Supercritical gasification of wastewater from updraft wood gasifiers

Supercritical water gasification (SCWG) of the wood tar fraction soluble in water is discussed. The mixture is collected downstream of an updraft wood gasification plant and presents tar compounds typical of low-temperature pyrolysis, with the highest yields attained by acetic acid, levoglucosan and 1-hydroxy-2-propanone. SCWG tests, using a laboratory-scale reactor with a plug-flow behavior, temperatures of 723–821 K, residence times of 46–114 s and initial total organic carbon (TOC) contents of 6.5–31 g/l (pressure equal to 25 MPa), show TOC conversion roughly between 30% and 70%. The corresponding yields of gas (l) with respect to the initial TOC contents (g) vary from 0.4 to 1. Gasification of TOC is well described by an irreversible, first-order, Arrhenius rate reaction with an activation energy of 75.7±22 kJ/mol and a pre-exponential factor of 897±30 s⁻¹. Quantification of 23 tar compounds of the product stream shows the prompt conversion of sugars and complex phenols, with the formation of intermediate products, such as furfurals, which successively decompose, and more thermally resistant species, such as acetic acid, propionic acid, 1,2-ethanediol, ketones and especially cresols and phenols.     

Surface imaging using holographic optical tweezers

We present an imaging technique using an optically trapped cigar-shaped probe controlled using holographic optical tweezers. The probe is raster scanned over a surface, allowing an image to be taken in a manner analogous to scanning probe microscopy (SPM), with automatic closed loop feedback control provided by analysis of the probe position recorded using a high speed CMOS camera. The probe is held using two optical traps centred at least 10 μm from the ends, minimizing laser illumination of the tip, so reducing the chance of optical damage to delicate samples. The technique imparts less force on samples than contact SPM techniques, and allows highly curved and strongly scattering samples to be imaged, which present difficulties for imaging using photonic force microscopy. To calibrate our technique, we first image a known sample--the interface between two 8 μm polystyrene beads. We then demonstrate the advantages of this technique by imaging the surface of the soft alga Pseudopediastrum. The scattering force of our laser applied directly onto this sample is enough to remove it from the surface, but we can use our technique to image the algal surface with minimal disruption while it is alive, not adhered and in physiological conditions. The resolution is currently equivalent to confocal microscopy, but as our technique is not diffraction limited, there is scope for significant improvement by reducing the tip diameter and limiting the thermal motion of the probe.     

Single excitons in InGaN quantum dots on GaN pyramid arrays

Fabrication of single InGaN quantum dots (QDs) on top of GaN micropyramids is reported. The formation of single QDs is evidenced by showing single sub-millielectronvolt emission lines in microphotoluminescence (μPL) spectra. Tunable QD emission energy by varying the growth temperature of the InGaN layers is also demonstrated. From μPL, it is evident that the QDs are located in the apexes of the pyramids. The fact that the emission lines of the QDs are linear polarized in a preferred direction implies that the apexes induce unidirected anisotropic fields to the QDs. The single emission lines remain unchanged with increasing the excitation power and/or crystal temperature. An in-plane elongated QD forming a shallow potential with an equal number of trapped electrons and holes is proposed to explain the absence of other exciton complexes.     

Glyconanomaterials: Emerging applications in biomedical research

Carbohydrates constitute the most abundant organic matter in nature, serving as structural components and energy sources, and mediating a wide range of cellular activities. The emergence of nanomaterials with distinct optical, magnetic, and electronic properties has witnessed a rapid adoption of these materials for biomedical research and applications. Nanomaterials of various shapes and sizes having large specific surface areas can be used as multivalent scaffolds to present carbohydrate ligands. The resulting glyconanomaterials effectively amplify the glycan-mediated interactions, making it possible to use these materials for sensing, imaging, diagnosis, and therapy. In this review, we summarize the synthetic strategies for the preparation of various glyconanomaterials. Examples are given where these glyconanomaterials have been used in sensing and differentiation of proteins and cells, as well as in imaging glycan-medicated cellular responses.      

High resolution scanning gate microscopy measurements on InAs/GaSb nanowire Esaki diode devices

Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy （SGM） is one such gating technique that adds crucial spatial information, accessing the localized properties of semiconductor devices. Nanowires represent a central device concept due to the potential to combine very different materials. However, SGM on semiconductor nanowires has been limited to a resolution in the 50-100 nm range. Here, we present a study by SGM of newly developed III-V semiconductor nanowire InAs/GaSb heterojunction Esaki tunnel diode devices under ultra-high vacuum. Sub-5 nm resolution is demonstrated at room temperature via use of quartz resonator atomic force microscopy sensors, with the capability to resolve InAs nanowire facets, the InAs/GaSb tunnel diode transition and nanoscale defects on the device. We demonstrate that such measurements can rapidly give important insight into the device properties via use of a simplified physical model, without the requirement for extensive calculation of the electrostatics of the system. Interestingly, by precise spatial correlation of the device electrical transport properties and surface structure we show the position and existence of a very abrupt （〈10 nm） electrical transition across the InAs/GaSb junction despite the change in material composition occurring only over 30-50 nm. The direct and simultaneous link between nanostructure composition and electrical properties helps set important limits for the precision in structural control needed to achieve desired device performance.     

