A direct comparison of one- and two-component dendritic self-assembled materials: elucidating molecular recognition pathways

This paper compares and contrasts, for the first time, one- and two-component gelation systems that are direct structural analogues and draws conclusions about the molecular recognition pathways that underpin fibrillar self-assembly. The new one-component systems comprise L-lysine-based dendritic headgroups covalently connected to an aliphatic diamine spacer chain via an amide bond, One-component gelators with different generations of headgroup (from first to third generation) and different length spacer chains are reported. The self-assembly of these dendrimers in toluene was elucidated using thermal measurements, circular dichroism (CD) and NMR spectroscopies, scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). The observations are compared with previous results for the analogous two-component gelation system in which the dendritic headgroups are bound to the aliphatic spacer chain noncovalently via acid-amine interactions. The one-component system is inherently a more effective gelator, partly as a consequence of the additional covalent amide groups that provide a new hydrogen bonding molecular recognition pathway, whereas the two-component analogue relies solely on intermolecular hydrogen bond interactions between the chiral dendritic headgroups. Furthermore, because these amide groups are important in the assembly process for the one-component system, the chiral information preset in the dendritic headgroups is not always transcribed into the nanoscale assembly, whereas for the two-component system, fiber formation is always accompanied by chiral ordering because the molecular recognition pathway is completely dependent on hydrogen bond interactions between well-organized chiral dendritic headgroups.

Seasonal variations of the physical and optical characteristics of Saharan Dust: results from the Dust outflow and Deposition to the Ocean (DODO) experiment

North African dust is important for climate through its direct radiative effect on solar and terrestrial radiation and its role in the biogeochemical system. The Dust Outflow and Deposition to the Ocean project (DODO) aimed to characterize the physical and optical properties of airborne North African dust in two seasons and to use these observations to constrain model simulations, with the ultimate aim of being able to quantify the deposition of iron to the North Atlantic Ocean. The in situ properties of dust from airborne campaigns measured during February and August 2006, based at Dakar, Senegal, are presented here. Average values of the single scattering albedo (0.99, 0.98), mass specific extinction (0.85 m^2 g^-1 , 1.14 m^2 g^-1 ), asymmetry parameter (0.68, 0.68), and refractive index (1.53--0.0005i,1.53--0.0014i) for the accumulation mode were found to differ by varying degrees between the dry and wet season, respectively. It is hypothesized that these differences are due to different source regions and transport processes which also differ between the DODO campaigns. Elemental ratios of Ca/Al were found to differ between the dry and wet season (1.1 and 0.5, respectively). Differences in vertical profiles are found between seasons and between land and ocean locations and reflect the different dynamics of the seasons. Using measurements of the coarse mode size distribution and illustrative Mie calculations, the optical properties are found to be very sensitive to the presence and amount of coarse mode of mineral dust, and the importance of accurate measurements of the coarse mode of dust is highlighted.

The spatial distribution and evolution characteristics of North Atlantic cyclones

A climatology of extratropical cyclones is produced using an objective method of identifying cyclones based on gradients of 1-km height wet-bulb potential temperature. Cyclone track and genesis density statistics are analyzed and this method is found to compare well with other cyclone identification methods. The North Atlantic storm track is reproduced along with the major regions of genesis. Cyclones are grouped according to their genesis location and the corresponding lysis regions are identified. Most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and the sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher 1-km height relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of preexisting “parent” cyclones. The evolution characteristics of composite west and east Atlantic cyclones have been compared. The ratio of their upper- to lower-level forcing indicates that type B cyclones are predominant in both the west and east Atlantic, with strong upper- and lower-level features. Among the remaining cyclones, there is a higher proportion of type C cyclones in the east Atlantic, whereas types A and C are equally frequent in the west Atlantic.

