Viscous effect on stagnation depth of bubbles in a vertically oscillating liquid column

Previous theories which evaluated the stagnation depth of bubbles in a vertically oscillating liquid column are reviewed, and it is pointed out that they used an insufficient criterion for determining stagnation. The correct condition, which states that stagnation means zero mean velocity rather than acceleration, necessitates the solution of the equation of motion of the bubble, and thus viscous drag has to be included. It is shown, in accordance with available experimental data, that the value of the dimensionless group M = ω⁴A²ρh/2gP_o (which gives the stagnation depth h) is not in general a constant, but is dependent on four other dimensionless groups. Although there is no reliable information concerning the drag coefficient curve for such a situation, it is suggested, on the basis of comparison between different drag coefficient curves, that the high values of M reported in the literature and not accounted for by theory are due to bubble shape deviations from sphericity in viscous flow.     

Cerebellum in attention-deficit hyperactivity disorder: a morphometric MRI study

Clinical, neuroanatomic, neurobehavioral, and functional brain-imaging studies suggest a role for the cerebellum in cognitive functions, including attention. However, the cerebellum has not been systematically studied in attention-deficit hyperactivity disorder (ADHD). We quantified the cerebellar and vermal volumes, and the midsagittal areas of three vermal regions, from MRIs of 46 right-handed boys with ADHD and 47 matched healthy controls. Vermal volume was significantly less in the boys with ADHD. This reduction involved mainly the posterior inferior lobe (lobules VIII to X) but not the posterior superior lobe (lobules VI to VII). These results remained significant even after adjustment for brain volume and IQ. A cerebello-thalamo-prefrontal circuit dysfunction may subserve the motor control, inhibition, and executive function deficits encountered in ADHD.     

High pressure ellipsometry: a novel method for measuring the optical properties and electronic structure of materials in diamond anvil cells

High pressure ellipsometry (HPE) method was developed for determining the index of refraction of opaque materials in a diamond anvil cell (DAC). A main difficulty in DAC-based HPE, namely, the pressure-induced birefringence developed in the diamond, was overcome enabling the extraction of the ellipsometric parameters of the sample. The method used was based on the fact that an unpolarized light is unaffected by a retarding optical element and thus reduces the number of unknown parameters in the problem. Because of technical difficulties in using unpolarized light, a linear combination of orthogonal polarizations was applied. In the experimental procedure, multiangle measurements of the ellipsometric parameter ψ are collected at each pressure and the data is fitted together with a measurement of the near normal reflectivity, in order to extract the complex index of refraction. As a test case, this procedure was used to measure the high pressure index of refraction of iron up to 30 GPa for light with wavelengths of 532 and 633 nm. From the index of refraction as a function of pressure the diamond-iron interface emissivity for different pressures was derived and from which the phase transition α → ε could be identified and characterized. The emissivity increases with pressure both at the α (0-9 GPa) and the ε phase (21-30 GPa) however decreases at the mixed α - ε (9-21 GPa) range. From the imaginary part of the index of refraction the pressure dependence of the energy skin depth of iron was extracted. It was found that the energy skin depth increases by an order of magnitude at 30 GPa relative to ambient conditions.     

Magnesium Science, Technology and Applications

The science, technology and applications of magnesium alloys are reviewed. The very low density of magnesium in combination with excellent castability is leading to increased use, despite poor galvanic corrosion resistance and a higher cost than aluminum, especially in automotive applications. Even further expansion of the magnesium market should come from an expanded design base, a better understanding of the scientific underpinning of magnesium alloys, and development of cost-affordable cast and wrought products.     

Ownership and governance of university teaching hospitals: let form follow function

Under the best of circumstances, the complex decision-making and resource-allocation processes of a state university (and often of a variety of state agencies important to the university) significantly hinder the ability of the university-owned hospital to make changes critical to its financial and, hence, its programmatic success. At worst, as was the case for the University of Maryland Hospital a decade ago, the hospital can become capital-starved and operationally deficient under the bureaucratic mantle of the state and university and find itself unable to respond to the fast-changing market, placing its viability in jeopardy. To remedy this situation at the University of Maryland Hospital, in 1984 the state created a separate not-for-profit corporation, the University of Maryland Medical System ("the Medical system"), governed by its own board of directors, with a mandate to assure sound business practices, outstanding patient care, access to patients from across the state for tertiary care, access for the local disadvantaged community for comprehensive care, and attention to the academic mission of the university and its school of medicine. The results include strong financial performance, the ability to recapitalize outmoded facilities and technology, growth of strong programs, and the recruitment of excellent chairs and faculty. The Medical System's success suggests that university teaching hospitals, which necessarily depend on patient care revenues, may best be served by (1) removing them from university governance, thus allowing them to give primacy to their mission of patient care, and (2) removing them from state ownership, thus allowing them to use sound business practices in the competitive health care environment. The challenge under this arrangement is to ensure that the teaching hospitals can still support the educational and research programs that distinguish them. By establishing its independent, actively involved board of directors, the Medical System has successfully responded to this challenge.     

Thyrotropin receptor cleavage at site 1 does not involve a specific amino acid motif but instead depends on the presence of the unique, 50 amino acid insertion

Thyrotropin (TSH) receptor (TSHR) A and B subunits are formed by intramolecular cleavage of the single chain receptor at two separate sites. The region involved in cleavage at Site 2 has been identified, but previous mutagenesis studies failed to identify Site 1. We now report fortuitous observations on the effect of trypsin on the TSHR that localizes a small region harboring Site 1. Thus, as detected by immunoblotting and by 125I-TSH cross-linking to TSHR expressed on the surface of intact CHO cells, trypsin clipped a small polypeptide fragment bearing a glycan moiety from the C terminus of the A subunit. Based on the TSHR primary structure, this small fragment (1-2 kDa) contains Asn-302. This information, together with estimation of the size of the deglycosylated A subunit relative to a series of C-terminal truncated TSHR ectodomain variants, places cleavage Site 1 in the vicinity of, or closely upstream to, residue 317. Remarkably, mutagenesis of every amino acid residue between residues 298-316 (present study) and 317-362 (previous data) did not prevent cleavage at Site 1. However, cleavage at this site was abrogated by deletion of a 50-amino acid segment (residues 317-366) unique to the TSHR in the glycoprotein hormone receptor family. In summary, these data provide novel insight into TSHR intramolecular cleavage. Cleavage at Site 1 does not depend on a specific amino acid motif and differs from cleavage at Site 2 by involvement of a mechanism requiring the presence of the enigmatic TSHR 50-amino acid "insertion."     

Visuospatial deficits predict rate of cognitive decline in autopsy-verified dementia with Lewy bodies.

Dementia with Lewy bodies (DLB) is often characterized by pronounced impairment in visuospatial skills, attention, and executive functions. However, the strength of the phenotypic expression of DLB varies and may be weaker in patients with extensive concomitant Alzheimer's disease (AD). To determine whether strength of the DLB clinical phenotype impacts cognitive decline, visuospatial and language tests were retrospectively used to predict 2-year rate of global cognitive decline in 22 autopsy-confirmed DLB patients (21 with concomitant AD) and 44 autopsy-confirmed "pure" AD patients. Generalized estimating equations (GEE) revealed a significant interaction such that poor baseline performances on tests of visuospatial skills were strongly associated with a rapid rate of cognitive decline in DLB but not AD (p