Characterization of Quasi-Keplerian, Differentially Rotating, Free-Boundary Laboratory Plasmas.

We present results from pulsed-power driven differentially rotating plasma experiments designed to simulate physics relevant to astrophysical disks and jets. In these experiments, angular momentum is injected by the ram pressure of the ablation flows from a wire array Z pinch. In contrast to previous liquid metal and plasma experiments, rotation is not driven by boundary forces. Axial pressure gradients launch a rotating plasma jet upward, which is confined by a combination of ram, thermal, and magnetic pressure of a surrounding plasma halo. The jet has subsonic rotation, with a maximum rotation velocity 23±3 km/s. The rotational velocity profile is quasi-Keplerian with a positive Rayleigh discriminant κ^{2}∝r^{-2.8±0.8} rad^{2}/s^{2}. The plasma completes 0.5-2 full rotations in the experimental time frame (∼150 ns).

The Digestive Diverticula in the Carnivorous Nudibranch, Melibe leonina, Do Not Contain Photosynthetic Symbionts.

A number of nudibranchs, including Melibe engeli and Melibe pilosa, harbor symbiotic photosynthetic zooxanthellae. Melibe leonina spends most of its adult life on seagrass or kelp, capturing planktonic organisms in the water column with a large, tentacle-lined oral hood that brings food to its mouth. M. leonina also has an extensive network of digestive diverticula, located just beneath its translucent integument, that are typically filled with pigmented material likely derived from ingested food. Therefore, the focus of this project was to test the hypothesis that M. leonina accumulates symbiotic photosynthetic dinoflagellates in these diverticula. First, we conducted experiments to determine if M. leonina exhibits a preference for light, which would allow chloroplasts that it might be harboring to carry out photosynthesis. We found that most M. leonina preferred shaded areas and spent less time in direct sunlight. Second, we examined the small green circular structures in cells lining the digestive diverticula. Like chlorophyll, they exhibited autofluorescence when illuminated at 480 nm, and they were also about the same size as chloroplasts and symbiotic zooxanthellae. However, subsequent electron microscopy found no evidence of chloroplasts in the digestive diverticula of M. leonina; the structures exhibiting autofluorescence at 480 nm were most likely heterolysosomes, consistent with normal molluscan digestion. Third, we did not find evidence of altered oxygen consumption or production in M. leonina housed in different light conditions, suggesting the lack of any significant photosynthetic activity in sunlight. Fourth, we examined the contents of the diverticula, using HPLC, thin layer chromatography, and spectroscopy. The results of these studies indicate that the diverticula did not contain any chlorophyll, but rather harbored other pigments, such as astaxanthin, which likely came from crustaceans in their diet. Together, all of these data suggest that M. leonina does sequester pigments from its diet, but not for the purpose of symbiosis with photosynthetic zooxanthellae. Considering the translucent skin of M. leonina, the pigmented diverticula may instead provide camouflage.

