Silica nanostructures against fungal growth: design and preparation of antifungal cotton fabrics

Cellulose - The preparation of antifungal-functionalized silica nanoparticles by covalent attachment of several silylated derivatives based on the topical antifungal agent Micozanole is described....     

Impact of productivity on cross-training configurations and optimal staffing decisions in hospitals

Cross-training of nursing staff has been used in hospitals to reduce labor cost, provide scheduling flexibility, and meet patient demand effectively. However, cross-trained nurses may not be as productive as regular nurses in carrying out their tasks because of a new work environment and unfamiliar protocols in the new unit. This leads to the research question: What is the impact of productivity on optimal staffing decisions (both regular and cross-trained) in a two-unit and multi-unit system. We investigate the effect of mean demand, cross-training cost, contract nurse cost, and productivity, on a two-unit, full-flexibility configuration and a three-unit, partial flexibility and chaining (minimal complete chain) configurations under centralized and decentralized decision making. Under centralized decision making, the optimal staffing and cross-training levels are determined simultaneously, while under decentralized decision making, the optimal staffing levels are determined without any knowledge of future cross-training programs. We use two-stage stochastic programming to derive closed form equations and determine the optimal number of cross-trained nurses for two units facing stochastic demand following general, continuous distributions. We find that there exists a productivity level (threshold) beyond which the optimal number of cross-trained nurses declines, as fewer cross-trained nurses are sufficient to obtain the benefit of staffing flexibility. When we account for productivity variations, chaining configuration provides on average 1.20% cost savings over partial flexibility configuration, while centralized decision making averages 1.13% cost savings over decentralized decision making.     

Thermooptical detection in microchips: from macro- to micro-scale with enhanced analytical parameters

In this paper, we compared the methods of photothermal spectroscopy used in different spatial scales, namely thermal-lens spectrometry (TLS) and thermal-lens microscopy (TLM) to enhance the performance parameters in analytical procedures. All of the experimental results were confirmed by theoretical calculation. It was proven that the design for both TLM and TLS, despite a different scale for the effect, is governed by the same signal-generating and probing conditions (probe beam diameter at the sample should be equal to the diameter of the blooming thermal lens), and almost does not depend on the nature of the solvent. Theoretical and experimental instrumental error curves for thermal lensing were coincident. TLM obeys the same law of instrumental error as TLS and shows better repeatability for the same levels of thermal-lens signals or absorbances. TLS is more advantageous for studying low concentrations in bulk, while TLM shows much lower absolute LODs due to better repeatability for low amounts. The behavior of the thermal-lens signal with different flow rates was studied and optimum conditions, with the minimum contribution to total error, were found. These conditions are reproducible, are in agreement with the existing theory of the thermal response in thermal lensing, and do not significantly affect the design of the optimum scheme for setups. TLM showed low LODs in solvent extraction (down to 10(-8) M) and electrokinetic separation (10(-7) M), which were shown to be governed by discussed instrumental regularities, instead of by microchemistry.     

On-target sample preparation of 4-sulfophenyl isothiocyanate-derivatized peptides using AnchorChip Targets

De novo sequencing of tryptic peptides by post source decay (PSD) or collision induced dissociation (CID) analysis using MALDI TOF-TOF instruments is due to the easy interpretation facilitated by the introduction of N-terminal sulfonated derivatives. Recently, a stable and cheap reagent, 4-sulfophenyl isothiocyanate (SPITC), has been successfully used for N-terminal derivatization. Previously described methods have always used desalting and concentration by reverse-phase chromatography prior to mass spectrometric analysis. Here we present an on-target sample preparation method based on AnchorChip target technology. The method was optimized for reduction of by-products and sensitivity with SPITC-derivatized tryptic BSA peptides, and successfully applied to protein identification from silver-stained two-dimensional electrophoretic gels of fish liver extracts. The method is simple and sensitive and allowed protein identification based on de novo sequencing and BLAST search from species with limited sequence information.     

Thermal behaviour study of some sol-gel TiO2 based materials

Among the great number of sol-gel materials prepared, TiO₂ holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light. This work has studied some un-doped and Pd-doped sol-gel TiO₂ nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous TiO₂ matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between the synthesis conditions and the properties of titania nanosized materials, such as thermal stability, phase composition, crystallinity, morphology and size of particles, and the influence of dopant was investigated. The influence of Pd on TiO₂ crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.     

Palladium nanoparticles supported on an organic-inorganic fluorinated hybrid material. Application to microwave-based heck reaction

Phosphine-free palladium nanoparticles were embedded in a fluorous organic-inorganic hybrid material 6b prepared by the sol-gel process. The use of Pdn.6b in the Heck coupling reaction under microwave irradiation has been investigated. Recycling studies have shown that the catalyst can be readily recovered and reused several times without significant loss of activity. Reactions and recovery of the solid-supported palladium catalyst system can be carried out in the presence of air, without any particular precaution.     

