Modeling of the optical characteristics for twin-channel laser (TCL) structures

The twin-channel laser (TCL) structure was the first laser design which incorporated the use of optical gain in the regions between the elements of an array-type device. In this paper, we describe the important parameters affecting the performance of TCL devices and extend our concepts to multielement (n > 2) laser arrays. Our calculations indicate that the presence of a uniform gain distribution over the width of the array is necessary for the excitation of the fundamental array mode and to achieve a single lobe far field. Secondly, lateral array mode stability is drastically reduced for arrays having many elements (n > 2) and will be difficult to achieve in practice. Lastly, we find that the near-field intensity in laser array structures is more spatially sensitive to asymetric perturbations induced by either current or geometry nonuniformities than single-element devices. We believe that some of these problems can possibly be minimized by the use of a new laser array geometry which incorporates an unequal number of array elements along the cavity length in order to spatially filter the unwanted array modes.     

Continued development of the Nimbus/University of Pittsburgh (UOP) axial flow left ventricular assist system

Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system.     

Erythema migrans-like rash illness at a camp in North Carolina: a new tick-borne disease?

BACKGROUND: Borrelia burgdorferi, the causative agent of Lyme disease, has never been isolated from a patient thought to have acquired Lyme disease in any southeastern state. OBJECTIVE: To investigate 14 cases of an erythema migrans (EM)-like rash illness that occurred during 2 summers at an outdoor camp in central North Carolina in an effort to determine the etiologic, epidemiological, and clinical aspects of this illness. METHODS: Using active surveillance, we identified cases of clinically diagnosed EM in residents and staff of the camp. We collected clinical and demographic information; history of exposure to ticks; acute and convalescent serum antibodies to B. burgdorferi, Rickettsia rickettsii, and Ehrlichia chaffeensis; and cultures for spirochetes from biopsy specimens of skin lesions. Serum samples from a group of residents and staff who did not develop rashes were tested for the same antibodies. We speciated ticks removed from people and collected from vegetation. RESULTS: We identified 14 cases of EM-like rash illness during the 2 summers. Of the 14 case-patients, 10 had associated mild systemic symptoms and 1 had documented fever. All 14 case-patients had removed attached ticks, and 8 remembered having removed a tick from the site where the rash developed a median of 12 days earlier (range, 2-21 days). One tick removed from the site where a rash later developed was identified as Amblyomma americanum, the Lone Star tick; 97% of ticks collected from vegetation and 95% of ticks removed from people were A. americanum. No spirochetes were isolated from skin biopsy specimens. Paired serum samples from 13 case-patients did not show diagnostic antibody responses to B. burgdorferi or other tick-borne pathogens. CONCLUSIONS: This investigation suggests the existence of a new tick-associated rash illness. We suspect that the disease agent is carried by A. americanum ticks. In the southern United States, EM-like rash illness should no longer be considered definitive evidence of early Lyme disease.     

N-methyl-D-aspartate-stimulated increases in intracellular calcium exhibit brain regional differences in sensitivity to inhibition by ethanol

To determine what effect ovariectomy and the accompanying sudden loss of circulating gonadal hormones has on spatial learning performance in the adult rat, two groups of rats were tested on the Lashley III simple alley maze following surgery. Ovariectomized animals were compared with a control group of animals that underwent laparotomy at the same time. The ovariectomized group evidenced superior performance on the maze task, as measured by latency to reach goal (running times) and error scores. It is suggested that this finding provides further evidence for the role of gonadal steroid hormones in the manipulation of functions related to learning and memory, especially in the hippocampus.     

Macromolecular assembly: chainmail stabilization of a viral capsid

The subunits that make up the capsid of a double-stranded DNA phage have been found to be arranged as covalently bonded, interlinked pentamer and hexamer rings. This remarkable 'chainmail' arrangement raises interesting new questions about macromolecular assembly.     

Immunogenicity of Plasmodium falciparum circumsporozoite protein multiple antigen peptide vaccine formulated with different adjuvants

Only low antibody levels were obtained from vaccinating human volunteers with single-chain peptide from the Plasmodium falciparum circumsporozoite protein (PfCSP). This resulted in modest protection against sporozoite challenge. In addition, HLA restriction limits the probability of synthesis of a vaccine effective for a diverse population. We report immunization studies with a multiple antigen peptide (MAP) system consisting of multiple copies of a B-cell epitope from the central repeat region of the PfCSP in combination with a universal T-cell epitope, the P2P30 portion of tetanus toxin. This MAP4(NANP)6P2P30 vaccine was highly immunogenic in four different strains of mice when used with various safe and nontoxic adjuvants. When this MAP vaccine was encapsulated in liposomes with lipid A and adsorbed to aluminium hydroxide and given three times at 4-week intervals, the resultant antibody prevented 100% of sporozoites from invading and developing into liver stage infection. This high degree of immunogenicity of MAP4(NANP)6P2P30 vaccine formulated in liposomes, lipid A and aluminum hydroxide provides the foundation for consideration of human trials with this formulation.