Varios nudibranquios, incluidos Melibe engeli y Melibe pilosa, albergan zooxantelas fotosintéticas simbióticas. Melibe leonina pasa la mayoría de su vida adulta en pastos marinos o quelpo, donde captura organismos planctónicos en la columna de agua con una gran capucha oral forrada por tentáculos que llevan comida a su boca. Melibe leonina también tiene una extensa red de divertículos digestivos, ubicados justo debajo de su tegumento translúcido, que generalmente están llenos de material pigmentado probablemente derivado de alimentos ingeridos. Por lo tanto, el objetivo de este proyecto fue evaluar la hipótesis de que M. leonina acumula dinoflagelados fotosintéticos simbióticos en estos divertículos. Primero, realizamos experimentos para determinar si M. leonina se orienta hacia la luz, lo cual permitiría a los cloroplastos que podría albergar el realizar la fotosíntesis. Descubrimos que la mayoría de M. leonina prefería las áreas sombreadas y pasaba menos tiempo bajo la luz solar directa. En segundo lugar, examinamos las pequeñas estructuras circulares verdes en las células que recubren los divertículos digestivos. Al igual que la clorofila, exhibieron autofluorescencia cuando se iluminaban a 480 nm, y también tenían aproximadamente el mismo tamaño que los cloroplastos y las zooxantelas simbióticas. No obstante, la microscopía electrónica no produjo evidencia de cloroplastos en los divertículos digestivos de M. leonina. Es probable que las estructuras que exhibieron autofluorescencia en 480 nm fuesen heterolisosomas, lo cual es consistente con la digestión normal de moluscos. En tercer lugar, no encontramos evidencia de un consumo o producción de oxígeno alterado en M. leonina alojadas varias condiciones lumínicas, lo cual sugiere la ausencia de actividad fotosintética significativa en la presencia de luz solar. En cuarto lugar, examinamos el contenido de los divertículos mediante HPLC, cromatografía en capa fina, y espectroscopia. Los resultados de estos estudios indican que los divertículos no contenían clorofila, pero si otros pigmentos como la astaxantina que probablemente provenía de crustáceos en su dieta. Nuestros datos sugieren que M. leonina secuestra pigmentos de su dieta, pero no con el propósito de la simbiosis con zooxantelas fotosintéticas. Teniendo en cuenta la piel translúcida de M. leonina, los divertículos pigmentados podrían quizás proporcionar camuflaje.

Experimental demonstration of an inertial collimation mechanism in nested outflows.

Interaction between a central outflow and a surrounding wind is common in astrophysical sources powered by accretion. Understanding how the interaction might help to collimate the inner central outflow is of interest for assessing astrophysical jet formation paradigms. In this context, we studied the interaction between two nested supersonic plasma flows generated by focusing a long-pulse high-energy laser beam onto a solid target. A nested geometry was created by shaping the energy distribution at the focal spot with a dedicated phase plate. Optical and x-ray diagnostics were used to study the interacting flows. Experimental results and numerical hydrodynamic simulations indeed show the formation of strongly collimated jets. Our work experimentally confirms the "shock-focused inertial confinement" mechanism proposed in previous theoretical astrophysics investigations.

Observation of self-similarity in the magnetic fields generated by the ablative nonlinear Rayleigh-Taylor instability.

Magnetic fields generated by the nonlinear Rayleigh-Taylor growth of laser-seeded three-dimensional broadband perturbations were measured in laser-accelerated planar targets using ultrafast proton radiography. The experimental data show self-similar behavior in the growing cellular magnetic field structures. These observations are consistent with a bubble competition and merger model that predicts the time evolution of the number and size of the bubbles, linking the cellular magnetic field structures with the Rayleigh-Taylor bubble and spike growth.

Supersonic radiatively cooled rotating flows and jets in the laboratory.

The first laboratory astrophysics experiments to produce a radiatively cooled plasma jet with dynamically significant angular momentum are discussed. A new configuration of wire array z pinch, the twisted conical wire array, is used to produce convergent plasma flows each rotating about the central axis. Collision of the flows produces a standing shock and jet that each have supersonic azimuthal velocities. By varying the twist angle of the array, the rotation velocity of the system can be controlled, with jet rotation velocities reaching approximately 18% of the propagation velocity.

The themes expressed in suicide calls to a telephone help line.

BACKGROUND: Little is known about the suicidal ideation of callers to telephone help lines even though these services are in the front line of suicide prevention efforts. Where thematic data are collected by telephone counseling agencies, it is rarely clear how the categories were constructed and the measurement properties of the instruments are rarely reported. METHODS: The call sheets kept by counselors on 409 suicide calls were content-analyzed, resulting in a reliable checklist comprising nine major themes. The prevalence of these themes within the sample was then determined and age and gender differences in the themes expressed by first-time callers (n = 189) were examined using logistic regression analysis. RESULTS: Almost equal numbers of male and female calls were received and the nine themes were mentioned a total of 981 times. Among first-time callers, males under 35 years were around 75% more likely to refer to relationship breakdown in their calls than were same-age females. Male callers were also around twice as likely to refer to material hardship. Females were four times more likely to refer to being the victim of abuse and nearly 60% more likely to refer to interpersonal and family problems. CONCLUSION: The vast majority of suicide callers expressed dissatisfaction with the quality of their intimate relationships, which suggests that the promotion of intimacy and coping strategies for relationship breakdown are central to the primary prevention of suicide.

Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae.

Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly slow rotation of most white dwarf stars.

Cryptosporidiosis in HIV-infected patients: diagnostic sensitivity of stool examination, based on number of specimens submitted.

OBJECTIVES: To determine the optimal number of stool specimens needed for the diagnosis of cryptosporidiosis. METHODS: Four hundred thirty-five admissions were reviewed (291 patients) in which stool specimens were examined for Cryptosporidium parvum oocysts (mean of 1.47 specimens per admission), using a modified acid-fast stain. The diagnostic yield of each specimen was determined. RESULTS: Cryptosporidium parvum oocysts were found in 81 of 435 admissions (18.6%). Ninety-six percent of the positive cases were detected on the first stool specimen analysis, and 100% were detected by the second specimen. CONCLUSIONS: Examination of one specimen is generally appropriate for the diagnosis of cryptosporidiosis in a hospitalized patient with AIDS presenting with diarrhea. Examination of a second specimen may be appropriate if the first specimen is negative and there is a high clinical index of suspicion.

Functional ablation of afferent nerves aggravates dextran sulphate sodium-induced colonic damage in rats.

Dextran sulphate sodium (DSS) is an oral agent capable of inducing chronic diarrhoea and colonic inflammation and necrosis in rats. The role of the afferent nerves in this model of colonic mucosal damage is not known. The hypothesis that functional ablation of the capsaicin-sensitive afferent nerves will aggravate DSS-induced colonic damage in rats was tested. Capsaicin pretreatment was used to ablate afferent nerve function and DSS was administered in the drinking water. Control rats received vehicle pretreatment and water without DSS. There were significant correlations between diarrhoea score, mucosal neutrophil infiltration, mucosal necrosis, and anaemia. Capsaicin pretreatment increased diarrhoea score and colonic mucosal neutrophil infiltration in the rats with colonic damage after 2 or 14 days of DSS. In addition, it induced anaemia and mortality in rats after 14 days of DSS. The data supports the hypothesis that functional ablation of the capsaicin-sensitive afferent nerves aggravates the colonic damage induced by DSS.

Anti-neutrophil serum attenuates dextran sulfate sodium-induced colonic damage in the rat.

BACKGROUND: The role of neutrophils in experimental colonic damage induced by dextran sulfate sodium is uncertain. We test the hypothesis that neutrophils are of pathogenic significance and anti-neutrophil serum will attenuate the colonic damage induced by oral dextran sulfate sodium in rats. METHODS: Rabbit anti-rat neutrophil serum (anti-neutrophil serum) or control rabbit serum was administered to, and circulating neutrophil count was monitored in, rats before and during feeding of dextran sulfate sodium or regular rat diet for 2 weeks. Histologic features of mucosal damage were evaluated in hematoxylin and eosin-stained proximal and distal colonic sections by a blinded observer. RESULTS: Oral dextran sulfate sodium induces weight loss, diarrhea, peripheral neutrophilia, and colonic damage. Anti-neutrophil serum induced neutropenia and significantly attenuated the weight loss, the neutrophil infiltration in the colon, and the mucosal necrosis and pathologic index in the distal colon. CONCLUSION: The data showing that anti-neutrophil serum attenuates distal colonic mucosal injury induced by dextran sulfate sodium support the hypothesis that neutrophils play a pathogenic role in this model of colonic mucosal damage.

Diagnosis of duodenal and ampullary epithelial neoplasms by endoscopic biopsy: a clinicopathologic and immunohistochemical study.

