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Kant's concept of natural purpose and the reflecting power of judgement.

This paper examines how in the 'Critique of teleological judgment' Kant characterized the concept of natural purpose in relation to and in distinction from the concepts of nature and the concept of purpose he had developed in his other critical writings. Kant maintained that neither the principles of mechanical science nor the pure concepts of the understanding through which we determine experience in general provide adequate conceptualizations of the unique capacities of organisms. He also held that although the concept of natural purpose was derived through reflection upon an analogy to human purposive activity in artistic production and moral action, it articulates a unique notion of intrinsic purposiveness. Kant restricted his critical reflections on organisms to phenomena that can be given to us in experience, criticizing speculations on their first origins or final purpose. But I argue that he held that the concept of natural purpose is a product of the reflecting power of judgment, rather than an empirical concept, and represents only the relation of things to our power of judgment. Yet it is necessary for the identification of organisms as organized and self-organizing, and as subject to unique norms and causal relations between parts and whole.

Biological Science Disciplines↗

Clinical evaluation of postpartum vaginal mucus reflects uterine bacterial infection and the immune response in cattle.

Bacteria contaminate the uterus of most dairy cattle after parturition and endometritis causes infertility. An endometritis score can be ascribed based on the vaginal mucus character and odour but it is not clear if the clinical score reflects the number of uterine bacteria or the inflammatory response. The present study tested the hypothesis that clinical evaluation of endometritis reflects the number of bacteria present in the uterus, and the acute phase protein response. Swabs (n = 328) were collected from the uterine lumen of dairy cattle, 21 and 28 days postpartum, vaginal mucus was scored for character and odour, and blood samples collected for acute phase protein measurement. Bacteria were identified following aerobic and anaerobic culture, and the bacterial growth density was scored semi-quantitatively. When bacteria were categorised by their expected pathogenic potential in the uterus, purulent or fetid odour vaginal mucus was associated with the growth density of pathogenic bacteria but not opportunist contaminants. When bacteria were analysed independently, Arcanobacterium pyogenes, Proteus and Fusobacterium necrophorum growth densities were associated with mucopurulent or purulent vaginal mucus. The bacterial growth densities for A. pyogenes, Escherichia coli, non-hemolytic Streptococci, and Mannheimia haemolytica were associated with a fetid mucus odour. Peripheral plasma concentrations of alpha(1)-acid glycoprotein were higher if there was a fetid compared with a normal vaginal mucus odour (1.50 +/- 0.09 mg/mL versus 1.05 +/- 0.02 mg/mL, P < 0.001), but did not differ significantly between vaginal mucus character scores. The evaluation of the character and odour of vaginal mucus reflects the number of bacteria in the uterus, and the acute phase protein response.

Actinomycetaceae↗

Attenuation coefficient estimation using experimental diffraction corrections with multiple interface reflections.

The ultrasonic attenuation coefficient of a fluid or solid is an acoustic parameter routinely estimated for the purpose of materials characterization and defect/disease detection. This paper describes a broadband attenuation coefficient estimation technique that combines two established estimation approaches. The key elements of these two approaches are: (1) the use of magnitude spectrum ratios of front surface, first back surface, and second back surface reflections from interfaces of materials with plate-like geometries, and (2) the use of an experimental diffraction correction approach to avoid diffraction losses. The combined estimation approach simplifies the attenuation coefficient estimation process by eliminating the need to explicitly make diffraction corrections or calculate reflection/transmission coefficients. The approach yields estimates of the attenuation coefficient, reflection coefficient, and material density. Models, experimental procedures, and signal analysis procedures, which support implementation of the approach, are presented. Attenuation coefficient and reflection coefficient estimates are presented for water and solid samples with estimates based on measurements made with multiple transducers.

Journal Article↗

Impact of localized inhomogeneity on the surface-wave velocity and bulk-wave reflection in solids.

