An equation for the description of volume and temperature dependences of the dynamics of supercooled liquids and polymer melts

A recently proposed expression to describe the temperature and volume dependences of the structural (or alpha) relaxation time is discussed. This equation satisfies the scaling law for the relaxation times, tau = f(TV^g), where T is temperature, V the specific volume, and g a material-dependent constant. The expression for the function f is shown to accurately fit experimental data for several glass-forming liquids and polymers over an extended range encompassing the dynamic crossover, providing a description of the dynamics with a minimal number of parameters. The results herein can be reconciled with previously found correlations of the isochoric fragility with both the isobaric fragility at atmospheric pressure and the scaling exponent g.Comment: to be published in the special edition of J. Non-Crystalline Solids honoring K.L. Nga

Volume Effects on the Glass Transition Dynamics

The role of jamming (steric constraints) and its relationship to the available volume is addressed by examining the effect that certain modifications of a glass-former have on the ratio of its isochoric and isobaric activation enthalpies. This ratio reflects the relative contribution of volume (density) and temperature (thermal energy) to the temperature-dependence of the relaxation times of liquids and polymers. We find that an increase in the available volume confers a stronger volume-dependence to the relaxation dynamics, a result at odds with free volume interpretations of the glass transition.Comment: 9 pages 5 figure

The Efficiency of Urban Planning Regulations on Environmental Management in Bamenda, North West Cameroon

In the past five decades or so, rapid rate of urbanisation and urban development and urban environmental planning and management has become a cardinal issue to urban dwellers, government institutions and professionals in the developed and developing countries. It is in furtherance to this that this paper examines the efficiency of urban planning regulations on environmental management in Bamenda. Field surveys, participant observations, questionnaire administration, interviews and on-the-spot appraisals constituted the main data sources. The findings have revealed that Bamenda is replete with an avalanche of robust urban planning regulations. Irrespective of these robust laws, it was pathetic to observe that the integration of environmental management into urban development planning was sub-optimal as over 63% of the respondents claimed ignorance on the existence of these legislations. In the context of such a seismic shift in awareness, most environmental benchmarks for sustainable urban planning have remained trapped in an environmental time-warp due to non-adherence to these regulations as a result of ignorance of their existence. This has brought about negative reverberations, ushering the urban environment of Bamenda into a frivolous path to profligacy. In order for sustainable urban planning and management to be deeply entrenched in Bamenda, this paper proffers for a synergy between government and non-government agencies responsible for urban development planning. Kewwords: Urban Planning, Management environmental management, urban developmen

ASIC Commercialization Analysis: Technology Portfolios and the Innovative Performance of ASIC Firms during Technology Evolution

We examine the relationship between application-specific integrated circuit (ASIC) firms’ technology portfolios and their innovative performance. This relationship is complex, and we hypothesize that it changes according to the stage of ASIC technology evolution. We test our hypotheses using a longitudinal dataset of 67 firms from the ASIC industry over the period 1986–2003. We find that ASIC technology evolution negatively moderates the effects of the size and diversity of the internal technology portfolio on ASIC firms’ innovative performance. This implies that, in earlier phases of ASIC technology evolution, successful ASIC firms developed large and diverse portfolios to cope with technological uncertainty. During later phases of ASIC technology evolution, they tend to have relatively smaller and less diverse portfolios, and they focus on unique, protectable, and exploitable advantages

Effect of entropy on the dynamics of supercooled liquids: New results from high pressure data

We show that for arbitrary thermodynamic conditions, master curves of the entropy are obtained by expressing S(T,V) as a function of TV^g_G, where T is temperature, V specific volume, and g_G the thermodynamic Gruneisen parameter. A similar scaling is known for structural relaxation times,tau = f(TV^g); however, we find g_G < g. We show herein that this inequality reflects contributions to S(T,V) from processes, such as vibrations and secondary relaxations, that do not directly influence the supercooled dynamics. An approximate method is proposed to remove these contributions, S_0, yielding the relationship tau = f(S-S_0).Comment: 10 pages 7 figure

