211 research outputs found
Extrapolated High-Order Propagators for Path Integral Monte Carlo Simulations
We present a new class of high-order imaginary time propagators for
path-integral Monte Carlo simulations by subtracting lower order propagators.
By requiring all terms of the extrapolated propagator be sampled uniformly, the
subtraction only affects the potential part of the path integral. The
negligible violation of positivity of the resulting path integral at small time
steps has no discernable affect on the accuracy of our method. Thus in
principle arbitrarily high order algorithms can be devised for path-integral
Monte Carlo simulations. We verify this claim is by showing that fourth, sixth,
and eighth order convergence can indeed be achieved in solving for the ground
state of strongly interacting quantum many-body systems such as bulk liquid
He.Comment: 9 pages and 3 figures. Submitted to J. Chem. Phy
Laser-induced rotation of iodine molecules in He-nanodroplets: revivals and breaking-free
Rotation of molecules embedded in He nanodroplets is explored by a
combination of fs laser-induced alignment experiments and angulon quasiparticle
theory. We demonstrate that at low fluence of the fs alignment pulse, the
molecule and its solvation shell can be set into coherent collective rotation
lasting long enough to form revivals. With increasing fluence, however, the
revivals disappear -- instead, rotational dynamics as rapid as for an isolated
molecule is observed during the first few picoseconds. Classical calculations
trace this phenomenon to transient decoupling of the molecule from its He
shell. Our results open novel opportunities for studying non-equilibrium
solute-solvent dynamics and quantum thermalization.Comment: 6+7 pages; 4+1 figures; 1 tabl
Microscopic description of anisotropic low-density dipolar Bose gases in two dimensions
A microscopic description of the zero energy two-body ground state and
many-body static properties of anisotropic homogeneous gases of bosonic dipoles
in two dimensions at low densities is presented and discussed. By changing the
polarization angle with respect to the plane, we study the impact of the
anisotropy, present in the dipole--dipole interaction, on the energy per
particle, comparing the results with mean field predictions. We restrict the
analysis to the regime where the interaction is always repulsive, although the
strength of the repulsion depends on the orientation with respect to the
polarization field. We present a series expansion of the solution of the zero
energy two-body problem which allows us to find the scattering length of the
interaction and to build a suitable Jastrow factor that we use as a trial wave
function for both a variational and diffusion Monte Carlo simulation of the
infinite system. We find that the anisotropy has an almost negligible impact on
the ground state properties of the many-body system in the universal regime
where the scattering length governs the physics of the system. We also show
that scaling in the gas parameter persists in the dipolar case up to values
where other isotropic interactions with the same scattering length yield
different predictions.Comment: 9 figures, 1 tabl
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Medication decision-making for patients with renal insufficiency in inpatient and outpatient care at a US Veterans Affairs Medical Centre: a qualitative, cognitive task analysis.
BackgroundMany studies identify factors that contribute to renal prescribing errors, but few examine how healthcare professionals (HCPs) detect and recover from an error or potential patient safety concern. Knowledge of this information could inform advanced error detection systems and decision support tools that help prevent prescribing errors.ObjectiveTo examine the cognitive strategies that HCPs used to recognise and manage medication-related problems for patients with renal insufficiency.DesignHCPs submitted documentation about medication-related incidents. We then conducted cognitive task analysis interviews. Qualitative data were analysed inductively.SettingInpatient and outpatient facilities at a major US Veterans Affairs Medical Centre.ParticipantsPhysicians, nurses and pharmacists who took action to prevent or resolve a renal-drug problem in patients with renal insufficiency.OutcomesEmergent themes from interviews, as related to recognition of renal-drug problems and decision-making processes.ResultsWe interviewed 20 HCPs. Results yielded a descriptive model of the decision-making process, comprised of three main stages: detect, gather information and act. These stages often followed a cyclical path due largely to the gradual decline of patients' renal function. Most HCPs relied on being vigilant to detect patients' renal-drug problems rather than relying on systems to detect unanticipated cues. At each stage, HCPs relied on different cognitive cues depending on medication type: for renally eliminated medications, HCPs focused on gathering renal dosing guidelines, while for nephrotoxic medications, HCPs investigated the need for particular medication therapy, and if warranted, safer alternatives.ConclusionsOur model is useful for trainees so they can gain familiarity with managing renal-drug problems. Based on findings, improvements are warranted for three aspects of healthcare systems: (1) supporting the cyclical nature of renal-drug problem management via longitudinal tracking mechanisms, (2) providing tools to alleviate HCPs' heavy reliance on vigilance and (3) supporting HCPs' different decision-making needs for renally eliminated versus nephrotoxic medications
Utilizing a user-centered approach to develop and assess pharmacogenomic clinical decision support for thiopurine methyltransferase
BACKGROUND:
A pharmacogenomic clinical decision support tool (PGx-CDS) for thiopurine medications can help physicians incorporate pharmacogenomic results into prescribing decisions by providing up-to-date, real-time decision support. However, the PGx-CDS user interface may introduce errors and promote alert fatigue. The objective of this study was to develop and evaluate a prototype of a PGx-CDS user interface for thiopurine medications with user-centered design methods.
