Chromate Generation by Chromate Depleted Subsurface Materials

Soluble chromate concentrations as high as 200 μg Cr L^-1 have been reported in water samples from monitoringwells tapping alluvial deposits allegedly contaminated bylaboratory waste as well as control wells off site andupgradient (shallow aquifer) near Davis California, U.S.A. In this report we present evidence that these Cr(VI) levelscould have been generated by geogenic processes rather thanby anthropogenic inputs. We tested the hypothesis thatnative Cr(III) has been and can be oxidized to chromate bynative manganese oxides. Twenty-three drill core samples(all unsaturated) were retrieved from depths varying from1.5 to 22.5 m in 6 different wells. Visible nodules ofMnO₂ were dispersed throughout many of the samples andcarbonates were also present. Sample pH values averagedabout 8.0 and organic C was mostly less than 1.0 g kg^-1. Total Mn and Cr averaged 835 and 191 mg kg^-1respectively. All samples had the capability to oxidizeadded Cr(III) to Cr(VI). To determine the inherent capabilityof the samples to produce Cr(VI) from native Cr(III), subsamples were extracted with 5 mM CaSO₄ plus 5 mM MgSO₄ until Cr(VI) was no longer detected. After freeze-drying, deionized-distilled water was added to theleached samples to approximately field capacity (0.03 MPa). Freeze drying did not generate Cr(VI). These samples wereincubated in polyethylene film bags at room temperature inthe dark. After 1 week incubation, water in the samples wasextracted by centrifugation and the extracts were analyzedfor Cr(VI). All of the samples generated Cr(VI), and theconcentrations in the extracts ranged from 20 to 100 μg Cr L^-1. Total chromium, endemic chromium VI and chromium VI generated in leached samples were not statistically different between samples from onsite and control samples taken offsite and upgradient in respect to the shallowest aquifer.     

Elastic wave velocities of lunar samples at high pressures and their geophysical implications

Ultrasonic measurement of P and S velocities of Apollo 11 lunar samples 10020, 10057, and 10065 to 5 kilobars pressure at room temperature shows a pronounced increase of velocity (as much as twofold) for the first 2 kilobars. The travel times predicted from the velocity-depth curve of sample 10057 are consistent with the results of the Apollo 12 seismic experiments. At pressures below 200 bars, the samples are highly attenuating; for both P and S waves, the value of Q is about 10.     

Direct patterning of modified oligonucleotides on metals and insulators by dip-pen nanolithography

The use of direct-write dip-pen nanolithography (DPN) to generate covalently anchored, nanoscale patterns of oligonucleotides on both metallic and insulating substrates is described. Modification of DNA with hexanethiol groups allowed patterning on gold, and oligonucleotides bearing 5'-terminal acrylamide groups could be patterned on derivatized silica. Feature sizes ranging from many micrometers to less than 100 nanometers were achieved, and the resulting patterns exhibited the sequence-specific binding properties of the DNA from which they were composed. The patterns can be used to direct the assembly of individual oligonucleotide-modified particles on a surface, and the deposition of multiple DNA sequences in a single array is demonstrated.     

Molecular sorting in the secretory pathway

Proteins can be secreted from animal cells by either a constitutive or a regulated pathway; those destined for regulated secretion are actively sorted into dense-core secretory granules. Although sorting is generally assumed to be accomplished by specific carriers, the nature of these carriers remains elusive. In this study, peptide hormones were used as affinity ligands to purify a set of 25-kilodalton proteins from canine pancreatic tissue. Their ligand specificities and patterns of expression have the characteristics of sorting carriers.     

Requirement of AMPA receptor GluR2 phosphorylation for cerebellar long-term depression

Cerebellar long-term depression (LTD) is a model of synaptic memory that requires protein kinase C (PKC) activation and is expressed as a reduction in the number of postsynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors. LTD was absent in cultured cerebellar Purkinje cells from mutant mice lacking the AMPA receptor GluR2 subunit and could be rescued by transient transfection with the wild-type GluR2 subunit. Transfection with a point mutant that eliminated PKC phosphorylation of Ser880 in the carboxy-terminal PDZ ligand of GluR2 failed to restore LTD. In contrast, transfection with a point mutant that mimicked phosphorylation at Ser880 occluded subsequent LTD. Thus, PKC phosphorylation of GluR2 Ser880 is a critical event in the induction of cerebellar LTD.     

