Manufacturing of high strength and high conductivity copper with laser powder bed fusion

Additive manufacturing (AM), known as 3D printing, enables rapid fabrication of geometrically complex copper (Cu) components for electrical conduction and heat management applications. However, pure Cu or Cu alloys produced by 3D printing often suffer from either low strength or low conductivity at room and elevated temperatures. Here, we demonstrate a design strategy for 3D printing of high strength, high conductivity Cu by uniformly dispersing a minor portion of lanthanum hexaboride (LaB6) nanoparticles in pure Cu through laser powder bed fusion (L-PBF). We show that trace additions of LaB6 to pure Cu results in an improved L-PBF processability, an enhanced strength, an improved thermal stability, all whilst maintaining a high conductivity. The presented strategy could expand the applicability of 3D printed Cu components to more demanding conditions where high strength, high conductivity and thermal stability are required.

Development of ELIP to Assess Physical Literacy for Emerging Adults: A Methodological and Epistemological Challenge

Purpose: Following increased interest in physical literacy (PL), development of appropriate tools for assessment has become an important next step for its operationalization. To forward the development of such tools, the objective of this study was to build the foundations of the Évaluation de la Littératie Physique (ELIP), designed to help reduce existing tensions in approaches to PL assessment that may be resulting in a low uptake into applied settings. Methods: We followed two steps: (1) the development of the first version of ELIP by deploying a Delphi method (n = 30); and (2) the modification of items through cognitive interviews with emerging adults (n = 32). Results: The expert consensus highlighted four dimensions of PL to be assessed-physical; affective; cognitive; and social-with new perspectives, including a preference for broad motor tests over fitness. Conclusion: Results offer new insights into the assessment of emerging adults' PL, but ELIP still requires further work concerning validity, reliability, and sensitivity.

EDP2PDF: a computer program for extracting a pair distribution function from an electron diffraction pattern for the structural analysis of materials

Pair distribution function (PDF) analysis is a powerful technique to understand atomic scale structure in materials science. Unlike X-ray diffraction (XRD)-based PDF analysis, the PDF calculated from electron diffraction patterns (EDPs) using transmission electron microscopy can provide structural information from specific locations with high spatial resolution. The present work describes a new software tool for both periodic and amorphous structures that addresses several practical challenges in calculating the PDF from EDPs. The key features of this program include accurate background subtraction using a nonlinear iterative peak-clipping algorithm and automatic conversion of various types of diffraction intensity profiles into a PDF without requiring external software. The present study also evaluates the effect of background subtraction and the elliptical distortion of EDPs on PDF profiles. The EDP2PDF software is offered as a reliable tool to analyse the atomic structure of crystalline and non-crystalline materials.

Fluoride-assisted detection of glutathione by surface Ce3+/Ce4+ engineered nanoceria

Nanoceria has evolved as a promising nanomaterial due to its unique enzyme-like properties, including excellent oxidase mimetic activity, which significantly increases in the presence of fluoride ions. However, this significant increase in oxidase activity has never been utilised as a signal enhancer for the detection of biological analytes partly because of the lack of understanding of the mechanism involved in this process. In this study, we show that the surface oxidation state of cerium ions plays a very crucial role in different enzymatic activities, especially the oxidase mimetic activity by engineering nanoceria with three different surface Ce⁴⁺/Ce³⁺ compositions. Using DFT calculations combined with Bader charge analysis, it is demonstrated that stoichiometric ceria registers a higher oxidase mimetic activity than oxygen-deficient ceria with a low Ce⁴⁺/Ce³⁺ ratio due to a higher charge transfer from a substrate, 3,3',5,5' tetramethylbenzidine (TMB), to the ceria surface. We also show that the fluoride ions can significantly increase the charge transfer from the TMB surface to ceria irrespective of the surface Ce⁴⁺/Ce³⁺ ratio. Using this knowledge, we first compare the fluoride sensing properties of nanoceria with high Ce⁴⁺ and mixed Ce⁴⁺/Ce³⁺ oxidation states and further demonstrate that the linear detection range of fluoride ions can be extended to 1-10 ppm for nanoceria with mixed oxidation states. Then, we also demonstrate an assay for fluoride assisted detection of glutathione, an antioxidant with elevated levels during cancer, using nanoceria with a high surface Ce⁴⁺/Ce³⁺ ratio. The addition of fluoride ions in this assay allows the detection of glutathione in the linear range of 2.5-50 ppm with a limit of detection (LOD) of 3.8 ppm. These studies not only underpin the role of the surface Ce⁴⁺/Ce³⁺ ratio in tuning the fluoride assisted boost in the oxidase mimetic activity of nanoceria but also its strategic application in designing better colourimetric assays.