METHODS:
This study had two phases: In phase I, we conducted qualitative interviews to assess providers' information needs. Interview transcripts were analyzed through a combination of inductive and deductive qualitative analysis to develop design requirements for a PGx-CDS user interface. Using these requirements, we developed a user interface prototype and evaluated its usability (phase II).
RESULTS:
In total, 14 providers participated: 10 were interviewed in phase I, and seven providers completed usability testing in phase II (3 providers participated in both phases). Most (90%) participants were interested in PGx-CDS systems to help improve medication efficacy and patient safety. Interviews yielded 11 themes sorted into two main categories: 1) health care providers' views on PGx-CDS and 2) important design features for PGx-CDS. We organized these findings into guidance for PGx-CDS content and display. Usability testing of the PGx-CDS prototype showed high provider satisfaction.
CONCLUSION:
This is one of the first studies to utilize a user-centered design approach to develop and assess a PGx-CDS interface prototype for Thiopurine Methyltransferase (TPMT). This study provides guidance for the development of a PGx-CDS, and particularly for biomarkers such as TPMT
Hypertension treatment intensification among stroke survivors with uncontrolled blood pressure
Objective
The study objective was to evaluate a pharmacist hypertension care management program within the patient-centered medical home.
Methods
This was a retrospective case-control study. Cases included all patients with hypertension who were referred to the care management program, and controls included patients with hypertension who were not referred to the program during the same 1-year period. Each case was matched to a maximum of 3 controls on the basis of primary care physician, age ±5 years, gender, diagnoses of diabetes and kidney disease, baseline systolic blood pressure ±10 mm Hg, and number of unique antihypertensive medications. Pharmacists provided a hypertension care management program under an approved scope of practice that allowed pharmacists to meet individually with patients, adjust medications, and provide patient education. Primary outcomes were systolic blood pressure and diastolic blood pressure at 6 and 12 months. Multivariate regression models compared each blood pressure end point between cases and controls adjusting for age, comorbidities, baseline blood pressure, and baseline number of blood pressure medications.
Results
A total of 573 patients were referred to the hypertension program; 86% (465/543) had at least 1 matched control and were included as cases in the analyses; 3:1 matching was achieved in 90% (418/465) of cases. At baseline, cases and controls did not differ with respect to age, gender, race, or comorbidity; baseline blood pressure was higher (139.9/80.0 mm Hg vs 136.7/78.2 mm Hg, P ≤ .0002) in the cases compared with controls. Multivariate regression modeling identified significantly lower systolic blood pressure for the cases compared with controls at both 6 and 12 months (6-month risk ratio [RR], 9.7; 95% confidence interval [CI], 2.7-35.3; 12-month RR, 20.3; 95% CI, 4.1-99.2; P < .01 for both comparisons). Diastolic blood pressure was significantly lower at 12 months (RR, 2.9; 95% CI, 1.2-7.1; P < .01) but not at 6 months (RR, 1.0; 95% CI, 0.31-3.4; P = .9) for the cases compared with controls.
