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Search Results: 1 - 10 of 198780 matches for " Adam D. West "
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Piezoelectrically-actuated time-averaged atomic microtraps
Adam D. West,Christopher G. Wade,Kevin J. Weatherill,Ifan G. Hughes
Physics , 2012, DOI: 10.1063/1.4736580
Abstract: We present a scheme for creating tight and adiabatic time-averaged atom-traps through the piezoelectric actuation of nanomagnetic structures. We show that potentials formed by the circular translation of magnetic structures have several advantages over conventional rotating-field techniques, particularly for high trap frequencies. As the magnitude of the actuation is changed the trapping potential can be changed adiabatically between harmonic 3D confinement and a toroidal trap.
Nanomagnetic engineering of the properties of domain wall atom traps
Thomas J. Hayward,Adam D. West,Kevin J. Weatherill,Thomas Schrefl,Ifan G. Hughes,Dan A. Allwood
Physics , 2011, DOI: 10.1063/1.3671631
Abstract: We have used the results of micromagnetic simulations to investigate the effects of nanowire geometry and domain wall magnetization structure on the characteristic parameters of magnetic atom traps formed by domain walls in planar ferromagnetic nanowires. It is found that when traps are formed in the near-field of a domain wall both nanowire geometry and wall structure have a substantial effect on trap frequency and adiabaticity. We also show that in certain regimes a trap's depth depends only on the amplitude of an externally applied rotating magnetic field, thus allowing it to be tuned independently of the trap's other critical parameters.
Effects of Aberrant Pax6 Gene Dosage on Mouse Corneal Pathophysiology and Corneal Epithelial Homeostasis
Richard L. Mort, Adam J. Bentley, Francis L. Martin, J. Martin Collinson, Panagiotis Douvaras, Robert E. Hill, Steven D. Morley, Nigel J. Fullwood, John D. West
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028895
Abstract: Background Altered dosage of the transcription factor PAX6 causes multiple human eye pathophysiologies. PAX6+/? heterozygotes suffer from aniridia and aniridia-related keratopathy (ARK), a corneal deterioration that probably involves a limbal epithelial stem cell (LESC) deficiency. Heterozygous Pax6+/Sey-Neu (Pax6+/?) mice recapitulate the human disease and are a good model of ARK. Corneal pathologies also occur in other mouse Pax6 mutants and in PAX77Tg/? transgenics, which over-express Pax6 and model human PAX6 duplication. Methodology/Principal Findings We used electron microscopy to investigate ocular defects in Pax6+/? heterozygotes (low Pax6 levels) and PAX77Tg/? transgenics (high Pax6 levels). As well as the well-documented epithelial defects, aberrant Pax6 dosage had profound effects on the corneal stroma and endothelium in both genotypes, including cellular vacuolation, similar to that reported for human macular corneal dystrophy. We used mosaic expression of an X-linked LacZ transgene in X-inactivation mosaic female (XLacZTg/?) mice to investigate corneal epithelial maintenance by LESC clones in Pax6+/? and PAX77Tg/? mosaic mice. PAX77Tg/? mosaics, over-expressing Pax6, produced normal corneal epithelial radial striped patterns (despite other corneal defects), suggesting that centripetal cell movement was unaffected. Moderately disrupted patterns in Pax6+/? mosaics were corrected by introducing the PAX77 transgene (in Pax6+/?, PAX77Tg/? mosaics). Pax6Leca4/+, XLacZTg/? mosaic mice (heterozygous for the Pax6Leca4 missense mutation) showed more severely disrupted mosaic patterns. Corrected corneal epithelial stripe numbers (an indirect estimate of active LESC clone numbers) declined with age (between 15 and 30 weeks) in wild-type XLacZTg/? mosaics. In contrast, corrected stripe numbers were already low at 15 weeks in Pax6+/? and PAX77Tg/? mosaic corneas, suggesting Pax6 under- and over-expression both affect LESC clones. Conclusions/Significance Pax6+/? and PAX77Tg/? genotypes have only relatively minor effects on LESC clone numbers but cause more severe corneal endothelial and stromal defects. This should prompt further investigations of the pathophysiology underlying human aniridia and ARK.