A longitudinal examination of changes in mental health among elite Canadian athletes

This study explored how athletes' symptoms of mental disorders changed over the course of pandemic year. Predictors of baseline levels and changes in symptoms of mental disorders were also examined. Surveys were completed four times throughout a year by Canadian athletes training for the 2020 Olympics/Paralympics (n_time1 = 186, n_time2 = 142, n_time3 = 123, n_time4 = 108). Surveys included demographics questions, measures of perceived stress, training load, social support, coping, self-esteem, depression, anxiety, and disordered eating. Data were analysed using descriptive statistics and latent growth modelling. The prevalence of mental disorder symptoms was high at baseline and there was no significant change over time. Scores for the three disorders were significantly correlated. Female athletes had higher scores for disordered eating at baseline. Higher levels of perceived stress predicted higher scores on mental disorder measures. Longitudinal tracking of symptoms of mental disorders among elite athletes is important because it allows researchers to explore whether disorder symptomologies change; rates of mental disorder symptoms were high at baseline and stayed high over the course of a year. More research is needed to explore possible gender differences in rates of disorder symptoms, and to understand how those symptoms change over time.

Solution Epitaxy of Halide Perovskite Thin Single Crystals for Stable Transistors

Halide perovskites hold promise for energy and optoelectronic applications due to their fascinating photophysical properties and facile processing. Among various forms, epitaxial thin single crystals (TSCs) are highly desirable due to their high crystallinity, reduced defects, and easy epitaxial integration with other materials. However, a cost-effective method for obtaining TSCs with perfect epitaxial features remains elusive. Here, we demonstrate a direct epitaxial growth of high-quality all-inorganic perovskite CsPbBr₃ TSCs on various substrates through a facile solution process under near-ambient conditions. Structural characterizations reveal a high-quality epitaxy between the obtained perovskite TSCs and substrates, thus leading to efficiently reduced defects. The resultant TSCs display a low trap density (∼10¹¹ cm^-3) and a long carrier lifetime (∼10.16 ns). Top-gate/top-contact transistors based on these TSCs exhibit high on/off ratios of over 10⁵, an optimal hole mobility of 3.9 cm² V^-1 s^-1, almost hysteresis-free operation, and high stability at room temperature. Such a facile approach for the high-yield production of perovskite epitaxial TSCs will enable a broad range of high-performance electronic applications.

Designing Undercoordinated Ni-Nx and Fe-Nx on Holey Graphene for Electrochemical CO2 Conversion to Syngas

In this study, we propose a top-down approach for the controlled preparation of undercoordinated Ni-N_x (Ni-hG) and Fe-N_x (Fe-hG) catalysts within a holey graphene framework, for the electrochemical CO₂ reduction reaction (CO₂RR) to synthesis gas (syngas). Through the heat treatment of commercial-grade nitrogen-doped graphene, we prepared a defective holey graphene, which was then used as a platform to incorporate undercoordinated single atoms via carbon defect restoration, confirmed by a range of characterization techniques. We reveal that these Ni-hG and Fe-hG catalysts can be combined in any proportion to produce a desired syngas ratio (1-10) across a wide potential range (-0.6 to -1.1 V vs RHE), required commercially for the Fischer-Tropsch (F-T) synthesis of liquid fuels and chemicals. These findings are in agreement with our density functional theory calculations, which reveal that CO selectivity increases with a reduction in N coordination with Ni, while unsaturated Fe-N_x sites favor the hydrogen evolution reaction (HER). The potential of these catalysts for scale up is further demonstrated by the unchanged selectivity at elevated temperature and stability in a high-throughput gas diffusion electrolyzer, displaying a high-mass-normalized activity of 275 mA mg^-1 at a cell voltage of 2.5 V. Our results provide valuable insights into the implementation of a simple top-down approach for fabricating active undercoordinated single atom catalysts for decarbonized syngas generation.

Nanoscale pathways for human tooth decay - Central planar defect, organic-rich precipitate and high-angle grain boundary

Understanding the pathways and mechanisms of human tooth decay is central to the development of both prophylaxes and treatments, but only limited information is presently available about the initiation of caries at the nanoscale. By combining atom probe tomography and high-resolution electron microscopy, we have found three distinct initial sites for human dental enamel dissolution: a) along the central dark line (CDL) within carbonated apatite nanocrystals, b) at organic-rich precipitates and c) along high-angle grain boundaries. 3D maps of the atoms within hydroxyapatite nanocrystallites in sound and naturally-decayed human dental enamel reveal a higher concentration of Mg and Na in the CDL. The CDL is therefore thought to provide a pathway for the exchange of ions during demineralization and remineralization. Mg and Na enrichment of the CDL also suggests that it is associated with the ribbon-like organic-rich precursor in amelogenesis. Organic-rich precipitates and high-angle grain boundaries were also shown to be more vulnerable to corrosion while low-angle grain boundaries remained intact. This is attributed to the lower crystallinity in these regions.

Relative age effects in the Movement Assessment Battery for Children-2: age banding and scoring errors

AIM

The Movement Assessment Battery for Children-2 (MABC-2) uses age-grouped scoring, which will result in relative motor functioning being overestimated for some children and underestimated for others. In this paper, we measure these errors and discuss their consequences.

