Computer Simulation of Three-Phase Equilibria for Some Water/n-Alkane Binary Systems.

In this work, the vapor-liquid-liquid equilibrium (VLLE) of the water/n-pentane, water/n-hexane, water/n-octane, and water/n-decane binary systems is calculated by computer simulation using the NVT-Gibbs ensemble (in the version of three simulation boxes) combined with the configurational bias Monte Carlo method. The combination of both methods, the molecular potential models used, and the simulation details allowed us to calculate the triphasic equilibrium properties of the systems studied: the densities of the three phases in equilibrium, their compositions, and potential energies. In previous works, these simulations were not carried out at a temperature range nor water/n-alkanes systems simulated in this work, probably because they are highly nonideal systems; so, to the best of our knowledge, this is the first time that this phenomenon is studied in detail. The results from VLLE simulations of the water/n-pentane system for temperatures from 343.2 to 435 K, the water/n-hexane system for temperatures from 373.11 to 473.15 K, the water/n-octane system for temperatures from 310.9 to 500 K, and for the water/n-decane system for temperatures from 374.15 to 525 K are reported here. The temperature range was selected in concordance with the experimental data available for an adequate study of the VLLE simulation results. The subcritical densities (vapor and liquid rich in n-alkane phases) at various temperatures fit well with the scaling law and the law of rectilinear diameters, allowing the estimation of upper critical end point temperature and density of the VLLE. The simulation results show a good prediction with experimental data reports in the literature.

An in vitro rumen incubation method to study exsheathment kinetics of Haemonchus contortus third-stage infective larvae.

This study developed and evaluated an in vitro rumen incubation (IVRI) method to describe the exsheathment kinetics of Haemonchus contortus third-stage infective larvae (L3) in ruminal liquor (RL). The specific objectives were (i) to standardize the IVRI method to facilitate the contact between L3 and RL as well as the larval recovery, and (ii) to apply the IVRI method to describe the exsheathment kinetics of H. contortus and to select the best fitting nonlinear model. Incubation devices containing H. contortus larvae were incubated according to the IVRI technique in cattle RL or PBS. The incubation conditions included RL mixed with a nitrogen-rich media, maintained at 39 °C, with pH = 7.0, vented with CO2 and manual agitation. The larvae were recovered after 0, 1, 3, 6, 9, 12, and 24 h. The exsheathed and ensheathed larvae were counted to estimate the exsheathment (%) in RL or PBS. Exsheathment in RL was analyzed with nonlinear regression models: Exponential, Gompertz, Logistic, Log-Logistic, and Weibull. The models' fit was compared to select the one that best described the exsheathment kinetics. The exsheathment in RL reached 6.52%, 20.65%, 58.22%, 69.24%, 73.08%, and 77.20% in 1, 3, 6, 9, 12, and 24 h, respectively. Although the Gompertz, Weibull, and Logistic models were adequate to describe the observed exsheathment, the Log-Logistic model had the best fit. The IVRI method using bovine RL represents a suitable tool for the study of the in vitro exsheathment kinetics of H. contortus L3.

Combined use of real-time PCR and serological techniques for improved surveillance of chronic and acute American trypanosomiasis in dogs and their owners from an endemic rural area of Neotropical Mexico.

In this study, the prevalence of T. cruzi infection was estimated in dogs and their owners from a rural community in Mexico using serological techniques for chronic infection cases, qPCR for acute phase cases, and a combination of both techniques to detect chronic and acute infections. Eighty-nine blood samples were collected from owners and their dogs for obtaining serum and parasite DNA. Prevalence was calculated using (i) positive cases detected in a serological test (ELISA and Western blot), (ii) positive cases detected in a qPCR test, and (iii) positive cases detected by both techniques. Sensitivity, specificity, and predictive values were determined individually for serology, qPCR and for both techniques used simultaneously. The prevalence observed varied: for serology, 25.8% of the dogs and 7.9% of the owners were seropositive, while for qPCR 29.2% of the dogs and 10.1% of the owners were identified as positive. Combination of serological and molecular techniques resulted in a prevalence of 38.2% for dogs and 12.4% for their owners. The sensitivity, specificity and predictive values calculated for both techniques improved when both techniques were used simultaneously (sensitivity of 92.4% and specificity of 100% for infected dogs and sensitivity of 93.4% and specificity of 100% for infected owners). Combined use of serological tests and qPCR allowed identifying a greater number of positive cases in dogs and their owners. This strategy may help implement adequate and timely epidemiological surveillance of American trypanosomiasis in order to prevent the appearance of new cases of Trypanosoma cruzi infections in endemic zones.

