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PubMed1986

Impaired hypoxic ventilatory drive in diabetic patients with autonomic neuropathy.

The mortality of diabetic patients with autonomic neuropathy (DAN) is higher than that in those without autonomic neuropathy (DM). To test the hypothesis that this may be due to respiratory rather than cardiac dysfunction, we evaluated ventilatory responses to isocapnic-hypoxic and hyperoxic-hypercapnic conditions in 14 diabetic patients (8 DAN and 6 DM) and compared the results with those in 8 normal subjects. In all groups tested there was a significant linear correlation between end-tidal CO2 and minute ventilation and between end-tidal CO2 and mouth occlusion pressure (p100), as an index of the drive to breathe. There were no significant differences between the slopes and intercepts in the groups tested. A significant linear correlation was found between the O2 saturation and both minute ventilation and p100. There were no significant differences in the relationship between minute ventilation and O2 saturation, but the slopes and the intercepts of the regression lines of p100 vs. O2 saturation were significantly different in the DAN compared with those in normal subjects and DM. Additionally, five of eight patients with DAN lost their ventilatory drive and ventilatory responses to hypoxemia compared with only one of six DM. These findings suggest that a disorder in the ventilatory response to hypoxemia exists in some DAN.

Adult↗

PubMed2002

QUICKI is useful for following improvements in insulin sensitivity after therapy in patients with type 2 diabetes mellitus.

To investigate whether quantitative insulin sensitivity check index (QUICKI) would be useful as an index of insulin resistance during the clinical course of type 2 diabetes mellitus, correlation between QUICKI and the index of the euglycemic hyperinsulinemic clamp study [clamp insulin resistance (clamp IR)] was evaluated in 60 patients with type 2 diabetes mellitus before and after treatment. The therapy program consisted of diet (1440-1720 kcal/d) and exercise (walking 10,000 steps daily) for 6 wk. QUICKI and clamp IR were significantly correlated before (r = 0.598, P < 0.0001) and after (r = 0.583, P < 0.0001) treatment. Neither the slope nor the intercept of the linear correlation between QUICKI and clamp IR measured before treatment was significantly different from those measured after treatment (slopes; F = 0.002, P = 0.96, intercepts; F = 2.65, P = 0.11). During treatment, the values of both QUICKI (8% change; P < 0.0001) and clamp IR (38% change; P < 0.0001) significantly increased and their changes were significantly correlated (r = 0.415, P < 0.01). In conclusion, QUICKI may become a useful method for the follow-up of insulin resistance during the treatment of patients with type 2 diabetes mellitus.

Diabetes Mellitus, Type 2↗

PubMed1990

Depression of ventilatory responses to hypoxia and hypercapnia after pentamorphone.

Pentamorphone is a novel, potent opiate with rapid onset and short duration of action that has been reported to produce analgesia with limited depression of ventilation. We quantified the effects of pentamorphone (0.08, 0.24, and 0.60 micrograms/kg, IV) on ventilatory responses to hypercapnia and hypoxia in 12 healthy volunteers. Normoxic hypercapnia and isocapnic hypoxia were induced through a rebreathing method. During each test we recorded ventilation (VE), end tidal carbon dioxide tension (PETCO2), and arterial oxygen saturation (SO2) using a pulse oximeter. Using linear regression analysis of the relationships between VE and PCO2 during hypercapnia and VE and SO2 during hypoxia, we determined the slope (slope CO2) and intercept (V55), both at PCO2 55 mm Hg, and the slope (slope O2) and intercept (V80) at SO2 80%. Pentamorphone produced dose-related reductions in the ventilatory responses to both hypercapnia and hypoxia. Maximal depression occurred 15 min after injection of pentamorphone with all doses; the highest dose (0.60 micrograms/kg) produced 48% and 53% reductions in slope CO2 and V55, and 42% and 22% reductions in slope O2 and V80, respectively, relative to parallel saline controls. The respiratory depressant actions of pentamorphone were short-lived, as all parameters returned to baseline levels within 45 min. Testing was continued for 180 min after injection, but no delayed ventilatory effects were detected, and minimal side effects were reported, even at the highest dose. The findings confirm previous reports that pentamorphone has limited ventilatory depressant effects in humans in doses that (in other studies) have been associated with clinically effective analgesia.

