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Biomedical subjects

K M Hill

Publications and source records attributed to K M Hill.

At least 19 recordsLinked to original sources
PubMed2006

Fluctuating velocity and momentum transfer in dense granular flows.

We show experimentally that in a free-surface granular flow the fluctuating velocity brings about momentum transfer at a considerable rate only very close to the free surface. Away from the free surface, where the flow is dense and stratified (or laminar), the fluctuating velocity plays no prominent dynamic role and stems passively from a kinematic constraint: The strata of particles must shake laterally as they slip past one another in the direction of the mean flow. Based on this insight, we formulate a simple model for the fluctuating velocity of dense granular flows. The predictions of the model agree well with our experimental measurements.

Journal Article↗
PubMed2004

Radial segregation patterns in rotating granular mixtures: waviness selection.

We model the radial segregation patterns that form in a thin rotating drum partially filled with beads of two sizes. We predict that the waviness (or amplitude-to-wavelength ratio, denoted w) of a pattern should be subjected to low-pass filtering with a cutoff waviness w(c) that depends strongly on the fill level of the drum. Then we perform experiments and find that w</=w(c) for all patterns, in accord with our prediction. We also find that w=w(c) for (and only for) steady patterns, and conclude that the waviness of a steady pattern is selected by the low-pass filtering.

Journal Article↗
PubMed2003

Structure and kinematics in dense free-surface granular flow.

We show that the structure of a dense, free-surface boundary layer granular flow is similar to the structure of a laminar liquid flow: There is a strong component of order (stratification parallel to the mean flow) superposed with a mild component of disorder (self-diffusion perpendicular to the mean flow). We also show that the self-diffusion coefficient scales with the mean velocity and propose a model that relates this scaling to the ordered structure of the flow. Last, we show that the structure of the flow imprints an oscillatory signature (similar to that found in confined granular flow) on the mean velocity profile.

Journal Article↗
PubMed2003

Do newly diagnosed lung cancer patients feel their concerns are being met?

Lung cancer is the leading cause of cancer death worldwide. It has a poor prognosis and the majority of those affected are elderly. Evidence suggests that providing clear, relevant information and addressing patients' concerns can make a worthwhile difference to patients. This study aimed to: explore the concerns of lung cancer patients shortly after diagnosis; and enquire whether these concerns had been discussed by their care teams. Eighty patients with a new diagnosis of primary lung cancer were interviewed 14-28 days after the date on which they were told the diagnosis. Interviews were conducted either in the hospital ward, outpatient clinic or at home. Participants were asked to rate 17 specific items of concern from 1 = 'not a worry' to 5 = 'extremely worried', plus one non-specific item. Patients rated at least two items as worrying them to some degree with a median of nine concerns being reported. Major concerns for patients were the illness itself; the future relating to the illness and concerns about the family. Overall, patients in the study felt that less than half of their concerns (43%) had been discussed by the care team. Although levels of concern about physical symptoms were relatively low, these had been more frequently addressed than the psychosocial issues, which were rated higher by patients. There were some differences in the number of concerns reported between males/females and younger/older age groups, but the pattern of concerns was similar. There were no differences in the level of concerns between treatment groups; the location of the interview nor in the interval between diagnosis and delivery of the checklist. This study supports previous findings that there is a need for health professionals to provide emotional support and respond to the psychosocial needs of patients by eliciting their concerns and attempting to address them in the early stages of the disease process.

Adaptation, Psychological↗
PubMed2001

Modes of granular segregation in a noncircular rotating cylinder.

Axial segregation is a well-known example of segregation of granular materials. However, at present, there is no conclusive explanation as to why it occurs. Most studies of axial segregation to date are based on cylinders with circular cross sections, and models focus on the character of the surface flow without accounting explicitly for the influence of any subsurface detail. The present experiments demonstrate that the cross section of the mixer has a significant influence on axial segregation and that subsurface dynamics are, in fact, important. Unlike circular mixers, in square mixers the subsurface segregation patterns change with filling level, as does the time dependence of axial segregation. Furthermore, when radial segregation patterns in noncircular mixers most closely resemble that observed for circular cylinders, the time dependence for axial band formation deviates the most. These results challenge segregation theories of axial segregation that ignore subsurface effects.

