A ductile damage criterion at various stress triaxialities

The paper discusses the effect of stress triaxiality on the onset and evolution of damage in ductile metals. A series of tests including shear tests and experiments oil smooth and pre-notched tension specimens wits carried Out for it wide range of stress triaxialities. The underlying continuum damage model is based oil kinematic definition of damage tensors. The modular structure of the approach is accomplished by the decomposition of strain rates into elastic, plastic and damage parts. Free energy functions with respect to fictitious undamaged configurations as well as damaged ones are introduced separately leading to elastic material laws which are affected by increasing damage. In addition, a macroscopic yield condition and a flow rule are used to adequately describe the plastic behavior. Numerical simulations of the experiments are performed and good correlation of tests and numerical results is achieved. Based oil experimental and numerical data the damage criterion formulated in stress space is quantified. Different branches of this function are taken into account corresponding to different damage modes depending oil stress triaxiality and Lode parameter. In addition, identification of material parameters is discussed ill detail. (C) 2007 Elsevier Ltd. All rights reserved.

Attenuation and damping of electromagnetic fields: influence of inertia and displacement current

New results for attenuation and damping of electromagnetic fields in rigid conducting media are derived under the conjugate influence of inertia due to charge carriers and displacement current. Inertial effects are described by a relaxation time for the current density in the realm of an extended Ohm`s law. The classical notions of poor and good conductors are rediscussed on the basis of an effective electric conductivity, depending on both wave frequency and relaxation time. It is found that the attenuation for good conductors at high frequencies depends solely on the relaxation time. This means that the penetration depth saturates to a minimum value at sufficiently high frequencies. It is also shown that the actions of inertia and displacement current on damping of magnetic fields are opposite to each other. That could explain why the classical decay time of magnetic fields scales approximately as the diffusion time. At very small length scales, the decay time could be given either by the relaxation time or by a fraction of the diffusion time, depending on whether inertia or displacement current, respectively, would prevail on magnetic diffusion.

Entropy production in irreversible systems described by a Fokker-Planck equation

We analyze the irreversibility and the entropy production in nonequilibrium interacting particle systems described by a Fokker-Planck equation by the use of a suitable master equation representation. The irreversible character is provided either by nonconservative forces or by the contact with heat baths at distinct temperatures. The expression for the entropy production is deduced from a general definition, which is related to the probability of a trajectory in phase space and its time reversal, that makes no reference a priori to the dissipated power. Our formalism is applied to calculate the heat conductance in a simple system consisting of two Brownian particles each one in contact to a heat reservoir. We show also the connection between the definition of entropy production rate and the Jarzynski equality.

Thermodynamics of aqueous solutions of polyelectrolytes: Experimental results for the activity of water in aqueous solutions of (a single synthetic polyelectrolyte and sodium chloride)

Experimental results for the activity of water in aqueous solutions of 10 single, synthetic polyelectrolytes (polysodium acrylate, polysodium methacrylate, polyammonium acrylate, polysodium ethylene sulfonate, and polysodium styrene sulfonate) and sodium chloride at 298.2 K are presented. The experimental work was performed by applying the isopiestic method with sodium chloride as a reference substance. As expected, the activity of water decreases when the concentration of a polyelectrolyte and/or sodium chloride increases. At constant concentration of a polyelectrolyte and sodium chloride, the activity of water depends on the monomer unit and the molecular mass of the polyelectrolyte. The new data are to be used in future work to develop and test models for the Gibbs excess energy of aqueous solutions of polyelectrolytes.

Thermodynamics of aqueous solutions of polyelectrolytes: Experimental results for the activity of water in aqueous solutions of some single synthetic polyelectrolytes

Experimental results for the activity of water in aqueous solutions of 10 single polyelectrolytes (two polysodium acrylates, two polysodium methacrylates, three polyammonium acrylates, two polysodium ethylene sulfonates, and one polysodium styrene sulfonate) at (298.2 and 323.2) K are reported. The isopiestic method was employed in these experiments with aqueous solutions of sodium chloride as references. The polyelectrolytes were characterized by three averaged molecular masses determined by gel permeation chromatography. Furthermore, the density and the refractive index increments of the aqueous polyelectrolyte solutions are reported. Although a similar pattern for the activity of water was observed for all systems (i.e., the osmotic coefficient increases with rising polyelectrolyte concentration), the experimental results show that this property depends on the monomer type as well as on the size of the polymer chain. The temperature (varied from (298.2 to 323.2) K) has only a small influence on the activity of water.