Metabolizable energy balance in hair sheep lambs artificially infected with Haemonchus contortus.

In sheep, infection with Haemonchus contortus may increase the need for energy, and this demand may vary according to the infection level. In this study, the energy intake, digestibility, and energy retention of lambs artificially infected with different levels of H. contortus were estimated. A total of 24 hair sheep lambs reared parasite-free were experimentally infected with H. contortus at one of three infection levels: non-infected (n = 6); infected with 300 infective larvae (L3) of H. contortus/kg body weight (BW) (n = 9); and infected with 500 H. contortus L3/kg BW (n = 9). The lambs were fed for an individual weight gain of 100 g/day, and intake of organic matter (OMI) and gross energy (GEI), digestible (DEI) and metabolizable energy (MEI) were measured weekly. The digestibility of organic matter (OMD) and GE (GED) and the metabolizable energy (ME) balance adjusted to zero nitrogen balance (MEadj) were measured for each lamb during the prepatent and patent periods of infection. From day 21 post-infection (PI), the individual eggs per gram (EPG) of feces and the total number of eggs in feces (TEF) were estimated weekly. After humane slaughter on day 42 PI, the worm burden (WB) was determined. Correlation and regression analyses were performed to estimate the relationships between the parasitological variables (L3, EPG, TEF and WB) and the response variables (OMI, GEI, DEI, MEI, OMD, GED, MEadj). During the prepatent period, there were no significant relationships of L3 with the response variables (OMI, GEI, DEI, MEI, OMD, GED, ME, MEadj). Similarly, during the patent period, no relationship was evident between infection (EPG, TEF or WB) and OMI, GEI, DEI, GED, OMD, ME or MEadj. Thus, the gradient of H. contortus infection examined in the present study did not influence energy balance in hair sheep lambs, and infection did not impose any detectable energy cost. Further studies are needed to fully assess the impact of H. contortus infection on energy metabolism in hair sheep.

Parasitic Zoonoses in Humans and Their Dogs from a Rural Community of Tropical Mexico.

A cross-sectional study was made on 89 inhabitants and their dogs from a rural community of Yucatan, Mexico, to determine the serological prevalence of some zoonotic parasitic agents. Samples were taken to monitor the presence and intensity of infection with gastrointestinal parasites in dogs. In humans, the serological prevalence of T. canis, T. gondii, and T. spiralis was 29.2%, 91.0%, and 6.7%, respectively. No associations were found between positive cases and studied variables. From the total of blood samples taken from dogs, 87 (97.6%) were seropositive to T. gondii; only 52 viable fecal samples were collected from dogs of which 46.2% had the presence of gastrointestinal parasites with low to moderate intensity; from those, 12% had the presence of T. canis. This study demonstrates the presence of the studied zoonotic agents in the area particularly T. gondii which suggest a common source of infection in dogs and humans and a high number of oocyts present in the environment. Preventive measures must be designed towards good prophylactic practices in domestic and backyard animals (T. canis and T. spiralis). Contaminated sources with T. gondii (food and water) should be further investigated in order to design effective control measures.

Structure factor and rheology of chain molecules from molecular dynamics.

Equilibrium and non-equilibrium molecular dynamics were performed to determine the relationship between the static structure factor, the molecular conformation, and the rheological properties of chain molecules. A spring-monomer model with Finitely Extensible Nonlinear Elastic and Lennard-Jones force field potentials was used to describe chain molecules. The equations of motion were solved for shear flow with SLLOD equations of motion integrated with Verlet's algorithm. A multiple time scale algorithm extended to non-equilibrium situations was used as the integration method. Concentric circular patterns in the structure factor were obtained, indicating an isotropic Newtonian behavior. Under simple shear flow, some peaks in the structure factor were emerged corresponding to an anisotropic pattern as chains aligned along the flow direction. Pure chain molecules and chain molecules in solution displayed shear-thinning regions. Power-law and Carreau-Yasuda models were used to adjust the generated data. Results are in qualitative agreement with rheological and light scattering experiments.

