Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Logistics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1993

Technical issues: logistics. AAMC.

The author states that she became interested in standardized patients (SPs) around 20 years ago as a means of developing a more uniform and effective way to provide instruction and evaluation of basic clinical skills. She reflects upon in detail: (1) the logistics of using SPs in teaching; (2) how SPs are used in assessment; (3) what aspects of performance SPs can be trained to record and evaluate; (4) issues concerning checklists; (5) evaluation of interviewing skills; (6) evaluation of written communication skills; (7) importance of defining what is being tested; (8) various kinds and uses of inter-station exercises and problems of scoring them; (9) case development and the various sources for case material; (10) ways to generate scores; (11) selecting and training SPs; (12) role of the faculty and primary importance of bedside training with real patients; and (13) pros and cons of national versus single-school efforts to use SPs. She concludes by cautioning that further research must be done before SPs can be used for high-stakes certifying and licensing examinations.

Education, Medical, Undergraduate↗
PubMed2002

Production logistics and radionuclidic purity aspects of 153Sm for radionuclide therapy.

153Sm, an attractive therapeutic radionuclide, was produced by neutron activation of both natural Sm2O3 and 98% enriched 152Sm2O3 targets. The production logistics and radionuclidic purity aspects of 153Sm obtained using both these targets are discussed with respect to the intended end use for metastatic bone pain palliation (MBPP) in terminal cancer patients and radiation synovectomy (RS) of medium size joints. The specific activity of 153Sm obtained was around 11 GBq x mg(-1) (approximately 300 mCi x mg(-1)) and 44 GBq x mg(-1) (approx. 1200 mCi x mg(-1)) from natural and enriched targets, respectively. The level of the long-lived radionuclidic impurity burden in 153Sm obtained from the natural Sm2O3 targets, namely, due to 154Eu (5 Bq x MBq(-1) 153Sm (5 nCi x mCi(-1) 153Sm)) and 155Eu (75 Bq x MBq(-1) 153Sm (75 nCi x mCi(-1) 153Sm)), appears low enough not to pose a problem, both in the palliative treatment of terminal cancer patients (at 1.85-2.22 GBq (50-60 mCi) dose) as well as in RS (at 74 MBq (2 mCi) dose). The 154Eu content in 153Sm from the enriched target was comparable, while, as expected, the level of 155Eu was nearly two orders of magnitude lower. There is a notable overall advantage of 153Sm over the use of 186Re, the other radionuclide of interest for the same purposes.

Drug Compounding↗
PubMed1988

Prediction of donor-specific transfusion sensitization. I. A linear logistic model.

Using linear logistic regression, six factors were identified as important predictors of risk of DST sensitization in a group of 195 patients. Factors increasing the risk were: percent panel reactive antibody (PRA), previous transplants, and pregnancy; those decreasing the risk were HLA antigens matched, third-party blood transfusions, and Imuran administration. From this analysis, the magnitude of the effect of each factor on the risk of sensitization was obtained. An equation was then obtained that can be used to compute an estimated probability of sensitization (PS) for each patient. As a test of predictive ability of the model, the PS was calculated for 66 patients in an independent patient group. These observations were arranged according to the estimated probability and then divided into intervals of risk. Overall, for each interval, a very high level of agreement was found between the predicted and actual number of sensitized patients. A total of 16.13 patients were predicted to become sensitized and 17 actually did.

Azathioprine↗
PubMed1989

An analysis of the determinants of hepatic allograft rejection using stepwise logistic regression.

Hepatic allograft rejection is currently diagnosed using both histologic and clinical criteria. The purpose of this study is to extract data from the allograft biopsy, which can establish the diagnosis of rejection with more precision. A total of 566 allograft biopsies were examined in 56 patients following orthotopic liver transplantation, and 35 variables were examined. Using stepwise logistic regression, only six of these variables affected the diagnosis of rejection. These were portal tract spillover, portal tract eosinophilia, portal vein endothelialitis, portal tract neutrophilia, central vein endothelialitis, and cholestasis. Coefficients of these variables were determined, and could be used to calculate the probability of rejection for a given biopsy. Using this model the probability of having rejection can be calculated using histologic data alone.

