Size-selective fractionation of nanoparticles at an application scale using CO2 gas-expanded liquids.

Size-based fractionation of nanoparticles remains a non-trivial task for the preparation of well-defined nanomaterials for certain applications and fundamental studies. Typical fractionation techniques prove to be inefficient for large nanoparticle quantities due to several factors including the expense of equipment, throughput constraints, and the amount of organic solvent waste produced. Through the use of the pressure-tunable physico-chemical properties of CO2-expanded liquids, a rapid, precise, and environmentally sustainable size-selective fractionation of ligand-stabilized nanoparticles is possible through simple variations in applied CO2 pressure. An apparatus capable of fractionating large quantities of nanoparticles into distinct fractions with the ability to control mean diameters and size distributions has been developed. This apparatus consists of three vertically mounted pressure vessels connected in series with needle valves. This process, at current design scales, operated at room temperature, and CO2 pressures between 0 and 50 bar, results in a batch size-selective fractionation of a concentrated nanoparticle dispersion. This paper presents this new apparatus and the separation results of various single pass fractionations as well as recursive fractionations.

Causal Role of Xylella fastidiosa in Oleander Leaf Scorch Disease.

ABSTRACT A lethal leaf scorch disease of oleander (Nerium oleander) appeared in southern California in 1993. A bacterium, Xylella fastidiosa, was detected by culturing, enzyme-linked immunoassay, and polymerase chain reaction in most symptomatic plants but not in symptomless plants or negative controls. Inoculating oleanders mechanically with X. fastidiosa cultures from diseased oleanders caused oleander leaf scorch (OLS) disease. The bacterium was reisolated from inoculated plants that became diseased. Three species of xylem sap-feeding leafhoppers transmitted the bacterium from oleander to oleander. The bacterium multiplied, moved systemically, and caused wilting in Madagascar periwinkle (Catharanthus rosea) and leaf scorch in periwinkle (Vinca major) in a greenhouse after inoculation with needle puncture. No bacterium was reisolated from grapevine (Vitis vinifera), peach (Prunus persica), olive (Olea europaea), California blackberry (Rubus ursinus), or valley oak (Quercus lobata) mechanically inoculated with OLS strains of X. fastidiosa. A 500-bp sequence of the 16S-23S ribosomal intergenic region of oleander strains showed 99.2% identity with Pierce's disease strains, 98.4% identity with oak leaf scorch strains, and 98.6% identity with phony peach, plum leaf scald, and almond leaf scorch strains.

Developmental patterns of human dental morphological traits.

A longitudinal series of casts of the deciduous and permanent dentitions of 827 children from Burlington Growth Centre study was examined for 5 traits: shovel-shape of the incisors, cusp six, cusp seven and protostylid of the mandibular molars, and Carabelli trait of the maxillary molars. The changing trait frequencies found support the concept of morphogenetic gradients of expression for non-metric traits from deciduous to permanent teeth. Tests of association showed that if shovelling was present on the deciduous incisors it would usually appear on the permanent successors. Tests of association between the other 4 traits on deciduous second molars and the permanent molars support the view that the second deciduous molar belongs to the total molar tooth district. This gradient expression of morphological traits would fit either the field or clone concepts, but it, and the intra-individual discordances for trait presence, probably reflects the great temporal spacing of dental development seen in man.

Physical therapy management of hand fractures.

Hand fractures can be a complicated management dilemma for both the general clinician and the specialist. To better equip the therapist to treat fractures in the hand, a brief review of bone and articular cartilage healing and the effects of immobilization are reviewed. Active, passive, and resistive exercises for the patient with hand fracture are reviewed in addition to treatment of the associated problems of scar formation, edema, and pain. Static and dynamic splinting techniques are also discussed.

Fate of Pierce's Disease Strains of Xylella fastidiosa in Common Riparian Plants in California.

The fate of strains of the bacterium Xylella fastidiosa that cause Pierce's disease of grapevines was investigated in 33 species of mostly perennial plants common in riparian habitats in northern coastal California grape-growing regions. Plants were inoculated in the field with needle puncture using cultured cells of X. fastidiosa as inoculum or inoculated in the laboratory with infective insect vectors (Graphocephala atropunctata). Populations of X. fastidiosa were highest in most plant species within 3 to 6 weeks of inoculation, followed by declines in populations of viable bacteria over the next 3 to 4 months. Homogenates of petioles of California black walnut (Juglans hindsii) and coffeeberry (Rhamnus californica) inhibited in vitro growth of X. fas-tidiosa, precluding culture of the bacterium from these plants. Big leaf maple (Acer macrophyl-lum), California buckeye (Aesculus californica), California blackberry (Rubus ursinus), coast live oak (Quercus agrifolia), elderberry (Sambucus mexicana), French broom (Genista monspessulanus), periwinkle (Vinca major), valley oak (Quercus lobata), and the grape root-stock Vitis rupestris supported systemic populations of X. fastidiosa that survived throughout the year outdoors in Napa Valley, California.

A discriminant function analysis of deciduous teeth to determine sex.