Dynamic evolution of supported metal nanocatalyst/carbon structure during single-walled carbon nanotube growth.

Single-walled carbon nanotubes (SCWNTs) have outstanding properties that depend on structural features such as their chirality. Thus, developing a strategy to control chirality during SWCNT synthesis is critical for the exploitation of nanotube-based technologies in fields such as electronics and biomedicine. In response to this need, tuning the nanocatalyst structure has been envisioned as a means to control the nanotube structure. We use reactive classical molecular dynamics to simulate nanotube growth on supported Ni(32), Ni(80), and Ni(160) nanoparticles at various metal/support interaction strengths (E(adh)). The initial carbon ring formation is shown to correlate to the nanoparticle surface structure, demonstrating the existence of a "template effect" through a dominant occupation of hollow sites. The E(adh) strength alters the dynamic/structural behavior of the nanoparticle, in turn influencing the interplay between nanotube and nanoparticle structures. For example, the contact region between the nanoparticle surface and the growing nanotube decreases as E(adh) increases because capillary forces that raise the metal into the nanotube are counteracted by the strong metal/support interaction. The nanoparticle mobility decreases as E(adh) increases, eliminating a possible inverse template effect but hindering defect annealing in detriment of the nanotube/nanoparticle structural correlation. On the other hand, the contact between the nanoparticle and the nanotube increases with nanoparticle size. However, the heterogeneity of the nanoparticle structure increases with size, reducing the structural correlation. These results suggest that an appropriate combination of nanoparticle size and strength of the catalyst/support interaction may enhance the desired template effect and bias formation of specific nanotube chiralities.

Maniobra de valsalva y tos en pacientes craniectomizados: observaciones ecográficas (modo B) en favor de la craneoplastia precoz / Valsalva manouver & cought in craniectomized patients: ultrasound observations (B mode) favouring early craneoplasty

Objetivo: evaluar los movimientos del parénquima encefálico durante la maniobra de Valsalva y la tos en pacientes craniectomizados y discutir sus implicancias fisiopatológicas y terapéuticas. Material y método. Catorce pacientes adultos con craniectomías mayores de 30 cm2 y colgajos pulsátiles fueron estudiados ecográficamente. La atención se focalizó en los cambios morfológicos intracraneanos inducidos por la maniobra de Valsalva y la tos.Resultados: durante la maniobra de Valsalva y la tos el cerebro fue propulsado en bloque hacia la craniectomía. Movimientos notorios se observaron a nivel centroencefálico y este fenómeno se atribuyó fundamentalmente al ascenso de LCR desde la columna y la distensión de las cisternas de la base. La magnitud de los cambios morfológicos fue proporcional al esfuerzo respiratorio y la presión intracraneana. Conclusiones: la maniobra de Valsalva y la tos provocaron cambios morfológicos bruscos e importantes a nivel centroencefálico, A la luz de teorías recientes se discuten las eventuales consecuencias de esta movilidad patológica sobre las estructuras témporomesiales y las funciones cognitivas. Estas observaciones constituyen un firme argumento en favor de la craneoplastia precoz.

Rehabilitación del ictus: modelo asistencial. Recomendaciones de la Sociedad Española de Rehabilitación y Medicina Física, 2009 / Stroke rehabilitation: Care model. Recommendations of the Spanish Society of Physical Medicine and Rehabilitation, 2009