Decomposition in soil and chemical characteristics of pollen

The input to soils made by pollen and its subsequent mineralization has rarely been investigated from a soil microbiological point of view even though the small but significant quantities of C and N in pollen may make an important contribution to nutrient cycling. The relative resistance to decomposition of pollen exines (outer layers) has led to much of the focus of pollen in soil being on its preservation for archaeological and palaeo-ecological purposes. We have examined aspects of the chemical composition and decomposition of pollen from birch (Betula alba) and maize (Zea mays) in soil. The relatively large N contents, small C-to-N ratios and large water-soluble contents of pollen from both species indicated that they would be readily mineralized in soil. When added to soil and incubated at 16 degrees C an amount of C equivalent to 22-26% of the added pollen C was lost as CO2 within 22 days, with the Z. mays pollen decomposing faster. For B. alba pollen, the water-soluble fraction decomposed faster than the whole pollen and the insoluble fraction decomposed more slowly over 22 days. By contrast, there were no significant differences in the decomposition rates of the different fractions from Z. mays pollen. Solid-state C-13 nuclear magnetic resonance (NMR) revealed no gross chemical differences between the pollen of these two species, with strong resonances in the alkyl- and methyl-C region (0-45 p.p.m.) indicative of aliphatic compounds, the O-alkyl-C (60-90 p.p.m.) and the acetal- and ketal-C region (90-110 p.p.m.) indicative of polysaccharides, and the carbonyl-C region indicative of peptides and carboxylic acids. In addition, both pollens gave a small but distinct resonance at 55 p.p.m. attributed to N-alkyl-C. The resonances attributed to polysaccharides were lost completely or substantially reduced after decomposition.

Decomposition in soil and chemical characteristics of pollen

The input to soils made by pollen and its subsequent mineralization has rarely been investigated from a soil microbiological point of view even though the small but significant quantities of C and N in pollen may make an important contribution to nutrient cycling. The relative resistance to decomposition of pollen exines (outer layers) has led to much of the focus of pollen in soil being on its preservation for archaeological and palaeo-ecological purposes. We have examined aspects of the chemical composition and decomposition of pollen from birch (Betula alba) and maize (Zea mays) in soil. The relatively large N contents, small C-to-N ratios and large water-soluble contents of pollen from both species indicated that they would be readily mineralized in soil. When added to soil and incubated at 16 degrees C an amount of C equivalent to 22-26% of the added pollen C was lost as CO2 within 22 days, with the Z. mays pollen decomposing faster. For B. alba pollen, the water-soluble fraction decomposed faster than the whole pollen and the insoluble fraction decomposed more slowly over 22 days. By contrast, there were no significant differences in the decomposition rates of the different fractions from Z. mays pollen. Solid-state C-13 nuclear magnetic resonance (NMR) revealed no gross chemical differences between the pollen of these two species, with strong resonances in the alkyl- and methyl-C region (0-45 p.p.m.) indicative of aliphatic compounds, the O-alkyl-C (60-90 p.p.m.) and the acetal- and ketal-C region (90-110 p.p.m.) indicative of polysaccharides, and the carbonyl-C region indicative of peptides and carboxylic acids. In addition, both pollens gave a small but distinct resonance at 55 p.p.m. attributed to N-alkyl-C. The resonances attributed to polysaccharides were lost completely or substantially reduced after decomposition.

Morphological and molecular characteristics of a new species of Pasteuria parasitic on Meloidogyne ardenensis

A species of the hyper-parasitic bacterium Pasteuria was isolated from the root-knot nematode Meloidogyne ardenensis infecting the roots of ash (Fraxinus excelsior). It is morphologically different from some other Pasteuria pathogens of nematodes in that the spores lack a basal ring on the ventral side of the spore and have a unique clumping nature. Transmission electron microscopy (TEM) showed that the clumps of spores are not random aggregates but result from the disintegration of the suicide cells of the thalli. Sporulation within each vegetative mycelium was shown to be asynchronous. In addition to the novel morphological features 16S rRNA sequence analysis showed this to be a new species of Pasteuria which we have called P. hartismeri. Spores of P. hartismeri attach to juveniles of root-knot nematodes infecting a wide range of plants such as mint (Meloidogyne hapla), rye grass (unidentified Meloidogyne sp.) and potato (Meloidogyne fallax). (c) 2007 Elsevier Inc. All rights reserved.

