Slipped capital femoral epiphysis associated with radiation therapy

We reviewed 32 children with 41 radiation-therapy associated slipped capital femoral epiphyses (RTASCFE). Ten were from the authors' institutions and 22 from the literature. Gender distribution was equal. The age at diagnosis of the malignancy was 4.3 +/- 3.1 years; the amount of radiation was 4,240 +/- 1,445 rads. Children with RTASCFE presented younger (10.4 +/- 3.2 years) than a routine SCFE. The average symptom duration was 5 +/- 6 months. Children with RTASCFE are usually thin (median weight, 10th percentile) in contrast to children with typical SCFE, who are usually obese (<95th percentile). The majority (82%) of the slips were mild, compared to routine SCFEs (approximately 50%); 28% were bilateral. There was a positive linear relationship between the age at presentation of the SCFE and the age at diagnosis of the malignancy; there was a negative linear relationship between the age at presentation of the SCFE and the amount of radiation therapy.     

Association between homeobox-containing gene MSX1 and the occurrence of limb deficiency

Impaired exercise capacity is a common finding in chronic obstructive pulmonary disease (COPD) patients. This reduction is not a simple consequence of airflow limitation. Peripheral muscle weakness, deconditioning and impaired gas exchange, were recognized as important contributors to exercise intolerance. In this overview, the contribution of peripheral muscle function and muscle training to exercise performance is discussed by means of three questions: 1) Is peripheral muscle dysfunction contributing to exercise limitation in COPD? 2) How do we measure peripheral muscle function? 3) Are peripheral muscle training modalities effective? At present, there is substantial evidence for peripheral muscle dysfunction. Both reduced force generating capacity as well as impaired muscle metabolism were observed and these findings contributed substantially to the reduced exercise capacity in COPD. Peripheral muscle strength measurements are feasible with mechanical or electronic devices and revealed muscle weakness in COPD patients. However, this weakness is not uniform for all muscle groups. Upper arm and leg muscles were more affected than hand muscles. This may, at least in part, be related to differences in the levels of inactivity between leg and hand muscles. In addition, muscle weakness is associated with impaired exercise capacity and symptoms of increased exertion during exercise. Endurance exercise training, i.e. cycling and treadmill walking, improved exercise capacity and was associated with alterations in muscle metabolism. Strength training of peripheral muscles showed increases in submaximal exercise performance and quality of life measures. These improvements were observed independently of the degree of airflow obstruction. The optimal training regimen (strength or endurance), and the muscle groups to be trained, remain to be determined.     

Statistical designs for familial aggregation

In the past two decades, it has become increasingly clear that genetic factors contribute to the aetiology of many common diseases including cancers, coronary disease, allergy and psychiatric disorders. While one goal of genetic epidemiological studies is to locate susceptibility genes for these complex diseases, it is important that strong evidence of familial aggregation be established at an early stage of research. In this paper, we discuss several study designs useful to address some issues such as (1) detecting familial aggregation, (2) testing for gene-environment interaction, (3) identifying homogeneous subgroups and (4) measuring magnitude and patterns of familial correlations. These designs include the conventional case-control design and the family case-control design. For each of these two study designs, we discuss analytical strategies as well as their strengths and weaknesses. Throughout, several examples from real studies are used for illustrative purposes.     

Evaluation of four probability distribution models for speckle in clinical cardiac ultrasound images

Segmenting cardiac ultrasound images requires a model for the statistics of speckle in the images. Although the statistics of speckle are well understood for the raw transducer signal, the statistics of speckle in the image are not. This paper evaluates simple empirical models for first-order statistics for the distribution of gray levels in speckle. The models are created by analyzing over 100 images obtained from commercial ultrasound machines in clinical settings. The data in the images suggests a unimodal scalable family of distributions as a plausible model. Four families of distributions (Gamma, Weibull, Normal, and Log-normal) are compared with the data using goodness-of-fit and misclassification tests. Attention is devoted to the analysis of artifacts in images and to the choice of goodness-of-fit and misclassification tests. The distribution of parameters of one of the models is investigated and priors for the distribution are suggested.     

