2,879 research outputs found
Experimental Analysis of Heat Transfer Characteristics and Pressure Drop through Screen Regenerative Heat Exchangers
This study investigated the effect on heat transfer and friction characteristics for screen regenerative heat exchangers with the screen thickness reduced by rolling. The experiments were performed on 250 and 325 mesh, 304 stainless steel screen using helium gas. Reynolds numbers, based on hydraulic radius, Re, were between 10 and 100. Both the Colburn factor, StPr2/3, and friction factor, f, decreased as the screen thickness was reduced. A correlation was found for predicting friction factor, f. The drag coefficient per screen remained nearly unchanged for thicknesses reduced not more than 30 percent. The decrease in Colburn factor was significant for Re less than 40. For Re between 40 and 100 the decrease in Colburn factor was less than the experimental uncertainty
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Current and Future Issues in the Development of Spinal Agents for the Management of Pain.
Targeting analgesic drugs for spinal delivery reflects the fact that while the conscious experience of pain is mediated supraspinally, input initiated by high intensity stimuli, tissue injury and/or nerve injury is encoded at the level of the spinal dorsal horn and this output informs the brain as to the peripheral environment. This encoding process is subject to strong upregulation resulting in hyperesthetic states and downregulation reducing the ongoing processing of nociceptive stimuli reversing the hyperesthesia and pain processing. The present review addresses the biology of spinal nociceptive processing as relevant to the effects of intrathecally-delivered drugs in altering pain processing following acute stimulation, tissue inflammation/injury and nerve injury. The review covers i) the major classes of spinal agents currently employed as intrathecal analgesics (opioid agonists, alpha 2 agonists; sodium channel blockers; calcium channel blockers; NMDA blockers; GABA A/B agonists; COX inhibitors; ii) ongoing developments in the pharmacology of spinal therapeutics focusing on less studied agents/targets (cholinesterase inhibition; Adenosine agonists; iii) novel intrathecal targeting methodologies including gene-based approaches (viral vectors, plasmids, interfering RNAs); antisense, and toxins (botulinum toxins; resniferatoxin, substance P Saporin); and iv) issues relevant to intrathecal drug delivery (neuraxial drug distribution), infusate delivery profile, drug dosing, formulation and principals involved in the preclinical evaluation of intrathecal drug safety
Critical interfaces in the random-bond Potts model
We study geometrical properties of interfaces in the random-temperature
q-states Potts model as an example of a conformal field theory weakly perturbed
by quenched disorder. Using conformal perturbation theory in q-2 we compute the
fractal dimension of Fortuin Kasteleyn domain walls. We also compute it
numerically both via the Wolff cluster algorithm for q=3 and via
transfer-matrix evaluations. We obtain numerical results for the fractal
dimension of spin cluster interfaces for q=3. These are found numerically
consistent with the duality kappa(spin) * kappa(FK)= 16 as expressed in
putative SLE parameters.Comment: 4 page
Interacting crumpled manifolds
In this article we study the effect of a delta-interaction on a polymerized
membrane of arbitrary internal dimension D. Depending on the dimensionality of
membrane and embedding space, different physical scenarios are observed. We
emphasize on the difference of polymers from membranes. For the latter,
non-trivial contributions appear at the 2-loop level. We also exploit a
``massive scheme'' inspired by calculations in fixed dimensions for scalar
field theories. Despite the fact that these calculations are only amenable
numerically, we found that in the limit of D to 2 each diagram can be evaluated
analytically. This property extends in fact to any order in perturbation
theory, allowing for a summation of all orders. This is a novel and quite
surprising result. Finally, an attempt to go beyond D=2 is presented.
Applications to the case of self-avoiding membranes are mentioned
Blackbody radiation shift in a 43Ca+ ion optical frequency standard
Motivated by the prospect of an optical frequency standard based on 43Ca+, we
calculate the blackbody radiation (BBR) shift of the 4s_1/2-3d_5/2 clock
transition, which is a major component of the uncertainty budget. The
calculations are based on the relativistic all-order single-double method where
all single and double excitations of the Dirac-Fock wave function are included
to all orders of perturbation theory. Additional calculations are conducted for
the dominant contributions in order to evaluate some omitted high-order
corrections and estimate the uncertainties of the final results. The BBR shift
obtained for this transition is 0.38(1) Hz. The tensor polarizability of the
3d_5/2 level is also calculated and its uncertainty is evaluated as well. Our
results are compared with other calculations.Comment: 4 page
C-Periodicity and the Physical Mass in the 3-State Potts Model
The standard infinite-volume definition of connected correlation function and
particle mass in the 3-state Potts model can be implemented in Monte Carlo
simulations by using C-periodic spatial boundary conditions. This avoids both
the breaking of translation invariance (cold wall b.c.) and the phase-dependent
and thus possibly biased evaluation of data (periodic boundary cconditions).
The numerical feasibility of the standard definitions is demonstrated by sample
computations on a 24*24*48 lattice.Comment: 13 pages + 5 figures Preprint Nos. IC/93/131 and TIFR/TH/93-2
Random RNA under tension
The Laessig-Wiese (LW) field theory for the freezing transition of random RNA
secondary structures is generalized to the situation of an external force. We
find a second-order phase transition at a critical applied force f = f_c. For f
f_c, the extension L as a function of
pulling force f scales as (f-f_c)^(1/gamma-1). The exponent gamma is calculated
in an epsilon-expansion: At 1-loop order gamma = epsilon/2 = 1/2, equivalent to
the disorder-free case. 2-loop results yielding gamma = 0.6 are briefly
mentioned. Using a locking argument, we speculate that this result extends to
the strong-disorder phase.Comment: 6 pages, 10 figures. v2: corrected typos, discussion on locking
argument improve
Veterinary Medical Libraries in the 21st Century
The purpose of this volume is to present a picture of information access and delivery by United States and Canadian academic veterinary medical libraries (VMLs) to the veterinary community and others with interests in the profession. This is done by discussing the resources that are available, as well as methods of delivery of that information. Our discussion of these topics will not only point out the unique aspects of these collections and services, but will also illustrate much that is in common with all medical collections and library services. As with all libraries, the goal of VMLs is to provide high quality service while looking after the information needs of their clientele through selection, acquisition, cataloging, and dissemination of materials and familiarizing their users with these resources. In the past decade, new challenges and opportunities for information specialists stem from the impact of technology on VMLs. Our goal with this volume is to be concise, but thorough about all of these topics.https://lib.dr.iastate.edu/library_books/1000/thumbnail.jp
TPX2 is required for postmitotic nuclear assembly in cell-free Xenopus laevis egg extracts
Cell division in many metazoa is accompanied by the disassembly of the nuclear envelope and the assembly of the mitotic spindle. These dramatic structural rearrangements are reversed after mitosis, when the mitotic spindle is dismantled and the nuclear envelope reassembles. The targeting protein for XKlp2 (TPX2) plays important roles in mitotic spindle assembly. We report that TPX2 depletion from nuclear assembly extracts prepared from Xenopus laevis eggs results in the formation of nuclei that are only about one fifth the size of control nuclei. TPX2-depleted nuclei assemble nuclear envelopes, nuclear pore complexes, and a lamina, and they perform nuclear-specific functions, including DNA replication. We show that TPX2 interacts with lamina-associated polypeptide 2 (LAP2), a protein known to be required for nuclear assembly in interphase extracts and in vitro. LAP2 localization is disrupted in TPX2-depleted nuclei, suggesting that the interaction between TPX2 and LAP2 is required for postmitotic nuclear reformation
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