METHOD

We pool data from two validation studies to obtain a sample of 278 children assessed with the MABC-2 (mean (SD) age: 5 years, 0 months (9.6 months); 142 female). We used regression to measure the association between standard score and relative age, and used these results to estimate misclassification rates at the MABC-2's recommended thresholds.

RESULTS

Movement Assessment Battery for Children-2 scores were distributed as expected (mean (SD) = 10.4 (2.8)). We estimated that the standard score varied by 2.76 units (0.92 SDs) per year of relative age. Depending on threshold and age bandwidth, this implies overall misclassification rates from 9% to 23%.

INTERPRETATION

Relative age differences in MABC-2 scores led to substantial systematic error for young children. These errors can affect MABC-2 validity, longitudinal stability and agreement with other tools, which may reduce the appropriateness of care offered to children. Scoring approaches that may reduce or eliminate these errors are outlined.

Atomic-scale compositional mapping reveals Mg-rich amorphous calcium phosphate in human dental enamel

Human dental enamel, the hardest tissue in the body, plays a vital role in protecting teeth from wear as a result of daily grinding and chewing as well as from chemical attack. It is well established that the mechanical strength and fatigue resistance of dental enamel are derived from its hierarchical structure, which consists of periodically arranged bundles of hydroxyapatite (HAP) nanowires. However, we do not yet have a full understanding of the in vivo HAP crystallization process that leads to this structure. Mg(2+) ions, which are present in many biological systems, regulate HAP crystallization by stabilizing its precursor, amorphous calcium phosphate (ACP), but their atomic-scale distribution within HAP is unknown. We use atom probe tomography to provide the first direct observations of an intergranular Mg-rich ACP phase between the HAP nanowires in mature human dental enamel. We also observe Mg-rich elongated precipitates and pockets of organic material among the HAP nanowires. These observations support the postclassical theory of amelogenesis (that is, enamel formation) and suggest that decay occurs via dissolution of the intergranular phase. This information is also useful for the development of more accurate models to describe the mechanical behavior of teeth.

Screening for Risk of Developmental Delay in a primary care setting using the Nippising District Developmental Screen

BACKGROUND: Early growth and development in the first five years of life is strongly associated with health outcomes. The Nipissing District Developmental Screen (NDDS) is a free parent-reported screening tool recommended by the Canadian Pediatric Society as one of the tools for developmental screening in children

OBJECTIVES: To determine the prevalence of a positive screen for risk of developmental delay in a cohort of healthy children at 18-months and 5 years. To identify risk factors (child, socio-demo-graphic and home environment) associated with a positive screen for risk of developmental delay.

DESIGN/METHODS: A cross-sectional study of healthy Canadian children attending 18-months and 5 year well-child visits between June 2008 and February 2015 was conducted through the TARGet Kids! practice-based research network. Multivariable logistic regression was used to identify risk factors associated with a positive screen for developmental delay. Risk factors of development delay identified from literature were:, male sex, low birth weight, low income, low maternal education, maternal unemployment, non-industrialized immigrant status, single parent family, only child and older maternal age.

RESULTS: 1086 children (53% male) at 18 months and 575 children (51% male) at 5 years were included in the final analysis. At 18 months, 341 (31.4%) of children (95% CI, 28.7% - 34.3%) and at 5 years 166 (28.9%) (95% CI, 25.2% -32.8%) were screen positive base on 1+ flag NDDS. At 18 months, children with a low birthweight (OR=1.66; 95% CI 1.22-2.28), with a mother with low education (OR=1.75; 95% CI 1.07-2.85), and those from non-industrialized immigrant families (OR=1.85; 95% CI 1.37-2.49) were associated with an increased odds of a positive screen for developmental delay based on the 1+ NDDS flag. A female child (OR=0.74; 95% CI 0.57-0.96) and an only child (OR=0.76; 95% CI 0.57-0.99) were associated with a decreased odds of a positive screen for developmental delay. At 5 years, factors associated with a positive screen for developmental delay based on the 1+ NDDS flag were: low maternal education (OR 2.24; 95% CI 1.14-4.39) (children had 2.24 times greater odds of a positive screen for developmental delay) and older maternal age (OR 1.05; 95% CI 1.00-1.09) (every 1-year increase in maternal age, children had 1.05 times greater odds of a positive screen for developmental delay). A female child was associated with a decreased odds of a positive screen for developmental delay (OR=0.66; 95% CI 0.46-0.96) based on the 1+ NDDS flag.

CONCLUSION: In a population of healthy urban children the NDDS identified 30% at both 18 month and 5 years at risk for developmental delay. Risk factors for developmental delay were associated with a positive NDDS screen.

Validity of the Ages and Stages Questionnaire to detect risk of Developmental Coordination Disorder in preschoolers

BACKGROUND

A reliable and valid screening tool for detecting children at risk for Developmental Coordination Disorder (DCD) is needed. The purpose of this study was to evaluate the ability of the Ages and Stages Questionnaire-Third Edition (ASQ-3) motor scales to detect children at risk for DCD in a community-based sample of children aged 3.5-5.5 years.

