Dielectric-barrier discharges in two-dimensional lattice potentials.

We use a pin-grid electrode to introduce a corrugated electrical potential into a planar dielectric-barrier discharge (DBD) system, so that the amplitude of the applied electric field has the profile of a two-dimensional square lattice. The lattice potential provides a template for the spatial distribution of plasma filaments in the system and has pronounced effects on the patterns that can form. The positions at which filaments become localized within the lattice unit cell vary with the width of the discharge gap. The patterns that appear when filaments either overfill or underfill the lattice are reminiscent of those observed in other physical systems involving 2D lattices. We suggest that the connection between lattice-driven DBDs and other areas of physics may benefit from the further development of models that treat plasma filaments as interacting particles.

Spontaneous pattern formation in an effectively one-dimensional dielectric-barrier discharge system

In a dielectric-barrier discharge between diametrically opposite sides of a narrow tube, discharge filaments stabilize at regular intervals along the tube's length. Three types of periodic patterns are observed, as is a disordered state in which filaments fire at apparently random positions and times. Time-resolved current measurements indicate that for each spatial pattern, a particular number of discharge stages occur during the voltage half-cycle. A preliminary model of the pattern-formation dynamics is described, motivating further work on time-resolved imaging and investigations of surface charge distributions.

Time-resolved imaging of spatiotemporal patterns in a one-dimensional dielectric-barrier discharge system.

A makeshift streak camera produces time-resolved images of filament patterns in a one-dimensional dielectric-barrier discharge system. The images reveal a variety of spatial and temporal structures, including temporally distinct discharge stages that occur at specific phases of the 12.5 kHz driving oscillation and spatially periodic filament arrays that are generated during the discharge stages. The data answer recent questions regarding time-averaged images of a similar system. Most notably, all but the simplest time-averaged images are due to the integration of multiple filament patterns generated in different discharge stages. Disordered states of the system are also examined. Some of these are spatially disordered but display temporal structure; others appear to lack both spatial and temporal order. Possibilities are suggested for investigations of surface-charge spreading and pattern stability in similar systems.

Childhood risks from the ferret.

The ferret is becoming an increasingly popular pet, yet the dangers of ferret ownership remain unrecognized by physicians and the general public. Reported are three incidents of ferret attacks in a 3-month period of time. The risk of attack is greatest in infants and small children. Wounds caused by ferret attacks must be evaluated for injury, infection, and rabies prophylaxis. Such attacks should be reported to animal control authorities. Physicians need to recognize the ferret as a risk to children.

Atropine methylbromide and glycopyrrolate. A comparative study during reversal of neuromuscular block.

Two quaternary anticholinergics, atropine methylbromide (methylatropine bromide, MAB) and glycopyrrolate (ROBINUL) were compared as adjuncts to neostigmine for the reversal of residual nondepolarising neuromuscular block. MAB 0.75 mg in combination with neostigmine 2 mg produced a marked initial rise in heart rate. This was significantly greater than that produced by the administration of glycopyrrolate 0.4 mg with neostigmine. The antisialogogue effects of the two anticholinergics were identical and the central nervous system status of the patients was similar. It is concluded that, with the doses used in this study, glycopyrrolate is a superior alternative to MAB and is the drug of choice if a quaternary ammonium anticholinergic is required.

Insulinoma: diagnosis and treatment.

A patient with an insulinoma, although rare, can be an interesting challenge to the critical care nurse. Recognition of signs and symptoms pointing to possible insulinoma is vital to prevent delays in appropriate treatment. Intensive nursing care is necessary in the preoperative, intraoperative, and postoperative stages of this condition.

Cesarean section rate: a comparison between family physicians and obstetricians.

This retrospective study compared the cesarean section rates of family physicians and obstetricians for low-risk pregnancies. The study populations (n = 492) were demographically similar. The overall cesarean section rate for the study was 7.5%. Chi-square analysis revealed a statistically significant higher rate of cesarean section for obstetricians compared to family physicians. Obstetricians were overall three times more likely to deliver by cesarean section than were family physicians (11.3% compared to 3.8%). This pattern persisted for normal-length Stage I and Stage II labors. Equal cesarean section rates were noted in prolonged labor patterns. The rate of fetal distress, meconium, or other complications was equal between family physicians and obstetricians; equivalent fetal outcomes and Apgar scores were noted. None of the studied patient factors explained the difference in cesarean section rates between family physicians and obstetricians.

Lifetime of the metastable 6s' [(1/2)](0) clock state in xenon.

To investigate the potential of a proposed optical frequency standard, we have measured the lifetime of the metastable 6s' [(1/2)](0) state in xenon. Magneto-optically trapped xenon atoms were prepared in the 6s' [(1/2)](0) state, and the time dependence of the vacuum-ultraviolet decay signature was analyzed. The total decay rate of 75(3) s(-1) is the sum of a 7.8(38)-s(-1) spontaneous emission rate (1-sigma uncertainties) and a much larger deexcitation rate that is due to a transition driven by room-temperature blackbody radiation.

Absolute Refractive Indices and Thermal Coefficients of Fused Silica and Calcium Fluoride Near 193 nm.

The refractive indices of several fused silica and calcium fluoride samples from different suppliers were measured with the minimum deviation method in the deep UV between 191 and 196 nm with a standard uncertainty of 7 ppm. For both materials the dispersion dn/dlambda near 193 nm and 20 degrees C was determined. In addition, we measured the thermal coefficients of the refractive index near 193 nm and between 15 and 25 degrees C.

Giant helium dimers produced by photoassociation of ultracold metastable atoms.

We produce giant, purely long-range helium dimers by photoassociation of metastable helium atoms in a magnetically trapped, ultracold cloud. The photoassociation laser is detuned close to the atomic 2(3)S1-2(3)P0 line and produces strong heating of the sample when resonant with molecular bound states. The temperature of the cloud serves as an indicator of the molecular spectrum. We report good agreement between our spectroscopic measurements and our calculations of the five bound states belonging to a 0(+)(u) purely long-range potential well. These previously unobserved states have classical inner turning points of about 150a(0) and outer turning points as large as 1150a(0).