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Biomedical subjects

Neil Anderson

Publications and source records attributed to Neil Anderson.

At least 19 recordsLinked to original sources
PubMed2006

Ultrafast photoinduced charge separation dynamics in polythiophene/SnO2 nanocomposites.

We present a study of photoinduced interfacial electron transfer (ET) dynamics of SnO2 nanocrystalline thin films sensitized by polythiophene derivatives (regioregular poly(3-hexylthiophene) (P3HT) and regiorandom poly(3-undecyl-2,2'-bithiophene) (P3UBT)). ET dynamics were measured by following the dynamics of injected electrons in SnO2 and polarons in the conjugated polymer using ultrafast mid-IR transient absorption spectroscopy. The rate of electron transfer from P3HT and P3UBT to SnO2 films was determined to occur on sub-picosecond time scale (120 +/- 20 fs). In P3HT/SnO2 composite, interchain charge transfer was found to compete with and reduce the quantum efficiency of interfacial electron transfer at high polymer loading. This interchain charge separation processes can be reduced in non-regioregular polymer or at low polymer loading levels.

Journal Article↗
PubMed2006

Solvent and linker influences on AQ(*-)/dA(*+) charge-transfer state energetics and dynamics in anthraquinonyl-linker-deoxyadenosine conjugates.

The goal of this work is to produce high yields of long-lived AQ(*-)/dA(*+) charge transfer (CT) excited states (or photoproducts). This goal fits within a larger context of trying generally to produce high yields of long-lived CT excited states within DNA nucleoside conjugates that can be incorporated into DNA duplexes. Depending upon the energetics of the anthraquinonyl (AQ) (3)(pi,pi) state as well as the reduction potentials of the subunits in particular anthraquinonyl-adenine conjugates, CT quenching of the AQ (3)(pi,pi*) state may or may not occur in polar organic solvents. In MeOH, bis(3',5'-O-acetyl)-N(6)-(anthraquinone-2-carbonyl)-2'-deoxyadenosine (AQCOdA) behaves as intended and forms a (3)(AQ(*-)/dA(*+)) CT state with a lifetime of 3 ns. However, in nonpolar THF the AQ(*-)/dA(*+) CT states of AQCOdA are too high in energy to be formed, and in DMSO a (1)(AQ(*-)/dA(*+)) CT state is formed but lives only 6 ps. Although the lowest energy excited state for AQCOdA in MeOH is a (3)(AQ(*-)/dA(*+)) CT state, for N(6)-(anthraquinone-2-methylenyl)-2'-deoxyadenosine (AQMedA) in the same solvent it is a (3)(pi,pi*) state. Changing the linking carbonyl in AQCOdA to methylene in AQMedA makes the anthraquinonyl subunit harder to reduce by 166 mV. This raises the energy of the (3)(AQ(*-)/dA(*+)) CT state above that of the (3)(pi,pi*) in AQMedA. The conclusion is that anthraquinonyl-dA conjugates will not have lowest energy AQ(*-)/dA(*+) CT states in polar organic solvents unless the anthraquinonyl subunit is also substituted with an electron-withdrawing group that raises the AQ-subunit's reduction potential above that of AQ. A key finding in this work is that the lifetime of the (3)(AQ(*-)/dA(*+)) CT excited state (ca. 3 ns) is ca. 500-times longer than that of the corresponding (1)(AQ(*-)/dA(*+)) CT excited state (ca. 6 ps).'

Journal Article↗
PubMed2006

Subsurface Raman imaging with nanoscale resolution.

We report on chemically specific, subsurface imaging with high spatial resolution. Using tip-enhanced Raman spectroscopy, we probe carbon nanotubes buried beneath a host dielectric media. We demonstrate our ability to map and resolve specific vibrational modes with 30 nm spatial resolution for dielectric layers with different thicknesses.

Materials Testing↗
PubMed2006

A construct-driven investigation of gender differences in a leadership-role assessment center.

This study examined gender differences in a large-scale assessment center for officer entry in the British Army. Subgroup differences were investigated for a sample of 1,857 candidates: 1,594 men and 263 women. A construct-driven approach was chosen (a) by examining gender differences at the construct level, (b) by formulating a priori hypotheses about which constructs would be susceptible to gender effects, and (c) by using both effect size statistics and latent mean analyses to investigate gender differences in assessment center ratings. Results showed that female candidates were rated notably higher on constructs reflecting an interpersonally oriented leadership style (i.e., oral communication and interaction) and on drive and determination. These results are discussed in light of role congruity theory and of the advantages of using latent mean analyses.

