Particle interactions and lattice dynamics: Scenarios for efficient bidirectional stochastic transport?

Intracellular transport processes driven by molecular motors can be described by stochastic lattice models of self-driven particles. Here we focus on bidirectional transport models excluding the exchange of particles on the same track. We explore the possibility to have efficient transport in these systems. One possibility would be to have appropriate interactions between the various motors' species, so as to form lanes. However, we show that the lane formation mechanism based on modified attachment/detachment rates as it was proposed previously is not necessarily connected to an efficient transport state and is suppressed when the diffusivity of unbound particles is finite. We propose another interaction mechanism based on obstacle avoidance that allows to have lane formation for limited diffusion. Besides, we had shown in a separate paper that the dynamics of the lattice itself could be a key ingredient for the efficiency of bidirectional transport. Here we show that lattice dynamics and interactions can both contribute in a cooperative way to the efficiency of transport. In particular, lattice dynamics can decrease the interaction threshold beyond which lanes form. Lattice dynamics may also enhance the transport capacity of the system even when lane formation is suppressed.Comment: 25 pages, 17 figures, 2 table

A model for bidirectional traffic of cytoskeletal motors

We introduce a stochastic lattice gas model including two particle species and two parallel lanes. One lane with exclusion interaction and directed motion and the other lane without exclusion and unbiased diffusion, mimicking a micotubule filament and the surrounding solution. For a high binding affinity to the filament, jam-like situations dominate the system's behaviour. The fundamental process of position exchange of two particles is approximated. In the case of a many-particle system, we were able to identify a regime in which the system is rather homogenous presenting only small accumulations of particles and a regime in which an important fraction of all particles accumulates in the same cluster. Numerical data proposes that this cluster formation will occur at all densities for large system sizes. Coupling of several filaments leads to an enhanced cluster formation compared to the uncoupled system, suggesting that efficient bidirectional transport on one-dimensional filaments relies on long-ranged interactions and track formation.Comment: 20 pages, 9 figure

Partially asymmetric exclusion models with quenched disorder

We consider the one-dimensional partially asymmetric exclusion process with random hopping rates, in which a fraction of particles (or sites) have a preferential jumping direction against the global drift. In this case the accumulated distance traveled by the particles, x, scales with the time, t, as x ~ t^{1/z}, with a dynamical exponent z > 0. Using extreme value statistics and an asymptotically exact strong disorder renormalization group method we analytically calculate, z_{pt}, for particlewise (pt) disorder, which is argued to be related to the dynamical exponent for sitewise (st) disorder as z_{st}=z_{pt}/2. In the symmetric situation with zero mean drift the particle diffusion is ultra-slow, logarithmic in time.Comment: 4 pages, 3 figure

Method for producing a supported catalyst

Abstract of WO9903581 The invention relates to a method for producing supported catalysts by impregnating or imbibing SiO2-based crystalline or amorphous support material with a pore diameter of 20 to 250 ANGSTROM with silasesquioxane metal complexes. Said supported catalysts are suitable for oxidising or epoxidising unsaturated hydrocarbons or alcohols

Surgeons’ and Emergency Physicians’ Perceptions of Trauma Management and Training

Objective: The study objective was to determine whether surgeons and emergency medicine physicians (EMPs) have differing opinions on trauma residency training and trauma management in clinical practice.Methods: A survey was mailed to 250 EMPs and 250 surgeons randomly selected.Results: Fifty percent of surgeons perceived that surgery exclusively managed trauma compared to 27% of EMPs. Surgeons were more likely to feel that only surgeons should manage trauma on presentation to the ED. However, only 60% of surgeons currently felt comfortable with caring for the trauma patient, compared to 84% of EMPs. Compared to EMPs, surgeons are less likely to feel that EMPs can initially manage the trauma patient (71% of surgeons vs. 92% of EMPs).Conclusion: EMPs are comfortable managing trauma while many surgeons do not feel comfortable with the complex trauma patient although the majority of surgeons responded that surgeons should manage the trauma.[WestJEM. 2009;10:144-149.

Growth and physiological responses of lettuce grown under pre-dawn or end-of-day sole-source light-quality treatments

The objective of this study was to evaluate growth and physiological responses of ‘Cherokee’ and ‘Waldmann’s Green’ lettuce (Lactuca sativa) exposed to small changes in light quality and intensity within a 24-h period. Three pre-dawn (PD; 0600 to 0700) and three end-of-day (EOD; 2100 to 2200) treatments were evaluated in the study, each providing 50 ± 2 μmol·m−2·s−1 of either blue, red, or broadband white light from light-emitting diodes (LEDs). To account for the main daily light integral (DLI), broadband white LEDs provided 210 ± 2 μmol·m−2·s−1 from 0700 to 2200 or from 0600 to 2100 for the PD or EOD treatments, respectively. A control treatment was included which provided 200 ± 2 μmol·m−2·s−1 of white light from 0600 to 2200. All treatments provided a DLI of 11.5 mol·m−2·day−1 over a 16-h photoperiod. Regardless of cultivar, no treatment difference was measured for hypocotyl length or leaf number. However, plants grown under EOD-blue or PD-white had up to 26% larger leaves than those grown under PD-red and 20% larger leaves than control. In addition, plants grown under EOD-blue produced up to 18% more shoot fresh mass compared to those grown under control, EOD-red, or PD-red. Contrasts for gas-exchange data collected during the main photoperiod showed that light quality was not significant within PD or EOD for any of the parameters evaluated. However, regardless of light quality, stomatal conductance (gs) and transpiration (E) were up to 34% and 42% higher, respectively, for EOD-grown plants compared to control. Our results suggest that 1 h of low intensity EOD-blue light has the potential to promote lettuce growth by increasing leaf area and shoot fresh mass when the main DLI from sole-source lighting is provided by broadband white LEDs

