Fabrication of fully enclosed paper microfluidic devices using plasma deposition and etching.

A fully enclosed paper microfluidic device has been fabricated using pentafluoroethane (PFE) plasma deposition followed by O2 plasma etching. Structures with one and two non-interacting, fully enclosed hydrophilic channels were generated in a single paper sheet using metal masks. Furthermore, by performing an additional O2 plasma step with a secondary mask, pinholes were created at the reaction zones for reagent loading. Finally, to demonstrate the functionality of the device, a glucose assay was performed. Quantitative analysis of glucose assays showed that the device can be used for the clinically relevant range of glucose. To our knowledge, this is the first time that such structures have been fabricated without paper stacking. Multi-layer devices have enhanced functionality relative to a single channel device, because the design space for creating networks of channels within the paper substrate is greatly expanded. The fluid-filled channels in the fabricated device are isolated, thereby preventing contamination due to handling and environmental exposure. Fluid evaporation can be inhibited by sealing the device with adhesive tape without contaminating the enclosed channels. The method described is a dry process and compatible with roll-to-roll technology, thus facilitating large scale production. The novel method to fabricate enclosed µ-PADs overcomes many of the limitations experienced with current approaches and thus offers an alternative means to develop low-cost point-of-care diagnostics for resource-limited settings.

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.

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.

A comparative study of outcomes and expenses following tetraplegia and paraplegia.

OBJECTIVE: A study was designed to directly compare individuals with tetraplegia and paraplegia to further explore neurological and functional outcomes and their impact on the expense of rehabilitation when controlling for level of completeness, age at the time of injury, and length of stay. METHODS: A sample was drawn from the National Spinal Cord Injury Database consisting of 2069 individuals, 1005 with paraplegia and 1064 with tetraplegia. RESULTS: Significant demographic differences were found between the 2 groups with regard to age, ethnicity, marital status, and employment status. Significant differences were found between the groups with regard to all individual outcome variables (p < .001) and expenses (p < .05). On average, patients with paraplegic injuries evidenced greater change and efficiency on a functional independence measure than patients with tetraplegia. In contrast, patients with tetraplegia showed greater changes and efficiency with regard to ASIA Motor Index scores. Higher rehabilitation expenses were found for patients with tetraplegia.

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.

Heavy-electron metals: new highly correlated States of matter.

Heavy-electron metals exhibit highly correlated electronic behavior at liquid helium temperatures, with conduction-electron masses some hundred times the free-electron mass. Whether "normal," antiferromagnetic, or superconducting, their electronic behavior differs drastically from their ordinary metallic counterparts. The physical origin of the large mass and unusual superconducting and magnetic properties is the strong coupling between the conduction electrons and the local f-electron moment fluctuations characteristic of these materials.

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.

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.