Adolescent↗
PubMed2006

Genetic characterization of Anaplasma ovis strains from bighorn sheep in Montana.

Wildlife reservoir species and genetic diversity of Anaplasma ovis (Rickettsiales: Anaplasmataceae) have been poorly characterized. Bighorn sheep (Ovis canadensis), captured in Montana from December 2004 to January 2005, were tested for antibodies to Anaplasma spp.; the presence of A. ovis was determined by the characterization of major surface protein msp4 sequences. Anaplasma antibodies were detected in 25/180 (14%) sampled bighorn sheep and A. ovis msp4 sequences were amplified by polymerase chain reaction (PCR) and sequenced from 9/23 (39%) of seropositive animals. All animals were negative by PCR for the related pathogens, Anaplasma phagocytophilum and Anaplasma marginale. All msp4 sequences identified in the bighorn sheep were identical and corresponded to a single A. ovis genotype that was identical to a sheep isolate reported previously from Idaho. The finding of a single genotype of A. ovis in this wild herd of bighorn sheep was in contrast to the genetic diversity reported for A. marginale in cattle herds in the western United States and worldwide. These results demonstrated that bighorn sheep may be a wildlife reservoir of A. ovis in Montana.

Anaplasma ovis↗
PubMed2005

Comparison of Py*+/dU*- charge transfer state dynamics in 5-(1-pyrenyl)-2'-deoxyuridine nucleoside conjugates with amido-, ethylenyl-, and ethynyl linkers.

Femtosecond, picosecond, and nanosecond transient absorbance (TA) and picosecond emission kinetics results are presented for three 5-(1-pyrenyl)-2'-deoxyuridine nucleosides each with a different two-atom linker joining pyrenyl C-1 to uracil C-5. The linkers are respectively -NHCO-, -(CH(2))(2)-, and -C[triple bond]C- for PAdU, PEdU, and PYdU. For all three nucleoside conjugates, most conformers undergo intramolecular charge transfer (CT) from their pyrenyl (1)(pi,pi) excited states to form Py(*+)/dU(*-) CT products in ultrashort times: <or=0.6 ps for PAdU, <or=30 ps for PEdU, and <or=100 ps for PYdU (instrumentally limited times). Additionally for all three nucleosides, a small fraction of conformers also undergoes slower intramolecular CT from their pyrenyl (1)(pi,pi) states in times as long as tens of nanoseconds. Importantly, for use of these nucleosides in studies of excess electron transport in DNA, the lifetimes the CT products in MeOH lengthen significantly in the above series: 6.0 ps for PAdU, 560 ps for PEdU (the shortest of three TA lifetime components), and 1.06 ns for PYdU. The effects on pyrenyl-dU nucleoside CT state dynamics due to adding oxygen via both aeration and oxygen saturation are also examined for the PEdU nucleoside in MeOH.

Amides↗
PubMed2005

Nanoscale vibrational analysis of single-walled carbon nanotubes.

We use near-field Raman imaging and spectroscopy to study localized vibrational modes along individual, single-walled carbon nanotubes (SWNTs) with a spatial resolution of 10-20 nm. Our approach relies on the enhanced field near a laser-irradiated gold tip which acts as the Raman excitation source. We find that for arc-discharge SWNTs, both the radial breathing mode (RBM) and intermediate frequency mode (IFM) are highly localized. We attribute such localization to local changes in the tube structure (n, m). In comparison, we observe no such localization of the Raman active modes in SWNTs grown by chemical vapor deposition (CVD). The direct comparison between arc-discharge and CVD-grown tubes allows us to rule out any artifacts induced by the supporting substrate.

Journal Article↗
PubMed2005

Migraine and risk of subarachnoid haemorrhage: a population-based case-control study.

OBJECTIVE: Evidence exists for an association between migraine and ischaemic stroke, but there is uncertainty about whether migraine is a risk factor for subarachnoid haemorrhage (SAH). METHODS: A multi-centre, population-based, case-control study using cases of first-ever SAH during 1995-98 and matched controls in four study centres in Australia and New Zealand. Self- or proxy-reported history, frequency and characteristics of headaches, classified according to 1988 International Headache Society diagnostic criteria. RESULTS: 206 of 432 (48%) cases and 236 of 473 (50%) controls had a history of headaches. The frequency and characteristics of headaches were similar between the two groups. No association was found in logistic regression analyses for history or frequency of headaches, or migraine headaches. CONCLUSIONS: No evidence was found for an association between recurrent headaches and SAH. Such information is important for counselling patients and families about the significance of past and ongoing headaches in relation to this illness.

