High-power antiguided laser array fabricated without the need forovergrowth

The fabrication of conventional semiconductor antiguided laser array structures involves etching of the array profile followed by an overgrowth step. In this letter, we report the fabrication of an antiguided laser array using zinc diffusion induced intermixing of a superlattice to create the necessary index step. The technique was used to fabricate a five-element, 10-μm center, antiguided laser array operating at 0.860 μm. The device operated at 1.2× diffraction limit to 3-W pulsed (total, both facets) and 1.6-W quasi-continuous-wave (CW) (100-μs pulses; total, both facets)     

High power antiguided laser array fabricated using a superlatticestructure

The operation of antiguided array lasers is dependent on the creation of an effective refractive index step between the antiguide core and the interelement regions. The authors describe a novel technique, using zinc diffusion to disorder a superlattice, for creating the necessary index step in a 10 element antiguided laser array operating at 0.860 μm. Output powers approach 400 mW per facet into a 3° (FWHM) beam. Use of this fabrication technique removes the need for overgrowth     

An object-oriented database for protein structure analysis

An object-oriented database system has been developed whichis being used to store protein structure data. The databasecan be queried using the logic programming language Prolog orthe query language Daplex. Queries retrieve information by navigatingthrough a network of objects which represent the primary, secondaryand tertiary structures of proteins. Routines written in bothProlog and Daplex can integrate complex calculations with theretrieval of data from the database, and can also be storedin the database for sharing among users. Thus object-orienteddatabases are better suited to prototyping applications andanswering complex queries about protein structure than relationaldatabases. This system has been used to find loops of varyinglength and anchor positions when modelling homologous proteinstructures.     

Trends in HIV-1 prevalence may not reflect trends in incidence in mature epidemics: data from the Rakai population-based cohort, Uganda

OBJECTIVES: To assess whether trends in serial HIV-1 prevalence reflect trend in HIV incidence, and to decompose the effects of HIV-1 incidence, mortality, mobility and compliance on HIV-1 prevalence in a population-based cohort. DESIGN: Two-year follow up (1990-1992) of an open cohort of all adults aged 15-59 years, resident in a sample of 31 representative community clusters in rural Rakai District, Uganda. METHODS: A detailed household enumeration was concluded at baseline and in each subsequent year. All household residents were listed, and all deaths and in- and out-migrations that occurred in the intersurvey year wee recorded. In each year, all consenting adults were interviewed and provided a serological sample; 2591 adults aged 15-59 years were enrolled at baseline. RESULTS: HIV prevalence among adults declined significantly 1990 and 1992 (23.4% at baseline, 21.8% in 1991, 20.9% in 1992; P < 0.05). Declining prevalence was also observed in subgroups, including young adults aged 15-24 years (from 20.6 to 16.2% over 3 years; P < 0.02), women of reproductive age (from 27.1 to 23.5%; P < 0.05), and pregnant women (from 25.4 to 20.0%; not significant), However, HIV incidence did not change significantly among all adults aged 15-59 years (2.1 +/- 0.4 per 100 person-years of observation (PYO) in 1990-1991 and 2.0 +/- 0.3 per 100 PYO in 1991-1992], nor in population subgroups. HIV-related mortality was high (13.5 per 100 PYO among the HIV-positive), removing more infected persons that were added by seroconversion. Net out-migration also removed substantial numbers of HIV-positive individuals. CONCLUSIONS: In this mature HIV epidemic, HIV prevalence declined in the presence of stable and incidence. HIV-related mortality contributed most to the prevalence decline. Prevalence was not an adequate surrogate measure of incidence, limiting the utility or serial prevalence measures in assessing the dynamics of the HIV epidemic and in evaluating the impact of current preventive strategies.     

Variation in expression of a bovine alpha-lactalbumin transgene in milk of transgenic mice

Transgenic mice were produced to study the production of bovine alpha-LA in their milk. A 7.6-kb fragment containing a bovine alpha-LA gene was purified and microinjected into pronuclear stage mouse embryos. This fragment contained 2.0 kb of 5' flanking region, the 1.7-kb coding region, and 2.7 kb of 3' flanking region. Out of 121 potential transgenic founder mice, 3 were identified as being transgenic by the polymerase chain reaction. Multiple mice from the second, third, and fourth generation from each line were milked, and the milk was analyzed using an ELISA assay and Western blots to determine the presence of bovine alpha-LA. Bovine alpha-LA was present at concentrations up to 1.5 mg of protein/ml of mouse milk. The high degree of expression variation between mice within each of the transgenic lines was a characteristic that has not been reported in other studies of transgene expression in milk. Production of bovine alpha-LA in the milk of these transgenic mice showed a high degree of variation both within a lactation and between mice within a line. The bovine alpha-LA concentration in a single line of transgenic mice exhibited as much as a 10-fold variation between mice. Variations as high as 3-fold were detected within a single lactation in the same mouse. These differences in expression appeared to be correlated with mouse milk production; bovine alpha-LA was higher on d 10 and 15 of lactation than on d 5. Transgenic mice that show variation in expression of a bovine gene might offer a unique system for studying quantitative traits in a laboratory model.     