Fluorite transition metal hydride induced destabilization of the MgH2 system in MgH2/TMH2 multilayers (TM=Sc, Ti, V, Cr, Y, Zr, Nb, La, Hf)

The structural changes in MgH2 induced by contact with fluorite transition metal hydrides (TMH2, TM=Sc, Ti, V, Cr, Y, Zr, Nb, La, Hf) have been studied using density-functional theory calculations. Models of MgH2(rutile)/TiH2(fluorite) and MgH2(fluorite)/TiH2(fluorite) multilayers with different Mg:TM ratios have been designed. With a fixed thickness of the TMH2 layer, structure transformation of MgH2 from rutile to fluorite occurs with a decrease in thickness of the MgH2 layer. The hydrogen desorption energy from the fluorite MgH2 layer in the multilayers is significantly lower than that of the bulk rutile MgH2. The structural deformation of the MgH2 layer due to the strain induced by TMH2 is found to be responsible for the destabilization of the Mg-H bond: the more structural deformation, the more destabilization of the Mg-H. Our results provide an important insight for the development of new hydrogen-storage materials with desirable thermodynamic properties

Clinical staging and prognostic factors in folliculotropic mycosis fungoides

Folliculotropic mycosis fungoides (FMF) is a distinct variant of mycosis fungoides (MF), the most prevalent type of cutaneous T cell lymphoma. FMF accounts for approximately 10% of all MF cases and is generally characterized by distinct clinical , histopathologic and prognostic features. The studies in this thesis were aimed to address questions regarding clinical staging, disease course, suitable treatment and prognosis of subgroups of patients with FMF. Alleen voor drukkosten van het proefschrift werd sponsoring ontvangen van: BAP Medical B.V., Eucerin, Galderma Benelux B.V., La Roche-Posay, Kyowa Kirin Pharma B.V., LEO Pharma B.V. en Olmed.LUMC / Geneeskund

Those Who Can, Do and They Teach Too: Faculty Clinical Productivity and Teaching

Objective: Academic emergency physicians (EPs) often feel that the demands of clinical productivity, income generation, and patient satisfaction conflict with educational objectives. The objective of this study was to explore whether the quality of faculty bedside teaching of residents correlated with high clinical productivity, measured by relative value units (RVUs). We also explored the strategies of high-performing faculty for optimal RVU generation and teaching performance.Methods: We performed a mixed method study using quantitative and qualitative methods to analyze the relationship between RVUs, patient satisfaction, and teaching performance. We examined the relationship between teaching performance ratings, patient satisfaction, and RVUs per hour using correlations. Following this initial analysis, we conducted semi-structured interviews with the eight faculty members who have the highest clinical (RVU) and educational productivity ratings to learn more about their strategies for success. Our Institutional Review Board approved this study.Results: We correlated resident evaluations of faculty with RVUs billed per hour. We conducted semi-structured interviews of faculty who led in both RVU productivity and resident evaluations. From these interviews, several themes emerged. When asked about how they excel in billing, most said that they pay attention to dictating a thorough chart on every patient and try to “stay busy” throughout their entire shift. When asked how they excel at resident education, most leading faculty said that they try to find a “teaching moment” and find small “clinical pearls” to pass along. Nevertheless, all eight leading faculty members believe that as the emphasis on billing productivity increases, resident and student education will suffer.Conclusion: Contrary to the opinion of some physicians, faculty can excel at both clinical productivity and resident education. This study found that highly efficient clinical productivity correlated with excellent resident teaching. This high level of performance did not appear to be at the expense of other important measures such as patient satisfaction or student teaching. [West J Emerg Med. 2011;12(2):254-257.

The partially asymmetric zero range process with quenched disorder

We consider the one-dimensional partially asymmetric zero range process where the hopping rates as well as the easy direction of hopping are random variables. For this type of disorder there is a condensation phenomena in the thermodynamic limit: the particles typically occupy one single site and the fraction of particles outside the condensate is vanishing. We use extreme value statistics and an asymptotically exact strong disorder renormalization group method to explore the properties of the steady state. In a finite system of $L$ sites the current vanishes as $J \sim L^{-z}$, where the dynamical exponent, $z$, is exactly calculated. For $0<z<1$ the transport is realized by $N_a \sim L^{1-z}$ active particles, which move with a constant velocity, whereas for $z>1$ the transport is due to the anomalous diffusion of a single Brownian particle. Inactive particles are localized at a second special site and their number in rare realizations is macroscopic. The average density profile of inactive particles has a width of, $\xi \sim \delta^{-2}$, in terms of the asymmetry parameter, $\delta$. In addition to this, we have investigated the approach to the steady state of the system through a coarsening process and found that the size of the condensate grows as $n_L \sim t^{1/(1+z)}$ for large times. For the unbiased model $z$ is formally infinite and the coarsening is logarithmically slow.Comment: 12 pages, 9 figure