Liquefaction and Deformation Analyses Using a Total Stress Approach

Estimating deformations due to seismically induced liquefaction is often accomplished with a series of simplified uncoupled analyses. An alternative approach is presented in this paper that builds upon this common practice while making significant improvements to the modeling quality. A two-dimensional finite-difference analysis is performed in the time domain using a simple plasticity-based constitutive model. The triggering of liquefaction is assessed in each element by continuously weighting the cyclic shear stress history. Liquefaction is initially predicted in the most susceptible elements and then progressively spreads as the earthquake continues. The properties of liquefied elements are adjusted at the instant of liquefaction to reflect the anticipated loss of strength and stiffness. Dynamic equilibrium is always maintained so that computed deformations are rationally affected by the structural response, progressing liquefaction, and gravity forces. The method is demonstrated through application to the Upper San Fernando Dam and its response to the San Fernando earthquake of 1971. The objective of this approach is to achieve a practical balance between a rigorous numerical and theoretical analysis and currently accepted practice.     

Building a retargetable local instruction scheduler

While high-performance architectures have included some Instruction-Level Parallelism (ILP) for at least 25 years, recent computer designs have exploited ILP to a significant degree. Although a local scheduler is not sufficient for generation of excellent ILP code, it is necessary as many global scheduling and software pipelining techniques rely on a local scheduler. Global scheduling techniques are well-documented, yet practical discussions of local schedulers are notable in their absence. This paper strives to remedy that disparity by describing a list scheduling framework and several important practical details that, taken together, allow implementation of an efficient local instruction scheduler that is easily retargetable for ILP architectures. The foundation of our machine-independent instruction scheduler is a timing model that allows easy retargetability to a wide range of architectures. In addition to describing how a general list-scheduler can be implemented within the framework of our timing model, experimental results indicate that lookahead scheduling can profoundly improve a scheduler's ability to produce a legal schedule. Further experimental data shows that deciding to schedule a data dependence DAG (DDD) in forward or reverse order depends significantly upon that target architecture, suggesting the possibility of scheduling in each direction and using the best of the two schedules. In contrast, experiments demonstrate little difference in code quality for schedules generated by either instruction-driven or operation-driven schedulers. Thus, the inherent flexibility of operation-driven methods suggests including that approach in a retargetable instruction scheduler. List scheduling is, of course, a heuristic scheduling method. A variety of scheduling heuristics are presented. In addition, the paper describes a method, using a genetic algorithm search, to ‘fine-tune’ the weights of twenty-four individual heuristics to form a DDD-node heuristic tuned to a specific architecture. © 1998 John Wiley & Sons, Ltd.     

Mass customisation

Mass production and personally tailored products are no longer considered opposite ends of the spectrum. The author recounts IBM's experiences in the days of the commodity PC. Once mass production relied on making all products exactly the same. `Customisation' is the opposite of this: making a product specifically for the individual customer. `Mass customisation' is a paradoxical idea that has only become possible with the arrival of modern manufacturing practices, such as just in time and total quality management. The author's interpretation of the phrase is simply: the process of reflecting very specific and varied customer requirements within a high volume production process without affecting lead time, cost or quality. Customers around the world, and in every conceivable activity, rightly demand more and more from their suppliers-impeccable quality, competitive prices, solutions as opposed to commodities and, of course, responsive and efficient after sales service. The author focuses on IBM's attempts to meet these demands in the arena of the personal computer     

No common major gene for apolipoprotein A-I and HDL3-C levels: evidence from bivariate segregation analysis

Apolipoprotein A-I (apo A-I) is the most abundant protein in high-density lipoprotein (HDL) particles, and it plays an important role in HDL metabolism. Both apo A-I and HDL cholesterol (HDL-C) levels are inversely associated with risk of cardiovascular disease. Segregation analyses suggest apo A-I levels are under the control of one or more major loci. Since HDL particles are heterogeneous in their composition and size, genetic influence on its subfractions (i.e., HDL2 and HDL3) could vary. A previous report showed evidence of a major locus controlling HDL3-C levels in a subset of the current study population. Because quantitative trait loci involved in complex diseases are likely to have pleiotropic effects on several related traits, it is possible to have a common major gene involved in regulating apo A-I and HDL3-C levels. We performed a bivariate segregation analysis of apo A-I and HDL3-C levels in 1,006 individuals from 137 families ascertained through probands undergoing elective, diagnostic coronary angiography at the Johns Hopkins Hospital. The results showed significant genetic correlation between these two traits, but the hypothesis of a common major gene was rejected. Bivariate segregation analysis favored a model with two genes controlling apo A-I and a third gene independently controlling HDL3-C, and the genetic correlation between these two traits is due to residual additive polygenes. Overall, results from this study suggest that there are distinct genetic mechanisms for apo A-I and HDL3-C levels. Future studies, especially linkage analysis, should consider distinct genetic mechanisms and multiple major gene loci.