Probing the pore wall structure of nanoporous carbons using adsorption

Hitherto, adsorption has been traditionally used to study only the porous structure in disordered materials, while the structure of the solid phase skeleton has been probed by crystallographic methods such as X-ray diffraction. Here we show that for carbons density functional theory, suitably adapted to consider heterogeneity of the pore walls, can be reliably used to probe features of the solid structure hitherto accessibly only approximately even by crystallographic methods. We investigate a range of carbons and determine pore wall thickness distributions using argon adsorption, with results corroborated by X-ray diffraction.

A novel method to prepare mesoporous nano-zirconia

A novel method to prepare mesoporous zirconia was developed. The synthesis was carried out in the presence of PEO surfactants via solid-state reaction. The materials exhibit strong diffraction peak at low 2-theta angle and their nitrogen adsorption/desorption isotherms are typical of IV type with H3 hysteresis loops. The pore structure examined by TEM can be described as wormhole domains. The tetragonal zirconia nanocrystals are uniform in size (around 1.5nm) and their pores center at around 4.6nm. The zirconia nanocrystal growth is mainly via an aggregation mechanism. This study also reveals that the PEO surfactants can interact with the Zr-O-Zr framework to reinforce the thermal stability of zirconia. The ratio of NaOH to ZrOCl2, crystallization and calcination temperature play an important role in the synthesis of mesoporous zirconia.

Noninvasive tests for arterial structure, function, and compliance: Do they identify risk or diagnose disease?

Background: Brachial artery reactivity (BAR), carotid intima-media thickness (IMT), and applanation tonometry for evaluation of total arterial compliance may provide information about preclinical vascular disease. We sought to determine whether these tests could be used to identify patients with coronary artery disease (CAD) without being influenced by their ability to identify those at risk ford CAD developing. Methods: We studied 100 patients and compared 3 groups: 35 patients with known CAD; 34 patients with symptoms and risk factors but no CAD identified by stress echocardiography (risk group); and 31 control subjects. BAR and IMT were measured using standard methods, and total arterial compliance was calculated by the pulse-pressure method from simultaneous radial applanation tonometry and pulsed wave Doppler of the left ventricular outflow. Ischemia was identified as a new or worsening wall-motion abnormality induced by stress. Results: In a comparison between the control subjects and patients either at risk for developing CAD or with CAD, the predictors of risk for CAD were: age (P = .01); smoking history (P = .002); hypercholesterolemia (P = .002); and hypertension (P = .004) (model R = 0.82; P = .0001). The independent predictors of CAD were: IMT (P = .001); BAR (P = .04); sex (P = .005); and hypertension (P = .005) (model R = 0.80; P = .0001). Conclusion: IMT, BAR, and traditional cardiovascular risk factors appear to identify patients at risk for CAD developing. However, only IMT was significantly different between patients at risk for developing CAD and those with overt CAD.

Population structure of the peridomestic mosquito Ochlerotatus notoscriptus in Australia

Ochlerotatus notoscriptus (Skuse) (Diptera: Culicidae) is the predominant peridomestic mosquito in Australia where it is the primary vector of dog heartworm, Dirofilaria immitis (Leidy), and a potentially important vector of arboviruses (Barmah Forest, Ross River) with geographical variation of vector competence. Although widespread, Oc. notoscriptus has low dispersal ability, so it may have isolated subpopulations. The identification of gene flow barriers may assist in understanding arbovirus epidemiology and disease risk, and for developing control strategies for this species. We investigated the population structure of Oc. notoscriptus from 17 sites around Australia, using up to 31 putative allozyme loci, 11 of which were polymorphic. We investigated the effect of larval environment and adult morphology on genetic variation. At least five subpopulations were found, four in New South Wales (NSW) and one unique to Darwin. Perth samples appear to be a product of recent colonization from the Australian east coast. For NSW sites, a Mantel test revealed an isolation by distance effect and spatial autocorrelation analysis revealed an area of effective gene flow of 67 km, which is high given the limited dispersal ability of this species. No consistent difference was observed between 'urban' and 'sylvan' habitats, which suggests frequent movement between these sites. However, a finer-scaled habitat study at Darwin revealed small but significant allele frequency differences, including for Gpi. No fixed allozyme differences were detected for sex, size, integument colour or the colour of species-diagnostic pale scales on the scutum. The domestic habit of Oc. notoscriptus and assisted dispersal have helped to homogenize this species geographically but population structure is still detectable on several levels associated with geographical variation of vector competence.