Journal Article↗
PubMed2001

N-terminal domains of the class ia phosphoinositide 3-kinase regulatory subunit play a role in cytoskeletal but not mitogenic signaling.

Phosphoinositide (PI) 3-kinases are required for the acute regulation of the cytoskeleton by growth factors. We have shown previously that in the MTLn3 rat adenocarcinoma cells line, the p85/p110alpha PI 3-kinase is required for epidermal growth factor (EGF)-stimulated lamellipod extension and formation of new actin barbed ends at the leading edge of the cell. We have now examined the role of the p85alpha regulatory subunit in greater detail. Microinjection of recombinant p85alpha into MTLn3 cells blocked both EGF-stimulated mitogenic signaling and lamellipod extension. In contrast, a truncated p85(1-333), which lacks the SH2 and iSH2 domains and does not bind p110, had no effect on EGF-stimulated mitogenesis but still blocked EGF-stimulated lamellipod extension. Additional deletional analysis showed that the SH3 domain was not required for inhibition of lamellipod extension, as a construct containing only the proline-rich and breakpoint cluster region (BCR) homology domains was sufficient for inhibition. Although the BCR domain of p85 binds Rac, the effects of the p85 constructs were not because of a general inhibition of Rac signaling, because sorbitol-induced JNK activation in MTLn3 cells was not inhibited. These data show that the proline-rich and BCR homology domains of p85 are involved in the coupling of p85/p110 PI 3-kinases to regulation of the actin cytoskeleton. These data provide evidence of a distinct cellular function for the N-terminal domains of p85.

Adenocarcinoma↗
PubMed2001

Living with severe COPD. A qualitative exploration of the experience of patients in Leeds.

A sample of 37 patients with severe chronic obstructive pulmonary disease (COPD) drawn from a larger group of 64 patients being studied in a randomized trial of nebulizer versus high-dose inhaler therapy, and similar in age and gender mix, was interviewed in depth, with a view to illuminating standardized outcome measures and improving the understanding of these patients' needs. Three patients are described in detail. The interview material was analysed using non-computerized methods. Quality of life was seen as depending mainly on family relationships, opportunities afforded locally for neighbourliness and freedom from fear, mobility and independence in the activities of daily living, and the absence or successful mitigation of symptoms of concomitant disease. Disease-specific, symptom-oriented outcome measures may miss these. Additionally, the near and repeatedly threatening approach of death recommended extension of a palliative approach to endstage COPD.

Activities of Daily Living↗
PubMed1999

Segregation-driven organization in chaotic granular flows.

An important industrial problem that provides fascinating puzzles in pattern formation is the tendency for granular mixtures to de-mix or segregate. Small differences in either size or density lead to flow-induced segregation. Similar to fluids, noncohesive granular materials can display chaotic advection; when this happens chaos and segregation compete with each other, giving rise to a wealth of experimental outcomes. Segregated structures, obtained experimentally, display organization in the presence of disorder and are captured by a continuum flow model incorporating collisional diffusion and density-driven segregation. Under certain conditions, structures never settle into a steady shape. This may be the simplest experimental example of a system displaying competition between chaos and order.

Journal Article↗
PubMed1999

Magnetic-field-induced optical transmittance in colloidal suspensions.

