Experimental Realization of a Relativistic Harmonic Oscillator

We report the experimental study of a harmonic oscillator in the relativistic regime. The oscillator is composed of Bose-condensed lithium atoms in the third band of an optical lattice, which have an energy-momentum relation nearly identical to that of a massive relativistic particle, with an effective mass reduced below the bare value and a greatly reduced effective speed of light. Imaging the shape of oscillator trajectories at velocities up to 98% of the effective speed of light reveals a crossover from sinusoidal to nearly photon-like propagation. The existence of a maximum velocity causes the measured period of oscillations to increase with energy; our measurements reveal beyond-leading-order contributions to this relativistic anharmonicity. We observe an intrinsic relativistic dephasing of oscillator ensembles, and a monopole oscillation with exactly the opposite phase of that predicted for non-relativistic harmonic motion. All observed dynamics are in quantitative agreement with longstanding but hitherto-untested relativistic predictions.Comment: 10 pages; 4 figure

Observation and uses of position-space Bloch oscillations in an ultracold gas

We report the direct observation and characterization of position-space Bloch oscillations using an ultracold gas in a tilted optical lattice. While Bloch oscillations in momentum space are a common feature of optical lattice experiments, the real-space center-of-mass dynamics are typically too small to resolve. Tuning into the regime of rapid tunneling and weak force, we observe real-space Bloch oscillation amplitudes of hundreds of lattice sites, in both ground and excited bands. We demonstrate two unique capabilities enabled by tracking of Bloch dynamics in position space: measurement of the full position-momentum phase-space evolution during a Bloch cycle, and direct imaging of the lattice band structure. These techniques, along with the ability to exert long-distance coherent control of quantum gases without modulation, may open up new possibilities for quantum control and metrology.Comment: 5 pages, 6 figure

Validity of a commercially available IgM ELISA test for diagnosing acute leptospirosis in high endemic districts of Sri Lanka

BackgroundLack of point of care diagnostics is a major challenge for control of human leptospirosis. Immunoglobulin M enzyme linked immunosorbent assays (IgM ELISA) have been widely used for the diagnosis of leptospirosis. The purpose of the present study was to determine the validity of IgM ELISA in the diagnosis of leptospirosis in a Sri Lankan context. MethodsConfirmed cases of leptospirosis from the 2008 Sri Lankan outbreak of leptospirosis and a group of leptospirosis excluded febrile patients were selected for the validation study. Disease confirmation and exclusion was carried out using either paired sample MAT (optimized for the region) or qPCR or both. A commercially available IgM ELISA kit was used and the procedure performed according to the manufacturers’ instruction in the Department of Microbiology, Faculty of Medicine, University of Peradeniya. ResultsThe study sample included 88 confirmed cases of leptospirosis and a comparison group of 71 acute fever patients.  Of the 88 confirmed cases selected, 53 reacted in IgM ELISA and of the comparison group, 38 gave a positive reaction. *MAT was carried out among acute and convalescent samples where the acute sample was obtained within the first 10 days of illness and the convalescent sample after the day 14. A regionally optimized MAT panel with 21 serovars were used for MATSensitivity and specificity of IgM ELISA, as a point of care diagnostic test for patients in this sample with acute leptospirosis, was 60.23% (95% CI 49.78, 69.82) and 46.48% (95% CI (35.36, 57.96) respectively. Diagnostic accuracy of the test was 54.09% (95% CI 46.34, 61.65 %). The ROC (Receiver-operator characteristic curve) curve for the IgM ELISA showed a value of .669 for area under the curve. Optimal cut off points were not detected due to the poor test parameters in this sample. ConclusionThis study shows the poor diagnostic capabilities of IgM ELISA during the acute phase of leptospirosis in high endemic settingsDOI: http://dx.doi.org/10.4038/sljid.v4i2.6952 Sri Lankan Journal of Infectious Diseases 2014; Vol.4(2):83-89</p