Intake, live-weight gain and carcass characteristics of beef cattle given diets based on forage maize silage harvested at different stages of maturity

Advancing maturity of forage maize is associated with increases in the proportion of dry matter (DM) and starch, and decreases in the proportions of structural carbohydrates in the ensiled crop. This experiment investigated the effects of three maize silages of 291 (low), 339 (medium) and 393 (high) g DM per kg fresh weight on the performance of 48 Simmental. Holstein-Friesian cattle. Equal numbers of steers (mean start weight = 503 (s.d. 31.3) kg) and heifers (mean start weight = 378 (s.d. 11.2) kg) were offered individually isonitrogenous diets composed of the three silages plus a protein supplement with minerals once daily until slaughter at the target live weight of 575 and 475 kg for steers and heifers, respectively. Intake was reduced on the low diet (P < 0.01) compared with the other two treatments. Dietary starch intake increased by a total of 1 kg/day between low and medium diets but by only 0.2 kg/day between medium and high diets. Unlike starch intake, total neutral-detergent fibre intake showed no significant difference (P > 0.05) between diets. There were no differences in live-weight gain between treatments but differences (P < 0.05) in food conversion efficiency indicated relative gains of 115, 100 and 102 g gain per kg DM intake for diets low, medium and high, respectively. There were no differences between diets in carcass weights, fat score and overall conformation.

Chemical composition and fermentation characteristics of grain and different parts of the stover from maize land races harvested at different growing periods in two zones of central Mexico

The objective of this work was to determine the rumen fermentation characteristics of maize land races used as forage in central Mexico. In vitro gas production (ml per 200 mg dry matter (DM)) incubations were carried out, and cumulative gas volumes were fitted to the Krishnamoorthy et al. (1991) model. The trial used a split-plot design with cultivation practices associated with maize colour (COL) as the main plot with three levels: white, yellow and black maize; growing periods (PER) were the split plots where PER1, PER2 and PER3 represented the first, second and third periods, respectively and two contrasting zones (Z1 = valley and Z2 = mountain) were used as blocking factors. The principal effects observed were associated with the maturity of the plants and potential gas production increased (P < 0.05) in stems (PER 1 = 51.8, PER2 = 56.3, PER3 = 58.4 ml per 200 mg DM) and in whole plant (PER 1 = 60.9, PER2 = 60.8, PER3= 70.9 ml per 200 mg DM). An inverse effect was observed with fermentation rates in leaves (P < 0.01) with 0.061, 0.053 and 0.0509 (per h) and in whole plant (P < 0.05) with 0.068, 0.057, 0.050 (per h) in PER1, PER2 and PER3 respectively. The digestibility of the neutral-detergent fibre (NDF) decreased with maturity especially in leaves (P < 0.05) with values of 0.71, 0.67 and 0.66 g/kg; in rachis (P < 0.01) 0.75, 0.72, and 0.65 in PER1, PER2 and PER3 respectively. The NDF content in leaves in leaves (668, 705 and 713 g/kg DM for PER1, PER2 and PER3, respectively), stems (580, 594 and 644 g/kg DM) and, husk (663, 774 and, 808 g/kg DM) increased (P < 0.05) with increasing plant maturity, rachis were significantly different between periods (P < 0.01). The structure with-the best nutritive characteristics was the husk, because it had the lowest fibre contents, especially in acid-detergent lignin, with values of 22.6, 28.6 and 37.6 g/kg DM in PER1, PER2 and PER3, respectively.

