Multipole Expansion of Bremsstrahlung in Intermediate Energy Heavy Ion Collisions

Using a multipole expansion of the radiated field generated by a classical electric current, we present a way to interprete the bremsstrahlung spectra of low energy heavy ion collisions. We perform the calculation explicitely for the system ^{12}C+ ^{12}C at 84AMeV and compare the result with the experimental data of E. Grosse et al. Using simple model assumptions for the electromagnetic source current we are able to describe the measured data in terms of coherent photon emission. In this context, the information contained in the measured data is discussed.Comment: LaTex, 4 Figure

Creating atom-number states around tapered optical fibres by loading from an optical lattice

We describe theoretically a setup in which a tapered optical nanofibre is introduced into an optical lattice potential for cold atoms. Firstly, we consider the disturbance to the geometry of the lattice potential due to scattering of the lattice lasers from the dielectric fibre surface and show that the resulting distortion to the lattice can be minimized by placing the fibre at an appropriate position in the lattice. We then calculate the modifications of the local potentials that are achievable by transmitting off-resonant light through the fibre. The availability of such a technique holds the potential to deterministically create and address small well-defined samples of atoms in the evanescent field of the tapered nanofibre.Comment: 7 pages. 6 figure

Electroencephalogram variability in patients with cirrhosis associates with the presence and severity of hepatic encephalopathy

BACKGROUND & AIMS: The outputs of physiological systems fluctuate in a complex manner even under resting conditions. Decreased variability or increased regularity of these outputs is documented in several disease states. Changes are observed in the spatial and temporal configuration of the electroencephalogram (EEG) in patients with hepatic encephalopathy (HE), but there is no information on the variability of the EEG signal in this condition. The aim of this study was to measure and characterize EEG variability in patients with cirrhosis and to determine its relationship to neuropsychiatric status. METHODS: Eyes-closed, awake EEGs were obtained from 226 patients with cirrhosis, classified, using clinical and psychometric criteria, as neuropsychiatrically unimpaired (n=127) or as having minimal (n=21) or overt (n=78) HE, and from a reference population of 137 healthy controls. Analysis of EEG signal variability was undertaken using continuous wavelet transform and sample entropy. RESULTS: EEG variability was reduced in the patients with cirrhosis compared with the reference population (coefficient of variation: 21.2% [19.3-23.4] vs. 22.4% [20.8-24.5]; p<0.001). A significant association was observed between EEG variability and neuropsychiatric status; thus, variability was increased in the patients with minimal HE compared with their neuropsychiatrically unimpaired counterparts (sample entropy: 0.98 [0.87-1.14] vs. 0.83 [0.75-0.95]; p=0.02), and compared with the patients with overt HE (sample entropy: 0.98 [0.87-1.14] vs. 0.82 [0.71-1.01]; p=0.01). CONCLUSIONS: Variability of the EEG is associated with both the presence and severity of HE. This novel finding may provide new insights into the pathophysiology of HE and provide a means for monitoring patients over time. LAY SUMMARY: Decreased variability or increased regularity of physiological systems is documented in several disease states. Variability of the electroencephalogram was found to be associated with both the presence and severity of brain dysfunction in patients with chronic liver disease

Matter wave solitons at finite temperatures

We consider the dynamics of a dark soliton in an elongated harmonically trapped Bose-Einstein condensate. A central question concerns the behavior at finite temperatures, where dissipation arises due to the presence of a thermal cloud. We study this problem using coupled Gross-Pitaevskii and $N$-body simulations, which include the mean field coupling between the condensate and thermal cloud. We find that the soliton decays relatively quickly even at very low temperatures, with the decay rate increasing with rising temperature.Comment: 6 pages, 2 figures, submitted to the Proceedings of QFS '0

Diagnosing Sporadic Creutzfeldt-Jakob Disease by the Detection of Abnormal Prion Protein in Patient Urine

