy dissipation?

We investigate quantum vortex ring dynamics at scales smaller than the inter-vortex spacing in quantum turbulence. Through geometrical arguments and high-resolution numerical simulations, we examine the validity of simple estimates for the mean free path and the structure of vortex rings post-reconnection. We find that a large proportion of vortex rings remain coherent objects where approximately 75% of their energy is preserved. This leads us to consider the effectiveness of energy transport in turbulent tangles. Moreover, we show that in low density tangles, appropriate for the ultra-quantum regime, ring emission cannot be ruled out as an important mechanism for energy dissipation. However at higher vortex line densities, typically associated with the quasi-classical regime, loop emission is expected to make a negligible contribution to energy dissipation, even allowing for the fact that our work shows rings can survive multiple reconnection events. Hence the Kelvin wave cascade seems the most plausible mechanism leading to energy dissipatio

Duplication events downstream of IRX1 cause North Carolina macular dystrophy at the MCDR3 locus

Autosomal dominant North Carolina macular dystrophy (NCMD) is believed to represent a failure of macular development. The disorder has been linked to two loci, MCDR1 (chromosome 6q16) and MCDR3 (chromosome 5p15-p13). Recently, non-coding variants upstream of PRDM13 (MCDR1) and a duplication including IRX1 (MCDR3) have been identified. However, the underlying disease-causing mechanism remains uncertain. Through a combination of sequencing studies on eighteen NCMD families, we report two novel overlapping duplications at the MCDR3 locus, in a gene desert downstream of IRX1 and upstream of ADAMTS16. One duplication of 43 kb was identified in nine families (with evidence for a shared ancestral haplotype), and another one of 45 kb was found in a single family. Three families carry the previously reported V2 variant (MCDR1), while five remain unsolved. The MCDR3 locus is thus refined to a shared region of 39 kb that contains DNAse hypersensitive sites active at a restricted time window during retinal development. Publicly available data confirmed expression of IRX1 and ADAMTS16 in human fetal retina, with IRX1 preferentially expressed in fetal macula. These findings represent a major advance in our understanding of the molecular genetics of NCMD and provide insights into the genetic pathways involved in human macular development

Thermal counterflow in a periodic channel with solid boundaries

We perform numerical simulations of finite temperature quantum turbulence produced through thermal counterflow in superfluid 4He, using the vortex filament model. We investigate the effects of solid boundaries along one of the Cartesian directions, assuming a laminar normal fluid with a Poiseuille velocity profile, whilst varying the temperature and the normal fluid velocity. We analyze the distribution of the quantized vortices, reconnection rates, and quantized vorticity production as a function of the wall-normal direction. We find that the quantized vortex lines tend to concentrate close to the solid boundaries with their position depending only on temperature and not on the counterflow velocity. We offer an explanation of this phenomenon by considering the balance of two competing effects, namely the rate of turbulent diffusion of an isotropic tangle near the boundaries and the rate of quantized vorticity production at the center. Moreover, this yields the observed scaling of the position of the peak vortex line density with the mutual friction parameter. Finally, we provide evidence that upon the transition from laminar to turbulent normal fluid flow, there is a dramatic increase in the homogeneity of the tangle, which could be used as an indirect measure of the transition to turbulence in the normal fluid component for experiments

Cerebral Small Vessel Disease and Functional Outcome Prediction after Intracerebral Haemorrhage

OBJECTIVE: To determine whether CT-based cerebral small vessel disease (SVD) biomarkers are associated with 6-month functional outcome after intracerebral hemorrhage (ICH), and whether these biomarkers improve the performance of pre-existing ICH score. METHODS: We included 864 patients with acute ICH from a multicentre, hospital-based prospective cohort study. We evaluated CT-based SVD biomarkers (white matter hypodensities [WMH]; lacunes; brain atrophy; and a composite SVD burden score) and their associations with poor 6-month functional outcome (modified Rankin Scale [mRS] score >2). The area under the receiver operating characteristic curve (AUROC) and Hosmer-Lemeshow test were used to assess discrimination and calibration of the ICH score with and without SVD biomarkers. RESULTS: In multivariable models (adjusted for ICH score components), WMH presence (OR 1.52, 95%CI 1.12-2.06), cortical atrophy presence (OR 1.80, 95%CI 1.19-2.73), deep atrophy presence (OR 1.66, 95%CI 1.17-2.34), and severe atrophy (either deep or cortical) (OR 1.94, 95%CI 1.36-2.74) were independently associated with poor functional outcome. For the ICH score, the AUROC was 0.71 (95%CI 0.68-0.74). Adding SVD markers did not significantly improve ICH score discrimination; for the best model (adding severe atrophy) the AUROC was 0.73 (95%CI 0.69-0.76). These results were confirmed when considering lobar and non-lobar ICH, separately. CONCLUSIONS: The ICH score has acceptable discrimination for predicting 6-month functional outcome after ICH. CT biomarkers of SVD are associated with functional outcome but adding them does not significantly improve ICH score discrimination

MRI and CT imaging biomarkers of cerebral amyloid angiopathy in lobar intracerebral hemorrhage