Adult↗

PubMed2004

Vocal mechanics in Darwin's finches: correlation of beak gape and song frequency.

Recent studies of vocal mechanics in songbirds have identified a functional role for the beak in sound production. The vocal tract (trachea and beak) filters harmonic overtones from sounds produced by the syrinx, and birds can fine-tune vocal tract resonance properties through changes in beak gape. In this study, we examine patterns of beak gape during song production in seven species of Darwin's finches of the Galápagos Islands. Our principal goals were to characterize the relationship between beak gape and vocal frequency during song production and to explore the possible influence therein of diversity in beak morphology and body size. Birds were audio and video recorded (at 30 frames s(-1)) as they sang in the field, and 164 song sequences were analyzed. We found that song frequency regressed significantly and positively on beak gape for 38 of 56 individuals and for all seven species examined. This finding provides broad support for a resonance model of vocal tract function in Darwin's finches. Comparison among species revealed significant variation in regression y-intercept values. Body size correlated negatively with y-intercept values, although not at a statistically significant level. We failed to detect variation in regression slopes among finch species, although the regression slopes of Darwin's finch and two North American sparrow species were found to differ. Analysis within one species (Geospiza fortis) revealed significant inter-individual variation in regression parameters; these parameters did not correlate with song frequency features or plumage scores. Our results suggest that patterns of beak use during song production were conserved during the Darwin's finch adaptive radiation, despite the evolution of substantial variation in beak morphology and body size.

Acoustics↗

PubMed1995

Effects of solar radiation and wind speed on metabolic heat production by two mammals with contrasting coat colours.

We report the first empirical data describing the interactive effects of simultaneous changes in irradiance and convection on energy expenditure by live mammals. Whole-animal rates of solar heat gain and convective heat loss were measured for representatives of two ground squirrel species, Spermophilus lateralis and Spermophilus saturatus, that contrast in coloration. Radiative heat gain was quantified as the decrease in metabolic heat production caused by the animal's exposure to simulated solar radiation. Changes in convective heat loss were quantified as the variation in metabolic heat production caused by changes in wind speed. For both species, exposure to 780 W m-2 of simulated solar radiation significantly reduced metabolic heat production at all wind speeds measured. Reductions were greatest at lower wind speeds, reaching 42% in S. lateralis and 29% in S. saturatus. Solar heat gain, expressed per unit body surface area, did not differ significantly between the two species. This heat gain equalled 14-21% of the radiant energy intercepted by S. lateralis and 18-22% of that intercepted by S. saturatus. Body resistance, an index of animal insulation, declined by only 10% in S. saturatus and 13% in S. lateralis as wind speed increased from 0.5 to 4.0 ms-1. These data demonstrate that solar heat gain can be essentially constant, despite marked differences in animal coloration, and that variable exposure to wind and sunlight can have important consequences for both thermoregulatory stress experienced by animals and their patterns of energy allocation.

Animals↗

PubMed1997

Contractile properties of obliquely striated muscle from the mantle of squid (Alloteuthis subulata) and cuttlefish (Sepia officinalis)

