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Background/Objectives This study aimed to determine the association between a Mediterranean diet and glycemic control and other cardiovascular risk factors among youth with type 1 diabetes (T1D).

To provide contemporary data on the aetiology of paediatric rhegmatogenous retinal detachment (RRD) in the UK population. Retrospective case series. Eighty-eight eyes in 82 patients (aged 0–16 years) were treated for RRD at Bristol Eye Hospital between 1 January 1990 and 31 December 2004. Seventy-three per cent of patients were male and the main predisposing factors were trauma (53%), associated conditions (27%), and high myopia (17%). Nineteen per cent of RRDs were idiopathic, and the majority of these were due to infero-temporal dialyses. The macula was detached on presentation in 66% of eyes. The principal causes of paediatric RRDs have not changed over the past 40 years. Those due to congenital cataracts, retinopathy of prematurity, uveitis, and glaucoma are now less prevalent, presumably reflecting advances in their management. Differences with other contemporary series may arise from geographical variation in the prevalence of myopia and other associated conditions, as well as institutional referral patterns. Full examination of the retinal periphery is advised for children with eye injuries (to exclude dialyses).

The signal intensity from inflamed extra-ocular muscles on short tau inversion recovery (STIR)-sequence magnetic resonance imaging (MRI) is known to correlate with clinical scores of thyroid eye disease (TED) severity. Twenty-one patients who had undergone repeated MRI scanning for TED were studied retrospectively. Signal intensity of extra-ocular muscles (from STIR-sequence MRI) and cross-sectional area (from STIR and T1 MRI) were correlated with Mourits' clinical activity score (CAS). The area of highest signal intensity within the most inflamed extra-ocular muscle, and the average cross-sectional signal intensity of the most inflamed extra-ocular muscle reliably correlated with CAS, and this was maintained as disease activity changed over time. In contrast, isolated measures of muscle cross-sectional area did not correlate with CAS. The extra-ocular muscle cross-sectional area calculated from STIR-sequence MR images was greater than that measured on T1 images. This suggests that muscle area from STIR-sequence MRI may also detect peri-muscular inflammation. We conclude that the peak signal intensity from the most inflamed extra-ocular muscle remains the most reliable correlate of clinical disease activity obtained from these images. STIR-sequence MRI scans provide a number of useful measures of disease activity in TED.

Microscopic calculations including energetic disorder and Coulomb correlations up to third order in the laser field are performed. The resulting four-wave-mixing signals show polarization-dependent dephasing induced by diagonal disorder. The correct modeling of this disorder-induced dephasing requires the proper inclusion of Coulomb correlations. The theoretical results are in good qualitative agreement with measurements performed on a variety of quantum-well samples.

We study the dependence of the biexciton binding energy on confinement in semiconductor quantum wells. A set of symmetrically strained (GaIn)As/Ga(PAs) quantum wells with different well depths and equal well widths is investigated by quantum beat spectroscopy based on transient degenerate four-wave mixing. The ratio of biexcitonic to excitonic binding energy increases with stronger confinement. This new experimental result is discussed in the framework of recent theoretical predictions and experimental results.

We study the dependence of the binding energies of excitonic molecules on the confinement in semiconductor quantum wells. A set of symmetrically strained (GaIn)As/Ga(PAs) quantum wells with different well depths and equal well widths is investigated with transient degenerate four-wave mixing. The ratio of biexcitonic to excitonic binding energy increases with stronger confinement. This experimental result is discussed in detail in the framework of recent theoretical predictions and experimental results.

Aims To determine the prevalence of plasma vitamin D (25-dihydroxyvitamin D) insufficiency in individuals with Type 1 diabetes and to determine the cross-sectional and longitudinal associations of plasma vitamin D with insulin resistance. Methods Participants from the SEARCH for Diabetes in Youth Study [n = 1426; mean age 11.2 years (sd 3.9)] had physician-diagnosed Type 1 diabetes [diabetes duration mean 10.2 months (sd 6.5)] with data available at baseline and follow-up (approximately 12 and 24 months after baseline). Insulin resistance was estimated using a validated equation. Cross-sectional and longitudinal multivariate logistic regression models were used to determine the association of plasma vitamin D with insulin resistance, adjusting for potential confounders. Results Forty-nine per cent of individuals had plasma vitamin D

We report results on selection rules and polarization conditions for quantum beating between light hole and heavy hole excitons in GaAs quantum wells. The measurements were conducted using time-integrated degenerate-four-wave-mixing in a three-pulse configuration. By choosing particular polarization configurations of the ultrashort optical pulses exciting heavy and light hole excitons simultaneously, degenerate four-wave-mixing signals show either quantum beating or no modulation at all. The experiments are analyzed using a model that takes into account exciton/exciton interaction.