The effect of a weak surface, near-surface and interfacial inhomogeneity on the frequency dependence of the surface wave velocity and of the SH (shear horizontal) wave reflectivity in isotropic elastic media is studied analytically and numerically. The inhomogeneity is modeled as an infinite planar layer with continuously varying properties. Weak inhomogeneity may markedly affect the dispersion of the Rayleigh velocity and especially of the reflectivity. It is demonstrated how this effect, particularly pronounced at high frequency, depends on the extent of inhomogeneity. The material data for damaged and ideal concrete and several simple examples of inhomogeneity profiles are utilized for the numerical calculations based on the Peano expansion. The use of explicit low- and high-frequency approximations is also exemplified. Among these, simple WKB asymptotics are shown to be particularly helpful for the Rayleigh velocity in the case of a prominent inhomogeneity attached to the surface and for the reflection on weak interfaces.

Models, Theoretical↗

Minimization of finite beam effects in the determination of reflection and transmission coefficients of an elastic layer.

A special data acquisition technique was applied to determine the acoustic plane-wave reflection and transmission properties of a plane-parallel aluminum plate. In this technique, the reflected and transmitted wavefield along a plane or line normal to the reflected or transmitted wave vector is recorded at equidistant receiver positions. The obtained traces are subsequently added up in the temporal domain to satisfy plane-wave conditions, thus effectively removing the effect of the limited beam of commonly used transducers. The agreement between plane-wave theory and experiment was found to be excellent, both in the temporal and in the frequency domain.

Aluminum↗

A model for reflectivity enhancement due to surface bound submicrometer particles.

Submicrometer particles filled with liquid perfluorocarbon have been shown to increase the ultrasound reflectivity of surfaces onto which they bind and, consequently, are seen as potential targeted contrast agents. The objective of this study is to explain the reflectivity enhancement as a result of the presence of randomly distributed particles on a surface. A model is presented where the diffraction-weighted scattering of all particles is summed over the exposed surface. Experiments were performed at frequencies ranging from 15 MHz to 60 MHz, with glass microbeads and perfluorohexane particles deposited on the surface of agar and Aqualene, a rubber closely matched to water, to confirm the validity of the model. Results showed that the model predicts the surface density and the frequency dependence of the reflectivity enhancement up to a density corresponding to twice the maximum packing of spheres on a surface (200% confluence fraction) for glass beads and a fifth (20% confluence fraction) for perfluorohexane particles. This suggests the possibility of predicting signal enhancement due to a bound contrast agent in simple geometries.

Contrast Media↗

Comparative effectiveness of solar disinfection using small-scale batch reactors with reflective, absorptive and transmissive rear surfaces.

This study investigated the enhancement of solar disinfection using custom-made batch reactors with reflective (foil-backed) or absorptive (black-backed) rear surfaces, under a range of weather conditions in India. Plate counts of Escherichia coli ATCC11775 were made under aerobic conditions and under conditions where reactive oxygen species (ROS) were neutralised, i.e. in growth medium supplemented with 0.05% w/v sodium pyruvate plus incubation under anaerobic conditions. While the addition of either an absorptive or a reflective backing enhanced reactor performance under strong sunlight, the reflective reactor was the only system to show consistent enhancement under low sunlight, where the process was slowest. Counts performed under ROS-neutralised conditions were slightly higher than those in air, indicating that a fraction of the cells become sub-lethally injured during exposure to sunlight to the extent that they were unable to grow aerobically. However, the influence of this phenomenon on the dynamics of inactivation was relatively small.

Absorption↗

Lack of local reflection of national changes in cesarean delivery rates: the Canadian experience.

OBJECTIVE: The purpose of this study was to determine whether national changes in cesarean delivery rates were reflected in the rates of individual maternity units. STUDY DESIGN: Cesarean delivery rate changes among the 240 largest maternity units in Canada were compared with national cesarean delivery rate changes for the years 1983 through 1992. The periods of interest for cesarean delivery rate changes were 1983 through 1988 (a period of increasing national rates), 1988 through 1992 (a period of decreasing national rates), and 1983 through 1992 (a period with similar national rates at the end points). RESULTS: For 1983-1988, 75% of the maternity units reflected changes that were not even in the same direction as those of the national mean changes. For the subperiods 1983-1992 and 1988-1992, these values were 48% and 53%, respectively. CONCLUSIONS: National trends in cesarean delivery rates do not reflect a uniform shift among maternity units, demonstrating the limitations of national means as goals for local practice.

