Numerical simulations of self-diffusiophoretic colloids at fluid interfaces

The dynamics of active colloids is very sensitive to the presence of boundaries and interfaces which therefore can be used to control their motion. Here we analyze the dynamics of active colloids adsorbed at a fluid-fluid interface. By using a mesoscopic numerical approach which relies on an approximated numerical solution of the Navier-Stokes equation, we show that when adsorbed at a fluid interface, an active colloid experiences a net torque even in the absence of a viscosity contrast between the two adjacent fluids. In particular, we study the dependence of this torque on the contact angle of the colloid with the fluid-fluid interface and on its surface properties. We rationalize our results via an approximate approach which accounts for the appearance of a local friction coefficient. By providing insight into the dynamics of active colloids adsorbed at fluid interfaces, our results are relevant for two-dimensional self assembly and emulsion stabilization by means of active colloids.

Prevalence of labrum and articular cartilage injuries of the hip on 3T magnetic resonance imaging of asymptomatic elite soccer players

OBJECTIVE

To establish the prevalence of lesions of the labrum and articular cartilage of the hip in asymptomatic elite soccer players by performing 3T magnetic resonance imaging.

METHODS

Eighty-four asymptomatic hips of 42 professional soccer players were evaluated. Male subjects older than 18 years were included. Cam and pincer deformity were defined as an alpha angle greater than 55 degrees and a lateral centre edge angle greater than 39 degrees, respectively. Labral injuries were classified with the Czerny classification and cartilage damage was classified with the Outerbridge classification. Specific statistical tests were used to establish the relationship between anatomical variances of the hip and the presence of chondral and labral injuries.

RESULTS

FAI morphology prevalence was 25%. Abnormalities such as cam (22.5%) and labral injuries (33.8%) were found. Those cases with reported labral injury were predominantly intrasubstance damage (18.8%). Anatomical features of FAI were found to be related to lesions of the femoral cartilage (P<.001), chondrolabral damage (P=.042), or both injuries (P<.001).

CONCLUSION

Asymptomatic labral or cartilaginous injuries of the hip were reported in 25% of the included professional soccer players. These injuries were associated with anatomical features of FAI.

Counterion effects on the ultrafast dynamics of charge-transfer-to-solvent electrons

We performed femtosecond transient absorption (TA) experiments to monitor the solvation dynamics of charge-transfer-to-solvent (CTTS) electrons originating from UV photoexcitation of ammoniated iodide in close proximity to the counterions. Solutions of KI were prepared in liquid ammonia and TA experiments were carried out at different temperatures and densities, along the liquid-gas coexistence curve of the fluid. The results complement previous femtosecond TA work by P. Vöhringer's group in neat ammonia via multiphoton ionization. The dynamics of CTTS-detached electrons in ammonia was found to be strongly affected by ion pairing. Geminate recombination time constants as well as escape probabilities were determined from the measured temporal profiles and analysed as a function of the medium density. A fast unresolved (τ < 250 fs) increase of absorption related to the creation/thermalization of solvated electron species was followed by two decay components: one with a characteristic time around 10 ps, and a slower one that remains active for hundreds of picoseconds. While the first process is attributed to an early recombination of (I, e^-) pairs, the second decay and its asymptote reflects the effect of the K⁺ counterion on the geminate recombination dynamics, rate and yield. The cation basically acts as an electron anchor that restricts the ejection distance, leading to solvent-separated counterion-electron species. The formation of (K⁺, NH₃, e^-) pairs close to the parent iodine atom brings the electron escape probability to very low values. Transient spectra of the electron species have also been estimated as a function of time by probing the temporal profiles at different wavelengths.

Low-frequency oscillations and convective phenomena in a density-inverted vibrofluidized granular system

Low-frequency oscillations (LFOs) are thought to play an important role in the transition between the Leidenfrost and convective states of a vibrated granular bed. This work details the experimental observation of LFOs, which are found to be consistently present for a range of driving frequencies and amplitudes, with particles of varying material and using containers of differing material properties. The experimentally acquired results show a close qualitative and quantitative agreement with both theory and simulations across the range of parameters tested. Strong agreement between experimental and simulation results was also observed when investigating the influence of sidewall dissipation on LFOs and vertical density profiles. This paper additionally provides evidence of two phenomena present in the Leidenfrost state: a circulatory motion over extended time periods in near-crystalline configurations, and a Leidenfrost-like state in which the dense upper region displays an unusual inverse thermal convection.

Solubilidad proteica, contenido de mioglobina, color y pH de la carne de pollo, gallina y codorniz

Las proteínas de la carne son responsables de diversas características de sus productos derivados. La solubilidad de las proteínas cárnicas puede ser un índice de otras propiedades funcionales importantes para el procesamiento de la carne, como la emulsificación, mientras que el contenido de mioglobina influye en su color. Con el objeto de evaluar la solubilidad de las proteínas sarcoplásmicas y miofibrilares así como el contenido de mioglobina en la carne de aves, se obtuvieron canales de pollo, gallina y codorniz a partir de mataderos comerciales; se aplicó un diseño completamente aleatorizado con arreglo factorial 3x2, siendo los factores: tipo de ave (pollo, gallina y codorniz) y porción corporal (carne de pechuga y carne de pierna) generándose seis tratamientos, tres repeticiones por tratamiento. Se observó interacción de los factores para: Luminosidad (L), grado de color rojo (a), pH, extracción de proteínas sarcoplásmicas y proteínas miofibrilares. El contenido de mioglobina fue afectado tanto por la porción corporal como por el tipo de ave, siendo superior en la pierna en comparación con la pechuga (0,99 y 0,47 mg/g carne, respectivamente), y siendo la codorniz la que presenta el mayor valor (1,13 mg/g) y el pollo el menor (0,37 mg/g). En todos los casos el pH de la carne de pierna fue superior al pH de la pechuga. En la extracción de las proteínas del sarcoplasma hubo una tendencia a obtener un mayor porcentaje de la pechuga, mientras que las proteínas miofibrilares se obtuvieron en mayor proporción en la porción de la pierna. La información generada sobre las características de la carne de estas aves es novedosa en Venezuela y puede contribuir a explicar el comportamiento de estas materias primas durante su procesamiento.

