Assessment of anastomotic reliability with pulse oximetry in graded intestinal ischemia: an experimental study in dogs

BACKGROUND/PURPOSE: Pulse oximetry has been proposed as an appropriate and feasible technique in the assessment of intestinal ischemia in recent years. In this study the authors aimed to assess the reliability of anastomoses in the dog small intestine in which there is graded irreversible ischemia as measured by pulse oxymeter. METHODS: In a control group of four dogs, without any devascularization, three small bowel anastomoses were formed in each dog. The study group consisted of 12 dogs. In each animal three intestinal segments with different levels of ischemia were created by ligating the marginal vessels proximally and distally in sequence beginning from the midpoint of the segmental vascular arcade. Preanastomotic pulse oximeter readings between 80% and 90% were assigned to mild ischemia, 70% and 80% to moderate, and 60% and 70% to severe ischemia group. Pulse oximetry measurements were obtained from probes applied to the antimesenteric serosal surfaces at the midpoint of small intestinal segments. A total of 48 intestinal segments (12 nonischemic in the control group and 36 with three different levels of ischemia in the study group) were transected in the midpoint and anastomosed in double layers. Postanastomotic SaO2 values were also noted. The anastomoses were evaluated 48 hours later macroscopically if there was any leakage, and biopsy specimens were obtained for histopathologic ischemic gradings. All results were studied statistically. RESULTS: Histopathologic grades between each group were statistically different (P < .01 for each comparison) except for control and mild ischemia groups (P > .05), worsening as the level of ischemia increased. Pre- and postanastomotic pulse oximetry measurements correlated very well with the histological gradings (r = -0.90, P < .001 and r = -0.93, P < 0.001 respectively). Number of anastomotic leakages were none in control, one in mild, nine in moderate, and 12 (all of the anastomoses) in severe ischemia groups. In the moderate ischemia group with an average preanastomotic pulse reading of 76.75%, each of the leaking anastomoses had a postanastomotic pulse measurement of lower than 70%. The finding that the difference between histopathologic grades of control and mild ischemia groups with average preanastomotic pulse measurements of 96% and 85%, respectively is not statistically significant enables us to suggest that a saturation of at least 85% is necessary for a reliable anastomosis. CONCLUSION: These results suggest clearly that anastomotic reliability can be predicted objectively with pulse oximetry.     

Determination of flavan-3-ols and trans-resveratrol in grapes and wine using HPLC with fluorescence detection

Concentrations of trans-resveratrol, catechin and epicatechin were analyzed in musts and wines produced from seven red and four white grape cultivars from various wine growing regions of Turkey. Phenolics were quantified using an HPLC method optimized for the separation of wine phenolics. Wine samples contained higher phenolics levels than the corresponding musts. With the exception of Semillion, white wines and musts contained lower concentrations of phenolics than red wines and musts. However, the white cultivar Semillion had the highest concentrations of catechin and epicatechin among all wine and must samples. Semillion wine catechin and epicatechin were 13.7 and 11.8 mg/L, respectively. The highest level of trans-resveratrol among the white cultivars was found in Narince wine (1.93 mg/L). Within the red wine and must cultivars, Bo?azkere, Öküzgozü, and Cabernet contained the highest concentrations of flavan-3-ols and trans-resveratrol. Catechin was the major phenolic in all wines and most musts. Epicatechin was the major phenolic in 6 of the 11 must samples, but none of the wine samples. trans-Resveratrol was generally found in lowest concentrations in both wines and musts.     

Temperature modeling and measurement of an electrokinetic separation chip

This work presents experimental [infrared (IR) thermography] and computational (finite element model) results of temperature distributions of an electrokinetic separation chip. Thermal characteristics of both the electrolyte solution and the polymer chip (SU-8) are taken into account in modeling temperature distributions during electrokinetic flow. Multiphysics and multiscale simulation couples electrostatics, heat transfer, and fluid dynamics. The accompanying IR thermography is a non-contact method, which can measure fractional temperature differences with sub-second time resolution. Any structures or temperature marker molecules interfering with the experiment are not needed. Nominal spot size in the IR measurements is 30 μm with a field of view of several millimeters enabling both local and chip-scale temperature monitoring simultaneously. As a result, we present a computer model for electrokinetic chips, which enables simulation of fractional temperature changes during electrophoresis under real operating conditions. The accuracy of the model is within ±1°C when the deviation in electrochemical processes is taken into account. The simulation results also suggest that the temperature on the chip surface qualitatively reflects the temperature inside the microchannel with an average offset of 1–2°C.     

Modal Identification Study of Vincent Thomas Bridge Using Simulated Wind-Induced Ambient Vibration Data

Abstract:   In this article, wind-induced vibration response of Vincent Thomas Bridge, a suspension bridge located in San Pedro near Los Angeles, California, is simulated using a detailed three-dimensional finite element model of the bridge and a state-of-the-art stochastic wind excitation model. Based on the simulated wind-induced vibration data, the modal parameters (natural frequencies, damping ratios, and mode shapes) of the bridge are identified using the data-driven stochastic subspace identification method. The identified modal parameters are verified by the computed eigenproperties of the bridge model. Finally, effects of measurement noise on the system identification results are studied by adding zero-mean Gaussian white noise processes to the simulated response data. Statistical properties of the identified modal parameters are investigated under an increasing level of measurement noise. The framework presented in this article will allow us to investigate the effects of various realistic damage scenarios in long-span cable-supported (suspension and cable-stayed) bridges on changes in modal identification results. Such studies are required to develop robust and reliable vibration-based structural health monitoring methods for this type of bridge, which is a long-term research objective of the authors.     