When Parents and Children Disagree:Diving into DNS Delegation Inconsistency

The Domain Name System (DNS) is a hierarchical, decentralized, and distributed database. A key mechanism that enables the DNS to be hierarchical and distributed is delegation [7] of responsibility from parent to child zones—typically managed by different entities. RFC1034 [12] states that authoritative nameserver (NS) records at both parent and child should be “consistent and remain so”, but we find inconsistencies for over 13M second-level domains. We classify the type of inconsistencies we observe, and the behavior of resolvers in the face of such inconsistencies, using RIPE Atlas to probe our experimental domain configured for different scenarios. Our results underline the risk such inconsistencies pose to the availability of misconfigured domains

Invariance of the Local Segmental Relaxation Dispersion in Polycyclohexylmethacrylate / Poly-alpha-Methylstyrene Blends

Dielectric spectroscopy was carried out on polycyclohexylmethacrylate (PCHMA) and its blend with poly-alpha-methylstyrene (PaMS) as a function of temperature and pressure. When measured at conditions whereby the local segmental relaxation time for the PCHMA was constant, the dispersion in the loss spectra had a fixed shape; that is, the relaxation time determines the breadth of the relaxation time distribution, independently of T and P. This result is known for neat materials and could be observed for the blend herein due to the nonpolar character of the PaMS and the degree of thermodynamic miscibility of the blend.Comment: 13 pages 5 figure

Interacting Open Wilson Lines in Noncommutative Field Theories

In noncommutative field theories, it was known that one-loop effective action describes propagation of non-interacting open Wilson lines, obeying the flying dipole's relation. We show that two-loop effective action describes cubic interaction among `closed string' states created by open Wilson lines. Taking d-dimensional noncommutative [\Phi^3] theory as the simplest setup, we compute nonplanar contribution at low-energy and large noncommutativity limit. We find that the contribution is expressible in a remarkably simple cubic interaction involving scalar open Wilson lines only and nothing else. We show that the interaction is purely geometrical and noncommutative in nature, depending only on sizes of each open Wilson line.Comment: v1: 27 pages, Latex, 7 .eps figures v2: minor wording change + reference adde

Alendronate or alfacalcidol in glucocorticoid-induced osteoporosis

BACKGROUND: Treatment with glucocorticoids is associated with bone loss starting soon after therapy is initiated and an increased risk of fracture. METHODS: We performed a randomized, double-placebo, double-blind clinical trial of 18 months' duration among patients with a rheumatic disease who were starting glucocorticoids at a daily dose that was equivalent to at least 7.5 mg of prednisone. A total of 201 patients were assigned to receive either alendronate (10 mg) and a placebo capsule of alfacalcidol daily or alfacalcidol (1 mu g) and a placebo tablet of alendronate daily. The primary outcome was the change in bone mineral density of the lumbar spine in 18 months; the secondary outcome was the incidence of morphometric vertebral deformities. RESULTS: A total of 100 patients received alendronate, and 101 received alfacalcidol; 163 patients completed the study. The bone mineral density of the lumbar spine increased by 2.1 percent in the alendronate group (95 percent confidence interval, 1.1 to 3.1 percent) and decreased by 1.9 percent in the alfacalcidol group (95 percent confidence interval, -3.1 to -0.7 percent). At 18 months, the mean difference of change in bone mineral density between the two groups was 4.0 percent (95 percent confidence interval, 2.4 to 5.5 percent). Three patients in the alendronate group had a new vertebral deformity, as compared with eight patients in the alfacalcidol group (of whom three had symptomatic vertebral fractures) (hazard ratio, 0.4; 95 percent confidence interval, 0.1 to 1.4). CONCLUSIONS: During this 18-month trial in patients with rheumatic diseases, alendronate was more effective in the prevention of glucocorticoid-induced bone loss than was alfacalcidol

Phase ordering in chaotic map lattices with conserved dynamics

Dynamical scaling in a two-dimensional lattice model of chaotic maps, in contact with a thermal bath, is numerically studied. The model here proposed is equivalent to a conserved Ising model with coupligs which fluctuate over the same time scale as spin moves. When couplings fluctuations and thermal fluctuations are both important, this model does not belong to the class of universality of a Langevin equation known as model B; the scaling exponents are continuously varying with the temperature and depend on the map used. The universal behavior of model B is recovered when thermal fluctuations are dominant.Comment: 6 pages, 4 figures. Revised version accepted for publication on Physical Review E as a Rapid Communicatio