Adult↗
PubMed2005

Nanoscale optical imaging of excitons in single-walled carbon nanotubes.

We present simultaneous near-field photoluminescence (PL) and Raman imaging of single-walled carbon nanotubes (SWNTs) with a spatial resolution better than 15 nm. Highly localized excitation is used to visualize the spatial extent of the contributing excited states. For SWNTs on glass, we typically observe highly confined PL from short segments of about 20 nm in length. The PL from micelle-encapsulated SWNTs on mica is extended along the tube up to several hundreds of nanometers. We find that near-field enhancement is much stronger for photoluminescence than for Raman scattering, an observation that is explained by the low intrinsic quantum yield of SWNTs.

Journal Article↗
PubMed2005

Stall dimensions and the prevalence of lameness, injury, and cleanliness on 317 tie-stall dairy farms in Ontario.

The study objectives were to provide a province-wide description of stall dimensions and the aspects of cattle welfare linked to stall design in the tie-stall industry. Data on stall design; stall dimensions; and the prevalence of lameness, injury, and hind limb and udder cleanliness in lactating dairy cattle were collected from a sample of 317 tie-stall farms across Ontario. The majority of the study farms (90%) had stalls with dimensions (length, width, tie-chain length, and tie rail height) that were less than the current recommendations. This may explain, in part, the prevalence of lameness measured as the prevalence of back arch (3.2%) and severe hind claw rotation (23%), hock lesions (44%), neck lesions (3.8%), broken tails (3%), dirty hind limbs (23%), and dirty udders (4.6%). Veterinarians and producers may use this information to compare farms with the industry averages and target areas in need of improvement.

Animal Welfare↗
PubMed2004

Diurnal, weekly, and seasonal variations in stroke occurrence in a population-based study in Auckland, New Zealand.

AIMS: To determine (via a population-based study in Auckland, New Zealand) if there are diurnal, weekly, or seasonal variations in the occurrence of stroke. METHODS: All new stroke events in Auckland residents were traced. Time of onset of the stroke was defined as the time when neurological symptoms were first noticed. The day of the week and month of onset were analysed for all strokes. RESULTS: 1711 patients were registered over 1 year. The rate ratios for the onset of stroke in each 6-hourly interval compared with reference interval (1800-2359 hours) were 0.74 (95% CI: 0.61-1.10) for 0000-0559 hours, 2.88 (95% CI: 2.48-3.34) for 0600-1159 hours and 1.74 (95% CI: 1.49-2.05) for 1200-1759 hours. Rate ratios of the seasonal occurrence of stroke compared with spring were 0.75 (95% CI: 0.65-0.86) for summer, 0.83 (95% CI: 0.73-0.95) for autumn and 1.08 (95% CI: 0.96-1.23) for winter. No weekly pattern of stroke occurrence was observed. CONCLUSIONS: Strokes were less likely to occur during the summer and autumn than in the winter or spring. There was an increase in the occurrence of stroke in the late morning. The results have implications for the provision of acute stroke services in the community and in hospital.

Humans↗
PubMed2004

Changes in stroke care at Auckland Hospital between 1996 and 2001.

AIMS: In 1996, we performed a descriptive audit of stroke care in Auckland Hospital. Since then, a mobile stroke team has been established. We have repeated the 1996 audit to assess changes in stroke management. METHODS: From 1 June to 30 September 2001, information was prospectively recorded for all patients with stroke. RESULTS: There were 177 strokes in 175 patients (92 men, mean age 70.9, standard deviation [SD] 14.9 years). Ninety-seven percent of patients had cerebral imaging (median 4.5 hours; interquartile range [IQR] 2.7-11.6). Acute aspirin was given to 78% of patients in 2001 and 40% in 1996 (p <0.001). Twenty-four percent of patients were kept 'nil by mouth' for at least 24 hours (46% in 1996, p <0.001). At discharge, 73% of patients were taking antiplatelet or anticoagulant therapy (61% in 1996, p <0.001). Only 50% of the patients with elevated discharge blood pressures were taking antihypertensives. There had been a reduction in the mean length of hospital stay to 16 days (21 days in 1996) but no significant change in mortality (14% compared with 17% in 1996). CONCLUSION: A stroke service may increase the attention to the 'processes' of stroke care and use of therapies, which are shown to be of benefit in randomised controlled trials.