The mechanical properties of obliquely striated muscle fibres were investigated using thin slices of mantle from squid Alloteuthis subulata and cuttlefish Sepia officinalis. Brief tetani or twitch stimuli were used as this pattern is likely to occur during jetting of the intact animal. The lengthactive force relationship for twitches and tetani (0.1s, 50Hz) was similar to that of vertebrate cross-striated fibres. Passive force at the length giving maximum tetanic force was 0.13±0.05P0 (mean ± s.e.m., N=6, where P0 is maximum isometric tetanus force) and increased steeply at longer lengths. Peak force in a brief isometric tetanus (0.2s, 100150Hz) was 262±16mNmm-2 cross-sectional area of wet tissue (N=6) for squid, and 226±19mNmm-2 (N=7) for cuttlefish. The forcevelocity relationship for isotonic shortening during twitches of squid mantle slices was a 'double hyperbolic' relationship as described for cross-striated fibres by Edman. Fitting Edman's equation to the results gave: P*=1.18±0.07, Vmax=2.43±0.11Ltws-1 and 1/G=0.69±0.13 (N=8), where P* is the intercept on the force axis expressed relative to Ptw, peak isometric twitch force, Vmax is the intercept on the velocity axis, Ltw is the length at which Ptw is produced and G is the constant expressing curvature. The large values of 1/G indicate that the forcevelocity relationship is not very curved. Maximum power was produced during shortening at 0.45±0.03Ptw (N=8). Maximum power during twitch contraction was 18.3±1.7mWg-1wetmass or, expressed in relative units, (V/Vmax)(P/Ptw), where V is the velocity during shortening and P is the force during shortening, was 0.16±0.01 (N=8), which is higher than that of many cross-striated locomotor muscles.

Journal Article↗

PubMed2002

The relationship between heart rate and rate of oxygen consumption in Galapagos marine iguanas (Amblyrhynchus cristatus) at two different temperatures.

To enable the use of heart rate (fH) for estimating field metabolic rate (FMR) in free-ranging Galapagos marine iguanas Amblyrhynchus cristatus, we determined the relationships between fH and mass-specific rate of oxygen consumption (sVO2) in seven iguanas before and during exercise on a treadmill and during the post-exercise period. The experiments were conducted at 27 and 35 degrees C, which are the temperatures that represent the lowest and highest average body temperatures of these animals in the field during summer. There were linear and significant relationships between fH and sVO2 at both temperatures (r(2)=0.86 and 0.91 at 27 degrees C and 36 degrees C, respectively). The slopes of the two regression lines did not differ, but there were significant differences in their intercepts. Thus, while heart rate can be used to predict FMR, the effects of temperature on the intercept of the regression must be taken into account when converting fH to sVO2. On the basis of our data, this can be achieved by applying the following formula: sVO2=0.0113fH-0.2983Q(10)((T(b)-27)/10). The increase in sVO2 with elevated body temperature results from an increase in fH, with no significant change in mass-specific oxygen pulse (sO(2) pulse; cardiac stroke volume times the difference in oxygen content between arterial and mixed venous blood). However, during exercise at both temperatures, increases in fH are insufficient to provide all of the additional O(2) required and there are also significant increases in the sO(2) pulses. This creates the situation whereby the same fH at the two temperatures can represent different values of sVO2.

Animals↗

PubMed1982

Solvent drag effect in drug intestinal absorption. II. Studies on drug absorption clearance and water influx.

In order to study the solvent drag effect, it was shown that back flux of absorbed drug from blood to intestinal lumen can be ignored but the back flux of water cannot. Then, apparent water influx was calculated as a new measure of solvent drag based on the model in which the back flux of D2O from blood to lumen was considered during absorption. Consequently, the correlation between drug absorption clearance (CLdrug) and apparent water influx was highly significant for benzoic acid, salicylic acid, p-hydroxybenzoic acid, antipyrine, cephalexin (CEX) and cefroxadine (CXD), resulting the high solvent drag effects were detected. The mean values of the slopes in the regression lines of CLdrug versus apparent water influx, i.e., sieving coefficients, were smaller than one for benzoic acid and salicylic acid, but the values were not significantly different from one. The sieving coefficients of the other drugs were significantly smaller than one. From these results, the molecular size dependence in the reflection from the intestinal membrane during absorption was clearly shown. And the intercepts of the regression lines including diffusive permeabilities were found to be significantly different from zero in CEX and CXD. On the basis of the sieving coefficients and intercept values obtained in such ways, the appropriateness of this model was discussed.

Animals↗

PubMed2003

Coronary flow--pressure relationship distal to epicardial stenosis.