Thermal convection and temperature inhomogeneity in a vibrofluidized granular bed: the influence of sidewall dissipation

Using a vertically vibrated, fully three-dimensional granular system, we investigate the impact of dissipative interactions between the particles in the system and the vertical sidewalls bounding it. We find that sidewall dissipation influences various properties of the bed including, but not limited to, the spatial distribution of granular temperatures, the functional form of velocity distributions, and the strength of convection. Simple, monotonic relationships are observed for all the aforementioned properties, including a striking linear relationship between convection strength and wall dissipation. We conclude that sidewall effects are not limited to the vicinity of the walls themselves, but extend into the bulk of the system and hence must be considered even in relatively wide, three-dimensional systems. We also propose the possibility of using the alteration of sidewall material as a method of "tuning" certain system parameters in situations where changing the bulk properties or driving parameters of a granular system may be undesirable.

[Congenital cytomegalovirus infection]

INTRODUCTION

Cytomegalovirus (CMV) is the most frequent cause of intrauterine infection and an important cause of auditory system damage and mental retardation in humans. Clinical presentation varies from asymptomatic form to lethal systemic dissemination.

OBJECTIVES

To describe clinical and laboratories manifestations, age at the moment of diagnostic, treatment and diagnostic test used in congenital cytomegalovirus infection.

POPULATION, MATERIAL AND METHODS

Observational, retrospective and descriptive study. Clinical histories of congenital CMV infected infants evaluated by Infectology Department of the Hospital General de Niños Dr. Ricardo Gutiérrez between January 2002 and December 2006 were analyzed.

RESULTS

Seventeen patients were evaluated. Mean age at diagnosis was 2.6 months. The most frequent symptom/sign were hepato-splenomegaly (76 %), jaundice (47 %), petechiae and hearing deficit (41 %). Anemia (53 %) and thrombocytopenia (40 %) were the most common laboratory abnormalities. Diagnosis was made exclusively by polymerase chain reaction (PCR)-CMV in one third of the patients, whereas one third was diagnosed by serology and the other third for both test. Five patients received ganciclovir as treatment. Only one had neutropenia.

CONCLUSIONS

Differential diagnosis of all newborns with hepatoesplenomegaly, jaundice and petechiae and anemia and/or thrombocytopenia must include congenital cytomegalo-virus infection. Early diagnosis allows a prompt intervention and a strict audiological follow up.

Clozapine may partially compensate for task-related brain perfusion abnormalities in risperidone-resistant schizophrenia patients

BACKGROUND

Previous reports show different cerebral activity patterns during treatment with clozapine and typical neuroleptics. However, to date no study has directly compared the brain activity patterns while subjects are undergoing treatment with clozapine and other atypical antipsychotics. This comparison is of interest, given the probably different mechanism of action of clozapine in comparison with other atypicals.

OBJECTIVE

To assess the effect of clozapine on perfusion deviations still evident during treatment with risperidone.

METHODS

Here we used hexamethylene-propylenaminoxime single photon emission computed tomography to compare the perfusion patterns observed during the performance of a Stroop test in 10 patients sequentially treated with risperidone and clozapine, owing to a lack of response to the former, and in 10 healthy controls.

RESULTS

Patients on risperidone showed decreased perfusion as compared to controls in the medial prefrontal, middle cingulate and insular regions, as well as increased activities in brain stem and the posterior hippocampus. After receiving clozapine, the same patients showed an even wider prefrontal perfusion deficit and the brain stem was still hyperactive, but the abnormalities in the cingulate cortex, insula and hippocampus had disappeared. Clinical improvement was directly related to an increase in thalamic perfusion.

CONCLUSION

Clozapine may alleviate hyperactivity in the limbic system in schizophrenia and may facilitate activation of the regions involved in cognitive tasks to a greater degree than risperidone, as well as eliciting greater inhibition of the PF region.

Nosocomial infections in a children's hospital in Argentina: impact of a unique infection control intervention program

OBJECTIVE

To assess the efficacy of parental education and use of parents as nursing assistants on reducing nosocomial infections.

DESIGN

Prospective study.

METHODS

Active surveillance for nosocomial infections was performed on two wards. On ward A, parents were educated about infection control practices and assisted nursing staff with routine tasks, so that nursing personnel could focus their efforts on procedures with higher risk of infection. Parental assistance was not sought on ward B, the comparison ward.

RESULTS

From October 1990 through September 1991, 1,081 patients were admitted to wards A (470) or B (611). The over-all nosocomial infection rate was 7.1 per 100 admissions; the nosocomial infection rate was significantly higher on ward B than ward A (63/611 vs 14/470; P<.001). Multivariate analysis identified risk factors for nosocomial infection on the two wards as age <2 years (P=.01), malnutrition (P=.005), duration of hospitalization (P<.001), ward B hospitalization (P=.003), and ward cleanliness score (P=.009); the distribution of patients with these factors was similar on the two wards.

CONCLUSIONS

Our data suggest that parental infection control education and recruitment to relieve nursing staff of routine low-risk procedures are economical and easily implemented measures to reduce nosocomial infections in hospitals with limited personnel resources in the developing world.