Dipolar origin of the gas-liquid coexistence of the hard-core 1:1 electrolyte model

We present a systematic study of the effect of the ion pairing on the gas-liquid phase transition of hard-core 1:1 electrolyte models. We study a class of dipolar dimer models that depend on a parameter R_c, the maximum separation between the ions that compose the dimer. This parameter can vary from sigma_{+/-} that corresponds to the tightly tethered dipolar dimer model, to R_c --> infinity, that corresponds to the Stillinger-Lovett description of the free ion system. The coexistence curve and critical point parameters are obtained as a function of R_c by grand canonical Monte Carlo techniques. Our results show that this dependence is smooth but non-monotonic and converges asymptotically towards the free ion case for relatively small values of R_c. This fact allows us to describe the gas-liquid transition in the free ion model as a transition between two dimerized fluid phases. The role of the unpaired ions can be considered as a perturbation of this picture.Comment: 16 pages, 13 figures, submitted to Physical Review

Kinematics and hydrodynamics of spinning particles

In the first part (Sections 1 and 2) of this paper --starting from the Pauli current, in the ordinary tensorial language-- we obtain the decomposition of the non-relativistic field velocity into two orthogonal parts: (i) the "classical part, that is, the 3-velocity w = p/m OF the center-of-mass (CM), and (ii) the so-called "quantum" part, that is, the 3-velocity V of the motion IN the CM frame (namely, the internal "spin motion" or zitterbewegung). By inserting such a complete, composite expression of the velocity into the kinetic energy term of the non-relativistic classical (i.e., newtonian) lagrangian, we straightforwardly get the appearance of the so-called "quantum potential" associated, as it is known, with the Madelung fluid. This result carries further evidence that the quantum behaviour of micro-systems can be adirect consequence of the fundamental existence of spin. In the second part (Sections 3 and 4), we fix our attention on the total 3-velocity v = w + V, it being now necessary to pass to relativistic (classical) physics; and we show that the proper time entering the definition of the four-velocity v^mu for spinning particles has to be the proper time tau of the CM frame. Inserting the correct Lorentz factor into the definition of v^mu leads to completely new kinematical properties for v_mu v^mu. The important constraint p_mu v^mu = m, identically true for scalar particles, but just assumed a priori in all previous spinning particle theories, is herein derived in a self-consistent way.Comment: LaTeX file; needs kapproc.st

The GEYSERS optical testbed: a platform for the integration, validation and demonstration of cloud-based infrastructure services

The recent evolution of cloud services is leading to a new service transformation paradigm to accommodate network infrastructures in a cost-scalable way. In this transformation, the network constitutes the key to efficiently connect users to services and applications. In this paper we describe the deployment, validation and demonstration of the optical integrated testbed for the “GEneralized architecture for dYnamic infrastructure SERviceS” (GEYSERS) project to accommodate such cloud based Infrastructure Services. The GEYSERS testbed is composed of a set of local physical testbeds allocated in the facilities of the GEYSERS partners. It is built up based on the requirements specification, architecture definition and per-layer development that constitutes the whole GEYSERS ecosystem, and validates the procedures on the GEYSERS prototypes. The testbed includes optical devices (layer 1), switches (layer 2), and IT resources deployed in different local testbeds provided by the project partners and interconnected among them to compose the whole testbed layout. The main goal of the GEYSERS testbed is twofold. On one hand, it aims at providing a validation ground for the architecture, concepts and business models proposed by GEYSERS, sustained by two main paradigms: Infrastructure as a Service (IaaS) and the coupled provisioning of optical network and IT resources. On the other hand, it is used as a demonstration platform for testing the software prototypes within the project and to demonstrate to the research and business community the project approach and solutions. In this work, we discuss our experience in the deployment of the testbed and share the results and insights learned from our trials in the process. Additionally, the paper highlights the most relevant experiments carried out in the testbed, aimed at the validation of the overall GEYSERS architecture

TGF-β1 Down-Regulation of NKG2D/DAP10 and 2B4/SAP Expression on Human NK Cells Contributes to HBV Persistence

The mechanism underlying persistent hepatitis B virus (HBV) infection remains unclear. We investigated the role of innate immune responses to persistent HBV infection in 154 HBV-infected patients and 95 healthy controls. The expression of NKG2D- and 2B4-activating receptors on NK cells was significantly decreased, and moreover, the expression of DAP10 and SAP, the intracellular adaptor proteins of NKG2D and 2B4 (respectively), were lower, which then impaired NK cell-mediated cytotoxic capacity and interferon-γ production. Higher concentrations of transforming growth factor-beta 1 (TGF-β1) were found in sera from persistently infected HBV patients. TGF-β1 down-regulated the expression of NKG2D and 2B4 on NK cells in our in vitro study, leading to an impairment of their effector functions. Anti-TGF-β1 antibodies could restore the expression of NKG2D and 2B4 on NK cells in vitro. Furthermore, TGF-β1 induced cell-cycle arrest in NK cells by up-regulating the expression of p15 and p21 in NK cells from immunotolerant (IT) patients. We conclude that TGF-β1 may reduce the expression of NKG2D/DAP10 and 2B4/SAP, and those IT patients who are deficient in these double-activating signals have impaired NK cell function, which is correlated with persistent HBV infection

