Acylation and Aroylation of 3-Phenylsydnone

Various 4-acyl or 4-aroyl sydnones 2 can be prepared in good to excellent yield by reaction of 4-(3-phenylsydnonyl) copper with the appropriate acid chlorides, both with or without palladium(0) catalysis.     

Measurement of protein in serum and rodent embryos by spectrophotometry at 215 and 225 nm

The Waddell quantitative method for total protein estimation was slightly modified and applied to sera and rodent embryos, and also compared to the Lowry method. It was not necessary to employ the Kjeldahl method to determine an instrument correction factor; reference sera were used to establish a standard curve. The results from this simplified Waddell method were reproducible from day to day with a high degree of accuracy. Comparative data obtained by total protein determination in three commercially available reference sera demonstrated a sensitivity in the modified Waddell method of 4.8 μg/ml with a precision of >96% and an accuracy of >93%. The overall precision in the determination of the total protein by the method in Day 12 rat embryos was >91% as compared to >86% in the Lowry method.     

Debromination of 4-Bromo-3-arylsydnones with Sodium Sulfite

4-Bromo-3-arylsydnones 1 are denominated to the corresponding 3-arylsydnones 2 in good to excellent yield using sodium sulfite in methanol/water. In contrast to previously employed reagents, the reduction is successful in the presence of electron-donating, electron- withdrawing and bulky groups.     

Wetting front instabilities: a three-dimensional experimental investigation

Wetting front instability or fingering experiments were conducted in three-dimensional infiltration columns, featuring stratified fine-over-coarse texture porous media, to investigate the influences of various soil and wetting phase properties on finger diameter and propagation velocity. The system parameter varied in this study included permeability, system flux rate, media size and gradation uniformity, initial moisture content, viscosity, density, and surface tension. The influence of each parameter is discussed and compared, where applicable, to the finding of previous studies. Finger diameter and velocity data were acquired using a neutron radioscopy based, real-time imaging system. Through the use of the imaging system, a very accurate and reliable experimental data set was produced for three-dimensional fingering events.     

Modelling the time-dependent flow over riblets in the viscous wall region

The flow over drag reducing riblets is examined computationally using a time-dependent model of the viscous wall region. The flow at the upper bound of the computational domain (y ⁺?40) is described using a streamwise eddy model consisting of two scales. A control-volume finite-element method utilizing triangular meshes is used to exactly fit the riblet cross-sectional geometry. Observations of the transient flow conditions suggest that the riblets limit the lateral spread of fluid inrushes towards the wall and retain low momentum fluid in the riblet valleys effectively isolating much of the wall from such inrushes. The generation of intermittent secondary vortices within the riblet valleys also occurs; however, these appear to be quite weak and fairly short-lived.     

Determination of the Vapor Pressure Curve of a Liquid in the Presence of a Nonvolatile Solute

We present a modification of the data analysis for the classical physical chemistry experiment Determination of Enthalpy of Vaporization by the Boiling-Point Method. The vapor pressures of solutions of both ionic and molecular compounds are determined at different temperatures. In this experiment we show that the enthalpy of vaporization change is dependent on the type and amount of nonvolatile solute present. Sets of data collected for different concentrations of sodium chloride, urea, and sucrose solutions are analyzed in order to determine H_vap and S_vap for pure water and for solutions of ionic and molecular solutes.Students perform the data analysis taking into consideration the activity coefficient for the solution and the mole fraction of the solvent. Simultaneous data analysis is introduced and results are used to explain the meaning of the physical parameters determined using this method of data analysis.     

Microelectrophoresis for the separation of DNA fragments.

