MgII absorption systems with W_0 > 0.1 \AA for a radio selected sample of 77 QSOs and their associated magnetic fields at high redshifts

We present a catalogue of MgII absorption systems obtained from high resolution UVES/VLT data of 77 QSOs in the redshift range 0.6 < z < 2.0, and down to an equivalent width W_0 > 0.1 \AA. The statistical properties of our sample are found to be in agreement with those from previous work in the literature. However, we point out that the previously observed increase with redshift of dN/dz for weak absorbers, pertains exclusively to very weak absorbers with W_0 < 0.1 \AA. Instead, dN/dz for absorbers with W_0 in the range 0.1-0.3 \AA actually decreases with redshift, similarly to the case of strong absorbers. We then use this catalogue to extend our earlier analysis of the links between the Faraday Rotation Measure of the quasars and the presence of intervening MgII absorbing systems in their spectra. In contrast to the case with strong MgII absorption systems W_0 > 0.3 \AA, the weaker systems do not contribute significantly to the observed Rotation Measure of the background quasars. This is possibly due to the higher impact parameters of the weak systems compared to strong ones, suggesting that the high column density magnetized material that is responsible for the Faraday Rotation is located within about 50 kpc of the galaxies. Finally, we show that this result also rules out the possibility that some unexpected secondary correlation between the quasar redshift and its intrinsic Rotation Measure is responsible for the association of high Rotation Measure and strong intervening MgII absorption that we have presented elsewhere, since this would have produced an equal effect for the weak absorption line systems, which exhibit a very similar distribution of quasar redshifts.Comment: Accepted for publication in ApJ. 12 pages, 8 figure

Absorption in dipole-lattice models of dielectrics

We develop a classical microscopic model of a dielectric. The model features nonlinear interaction terms between polarizable dipoles and lattice vibrations. The lattice vibrations are found to act as a pseudo-reservoir, giving broadband absorption of electromagnetic radiation without the addition of damping terms in the dynamics. The effective permittivity is calculated using a perturbative iteration method and is found to have the form associated with real dielectrics. Spatial dispersion is naturally included in the model and we also calculate the wavevector dependence of the permittivity.Comment: 13 pages, 9 figures; references added to section

Why overlearned sequences are special: distinct neural networks in the right hemisphere for ordinal sequences

Written and spoken words activate left hemisphere areas involved in language processing. However, we here show that overlearned sequences (e.g. letters, numbers, weekdays, months) involve an unexpected right hemispheric activation in both the middle temporal gyrus and temporoparietal junction. Our findings offer a framework for understanding neuropsychological patterns seen in conditions such as synesthesia, in which anomalous perceptual experiences are triggered by overlearned sequences, and also in semantic dementia, in which left hemisphere damage disrupts word knowledge even while sequences can be spared

Thermal feedback in Si JFETs operating at low temperatures

Thermal feedback theory for silicon junction FET operating at low temperature

Predictability engenders more efficient neural responses

The neural response to a stimulus diminishes with repeated presentations, a phenomenon known as repetition suppression. We here use neuroimaging to demonstrate that repetition suppression appears to be a special case of &#x22;prediction suppression&#x22;--that is, the brain shows diminishing activity when subsequent stimuli in a train are predictable. This demonstration supports the hypothesis that the brain dynamically leverages prediction to minimize energy consumption

Puncture discharges in surface dielectrics as contaminant sources in spacecraft environments

Spacecraft in geosynchronous orbits are known to become charged to large negative potentials during the local midnight region of the satellite orbit. Such discharges have been studied by the electron beam irradiation of dielectric samples in a vacuum environment. In addition to static measurements and photographic examination of the puncture discharges in Teflon samples, the transient characteristics of the electrical discharges are determined from oscillographs of voltage and current and by charged particle measurements employing a biased Faraday cup and a retarding potential analyzer. Using these latter techniques, studies of angular and energy distributions of charged particles have indicated an initial burst of high energy electrons (5 x 10 to the 13th power per discharge at energies greater than 300 eV) followed by a less intense burst of lower energy negative particles. Positive ions are emitted from the discharge site in an initial high velocity burst followed by a lower velocity burst tentatively identified as carbon

A Bare Molecular Cloud at z~0.45

Several neutral species (MgI, SiI, CaI, FeI) have been detected in a weak MgII absorption line system (W_r(2796)~0.15 Angstroms) at z~0.45 along the sightline toward HE0001-2340. These observations require extreme physical conditions, as noted in D'Odorico (2007). We place further constraints on the properties of this system by running a wide grid of photoionization models, determining that the absorbing cloud that produces the neutral absorption is extremely dense (~100-1000/cm^3), cold (<100 K), and has significant molecular content (~72-94%). Structures of this size and temperature have been detected in Milky Way CO surveys, and have been predicted in hydrodynamic simulations of turbulent gas. In order to explain the observed line profiles in all neutral and singly ionized chemical transitions, the lines must suffer from unresolved saturation and/or the absorber must partially cover the broad emission line region of the background quasar. In addition to this highly unusual cloud, three other ordinary weak MgII clouds (within densities of ~0.005/cm^3 and temperatures of ~10000K) lie within 500 km/s along the same sightline. We suggest that the "bare molecular cloud", which appears to reside outside of a galaxy disk, may have had in situ star formation and may evolve into an ordinary weak MgII absorbing cloud.Comment: 15 pages, 4 figures, 4 tables, ApJ accepte

