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Biomedical subjects

David R Williams

Publications and source records attributed to David R Williams.

At least 73 records · Page 4Linked to original sources
PubMed2004

Health disparities based on socioeconomic inequities: implications for urban health care.

Health is unevenly distributed across socioeconomic status. Persons of lower income, education, or occupational status experience worse health and die earlier than do their better-off counterparts. This article discusses these disparities in the context of urban medical practice. The article begins with a discussion of the complex relationship among socioeconomic status, race, and health in the United States. It highlights the effects of institutional, individual, and internalized racism on the health of African Americans, including the insidious consequences of residential segregation and concentrated poverty. Next, the article reviews health disparities based on socioeconomic status across the life cycle, beginning in fetal health and ending with disparities among the elderly. Potential explanations for these socioeconomic-based disparities are addressed, including reverse causality (e.g., being poor causes lower socioeconomic status) and confounding by genetic factors. The article underscores social causation as the primary explanation for health disparities and highlights the cumulative effects of social disadvantage across stages of the life cycle and across environments (e.g., fetal, family, educational, occupational, and neighborhood). The article concludes with a discussion of the implications of health disparities for the practice of urban medicine, including the role that concentration of disadvantage plays among patients and practice sites and the need for quality improvement to mitigate these disparities.

Cities↗
PubMed2004

Food insufficiency and physical and mental health in a longitudinal survey of welfare recipients.

Food insufficiency is a significant problem in the United States, and poor African American women with children are at especially high risk. An inadequate household food supply can potentially affect the well-being of household members, but it is difficult to distinguish the effects of food insufficiency from risk factors for poor health that are also common among the food insufficient, such as poverty. We examined food insufficiency and physical and mental health among African American and white women (n = 676) who were welfare recipients in 1997. Controlling for common risk factors, women who reported food insufficiency in both 1997 and 1998 were more likely to report fair or poor health at the later date. Food insufficiency in 1998 was significantly associated with meeting the diagnostic screening criteria for recent major depression. Food insufficiency at both times and in 1998 only was related to women's sense of mastery. These findings add to growing evidence that household food insufficiency is associated with poor physical and mental health.

Adolescent↗
PubMed2004

Attendance at religious services and mortality in a national sample.

Research and theory increasingly suggest that attendance at religious services is protective against premature mortality. However, prior studies are limited and do not extensively explore potential explanations for the relationship, especially in terms of religious beliefs and behaviors associated with service attendance. This study estimates the impact of service attendance on mortality in a national probability sample and provides the most extensive empirical examination of potential explanations. Individuals who report attending religious services once a month or more (just over 50 percent of the population) have a 30-35 percent reduced risk of death over a 7.5 year follow-up period after adjusting for potential confounding factors. Consistent with prior research, 20-30 percent of this effect may be explained by better health behaviors (especially physical activity) among regular service attendees. Surprisingly, other religious beliefs and behaviors do not explain, and often tend to suppress, the association between service attendance and mortality.

Adult↗
PubMed2004

Deconvolution of adaptive optics retinal images.

We quantitatively demonstrate the improvement to adaptively corrected retinal images by using deconvolution to remove the residual wave-front aberrations. Qualitatively, deconvolution improves the contrast of the adaptive optics images. In this work we demonstrate that quantitative information is also increased by investigation of the improvement to cone classification due to the reduction in confusion of adjacent cones because of the extended wings of the point-spread function. The results show that the error in classification between the L and M cones is reduced by a factor of 2, thereby reducing the number of images required by a factor of 4.

Algorithms↗
PubMed2004

Negotiation as relationship-building in healthcare organizations: a case study exercise.

A key skill needed by healthcare managers is an ability to simultaneously maintain and enhance relationships with multiple stakeholders, most notably clinical professionals, through the process of decision-making and negotiation. Additionally, healthcare managers need to be able to actively integrate various components of functional areas into their decision-making process. This article presents two exercises that serve the following purposes: (1) it can help raise students' awareness of the complexity involved in decision-making and negotiating, (2) it can create an understanding that decision-making and negotiations are embedded in a larger context involving multiple relationships between parties, and (3) it can be used as a means to measure the student's integrative ability within the traditional curriculum of an MHA program.

Curriculum↗
PubMed2003

Leucascandrolide A: a second generation formal synthesis.

