Nonlinear properties analysis on rutting behaviour of bituminous materials with different air void contents

Rutting is one of the major distresses of flexible pavement. It is defined as the formation of longitudinal depressions along the wheel paths caused by the progressive movement of materials under traffic loading in the asphalt pavement layers or in the underlying base through consolidation or plastic flow. This structural damage has a negative financial impact to the economy. In this study, the rutting behaviour of bituminous materials with different air void contents was investigated. The dynamic cyclic compression testing was carried out to establish nonlinear material models with multiple regression technique. With the specified material models, finite element analysis was carried out to study the rutting behaviour of the wearing course materials with different air void contents in a flexible pavement structure. The simulation result shows that the rutting depth is small at the air void contents of 4.5–8% for wearing course materials. However, for the air void contents above or below this range, the rutting resistance reduces, and thus the rutting depth increases. To verify this simulation result, wheel tracking tests were performed to obtain laboratory data, and the test data was found to be very close to the simulated one. This proved that the developed nonlinear model is applicable to simulate the rutting performance of bituminous mixture and it is a convenient and economical method to be used for the design of bituminous mixtures for both new and rehabilitated pavements.     

Fluorescent dye labeled bacteriophages--a new tracer for the investigation of viral transport in porous media: 1. Introduction and characterization

A new method for the study of pathogen transport in porous media is presented. The method is based on conjugation of fluorescent dyes to target bacteriophages and application of the modified bacteriophages for tracer studies. We demonstrate that the relevant transport determining properties of Rhodamine and several fluorescein-labeled phages are practically identical to those of the native bacteriophages. The advantages of the proposed method relative to direct enumeration of bacteriophages by plaque forming unit method, turbidity, fluorescent microspheres, and other alternative tracers are discussed. Notable advantages include simple quantitation by optical methods, unbiased signals even when virus aggregates are formed, and the ability to decouple inactivation kinetics from transport phenomena. Additionally, the signal reflects the removal and transport of the studied microorganism and not a surrogate.     

Organically modified silica sol-mediated capillary electrophoresis

We describe in this paper the use of ormosil (organically modified silica) sols as additives to the run buffer for selectivity manipulations between solutes in capillary electrophoresis. CE systems that contain sol additives in the run buffer can be thought of as pseudocapillary electrochromatography. Three sols based on different types of silanes were studied. Methyltrimethoxysilane (MTMOS)-based sol was found to improve selectivities between various aromatic acids. Aminopropyltrimethoxysilane (APS) sol interacts differently with structural isomers of aromatic acids than does MTMOS. At low pH with APS sol in the run buffer, neutral solutes can be separated, as well. The separation of the neutral solutes seems to be facilitated by the formation of hydrogen bonds between the solutes and the APS sol. APS and N-[3-(trimethoxysilyl)propyl]-ethylenediamine (EDAS) affect the separation of the same compounds differently, thus indicating that even small changes of the functional groups of the sol have pronounced effect on the interactions between the sols and the solutes.     

Effect of intraband carrier relaxation on the threshold characteristics of quantum well lasers

The effect of intraband carrier relaxation on the threshold characteristics of InGaAsP quantum well (QW) lasers is studied. The dependence of the intraband hole-hole relaxation time τ _int on temperature and carrier density is analyzed. It is shown that taking into account the finiteness of τ _int and its dependence on temperature and carrier density strongly affects the gain and the threshold current density of QW lasers.     

A kinetic method for HO2*/O2*- determination in advanced oxidation processes

A new kinetic method is developed for the determination of hydroperoxyl radical (HO(2)(*))/superoxide radical (O(2)(*)(-)) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO(2)(*)/O(2)(*)(-) as produced in the UV/H(2)O(2) process. This new method is based on the reduction of Fe(3+)-EDTA into Fe(2+)-EDTA by HO(2)(*)/O(2)(*)(-) and the well-known Fenton-like reaction of H(2)O(2) and Fe(2+)-EDTA to yield the hydroxyl radicals (OH(*)). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (lambda(ex) = 320 nm; lambda(em) = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 x 10(-)(11) M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interferences often found in aqueous phase.     

Variable Bias Current in Magnetic Bearings for Energy Optimization

We introduce an adaptive variable bias current control scheme to minimize the energy consumption of magnetic bearings without altering the dynamic performance. We developed analytical expressions for the optimum bias current settings for both differential and unidirectional modes of operation as a function of the orbit size and the desired bearing stiffness. The orbit size is measured in situ by a recursive Fourier coefficient calculation. The analytical results are presented in normalized variables, and hence can be applied to any size and type of magnetic bearing. Both zero and nonzero static load cases are considered. We show analytically that, under variable bias current operation, the differential mode provides better energy efficiency and stiffness capacity than the unidirectional mode. We present the energy consumption data obtained experimentally on a flexible rotor magnetic bearing rig. The data show that, with the proposed variable bias current approach, a significant energy saving can be obtained without deterioration of dynamic performance     

Microfluidic Synthesis of pH‐Sensitive Multicompartmental Microparticles for Multimodulated Drug Release

Stimuli‐responsive carriers releasing multiple drugs have been researched for synergistic combinatorial cancer treatment with reduced side‐effects. However, previously used drug carriers have limitations in encapsulating multiple drug components in a single carrier and releasing each drug independently. In this work, pH‐sensitive, multimodulated, anisotropic drug carrier particles are synthesized using an acid‐cleavable polymer and stop‐flow lithography. The particles exhibit a faster drug release rate at the acidic pH of tumors than at physiological pH, demonstrating their potential for tumor‐selective drug release. The drug release rate of the particles can be adjusted by controlling the monomer composition. To accomplish multimodulated drug release, multicompartmental particles are synthesized. The drug release profile of each compartment is programmed by tailoring the monomer composition. These pH‐sensitive, multicompartmental particles are promising drug carriers enabling tumor‐selective and multimodulated release of multiple drugs for synergistic combination cancer therapy.