University of Iowa

About: University of Iowa is a education organization based out in Iowa City, Iowa, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 49229 authors who have published 109171 publications receiving 5021465 citations. The organization is also known as: UI & The University of Iowa.

Quasistatic Contact Problems in Viscoelasticity and Viscoplasticity

Abstract: Nonlinear variational problems and numerical approximation: Preliminaries of functional analysis Function spaces and their properties Introduction to finite difference and finite element approximations Variational inequalities Mathematical modelling in contact mechanics: Preliminaries of contact mechanics of continua Constitutive relations in solid mechanics Background on variational and numerical analysis in contact mechanics Contact problems in elasticity Contact problems in viscoelasticity: A frictionless contact problem Bilateral contact with slip dependent friction Frictional contact with normal compliance Frictional contact with normal damped response Other viscoelastic contact problems Contact problems in visocplasticity: A Signorini contact problem Frictionless contact with dissipative potential Frictionless contact between two viscoplastic bodies Bilateral contact with Tresca's friction law Other viscoelastic contact problems Bibliography Index

Dystroglycan is essential for early embryonic development: disruption of Reichert's membrane in Dag1-null mice.

Abstract: Dystroglycan is a central component of the dystrophin-glycoprotein complex (DGC), a protein assembly that plays a critical role in a variety of muscular dystrophies. In order to better understand the function of dystroglycan in development and disease, we have generated a null allele of dystroglycan (Dag1neo2) in mice. Heterozygous Dag1neo2 mice are viable and fertile. In contrast, homozygous Dag1neo2 embryos exhibit gross developmental abnormalities beginning around 6.5 days of gestation. Analysis of the mutant phenotype indicates that an early defect in the development of homozygous Dag1neo2 embryos is a disruption of Reichert's membrane, an extra-embryonic basement membrane. Consistent with the functional defects observed in Reichert's membrane, dystroglycan protein is localized in apposition to this structure in normal egg cylinder stage embryos. We also show that the localization of two critical structural elements of Reichert's membrane--laminin and collagen IV--are specifically disrupted in the homozygous Dag1neo2 embryos. Taken together, the data indicate that dystroglycan is required for the development of Reichert's membrane. Furthermore, these results suggest that disruption of basement membrane organization might be a common feature of muscular dystrophies linked to the DGC.

Alcohol-induced neuronal loss in developing rats: increased brain damage with binge exposure.

Abstract: A rat model of third trimester fetal alcohol exposure was used to determine whether a smaller daily dose of alcohol can induce more severe microencephaly and neuronal loss than a larger dose, if the small dose is consumed in such a way that it produces higher blood alcohol concentrations (BACs). The possibility of regional differences within the developing brain to alcohol-induced neuronal loss was also investigated. Sprague-Dawley rat pups were reared artificially over postnatal Days 4-10 (a period of rapid brain growth similar to that of the human third trimester). Two groups received a daily alcohol dose of 4.5 g/kg, administered either as a 5.1% solution in four of the 12 daily feedings or as a 10.2% solution in two of the 12 feedings. A third group received a higher daily dose (6.6 g/kg) administered as a 2.5% solution in every feeding. Gastrostomy and suckle controls were also reared. On postnatal Day 10, the animals were perfused, and brain weights were obtained. In the hippocampal formation, cell counts were made of the pyramidal cells of fields CA1 and CA2/3, the multiple cell types of CA4 and the granule cells of the dentate gyrus. In the cerebellum, Purkinje cells and granule cells were counted in each of the ten lobules of the vermis. The lower daily dose (4.5 g/kg) condensed into two or four feedings produced high maximum BACs (means of 361.6 and 190.7 mg/dl, respectively) and significant microencephaly and cell loss, relative to controls. The higher daily dose (6.6 g/kg), administered continuously, resulted in low BACs (mean of 39.2 mg/dl) and induced no microencephaly or cell loss. Regional differences in neuronal vulnerability to alcohol were evident. In the hippocampus, CA1 neuronal number was significantly reduced only by the most condensed alcohol treatment, while CA3, CA4, and the dentate gyrus populations were not reduced with any alcohol treatment. In the cerebellum, some lobules suffered significantly greater Purkinje cell loss and granule cell loss than did others. The regions in which Purkinje cells were most mature at the time of the alcohol exposure were the most vulnerable to Purkinje cell loss.

A revised CES-D measure of depressive symptoms and a DSM-based measure of major depressive episodes in the elderly.

Abstract: This study examines the psychometric properties of two new abbreviated versions of standard measures of depression, a revised eight-item Center for Epidemiological Studies-Depression Scale (CES-D) and a short-form Composite International Diagnostic Interview (short-form CIDI). A sample of 6,133 elders, age 70 years or older, completed both measures as part of the Asset and Health Dynamics Study of the Oldest Old. The revised CES-D had an internal consistency and factor structure comparable to that of prior versions of the CES-D. The sources of discordance between the two measures were examined and the two measures were compared on self-report of four clinical variables: medical illness, physician diagnosis, psychiatric treatment, and antidepressant or tranquilizer use. Both measures were associated with self-report of physician diagnosis and psychiatric treatment. Respondents positive for depression on the CES-D reported higher rates of antidepressant use. Respondents positive on the short-form CIDI only did not report more antidepressant use than nondepressed respondents.

Well-posedness in Sobolev spaces of the full water wave problem in 3-D

Abstract: We consider the motion of the interface separating an inviscid, incompressible, irrotational fluid from a region of zero density in three-dimensional space; we assume that the fluid region is below the vacuum, the fluid is under the influence of gravity and the surface tension is zero. Assume that the density of mass of the fluid is one, the gravitational field is (0, 0,−1), the free interface is Σ(t) at time t ≥ 0, and the fluid occupies the region Ω(t). The motion of the fluid is described by vt + v · ∇v = −(0, 0, 1)−∇p on Ω(t), t ≥ 0 (Euler’s equation), (1.1) div v = 0 on Ω(t), t ≥ 0 (incompressible), (1.2) curl v = 0, on Ω(t), t ≥ 0 (irrotational), (1.3) where v = (v1, v2, v3) is the fluid velocity, p is the fluid pressure. Since we neglect the surface tension, the pressure is zero on the interface. So on the interface: p = 0, on Σ(t), (1.4) (1, v) is tangent to the free surface (t, Σ(t)). (1.5) We want to find solutions of system (1.1)-(1.5), taking prescribed initial data, such that for every fixed t ≥ 0, Σ(t) approaches the xy-plane at infinity, and |v(x, y, z; t)| → 0, |vt(x, y, z; t)| → 0, as |(x, y, z)| → ∞. Since the fluid is assumed irrotational, incompressible, we can reduce the study of the entire motion to the motion of the free surface. The above model is a 3-D water wave model. It is generally known that when surface tension is neglected, the motion of the interface between an inviscid fluid and vacuum under the influence of gravity can be subject to Taylor instability [8], [22]. In a previous work [24], we studied the 2-dimensional water wave model; we showed that for a 2-D water wave, the sign condition relating to Taylor instability always holds for nonself-intersecting interface, that is, the motion of the interface is not subject to Taylor instability. We showed further that the 2-D full nonlinear water wave problem is uniquely solvable in Sobolev spaces, locally in time, for any initially nonself-intersecting interface. Earlier works on the well-posedness in Sobolev spaces of the 2-D water wave problem include Nalimov [18], Yosihara [25], and Walter Craig [6], where the main results concern the well-posedness of the