A convergent, second generation formal synthesis of (+)-Leucascandrolide A (1) has been efficiently achieved by providing a flexible, enantiocontrolled strategy toward the bioactive macrolactone component. Advancements for stereocontrol in asymmetric allylation methodology are discussed. Efforts feature novel results for reductions using the Terashima hydride reagent. [structure: see text]

Allyl Compounds↗
PubMed2003

Total synthesis of (-)-stemonine.

[reaction: see text] An enantioselective total synthesis of (-)-stemonine (1) is reported via a convergent assembly of the acyclic precursor 2. Key transformations include a Staudinger-aza-Wittig reaction to form the central perhydroazepine ring system and an iodine-induced tandem cyclization to construct the pyrrolidino-butyrolactone framework.

Alkaloids↗
PubMed2003

Total synthesis of (+)-4,5-deoxyneodolabelline.

The first total synthesis of the marine dolabellane diterpene (+)-4,5-deoxyneodolabelline (1) has been accomplished. The highly efficient approach is characterized by the convergent assembly of dihydropyrans 2ab and cyclopentylsilanes 3ab. Allylic silane 3a was prepared from 2-methyl-2-cyclopentenone via a copper-catalyzed 1,4-addition followed by diastereoselective alkylation of the resulting enolate. A chemical resolution of racemic cyclopentanone 8 was effected by (S)-CBS-catalyzed borohydride reduction. Direct hydroxymethylation of the enantioenriched ketone 8 to form allylic alcohol 14 was achieved by a Stille palladium-catalyzed cross-coupling from the cyclopentenyl triflate 13. Treatment of the corresponding allylic phosphate 15 with trimethylsilylcopper reagent provided for displacement with allylic transposition yielding the exocyclic allylsilane 3a with excellent diastereoselectivity. Dihydropyrans 2a and 2b were prepared from optically pure acyclic acetals via ring-closing metathesis. Coupling of 3a and 2a or 2b via the carbon-Ferrier protocol gave trans-2,6-disubstituted dihydropyrans 30 and 35 with complete stereoselectivity. Vanadium-based pinacol coupling reactions were explored for closure of the medium-sized carbocycle to yield syn-diol 33. X-ray diffraction studies of the monobenzoate 34 have provided unambiguous stereochemical assignments. Substantial ring strain accounted for the lack of alkene products typical of reductive elimination using TiCl(3) and zinc-copper couple (McMurry) conditions leading to 37. Finally, the natural product 1 was obtained via Swern oxidation of the diol 37.

Alkylation↗
PubMed2003

Separate effects of the microkeratome incision and laser ablation on the eye's wave aberration.

PURPOSE: To study the optical changes induced by the microkeratome cut, the subsequent laser ablation, and the biomechanical healing response of the cornea in normal laser in situ keratomileusis (LASIK) eyes. DESIGN: Prospective randomized clinical trial. METHODS: A Hansatome microkeratome was used to cut a corneal flap in one eye (study eye) of 17 normal myopic patients and a subsequent laser ablation was performed 2 months after this initial microkeratome incision. Control eyes received conventional LASIK treatments at the latter time point. The wave aberration of both the study and contralateral control eyes were measured over a 6-mm pupil with a Shack-Hartmann wavefront sensor for all preoperative, postflap cut, and postablation visits. RESULTS: The eye's higher order aberrations had a small, but significant increase (P =.03) of approximately 30% 2 months after cutting a flap. No systematic changes were observed in nearly all Zernike coefficients from their preoperative levels at 2 months postflap cut. A significant difference between the study and control eyes was observed for one trefoil mode, Z(3)(3) (P =.04). CONCLUSIONS: There was a wide variation in the response of individual Zernike modes across patients after cutting a flap. The majority of spherical aberration induced by the LASIK procedure seems to be due to the laser ablation and not the microkeratome cut. In addition, the total and higher order root mean square of wavefront errors were nearly identical for both the study and control eyes 3-months after the laser ablation, indicating that a procedure in which the incision and the ablation are separated in time to better control aberrations does not compromise the outcome of a conventional LASIK treatment.

Adult↗
PubMed2003

Psychiatric disorders and substance dependence among unmarried low-income mothers.

