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Biomedical subjects

R L Jaffe

Publications and source records attributed to R L Jaffe.

12 recordsLinked to original sources
PubMed2006

Parity doubling and SU(2)LxSU(2)R restoration in the hadron spectrum.

We construct the most general nonlinear representation of chiral SU(2)LxSU(2)R broken down spontaneously to the isospin SU(2), on a pair of hadrons of same spin and isospin and opposite parity. We show that any such representation is equivalent, through a hadron field transformation, to two irreducible representations on two hadrons of opposite parity with different masses and axial-vector couplings. This implies that chiral symmetry realized in the Nambu-Goldstone mode does not predict the existence of degenerate multiplets of hadrons of opposite parity nor any relations between their couplings or masses.

Journal Article↗
PubMed2006

Casimir Interaction between a plate and a cylinder.

We find the exact Casimir force between a plate and a cylinder, a geometry intermediate between parallel plates, where the force is known exactly, and the plate sphere, where it is known at large separations. The force has an unexpectedly weak decay approximately L/[H3 ln(H/R)] at large plate-cylinder separations H (L and R are the cylinder length and radius), due to transverse magnetic modes. Path integral quantization with a partial wave expansion additionally gives a qualitative difference for the density of states of electric and magnetic modes, and corrections at finite temperatures.

Journal Article↗
PubMed2005

Attractive Casimir forces in a closed geometry.

We study the Casimir force acting on a conducting piston with arbitrary cross section. We find the exact solution for a rectangular cross section and the first three terms in the asymptotic expansion for small height to width ratio when the cross section is arbitrary. Though weakened by the presence of the walls, the Casimir force turns out to be always attractive. Claims of repulsive Casimir forces for related configurations, like the cube, are invalidated by cutoff dependence.

Journal Article↗
PubMed2004

Hydrodynamic properties of carbon nanotubes.

We study water flowing past an array of single walled carbon nanotubes using nonequilibrium molecular dynamics simulations. For carbon nanotubes mounted with a tube spacing of 16.4 x 16.4 nm and diameters of 1.25 and 2.50 nm, respectively, we find drag coefficients in reasonable agreement with the macroscopic, Stokes-Oseen solution. The slip length is -0.11 nm for the 1.25 nm carbon nanotube, and 0.49 for the 2.50 nm tube for a flow speed of 50 m/s, respectively, and 0.28 nm for the 2.50 nm tube at 200 m/s. A slanted flow configuration with a stream- and spanwise velocity component of 100 ms(-1) recovers the two-dimensional results, but exhibits a significant 88 nm slip along the axis of the tube. These results indicate that slip depends on the particular flow configuration.

Computer Simulation↗
PubMed2004

Casimir effect and geometric optics.

We propose a new approach to the Casimir effect based on classical ray optics. We define and compute the contribution of classical optical paths to the Casimir force between rigid bodies. We reproduce the standard result for parallel plates and agree over a wide range of parameters with a recent numerical treatment of the sphere and plate with Dirichlet boundary conditions. Our approach improves upon the proximity force approximation. It can be generalized easily to other geometries, other boundary conditions, to the computation of Casimir energy densities, and to many other situations.

Journal Article↗
PubMed2001

Quantum energies of interfaces.

We present a method for computing the one-loop, renormalized quantum energies of symmetrical interfaces of arbitrary dimension and codimension using elementary scattering data. Internal consistency requires finite-energy sum rules relating phase shifts to bound state energies.

Journal Article↗
PubMed1998

Tracheobronchial injuries after blunt chest trauma in children--hidden pathology.

BACKGROUND: Blunt thoracic injuries in children are unique because the pliability of the chest wall allows transmission of massive external force directly into the mediastinum. Children presenting after blunt chest trauma may have complete disruption of the airway with little external sign of injury. Without prompt diagnosis and appropriate treatment, the risk for progressive respiratory failure is high. METHODS: Four children with tracheobronchial injuries were referred to a pediatric trauma center from 1994 to 1997. All children, age 18 months to 13 years, suffered unusual crush injuries. All diagnoses were based on unresolved pneumothorax or pneumomediastinum. RESULTS: Bronchoscopy identified the location of injury as posterior trachea (n = 1) and right mainstem bronchus (n = 2). A tertiary bronchial injury (n = 1) was missed by initial tracheogram and subsequent bronchoscopy but identified during surgical exploration. All children survived after thoracotomy and primary repair of the injury. CONCLUSIONS: Tracheobronchial disruption is a rare, life-threatening injury. Suspicion should be high when pneumomediastinum and pneumothorax are refractory to adequate pleural drainage. Flexible bronchoscopy with intubation distal to the injury may be necessary to prevent loss of the airway. Advance preparation should include setups for bronchoscopy, thoracotomy, and cardiopulmonary bypass. Patient survival depends on preparation and prompt surgical intervention.

Adolescent↗
PubMed1990

Electroconvulsive therapy and major depression in Down's syndrome.

The authors treated two patients who had Down's syndrome and major depression with a combination of inpatient and outpatient electroconvulsive therapy (ECT). They found only 10 other similar published cases, although none involved outpatient ECT. Their experience, in conjunction with that reported in the literature, indicates that ECT is a safe and effective treatment for depressed mentally retarded individuals, including those who respond poorly to antidepressants.

Adolescent↗
PubMed1983

Urinary mutagen levels in smokers.

Urinary mutagen levels were measured over an 8-week period in a group of 13 smokers. Individual urinary mutagen levels were observed to be relatively constant and while there was a general correlation between mutagen excretion levels and cigarette consumption, individuals' excretion levels could not be predicted on the basis of either the numbers of cigarettes smoked or the tar content of the cigarettes.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Rapid assay of cytotoxicity using Tetramitus flagellates.

A simple test for measuring cytotoxic agents has been developed using the flagellate phenotype of Tetramitus rostratus. The test measures dose-dependent inhibition of cell division by individual agents such as 4-nitroquinoline-N-oxide and other mutagens. Dose-response data are given also for mixtures including coal tar pitch condensate, centrifuged particles obtained from tap water, and water concentrates prepared with XAD-2 resin. Because Tetramitus flagellates have a gullet and are particle-feeders, the assay allows for cytotoxic measurements of whole particles without prior extraction or solvent substitution procedures. The cytotoxic activities observed may reflect genotoxic activity, since all chemicals that produced a positive response are genotoxic in other test systems.

4-Nitroquinoline-1-oxide↗