A time-resolved study of rotational and vibrational excitation and relaxation in the13CH3F optically pumped far-infrared laser

The rotational and vibrational energy transfer processes of the¹³CH3F optically pumped far-infrared (OPFIR) laser have been studied in a time-resolved experiment. The experiment uses a tunable millimeter and submillimeter spectroscopic technique as a diagnostic probe. Included are observations of the fastDelta Jprocesses that closely connect otherJstates withinK = 3to the directly pumpedJ = 5level, a vibrational swapping mechanism that transfers excitation fromK = 3to otherKstates, vibrational relaxation due to both wall collisions and molecule-molecule collisions, the nonunity probability of vibrational deactivation in a wall collision, and pump saturation and hole burning effects due to the CO2pump laser. All of these observations are accounted for in the context of a numerical simulation. This results in a complete map of all of the collision-induced rotation-vibration transitions of importance to this basic OPFIR system including quantitative cross sections for the relevant processes.     

The thermal response to deformation to fracture of a carbon/epoxy composite laminate

The thermoelastic response to deformation of carbon-fibre/epoxy-resin composite laminates has been considered theoretically, and compared with experimental results. It is found that the surface temperature is strongly dependent on the near-surface lay-up. The total thermal response to tensile testing to failure is also reported. The results indicate that a simple, but accurate, estimation of the yield strength in composites is possible by measuring the thermoelastic limit strength, and that microstructural ‘events’ are detectable by measuring the surface temperature with sufficiently high resolution.     

Molecular approaches for the detection of truffle species in processed food products

Molecular identification techniques were applied in order to analyse food products containing fragments of some Tuber species. Samples of fungal DNA were processed by analyses of the internal transcribed spacer (ITS) region. The polymerase chain reaction (PCR) using truffle species‐specific primers, multiplex PCR, restriction fragment length polymorphism (RFLP) analysis, sequencing of the ITS region and specific oligonucleotide probe hybridisation were used. The results obtained demonstrate the applicability of these molecular strategies to the identification of truffles, even when their morphological characteristics are difficult to interpret owing to the drastic treatments utilised in food preparation or the use of unripe fruit bodies (lacking spores). Furthermore, testing was also possible starting from very small amounts of sample and degraded DNA. The methods described have important applications in both the production and sale of such food products, in order to avoid fraud and reveal the possible presence of other fungal species. © 2002 Society of Chemical Industry     

Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure

BACKGROUND: Mechanical, histological, and biochemical improvement has been described in patients after left ventricular assist device (LVAD) support. Explantation of the LVADs without heart transplantation has been described in selected patients who received this therapy as a bridge to transplantation. METHODS AND RESULTS: A retrospective review of patients receiving a mechanical bridge to transplantation at Columbia Presbyterian Hospital after July 21, 1991, was performed to determine the incidence of patients in whom the device was successfully explanted. From August 1, 1996, to February 1, 1998, we prospectively attempted to identify potential explant candidates by the use of exercise testing. During this time, we recruited 39 consecutive patients after insertion of the Thermo Cardiosystems vented electric device to participate in the following study. Approximately 3 months after device implantation, a maximal exercise test with hemodynamic monitoring and respiratory gas analysis was performed with the LVAD in the automated mode. The electric device was interfaced with a pneumatic console such that the rate could be decreased to 20 cycles/min. Hemodynamic measurements were recorded as the device rate was decreased. A repeat exercise test was then performed if the patient remained hemodynamically stable. A retrospective chart review of 111 LVAD recipients at our institution identified only 5 successful explant patients. Eighteen of the 39 patients were studied. Fifteen patients exercised with maximal device support. At peak exercise, VO2 averaged 14.5+/-3.6 mL. kg-1. min-1; LVAD flow, 8.0+/-1.3 L/min; Fick cardiac output, 11.4+/-3.3 L/min; and pulmonary capillary wedge pressure, 13+/-4 mm Hg. Seven patients remained normotensive and could exercise at a fixed rate of 20 cycles/min. In these patients, peak VO2 declined from 17.3+/-3.9 to 13.0+/-6.1 mL. kg-1. min-1. In one of these patients, the device was explanted. CONCLUSIONS: Significant myocardial recovery after LVAD therapy in patients with end-stage congestive heart failure occurs in a small percentage of patients. Most of these patients have dilated cardiomyopathy. Exercise testing may be a useful modality to identify those patients in whom the device can be explanted.     

