Increase In Excess Research Articles

Atomistic Simulation of Orientation of Methyl Groups and Methylene Bisectors, and Surface Segregation, in Freely Standing Thin Films of Atactic Poly(ethylene-co-propylene)

Atomistically detailed models of free-standing thin films of random poly(ethylene-co-propylene) were produced using a method recently applied to atactic polystyrene (Clancy, et al. J. Phys. Chem. B 2001, 105, 11493). Monte Carlo simulations of the copolymer were carried out at ethylene fractions that cover the entire range of composition investigated in a recent experimental work (Opdahl, et al. J. Phys. Chem. B 2002, 106, 5212) based on sum-frequency generation (SFG) spectroscopy. We find that there is a minor enrichment of methyl groups on the surface, as compared to the bulk composition. Interestingly, the orientation distribution of methyl and methylene units is not unimodal. For methyl units, there is about 50% probability of orientation perpendicular to the surface. The other 50% are randomly oriented. For the methylene bisector, the simulation shows that the distribution has two broad peaks at opposite angles (at 180° apart) to the surface normal. More conclusive results may be obtained by using larger sample sizes and analysis of a larger number of snapshots, both of which increase the computation time significantly. The opposite angle pairs nearly cancel each other in the computation of an average order parameter and give us a misleading net result that the bisectors are randomly oriented. With increasing ethylene fraction, the orientation distribution of methyl and methylene units tends to become more uniform; however, this change is small. The strong average orientation of methyl groups and weak average orientation of methylene groups is in agreement with experiments. However, the simulation does not show the significant relative increase in the surface methyl groups contributing to the SFG signal as compared to the bulk concentration or an increase in average orientation of methylene units, with an increase in the ethylene fraction, as inferred from the experimental results. We find that the raw experimental data obtained with an increase in ethylene fraction can be explained by the changes in the number of methyl and methylene groups on the surface rather than the increase in surface excess of the methyl groups contributing to the SFG signal, trans cancellation, and increase in orientation of methylene bisectors as deduced from the experiments.

Estimation of ultrasound induced cavitation bubble temperatures in aqueous solutions

Mean acoustic cavitation bubble temperatures have been measured in a series of aqueous solutions containing C 1– C 5 aliphatic alcohols, at 355 kHz. The method relies on the distribution of hydrocarbon product yields produced from the recombination of methyl radicals generated on the thermal decomposition of the alcohols. The mean bubble temperature was found to decrease with increasing concentration of alcohol with the effect being more pronounced the higher the molecular weight (the lower the vapour pressure) of the alcohol. It is shown that the decrease in the temperatures measured correlates very well with an increase in the surface excess of the alcohol, similar to that previously reported for the quenching of sonoluminescence in aqueous solutions containing alcohols [J. Phys. Chem. B 101 (1997) 10845; J. Phys. Chem. B 103 (1999) 9231]. The measured temperatures ranged from 4600 ± 200 K at zero alcohol concentration to 2300 ± 200 K at 0.5 M t-butanol. The validity of the method is discussed and it is concluded that even though a number of assumptions need to be applied the results appear to indicate that the method gives an accurate measure of the mean bubble temperature.

Diastereoselectivity in the Synthesis of Unnatural α-Amino Acid Esters by Phase Transfer Catalysis

Two unnatural α-amino acid esters were prepared in good yields via phase transfer catalyzed Michael addition of ethyl N-acetylaminocyanoacetate to chalcone and benzalketone. For both α- enones, a progressive increase in product diastereomeric excess (d.e.) was observed during the course of reaction, even in the absence of quaternary ammonium salt. However, for a fixed reaction time, higher d.e. values were obtained under phase transfer catalytic condition. Analogous reactions were performed using S-aryl thiocinnamates as Michael acceptors, affording a 2-pyrrolidinone in good yield but low d.e. These results were interpreted on the basis of the reversibility of the Michael reaction

Worldwide Variation in Life-Span Sexual Dimorphism and Sex-Specific Environmental Mortality Rates

