PubMed Health⌕ Search

Biomedical subjects

D W Hess

Publications and source records attributed to D W Hess.

7 recordsLinked to original sources
PubMed2003

Lattice trapping barriers to brittle fracture.

We present a multiscale simulation of a crack in silicon under tensile loading that is consistent with experiment; fracture is brittle with a modest lattice-trapping energy barrier to crack propagation. Our multiscale molecular-dynamics simulation has a tight-binding description of bonding near the crack tip embedded in an empirical-potential (EP) region. Forces on atoms in the tight-binding region are computed using a Green's function method. Comparing our multiscale simulation with EP simulations shows that the EP models severely overestimate lattice trapping, explaining the failure of the Griffith criterion and the dramatic differences in crack morphology. A two-length-scale model for the lattice-trapping energy barrier correctly predicts the critical load for brittle fracture. We argue that lattice trapping plays an important role in the brittle-to-ductile transition.

Journal Article↗
PubMed2000

Predictors for return to work after spinal cord injury: a 3-year multicenter analysis.

OBJECTIVE: To examine the ability of the Motor Index Score (MIS), in combination with demographic variables, to predict return to work during a 3-year period for individuals with spinal cord injury (SCI). METHODS: Prospectively collected data, between 1986 and 1995, submitted to the National Spinal Cord Injury Statistical Center were analyzed to determine the prediction of return to work utilizing variables of education, ethnicity, age, marital status, gender, and MIS. Individuals, aged 18 to 65 yrs, employed at the time of their injury, were evaluated at discharge from rehabilitation and at 1 (YR1), 2 (YR2), and 3 (YR3) years postinjury (sample sizes of 1,857, 1,486, and 1,177, respectively). RESULTS: The most important predictors of return to work were education, MIS, ethnicity, and age at onset of SCI. These variables resulted in a high rate of accuracy for predicting across all 3 yrs (YR1, 81%; YR2, 82%; YR3, 77%). CONCLUSIONS: The ability to predict return to work after SCI was shown utilizing MIS and demographic variables, with nearly 80% accuracy. This suggests that return to work after SCI is a dynamic process, with the level of importance of each variable changing with time postinjury.

Adolescent↗
PubMed1998

Biliopancreatic diversion with a duodenal switch.

BACKGROUND: This paper evaluates biliopancreatic diversion combined with the duodenal switch, forming a hybrid procedure which is a combination of restriction and malabsorption. METHODS: The evaluation is of the first 440 patients undergoing this procedure who had had no previous bariatric surgery. The mean starting weight was 183 kg, with 41% of our patients considered super morbidly obese (BMI > 50). RESULTS: There was an average maximum weight loss of 80% excess weight by 24 months postoperation; this continued at a 70% level for 8 years. Major complications were found in almost 9% of the cases. There were two perioperative deaths, one from pulmonary embolism and one from acute pulmonary obstruction. There were 36 type II diabetics, all of whom have discontinued medication following the surgery. Seventeen revisions were performed to correct excess weight loss and low protein levels. There have been no marginal ulcers, no cases of dumping syndrome, no foreign material used, and the procedure is a pyloric saving procedure which is functionally reversible. CONCLUSIONS: This operation has vastly improved the lives of seriously obese patients with many comorbidities. All type II diabetics have essentially been cured of their disease. The procedure was tolerated well and patients are quite satisfied. There was minimal regain of weight with this method.

Adult↗
PubMed1981

Learning-disordered children's evoked potentials during sustained attention.

Evoked potentials and performance of 19 learning-disordered (LD) and 19 normally achieving children were studied in two versions of the Continuous Performance Test (CPT). In both CPT procedures, LD children made more errors of omission and commission than did normal children. Evoked potential differences between groups were especially prominent in the more difficult BX version of the CPT. LD children displayed significantly smaller late positive components (LPC) of the evoked potential to critical stimuli in the task. There were no LPC differences between diagnostic groups for noncritical stimulus categories. The results suggest a deficit in behavioral and cortical indices of sustained attention among LD children.

Adolescent↗
PubMed1981

A comparison of unwed pregnant teenagers and nulligravid sexually active adolescents seeking contraception.

Unwed pregnant adolescents were contrasted with nulligravid teenagers seeking contraception. Pregnant subjects were less likely to employ or plan to use contraceptives. Gravid subjects more often described their boyfriends as happy about the pregnancy and expressed a desire for a pregnancy. Nulligravid youngsters described their parents as more disapproving of their premarital sexual activity. There is a need for counseling programs, including adolescents of both sexes, and aimed at the modification of attitudes toward contraception.

Adolescent↗