Constraints on DD Dimensional Warped Spaces

In order to investigate the phenomenological implications of allowing gauge fields to propagate in warped spaces of more than five dimensions, we consider a toy model of a space warped by the presence of a anisotropic bulk cosmological constant. After solving the Einstein equation, three classes of solutions are found, those in which the additional ($D>5$) dimensions are growing, shrinking or remaining constant. It is found that gauge fields propagating in these spaces have a significantly different Kaluza Klein (KK) mass spectrum and couplings from that of the Randall and Sundrum model. This leads to a greatly reduced lower bound on the KK scale, arising from electroweak constraints, for spaces growing towards the IR brane.Comment: 6 pages, 5 figures PASCOS2010 International Symposium proceedin

Relationship between Local Molecular Field Theory and Density Functional Theory for non-uniform liquids

The Local Molecular Field Theory (LMF) developed by Weeks and co-workers has proved successful for treating the structure and thermodynamics of a variety of non-uniform liquids. By reformulating LMF in terms of one-body direct correlation functions we recast the theory in the framework of classical Density Functional Theory (DFT). We show that the general LMF equation for the effective reference potential phi_R follows directly from the standard mean-field DFT treatment of attractive interatomic forces. Using an accurate (Fundamental Measures) DFT for the non-uniform hard-sphere reference fluid we determine phi_R for a hard-core Yukawa liquid adsorbed at a planar hard wall. In the approach to bulk liquid-gas coexistence we find the effective potentials exhibit rich structure that can include damped oscillations at large distances from the wall as well as the repulsive hump near the wall required to generate the low density 'gas' layer characteristic of complete drying. We argue that it would be difficult to obtain the same level of detail from other (non DFT based) implementations of LMF. LMF emphasizes the importance of making an intelligent division of the interatomic pair potential of the full system into a reference part and a remainder that can be treated in mean-field approximation. We investigate different divisions for an exactly solvable one- dimensional model where the pair potential has a hard-core plus a linear attractive tail. Results for the structure factor and the equation of state of the uniform fluid show that including a significant portion of the attraction in the reference system can be much more accurate than treating the full attractive tail in mean-field approximation. We discuss further aspects of the relationship between LMF and DFT.Comment: 35 pages, 10 Fig

Ekho: A Tool for Recording and Emulating Energy Harvesting Conditions

Harvested energy makes it possible to deploy sensing devices long-term with minimal required upkeep. However, as devices shrink, unpredictable power supplies make it difficult for system designers to anticipate the behavior of these devices. Ekho is tool that records and emulates energy harvesting conditions in order to enable accurate and repeatable testing of these sensing devices. Ekho uses the concept of I-V curves — curves that describe harvesting current in relation to supply voltage — in order to accurately represent harvesting conditions in a form that is independent of the sensing platform and the type of energy that is being harvested. This paper describes extensions to Ekho; it presents the design and an improved implementation, as well as preliminary testing and results. My role in this project has been to reimplement and to extend Ekho. This software was unmaintainable and considerably limited in its ability to emulate energy harvesting conditions. The first implementation of Ekho was a hardware design for an FPGA, which made use of specialized circuits. I refactored this code for a microcontroller, achieving even better performance than before: this new implementation can record harvesting conditions and can emulate changing I-V curves, and I have added back-end programs to ease processing and formatting of data. Initial results show that Ekho is able to replay I-V surfaces while readjusting to the harvesting conditions as frequently as once in 4.3μs. Ekho is able to emulate changing energy conditions, adapting both to changes in supply voltage and energy availability. Ekho can update the I-V curve, which the I-V controller holds in memory during emulation, as frequently as once per millisecond. These results show that Ekho is responsive to changes in the harvesting current and could be working properly

The standard mean-field treatment of inter-particle attraction in classical DFT is better than one might expect

In classical density functional theory (DFT) the part of the Helmholtz free energy functional arising from attractive inter-particle interactions is often treated in a mean-field or van der Waals approximation. On the face of it, this is a somewhat crude treatment as the resulting functional generates the simple random phase approximation (RPA) for the bulk fluid pair direct correlation function. We explain why using standard mean-field DFT to describe inhomogeneous fluid structure and thermodynamics is more accurate than one might expect based on this observation. By considering the pair correlation function $g(x)$ and structure factor $S(k)$ of a one-dimensional model fluid, for which exact results are available, we show that the mean-field DFT, employed within the test-particle procedure, yields results much superior to those from the RPA closure of the bulk Ornstein-Zernike equation. We argue that one should not judge the quality of a DFT based solely on the approximation it generates for the bulk pair direct correlation function.Comment: 9 pages, 3 figure