In all human populations mean life span of women generally exceeds that of men, but the extent of this sexual dimorphism varies across different regions of the world. Our purpose here is to study, using global demographic and environmental data, the general tendency of this variation and local deviations from it. We used data on male and female life history traits and environmental conditions for 227 countries and autonomous territories; for each country or territory the life-span dimorphism was defined as the difference between mean life spans of women and men. The general tendency is an increase of life-span dimorphism with increasing average male-female life span; this tendency can be explained using a demographic model based on the Makeham-Gompertz equation. Roughly, the life-span dimorphism increases with the average life span because of an increase in the duration of expressing sex- and age-dependent mortality described by the second (exponential) term of the Makeham-Gompertz equation. Thus we investigated the differences in male and female environmental mortality described by the first term of the Makeham-Gompertz equation fitted to the data. The general pattern that resulted was an increase in male mortality at the highest and lowest latitudes. One plausible explanation is that specific factors tied to extreme latitudes influence males more strongly than females. In particular, alcohol consumption increases with increasing latitude and, on the contrary, infection pressures increase with decreasing latitude. This finding agrees with other observations, such as an increase in male mortality excess in Europe and Christian countries and an increase in female mortality excess in Asia and Muslim countries. An increase in the excess of female mortality may also be due to increased maternal mortality caused by an increase in fertility. However, this relation is not linear: In regions with the highest fertility (e.g., in Africa) the excess of female mortality is smaller than in regions with relatively lower fertility (e.g., in Asia). A possible explanation of this phenomenon is an evolutionary adaptation of women to the pressures of extremely high fertility by means of some reduction of their maternal mortality.

Synthesis of both enantiomers of a P-chirogenic 1,2-bisphospholanoethane ligand via convergent routes and application to rhodium-catalyzed asymmetric hydrogenation of CI-1008 (pregabalin).

Both enantiomers of a P-chirogenic 1,2-bisphospholanoethane ligand are synthesized via two convergent methods. The first method relies on the chiral alkylation of 1-((-)-menthoxy)phospholaneborane using a s-BuLi/(-)-sparteine derived chiral base. Only one enantiomer of the catalyst could be synthesized via this method because only one antipode of sparteine is available in nature. The second route relies on the combination of methylphosphine borane and a chiral 1,4-diol. Either enantiomer of the ligand can be synthesized via the second route from the appropriate enantiomer of the 1,4-diol. Asymmetric hydrogenation using catalyst precursor 36 on acetamidoacrylic acid derivatives provided modest to good enantioselectivity (77-95% ee) under low H(2) pressure (30 psi). Asymmetric hydrogenation of CI-1008 (pregabalin) precursors, 39 and 40, provided good enantioselectivities (92%) at high catalyst loading (1 mol %) and low pressure (30 psi). Enantiomeric excesses dropped sharply with catalyst loading at this pressure. Increasing the pressure of H(2) caused a significant increase in enantiomeric excess for low catalyst loading reactions. Several studies were undertaken to further investigate the enantioselectivity dependence on both pressure and catalyst loading.

Influence of the Nature of Crosslinking Agent on the Oxidation Behavior of Crosslinked Polystyrene‐Supported Polyoxyethylene Bound Permanganate

Polystyrene‐supported polyoxyethylene (PSPOE) bound permanganate with varying crosslinking agents have been prepared and used as a new class of recyclable oxidizing agents for low molecular weight alcohols and aldehydes. The effect of the nature of crosslinking agents on the oxidation reactions was studied in detail. The crosslinking agents used were ethyleneglycol dimethacrylate (EGDMA), 1,4‐butanediol dimethacrylate (BDDMA), and 1,6‐hexanediol diacrylate (HDODA). Polymer supports were synthesized by free radical suspension polymerization. Chloromethylation was done using the Friedel‐Crafts reaction. A cyclic polyether type compound was developed by the reaction of functionlized resin with polyethylene glycol (PEG600) and sodium. Polystyrene‐supported polyoxyethylene was equilibrated with potassium permanganate in benzene to give the oxidizing agent. The results reveal that the reactivity of HDODA‐crosslinked system shows higher reactivity than the BDDMA, and EGDMA‐crosslinked systems. This is due to higher flexibility of the HDODA‐crosslinked system compared to the BDDMA, and EGDMA‐crosslinked systems. The effect of solvent, temperature, and molar concentration of the reagent on oxidation were carried out using benzoin to benzil as the model reaction. For a less flexibile EGDMA‐crosslinked resin, tetrahydrofuran (THF) is the best solvent, for BDDMA‐crosslinked system dioxane and for the highly flexible HDODA‐crosslinked system CHCl3 is found to be best. In all cases, the reactivity of the reagent increased with an increase in temperature and molar excess of the reagent.