METHODS

One hundred and sixty parent-child pairs were recruited from community-based organizations. Children were eligible if they spoke English and had no known physical impairments. Eligible parents were asked to fill out the ASQ-3, following which their child's fine motor and gross motor proficiency was assessed using the Movement Assessment Battery for Children-Second Edition (MABC-2). DCD risk was defined as those children scoring at or below the 16th percentile on the MABC-2. Sensitivity and specificity of the fine and gross motor areas of the ASQ-3 were examined and referenced against the DCD risk classification.

RESULTS

The ASQ-3 total motor score correlated moderately with overall standard score on the MABC-2 (r = 0.41; p < 0.001). Regardless of the ASQ-3 cut-off used, sensitivities of the ASQ-3 fine motor or gross motor scale to detect DCD risk were low at 21-47%, whereas specificities were high at 89-96%.

CONCLUSION

Early identification of motor skill delays is important in order to intervene and hopefully prevent the associated negative health consequences. However, because of the low sensitivity of the ASQ-3 motor scales, these results suggest that the ASQ-3 is not an appropriate screening tool to identify children at risk for DCD in the preschool population.

The Hidden Pathways in Dense Energy Materials - Oxygen at Defects in Nanocrystalline Metals

Highly abundant oxygen-rich line defects (blue) can act as fast oxygen transport paths. These defects show similar chemistry and therefore similar catalytic activity to the materials surface. These results provide the opportunity to design and produce simple scalable structures as catalysts, whose functionality derives from internal defects rather than from the materials surfaces.

Caregiving, single parents and cumulative stresses when caring for a child with cancer

BACKGROUND

Single parents whose children have cancer are a marginalized group who report less family centred care, and therefore, less quality cancer care for their children. As such, the aims of this study were to explore how single parents of children with cancer describe their caregiving experiences and to understand their contextual life stressors.

METHODS

A constructivist grounded theory method was used. Qualitative interviews with 29 single parents of children with cancer who were at least 6 months post-diagnosis were recruited between November 2009 and April 2011 from four hospitals across Canada. Line-by-line coding was used to establish codes and themes and constant comparison was used to establish relationships among emerging codes and conceptual themes.

RESULTS

The first set of findings report on caregiving duties including: emotional tasks, informational tasks and physical tasks. The second set of findings report on the contextual picture of parent's lives including their living conditions, their physical and mental health and their family histories of disruption, trauma and disease.

CONCLUSIONS

Single parents caring for children with cancer were found to experience several cumulative stressors in addition to the current strain of caring for a child with cancer. The synergy of these cumulative stresses with the added strain of caregiving for a child with cancer may have long-term health and financial implications for parents. Broad-based policy interventions should focus on relieving the chronic strains associated with being a single parent of a child with cancer.

Childhood cognitive ability and its relationship with anxiety and depression in adolescence

BACKGROUND

Childhood cognitive ability may have protective effects against internalizing symptoms in adolescence, although this may depend on the time of symptom assessment and child gender. Also, the effects of childhood stressors on adolescent internalizing symptoms may be moderated by childhood cognitive ability.

METHODS

The sample included 4405 individuals from the Canadian National Longitudinal Study of Children and Youth (NLSCY). Between ages 4-5 and 10-11, children completed a test of verbal ability and scholastic aptitude and a series of mathematics computation tests. Internalizing symptoms were assessed via self-reports at ages 12-13 and 14-15.

RESULTS

Greater cognitive ability was generally associated with decreased odds of internalizing symptoms at age 12-13. However, greater cognitive ability generally increased, or had no effect on, the odds of internalizing symptoms at age 14-15. Some of the effects of childhood cognitive ability varied with child gender. Also, childhood cognitive ability attenuated the effects of family dysfunction and chronic illness throughout childhood on subsequent internalizing symptoms.

LIMITATIONS

These data are largely subject to some degree of reporting bias, the tests of cognitive ability are limited and may not represent overall cognitive ability, and there may be intermediary variables that account for the relationship between childhood cognitive ability and adolescent internalizing symptoms.

CONCLUSION

Results suggest that programs attempting to increase early cognitive skills may be particularly beneficial for girls. Also, an increased focus on cognitive skills may attenuate the negative effects of some stressors on subsequent anxious and depressive symptoms, regardless of child gender.

Descriptive and factor analysis of the Developmental Coordination Disorder Questionnaire (DCDQ'07) in a population-based sample of children with and without Developmental Coordination Disorder

BACKGROUND

The Developmental Coordination Disorder Questionnaire (DCDQ'07) discriminates children with Developmental Coordination Disorder (DCD) from their peers. Studies employing the DCDQ have typically used clinical samples. To further validate the DCDQ'07, this study: (1) described its distributions in a population-based sample, and a sample of children with DCD; (2) explored sex and age differences at important cut-points; and (3) examined its factor structure.

