Isolation and Cultivation of a Xylanolytic Bacillus subtilis Extracted from the Gut of the Termite Reticulitermes santonensis

The aim of this work was the isolation of xylanolytic microorganisms from the digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after the hydrolysis of xylans can be further fermented to provide bioethanol. A xylanolytic strain of Bacillus subtilis was isolated from the hindgut of the termite and displayed amylase and xylanase activities. The bacterium was grown on media containing agricultural residues: wheat bran, wheat distiller’s grains, and rapeseed oil cake. Wheat bran led to the highest induction of xylanase activity, although the development of the strain was less fast than in the other media. It was possible to reach maximal xylanase activities of 44.3, 33.5, and 29.1 I.U./ml in the media containing wheat bran, wheat distiller’s grains, and rapeseed oil cake, respectively. Mass spectrometry identified a wide range of xylose oligomers, highlighting an endoxylanase activity. The enzyme was stable up to 45 °C and displayed an optimal pH close to 8.     

High-valent diiron species generated from N-bridged diiron phthalocyanine and H(2)O(2)

N-bridged diiron tetra-tert-butylphthalocyanine activates H(2)O(2) to form anionic hydroperoxo complex [(Pc)Fe(IV)=N-Fe(III)(Pc)-OOH](-) prone to heterolytic cleavage of O-O bond with the release of OH(-) and formation of neutral diiron oxo phthalocyanine cation radical complex, PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. ESI-MS data showed stability of the Fe-N-Fe binuclear structure upon formation of this species, capable of oxidizing methane and benzene via O-atom transfer. The slow formation kinetics and the high reactivity preclude direct detection of this oxo complex by low temperature UV-vis spectroscopy. However, strong oxidizing properties and the results of EPR study support the formation of PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. Addition of H(2)O(2) at -80 °C led to the disappearance of iron EPR signal and to the appearance of the narrow signal at g = 2.001 consistent with the transient formation of PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. In the course of this study, another high valent diiron species was prepared in the solid state with 70% yield. The M?ssbauer spectrum shows two quadrupole doublets with δ(1) = -0.14 mm s(-1), ΔE(Q1) = 1.57 mm s(-1) and δ(2) = -0.10 mm s(-1), ΔE(Q2) = 2.03 mm s(-1), respectively. The negative δ values are consistent with formation of Fe(iv) states. Fe K-edge EXAFS spectroscopy reveals conservation of the diiron Fe-N-Fe core. In XANES, an intense 1s → 3d pre-edge feature at 7114.4 eV suggests formation of Fe(iv) species and attaching of one oxygen atom per two Fe atoms at the 1.90 ? distance. On the basis of M?ssbauer, EPR, EXAFS and XANES data this species was tentatively assigned as (Pc)Fe(IV)=N-Fe(IV)(Pc)-OH which could be formed from PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O by hydrogen atom abstraction from a solvent molecule. Thus, despite unfavourable kinetics, we succeeded in the preparation of the first dirion(iv) phthalocyanine complex with oxygen ligand, generated in the (Pc)Fe(IV)=N-Fe(III)(Pc) - H(2)O(2) system capable of oxidizing methane.     

Validity of rough surface backscattering models

A study of the regions of validity for rough surface scattering models is conducted for surfaces with Gaussian and power law power spectra. Models included in the study are physical optics (PO), geometrical optics, small perturbation method and small slope approximation. The range of validity of the PO model is commonly described by a bound on the radius curvature of the surface relative to the electromagnetic wavelength. We show empirically that for backscattering the region of accuracy is more accurately described by a bound on surface slope. For surfaces with a Gaussian power spectrum, the PO model is accurate to within 2 dB for RMS surface slope values less than 0.59 cos³θ. For surfaces with a power law power spectral density, the PO model is accurate for significant slope values (RMS surface height/wavelength of the dominant spectral peak) less than 0.037 cos³θ. These conditions are valid up to approximately 30°. The regions of validity of other models in the study are also shown to be well approximated by bounds on surface slope.     

Rhenium fac tricarbonyl bisimine complexes: biologically useful fluorochromes for cell imaging applications

A series of lipophilic and hydrophilic fac tricarbonyl rhenium bisimine complexes have been prepared, their membrane-permeabilities explored in liposomes and their potential for application in fluorescence microscopy cell imaging demonstrated in the first application of MLCT-fluorescent rhenium complexes in cell imaging.     

