Measurement of total acid number (TAN) and TAN boiling point distribution in petroleum products by electrospray ionization mass spectrometry

We report a new method for rapid measurement of total acid number (TAN) and TAN boiling point (BP) distribution for petroleum crude and products. The technology is based on negative ion electrospray ionization mass spectrometry (ESI-MS) for selective ionization of petroleum acid and quantification of acid structures and molecular weight distributions. A chip-based nanoelectrospray system enables microscale (<200 mg) and higher throughput (20 samples/h) measurement. Naphthenic acid structures were assigned based on nominal masses of a set of predefined acid structures. Stearic acid is used as an internal standard to calibrate ESI-MS response factors for quantification purposes. With the use of structure-property correlations, boiling point distributions of TAN values can be calculated from the composition. The rapid measurement of TAN BP distributions by ESI is demonstrated for a series of high-TAN crudes and distillation cuts. TAN values determined by the technique agree well with those by the titration method. The distributed properties compare favorably with those measured by distillation and measurement of TAN of corresponding cuts.     

Chemical reaction modeling of industrial scale nitrocellulose production for military applications

A model was developed to describe the nitration of cellulose in mixed acids used in the production of military grade nitrocellulose. Acid dissociation, swelling, diffusion, and chemical reaction were considered to model the nitration of industrially important cellulose materials for given reaction times and conditions. This model is supported by experimental work conducted to measure the dynamics of swelling and diffusion in wood pulp slivers, and the model was validated using the results of lab-scale nitration reactions. Microcomputed tomography was also used to perform a structural analysis of wood pulp slivers that were cut on industrial, rotary cutting machines to evaluate features that may influence the reactivity of these materials.     

Dynamic, 3D Schiff base networks for medical applications

In this study, we utilized the reversible property of aqueous Schiff bases to design a dynamic three-dimensional (3D) network. Two derivatized polysaccharides—acrylated chitosan (aCHN) and oxidized dextran (oDEX)—form a 3D network rapidly (<10 s) in situ without the use of external crosslinking agents. Reversible Schiff base ( NC ) pairs are formed between the amines of aCHN and aldehydes of oDEX. These bonds are mobile and reversible, allowing the network to form additional bonds, leading to lower energy state and densification. In the presence of a primary organic amine, the network dissolves completely, demonstrating network reversibility. The network has strong cohesion (85 ± 7 mmHg) and adhesion (0.017 ± 0.003 MPa) strengths. Rheological examination of the network demonstrates that both elastic storage (G') and viscous loss (G") moduli do not plateau but keep increasing over time. The network shrinks continuously over time, expelling fluid even when completely immersed in physiological solution, in contrast with conventional crosslinked networks that imbibe water and swell. Both rheology and shrinkage demonstrate the dynamic nature of the aCHN–oDEX networks. The dynamic nature of these networks is tunable and the properties of gelation, rheology, cohesion, adhesion, and densification can be modulated depending on the application of interest.     

Rheology,morphology and properties of LCP/Nylon 66 composite fibers

The rheology, morphology and properties of the composite systems of LCP, Vectra A^TM 950 and Nylon 66 were investigated. The viscocity ratio of LCP and matrix has strong influence on their morphology. For LCP blends, the viscosity ratio of LCP is a critical factor in determining the blend morphology. The optical micrographs show that the good fibrillation can be achieved when the viscocity of the dispersed LCP phase is less than that of the Nylon 66 matrix at 310°C. The dispersed LCP domains tend to be spherical or cluster‐like when the viscosity ratio of the disperesed LCP phase and the Nylon 66 matrix is more than 1 at 280°C. The scanning electron microscopy (SEM) and optical micrograph observations show that Nylon 66 is immiscible with LCP, and there are two distinct phases in the blends. The morphology of LCP phase changes with the composition. LCP exhibits a fine fibril dispersed phase in the Nylon 66 matrix in the low LCP concentration. With an increase in LCP concentration, the morphology of LCP phase is changed form a fine fibril dispersed phase to a perfectly aligned continuous fiber reinforced phase in the rich LCP concentration. The tensile moduli increase with LCP concentration, especially in the rich LCP concentration. The tensile strengths increase with LCP concentration only when LCP concentration is above 40 wt%. Compared to the pure Nylon 66 fiber, the 40 wt% LCP composite sample shows a 982.1% increase in tensile modulus and a 123.3% increase in tensile strength. The mechanical properties of composite fibers are below the rule of mixtures if the LCP concentration is low, but above the rule of mixtures if the LCP concentration is high.     

Dopamine decreases the excitability of layer V pyramidal cells in the rat prefrontal cortex

In both primates and rodents, the prefrontal cortex (PFC) is highly innervated by dopaminergic fibers originating from the ventral tegmental area, and activation of this mesocortical dopaminergic system decreases spontaneous and evoked activity in the PFC in vivo. We have examined the effects of dopamine (DA), over a range of concentrations, on the passive and active membrane properties of layer V pyramidal cells from the rat medial PFC (mPFC). Whole-cell and perforated-patch recordings were made from neurons in rat mPFC. As a measure of cell excitability, trains of action potentials were evoked with 1-sec-long depolarizing current steps. Bath application of DA (0.05-30 microM) produced a reversible decrease in the number of action potentials evoked by a given current step. In addition, DA reversibly decreased the input resistance (RN) of these cells. In a subset of experiments, a transient increase in excitability was observed after the washout of DA. Control experiments suggest that these results are not attributable to changes in spontaneous synaptic activity, age-dependent processes, or strain-specific differences in dopaminergic innervation and physiology. Pharmacological analyses, using D1 agonists (SKF 38393 and SKF 81297), a D1 antagonist (SCH 23390), a D2 receptor agonist (quinpirole), and a D2 antagonist (sulpiride) suggest that decreases in spiking and RN are mediated by D2 receptor activation. Together, these results demonstrate that DA, over a range of concentrations, has an inhibitory effect on layer V pyramidal neurons in the rat mPFC, possibly through D2 receptor activation.     