METHODS

This secondary analysis of data collected from 23 schools (n = 3151) included a sample of 3070 children (1526 boys, 1544 girls) and a sample of 122 children (73 boys, 49 girls) who met DCD diagnostic criteria. DCDQ'07 distributions were described by age and sex. Chi-square analyses were conducted using three clinically important percentile ranges; a factor analysis explored the construct validity of DCDQ scores.

RESULTS

Parents of 3070 children (97.4%) completed the questionnaire independently. Significant sex differences were noted in both samples. Significant differences in proportions by sex, and DCDQ means by age were found in the population sample. A three-factor solution was found, accounting for 70.3% of the variance.

CONCLUSIONS

This is one of the largest studies using the DCDQ'07 with a non-clinical sample. The three-factor solution, including item loading, was consistent with previous research. When using DCDQ cut-offs it is important to consider sex and age.

Thin film composites of nanocrystalline ZrO(2) and diamond-like carbon: Synthesis, structural properties and bone cell proliferation

We report on the synthesis of thin composites of diamond-like carbon (DLC) and nanocrystalline ZrO(2) deposited using pulsed direct current plasma-enhanced chemical vapor deposition at low temperatures (<120 degrees C). Films containing up to 21at.% Zr were prepared (hydrogen was not included in the calculation) and their structural and surface properties were determined using a number of spectroscopic methods and contact angle measurements. Bone cell adhesion to the films was studied using a 3 day cell culture with osteoblasts. These nanocomposites (DLC-ZrO(2)) consist of tetragonal ZrO(2) nanocrystals with an average size of 2-5 nm embedded in an amorphous matrix consisting predominantly of DLC. The surface water contact angle of the films increased from approximately 60 degrees to 80 degrees as the Zr content increased from 0 to 21at.%. The cell culture study revealed that although the cell counts were not significantly different, the morphology of the osteoblasts growing on the DLC-ZrO(2) nanocomposites was markedly different from that of cells growing on DLC alone. Cells growing on the DLC-ZrO(2) surfaces were less spread out and had a smaller cell area in comparison with those growing on DLC surfaces. In some areas on the DLC-ZrO(2) surfaces, large numbers of cells appeared to coalesce. It is postulated that the difference in cell morphology between osteoblasts on DLC-ZrO(2) surfaces and DLC surfaces is related to the presence of very small tetragonal nanocrystals of ZrO(2) in the composite film.

Concurrent and construct validation of the short form of the Bruininks-Oseretsky Test of Motor Proficiency and the Movement-ABC when administered under field conditions: implications for screening

RATIONALE

Among the most widely used instruments to assess developmental co-ordination disorder (DCD) in children are the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) and the Movement Assessment Battery for Children (M-ABC). However, there is little research on agreement between these tests, when administered to children in field-based settings by trained non-clinicians.

METHOD

Ten of 75 schools participating in a larger study were randomly selected. All children in grade 4 (n= 340) in each of these schools were assessed at the same time using both the BOTMP-SF and the M-ABC in May of 2005. The order of tests was balanced, with an average gap in time between tests of 10-15 min. All tests were administered by trained research assistants.

RESULTS

The correlation between tests was moderate (r= 0.50, P < 0.01). Kappas were low at the fifth (k= 0.19) and 15th (k= 0.29) percentile cut-points, which are generally used to identify cases of DCD. Re-analysis using the relative improvement over chance (RIOC) statistic, however, revealed slightly better agreement at both cut-points (fifth percentile, RIOC = 0.29; 15th percentile, RIOC = 0.47). Children who scored as probable for DCD on both motor tests, as well as on only the BOTMP-SF, had higher body mass index, poorer physical fitness and lower levels of teacher-reported physical ability than those positive for DCD on the M-ABC only or those who scored negatively on both tests.

DISCUSSION

In general, the agreement between tests, even after adjustment for RIOC, was poor. Children identified with poor motor competence by both tests or by the BOTMP-SF only are at particular risk for poor physical fitness, overweight/obesity and physical inactivity. It appears that each assessment measures different dimensions of motor ability but that under field-based conditions the M-ABC may be less useful when applied by non-clinicians.

Comparing probable case identification of developmental coordination disorder using the short form of the Bruininks-Oseretsky Test of Motor Proficiency and the Movement ABC

Aim Despite its widespread current use in research and its potential for future application, the validity of the short form of the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP-SF) when administered by trained lay assessors is not known. This paper reports the results of case identification using the Movement Assessment Battery for Children (M-ABC) in a group of children scoring below the sixth percentile on the BOTMP-SF. Methods The BOTMP-SF was administered by trained research assistants to 2058 children. In total, 24 of 128 children aged 10 (n = 10), 11 (n = 10) or 12 (n = 4) scoring below the sixth percentile were randomly selected for further assessment by a paediatric occupational therapist using the M-ABC and the Kaufman Brief Intelligence Test. Results Twenty-one of 24 children positive for motor co-ordination problems on the BOTMP-SF scored below the 15th percentile of the M-ABC, a positive predictive value (PPV) of 0.88 [95% confidence interval (CI) = 0.69 to 0.96]. Fifteen of these children were below the fifth percentile (PPV = 0.63; 95% CI = 0.43 to 0.79). Conclusions The BOTMP-SF seems to be a reasonable alternative to case identification when clinical assessment with the M-ABC is not feasible. Further research is needed to examine the sensitivity and specificity of the short form when used for this purpose.