Canada↗

Polarized task lighting to reduce reflective glare in open-plan office cubicles.

This ergonomic study deals with the common situation where a glossy document is placed between a viewer and an under-shelf task light source in a common open-plan office cubicle workstation. With a task lamp in front, when looking at a document a viewer sees two images, the document itself and specular glare, which is the reflected image of the light source. Specular glare or veiling reflection causes eye discomfort, makes it difficult to read a document and has been thought to contribute to eyestrain. This paper analyzes the application of polarized lighting for this specific situation. The use of a linear polarized light source helps to minimize specular glare by darkening the reflected image of the light source on the document. The performance and predictive optimization of the use of polarized lighting in this situation is investigated according to female and male viewer height demographics. Theoretical predictions and light measurement analysis of specular glare reduction are compared with empirical results from testing on a panel of humans on semi-gloss finish and matte finish papers. This study shows that with the right alteration of a polarized light source position, specular glare may be significantly reduced, and correlations exist between the theory, empirical measurements and the human response to specular glare reduction.

Analysis of Variance↗

Cell volume kinetics of adherent epithelial cells measured by laser scanning reflection microscopy: determination of water permeability changes of renal principal cells.

The water channel aquaporin-2 (AQP2), a key component of the antidiuretic machinery in the kidney, is rapidly regulated by the antidiuretic hormone vasopressin. The hormone exerts its action by inducing a translocation of AQP2 from intracellular vesicles to the cell membrane. This step requires the elevation of intracellular cyclic AMP. We describe here a new method, laser scanning reflection microscopy (LSRM), suitable for determining cellular osmotic water permeability coefficient changes in primary cultured inner medullary collecting duct (IMCD) cells. The recording of vertical-reflection-mode x-z-scan section areas of unstained, living IMCD cells proved useful and valid for the investigation of osmotic water permeability changes. The time-dependent increases of reflection-mode x-z-scan section areas of swelling cells were fitted to a single-exponential equation. The analysis of the time constants of these processes indicates a twofold increase in osmotic water permeability of IMCD cells after treatment of the cells both with forskolin, a cyclic AMP-elevating agent, and with Clostridium difficile toxin B, an inhibitor of Rho proteins that leads to depolymerization of F-actin-containing stress fibers. This indicates that both agents lead to the functional insertion of AQP2 into the cell membrane. Thus, we have established a new functional assay for the study of the regulation of the water permeability at the cellular level.

Actins↗

Transport across homoporous and heteroporous membranes in nonideal, nondilute solutions. I. Inequality of reflection coefficients for volume flow and solute flow.

The Kirkwood formulation of the Stefan-Maxwell equations is used to develop the transport equations for a membrane bounded by nonideal, nondilute solutions. The reflection coefficients for volume flow and solute flow are not equal but are related by a simple expression that depends on the concentration of the bounding solutions. The ratio of the two coefficients is independent of heteroporous membrane structure and the thickness of adjacent boundary layers. Experimental measurements of these reflection coefficients for sucrose transport across Cuprophan verify this relationship; this indicates that the Onsager reciprocal relation, which is assumed by the theory, holds for nonideal, nondilute solutions. The two reflection coefficients may be made operationally identical by a simple redefination of the osmotic driving force.

Biological Transport↗

Quantitative analysis of molecular orientation in chlorophyll a Langmuir monolayer: a polarized visible reflection spectroscopic study.

Polarized visible reflection spectra of a chlorophyll a (Chl.a) Langmuir monolayer have been measured in situ at various surface pressures. By applying Hansen's optics to the three-phase plane-bounded system (air/Chl.a monolayer/water), the negative reflection absorbances observed were reproduced satisfactorily by the theoretical calculation. Molecular orientation of Chl.a in the monolayer was evaluated quantitatively as a function of surface pressure, from the reflection absorbance of p- and s-polarized spectra of the red (Qy) band. It has been proven that Chl.a molecules in the monolayer form aggregates (islands) even in the low surface pressure region and that during the monolayer compression the molecules are gradually reorganized from inhomogeneous islands to ordered structures, with the chromophores oriented on the average vertically to the water surface.

Chlorophyll↗

Polarization-modulated infrared spectroscopy and x-ray reflectivity of photosystem II core complex at the gas-water interface.

The state of photosystem II core complex (PS II CC) in monolayer at the gas-water interface was investigated using in situ polarization-modulated infrared reflection absorption spectroscopy and x-ray reflectivity techniques. Two approaches for preparing and manipulating the monolayers were examined and compared. In the first, PS II CC was compressed immediately after spreading at an initial surface pressure of 5.7 mN/m, whereas in the second, the monolayer was incubated for 30 min at an initial surface pressure of 0.6 mN/m before compression. In the first approach, the protein complex maintained its native alpha-helical conformation upon compression, and the secondary structure of PS II CC was found to be stable for 2 h. The second approach resulted in films showing stable surface pressure below 30 mN/m and the presence of large amounts of beta-sheets, which indicated denaturation of PS II CC. Above 30 mN/m, those films suffered surface pressure instability, which had to be compensated by continuous compression. This instability was correlated with the formation of new alpha-helices in the film. Measurements at 4 degreesC strongly reduced denaturation of PS II CC. The x-ray reflectivity studies indicated that the spread film consists of a single protein layer at the gas-water interface. Altogether, this study provides direct structural and molecular information on membrane proteins when spread in monolayers at the gas-water interface.

Biophysical Phenomena↗

Determination of red blood cell shape recovery time constant in a Couette system by the analysis of light reflectance and ektacytometry.

Red blood cell (RBC) shape change under shear is generally reversible, with the time course of shape recovery a function of the elastic and viscous properties of the RBC membrane. RBC shape recovery can be investigated, using several different techniques, to provide information about the membrane material properties that are not directly accessible by frequently used methods to assess RBC deformability (e.g., micropore filtration). In the present study, RBC shape recovery was studied in a Couette system after abrupt cessation of shear, either by analyzing the time course of laser light reflection or by serial measurements of elongation indexes from laser diffraction patterns. The time course of shape recovery monitored with both techniques can be described with an exponential equation. Calculated time constants for normal human RBC were 119 +/- 17 msec and 97 +/- 15 msec as measured by light reflection and ektacytometry, respectively. Treatment of RBC with glutaraldehyde resulted in dose-dependent decreases in the shape recovery time constant. Heat treatment (48 degrees C, 20 min), which is known to increase mainly the shear elastic modulus of the membrane, decreased the time constant by 65%. In contrast, wheat germ agglutinin treatment increased the shape recovery time constant by 22%, presumably by increasing membrane surface viscosity. Our results indicate that the shape recovery time constant of RBC can be measured easily and accurately by computerized light reflection analysis.

Computers↗

Increased renal reflectivity in sickle cell disease: prevalence and characteristics.

Renal ultrasound appearances have been examined in 315 patients with sickle cell disease aged 10-20 years, followed in a cohort study from birth. There were three different echo patterns. A normal appearance (type 1) occurred in 235 (75%) of all subjects, and in 159/179 (89%) with homozygous sickle cell (SS) disease. A diffuse increase in reflectivity throughout the kidney (type 2), similar to that of adjacent liver, occurred in 17 patients (5%). Widespread confluent or focal increase in reflectivity confined to the renal medulla (type 3) occurred in 63 (20%) of the total group, and was much more common in the mild genotypes of sickle cell-haemoglobin C disease (41/111, 37%) and sickle cell-beta+ thalassaemia (15/19, 79%) than in SS disease (5/179, 3%). We speculate that type 2 changes may reflect diffuse glomerular and interstitial fibrosis, and that type 3 resembles changes seen in sub-clinical nephrocalcinosis, and could be due to iron deposition.

