Biochemical sensor tubing for point-of-care monitoring of intravenous drugs and metabolites

In medical facilities, there is strong motivation to develop detection systems that can provide continuous analysis of fluids in medical tubing used to either deliver or remove fluids from a patient's body. Possible applications include systems that increase the safety of intravenous (IV) drug injection and point-of-care health monitoring. In this work, we incorporated a surface-enhanced Raman scattering (SERS) sensor comprised of an array of closely spaced metal nanodomes into flexible tubing commonly used for IV drug delivery and urinary catheters. The nanodome sensor was fabricated by a low-cost, large-area process that enables single use disposable operation. As exemplary demonstrations, the sensor was used to kinetically detect promethazine (pain medication) and urea (urinary metabolite) within their clinically relevant concentration ranges. Distinct SERS peaks for each analyte were used to demonstrate separate detection and co-detection of the analytes.     

Organotin biocides. X. Synthesis,structure and biocidal activity of organotin derivatives of 2-mercaptobenzothiazole, 2-mercaptobenzoxazole and 2-mercaptobenzimidazole

Ten organotin derivatives of 2-mercaptobenzothiazole (Hmbt), 2-mercaptobenzoxazole (Hmbo) and 2-mercaptobenzimidazole (Hmbi) have been synthesised and thier structures characterised by spectroscopic methods. Triorganotin derivatives are all S-bonded to the ligand and four-coordinate at tin except Bu₃Sn(mbo) which is five-coordinate trans-ONSnR₃ polymer at 78K. The crystal structure of Cy₃Sn(mbt) has been determined and confirms the tetrahedral geometry at tin. Bu₂Sn(mbt)₂ is weakly six-coordinate by N,S chelating ligands. Biocidal activity patterns are presented for Cy₃Sn(mbt), Ph₃Sn(mbt) and Ph₃Sn(mbo).     

Temperature dependence of the quadrupole interaction in potassium heptafluohafnate

The quadrupole interaction between the tantalum nucleus and its environment in potassium heptafluohafnate incorporating radioactive¹⁸¹Hf has been studied over the temperature range from 77 K to 318 K. A discontinuity in the field gradient tensor is observed at 250 K together with a more gradual alteration with midpoint temperature of approximately 210 K. Below 250 K, the data indicate two inequivalent sites for the tantalum nuclei. The values obtained for the electric field gradient tensor suggest that motional averaging may be significant in this compound.     

Calibration of stresscoat by impact

A method for calibrating Stresscoat at very high rates of strain is presented. The method makes use of an impact pulse traveling in a thin rod at sonic velocity. Results of five tests on Stresscoat 1207 indicate a sensitivity of sixty percent of the static value. There is also evidence that the sensivitivity is a function of the strain rate.     

Thymine‐functionalized polystyrenes for applications in biotechnology. III. Increasing the thymine loading via a new synthetic pathway

In this article, we report an efficient method for the synthesis of thymine‐functionalized polystyrene microspheres. First, poly(styrene‐co‐4‐chloromethylstyrene) copolymers slightly crosslinked with divinylbenzene were synthesized in batch free‐radical emulsion copolymerization. Microspheres with a particle size of ～40–70 nm were obtained with greater than 99% conversion. The chloromethylstyrene (CMS) groups were then converted into thymylmethylstyrene (TMS) in a two‐phase system with greater than 80% efficiency, and up to a 45 mol % thymine loading was achieved. The functionalized microspheres were characterized by elemental analysis, Fourier transform infrared, and X‐ray photoelectron spectroscopy. The analyses revealed partial hydrolysis of the CMS functionalities, yielding hydroxymethyl functional groups in addition to the thymine functionalities. These copolymers have potential applications in biotechnology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5545–5553, 2005     

On cycling in the network simplex method

There are well-known examples of cycling in the linear programming simplex method having basis size two and requiring only six pivots. We prove that any example having basis size two for the network simplex method requires at least ten pivots. We also present an example that achieves this lower bound. In addition, we show that an attractive variant of Cunningham's noncyling method does admit cycling.     

The absolute maximum payoff in differential games and optimal control

This paper deals with a differential game or optimal control problem in which the payoff is the maximum (or minimum), during play, of some scalar functionK of the statex. This unconventional payoff has many practical applications. By defining certain auxiliary games for a significant class of problems, one can show how to solve the general case where more than one maximum ofk(t)=K[x(t)] occurs under optimal play. For a subclass of such problems, it is found thatclosed optimal solutions can exist on certain surfaces in the playing space. As the playing interval becomes indefinitely long, the open optimal trajectories converge to (or diverge from) such surfaces. In particular, for two-dimensional problems of this subclass, the closed optimal trajectories are periodic and called periodic barriers. They are analogous to limit cycles in uncontrolled nonlinear systems.The writer is indebted to Dr. R. Isaacs for many stimulating conversations in connection with this study.     

Incompatibility of BCS pairing and the Peierls distortion in linear chain systems

We have solved the coupled gap equations for a one dimensional electron gas which can undergo both a Peierls insulating and a BCS superconducting transition. We find that, except for a very special case, (i) only one of the order parameters can be non-vanishing and (ii) there is only one critical temperature. We conclude that, independent of the pairing interaction strength, if the Peierls transition occurs, there can be no BCS superconductivity, and conversely.     

An analysis of the structure of the iridium (111) surface by low-energy electron diffraction

Elastic low-energy electron diffraction (LEED) intensity versus voltage (I-V) measurements for the clean Ir(111) surface have been obtained. Seven specular I-V spectra were measured from 15 to 975 eV at incident angles from 7° to 62.5° relative to the surface normal. The outermost atomic layer spacing of the unreconstructed Ir(111) surface was determined both by the convolution-transform method we have presented previously (including certain convenient modifications) and by dynamical calculations. Results from the analysis of the I-V spectra by the convolution-transform method indicate that the outermost Ir(111) layer spacing is either unrelaxed or contracts by 4% of its bulk value depending upon whether the θ=7° data or the θ = 25° data are used. In agreement with this, the dynamical calculations show that the outermost Ir(111) layer spacing contracts by 2.5± 5% and, in addition, that the registry of the first layer of the crystal surface is not shifted, maintaining the fcc structure.