Developmental coordination disorder and overweight and obesity in children aged 9–14 y

Developmental coordination disorder (DCD) is a significant problem that affects between 5 and 9% of all children. Since children with DCD are less likely than their non-DCD peers to participate in physical activities, they may be at greater risk for overweight and obesity. In this report, we examine the relationship between DCD and overweight and obesity in a sample of 578 children aged 9-14 y. We also examine whether the relationship between DCD and overweight/obesity is the same for boys and girls, taking into account sex and age-appropriate differences in percentage body fat and body mass index (BMI) criteria. Our results show that for boys, DCD may be a risk factor for overweight/obesity in childhood and early adolescence. For girls, there is no difference in the prevalence of overweight/obesity between children with and without the disorder.

Improving loblolly pine somatic embryo maturation: comparison of somatic and zygotic embryo morphology, germination, and gene expression

Clonal production of loblolly pine ( Pinus taeda L.) through somatic embryogenesis has the potential to meet the increasing industrial demands for high-quality uniform raw materials. A major barrier to the commercialization of this technology is the low quality of the resulting embryos. Twenty-five newly initiated loblolly pine genotypes were followed through the process of liquid culture establishment, embryo maturation, germination, and retrieval from cryogenic storage. A maturation medium, capable of promoting the development of loblolly pine somatic embryos that can germinate, is presented that combines 1/2 P6 modified salts, 2% maltose, 13% polyethylene glycol 8000 (PEG), 5 mg/l abscisic acid (ABA), and 2.5 g/l Gelrite. A procedure for converting and acclimating germinants to growth in soil and greenhouse conditions is also described. A set of somatic seedlings, produced from the maturation medium, showed 100% survival when planted in a field setting. Somatic seedlings showed normal yearly growth relative to standard seedlings from natural seed. The quality of the resulting embryos was examined and compared to that of zygotic embryos using such parameters as morphology, dry weight, germination performance, and gene expression. All of the observations that were made support the conclusion that even with the new maturation medium somatic embryos grow approximately only halfway through the normal sequence of development and then prematurely discontinue growth.

An aquaglyceroporin is abundantly expressed early in the development of the suspensor and the embryo proper of loblolly pine

In contrast to angiosperms, pines and other gymnosperms form well-developed suspensors in somatic embryogenic cultures. This creates a useful system to study suspensor biology. In a study of gene expression during the early stages of conifer embryogenesis, we identified a transcript, PtNIP1;1, that is abundant in immature loblolly pine (Pinus taeda) zygotic and somatic embryos, but is undetectable in later-stage embryos, megagametophytes, and roots, stems, and needles from 1 year-old seedlings. Analysis of PtNIP1;1 transcript in embryo proper and suspensor tissues by reverse transcription-polymerase chain reaction suggests preferential expression in the suspensor. Based on comparisons of derived amino acid sequences, PtNIP1;1 belongs to the nodulin-like members of the major intrinsic protein superfamily branch of the aquaporin (major intrinsic protein) superfamily. Through heterologous expression in Xenopus laevis oocytes and the yeast (Saccharomyces cerevisiae) fps1(-) mutant, PtNIP1;1 has been shown to be an active aquaglyceroporin.

Major depressive disorder and marital transition among mothers: results from a national panel study

This analysis employs a national panel study to examine the relationship between marital transition and depression among mothers within the framework of selection and causation processes. The data come from the two-wave, longitudinal National Population Health Survey (NPHS) by Statistics Canada collected in 1994 and again in 1996 focusing on women between 20 and 65 years of age with children living at home (N = 2169). Compared with mothers who remain married, mothers making the transition into single-parenthood had a significantly higher rate of major depression at Time 1, which increased, but not significantly, at Time 2. This suggests that a selection effect may explain the elevated levels of depression among mothers experiencing a marital disruption. Rates of depression among single-parent mothers making the transition into a marital relationship did not decrease significantly between waves nor did the rate differ significantly from stable single-parent mothers at Time 1 or Time 2, suggesting that movement into marriage is not a protective factor.

Focused ion beam in dental research

Focused ion beam (FIB) has been available for over 10 yrs but until recently its usage has been confined to the semiconductor industry. It has been developed as an important tool in defect analysis, circuit modification and recently transmission electron microscope sample preparation. This paper introduces FIB and demonstrates its application in dental research. Its ion and electron imaging modes complement the SEM while its ability to prepare TEM samples from a wide range of material will allow the study of new types of adhesive interface. As an example, its use is described in the characterization of the interface of resin to a tribochemically treated surface of an experimental fiber-reinforced resin-based composite. As with all new techniques, the initial learning curve was difficult to manage. This new instrument offers opportunities to expand research in dental materials to areas not possible before.