Manipulating ultracold atoms with a reconfigurable nanomagnetic system of domain walls
Adam D. West,Kevin J. Weatherill,Thomas J. Hayward,Paul W. Fry,Thomas Schrefl,Mike R. J. Gibbs,Charles S. Adams,Dan A. Allwood,Ifan G. Hughes
Physics , 2011, DOI: 10.1021/nl301491m
Abstract: The divide between the realms of atomic-scale quantum particles and lithographically-defined nanostructures is rapidly being bridged. Hybrid quantum systems comprising ultracold gas-phase atoms and substrate-bound devices already offer exciting prospects for quantum sensors, quantum information and quantum control. Ideally, such devices should be scalable, versatile and support quantum interactions with long coherence times. Fulfilling these criteria is extremely challenging as it demands a stable and tractable interface between two disparate regimes. Here we demonstrate an architecture for atomic control based on domain walls (DWs) in planar magnetic nanowires that provides a tunable atomic interaction, manifested experimentally as the reflection of ultracold atoms from a nanowire array. We exploit the magnetic reconfigurability of the nanowires to quickly and remotely tune the interaction with high reliability. This proof-of-principle study shows the practicability of more elaborate atom chips based on magnetic nanowires being used to perform atom optics on the nanometre scale.
Arkansas pharmacists’ perceptions toward emergency contraception and nonprescription Plan B
Hopkins D,West D
Pharmacy Practice (Granada) , 2008,
Abstract: Objective: This study describes Arkansas pharmacists’ knowledge, attitudes, and beliefs regarding emergency contraception. Methods: A cross-sectional survey was conducted among a convenience sample of pharmacists prior to a continuing education lecture. The 16-item survey included multiple choice and true/false questions to assess knowledge in addition to Likert-type scale questions regarding attitudes and beliefs. Frequency and descriptive statistics were calculated for all variables.Results: Eighty-eight pharmacists completed the survey. A majority (73%) knew that Plan B had been FDA-approved for nonprescription use yet 42% believed that it works by disrupting a newly implanted ovum. On a scale from 1-5 where 5=strongly agree, the mean item score was 3.2 for whether emergency contraception should be available for nonprescription use with counseling and 1.6 for nonprescription use without counseling. When asked what they would do if presented with a request for emergency contraception, 45.8% indicated they would dispense the drug, 22.9% would refer the patient to another pharmacist or pharmacy, 3.6% would refuse to dispense, and 27.7% were not sure. Almost half (48.6%) did not believe they were competent instructing patients on the use of emergency contraception. Conclusions: The results show that pharmacists could benefit from additional training on emergency contraception.
Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. III. The "Wide" L3.5/L4 Dwarf Binary 2MASS J15500845+1455180AB
Adam J. Burgasser,Saurav Dhital,Andrew West
Physics , 2009, DOI: 10.1088/0004-6256/138/6/1563
Abstract: We report the identification of 2MASS J15500845+1455180 as a 0"9 L dwarf visual binary. This source is resolved in Sloan Digital Sky Survey (SDSS) images and in near-infrared imaging with the IRTF SpeX imager/spectrometer. The two components, oriented along a north-south axis, have similar brightnesses in the near-infrared (Delta{K} ~ 0.2 mag), although the fainter northern component is redder in J-K color. Resolved near-infrared spectroscopy indicates spectral types of L3.5 and L4, consistent with its L3 combined-light optical classification based on SDSS data. Physical association is confirmed through common proper motion, common spectrophotometric distances and low probability of chance alignment. The projected physical separation of 2MASS J1550+1455AB, 30+/-3 AU at an estimated distance of 33+/-3 pc, makes it the widest L dwarf-L dwarf pair identified to date, although such a separation is not unusual among very low-mass field binaries. The angular separation and spectral composition of this system makes it an excellent target for obtaining a precise lithium depletion age, and a potential age standard for low-temperature atmosphere studies.
