Development of quantitative cell-based enzyme assays in microdroplets

We describe the development of an enzyme assay inside picoliter microdroplets. The enzyme alkaline phosphatase is expressed in Escherichia coli cells and presented in the periplasm. Droplets act as discrete reactors which retain and localize any reaction product. The catalytic turnover of the substrate is measured in individual droplets by monitoring the fluorescence at several time points within the device and exhibits kinetic behavior similar to that observed in bulk solution. Studies on wild type and a mutant enzyme successfully demonstrated the feasibility of using microfluidic droplets to provide time-resolved kinetic measurements.     

The shape of warmth: temperature profiles in living rooms

The most commonly used family of models in representing the UK building stock, BREDEM (the Building Research Establishment Domestic Energy Models), assume that all homes exhibit the same heating pattern and hence can be expected to have similar temperature profiles over the course of a day. The presented research shows that homes differ significantly in their respective temperature profile over the course of the day. A cluster analysis performed on temperature data from 275 living rooms in English homes over three winter months resulted in four different clusters of temperature profiles. The clusters differ significantly in their shape, as revealed by visual inspection, and supported by significant differences in minimum and maximum temperatures and temperature variability across the day. About 40% of homes showed a bimodal temperature pattern as assumed under BREDEM. However, the remaining 60% showed very different profiles. These findings challenge the assumption that one standard pattern fits all homes. Different temperature demand profiles have important implications for future peak power demands, particularly if domestic space heating is switched to electricity. It is also helpful for relating occupant demographics to appropriate forms of fabric retrofit.     

Infants' emotion expressions to acute pain: Developmental change and stability of individual differences.

Differential emotions theory predicts stability of individual emotion-expression styles but developmental changes in relations between emotion-eliciting events and particular emotions. These propositions were examined in a longitudinal study of infants' emotion expressions to a painful medical procedure. The type and duration of emotion expressions of 2- to 7-month-old infants (N?=?25) in response to the acute pain of diphtheria-pertussis-tetanus (DPT) inoculations predicted their emotion expressions to the same event at 19 months of age. Results also confirmed those of a previous cross-sectional study showing that particular expressions to painful stimulation occurred with regularity and that the durations of these expressions changed differentially with age (Izard, Hembree, Dougherty, & Spizzirri, 1983). The current longitudinal study showed both stability of individual emotion-expression patterns and developmental changes in event–emotion relations over the first year and a half of life. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Field and excitation dependent ultrasonic attenuation in3He-B

Sound absorption of³He-B at 0 bar was studied at a frequency of 10 MHz. We performed pulsed experiments with different pulse lengths (4 to 15 s) and pulse powers (0.1 to 160 W) in the temperature range 0.2 < T/T_C < 2. For pulse power less than pth 50 W, and in the temperature range 0.4 to 0.8 T_c and zero field, the attenuation coefficient a decreases monotonically at about 0.2 cm^–1 per decade of power. Above pth. increases up to values of 3.5 cm^–1 and 1.9 cm^–1 at highest power for temperatures of 0.8 T_c and 0.4 T_c, respectively. At pulse power around 100 W and at the lowest temperatures, the attenuation changes within the first 200 s after the application of the pulse; also increases with increasing field. In the normal fluid decreases with increasing power. All of our observations are lacking a rigorous theoretical understanding.     

Modeling the Dielectric Response and Relaxation Spectra of Relaxor Ferroelectrics

A multi-Debye relaxation model that is based upon the Boltzmann superposition principle has been used to determine the frequency-dispersion behavior of Pb(Mg_1/3-Nb_2/3)O₃ (PMN) and Pb_0.88La_0.08(Zr_0.65Ti_0.35)O₃ (PLZT 8/65/35) relaxor ferroelectrics. For PMN, relaxation times on the order of seconds contribute to the dispersive character of the dielectric properties. A defect-relaxation mechanism that involves Mg cation hopping in a structure that is composed of interpenetrating 〈111〉 chains of ordered Pb(Mg_1/2Nb_1/2)O₃ is proposed for PMN. Motion of the Mg cations results in destruction and reconstruction of these ordered chains, which contributes to the dispersive character of PMN.     

NovaSil clay does not affect the concentrations of vitamins A and E and nutrient minerals in serum samples from Ghanaians at high risk for aflatoxicosis

To assess the potential interference of NovaSil (NS) clay with micronutrients in humans, vitamins A and E and minerals (15 nutrient and 15 non-nutrient minerals) were measured in serum samples from a 3-month intervention trial with NS. Participants (n = 177) were randomly divided into three groups that received 3.0 g NS day(-1) (high dose, HD), 1.5 g NS day(-1) (low dose, LD), or placebo (PL). Levels of vitamins A and E in serum were comparable among the three study groups at baseline, 1 month and 3 months of NS intervention. Gender-stratified non-parametric mixed-effect model analysis showed no significant effects of dose and dose-time interaction for levels of vitamins A and E. A significant time effect was detected; however, it was limited to an increase in vitamin E in the male participants over the course of the study. No significant differences were found in levels of the nutrient and non-nutrient minerals between the HD and PL groups at baseline and 3 months of NS intervention, except for strontium levels. Strontium was significantly increased (p < 0.001) in the HD group (male = 113.65 +/- 28.00 microg l(-1); female = 116.40 +/- 24.26 microg l(-1)) compared with the PL group (male = 83.55 +/- 39.90 microg l(-1); female = 90.47 +/- 25.68 microg l(-1)) following the 3-month intervention with NS. These results, combined with safety and efficacy data, confirm that NS clay is highly effective in reducing aflatoxin exposure and acts as a selective enterosorbent that does not affect the serum concentrations of important vitamins and nutrient minerals in humans.     

Polarization Switching of and Electron Emission from Lead Lanthanum Zirconate Titanate Ceramics

This paper focuses on understanding the influence of ma-terial properties on the complicated ferroelectric (FE) emis-sion process. Three different compositions in the lead lan-thanum zirconate titanate (PLZT) system were chosen for study, based on their widely different dielectric and ferro-electric properties: antiferroelectric (AFE) 2/95/5, "nor-mal" ferroelectric 8/65/35, and nonferroelectric 15/65/35. Repeatable emission was obtained from the 2/95/5 compo-sition, which could also be modulated at high frequency (200 kHz). The fast AFE ⇆ FE phase transition is respon-sible for the FE emission properties of this material, which is supported by the relationship between the switching cur-rent and the emission current. Comparatively, FE emission from the 8/65/35 composition degraded rapidly, which was attributed to decreases in the remanent polarization. No emission signal was detected from the 15/65/35 composi-tion, because no switching activity occurs, which can be interpreted as additional evidence that electron emission from the previously mentioned two compositions was in-deed a FE emission process.     

Tetracycline-encapsulated P(3HB) microsphere-coated 45S5 Bioglass®-based scaffolds for bone tissue engineering

Bioglass^®-based scaffolds for bone tissue engineering have been developed, which can also serve as carriers for drug delivery. For this, P(3HB) microspheres (PMSs) loaded with tetracycline were fabricated and immobilised on the scaffold surfaces by a modified slurry dipping technique. The sustained drug delivery ability in simulated body fluid was confirmed by using UV–Vis absorption spectroscopy measurements. The MTT assay using mouse fibroblast cells provided evidence that the tetracycline loaded microspheres produced in this study show limited cytotoxicity. The scaffolds developed in this work provide mechanical support, adequate 3D surface roughness, bioactivity and controlled drug delivery function, and are thus interesting candidates for bone tissue engineering applications.