Intravitreal sustained-release cyclosporine in the treatment of experimental uveitis

Nine building projects are briefly described, including four new libraries, two renovations, and three combined renovations and additions. The libraries range in size from 657 square feet to 136,832 square feet, with seating varying from 14 to 635. Three hospital libraries and four academic health sciences libraries are described in more detail. In each case an important consideration was the provision for computer access. Two of the libraries expanded their space for historical collections. Three of the libraries added mobile shelving as a way of storing print materials while providing space for other activities.     

Lot splitting to minimize average flow-time in a two-machine flow-shop

Lot splitting is a technique for accelerating the flow of work by splitting job lots into sublots, In this paper we investigate the lot splitting scheduling problem in a two-machine flow-shop environment with detached setups and with batch availability. The performance measure considered is the average flow-time which is indicative of the increasingly important manufacturing lead-time. Our contribution is both theoretic and practical for the case of general (not necessarily equal) sublots. We identify properties of the optimal solution and develop a solution procedure to solve the problem. We then present a computational study which indicates that our solution technique is very efficient.     

Characterization of serine and threonine phosphorylation sites in beta-elimination/ethanethiol addition-modified proteins by electrospray tandem mass spectrometry and database searching

A new method for the characterization of serine and threonine phosphorylation sites in proteins has been developed. After modification of a phosphoprotein by beta-elimination/ethanethiol addition and conversion of phosphoserine and phosphothreonine residues to S-ethylcysteinyl or beta-methyl-S-ethylcysteinyl residues, the modified protein was subjected to proteolytic digestion. Resulting digests were analyzed by a combination of microbore liquid chromatography, electrospray ionization tandem (MS/MS) ion trap mass spectrometry and database searching to identify original phosphorylated residues. The computer program utilized (SEQUEST) is capable of identifying peptides and modified residues from uninterpreted MS/MS spectra, and using this method, all of the five known phosphorylation sites in bovine beta-casein were identified. Application of the method to multiply phosphorylated human high molecular weight neurofilament protein (NF-H) resulted in the identification of 21 peptides and their modified residues and hence, the in vivo phosphorylation sites. These included 26 KSP and 1 KTP site, all of which occur in the KSP repeat C-terminal tail domain (residues 502-823). One site at residue 518 was previously uncharacterized. A novel non-KSP serine at residue 421 near the KLLEGEE region in a IPFSLPE motif was characterized as phosphorylated (or glycosylated). The 27 characterized phosphorylation sites occur at S/TP residues in the following motifs: KSPVKEE, KSPAEAK, KSPEKEE, KSPAEVK, KSPEKAK, KSPPEAK, KSPVKAE, and KTPAKEE. On the basis of kinase consensus sequences, all of these motifs, including the previously unreported KTPAKEE motif, can be phosphorylated by proline-directed kinases. Advantages of the new method vis-a-vis our previously reported method [Jaffe, H., Veeranna, Shetty, K. T., and Pant, H. C. (1998) Biochemistry 37, 3931-3940] include (i) production of diastereomers eluting at different retention times increased the chances of peptide identification, (ii) increased hydrophobicity and hence retention time of the modified peptides, (iii) facilitation of positive ion production, and (iv) increased susceptibility to tryptic digestion as a result of conversion of negatively charged phosphorylated residues to neutral S-ethylcysteine or beta-methyl-S-ethylcysteine residues.     

A view of telecommunications network evolution

While deployment of new network technologies has not been steady over the years, it is useful to take a long-term view of how major new telecommunications infrastructures evolve. Since the beginning of this decade, we have witnessed the emergence of new generations of three major communication networks. This article addresses the market conditions, technology innovations, and services driving the need for intelligent all-optical, 3G wireless, and QoS-based packet networks. Market forces such as traffic and subscriber growth, equipment cost reduction, and new technology penetration have a deep impact on network buildouts. Technology innovations abound, especially in the optical domain. For example, Raman amplification, pure optical switches, and tunable lasers have had a major impact on the architecture of optical networks. Many key services, such as streaming audio and high-quality image transfer, were not possible using wireless access because of its limited bandwidth and performance. With 3G wireless technology, a true mobile Internet will become a reality. Businesses have shied away from the use of the public Internet because of service quality. Thanks to advances in MPLS and service intelligence, this is expected to change. For each type of network, we survey the key factors shaping its evolution and implications on network architectures.     

Six-week postpartum maternal self-criticism and dependency and 4-month mother-infant self- and interactive contingencies.

Associations of 6-week postpartum maternal self-criticism and dependency with 4-month mother-infant self- and interactive contingencies during face-to-face play were investigated in 126 dyads. Infant and mother face, gaze, touch, and vocal quality were coded second by second from split-screen videotape. Self- and interactive contingencies were defined as auto- and lagged cross-correlation, respectively, using multilevel time-series models. Statistical significance was defined as p