Biomedical subjects

Andrew Duncan

Publications and source records attributed to Andrew Duncan.

5 recordsLinked to original sources

PubMed2005

Controlling polymer adhesion with "pancakes".

Topographical patterns are used to selectively tune the adhesion of polymers. Although nature has provided guidance, relatively little is known of how topographic patterns can be intelligently used not only to enhance adhesion but, more importantly, to tune adhesion. We demonstrate that properly designed, low-aspect-ratio posts can alter adhesion from 20% to 400% the value of conventional adhesion descriptors for nonpatterned interfaces. This control is not related to the magnitude of interfacial area but, rather, to altering the local separation processes at an interface by geometry. We establish general relationships that govern the interaction between material properties, pattern length scales, and the control of adhesion. These relationships provide insight into the mechanisms of adhesion for examples in nature, such as the gecko, while also providing concrete guidance for the future design of "smart" adhesives and coatings with nanoscale patterns.

Journal Article↗

PubMed2005

Comparison of frontal plane trunk kinematics and hip and knee moments during anticipated and unanticipated walking and side step cutting tasks.

BACKGROUND: Frontal plane trunk and lower extremity adjustments during unanticipated tasks are hypothesized to influence hip and knee neuromuscular control, and therefore, contribute to anterior cruciate ligament (ACL) injury risk. The aims of this study were to examine frontal plane trunk/hip kinematics and hip and knee moments (measures of neuromuscular control) during unanticipated straight and side step cut tasks. METHODS: Kinematic and kinetic variables were collected while subjects performed two anticipated tasks, including walking straight (ST) and side step cutting (SS), and two unanticipated tasks (STU and SSU). Foot placement, thorax-pelvis-hip kinematic variables and hip and knee moments were calculated over the first 30% of stance. FINDINGS: Hip abduction angles and knee moments were significantly affected by task and anticipation. Hip abduction angles decreased, by 4.0-7.6 degrees , when comparing the SSU task to the ST, STU and SS tasks. The hip abduction angles were associated with foot placement and lateral trunk orientation. INTERPRETATION: Hip abduction angles and foot placement, not lateral trunk flexion influence trunk orientation. Anticipation influences hip and knee neuromuscular control and therefore may guide the development of ACL prevention strategies.

Adaptation, Physiological↗

PubMed2005

Knee and hip angle and moment adaptations during cutting tasks in subjects with anterior cruciate ligament deficiency classified as noncopers.

STUDY DESIGN: Two-factor mixed-design study, with factors including group (control and noncoper) and task (sidestep, crossover, and straight). OBJECTIVES: To compare the knee and hip joint angles and moments of control subjects and subjects with an anterior cruciate ligament (ACL) deficient knee classified as noncopers, during a sidestep, crossover, and straight-ahead task. BACKGROUND: Subjects with ACL deficiency primarily note difficulty with cutting tasks as opposed to straight-ahead tasks. Yet, previous studies have primarily focused on straight-ahead tasks. METHODS AND MEASURES: Fifteen subjects with ACL deficiency classified as noncopers, based on the number of giving-way episodes (>1) and global question of knee function (<60%), were included in this study. These subjects (10 male, 5 female; age range, 18-49 years) were compared to a healthy control group (7 male, 7 female; age range, 19-47 years). Position data collected at 60 Hz were combined with anthropometric and ground reaction force data collected at 420 Hz to estimate 3-dimensional knee and hip joint angles and moments. All subjects performed 3 tasks including a step and 45 degrees sidestep cut, step and 45 degrees crossover cut, and step and proceed straight. Two-way mixed-model ANOVAs were used to compare peak angle and moment variables between 10% to 30% of stance. RESULTS: The ACL-deficient noncoper group had 1.8 degrees to 5.7 degrees less knee flexion angle compared to the control group across tasks (P<.043). The ACL-deficient noncoper group used 22% to 27% lower knee extensor moment during weight acceptance compared to the control group (P<.001). The sagittal plane hip extensor moments were 34% to 39% higher in the ACL-deficient noncoper group compared to the control group (P<.025). Hip frontal (P<.037) and transverse plane (P<.04) moments also distinguished the ACL-deficient noncoper from the control group. CONCLUSIONS: This study suggests that individuals who do not cope well after ACL injury rely on a hip control strategy during cutting tasks.

Adaptation, Physiological↗

PubMed2003

Reagentless detection of microorganisms by intrinsic fluorescence.

Quick and accurate detection of microbial contamination is accomplished by a unique combination of leading-edge technologies described in this and the accompanying paper. In this contribution, a hand-held prototype instrument is described which is capable of statistically sampling the environment for microbial contamination and determining cell viability. The technology is sensitive enough to detect very low levels ( approximately 20 cells/cm(2) or cm(3)) of microbes in seconds.

Bacteria↗

PubMed2002

Role of catalase in the smooth muscle relaxant actions of sodium azide and cyanamide.

The aim of this study was to determine the role of catalase in the smooth muscle relaxant actions of sodium azide and cyanamide. The effects of 3-amino-1,2,4-triazole suggested a role for this enzyme in the relaxant actions of sodium azide on rat aorta and bovine retractor penis muscle and cyanamide on rat aorta. Moreover, results obtained using a difference spectrophotometric assay based upon the oxidation of haemoglobin were consistent with the catalase-dependent oxidation of sodium azide to nitric oxide (NO) and of cyanamide to nitroxyl anion. Surprisingly, however, no free nitric oxide or nitroxyl was detected in solution using a sensitive electrode. This anomaly might be explained if the stable complexes of catalase with nitric oxide or nitroxyl do not release their respective ligand except to sites of high affinity, such as the haemoglobin employed in the difference spectrophotometric assay, or indeed, the soluble guanylate cyclase within the smooth muscle.

Amitrole↗