An inductively powered telemetry system for temperature, EKG, and activity monitoring

An implant telemetry system for the simultaneous monitoring of temperature, activity, and EKG from small animals, such as rats, was designed with the feature that instead of a battery the system is energized by an inductive field. A 250 kHz resonant coil surrounds the cage (30 x 30 x 20 cm) and provides the approximately 100 microns of power required to operate the implant transmitter while allowing the animal unrestrained movement in the cage. The implant can also be battery operated if desired. RF transmission is in the 8-10 MHz band, which allows the use of a simple, essentially single IC chip, receiver

A long-range and long-life telemetry data-acquisition system for heart rate and multiple body temperatures from free-ranging animals

The system includes an implantable transmitter, external receiver-retransmitter collar, and a microprocessor-controlled demodulator. The size of the implant is suitable for animals with body weights of a few kilograms or more; further size reduction of the implant is possible. The ECG is sensed by electrodes designed for internal telemetry and to reduce movement artifacts. The R-wave characteristics are then specifically selected to trigger a short radio frequency pulse. Temperatures are sensed at desired locations by thermistors and then, based on a heartbeat counter, transmitted intermittently via pulse interval modulation. This modulation scheme includes first and last calibration intervals for a reference by ratios with the temperature intervals to achieve good accuracy even over long periods. Pulse duration and pulse sequencing are used to discriminate between heart rate and temperature pulses as well as RF interference

H ingestion into He-burning convection zones in super-AGB stellar models as a potential site for intermediate neutron-density nucleosynthesis

We investigate the evolution of super-AGB (SAGB) thermal pulse (TP) stars for a range of metallicities (Z) and explore the effect of convective boundary mixing (CBM). With decreasing metallicity and evolution along the TP phase, the He-shell flash and the third dredge-up (TDU) occur closer together in time. After some time (depending upon the CBM parametrization), efficient TDU begins while the pulse-driven convection zone (PDCZ) is still present, causing a convective exchange of material between the PDCZ and the convective envelope. This results in the ingestion of protons into the convective He-burning pulse. Even small amounts of CBM encourage the interaction of the convection zones leading to transport of protons from the convective envelope into the He layer. H-burning luminosities exceed 10⁹ (in some cases 10¹⁰) L⊙. We also calculate models of dredge-out in the most massive SAGB stars and show that the dredge-out phenomenon is another likely site of convective-reactive H-¹²C combustion. We discuss the substantial uncertainties of stellar evolution models under these conditions. Nevertheless, the simulations suggest that in the convective-reactive H-combustion regime of H ingestion the star may encounter conditions for the intermediate neutron capture process (i-process). We speculate that some CEMP-s/r stars could originate in i-process conditions in the H ingestion phases of low-Z SAGB stars. This scenario would however suggest a very low electron-capture supernova rate from SAGB stars. We also simulate potential outbursts triggered by such H ingestion events, present their light curves and briefly discuss their transient properties

Carbon-rich presolar grains from massive stars : subsolar ¹²C/¹³C and ¹⁴N/¹⁵N ratios and the mystery of ¹⁵N

Carbon-rich grains with isotopic anomalies compared to the Sun are found in primitive meteorites. They were made by stars, and carry the original stellar nucleosynthesis signature. Silicon carbide grains of Type X and C and low-density (LD) graphites condensed in the ejecta of core-collapse supernovae. We present a new set of models for the explosive He shell and compare them with the grains showing ¹²C/¹³C and ¹⁴N/¹⁵N ratios lower than solar. In the stellar progenitor H was ingested into the He shell and not fully destroyed before the explosion. Different explosion energies and H concentrations are considered. If the supernova shock hits the He-shell region with some H still present, the models can reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycle isotopic signatures are obtained, including a large production of ¹³C and ¹⁵N. The short-lived radionuclides ²²Na and ²⁶Al are increased by orders of magnitude. The production of radiogenic ²²Ne from the decay of ²²Na in the He shell might solve the puzzle of the Ne-E(L) component in LD graphite grains. This scenario is attractive for the SiC grains of type AB with ¹⁴N/¹⁵N ratios lower than solar, and provides an alternative solution for SiC grains originally classified as nova grains. Finally, this process may contribute to the production of ¹⁴N and ¹⁵N in the Galaxy, helping to produce the ¹⁴N/¹⁵N ratio in the solar system

Elemental bio-imaging of melanoma in lymph node biopsies

The spatial distribution of trace elements in human lymph nodes partially infiltrated by melanoma cells was determined by elemental bio-imaging. Imaging of 31P within the nodal capsule and normal lymph node tissue showed a clear demarcation of the tumour boundary, with a significant decrease in relative 31P concentration within the tumour. The location of the tumour boundary was confirmed by haematoxylin and eosin staining of serial sections and observation by light microscopy. Further enhancement of the tumour boundary was achieved by imaging the 31P/34S ratio. 31P/66Zn ratio images showed a decreasing ratio beyond the tumour boundary that extended into peritumour normal lymph node tissue. © The Royal Society of Chemistry