To assess the coronary flow velocity - pressure relationship distal to a stenosis, and to evaluate the influence of microvascular abnormalities on this relationship, coronary flow velocity and coronary pressure were measured simultaneously in 38 patients (42 vessels). The instantaneous peak coronary flow velocity was plotted against the simultaneous measured distal coronary pressure, and the slope of the relation in the phase of diastolic flow decrease was calculated as the flow - pressure slope index (FPSI) and the X-intercept of the slope was calculated as zero-flow pressure (Pzf). The slope of the curve increased from 2.0+/-2.6 to 4.5+/-4.1 (p<0.001) and the X-intercept decreased from 42+/-16 to 27+/-13 mmHg (p<0.001) after papaverine injection. After successful coronary intervention, Pzf increased from 23+/-10 to 35+/-11 (p<0.01) and FPSI decreased from 6.8+/-5.1 to 3.5+/-1.8 (p<0.05). Pzf was higher in patients with an old myocardial infarction. It is feasible to assess the relationship between coronary flow and pressure distal to a stenosis in the clinical setting, and the relationship may provide additional information regarding coronary microcirculation. Microvascular abnormalities may play an important role in the coronary flow - pressure relationship distal to stenosis.

Aged↗

PubMed2006

Current assays overestimate 25-hydroxyvitamin D3 and underestimate 25-hydroxyvitamin D2 compared with HPLC: need for assay-specific decision limits and metabolite-specific assays.

BACKGROUND: Clinical demand for quick, cheap, precise and accurate 25-hydroxyvitamin D (25(OH)D) results has led to the development of a variety of assay methods. Lack of standardization of these methods has resulted in inter-method disagreement and challenged whether current assays recognize 25(OH)D2 and 25(OH)D3 equally. METHODS: We studied 172 patient samples from hip fracture cases using DiaSorin (DS) and IDS radioimmunoassays and the Nichols Advantage-automated protein binding assay (NA-CLPBA) in comparison to high-performance liquid chromatography (HPLC). 52 patient samples were analysed before and after three months treatment with 1000 IU of daily ergocalciferol (vitamin D2). RESULTS: Linear regression analysis in pre-treatment samples demonstrated a positive Y-intercept for each immunoassay compared with HPLC, and a slope that varied from 0.64 (IDS) to 0.97 (DS, NA-CLPBA). Bland Altman analysis demonstrated that all the three assays had a proportional positive bias relative to HPLC at values from 20 to 50 nmol/L. Regression analysis of post-treatment samples demonstrated a slope that was not significantly different from zero for the IDS and NA-CLPBA and 0.2 for the DS method, with a positive intercept for all assays of between 8 and 22, indicating less than 50% of 25(OH)D2 measured by HPLC was detected. CONCLUSIONS: These results demonstrate the need for assay-specific decision limits for 25(OH)D3 in order to define appropriate thresholds for treatment institution. Treatment with vitamin D2 may not be accurately monitored with any of the three commercial assays studied. Clinicians and biochemists who continue to use 25(OH)D assays need to be urgently informed of these issues.

25-Hydroxyvitamin D 2↗

PubMed2001

Acceptance of syphilis screening among residents of high-STD-risk Houston communities.

The purpose of this study was to assess the rate of acceptance of street-intercept syphilis screening and to identify barriers to screening among residents of 2 Houston communities with high rates of syphilis. Each of 691 people who participated in a street-intercept survey about syphilis was offered a free syphilis test immediately after completion of the survey. Acceptors of screening had blood drawn at the site of the interview, and blood samples were tested by rapid plasma reagin (RPR) and a confirmatory microhaemagglutination-Treponema pallidum (MHA-TP) for those with a positive antibody reaction on the RPR. On-street syphilis screening was accepted by 26% of the sample. The most common reason for refusal was not wanting to have blood drawn (19.5%). Among those screened for syphilis (n=148), seroprevalence was 19%, with 33% of women testing positive and 10% of men. The results of this study point to a need for increased case-finding, standard screening recommendations, and interventions targeting specific barriers to syphilis screening.