IMPORTANCE: Creutzfeldt-Jakob disease (CJD) is a fatal neurodegenerative disorder associated with the accumulation of infectious abnormal prion protein through a mechanism of templated misfolding. A recent report has described the detection of abnormal prion protein in the urine of patients with variant CJD (vCJD) using protein misfolding by cyclic amplification, which was apparently absent in the more common sporadic form of CJD (sCJD). A noninvasive diagnostic test could improve early diagnosis of sCJD and, by screening donations, mitigate the potential risks of prion transmission through human urine–derived pharmaceuticals. Here, we describe the adaptation of the direct detection assay, developed originally as a blood test for vCJD, for the detection of disease-associated prion protein in urine samples from patients with sCJD. OBJECTIVE: To determine the feasibility of sCJD diagnosis by adaptation of an established vCJD diagnostic blood test to urine. DESIGN, SETTINGS AND PARTICIPANTS: This retrospective, cross-sectional study included anonymized urine samples from healthy nonneurological control individuals (n = 91), patients with non-prion neurodegenerative diseases (n = 34), and patients with prion disease (n = 37) of which 20 had sCJD. Urine samples obtained during the Medical Research Council PRION-1 Trial, the National Prion Monitoring Cohort Study, and/or referred to the National Prion Clinic or Dementia Research Centre at the National Hospital for Neurology and Neurosurgery in the United Kingdom. MAIN OUTCOMES AND MEASURES: Presence of sCJD infection determined by an assay that captures, enriches, and detects disease-associated prion protein isoforms. RESULTS: A total of 162 samples were analyzed, composed of 91 normal control individuals (51 male, 33 female, and 7 not recorded), 34 neurological disease control individuals (19 male and 15 female), and 37 with prion disease (22 male and 15 female). The assay’s specificity for prion disease was 100% (95% CI, 97%-100%), with no false-positive reactions from 125 control individuals, including 34 from a range of neurodegenerative diseases. In contrast to a previous study, which used a different method, sensitivity to vCJD infection was low (7.7%; 95% CI, 0.2%-36%), with only 1 of 13 patients with positive test results, while sensitivity to sCJD was unexpectedly high at 40% (95% CI, 19%-64%). CONCLUSIONS AND RELEVANCE: We determined 40% of sCJD urine sample results as positive. To our knowledge, this is the first demonstration of an assay that can detect sCJD infection in urine or any target analyte outside of the central nervous system. Urine detection could allow the development of rapid, molecular diagnostics for sCJD and has implications for other neurodegenerative diseases where disease-related assemblies of misfolded proteins might also be present in urine

Bank vole prion protein extends the use of RT-QuIC assays to detect prions in a range of inherited prion diseases

The cerebrospinal fluid (CSF) real-time quaking-induced conversion assay (RT-QuIC) is an ultrasensitive prion amyloid seeding assay for diagnosis of sporadic Creutzfeldt-Jakob disease (CJD) but several prion strains remain unexplored or resistant to conversion with commonly used recombinant prion protein (rPrP) substrates. Here, bank vole (BV) rPrP was used to study seeding by a wide range of archived post-mortem human CSF samples from cases of sporadic, acquired and various inherited prion diseases in high throughput 384-well format. BV rPrP substrate yielded positive reactions in 70/79 cases of sporadic CJD [Sensitivity 88.6% (95% CI 79.5-94.7%)], 1/2 variant CJD samples, and 9/20 samples from various inherited prion diseases; 5/57 non-prion disease control CSFs had positive reactions, yielding an overall specificity of 91.2% (95% CI 80.1-97.1%). Despite limitations of using post-mortem samples and our results' discrepancy with other studies, we demonstrated for the first time that BV rPrP is susceptible to conversion by human CSF samples containing certain prion strains not previously responsive in conventional rPrPs, thus justifying further optimisation for wider diagnostic and prognostic use

Oscillations and interactions of dark and dark-bright solitons in Bose-Einstein condensates

Solitons are among the most distinguishing fundamental excitations in a wide range of non-linear systems such as water in narrow channels, high speed optical communication, molecular biology and astrophysics. Stabilized by a balance between spreading and focusing, solitons are wavepackets, which share some exceptional generic features like form-stability and particle-like properties. Ultra-cold quantum gases represent very pure and well-controlled non-linear systems, therefore offering unique possibilities to study soliton dynamics. Here we report on the first observation of long-lived dark and dark-bright solitons with lifetimes of up to several seconds as well as their dynamics in highly stable optically trapped $^{87}$Rb Bose-Einstein condensates. In particular, our detailed studies of dark and dark-bright soliton oscillations reveal the particle-like nature of these collective excitations for the first time. In addition, we discuss the collision between these two types of solitary excitations in Bose-Einstein condensates.Comment: 9 pages, 4 figure

Vibrational signatures for low-energy intermediate-sized Si clusters

We report low-energy locally stable structures for the clusters Si20 and Si21. The structures were obtained by performing geometry optimizations within the local density approximation. Our calculated binding energies for these clusters are larger than any previously reported for this size regime. To aid in the experimental identification of the structures, we have computed the full vibrational spectra of the clusters, along with the Raman and IR activities of the various modes using a recently developed first-principles technique. These represent, to our knowledge, the first calculations of Raman and IR spectra for Si clusters of this size

Lisht as a New Kingdom glass-making site with its own chemical signature

Lisht is one of a few New Kingdom sites with known glass-working debris. Here, we present evidence for the primary production of glass at Lisht, including crucible fragments and semi-finished glass. We also provide 12 new chemical analyses of glass from Lisht, including trace elements. We argue that the glass made at Lisht has a specific chemical signature within the broader range of Late Bronze Age glass compositions from Egypt, further underlining the former existence of primary glass production there and offering the possibility of identifying Lisht-made glass elsewhere in Egypt and beyond