Biopsy↗
PubMed2006

Logistic regression analysis for glaucoma diagnosis using Stratus Optical Coherence Tomography.

PURPOSES: The purposes of this study are to investigate the diagnostic performance of logistic regression analysis (LRA) applied to multidimensional information on glaucoma disease and to determine the area under receiver operator characteristic curves (AROCs) for differentiating between normal and glaucomatous eyes in the Taiwan Chinese population based on the summary data from the Stratus Optical Coherence Tomography (OCT). METHODS: One randomly selected eye from each of the 89 patients with glaucoma and from each of the 88 age- and gender-matched normal individuals were included in the study. Nine glaucomatous eyes and eight normal eyes were excluded as a result of poor OCT scans. Finally, 80 normal eyes and 80 glaucomatous eyes (mean deviation, -4.5 +/- 4.12 dB) were analyzed. The whole dataset was split into four equal sets. Each set combines 20 patients with glaucoma and 20 normal individuals. Fourfold crossvalidation was conducted. Retinal nerve fiber layer thickness and optic nerve head were measured by Stratus OCT in each patient. Twenty-five OCT parameters were included in a LRA method to determine the best combination of parameters for discriminating between glaucomatous and healthy eyes based on AROCs. RESULTS: With the LRA method, the AROC for glaucoma detection was 0.911 with sensitivity at 80% and 90% specificity were 83.7% and 80.0%, respectively. CONCLUSIONS: Compared with the OCT-provided parameters, the LRA method improved the ability to differentiate between normal and glaucomatous eyes in the Taiwan Chinese population.

Adolescent↗
PubMed1999

Desynchronization of chaos in coupled logistic maps.

When identical chaotic oscillators interact, a state of complete or partial synchronization may be attained in which the motion is restricted to an invariant manifold of lower dimension than the full phase space. Riddling of the basin of attraction arises when particular orbits embedded in the synchronized chaotic state become transversely unstable while the state remains attracting on the average. Considering a system of two coupled logistic maps, we show that the transition to riddling will be soft or hard, depending on whether the first orbit to lose its transverse stability undergoes a supercritical or subcritical bifurcation. A subcritical bifurcation can lead directly to global riddling of the basin of attraction for the synchronized chaotic state. A supercritical bifurcation, on the other hand, is associated with the formation of a so-called mixed absorbing area that stretches along the synchronized chaotic state, and from which trajectories cannot escape. This gives rise to locally riddled basins of attraction. We present three different scenarios for the onset of riddling and for the subsequent transformations of the basins of attraction. Each scenario is described by following the type and location of the relevant asynchronous cycles, and determining their stable and unstable invariant manifolds. One scenario involves a contact bifurcation between the boundary of the basin of attraction and the absorbing area. Another scenario involves a long and interesting series of bifurcations starting with the stabilization of the asynchronous cycle produced in the riddling bifurcation and ending in a boundary crisis where the stability of an asynchronous chaotic state is destroyed. Finally, a phase diagram is presented to illustrate the parameter values at which the various transitions occur.

Journal Article↗
PubMed2000

Noise-aided control of chaotic dynamics in a logistic map

Controlling chaos involves employing small perturbations to a control parameter, resulting in the stabilization of the system (naturally chaotic) on one of the infinite unstable periodic orbits embedded in the chaotic attractor. In this Brief Report we study the constructive role of external noise in increasing the efficiency of controlling chaos. Using a logistic map as an example, control of chaotic dynamics is achieved using a linear delayed-feedback strategy. Working in the subthreshold regime of control (where the value of control constant is less than the minimum value required to stabilize the period-1 target state), system dynamics in the presence of superimposed noise (system plus control plus noise) exhibit a resonance effect. Furthermore it is observed that the time required to reach the target state decreases appreciably in the presence of an optimum level of noise.

Journal Article↗
PubMed2000

Logistic map with a delayed feedback: Stability of a discrete time-delay control of chaos.

