The use of external, noninvasive pacing for the termination of supraventricular tachycardia in the emergency department setting

STUDY OBJECTIVE: To determine the potential feasibility of external cardiac pacing for the termination of sustained supraventricular tachycardia in the emergency department setting. TYPE OF PARTICIPANTS: Three men and two women (mean age, 34 years) who presented to the ED with a narrow-complex, hemodynamically stable tachycardia that was later proven to be supraventricular in origin. INTERVENTION: Each patient underwent external overdrive pacing using a modified external pacemaker at a pulse amplitude of 120 mA and a rate between 240 and 280 pulses per minute. RESULTS: In four patients, external cardiac pacing was able to successfully terminate the tachycardia without complication. In one patient, the pacemaker was not able to terminate the tachycardia. CONCLUSION: We conclude that external, noninvasive pacing is a feasible means of terminating supraventricular tachycardia in the ED setting.     

Effect of steel microfibers on corrosion of steel reinforcing bars

Steel microfiber reinforcement was previously found to be successful in mitigating alkali silica reaction in concrete, an expansive phenomenon. The use of steel microfibers to mitigate rebar corrosion, another expansive reaction, was investigated. Mortar specimens with and without steel microfiber reinforcement were exposed to a corrosive environment. All specimens were prepared with water/cement ratios of both 0.40 and 0.55, cured for 28 days, and then submerged in aerated 3.5% NaCl solution. The corrosion behavior of the specimens was monitored via electrochemical measurements. Three types of electrochemical tests were performed: corrosion potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Chloride concentration measurements and microscopic analysis were performed as well. The polarization curves, Tafel, and polarization resistance measurements indicate that the steel rebar in the microfiber-reinforced mortars are more resistant to corrosion than the rebar in the control mortars, despite higher chloride concentrations. Furthermore, the steel microfiber-reinforced cement based materials have a lower electrolytic resistance. This is not indicative of a higher corrosion rate, which would be the case if it had been observed in standard mortar specimens.     

Single-fibre polymer composites

We have used Raman spectroscopy to measure the axial stress distribution along a fibre during a quasi-static single fibre pull-out test. The stress distribution at the debonding front during the progress of debonding gives the maximum interfacial shear strength _s directly. In addition, the stress distribution along the fibre after debonding can be used to evaluate the interfacial normal stress and the frictional coefficient. For the plasma treated high modulus polyethylene (PE) fibres used here, _s is found to be 28 MPa by this method, while the apparent mean interfacial shear strength _a obtained from the regular single fibre pull-out test varies from 3 to 15 MPa with the fibre embedded length I _e. Stress distributions derived from the shear-lag theory fit the experimental data for fully bonded fibres well, giving values for the shear-lag constant K and the stress transfer length 1/ [1]. According to the shear-lag theory, _s = l _eacoth(l _e). If can be found for a given system from Raman spectroscopy, _s can be evaluated from the pull-out test using this equation.The regular pull-out tests, corrected for residual stress and interfacial friction, give the same _s but not the same or pull-out load as the slower Raman test. The shear-lag constant K can be expressed as a function of the matrix shear modulus and geometric terms. One of these terms is the effective interfacial radius, r _e, the radius at which the strain in the matrix equals the average matrix strain. Raman measurements indicate that r _e is small, only four times the fibre radius. This result is supported by polarizing optical microscopy. The model of Greszczuk [2], which assumes a uniform shear within an effective interaction thickness b _i, gives a similar result. We find that b _i = 20 m, about twice the fibre radius. Using the pull-out test data, as for other fibre composites, b _i and r _e predicted by shear-lag theories do not agree with the results of microscopy to this extent. In these cases _s is much larger than the yield strength of the matrix and as neither treatment considers plastic deformation of the matrix agreement should not be expected.     