A series of 19 duodenal and 16 ampullary neoplasms was studied to determine their pathologic features on endoscopic biopsy, to evaluate the diagnostic accuracy of this procedure, and to assess the usefulness of immunohistochemical staining for carcinoembryonic antigen (CEA) in these neoplasms. The 11 benign neoplasms (31 per cent) were adenomas, five of which had focal hyperplastic features; the 24 malignant neoplasms (69 per cent) included ten intestinal-type carcinomas (resembling colonic carcinoma), seven anaplastic carcinomas (resembling diffuse gastric carcinoma), two adenocarcinomas in situ, and five lesions of unoriented, cytologically malignant epithelium. Malignancy was suspected endoscopically in 19 of 24 carcinomas, and the majority of the benign neoplasms were described as polyps or plaques. Resections (performed in 20 cases) demonstrated the accuracy of the biopsy diagnoses in 17 cases (85 per cent). In the three discordant cases, diagnosed by biopsy as adenoma in two cases and carcinoma in situ in one, coexistent in situ or infiltrating carcinomas were identified in the resected specimens. Carcinoembryonic antigen (20 cases) was identified mostly along glycocalyceal borders in normal and adenomatous tissues, whereas the carcinomas also showed strong cytoplasmic staining for CEA. Endoscopic biopsy is a valuable procedure in the diagnosis of duodenal and ampullary neoplasms. Correlation of the pathologic features of biopsy specimens with endoscopic appearances may result in more accurate diagnoses.

Significance of gastrointestinal cytomegalovirus infection in homosexual males.

Gastrointestinal cytomegalovirus (CMV) infection usually occurs in immunosuppressed patients and has recently been reported in patients with the acquired immune deficiency syndrome (AIDS). Serological evidence of CMV infection and a variety of traumatic and infectious gastrointestinal disorders are known to occur in nonimmunosuppressed homosexual males. However, the significance of gastrointestinal CMV infection in nonimmunosuppressed homosexual males is not well known. Three unusual cases of gastrointestinal CMV infection in homosexual males are presented. Infection of a Kock pouch in one patient and an anal ulcer in another, occurred as part of a CMV mononucleosis syndrome. In the third patient, CMV was found in an acutely inflamed appendix. Although gastrointestinal CMV infection has been reported frequently in patients with AIDS, our patients showed no evidence of immunosuppression or AIDS 6 wk to 1 year later. Gastrointestinal CMV infection in homosexual males with gastrointestinal disease should not be considered indicative of AIDS.

In vitro antimicrobial susceptibility of penicillinase-producing and intrinsically resistant Neisseria gonorrhoeae strains.

The in vitro susceptibility of penicillinase-producing and intrinsically resistant Neisseria gonorrhoeae strains to 13 antimicrobial agents was tested. Regardless of the type of resistance, these organisms remained quite susceptible to newer cephalosporin agents, including moxalactam, cefoperazone, cefotaxime, and ceftazidime.

Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from lactoferrin.

The ability of 107 Neisseria isolates to compete for iron with human lactoferrin (LF) was examined. Each of 15 meningococci, 53% of 59 selected gonococci, and 24% of 33 commensal Neisseria could use LF-bound iron for growth. Isolates which could not obtain iron from LF were growth inhibited when sufficient LF was added to defined agar medium to bind available free iron. No difference was observed in the ability of colony type 1 and colony type 4 gonococci of the same strain to compete with LF for iron. LF was growth inhibitory for 50% of 22 disseminated disease isolates (DGI strains) and 51% of 35 local urogenital disease isolates (UGI strains). Only 14% of gonococcal isolates requiring arginine, hypoxanthine, and uracil for growth were able to compete with LF for iron, whereas 87% of all other gonococcal isolates could do so (P less than 0.005). Ability to obtain iron from LF does not appear to be required for survival of Neisseria on mucosal surfaces, nor essential for invasion of the bloodstream by gonococci. However, ability to utilize LF as a source of iron may contribute to differences in pathogenicity among certain gonococcal isolates.

High-frequency conjugal transfer of a gonococcal penicillinase plasmid.