Through simulation and experiment we demonstrate that when a magnetic field is applied to a suspension of magnetic particles, the optical attenuation length along the direction of the field increases dramatically, due to the formation of chainlike structures that allow the transmission of light between the strongly absorbing particles. This phenomenon is interesting for two reasons; first, there might be practical applications for this effect, such as optical-fiber-based magnetic field sensors, and second, measuring the time evolution of the optical attenuation length enables us to determine the kinetics of structure formation, which can be compared to the predictions of simulation and theory. In agreement with both simulation and theory, the optical attenuation length increases as a power of time, but much less light is actually transmitted than expected, especially at higher particle concentrations. We conclude that particle roughness, which is not included in either theory or simulation, plays a significant role in structural development, by pinning structures into local minima.

Journal Article↗
PubMed1997

Determination of the metabolites of the herbicide dimethyl tetrachloroterephthalate in drinking water by high-performance liquid chromatography with gas chromatography/mass spectrometry confirmation.

Two metabolites of the herbicide dimethyl tetrachloroterephthalate, (DCPA), monomethyl tetrachloroterephthalate (MM) and tetrachloroterephthalic acid (TCPA), are assayed via high-performance liquid chromatography with ion paring. Samples are analyzed via direct injection, without preparation, and analyte detection is accomplished with an ultraviolet photodiode array detector. The metabolites are extracted from positive samples with a petroleum ether/diethyl ether mixture, derivatized with N,O-bis(trimethylsilyl) trifluoracetamide, and confirmed by way of gas chromatography/mass spectrometry. The HPLC analysis of 200 spiked drinking water samples yielded a recovery range of 92-106% with a mean recovery of 101% for TCPA and a recovery range of 92-101% with a mean recovery of 96% for MM. The minimum detection limits for TCPA and MM were 2.4 and 2.7 micrograms/L, respectively. In addition, the GC/MS analysis of spiked reagent water yielded mean recoveries of 91% for MM and 86% for TCPA. Twenty drinking water samples were split and analyzed by the HPLC and GC/MS methods and by USEPA Method 515.1. Comparable results were obtained. The HPLC method, which is amenable to automation, typically allows for the analysis of up to 40 samples overnight.

Chromatography, High Pressure Liquid↗
PubMed1995

Clinical applicability and test-retest reliability of an external perturbation test of balance in stroke subjects.

We address the test-retest reliability and clinical applicability of an adapted external perturbation balance assessment, ie, the Postural Stress Test (PST). Repeated-measures were designed to assess the clinical features of a component of balance disorder in stroke. Twenty ambulatory stroke patients and 20 age-, gender-, height-, and weight-matched healthy control subjects participated in this study. Stroke patients were tested (using the adapted PST) on 4 separate days; matched control subjects were tested on one occasion. With the subject standing, backward perturbation forces were applied at the level of the center of gravity. Postural reactions to the test were scored in real-time and from videotape, from two different viewing angles, ie, 45 degrees and 90 degrees to the saggital plane. Scores (out of a maximal of 81) were ascertained using a 10-point subjective-observational scale. None of the control subjects fell during testing; four of the hemiplegic subjects fell. Subjects were protected from potential injury by a custom-designed safety harness system. For the hemiplegic subjects, intraclass correlation coefficients (ICCs), calculated as the reliability of any one occasion, ranged from 0.71 to 0.77, whereas those calculated as the reliability of the mean of the first two occasions ranged from 0.83 to 0.93. Although scores on the fourth occasion were significantly greater than those on the third occasion, both being significantly greater than those on the first and second test occasions (p < .05), differences were less than 5 points on the 81-point scale.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Capturing the multiple contributions of the CNS role: a criterion-based evaluation tool.

The CNSs at a community hospital found that tools used to evaluate their performance did not reflect the wide variety of activities native to the CNS role within the institution. A six-member working group came to consensus on practice behaviors, and ordered them into a hierarchy of performance levels. The resulting role description and evaluation tool provides flexibility in application to unit-based, centralized, and specialty-based positions. The benefits of the new role description and evaluation tool to the organization and individual are multiple and serve to highlight the unique talents the role can bring to nursing.

Employee Performance Appraisal↗
PubMed1993

An overhead harness and trolly system for balance and ambulation assessment and training.