Adult↗

PubMed1989

[Effects of noise on sleep. Part 2. A case report of the effects of three levels of stationary sound on sleep parameters].

The effect of steady noise on sleep was examined experimentally for 24 nights by sleep polygraphy of a twenty-eight-year-old man. The parameters used for sleep polygraphy were sleep stage, sleep latency, frequency of sleep stage shift per hour, average sleep depth, the gradient and intercept of a regression line of sleep depth against time, and subjective sleep. The sleep stage was judged and estimated based on the criteria of Rechtschaffen & Kales by the authors' original system using a microcomputer. For the calculation of sleep depth at a given time, stages W (waking), 1, REM, 2, 3 and 4 were weighted to be 0, 1, 1.5, 2, 3 and 4, respectively. Sleep parameters were compared between the data of non-noise and noise-exposed nights. The noise exposure was overnight stationary pink noise of 40, 50 and 60 dB (A). General findings were a decreased REM stage, an increased stage 2, and deepened average sleep depth of the 60 dB (A)-night sleep compared with the control and 40 dB(A) exposure nights. When the control nights were excluded and parameters were compared between the three levels of stationary noise exposure, stage 2, the intercept of the regression line, and average sleep depth were increased almost in proportion to the increased noise exposure. In contrast, sleep latency, frequencies of sleep stage shift, stages W, 1, 3, MT, and REM, as well as the gradient of the regression line were decreased with increased noise exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

Pressure-flow relationship and longitudinal distribution of pulmonary vascular resistance in heartworm-infected dogs.

The pressure-flow relationships and the longitudinal distributions of pulmonary vascular resistance in normal and heartworm-infected (HWI) dogs were compared in an isolated, blood perfused preparation. The pulmonary circulation was partitioned into pulmonary arterial, middle, and venous segment based on the concept of a five element lumped model. The pulmonary arterial pressure-flow relationships were found to be non-linear and convex to the pressure axis in both normal and HWI lungs. The pressure-flow relationships of the pulmonary arterial and venous segment were linear and these slopes in the HWI lungs were significantly higher than the normal lungs. The pressure gradient of the middle segment was increased as flow increased at lower flow range, however, it was not increased during higher perfusion range in both lungs. At higher flow, the pressure gradient of the middle segment in the HWI lungs was significantly higher than the normal lungs. These results suggest that the ohmic resistance was almost equal to the sum of the two slopes of the pressure-flow relationships of the pulmonary arterial and venous segment because the pressure gradient of the middle segment was not altered as flow increased during higher perfusion rate. Because the slopes of the pressure-flow relationships of the pulmonary arterial and venous segment were increased with heartworm infection, the ohmic resistance of HWI lungs would be higher than normal lungs. The intercept pressure on the pressure axis of the linear portion of the pulmonary arterial pressure-flow relationship, a critical closing pressure, was regarded as pressure gradient of the middle segment during higher perfusing rate because the intercept pressures of pressure-flow relationships of pulmonary arterial and venous segment were almost equal to zero. Therefore, the critical closing pressure of HWI lungs would be higher than normal lungs. The pulmonary hypertension of filariasis appears to be due to an increase in ohmic resistance and elevated critical closing pressure.

Animals↗

PubMed1998

Predictive performance of ten equations for estimating creatinine clearance in cardiac patients. Iohexol Cooperative Study Group.

