Filter efficiency as a function of nanoparticle velocity and shape

The filtration efficiency of a conventional fibrous filter was investigated with particular emphasis on the removal of particles with different shapes. A previous study has shown that particles of spherical shape are removed from the gas carrier with efficiencies which are higher when compared to cubic particles of the same aerodynamic size. In this project, to challenge our previously made explanation, spherical PSL and cubic MgO particles were tested along with particles of sodium chloride (NaCl) of intermediate shape (cubic particles with rounded edges) at a range of filtration velocities from 5 to 20 cm/s. It was found that particles of NaCl are removed with efficiencies lower then those for PSL particles but higher than the efficiencies for cubic particles of MgO, at the lowest filtration velocity when inertial effects are negligible. The rounded NaCl particles, depending on the geometry of the contact, could either land on the rounded corner and hence roll, land on a sharp edge and hence tumble, or slide. This range of options alters the probability of detachment of the particle. The difference between the filter efficiencies for cubic MgO particles and intermediate shaped NaCl particles is decreasing with the increase in velocity. With increasing velocity, the filtration efficiency of the cubic MgO particles, exceeds the filtration efficiency for the intermediate shaped NaCl particles, due to the dominating inertial effects of the denser, and hence heavier, MgO particles. This paper shows the results of these experiments and, we hope, will ignite the interest of the aerosol community towards further theoretical analysis of the phenomenon.     

Cardiovascular risk factor levels in adults with mental retardation

Cardiovascular risk factors in a population of adults with mental retardation were examined. The subjects resided in three types of settings (16+ bed facility, group home, and natural family) and were measured on the following parameters: blood lipids, obesity, and smoking. The data were compared to a nonretarded population and to the guidelines established by the National Cholesterol Education Program. Results indicated that adults with mental retardation had cardiovascular risk profiles similar to those of individuals without mental retardation in the Framingham Offspring Study and that to the extent that cardiovascular health is a concern to the general population, it must also be a concern for individuals with mental retardation.     

Structure-function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E

Bioactive peptides have multiple conformations in solution but adopt well-defined conformations at lipid surfaces and in interactions with receptors. We have used side chain lactam cross-links to stabilize secondary structures in the following peptide models of a conserved N-terminal domain of apolipoprotein E (cross-link periodicity in parentheses): I, H2N-GQTLSEQVQEELLSSQVTQELRAG-COOH (none); III, [sequence; see text] (i to i + 3); IV,[sequence; see text] (i to i + 4); IVa, [sequence, see text] (i to i + 4) (lactams above the sequence, potential salt bridges below the sequence). We previously demonstrated [Luo et al. (1994) Biochemistry 33, 12367-12377; Braddock et al. (1996) Biochemistry 35, 13975-13984] that peptide III, containing lactam cross-links between the i and i + 3 side chains, enhances specific binding of LDL via a receptor other than the LDL-receptor. Peptide III in solution consists of two short alpha helices connected by a non alpha helical segment. Here we examine the hypothesis that the domain modeled by peptide III is one antipode of a conformational switch. To model another antipode of the switch, we introduced two strategic modifications into peptide III to examine structure-function relationships in this domain: (1) the spacing of the lactam cross-links was changed (i to i + 4 in peptides IV and IVa) and (2) peptides IV and IVa contain the two alternative sequences at a site of a possible end-capping interaction in peptide III. The structure of peptide IV, determined by 2D-NMR, is alpha helical across its entire length. Despite the remarkable degree of structural order, peptide IV is biologically inactive. In contrast, peptides III and possibly IVa contain a central interruption of the alpha helix, which appears necessary for biological activity. These and other studies support the hypothesis that this domain is a conformational switch which, to the extent that it models apolipoprotein E itself, may modulate interactions between apo E and its various receptors.     

Cloud Stabilization of Orange Juice by High Pressure Processing

High pressure processing (HPP) was investigated as a means to preserve cloud in freshly squeezed orange juice. Cloud loss is a major quality defect in orange juice, and methods of preserving cloud without the extreme temperatures used in commercial pasteurization are desirable. Pressures from 500 to 900 MPa were investigated at dwell times of 1 sec, 1 min and 10 min. Higher pressures and longer processing times were more effective at preserving cloud, while all treatments yielded a microbially stable product. A 90-day shelf life under refrigeration conditions could be achieved using pressures of 700 MPa and higher combined with treatment times of 1 min.