Powered oscillator using ignitron switches

A 10-MVA-scale resonant oscillator, powered by a pulse-forming network and switched with a pair of commutating mercury ignitrons, was developed for the MST reversed-field pinch plasma-confinement experiment. A novel feature of this circuit is its commutation mechanism, wherein each turning on of one ignitron causes a reverse voltage transient that turns off the other. Two of these oscillators are used in oscillating-field current-drive tests, in which they are capable of nearly 1MW net input power to the plasma, with resonant frequencies of a few 100 Hz for pulse durations of a few tens of ms, being precharged for immediate full amplitude. We describe the circuit and its operation, and discuss features that allow reliable, high-current commutation of the ignitrons and exploit their low switching impedance.

Consistent cytotoxic-T-lymphocyte targeting of immunodominant regions in human immunodeficiency virus across multiple ethnicities

Although there is increasing evidence that virus-specific cytotoxic-T-lymphocyte (CTL) responses play an important role in the control of human immunodeficiency virus (HIV) replication in vivo, only scarce CTL data are available for the ethnic populations currently most affected by the epidemic. In this study, we examined the CD8(+)-T-cell responses in African-American, Caucasian, Hispanic, and Caribbean populations in which clade B virus dominates and analyzed the potential factors influencing immune recognition. Total HIV-specific CD8(+)-T-cell responses were determined by enzyme-linked immunospot assays in 150 HIV-infected individuals by using a clade B consensus sequence peptide set spanning all HIV proteins. A total of 88% of the 410 tested peptides were recognized, and Nef- and Gag-specific responses dominated the total response for each ethnicity in terms of both breadth and magnitude. Three dominantly targeted regions within these proteins that were recognized by >90% of individuals in each ethnicity were identified. Overall, the total breadth and magnitude of CD8(+)-T-cell responses correlated with individuals' CD4 counts but not with viral loads. The frequency of recognition for each peptide was highly correlated with the relative conservation of the peptide sequence, the presence of predicted immunoproteasomal cleavage sites within the C-terminal half of the peptide, and a reduced frequency of amino acids that impair binding of optimal epitopes to the restricting class I molecules. The present study thus identifies factors that contribute to the immunogenicity of these highly targeted and relatively conserved sequences in HIV that may represent promising vaccine candidates for ethnically heterogeneous populations.

Programmable high-bit-rate pattern generator with a segmented semiconductor optical amplifier

We have demonstrated that spatial gain modulation in a segmented semiconductor optical amplifier can be converted to a temporal signal. A four-segment amplifier was used to generate digital return-to-zero patterns at 40 Gbits/s , and this technique should be readily scalable to more than 100 Gbits/s .

Necrotizing fasciitis. The changing spectrum

Necrotizing fasciitis, by nature of its high inoculum of aggressive bacteria and the depth of the fascial involvement, is one of the most serious infections known to humans. Rapid tissue destruction of skin and fascia, along with bacteremia, is common. The mortality for this disease is much higher than that for cellulitis. Unfortunately, delay in diagnosis occurs commonly. The emergence of toxic shock strains of Streptococcus leading to fasciitis with organ dysfunction makes it necessary to make a rapid diagnosis and institute early antibiotic and surgical interventions.

Effects of Free Recall of Grouping Pictures, Picture Names, and Complete Picture Descriptions

The double-encoding hypothesis is one explanation for the superior free recall of picture stimuli compared to recall of the same stimuli in word form. This study attempted to describe fully in words the picture stimuli that were presented, because a picture's simple word label obviously is not equivalent in complexity to the picture itself. Pictures, their simple labels, and a series of words that completely described the pictures were presented to 90 Ss. Results indicated stimuli in the picture form were remembered better than both kinds of word stimuli. These results supported the double-encoding hypothesis.

Developmental Effects on Free Recall of Grouping Pictures and Words

The double-encoding hypothesis explains why superior free recall of picture stimuli compared to their equivalent word forms has been demonstrated to be valid with university level Ss. Two experiments compared the effects of grouping words and pictures to determine if there is a developmental factor involved in modifying the double-encoding hypothesis. Experiment 1 found that freshmen university students who grouped pictures or words remembered more pictures (p < .01), thus supporting the double-encoding hypothesis. Experiment 2 found no significant differences when sixth-grade students grouped pictures or words (p > .05), thus not supporting the double-encoding hypothesis. Recommendations for future studies were made.

Adult body temperature and heated humidification of anesthetic gases during general anesthesia

To determine the effects on body temperature of heating and humidifying inspired anesthetic gases to 37 C and 100% relative humidity, 42 men who had major surgical procedures under general anesthesia were studied. Group 1 (control) consisted of 10 patients who inspired gases from a standard semicircle absorber system with no added humidity. The mean nasopharyngeal temperature decreased significantly from 36.2 +/- 0.1 C to 34.9 +/- 0.2 C. Ten other patients, group 2, inspired gases that were heated and humidified. Mean nasopharyngeal temperature was maintained at 36.4 +/- 0.2 C with no significant changes throughout the study. One patient in this group became hypothermic, but only transiently. Ten patients, group 3, were allowed to become hypothermic before gases were heated and humidified. The mean nasopharyngeal temperature increased significantly from 34.7 +/- 0.2 C to 36.0 +/- 0.3 C during 4 hours of heated humidification. For groups 4 and 5, six patients each, gases were heated and humidified on alternate hours. The responses of the two groups demonstrated a causal relationship between the heating and humidifying of inspired gases and an increased mean nasopharyngeal temperature. It is concluded that heating and humidifying gases to 37 C and 100% relative humidity effectively maintains normothermia and rewarms hypothermic adults during general anesthesia.

Growth of hygroscopic aerosols in a model of bronchial airways

Experiments have been performed on the "breathing" of micron-size hygroscopic aerosols in and out of a four-generation model of the bronchial tree. Comparison of the experimental results on aerosol growth in the model with the classical theory for dilute aqueous solutions of nonpolar salts shows a) that the theory is applicable to conditions in the airways, b) that to a high degree of approximation the process represents deposition followed by growth, and c) that there is a significant amount of trapping of particles near their equilibrium size in the deeper model tubes. These experiments are the first to verify that the classical particle growth theory is applicable to the particle sizes and environmental conditions present in the human airways during hygroscopic aerosol therapy. This theory will be useful in designing an optimal hygroscopic aerosol delivery system, but several questions including the method of generation and the effect of drug solutions on particle equilibriums remain to be answered.

Affect and meaningfulness as variables in mediate association

Affect and meaningfulness in verbal mediation were studied. The design of the study included Phase I, which varied the affect levels (high and low) while holding meaningfulness constant at a medium level, and Phase II, which varied both the affect level (high and low) of the mediators and the level of meaningfulness (high and low) of the non-mediators. Results showed that high-affect mediators produced superior mediation and that an affect by meaningfulness interaction occurred. High affect was more potent than high meaningfulness in producing superior mediation.

Visual imagery and level of mediator abstractness in induced mediation paradigms

Two objective tests, presumed to measure S's ability to form visual images, were administered to 240 seventh grade students. On the basis of test scores, equal numbers of Ss were assigned to visualizer and non-visualizer categories. Ss in each category were now assigned at random to one of four conditions and their performance compared in a mediate association learning experiment. Paradigms were designed to compare visualizers and non-visualizers on learning tasks which used concrete and abstract nouns as mediators. The findings showed that mediation was related both to the type of mediator used in the paradigm and S's ability to visualize.