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Search Results: 1 - 10 of 286821 matches for " W R Newell "
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Insecta, Ephemeroptera: Range extensions and new state records from far western Montana, U.S.A.
McCafferty, W. P.,Newell, R. L.
Check List , 2007,
Abstract:
Preliminary study into the components of the fear-avoidance model of LBP: change after an initial chiropractic visit and influence on outcome
Jonathan R Field, Dave Newell, Peter W McCarthy
Chiropractic & Manual Therapies , 2010, DOI: 10.1186/1746-1340-18-21
Abstract: Seventy one new patients with lower back pain as their primary complaint presenting for chiropractic care to one of five clinics (nine chiropractors) completed questionnaires before their initial visit (pre-visit) and again just before their second appointment (post-visit). One month after the initial consultation, patient global impression of change (PGIC) scores were collected. Pre visit and post visit psychological domain scores were analysed for any association with outcomes at 1 month.Group mean scores for Fear Avoidance Beliefs (FAB), catastrophisation and self-efficacy were all improved significantly within a few days of a patient's initial chiropractic consultation. Pre-visit catastrophisation as well as post-visit scores for catastrophisation, back beliefs (inevitability) and self-efficacy were weakly correlated with patient's global impression of change (PGIC) at 1 month. However when the four assessed psychological variables were dichotomised about pre-visit group medians those individuals with 2 or more high variables post-visit had a substantially increased risk (OR 36.4 (95% CI 6.2-213.0) of poor recovery at 1 month. Seven percent of patients with 1 or fewer adverse psychological variables described poor benefit compared to 73% of those with 2 or more.The results presented suggest that catastrophisation, FAB and low self-efficacy could be potential barriers to early improvement during chiropractic care. In most patients presenting with higher psychological scores these were reduced within a few days of an initial chiropractic visit. Those patients who exhibited higher adverse psychology post-initial visit appear to have an increased risk of poor outcome at 1 month.Trials comparing physical therapies, including chiropractic, to other types of care have generally found them to provide superior benefits for lower back pain patients, but often only marginally [1,2]. It has been suggested that this may, in part, be due to the presence of subgroups of patien
Reconstruction of Atomic Ionization Probabilities in Intense Laser Fields
T. R. J. Goodworth,W. A. Bryan,I. D. Williams,W. R. Newell
Physics , 2005, DOI: 10.1088/0953-4075/38/17/001
Abstract: Application of a parallel-projection inversion technique to z-scan spectra of multiply charged xenon and krypton ions, obtained by non-resonant field ionization of neutral targets, has for the first time permitted the direct observation of intensity-dependent ionization probabilities. These ionization efficiency curves have highlighted the presence of structure in the tunnelling regime, previously unobserved under full-volume techniques.
Observation of multiple ionization pathways for OCS in an intense laser field resolved by three-dimensional covariance mapping and visualized by hierarchical ionization topology
W. A. Bryan,W. R. Newell,J. H. Sanderson,A. J. Langley
Physics , 2006, DOI: 10.1103/PhysRevA.74.053409
Abstract: The two- and three-body Coulomb explosion of carbonyl sulfide (OCS) by 790 nm, 50 fs laser pulses focussed to $\approx $ 10$^{16}$ Wcm$^{-2}$ has been investigated by three-dimensional covariance mapping technique. For the first time in a triatomic molecule, a single charge state, in this case the trication, has been observed to dissociate into two distinct energy channels. With the aid of a three dimensional visualization technique to reveal the ionization hierarchy, evidence is presented for the existence of two sets of ionization pathways resulting from these two initial states. While one group of ions can be modeled using a Classical enhanced ionization model, the second group, consisting of mainly asymmetric channels, can not. The results provide clear evidence that an enhanced ionization approach must also be accompanied by an appreciation of the effects of excited ionic states and multi-electronic processes.
Controlled redistribution of vibrational population by few-cycle strong-field laser pulses
W. A. Bryan,C. R. Calvert,R. B. King,J. B. Greenwood,W. R. Newell,I. D. Williams
Physics , 2012, DOI: 10.1039/C1FD00042J
Abstract: The use of strong-field (i.e. intensities in excess of 10^13 Wcm-2) few-cycle ultrafast (durations of 10 femtoseconds or less) laser pulses to create, manipulate and image vibrational wavepackets is investigated. Quasi-classical modelling of the initial superposition through tunnel ionization, wavepacket modification by nonadiabatically altering the nuclear environment via the transition dipole and the Stark effect, and measuring the control outcome by fragmenting the molecule is detailed. The influence of the laser intensity on strong-field ultrafast wavepacket control is discussed in detail: by modifying the distribution of laser intensities imaged, we show that focal conditions can be created that give preference to this three-pulse technique above processes induced by the pulses alone. An experimental demonstration is presented, and the nuclear dynamics inferred by the quasi-classical model discussed. Finally, we present the results of a systematic investigation of a dual-control pulse scheme, indicating that single vibrational states should be observable with high fidelity, and the populated state defined by varying the arrival time of the two control pulses. The relevance of such strong-field coherent control methods to the manipulation of electron localization and attosecond science is discussed.
