Concealed mechanical bradycardia: an indication for permanent pacemaker implantation

We report a 51-year-old man with severe ischemic cardiomyopathy and heart failure in whom incessant bigeminal ventricular ectopy failed to generate a detectable arterial pressure. This created a mechanical bradycardia despite an adequate electrical heart rate. Dual chamber pacing increased the effective heart rate and allowed discontinuation of an intraaortic balloon pump from which the patient could not otherwise be weaned.     

A rapid High Performance Liquid Chromatographic (HPLC) method for the simultaneous determination of seven UV filters found in sunscreen and cosmetics

A rapid High Performance Liquid Chromatographic (HPLC) method was developed for the simultaneous determination of seven Ultra Violet (UV) filters most commonly found in cosmetics and sunscreen. The object of the method development was to provide a reliable rapid method, that would simultaneously separate a combination of the UV Filters, most commonly found in cosmetics and sunscreen products, utilizing a minimum of environmentally friendly solvents. The compounds separated were: benzophenone 3 (BZ3), methylbenzildene camphor (MBC), octyl dimethyl PABA (ODP), octocrylene (OCR), octyl methoxycinnamate (OMC), butyl – methoxydibenzoylmethane (BDM) and octyl salicylate (OS). An adjusted mobile phase consisting of ethanol and 1% acetic acid, combined with a Thermo Hypersil C₁₈ BDS 3 micron column resulted in a method, which allowed the analysis of the seven compounds in seven minutes. The proposed method was validated utilising the International Congress on Harmonisation (ICH) and the Food and Drug Administration (FDA) guidelines. All parameters examined were found to be well within the stated guidelines.     

Human visual system-based image enhancement and logarithmic contrast measure.

Varying scene illumination poses many challenging problems for machine vision systems. One such issue is developing global enhancement methods that work effectively across the varying illumination. In this paper, we introduce two novel image enhancement algorithms: edge-preserving contrast enhancement, which is able to better preserve edge details while enhancing contrast in images with varying illumination, and a novel multihistogram equalization method which utilizes the human visual system (HVS) to segment the image, allowing a fast and efficient correction of nonuniform illumination. We then extend this HVS-based multihistogram equalization approach to create a general enhancement method that can utilize any combination of enhancement algorithms for an improved performance. Additionally, we propose new quantitative measures of image enhancement, called the logarithmic Michelson contrast measure (AME) and the logarithmic AME by entropy. Many image enhancement methods require selection of operating parameters, which are typically chosen using subjective methods, but these new measures allow for automated selection. We present experimental results for these methods and make a comparison against other leading algorithms.     

Two-Wavelength switching of luciferase activity using caged compounds

Firefly luciferase, luciferin, 1-(3,4-dimethoxy-6-nitrophenyl) elthyl ATP and 1-(2-nitrophenyl) ethyl acetic acid were immobilised in an agarose gel matrix. By illuminating the gel with 350 nm light through a mask, a positive bioluminescent pattern was written on to the gel by releasing ATP in the illuminated areas. The gel was then illuminated with a brpadbnand UV light through a second mask to release acetic acid, lowering the local pH and deactivating the enzyme. This produced a negative image of the second mask superimposed on the positive image of the first mask. The system represents a two-wavelength switch in which one wavelength of light activates the enzyme while a second deactivates it. This demonstrates the feasibility of using biological molecules as logic element in future devices.     

Age of learning affects rate-dependent processing of stops in a second language

The aim of this study was to assess the effect of speaking rate changes on the perception of English stop consonants by four groups of subjects: English and Spanish monolinguals, 'early' Spanish/English bilinguals who learned English in childhood, and 'late' bilinguals who learned English in adulthood. Subjects identified, and then later rated for goodness as exemplars of the English /p/ category, the members of two voice onset time (VOT) continua. The English monolinguals identified a well-defined range of VOT stimuli as English /p/, and stimuli with longer VOT values as 'exaggerated' instances of English /p/. Their goodness ratings increased as VOT increased, then showed a systematic decrease as VOT began to exceed values typical for English /p/. The English monolinguals' goodness ratings also varied systematically as a function of speaking rate, which was simulated in the two continua by varying syllable duration. The Spanish monolinguals, on the other hand, failed to consistently identify any of the stimuli as English /p/. Although speaking rate influenced their goodness ratings, the Spanish monolinguals' rate effects differed significantly from the English monolinguals'. The early bilinguals resembled the English monolinguals, and differed from the Spanish monolinguals to a greater extent than did the late Spanish/English bilinguals. This was taken as support for the hypothesis that early bilinguals are more likely than are late bilinguals to establish new phonetic categories for stop consonants in a second language.