The functional state of the hemostasis system in traumatologic and orthopedic patients with atherosclerosis

Coagulopathy after sever injury predicts the requirements of blood products, organ failure and mortality in traumatic patients. The early onset and complexity of traumatic coagulopathy preclude the understanding the underlying mechanism. The aim of the study is to characterize the early coagulation alteration in a swine model with multi-trauma and shock.Twelve pigs were subjected to multi-trauma (femur fracture, laparotomy, 10 cm intestine resection and grade III injury of liver) and hemorrhaged to a mean arterial pressure (MAP) of 40 mmHg. Physiologic parameters and coagulation variables (prothrombin time (PT), international normalized ratio (INR), fibrinogen, antithrombin-III (AT-III) activity, D-dimer and thromboelastography (TEG)) were measured after instrumentation (baseline), 5 min after multi-trauma (after trauma), 10 min (early shock) and 40 min (late shock) after hemorrhage. A group of 6 instrumented pigs were used as control.Multi-trauma and hemorrhage caused significant increase of base excess (BE) and lactate (p < 0.05). PT shortened after multi-trauma but increased significantly at late shock (p < 0.05). Fibrinogen reduced greatly after trauma and at early shock (p < 0.05), while remained stable afterwards. AT-III activity decreased throughout the experiment. Reaction time (R) shortened after trauma and at early shock (both p < 0.05). Maximal amplitude (MA) decreased significantly during the shock period.After traumatic hemorrhagic shock, hypercoagulation turned into hypocoagulation in a short period, which was probably caused by hypoperfusion.

The First Stars

The possible nature of the first generation of stars is considered, using a star of 25M⊙as an example. General nucleosynthesis and the production of CNO catalysts is examined in detail. The increase in neutron excess and its significance for yields from explosive burning is discussed. An estimate of the ratio of ionizing photons to heavy elements produced is derived, for use in early universe simulations.

Oxygen-17 excesses of the Central Namib gypcretes: spatial distribution

We present here sulfate oxygen isotopic data (72 samples with both δ 18O and δ 17O) systematically collected from the Central Namib Desert. Surface soils from two shore-inland (west–east) transects exhibit a gradual increase in the sulfate oxygen-17 excess (Δ 17O= δ 17O−0.52 δ 18O) until at ca. 70 km inland, where no continuous gypcrete deposit is observed further east (inland). The oxygen isotopic compositions for water-soluble sulfates extracted from soils and gypcretes range from 8.3 to 13.3‰ and 0.06 to 1.11‰ for δ 18O and Δ 17O, respectively. The lateral pattern is similar to what has been seen in the cold deserts of the Antarctic dry valleys. However, unlike the dry valleys, no discernible correlation is found between δ 18O and Δ 17O, or between the depth of soil horizon and Δ 17O in the Namib. Possible explanations include a relatively smaller component of dimethylsulfide (DMS)-derived sulfate in the total gypsum deposits and/or more active surface processes (e.g., flooding and leaching) in the Central Namib Desert than in the Antarctic cold deserts. Although current state of knowledge is insufficient to delineate quantitatively the sulfate contributions from different sources and reactions, the measurement of sulfate Δ 17O does identify an unmistakable atmospheric sulfate component and provides additional independent information regarding sources and reactions.

The altitude effect on the isotopic composition of tropical rains

Data on the Isotopic composition of yearly and monthly precipitation samples collected at various altitudes on Mount Cameroon, Africa, and in two transects from the Amazon to the Altiplano in Bolivia, South America, are presented. In Bolivia, the 2H/ 1H and 18O/ 16O ratios show seasonal variations, with lower values in the summer rainy months with respects to the winter dry ones. The δ 2H and δ 18O values are linearly correlated with a slope of 7.5 in all seasons, but the intercept is higher in winter than in summer. The δ-gradient vs. altitude is larger in rainy periods. The isotopic data are fitted by using a numerical model based on Rayleigh adiabatic condensation process. Model simulations show that the δ–altitude relationship slightly deviates from linearity, because the slope increases with altitude due to the lowering of temperature and the consequent increase of the condensation rate of atmospheric vapour. The parameters which most affect the shape of δ–altitude relationships are the temperature vertical gradient (lapse rate) and the initial relative humidity of the ascending air masses, while a change of the initial isotopic composition of water vapour determines a shift of the curve along the δ-axis. In addition, the model explains the observed increase of the deuterium excess with altitude.