We report time-resolved degenerate four-wave-mixing experiments on a high-quality single GaAs quantum well. The signals for parallel and cross-polarized exciting pulses show pronounced quantum beats with different frequencies corresponding to the heavy/light-hole splitting and the biexciton binding energy, respectively. Comparison of the experimental data with solutions of the optical Bloch equations for a phenomenological model system shows that these features result from strong contributions of the biexcitonic state. The importance of biexcitons to the nonlinear coherent response of the two-dimension exciton is further confirmed by the frequency dependence of the time-integrated four-wave-mixing signal amplitudes measured for the two polarization geometries.

Four-wave-mixing (FWM) experiments using a dynamical density matrix model of the semiconductor band edge are discussed. Higher-order correlation functions are retained which arc neglected in the commonly used RPA treatment leading to the semiconductor Bloch equations. In order to terminate the hierarchy of the equations of motion for the higher-order density matrices systematically a truncation scheme controlled by orders in the driving field is applied. For any prescribed order n in the exciting field a closed set of equations is obtained from which the dielectric response up to order n can be calculated exactly. In addition it turns out that in a coherently driven system part of the remaining density matrices become redundant and can be eliminated. Four-wave-mixing experiments are dominated by third-order contributions. Applying the above-described results one ends up with only two functions in this case. These are the excitonic and the biexcitonic transition densities. As an applica tion of our method the example of a GaAs single quantum well is studied. Two pulses with finite lengths are assumed such that both heavy-and light-hole excitons are excited. The influence of the biexciton contribution on the polarization properties of the FWM signal is analyzed and compared with experimental results.

Incontinentia pigmenti (IP) is a rare X linked genetic disorder, which predominantly affects females. The mutations are usually lethal in males. Two male cases are presented; a genetic mosaic for the common IP deletion and another in whom the genetic abnormality has not yet been characterised. Emphasis is placed on the ocular features present in this disorder and in particular a novel corneal feature and its possible aetiology.

The aim of this pilot study was to generate an initial estimate of the prevalence and correlates of diabetic retinopathy in a racially and ethnically diverse sample of youth with Type 1 and Type 2 diabetes mellitus.A pilot study was conducted among 222 individuals with Type 1 diabetes (79% non-Hispanic white, 21% other) and 43 with Type 2 diabetes (28% non-Hispanic white, 72% other), all of5 years duration (mean duration 6.8 years) who participated in the SEARCH for Diabetes in Youth study. Diabetic retinopathy was assessed using non-mydriatic retinal photography of both eyes.The prevalence of diabetic retinopathy was 17% for Type 1 diabetes and 42% for Type 2 diabetes (odds ratio 1.50, 95% CI 0.58-3.88; P = 0.40 adjusted for age, duration, gender, race/ethnicity, parental education and HbA(1c). HbA(1c) was significantly higher among those with any diabetic retinopathy (adjusted mean 79 mmol/mol, 9.4%) vs. no diabetic retinopathy (adjusted mean 70 mmol/mol, 8.6%) (P = 0.015). LDL cholesterol was also significantly higher among those with any diabetic retinopathy (adjusted mean 107.2 mg/dl) compared with those without diabetic retinopathy (adjusted mean 97.9 mg/dl) (P = 0.04).The prevalence of diabetic retinopathy in contemporary young individuals was substantial, particularly among minority youth and those with Type 2 diabetes. Further long-term study of diabetic retinopathy in youth is needed.

The observation of biexcitonic contributions to time-resolved pump-probe measurements of a 25 nm multiple quantum well are reported. Results from wavelength and polarization dependent studies of the differential transmission in the vicinity of the heavy hole exciton transition demonstrate the strong influence of the biexciton state on the nonlinear response. Intensity dependent measurements are consistent with biexciton formation. The previously predicted angle dependence of the beating between light and heavy hole excitons is also observed.

