An occupancy problem involved in multiaccess communication systems

AbstractAn occupancy problem involved in multiaccess communication systems is studied. We are primarily interested in the prbability of the number of successful time slots after n consecutive time slots for contention with the initial number of users being k. Two different approaches are used to derive the required probability: one is based on the concept of multiple summations and the other uses the theory of Markov chain. It is shown that the latter approach is more computationally efficient than the former

Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts

We present a novel and convenient mean-field method, and apply it to study the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br). The method, which fully exploits the crystal symmetry, allows one to obtain the mean-field solution of the 2D Hubbard model for very large lattices, up to 6x10^5 sites, yielding a reliable description of the phase boundary in a wide region of the parameter space. The metal/antiferromagnet transtion appears to be second order, except for a narrow region of the parameter space, where the transition is very sharp and possibly first order. The cohexistence of metallic and antiferromagnetic properties is only observed for the transient state in the case of smooth second order transitions. The relevance of the present resaults to the complex experimental behavior of centrosymmetric k-phase BEDT-TTF salts is discussed.Comment: 9 pages in PS format, 7 figures (included in PS), 1 tabl

Specific Heat of Sr4Ru3O10

We have measured the specific heat of single crystals of the triple-layer Ruddlesden-Popper material, Sr4Ru3O10, grown both in an image furnace and by flux-growth. The flux grown sample has a sharp mean-field-like anomaly at the onset of magnetic order, Tc = 102 K, but a much broader anomaly, indicative of residual heterogeneity, is observed for the image furnace sample. Even for the flux grown sample, however, the anomaly is at least an order of magnitude smaller than one would expect for complete ordering of the spins. Neither sample exhibits an anomaly at Tm ~ 50 K, where magnetic measurements suggest that basal plane antiferromagnetism sets in. Anomalous behavior (e.g. consistent with a term in the specific heat ~ T^3/2 as would be observed for a three-dimensional ferromagnet with weak exchange) is observed at low temperatures for both samples, indicative of the unusual magnetic order in this material.Comment: 14 pages including 4 figure

Reconstructing the Equation of State for Dark Energy In the Double Complex Symmetric Gravitational Theory

We propose to study the accelerating expansion of the universe in the double complex symmetric gravitational theory (DCSGT). The universe we live in is taken as the real part of the whole spacetime ${\cal M}^4_C(J)$ which is double complex. By introducing the spatially flat FRW metric, not only the double Friedmann Equations but also the two constraint conditions $p_J=0$ and $J^2=1$ are obtained. Furthermore, using parametric $D_L(z)$ ansatz, we reconstruct the $\omega^{'}(z)$ and $V(\phi)$ for dark energy from real observational data. We find that in the two cases of $J=i,p_J=0$ and $J=\epsilon,p_J\neq 0$, the corresponding equations of state $\omega^{'}(z)$ remain close to -1 at present ($z=0$) and change from below -1 to above -1. The results illustrate that the whole spacetime, i.e. the double complex spacetime ${\cal M}^4_C(J)$, may be either ordinary complex ($J=i,p_J=0$) or hyperbolic complex ($J=\epsilon,p_J\neq 0$). And the fate of the universe would be Big Rip in the future.Comment: 5 pages, 5 figures, accepted by Commun. Theor. Phy

R&D of Accelerator Structures at SLAC

The research activities for accelerator structures at SLAC are reviewed including the achievement via the main linac design for the Next Linear Collider (NLC), the program adjustment after the decision of the International Linear Collider (ILC) to be based on superconducting technology, and the work progress for the ILC, photon science at SLAC and basic accelerator structure studies

Weibel-Palade body formation and exocytosis in von Willebrand disease

The studies presented in this thesis explored several pathogenic mechanisms underlying von Willebrand disease that is characterized by a quantitative or functional deficiency of von Willebrand factor, in particular with respect to intracellular storage in Weibel-Palade body and regulated secretion of von Willebrand factor. By using molecular biology, confocal and electron microscopic techniques, storage and secretion of von Willebrand factor were analyzed for von Willebrand disease variants identified in the patients. These studies advanced our understanding of von Willebrand disease at the molecular and cellular levels. HEK293 cells and endothelial cells derived from patients__ peripheral blood were established as two useful model-systems for examining von Willebrand factor structure-function relationships in the context of von Willebrand disease. Using these model-systems we have demonstrated that von Willebrand factor mutations may impair its storage and secretion and thus lead to a quantitative deficiency of this factor in the patients. Furthermore, we demonstrated that alteration in the structure of von Willebrand factor, by natural mutations that occur in von Willebrand disease patients, modulates von Willebrand factor string formation and function. We propose that alteration in von Willebrand factor string formation and function may be another new mechanism that contributes to the bleeding tendency in von Willebrand disease.Einthoven Laboratory for Experimental Vascular Medicine, Department of Thrombosis and Hemostasis, LUMCUBL - phd migration 201