Left to Chance: Gifted Students and Recreational Reading

This qualitative multiple case study explored the factors that impact the recreational reading selections of gifted students. Eleven students in grades four and five participated in the study. The methods of data collection included in-depth personal interviews and analysis of library circulation records and independent reading program data. The Theory of Reasoned Action was used as a framework to examine the answers to the research question and subquestions and three areas of concern were identified. Those areas are: 1) The role of the school librarian in recreational reading selections, 2) The impact of assigned reading on recreational reading, and 3) Gifted boys’ motivation to read. Findings from this study indicated that though gifted students make most selections independently, they are heavily influenced by their peers when selecting recreational reading materials. However, the school librarian can have an impact on these choices as well. Assigned reading impacts what gifted students read recreationally and how they view the practice. Finally, gifted boys appear to read less recreationally than their female peers. Suggestions for changes in policy, practice, and future research in these areas of concern are provided

The Last Eight-Billion Years of Intergalactic CIV Evolution

We surveyed the HST UV spectra of 49 low-redshift quasars for z < 1 CIV candidates, relying solely on the characteristic wavelength separation of the doublet. After consideration of the defining traits of CIV doublets (e.g., consistent line profiles, other associated transitions, etc.), we defined a sample of 38 definite (group G = 1) and five likely (G = 2) doublets with rest equivalent widths W_r for both lines detected at >= 3 sigma. We conducted Monte-Carlo completeness tests to measure the unblocked redshift (dz) and co-moving pathlength (dX) over which we were sensitive to CIV doublets of a range of equivalent widths and column densities. The absorber line density of (G = 1+2) doublets is dN/dX = 4.1+0.7/-0.6 for log N(C^+3) >= 13.2, and dN/dX has not evolved significantly since z = 5. The best-fit power-law to the G = 1 frequency distribution of column densities f(N(C^+3)) = k(N(C^+3)/N_0)^alpha_N has coefficient k = (0.67+0.18/-0.16) x 10^-14 cm^2 and exponent alpha_N = -1.50+0.17/-0.19, where N_0 = 10^14 cm^-2. Using the power-law model of f(N(C^+3)), we measured the C^+3 mass density relative to the critical density: Omega(C^+3) = (6.20+1.82/-1.52) x 10^-8 for 13 <= log N(C^+3) <= 15. This value is a 2.8+/-0.7 increase in Omega(C^+3) compared to the error-weighted mean from several 1 < z < 5 surveys for CIV absorbers. A simple linear regression to Omega(C^+3) over the age of the Universe indicates that Omega(C^+3) has slowly but steadily increased from z = 5 --> 0, with dOmega(C^+3)/dt_age = (0.42+/-0.2) x 10^-8 Gyr^-1.Comment: 61 pages; accepted by ApJ; includes changes based on referee repor

Whole-cell Voltage Clamp Of Junctional Conductances In Insect Cell Pairs

Gap junction (GJ) channels are dynamic intercellular structures that open and close (gate) in response to cellular signals (e.g. voltage), and may be important in regulating cell-to-cell communication in insect development. This thesis presents one of the first biophysical characterizations of GJ channels in insect cell pairs. Double whole-cell voltage-clamp techniques were employed on epidermal cells from the larval flour beetle, Tenebrio molitor, to measure the conductances and substate gating properties of individual GJ channels and the effects of voltage and ATP on gating. In addition, these techniques were used to examine the early events of rapid GJ formation between hemocyte couplets from the cockroach, Periplaneta americana. For this, methods were developed for isolating epidermal cells and for preventing rapid flattening of hemocytes by using lipophorin-coated coverlips.;GJ formation between hemocyte couplets occurred within one second after contact and junctional conductance (G{dollar}\rm\sb{lcub}J{rcub}{dollar}) increased in steps of {dollar}\sim{dollar}345 pS. Each step corresponds to a new channel added to the growing gap junction.;Pharate pupal epidermal (PPE) and newly-moulted epidermal (NME) cells suitable for whole-cell recording were isolated. Single cells from both stages had large nonjunctional resistances ({dollar}\u3e{dollar}5 G{dollar}\Omega{dollar}). NME but not PPE cells expressed a hyperpolarization-activated inward current.;Isolated PPE and NME cell pairs had functional gap junctions. G{dollar}\rm\sb{lcub}J{rcub}{dollar} dropped during whole-cell recording, however, adding 5 mM ATP but not nonhydrolysable ATP analogues to the pipette solution slowed uncoupling suggesting that ATP probably acts through an ATP-utilizing enzymatic process.;G{dollar}\rm\sb{lcub}J{rcub}{dollar} in epidermal cells is mostly membrane-potential (V{dollar}\rm\sb{lcub}M{rcub}{dollar}) dependent, although transjunctional-voltage dependence is also present.;Conductances of individual GJ channels in poorly-coupled PPE cell pairs were large (197 to 403 pS). This GJ channel is one of the first described capable of existing in a range of partially-closed substates.;GJ-channel gating mechanisms presented herein may be important in regulating cell-to-cell communication in insects. For instance, V{dollar}\rm\sb{lcub}M{rcub}{dollar}-dependence may provide a mechanism for controlling the overall level of coupling. Moreover, GJ-channel substates may account for selective regulation of junctional permeability in developing tissues