The Behaviors of Ferro-Magnetic Nano-Particles In and Around Blood Vessels under Applied Magnetic Fields.

In magnetic drug delivery, therapeutic magnetizable particles are typically injected into the blood stream and magnets are then used to concentrate them to disease locations. The behavior of such particles in-vivo is complex and is governed by blood convection, diffusion (in blood and in tissue), extravasation, and the applied magnetic fields. Using physical first-principles and a sophisticated vessel-membrane-tissue (VMT) numerical solver, we comprehensively analyze in detail the behavior of magnetic particles in blood vessels and surrounding tissue. For any blood vessel (of any size, depth, and blood velocity) and tissue properties, particle size and applied magnetic fields, we consider a Krogh tissue cylinder geometry and solve for the resulting spatial distribution of particles. We find that there are three prototypical behaviors (blood velocity dominated, magnetic force dominated, and boundary-layer formation) and that the type of behavior observed is uniquely determined by three non-dimensional numbers (the magnetic-Richardson number, mass Péclet number, and Renkin reduced diffusion coefficient). Plots and equations are provided to easily read out which behavior is found under which circumstances (Figures 5, 6, 7, and 8). We compare our results to previously published in-vitro and in-vivo magnetic drug delivery experiments. Not only do we find excellent agreement between our predictions and prior experimental observations, but we are also able to qualitatively and quantitatively explain behavior that was previously not understood.

Magnetic nanoparticle transport within flowing blood and into surrounding tissue.

Magnetic drug delivery refers to the physical confinement of therapeutic magnetic nanoparticles to regions of disease, tumors, infections and blood clots. Predicting the effectiveness of magnetic focusing in vivo is critical for the design and use of magnetic drug delivery systems. However, current simple back-of-the-envelope estimates have proven insufficient for this task. In this article, we present an analysis of nanoparticle distribution, in and around a single blood vessel (a Krogh tissue cylinder), located at any depth in the body, with any physiologically relevant blood flow velocity, diffusion and extravasation properties, and with any applied magnetic force on the particles. For any such blood vessel our analysis predicts one of three distinct types of particle behavior (velocity dominated, magnetic dominated or boundary-layer formation), which can be uniquely determined by looking up the values of three nondimensional numbers we define. We compare our predictions to previously published magnetic-focusing in vitro and in vivo studies. Not only do we find agreement between our predictions and prior observations, but we are also able to quantitatively explain behavior that was not understood previously.

[Housework, gender and health in the working population]. / Trabajo doméstico, género y salud en población ocupada.

OBJECTIVE: To analyse the relation between domestic workload and self-perceived health status among workers and to examine whether there are gender inequalities. METHODS: The selected population were the 215 men and 106 women younger than 65 years interviewed in the Terrassa Health Survey, 1998 who had a paid work and were married or cohabiting. Adjusted odds ratios (aOR) by domestic workload, age and occupational social class with their 95% confidence intervals (CI) were calculated. RESULTS: Whereas among men domestic workload was not associated with health status, among women poor self-perceived health status was positively related to household size (aOR = 3.65; 95% IC = 1.06-12.54) and to lack of a person for doing domestic tasks (aOR = 4.43; 95% CI = 1.05-18.62). CONCLUSION: Both household characteristics and having a support for facing domestic tasks play an important role in gender health inequalities.

[Haemophilus influenzae type b invasive disease and meningococcal disease: incidence and characteristics in Barcelona, 1994-1995. Work Group IMS-IUSPC for Surveillance and Control of Meningitis]. / Enfermedad invasiva por Haemophilus influenzae tipo b y enfermedad meningocócica: incidencia y características en Barcelona, 1994-1995. Grupo de Trabajo IMS-IUSPC para la Vigilancia y el Control de las Meningitis.

BACKGROUND: The purpose of the study is to estimate the incidence of Haemophilus influenzae type b invasive disease (HibID) and meningococcal disease (MD) in Barcelona (Catalonia, Spain) for the years 1994-1995. MATERIAL AND METHODS: Data were obtained from the nominal registry of the surveillance system for reportable transmissible diseases of the Barcelona City Health Department, combining the reporting system with active surveillance, including microbiological reports and the review of hospital discharge registries to ensure completeness. RESULTS: During this two-years period there were 17 cases of HibID (12 meningitis), and for 12 cases there was a laboratory confirmation. The annual incidence rate can be estimated at 15.4 cases of HibID for 100,000 children below 5 years of age, and 4.5 cases for 100,000 children below 15 years. The annual incidence rates for Hib meningitis were 3.2 for 100,000 below 15 years. There were 60 cases of MD, and for 33 there was a laboratory confirmation, with a majority of serogroup B. The annual incidence rate of MD can be estimated at 32.6 cases for 100,000 below 5 years and 16 cases for 100,000 below 15 years. The incidence rate of meningococcal meningitis is at least 5.9 cases for 100,000 below 15 years of age. CONCLUSIONS: These results confirm the relatively low incidence of Hib meningitis in Barcelona, Spain, while the Hib vaccine was not in systematic use, much lower than the incidence of MD. The incidence rates are similar to all other population-based studies in Spain, except for the Basque Country study.

Use of an iridium electrode for direct measurements of pI of proteins after isoelectric focusing in polyacrylamide gel.

The use of an iridium microelectrode 0.5 mm in diameter is proposed for measuring the pH gradient in polyacrylamide gels after isoelectric focusing. The electrode exhibits a perfectly linear potential/pH relationship; thus it can be used directly in conjunction with a pH meter using the pH scale for readings. pH equilibrium values are rapidly reached (10-15 s) and pI determinations are obtainable with good accuracy (better than 0.1 pH).