Computer simulation study of collective dynamics in the glass former Ca(NO3)(2)center dot 4H(2)O

Time correlation functions of current fluctuations were calculated by molecular dynamics (MD) simulations in order to investigate sound waves of high wavevectors in the glass-forming liquid Ca(NO3)(2)center dot 4H(2)O. Dispersion curves, omega(k), were obtained for longitudinal (LA) and transverse acoustic (TA) modes, and also for longitudinal optic (LO) modes. Spectra of LA modes calculated by MD simulations were modeled by a viscoelastic model within the memory function framework. The viscoelastic model is used to rationalize the change of slope taking place at k similar to 0.3 angstrom(-1) in the omega(k) curve of acoustic modes. For still larger wavevectors, mixing of acoustic and optic modes is observed. Partial time correlation functions of longitudinal mass currents were calculated separately for the ions and the water molecules. The wavevector dependence of excitation energies of the corresponding partial LA modes indicates the coexistence of a relatively stiff subsystem made of cations and anions, and a softer subsystem made of water molecules. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751548]

Outcomes of Epileptic Spasms in Patients Aged Less Than 3 Years: Single-Center United States Experience

Retrospective review was performed of children aged <3 years with epileptic spasms at our center from 2004-2010. Short-term (<6 months) and long-term (>= 6 months) outcomes were assessed. We included 173 children (104 boys; median age of onset, 6.8 months) with epileptic spasms of known (62%) and unknown (38%) etiology. Treatments included adrenocorticotropic hormone (n = 103), vigabatrin (n = 82), phenobarbital (n = 34), and other agents (n = 121). Short-term treatment with adrenocorticotropic hormone and vigabatrin provided better epileptic spasm control in groups with known and unknown etiology than other agents. At follow-up (6-27 months), 54% of children manifested seizures, and 83% manifested developmental delay. Known etiology was a predictor of poor developmental outcome (P = 0.006), whereas bilateral/diffuse brain lesions predicted both poor development and seizures (P = 0.001 and 0.005, respectively). Initial presentations of epileptic spasms with hypotonia or developmental delay most strongly predicted both seizures and neurodevelopmental outcomes (P < 0.001). In a child presenting with epileptic spasms with developmental delay or hypotonia, no specific treatment may offer superior benefit. (c) 2012 Elsevier Inc. All rights reserved.

Opportunistic and Other Infections in HIV-Infected Children in Latin America Compared to a Similar Cohort in the United States

Opportunistic and other infections have declined since the introduction of highly active antiretroviral therapy (HAART) in developed countries but few studies have addressed the impact of HAART in HIV-infected children from developing countries. This study examines the prevalence and incidence of opportunistic and other infections in Latin America during the HAART era. Vertically HIV-infected children enrolled in a cohort study between 2002 and 2007 were followed for the occurrence of 29 targeted infections. Cross-sectional and longitudinal analyses were performed to calculate the prevalence of infections before enrollment and the incidence rates of opportunistic and other infections after enrollment. Comparisons were made with data from a U. S. cohort (PACTG 219C). Of the 731 vertically HIV-infected children 568 (78%) had at least one opportunistic or other infection prior to enrollment. The most prevalent infections were bacterial pneumonia, oral candidiasis, varicella, tuberculosis, herpes zoster, and Pneumocystis jiroveci pneumonia. After enrollment, the overall incidence was 23.5 per 100 person-years; the most common infections (per 100 person-years) were bacterial pneumonia (7.8), varicella (3.0), dermatophyte infections (2.9), herpes simplex (2.5), and herpes zoster (1.8). All of these incidence rates were higher than those reported in PACTG 219C. The types and relative distribution of infections among HIV-infected children in Latin America in this study are similar to those seen in the United States but the incidence rates are higher. Further research is necessary to determine the reasons for these higher rates.