Effect of large volume injection of hydrophobic solvents on the retention of less hydrophobic pharmaceutical solutes in RP-LC

Injection of large volumes of samples in solvents other than mobile phase composition has been proved for some less hydrophobic compounds. Thus, the retention behavior of several compounds of pharmaceutical interest (isosorbide-2-nitrate, isosorbide-5-nitrate, tropicamide, pentoxifylline, and methyl p-hydroxybenzoate) was studied by using different hydrophobic solvents (n-hexane, n-heptane, or i-octane) as sample solvents. Two types of stationary phases were used: octyl and octadecyl modified silica (both of Zorbax Eclipse type). The experiments showed a linear dependence between capacity factor of each solute and sample injection volume, up to maximum volume values of about 680 microL for C8 stationary phase and 580 microL for C18 stationary phase, when the solutes are no longer retained in stationary phase. Injection of large volumes of these hydrophobic solvents is thus possible in RP-LC with a gradual reduction of retention and peak efficiency. Two major conditions are however necessary in order to apply such an injection approach: the solutes must have a proper solubility in hydrophobic solvents and meanwhile they have to be less hydrophobic than the sample solvent in order to avoid competition with solvent molecules in partitioning between mobile and stationary phases.     

Pesticide analysis by MEKC on a microchip with hydrodynamic injection from organic extract

An integrated microchip for monitoring carbamate pesticides in environmental water using continuous flow chemical processes is under development, i. e., the integration of hydrolysis, azo-derivatization, liquid-liquid extraction, electrophoretic separation, and quantification. The separation of the derivatives of four carbamate pesticides (carbaryl, carbofuran, propoxur, and bendiocarb) extracted in the continuous flow of a 1-butanol phase was studied in a silica microchip using micellar EKC. A baseline separation of four pesticide derivatives was achieved on a silica chip using hydrodynamic injection with electroosmotic gating. Detection using a thermal lens microscope showed good linearity in the concentration range of 10(-6 )-10(-5 )M with an LOD of 5 x 10(-7) M, which is superior to that of conventional CE with UV absorption detection at a level of 10(-4) M.     

Selective partial reduction of quinolines: Hydrosilylation vs. transfer hydrogenation

Two mild and versatile catalytic routes give regioselective hydrogenation of the heterocyclic ring of quinoline derivatives avoiding the high pressures of hydrogen required in the conventional hydrogenation route. Hydrosilylation using H₃SiPh and catalyzed by [Rh(nbd)(PPh₃)₂]PF₆ at room temperature gives dihydroquinoline, a product not obtainable via direct hydrogenation. Hydrosilylation of the CN bond of PhCHNPh is also observed under these conditions while PhCHCHPh is unreactive. Initial in situ disproportionation of phenylsilane to H₂SiPh₂ and SiH₄, catalyzed by the same catalyst, was required for substrate reduction, as SiH₄ proved to be the active reductant. No N-silyl intermediates were ever observed, hydrolysis presumably occurring in situ. This disproportionation reaction is of potential use in gaining access to silane (SiH₄), a material otherwise not readily available. In a separate approach, transfer hydrogenation from isopropanol using [Ir(cod)(NHC)PPh₃]BF₄ (NHC = 1-neopentyl-4-n-butyl triazole-5-ylidene) as catalyst exclusively produces the tetrahydro product.     

Imidazolium carboxylates as versatile and selective N-heterocyclic carbene transfer agents: synthesis, mechanism, and applications

N,N'-Disubstituted imidazolium carboxylates, readily synthetically available, isolable, air- and water-stable reagents, efficiently transfer N-heterocyclic carbene (NHC) groups to Rh, Ir, Ru, Pt, and Pd, to give novel NHC complexes, e.g., [Pd(NHC)3OAc]OAc and [Pt(NHC)3Cl]Cl (NHC = 1,3-dimethyl imidazol-2-ylidene). The NHC esters are also effective. Tuning the reaction conditions for NHC transfer can give either mono- or bis-NHCs, or bis- and tris-NHCs. A net N to C rearrangement of the N-alkyl imidazole complex to the corresponding NHC complex was seen with (MeO)2CO (DMC). DFT calculations identify the steps needed to form the carboxylate from imidazole and DMC: SN2 methyl transfer from DMC to imidazole, followed by proton transfer from the imidazolium CH to the carboxylate counterion, produces the free NHC H-bonded to MeOH with a weakly associated CO2. The nucleophilic NHC attacks CO2 to form NHC-CO2. NHC transfer to the metal with loss of CO2 has been calculated for Rh(cod)Cl. A proposed two-cis-site reactivity model rationalizes the experimental data: two such vacant sites at the metal are needed to allow coordination of the NHC-CO2 carboxylate and subsequent CC cleavage with NHC transfer. Partial cod decoordination or chloride loss is thus required for Rh(cod)Cl. Chloride dissociation, calculated to be easier in polar solvent, is confirmed experimentally from the retarding effect of excess chloride.