Installation Induced Stresses For Grouted Roof Bolts

The judicious use of roof bolts in stabilizing underground openings necessitates the ability to determine the state of stress in and around such bolts. A method of modeling a system of roof bolts is presented. This method is then applied in the determination of the state of stress due to bolt tightening. Two specific roof bolt configurations are considered: a fully grouted post-tensioned bolt and a post-tensioned bolt with grouted-end anchorage. The analysis showed that the grout annulus transferred nearly all of the bolt load 3nto the rock within a distance of 12 hole diameters from the point of bolt load application. © 1976

Highly Dispersive Spin Excitations in the Chain Cuprate Li2CuO2

We present an inelastic neutron scattering investigation of Li2CuO2 detecting the long sought quasi-1D magnetic excitations with a large dispersion along the CuO2-chains studied up to 25 meV. The total dispersion is governed by a surprisingly large ferromagnetic (FM) nearest-neighbor exchange integral J1=-228 K. An anomalous quartic dispersion near the zone center and a pronounced minimum near (0,0.11,0.5) r.l.u. (corresponding to a spiral excitation with a pitch angle about 41 degree point to the vicinity of a 3D FM-spiral critical point. The leading exchange couplings are obtained applying standard linear spin-wave theory. The 2nd neighbor inter-chain interaction suppresses a spiral state and drives the FM in-chain ordering below the Ne'el temperature. The obtained exchange parameters are in agreement with the results for a realistic five-band extended Hubbard Cu 3d O 2p model and L(S)DA+U predictions.Comment: 6 pages, 4 figures, submitted to Europhys. Let

Sound Multi-Party Business Protocols for Service Networks

Service networks comprise large numbers of long-running, highly dynamic complex end-to-end service interactions reflecting asynchronous message flows that typically transcend several organizations and span several geographical locations. At the communication level, service network business protocols can be flexible ranging from conventional inter-organizational point-to-point service interactions to fully blown dynamic multi-party interactions of global reach within which each participant may contribute its activities and services. In this paper we introduce a formal framework enriched with temporal constraints to describe multiparty business protocols for service networks. We extend this framework with the notion of multi-party business protocol soundness and show how it is possible to execute a multi-party protocol consistently in a completely distributed manner while guaranteeing eventual termination

Coalescent angiogenesis—evidence for a novel concept of vascular network maturation

Angiogenesis describes the formation of new blood vessels from pre-existing vascular structures. While the most studied mode of angiogenesis is vascular sprouting, specific conditions or organs favor intussusception, i.e., the division or splitting of an existing vessel, as preferential mode of new vessel formation. In the present study, sustained (33-h) intravital microscopy of the vasculature in the chick chorioallantoic membrane (CAM) led to the hypothesis of a novel non-sprouting mode for vessel generation, which we termed "coalescent angiogenesis." In this process, preferential flow pathways evolve from isotropic capillary meshes enclosing tissue islands. These preferential flow pathways progressively enlarge by coalescence of capillaries and elimination of internal tissue pillars, in a process that is the reverse of intussusception. Concomitantly, less perfused segments regress. In this way, an initially mesh-like capillary network is remodeled into a tree structure, while conserving vascular wall components and maintaining blood flow. Coalescent angiogenesis, thus, describes the remodeling of an initial, hemodynamically inefficient mesh structure, into a hierarchical tree structure that provides efficient convective transport, allowing for the rapid expansion of the vasculature with maintained blood supply and function during development

948-46 Preserved Cardiac Baroreflex Control of Renal Cortical Blood Flow in Advanced Heart Failure Patients: A Positron Emission Tomography Study

