A perturbation solution for compressible viscous channel flows

The two-dimensional compressible Navier-Stokes equations are solved by a perturbation expansion in the parameter (Mach number)²/Reynolds number. A fortieth-order solution is generated by a computer algorithm. These series are then summed as convergent series of diagonal Padé approximants. Effectively-exact solutions have been found for Reynolds numbers between zero and 1000 and a range of subsonic Mach numbers in the case of fully-developed isothermal flow between parallel side walls. Choking of the flow is shown to occur for a moderate value of channel Reynolds number. The two-dimensional velocity and pressure fields are obtained. The engineering assumption that friction factor is sensibly independent of Mach number may lead to significant underprediction of head loss in the laminar flow regime.     

Meta-analysis of DRD3 gene and schizophrenia: ethnic heterogeneity and significant association in Caucasians

BACKGROUND: Children with asthma may be at increased risk for low immunization rates given that they have recurrent illnesses that often result in acute care visits to their pediatrician, visits to the emergency room, admissions to the hospital, and visits to subspecialists, where immunizations are not routinely administered. OBJECTIVES: To assess immunization rates for routine and influenza vaccines in children with asthma and assess factors that may contribute to delay. METHODS: We conducted a cross-sectional survey of 117 children aged 6 to 48 months with onset of asthma within the first 15 months of life. Subjects were recruited from an allergy and immunology clinic at an urban, tertiary care center. Those judged to have immunization delay did not have the required 4 DTP, 3 OPV, and 1 MMR vaccine by age 24 months (4:3:1 series). Receipt of influenza vaccine was determined for eligible children with moderate to severe asthma. RESULTS: Seventy-four (80%) children had up-to-date immunizations at age 24 months. Those with delay had fewer visits to a subspecialist than those who were up-to-date (1 versus 2 visits P = .010). Twenty-two (25%) of 87 eligible subjects received influenza vaccine. Recipients were more likely to have been hospitalized than nonrecipients (77% versus 49%, P = .022). CONCLUSIONS: Though the majority of young children with asthma were up-to-date for routine immunizations, only 25% of children with moderate to severe asthma received influenza vaccine. Greater efforts must be made by pediatricians and asthma subspecialists to ensure that children with moderate to severe asthma are immunized against influenza virus.     

Solution structure of the minor conformer of a DNA duplex containing a dG mismatch opposite a benzo[a]pyrene diol epoxide/dA adduct: glycosidic rotation from syn to anti at the modified deoxyadenosine

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants whose metabolism in mammals results in deleterious cell transformation. Covalent modification of DNA by diol epoxides metabolically formed from PAHs such a benzo[a]pyrene (BaP) provides a mechanism for the genotoxicity, mutagenicity, and carcinogenicity of PAHs. We had previously reported NMR evidence for a minor conformer of the duplex d(G1G2T3C4A5*C6G7A8G9).d(C10T11C12G13G14G15A16C17C18) containing a dG14 mismatch opposite a dA5* residue modified at the exocyclic amino group by trans addition to (+)-(7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene [Yeh, H.J.C., Sayer, J.M., Liu, X., Altieri, A.S., Byrd, R.A., Lashman, M.K., Yagi, H., Schurer, E.J., Gorenstein, D.G., & Jerina, D.M. (1995) Biochemistry 34, 13570-13581]. In the present work, we describe the structure of this minor conformer (ca. 17% of the total conformer population). This represents the first structural determination of a minor conformer of a carcinogen-lesion DNA adduct. Two-dimensional NOESY, ROESY, TOCSY, and exchange-only spectra at 750 MHz allowed nearly complete sequential assignment of both conformers. In the minor conformer, the adducted base assumes an anti-glycosidic torsion angle whereas in the major conformer it assumes an unusual syn-glycosidic torsion angle. The aromatic hydrocarbon in the minor conformer is intercalated between dG13 and dG14, preserving the energetically favorable stacking interactions found in the major conformer. The major structural differences between the two conformers appear to be near the lesion site as evidenced by the large chemical shift differences between major and minor conformer protons near the lesion site; away from this site, the chemical shifts of the major and minor conformer protons are nearly identical. Because any of the conformations of benzo[a]pyrene diol epoxide-modified DNA may contribute to tumorigenic activity, structural determination of all conformations is essential for the elucidation of the mechanism of cell transformation initiated by covalent modification of DNA by PAHs.     

