Search PubMed⌕ Search

Biomedical subjects

Mark Taylor

Publications and source records attributed to Mark Taylor.

At least 199 records · Page 11Linked to original sources
PubMed2004

Initial stability of ankle arthrodesis with three-screw fixation. A finite element analysis.

OBJECTIVE: Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws. DESIGN: Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and subjected to loads likely to affect the ankle postoperatively. BACKGROUND: More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces. METHODS: Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis. RESULTS: Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis. CONCLUSIONS: Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site.

Ankle Joint↗
PubMed2004

Teaching practicing surgeons critical appraisal skills with an Internet-based journal club: A randomized, controlled trial.

BACKGROUND: The effectiveness of interventions for developing critical appraisal skills in practicing physicians has not been studied, despite the documented importance of reading the literature in caring for patients and in continuing professional development. The objective of this study was to evaluate whether an Internet-based intervention would lead to enhanced critical appraisal skills in practicing surgeons. METHODS: General surgeons who agreed to participate were randomized into 2 groups. The intervention was a curriculum in critical appraisal skills that included a clinical and methodologic article, a listserve discussion, and clinical and methodologic critiques. The control group received only the clinical articles. The primary outcome measure was a previously validated 2-hour test of critical appraisal. RESULTS: Of the 55 surgeons who completed the examination, subjects in the intervention group performed better on the test of critical appraisal skills than those in the control group (mean score: intervention group, 58% +/- 8 vs control group, 50% +/- 8), with a large effect size of 1.06 standard deviation units (t+3.92, P <.0001). Training conditions accounted for 22% of the variance in total scores. CONCLUSIONS: A multifaceted, Internet-based intervention resulted in improved critical appraisal skills of practicing general surgeons.

Adult↗
PubMed2004

Time resolved solvent rearrangement dynamics.

Ultrafast pump-probe studies of I2- recombination in size-selected I2- (CO2)n cluster ions demonstrate long time coherent motions in size-selected clusters and the resulting non-statistical energy flow in the cluster. For I2- photodissociated to produce either I- + I or I- + I*, we identify a solvent-driven energy transfer process without a condensed phase counterpart. The mechanism involved is a Marcus-like solvent-driven curve crossing, with the driving force arising from asymmetric solvation, not just from solvent orientation. By substituting another halogen for one I atom, we "break" the I2- symmetry, and thus obtain direct information on the electron transfer process. New experiments on IBr- (CO2)n photodissociation products confirm the behavior suspected in the I2- studies. Time-resolved experiments on IBr- and theoretical modeling of the dynamics provide quantitative information on the multiple curve crossings encountered in the recombination process. In related investigations, femtosecond negative ion-neutral-positive ion charge reversal apparatus is employed to investigate transient neutral species evolving along a reaction coordinate. We report studies of the rearrangement dynamics of Cu(OH2) produced by photodetachment of the corresponding anion. Following a controlled delay period, a second ultrafast tunable laser pulse initiates resonant multiphoton photoionization of the time-evolving Cu...OH2 complex. The time-resolved Cu+ and Cu+(OH2) signals provide information both on the prompt dissociation of the complex and on energy redistribution between internal rotational and radial modes of the evolving complex. Calculations of the time evolution of the anion geometric configuration on the neutral potential energy surface yield deeper insight into the nature of the rearrangement process and the energy flow within the complex.

Journal Article↗
PubMed2004

Finite element analysis of the human ACL subjected to passive anterior tibial loads.

In this study, a constitutive law based on a nearly incompressible transversely isotropic hyperelastic potential is proposed to describe the mechanical behaviour of the anterior cruciate ligament (ACL). The constitutive formulation is valid for arbitrary kinematics (finite elasticity) and is thermodynamically admissible. Based on anatomic measurements performed on a human cadaveric knee specimen, a three-dimensional continuum finite element model of the ACL was developed. The numerical model was used to simulate clinical procedures such as the Lachman and drawer tests, which are performed to assess the existence and severity of an ACL injury. Finite element analyses showed that the two procedures have distinct effects on the behaviour of the ACL and provided new insights into the stress distributions. Moreover, good qualitative and quantitative agreement was found between the present study and results obtained experimentally in comparable conditions.

Anterior Cruciate Ligament↗
PubMed2004

The psychological impact of September 11 terrorism on Australian inpatients.

OBJECTIVE: To investigate the psychological impact on Australian hospital patients of the media coverage of the September 11 (9/11) terrorist attack. METHODS: Thirty psychiatry and 26 matched medical and surgical inpatients were assessed. RESULTS: Both reported and observed distress was common. Women reported significantly more distress than men. Individuals with psychiatric illness were significantly more varied in their attribution of cause for 9/11. Seven patients (29%) with pre-existing psychosis became delusional surrounding the events, but there were no significant differences between the psychiatry and the medical and surgical inpatients. CONCLUSIONS: Clinical impressions were confirmed, namely, that a large proportion of hospital inpatients were adversely affected by TV footage of the 9/11 terrorist attack. Most vulnerable were those already with a mental disorder, particularly those with a pre-existing psychotic illness.

Adaptation, Psychological↗
PubMed2004

Potato virus X-induced gene silencing in leaves and tubers of potato.

Virus induced gene silencing (VIGS) is increasingly used to generate transient loss-of-function assays and has potential as a powerful reverse-genetics tool in functional genomic programs as a more rapid alternative to stable transformation. A previously described potato virus X (PVX) VIGS vector has been shown to trigger silencing in the permissive host Nicotiana benthamiana. This paper demonstrates that a PVX-based VIGS vector is also effective in triggering a VIGS response in both diploid and cultivated tetraploid Solanum species. We show that systemic silencing of a phytoene desaturase gene is observed and maintained throughout the foliar tissues of potato plants and was also observed in tubers. Here we report that VIGS can be triggered and sustained on in vitro micropropagated tetraploid potato for several cycles and on in vitro generated microtubers. This approach will facilitate large-scale functional analysis of potato expressed sequence tags and provide a noninvasive reverse-genetic approach to study mechanisms involved in tuber and microtuber development.

Base Sequence↗
PubMed2004

The effect of bone quality on the stability of ankle arthrodesis. A finite element study.

BACKGROUND: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. METHODS: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. RESULTS: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. CONCLUSIONS: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. CLINICAL RELEVANCE. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.

Ankle Joint↗
PubMed2004

Brain volumes in adult survivors of very low birth weight: a sibling-controlled study.

OBJECTIVES: To establish whether adults who were born very low birth weight (VLBW) show altered volumes of certain brain structures. METHODS: Unmatched case-control study was conducted of 33 individuals from a cohort of VLBW (<1500 g) infants who were born between 1966 and 1977 and 18 of their normal birth weight siblings. Whole brain, gray matter, ventricular, corpus callosum, and hippocampal volumes were measured on structural magnetic resonance imaging scans. RESULTS: VLBW individuals had a 46% increase in total ventricular volume and a 17% reduction in posterior corpus callosum volume. No differences in whole brain, gray matter, or hippocampal volumes were observed. CONCLUSION: Specific differences exist in the volumes of certain brain structures in adults who were born VLBW compared with their normal birth weight siblings.

Adult↗