Quantifying and Controlling Prethermal Nonergodicity in Interacting Floquet Matter

The use of periodic driving for synthesizing many-body quantum states depends crucially on the existence of a prethermal regime, which exhibits drive-tunable properties while forestalling the effects of heating. This dependence motivates the search for direct experimental probes of the underlying localized nonergodic nature of the wave function in this metastable regime. We report experiments on a many-body Floquet system consisting of atoms in an optical lattice subjected to ultrastrong sign-changing amplitude modulation. Using a double-quench protocol, we measure an inverse participation ratio quantifying the degree of prethermal localization as a function of tunable drive parameters and interactions. We obtain a complete prethermal map of the drive-dependent properties of Floquet matter spanning four square decades of parameter space. Following the full time evolution, we observe sequential formation of two prethermal plateaux, interaction-driven ergodicity, and strongly frequency-dependent dynamics of long-time thermalization. The quantitative characterization of the prethermal Floquet matter realized in these experiments, along with the demonstration of control of its properties by variation of drive parameters and interactions, opens a new frontier for probing far-from-equilibrium quantum statistical mechanics and new possibilities for dynamical quantum engineering

Low Serum Paraoxonase; A Risk Factor for Coronary Artery Disease?

Objective: Serum Paraoxonase (PON) is a calcium dependent esterase which hydrolyses organophosphates. However, evidence exists for protective effect of PON against oxidative damage. PON has three genetic polymorphism (PON-1, PON-2, PON-3). The PON-1 has shown to provide resistance to development of atherosclerosis by protecting lipoprotein against oxidative modifications. Therefore, a study was performed to assess the relationship between Coronary Artery Disease (CAD) and PON-1 activity. Methods: A comparative cross-sectional study was performed with 33 angiogram positive patients and 48 healthy volunteers. Blood samples were collected after a 10 hours fast from controls and from patients who were awaiting angiogram test. Samples were analyzed for PON-1 activity using ELISA method. Data were analyzed using SPSS 15.0 statistical software. Results: The PON-1 concentration of angiogram positive cases and healthy volunteers (controls) were in the range 7.9 – 78.7 ug/ml and 14.9 – 395.2 ug/ml respectively. Angiogram positive cases showed significantly low (mean 36.7 ug/ml; P < 0.05) PON-1 activity when compared to controls (mean 111.5 ug/ml) suggesting that the low PON-1 activity has a potential to lead to an increased risk of CAD. Conclusion: The PON-1 activity may be a useful sensitive marker for assessment of CAD

Use of a rapid diagnostic test to detect cutaneous leishmaniasis in Sri Lanka

Objectives: This study was initiated to determine the sensitivity and specificity of a commercially available rapid diagnostic test (RDT) to detect leishmania antigen in cutaneous leishmaniasis(CL) skin lesions among Sri Lankan patients compared to PCR and Slit skin smear(SSS).Methods: Patients clinically suggestive of CL lesions were subjected to parasitological investigations. The clinical history was collected by the researcher. Samples were collected by a qualified trained medical officer from the suspected CL lesions at the dermatology clinic in the Hambantota hospital and from the patients coming to the Department of Parasitology, Faculty of Medical Sciences, University of Sri Jayewardenepura. RDT was done at the Hambantota hospital and samples were brought to the Department of Parasitology, to perform SSS, PCR and cultures.Results: Fifty samples have been collected thus far and PCR was performed only in 48 samples. Out of the 50 samples only 9 were positive by RDT and 32 by SSS and PCR. The 9 samples that were positive for RDT were positive by SSS and 7 positive by PCR. Of the 41 samples that were negative by RDT, 16 were negative by PCR as well as SSS.Conclusions: From the data collected it can concluded that RDT is not the best method to diagnose CL skin lesions in patients in Sri Lanka. Also it confirms that the best method to diagnose leishmaniasis is PCR