Time-dependent load performance of notched wood-concrete composite beams

Researchers at Colorado State University (CSU) are examining the feasibility of using wood-concrete composite floor/deck systems as an alternative to concrete floor slab systems. The primary aim is to show that a structurally effective, durable solid wood-concrete layer can replace the cracked portion of the concrete slab and its rebar. Concrete needs a companion material to account for its lack of tension carrying ability. Wood is good in tension, if tension defects such as knots do not exist. Since the wood layer deck can replace the formwork for a solid slab, the gain is to leave it in place and use it structurally to reduce the concrete slab thickness by about 50% by interconnecting the wood and concrete layers. Ceccotti (1995) has closely examined wood-concrete flooring systems and provided a summation of many of the benefits compared to light frame wood floors. These include: 1) reduction of the vibration problems associated with timber structures, 2) an improvement of the sound insulation, 3) better fire resistance, 4) better seismic behaviour, and 5) reduction in the likelihood of catastrophic failure. The competitive merit of such mixed construction is borne out by several examples of successful commercial projects in Europe (Natterer, 1998). The concept has also been tried in the reconstruction of timber floors and ceilings (Toratti and Kevarinmaki, 2001). Layered wood-concrete composites exhibit composite behavior that is it is bounded by two extreme limits. The upper limit (‘fully composite’) is when the interface between the layers is considered perfectly bonded and allows no relative motion (‘slip’). The lower limit (‘non-composite’) is when the layers are completely unbounded with neither mechanical bond nor friction taking place between the two layers. For non-composite behavior, no interlayer shear transfer takes place. The actual circumstance is that the layer beam exhibits partial composite behavior while also experiencing slip between the layers. Actual systems are stiffer than the non-composite limit state while less stiff than the fully composite state. Prior to conducting load tests of layered floor/deck specimens, preliminary load tests of layered wood-concrete beams where done by Fast et al. (2003). This included subjecting specimens to either creep tests and/or cyclic loading tests which simulate their typical service life. Results were used to evaluate the efficiency of the beam specimens as related to the degree of partial composite action achieved

Long-term behaviour of wood-concrete composite beams with notched connection detail

Investigates the long-term behaviour of wood-concrete composite floor/deck systems with shear key/anchor connection detail. The beam specimens were first monitored in time after the concrete placement on the wood deck, and then subjected to a sustained load. The experimental results have also been extended to the entire service life of the structure using a Finite Element model. The primary observations are: (i) the bleeding of the fresh concrete is not an issue for the durability of the wood deck; (ii) the type of construction (shored, unshored) is of little influence for the structural performance; (iii) the deflection increases quite significantly over the time because of the rheological phenomena of the component materials. The use of concrete with reduced shrinkage and the pre-cambering of the wood deck are two possible ways to reduce the long-term deflection. The experimental and numerical results are finally compared with those obtained using a simplified approach, showing that the simplified approach leads to reasonably good accuracy

UNIVERSITY TRANSPORTATION SURVEY: TRANSPORTATION IN UNIVERSITY COMMUNITIES

Universities and transit agencies across the United States have been finding innovative ways of providing and financing mobility services on and around university campuses. Many transit agencies are providing substantially more service and moving substantially more riders than their counterparts in nonuniversity environments. Determining what types of relationships exist between transit performance and university policies or practices is the research premise. To that end, the purpose is to document the types of transportation policies, demographics, and land use characteristics that exist on university campuses, and to examine the relationship between transit performance, land use on university campuses, types of university communities, university transportation and parking policies, and student demographics. These characteristics of university transportation systems were examined through demographic data and a mailed questionnaire. The questionnaire was sent to 48 universities and transit agencies across the United States, with 23 responding with enough valid data and information to be included in the study. It has been demonstrated in a significant number of university communities across the country that transit performance is enhanced dramatically by certain fare policies. However, that enhancement differs from one community to the next. It is believed that the answer to maximizing transit performance can be found in a combination of factors and that the optimum mix can be identified empirically

Flame quenching by the wall-fundamental characteristics

Knowledge of flame-wall interaction allowed us to understand the phenomena of near wall combustion and flame extinction. The study of near wall flame propagation is important because it is related to engineering applications, such as possible misfiring in internal combustion engines, optimization of combustion, and reduction of unburned hydrocarbons in the combustion products. In the present work different characteristics of the quenching distance were measured in square narrow quenching channels. The channel widths were changed from 2.5mm to 15mm, their length being 30cm. Propane/air mixture was employed in experiments. Direct visualization has been used to observe flame behaviour under quenching conditions. Numerical simulation revealed structure of limit flames during their propagation in quenching channels. It was found satisfactory agreement between numerical calculations and experiments. In conclusions it was confirmed that flame quenching depends on the relation between heat release rate to heat loss rate. Dead space appeared to be larger for rich mixtures in comparison with the lean ones. Flame curvature reached maximum value for stoichiometry and decreased for leaner or richer mixtures