Age and environment affect constitutive immune function in Red Knots (Calidris canutus)

We studied subspecies, age and environmental effects on constitutive immune function (natural antibody and complement titres, haptoglobin activity and leukocyte concentrations) in Red Knots (Calidris canutus). We compared C. c. islandica and C. c. canutus in the Wadden Sea and found no difference in immune function between subspecies. However, C. c. canutus on their wintering grounds in Banc d’Arguin had higher natural antibody and lower complement levels than C. c. canutus or C. c. islandica in the Wadden Sea. This suggests that immune function is determined more by the surrounding environment than by subspecies. We also compared age classes in the Wadden Sea and found that first year birds had significantly lower natural antibody levels than adults, but that second year birds no longer differed from adults. Finally, we examined the interaction of age and environment in Banc d’Arguin. We found that first year birds (but not adults) in a low quality habitat had higher leukocyte concentrations than first year birds or adults in a high quality habitat. Differences in available resources and defence needs between environments, and differences among individuals differentially distributed between sites, are likely important contributors to the variation in immune function we report. Future studies, which examine these factors on wild birds, will be important for our understanding of how animals function in their natural environment.

Self-aligned fabrication process for silicon quantum computer devices

We describe a fabrication process for devices with few quantum bits (qubits), which are suitable for proof-of-principle demonstrations of silicon-based quantum computation. The devices follow the Kane proposal to use the nuclear spins of 31P donors in 28Si as qubits, controlled by metal surface gates and measured using single electron transistors (SETs). The accurate registration of 31P donors to control gates and read-out SETs is achieved through the use of a self-aligned process which incorporates electron beam patterning, ion implantation and triple-angle shadow-mask metal evaporation

Radio-frequency operation of a double-island single-electron transistor

We present results on a double-island single-electron transistor (DISET) operated at radio-frequency (rf) for fast and highly sensitive detection of charge motion in the solid state. Using an intuitive definition for the charge sensitivity, we compare a DISET to a conventional single-electron transistor (SET). We find that a DISET can be more sensitive than a SET for identical, minimum device resistances in the Coulomb blockade regime. This is of particular importance for rf operation where ideal impedance matching to 50 Ohm transmission lines is only possible for a limited range of device resistances. We report a charge sensitivity of 5.6E-6 e/sqrt(Hz) for a rf-DISET, together with a demonstration of single-shot detection of small (<=0.1e) charge signals on microsecond timescales.Comment: 6 pages, 6 figure

Monitoring scan asymmetry of microwave humidity sounding channels using simultaneous all angle collocations (SAACs)

Simultaneous all angle collocations (SAACs) of microwave humidity sounders (AMSU-B and MHS) on-board polar orbiting satellites are used to estimate scan-dependent biases. This method has distinct advantages over previous methods, such as that the estimated scan-dependent biases are not influenced by diurnal differences between the edges of the scan and the biases can be estimated for both sides of the scan. We find the results are robust in the sense that biases estimated for one satellite pair can be reproduced by double differencing biases of these satellites with a third satellite. Channel 1 of these instruments shows the least bias for all satellites. Channel 2 has biases greater than 5 K, thus needs to be corrected. Channel 3 has biases of about 2 K and more and they are time varying for some of the satellites. Channel 4 has the largest bias which is about 15 K when the data are averaged for 5 years, but biases of individual months can be as large as 30 K. Channel 5 also has large and time varying biases for two of the AMSU-Bs. NOAA-15 (N15) channels are found to be affected the most, mainly due to radio frequency interference (RFI) from onboard data transmitters. Channel 4 of N15 shows the largest and time varying biases, so data of this channel should only be used with caution for climate applications. The two MHS instruments show the best agreement for all channels. Our estimates may be used to correct for scan-dependent biases of these instruments, or at least used as a guideline for excluding channels with large scan asymmetries from scientific analyses

