Bistatic LIDAR experiment proposed for the shuttle/tethered satellite system missions

A new experiment concept has been proposed for the shuttle/tethered satellite system missions, which can provide high resolution, global density mappings of certain ionospheric species. The technique utilizes bistatic LIDAR to take advantage of the unique dual platform configuration offered by these missions. A tuned, shuttle-based laser is used to excite a column of the atmosphere adjacent to the tethered satellite, while triangulating photometic detectors on the satellite are employed to measure the fluorescence from sections of the column. The fluorescent intensity at the detectors is increased about six decades over both ground-based and monostatic shuttle-based LIDAR sounding of the same region. In addition, the orbital motion of the Shuttle provides for quasi-global mapping unattainable with ground-based observations. Since this technique provides such vastly improved resolution on a synoptic scale, many important middle atmospheric studies, heretofore untenable, may soon be addressed

Preparation and optical properties of GA(x)IN(1-x)P alloys

The solution crystallization method was used to obtain Ga(z)In(1-x)P alloys for all values of x desired between zero and 1. The method of preparation makes it possible to crystallize the solid at a constant temperature. The points obtained by cathodoluminescence are nearly in straight lines. The optical absorption thresholds are confirmed in the results and make it possible to define the nature of the transitions except when x is in the neighborhood of 0.65. These determinations agree with those of Hilsum and Porteus (1968), but are not in agreement with those obtained by Lorenz et al, (1968)

Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55µm

We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55µm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120W/km respectively at 1.55µm. These predictions are consistent with the experimentally determined dispersion of +12.5ps/nm/km at 1.55µm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55µm using a 1.5m length of the fiber

Expanding the epidemiological understanding of hepatitis C in South Africa: Perspectives from a patient cohort in a rural town

Background. The epidemiology of hepatitis C virus (HCV) in the general population of South Africa (SA) is incompletely understood. A high HCV prevalence in key populations is known, but data are limited in terms of a broader understanding of transmission risks in our general population.Objectives. To investigate a patient cohort with HCV infection clustering in a rural SA town, in order to identify possible HCV transmission risks, virological characteristics, phylogenetic data and treatment outcomes.Methods. A cluster of patients with positive HCV serology, previously identified from laboratory records, were contacted by a local district hospital and offered confirmatory testing for HCV viraemia where needed. Those with confirmed HCV RNA were invited to a local hospital visit, where relevant demographic information was recorded, clinical assessment performed and a confidential questionnaire administered. HCV population-based sequencing was performed on HCV NS3/4A, NS5A and NS5B using polymerase chain reaction-specific or M13 universal primers, and sequences were aligned using BioEdit 7.2.5. Phylogenetic trees were constructed. Clinical assessments included liver fibrosis determination with FibroScan (cut-off ≥12.5 kPa = F4). Patients were offered treatment, and sustained virological response (SVR) was confirmed by undetectable HCV RNA at least 12 weeks after the end of treatment.Results. Twenty-one patients, all from the same town, median (interquartile range (IQR)) age 64 (59 - 70) years, 57% female, were evaluated. Of these, 24% (n=5) were HIV co-infected, stable on antiretrovirals. The median (IQR) alanine aminotransferase level was 51 (31 - 89) U/L, with fibrosis distribution including 29% F1, 29% F2, 9% F3 and 33% F4 METAVIR fibrosis. Virologically, two genotypes were observed: 62% (n=13) genotype (GT) 1b and 38% (n=8) GT5a. No patient had ever used injecting drugs, 14% (n=3) had received blood products before 1992, and 9.5% (n=2) had undergone traditional healer-administered scarification. All (n=21) reported attendance at a single primary care clinic in the past, with most (n=20) recalling having received parenteral therapies at the clinic. Phylogenetic analysis of the HCV NS5A and NS5B regions confirmed GT1b and GT5a genotypes and formed two separate clusters within their respective genotypes, suggesting a common source for each genotype infection. Most patients received treatment with sofosbuvir/daclatasvir, 1 was treated with sofosbuvir/velpatasvir, and 1 was re-treated with sofosbuvir/velpatasvir/voxilaprevir. Per protocol SVR was 95%, with the non-SVR patient successfully re-treated.Conclusions. Data from a rural town cluster of patients suggest parenteral medical exposure as the probable common source of hepatitis C transmission risk. The cohort was of older age with a significant number having advanced fibrosis or cirrhosis, suggesting HCV acquisition in the distant past. Using a simplified care approach, treatment outcomes were very good

Trapping of single atoms in cavity QED

By integrating the techniques of laser cooling and trapping with those of cavity quantum electrodynamics (QED), single Cesium atoms have been trapped within the mode of a small, high finesse optical cavity in a regime of strong coupling. The observed lifetime for individual atoms trapped within the cavity mode is $\tau \approx 28$ms, and is limited by fluctuations of light forces arising from the far-detuned intracavity field. This initial realization of trapped atoms in cavity QED should enable diverse protocols in quantum information science.Comment: 4 pages, 4 figure

