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The surface topography and pore structure of ultrafiltration membranes can be investigated with atomic force microscopy. In this study, it was found that the substitution of ethanol for water as the immersion medium improved the resolution of the fine structure of 10K polyethersulfone ultrafiltration membranes. Pores in the membrane surface from 7 to 9 nm in diameter were measured, which coincides with the range expected for 10,000 molecular weight cutoff (MWCO) ultrafiltration membranes. It is believed that this image enhancement results from increased damping and concomitant noise reduction resulting from the higher viscosity of ethanol in contrast to water.

AFM and SEM were used to investigate the surface structure and morphology of 10,000, 30,000, and 100,000 dalton molecular weight cutoff (MWCO) polyethersulfone (PES) ultrafiltration membranes, and the results are compared. Although both approaches reveal the pore structure in the 30,000 and 100,000 MWCO membranes, the pore diameters derived from SEM are smaller than those measured by AFM. This discrepancy is a result of the diminution in pore difmensions during the sample preparation for SEM. In contrast to SEM, which requires a high vacuum both during heavy metal coating and during examination, AFM can be performed on wet ultrafiltration membranes

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to investigate the surface structure and topography of polyvinylidene fluoride (PVDF) microfiltration membranes. A structure with nodules, nodule aggregates, and supernodular aggregates consistent with the Four Tiers of Structure Model for integrally skinned phase inversion membranes advanced by Kesting is observed. AFM reveals very uniform nodule aggregates with intermediate sized pores in their interstitial regions. These nodule aggregates exist in larger assemblies of supernodular aggregates, which possess much larger pres at their boundaries. These pores are surface extensions of the openings between cells in the matrix. The smallest sized pores are detected in the nodule aggregate themselves between assemblies of nodules and are attributed to internal stresses developed as crystallization occurs after the coagulation process.

We report a near-field scanning optical microscope using a solid immersion lens having a sharp tip that is mounted to a cantilever. The sharp tip allows the sample to enter the near field of the illumination. The cantilever provides sensitive control of forces. We describe two types of near-field optical contrast, interference and reflection, that simultaneously measure surface topography and reflectivity. Using a super-hemispherical lens with index n=2.2 and 442 nm illumination, the microscope resolves optical features smaller than 150 nm, a factor of 2 improvement over a conventional optical microscope.

The atomic force microscope (AFM) is now a fairly widely used metrological tool for measuring surfaces with nanometer-scale precision, in 3-D. A number of biologists have noticed that untreated biological cells and molecules deposited onto surfaces can also be analyzed by AFM in air or fluids provided the AFM imaging forces do not greatly excede the compressiblity of the specimen. What has gone largely unnoticed in the biological microscopy community is the fact that AFM provides a wealth of opportunity with regard to 3D, nanometer-scale morphometric and biochemical measurements of biomaterials, cells and molecules. The ability to obtain such precise length-scale measurements on biological structures does open up a whole new branch of biological microscopy- something we have termed, Biometrology. A broad definition of Biometrology is, the science of quantifying biological structures such that the measured quantities give rise to biological or diagnostic information.

Bioassays, including immunoassays, enzyme assays, and assays using enzyme electrodes, and nucleic acid hybridization probes have been the subject of considerable industrial and academic research. New bioassay methods have applications in the medical, chemical, pharmaceutical, and food products industries. Recent US patents and scientific literature on a variety of new bioassay methods are surveyed. A description of these patents and a list of references are given.

A computerized transverse-axial x-ray scanning tomography system has been constructed and operated using inexpensive and readily available components. The system is used only for the scanning of phantoms and the image reconstruction is carried out on an IBM 360/75. Images reconstructed from data taken by the device are able to resolve radiographic density variations of about 1/2% over distances of 0.5 cm.

In vitro and in vivo indicator-dilution measurements are made with a fluorescent indicator and a novel detection system using a catheter containing a single optical fiber that carries both the exciting and returning fluorescent light. These fluorescent-dilution measurements are compared with simultaneous green dye-dilution measurements. The double-indicator-dilution measurement of extravascular lung water using heat and fluorescence is compared with gravimetric measurements. Also investigated is the sensitivity of the fluorescent measurement to changes in O2 saturation and hematocrit of the blood. An example of the measurement of a right-to-left heart shunt with this new indicator is given.

The isometric tension development of a one-dimensional regionally ischemic muscle was analyzed theoretically. The model consist of a one-dimensional normal segment in series with a one-dimensional ischemic segment. Each segment is modeled as a three-element muscle. The inputs to the various elements, except the contractile element in ischemic segment, were obtained from published data for cat papillary muscles. To be consistent with segment length measurements on ischemic canine hearts, it was assumed that the ischemic contractile element contracted normally at the beginning of contraction and then at some tension, TM, fell behind in its rate of tension development compared to the contractile element in the normal segment. Rate of tension development of various lengths of the ischemic segment and strengths of the ischemic contractile element. At the tension, TM, the ischemic segment begins undergoing paradoxical expansion and, simultaneously, as a result of the expansion. the time derivative of the tension produced by the regionally ischemic muscle exhibits a sudden decrease.