Potential of thermophilic bioleaching, effect of temperature on the process performance

Includes bibliographies.Bioleaching is a biohydrometallurgical process whereby mineral sulphides are metabolically oxidised by microorganisms, releasing precious metals encapsulated in them. This pre-treatment is based on the action of microorganisms affecting oxidation of reduced sulphur species and ferrous iron to sulphate and ferric iron respectively. Conventionally Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans are implemented in this process in the region of 40-45°C and pH 1.8. A high temperature (65- 800C) process, utiltising thermophilic archaea such as Sulfolobus spp. can be considered as an alternative to current bioleaching practice. Literature indicates that there is an overall increase, 6 fold on average, in the rate of leaching due to the use thermophilic organisms. Bioleaching. involves nutrient transfer to microorganisms and interactions between several ionic species, including iron and sulphate. Thus, it is necessary to investigate the effect of the increased temperature on the gas-liquid mass transfer as well as ionic speciation of the system. Hence, the objectives of the present research were established as follows: to elucidate the effect of temperature on mass transfer from a theoretical point of view to establish whether ionic speciation is a contributing factor in thermophilic bioleaching to develop a generic and flexible means of representing ionic specie

Measurements Of Excited-state Population Ratios Of Atomic Hydrogen Produced By Charge-exchange Neutralization Of Energetic Proton Beams

Excited-state population ratios for atomic hydrogen have been measured for energetic hydrogen ions neutralized by charge exchange with a number of different metallic vapors and permanent gases. Electric field ionization techniques were used to determine excitation ratios. Detection of the energetic ions and neutrals was accomplished using partially depleted surface-barrier detectors. Counting, using phase-detection techniques in which an add-subtract scaler was phased to the signal, provided an improved signal-to-noise ratio. Two methods were used to provide desired targets. Metallic vapor and permanent-gas thin targets of the order of 10-5 mTorr cm were produced as chopped neutral beams, using conventional crossed-beam techniques. Gas cells were used to extend these measurements with permanent gases to targets up to seven orders of magnitude thicker. In the latter case, the ion beam was interrupted electrically. Targets investigated were magnesium, potassium, barium, hydrogen, nitrogen, thallium, Freon, water vapor, ammonia, and perfluorodimethylcyclohexane (C8F16). © 1970 The American Physical Society

Do depressive symptoms predict cancer incidence?: 17-year follow-up of the Whitehall II study

Objective: To explore the association between depressive symptom history and cancer incidence. Methods: Affective/emotional depressive symptoms were assessed using the General Health Questionnaire (GHQ-30) depression sub-scale across phase 1 (1985-1988), phase 2 (1989-1990), and phase 3 (1991-1994) of the Whitehall II prospective cohort study; ‘chronic’= depressive episode at phase 1, 2 and 3; ‘new’= depressive episode at phase 3 only. Cancer Incidence was obtained from the National Health Service Central Register with an average follow-up of 15.6 years (range 0.08–17.4). The study sample consisted of 6983 participants, aged 35–55 years at baseline. Results were adjusted for age, sex, socio-economic position, health behaviours, health status/conditions, medication, and social support. Results: Over a 17.4 year follow-up, chronic depressive symptoms did not increase the risk of cancer incidence compared to those who never experienced symptoms (hazard ratio (HR)=1.03, 95% confidence interval (CI): 0.71-1.49). Participants who experienced new depressive symptoms had an increased risk of cancer incidence in the first 9 years of follow-up (HR=1.89, 95% CI: 1.23-2.90) but no increased risk in later years (HR=0.84, 95% CI: 0.52-1.35). Conclusion: Chronic depressive symptoms were not associated with cancer incidence. In contrast, new-onset symptoms were associated with a substantially increased risk, possibly due to reverse causality

Dynamical density functional theory for dense atomic liquids

Starting from Newton's equations of motion, we derive a dynamical density functional theory (DDFT) applicable to atomic liquids. The theory has the feature that it requires as input the Helmholtz free energy functional from equilibrium density functional theory. This means that, given a reliable equilibrium free energy functional, the correct equilibrium fluid density profile is guaranteed. We show that when the isothermal compressibility is small, the DDFT generates the correct value for the speed of sound in a dense liquid. We also interpret the theory as a dynamical equation for a coarse grained fluid density and show that the theory can be used (making further approximations) to derive the standard mode coupling theory that is used to describe the glass transition. The present theory should provide a useful starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte