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Biomedical subjects

K L Pinder

Publications and source records attributed to K L Pinder.

16 recordsLinked to original sources
PubMed2006

Effects of residence time distribution and packing on methanol oxidation in biotrickling filter.

The effects of residence time distribution (RTD) on biotrickling filter systems and the comparison of the maximum elimination capacity (EC) and poisoning limits as functions of loadings of two packing media, Celite Biocatalyst Carrier R-635 and a subituminous coal, were studied. To alter the RTD patterns in the two reactor columns, two baffle designs were chosen. The RTD tests were done under dry conditions, over a range of airflow rates, with zero baffle, one baffle, and two baffles added into each column. Mixed culture from compost was used to acclimate the bed for the methanol removal efficiency study. No nutrients were added in the coal column. To study the poisoning limit, the inlet methanol concentration was randomly increased until a severe drop in removal efficiency occurred. From the RTD tests and the removal efficiency runs, which did not result in 100% conversion, number of tank-in-series (N) values, maximum EC values, and rate constants of each column with different baffle configurations could be obtained. Results from duplicate runs showed that addition of baffles decreased the N values of the columns and increased the back mixing in both systems. Maximum EC values, critical loadings, and poisoning limits also increased with increasing back mixing. Coal was superior to Celite Biocatalyst Carrier R-635 because it gave good conversions without additional nutrients. In all runs, the rate of methanol removal was controlled by a zero order process.

Air Pollutants↗
PubMed2001

Development and performance of an alternative biofilter system.

Step tracer tests were carried out on lab-scale biofilters to determine the residence time distributions (RTDs) of gases passing through two types of biofilters: a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow. Results were used to define the flow patterns in the reactors. "Non-ideal flow" indicates that the flow reactors did not behave like either type of ideal reactor: the perfectly stirred reactor [often called a "continuously stirred tank reactor" (CSTR)] or the plug-flow reactor. The horizontal biofilter with back-mixing was able to accommodate a shorter residence time without the usual requirement of greater biofilter surface area for increased biofiltration efficiency. Experimental results indicated that the first bed of the modified biofilter behaved like two CSTRs in series, while the second bed may be represented by two or three CSTRs in series. Because of the flow baffles used in the horizontal biofilter system, its performance was more similar to completely mixed systems, and hence, it could not be modeled as a plug-flow reactor. For the standard biofilter, the number of CSTRs was found to be between 2 and 9 depending on the airflow rate. In terms of NH3 removal efficiency and elimination capacity, the standard biofilter was not as good as the modified system; moreover, the second bed of the modified biofilter exhibited greater removal efficiency than the first bed. The elimination rate increased as biofilter load increased. An opposite trend was exhibited with respect to removal efficiency.

Air Pollutants, Occupational↗
PubMed2000

Mechanical properties of the tracheal mucosal membrane in the rabbit. I. steady-state stiffness as a function of age.

Airway responsiveness is exaggerated in infancy and declines with maturation. These age-related differences (R.S. Tepper, T. Du, A. Styhler, M. Ludwig, and J.G. Martin. Am. J. Respir. Crit. Care Med. 151: 836-840, 1995; R.S. Tepper, S.J. Gunst, C.M. Doerschuk, Y. Shen, and W. Bray. J. Appl. Physiol. 78: 505-512, 1995; R.S. Tepper, J. Stevens, and H. Eigen. Am. J. Respir. Crit. Care Med. 149: 678-681, 1994) could be due to changes in the smooth muscle, the lung, and/or the airway wall. Folding of the mucosal membrane can provide an elastic load (R.K. Lambert, J. Appl. Physiol. 71: 666-673, 1991), which impedes smooth muscle shortening. We hypothesized that increased stiffness of the mucosal membrane occurs during aging, causing an increased mechanical load on airway smooth muscle and a decrease in airway responsiveness. Forty female New Zealand White rabbits between 0.75 and 35 mo of age were studied. Rectangular mucosal membrane strips oriented both longitudinally and circumferentially to the long axis of the trachea were dissected, and the stress-strain relationships of each strip were tested. The results showed that the membrane was stiffer in the longitudinal than in the circumferential direction of the airway. However, there was no significant change with age in either orientation. We conclude that the mechanical properties of the airway mucosal membrane did not change during maturation and were not likely to influence age-related changes in airway responsiveness.

Aging↗
PubMed2000

Mechanical properties of the tracheal mucosal membrane in the rabbit. II. Morphometric analysis.

Folding of the airway mucosal membrane provides a mechanical load that impedes airway smooth muscle contraction. Mechanical testing of rabbit tracheal mucosal membrane showed that the membrane is stiffer in the longitudinal than in the circumferential direction of the airway. To explain this difference in the mechanical properties, we studied the morphological structure of the rabbit tracheal mucosal membrane in both longitudinal and circumferential directions. The collagen fibers were found to form a random meshwork, which would not account for differences in stiffness in the longitudinal and circumferential directions. The volume fraction of the elastic fibers was measured using a point-counting technique. The orientation of the elastic fibers in the tissue samples was measured using a new method based on simple geometry and probability. The results showed that the volume fraction of the elastic fibers in the rabbit tracheal mucosal membrane was approximately 5% and that the elastic fibers were mainly oriented in the longitudinal direction. Age had no statistically significant effect on either the volume fraction or the orientation of the elastic fibers. Linear correlations were found between the steady-state stiffness and the quantity of the elastic fibers oriented in the direction of testing.

Animals↗
PubMed1997

Fast Fourier transform analysis of dynamic data: sine wave stress-strain analysis of biological tissue.

We propose an improvement to the dynamic oscillation method using as an example the measurement of the tensile stiffness of the rabbit tracheal mucosal membrane. A sine wave oscillation technique was used to study the tissue mechanical properties. A mathematical model was developed using fast Fourier analysis. After mathematically eliminating the machine response, this analysis reveals the tissue frequency response over a wide range of frequencies. This study addresses the advantages of using Fourier analysis to interpret dynamic properties of biological tissue and provides a complete description of how to obtain the pure tissue response.

Animals↗
PubMed1993

Psychiatric disorder in patients with advanced breast cancer: prevalence and associated factors.

The prevalence of psychiatric disorder and associated factors has been examined in 139 women with advanced breast cancer. Patients completed a self-report assessment of mood, the Hospital Anxiety and Depression Scale (HAD). They were also interviewed to obtain sociodemographic details, UICC performance status and past psychiatric history. Overall, 35 (25%) scored 11 or above (out of a maximum of 21) on either the anxiety or the depression subscales, or both, of the HAD and were therefore probable cases of anxiety and/or depression. These patients are likely to benefit from psychosocial intervention. Clinical anxiety was unrelated to any sociodemographic or disease related factors. Clinical depression was significantly more prevalent amongst patients in the lower socioeconomic classes (P = 0.01) and those with poor performance status (P = 0.007). Depression can be difficult to detect in patients with advanced breast cancer and these factors may be useful indicators to clinicians of patients at high risk of this disorder.

Adult↗
PubMed1986

Digital simulation of pulmonary microvascular exchange.

A previously published analog computer simulation of blood to lymph fluid and protein transport in the human lung [Microvascular Research 27, 51-70 (1984)] has been converted to a digital program. Comparisons have been made between the predictions of the two programs for both transient and steady state responses to perturbations. The advantages of each program are discussed. The FORTRAN simulation, including the input and output files are explained. Copies of the program will be made for anyone who wishes to use it.

Body Fluids↗
PubMed1984

Mechanical response of reconstituted, freeze-dried collagen under compressive loads.

The mechanical response under uniaxial compression of collagen discs, made from freeze-dried collagen reconstituted at acid pH, was investigated at 22, 29.5 and 35 degrees C. The pH during compression was maintained at the physiological level of 7.4. The fluid transport model developed by Bert (1970) was fitted to the data. Assumptions, made in the development of the model, were tested and the range of reliability of the model is discussed. The two fitting parameters of the model were found to be stronger functions of hydration than was previously reported. The compressive response of collagen was found to be only weakly influenced by temperature. At 35 degrees C there was evidence of thermal degradation. Some creep was noted at times greater than five half-times, but no attempt was made to quantify it.

Biomechanical Phenomena↗
PubMed1984

Pulmonary microvascular exchange: an analog computer simulation.

An analog computer simulation of human pulmonary microvascular exchange was programmed and tested. This model of blood-to-lymph transport is based on a compartmental analysis of the lungs and has the capacity to describe fluid volumes, plasma protein content, flows and pressures for both normal and perturbed conditions. Normal conditions were predicted and shown to be in agreement with the literature. The trends in the response of the lungs to changes in microvascular pressure is shown also to agree with the literature both for steady state and transient predictions. The results of a sensitivity analysis, which demonstrates the response of the lungs to a variety of perturbations, is also reported. The simulation predicts reasonable results for normal, transient, and perturbed conditions in human lungs.

Blood Proteins↗
PubMed1982

Lymph flow characteristics and microvascular exchange: an analog computer simulation.

Lymphatic flow characteristics, which include both progressive lymphatic blockage and plateau of lymph flow with increasing interstitial fluid volume, were incorporated into an analog computer simulation of microvascular exchange, and their effects on interstitial fluid volume and protein content were investigated. The steady state and transient response of the microcirculation to changes in the properties of the lymph flow system are reported. The interstitial fluid and protein content is investigated as a function of venous pressure and for changes associated with the lymph flow characteristics. The interstitial protein content is generally more sensitive to changes in the lymph flow properties than is interstitial fluid volume. Properties of lymphatic drainage of tissues as they effect microvascular exchange are discussed.

Computers↗
PubMed1979

Rheological properties of skin components under compressive load.

Characterization was made of the mechanical properties under compression of four major skin components (collagen, elastin, chondroitin sulfate, and hyaluronic acid) placed in a gel matrix. Using the previous theoretical work of Bert et al., thickness under compression was related to degree of hydration and the results expressed in terms of pressure vs. hydration. All measurements were conducted at 14 degrees C, 21 degrees C, and 25 degrees C. Application of the findings to a model based on the finite deformation strain-energy theory of Aubert indicate that collagen, elastin, and chondroitin sulfate show a viscoelastic response under compression. On the other hand, hyaluronic acid and gelatin exhibit rubber-like behavior.

Chondroitin↗