Determination Of Iron In Iron Ores Using Enthalpimetric Flow Injection Analysis

A method is described in which a dissolved sample of iron ore is injected into a flow manifold, after passing through a silver reductor column. The sample then merges with a dichromate solution and generates an enthalpimetric signal due to the oxidation of iron(II). The precision of the proposed method is approximately 0.3% and the sampling rate is 85 samples per hour. Interference from vanadium was negligible and titanium did not interfere. The results of the analysis of samples of iron ores by the proposed method agree with those obtained by titrimetric analysis.111785785

Causal explanation for observed superluminal behavior of microwave propagation in free space

In this paper we present a theoretical analysis of an experiment by Mugnai and collaborators where superluminal behavior was observed in the propagation of microwaves. We suggest that what was observed can be well approximated by the motion of a superluminal X wave. Furthermore the experimental results are also explained by the so called scissor effect which occurs with the convergence of pairs of signals coming from opposite points of an annular region of the mirror and forming an interference peak on the intersection axis traveling at superluminal speed. We clarify some misunderstandings concerning this kind of electromagnetic wave propagation in vacuum.Comment: 9 pages, 3 figures, accepted for publication in Physics Letters

Magnetic Field Dependence Of The Curie-weiss Paramagnetism In Crv Alloys

The determination of the magnetic properties of antiferromagnetic Cr alloys requires careful consideration of the influence of the applied magnetic field. In this work we show that alloys of Cr-x at. % V present a Curie-Weiss paramagnetism above the Néel temperature, which is suppressed by a characteristic field HL. Samples with x=0.1, 0.2, and 0.4 were investigated through measurements of the magnetic susceptibility as a function of temperature, for different values of the magnetic field. A magnetic phase diagram showing the characteristic line HL vs x at. % V is proposed. © 1997 American Institute of Physics.818 PART 2A42094211Suzuki, T., Takaki, H., (1964) J. Phys. Soc. Jpn., 19, p. 1241Suzuki, T., (1966) J. Phys. Soc. Jpn., 21, p. 442Aidun, R., Arajs, S., Moyer, C.A., (1985) Phys. Status Solidi B, 128, p. 133Hill, P., Ali, N., De Oliviera, A.J.A., Ortiz, W.A., De Camargo, P.C., Fawcett, E., (1994) J. Phys. Condens. Matter., 6, p. 1761De Oliveira, A.J.A., Otriz, W.A., De Camargo, P.C., Galkin, V.Yu., (1996) J. Magn. Magn. Mater., 152, p. 86De Oliveira, A.J.A., De Lima, O.F., De Camargo, P.C., Ortiz, W.A., Fawcett, E., (1996) J. Phys. Condens. Matter., 8, pp. L403Benediktsson, G., Hedman, L., Aström, H.U., Rao, K.V., (1982) J. Phys. F, 12, p. 1439Booth, J.G., (1964) Phys. Status Solidi, 7 K, p. 157Bender, D., Müller, J., (1970) Phys. Kondens. Mater., 10, p. 342Buzdin, A.I., Men'shov, V.N., Tugushev, V.V., (1986) Zh. Eksp. Teor. Fiz., 91, p. 2204(1986) Sov. Phys. JETP, 64. , Engl. TranslTugushev, V.V., (1992) Modulated and Localized Structures of the Spin-Density Wave in Itinerant Antiferromagnets in Electronic Phase Transitions, p. 237. , edited by W. Hanke and Yu. Koapev Elsevier, AmsterdamDe Oliveira, A.J.A., De Lima, O.F., Ortiz, W.A., De Camargo, P.C., (1995) Solid State Commun., 96, p. 383De Oliveira, A.J.A., (1996), PhD. thesis, Universidade Federal de São Carlo

Synergistic warm inflation

We consider an alternative warm inflationary scenario in which $n$ scalar fields coupled to a dissipative matter fluid cooperate to produce power--law inflation. The scalar fields are driven by an exponential potential and the bulk dissipative pressure coefficient is linear in the expansion rate. We find that the entropy of the fluid attains its asymptotic value in a characteristic time proportional to the square of the number of fields. This scenario remains nearly isothermal along the inflationary stage. The perturbations in energy density and entropy are studied in the long--wavelength regime and seen to grow roughly as the square of the scale factor. They are shown to be compatible with COBE measurements of the fluctuations in temperature of the CMB.Comment: 13 pages, Revtex 3 To be published in Physical Review

Walking training improves systemic and local pathophysiological processes in intermittent claudication