Gel-drawn fibres of poly(vinyl alcohol)

Semi-crystalline gels of several samples of poly(vinyl alcohol) were made from solutions in which the polymer concentration varied from 2.0 to 15.0%. Entanglement density in the material was in this way reduced from the melt entanglement density. When gels were partially dried and drawn isothermally the maximum draw ratio increased with drawing temperature up to 11 to 14 at 140 to 180 C. A meltcast film could be drawn to 6.8 times at 140 C. Drawn material had a crystallinity of 55 to 80%, while that of isotropic material was 20 to 55%. Gels of lower initial concentration (lower entanglement density) could be drawn to greater extensions at a given draw temperature and had better mechanical properties. Young's modulus increased with draw ratio to values very close to those for polyethylene fibres drawn by the same amount. Young's modulus was independent of drawing temperature or degree of crystallinity, but on comparing drawn gels of the same draw ratio, crystallinity and crystalline orientation, those of lower entanglement density had a higher Young's modulus.     

Field Evaluation of Crushed Glass–Dredged Material Blends

Based on the laboratory results reported in a companion paper, three crushed glass–dredged material (CG–DM) blends were prepared and evaluated in the field to explore the feasibility of using CG–DM blends in general, embankment and structural fill applications. A trailer-mounted pugmill successfully prepared 20/80, 50/50, and 80/20 CG–DM blends (dry weight percent CG content reported first) within a tolerance of ±5 dry % by weight of the targeted percentages. Blending criteria were routinely met at pugmill throughputs up to 1,500?m3/day. The constructed 20/80 CG–DM embankment was compacted to a minimum of 90% modified Proctor compaction, whereas the 50/50 and 80/20 CG–DM embankments were constructed to a minimum of 95% modified Proctor compaction. Twenty to 80% CG addition to DM resulted in 1.5–5.5?kN/m3 increases in field dry densities above 100% DM, densities not achievable with other DM stabilization techniques such as Portland cement, fly ash, and/or lime (PC/FA/lime) addition. CG substantially improved the workability of DM allowing construction with conventional equipment and three person crew while achieving very consistent and reproducible results during a timeline of frequent and heavy precipitation events. The 20/80, 50/50, and 80/20 CG–DM embankments were characterized by average cone tip resistances on the order of 1.0, 1.5, and 2.0?MPa, respectively. An environmental evaluation of 100% CG, DM and 50/50 CG–DM blend samples coupled with an economic analysis of a scaled-up commercial application illustrated that the CG–DM blending approach is potentially more cost effective than PC/FA/lime stabilization approaches. These features of CG–DM blending make the process attractive for use in urban and industrial settings.     

Origin of contrast effects in the electron microscopy of polymers

When polyethylene single crystals are mounted on a substrate less rigid than the usual evaporated carbon, they undergo considerable dimensional changes in the electron beam. In particular, crystals mounted on collodion expand by 22±2% in every direction in the plane of the lamellae. No induction period is observed and the expansion continues after all crystalline order has been destroyed. Since irradiation increases the density of bulk polyethylene, it is presumed that the lamellae become thinner as they expand. A similar but lesser expansion occurs on irradiation in the electron microscope at liquid helium temperatures, and when crystals are mounted on formvar films. In a solution grown lamellar crystal of polyethylene, most of each molecule is straight and aligned along thec axis, which is nearly perpendicular to the plane of the lamella. Radiation damage in the electron microscope introduces disorder, and these results imply that the effect of this disorder is to reduce the mean molecular dimension alongc, and increase it in the plane perpendicular toc. Polymer chains are generally highly oriented in crystalline regions, so this qualitative explanation would imply similar effects in other systems. These effects have important implications for the contrast observed in the electron microscopy of polymers.     

Attribution difficulty and memory for attribution-relevant information.

Compared the processing and retrieval of attribution-relevant information when the attributional inference is easy or difficult to make. Ss attributed behavioral events to the person or to the situation, based on several items of context information. Each context sentence implied either the person or the entity as causal agent. When the attributional inference was difficult to make (an equal number of context sentences implied actor and entity as the causal agent), Ss recalled more of the behavioral events, recalled more context sentences, and were less confident in their attributions than when the attributional inference was easy to make (most context sentences implied the same causal agent). Ss also recalled context information that was implicationally incongruent with the majority of the other context sentences with a higher probability than when that same information was implicationally congruent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increasing automobile seat belt use: An intervention emphasizing risk susceptibility.

