Stabilization of Liner Implosions via a Dynamic Screw Pinch.

Magnetically driven implosions are susceptible to magnetohydrodynamic instabilities, including the magneto-Rayleigh-Taylor instability (MRTI). To reduce MRTI growth in solid-metal liner implosions, the use of a dynamic screw pinch (DSP) has been proposed [P. F. Schmit et al., Phys. Rev. Lett. 117, 205001 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.205001]. In a DSP configuration, a helical return-current structure surrounds the liner, resulting in a helical magnetic field that drives the implosion. Here, we present the first experimental tests of a solid-metal liner implosion driven by a DSP. Using the 1-MA, 100-200-ns COBRA pulsed-power driver, we tested three DSP cases (with peak axial magnetic fields of 2 T, 14 T, and 20 T) and a standard z-pinch (SZP) case (with a straight return-current structure and thus zero axial field). The liners had an initial radius of 3.2 mm and were made from 650-nm-thick aluminum foil. Images collected during the experiments reveal that helical MRTI modes developed in the DSP cases, while nonhelical (azimuthally symmetric) MRTI modes developed in the SZP case. Additionally, the MRTI amplitudes for the 14-T and 20-T DSP cases were smaller than in the SZP case. Specifically, when the liner had imploded to half of its initial radius, the MRTI amplitudes for the SZP case and for the 14-T and 20-T DSP cases were, respectively, 1.1±0.3 mm, 0.7±0.2 mm, and 0.3±0.1 mm. Relative to the SZP, the stabilization obtained using the DSP agrees reasonably well with theoretical estimates.

Peanut avoidance and peanut allergy diagnosis in siblings of peanut allergic children.

BACKGROUND: Studies suggest that siblings of children with peanut allergy (PNA) have a higher prevalence of PNA than the general population. OBJECTIVES: The Canadian Peanut Allergy Registry was used to assess the percentage of siblings of registered index PNA children who were 1) never exposed to peanut or 2) reportedly diagnosed with PNA by a physician without either a history of allergic reaction or a confirmatory testing. Sociodemographic and clinical factors that may be associated with either outcome were evaluated. METHODS: Parents completed a questionnaire on siblings' sociodemographic characteristics, exposure and reaction to peanut, confirmatory tests performed and whether PNA had been diagnosed. RESULTS: Of 932 Registry families, 748 families responded, representing 922 siblings. 13.6% of siblings had never been exposed to peanut, 70.4% (n = 88) of which were born after the index child. Almost 9% of siblings (80) were reported as PNA, but almost half of this group had no history of an allergic reaction to peanut, including five children who also had no testing to confirm PNA. Of these 5, 4 were born after PNA diagnosis in the index child. In a multivariate regression analysis for siblings at least 3 years old, those born after PNA diagnosis in the index child were more likely to have never been exposed to peanut. In a univariate analysis, siblings born after the diagnosis of PNA in the index child were more likely to be diagnosed with PNA without supportive history or confirmatory testing. CONCLUSIONS AND CLINICAL RELEVANCE: These data estimate that more than 10% of siblings of PNA patients will avoid peanut and that siblings born after the diagnosis of PNA in an index child are more likely to have never been exposed. Educational programs and guidelines that caution against unnecessary avoidance are required.

Lack of efficacy of humidification in the treatment of croup: Why do physicians persist in using an unproven modality?

BACKGROUND: Humidification is a time-honoured therapy for childhood croup (acute laryngotracheobronchitis). Despite a paucity of evidence supporting its use, many physicians, nurses and parents still apply this treatment. Our objective was to summarize available evidence and assess the rationale for the ongoing use of humidity to treat childhood croup. METHODS: Searches of both MEDLINE and the Cochrane Database were conducted for English-language original or review literature on the treatment of croup with humidity, for the years 1966-1999. RESULTS: Only 2 published studies have attempted to evaluate humidification therapy for croup, and none has been published since 1984. There is no published evidence to support the commonly held empirical view that humidity helps alleviate the symptoms of childhood croup, and no understanding of which factors of moisture or temperature affect patient outcomes. Risks may include scalding and unnecessary discomfort. INTERPRETATION: There is no strong evidence supporting the use of humidity in the treatment of croup. Although such treatment is still widely used, it is not without risk, and further trials are required to address its efficacy.

A simple "new" method to accelerate clearance of carbon monoxide.

The currently recommended prehospital treatment for carbon monoxide (CO) poisoning is administration of 100% O(2). We have shown in dogs that normocapnic hyperpnea with O(2) further accelerates CO elimination. The purpose of this study was to examine the relation between minute ventilation (V E) and the rate of elimination of CO in humans. Seven healthy male volunteers were exposed to CO (400 to 1,000 ppm) in air until their carboxyhemoglobin (COHb) levels reached 10 to 12%. They then breathed either 100% O(2) at resting V E (4.3 to 9.0 L min) for 60 min or O(2) containing 4.5 to 4.8% CO(2) (to maintain normocapnia) at two to six times resting V E for 90 min. The half-time of the decrease in COHb fell from 78 +/- 24 min (mean +/- SD) during resting V E with 100% O(2) to 31 +/- 6 min (p < 0. 001) during normocapnic hyperpnea with O(2). The relation between V E and the half-time of COHb reduction approximated a rectangular hyperbola. Because both the method and circuit are simple, this approach may enhance the first-aid treatment of CO poisoning.

Isocapnic hyperpnea accelerates carbon monoxide elimination.

A major impediment to the use of hyperpnea in the treatment of CO poisoning is the development of hypocapnia or discomfort of CO2 inhalation. We examined the effect of nonrebreathing isocapnic hyperpnea on the rate of decrease of carboxyhemoglobin levels (COHb) in five pentobarbital-anesthetized ventilated dogs first exposed to CO and then ventilated with room air at normocapnia (control). They were then ventilated with 100% O2 at control ventilation, and at six times control ventilation without hypocapnia ("isocapnic hyperpnea") for at least 42 min at each ventilator setting. We measured blood gases and COHb. At control ventilation, the half-time for elimination of COHb (t1/2) was 212 +/- 17 min (mean +/- SD) on room air and 42 +/- 3 min on 100% O2. The t1/2 decreased to 18 +/- 2 min (p < 0.0005) during isocapnic hyperpnea. In two similarly prepared dogs treated with hyperbaric O2, the t1/2 were 20 and 28 min. We conclude that isocapnic hyperpnea more than doubles the rate of COHb elimination induced by normal ventilation with 100% O2. Isocapnic hyperpnea could improve the efficacy of the standard treatment of CO poisoning, 100% O2 at atmospheric or increased pressures.