Transient response of a planar participating medium subjected to a train of short-pulse radiation

Transient response of a planar participating medium subjected to a short-pulse diffuse or collimated radiation is investigated. The pulse-width of the radiation is of the order of a nano-second. Short-pulse radiation can have a step or a Gaussian temporal variation. The homogenous participating medium with diffuse-gray boundaries is absorbing and scattering. The north boundary of the participating medium can be under the influence of a pulse train consisting of 1–4 pulses. The analysis is done using the finite volume method. Effects of the extinction coefficient and the scattering albedo on transmittance and reflectance signals are studied for a train of pulses. Unlike the previous studies with a single-pulse, a train of pulses provides more useful information about the medium.     

Heterogeneous integration through electrokinetic migration

We apply basic electrophoretic motion to semiconductor materials engineering for development of the next level of heterogeneous integration technology. Furthermore, we demonstrate the utility of these tools in integration of inorganic devices with biological species in order to explore the utility of these tools in biotechnological applications.Electrical and optical addressing techniques are shown to allow for more rapid and parallel patterning of biological species and inorganic objects     

The effect of interactions on the saturation remanence of particulate assemblies

The effect of interactions on the saturation remanence of assemblies of identical, uniaxially anisotropic, single-domain particles is calculated using a spatial-mean interaction field. The particle easy-axis directions are assumed known and given by a distribution function. The remanence is determined by finding the magnetization orientation functional of the particle easy-axis orientation which minimizes the total assembly energy. Curves of remanence versus interaction strength (assembly packing fraction) are shown for a) randomly oriented assemblies of spherical particles with uniaxial crystalline anisotropy only, b) randomly oriented assemblies of acicular particles with shape anisotropy, and c) oriented assemblies of acicular particles with 6:1 aspect ratio. Disregarding external sample-shape demagnetization effects, this model always yields increased remanences due to interactions. A criterion is given which predicts when external shape effects are capable of dominating the net interaction field to yield a reduction in remanence. The applicability of these results and extensions of the theory are discussed in relation to particle assemblies in magnetic tape and high coercivity CoNiP films.     

Factors affecting amine production in Streptococcus cremoris

S. cremoris produced highest growth and amine production in 24 h at 30°C. The optimum pH for the synthesis of histamine, tyramine and tryptamine by S. cremoris was observed at pH 5·5. Maximum production of different amines was obtained in the absence of NaCl. As the rate of incorporation of NaCl in the basal medium was increased beyond 0·5%, the level of amine production was considerably suppressed with concomitant decrease in cell growth.     

The incidence, morbidity, and mortality of surgical procedures after orthotopic heart transplantation

OBJECTIVE: The authors present their experience with patients having undergone orthotopic heart transplantation (OHT) in whom surgical conditions subsequently developed that required operative intervention. The incidence, morbidity, and mortality of these procedures are reported. SUMMARY BACKGROUND DATA: Several studies have evaluated the management options of biliary tract disease after OHT. Multiple reports of patients having undergone OHT who subsequently underwent peripheral vascular reconstructions, plastic reconstructive, and thoracic procedures also have been published. METHODS: A chart review of 349 patients who underwent OHT between 1985 and 1996 was conducted to identify surgical procedures that were required in the post-transplant period. Their outcomes are reported. RESULTS: Of 349 patients who underwent OHT, conditions requiring 94 surgical procedures developed in 54 patients (15%). Biliary tract disease developed in 17 patients (5%) who required cholecystectomy, 2 of the 5 patients with acute cholecystitis died. Eight patients (2%) underwent orthopedic procedures with no operative mortality. Flap advancements for sternal wound infections were performed in five patients and four deaths occurred. Seventeen thoracic procedures were performed in 11 patients with an overall mortality of 45%. Twenty-one vascular procedures were performed on 17 patients with 1 delayed death due to a malignancy. Seven patients underwent procedures of the colon and rectum with no mortality. Seven patients underwent repair of inguinal or incisional hernias with no mortality. Various infections occurred with one resultant death after operative intervention. Six procedures were performed for diseases of the small intestine with no resultant mortalities. CONCLUSIONS: Patients having undergone OHT and chronic immunosuppression are at increased risk of having complications develop from infection. Acute cholecystitis and sternal wound infection caused an inordinate risk of complications and death. Malignancies developed in four patients who required surgical intervention. A heightened awareness of coexisting peripheral vascular disease in patients transplanted for ischemic cardiomyopathy should exist. Close screening before surgery and surveillance after surgery to identify risk factors for infection and vascular disease and to screen for malignancies are essential.     

