MARANGONI AND ELECTRIC FIELD EFFECTS UPON MASS TRANSFER TO TRANSLATING DROPS

Interfacial stresses arising from the transfer of an interfacial tension-lowering solute (Marangoni effects) or the presence of an electric field may significantly alter the interfacial velocity of a moving droplet with consequent effects upon the rate of convective mass exchange between the drop and the external medium. The present theoretical study considers separately the Marangoni and electric field effects and delineates the conditions under which mass transfer enhancement should be observed. For Peclet numbers in the range of 10-100, enchancement is predicted for a Marangoni to Peclei number ratio of 100 or for a dimensionless electric velocity of 0.1, As an example, numerical results for a Peclet number of 50 indicate an increase of approximately 20% in the mass transfer coefficient for either a Marangoni number of 5000 or a dimensionless electric velocity of 0.5 for phases of comparable transport properties and solute solubilities.     

Seasonal Effects of Hydropeaking on Growth,Energetics and Movement of Juvenile Atlantic Salmon (Salmo Salar)

The performance and movements of juvenile Atlantic salmon Salmo salar exposed to variable water discharge (simulating hydropeaking) but with a stable water‐covered area were studied in six experimental stream channels, both during the winter and summer. Thirty fish were stocked into each channel, and the growth, body fat and movements of the fish were followed for about 2.5 months in each season. During the winter, no effect of hydropeaking was documented on performance or movement. In the summer, fish experiencing hydropeaking had lower body mass, lower body fat, and higher movement rates than the control fish. In general, effect sizes were small, and the rapid and frequent changes in water discharge and water level in the present study had small effects on the performance of juvenile Atlantic salmon. The cumulative long‐term effect at the population level is unknown, but a reduced growth rate of 10% and a reduction in body fat of 16% in the hydropeaking experiments in the summer might to some extent translate into increased smolt age and lower overwintering survival. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermoelectric temperature control device for vapor pressure measurements

The static method of measuring equilibrium vapor pressure requires locating the sample at the coldest part of the apparatus to avoid errors due to evaporation and recondensation elsewhere. This paper describes a device that can hold the sample 1 K below the temperature of the surrounding air without a liquid bath. It comprises a pair of thermoelectric elements and two thermometers attached to an insulated aluminum block. The device can operate as high as 200?°C while controlling the sample with a precision of 0.02 K; below 110?°C, the precision is 2 mK. Also described is a method to measure the small temperature offset due to heat flow between the sample and the surrounding aluminum block. The uncertainty due to the offset is small compared to the 6 mK uncertainty due to the thermometer.     

Growth and optical properties of In x Ga1−x P nanowires synthesized by selective-area epitaxy

Ternary Ⅲ-Ⅴ nanowires (NWs) cover a wide range of wavelengths in the solar spectrum and would greatly benefit from being synthesized as position-controlled arrays for improved vertical yield,reprodudbility,and tunable optical absorption.Here,we report on successful selective-area epitaxy of metal-particle-free vertical InxGa1-xP NW arrays using metal-organic vapor phase epitaxy and detail their optical properties.A systematic growth study establishes the range of suitable growth parameters to obtain uniform NW growth over a large array.The optical properties of the NWs were characterized by room-temperature cathodoluminescence spectroscopy.Tunability of the emission wavelength from 870 nm to approximately 800 nm was achieved.Transmission electron microscopy and energy dispersive X-ray measurements performed on crosssection samples revealed a pure wurtzite crystal structure with very few stacking faults and a slight composition gradient along the NW growth axis.     

Apolipoprotein E*3-Leiden transgenic mice as a test model for hypolipidaemic drugs

PURPOSE: We report an investigation into the distribution of proteoglycans (PGs) in normal, organ-cultured and dextran-treated human corneas. METHODS: Immunogold labeling was carried out at the electron microscope level to localize keratan sulphate (KS), chondroitin sulphate (CS), and heparan sulphate (HS) PGs. RESULTS: High levels of labeling for CS was found in the epithelium, endothelium, and keratocytes, with light labelling present in the basement membranes and the corneal stroma. Labeling for HS was present in the epithelium, endothelium, and keratocytes, with intense labeling present at the endothelium/Descemet's membrane interface and the epithelium/Bowman's layer interface. Large filaments were also observed in these regions in cuprolinic blue-stained specimens. Keratan sulphate was present at high levels in the stroma and the basement membranes with low levels present within the keratocytes, epithelium, and endothelium. The pattern of KS labeling along the collagen fibrils in the stroma sometimes showed evidence of periodicity. Organ-cultured corneas had extensive collagen-free "lakes," the interior of which immunolabeled positively for KS and showed staining with cuprolinic blue. The lakes were greatly reduced in the dextran-treated samples. CONCLUSION: This investigation determined the ultrastructural distribution of KS, CS, and HS PGs in human cornea and showed that organ culture is associated with a change in distribution of stromal PGs.     