The survival, growth and carcase characteristics of crossbred beef cattle in Tanzania

Sires of seven Bos taurus beef breeds were mated with Bos indicus Boran cows at two sites, one near sea level and the other at about 1000 m altitude, and over three years. Purebred Boran calves provided controls for comparisons between sire breeds for growth to 4 years of age, mortality and carcase characteristics in a range environment where all the animals were kept under a similar management regime. Numerous sire breed x site, sire breed x year of birth and site x year of birth interactions were established. Mortality was high, but there was no significant sire breed effect, although purebred Borans had a higher survival than crossbred calves. There was no significant difference between genotypes in birth weight. Generally, Bos taurus cross steers achieved greater live weight gains and heavier carcase weights at 4 years of age than did purebred Borans. Limousin-cross steers had significantly (p<0.05) less fat in the tenth rib sample joint than any of the other genotypes. A productivity index that combined calf survival and carcase weight indicated that the Chianina crosses were more productive than any other genotype at either site. Purebred Borans were more productive than all the Bos taurus crossbreds with the exception of the Chianina crosses at site 1, but were only superior to the Limousin crosses at site 2, which was at the higher altitude. When lean meat yield was introduced into the productivity index, the Boran purebreds were the least productive at site 2.

Microstructure and thermal characteristics of Thai indigenous and broiler chicken muscles

The microstructure and thermal characteristics of Thai indigenous (Gallus domesticus) and broiler chicken (commercial line CP707) biceps femoris and pectoralis muscles were determined. Perimysium thicknesses were 14.2 mum for biceps femoris muscle and 7.10 mum for pectoralis muscle of indigenous chicken muscles, thicker than those of broiler muscles, which were 9.93 mum for biceps femoris muscle and 3.87 mum for pectoralis muscle (P < 0.05). Five endothermic peaks with peak transition temperatures (T-p) of 54.9, 61.7, 65.4, 70.6, and 76.1degreesC were obtained for broiler pectoralis muscle, whereas only 3 endothermic peaks (T-P of 56.6, 62.6, and 74.9degreesC were obtained for broiler biceps femoris muscle. Thai indigenous biceps femoris and pectoralis muscles had endothermic peaks with T-P ranges of 53.5 to 54.8, 60.7 to 61.9, and 75.9 to 76.9degreesC. The fiber diameters of Thai indigenous chicken muscles were greater (P < 0.05) than those of the broiler, 31.7 vs. 20.4 mum for biceps femoris muscle and 28.9 vs. 26.6 pm for pectoralis muscle, respectively. After cooking at 80degreesC for 10 min, the fiber diameter of indigenous chicken muscles significantly decreased while those of the broiler significantly increased. The mean of sarcomere lengths of the raw muscles ranged from 1.56 to 1.64 mun and decreased to 0.92 to 1.32 mum (P < 0.001) for broiler muscles and 1.22 to 1.35 mum (P < 0.001) for indigenous chicken muscles after cooking. The perimysium and endomysium of broiler muscles melted after cooking at 80degreesC, however, only slight disintegration was observed in these tissues in the indigenous chicken muscles.

The effect of free Ca2+ on the heat stability and other characteristics of low-heat skim milk powder

Low-heat skim milk powder (SMP), reconstituted to 25% total solids, was found to have poor heat stability. This could be improved by reducing the free Ca2+ concentration to 1.14 mm, or lower, by the addition of either Amberlite IR-120 ion-exchange resin in its sodium form or tri-sodium citrate in skim milk prior to evaporation and spray drying. Reduction in Ca2+ concentration was accompanied by increases in pH, particle size, and kinematic viscosity, and by a reduction in zeta-potential and changes in colour. In-container sterilisation of the reconstituted powder increased particle size, zeta-potential, kinematic viscosity and a* and b* values. However. Ca2+ concentration, pH and whiteness decreased. This study elucidated the importance of Ca2+ concentration and pH on heat stability of low-heat SMP, suggesting that Ca2+ concentration and pH in bulk milk are useful indicators for ensuring that spray dried milk powder has good heat stability. (C) 2009 Elsevier Ltd. All rights reserved.