BACKGROUND: Cerebral amyloid angiopathy (CAA), a common cause of intracerebral hemorrhage (ICH), is diagnosed using the Boston criteria including magnetic resonance imaging (MRI) biomarkers (cerebral microbleeds (CMBs) and cortical superficial siderosis (cSS). The simplified Edinburgh criteria include computed tomography (CT) biomarkers (subarachnoid extension (SAE) and finger-like projections (FLPs)). The underlying mechanisms and diagnostic accuracy of CT compared to MRI biomarkers of CAA are unknown. METHODS: We included 140 survivors of spontaneous lobar supratentorial ICH with both acute CT and MRI. We assessed associations between MRI and CT biomarkers and the diagnostic accuracy of CT- compared to MRI-based criteria. RESULTS: FLPs were more common in patients with strictly lobar CMB (44.7% vs 23.5%; p = 0.014) and SAE was more common in patients with cSS (61.3% vs 31.2%; p = 0.002). The high probability of the CAA category of the simplified Edinburgh criteria showed 87.2% (95% confidence interval (CI): 78.3-93.4) specificity, 29.6% (95% CI: 18.0-43.6) sensitivity, 59.3% (95% CI: 38.8-77.6) positive predictive value, and 66.4% (95%: CI 56.9-75.0) negative predictive value, 2.3 (95% CI: 1.2-4.6) positive likelihood ratio and 0.8 (95% CI 0.7-1.0) negative likelihood ratio for probable CAA (vs non-probable CAA), defined by the modified Boston criteria; the area under the receiver operating characteristic curve (AUROC) was 0.62 (95% CI: 0.54-0.71). CONCLUSION: In lobar ICH survivors, we found associations between putative biomarkers of parenchymal CAA (FLP and strictly lobar CMBs) and putative biomarkers of leptomeningeal CAA (SAE and cSS). In a hospital population, CT biomarkers might help rule-in probable CAA (diagnosed using the Boston criteria), but their absence is probably not as useful to rule it out, suggesting an important continued role for MRI in ICH survivors with suspected CAA

Association between critical care admission and 6-month functional outcome after spontaneous intracerebral haemorrhage

BACKGROUND: There is uncertainty about the clinical benefit of admission to critical care after spontaneous intracerebral haemorrhage (ICH). PURPOSE: We investigated factors associated with critical care admission after spontaneous ICH and evaluated associations between critical care and 6-month functional outcome. METHODS: We included 825 patients with acute spontaneous non-traumatic ICH, recruited to a prospective multicenter observational study. We evaluated the characteristics associated with critical care admission and poor 6-month functional outcome (modified Rankin Scale, mRS > 3) using univariable (chi-square test and Wilcoxon rank-sum test, as appropriate) and multivariable analysis. RESULTS: 286 patients (38.2%) had poor 6-month functional outcome. Seventy-seven (9.3%) patients were admitted to critical care. Patients admitted to critical care were younger (p < 0.001), had lower GCS score (p < 0.001), larger ICH volume (p < 0.001), more often had intraventricular extension (p = 0.008) and underwent neurosurgery (p < 0.001). Critical care admission was associated with poor functional outcome at 6 months (39/77 [50.7%] vs 286/748 [38.2%]; p = 0.034); adjusted OR 2.43 [95%CI 1.36-4.35], p = 0.003), but not with death (OR 1.29 [95%CI 0.71-2.35; p = 0.4). In ordinal logistic regression, patients admitted to critical care showed an OR 1.47 (95% CI 0.98-2.20; p = 0.07) for a shift in the 6-month modified Rankin Scale. CONCLUSIONS: Admission to critical care is associated with poor 6-month functional outcome after spontaneous ICH but not with death. Patients admitted to critical care were a priori more severely affected. Although adjusted for main known predictors of poor outcome, our findings could still be confounded by unmeasured factors. Establishing the true effectiveness of critical care after ICH requires a randomised trial with clinical outcomes and quality of life assessments

Primary cerebral alveolar rhabdomyosarcoma in adult

Primary cerebral rhabdomyosarcomas are very rare and malignant tumors that occur predominantly in the posterior fossa of pediatric patients. We report a rare case of primary cerebral rhabdomyosarcoma located in the supratentorial compartment of a 51 year-old woman together with a review of the pertinent Literature especially regarding the histological diagnosis and pitfalls

Theory of Multidimensional Solitons

We review a number of topics germane to higher-dimensional solitons in Bose-Einstein condensates. For dark solitons, we discuss dark band and planar solitons; ring dark solitons and spherical shell solitons; solitary waves in restricted geometries; vortex rings and rarefaction pulses; and multi-component Bose-Einstein condensates. For bright solitons, we discuss instability, stability, and metastability; bright soliton engineering, including pulsed atom lasers; solitons in a thermal bath; soliton-soliton interactions; and bright ring solitons and quantum vortices. A thorough reference list is included.Comment: review paper, to appear as Chapter 5a in "Emergent Nonlinear Phenomena in Bose-Einstein Condensates: Theory and Experiment," edited by P. G. Kevrekidis, D. J. Frantzeskakis, and R. Carretero-Gonzalez (Springer-Verlag

Helicity within the vortex filament model

Kinetic helicity is one of the invariants of the Euler equations that is associated with the topology of vortex lines within the fluid. In superfluids, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in a helicity that does not retain its key attribute as a quadratic invariant. By defining a spanwise vector to the vortex through the use of a Seifert framing, we are able to introduce twist and henceforth recover the key properties of helicity. We present several examples for calculating internal twist to illustrate why the centreline helicity alone will lead to ambiguous results if a twist contribution is not introduced. Our choice of the spanwise vector can be expressed in terms of the tangential component of velocity along the filament. Since the tangential velocity does not alter the configuration of the vortex at later times, we are able to recover a similar equation for the internal twist angle to that of classical vortex tubes. Our results allow us to explain how a quasi-classical limit of helicity emerges from helicity considerations for individual superfluid vortex filaments