Removal of the N-linked glycan structure from the peanut peroxidase prxPNC2: Influence on protein stability and activity

Lines of transgenic tobacco have been generated that are transformed with either the wild-type peanut peroxidase prxPNC2 cDNA, driven by the CaMV3 5S promoter (designated 35S::prxPNC2-WT) or a mutated PNC2 cDNA in which the asparagine residue (Asn(189)) associated with the point of glycan attachment (Asn(189)) has been replaced with alanine (designated 35S::prxPNC2-M). PCR, using genomic DNA as template, has confirmed the integration of the 35S::prxPNC2-WT and 35::prxPNC2-M constructs into the tobacco genome, and western analysis using anti-PNC2 antibodies has revealed that the prxPNC2-WT protein product (PNC2-WT) accumulates with a molecular mass of 34,670 Da, while the prxPNC2-M protein product (PNC2-M) accumulates with a molecular mass of 32,600 Da. Activity assays have shown that both PNC2-WT and PNC2-M proteins accumulate preferentially in the ionically-bound cell wall fraction, with a significantly higher relative accumulation of the PNC2-WT isoenzyme in the ionically-bound fraction when compared with the PNC2-M isoform. Kinetic analysis of the partially purified PNC2-WT isozyme revealed an affinity constant (apparent K-m) of 11.2 mM for the reductor substrate guaiacol and 1.29 mM for H2O2, while values of 11.9 mM and 1.12 mM were determined for the PNC2-M isozyme. A higher Arrenhius activation energy (E,,) was determined for the PNC2-M isozyme (22.9 kJ mol(-1)), when compared with the PNC2-WT isozyme (17.6 kJ mol(-1)), and enzyme assays have determined that the absence of the glycan influences the thermostability of the PNC2-M isozyme. These results are discussed with respect to the proposed roles of N-linked glycans attached to plant peroxidases. (c) 2005 Elsevier Ltd. All rights reserved.

Discovery of a large-scale wall in the direction of Abell 22

We report on the discovery of a large-scale wall in the direction of Abell 22. Using photometric and spectroscopic data from the Las Campanas Observatory and Anglo-Australian Telescope Rich Cluster Survey, Abell 22 is found to exhibit a highly unusual and striking redshift distribution. We show, by examining the galaxy distributions both in redshift space and on the colour-magnitude plane, that Abell 22 exhibits a foreground wall-like structure. A search for other galaxies and clusters in the nearby region using the 2dF Galaxy Redshift Survey data base suggests that the wall-like structure is a significant large-scale, non-virialized filament which runs between two other Abell clusters either side of Abell 22. The filament stretches over at least > 40 h(-1) Mpc in length and 10 h(-1) Mpc in width at the redshift of Abell 22.

Multigradient field-active contour model for multilayer boundary detection of ultrasound rectal wall image

Extraction and reconstruction of rectal wall structures from an ultrasound image is helpful for surgeons in rectal clinical diagnosis and 3-D reconstruction of rectal structures from ultrasound images. The primary task is to extract the boundary of the muscular layers on the rectal wall. However, due to the low SNR from ultrasound imaging and the thin muscular layer structure of the rectum, this boundary detection task remains a challenge. An active contour model is an effective high-level model, which has been used successfully to aid the tasks of object representation and recognition in many image-processing applications. We present a novel multigradient field active contour algorithm with an extended ability for multiple-object detection, which overcomes some limitations of ordinary active contour models—"snakes." The core part in the algorithm is the proposal of multigradient vector fields, which are used to replace image forces in kinetic function for alternative constraints on the deformation of active contour, thereby partially solving the initialization limitation of active contour for rectal wall boundary detection. An adaptive expanding force is also added to the model to help the active contour go through the homogenous region in the image. The efficacy of the model is explained and tested on the boundary detection of a ring-shaped image, a synthetic image, and an ultrasound image. The experimental results show that the proposed multigradient field-active contour is feasible for multilayer boundary detection of rectal wall