The logistic map with a delayed feedback is studied as a generic model. The stability of the model and its bifurcation scheme is analyzed as a function of the feedback amplitude and of the delay. Stability analysis is performed semianalytically. A relation between the delay and the periodicity of the orbit, which explains why some terms used in chaos control are ineffective, was found. The consequences for chaos control are discussed. The structure of bifurcations is found to depend strongly on the parity and on the length of the delay. Boundary crisis, the tangent, the Neimark, as well as the period-doubling bifurcations occur in this system. The effective dimension of the model is also discussed.

Journal Article↗
PubMed2002

Universal renormalization-group dynamics at the onset of chaos in logistic maps and nonextensive statistical mechanics.

We uncover the dynamics at the chaos threshold mu infinity of the logistic map and find that it consists of trajectories made of intertwined power laws that reproduce the entire period-doubling cascade that occurs for mu<mu infinity. We corroborate this structure analytically via the Feigenbaum renormalization-group (RG) transformation and find that the sensitivity to initial conditions has precisely the form of a q exponential, of which we determine the q index and the q-generalized Lyapunov coefficient lambda(q). Our results are an unequivocal validation of the applicability of the nonextensive generalization of Boltzmann-Gibbs statistical mechanics to critical points of nonlinear maps.

Journal Article↗
PubMed2003

Correlated noise in a logistic growth model.

The logistic differential equation is used to analyze cancer cell population, in the presence of a correlated Gaussian white noise. We study the steady state properties of tumor cell growth and discuss the effects of the correlated noise. It is found that the degree of correlation of the noise can cause tumor cell extinction.

Journal Article↗
PubMed2003

Delay-induced synchronization phenomena in an array of globally coupled logistic maps.

We study the synchronization of a linear array of globally coupled identical logistic maps. We consider a time-delayed coupling that takes into account the finite velocity of propagation of the interactions. We find globally synchronized states in which the elements of the array evolve along a periodic orbit of the uncoupled map, while the spatial correlation along the array is such that an individual map sees all other maps in his present, current, state. For values of the nonlinear parameter such that the uncoupled maps are chaotic, time-delayed mutual coupling suppresses the chaotic behavior by stabilizing a periodic orbit that is unstable for the uncoupled maps. The stability analysis of the synchronized state allows us to calculate the range of the coupling strength in which global synchronization can be obtained.

Journal Article↗
PubMed2004

Nonextensive Pesin identity: exact renormalization group analytical results for the dynamics at the edge of chaos of the logistic map.

We show that the dynamical and entropic properties at the chaos threshold of the logistic map are naturally linked through the nonextensive expressions for the sensitivity to initial conditions and for the entropy. We corroborate analytically, with the use of the Feigenbaum renormalization group transformation, the equality between the generalized Lyapunov coefficient lambda(q) and the rate of entropy production, K(q), given by the nonextensive statistical mechanics. Our results advocate the validity of the q -generalized Pesin identity at critical points of one-dimensional nonlinear dissipative maps.

Journal Article↗
PubMed2005

Parallels between the dynamics at the noise-perturbed onset of chaos in logistic maps and the dynamics of glass formation.

We develop the characterization of the dynamics at the noise-perturbed edge of chaos in logistic maps in terms of the quantities normally used to describe glassy properties in structural glass formers. Following the recognition [Phys. Lett. A 328, 467 (2004)] that the dynamics at this critical attractor exhibits analogies with that observed in thermal systems close to vitrification, we determine the modifications that take place with decreasing noise amplitude in ensemble- and time-averaged correlations and in diffusivity. We corroborate explicitly the occurrence of two-step relaxation, aging with its characteristic scaling property, and subdiffusion and arrest for this system. We also discuss features that appear to be specific to the map.

Journal Article↗
PubMed2006

Chaos edges of z-logistic maps: connection between the relaxation and sensitivity entropic indices.