Microfluidic devices for culturing primary mammalian neurons at low densities

Microfluidic devices have been used to study high-density cultures of many cell types. Because cell-to-cell signaling is local, however, there exists a need to develop culture systems that sustain small numbers of neurons and enable analyses of the microenvironments. Such cultures are hard to maintain in stable form, and it is difficult to prevent cell death when using primary mammalian neurons. We demonstrate that postnatal primary hippocampal neurons from rat can be cultured at low densities within nanoliter-volume microdevices fabricated using polydimethylsiloxane (PDMS). Doing so requires an additional fabrication step, serial extractions/washes of PDMS with several solvents, which removes uncrosslinked oligomers, solvent and residues of the platinum catalyst used to cure the polymer. We found this step improves the biocompatibility of the PDMS devices significantly. Whereas neurons survive for > or = 7 days in open channel microdevices, the ability to culture neurons in closed-channel devices made of untreated, native PDMS is limited to < or = 2 days. When the closed-channel PDMS devices are extracted, biocompatibility improves allowing for reliable neuron cultures at low densities for > or = 7 days. Comparisons made to autoclaved PDMS and native, untreated PDMS reveal that the solvent-treated polymer is superior in sustaining low densities of primary neurons in culture. When neuronal affinity for local substrates is observed directly, we find that axons localize to channel corners and prefer PDMS surfaces to glass in hybrid devices. When perfusing the channels with media by gravity flow, cultured hippocampal neurons survive for > or = 11 days. Extracting PDMS improves biocompatibility of microfluidic devices and thus enables the study of differentiation of identifiable neurons and the characterization of local extracellular signals.     

Solid-phase microextraction and gas chromatography–mass spectrometry for analysis of phenols and nitrophenols in rainwater,as their <Emphasis Type="Italic">t</Emphasis>-butyldimethylsilyl derivatives

Solid-phase microextraction (SPME) coupled with gas chromatography–mass spectrometry has been used for analysis of four phenols and sixteen nitrophenols in rainwater samples. Analytes were extracted from the water in the immersion mode and derivatised for 5 min during direct desorption in the GC injector. Before desorption, 2 μL N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MDBSTFA) was introduced into the injector, which was maintained at 280 °C. Different conditions affecting extraction efficiency were studied, including temperature, type of microextraction fibre, and effect of pH and ionic strength. Five different fibre coatings were tested: 85-μm polyacrylate (PA), 100-μm polydimethylsiloxane (PDMS), 65-μm Carbowax–divinylbenzene (CW–DVB), 75-μm Carboxen–polydimethylsiloxane (CAR–PDMS), and 65-μm polydimethylsiloxane–divinylbenzene (PDMS–DVB). The best conditions were use of PA fibres for 40 min at ambient temperature (75 g NaCl per 100 mL, pH 3.0). MDBSTFA was used as derivatising agent because it enables analysis of phenols derivatives with high confidence in identification, because in electron-impact mode TBDMS–phenol derivatives produce the specific M–57 ion. Quantification was achieved by using 4-nitrophenol-d4, at 1 mg L⁻¹, as internal standard. Linearity was good, with correlation coefficients in the range 0.9888 (o-cresol) to 0.9987 (dinitro-o-cresol, DNOC). Detection limits varied between 0.208 and 99.3 μg L⁻¹ and quantification limits between 0.693 and 331 μg L⁻¹. Uncertainties varied between 8.7% (phenol) and 17.9% (4-methyl-2-nitrophenol). The method was successfully applied to the analysis of rainwater collected at urban and rural sites in Alsace (East of France). Because of derivatisation in the injector and the associated high temperature, the lifetime of the fibre is severely reduced.     

Integral resource capacity planning for inpatient care services based on bed census predictions by hour

The design and operations of inpatient care facilities are typically largely historically shaped. A better match with the changing environment is often possible, and even inevitable due to the pressure on hospital budgets. Effectively organizing inpatient care requires simultaneous consideration of several interrelated planning issues. Also, coordination with upstream departments like the operating theatre and the emergency department is much-needed. We present a generic analytical approach to predict bed census on nursing wards by hour, as a function of the Master Surgical Schedule and arrival patterns of emergency patients. Along these predictions, insight is gained on the impact of strategic (ie, case mix, care unit size, care unit partitioning), tactical (ie, allocation of operating room time, misplacement rules), and operational decisions (ie, time of admission/discharge). The method is used in the Academic Medical Center Amsterdam as a decision-support tool in a complete redesign of the inpatient care operations.