Aged↗
PubMed2003

Regulation of supply and demand for maternal nutrients in mammals by imprinted genes.

The placenta has evolved in eutherian mammals primarily to provide nutrients for the developing fetus. The genetic control of the regulation of supply and demand for maternal nutrients is not understood. In this review we argue that imprinted genes have central roles in controlling both the fetal demand for, and the placental supply of, maternal nutrients. Recent studies on Igf2 (insulin-like growth factor 2) knockout mouse models provide experimental support for this hypothesis. These show effects on placental transport capacity consistent with a role of IGF-II in modulating both the placental supply and fetal demand for nutrients. Imprinting of genes with such functions may have coevolved with the placenta and new evidence suggests that transporter proteins, as well as the regulators themselves, may also be imprinted. These data and hypotheses are important, as deregulation of supply and demand affects fetal growth and has long term consequences for health in mammals both in the neonatal period and, as a result of fetal programming, in adulthood.

Animals↗
PubMed2003

A meta-analytic study of general mental ability validity for different occupations in the European community.

A comprehensive meta-analysis of the validity of general mental ability (GMA) measures across 12 occupational categories in the European Community (EC) is presented. GMA measures showed that there is validity generalization and large operational validities for job performance and training success in 11 occupational groups. Results also showed that job complexity moderated the magnitude of the operational validity of GMA tests across three levels of job complexity: low, medium, and high. In general, results were similar to those found in the United States, although the European findings showed a slightly larger magnitude of operational validity in some cases. Theoretical and practical implications of these findings for personnel selection are discussed. ((c) 2003 APA, all rights reserved)

Aptitude↗
PubMed2003

Malignancy-associated changes in lactiferous duct epithelium.

OBJECTIVE: To determine whether cells from histologically normal appearing epithelium of the lactiferous duct from women with a remote ductal lesion in the breast provide any clues indicating the existence of such a lesion. STUDY DESIGN: Tissue sections cut to 4 microns and stained with hematoxylin and eosin were prepared from duct tissue of 20 women with breast lesions and of 20 women free of any such lesion who had undergone mammoplastic procedures or resection for benign reasons. One hundred nuclei were measured from each case. Measures of nuclear deviation from normal were computed, discriminant functions were derived, and multivariate significance tests were conducted. RESULTS: Nuclei from histologically normal appearing regions of lactiferous duct epithelium from women harboring distant lesions exhibited changes in the distribution pattern of their nuclear chromatin, indicating the presence of these lesions. The statistical significance of these changes was documented. The changes were clearly evident in all 20 subjects with lesions and were not observed in 19 of the 20 subjects without lesions. CONCLUSION: The results suggest that studies aimed at detecting malignancy-associated changes in cells collected by ductal lavage might lead to a minimally invasive screening procedure for breast lesions.

Adult↗
PubMed2002

GH and epidermal growth factor signaling in normal and Laron syndrome fibroblasts.

We have investigated and compared GH and epidermal growth factor (EGF) signaling in primary human skin fibroblasts from normal subjects and subjects with GH-binding protein-positive Laron syndrome (LS). In normal human fibroblasts, GH and EGF activate the tyrosine phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT5b; in LS fibroblasts, EGF does, but GH does not. GH also activates the tyrosine phosphorylation of Janus kinase (JAK)2 in normal, but not LS, fibroblasts. Similarly, both GH and EGF activate MAPK in normal fibroblasts, but only EGF does in the LS fibroblasts. As in the 3T3-F442A mouse preadipocyte cell line, GH signaling to mitogen-activated protein kinase is partially inhibited by wortmannin treatment, indicating a role for phosphatidylinositol 3-kinase (PI3K) in this signaling pathway. The exogenous expression of the GH receptor in one family of LS fibroblasts (H1) but not the other (M) restores signaling to a STAT5 reporter element. Together, these results indicate that the mechanism of defective GH signaling in two families of LS fibroblasts are different but that both occur at a level close to, and specific for, the GH receptor.

Abnormalities, Multiple↗