Computer vision methods for the study of spinodal decomposition in polymer blends

We demonstrate the use of computer vision techniques and optical microscopy to follow the kinetics and microstructure during spinodal decomposition of a polymer blend. Among other features, the mean of the population of the local maxima of the gradients in each image is computed; this global feature is shown to co-develop with the phase separation of the blend. An algorithm is presented which employs the gradient magnitude technique to analyze optical images of spinodally decomposing polymer blends. This algorithm has been used to extract the Cahn-Hilliard spinodal growth rates for a binary blend of polystyrene with poly(vinyl methyl ether). We show that the spinodal temperature can be found from the temperature dependence of this growth rate. We also show how additional shape features such as compactness might be used to study, the same binary blend.     

Small‐angle neutron scattering of poly(styrene)/poly(acrylic acid–ethyl acrylate) copolymers: The effect of the degree of hydrolysis of the poly(acrylic acid–ethyl acrylate) block

We report the results of systems based on polystyrene‐poly(ethyl acrylate) (PEA) diblocks, which self‐assemble in aqueous solutions to form spherical micelles. Previous work has shown that the rheological properties of these solutions, in particular the gel–liquid transition, can be tuned through the use of a simple hydrolysis reaction to convert PEA to poly(acrylic acid) (PAA). We studied the effect of the extent of hydrolysis on the self‐assembly and micellar interactions. Small‐angle neutron scattering (SANS) spectra were fit with a variety of models to determine the micelle structure. As more PEA was converted to PAA (i.e., as the corona became more charged and more hydrophilic), the micellar aggregation number decreased, analogous to observations of other polymeric micelles. This effect could impact the gel–liquid transition and rheology in this system and in similar micellar block copolymer gels. Finally, our SANS spectra qualitatively agreed with predictions for attractive colloidal glasses, confirming the idea that the elasticity of these gels arises from the jamming of micelles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 490–497, 2004     

Prolongation of the p53 response to DNA strand breaks in cells depleted of PARP by antisense RNA expression

The observation that 3-aminobenzamide, which inhibits a variety of ADP-ribose transferases, prolongs the gamma-irradiation-induced increase in intracellular p53 concentration suggested that one or more of such enzymes may determine the duration of the p53 response during G1 arrest. The role of poly(ADP-ribose) polymerase (PARP), an abundant nuclear enzyme activated by DNA strand breaks, in the p53 response to y-irradiation was investigated in Burkitt's lymphoma AG876 cells stably transfected with an inducible PARP antisense construct. Immunoblot analysis revealed that the cellular content of PARP was reduced to virtually undetectable levels after incubation of transfected cells for 72 h with the inducer dexamethasone. In noninduced antisense cells, the p53 concentration reached a maximum 2 h after exposure to 6.3 Gy of gamma-radiation and returned to control values by 4 h. In contrast, the p53 response in PARP-depleted antisense cells peaked at 4 h, with the levels of p53 remaining elevated for up to 12 h after y-irradiation. The maximal increase in p53 concentration was similar in both induced and noninduced cells. These results thus indicate that PARP activity, in part, determines the duration, but not the magnitude, of the p53 response to DNA damage.     

Nanolubrication: Characterization of patterned lubricant films on magnetic hard disks

Patterned lubricant films on magnetic hard disks offer potential advantages in controlled bonding sites, higher average shear strength, and longer durability. However, since the lubricant film thickness is at 1 or 2 nm, characterization of the pattern is difficult. Normal atomic force microscopic techniques can only image very small area in the nanometer range and the sharp tip can potentially modify the pattern. A wide area optical technique is needed to characterize the patterns. This paper examines patterned lubricant film using an optical surface analyzer (OSA) to image the bonded phase and mobile phase of an alcohol functionalized perfluoropolyether (PFPE) on magnetic hard disks. The phase shift signal and reflectivity intensity of the polarized light spectra provide clear optical images of the lubricant film at nanometer thickness. Optical images were successfully obtained before and after the buffing process and the ramp load and unload (L/UL) testing. Results of 100% bonded, 100% mobile, and 20% zigzag patterned lubricant films confirm that the patterned lubricant films can control the bonded/mobile ratio of such films better.