Insight into the effects of confined hydrocarbon species on the lifetime of methanol conversion catalysts.

The methanol-to-hydrocarbons reaction refers collectively to a series of important industrial catalytic processes to produce either olefins or gasoline. Mechanistically, methanol conversion proceeds through a 'pool' of hydrocarbon species. For the methanol-to-olefins process, these species can be delineated broadly into 'desired' lighter olefins and 'undesired' heavier fractions that cause deactivation in a matter of hours. The crux in further catalyst optimization is the ability to follow the formation of carbonaceous species during operation. Here, we report the combined results of an operando Kerr-gated Raman spectroscopic study with state-of-the-art operando molecular simulations, which allowed us to follow the formation of hydrocarbon species at various stages of methanol conversion. Polyenes are identified as crucial intermediates towards formation of polycyclic aromatic hydrocarbons, with their fate determined largely by the zeolite topology. Notably, we provide the missing link between active and deactivating species, which allows us to propose potential design rules for future-generation catalysts.

Shaping ultrafast laser inscribed optical waveguides using a deformable mirror.

We use a two-dimensional deformable mirror to shape the spatial profile of an ultrafast laser beam that is then used to inscribe structures in a soda-lime silica glass slide. By doing so we demonstrate that it is possible to control the asymmetry of the cross section of ultrafast laser inscribed optical waveguides via the curvature of the deformable mirror. When tested using 1.55 mum light, the optimum waveguide exhibited coupling losses of approximately 0.2 dB/facet to Corning SMF-28 single mode fiber and propagation losses of approximately 1.5 dB.cm(-1). This technique promises the possibility of combining rapid processing speeds with the ability to vary the waveguide cross section along its length.

Helicobacter pylori-Mediated Protection from Allergy Is Associated with IL-10-Secreting Peripheral Blood Regulatory T Cells.

Helicobacter pylori infections are usually established in early childhood and continuously stimulate immunity, including T-helper 1 (Th1), Th17, and regulatory T-cell (Treg) responses, throughout life. Although known to be the major cause of peptic ulcer disease and gastric cancer, disease occurs in a minority of those who are infected. Recently, there has been much interest in beneficial effects arising from infection with this pathogen. Published data robustly show that the infection is protective against asthma in mouse models. Epidemiological studies show that H. pylori is inversely associated with human allergy and asthma, but there is a paucity of mechanistic data to explain this. Since Th1 and Treg responses are reported to protect against allergic responses, we investigated if there were links between the human systemic Th1 and Treg response to H. pylori and allergen-specific IgE levels. The human cytokine and T-cell responses were examined using peripheral blood mononuclear cells (PBMCs) from 49 infected and 58 uninfected adult patients. Concentrations of total and allergen-specific plasma IgE were determined by ELISA and ImmunoCAP assays. These responses were analyzed according to major virulence factor genotypes of the patients' colonizing H. pylori strains. An in vitro assay was employed, using PBMCs from infected and uninfected donors, to determine the role of Treg cytokines in the suppression of IgE. Significantly higher frequencies of IL-10-secreting CD4(+)CD25(hi) Tregs, but not H. pylori-specific Th1 cells, were present in the peripheral blood of infected patients. Total and allergen-specific IgE concentrations were lower when there was a strong Treg response, and blocking IL-10 in vitro dramatically restored IgE responses. IgE concentrations were also significantly lower when patients were infected with CagA(+) strains or those expressing the more active i1 form of VacA. The systemic IL-10(+) Treg response is therefore likely to play a role in H. pylori-mediated protection against allergy in humans.

Adaptive beam profile control using a simulated annealing algorithm.

We present a programmable beam-shaping method based on the combination of a deformable mirror membrane mirror and a simulated annealing algorithm. The algorithm iteratively adjusts the control voltages of 37 independent electrodes to reduce the variance between the chosen shape and the actual beam shape. The experimental results show that the system is capable of adaptively creating, on demand, Gaussian and super-Gaussian beam profiles that closely match the desired target parameters.

Designer femtosecond pulses using adaptive optics.

We describe a femtosecond pulse shaper using a deformable membrane mirror. The pulses are measured with a real time second-harmonic-generation frequency-resolved optical gating system. Pulse shapes are modified according to a prescribed spectral phase. Accurate spectral phase design as well as pulse intensity modulation was achieved by using negative feedback mirror-surface control. Convergence to the chosen spectral phase design was typically achieved within several seconds.

