Depth profiling of 4-acetamindophenol-doped poly(lactic acid) films using cluster secondary ion mass spectrometry

The feasibility of using cluster secondary ion mass spectrometry for depth profiling of drug delivery systems is explored. The behavior of various biodegradable polymer films under dynamic SF(5)(+) primary ion bombardment was investigated, including several films doped with model drugs. The SF(5)(+) depth profiles obtained from these biodegradable polymer films showed very little degradation in secondary ion signal as a function of increasing primary ion dose, and it was discovered that the characteristic ion signals for the polymers remained constant for ion doses up to approximately 5 x 10(15) ions/cm(2). These results suggest that the polyester structure of the biodegradable polymers studied here allows for a greater ability to depth profile due to ease of main chain scission. Attempts were also made to depth profile through a series of poly(lactic acid) (PLA) films containing varying concentrations of the drug 4-acetamidophenol. The depth profiles obtained from these films show very little decrease in both the 4-acetamidophenol molecular ion and PLA fragment ion signals as a function of increasing SF(5)(+) primary ion dose. Similar results were obtained with theophylline-doped PLA films. These results show that, in some drug delivery devices, it is possible to monitor the distribution of a drug as a function of depth by using cluster primary ion beams.     

Copper oxide coated polyester fabrics with enhanced catalytic properties towards the reduction of 4-nitrophenol

A novel functional polyester fabric (PF) was successfully prepared by a facile method. PF were coated by copper oxide (CuO) followed by chemical grafting of 3-chloropropyltriethoxysilane (ClPTES) and diethanolamine (DEA). The morphology and structure of the resulting material PF@CuO–Si–N(OH)₂ was characterized by X-ray diffraction, scanning electron and optical microscopy, thermogravimetry and Fourier-transformed infrared spectroscopy. The results revealed that the CuO particles were densely surrounded PF, and the covalent surface-grafting of ClPTES and DEA within PF was confirmed. It was also demonstrated that CuO/ClPTES/DEA addition generated new functional sites at the PF surface, improving the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The prepared PF@CuO–Si–N(OH)₂ exhibited high catalytic activity with appreciable cycling stability for the reduction of 4-NP to 4-AP, even after six successive cycles with nearly 90% conversion. Hence, it may be conclude that the catalytic activity and stability of this catalyst allows envisaging great prospect for large scale reduction of 4-NP.     

Tijuana-San Diego: Globalization and the transborder metropolis

This paper explores the degree to which the Tijuana-San Diego metropolitan region functions as a transborder metropolis. It is shown that the border is quite porous, especially for work and shopping. In addition, the two metropolitan economies are much more complementary than competitive, with San Diego specializing in high-order services and the new economy while Tijuana primarily functions as a manufacturing center, based on maquiladora. However, much more cooperation and collaboration are needed in several areas: improving trade infrastructure; addressing the deficits in social infrastructure (especially in Tijuana); making the border crossings more user-friendly; expanding educational opportunities for Latinos in both areas; more priority to environmental problems, especially air quality and sewerage; attempting to reduce the public sector fiscal differentials between the two areas; and more attention to income distribution issues.     

Locational signals to reduce network investments in smart distribution grids: What works and what not?

Locational pricing can reduce the investment needs arising in distribution networks from the transformation towards smart grids with high shares of renewable generation. We analyse different approaches. Locational signals in a general tariff plan for either energy or network pricing require substantial system reform which impedes feasibility. We propose smart contracts with locational elements as hybrid form. System reform is only modest since contractual solutions emerge in smart grids anyhow. The responsibility for tariff setting stays with the network operator. The regulator’s task is limited to incentivizing efficient network investment and allowing network operators maximum flexibility in contract design.     

Post-test calculation and uncertainty analysis of the experiment QUENCH-07 with the system code ATHLET-CD

In the frame of developmental assessment and code validation, a post-test calculation of the test QUENCH-07 was performed with ATHLET-CD. The system code ATHLET-CD is being developed for best-estimate simulation of accidents with core degradation and for evaluation of accident management procedures. It applies the detailed models of the thermal-hydraulic code ATHLET in an efficient coupling with dedicated models for core degradation and fission products behaviour. The first step of the work was the simulation of the test QUENCH-07 applying the modelling options recommended in the code User's Manual (reference calculation). The global results of this calculation showed a good agreement with the measured data. This calculation was complemented by a sensitivity analysis in order to investigate the influence of a combined variation of code input parameters on the simulation of the main phenomena observed experimentally. Results of this sensitivity analysis indicate that the main experimental measurements lay within the uncertainty range of the corresponding calculated values. Among the main contributors to the uncertainty of code results are the heat transfer coefficient due to forced convection to superheated steam–argon mixture, the thermal conductivity of the shroud isolation and the external heater rod resistance. Uncertainties on modelling of B₄C oxidation do not affect significantly the total calculated hydrogen release rates.     

The Scientific Laboratory Instrument to Computer Coupler

Small inexpensive microprocessor based computers can be used to connect a wide variety of biomedical laboratory instruments to a large central time-sharing computer system. The Scientific Laboratory instrument to computer coupler (SLICC) is built around the 8080 microprocessor and has a modular bus structured design which permits the mininijzation of costs for each custom installation. The microprocessor acquires analog and digital data from laboratory equipment, formats it for transmission to the central computer, and can accept and display results returned to it from the central computer. The SLICC has some local storage capability to buffer data when the central computer is unavailable as well as to smooth out the data transfer rate. In addition, the SLICC can be used to interactively control laboratory experiments.     

Evaluation of the isotope dilution technique for determining ileal endogenous nitrogen excretion in the rat

Three body amino acid pools (plasma free, plasma bound and small intestinal tissue) were evaluated as precursors to allow measurement using the isotope dilution technique of endogenous excretion at the terminal ileum of animals. Eighteen 150-g bodyweight rats were given either a protein-free, an enzyme-hydrolysed casein based or a synthetic amino acid based diet, and digesta were collected from the terminal ileum. The animals had been subjected to a constant 8-day infusion of tritiated leucine via subcutaneously implanted osmotic mini pumps. Specific activities (dpm nM^?1 leucine) of the ileal digesta and the plasma free, plasma bound and small intestinal tissue pools were determined and the specific activity for the ileal digesta was expressed as a proportion of the respective precursor pool value to give dilution factors for each dietary treatment. For the protein-free diet, where the ileal nitrogenous flow is endogenous by definition, the dilution factor for an appropriate precursor pool would be unity. For the hydrolysed casein and synthetic amino acid diets, in which the peptides and amino acids are expected to be virtually completely absorbed anterior to the ileum, high dilution factors (close to unity) would be expected. The mean dilution factors based on the plasma free amino acid pool were untenably low (0-2 to 0-3). For the plasma bound amino acid pool mean dilution factors of 1-3 were found for animals given the protein-free and synthetic amino acid diets, while a lower value (0-7) was obtained for the hydrolysed casein treatment. Untenably high factors (1-5) were found with the small intestinal tissue for the protein-free and synthetic amino acid treatments, while the corresponding value for the hydrolysed caseinfed rats was unity. The dilution factor data within treatments were highly variable, and none of the pools examined gave consistently reliable results and could thus be accepted as a valid precursor pool for the endogenous proteins.