Designing a Controller for a Multi-Train Multi-Track System

The use of formal methods for analyzing and synthesizing a controller for a multi-train multi-track railway system is discussed. The research was motivated by a case study involving the Bay Area Rapid Transit (BART) system. The overall goal is to design a train acceleration control function that enables trains to be safely placed but also increases system throughput. The use of a modeling language for specifying safety properties and a control function is illustrated. The program transformation methodology supported in the HATS system is employed to generate an efficient implementation from a high-level specification of a controller. This implementation can then be used to simulate the controller behavior, thus further enhancing confidence in the design. Properties of optimization transformations can be verified using an rewrite-rule based induction theorem prover Rewrite Rule Laboratory (RRL).     

Direct integration of micromachined pipettes in a flow channel forsingle DNA molecule study by optical tweezers

We have developed a micromachined flow cell consisting of a flow channel integrated with micropipettes. The flow cell is used in combination with an optical trap setup (optical tweezers) to study mechanical and structural properties of λ-DNA molecules. The flow cell was realized using silicon micromachining including the so-called buried channel technology to fabricate the micropipettes, the wet etching of glass to create the flow channel, and the powder blasting of glass to make the fluid connections. The volume of the flow cell is 2 μl. The pipettes have a length of 130 μm, a width of 5-10 μm, a round opening of 1 μm and can be processed with different shapes. Using this flow cell we stretched single molecules (λ-DNA) showing typical force-extension curves also found with conventional techniques. These pipettes can be also used for drug delivery, for injection of small gas bubbles into a liquid flow to monitor the streamlines, and for the mixing of liquids to study diffusion effects. The paper describes the design, the fabrication and testing of the flow cell     

One-dimensional axial simulation of electric double layer overlap effects in devices combining micro- and nanochannels

This paper presents a numerical steady-state model of ion transport in micro- and nanofluidic devices with widely varying geometric scale, such as transitions between micro- and nanochannels. Finite element or finite volume simulation of such problems is challenging, due to the number of elements needed to produce a satisfactory mesh. Here, only the lengthwise channel dimension is meshed; standard analytical approximations are used to incorporate cross-channel properties. Singularly perturbed cases are built up by continuation. The method is shown to reproduce our previously reported measurements of electric double-layer effects on conductivity, ion concentration, and ion enhancement and depletion. Comparison with 2-D simulations reported in the literature shows that effects on accuracy due to the 1-D approximation are small. The model incorporates analytical models of surface charge density taken from the literature. This enables predictive simulation with reasonable accuracy using published parameter values, or these values may be tuned based on experiment to give improved results. Use of the model for iterative design and parameter estimation is demonstrated.     

Muscular capabilities and workload of flight attendants for pushing and pulling trolleys aboard aircraft

Increasingly in the recent years, passengers’ services are extended into the ascent and descent flight phases on short distance flights. Trolleys containing the required meal and beverage items are used for these service operations and pushed or pulled along the aisles of the aircraft. Flight attendants reported about increased musculo-skeletal disorders and had been complaining about high physical workload from handling trolleys. In order to ensure acceptable load levels for pushing or pulling operations of trolleys, the physical capabilities of the collective “flight attendants” had been investigated by means of force measurements at maximum voluntary contraction (MVC) level and associated relevant anthropometrical and biometrical data. CEN and ISO standards as well as international and national German methods were used to derive recommended force limits for pushing/pulling operations with respect to the physical capabilities of the target group “flight attendants”. Comparing these recommended limits with the force requirements per shift under various conditions of trolley handlings (inclination of the floor, type and weight of trolley, mode of handling, frequency of operation) showed that especially for higher floor inclinations and trolley weights, flight attendants work (substantially) above recommended limits. It became also apparent that the handling of half-size trolleys is unexpectedly high demanding due to high vertical force components, caused by the unfavorable location of their center of gravity.

Relevance to industry

On short-distance flights, passengers’ services are performed by means of trolleys from the ascent to the descent flight phases. Flight attendants had been complaining about high physical workload. This study offers recommendations on maximum force limits for the handling of trolleys with respect to the muscular capacities and work situations of flight attendants on short-distance flights.