Laser Treatment of Sintered Silicon Carbide Surface for Enhanced Hydrophobicity

In this study, laser treatment of sintered SiC surfaces is carried out to enhance the surface hydrophobicity. Morphological and metallurgical changes of the treated surfaces are evaluated using optical and scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction (XRD). Microhardness and fracture toughness are measured using indentation tests. The residual stresses present are determined using the XRD technique. The wetting characteristics of the treated surfaces are assessed through contact angle measurements. It is found that the laser-treated surfaces consist of fine grooves and pillars and that the resulting surface roughness enhances the surface hydrophobicity. The fracture toughness of the treated surface is reduced possibly because of the microhardness increase at the surface. The residual stress formed in the surface region is on the order of 1.8 GPa, and it is compressive.     

On-Line Characterization of Morphology and Water Adsorption on Fumed Silica Nanoparticles

The first wetting layer on solid nanoparticles has direct implications on the roles these particles play in industrial processes and technological applications as well as in the atmosphere. We present a technique for online measurements of the adsorption of the first few water layers onto insoluble aerosol nanoparticles. Atomized fumed silica nanoparticles were dispersed from aqueous suspension and their hygroscopic growth factors (HGF) and number of the adsorbed water layers at subsaturated conditions were measured using a nanometer hygroscopic tandem differential mobility analyzer (HTDMA). Particle morphology was characterized by electron microscopy and particle density was determined by mobility analysis. The HGFs of the size-selected particles at mobility diameters from 10 to 50 nm at 90% relative humidity (RH) varied from 1.05 to 1.24, corresponding to 2–6 layers of adsorbed water. The morphology of the generated fumed silica nanoparticles varied from spheres at 8–10 nm to agglomerates at larger diameters with effective density from 1.7 to 0.8 g/cm³ and fractal dimension of 2.6. The smallest spheres and agglomerates had the highest HGFs. The smallest particles with diameters of 8 and 10 nm adsorbed two to three water layers in subsaturated conditions, which agreed well with the Frenkel, Halsey, and Hill (FHH) isotherm fitting. In comparison to the small spheres or large agglomerates, the compact agglomerate structure containing a few primary particles increased the number of adsorbed water layers by a factor of ～1.5. This was probably caused by the capillary effect on the small cavities between the primary particles in the agglomerate.     

Adhesion, spreading and osteogenic differentiation of mesenchymal stem cells cultured on micropatterned amorphous diamond, titanium, tantalum and chromium coatings on silicon

It was hypothesized that human mesenchymal stromal cell (hMSC) can be guided by patterned and plain amorphous diamond (AD), titanium (Ti), tantalum (Ta) and chromium (Cr) coatings, produced on silicon wafer using physical vapour deposition and photolithography. At 7.5 h hMSCs density was 3.0–3.5× higher (P < 0.0003, except Ti) and cells were smaller (68 vs. 102 μm, P 0.000006–0.02) on patterns than on silicon background. HMSC-covered surface of the background silicon was lower on Ti than AD patterns (P = 0.015), but at 5 days this had reversed (P = 0.006). At 7.5 h focal vinculin adhesions and actin cytoskeleton were outgoing from pattern edges so cells assumed geometric square shapes. Patterns allowed induced osteogenesis, but less effectively than plain surfaces, except for AD, which could be used to avoid osseointegration. All these biomaterial patterns exert direct early, intermediate and late guidance on hMSCs and osteogenic differentiation, but indirect interactions exist with cells on silicon background.     

Boiling characteristics of ternary mixtures inside enhanced surface tubing

Two phase flow characteristics such as coefficient of heat transfer and pressure drop observed during boiling of ternary azeotropic refrigerant mixtures R-404A (R-125/RR--134a/R-143a:44/4/52), R-407B (R-32/R-125/R-134a: 10/70/20), R-407C (R-32/R-125/R-134a:23/25/52) and R-408A (R-22/R-125/R-143a:46/7/47) are presented and analyzed in this paper.Experiments showed that for Reynolds numbers higher than 4.5 E04, R-408A and R-404A appear to have greater heat transfer rates than the other blends under investigation. Furthermore, it is quite evident from this data that at higher Reynolds number R-404A and R-408A have the highest pressure drop while R-407 experiences the lowest pressure drop among the refrigerants under investigation.     

Fundamental mechanisms of bonding of glass fiber reinforced polymer reinforcement to concrete

Fundamental mechanisms of bonding between glass fiber reinforced polymer (GFRP) bar and concrete are presented. Contributions from chemical bonding, bearing resistance, and frictional resistance to bond were delineated by measuring the following: the load corresponding to complete debonding of the bar, the load corresponding to onset of sliding and pullout of the bar along the entire embedment length, and the frictional load corresponding to frictional resistance to sliding. Research findings indicate that while chemical bonding was the main contributor to the interfacial bond strength, the other two mechanisms contributed to the pullout strength of the bar. Correlation between the bar’s surface geometry and the contributions from the three mechanisms are discussed.