A microwave digestion-based determination of low molecular weight organic acids in Bayer process liquor.

A new technique for the determination of low molecular weight organic acids in Bayer process liquors is reported. The acids are partitioned from acidified liquor into butanol, followed by butylation using microwave heating. This method is both rapid (sample preparation time < 15 min) and capable of detecting acids larger than previously reported in the low molecular weight fraction (up to RMM 176). A standard solution containing 15 acids was used to calibrate the technique and 13 of these acids were detected and quantified in a Bayer liquor sample.

Sudden infant death syndrome and hibernation: is there a link?

Two very large bodies of information seem to overlap, one being the epidemiological and pathological studies on sudden infant death syndrome (SIDS), the other being the research on hibernation. Until now, these two phenomena have been studied independently; however, it will be argued here that the role of the pineal gland, that of brown adipose tissue (BAT) and sleep patterns in both endothermic hibernating mammals and those babies presenting as SIDS provide clues and support for the hypothesis that SIDS is pathoplastic to the hibernatory response.

Doppler imaging system: an optical device for measuring vector winds. 1: General principles.

The Doppler imaging system is a Fabry-Perot spectrometer adapted to use a spatially sensitive photon detector to provide each of several instrument stations with a full 2-D imaging capability. Line-of-sight winds are determined from the Doppler shifts for each spatially defined pixel. Full vector wind fields may be obtained using three instrument stations and, at the cost of increased data processing and a priori information requirements, from two or even one instrument station. The proposal outlined here is for a bistatic system with ground-based instruments located at stations separated by some 200 km, each using wide-angle foreoptics(120 degrees) to observe upper atmospheric emissions in the vicinity of the auroral oval. Such a system should be capable of measuring winds, using, for example, the OI 630-nm emission, on a 2-D spatial grid, over a region up to approximately 800-km diam, with 50-km square pixels, and yield wind measurements with accuracies +/-20 m/sec in integration times of approximately 10 min.

Simultaneous multiplane imaging with a distorted diffraction grating.

We describe a simple technique for simultaneously imaging multiple layers within an object field onto a single camera. The approach uses a binary diffraction grating in which the lines are distorted such that a different level of defocus is associated with each diffraction order. The design of the gratings is discussed, and their ability to image multiple object planes is validated experimentally. Extension of the technique for spherical-aberration correction is described, and it is shown how the gratings can be used as part of a wave-front-sensing system.

Combined temperature and strain measurement with a dispersive optical fiber Fourier-transform spectrometer.

We report simultaneous measurement of strain and temperature in single-mode optical fiber by broadband interferometry. A Mach-Zehnder interferometer, illuminated by a xenon-arc lamp, has a sensing element in one arm. Scanning an air path generates interferograms that are calibrated by a monochromatic reference interferogram. Values of group delay and dispersion, obtained from the phase of the fast Fourier transform of the sampled interferogram, give strain and temperature through a well-conditioned matrix transformation without phase ambiguity. We obtained measurement ranges and resolutions of 1500 +/- 12 microstrain and 25.0 +/- 0.4 K using a 0.8-m sensing element.

Phase-diversity wave-front sensing with a distorted diffraction grating.

We describe a novel wave-front sensor comprising a distorted diffraction grating, simple optics, and a single camera. A noniterative phase-diversity algorithm is used for wave-front reconstruction. The sensor concept and practical implementation are described in detail, and performance is validated against different Zernike modes and a representative atmospheric phase map.

Balancing optical path lengths in broadband fiber interferometers.

A simple model is used to show that control of dispersion in an all-fiber stellar interferometer is feasible. From the results we assume that an interferometer control system is available in which both temperature and strain are used to balance the interferometer. Within the restriction of a single polarization mode, it is shown that vacuum path errors before the coupling of starlight into the fibers as well as fiber-length differences and environmental differences between two fibers can be corrected to high order.

Measurement of the wavelength dependence of beam divergence for photonic crystal fiber.

We report measurements of the wavelength dependence of beam divergence for single-mode photonic crystal fiber. These measurements confirm predictions of strongly wavelength-dependent beam divergence, consistent with the effective-index model for the photonic crystal cladding material.