Incorporating Memory Effects in Phase Separation Processes

We consider the modification of the Cahn-Hilliard equation when a time delay process through a memory function is taken into account. We then study the process of spinodal decomposition in fast phase transitions associated with a conserved order parameter. Finite-time memory effects are seen to affect the dynamics of phase transition at short times and have the effect of delaying, in a significant way, the process of rapid growth of the order parameter that follows a quench into the spinodal region. These effects are important in several systems characterized by fast processes, like nonequilibrium dynamics in the early universe and in relativistic heavy-ion collisions.Comment: 5 pages, 2 eps figures. Version in press Phys. Lett.

Unfolding Smooth Prismatoids

We define a notion for unfolding smooth, ruled surfaces, and prove that every smooth prismatoid (the convex hull of two smooth curves lying in parallel planes), has a nonoverlapping “volcano unfolding.” These unfoldings keep the base intact, unfold the sides outward, splayed around the base, and attach the top to the tip of some side rib. Our result answers a question for smooth prismatoids whose analog for polyhedral prismatoids remains unsolved

Entropy production in phase field theories

Allen-Cahn (Ginzburg-Landau) dynamics for scalar fields with heat conduction is treated in rigid bodies using a non-equilibrium thermodynamic framework with weakly nonlocal internal variables. The entropy production and entropy flux is calculated with the classical method of irreversible thermodynamics by separating full divergences.Comment: 5 pages, no figure

Coulomb-hadron phase factor and spin phenomena in a wide region of transfer momenta

The Coulomb-hadron interference effects are examined at small and large $t$. The methods for the definition of spin-dependent parts of hadron scattering amplitude are presented. The additional contributions to analyzing power $A_N$ and the double spin correlation parameter $A_{NN}$ owing to the electromagnetic-hadron interference are determined in the diffraction dip domain of high-energy elastic hadron scattering.Comment: 9 pages, LaTeX, 4 figure

Two Stages in the evolution of binary alkali Bose-Einstein condensate mixtures towards phase segregation

Two stages of quantum spinodal decomposition is proposed and analyzed for this highly non-equilibrium process. Both time and spatial scales for the process are found. Qualitative agreement with existing data is found. Some cases the agreements are quantitative. Further experimental verifications are indicated.Comment: late

Clinical-epidemiological features of HIV-infected patients diagnosed at age of 50 years or older

HIV/AIDS prevention and care efforts are directed to individuals of reproductive age (15–49 yrs). With the extension of sexual life of older people, they became a growing population at risk of HIV infection, usually not included in prevention strategies. In order to evaluate clinical profile of HIV/AIDS pts diagnosed at 50 yrs or older assisted in an HIV outpatient center in Buenos Aires, we retrospectively assessed clinical records of pts initiating care between Jan 1986 and Dec 2011. Age, CD4 cells and viral load (pVL) at HIV diagnosis and most recent value, opportunistic infections (OIs), co-morbidities and antiretroviral therapy (ARV) were recorded. Of 10,998 pts assisted in the 26-yr period, 495 (4.5%) were≥50 yrs old at HIV diagnosis; median annual diagnoses: 18.5 (IQR 3.3–30.3) without significant changes in the last 20 yrs. Demographics: median age 54.7 yrs (IQR 51.8–59.2, rank 50–80), 76.6% male. Risk behavior: HTX 61.4%, MSM 34.1%, others 4.4%. 55.4% of HIV diagnoses occurred during hospitalization or simultaneously with acute OIs. One third (n=176) had AIDS at diagnosis, 24% had history of STDs. HCV co-infection 5.7%, past HBV infection 28.1% and chronic HBV infection 5.1%. Median CD4 cells at HIV diagnosis: 223.5 (13.7%) (IQR 98.8–420.3), initial pVL 60,000 cp/mL (IQR 9,995.5–208,391). 69.3% of pts started ARV therapy during follow-up (FU), and the median time between diagnosis and treatment initiation was 3.4 mo (IQR 0.7–14); 56.9% of them started a non-nucleoside-based regimen (ZDV/3TC/EFV), 28.3% a PI-based regimen (ZDV/3TC/IDV) and 14.6% a nucleoside-based regimen (ZDV/ddI pre-HAART era). After a year (±6 mo), 63.8% pts achieved undetectable pVL and gained 136 CD4 cells from BSL (IQR 83–204). After 40.6 mo of FU (IQR 6.7-89.8), 66.3% are alive, 7.1% died (68.6% of HIV-related diseases) and 26.7% are lost to FU. Co-morbidities were present in 125 (25.3%), mainly hypertension, increased lipids, CVD and DBT. Among treated pts, 70.6% achieved pVL<50 cp/mL, with a median increase of CD4 cells up to 410 (22%) (IQR 281.5–563.9) from BSL. 51% (176) changed ARV therapy due to toxicity/AE: 54.5%, ARV failure: 29.5% and simplification: 14.8%. Stable HIV epidemic in older people reinforce the need of specific prevention approaches, while growing age of HIV individuals in care highlights to consider risks associated to older age. Late presentation to care needs to be specifically addressed. Response to treatment is remarkable high in this population