Cardiac baroreflex (CBR) control of forearm blood flow (FBF) is blunted or reversed in humans with heart failure (HF). but little is known about CBR control of renal cortical blood flow (RCBF) in HF due to technical limitations. Positron emission tomography (PET) 0–15 water is a new, precise method to measure RCBF quantitatively. We compared CBR control of RCBF and FBF (venous plethysmography) in 8 patients with HF (mean age, 47±3 y, ejection fraction 0.25±0.02) and 10 normal humans (mean age 35±5 y) during CBR unloading with phlebotomy (450ml). In 5 normals, cold pressor test was used as a strong, non-baroreflex mediated stimulus to vasoconstriction.ResultsPhlebotomy decreased central venous pressure (p <0.001), but did not change mean arterial pressure or heart rate in HF patients or controls. The major findings of the study are: 1) At rest, RCBF is markedly diminished in HF vs normals (2.4±0.1 vs 4.3±0.2ml/min/g, p < 0.001). 2) In normal humans during phlebotomy, FBF decreased substantially (basal vs phlebotomy: 3.3±0.4 vs 2.6±0.3 ml/min/100 ml, p=0.021, and RCBF decreased slightly, but significantly (basal vs phlebotomy: 4.3±0.2 vs 4.0±0.3 ml/min/g, p=0.01). 3) The small magnitude of reflex renal vasoconstriction is not explained by the inability of the renal circulation to vasoconstrict since the cold pressor stimulus induced substantial decreases in RCBF in normals (basal vs cold pressor: 4.4±0.1 vs 3.7±0.1 ml/min/g, p=0.003). 4) In humans with heart failure during phlebotomy, FBF did not change (basal vs phlebotomy: 2.6±0.3 vs 2.7±0.2 ml/min/100 ml, p=NS), but RCBF decreased slightly but significantly (basal vs phlebotomy: 2.4±0.1 vs 2.1±0.1 ml/min/g, p=0.01). Thus, in patients with heart failure, there is an abnormality in cardiopulmonary baroreflex control of the forearm circulation, but not the renal circulationConclusionThis study 1) shows the power of PET to study physiologic and pathophysiologic reflex control of the renal circulation in humans, and 2) describes the novel finding of selective dysfunction of cardiac baroreflex control of the forearm circulation, but its preservation of the renal circulation, in patients with heart failur

Significant fatigue life enhancement in multiscale doubly-modified fiber/epoxy nanocomposites with graphene nanoplatelets and reduced-graphene oxide

ABSTRACT: We report the fatigue behavior of a novel multiscale fiberglass/epoxy composite modified with reduced-graphene oxide (rGO) and graphene nanoplatelets (GNP). A novel and cost-effective fabrication method based on vacuum assisted resin transfer molding (VARTM) method was used for manufacturing the composite laminates. Morphological and mechanical analysis of composites showed a successful dispersion of nano-fillers and a remarkable improvement in fatigue life of the nanocomposites. The experimental results revealed that all rGO concentrations resulted in a significant increase in fatigue life of the nanocomposites. These enhancements can be explained by the creation of stronger links between the nanoparticles fiberglass and epoxy. The experimental results also showed that lower concentrations of GNPs lead to an increase in fatigue life of nanocomposites; however, a decrease in their fatigue life can be seen at higher loadings

Quantification and parametric imaging of renal cortical blood flow in vivo based on Patlak graphical analysis

Quantification and parametric imaging of renal cortical blood flow in vivo based on Patlak graphical analysis. Patlak graphical analysis was applied to quantify renal cortical blood flow with N-13 ammonia and dynamic positron emission tomography. Measurements were made in a swine model of kidney transplantation with a wide range of normal and abnormal renal blood flows (N = 57 studies) and in 20 healthy human volunteers (N = 45 studies). Estimates of renal cortical blood flow by the Patlak method were compared to those from a two-compartment model for N-13 ammonia. In addition, estimates of renal cortical blood flow by the N-13 ammonia PET approach were compared in 10 normal human volunteers to estimates by the metabolically inert, freely diffusible O-15 water and a one-compartment model. Patlak graphical analysis estimates of renal cortical blood flow correlated linearly with the standard two-compartment model in pigs (y = -0.05 + 1.01x, r = 0.99) and in humans (y = 0.57 + 0.88x, r = 0.93). Estimates of renal cortical blood flow by O-15 water in human volunteers were also linearly correlated with those by N-13 ammonia and the Patlak graphical analysis (y = 0.71 + 0.84x, r = 0.86). Renal cortical blood flow estimates were highly reproducible both with N-13 ammonia and O-15 water measurements in humans. It is concluded that the Patlak graphical analysis with N-13 ammonia dynamic positron emission tomographic imaging renders accurate and reproducible estimates of renal cortical blood flow. Moreover, the graphical analysis approach is 1,000 times faster than the standard model fitting approach and suitable for generating parametric images of renal blood flow in the clinical setting