Gonococci containing a 24 X 10(6)-dalton conjugal plasmid were able to mobilize for transfer a smaller, non-self-transmissible penicillinase (Pcr) plasmid with high frequency under appropriate conditions. In some strains, over 10% of donor colony-forming units transferred the Pcr plasmid in a mating of less than 2 h, which suggests that the conjugal system was naturally derepressed. Colony-opacity variants containing different quantities of an approximately 28,000-dalton outer membrane protein were altered in their ability to act as conjugal donors and recipients. Maximal transfer of the Pcr plasmid was observed between transparent donors and recipients, lacking appreciable amounts of the 28,000-dalton protein. Under conditions of high-frequency Pcr plasmid mobilization, no conjugal mobilization of chromosomal markers could be discerned.

Genetic locus (nmp-1) affecting the principal outer membrane protein of Neisseria gonorrhoeae.

An increase in the apparent molecular weight of the principal outer membrane protein (POMP) of Neisseria gonorrhoeae is associated with introduction of the penB2 genetic marker, which results in low-level, relatively nonspecific antibiotic resistance. Limited proteolysis of the two forms of POMP showed that they had few if any peptides in common. The nonspecific antibiotic resistance of penB2 was separated from the change in POMP by genetic transformation and by isolation of spontaneous penB mutants that showed no change in POMP. The genetic locus involved in the change from one POMP to another, which we have designated nmp-1, is closely linked to, but not identical with, penB2.

Conjugative plasmids in Neisseria gonorrhoeae.

A conjugation system initially discovered in beta-lactamase-producing gonococci mobilized small non-selftransmissible R plasmids encoding beta-lactamase (penicillinase) production into other gonococci, Neisseria, and Escherichia coli. This conjugation system was mediated by a separate selftransmissible plasmid of 23.9 X 10(6) daltons, pFA2. Conjugative plasmids capable of mobilizing R plasmids were also found in nearly 8% of the non-penicillinase-producing gonococci. These were similar to pFA2 in size, buoyant density, and restriction endonuclease digest patterns but were less efficient than pFA2 in mobilization of the penicillinase plasmid pFA3. The presence of conjugative plasmids in gonococci isolated before the appearance of penicillinase-producing strains indicates that a conjugation system for plasmid transfer predated the appearance of R plasmids in gonococci.

Cardiac arrhythmias associated with treadmill claudication testing.

Eighty-one consecutive patients of an average age of 58 years with suspected lower limb arterial disease underwent standard 5-minute treadmill claudication testing. Prior to, during, and after testing the patients were monitored electrocardiographically. The number of electrocardiographic abnormalities seen in 81 patients undergoing study increased from 33 (40.6%) at rest to 49 (60.5%) with exercise. The commonest abnormalities encountered with exercise were the development and increased incidence of paroxysmal beats and ST-T wave changes which, in some instances, became life-threatening, aborting the test. Since the principal hazard for patients with claudication appears to derive from an increase propensity to cardiac mortality and morbidity, rather than from the consequences of impaired circulation to the limb, electrocardiographic monitoring during treadmill claudication testing, though little practiced, is strongly advised.

Conjugal transfer of the gonococcal penicillinase plasmid.

Certain gonococci, which heretofore have lacked a conjugal mating system, can sexually transfer a small plasmid (4.5 x 10)6) daltons) which carries the gene for beta-lactamase production. Frequencies of conjugal transfer were similar into diverse recipients (other gonococci, Neisseria flava, and Escherichia coli), which suggests that gonococci may transfer the plasmid promiscuously in nature.

Factors affecting genetic transformation of Neisseria gonorrhoeae.

Piliated gonococci were competent in genetic transformation in all stages of growth in minimal and enriched media, but nonpiliated cells were almost totally incompetent. Uptake of deoxyribonucleic acid into a deoxyribonuclease-insensitive state was observed only in competent piliated cells. Competence was not affected by washing of competent cells or treatment of competent cells with proteolytic enzymes. Expression of competence required presence of any of several different monovalent or divalent cations, as well as a utilizable source of energy. Efforts to produce genotypically or phenotypically competent derivatives of nonpiliated cells were unsuccessful. These experiments are consistent with the idea that pili may play a role in the irreversible uptake of transforming deoxyribonucleic acid by the gonococcus, but fail to provide evidence for other types of competence factors.