Studies of deciduous teeth have concluded that crown size differences in these teeth between males and females are not reliable sex discriminators, in contrast to such differences in permanent teeth. This study measured the mesiodistal and faciolingual crown diameters of all deciduous teeth, as well as those of the permanent first molars, of 162 children from the Burlington Orthodontic Growth Study, conducted earlier in Burlington, Ontario, Canada. All 40 deciduous tooth diameters (20 mesiolingual and 20 faciolingual) were significantly different between the sexes, as were the permanent tooth diameters. Using three to five measurements of deciduous teeth, discriminant analyses of several samplings of these children produced discriminant functions in which 76 to 90% of the holdout samples were correctly classified by sex. Combinations of deciduous and permanent measurements were used to classify 83 to 85% of the holdout samples correctly. When compared with published data on other sample populations, the Burlington group is the most dimorphic for deciduous teeth and is within the range of permanent tooth dimorphisms of other populations. The level of classification accuracy, when using discriminant analysis of the deciduous teeth, can approach the accuracy levels of analysis using the permanent teeth.

Midline facial tissue thicknesses of subadults from a longitudinal radiographic study.

Fourteen midline facial tissue measurements were taken from 615 tracings of lateral radiographs of subadults aged 8 to 20 years. The data were collected to examine two questions: First, are there differences in facial soft tissue measurements between female and male subadults? Second, do facial tissue thicknesses change as children grow? Results indicate that males exhibit greater tissue thickness measurements than females but only significantly so after age 14. Results further indicate a trend of increased facial tissue thickness as individuals grow; however, correlations are weak and suggest that other unknown factors are involved. Data presented here can be of practical application for facial reproduction in forensic cases.

Evaluation of morphological and histological adult skeletal age-at-death estimation techniques using ribs.

Adult age-at-death estimation standards were applied to an independent sample (N = 50, 55) of documented ages 17.5 to 95 years. Estimates derived from the sternal rib end morphological and from the cortical rib histological techniques were compared with each other and to the documented ages. Comparisons to the documented ages reveal no statistically significant differences between the techniques. However, the comparison of each individual's estimates show a poor correlation (r = 0.54) despite the equal performance of the age estimations on the entire sample. Averaging of the two rib age estimates results in an estimate with a stronger Pearson's r (0.86) and a lower standard error of the estimate (7.5 years).

Surface and cross-sectional comparisons of bone growth remodeling.

Broad, regional surface and cross-sectional assessments of growth remodeling in the macaque and human lower limb bones were compared using thin sections, stereomicroscopy and scanning election microscopy. In general, areas identified by cortical tissue type in thin sections as depository showed smooth surfaces under the SEM. Areas identified as resorptive in cross section always showed resorption lacunae with the SEM. Actively forming bone surfaces as described by previous SEM studies were not encountered even though rapidly forming cortical tissues were encountered with the light microscope. These results are consistent both for fresh and exhumed bone.

Dimensional and discrete dental trait asymmetry relationships.

Inuit (Eskimos) from the Foxe Basin region of the Northwest Territories, Canada, were studied to ascertain the amount of dimensional and morphological asymmetry in their dentitions. The results indicate that dimensional asymmetry does not appear to be greater on either the maxillary or mandibular teeth. Both types of asymmetry show partial conformity to the model of tooth fields with an increasing amount of asymmetry as one goes distally in each tooth group. The morphological asymmetry exception, the mandibular incisors, follows Dahlberg's "Field Concept." Rank-order correlations between the amount of dimensional asymmetry and morphological asymmetry reveal no detectable patterns. There appear to be no associations between the presence or absence of morphological asymmetry and the size of the tooth. This lack of association might be explained by differences in developmental timing of tooth dimensions and morphological traits; however, such a hypothesis requires experimental testing. In this population and those for which published results are available, it is practically impossible to overcome the "noise" level and test recent hypotheses regarding random dental asymmetry.

A family study of two skeletal variants: atlas bridging and clinoid bridging.

The frequency of two non-metric skeletal traits, atlas bridging and clinoid bridging, were examined serially in a randomly chosen sample of 147 families who participated in the Burlington Growth Study. The sample is representative of an Ontario white Anglo-Saxon population. Partial and complete atlas briging occurred in 29.2% of the sample, partial and complete clinoid bridging in 15.2%. Atlas bridging appears at an average age of 10.7 years, clinoid bridging at seven years, demonstrating that these characters are not simply expressions of soft tissue sclerosis in old age. Both traits show no strong associations with bone robusticity although atlas bridging is slightly more frequent in males. Both traits are more frequent in relatives of affected individuals than in the sample as a whole. Correlations between parents and offspring and between sibs are highly significant for atlas bridging, less so far clinoid bridging. These traits should fit either a single gene or quasi-continuous, polygenic model of inheritance. Several tests for polygenic inheritance such as the correlation between first and second born sibs' trait condition, the relationship between trait expression in offspring and total trait incidence in affected parents, and the correlation between trait frequency and expressivity on an intergroup basis were all positive for atlas bridging. The evidence for polygenic inheritance of clinoid bridging is weaker but suggestive. The results obtained in this study for atlas bridging are comparable to data from one earlier family study. The evidence suggests that these two traits should prove useful as genetic markers in skeletal population studies although there is still need for careful control over trait observation and description. Future research should attempt to measure non-metric traits continuously when their underlying distributions are known to be graded.