OBJECTIVE: The predictive performance of 10 equations used to estimate creatinine clearance (Clcr) was assessed retrospectively from data collected on 420 patients. DESIGN: This study is a retrospective data analysis of information collected on hemodynamically stable patients awaiting coronary angiography during the Iohexol Cooperative Study. SETTING: The Iohexol Cooperative Study was a multicenter study that compared nephrotoxicity of high- and low-osmolar contrast media in patients undergoing coronary angiography. Data used for this analysis were preangiography 24-hour urine collections that were primarily collected in hospitalized patients. PATIENTS: Patients selected from the Iohexol Cooperative Study database for analysis were participants categorized into one or more of six subgroups: elderly (n = 222), hypoalbuminemic (n = 25), chronic renal insufficiency (n = 128), low serum creatinine (n = 115), obese (n = 208), and diabetic (n = 191) who had baseline urine collections of at least 24 hours. OUTCOME MEASURES: Predictive performance was assessed using bias, precision, slopes, and y-intercepts. RESULTS: The Salazar-Corcoran equation was unbiased in the entire group as well as in five of the subgroups. The Cockcroft-Gault equation was unbiased in three of the subgroups. All other equations were biased in predicting Clcr in the entire group as well as in at least four of the subgroups. Precision was generally poor. All slopes were significantly different than one and all y-intercepts were significantly different than zero (p < 0.01). Correlation coefficients were between 0.63 and 0.79 with the exceptions of the low serum creatinine subgroup (r values 0.35-0.64) and the Davis-Chandler equation (r values 0.35-0.71 across groups). CONCLUSIONS: Of the equations studied, Salazar-Corcoran and Cockcroft-Gault appear to be the best for predicting Clcr.

Aged↗

PubMed2007

Effect of enzyme replacement therapy with imiglucerase on BMD in type 1 Gaucher disease.

UNLABELLED: The effect of ERT with imiglucerase on BMD in type 1 GD was studied using BMD data from the International Collaborative Gaucher Group Gaucher Registry. Data were analyzed for 160 untreated patients and 342 ERT-treated patients. Imiglucerase significantly improves BMD in patients with GD, with 8 years of ERT leading to normal BMD. INTRODUCTION: The objective was to determine the effect of enzyme replacement therapy (ERT; Cerezyme, imiglucerase) on BMD in type 1 Gaucher disease (GD). MATERIALS AND METHODS: The study population included all adults (men, 18-70 years; women, 18-50 years) enrolled in the International Collaborative Gaucher Group (ICGG) Gaucher Registry for whom lumbar spine BMD measurements were available. BMD data with up to 8 years of follow-up were analyzed for 160 patients who received no ERT and 342 patients treated with ERT alone. BMD was assessed by DXA of the lumbar spine. Z scores for patients with GD were compared with a reference population. From the model's estimate, percent of patients by age and sex with osteoporosis (T score < or = -2.5) were calculated. RESULTS: DXA Z scores for patients with GD in the no ERT (untreated) group were significantly below normal (y intercept = -0.80 Z score units, p < 0.001) and remained approximately 1 SD below the reference population over time (slope = -0.010 Z score units per year, p = 0.68). The DXA Z scores for patients with GD who received ERT at a dose of 60 U/kg/2 weeks were significantly lower than the reference population at baseline (y-intercept = -1.17 Z score units, p < 0.001), but improved significantly over time (slope = +0.132 Z score units per year, p < 0.001). A significant dose-response relationship was noted for the ERT group, with the slopes for the three main dosing groups of 15, 30, and 60 U/kg/2 weeks of +0.064, +0.086, and +0.132 Z score units per year, respectively. The BMD of patients with GD treated with ERT increased to -0.12 (60 U/kg/2 weeks), -0.48 (30 U/kg/2 weeks), and -0.66 (15 U/kg/2 weeks) SD of the mean of the reference population after 8 years of ERT, approaching the reference population. Estimated risk of osteoporosis of this GD population, if left untreated, ranged from approximately 10 to 30% in women and 10% to 25% in men. CONCLUSIONS: ERT with imiglucerase (Cerezyme) may increase BMD in patients with GD. Response to treatment with imiglucerase is slower for BMD than for hematologic and visceral aspects of GD. A normal (age- and sex-adjusted) BMD should be a therapeutic goal for patients with type 1 GD.

Absorptiometry, Photon↗

PubMed1997

A preliminary evaluation of the lunar expert-XL for bone densitometry and vertebral morphometry.