The efficacy of a generic doxycycline tablet in the treatment of canine monocytic ehrlichiosis

The objective of the present study was to evaluate the therapeutic efficacy of a generic doxycycline tablet (DoxyVet®) against Ehrlichia canis infection in dogs. Canine monocytic ehrlichiosis is caused by the bacterium E. canis and transmitted by the brown kennel tick (Rhipicephalus sanguineus). Six disease-free and tick-free dogs were infested with E. canisinfected ticks. Once diagnosed (with polymerase chain reaction [PCR] analysis and platelet counts) as positive for infection, doxycycline tablets were administered orally once a day for 20 consecutive days, at a target dose level of 10 mg/kg. The actual dose administered was calculated as ranging between 10 mg/kg and 11.7 mg/kg. The PCR analysis, 28 days after the first administration of the tablets, failed to detect E. canis in any of the dogs. On Day 56 of the study, four of the dogs were diagnosed with E. canis for the second time and a fifth dog was diagnosed on Day 70. The platelet counts of the sixth dog remained within normal levels and it was discharged from the study on Day 84. Doxycycline tablets were then administered to the remaining five infected dogs for 28 consecutive days. Four of these dogs had no positive PCR results during the following 3 months. The fifth dog was diagnosed with E. canis for the third time 58 days after the last tablets of the second treatment had been administered, after which it was rescue treated (doxycycline for a further 28 days). The results indicate that doxycycline administered in tablet form (DoxyVet®) at 10 mg/kg – 11.7 mg/kg body mass once daily for 28 consecutive days clears most dogs of infection. The importance of a concomitant tick-control programme is therefore stressed

Cavity cooling of a single atom

All conventional methods to laser-cool atoms rely on repeated cycles of optical pumping and spontaneous emission of a photon by the atom. Spontaneous emission in a random direction is the dissipative mechanism required to remove entropy from the atom. However, alternative cooling methods have been proposed for a single atom strongly coupled to a high-finesse cavity; the role of spontaneous emission is replaced by the escape of a photon from the cavity. Application of such cooling schemes would improve the performance of atom cavity systems for quantum information processing. Furthermore, as cavity cooling does not rely on spontaneous emission, it can be applied to systems that cannot be laser-cooled by conventional methods; these include molecules (which do not have a closed transition) and collective excitations of Bose condensates, which are destroyed by randomly directed recoil kicks. Here we demonstrate cavity cooling of single rubidium atoms stored in an intracavity dipole trap. The cooling mechanism results in extended storage times and improved localization of atoms. We estimate that the observed cooling rate is at least five times larger than that produced by free-space cooling methods, for comparable excitation of the atom

A MEMS device for continuously tunable optical buffering

We present design and fabrication of free-standing InP optical waveguides for MEMS-actuated optical buffering. A continuously tunable delay time of 10ps is predicted in a 1mm long device with the operation voltage of 3V

Design and fabrication of indium phosphide air-bridge waveguides with MEMS functionality

We present the design and fabrication of a dual air-bridge waveguide structure integrated with MEMS functionality. The structure is designed to function as a tunable optical buffer for telecommunication application. The optical buffer structure is based on two parallel waveguides made of high refractive index material with subwavelength dimensions. They are suspended in air, and are separated by a sub-micron air gap. Due to the fact that the size of the waveguides is much smaller than the wavelength of light that propagates in the structure, a significant fraction of the optical mode is in the air gap between the waveguides. By changing the size of the air gap using MEMS techniques, we can vary this fraction and hence the effective refractive index of the waveguide structure, thus generating tunable optical delay.The optical buffer structure was grown on an InP substrate by molecular beam epitaxy, and the device layer was made of InGaP. An InGaAs layer was sandwiched between the device layer and the substrate to serve as a sacrificial layer. The sub-micron waveguides, their supports in the form of side pillars with tapered shapes in order to minimize optical losses, and the MEMS structures were patterned using electron beam lithography and plasma etching. Electrodes were integrated into the structure to provide electrostatic actuation. After the sample patterning, the waveguide structure was released using HF etch. Our simulations predict that by varying the waveguide separation from 50 nm to 500 nm, we could achieve a change in propagation delay by a factor of two

Optical decay from a Fabry-Perot cavity faster than the decay time

The dynamical response of an optical Fabry-Perot cavity is investigated experimentally. We observe oscillations in the transmitted and reflected light intensity if the frequency of the incoupled light field is rapidly changed. In addition, the decay of a cavity-stored light field is accelerated if the phase and intensity of the incoupled light are switched in an appropriate way. The theoretical model by M. J. Lawrence em et al, JOSA B 16, 523 (1999) agrees with our observations.Comment: submitted to Josa