A seat-belt (SB) promotion program was implemented that was based on the finding by the 1st author (1984) that many people fail to take their SB use into account when thinking about their risk of being injured in an automobile accident. The goal of the program was to increase SB use by making the link between SB use and personal risk more salient. The program was instituted at the headquarters of a large corporation. Five weeks of baseline observations were followed by 1-wk active intervention program composed of stickers for car dashboards, permanent signs in the parking deck, and temporary signs in the cafeteria. Six weeks of posttreatment observations showed that the number of people using SBs increased 31% at one entrance and 7% at the other, with both increases statistically significant. SB use at a control site was stable during this period. Six months following the intervention, the number of people using SBs had climbed 61% above baseline at one entrance and 33% above the baseline at the other. Interviews before and after the program did not reveal the anticipated increase in spontaneous references to SB use as a risk factor for auto injury. Possible reasons for the success of the intervention and for the differential impact at 2 parking deck entrances are discussed. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How to manage quality assurance at laboratories? A specialist''s examination is necessary in the specialty of clinical chemistry

Two thousand plus (2,000+) assisted laser surgical procedures were performed between July 1986 and November 1993. Multiwavelength specialties: Argon, CO2 and NdYAG usage include: general surgery, thoracic surgery, neurosurgery, ophthalmology, and gynecology. 65% of the patients were female whose ages range from 6 to 105 years. Endoscopic vs. handheld procedures ratios 1:1. In 95% of the cases attended, the procedures were performed for benign conditions. The office hospital usage distribution was 60-40%. The office morbidity was 0.8% (16 out of 2,000 cases) and a mortality of 0.15% (3 out of 2,000 cases). A reported 100% safety compliance was seen. Laser assisted surgery is a safe, effective and reliable option available to the surgeon's armamentarium. It appears that in some procedures it will allow shorter hospital stays and an earlier return of the patient to his/her normal routine.     

Acid-base and electrolyte effects of shortening steeplechase in a three-day-event

This study was designed to characterise the acid-base and electrolyte effects of shortening the distance required during steeplechase (Phase B) in the face of hot and humid weather conditions during a treadmill-simulated Speed and Endurance test. Eight conditioned Thoroughbred horses underwent 3 randomised permutations of a standardised exercise test on a high speed treadmill. Each test consisted of trotting at 3.7 m/s for 10 min (Phase A); galloping at 11 m/s (Phase B) for 4 (cool laboratory conditions), 3 (hot and humid), or 2 (hot and humid) min; trotting at 3.7 m/s for 30 min (Phase C); and walking at 1.8 m/s for 10 min (Phase X). The treadmill slope was 4% for trotting and galloping and 0% for walking. Cool versus hot and humid conditions were 20 degrees C and 50-60% relative humidity vs. 26-28 degrees C and 80-85% relative humidity, respectively. Pulmonary artery blood samples were obtained at rest prior to exercise (Rest); at the end of Phases A (A10) and B (B2-4); at 10 (C10), 20 (C20) and 30 (C30) min through Phase C; and at 5 min into Phase X (X5). Additional samples for lactate (LA) and glucose (GLC) analysis were obtained 5 min into Phase C (C5) and at the end of Phase X (X10). Samples were analysed for packed cell volume (PCV), haemoglobin (HB), total plasma protein (TP), sodium (Na), potassium (K), chloride (Cl), anion gap (AG), plasma glucose (GLC) and lactate (LA), pH, PCO2, bicarbonate (HCO3) and base excess (BE). Shortening steeplechase distance by 50% under hot and humid conditions (2 min B) resulted in a consistent return to control measurements (4 min B) only for plasma LA. Changes in PCV, HB, TP, K and Cl were related more to the longer galloping distance in the 4 min B trials than to hot vs. cold laboratory conditions. Alternatively, changes in LA, GLC, pH, PCO2 and AG were more related to hot and humid laboratory conditions than they were to galloping distance. These latter variables, when combined with physical measures such as core temperature, bodyweight loss, point of fatigue on Phase C and recovery heart rates may serve as the best monitors of positive responses in future studies of proposed modifications to Phase C, rather than those variables which were more distance than weather-related.