Localization of plane reflectors using a wide-beamwidth ultrasoundtransducer arrangement

Using a wide-beamwidth ultrasound transducer arrangement to measure the geometric position of plane reflectors is studied. The localization of objects is based on the computation of the time of flight (TOF) of the acoustic echoes by the determination of the intersection point of the acoustic wave fronts; the geometrical position of the object is then estimated. As no mechanical moving devices are involved in the ranging process, and fewer TOF measurements are required than that of an active phased linear array, the system features intrinsically high operational reliability and fast dynamic response     

A ubiquitin-specific protease that efficiently cleaves the ubiquitin-proline bond

Ubiquitin is a small eukaryotic protein that is synthesized naturally as one of several fusion proteins, which are processed by ubiquitin-specific proteases to release free ubiquitin. The expression of heterologous proteins as fusions to ubiquitin in either prokaryotic or eukaryotic hosts often dramatically enhances their yield, and allows the exposure of any amino acid following cleavage of ubiquitin. The single exception is when proline is the amino acid immediately following ubiquitin; the ubiquitin-proline bond is poorly cleaved by presently studied ubiquitin-specific proteases. We show that the mouse ubiquitin-specific protease Unp, and its human homolog Unph, can efficiently cleave the ubiquitin-proline bond in ubiquitin fusion proteins of different sizes. N-terminal sequencing of the cleavage products reveals that cleavage occurs precisely at the ubiquitin-proline junction. The biological significance of this cleavage activity is unclear, as ubiquitin-proline fusions do not occur naturally. However, it may indicate a different catalytic mechanism for these ubiquitin-specific proteases and/or that they can cleave ubiquitin-like proteins. Unp and Unph thus represent versatile ubiquitin-specific proteases for cleaving ubiquitin-fusion proteins in biotechnology and basic research, regardless of both the amino acid immediately following ubiquitin, and the size of the fusion partner.     

Study on the mitoxantrone ethylcellulose microspheres for liver artery embolization

Intraoperative EEG-monitoring needs to discriminate random fluctuations from real systematic variations (trends). This task is made more difficult by several types of artifacts. With the goal of supporting visual EEG evaluation, a new trend-detection algorithm is presented which is based on spectral analysis and a post-processing dynamic linear model, the latter introduced by Harrison and Stevens. A gradient value provided by this model is exploited to determine the onset and relative extent of an existing trend. Artifacts are detected by several threshold measures for the original signal and its first derivative. The system was validated using a set of intraoperative EEGs recorded during carotid endarterectomy.     

Modeling studies of fluid flow below flash-smelting burners including transient behavior

Water-model experiments were carried out on 1:14-scale models of venturi, distributor, and jet-flow burners to ascertain flow patterns at varying Reynolds numbers (60,000 to 507,000) using time-lapse streak photography and video streak photography. Digital particle image velocimetry (DPIV) was used to determine the axial and radial velocities and to estimate the turbulence kinetic-energy field beneath the distributor burner. In the DPIV experiments, a temporal instability in the main jet exiting from the burner occurred at a Reynolds number=104,000, a Strouhal number≈3×10⁻³, and a large expansion ratio (shaft/burner-diameter ratio=10). The main jet usually pointed away from the burner inlet but was also observed to fluctuate and precess in a quasi-random fashion. Recom-mendations are made for improving flash-smelting burner performance by promoting conditions to eliminate precessing. The use of higher Reynolds numbers was recommended to improve both the use of shaft volume and the mixing of the concentrate particles and gas stream. A three-dimensional (3-D) mathematical model was used to simulate the water flow through the distributor burner, shaft, and settler. The predicted velocity field consisted of a main jet pointing away from the burner inlet and a large recirculation zone in the center of the shaft. The predicted and measured velocity magnitudes compared well in the recirculation zone, but the steady-state mathematical model predicted higher velocity values in the main jet than were experimentally determined.