Twenty-First Century Glucocorticoid Receptor Molecular Biology

Glucocorticoids are central to homeostasis as a function of the circadian cycle, temporally preceding circulating adrenaline concentration circadian fluctuations. Virtually, all cell types express the glucocorticoid receptor (GR). GR is a transcription factor that activates gene expression by binding to enhancers. Intriguingly, not all cell types respond to GR stimulation in the same fashion at the molecular level. This indicates that GR activity is subject to epigenetic control. We discuss the molecular basis for epigenetic control of GR action at the genomic level, including the concept of topologically associating domains which may restrain the roaming range of distal enhancers. Furthermore, much evidence indicates that GR can repress gene expression programs. We therefore discuss current concepts of the molecular basis of GR-mediated gene expression repression, including non-genomic mechanisms that involve mRNA destabilization

The Analysis of SKP1 Gene Expression in Physiological Male Sterility Induced by Chemical Hybridizing Agent SQ-1 in Wheat (Triticum aestivum L.)

Physiological male sterility induced by the chemical hybridizing agent (CHA) overcomes problems of maintenance of sterile lines and restorers. However, the mechanism of sterility is unclear. The process of tapetum of CHA-treated ‘Xi’nong 2611’ at uninucleate, binucleate and trinucleate were compared with control to determine if tapetum varying differently during developmental stages. Tapetal degradation in CHA-treated ‘Xi’nong 2611’ began at late uninucleate stage, somewhat earlier than control plants. Cytological observations indicated that the gradual degradation of the tapetum in CHA-treated ‘Xi’nong 2611’ was initiated and terminated earlier than in the control. These findings implied that CHA-induced male sterility was related to abnormally early tapetal degradation. In order to indicate the role of the SKP1 gene in fertility/sterility in wheat, its expression was assessed in anthers at uninucleate, binucleate and trinucleate stages. SKP1 expression was reduced in the later developmental stages, and there was an obvious decrease from the uninucleate to trinucleate stages. Higher expression of the SKP1 gene occurred in ‘Xi’nong 2611’ compared to CHA-treated ‘Xi’nong 2611’. This implied that SKP1 gene expression was inhibited during the fertility transformation process and was related to transformation from fertility to sterility. Moreover, the results from this study suggest that SKP1 plays an essential role of conducting fertility in physiological male sterility

The effects of local voids and imperfections of surrounding rock on the performance of existing tunnel lining

Local voids and imperfections may exist around the tunnel due to reasons such as inadequate back infill behind the lining, insufficient local lining thickness, ground water erosion, and other imperfect construction related activities. Such local voids and imperfections generally will lead to local contact loss and discontinuity in the ground-lining interaction. This paper evaluates the effect of local voids and imperfections developing around the tunnel vault area on the mechanical performance of tunnel lining. Based on field investigation results, a series of voids and imperfections with different geometries are defined to reflect cases resulting from different causes. Numerical parametric analyses were performed to investigate how those voids and imperfections influence the internal force and the safety factor of the lining, and the reinforced concrete lining were modelled with the smeared crack model to examine the development of cracking directions and patterns. Furthermore, the numerical approach was verified by comparing with field investigations and measurements. This study aims to investigate the most unsafe situation due to local voids and imperfections around the tunnel, and the modelled cracking feature shows a way to preliminary evaluate the possible local voids and imperfections behind tunnel lining based on field observation

Hidden symmetries for thermodynamics and emergence of relativity

Erik Verlinde recently proposed an idea about the thermodynamic origin of gravity. Though this is a beautiful idea which may resolve many long standing problems in the theories of gravity, it also raises many other problems. In this article I will comment on some of the problems of Verlinde's proposal with special emphasis on the thermodynamical origin of the principle of relativity. It is found that there is a large group of hidden symmetries of thermodynamics which contains the Poincare group of the spacetime for which space is emergent. This explains the thermodynamic origin of the principle of relativity.Comment: V1: 4 pages, comments/criticisms welcomed; V2: references added; V3: typos and minor corrections? V4? substantial changes in Section 3 and other parts mad