BACKGROUND Low-density lipoprotein (LDL) subclass phenotype B, characterized by predominance of small, dense LDL particles, is associated with elevated plasma triglycerides and apolipoprotein B and with lower high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I. Because these abnormalities resemble the dyslipidemia of insulin resistance, we examined associations of LDL subclass phenotype with plasma insulin levels and with other aspects of the insulin resistance syndrome. METHODS AND RESULTS LDL subclass phenotypes were determined by gradient gel electrophoresis in 682 female twins aged 30 to 91 years who participated in the second examination of the Kaiser Permanente Women Twins Study. Prevalence of phenotype B and the intermediate phenotype (I) increased strongly with age, obesity, and non-insulin-dependent diabetes. In multivariate analysis of nondiabetic women, phenotype B or I was independently associated with each aspect of the insulin resistance syndrome, including higher plasma triglycerides, waist-hip ratio, fasting and postload insulin levels, and systolic blood pressure and lower HDL cholesterol levels after adjustment for age and body mass index. The prevalence of phenotype B or I rose progressively from 5.6% in women with no manifestations of the insulin resistance syndrome to 100% in women with four syndrome components. In 25 nondiabetic, monozygotic twin pairs discordant for subclass phenotype, the twins with phenotype B (or I) had significantly higher levels of body mass index, waist-hip ratio, and systolic blood pressure than their twins with phenotype A. Thus, nongenetic variation in these risk factors is important in explaining their associations with LDL subclass phenotype. CONCLUSIONS Small, dense LDL is an integral feature of the insulin resistance syndrome. Nongenetic (ie, behavioral or environmental) factors are important for the expression of the phenotype and for its association with other heart disease risk factors.

Hydroview intraocular lenses (IOLs) have been associated with symptomatic opacification of the optic necessitating IOL exchange. Glare and misty vision have been noted as common presenting symptoms. This study's purpose was to investigate the impact of IOL opacification on objective measurements of visual function, including glare, and on vision-related quality of life. All patients who underwent Hydroview IOL implantation at Bristol Eye Hospital between December 2000 and the end of February 2001 were invited for assessment along with patients found to have Hydroview IOL opacification in routine ophthalmic clinics. Glare, visual acuity, contrast sensitivity, visual field, and colour vision were assessed. Vision-related quality of life and subject's symptoms were determined by questionnaire. IOL opacification was assessed by slit lamp bio-microscopy and anterior segment photography. Data from 129 patients were analysed. Fifty subjects had opacified IOLs and 79 clear IOLs. Subjects with opacified IOLs showed dramatically higher levels of glare (adjusted mean difference of 0.63 log units 95% CI, 0.45–0.82; P

We describe the operating characteristics of a femtosecond optical parametric oscillator employing chirped mirrors for intracavity group-velocity dispersion compensation. Pumped by 760 mW of power from a self-mode-locked Ti:sapphire laser, this device provides 100-fs near-transform-limited pulses continuously tunable from 1.18 to 1.32 microm with an average power of 100-180 mW. The limitations of the present setup and strategies for further pulse shortening are discussed.

We report on the performance of widely tunable femtosecond and continuous-wave Ti:sapphire lasers that use a newly developed ultrabroadband mirror set. The mirrors exhibit high ref lectivity (R . 99%) and smooth variation of group delay versus frequency over a wavelength range from 660 to 1060 nm. Mode-locked operation with pulse durations of 85 fs was achieved from 693 to 978 nm with only one set of ultrabroadband mirrors.  1997 Optical Society of America

The polarization dependence of the coherent optical response of GaAs QWS reveals that modelling of 2D excitons as non-interacting two-level systems is inadequate. Extensions of the model taking into account many-body Coulomb effects and disorder-induced coupling of the valence band states results in a fairly good description of all experimental data.

The prevalence of selected health indicators were compared among the Catawba Indians, African Americans, and whites in South Carolina, considering the possible role of rural locality and education.Catawba members were respondents of a 1998 survey (N = 808). Other South Carolina residents were respondents of the 1995-1997 Behavioral Risk Factor Survey (4,150 whites and 1,413 African Americans). Prevalence of cardiovascular disease, diabetes, hypertension, overweight, poor health, smoking, physical inactivity, and poor diet were compared among the racial/ethnic groups. Logistic regression analyses were conducted within strata of urban/rural locality and education to determine whether these factors were associated with the adverse health indicators.Both Catawba and African Americans had higher prevalence of diabetes, hypertension, overweight, poor health, physical inactivity, and poor diet than whites. In addition, prevalence of diabetes, poor health, smoking, and poor diet were higher among the Catawba than among African Americans. Restricting the analyses to comparisons within urban/rural locality had little effect, whereas restricting the analyses to comparisons by education level eliminated many of the disparities among those with low education.Prevalence of chronic disease and adverse health behavior are higher among the Catawba than among other residents of South Carolina, especially compared with white residents.

