13,992 research outputs found
A Stochastic Compartmental Model for Fast Axonal Transport
In this paper we develop a probabilistic micro-scale compartmental model and
use it to study macro-scale properties of axonal transport, the process by
which intracellular cargo is moved in the axons of neurons. By directly
modeling the smallest scale interactions, we can use recent microscopic
experimental observations to infer all the parameters of the model. Then, using
techniques from probability theory, we compute asymptotic limits of the
stochastic behavior of individual motor-cargo complexes, while also
characterizing both equilibrium and non-equilibrium ensemble behavior. We use
these results in order to investigate three important biological questions: (1)
How homogeneous are axons at stochastic equilibrium? (2) How quickly can axons
return to stochastic equilibrium after large local perturbations? (3) How is
our understanding of delivery time to a depleted target region changed by
taking the whole cell point-of-view
Regulation of Leaf Senescence by Cytokinin, Sugars, and Light. Effects on NADH-Dependent Hydroxypyruvate Reductase
The aim of this study was to investigate the interactions between cytokinin, sugar repression, and light in the senescence-related decline in photosynthetic enzymes of leaves. In transgenic tobacco (Nicotiana tabacum) plants that induce the production of cytokinin in senescing tissue, the age-dependent decline in NADH-dependent hydroxypyruvate reductase (HPR), ribulose-1,5-bisphosphate carboxylase/oxygenase, and other enzymes involved in photosynthetic metabolism was delayed but not prevented. Glucose (Glc) and fructose contents increased with leaf age in wild-type tobacco and, to a greater extent, in transgenic tobacco. To study whether sugar accumulation in senescing leaves can counteract the effect of cytokinin on senescence, discs of wild-type leaves were incubated with Glc and cytokinin solutions. The photorespiratory enzyme HPR declined rapidly in the presence of 20 mM Glc, especially at very low photon flux density. Although HPR protein was increased in the presence of cytokinin, cytokinin did not prevent the Glc-dependent decline. Illumination at moderate photon flux density resulted in the rapid synthesis of HPR and partially prevented the negative effect of Glc. Similar results were obtained for the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. It is concluded that sugars, cytokinin, and light interact during senescence by influencing the decline in proteins involved in photosynthetic metabolism
High hydrogen yield and purity from palm empty fruit bunch and pine pyrolysis oils
The benefits of CO 2 sorption enhanced steam reforming using calcined dolomite were demonstrated for the production of hydrogen from highly oxygenated pyrolysis oils of the agricultural waste palm empty fruit bunches (PEFB) and pine wood. At 1 atm in a down-flow packed bed reactor at 600 °C, the best molar steam to carbon ratios were between 2 and 3 using a Ni catalyst. After incorporating steam-activated calcined dolomite as the CO 2 sorbent in the reactor bed, the H 2 yield from the moisture free PEFB oil increased from 9.5 to 10.4 wt.% while that of the pine oil increased from 9.9 to 13.9 wt.%. The hydrogen purity also rose from 68 to 96% and from 54 to 87% for the PEFB and pine oils respectively, demonstrating very substantial sorption enhancement effects
Enhanced Convergence and Robust Performance of Randomized Dynamical Decoupling
We demonstrate the advantages of randomization in coherent quantum dynamical
control. For systems which are either time-varying or require decoupling cycles
involving a large number of operations, we find that simple randomized
protocols offer superior convergence and stability as compared to deterministic
counterparts. In addition, we show how randomization always allows to
outperform purely deterministic schemes at long times, including combinatorial
and concatenated methods. General criteria for optimally interpolating between
deterministic and stochastic design are proposed and illustrated in explicit
decoupling scenarios relevant to quantum information storage.Comment: 4 pages, 3 figures, replaced with final versio
Switching modalities in a sentence verification task: ERP evidence for embodied language processing
In an event related potential (ERP) experiment using written language materials only, we investigated a potential modulation of the N400 by the modality switch effect. The modality switch effect occurs when a first sentence, describing a fact grounded in one modality, is followed by a second sentence describing a second fact grounded in a different modality. For example, "A cellar is dark" (visual), was preceded by either another visual property "Ham is pink" or by a tactile property "A mitten is soft." We also investigated whether the modality switch effect occurs for false sentences ("A cellar is light"). We found that, for true sentences, the ERP at the critical word "dark" elicited a significantly greater frontal, early N400-like effect (270370 ms) when there was a modality mismatch than when there was a modality-match. This pattern was not found for the critical word "light" in false sentences. Results similar to the frontal negativity were obtained in a late time window (500700 ms). The obtained ERP effect is similar to one previously obtained for pictures. We conclude that in this paradigm we obtained fast access to conceptual properties for modality-matched pairs, which leads to embodiment effects similar to those previously obtained with pictorial stimuli
Impact of Facilitator Co-Location and Alignment on the Efficacy of Group Support Systems Employed in a Distributed Setting
Group Support Systems (GSSs) are a combination of hardware, software, and human facilitation designed and employed to increase the effectiveness and efficiency of decision making groups. Engineers at the Sustainment Logistics Branch of the Air Force Research Laboratory have recently proposed employing the technology in a distributed setting to conjoin geographically separated members of decision making groups in order to facilitate the reengineering of logistics processes in an any place/any time environment To date GSSs have been studied and employed primarily in the same time/same place setting. Consequently, little is known or understood of the effects that use of these systems may have on the group dynamic when employed in the distributed setting. This thesis examines how two elements of GSS configuration, the location and alignment of the meeting facilitator, may impact system users\u27 perceptions of situational equity, their attitudes towards the efficacy of the technology, their information sharing behavior, and the quality of decisions reached by user groups. The results of the work evidence that isolation of the facilitator from meeting members is desirable, and that facilitator neutrality is essential to the efficacy of such systems deployed in the distributed setting
Hugo Bettauer’s \u3cem\u3eDie Stadt Ohne Juden: \u3c/em\u3eA Prophetic Novel of Austria’s Interwar Years
In 1922 the Austrian journalist and author Hugo Bettauer published a novel entitled Die Stadt ohne Juden. Ein Roman von ubermorgen.* In this book the Austrian government expels all Jewish citizens, but recalls them at the end of the novel because the country cannot get along without them. This theme and the circumstances of the author justify a closer look at this relatively unknown book
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