Supernova Fallback: A Possible Site for the r-Process

The conditions for the leading r-process site candidate, neutrino-driven winds, can not be reproduced self-consistently in current supernova models. For that reason, we investigate an alternate model involving the mass ejected by fallback in a supernova explosion, through hydrodynamic and nucleosynthesis calculations. The nucleosynthetic products of this ejected material produces r-process elements, including those in the vicinity of the elusive 3rd peak at mass number 195. Trans-iron element production beyond the second peak is made possible by a rapid (<1ms) freezeout of alpha particles which leaves behind a large nucleon (including protons!) to r-process seed ratio. This rapid phase is followed by a relatively long (>15 ms) simmering phase at ~2e9 K, which is the thermodynamic consequence of the hydrodynamic trajectory of the turbulent flows in the fallback outburst. During the slow phase high mass elements beyond the second peak are first made through rapid capture of both protons and neutrons. The flow stays close to valley of stability during this phase. After freeze-out of protons the remaining neutrons cause a shift out to short-lived isotopes as is typical for the r-process. A low electron fraction isn't required in this model, however, the detailed final distribution is sensitive to the electron fraction. Our simulations suggest that supernova fallback is a viable alternative scenario for the r-process.Comment: 12 pages (including 3 figures), submitted to ApJ, comments welcom

Neutrino Transport in Strongly Magnetized Proto-Neutron Stars and the Origin of Pulsar Kicks: The Effect of Asymmetric Magnetic Field Topology

In proto-neutron stars with strong magnetic fields, the cross section for $\nu_e$ ($\bar\nu_e$) absorption on neutrons (protons) depends on the local magnetic field strength due to the quantization of energy levels for the $e^-$ ($e^+$) produced in the final state. If the neutron star possesses an asymmetric magnetic field topology in the sense that the magnitude of magnetic field in the north pole is different from that in the south pole, then asymmetric neutrino emission may be generated. We calculate the absorption cross sections of \nue and \bnue in strong magnetic fields as a function of the neutrino energy. These cross sections exhibit oscillatory behaviors which occur because new Landau levels for the $e^-$ ($e^+$) become accessible as the neutrino energy increases. By evaluating the appropriately averaged neutrino opacities, we demonstrate that the change in the local neutrino flux due to the modified opacities is rather small. To generate appreciable kick velocity ($\sim 300$ km~s$^{-1}$) to the newly-formed neutron star, the difference in the field strengths at the two opposite poles of the star must be at least $10^{16}$~G. We also consider the magnetic field effect on the spectral neutrino energy fluxes. The oscillatory features in the absorption opacities give rise to modulations in the emergent spectra of $\nu_e$ and $\bar\nu_e$.Comment: AASTeX, 25 pages. Expanded introduction and references. This revised version was accepted by ApJ in April 1998 (to appear in the Oct 1 issue

Double Neutron Star Systems and Natal Neutron Star Kicks

We study the four double neutron star systems found in the Galactic disk in terms of the orbital characteristics of their immediate progenitors and the natal kicks imparted to neutron stars. Analysis of the effect of the second supernova explosion on the orbital dynamics, combined with recent results from simulations of rapid accretion onto neutron stars lead us to conclude that the observed systems could not have been formed had the explosion been symmetric. Their formation becomes possible if kicks are imparted to the radio-pulsar companions at birth. We identify the constraints imposed on the immediate progenitors of the observed double neutron stars and calculate the ranges within which their binary characteristics (orbital separations and masses of the exploding stars) are restricted. We also study the dependence of these limits on the magnitude of the kick velocity and the time elapsed since the second explosion. For each of the double neutron stars, we derive a minimum kick magnitude required for their formation, and for the two systems in close orbits we find it to exceed 200km/s. Lower limits are also set to the center-of-mass velocities of double neutron stars, and we find them to be consistent with the current proper motion observations.Comment: 25 pages, 6 figs (9 parts), 4 tables, AASTeX, Accepted in Ap

Hyper-Accreting Black Holes and Gamma-Ray Bursts

A variety of current models for gamma-ray bursts (GRBs) suggest a common engine - a black hole of several solar masses accreting matter from a disk at a rate 0.01 to 10 solar masses per second. Using a numerical model for relativistic disk accretion, we have studied steady-state accretion at these high rates. Inside a radius ~ 10**8 cm, for accretion rates greater than about 0.01 solar masses per second, a global state of balanced power comes to exist between neutrino losses, chiefly pair capture on nucleons, and dissipation. Energy emitted in neutrinos is less, and in the case of low accretion rates, very much less, than the maximum efficiency factor for black hole accretion (0.057 for no rotation; 0.42 for extreme Kerr rotation) times Mdot c**2. The efficiency for producing a pair fireball along the rotational axis by neutrino annihilation is calculated and found to be highly variable and very sensitive to the accretion rate. For some of the higher accretion rates studied, it can be several per cent or more; for accretion rates less than 0.05 solar masses per second, it is essentially zero. The efficiency of the Blandford-Znajek mechanism in extracting rotational energy from the black hole is also estimated. In light of these results, the viability of various gamma-ray burst models is discussed and the sensitivity of the results to disk viscosity, black hole rotation rate, and black hole mass explored. A diverse range of GRB energies seems unavoidable and neutrino annihilation in hyper-accreting black hole systems can explain bursts up to 10**52 erg. Larger energies may be inferred for beaming systems.Comment: 46 pages, includes 9 figures, LaTeX (uses aaspp4.sty), accepted by The Astrophysical Journal. Additional solutions in Tables and Figs. 4 and 5, minor revisions to text, references adde