Safe assessment of standing balance and gait is often jeopardized by the potential for falls, which may have major physical and legal consequences. This article describes the design and use of a system that enhances the safety of the patient and clinician during balance and gait assessment and training. The system consists of an overhead track and moveable trolly that allows the patient, while secured in a simple body harness, the freedom to ambulate, perform functional types of activities, and fall with minimal risk of injury. As a result, a single therapist can more readily assess balance and ambulation, as well as provide training for these skills. In addition, the therapist is free to observe the patient's movements from any position, without direct physical contact. Practically, the system described may allow ambulation training sooner after injury or surgery, permit training in weight-bearing or partial weight-bearing activities with or without assistive devices, and allow the clinician to focus on assessment and training, rather than on patient safety.

Accidental Falls↗
PubMed1991

Altered daylength affects dendritic structure in a song-related brain region in red-winged blackbirds.

Substantial neural and behavioral plasticity occurs in the avian song system in adulthood. Changes in the volume of one of the song control nuclei, robustus archistriatalis (RA), have been associated with seasonal changes in singing behavior in adult canaries (Serinus canarius) and red-winged blackbirds (Agelaius phoeniceus). The present work assessed the effects of changed daylength on dendritic morphology in RA in adult male red-winged blackbirds. Brains from hand-reared red-winged blackbirds maintained on long days or long days followed by short days were stained with a Golgi-Cox procedure. Dendritic morphology and spine density of type IV neurons from nucleus RA were compared between long and short day birds. Neurons from short day birds have smaller dendritic fields than neurons from long day birds, with the difference greatest for distal dendrites. In addition, the density of dendritic spines is significantly smaller for neurons from short day birds. Together, these changes result in the loss of approximately 40% of the spines on this neuron class. In previous work in adult female canaries, external testosterone administration has been shown to be associated with increases in dendritic field size and synapse number. The similarity of the neuronal changes in RA that are associated with the two sorts of manipulations suggest that some consequences of altered daylength are mediated by changes in the levels of gonadal steroids.

Animals↗
PubMed1988

Immunohistochemical and biochemical analysis of serotonin and substance P colocalization in the nucleus tractus solitarii and associated afferent ganglia of the rat.

In a previous study of afferent projections to the nucleus tractus solitarii (NTS), it was shown that over half of the retrogradely-labelled neurons in the nucleus raphe pallidus contained serotonin-immunoreactivity and over half of these neurons contained substance P-immunoreactivity, suggesting that these two putative neurotransmitters are colocalized in NTS-afferent neurons. The objectives of the present study were to 1) directly determine if varicosities in the NTS, the area postrema (AP), and the dorsal motor nucleus of the vagus nerve (DMN) do contain both transmitters, 2) determine if primary afferent neurons in the nodose and pretrosal ganglia might also colocalize serotonin and substance P, and 3) quantify the amount of substance P that is contained in serotonergic varicosities in the NTS. Distributions and colocalization of substance P and serotonin in the NTS were studied using dual-color immunohistochemistry, while the quantity of substance P in serotonergic varicosities was assessed by radioimmunoassay (RIA) using micropunches from the NTS of 5,7-dihydroxytryptamine-(5,7 DHT-) and vehicle-treated rats. Varicosities that contained both serotonin- and substance P-immunoreactivity were found in the NTS, the DMN, and the AP. Double-labelled varicosities were common in the NTS and DMN (i.e., qualitatively similar to the density seen in the hypoglossal nucleus and in the ventral horn of the cervical spinal cord); however, the vast majority of the varicosities in these autonomic areas only displayed immunoreactivity for one or the other of these transmitters. This paucity of doubly-labelled varicosities, in comparison to the number of singly-labelled varicosities, was reflected in the lack of a significant decrease in substance P levels as determined by RIA of micropunches taken from caudal and intermediate levels of the NTS in 5,7 DHT- and vehicle-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