Adolescent↗

Gastroduodenal mucosal hemodynamics by endoscopic reflectance spectrophotometry.

The reflectance spectrophotometric technique measures an index of mucosal hemoglobin concentration and an index of oxygen saturation by spectral analysis of light reflected from the mucosal surface. Using a commercially available unit, a technique for obtaining reproducible endoscopic measurements with acceptable intraobserver and interobserver variability was developed in the anesthetized dogs. The reflectance spectrophotometric finding that experimentally induced prehepatic portal hypertension did not affect gastric mucosal blood flow was confirmed by hydrogen gas clearance measurements. Endoscopic studies in patients with active duodenal ulcer disease revealed a higher index of mucosal hemoglobin concentration and a normal index of oxygen saturation (i.e., an increase in blood flow) at the margin of the ulcer compared with the adjacent normal appearing mucosa.

Animals↗

Factors influencing reflectance spectrophotometric measurements of gastrointestinal mucosal blood flow.

Although the technique of endoscopic reflectance spectrophotometry has been applied in clinical studies, factors that modify the reproducibility of measurements have not been assessed systematically. To determine the limitations of the technique, measurements were made while endoscopic light intensity, systemic oxygen saturation, and orientation of the measuring probe were varied. The effects of hemorrhagic hypotension and exposure of the mucosa to 10% dextrose were also studied. When a large number (n = 480) of measurements in the human colon were considered, endoscopic light significantly decreased the index of oxygen saturation (ISO2) and increased the index of hemoglobin concentration (IHB). The decrease in ISO2, however, was small and unlikely to be of clinical importance despite being statistically significant. In one subject with chronic lung disease and baseline hypoxemia, administration of supplemental oxygen significantly increased oxygen saturation at the finger tip as measured by an oximeter and ISO2 of the buccal mucosa as measured by reflectance spectrophotometry. Varying the angle between the measuring probe and the gastric mucosa in rats from 90 degrees to 60 degrees did not affect ISO2 or IHB measurements. At 45 degrees, however, IHB but not ISO2 was significantly increased. Ischemia subsequent to induction of hemorrhagic hypotension and hyperemia induced by administration of 10% dextrose could be demonstrated reproducibly. We conclude that by lowering the intensity of endoscopic light and providing supplemental oxygen, errors in the measurement of IHB and ISO2, respectively, can be minimized. Minor deviations from the perpendicular orientation do not significantly affect ISO2 and IHB measurements. Attention to these details enhances the accuracy of endoscopic reflectance spectrophotometric recordings of ISO2 and IHB in clinical studies.

Animals↗

Determination of cholesterol in atherosclerotic plaques using near infrared diffuse reflection spectroscopy.

The aim of this investigation was to examine whether near infrared diffuse reflection spectroscopy is an acceptable tool for the determination of cholesterol content in atherosclerotic plaques. Using an FT-spectrophotometer (lambda=1000-2500 nm) and fiberoptic systems (d=4 mm), the cholesterol content could be determined in mixtures of the primary compounds of the aortic wall with acceptable precision. Considering the inhomogeneous distribution of cholesterol and cholesterol esters in atherosclerotic plaques the determination of total cholesterol using this method is of acceptable efficacy, even though the calibration procedure did not reflect the composition correctly. Using an energy dose of less than 100 mW/cm(2) to avoid damage to endothelial cells, arterial tissue of about 170-200 microm thickness attenuates the reflected NIRS signal by up to 50%. Cholesterol levels could be determined accurately in atherosclerotic lesions in human aortic specimens obtained by autopsy. The correlation coefficient between the NIRS results and those of HPLC analysis calculated in the investigation of 82 different areas of 18 human aortic specimens was 0.926 (y=0.869x+0. 771, external validation). Acceptable results were also achieved by means of a coronary-catheterlike fiberoptic strand (d=l mm), despite the worsened signal/noise ratio. The results show that the development of a coronary catheter using NIRS appears to be possible in principle.

Arteriosclerosis↗