A methodology has been developed which significantly reduces the linear dimension necessary for the electrophoretic separation of DNA fragments and oligonucleotides. DNA fragments are rapidly separated into compact, resolvable microscopic banding patterns which can be detected using a high-resolution electronic imaging system. Separations can be carried out in either capillary tube or thin-layer (slab) microgel formats of one centimeter or less in length. The complete separation of all eleven fragments (1353 to 72 base pairs) of the pi X174 DNA/HaeIII restriction ladder was achieved in a total running distance of less than 2 mm and in less than 2 min. The observed band widths for the larger fragments (1353-603 bp) ranged from 18 to 25 microns, with the intermediate and smaller fragments (310 to 72 bp) ranging from 30 microns to 60 microns. The ethidium bromide-stained microgels were analyzed using an epifluorescent microscope combined with an intensified charged coupled device imaging system. In other experiments, single-base resolution of fluoresceinated oligonucleotides in the 20-30 nucleotide range was demonstrated. DNA sequencing may be possible with further optimization. This new methodology departs from the conventional gel formulations and electrophoretic procedures used for the separation DNA fragments. High voltage gradients and the use of highly concentrated and crosslinked homogeneous polyacrylamide gels effects the rapid separation of DNA fragments in very short distances. Analysis of the microgels with proteins of known size (Stokes radius) indicates that separations are occurring in gels with pore sizes close to the diameter of double-stranded DNA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Theoretical prediction of collision efficiency between adhesion-deficient bacteria and sediment grain surface

Our earlier results concerning bacterial transport of an adhesion-deficient strain Comamonas sp. (DA001) in intact sediment cores from near South Oyster, VA demonstrated that grain size is the principle factor controlling bacterial retention, and that Fe and Al hydroxide mineral coatings are of secondary importance. The experimentally determined collision efficiency (α) was in the range of 0.003–0.026 and did not correlate with the Fe and Al concentration. This study attempts to theoretically predict α, and identifies factors responsible for the observed low α. The modified Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate the total intersurface potential energy as a function of separation distance between bacterial and sediment surfaces and to provide insights into the relative importance of bacterial and sediment grain surface properties in controlling magnitude of α. Different models for calculating theoretical α were developed and compared. By comparing theoretical α values from different models with previously published experimental α values, it is possible to identify a suitable model for predicting α. When DA001 bacteria interact with quartz surfaces, the theoretical α best predicts experimental α when DA001 cells are reversibly attached to the secondary minimum of the energy interaction curve and α depends on the probability of escape from that energy well. No energy barrier opposes bacterial attachment to clean iron oxide surface of positive charge at sub-neutral pH, thus the model predicts α of unity. When the iron oxide is equilibrated with natural groundwater containing 5–10 ppm of dissolved organic carbon (DOC), its surface charge reverses, and the model predicts α to be on the order of 0.2. The theoretical for DA001 in the natural sediments from South Oyster, VA was estimated by representing the surface potential of the sediment as a patch-wise binary mixture of negatively charged quartz (ζ=−60 mV) and organic carbon coated Fe–Al hydroxides (ζ=−2 mV). Such a binary mixing approach generates α that closely matches the experimental α. This study demonstrates that it is possible to predict α from known bacterial and grain surface properties.     

Modelling the time dependent flow over riblets in the viscous wall region

The flow over riblets is examined computationally using a time dependent model of the viscous wall region. This 2 1/2 D model, developed by Hatziavramidis and Hanratty (1979) and modified by Nikolaides (1984) and Chapman and Kuhn (1981, 1986) assumes homogeneity in the streamwise direction so that the flow is solved only in the cross-sectional plane. The flow at the upper boundary of the computational domain (y ⁺ 40) is described using a streamwise eddy model consisting of two scales, one of the streak spacing (⁺ 100), which dominates vertical momentum transport, and a larger scale that accounts for the influence of large outer flow eddies.The protrusion height concept (Bechert and Bartenwerfer, 1989) is used to define ay ⁺=0 location for surfaces with riblets. A control volume finite element method utilizing triangular meshes is used to exactly fit the riblet cross-sectional geometry. Results obtained using fairly large riblets compare well with the limited experimental evidence available. Observations of the transient flow suggest that the riblets interact with the near-wall streamwise vortices, weakening them by the generation of intermittent secondary vortices within the riblet valleys. The riblets also appear to limit the lateral spread of inrushes towards the wall and retain low momentum fluid in the riblet valleys effectively isolating much of the wall from such inrushes.