Central to the use of fluorescein in vascular diagnosis is the requirement that the intensity of evoked fluorescence be proportional to blood flow. With the introduction of the digital dermofluorometer, a device that quantitates cutaneous fluorescence, establishment of this relationship has become possible. After experimentally producing measured reductions in the distal aortic flow of eight rabbits, the ratio of fluorescence in the flow-restricted and unrestricted areas was obtained by measuring hind- and forelimb fluorescence. At any time between 20 and 60 minutes following a bolus injection of sodium fluorescein (1 mg/kg body weight), there was a significant linear relationship (p less than 0.05, r greater than 0.75) between residual aortic flow and the ratio of hind-/forelimb fluorescence. Simultaneously obtained plasma fluorescein concentrations decayed rapidly by first-order kinetics with a half-life of 12.5 minutes, regardless of the degree of distal aortic occlusion. The time course of the rise and fall of cutaneous fluorescence was slower than that of the plasma fluorescein concentration, proving that interstitial rather than intravascular fluorescein was responsible for the measured fluorescence. We conclude that the intensity of tissue fluorescence is linearly related to blood flow and that conclusions regarding perfusion may be drawn from relative fluorescence at any time between 20 and 60 minutes following a bolus injection of fluorescein. Furthermore, the passage of fluorescein into the interstitium is dependent on a time-limited diffusion process, which along with flow, establishes the time to peak and the absolute amplitude of the tissue fluorescence curve.

Extravascular lung water (EVLW) and cardiac output (CO) were determined in 21 mongrel dogs using the thermal-green dye double indicator dilution technique. In 12 of the animals the renal vessels were ligated bilaterally to increase peripheral resistance and reduce cardiac output without altering actual EVLW. Measurements before and after renal pedicle ligation revealed an average 47 per cent decrease in cardiac output with an 11 per cent increase in measured lung water. In the remaining nine animals an external arteriovenous fistula was constructed to reduce afterload and increase cardiac output. In the baseline state, opening the fistula caused a 63 per cent increase in cardiac output with a simultaneous five per cent decrease in measured EVLW. This second group of animals was then given intravenous acid sufficient to cause 30-50 per cent increases in EVLW. Measurements of EVLW and CO with the fistula open and closed were continued for three hours. The inverse relation between cardiac output and EVLW continued. The results of these experiments show that cardiac output does exert a small effect on the measurement of EVLW.

The homogeneous fluorescent immunoassay described above allows one to measure the brightness of fluorescently tagged carrier particles that are suspended in a background of free, unbound fluorescent sources. We have demonstrated the feasibility of our technique using a gentamicin competitive assay as well as idealized model systems. We have seen that the fluctuation-correlation method is able to discriminate against free background sources because each fluorescing particle in solution contributes to the correlation peak [Eq. (4)] with a weighting equal to the square of its respective intensity. Hence, a few very bright sources contribute disproportionately to the "signal" relative to many weak ones. To take advantage of this property, one would therefore design an assay that uses relatively larger carrier particles, each of which is capable of binding on the order of 10(3) to 10(4) tagged antibodies or antigens. Unfortunately, the nonlinear dependence of the correlation peak on the brightness of the fluorescing species causes the technique to be perturbed by carrier particle aggregation; the apparent bound fluorescence intensity increases with the extent of aggregation. The latter may be an unavoidable consequence of performing assays using raw blood serum, for example. The ultimate usefulness of this method will depend on its sensitivity and speed when applied to "real" assays of clinical significance. These characteristics will be influenced by a number of technical details. Given our limited experience with the method thus far, it would appear that its principal drawback is its relatively slow speed. In order to decrease the time needed for a reliable measurement, one must average the random fluctuations in the fluorescent intensity to zero more quickly. In principle, this can be accomplished by decreasing the shot noise by collecting a larger fraction of the fluorescent light, and increasing the sampling rate. The method requires rather complicated instrumentation; it is by no means clear that this level of complexity is justified given the realistic level of sensitivity that will be obtained by this technique.

Extravascular lung water (EVLW) was measured at the bedside in 12 patients with the thermal-green dye double indicator dilution method using a microprocessor. The EVLW ranged from 3.3 to 17.2 ml/kg body weight; in patients without pulmonary problems we have found an average EVLW of 5.7 ml/kg body weight. The method involves easy calculations and is reproducible and accurate.

Der Messung des extravasalen Lungenwassers (EVLW) wird heute eine Schlusselstellung bei der Bearbeitung wichtiger klinischer und experimenteller Probleme beigemessen. Alle Versuche, das Lungenwasser mit Isotopen nach der Methode von CHINARD 2 zu messen enttauschten. Durch die Unzulanglichkeit der Indikatoren wurden nur 30 - 70 % des wahren EVLW gemessen. Erst mit der Anwendung von „Thermal - green dye“- und „Thermo-Konduktivitat“-Dilutionsmethoden konnte das EVLW exakt bestimmt werden. Die aufwendige und zeitraubende Auswertung der Dilutionskurven verhinderte jedoch die breite klinische Anwendung