Probing Stellar Populations in the Outskirts of NGC4244

We are using Subaru/Suprime-Cam to survey the luminous resolved stellar populations in the outskirts of galaxies lying beyond the Local Group. We report here on first results from our analysis of the low mass edge-on galaxy, NGC 4244, lying at 4.4 Mpc. Red giant branch stars are clearly resolved in the outer disk and extraplanar regions and our preliminary stellar density maps suggest the presence of an extended and asymmetric stellar component reaching significant distances above the disk plan

Red Quasars and Quasar Evolution: the Case of BALQSO FIRST J155633.8+351758

We present the first near-IR spectroscopy of the z=1.5 radio-loud BALQSO FIRST J155633.8+351758. Both the Balmer decrement and the slope of the rest-frame UV-optical continuum independently suggest a modest amount of extinction along the line of sight to the BLR (E(B-V)~0.5 for SMC-type screen extinction at the QSO redshift). The implied gas column density along the line of sight is much less than is implied by the weak X-ray flux of the object, suggesting that either the BLR and BAL region have a low dust-to-gas ratio, or that the rest-frame optical light encounters significantly lower mean column density lines of sight than the X-ray emission. From the rest-frame UV-optical spectrum, we are able to constrain the stellar mass content of the system. Comparing the maximal stellar mass with the black hole mass estimated from the bolometric luminosity of the QSO, we find that the ratio of the black hole to stellar mass may be comparable to the Magorrian value, which would imply that the Magorrian relation is already in place at z=1.5. However, multiple factors favor a much larger black hole to stellar mass ratio. This would imply that if the Magorrian relation characterizes the late history of QSOs, and the situation observed for F1556+3517 is typical of the early evolutionary history of QSOs, central black hole masses develop more rapidly than bulge masses. [ABRIDGED]Comment: 23 pages, 4 embedded postscript figures; Accepted for publication in The Astronomical Journal, December 200

Development and operation of the twin radio frequency single electron transistor for solid state qubit readout

Ultra-sensitive detectors and readout devices based on the radio frequency single electron transistor (rf-SET) combine near quantum-limited sensitivity with fast operation. Here we describe a twin rf-SET detector that uses two superconducting rf-SETs to perform fast, real-time cross-correlated measurements in order to distinguish sub-electron signals from charge noise on microsecond time-scales. The twin rf-SET makes use of two tuned resonance circuits to simultaneously and independently address both rf-SETs using wavelength division multiplexing (WDM) and a single cryogenic amplifier. We focus on the operation of the twin rf-SET as a charge detector and evaluate the cross-talk between the two resonance circuits. Real time suppression of charge noise is demonstrated by cross correlating the signals from the two rf-SETs. For the case of simultaneous operation, the rf-SETs had charge sensitivities of $\delta q_{SET1} = 7.5 \mu e/\sqrt{Hz}$ and $\delta q_{SET2} = 4.4 \mu e/\sqrt{Hz}$.Comment: Updated version, including new content. Comments most welcome: [email protected] or [email protected]

Electromagnetic Radiation Hardness of Diamond Detectors

The behavior of artificially grown CVD diamond films under intense electromagnetic radiation has been studied. The properties of irradiated diamond samples have been investigated using the method of thermally stimulated current and by studying their charge collection properties. Diamonds have been found to remain unaffected after doses of 6.8 MGy of 10 keV photons and 10 MGy of MeV-range photons. This observation makes diamond an attractive detector material for a calorimeter in the very forward region of the proposed TESLA detector.Comment: 19 pages, 9 figure

Density dependent spin polarisation in ultra low-disorder quantum wires

There is controversy as to whether a one-dimensional (1D) electron gas can spin polarise in the absence of a magnetic field. Together with a simple model, we present conductance measurements on ultra low-disorder quantum wires supportive of a spin polarisation at B=0. A spin energy gap is indicated by the presence of a feature in the range 0.5 - 0.7 X 2e^2/h in conductance data. Importantly, it appears that the spin gap is not static but a function of the electron density. Data obtained using a bias spectroscopy technique are consistent with the spin gap widening further as the Fermi-level is increased.Comment: 5 Pages 4 Figures email:[email protected]