Synchronization and Anti-synchroniztion of Dynamically Coupled Networks
Malgorzata Turalska,Adam Svenkeson,Bruce J. West
Physics , 2015,
Abstract: We consider the coupling between two networks, each having N nodes whose individual dynamics is modeled by a two-state master equation. The intra-network interactions are all to all, whereas the inter-network interactions involve only a small percentage of the total number of nodes. We demonstrate that the dynamics of the mean field for a single network has an equivalent description in terms of a Langevin equation for a particle in a double-well potential. The coupling of two networks or equivalent coupling of two Langevin equations demonstrates synchronization or antisynchronization between two systems, depending on the sign of the interaction. The anti-synchronized behavior is explained in terms of the potential function and the inter-network interaction. The relative entropy is used to establish that the conditions for maximum information transfer between the networks are consistent with the Principle of Complexity Management and occurs when one system is near the critical state. The limitations of the Langevin modeling of the network coupling are also discussed.
D. J. West
Journal of Venomous Animals and Toxins , 1998, DOI: 10.1590/s0104-79301998000100009
CARMA Survey Toward Infrared-bright Nearby Galaxies (STING): Molecular Gas Star Formation Law in NGC4254
Nurur Rahman,Alberto D. Bolatto,Tony Wong,Adam K. Leroy,Fabian Walter,Erik Rosolowsky,Andrew A. West,Frank Bigiel,Juergen Ott,Rui Xue,Rodrigo Herrera-Camus,Katherine Jameson,Leo Blitz,Stuart N. Vogel
Physics , 2010, DOI: 10.1088/0004-637X/730/2/72
Abstract: This study explores the effects of different assumptions and systematics on the determination of the local, spatially resolved star formation law. Using four star formation rate (SFR) tracers (H\alpha with azimuthally averaged extinction correction, mid-infrared 24 micron, combined H\alpha and mid-infrared 24 micron, and combined far-ultraviolet and mid-infrared 24 micron), several fitting procedures, and different sampling strategies we probe the relation between SFR and molecular gas at various spatial resolutions and surface densities within the central 6.5 kpc in the disk of NGC4254. We find that in the high surface brightness regions of NGC4254 the form of the molecular gas star formation law is robustly determined and approximately linear and independent of the assumed fraction of diffuse emission and the SFR tracer employed. When the low surface brightness regions are included, the slope of the star formation law depends primarily on the assumed fraction of diffuse emission. In such case, results range from linear when the fraction of diffuse emission in the SFR tracer is ~30% or less (or when diffuse emission is removed in both the star formation and the molecular gas tracer), to super-linear when the diffuse fraction is ~50% and above. We find that the tightness of the correlation between gas and star formation varies with the choice of star formation tracer. The 24 micron SFR tracer by itself shows the tightest correlation with the molecular gas surface density, whereas the H\alpha corrected for extinction using an azimuthally-averaged correction shows the highest dispersion. We find that for R<0.5R_25 the local star formation efficiency is constant and similar to that observed in other large spirals, with a molecular gas depletion time ~2 Gyr.
CARMA Survey Toward Infrared-bright Nearby Galaxies (STING) II: Molecular Gas Star Formation Law and Depletion Time Across the Blue Sequence
Nurur Rahman,Alberto D. Bolatto,Rui Xue,Tony Wong,Adam K. Leroy,Fabian Walter,Frank Bigiel,Erik Rosolowsky,David B. Fisher,Stuart N. Vogel,Leo Blitz,Andrew A. West,Juergen Ott
Physics , 2011, DOI: 10.1088/0004-637X/745/2/183
Abstract: We present an analysis of the relationship between molecular gas and current star formation rate surface density at sub-kpc and kpc scales in a sample of 14 nearby star-forming galaxies. Measuring the relationship in the bright, high molecular gas surface density ($\Shtwo\gtrsim$20 \msunpc) regions of the disks to minimize the contribution from diffuse extended emission, we find an approximately linear relation between molecular gas and star formation rate surface density, $\nmol\sim0.96\pm0.16$, with a molecular gas depletion time $\tdep\sim2.30\pm1.32$ Gyr. We show that, in the molecular regions of our galaxies there are no clear correlations between \tdep\ and the free-fall and effective Jeans dynamical times throughout the sample. We do not find strong trends in the power-law index of the spatially resolved molecular gas star formation law or the molecular gas depletion time across the range of galactic stellar masses sampled (\mstar $\sim$$10^{9.7}-10^{11.5}$ \msun). There is a trend, however, in global measurements that is particularly marked for low mass galaxies. We suggest this trend is probably due to the low surface brightness CO, and it is likely associated with changes in CO-to-H2 conversion factor.
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