Correlates of dysphoria in Canadian seniors: the Canadian Study of Health and Aging

OBJECTIVE

To examine the correlates of dysphoria in elderly Canadians.

METHOD

Randomly sampled elderly underwent screening in 1992 (CSHA-1) and in 1997 (CSHA-2). Community-living subjects without dementia at CSHA-1 were re-interviewed at CSHA-2 (n = 5234). A score < 53 on the mental health component of the Medical Outcomes Study Questionnaire (SF-36) was used to measure dysphoria. Sociodemographic, functional, social support, disease and lifestyle correlates of dysphoria were examined.

RESULTS

4.76% of men, and 8.59% of women were classified as dysphoric. The occurrence declined with age. In multivariate analyses, chronic pain, poor self-rated health, functional dependency and, in men only, being married, were significantly related to dysphoria. Perceived social support remained significant after controlling for sociodemographic, functional and disease variables.

CONCLUSION

Dysphoria is common among the elderly, especially elderly women. Given the interrelationships and number of correlates of dysphoria, elderly Canadians require broad programs promoting health and social support as well as functional and economic independence.

Abg1: a novel gene up-regulated by abscisic acid in guard cells of Vicia faba L

A novel gene (abg1) was isolated by differential display RT-PCR from guard cells of Vicia faba L. Abg1 transcript accumulated in guard cells that were incubated with 5 microM S(+)-ABA for 1 h. The full-length abg1 cDNA was 753 bp, which included a 513 bp coding region. The deduced 17.8 kDa protein shared sequence similarity with several desiccation-related proteins reported in plants.

The effect of sociodemographics, social stressors, health status and psychosocial resources on the age-depression relationship

This study examines how an extensive set of covariates identified in previous research--sociodemographics, social stressors, health status and psychosocial resources--influence the age-depression relationship. The analyses were based on data collected for the 1994 National Population Health Survey (N = 16,291) by Statistics Canada. Analyses were conducted using OLS regression for generalized distress and logistic regression for major depressive episode. The relationship between age and both outcomes was linear and negative after controlling for sociodemographics. Controlling for social stress reduced levels of depression among younger cohorts while controlling for poor health status reduced levels of depression among the elderly. Controlling for psychosocial resources generally reduced the level of depression among older cohorts, however, the results were mixed across outcomes. The inclusion of all covariates appears to negate the effects of one another in that the fully adjusted relationships between age and depression across both outcomes were not significantly different from their bivariate relationships.

12-month prevalence of depression among single and married mothers in the 1994 National Population Health Survey

While a number of studies have documented higher period prevalence rates of depression among single as compared to married mothers, all of the data have been based upon community surveys of mental illness. In Canada, all of the published work comes from Ontario. As a result, we do not know whether these results hold true for other regions of the country. Using a nationally representative sample, we find, consistent with previous work, that single mothers have almost double the 12-month prevalence rates of married mothers (15.4% versus 6.8%). As well, there are no significant differences in rates of depression between single and married mothers by region/province of the country. Our findings are compared with other epidemiologic data on the mental health of single mothers from Ontario.

Time since immigration and excess body weight

OBJECTIVES

To examine the relationship between time since immigration and excess body weight.

METHODS

Secondary data analysis of a cross-sectional survey of 19,600 Canadians.

RESULTS

The prevalence of excess weight (BMI > 25) increases with time since immigration for both men and women. After controlling for birthplace, socio-demographic, lifestyle and health correlates, only female immigrants (less than five years) are significantly less likely to have BMI scores greater than 25 kg/m2 compared to those born in Canada. Stratified analyses, however, revealed similar findings for Asian men who had immigrated less than five years prior to the survey.

DISCUSSION

Our results suggest that length of time since immigration is an important risk factor for excess weight. Further research with longitudinal data, more reliable measures of ethnicity and anthropometric measures of weight are required to confirm these initial findings.

Reducing economic disparity to achieve better health: modelling the effect of adjustments to income adequacy on self-reported morbidity among the elderly in Canada

Class differentials in health have been documented extensively in the sociological literature of the past two decades. Although sociologists have been concerned with analyzing the relationship between social class and health, less attention has been paid to modelling the effects of minimizing social disparities on health outcomes. From a sub-sample (N = 1,943) of elderly respondents aged 65 and over, four logistic regression equations where income adequacy was shown to be correlated with morbidity were selected. By adjusting the scores on the income adequacy variable, we were able to model the effect of shifting individuals from lower to higher income groups. The most dramatic results were obtained after all respondents were shifted into the highest income adequacy classification. A more realistic hypothetical model, the transfer of individuals from the lowest income group to the next category, produced the least attractive reduction in morbidity. Obviously, income adjustment alone is insufficient. Findings are discussed in terms of interventions to prevent economic disparity in old age.