Chaos thresholds of the z-logistic maps x(t+1)=1-a|xt|(z) (z>1; t=0,1,2,...) are numerically analyzed at accumulation points of cycles 2, 3, and 5 (three different cycles 5). We verify that the nonextensive q-generalization of a Pesin-like identity is preserved through averaging over the entire phase space. More precisely, we computationally verify lim(t-->infinity) [formula-see text], where the entropy S(q) [formula-see text], the sensitivity to the initial conditions xi(triple bond)lim(Deltax(0)-->0)Deltax(t)/Deltax(0), and ln(q)x(triple bond)(x(1-q-1/(1-q)(ln(1)x=ln x). The entropic index [formula-see text], and the coefficient [formula-see text] depend on both z and the cycle. We also study the relaxation that occurs if we start with an ensemble of initial conditions homogeneously occupying the entire phase space. The associated Lebesgue measure asymptotically decreases as 1/t(1/q(rel)-1)(q(rel>1). These results (i) illustrate the connection (conjectured by one of us) between sensitivity and relaxation entropic indices, namely, [formula-see text], where the positive numbers Alpha(n), alpha(n) depend on the cycle; (ii) exhibit an unexpected scaling, namely, [formula-see text].

Journal Article↗
PubMed2006

An analysis of international health care logistics: the benefits and implications of implementing just-in-time systems in the health care industry.

PURPOSE: The primary purpose of this study is to undertake a diagnostic investigation of the international health care logistical environment and determine whether regulatory policies or industry procedures have hindered the implementation of just-in-time (JIT) systems and then to recommend operational improvements to be achieved by implementing JIT Systems. DESIGN/METHODOLOGY/APPROACH: The analysis was conducted in a systematic manner and compared the anticipated benefits with benefits validated in other industries from the implementation of JIT. An extensive literature review was conducted. FINDINGS: In this particular study the cost and benefit outcomes achieved from a health care JIT implementation were compared with those achieved by the manufacturing, service, and retail industries. Chiefly, it was found that the health service market must be restructured to encourage greater price competition among priorities. A new standardization process should eliminate duplication of products and realize substantial savings. ORIGINALITY/VALUE: The analysis was conducted in a systematic manner and compared the anticipated benefits with benefits validated in other industries from the implementation of JIT.

Efficiency, Organizational↗
PubMed2000

Interpreting parameters in the logistic regression model with random effects.

Logistic regression with random effects is used to study the relationship between explanatory variables and a binary outcome in cases with nonindependent outcomes. In this paper, we examine in detail the interpretation of both fixed effects and random effects parameters. As heterogeneity measures, the random effects parameters included in the model are not easily interpreted. We discuss different alternative measures of heterogeneity and suggest using a median odds ratio measure that is a function of the original random effects parameters. The measure allows a simple interpretation, in terms of well-known odds ratios, that greatly facilitates communication between the data analyst and the subject-matter researcher. Three examples from different subject areas, mainly taken from our own experience, serve to motivate and illustrate different aspects of parameter interpretation in these models.

Animals↗
PubMed1992

Mantel-Haenszel techniques and logistic regression: always examine one's data first and don't overlook the simpler techniques.

The authors point out that, in addition to logistic regression, there are other, simpler techniques available for making an adjusted estimate of association between an outcome and a risk factor. Also, the consequence of mismodelling with regression, i.e. of missing the real relationship between an outcome and a risk factor, is illustrated with an example. The need to 'examine one's data' prior to performing multivariable techniques is emphasised.

Epidemiologic Methods↗
PubMed1986

Logistics of early management of head and spinal injuries.

The logistics of early management have been studied in a series of 1161 patients with head and/or spinal injuries, who were admitted to hospital in NSW in 1977-78. Special attention has been given to three subgroups: 336 head injuries with records of impaired consciousness before first hospital admission, 355 head injuries later transferred because of deterioration, and 202 serious spinal injuries. It was found that in at least 18% of unconscious head injuries, and a similar percentage of spinal injuries, first aid and transport to hospital were provided by ambulances recorded to have only one trained staff member. In country areas, 41% of unconscious head injuries reached hospital after periods of time exceeding 1 h. For administrative as well as geographic reasons, more than 80% of initially unconscious head injuries and spinal injuries were first admitted to hospitals without neurosurgical and/or spinal services; the majority of cases in both groups, therefore, had to be transferred to other hospitals, often within 6 h of first admission. In the subgroup of cases transferred because of deterioration, mortality increased with distance from a neurosurgical unit. These findings are related to the concept of an integrated regional trauma service.

Ambulances↗