Does palpability of primary cutaneous melanoma predict dermal invasion?

BACKGROUND: Relatively few studies have addressed the question of whether clinical estimation of melanoma thickness by palpation can accurately predict its histologic thickness. If palpability was a reliable predictor of dermal invasion, it could be used to define the surgical margin. OBJECTIVE: We sought to determine whether clinical elevation of melanoma could be used to predict the presence or absence and the degree of dermal invasion in patients with stage 1 cutaneous melanoma. METHODS: Melanomas in 165 patients were categorized by one observer as flat, just palpable, palpable, or nodular. This was compared with histologic measurements of tumor thickness. RESULTS: Overall there was significant correlation between the degree of palpability of melanoma and the presence or absence of dermal invasion (p<0.001), Breslow thickness (p<0.0001), and Clark level (p<0.001). However, the relation between palpability and Breslow thickness for invasive melanomas less than 1 mm thick was weaker (n=62, p=0.053), and the correlation between elevation and Clark level was not significant for invasive melanomas less than 4 mm thick (n=111, p>0.999). CONCLUSION: We conclude that palpability of melanoma is an inadequate guide to the presence or absence and degree of dermal invasion in melanomas less than 1 mm thick and cannot be used to determine the surgical margin.     

Age of onset of drug use and its association with DSM-IV drug abuse and dependence: results from the National Longitudinal Alcohol Epidemiologic Survey

Although adaptive explanations for menstruation go back at least twenty-five hundred years, in the last decade two new hypotheses have been advanced. The first suggests that menstruation evolved to cleanse the uterus of pathogens introduced by sperm, and the second argues that the function of endometrial regression (with the associated menstruation in humans) is to save energy by getting rid of tissue, rather than maintaining it in the absence of an available blastocyst. Both these suggestions may be questioned on the grounds that they do not take into account the physiology of the reproductive processes involved. Menstruation is not an independent physiological process and is unlikely to have been selected for independently of the evolutionary events that led to it. Furthermore, most primitive menstruating animals would have menstruated infrequently, and many may have reproduced or died without ever menstruating. In order to provide a context for understanding how menstruation may have come about, the evolution of the female vertebrate reproductive tract is briefly reviewed. In later stages, the coevolution of the embryo and uterus resulted in an intimate association between the trophoblast and the uterine blood vessels. As the embryo became more invasive, the uterus responded with increased cellular growth and differentiation of the endometrium to accommodate it. This reached its peak in mammals (such as rodents and humans), where the embryo passes through the epithelium into the endometrial stroma, which responds with differentiation of cells and blood vessels. Progesterone, secreted after ovulation, plays a crucial role in preparation for pregnancy. In addition to its well-known effects on the uterus, progesterone may be important in suppressing the inflammatory reaction that would be expected in response to the presence of a foreign body, such as an embryo. It is also suggested that vascular and cellular differentiation of the endometrial stroma has evolved by adaptation of the inflammatory (granulation tissue) reaction. When progesterone levels fall at the end of the cycle, there is tissue breakdown and bleeding. The uterus then reforms for the next ovulatory cycle. It is shown that the female reproductive tract has multiple functions that must occur in sequence. The coevolution of the embryo and maternal tract thus led to the close contact of two genetically different tissues, and problems such as the inflammatory reaction had to be overcome. Menstruation is a necessary consequence of these evolutionary changes, and needed no adaptive value in order to evolve.     

Reduction of triceps muscle force after shortening of the distal humerus: a computational model

A retrospective case reference study examining the use of alcohol and tobacco in 303 women aged 40 or over suffering from oral or oropharyngeal cancer was conducted in the south-west Netherlands. Both alcohol and tobacco consumption are important in the development of oral and oropharyngeal cancer with increased consumption of both markedly increasing the risks of cancer, but alcohol having the greater effect.     

Impact fracture behavior of continuous glass fiber-reinforced nylon 6

The impact fracture toughness of nylon 6/continuous glass fiber composites at four levels of fiber content has been studied. The composites were produced by anionically polymerizing caprolactam within a glass mat using a vacuum injection technique. Application of linear elastic fracture mechanics to characterize the impact fracture toughness of the composites, using an energy approach (G_IC), has been found to be applicable provided that a correction is made for the size of the damage zone. The concept of J_c, fracture energy per unit ligament area, has also been applied to the composites and agreement between G_IC and J_c has been found to be reasonably satisfactory. The ratio of crack propagation energy to the total energy absorbed (ductility index) has also been calculated. The ductility index was found to be close to one for the composites, indicating that additional energy is involved in propagating the fracturing cracks probably due to fiber debonding and/or crack blunting and fiber pullout. Fractographic examination of the impact fracture surface confirmed the presence of these features.     

Soccer ball anisotropy modelling

The work presented in this paper details the development of a finite element (FE) model of a soccer ball, allowing for a greater understanding of the performance of soccer balls under dynamic conditions that are representative of play. The model consists of composite shell elements that include a hyperelastic strain energy potential equation to define the latex bladder layer and a plane stress orthotropic elastic material model to define the anisotropic woven fabric outer panels. The model was validated through a series of experimental impact tests whereby the ball was impacted normal to a rigid plate at an inbound velocity of approximately 34 ms⁻¹ (76 mph), with each impact recorded using high speed video (HSV) techniques. It was found that the combined effects of ball design and panel material anisotropy resulted in impact properties such as coefficient of restitution, contact time, deformation and the 2D shape taken up by the ball at maximum deformation, to vary with pre-impact ball orientation. The model showed good agreement with the measurements, and its ability to represent the effects of anisotropy in ball design.     

Performance under capitation: the true cost of infrastructure

Administrative costs are a major item of concern for capitated provider groups, who must maintain a sophisticated infrastructure to allow them to manage and deliver clinical care to their patients under a fixed budget. The cost of this infrastructure is under steady upward pressure, as HMOs delegate more activities to providers and step up their reporting requirements. Our experience in establishing an infrastructure for a provider network is reported, and indicates substantial costs for both start-up and ongoing operations, which are highly volume dependent. A powerful case exists in favor of centralizing and pooling administrative infrastructure across related provider groups.     

Mapping Escherichia coli elongation factor Tu residues involved in binding of aminoacyl-tRNA

Two residues of Escherichia coli elongation factor Tu involved in binding of aminoacyl-tRNA were identified and subjected to mutational analysis. Lys-89 and Asn-90 were each replaced by either Ala or Glu. The four single mutants were denoted K89A, K89E, N90A, and N90E, respectively. The mutants were characterized with respect to thermal and chemical stability, GTPase activity, tRNA affinity, and activity in an in vitro translation assay. Most conspicuously tRNA affinities were reduced for all mutants. The results verify our structural analysis of elongation factor Tu in complex with aminoacyl-tRNA, which suggested an important role of Lys-89 and Asn-90 in tRNA binding. Furthermore, our results indicate helix B to be an important target site for nucleotide exchange factor EF-Ts. Also the mutants His-66 to Ala and His-118 to either Ala or Glu were characterized in an in vitro translation assay. Their functional roles are discussed in relation to the structure of elongation factor Tu in complex with aminoacyl-tRNA.