We have evaluated the Lunar Expert-XL for standard bone mineral densitometry (BMD) and for morphometric imaging of the spine in the lateral projection. The short-term precision in vitro of the Expert-XL for BMD measurements was 0.7% for the Hologic and European spine phantoms, and the long-term stability (15-month) measurements had a 1.1% coefficient of variation. The precision in vivo for three operators examining a group of 10 premenopausal women was 0.9-1.5% for lumbar spine (L2-L4), 1.7-2.2% for the femoral neck, and 0.9% for the total hip region of interest. For a group of nine postmenopausal women, the lumbar spine, femoral neck, and total femur precision ranges were 2.0-2.4, 1.2-2.9, and 1.6-1.7% respectively. For L2-L4, BMD comparison between the Expert-XL and DPX-L yielded a correlation coefficient of r = 0.98, a slope of 0.86, and an intercept of 0.139 g/cm2. The femoral neck results were r = 0.92, slope = 1.00, and intercept = 0.03 g/cm2. In an evaluation of the Expert-XL for lateral morphometry, we employed a group of 16 postmenopausal women. Comparison of vertebral dimensions between the Expert-XL and radiographic morphometry showed strong agreement (r = 0.97), but the interobserver variability for vertebral height was higher for the Expert-XL than for radiographs (3-5% vs. 1-2%). In a subset of four women who had repeat scans, the interscan precision for measuring vertebral dimensions was 1.9, 4.1, and 43% for the L1-L4, T12-T8, and T7-T5 levels respectively. In the Expert-XL images, it was possible to identify clearly L4-T4 in 10 of 16 patients and L4-T6 in 15 of 16, indicating potential utility for vertebral fracture prescreening.

Absorptiometry, Photon↗

PubMedDate not supplied

Social and behavioral determinants of self-reported STD among adolescents.

CONTEXT: Adolescents have among the highest sexually transmitted disease (STD) rates. Rich data are now available to characterize the social and behavioral factors that affect adolescent STD risk. METHODS: Data from Wave 1 (1995) of the National Longitudinal Study of Adolescent Health (Add Health) are used to estimate school, neighborhood, family and individual level effects on acquiring an STD. Data from Waves 1 and 2 (1996) of Add Health are also used to estimate the effects of prior STD acquisition and other factors on STD occurrence between waves. Random intercept logistic regression and random intercept piecewise exponential hazard regression are used to account for possible clustering in the Add Health data. RESULTS: Seven percent of sexually experienced teenagers reported ever having had an STD as of Wave 1, and almost 7% reported having had an STD between Waves 1 and 2. Respondents' age, gender, race or ethnicity, and their family background, neighborhood and school characteristics affect STD acquisition at Wave 1. Among teenagers who were sexually experienced at Wave 1, younger age at first intercourse elevates STD risk. Other factors contribute, but to a lesser degree. For acquisition of an STD between Waves 1 and 2, females, blacks, teenagers with lower levels of mother's education and those who have had a prior STD are at higher risk. CONCLUSIONS: Multiple social and behavioral factors influence lifetime history of STD. Age at first intercourse and STD history affect subsequent STD acquisition. Self-reports of STD acquisition in probability samples of the general population are useful.

Adolescent↗

PubMed2002

Thermally assisted recording of holographic gratings in semicrystalline azobenzene-containing polymers.

We examine optically induced birefringence in semicrystalline azopolymer films that are held at glass-transition temperature Tg. The birefringence increases markedly after interception of the pump beam; the saturation value depends on exposure time. In addition, the induced birefringence is completely erased by irradiation with a circularly polarized beam at Tg. Using this thermally assisted method, we demonstrate the holographic recording of a test image. The intensity of the diffracted beam also increases after interception of the writing beams. Furthermore, the retrieved image is found to have a resolution of approximately 30 lp/mm. This resolution is comparable with that of the optical setup that is used. Accordingly, the thermally assisted recording by use of semicrystalline azopolymers is a promising method for reversible holographic storage.

Journal Article↗