In 1998, the Catawba Diabetes and Health Survey (CDHS) was conducted among adult members of the Catawba Indian Nation living in the Carolinas to determine the prevalence of diabetes and other health conditions, and to assess the population's health-related behaviors.A population-based sample of adult members of the Catawba Indian Nation (N = 633) were surveyed by telephone or in person regarding health status and health-related behaviors. Logistic regression was used to determine demographic and behavioral correlates of diabetes, hypertension, and overweight among the Catawba.Age-adjusted prevalence rates of self-reported diabetes, hypertension and overweight were 12.3%, 29.1%, and 63.8%, respectively. Older age was related to diabetes, hypertension, and overweight (P.0001 each), and heavier weight status was related to diabetes (P = .026) and hypertension (P.0001). Nearly 40% of the Catawba are physically inactive (29.5% men, 46.5% women). Physical inactivity was related to diabetes and hypertension among men only, and related to overweight among women only (P.05 each). Current smoking was inversely related to overweight among men and women (P = .002). Dietary behavior was not associated with the health outcomes.Given the high rates of overweight and physical inactivity, reducing the rates of both may be very important for the health of the Catawba, considering their association with diabetes and hypertension.

Terminal warm blood cardioplegia, "Hot shot", is the method for providing an energy replenishment and/or early recovery of aerobic metabolism without electromechanical activity at initial reperfusion. The mechanism of beneficial effects of this Hot Shot is multifactorial. This study was designed to assess the effects of terminal warm blood cardioplegia by comparing with oxygenated terminal warm crystalloid cardioplegia.In Group HS-B, n=8 (oxygenated blood; 37 degrees C, Ht: 20%, K+ 20 mEq/l, pH 7.237, PO2 219 mmHg) and in Group HS-C, n=8 (bloodless oxygenated (5% CO2+95%O2) crystalloid, 37 degrees C, K+ 20 mEq/l, pH 7.435, PO2 624 mmHg), terminal warm cardioplegia (20 ml/kg for 5 minutes) was studied in the isolated blood perfused neonatal lamb heart following 2 hr of cardioplegic ischemia. Another eight hearts served as control without any kind of terminal cardioplegia. After 60 min of reperfusion, LV function was measured. Coronary blood flow (CBF), oxygen content, and oxygen consumption (MVO2) were measured and the oxygen extraction ratio was calculated in Group HS-B and HS-C during terminal cardioplegia and/or reperfusion. Results are given as % recovery of preischemic values.HS-B as well as HS-C groups showed better functional recovery in maximum developed pressure (DP: 78.0+/-8.3 in HS-B vs 65.2+/-9.2%; p=0.018), maximum dp/dt (67.3+/-6.2 in HS-B, 65.3+/-7.4 in HS-C vs 55.8+/-5.0%; p=0.003, p=0.02), DP V10 (87.1+/-8.5 in HS-B vs 67.2+/-9.9%; p=0.0001), and peak dp/dt V10 (76.4+/-7.6 in HS-B, 69.8+/-8.1 in HS-C vs 58.6+/-6.9 %; p=0.0001) than the control group. Between the HS-B and HS-C groups, HS-B showed better functional recovery in terms of DP V10 (p=0.01). Oxygen delivery of terminal cardioplegia was almost four times higher in HS-B group (90.4+/-17.7 vs 18.7+/-1.1 mcl/ml), contrarily, HS-C group showed four times higher oxygen extraction ratio compared to HS-B group (0.78+/-0.06 vs 0.18+/-0.11), thus oxygen consumption during hot shot was maintained at the same level in both groups. CBF in the control group was lower than that in the other groups at 60 min of reperfusion.Reperfusion with both terminal warm cardioplegia including blood and oxygenated crystalloid cardioplegia resulted in better recovery of function and higher levels of CBF with slightly better function in terminal warm blood cardioplegia.

Patient, surgical, and lens-related factors, and their association with Hydroview intraocular lens opacification

The prospective association of insulin and hypertension has been under debate in the context of the development of the insulin resistance or multiple metabolic syndrome. We examined the predictive associations of fasting serum insulin with incident hypertension occurring alone or as part of the multiple metabolic syndrome.Analyses were restricted to 5221 middle-aged participants of the Atherosclerosis Risk in Communities Study cohort who were free of component disorders of the multiple metabolic syndrome (hypertension; diabetes; high triglycerides and/or low HDL cholesterol (dyslipidaemias)) at baseline.A total of 1018 individuals developed hypertension, 801 in the absence of components of the metabolic syndrome and 217 in combination with diabetes or dyslipidaemias, between 1987 and 1993.Elevated fasting insulin (top quartile versus lowest quartile) was associated with overall incident hypertension in European Americans [hazard rate ratio (HRR) 2.0, 95% confidence interval (CI) 1.7-2.4] but the results were inconclusive in African Americans (HRR 1.3, 95% CI 0.9-1.8) after adjustment for age, gender and study centre. Among European Americans, body mass index and abdominal girth only partly explained the observed association. Elevated fasting insulin was more strongly predictive of hypertension occurring as a component of the multiple metabolic syndrome (HRR 2.4, 95% CI 1.5-3.9) than of hypertension occurring alone (HRR 1.3, 95% CI 1.0-1.7) adjusting statistically for age, gender, study centre, body mass index and abdominal girth.The results are consistent with the concept of an aetiological heterogeneity for hypertension and may explain previously reported inconsistent findings on the association of insulin with incident hypertension.