Irreversible blindness in juvenile systemic lupus erythematosus

Blindness caused by severe vasculitis or uveitis is rare in juvenile systemic lupus erythematosus (JSLE) patients. In a 27-year period, 5367 patients were followed at our Paediatric Rheumatology Division and 263 (4.9%) patients had JSLE (American College of Rheumatology criteria). Of note, two (0.8%) of them had irreversible blindness. One of them presented with cutaneous vasculitis and malar rash, associated with pain and redness in both eyes, impairment of visual acuity due to iridocyclitis and severe retinal vasculitis with haemorrhage. Another patient had peripheral polyneuropathy of the four limbs and received immunosuppressive drugs. Three weeks later, she developed diffuse herpes zoster associated with acute blindness due to bilateral retinal necrotizing vasculitis compatible with varicella zoster virus ocular infection. Despite prompt treatment, both patients suffered rapid irreversible blindness. In conclusion, irreversible blindness due to retinal vasculitis and/or uveitis is a rare and severe lupus manifestation, particularly associated with disease activity and viral infection. Lupus (2011) 20, 95-97.

Anesthetic efficacy of inferior alveolar nerve block plus buccal infiltration or periodontal ligament injections with articaine in patients with irreversible pulpitis in the mandibular first molar

Objective. We compared the anesthetic efficacy of inferior alveolar nerve block (IANB) plus buccal infiltration (BI) and IANB plus periodontal ligament (PDL) articaine injections in patients with irreversible pulpitis in the mandibular first molar. Study design. Fifty-seven volunteers, patients with irreversible pulpitis in the mandibular first molar admitted to the Department of Stomatology, Second Affiliated Hospital, Sun Yat-Sen University, randomly received conventional IANB, containing 1.7 mL 4% articaine/HCl with 1:100,000 epinephrine, plus either BI or PDL injections containing 0.4 mL articaine/HCl with 1: 100,000 epinephrine. The patients recorded the pain of the injections and endodontic access on a Heft-Parker visual analog scale (VAS). Results. According to the VAS scores, all patients experienced no or mild pain with BI and PDL injections after the application of IANB. Anesthetic success occurred in 81.48% for IANB plus BI (IANB/BI) compared with 83.33% for IANB plus PDL injection (IANB/PDL injection). None of the observed differences between the 2 groups was significant (P > .05). Conclusion. Both injection combinations resulted in high anesthetic success in patients with irreversible pulpitis in the mandibular first molar. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:e89-e93)

On phantom thermodynamics

The thermodynamic properties of dark energy fluids described by an equation of state parameter omega = p/rho are rediscussed in the context of FRW type geometries. Contrarily to previous claims, it is argued here that the phantom regime omega < -1 is not physically possible since that both the temperature and the entropy of every physical fluids must be always positive definite. This means that one cannot appeal to negative temperature in order to save the phantom dark energy hypothesis as has been recently done in the literature. Such a result remains true as long as the chemical potential is zero. However, if the phantom fluid is endowed with a non-null chemical potential, the phantom field hypothesis becomes thermodynamically consistent, that is, there are macroscopic equilibrium states with T > 0 and S > 0 in the course of the Universe expansion. (C) 2008 Elsevier B.V. All rights reserved.

HOST-MEDIATED INDUCTION OF alpha-AMYLASES BY LARVAE OF THE MEXICAN BEAN WEEVIL Zabrotes subfasciatus (COLEOPTERA: CHRYSOMELIDAE: BRUCHINAE) IS IRREVERSIBLE AND OBSERVED FROM THE INITIATION OF THE FEEDING PERIOD

Larvae of Zabrotes subfasciatus secrete alpha-amylases that are insensitive to the alpha-amylase inhibitor found in seeds of Phaseolus vulgaris. By analyzing amylase activities during larval development on P. vulgaris, we detected activity of the constitutive amylase and the two inducible amylase isoforms at all stages. When larvae were transferred from the non alpha-amylase inhibitor containing seeds of Vigna unguiculata to P. vulgaris, the inducible alpha-amylases were expressed at the same level as in control larvae fed on P. vulgaris. Interestingly, when larvae were transferred from seeds of P. vulgaris to those of V. unguiculata, inducible alpha-amylases continued to be expressed at a level similar to that found in control larvae fed P. vulgaris continuously. When 10-day-old larvae were removed from seeds of V. unguiculata and transferred into capsules containing flour of P. vulgaris cotyledons, and thus maintained until completing 17 days ( age when the larvae stopped feeding), we could detect higher activity of the inducible alpha-amylases. However, when larvae of the same age were transferred from P. vulgaris into capsules containing flour of V. unguiculata, the inducible alpha-amylases remained up-regulated. These results suggest that the larvae of Z. subfasciatus have the ability to induce insensitive amylases early in their development. A short period of feeding on P. vulgaris cotyledon flour was sufficient to irreversibly induce the inducible alpha-amylase isoforms. Incubations of brush border membrane vesicles with the alpha-amylase inhibitor 1 from P. vulgaris suggest that the inhibitor is recognized by putative receptors found in the midgut microvillar membranes. (C) 2010 Wiley Periodicals, Inc.