Socioeconomic position. Lifestyle and health among Canadians aged 18 to 64: a multi-condition approach

Although a sizeable literature documents the link between socioeconomic position and health in Britain and the United States, much less work has been conducted in Canada. Moreover, what work has been done has been limited to single outcomes such as self-rated health or age-adjusted mortality. Very little has been conducted using multiple health outcomes, although doing so has been advocated. Using the 1991 General Social Survey on Health, we extended an earlier analysis to explore whether or not "condition-specific" relationships exist between socioeconomic position, lifestyle, and health among working age Canadians. We distinguished four patterns in terms of education and income adequacy. The effects of occupation did not fit into any simple pattern. Measures of lifestyle appear to mediate the relationship between education and morbidity, but not between income adequacy and morbidity. Findings are discussed in terms of the theoretical, methodological and policy implications of a condition-specific approach.

Correlates of body weight in the 1994 National Population Health Survey

OBJECTIVE

This study examines three specific questions about obesity and overweight, using a nationally representative sample of Canadians. Are sociodemographic and lifestyle behaviors associated with body weight? Is body weight correlated with specific health outcomes? Has the prevalence of obesity in Canada changed since 1978?

METHODS

Secondary data analysis of a cross-sectional survey.

SAMPLE

This study uses the 1994 National Population Health Survey (NPHS) by Statistics Canada. It is a stratified random sample of 19600 Canadians across all provinces.

RESULTS

The results show that age, gender, education, birth place and region, are significantly associated with obesity. When a lower criterion is used for overweight and obesity (body mass index, BMI > or = 25), dummy variables for marital status and occupation are also significant. Second, obesity is associated with poorer self-rated health, high blood pressure, heart disease, diabetes, arthritis, respiratory and stomach problems. For those respondents who have a BMI score of 25 or greater, there is also an association with stroke. Finally, it is unclear whether the prevalence of obesity has changed. However, there appears to be a systematic difference between studies using actual height and weight measurements (anthropometric) vs self-reported measurements.

CONCLUSIONS

Weight can be considered a modifiable risk factor and reductions in the prevalence of obesity should reduce the risk of specific chronic conditions. Provincial variations in the prevalence of obesity (BMI > or = 27) and overweight and obesity (BMI > or = 25) suggest that collapsing provinces into regions may obscure important inter-provincial differences in body weight. More research is required to assess whether or not obesity is decreasing in Canada. Some of the limitations of self-reported data are discussed.

Age and depression in a nationally representative sample of Canadians: a preliminary look at the National Population Health Survey

There are considerable inconsistencies in the literature concerning the relationship between age and depression. Recently, however, two independent studies in the U.S. have shown that the distribution is U-shaped with the lowest reported levels of depression at ages 45-49. Three reasons for past inconsistencies are identified and addressed using the 1994 National Population Health Survey by Statistics Canada. Using both a distress scale and a diagnostic measure, a substantially different relationship was found. The prevalence of distress decreased steadily with age until about 65, with only a slight increase afterwards for both males and females. After the introduction of several sociodemographic covariates, however, this relationship was clearly negative. These findings are discussed in terms of future research questions.

Age and depression in a nationally representative sample of Canadians: a preliminary look at the National Population Health Survey

There are considerable inconsistencies in the literature concerning the relationship between age and depression. Recently, however, two independent studies in the U.S. have shown that the distribution is U-shaped with the lowest reported levels of depression at ages 45-49. Three reasons for past inconsistencies are identified and addressed using the 1994 National Population Health Survey by Statistics Canada. Using both a distress scale and a diagnostic measure, a substantially different relationship was found. The prevalence of distress decreased steadily with age until about 65, with only a slight increase afterwards for both males and females. After the introduction of several sociodemographic covariates, however, this relationship was clearly negative. These findings are discussed in terms of future research questions.

Cloning of a cDNA for a chitinase homologue which lacks chitin-binding sites and is down-regulated by water stress and wounding

A cDNA clone (pLP6) of a gene which is repressed under water deficit was isolated from a loblolly pine (Pinus taeda L.) cDNA library and characterized. The predicted polypeptide encoded by pLP6 bears strong resemblance to a number of Class I chitinases. However, LP6 lacks most of the amino-terminal and, consequently the signal peptide, cysteine-rich chitin-binding domain and glycine/proline-rich "hinge' region, diagnostic of Class I chitinases, are absent. Although the cDNA is similar in size to its mRNA, the long open reading frame encoding the LP6 protein commences halfway through the mRNA, implying a 5'-untranslated region of over 700 nucleotides. Subfragments from the 5' end of pLP6 hybridize to the same mRNA as do probes consisting of the entire cDNA. Reverse transcription(RT)-PCR experiments confirm that the cDNA derives from a single mRNA molecule. Analysis of the 5'-UTR revealed six upstream open reading frames and four inverted repeat structures. Expression of the pLP6 gene is repressed by water deficit stress and wounding. Possible functions and origin of this gene are discussed.