Diabetic retinopathy (DR) is a major cause of visual impairment and blindness in adults. Antioxidant nutrients, such as vitamins C and E and beta-carotene, may be protective of some eye disorders, such as cataract and age-related macular degeneration, but a relationship between these nutrients and DR has yet to be defined. The purpose of this study was to examine the relation between dietary and supplement intakes of vitamins C, E, and beta-carotene and the risk of DR.Both cross-sectional and longitudinal data were collected from participants in the San Luis Valley Diabetes Study, including non-Hispanic white and Hispanic adults in southern Colorado.A total of 387 participants with type 2 diabetes completed at least 1 complete retinal examination and 24-hour dietary recall (including vitamin supplement use).Type 2 diabetes was defined according to World Health Organization criteria. DR was assessed by retinal photographs, using the Airlie House criteria to classify DR as none, background, preproliferative, or proliferative. Data for both eyes, from up to three clinic visits per participant, were used for analysis. Ordinal logistic regression analysis was used, taking advantage of multiple clinic visits by individual participants and observations from both eyes, to assess the risk for increased DR severity over time as a function of changes in intake of vitamin C, vitamin E, and beta-carotene. Six categories of intake for each nutrient (first to fourth quintiles and ninth and tenth deciles) were considered to ascertain any potential threshold effect. Analyses accounted for age, duration of diabetes, insulin use, ethnicity, glycated hemoglobin, hypertension, gender, and caloric intake.An increase over time in vitamin C intake from the first to ninth deciles was associated with a risk for increased severity of DR (odds ratio = 2.21, P = 0.01), although excess risk was not observed for the tenth decile or the second through fourth quintiles compared to the first quintile. Increased intake of vitamin E was associated with increased severity of DR among those not taking insulin (odds ratios = 2.69, 2.59, 3.33, 5.65, 3.79; P0.02, for an increase over time from the first to the second through fourth quintiles and ninth and tenth deciles, respectively). Among those taking insulin, increased intake of beta-carotene was associated with a risk for severity of DR (odds ratio = 3.31, P = 0.003, and 2.99, P = 0.002, respectively, for the ninth and tenth deciles compared to the first quintile).No protective effect was observed between antioxidant nutrients and DR. Depending on insulin use, there appeared to be a potential for deleterious effects of nutrient antioxidants. Further research is needed to confirm associations of nutrient antioxidant intake and DR.

The natural history of the multiple metabolic syndrome (MMS) and its predictors has rarely been addressed in population samples. This study evaluated the predictive role of fasting serum insulin, body mass index (BMI), and waist-to-hip ratio (WHR) on the development of incident MMS components (diabetes, hypertension, and dyslipidemias) over the course of three years.The study population comprised the cohort of middle-aged African American and European American men and women of the Atherosclerosis Risk in Communities Study (1987-1992).Among 6113 individuals free of MMS components at baseline, high insulin (14 microU/ ml) was independently predictive of the development of one or more MMS components (OR:1.5, 95% CI:1.2-1.8), as was a BMIor = 30 (OR:1.7, 95% CI:1.4-2.0), and a high WHR (0.98) (OR:1.5, 95% CI:1.3-1.8) adjusting statistically for age, gender, and ethnicity/center. These associations were markedly stronger for combinations of MMS components (two or more) than for isolated components.The findings confirm earlier reports on the predictive role of insulin, BMI, and WHR, and suggest that these antecedent factors may be integral to the development of combinations of disorders, i.e., the particular clustering identified as the MMS.

Persons with non-insulin-dependent diabetes mellitus (NIDDM) are at increased risk for cardiovascular disease, partly due to concomitant worsening of traditional risk factors including dyslipidemia and hypertension. Based on evidence from small, controlled clinical trials, we hypothesized that increased intake of vitamin C would be associated with improved cardiovascular disease (CVD) risk factor status among community-dwelling persons with NIDDM.In separate but parallel statistical analyses, hypotheses were evaluated among persons with NIDDM confirmed by WHO criteria from the Insulin Resistance Atherosclerosis Study (IRAS, n = 520) and from the San Luis Valley Diabetes Study (SLVDS, n = 422). For IRAS, diet and vitamin supplement use was assessed by food frequency interview and for SLVDS, by 24-hr dietary recall interview.Mean vitamin C intake (mg/day) was 275 for IRAS and 133 for SLVDS, including supplements. In cross-sectional regression models from each data set, vitamin C intake was not associated with systolic or diastolic blood pressure nor with HDL-C, LDL-C, or triglycerides (P values0.10; adjusted for calories, demographic and lifestyle variables, obesity, diabetes duration, and medications). In prospective analyses including 285 SLVDS participants, baseline vitamin C intake was not related to any of these CVD risk factors measured an average of 4 years later nor to change in CVD risk factor status during the follow-up period.We conclude that, across a wide range of intake, vitamin C does not appear to be associated with improved CVD risk factor status among community-dwelling persons with diabetes.