Mesoporous nanocrystalline zirconia with lamellar and MSU structure

Without introduction of any stabilizer, the mesoporous nanocrystalline zirconia with lamellar and MSU structure was obtained via solid state reaction coupled with surfactant templating method. The phase, surface area and pore structure of zirconia prepared with this novel method could be designed, tailored and controlled by varying synthesis parameters. The phase transformation was controlled by particle size. The mesostructure possesses nanocrystalline pore wall, which renders it more thermally stable than amorphous framework. The results suggest strongly that in solid state synthesis system mesostructure formation still follow the supramolecular self-assembly mechanism. The lamellar and reverse hexagonal structure could be transformed at different OH-/Zr molar ratios in order to sustain the low surface energy of the mesophases. The lamellar structure was preferred at higher OH-/Zr molar ratios but reverse hexagonal was at low ratios.

Structure of saccharose-based carbon and transport of confined fluids: hybrid reverse Monte Carlo reconstruction and simulation studies

We present results of the reconstruction of a saccharose-based activated carbon (CS1000a) using hybrid reverse Monte Carlo (HRMC) simulation, recently proposed by Opletal et al. [1]. Interaction between carbon atoms in the simulation is modeled by an environment dependent interaction potential (EDIP) [2,3]. The reconstructed structure shows predominance of sp(2) over sp bonding, while a significant proportion of sp(3) hybrid bonding is also observed. We also calculated a ring distribution and geometrical pore size distribution of the model developed. The latter is compared with that obtained from argon adsorption at 87 K using our recently proposed characterization procedure [4], the finite wall thickness (FWT) model. Further, we determine self-diffusivities of argon and nitrogen in the constructed carbon as functions of loading. It is found that while there is a maximum in the diffusivity with respect to loading, as previously observed by Pikunic et al. [5], diffusivities in the present work are 10 times larger than those obtained in the prior work, consistent with the larger pore size as well as higher porosity of the activated saccharose carbon studied here.

Perindopril, an angiotensin converting enzyme inhibitor, in pulmonary hypertensive rats: comparative effects on pulmonary vascular structure and function

1 Hypoxic pulmonary hypertension in rats (10% O-2, 4 weeks) is characterized by changes in pulmonary vascular structure and function. The effects of the angiotensin converting enzyme inhibitor perindopril (oral gavage, once daily for the 4 weeks of hypoxia) on these changes were examined. 2 Perindopril (30 mg kg(-1) d(-1)) caused an 18% reduction in pulmonary artery pressure in hypoxic rats. 3 Structural changes (remodelling) in hypoxic rats included increases in (i) critical closing pressure in isolated perfused lungs (remodelling of arteries (50 mu m 0.d.) and (ii) medial wall thickness of intralobar pulmonary arteries, assessed histologically (vessels 30-100 and 101-500 mu m o.d.). Perindopril 10 and 30 mg kg(-1) d(-1) attenuated remodelling in vessels less than or equal to 100 mu m (lungs and histology), 30 mg kg(-1) d(-1) was effective in vessels 101-500 mu m but neither dose prevented hypertrophy of main pulmonary artery. 3 mg kg(-1) d(-1) was without effect. 4 Perindopril (30 mg kg(-1) d(-1)) prevented the exaggerated hypoxic pulmonary vasoconstrictor response seen in perfused lungs from hypoxic rats but did not prevent any of the functional changes (i.e. the increased contractions to 5-HT, U46619 (thromboxane-mimetic) and K+ and diminished contractions to angiotensins I and II) seen in isolated intralobar or main pulmonary arteries. Acetylcholine responses were unaltered in hypoxic rats. 5 We conclude that, in hypoxic rats, altered pulmonary vascular function is largely independent of remodelling. Hence any drug that affects only remodelling is unlikely to restore pulmonary vascular function to normal and, like perindopril, may have only a modest effect on pulmonary artery pressure.