In vivo induction of specific cytotoxic T lymphocytes in mice and rhesus macaques immunized with DNA vector encoding an HIV epitope fused with hepatitis B surface antigen

BACKGROUND: In human blood basophils, cross-linking the high-affinity IgE receptor Fc epsilonRI with multivalent antigen activates a signaling pathway leading to Ca2+ mobilization, actin polymerization, shape changes, secretion, and cytokine production. METHODS AND RESULTS: The role of tyrosine kinases in human Fc epsilonRI signaling was explored by using human basophils isolated by Percoll gradient centrifugation followed by negative and/or positive selection with antibody-coated magnetic beads. Fc epsilonRI cross-linking of more than 95% pure basophil preparations activates the protein-tyrosine kinases Lyn and Syk, previously linked to Fc epsilonRI-coupled rodent mast cell activation, as well as Zap-70, previously implicated in T-cell receptor signaling, and causes the tyrosine phosphorylation of multiple proteins. The presence of Lyn, Syk, and Zap-70 in basophils was confirmed by Western blotting in lysates of highly purified basophils and independently by confocal fluorescence microscopy in cells labeled simultaneously with kinase-specific antibodies and with the basophil-specific antibody 2D7. Comparable amounts of Lyn and Syk were found in basophils and B cells, whereas T cells appear to have greater amounts of Zap-70 than basophils. The tyrosine kinase inhibitor piceatannol spares IgE-mediated Lyn activation but inhibits IgE-induced Syk and Zap-70 activation as well as overall protein tyrosine phosphorylation and secretion. Overall protein-tyrosine phosphorylation increases steadily over a range of anti-IgE concentrations that are low to optimal for secretion. However, tyrosine phosphorylation continues to increase at high anti-IgE concentrations that elicit very little secretion (the characteristic high-dose inhibition of secretion). CONCLUSIONS: Our data demonstrate the association of anti-IgE-stimulated, protein-tyrosine phosphorylation by a cascade of tyrosine kinases, including Zap-70 as well as Lyn and Syk, with the initiation of Fc epsilonRI-mediated signaling in human basophils.     

A hypoelastic model for soils—II: A class of hypoelastic materials. Properties

A study of the mechanical behaviour of a special class of hypoelastic materials taking into account different stress histories.     

Methods of non-linear stochastic dynamics for the assessment of structural fragility

Some of the external events which can significantly contribute to the overall risk of a nuclear power plant, give rise to a dynamic excitation of the structural components which form the plant. The computation of the risk associated with these external events requires an investigation of the behaviour of the structural components beyond the elastic limit. The stochastic nature of the excitation, then, leads one to deal with a non-linear stochastic dynamic problem.

No general method of solution exists for such a problem when large structural systems are considered, although classical methods of propagating uncertainty have been successfully employed. This paper investigates the possibility of formulating an approach founded on a suitable equivalent linearization technique. In particular the authors make operative a new method of fragility analysis to be applied directly to the linearized system.

The numerical example considers a framed structural component: its aim is to show the degree of accuracy that can be reached by the approach formulated in the paper.     

MTBE ambient water quality criteria development: a public/private partnership

A public/private partnership was established in 1997, under the administrative oversight of the American Petroleum Institute (API), to develop aquatic toxicity data sufficient to calculate ambient water quality criteria for methyl tertiary-butyl ether (MTBE), a gasoline oxygenate. The MTBE Water Quality Criteria Work Group consisted of representatives from private companies, trade associations, and USEPA. Funding was provided by the private entities, while aquatic biological/toxicological expertise was provided by industry and USEPA scientists. This public/private partnership constituted a nonadversarial, cost-effective, and efficient process for generating the toxicity data necessary for deriving freshwater and marine ambient water quality criteria. Existing aquatic toxicity data were evaluated for acceptability, consistent with USEPA guidance, and nineteen freshwater and marine tests were conducted by commercial laboratories as part of this effort to satisfy the federal criteria database requirements. Definitive test data were developed and reported under the oversight of industry study monitors and Good Laboratory Practice standards auditors, and with USEPA scientists participating in advisory and critical review roles. Calculated, preliminary freshwater criteria for acute (Criterion Maximum Concentration) and chronic (Criterion Continuous Concentration) exposure effect protection are 151 and 51 mg MTBE/L, respectively. Calculated, preliminary marine criteria for acute and chronic exposure effect protection are 53 and 18 mg MTBE/L, respectively. These criteria values may be used for surface water quality management purposes, and they indicate that ambient MTBE concentrations documented in U. S. surface waters to date do not constitute a risk to aquatic organisms.     

A redundancy eliminating approach to linearly independent rings selection in the ring perception problem

Based on a recently published efficient, exact algorithm to solve the ring perception problem, a new approach is presented to feed the linear independence test on rings to enter a minimal basis with no duplicate information, thus reducing calls to the most demanding procedure in terms of computational order. The efficiency of a perfect hashing algorithm is actually met by a “pre-filtering” method derived from simple considerations.