In non-ischaemic central retinal vein occlusion (niCRVO), the two principal determinants of final visual acuity are visual acuity and the presence of macular oedema at initial presentation.1,2 Data from the Central Vein Occlusion Study Group2 suggested that of patients with CRVO with an initial acuity better than 6/15, 65% maintain this, whereas patients with presenting acuities between 6/15 and 6/60, 81% remain the same or get worse (19% improve to 6/12 or better, 44% remain between 6/15, and 6/60 and 37% are worse than 6/60). Up to 34% of niCRVO may progress to the ischaemic variant with its attendant complications within 3 years.2 However, in some studies 83% of indeterminate cases progress to ischaemic CRVO.1 The creation of a chorioretinal venous anastomosis (CRVA) improved visual acuity in some patients, decreased macular oedema, and reduced the incidence of progression to ischaemic CRVO.3–5 These important observations provide the basis for the study we carried out. During the study period 11 patients (table 1) were enrolled according to the trial protocol (see appendix). All anastomoses were patent (on fluorescein angiography and if not repeated, see appendix). Mean patient age and mean pretreatment (T0) visual acuities, retinal thickness (by optical coherence tomography, …

Ti:sapphire laser-pumped optical parametric oscillators (OPO’s) are attractive sources for tunable femtosecond light pulses in the visible1, 2 and near-infrared3–5 spectral ranges. Generation of femtosecond transform-limited pulses shorter than the pump pulse necessitates compensation of the group-delay dispersion (GDD) that originates from both material dispersion and self-phase modulation in the nonlinear crystal. Previously this GDD compensation was accomplished by insertion of prism pairs into the resonator1–4.

The recent progress in the development of ultrashort laser pulses enables observations of the coherent dynamics of excitons in quantum wells (QW) with less than 100 fs time resolution by transient degenerate-four-wave-mixing (DFWM). Such investigations have attracted rapidly growing attention as a powerful technique to explore nonlinear processes in semiconductors which may have enormous potential for future semiconductor device applications. Only very recently the role of many-body exciton-exciton interaction effects for the magnitude of the nonlinear optical response as well as for the optical dephasing rate has been studied in detail. So far, the discussion has been confined, however, to the coupling of excitons via Coulomb fields1. For GaAs multiple QW (MQW) samples, this interaction mechanism seems to be negligible for excitons excited in different wells if the barrier thickness exceeds values of 10–15 nm so that tunneling processes of carriers between the different wells can be excluded.

The homogeneous and inhomogeneous linewidth of excitonic transitions characterize the interfacial quality of QW structures.1 We measured the inhomogeneous linewidth Γ inh by cw photoluminescence (PL) and reflectivity (REF) spectra on a series of undoped single CdTe/Cdl-xZnxTe QW’s with x = 0.16 – 0.18 and thickness L between 18 A and 112 A. We determined the zero-exciton-density- and zero-temperature-limit of the homogeneous linewidth Γ hom by density and temperature dependent degenerate-four-wave-mixing (DFWM) experiments. In these experiments, a mode locked Ti:Sapphire laser operating at 76 MHz was used. For a selective, resonant excitation of the exciton transition the bandwidth of 120-fs pulses was reduced to a pulsewidth of 4 meV, corresponding to 800 fs.

The polarization dependence of time-integrated (TI) and time-resolved (TR) degenerate four-wave-mixing (DFWM) on the lowest heavy hole (hh) and light hole (lh) exciton transitions in GaAs quantum wells (QW) demonstrates that heavy and light hole excitons cannot be described in the framework of the two non-interacting three-level systems with opposite circular polarization selection rules suggested by Schmitt-Rink et al.1 In several recent papers, 2–5 we have shown that the discrepancies between experiment and theory can be resolved if many-body Coulomb interactions and disorder-induced coupling of excitonic states are taken into account. Exciton/exciton Coulomb interaction which involves a variation of the local electric fields (LFE), excitation-induced dephasing (EID) and energy shifts of excitonic states, especially the formation of biexcitons (BIF), is phenomenologically implemented into the theory by solving the optical Bloch equations for multi-level model systems which represent single-exciton and two-exciton contributions to the nonlinear optical response by discrete transitions with adjustable oscillator strengths, dephasing rates, and frequencies. Comparison of a large variety of experimental data with theoretical curves calculated with this model demonstrates, in particular, the important contribution of the heavy hole biexciton to the third-order nonlinear optical response of GaAs QW’s. Whereas modulation of the signal with a frequency corresponding to the biexciton binding energy are the unique “fingerprint” for the formation of biexcitons, their importance is further proved by the polarization dependence of the signal strength.

