Bio-medical flow sensor

A bio-medical flow sensor including a packageable unit of a bottle, tubing and hypodermic needle which can be pre-sterilized and is disposable. The tubing has spaced apart tubular metal segments. The temperature of the metal segments and fluid flow therein is sensed by thermistors and at a downstream location heat is input by a resistor to the metal segment by a control electronics. The fluids flow and the electrical power required for the resisto to maintain a constant temperature differential between the tubular metal segments is a measurable function of fluid flow through the tubing. The differential temperature measurement is made in a control electronics and also can be used to control a flow control valve or pump on the tubing to maintain a constant flow in the tubing and to shut off the tubing when air is present in the tubing

Electrophotolysis oxidation system for measurement of organic concentration in water

Methods and apparatus for determining organic carbon in aqueous solution are described. The method comprises subjecting the aqueous solution to electrolysis, for generating oxygen from water, and simultaneously to ultraviolet radiation, for oxidation of substantially all organic carbon to carbon dioxide. The carbon dioxide is measured and the value is related to the concentration of organic carbon in the aqueous solution

Weak momentum scattering and the conductivity of graphene

Electrical transport in graphene offers a fascinating parallel to spin transport in semiconductors including the spin-Hall effect. In the weak momentum scattering regime the steady-state density matrix contains two contributions, one linear in the carrier number density $n$ and characteristic scattering time $\tau$, the other independent of either. In this paper we take the Liouville equation as our starting point and demonstrate that these two contributions can be identified with pseudospin conservation and non-conservation respectively, and are connected in a non-trivial manner by scattering processes. The scattering term has a distinct form, which is peculiar to graphene and has important consequences in transport. The contribution linear in $\tau$ is analogous to the part of the spin density matrix which yields a steady state spin density, while the contribution independent of $\tau$, is analogous to the part of the spin density matrix which yields a steady state spin current. Unlike in systems with spin-orbit interactions, the $n$ and $\tau$-independent part of the conductivity is reinforced in the weak momentum scattering regime by scattering between the conserved and non-conserved pseudospin distributions.Comment: 10 pages. Accepted for publication in Phys. Rev.

Statistical characterization of phenolic-novolak structures

Three statistical methods of general validity are valuable for characterizing any polymer which results from chain polymerization of multifunctional branching monomers linked through bifunctional monomers

Tunneling between Dilute GaAs Hole Layers

We report interlayer tunneling measurements between very dilute two-dimensional GaAs hole layers. Surprisingly, the shape and temperature-dependence of the tunneling spectrum can be explained with a Fermi liquid-based tunneling model, but the peak amplitude is much larger than expected from the available hole band parameters. Data as a function of parallel magnetic field reveal additional anomalous features, including a recurrence of a zero-bias tunneling peak at very large fields. In a perpendicular magnetic field, we observe a robust and narrow tunneling peak at total filling factor $\nu_T=1$, signaling the formation of a bilayer quantum Hall ferromagnet.Comment: Revised to include additional data, new discussion

Effect of discontinuities in surface catalytic activity on laminar heat transfer in arc-heated nitrogen streams

Discontinuity effects in surface catalytic activity on laminar heat transfer in arc heated nitrogen stream

Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings

We measure an anomalous magnetoresistance peak within the lowest Landau level (nu = 1) minimum of a two-dimensional hole system on (110) GaAs. Self-consistent calculations of the valence band mixing show that the two lowest spin-index Landau levels anticross in a perpendicular magnetic field B consistent with where the experimental peak is measured, Bp. The temperature dependence of the anomalous peak height is interpreted as an activated behavior across this anticrossing gap. Calculations of the spin polarization in the lowest Landau levels predict a rapid switch from about -3/2 to +3/2 spin at the anticrossing. The peak position Bp is shown to be affected by the confinement electrostatics, and the utility of a tunable anticrossing position for spintronics applications is discussed.Comment: 4 pages, 4 figure

Performance analysis of grazing incidence imaging systems

An exact expression relating the coordinates of a point on the incident ray, a point of reflection from an arbitrary surface, and a point on the reflected ray is derived. The exact relation is then specialized for the case of grazing incidence, and first order and third order systematic analyses are carried out for a single reflective surface and then for a combination of two surfaces. The third order treatment yields a complete set of primary aberrations for single element and two element systems. The importance of a judicious choice for a coordinate system in showing field curvature to clearly be the predominant aberration for a two element system is discussed. The validity of the theory is verified through comparisons with the exact ray trace results for the case of the telescope