Objective: This study examined the impact of submaximal walking training (WT) on local and systemic nitric oxide (NO) bioavailability, inflammation, and oxidative stress in patients with intermittent claudication (IC). Methods: The study employed a randomised, controlled, parallel group design and was performed in a single centre. Thirty-two men with IC were randomly allocated to two groups: WT (n = 16, two sessions/week, 15 cycles of two minutes walking at an intensity corresponding to the heart rate obtained at the pain threshold interspersed by two minutes of upright rest) and control (CO, n = 16, two sessions/week, 30 minutes of stretching). NO bioavailability (blood NO and muscle nitric oxide synthase [eNOS]), redox homeostasis (catalase [CAT], superoxide dismutase [SOD], lipid peroxidation [LPO] measured in blood and muscle), and inflammation (interleukin-6 [IL-6], C-reactive protein [CRP], tumour necrosis factor α [TNF-α], intercellular adhesion molecules [ICAM], vascular adhesion molecules [VCAM] measured in blood and muscle) were assessed at baseline and after 12 weeks. Results: WT statistically significantly increased blood NO, muscle eNOS, blood SOD and CAT, and muscle SOD and abolished the increase in circulating and muscle LPO observed in the CO group. WT decreased blood CRP, ICAM, and VCAM and muscle IL-6 and CRP and eliminated the increase in blood TNF-α and muscle TNF-α, ICAM and VCAM observed in the CO group. Conclusion: WT at an intensity of pain threshold improved NO bioavailability and decreased systemic and local oxidative stress and inflammation in patients with IC. The proposed WT protocol provides physiological adaptations that may contribute to cardiovascular health in these patients

Gravitational field around a time-like current-carrying screwed cosmic string in scalar-tensor theories

In this paper we obtain the space-time generated by a time-like current-carrying superconducting screwed cosmic string(TCSCS). This gravitational field is obtained in a modified scalar-tensor theory in the sense that torsion is taken into account. We show that this solution is comptible with a torsion field generated by the scalar field $\phi$. The analysis of gravitational effects of a TCSCS shows up that the torsion effects that appear in the physical frame of Jordan-Fierz can be described in a geometric form given by contorsion term plus a symmetric part which contains the scalar gradient. As an important application of this solution, we consider the linear perturbation method developed by Zel'dovich, investigate the accretion of cold dark matter due to the formation of wakes when a TCSCS moves with speed $v$ and discuss the role played by torsion. Our results are compared with those obtained for cosmic strings in the framework of scalar-tensor theories without taking torsion into account.Comment: 21 pages, no figures, Revised Version, presented at the "XXIV- Encontro Nacional de Fisica de Particulas e Campos ", Caxambu, MG, Brazil, to appear in Phys. Rev.

Morris-Thorne wormholes with a cosmological constant

First, the ideas introduced in the wormhole research field since the work of Morris and Thorne are briefly reviewed, namely, the issues of energy conditions, wormhole construction, stability, time machines and astrophysical signatures. Then, spherically symmetric and static traversable Morris-Thorne wormholes in the presence of a generic cosmological constant are analyzed. A matching of an interior solution to the unique exterior vacuum solution is done using directly the Einstein equations. The structure as well as several physical properties and characteristics of traversable wormholes due to the effects of the cosmological term are studied. Interesting equations appear in the process of matching. For instance, one finds that for asymptotically flat and anti-de Sitter spacetimes the surface tangential pressure of the thin-shell, at the boundary of the interior and exterior solutions, is always strictly positive, whereas for de Sitter spacetime it can take either sign as one could expect, being negative (tension) for relatively high cosmological constant and high wormhole radius, positive for relatively high mass and small wormhole radius, and zero in-between. Finally, some specific solutions with generic cosmological constant, based on the Morris-Thorne solutions, are provided.Comment: latex, 49 pages, 8 figures. Expanded version of the paper published in Physical Review

Observational Constraints on Chaplygin Quartessence: Background Results

We derive the constraints set by several experiments on the quartessence Chaplygin model (QCM). In this scenario, a single fluid component drives the Universe from a nonrelativistic matter-dominated phase to an accelerated expansion phase behaving, first, like dark matter and in a more recent epoch like dark energy. We consider current data from SNIa experiments, statistics of gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in galaxy clusters. We investigate the constraints from this data set on flat Chaplygin quartessence cosmologies. The observables considered here are dependent essentially on the background geometry, and not on the specific form of the QCM fluctuations. We obtain the confidence region on the two parameters of the model from a combined analysis of all the above tests. We find that the best-fit occurs close to the $\Lambda$CDM limit ($\alpha=0$). The standard Chaplygin quartessence ($\alpha=1$) is also allowed by the data, but only at the $\sim2\sigma$ level.Comment: Replaced to match the published version, references update