Autosomal dominant chondrodysplasia punctata or Conradi-Hunermann disease1 is a rare disorder with variable expressivity. It is characterised by dysplastic skeletal changes with premature punctate epiphyseal and paravertebral calcification, associated with moderate growth deficiency, scoliosis, limb asymmetry, flexion contractures of the hips, knees and elbows, talipes equinovarus, short neck, frontal bossing, nasal bone hypoplasia with characteristic “koala” facies and dystrophic changes in hair and skin.2,3 Among the ocular features reported, cataracts are by far the most common, occurring in about 20% of cases of Conradi-Hunermann disease compared with a much higher incidence (>66%) in the more severe (and usually lethal) autosomal recessive and X linked dominant forms the disease.2,4,5 In addition, optic atrophy, microphthalmos, iris hypoplasia, and Axenfeld-Rieger syndrome have been described.6,7 We describe unusual vitreoretinal abnormalities in a 28 year old woman with Conradi-Hunermann disease. Her original diagnosis had been made in childhood based on clinical and radiological …

The Insulin Resistance Atherosclerosis Study (IRAS) is the first epidemiologic study designed to assess the relationships between insulin resistance, insulinemia, glycemia, other components of the insulin resistance syndrome, and prevalent cardiovascular disease (CVD) in a large multiethnic cohort. Over 1600 men and women were recruited from four geographic areas to represent a range of glucose tolerance (normal, impaired, and diabetic) and ethnicity (hispanic, non-Hispanic white, and African-American). Insulin resistance was assessed directly using the frequently sampled intravenous glucose tolerance test with minimal model analysis. Intimal-medial carotid artery wall thickness, an indicator of atherosclerosis, was measured using B-mode ultrasonography. Prevalent CVD was assessed by questionnaire and resting electrocardiography. This report describes the design of the study and provides the recruitment results. Forthcoming cross-sectional analyses will help to disentangle the association between insulin resistance and CVD, apart from the concomitant hyperinsulinemia and related CVD risk factors.

A three-pulse degenerate four-wave-mixing experiment and its theoretical analysis reveal contributions of local field and biexciton effects to the nonlinear optical response of the two-dimensional exciton. Quantum beats with a frequency equivalent to the biexciton binding energy appear only for specific polarizations. Polarization-dependent spectrally resolved four-wave mixing shows an additional peak that is separated from the 1s heavy-hole exciton line by the biexciton binding energy. These experimental results are in good agreement with the optical selection rules of the theoretical model, providing evidence for biexcitonic contributions to the four-wave mixing.

Background. Genetic factors are firmly established as determinants of plasma lipoprotein(a) [Lp(a)] concentration. This study focused on behavioral or environmental factors that might also explain some of the variation in levels of this cardiovascular disease risk factor. Methods. The study considers the 644 women twins (597 whites, 47 blacks; ages 30-91 years) who participated in the second examination of the Kaiser Permanente Women Twins Study. Cross-sectional associations of behaviors and environmental factors with Lp(a) concentration were studied before and after removing genetic influences on Lp(a) levels. Results. Lp(a) levels were substantially higher among blacks than whites (P < 0.0001). The distribution of apo(a) size phenotypes also differed between blacks and whites, but this variation did not explain the difference in Lp(a) levels. A positive association of Lp(a) concentration with age was noted among blacks (P = 0.06) but not among whites (P = 0.86). No evidence was found for associations of Lp(a) with menopausal status, cigarette smoking, alcohol consumption, total or heavy recreational physical activity, 11-year weight gain, use of several antihypertensive medications, or diabetes status in either race. Among postmenopausal women, however, estrogen replacement therapy was associated with lower Lp(a) levels among whites (7.9 vs 9.9 mg/dl, P = 0.05). Removing genetic variation in Lp(a) concentration by matching 171 monozygotic (MZ) twins to their genetically identical co-twins did not alter these findings. Conclusion. The plasma concentration of Lp(a), unlike other lipoprotein risk factors for heart disease, has few behavioral or environmental correlates, at least among white women. Neither behavioral or environmental factors nor variation in the apo(a) size phenotype appeared to explain the higher mean Lp(a) levels among black compared with white women; further study seems warranted in larger samples of black women.

Rapid progress in the development of mode-locked laser systems during the past decade has boosted the time resolution attainable in nonlinear optical spectroscopy well below 100 fs. Ti: sapphire lasers which can directly generate pulses as short as 12 fs [1] mark the most recent milestone of this evolution. This new generation of fs solid state lasers surpasses the older colliding-pulse mode-locked (CPM) dye laser [2] by far with respect to output power and stability, and most importantly, by the broad tunability of the fs output between 680–1000 nm. Combining these lasers with frequency converters like harmonic generators [3] or optical parametric oscillators [4] extends the tunability range to the ultraviolet, visible, near and middle infrared regime.

We demonstrate the LO-phonon Raman intensity in GaAs/AlAs multiple quantum wells to be inversely proportional to the exciton homogeneous linewidth for photon energies resonant with the band-edge exciton. The strongest Raman scattering is seen at the low-energy side of the exciton peak, where the homogeneous linewidth is narrowest. The energy dependence of the linewidth deduced from the resonance Raman profile agrees well with that measured directly by degenerate-four-wave mixing.

Non-insulin-dependent diabetes mellitus is 2-5 times more common in Hispanics than in non-Hispanic whites in the United States. The authors conducted this case-control study in two Colorado counties from 1984 to 1986 to determine whether known risk factors for non-insulin-dependent diabetes mellitus explained the excess incidence in Hispanics. There were 279 subjects with prevalent diabetes and 488 subjects with normal glucose tolerance who were eligible for this analysis. After adjustment for age and sex, results showed that Hispanics were 3.5 times more likely than non-Hispanic whites to have non-insulin-dependent diabetes mellitus (95% confidence interval 2.4-4.9). The excess risks of diabetes associated with body mass index, subscapular and triceps skinfold thickness, family history of diabetes, and income were similar in Hispanics and non-Hispanic whites, after adjustment for age and sex. However, 1-unit increases in subscapular/triceps skinfold ratio and waist/hip ratio were associated with greater increases in risk among non-Hispanic whites than among Hispanics. When risk factors were entered into logistic regression models simultaneously, higher subscapular skinfolds, a higher waist/hip ratio, family history of diabetes, older age, male sex, and lower income were independently associated with non-insulin-dependent diabetes mellitus in both ethnic groups. No association was found with skin reflectance, a marker for Amerindian admixture. While the excess risk of diabetes in Hispanics was reduced, a significant 1.9-fold excess risk in Hispanics remained. Further studies are needed to understand factors contributing to the excess prevalence of diabetes in Hispanic Americans.

We report on the performance of widely tunable femtosecond and continuous-wave Ti:sapphire lasers that use a newly developed ultrabroadband mirror set. The mirrors exhibit high reflectivity (R>99%) and smooth variation of group delay versus frequency over a wavelength range from 660 to 1060 nm. Mode-locked operation with pulse durations of 85 fs was achieved from 693 to 978 nm with only one set of ultrabroadband mirrors.

We describe a novel three-pulse degenerate four-wave mixing configuration that permits the direct observation of the coherence between the σ+ and the σ− exciton states in a GaAs quantum well excited in a two-photon process. It is found that the phase coherence between the two single heavy-hole exciton states decays with a time constant that is considerably longer than the dephasing time of the coherence between these states and the ground state (interband coherence). All the experimental data are well described by numerical solutions of the optical Bloch equations for a phenomenological multilevel model.

Gene replacement mediated by Tn5 sequences was used to integrate the Bacillus thuringiensis subsp. kurstaki HD-1 delta-endotoxin gene (tox) into the chromosome of two corn root-colonizing strains of Pseudomonas fluorescens. A Tn5 transposase deletion element containing the tox gene (delta Tn5-tox) was substituted for a Tn5 element previously present in the P. fluorescens chromosome. Two classes of delta Tn5-tox elements were made. The first class encodes kanamycin resistance in addition to the Tox protein, whereas the second class encodes only the Tox protein. Both classes of delta Tn5-tox elements can no longer transpose, owing to a 324-base-pair deletion in the transposase gene of IS50R, minimizing the potential for horizontal gene transfer of the tox gene to other bacterial species. A frameshift mutation in the transposase gene of IS50L was also constructed to eliminate the possibility of suppression or of a spontaneous reversion at the ochre termination codon that would create an active transposase. Expression of the Tox protein in P. fluorescens strains 112-12 and Ps3732-3-7 was demonstrated by an immunological assay (Western blot) and toxicity against larvae of the tobacco hornworm (Manduca sexta).