A family study of craniofacial dimensions in the Burlington Growth Centre sample.

Lateral cephalometric radiographs were used to study the similarities in craniofacial dimensions between members of 147 families. Standard product-moment and intraclass correlation coefficients were calculated for a selected series of measurements to compare parents to offspring and sibs to sibs. To assess further the use of the parents' records in predicting a child's craniofacial features, r2 values were calculated and multiple regression analyses were performed for the various pairings of related individuals. Results show a high level of significant correlations between first-degree relatives which are compatible with a polygenic theory of inheritance. These data give no evidence of added effects of autosomal dominance and sex-linkage. As might be expected, the use of multiple measurements from both parents gives the best results when one is attempting to predict a child's craniofacial dimensions. This suggests that information from the parents and siblings of a patient can be quite useful in clinical orthodontic treatment.

Dental caries in nineteenth century upper Canada.

This study examines the presence of dental caries in a large sample of adult skeletons from the 19th century cemetery of St. Thomas' Anglican Church in Belleville, Ontario. The cemetery was used from 1821 to 1874. Caries prevalence and frequencies of diseased and missing teeth were calculated both by observing summary statistics of individual rates and by the total sample of teeth. Postmortem tooth loss is low in this sample and antemortem tooth loss is highest in first mandibular molars, all other molars and then premolars. Age at death, but not sex, was found to be significantly related to the overall Caries Rate while both age and sex were significantly associated with the Diseased-Missing Index. The increase in diseased and missing teeth in older individuals is expected while the sex difference is not explained by simple dietary factors. When compared to reports on British and American samples, caries and antemortem tooth loss in the St. Thomas' sample is most similar to a pre-1850 British group and higher than American samples. Although there is undoubtedly a complex of factors contributing to caries prevalence in this sample, more data are required from large historic samples, particularly from the American northeast and late 19th century Britain, to have a clearer understanding of the influence of diet, cultural, and environmental factors affecting caries rates in historic populations.

Age differences in stable carbon and nitrogen isotope ratios in a population of prehistoric maize horticulturists.

Stable carbon isotope ratios in prehistoric human bone collagen have been used extensively to document the introduction and intensification of maize horticulture in notheastern North America. Most previous studies are based on small samples of adults who are assumed to characterize the diet of the population. In this study, all 29 individuals buried within an Ontario Iroquoian village site dated A.D. 1530-1580 were analysed for stable isotopes of carbon and nitrogen. Age distribution of the sample ranges from preterm to elderly. Significant negative correlations between age and delta 13C, and age and delta 15N values were found. High delta 13C values in infants and young children (delta 13C = -6.8 to -12.3) suggest a weaning diet high in maize. High delta 15N values in infants relative to adults suggest a trophic level effect during breast-feeding which has been reported in a modern sample by Tuross et al. (Am. J. Phys. Anthropol., 1993). In addition to the isotopic evidence for extremely high carbohydrate (maize) intake, the MacPherson sample includes two juveniles aged 3-4 years, exhibiting circular caries. No other cases of this condition are known in the extensively studied southern Ontario skeletal collections. Together the evidence from dentition and stable carbon isotopes indicates a very high carbohydrate diet in subadults. Circular caries result from developmental stress during enamel formation with subsequent caries formation in areas of thinner enamel. These findings are relevant to studies of infant and early childhood morbidity and mortality among prehistoric maize horticulturists.

Investigating the weaning process in past populations.

The 19th century St. Thomas'Anglican churchyard in Belleville, Ontario, Canada is associated with a large and well-preserved infant skeletal collection (n = 149) and good-quality parish records that document interments in the graveyard (1821-1874). By using a combination of historical demographic and stable nitrogen isotope analyses on the parish records and skeletal remains, respectively, a general pattern of extended nursing for about 14 months, introduction of foods other than breast milk by around 5 months of age, and variation in breast-feeding and weaning behaviours were detected for St. Thomas' infants. The results demonstrate that it is possible to go beyond the concept of weaning age to explore the weaning process in past populations when appropriate and large samples of documentary and skeletal data are available.

Harris lines: a study of age-associated bias in counting and interpretation.

Harris lines are regularly used in paleopathology as indicators of episodic nonspecific stress, but the methodology for their use has not been clearly established. We studied radiographs of the distal shaft of the tibia in 82 immature and 49 mature subjects from a medieval burial site and compared the number of Harris lines and observer error according to age categories. We found statistically significant differences in both line counts and in observer error by age groups. In conclusion, studies of Harris lines must take into account age variation in order to be validated.

Technical note: improved DNA extraction from ancient bones using silica-based spin columns.

We describe a simple method for extracting polymerase chain reaction-amplifiable DNA from ancient bones without the use of organic solvents. Bone powders are digested with proteinase K, and the DNA is purified directly using silica-based spin columns (QIAquick3, QIAGEN). The efficiency of this protocol is demonstrated using human bone samples ranging in age from 15 to 5,000 years old.