32,453 research outputs found
Evaluation of commercial pyroelectric detectors
A series of commercially available pyroelectric detectors made from PVF2, LTO, SBN, and TGS were evaluated in terms of responsivity and detectivity as a function of frequency. The performance of the detectors evaluated was very different, depending upon the manufacturer of the detector, and this dependency was primarily related to the thickness of the various detectors. The best detectors of each material were comparable in performance at frequencies around 10 Hz but differed radically at frequencies above 100 Hz
Bony metastases from breast cancer: a study of foetal antigen 2 as a blood tumour marker.
Background : Foetal antigen 2 (FA-2), first isolated in the amniotic fluid, was shown to be the circulating form of the aminopropeptide of the alpha 1 chain of procollagen type I. Serum concentrations of FA-2 appeared to be elevated in a number of disorders of bone metabolism. This paper is the first report of its role as a marker of bone metabolism in metastatic breast cancer.
Methods: Serum FA-2 concentrations were measured by radioimmunoassay in 153 women with different stages of breast cancer and in 34 normal controls.
Results: Serum FA-2 was significantly elevated in women with bony metastases (p < 0.015). Its levels were not significantly different among women with non-bony metastases, with non-metastatic disease, as well as among normal controls.
Conclusions: FA-2 is a promising blood marker of bone metabolism. Further studies to delineate its role in the diagnosis and management of bony metastases from breast cancer are required
High field CdS detector for infrared radiation
New and highly sensitive method of detecting infrared irradiation makes possible solid state infrared detector which is more sensitive near room temperature than usual photoconductive low band gap semiconductor devices. Reconfiguration of high field domains in cadmium sulphide crystals provides basis for discovery
A study of beryllium and beryllium-lithium complexes in single crystal silicon
When beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 MeV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-MeV level is due to a more complex beryllium configuration than the 191-MeV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two acceptor levels at 106 MeV and 81 MeV. Quenching and annealing studies indicate that these levels are due to lithium forming a complex with the defects responsible for the 191-MeV and 145-MeV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-MeV beryllium level is split into two levels, presumably by internal strains. Tentative models are proposed
Squeezing out the last 1 nanometer of water: A detailed nanomechanical study
In this study, we present a detailed analysis of the squeeze-out dynamics of
nanoconfined water confined between two hydrophilic surfaces measured by
small-amplitude dynamic atomic force microscopy (AFM). Explicitly considering
the instantaneous tip-surface separation during squeezeout, we confirm the
existence of an adsorbed molecular water layer on mica and at least two
hydration layers. We also confirm the previous observation of a sharp
transition in the viscoelastic response of the nanoconfined water as the
compression rate is increased beyond a critical value (previously determined to
be about 0.8 nm/s). We find that below the critical value, the tip passes
smoothly through the molecular layers of the film, while above the critical
speed, the tip encounters "pinning" at separations where the film is able to
temporarily order. Pre-ordering of the film is accompanied by increased force
fluctuations, which lead to increased damping preceding a peak in the film
stiffness once ordering is completed. We analyze the data using both
Kelvin-Voigt and Maxwell viscoelastic models. This provides a complementary
picture of the viscoelastic response of the confined water film
High field CdS detector for infrared radiation
An infrared radiation detector including a cadmium sulfide platelet having a cathode formed on one of its ends and an anode formed on its other end is presented. The platelet is suitably doped such that stationary high-field domains are formed adjacent the cathode when based in the negative differential conductivity region. A negative potential is applied to the cathode such that a high-field domain is formed adjacent to the cathode. A potential measuring probe is located between the cathode and the anode at the edge of the high-field domain and means are provided for measuring the potential at the probe whereby this measurement is indicative of the infrared radiation striking the platelet
Orbit-resolved photometry and echelle spectroscopy of the cataclysmic variable ST LMi during a 2007 high state
We present high-resolution echelle spectra and contemporaneous photometry of the polar ST LMi during a high state in 2007 March. Emission lines at Hα, He I λ5876, and He I λ7065 show similar line profiles over orbital phase and have narrow and broad components. These profile changes with phase are very similar to those reported in earlier high-state studies of ST LMi. The radial velocity curves from double Gaussian fits to the line profiles are interpreted as two crossing curves, neither of which is coincident with the orbital motion of the secondary star. We attribute one component to infall motions near the white dwarf and the other to a gas streaming along magnetic field lines connecting the two stars
Transport theory yields renormalization group equations
We show that dissipative transport and renormalization can be described in a
single theoretical framework. The appropriate mathematical tool is the
Nakajima-Zwanzig projection technique. We illustrate our result in the case of
interacting quantum gases, where we use the Nakajima-Zwanzig approach to
investigate the renormalization group flow of the effective two-body
interaction.Comment: 11 pages REVTeX, twocolumn, no figures; revised version with
additional examples, to appear in Phys. Rev.
Making Sense of the Legendre Transform
The Legendre transform is an important tool in theoretical physics, playing a
critical role in classical mechanics, statistical mechanics, and
thermodynamics. Yet, in typical undergraduate or graduate courses, the power of
motivation and elegance of the method are often missing, unlike the treatments
frequently enjoyed by Fourier transforms. We review and modify the presentation
of Legendre transforms in a way that explicates the formal mathematics,
resulting in manifestly symmetric equations, thereby clarifying the structure
of the transform algebraically and geometrically. Then we bring in the physics
to motivate the transform as a way of choosing independent variables that are
more easily controlled. We demonstrate how the Legendre transform arises
naturally from statistical mechanics and show how the use of dimensionless
thermodynamic potentials leads to more natural and symmetric relations.Comment: 11 pages, 3 figure
- …