Inhibition of [methyl-3H]diazepam binding to rat brain membranes in vitro by dinatin and skrofulein

Two flavones, 4',5,7-trihydroxy-6-methoxy flavone (dinatin) and 4',5-dihydroxy-6, 7-dimethoxy flavone (skrofulein), were extracted from Artemisia herba alba L. Dinatin and skrofulein inhibited the binding of [methyl-3H]diazepam to rat brain membranes in vitro with IC50 of 1.3 and 23 mumol.L-1, respectively. The GABA-ratios (the ratio of IC50 values in the absence/presence of GABA in the binding assay) were 1.1 and 1.2 for dinatin and skrofulein, respectively. Both flavones induced a slight increase in [35S] TBPS binding. The data suggest that the flavones are antagonists or partial agonists of benzodiazepine receptors.     

DIVE—A platform for multi-user virtual environments

The Distributed Interactive Virtual Environment (DIVE) is an experimental software platform for the development of multi-user virtual reality applications. DIVE uses active replication and reliable multicast protocols to distribute data between participants. The distribution model enables a large number of users and applications to participate and interact in the same virtual environment. The DIVE platform offers a wide range of interaction support and user-related abstractions to ease the task of application and user interface construction.     

Measured and simulated nitrogen dynamics in winter wheat and a clay soil subjected to drought stress or daily irrigation and fertilization

The temporal dynamics of N in above- and below-ground parts of winter wheat and the dynamics of soil mineral-N were measured in the field in four treatments in wheat and a grass ley (L). The wheat treatments were: control (C), drought (D), daily irrigation (I), and daily irrigation and fertilization (IF). Nitrogen (20 g m^–2) was supplied as single doses in spring in C, D, and I, and according to a logistic N uptake function in IF. L, which was under establishment, was irrigated and fertilized in the same way as IF, but the total amount applied was only 5.6 g N m^–2. A soil nitrogen simulation model, SOILN, was used to combine crop and soil N data with measured litter decomposition rates and other major parts of the nitrogen cycle to calculate annual N budgets, based on daily model calculations. The dynamic patterns of crop N uptake and soil mineral N were similar in C, D, and I, although different in magnitude, but different in IF. Plant N uptake in C, D, and I was almost nil after anthesis, whereas it continued in IF until harvest. Generally, simulated soil mineral N levels (0–90 cm) agreed reasonably well with measurements on a yearly time scale, whereas their short-term dynamics were less well described by the simulations. We tested the hypothesis that the short-term variations were due to processes not included in the model,i.e., the loss of recently taken up plant N via roots during the growing season, and microbial N immobilization and remineralization processes induced by root-derived carbon. A simulated input to the soil of 150 g C m^–2 in IF, mimicking root-derived C, resulted in an improved agreement between simulated and measured short-term mineral N dynamics. Because of irrigation, net N mineralization of soil organic material in I and IF was about twice that in C and D, while that in L was about three times higher due to irrigation and high soil temperatures. Simulated N leaching during the following winter was highest in L, followed by I, IF, C and D. Measurements and simulations of N amounts in the system indicated that daily fertilization decreased N leaching compared with single-dose fertilization.     

Texture promoting capacity and EPS formation by lactic acid bacteria in three different oat-based non-dairy media

Four strains of lactic acid bacteria were used as pure or mixed cultures to investigate the texture-promoting capacity and exopolysaccharides (EPS) formation in three different oat-based, non-dairy milk products, Adavena G40, Adavena M40 (both with a dry matter content of 20%) and Mill Milk (with a dry matter content of 10%). Viscosity was measured at two different shear rates during 2 min of shear thinning. The highest viscosity was measured at a shear rate of 129 s^-1 when a mixed culture consisting of Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 and Lactobacillus brevis DSM 1269 was grown at 30 °C in the medium containing mostly glucose as the carbohydrate source (Adavena G40). The mixed culture consisting of Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 and Streptococcus thermophilus DSM 20259 gave the highest viscosity when using the medium with a dry matter content of 20% and maltose as the main carbohydrate source (Adavena M40). The EPS formation in the Adavena G40 medium was confirmed by isolating the soluble polymer fraction after fermentation. A higher yield of polymer dry mass was obtained from the samples with higher viscosity. The study shows that the co-operative growth that occurs when using mixed cultures also influences the EPS formation and final viscosity in the different oat-based media. This knowledge is of importance when strains are selected for the development of new kinds of fermented, oat-based, non-dairy products.