Objetivos: La Sociedad Española de Medicina Física y Rehabilitación elabora un documento de recomendaciones de buena práctica clínica sobre el modelo asistencial en la rehabilitación (RHB) del ictus basadas en la experiencia clínica y el consenso de los autores y las guías de práctica clínica de referencia. Estrategia de búsqueda: La búsqueda se centra en guías de práctica clínica y artículos relevantes sobre el modelo asistencial en la RHB del ictus en las bases de datos MEDLINE, Embase y Cochrane Databases desde enero de 2004 hasta enero de 2009.Selección de estudios: Se seleccionan ensayos clínicos aleatorizados, metaanálisis, revisiones sistemáticas y artículos de revisión sobre el modelo asistencial en la RHB del ictus. Síntesis de resultados: El programa rehabilitador del ictus es un proceso complejo que requiere un abordaje multidisciplinario, siendo elementos claves el inicio precoz, la intensidad adecuada, la evaluación periódica y la participación activa de pacientes y cuidadores. Conclusiones: En todos los niveles de atención sanitaria y sociosanitaria, hospitalaria o comunitaria se debe asegurar la atención de RHB a cargo de un equipo multidisciplinario, coordinada por un médico especialista en RHB con adecuados niveles de organización y experiencia de los profesionales (AU)

Objectives: The Spanish Society of Physical Medicine and Rehabilitation has elaborated a document of good clinical practice recommendations on the care model in stroke rehabilitation based on the clinical experience and consensus of the authors and reference clinical practice guides. Search strategy: The search was focused on clinical practice guides and articles related with the care model in stroke rehabilitation in the MEDLINE, EMBASE and COCHRANE DATABASES from January 2004 to January 2009.Selection of studies Randomized clinical trials, meta-analyses, systematic reviews and review articles on the care model in stroke rehabilitation were selected. Synthesis of results: The stroke rehabilitation program is a complex procedure that requires a multidisciplinary approach. Its key elements are early initiation, adequate intensity, periodic evaluation and active participation of the patients and caregivers. Conclusions: Rehabilitation care under the responsibility of a multidisciplinary team, coordinated by a medical specialist in rehabilitation with adequate levels of organization and experience of the professionals should be assured on all health a and socio-health care, hospital or community levels (AU)

Digestibility of Duddingtonia flagrans chlamydospores in ruminants: in vitro and in vivo studies.

BACKGROUND: The use of Duddingtonia flagrans as a tool for the biological control of gastrointestinal nematodes (GIN) is a promising alternative to anthelmintics. The chlamydospores of D. flagrans are orally dosed and their thick cell wall gives them the capacity to resist digestion and pass through the gastrointestinal tract (GIT). Chlamydospores reaching the faeces are able to germinate and trap nematode larvae. The efficacy of this control method is based on reducing the numbers of infective larvae leaving the faeces. Techniques have recently been developed for quantifying the numbers of chlamydospores in faeces. As the number of non-digested spores could be relevant in the design and optimization of dosing programmes for the control of GIN infective larvae, the aim of the present study was to estimate the loss of D. flagrans chlamydospores during their passage through the ruminant gastrointestinal tract using in vitro and in vivo techniques. RESULTS: After in vitro rumen digestion, chlamydospore recovery was not different from the quantity originally incubated (undigested spores) (P > 0.05). In vitro rumen+abomasum digestion caused nearly 36% loss of the chlamydospores originally incubated (P < 0.05). Germination of chlamydospores classified as viable was 24.3%. Chlamydospores classified as non-viable did not germinate. Rumen digestion resulted in more spore germination (R1 = 35.7% and R2 = 53.3%) compared to no digestion (time 0 h = 8.7%). Subsequent abomasal digestion reduced germination (R1+A = 25%) or stopped it (R2+A = 0%). In vivo apparent chlamydospore digestibility in sheep showed a loss of 89.7% of the chlamydospores (P < 0.05). CONCLUSIONS: The loss of chlamydospores was evident under in vitro and in vivo conditions. Negligible amounts of spores were lost during the in vitro rumen digestion. However, in vitro rumen+abomasum digestion resulted in a chlamydospore loss of approximately 36%. In vivo passage through the sheep GIT resulted in a total loss of 89.7% of the orally administered spores.

Nonequilibrium molecular dynamics of the rheological and structural properties of linear and branched molecules. Simple shear and poiseuille flows; instabilities and slip.

