In vitro study of continuous wave Doppler spectral changes resulting from stenoses and bulbs

Quantitative analysis of continuous wave (CW) Doppler spectra by measurements of peak frequency and spectral broadening is an important non-invasive method for detecting disturbed flow caused by carotid arterial stenosis. It is known that severe stenoses can be detected; however, the spectral changes associated with minor or moderate stenoses may not be detected or can potentially be confused with those produced by flow disturbances in the normal carotid bulb. In order to determine if the flow disturbances in a normal bulb and those associated with a minor stenosis produce significant spectral changes, Doppler spectra were recorded from straight tubes with bulbs or stenoses in an in vitro model with steady flow rates of 400, 600, and 800 cc/min (Reynolds numbers of 1700, 2600, and 3500). Stenoses greater than approximately 30% cross-sectional area were associated with an increased peak frequency and increased spectral broadening as measured by spectral broadening index (SBI), coefficient of variation (CV), coefficient of skewedness (CS) and coefficient of kurtosis (CK). Stenoses less than 30% were not detected. With flow rates of 400 and 600 cc/min, the presence of a bulb did not affect peak frequency or the extent of spectral broadening. With a higher flow rate (800 cc/min), there was an increase in SBI, CV and CS but no increase in peak frequency. Based on the results of these in vitro steady flow experiments in straight tubes, we conclude that increased peak frequency and spectral broadening are the result of a stenosis greater than 30% cross-sectional area.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrochemical evidence of the adsorption of alkanethiols on two sites on Ag(111)

We present spectroscopic and electrochemical results consistent with the adsorption of alkanethiols on two sites and the formation of a very densely packed, stable, monolayer on Ag(111). A surface coverage of alkanethiols of 8.5 (±0.4)×10^?10 mol cm^?2 was calculated from the charge associated with the reduction of a monolayer of alkanethiols. Alkanethiol modified Ag(111) electrodes were found to have lower capacitances than the alkanethiol modified Au(111) electrodes. The lower capacitances are due to the higher surface concentration of alkanethiols on Ag(111). The very low intensity of the methylene CH stretching bands of alkanethiols with alkane chains of four to nine carbons chemisorbed on Ag(111) suggests a vertical orientation of all-trans alkane chains. No vibrational evidence of oxidation of the chemisorbed alkanethiols was found after exposure to air for up to 6 weeks. A fine structure consisting of two current peaks was observed in all cyclic voltammograms of the reduction of chemisorbed alkanethiols. This revealed that the reduction of chemisorbed alkanethiols occurs in two steps on Ag(111). Chronoamperometric measurements also support a two-step reductive desorption of alkanethiols. The high surface concentration of alkanethiols and the orientation of the alkane chains suggest that the fine structure in the voltammograms is due to the reduction of the alkanethiols from two adsorption sites.     

Surrogate markers for atherosclerosis in overweight subjects with atherogenic dyslipidemia: the GEMS project

Metabolic syndrome is a constellation of major risk factors for cardiovascular disease. In affected individuals with this syndrome, the independent contribution of low high-density lipoprotein-cholesterol and increased triglyceride levels to the development of atherosclerosis remains to be clarified. We assessed the relationship between these 2 parameters and several surrogate markers for atherosclerosis. One hundred and twenty overweight cases, defined as having high-density lipoprotein-cholesterol (or=75 percentile) were compared with 120 discordant overweight controls defined on lipid values (high-density lipoprotein-cholesterol >or=50 percentile and triglycerides 相似文献   

Chronic insomnia, quality-of-life, and utility scores: comparison with good sleepers in a cross-sectional international survey

Background

Chronic insomnia has a recognized impact on health-related quality-of-life (HRQoL) but data on utility scores across countries are lacking. The objective of the present study was to assess health related quality of life (HRQoL) and utility scores in individuals from three different countries (USA, France, and Japan), comparing sufferers of chronic insomnia to good sleepers.