Higgs signals and hard photons at the Next Linear Collider: the ZZZZ-fusion channel in the Standard Model

In this paper, we extend the analyses carried out in a previous article for $WW$-fusion to the case of Higgs production via $ZZ$-fusion within the Standard Model at the Next Linear Collider, in presence of electromagnetic radiation due real photon emission. Calculations are carried out at tree-level and rates of the leading order (LO) processes e^+e^-\rightarrow e^+e^- H \ar e^+e^- b\bar b and e^+e^-\rightarrow e^+e^- H \ar e^+e^- WW \ar e^+e^- \mathrm{jjjj} are compared to those of the next-to-leading order (NLO) reactions e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- b\bar b \gamma and e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- WW (\gamma) \ar e^+e^- \mathrm{jjjj}\gamma, in the case of energetic and isolated photons.Comment: 12 pages, LaTeX, 5 PostScript figures embedded using epsfig and bitmapped at 100dpi, complete paper including high definition figures available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9611.ps or at http://www.hep.phy.cam.ac.uk/theory/papers

Phase Segregation Dynamics in Particle Systems with Long Range Interactions I: Macroscopic Limits

We present and discuss the derivation of a nonlinear non-local integro-differential equation for the macroscopic time evolution of the conserved order parameter of a binary alloy undergoing phase segregation. Our model is a d-dimensional lattice gas evolving via Kawasaki exchange dynamics, i.e. a (Poisson) nearest-neighbor exchange process, reversible with respect to the Gibbs measure for a Hamiltonian which includes both short range (local) and long range (nonlocal) interactions. A rigorous derivation is presented in the case in which there is no local interaction. In a subsequent paper (part II), we discuss the phase segregation phenomena in the model. In particular we argue that the phase boundary evolutions, arising as sharp interface limits of the family of equations derived in this paper, are the same as the ones obtained from the corresponding limits for the Cahn-Hilliard equation.Comment: amstex with macros (included in the file), tex twice, 20 page

Size-dependent spinodal and miscibility gaps for intercalation in nano-particles

Using a recently-proposed mathematical model for intercalation dynamics in phase-separating materials [Singh, Ceder, Bazant, Electrochimica Acta 53, 7599 (2008)], we show that the spinodal and miscibility gaps generally shrink as the host particle size decreases to the nano-scale. Our work is motivated by recent experiments on the high-rate Li-ion battery material LiFePO4; this serves as the basis for our examples, but our analysis and conclusions apply to any intercalation material. We describe two general mechanisms for the suppression of phase separation in nano-particles: (i) a classical bulk effect, predicted by the Cahn-Hilliard equation, in which the diffuse phase boundary becomes confined by the particle geometry; and (ii) a novel surface effect, predicted by chemical-potential-dependent reaction kinetics, in which insertion/extraction reactions stabilize composition gradients near surfaces in equilibrium with the local environment. Composition-dependent surface energy and (especially) elastic strain can contribute to these effects but are not required to predict decreased spinodal and miscibility gaps at the nano-scale