A PRELIMINARY ANALYSIS OF THE ENERGY TRANSFER BETWEEN THE DARK SECTORS OF THE UNIVERSE

We study the mutual interaction between the dark sectors (dark matter and dark energy) of the Universe by resorting to the extended thermodynamics of irreversible processes and constrain the former with supernova type Ia data. As a by-product, the present dark matter temperature results are not extremely small and can meet the independent estimate of the temperature of the gas of sterile neutrinos.

A Precise Formulation of the Third Law of Thermodynamics

The third law of thermodynamics is formulated precisely: all points of the state space of zero temperature I""(0) are physically adiabatically inaccessible from the state space of a simple system. In addition to implying the unattainability of absolute zero in finite time (or ""by a finite number of operations""), it admits as corollary, under a continuity assumption, that all points of I""(0) are adiabatically equivalent. We argue that the third law is universally valid for all macroscopic systems which obey the laws of quantum mechanics and/or quantum field theory. We also briefly discuss why a precise formulation of the third law for black holes remains an open problem.

Reversible and irreversible magnetization components behavior in Ni nanowires

Polycrystalline Ni nanowires were electrodeposited in nanoporous anodized alumina membranes with mean diameter of approximately 42 nm. Their magnetic properties were studied at 300 K, by measurements of recoil curves from demagnetized state and also from saturated state. M(rev) and M(irr) components were obtained and M(rev)(M(irr)) H curves were constructed from the experimental data. These curves showed a behavior that suggests a non-uniform reversal mode influenced by the presence of dipolar interactions in the system. A qualitative approach to this behavior is obtained using a Stoner-Wohlfarth model modified by a mean field term and local interaction fields. (C) 2008 Elsevier B.V. All rights reserved.

Phantom accretion by black holes and the generalized second law of thermodynamics

The accretion of a phantom fluid with non-zero chemical potential by black holes is discussed with basis on the generalized second law of thermodynamics. For phantom fluids with positive temperature and negative chemical potential we demonstrate that the accretion process is possible, and that the condition guaranteeing the positiveness of the phantom fluid entropy coincides with the one required by the generalized second law. (C) 2010 Elsevier B.V. All rights reserved.

Thermodynamic characterization of the palm tree Roystonea regia peroxidase stability

The structural stability of a peroxidase, a dimeric protein from royal palm tree (Roystonea regia) leaves, has been characterized by high-sensitivity differential scanning calorimetry, circular dichroism, steady-state tryptophan fluorescence and analytical ultracentifugation under different solvent conditions. It is shown that the thermal and chemical (using guanidine hydrochloride (Gdn-HCl)) folding/unfolding of royal palm tree peroxidase (RPTP) at pH 7 is a reversible process involving a highly cooperative transition between the folded dimer and unfolded monomers, with a free stabilization energy of about 23 kcal per mol of monomer at 25 degrees C. The structural stability of RPTP is pH-dependent. At pH 3, where ion pairs have disappeared due to protonation, the thermally induced denaturation of RPTP is irreversible and strongly dependent upon the scan rate, suggesting that this process is under kinetic control. Moreover, thermally induced transitions at this pH value are dependent on the protein concentration, allowing it to be concluded that in solution RPTP behaves as dimer, which undergoes thermal denaturation coupled with dissociation. Analysis of the kinetic parameters of RPTP denaturation at pH 3 was accomplished on the basis of the simple kinetic scheme N ->(k) D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state, and D is the denatured state, and thermodynamic information was obtained by extrapolation of the kinetic transition parameters to an infinite heating rate. Obtained in this way, the value of RPTP stability at 25 degrees C is ca. 8 kcal per mole of monomer lower than at pH 7. In all probability, this quantity reflects the contribution of ion pair interactions to the structural stability of RPTP. From a comparison of the stability of RPTP with other plant peroxidases it is proposed that one of the main factors responsible for the unusually high stability of RPTP which enhances its potential use for biotechnological purposes, is its dimerization. (c) 2008 Elsevier Masson SAS. All rights reserved.

Irreversible inhibition of human cathepsins B, L, S and K by hypervalent tellurium compounds

The inhibition of human cysteine cathepsins B, L, S and K was evaluated by a set of hypervalent tellurium compounds (telluranes) comprising both organic and inorganic derivatives. All telluranes studied showed a time-and concentration-dependent irreversible inhibition of the cathepsins, and their second-order inactivation rate constants were determined. The organic derivatives were potent inhibitors of the cathepsins and clear specificities were detected, which were parallel to their known substrate specificities. In all cases, the activity of the tellurane-inhibited cathepsins was recovered by treatment of the inactivated enzymes with reducing agents. The maximum stoichiometry of the reaction between cysteine residues and telluranes were also determined. The presented data indicate that it is possible to design organic compounds with a tellurium(IV) moiety as a novel warhead that covalently modifies the catalytic cysteine, and which also form strong interactions with subsites of cathepsins B, L, S and K, resulting in more specific inhibition.