Quasi-classical model of dynamic molecular structure and non-destructive wavepacket manipulation by ultrashort laser pulses
W A Bryan,C R Calvert,R B King,G R A J Nemeth,J B Greenwood,I D Williams,W R Newell
Physics , 2010, DOI: 10.1088/1367-2630/12/7/073019
Abstract: A quasi-classical model (QCM) of molecular dynamics in intense femtosecond laser fields has been developed, and applied to a study of the effect of an ultrashort `control' pulse on the vibrational motion of a deuterium molecular ion in its ground electronic state. A nonadiabatic treatment accounts for the initial ionization-induced vibrational population caused by an ultrashort `pump' pulse. In the QCM, the nuclei move classically on the molecular potential as it is distorted by the laser-induced Stark shift and transition dipole. The nuclei then adjust to the modified potential, non-destructively shifting the vibrational population and relative phase. This shift has been studied as a function of control pulse parameters. Excellent agreement is observed with predictions of time-dependent quantum simulations, lending confidence to the validity of the model and permitting new observations to be made. The applicability of the QCM to more complex multi-potential energy surface molecules (where a quantum treatment is at best difficult) is discussed.
Recognising the recognition heuristic for what it is (and what it's not)
Ben R. Newell
Judgment and Decision Making , 2011,
Abstract: The diversity, ingenuity and differences of opinion displayed in the articles of the recent special issues on the recognition heuristic are testament to the power and theoretical fertility of a simple idea about the role of recognition in decision making. In this brief comment I mention a number of these papers, but my focus is on points of agreement and disagreement with the conclusions drawn by Gigerenzer and Goldstein (2011) in their review of a decade's worth of research on the recognition heuristic.
On the recollision-free excitation of krypton during ultrafast multi-electron tunnel ionization
W A Bryan,S L Stebbings,J McKenna,E M L English,M Suresh,J Wood,B Srigengan,I C E Turcu,I D Williams,W R Newell
Physics , 2005, DOI: 10.1088/0953-4075/39/13/S08
Abstract: The probability of multiple ionization of krypton by 50 femtosecond circularly polarized laser pulses, independent of the optical focal geometry, has been obtained for the first time. The excellent agreement over the intensity range 10 TWcm-2 to 10 PWcm-2 with the recent predictions of A. S. Kornev et al [Phys. Rev. A v.68, art.043414 (2003)] provides the first experimental confirmation that non-recollisional electronic excitation can occur in strong field ionization. This is particularly true for higher stages of ionization, when the laser intensity exceeds 1 PWcm-2 as the energetic departure of the ionized electron(s) diabatically distorts the wavefunctions of the bound electrons. By scaling the probability of ionization by the focal volume, we discusses why this mechanism was not apparent in previous studies.
How to make a risk seem riskier
Carissa Bonner,Ben R. Newell
Judgment and Decision Making , 2008,
Abstract: Which statement conveys greater risk: ``100 people die from cancer every day'' or ``36,500 people die from cancer every year''? In statistics where both frequencies and temporal information are used to convey risk, two theories predict opposite answers to this question. Construal level theory predicts that ``100 people die from cancer every day'' will be judged as more risky, while the ratio bias predicts that the equivalent ``36,500 people die from cancer every year'' will result in higher risk judgments. An experiment investigated which format produces higher risk ratings, and whether ratings are influenced by increasing the salience of the numerical or temporal part of the statistic. Forty-eight participants were randomly assigned to a numerical, temporal or control salience condition, and rated risk framed as number of deaths per day or per year. The year format was found to result in higher perceived risk, indicating that the ratio bias effect is dominant, but there was no effect of salience.
Isolated vibrational wavepackets in D2+: Defining superposition conditions and wavepacket distinguishability
W. A. Bryan,J. McKenna,E. M. L. English,J. Wood,C. R. Calvert,R. Torres,D. S. Murphy,I. C. E. Turcu,J. L. Collier,J. F. McCann,I. D. Williams,W. R. Newell
Physics , 2007, DOI: 10.1103/PhysRevA.76.053402
Abstract: Tunnel ionization of room-temperature D$_2$ in an ultrashort (12 femtosecond) near infra-red (800 nm) pump laser pulse excites a vibrational wavepacket in the D2+ ions; a rotational wavepacket is also excited in residual D2 molecules. Both wavepacket types are collapsed a variable time later by an ultrashort probe pulse. We isolate the vibrational wavepacket and quantify its evolution dynamics through theoretical comparison. Requirements for quantum computation (initial coherence and quantum state retrieval) are studied using this well-defined (small number of initial states at room temperature, initial wavepacket spatially localized) single-electron molecular prototype by temporally stretching the pump and probe pulses.
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