A fractal analysis of external diffusion limited first-order kinetics for the binding of antigen by immobilized antibody

A fractal analysis of external diffusion limited first-order kinetics for the binding of antigen in solution by immobilized antibody on a fibre-optic biosensor indicates that as the fractal parameter (measure of "disorder" on the surface) increases the rate of binding and the amount of antigen bound to the antibody on the surface decreases. The fractal analysis and exponential type binding rate coefficients are used to analyze the influence of time-dependent binding rate coefficients on external diffusion limited kinetics. A decrease in the binding rate coefficients with time decreases the Damkohler number (decrease in the mass transfer limitations) leading to an increase in the rate of binding and the amount of antigen bound to the antibody on the surface, as expected. An increase in the (exponential) binding rate coefficient with time leads to unusual shapes of the binding curves. The time-dependent binding rate coefficients provide a more realistic picture of the binding of antigen in solution to the antibody covalently attached to the surface, and should assist in the control and manipulation of these interactions at the surface. A value of the fractal dimension of the surface of 2.96 to 2.97 obtained for our system characterizes the anomalies in the reaction-diffusion system and the heterogeneity of the surface.     

Zinc equilibria in submerged sodic soils as influenced by application of amendments

In a pot culture experiment, the effect of gypsum (50% of soil requirement), pyrites (equivalent to gypsum), farmyard manure (0.5 g per 100g soil) and Zn (10mg Zn kg^–1 soil) on Zn equilibria in Ghabdan and Langrian series of sodic soils was studied. The equilibrium soil solutions collected anaerobically after 1, 14, 28, 42, 56, 70 and 84 days of submergence were analysed for pH, EC, HCO₃ and Zn. Submergence markedly decreased soil solution pH and Zn up to 14 days and thereafter, the former slightly increased and the latter continued to decrease. Addition of amendments decreased soil solution pH in the order gypsum, pyrites and farmyard manure (FYM) and increased Zn concentration in the order FYM, gypsum and pyrites. The values of Zn potential (pZn + 2pOH) were within the range of pKsp for Zn(OH)₂-Zn²⁺ (aq) from 16 to 84 days of submergence in Ghabdan soil and from 9 to 42 days of submergence in Langrian soil, where later it shifted to ZnCO₃-Zn²⁺ (aq) system. Addition of FYM, pyrites and gypsum shortened the period of predominant existence of Zn(OH)₂-Zn²⁺ (aq) system to 40, 30 and 12 days in Ghabdan soil and 30, 20 and 6 days in Langrian soil respectively. After these periods the system was saturated with respect to ZnCO₃-Zn²⁺ (aq) except gypsum treatment where Zn-soil (unknown solid phases) -Zn²⁺ (aq) system controlled the solubility of Zn after 38 and 28 days of submergence of Ghabdan and Langrian soil respectively.     

Emergent properties of networks of biological signaling pathways

Many distinct signaling pathways allow the cell to receive, process, and respond to information. Often, components of different pathways interact, resulting in signaling networks. Biochemical signaling networks were constructed with experimentally obtained constants and analyzed by computational methods to understand their role in complex biological processes. These networks exhibit emergent properties such as integration of signals across multiple time scales, generation of distinct outputs depending on input strength and duration, and self-sustaining feedback loops. Feedback can result in bistable behavior with discrete steady-state activities, well-defined input thresholds for transition between states and prolonged signal output, and signal modulation in response to transient stimuli. These properties of signaling networks raise the possibility that information for "learned behavior" of biological systems may be stored within intracellular biochemical reactions that comprise signaling pathways.     

Electrical,Rutherford backscattering and transmission electron microscopy studies of furnace annealed zinc implanted GaAs

Electrical, Rutherford backscattering and transmission electron microscopy measurements have been carried out on GaAs samples implanted with 150 keV, 1.10¹⁵ zinc ions/cm² and furnace annealed in the temperature range from room temperature to 900°C. A correlation between three types of measurement technique was established and four distinct annealing stages have been identified. For perfect recrystallization and maximum electrical activation an annealing temperature of 900°C is required. The maximum peak hole concentration was in the range 1–2.10¹⁹ holes/cm³.     

Phosphorus diffusion in gallium arsenide

The formation of monocrystalline GaAs_1?xP_x by the solid state diffusion of phosphorus into monocrystalline GaAs at a phosphorus pressure of 35 atm has been confirmed by X-rays and reflectivity measurements. Phosphorus distribution in GaAs specimens diffused in the temperature range 800–1100°C has been determined by reflectance studies. The diffusion coefficient and the activation energy computed from the known phosphorus distributions in the diffused specimens are found to depend on the content of phosphorus in the diffused region. The variation of the depth of GaAs_1?xP_x-GaAs junction with time (at a fixed temperature, 1000°C) and temperature (for a fixed time, 24.5 hr) has been studied.     

Electrical properties of phosphorus diffused GaAs

The electrical parameters, i.e. mobility, resistivity and ionization energy, of the dopant (Se) have been determined at different depths in phosphorus diffused GaAs. These values have been compared with those obtained for the epitaxially grown specimens.     

Comparison of teaching the basic electrocardiographic concept of frontal plane QRS axis using the classical versus the orderly electrocardiogram limb lead displays

This study compares the effectiveness of teaching the calculation of frontal plane QRS axis with the use of the classical versus the orderly electrocardiographic limb lead display. Eighty-three students from two environments were randomized into two groups and were taught to determine frontal plane axis with one of the methods. The accuracy and time to determine the axis were tested on 10 electrocardiograms. In the United States the group using the classical display achieved 4.2 (+/-2.7) correct answers, whereas those using the orderly method achieved 6.8 (+/-3.0) (p = 0.0006). The classical group used 9.2 (+/-2.8) minutes to complete the test, whereas the orderly group needed 7.2 (+/-2.0) minutes (p = 0.015). The results achieved in Sweden were similar. The use of the orderly electrocardiographic limb lead display results in greater diagnostic accuracy in less time than the classical display when determining the frontal plane QRS axis.     

High in situ rat intestinal permeability of artemisinin unaffected by multiple dosing and with no evidence of P-glycoprotein involvement

PURPOSE: To evaluate inflammation after clear corneal incision (CCI) cataract surgery in patients with noninsulin-dependent diabetes mellitus and no retinopathy. METHODS: Forty patients with diabetes and 40 age-matched controls had standardized temporal CCI cataract surgery with implantation of a foldable intraocular lens. Anterior chamber flare was evaluated in an undilated eye with a laser flare-cell meter preoperatively and 1, 3, 7, 14, and 28 days postoperatively. RESULTS: In both groups, flare and cell values increased on the first postoperative day and successively decreased on the following days. Flare had not recovered to preoperative values by day 28. At no time was there a significant mean difference in cell and flare between the 2 groups. CONCLUSION: It does not appear necessary to alter the postoperative therapeutic regimen in patients with type 2 diabetes mellitus and no retinopathy.