High intensity focused ultrasound: a method of hemostasis.

Acoustic hemostasis is a new field of ultrasound research in which high intensity focused ultrasound (HIFU) is used to induce hemostasis in actively bleeding, injured solid organs and blood vessels. In animal studies, moderate to profuse bleeding from parenchymal and vascular injuries has been arrested within approximately 1 minute of HIFU application, even when a large dose of heparin was administered. Moreover, acoustic hemostasis has shown promise in cauterizing large regions of liver, providing a method for bloodless resectioning of abnormal tissue. Two distinct physical mechanisms of HIFU appear to contribute to hemostasis: (1) a thermal mechanism in which absorption of sound leads to temperature elevations, and (2) mechanical mechanisms (acoustic cavitation) in which gas and vapor-filled voids oscillate with large displacement amplitudes. While the thermal mechanism results in a temperature increase in excess of 70 degrees C in about 1 second, the mechanical mechanism appears to result in structural disruption of tissue and possible release of coagulation-inducing tissue factors. Of utmost importance in further development of HIFU as a clinical tool is targeting and monitoring of the HIFU treatment. We have obtained initial success in integrating HIFU with ultrasound imaging so as to develop an image-guided therapy system. Image-guided acoustic hemostasis may provide a valuable method of hemostasis in surgical and prehospital settings with applications in trauma and elective surgery.

Adsorption of ammonium perfluorooctanoate at the air–water interface

The effect of solution conditions on the structure and composition of ammonium perfluorooctanoate (APFO) layers at the air–water interface has been examined using the technique of neutron reflection. The surface excess was found to decrease with increasing temperature, but the overall thickness of the layer showed an opposite trend and increased. This observation indicates that with the increase of thermal motion, the layer becomes thicker but more loosely packed. Addition of salt resulted in an increase in the surface excess and under this condition, the layer also became thicker. Both temperature rise and salt addition reduced the surface tension, resulting in the roughening of surface layers. If the effect of thermal capillary waves is removed, the thickness of the layers is always close to 13 Å which is comparable to the fully extended length of the APFO molecule. The relative location between the layer and water was determined using the more direct approach of the kinematic approximation involving reflectivity measurements using different ratios of H 2O and D 2O. The cross-distances between the centers of APFO layers and those of water were found to be 4.5 Å under the different solution conditions. These cross-distances would suggest a substantial mixing between the APFO layers and water, but after the removal of capillary wave roughness, the extent of mixing was close to 30% which is similar to that found for hydrocarbon surfactants.

Genetic and demographic variation among colour morphs of cabrilla sea bass

The Mediterranean cabrilla sea bass Serranus cabrilla exhibits two colour morphs (red and yellow) that appear to be depth segregated, with yellow individuals found below 20 m and red ones found above 20 m. Morphology and otolith analyses show that yellow fish are larger and older. There were similar allelic frequencies between colour morphs, but significant differences in the genotypic frequencies with an increase of excess of heterozygotes in yellow specimens. It is proposed that the yellow fish are older and develop from younger red fish that have migrated to deeper water.

Synthesis of achiral, but unsymmetric, seven-membered rhodium(I)-chelates for hydrogenation in the chiral environment of alkyl polyglucoside micelles

Chiral rhodium(I) chelates containing a seven-membered ring are well-known active catalysts for the asymmetric hydrogenation of amino acid precursors. A high conformational flexibility allows their enantioselectivity to be strongly influenced by modifiers. Now we show the nature of the counter-ions to have a large influence in apolar solvents. In addition, the presence of micelle forming alkyl polyglycosides as amphiphiles causes a remarkable increase in the enantiomeric excess (%ee). However, on achiral catalysts this enantioselectivity inducing effect scarcely exceeds the standard deviation for the gas chromatographic determination of the enantiomeric ratio. This is also true for the application of unsymmetric P, P′-ligands such as 3-phosphinopropyl-phosphinites or butane-1,4-diyl-bis(phosphines) carrying different P′ -aryl groups, for which synthetic routes are given.