The study reported in this article examined the prevalence of mental health disorders and the sociodemographic factors associated with having a mental health disorder in a probability sample of 185 African American and white single mothers. Logistic regression analyses revealed that race (being white) and being on welfare were associated with increased risk of having a mental health disorder, when controlling for other sociodemographic variables. The association of welfare status and psychiatric disorders highlights the need for access to mental health services for this population. Implications for low-income women making the transition from welfare to employment are discussed.

Adolescent↗
PubMed2003

Racism and cardiovascular disease in African Americans.

This article provides an overview of the evidence on the ways racism can affect the disproportionate rates of cardiovascular disease (CVD) in African Americans. It describes the significant health disparities in CVD for blacks and whites and suggests that racial disparities should be understood within the context of persistent inequities in societal institutions and relations. Evidence and potential pathways for exploring effects of 3 levels of racism on cardiovascular health risk factors and outcomes are reviewed. First, institutional racism can lead to limited opportunities for socioeconomic mobility, differential access to goods and resources, and poor living conditions that can adversely affect cardiovascular health. Second, perceived/personally mediated racism acts as a stressor and can induce psychophysiological reactions that negatively affect cardiovascular health. Third, in race-conscious societies, such as the United States, the negative self-evaluations of accepting negative cultural stereotypes as true (internalized racism) can have deleterious effects on cardiovascular health. Few population-based studies have examined the relationship between racism and CVD. The findings, though suggestive of a positive association, are neither consistent nor clear. The research agenda of the Jackson Heart Study in addressing the role of racism in CVD is presented.

Black or African American↗
PubMed2003

A method to predict refractive errors from wave aberration data.

We explored the impact of the eye's higher-order aberrations on subjective refraction comparing two classes of methods for estimating refractive state, one based directly on the wave aberration defined in the pupil plane and another based on the retinal image plane. The method defined in the pupil plane chose the sphere and cylinder that either minimized the wave aberration root mean square or minimized the sum of all the spherical and cylindrical components in the wave aberration. The method defined in the image plane chose the sphere and cylinder that optimized an image-quality metric such as the Strehl intensity ratio, the entropy and the intensity variance of the point-spread function, the volume under the modulation transfer function, or the volume under the contrast-sensitivity function. All these methods were compared in a population of six eyes for which we measured both the wave aberration with a Shack-Hartmann wavefront sensor and the subjective refraction under identical conditions. Pupil plane methods predicted subjective refraction poorly. The mean absolute error of the prediction, in spherical equivalent, was about 0.5 D (range, 0.1 to 0.8 D) and increased with increases in higher-order aberrations. However, for all the retinal image plane methods, the mean error between predicted and subjective refraction was about 0.1 D (range, 0 to 0.25 D). The reliability of the method based on the image-quality optimization was further confirmed in a large population of 146 eyes. In conclusion, higher-order aberrations influence the amount of sphere and cylinder required to correct vision. The results indicate that subjective refraction can be predicted from the eye's optics alone by optimizing computed retinal image quality.

Adult↗
PubMed2003

The reflectance of single cones in the living human eye.

PURPOSE: Individual cones were imaged in the living human eye with the Rochester adaptive optics ophthalmoscope. In all eyes, there were large differences in the reflectance of different cones, even when all the photopigment was bleached. To help understand what produces this spatial variation, the investigators explored whether it is a static or a dynamic property of the cone mosaic. METHODS: Fully bleached cone images were acquired in three eyes with an adaptive optics system. Images were collected over a 10-minute period approximately every hour for 24 hours. The temporal variation in cone directionality was measured in one eye. Finally, the experimental data on the temporal variation of absorption were compared with findings in various models of reflectance. RESULTS: Cone reflectance changes over time appear to be independent from cone to cone. These temporal changes are present in all three cone classes. The spatiotemporal variation in cone reflectance is not caused by the spatiotemporal variation in the optical axes of cones. This, along with the modeling results, suggest that changes in the reflectance affect the light that passes through photopigment in the receptors rather than the stray light, and that the changes are related to the outer segment-retinal pigment epithelium (RPE) interface. CONCLUSIONS: The reflectance of individual cones is a dynamic property of the mosaic. Changes can be observed over periods of minutes as well as many hours. The cause of the variation is not known but may be related to the process of disc shedding in receptors.

Adult↗