Nonequilibrium molecular-dynamics simulations are performed for linear and branched chain molecules to study their rheological and structural properties under simple shear and Poiseuille flows. Molecules are described by a spring-monomer model with a given intermolecular potential. The equations of motion are solved for shear and Poiseuille flows with Lees and Edward's [A. W. Lees and S. F. Edwards, J. Phys. C 5, 1921 (1972)] periodic boundary conditions. A multiple time-scale algorithm extended to nonequilibrium situations is used as the integration method, and the simulations are performed at constant temperature using Nose-Hoover [S. Nose, J. Chem. Phys. 81, 511 (1984)] dynamics. In simple shear, molecules with flow-induced ellipsoidal shape, having significant segment concentrations along the gradient and neutral directions, exhibit substantial flow resistance. Linear molecules have larger zero-shear-rate viscosity than that of branched molecules, however, this behavior reverses as the shear rate is increased. The relaxation time of the molecules is associated with segment concentrations directed along the gradient and neutral directions, and hence it depends on structure and molecular weight. The results of this study are in qualitative agreement with other simulation studies and with experimental data. The pressure (Poiseuille) flow is induced by an external force F(e) simulated by confining the molecules in the region between surfaces which have attractive forces. Conditions at the boundary strongly influence the type of the slip flow predicted. A parabolic velocity profile with apparent slip on the wall is predicted under weakly attractive wall conditions, independent of molecular structure. In the case of strongly attractive walls, a layer of adhered molecules to the wall produces an abrupt distortion of the velocity profile which leads to slip between fluid layers with magnitude that depends on the molecular structure. Finally, the molecular deformation under flow depends on the attractive force of the wall, in such a way that molecules are highly deformed in the case of strong attracting walls.

Critical flocculation density of dilute water-in-CO2 emulsions stabilized with block copolymers.

The critical flocculation density (CFD), that is, the CO(2) density below which flocculation occurs, was studied for dilute water-in-CO(2) (W/C) miniemulsions stabilized with poly(1,1-dihydroperfluorooctyl methacrylate)-b-poly(ethylene oxide) (PFOMA-b-PEO) surfactants. The CFD, which was measured by turbidimetry, decreased as the PFOMA molecular weight was increased, the average droplet size was decreased, the surfactant loading was increased, and the temperature was increased. A simple model, which addressed both the van der Waals attraction between droplets and osmotic solvent-tail interactions, was in good qualitative agreement with the experimentally observed trends for the CFD and predicted a decrease in emulsion stability as the CO(2) density was lowered toward the theta density for PFOMA in bulk CO(2).

Efficacy, safety and predictive factors of therapeutic success with sildenafil for erectile dysfunction in patients with different spinal cord injuries.

STUDY DESIGN: Multicenter, open, prospective, before-after study. OBJECTIVE: To assess the efficacy and safety of sildenafil therapy for erectile dysfunction in patients with spinal cord injury, and the association between the response to sildenafil and factors such as causes and levels of spinal cord injury, grade of ASIA deficit, time since injury, orgasmic perception, and degree of baseline erection. SETTING: Homes of outpatients of 16 spinal cord injury units in Spain. METHOD: One hundred and seventy patients with erectile dysfunction secondary to spinal cord injury, from whom baseline data were collected on their sexual function, and who started treatment with sildenafil 50 mg. An efficacy assessment was made by the patient and his partner, and the score of the International Index of Erectile Function (IIEF) was recorded. RESULTS: It was reported by 88.2% of the patients and 85.3% of their partners that treatment with sildenafil had improved their erections, regardless of the baseline characteristics of the spinal cord injury and erectile function. In responders, this improvement was confirmed by an increase from 12.5 to 24.8 points (P<0.001) of the Erectile Function Domain of IIEF. A significant improvement was also seen in patients' satisfaction with sexual activity and general satisfaction derived from sexual life. Preservation of orgasmic perception and a baseline degree of erection of 3 or 4 (P=0.006) were predictors of therapeutic success. No serious adverse events occurred. CONCLUSION: Sildenafil is an effective, well-tolerated treatment for erectile dysfunction caused by spinal cord injury, regardless of the cause, neurological level, ASIA grade, and time since injury. SPONSORSHIP: Spanish Society of Paraplegia.