Proximal Adsorption of Cationic Surfactant on Silica at Equilibrium

The equilibrium force between a glass particle and a silica sheet in aqueous solution was measured as a function of the separation and chemical potential of the surfactant dodecyltrimethylammonium bromide. A Maxwell relation was used to transform data from these force measurements into the change in adsorption of the surfactant as a function of separation. At low concentrations, when the isolated solid−liquid interface is negatively charged, the surfactant adsorbs as the surfaces approach. Under some circumstances, surfactant adsorption exceeds the level necessary to regulate the surface charge. In the range of concentrations (cmc = critical micelle concentration) cmc/130−cmc/10, the interaction energy is much more negative than the expected van der Waals interaction between silica or hydrocarbon surfaces and is approximately constant. In this concentration range, the adsorption is independent of the separation for separations greater than about 7 nm. However, changes in contact adhesion show that there is a large increase in adsorption when the surface separation decreases from 7 nm to contact. From cmc/10 to the cmc, the interaction becomes more repulsive and the surfactant desorbs as the surfaces approach each other. When the surfaces approach in 4 cmc solution, there is first a large increase in surface excess and then a large decrease in surface excess. The large increase in surface excess corresponds to a depletion force, and the large decrease occurs as the surfactant is squeezed off the silica. The fact that the surfactant must be squeezed out from between the surfaces to obtain an adhesive interaction above the cmc requires the adhesion to decrease on the addition of the surfactant to the solution. At even higher concentrations (8 cmc and greater), the energy and the surface excess are oscillatory functions of the separation. The pressure between the surfaces in these concentrated solutions is well described by an osmotic interaction with the concentration derived from the surface excess and a constant osmotic coefficient.

The Influence of Selected Factors on the Perceptions of Managers of Small Business Firms Regarding Legal Firms

The South African service provider is faced with an increasingly turbulent and complex competitive environment (Griffith & Rust, 1997:109-116). Factors that impact specifically on the environment of service firms (such as the providers of legal services) include the growing importance of consumerism and a drastic increase in competition (Harrel & Fors, 1992:299-306). The latter factor has a number of causes, amongst others, a stagnating economy (Griffith & Rust, 1997:109-116). A factor that impacts directly on the growing competition amongst providers of legal services is the increase in law graduates and commensurate increase in qualified attorneys and advocates entering the market. Figures supplied by the Law Society of the Cape of Good Hope and the Law Society of the Transvaal indicate an increase in excess of 50% in the number of practising attorneys in both the former provinces of the Cape and Transvaal between the years 1990 and 1997. This article presents an exploratory study establishing the relative value attached by small business in South Africa to certain factors, inter alia advertising and location, pertaining to firms providing legal services. A better understanding of the importance of these factors will assist legal firms to improve service delivery thereby improving profitability.

Effects of xylazine on acid-base balance and arterial blood-gas tensions in goats under different environmental temperature and humidity conditions.

The effects of acute exposure to 3 different temperature and humidity conditions on arterial blood-gas and acid-base balance in goats were investigated after intravenous bolus administration of xylazine at a dose of 0.1 mg/kg. Significant (P<0.05) changes in the variables occurred under all 3 environmental conditions. Decreases in pH, partial pressure of oxygen and oxyhaemoglobin saturation were observed, and the minimum values for oxygen tension and oxyhaemoglobin saturation were observed within 5 min of xylazine administration. The pH decreased to its minimum values between 5 and 15 min. Thereafter, the variables started to return towards baseline, but did not reach baseline values at the end of the 60 min observation period. Increases in the partial pressure of carbon dioxide, total carbon dioxide content, bicarbonate ion concentration, and the actual base excess were observed. The maximum increase in the carbon dioxide tension occurred within 5 min of xylazine administration. The increase in the actual base excess only became significant after 30 min in all 3 environments, and maximal increases were observed at 60 min. There were no significant differences between the variables in the 3 different environments. It was concluded that intravenous xylazine administration in goats resulted in significant changes in arterial blood-gas and acid-base balance that were associated with hypoxaemia and respiratory acidosis, followed by metabolic alkalosis that continued for the duration of the observation period. Acute exposure to different environmental temperature and humidity conditions after xylazine administration did not influence the changes in arterial blood-gas and acid-base balance.

Asymmetric allylic alkylation of cycloalkenediol diacetates using a chiral phosphine ligand bearing a carboxyl group

Asymmetric induction in the allylic alkylation of cycloalkenediol diacetates was performed using a chiral alkylphosphine ligand bearing a carboxyl group, 3-(diphenylphosphino)butanoic acid. An increase in enantiomeric excess of the monoalkylated products of cis-cycloalkenediol diacetates was observed through a sequential asymmetric allylic alkylation–kinetic resolution process.

