163 research outputs found
Personal And Real Property—Referendum Unnecessary for Acquisition of Property Pursuant to Local Finance Law
Matter of Town Bd. of Town of Islip, 12 N.Y.2d 321, 189 N.E.2d 808, 239 N.Y.S.2d 541 (1963)
Invariance of Structure in an Aging Colloidal Glass
We study concentrated colloidal suspensions, a model system which has a glass
transition. The non-equilibrium nature of the glassy state is most clearly
highlighted by aging -- the dependence of the system's properties on the time
elapsed since vitrification. Fast laser scanning confocal microscopy allows us
to image a colloidal glass and track the particles in three dimensions. We
analyze the static structure in terms of tetrahedral packing. We find that
while the aging of the suspension clearly affects its dynamics, none of the
geometrical quantities associated with tetrahedra change with age.Comment: Submitted to the proceedings of "The 3rd International Workshop on
Complex Systems" in Sendai, Japa
Self-Organized Criticality Below The Glass Transition
We obtain evidence that the dynamics of glassy systems below the glass
transition is characterized by self-organized criticality. Using molecular
dynamics simulations of a model glass-former we identify clusters of
cooperatively jumping particles. We find string-like clusters whose size is
power-law distributed not only close to T_c but for ALL temperatures below T_c,
indicating self-organized criticality which we interpret as a freezing in of
critical behavior.Comment: 4 pages, 3 figure
Correlations of Structure and Dynamics in an Aging Colloidal Glass
We study concentrated colloidal suspensions, a model system which has a glass
transition. Samples in the glassy state show aging, in that the motion of the
colloidal particles slows as the sample ages from an initial state. We study
the relationship between the static structure and the slowing dynamics, using
confocal microscopy to follow the three-dimensional motion of the particles.
The structure is quantified by considering tetrahedra formed by quadruplets of
neighboring particles. We find that while the sample clearly slows down during
aging, the static properties as measured by tetrahedral quantities do not vary.
However, a weak correlation between tetrahedron shape and mobility is observed,
suggesting that the structure facilitates the motion responsible for the sample
aging.Comment: Submitted to Solid State Communication
Forced motion of a probe particle near the colloidal glass transition
We use confocal microscopy to study the motion of a magnetic bead in a dense
colloidal suspension, near the colloidal glass transition volume fraction
. For dense liquid-like samples near , below a threshold force
the magnetic bead exhibits only localized caged motion. Above this force, the
bead is pulled with a fluctuating velocity. The relationship between force and
velocity becomes increasingly nonlinear as is approached. The
threshold force and nonlinear drag force vary strongly with the volume
fraction, while the velocity fluctuations do not change near the transition.Comment: 7 pages, 4 figures revised version, accepted for publication in
Europhysics Letter
Predictors of Patient-reported Outcomes after TKR not Included in Risk Models Based on Administrative Data
Introduction: Because total knee replacement (TKR) surgery is performed to relieve pain and improve physical function in patients with advanced arthritis, patient-reported outcomes (PROs) are important to assess TKR effectiveness. The UK and others require PROs. Understanding pre-existing clinical factors that influence PROs after surgery is needed before comparing PROs across providers. We evaluated the roles of medical and musculoskeletal comorbidities in explaining variation in 6 month post-TKR pain relief and functional gain in a national cohort of TKR patients.
Materials & methods: FORCE-TJR, funded by the Agency for Healthcare Research and Quality (AHRQ), is a national consortium in which 100% patients, surgeons and hospitals submit data: patients demographics (age, gender, BMI, race), complete medical and musculoskeletal comorbidities, PROs including SF-36 Physical Component Score (PCS), Knee injury and Osteoarthritis Outcome Score (KOOS), clinically refined adverse events and implant data. Predictors of change in pre-to-6 month post-TKR pain and function were examined using linear mixed models adjusting for clustering within site.
Results: TKR patients had a mean age of 67 years, mean BMI of 31.2, were 63% female and 4.5% black, 9% with Charlson Comorbidity Index (CCI) of 2-5, 15% with CCI of 6, 7% moderate/severe pain in 2-3 knee/hip joints, 27% moderate/severe lumbar pain. After adjusting for socio-demographic factors, significant predictors of poorer 6 month post-TKR pain included poorer emotional health, higher CCI, 1-2 nonsurgical hip/knee joints with moderate/severe pain, any lumbar pain at time of TKR. These same factors also predicted poorer 6 month function.