Conclusions
Patients who were referred to the pharmacist hypertension care management program had a significant improvement in most blood pressure outcomes. This program may be an effective method of improving blood pressure control among patients in a medical home model of primary care
Reducing prescribing errors through creatinine clearance alert redesign
Background
Literature has shown that computerized creatinine clearance alerts reduce errors during prescribing, and applying human factors principles may further reduce errors. Our objective was to apply human factors principles to creatinine clearance alert design and assess whether the redesigned alerts increase usability and reduce prescribing errors compared with the original alerts.
Methods
Twenty Veterans Affairs (VA) outpatient providers (14 physicians, 2 nurse practitioners, and 4 clinical pharmacists) completed 2 usability sessions in a counterbalanced study to evaluate original and redesigned alerts. Each session consisted of fictional patient scenarios with 3 medications that warranted prescribing changes because of renal impairment, each associated with creatinine clearance alerts. Quantitative and qualitative data were collected to assess alert usability and the occurrence of prescribing errors.
Results
There were 43% fewer prescribing errors with the redesigned alerts compared with the original alerts (P = .001). Compared with the original alerts, redesigned alerts significantly reduced prescribing errors for allopurinol and ibuprofen (85% vs 40% and 65% vs 25%, P = .012 and P = .008, respectively), but not for spironolactone (85% vs 65%). Nine providers (45%) voiced confusion about why the alert was appearing when they encountered the original alert design. When laboratory links were presented on the redesigned alert, laboratory information was accessed 3.5 times more frequently.
Conclusions
Although prescribing errors were high with both alert designs, the redesigned alerts significantly improved prescribing outcomes. This investigation provides some of the first evidence on how alerts may be designed to support safer prescribing for patients with renal impairment
Short-Term Medical Costs of a VHA Health Information Exchange: A CHEERS-Compliant Article.
The Virtual Lifetime Electronic Record (VLER) Health program provides the Veterans Health Administration (VHA) a framework whereby VHA providers can access the veterans’ electronic health record information to coordinate healthcare across multiple sites of care. As an early adopter of VLER, the Indianapolis VHA and Regenstrief Institute implemented a regional demonstration program involving bi-directional health information exchange (HIE) between VHA and non-VHA providers.The aim of the study is to determine whether implementation of VLER HIE reduces 1 year VHA medical costs.A cohort evaluation with a concurrent control group compared VHA healthcare costs using propensity score adjustment. A CHEERs compliant checklist was used to conduct the cost evaluation.Patients were enrolled in the VLER program onsite at the Indianapolis VHA in outpatient clinics or through the release-of-information office.VHA cost data (in 2014 dollars) were obtained for both enrolled and nonenrolled (control) patients for 1 year prior to, and 1 year after, the index date of patient enrollment.There were 6104 patients enrolled in VLER and 45,700 patients in the control group. The annual adjusted total cost difference per patient was associated with a higher cost for VLER enrollees 807–1433) (P < 0.01) (in 2014 dollars) than VLER nonenrollees.Short-term evaluation of this demonstration project did not show immediate reductions in healthcare cost as might be expected if HIE decreased redundant medical tests and treatments. Cost reductions from shared health information may be realized with longer time horizons
Rotational coherence spectroscopy of molecules in helium nanodroplets: Reconciling the time and the frequency domains
Alignment of OCS, CS and I molecules embedded in helium nanodroplets
is measured as a function of time following rotational excitation by a
non-resonant, comparatively weak ps laser pulse. The distinct peaks in the
power spectra, obtained by Fourier analysis, are used to determine the
rotational, B, and centrifugal distortion, D, constants. For OCS, B and D match
the values known from IR spectroscopy. For CS and I, they are the first
experimental results reported. The alignment dynamics calculated from the
gas-phase rotational Schr\"{o}dinger equation, using the experimental
in-droplet B and D values, agree in detail with the measurement for all three
molecules. The rotational spectroscopy technique for molecules in helium
droplets introduced here should apply to a range of molecules and complexes.Comment: ASC and LC contributed equally. 7 pages, 3 figure
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