Methods

A cross-sectional survey (SLEEPI-i) of 4067 persons in the US (n = 1298; 478 good sleepers and 820 patients with insomnia), France (n = 1858; 998 good sleepers and 860 patients with insomnia) and Japan (n = 911; 506 good sleepers and 405 patients with insomnia). Enrollment and data collection using consumer panels were web-based in the US and France, and gathered via a postal survey in Japan. People with chronic insomnia (>6 months) were selected based on Insomnia Severity Index scores (ISI). Severity of insomnia was assessed using the ISI score and HRQoL was assessed using the self-administered Short-Form SF-36 Health Survey. Utility scores were derived using the algorithm developed by Brazier et al. Multivariate analyses were used to adjust for potential confounding factors.

Results

In all countries, people with chronic insomnia (40% treated) reported lower SF-36 scores in each of eight domains compared with good sleepers (P < .0001). Chronic insomnia was associated with significantly lower utility scores compared with good sleepers (mean scores 0.63 versus 0.72 in the US, 0.57 versus 0.67 in France, and 0.67 versus 0.77 in Japan, P < .0001).

Conclusions

This survey suggests that chronic insomnia is associated with significant impairment of HRQoL and decreased utilities across the different geographical regions studied.     

The standardized exposure index for digital radiography: an opportunity for optimization of radiation dose to the pediatric population

The exposure index is currently a method by which digital radiography manufacturers provide feedback to the technologist regarding the estimated exposure on the detector, as a surrogate for image signal-to-noise ratio and an indirect indication of digital image quality. Unfortunately, there are as many exposure index values and methods as there are manufacturers, and in an environment with multiple vendors and a need to share data across institutions and dose registry databases, the situation is complicated. Fortunately, a new exposure index of digital X-ray imaging systems has been implemented. Developed concurrently by the International Electrotechnical Commission and the American Association of Physicists in Medicine in cooperation with digital radiography system manufacturers, the index has been implemented as an international standard. As explained, the exposure index does not indicate patient dose but rather a linearly proportional estimate of the incident radiation exposure to the detector. However, the use of the standardized exposure index and its associated target exposure index and deviation index values will likely lead to improved technologist performance in terms of uniformity and use of optimized radiographic techniques, leading to safer care of children needing radiographic examinations. Radiologists will benefit from standardized terminology, and institutions and clinics will be able to compare exposure index values with others through a national dose index registry database now under development. The Alliance for Radiation Safety in Pediatric Imaging, in its role as a benefactor of and advocate for the pediatric patient, is using the Image Gently campaign to disseminate information regarding the exposure index standard for digital radiography so that these benefits can be achieved in a rapid and effective manner.     

Acetylcholine release is elicited in the visual cortex, but not in the prefrontal cortex, by patterned visual stimulation: a dual in vivo microdialysis study with functional correlates in the rat brain

By its projections to the primary visual and the prefrontal cortices, the basal forebrain cholinergic system is involved in cognitive processing of sensory stimuli. It has been suggested that visual stimulus-induced cholinergic activation of the visual cortex may exert a permissive role on thalamocortical inputs. However, it is not known if visual stimulation elicits cholinergic activation of high-order brain areas in the absence of attentional need. In the present study, we measured the effects of patterned visual stimulation (horizontal grating) on the release of acetylcholine with dual-probe in vivo microdialysis in the visual and the prefrontal cortices of anesthetized rats. We also used retrograde tracing to determine the anatomical relationships of cholinergic neurons with neurons of the visual system and the prefrontal cortex. Finally, we evaluated a functional correlate of this stimulation, namely c-fos immunolabeling. Patterned visual stimulation elicited significant increases in acetylcholine release in the visual cortex, accompanied by an increased number of c-fos immunoreactive neurons in this brain area. In contrast, in the prefrontal cortex, neither the level of acetylcholine release nor the number of c-fos immunoreactive neurons was significantly changed because of the stimulation. Cholinergic basal forebrain neurons projecting to the visual or the prefrontal cortices were both localized within the horizontal limb of the diagonal band of Broca but were not immunoreactive for c-fos during visual stimulation. No parts of the visual system were found to directly project to these basal forebrain neurons. These results suggest the differential involvement of cholinergic projections in the integration of sensory stimuli, depending on the level of activity of the targeted cortical area.