Conclusion: Before adopting PROs as a standard measure of TKR outcome, a complete understanding of pre-existing clinical factors associated with poorer pain relief and functional gain is needed. Greater musculoskeletal, and medical, comorbid conditions were associated with post-operative PROs and should be included in risk-adjustment models before cross-hospital comparisons can be made
The Validity of Patient-Reported Short-Term Complications following Total Hip and Knee Arthroplasty
Introduction: Given the lack of national data on outcomes of on patients who undergo total joint arthroplasty (TJA) and the limitations of hospital databases to capture information on patients who seek post-TJA care elsewhere, there is growing interest in using patient self-report to identify possible complications following surgery. We examined the concordance between patients self-report of potential short-term complications with review of available medical records as well as the location of the reported post-operative care.
Material & Methods: Patients undergoing primary hip or knee arthroplasty from 7/1/11 through 12/3/12 participating in a tertiary care center were identified. Patients completed a 6-month post-operative survey regarding needing evaluation at an emergency department, day surgery or hospitalization for possible medical or mechanical complications and the location of care. We reviewed available inpatient and outpatient medical records to identify the location of postoperative care as well as the validity of patient self-report (sensitivity, specificity, positive predictive values and negative predictive values).
Results: There were 413 patients who had 431 surgeries and completed the 6-month questionnaire. Patients reported 40 medical encounters including emergency department, day surgery or inpatient care resulting in a 9% reported complication rate, of which 20% occurred at outside hospitals Overall patient self-report of emergency department, day surgery and inpatient care for possible complications was both sensitive (82%) and specific (100%). The positive predictive value was 100% and negative predictive value 98%.
Conclusion: Given the prevalence of events requiring care at outlying hospitals and the accuracy of self-report, methods that directly engage patients can augment current surveillance procedures
Aging in Dense Colloids as Diffusion in the Logarithm of Time
The far-from-equilibrium dynamics of glassy systems share important
phenomenological traits. A transition is generally observed from a
time-homogeneous dynamical regime to an aging regime where physical changes
occur intermittently and, on average, at a decreasing rate. It has been
suggested that a global change of the independent time variable to its
logarithm may render the aging dynamics homogeneous: for colloids, this entails
diffusion but on a logarithmic time scale. Our novel analysis of experimental
colloid data confirms that the mean square displacement grows linearly in time
at low densities and shows that it grows linearly in the logarithm of time at
high densities. Correspondingly, pairs of particles initially in close contact
survive as pairs with a probability which decays exponentially in either time
or its logarithm. The form of the Probability Density Function of the
displacements shows that long-ranged spatial correlations are very long-lived
in dense colloids. A phenomenological stochastic model is then introduced which
relies on the growth and collapse of strongly correlated clusters ("dynamic
heterogeneity"), and which reproduces the full spectrum of observed colloidal
behaviors depending on the form assumed for the probability that a cluster
collapses during a Monte Carlo update. In the limit where large clusters
dominate, the collapse rate is ~1/t, implying a homogeneous, log-Poissonian
process that qualitatively reproduces the experimental results for dense
colloids. Finally an analytical toy-model is discussed to elucidate the strong
dependence of the simulation results on the integrability (or lack thereof) of
the cluster collapse probability function.Comment: 6 pages, extensively revised, final version; for related work, see
http://www.physics.emory.edu/faculty/boettcher/ or
http://www.fysik.sdu.dk/staff/staff-vip/pas-personal.htm
Direct visualization of aging in colloidal glasses
We use confocal microscopy to directly visualize the dynamics of aging
colloidal glasses. We prepare a colloidal suspension at high density, a simple
model system which shares many properties with other glasses, and initiate
experiments by stirring the sample. We follow the motion of several thousand
colloidal particles after the stirring and observe that their motion
significantly slows as the sample ages. The aging is both spatially and
temporally heterogeneous. Furthermore, while the characteristic relaxation time
scale grows with the age of the sample, nontrivial particle motions continue to
occur on all time scales.Comment: submitted to proceedings for Liquid Matter Conference 200
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