Determination of cadmium and lead in foods by graphite furnace atomic absorption spectrometry with Zeeman background correction: test with certified reference materials

Two methods for the determination of cadmium and lead based on graphite furnace atomic absorption spectrometry (GFAAS) with Zeeman background correction are described. The main difference between the methods is the method of sample destruction, bomb digestion versus dry ashing. The precision and accuracy of the methods has been tested by analysing 16 different reference materials, with cadmium concentrations varying from 2.9 micrograms/kg to 2.7 mg/kg and lead concentrations from 44 micrograms/kg to 13.5 mg/kg. The methods produced results which differ, with a few exceptions, less than 10% from the certified contents, with relative standard deviations of around 5%. The methods are not difficult to carry out, are not very laborious and without modifications are applicable to a large variety of products. The sample solutions obtained can also be used for the determination of other elements, e.g. Al, Cr, Cu, Hg, Mn, Ni and Zn. The detection limits, for test portions of 1 and 5 g (wet products) are 0.5-1 microgram/kg for cadmium and 5-20 micrograms/kg for lead.     

Focal cognitive deficits in dementia of the Alzheimer type.

It is widely accepted that the natural history of Alzheimer type-dementia is accurately described by a relatively fixed, invariant sequence of stages of behavioral, cognitive, and neurological symptoms. This stage-wise deterioration model is examined and found wanting. The evidence shows that there is no generalization about the inevitable ordering of symptoms that has not been contradicted by reports in the literature. Two alternatives to the stage-wise model are discussed, both of which reject the notion of a homogeneous disintegration of function and take as a goal the delimitation of a set of symptom domains that define and differentiate patients. Of these 2 alternatives, the subgroups model and the multiple components model, the latter seems to accord best with the available data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Power Doppler imaging of carotid artery stenosis. Comparison with color Doppler flow imaging and angiography

BACKGROUND AND PURPOSE: Power Doppler imaging (PDI) is a new sonographic technique that has recently been introduced for vascular application. Since the technical principles of PDI may provide increased sensitivity to visualize the continuity of blood flow in arterial stenoses, we investigated the diagnostic significance of PDI and the intermethod relationship for the measurement and classification of internal carotid artery (ICA) stenosis in comparison with both color Doppler flow imaging (CDFI) and angiography. METHODS: One hundred patients with a total of 128 ICA stenoses (50% to 69%, n = 37; 70% to 79%, n = 27; 80% to 99%, n = 64) and 12 ICA occlusions were consecutively investigated by means of PDI, CDFI, and intra-arterial angiography (n = 48). Reduction of the intrastenotic lumen was measured on longitudinal and transverse views of PDI and CDFI for the calculation of the degree of diameter and area stenosis, respectively. Angiographic stenosis was determined with the use of the North American Symptomatic Carotid Endarterectomy Trial (NASCET), European Carotid Surgery Trial (ECST), and common carotid (CC) methods. RESULTS: PDI provided significantly more excellent or good (92% versus 79%; P < .01) displays of the intrastenotic lumen than CDFI, particularly in complicated high-grade stenosis. While linear regression analysis demonstrated a high overall correlation between PDI and CDFI for diameter (r = .88; P < .001) and area stenosis (r = .79; P < .001), categorization of ICA stenosis revealed best agreement for 80% to 99% area stenoses. Since angiography frequently either underclassified (NASCET method) or overclassified (ECST, CC methods) the degree of ICA stenosis in comparison to both PDI and CDFI, the sonographic-angiographic correlation was only moderate (regression coefficients ranged from .62 to .70; P < .001). CONCLUSIONS: PDI further improves the assessment of ICA stenosis by providing better visualization of the stenotic vascular lumen than CDFI. Sonographic imaging of the stenotic plaque on both PDI and CDFI provided a direct measurement of the local degree of stenosis, while the angiographic grade of stenosis essentially depended on the method used for evaluation.     

Naturalistic action impairment in closed head injury.

The authors sought to determine whether errors of action committed by patients with closed head injury (CHI) would conform to predictions derived from frontal lobe theories. In Study 1, 30 CHI patients and 18 normal controls performed routine activities, such as wrapping a present, under conditions of graded complexity. CHI patients committed more errors even on the simplest condition; but, except for a higher proportion of omitted actions, their error profile was very similar to that of controls. Study 2 involved a subset of patients whose performance in Study 1 was within normal limits. When these high functioning patients were asked to perform the routine tasks under still more taxing conditions, they, too, committed errors in excess of the control group. Accounts based on frontal mechanisms have a difficult time explaining the overall pattern of findings. An alternative based on limited-capacity resources is suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid word learning in 13- and 18-month-olds.

A number of theorists have argued that the productive naming explosion results from advances in abilities that underlie language learning (e.g., the realization that words are symbols, changes in conceptual structure, or the onset of word learning constraints). If any of these accounts are accurate, there should be parallel developments in comprehension. To explore this issue, 4 studies assessed whether pre- and postnaming explosion children differ in their ability to learn a new word after limited exposure. 13- and 18-mo-olds heard a new object label just 9 times in a 5-min training session and then their comprehension was assessed in a multiple-choice procedure. Under favorable testing conditions, both 18- and 13-mo-olds showed comprehension of the new word, even after a 24-hr delay. These results suggest that well before the productive naming explosion, children can learn a new object label quickly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)