Distinguishing inchworm and hand-over-hand processive kinesin movement by neck rotation measurements

The motor enzyme kinesin makes hundreds of unidirectional 8-nanometer steps without detaching from or freely sliding along the microtubule on which it moves. We investigated the kinesin stepping mechanism by immobilizing a Drosophila kinesin derivative through the carboxyl-terminal end of the neck coiled-coil domain and measuring orientations of microtubules moved by single enzyme molecules at submicromolar adenosine triphosphate concentrations. The kinesin-mediated microtubule-surface linkage was sufficiently torsionally stiff (>/=2.0 +/- 0.9 x 10(-20) Newton meters per radian2) that stepping by the hypothesized symmetric hand-over-hand mechanism would produce 180 degree rotations of the microtubule relative to the immobilized kinesin neck. In fact, there were no rotations, a finding that is inconsistent with symmetric hand-over-hand movement. An alternative "inchworm" mechanism is consistent with our experimental results.     

Numerical implementation of modified Coulomb-Mohr yield criterion for anisotropic and asymmetric materials

Development and numerical implementation for an elastoplastic constitutive model for anisotropic and asymmetric materials are presented in this paper. The Coulomb-Mohr yield criterion was modified to consider both the anisotropic and asymmetric properties. The modified yield criterion is an isotropic function of the principal values of a symmetric matrix which is linearly transformed from the Cauchy stress space. In addition to the constitutive equation, the numerical treatment for the singularity in the vertex region of yield surface and stress integration algorithm based on elastoplasticity were presented. In order to assess the accuracy of numerical algorithm, isoerror maps were considered. Also, extension of a strip with a circular hole was simulated and results compared with those obtained using the (smooth) Mises yield criterion to validate stress output for a complex stress state.     

Constitutive equations based on cell modeling method for 3D circular braided glass fiber reinforced composites

The cell modeling homogenization method to derive the constitutive equation considering the microstructures of the fiber reinforced composites has been previously developed for composites with simple microstructures such as 2D plane composites and 3D rectangular shaped composites. Here, the method has been further extended for 3D circular braided composites, utilizing B-spline curves to properly describe the more complex geometry of 3D braided composites. For verification purposes, the method has been applied for orthotropic elastic properties of the 3D circular braided glass fiber reinforced composite, in particular for the tensile property. Prepregs of the specimen have been fabricated using the 3D braiding machine through RTM (resin transfer molding) with epoxy as a matrix. Experimentally measured uniaxial tensile properties agreed well with predicted values obtained for two volume fractions.     

Compositional and digestibility changes in sprouted barley and canola seeds

Barley and canola seeds were sprouted over a 5 day period, in laboratory conditions under room temperature (22°C) and room lighting. Following initial hydration, seeds were kept moist by wetting the germination trays at 9 a.m., 1 p.m. and 6 p.m. daily. A parallel germination experiment using 200 g quantities of seeds in petri dishes was conducted. Starting from the second day of germination, and every day, dishes of germinating seeds were removed, oven-dried, weighed and milled for proximate and chemical analysis. Seeds from the main germination experiment were fed in a digestibility trial to Wistar rats. Results indicated that sprouting was associated with depletion of many nutrients in both barley and canola, the major losses being in respect of dry matter, gross energy and triglycerides. In barley (but not in canola) sprouting was associated with significant increases in crude fiber and diglyceride content. In canola, there were significant losses in lipid content and increases in phytosterol and phospholipid content. Digestibility data showed an enhancement in digestibility of nutrients in barley but not in canola, implying that sprouting improved nutritional quality of barley but not canola.     

On-line monitoring of cellulase treatment by differential refractometer

Cellulase treatment of cellulose fibers needs to be monitored to give proper weight loss without significant strength loss. On-line monitoring of cellulase treatment is presented which can monitor the weight loss of cotton fabrics by measuring differential refractive index in real time. On-line monitoring was tried under the condition where the cellulase treatment of scoured 100% cotton knits would give weight loss of about 6.6% during one hour cellulase treatment. For comanalyses processing solutions with treatment time of 5, 10, 20, 30, 45 and 60 minutes were taken out, and subjected to sugar analyses using total organic carbon (TOC), and dinitrosalicylic acid (DNS) method as well as HPLC analyses. HPLC analyses showed that cellobiose and glucose were the major components resulting from cellulase treatment of cotton fabric. TOC and differential refractive index measurement proved to be linear to total sugar concentration while DNS method result was dependent on the type of sugar. Various sugar concentrations of the processing solutions measured by these methods were compared with HPLC measurements and correlated with the actual weight loss of the cotton fabric processed. The on-line monitoring device using differential refractometer gave a real time signal which was independent of the ratio of cellobiose and glucose but dependent on the total sugar concentration. The device was also non-destructive.