Differential phenotypic and genotypic characteristics of qnrS1-harboring plasmids carried by hospital and community commensal enterobacteria

The qnrS1 gene induces reduced susceptibility to fluoroquinolones in enterobacteria. We investigated the structure, antimicrobial susceptibility phenotype, and antimicrobial resistance gene characteristics of qnrS1 plasmids from hospitalized patients and community controls in southern Vietnam. We found that the antimicrobial susceptibilities, resistance gene characteristics, and plasmid structures of qnrS1 plasmids from the hospital differed from those from the community. Our data imply that the characteristics of the two plasmid groups are indicative of distinct selective pressures in the differing environments.

Cognitive, affective and behavioural characteristics of mothers with anxiety disorders in the context of child anxiety disorder

Parental emotional distress, particularly high maternal anxiety, is one of the most consistent predictors of child anxiety treatment outcome. In order to identify the cognitive, affective and behavioural parenting characteristics of mothers of children with anxiety disorders who themselves have an anxiety disorder, we assessed the expectations and appraisals of 88 mothers of anxious children (44 not anxious (NONANX) and 44 with a current anxiety disorder (ANX)) before and after interacting with their 7-12 year old children. There were no observed differences in anxiety and avoidance among children of ANX and NONANX mothers, but, compared to NONANX mothers, ANX mothers held more negative expectations and differed on observations of intrusiveness, expressed anxiety, warmth and the quality of the relationship. Associations were moderated by the degree to which children expressed anxiety during the tasks. Maternal reported negative emotions during the task significantly mediated the association between maternal anxiety status and the observed quality of the relationship. These findings suggest that maternal anxiety disorder is associated with reduced tolerance of children’s negative emotions. This may interfere with the maintenance of a positive, supportive mother-child interaction under conditions of stress, and as such impede optimum treatment outcomes. The findings identify potential cognitive, affective and behavioural targets to improve treatment outcomes for children with anxiety disorders in the context of a current maternal anxiety disorder.

Genetic relatedness and phenotypic characteristics of Treponema associated with human periodontal tissues and ruminant foot disease

Treponema have been implicated recently in the pathogenesis of digital dermatitis (DID) and contagious ovine digital dermatitis (CODD) that are infectious diseases of bovine and ovine foot tissues, respectively. Previous analyses of treponemal 16S rDNA sequences, PCR-amplified directly from DID or CODD lesions, have suggested relatedness of animal Treponema to some human oral Treponema species isolated from periodontal tissues. In this study a range of adhesion and virulence-related properties of three animal Treponema isolates have been compared with representative human oral strains of Treponema denticola and Treponema vincentii. In adhesion assays using biotinylated treponemal cells, T denticola cells bound in consistently higher numbers to fibronectin, laminin, collagen type 1, gelatin, keratin and lactoferrin than did T. vincentii or animal Treponema isolates. However, animal DID strains adhered to fibrinogen at equivalent or greater levels than T denticola. All Treponema strains bound to the amino-terminal heparin l/fibrin I domain of fibronectin. 16S rDNA sequence analyses placed ovine strain UB1090 and bovine strain UB1467 within a cluster that was phylogenetically related to T vincentii, while ovine strain UB1466 appeared more closely related to T denticola. These observations correlated with phenotypic properties. Thus, T denticola ATCC 35405, GM-1, and Treponema UB1466 had similar outer-membrane protein profiles, produced chymotrypsin-like protease (CTLP), trypsin-like protease and high levels of proline iminopeptidase, and co-aggregated with human oral bacteria Porphyromonas gingivalis and Streptococcus crista. Conversely, T vincentii ATCC 35580, D2A-2, and animal strains UB1090 and UB1467 did not express CTLP or trypsin-like protease and did not co-aggregate with P. gingivalis or S. crista. Taken collectively, these results suggest that human oral-related Treponema have broad host specificity and that similar control or preventive strategies might be developed for human and animal Treponema-associated infections.