From accumulation to discharge: modification of stable isotopes during glacial and post-glacial processes

The isotopes of the water molecule (tritium, deuterium and oxygen-18) are considered to be ideal tracers of the water cycle, an isobalance of accumulation and discharge from glaciated areas is therefore challenging. In this article we review data from the Alps concerning both the isotopic information of accumulated snow and ice and the relevant information of glacial discharge on a local to regional scale. In the Alps the seasonal distribution of accumulated snow is governed by small-scale meteorology and exposition and distribution of cold and temperate glaciers. From comparison with direct precipitation measurements it follows that uncontrolled erosive loss of parts of the seasonal (mainly winter) snow cover is more important for input-output considerations of glacial discharge, reconstruction of mean accumulation rates and palaeotemperatures by means of isotopes, than occasional melting or even rainfall events. The order of magnitude of the latter is controlled by laboratory and field experiments. Sublimation and evaporation turn out to be of minor influence if only the absolute values and not the deuterium excess (the relationship of both stable isotopes, deuterium and oxygen-18) is considered. Nevertheless, during warming periods a pronounced increase of deuterium excess caused by intensive melting and evaporation may be used as an additional climate indicator. The different isotopic signature of the seasonal snow cover, old glacier ice and groundwater stored in the glacier bed enables a quantitative separation of the individual water components discharging at a given time of the day or the season. Although several detailed isotope studies are reported, a complete isobalance from glaciated areas based on an interdisciplinary approach, including hydrology and glaciology, is still missing. The hydroclimatic imprint of the discharge from glaciated areas remains even on a regional scale. Snowmelt shifts the more negative isotope values from winter precipitation to the summer months. Interannual climatic variability and changes in seasonal distribution of precipitation (for instance reduced winter precipitation during the late 1980s) are recorded by the stable isotopes in precipitation and discharge as well indicating that the modification of the isotopic information during glacial and post-glacial processes does not override climatic trends.

Role of the splanchnic circulation in acid-base balance during cardiopulmonary bypass.

The role of the splanchnic circulation in the development of the metabolic acidosis of cardiopulmonary bypass (CPB) is not fully understood. New quantitative methods of acid-base balance now offer the ability to define this phenomenon more accurately. Accordingly, we studied acid-base changes across the splanchnic circulation during CPB and defined and quantified the factors that contributed to acid-base balance. Prospective cohort study. Tertiary institution. Ten patients undergoing CPB for coronary artery bypass surgery. Sampling of arterial and hepatic venous blood at four time intervals: postinduction, on CPB during cooling and rewarming, and at skin closure. Measurement of serum Na+, K+, Mg++, Ca++, Cl-, HCO3-, and phosphate concentrations, arterial and hepatic venous blood gases and serum albumin, and lactate and pyruvate concentrations at each collection point. Analysis of findings according to quantitative physicochemical principles. All patients developed a mild metabolic acidosis with a decrease in median serum bicarbonate concentration from 24.97 mEq/L after induction to 22.29 mEq/L at cooling and 22.23 mEq/L at rewarming (p < .05). Before CPB, the pH decreased by 0.0275 (p < .05) across the splanchnic circulation, representing an increase of 2.26 nmol/L of hydrogen ions. Nevertheless, the splanchnic circulation induced a metabolic alkalosis, with a median transsplanchnic increase in the base excess of 1.50 mEq/L (p < .05). This change was largely due to a decrease in serum chloride and lactate concentration across the splanchnic circulation (p < .05). The acidifying effect of the splanchnic circulation was therefore the result of cell respiration with a median increase in carbon dioxide tension of 5.75 mm Hg (p < .05), causing the strong ion difference effective to increase by 1.94 mEq/L (p < .05). There were no other anions or acids added to the circulation by splanchnic organs (no change in strong ion gap). During and after CPB the splanchnic metabolic alkalinizing effect continued and the respiratory acidifying effect was reduced. This caused the splanchnic circulation to be pH neutral at these times. Using quantitative biophysical methods it can be demonstrated that the splanchnic circulation does not contribute to the metabolic acidosis of CPB, and that it continues to have a metabolic alkalinizing effect involving significant lactate extraction. However, its respiratory acidifying effect continues, although at a reduced rate.