Kco Values Research Articles

Anxiety in Patients with Post-COVID Syndrome: Associated Factors.

The term "post-COVID-19 syndrome" describes a range of symptoms persisting beyond the acute phase of the disease. These symptoms predominantly include fatigue, muscle pain, shortness of breath, and psychological issues. Research additionally suggests the possibility of long-term neurological and psychiatric impairment associated with COVID-19. The study included patients who visited the post-COVID outpatient clinic between April 2020 and June 2022. The examination included the detailed history taking, including the COVID-19 course, posteroanterior chest X-ray and pulmonary function tests. Anxiety level was assessed using the Beck Anxiety Inventory (BAI). The relationship between anxiety, demographic data, and course of the disease, need for hospital admission during the acute phase, oxygen therapy, post-inflammatory changes on the chest X-ray and lung function parameters was investigated. This study included 1756 patients who experienced COVID-19 and visited a post-COVID outpatient clinic. The majority of individuals experienced a mild form of the infection. The results showed that younger age and female gender were associated with significantly higher anxiety scores. Inpatients had lower BAI values than those who were not hospitalized during acute phase. Patients with post-inflammatory changes on chest X-ray had surprisingly lower BAI values. Lower values of FEV1 (forced expiratory volume in 1 second), DLCO (diffusing capacity of the lungs for carbon monoxide), and KCO (carbon monoxide transfer coefficient) were associated with significantly higher BAI values. Female gender was associated with higher levels of anxiety. In contrast, higher FEV1 values reduced the risk of a pathological level of anxiety. In our study, the influence of age, gender, inpatient care during the acute phase of infection, the presence of post-inflammatory changes on the chest diagram and selected parameters of lung function (FEV1, DLCO, and KCO) were shown to be important factors in the assessment of anxiety symptoms in post-COVID patients.

Obesity-related Changes in Diffusing Capacity and Transfer Coefficient of the Lung for Carbon Monoxide and Resulting Patterns of Abnormality across Reference Equations.

Rationale: In 2017, an American Thoracic Society/European Respiratory Society Task Force report recommended further research on the effects that body mass index (BMI) has on diffusing capacity of the lung for carbon monoxide (DlCO), the transfer coefficient (Kco), and the alveolar volume (VA). Objectives: Our goals were to 1) quantify the magnitude and direction of change to measured and predicted DlCO values as BMI increases in patients free of cardiopulmonary disease and 2) identify how BMI and obesity-related changes differ by reference set. Methods: Using data from a prospective cohort study of service members free of cardiopulmonary disease, we modeled the effect that BMI has on measured values of DlCO, Kco, and VA, after adjusting for age, sex, hemoglobin (Hgb), and height. We then referenced DlCO, Kco, and VA to normal values using four different reference equations. Results: There were 380 patients with data available for analysis, and 130 had a BMI ⩾ 30 kg/m2 (87.7% class I obesity). After controlling for age, sex, Hgb, and height, increased BMI was significantly associated with Kco (β = 0.09, P < 0.01) and VA (β = -0.15, P < 0.01) but not DlCO. After adjustment for Hgb, for every 5-kg/m2 increase in BMI, the mean increase in percent predicted (PPD) values ranged from 4.2% to 6.5% and from 5.0% to 7.5% for DlCO and Kco, respectively; and the mean decrease in VA PPD was 3.2-4.0%. In the presence of obesity (BMI ⩾ 30 kg/m2), the prevalence of DlCO and Kco abnormalities dropped by 4.1-12.1% and 0.4-16.3%, respectively, across equations, whereas VA abnormalities increased from 7.7% to 9.9%. Eliminating 163 patients with abnormal trans-thoracic echocardiogram (TEE), high-resolution computed tomographic (HRCT) scan, or Hgb altered the magnitude of relationships, but significance was preserved. Conclusions: In an otherwise healthy population with predominantly class I obesity and normal TTE, HRCT scan, and Hgb, we found that Kco and VA were more affected by BMI than DlCO. Increases in PPD values varied across equations and were modest but significant and could change clinical decision making by reducing sensitivity for detecting gas-exchange abnormalities. BMI and obesity had the smallest effect on Global Lung Function Initiative PPD values.

Clinical and functional characteristics of individuals with alpha-1 antitrypsin deficiency: EARCO international registry

BackgroundAlpha-1 antitrypsin deficiency (AATD) is a rare disease that is associated with an increased risk of pulmonary emphysema. The European AATD Research Collaboration (EARCO) international registry was founded with the objective of characterising the individuals with AATD and investigating their natural history.MethodsThe EARCO registry is an international, observational and prospective study of individuals with AATD, defined as AAT serum levels < 11 μM and/or proteinase inhibitor genotypes PI*ZZ, PI*SZ and compound heterozygotes or homozygotes of other rare deficient variants. We describe the characteristics of the individuals included from February 2020 to May 2022.ResultsA total of 1044 individuals from 15 countries were analysed. The most frequent genotype was PI*ZZ (60.2%), followed by PI*SZ (29.2%). Among PI*ZZ patients, emphysema was the most frequent lung disease (57.2%) followed by COPD (57.2%) and bronchiectasis (22%). Up to 76.4% had concordant values of FEV1(%) and KCO(%). Those with impairment in FEV1(%) alone had more frequently bronchiectasis and asthma and those with impairment in KCO(%) alone had more frequent emphysema and liver disease. Multivariate analysis showed that advanced age, male sex, exacerbations, increased blood platelets and neutrophils, augmentation and lower AAT serum levels were associated with worse FEV1(%).ConclusionsEARCO has recruited > 1000 individuals with AATD from 15 countries in its first 2 years. Baseline cross sectional data provide relevant information about the clinical phenotypes of the disease, the patterns of functional impairment and factors associated with poor lung function.Trial registrationwww.clinicaltrials.gov (ID: NCT04180319)

Maize Crop Coefficients under Variable and Fixed (Uniform) Rate Irrigation and Conventional and Variable Rate Fertilizer Management in Three Soil Types

Maize (Zea mays L.) evapotranspiration crop coefficients (Kc) that are needed to estimate crop evapotranspiration (ETc) using the two-step approach for variable rate irrigation and nitrogen management under different soil types have not been investigated or quantified. In this research, alfalfa- and grass-reference crop coefficients (Kcr and Kco) curves were developed for fixed rate or uniform rate fertigation (FRF), variable rate fertigation (VRF) and pre-plant nitrogen (PP) management under fixed rate or uniform rate irrigation (FRI) and variable rate irrigation (VRI) for three soil types [Crete silt loam (S1), Hastings silty clay loam (2) and Hastings silt loam (S3)] in 2015, 2016 and 2017 growing seasons. Irrigation and nitrogen management strategies, as well as soil type, all influenced the Kcr and Kco values, which exhibited inter-annual variation. On average, greater variation in Kc curves between FRF, VRF and PP nitrogen treatment were observed under VRI treatments as compared with FRI. Results showed that Kc values are more dependent on the amount rather than the timing of the nitrogen application. In all three seasons, higher Kc values were observed in the FRI treatment than VRI with Kcr, ranging from 0.07 to 1.30 in FRI and 0.07 to 1.20 in VRI. Kc curves also differed between nitrogen treatments and the difference was more prominent in the VRI treatments than in the FRI in all years. In general, maximum Kc was observed in PP nitrogen treatment, followed by FRF and VRF. On a monthly average basis, maximum Kc values were observed in July and August in all soil types and minimum Kc values were observed in June. When soil types are considered, overall, the maximum Kcr value was observed in FRI-PP treatment in S1 (1.02), FRI-VRF treatment in S2 (1.06) and FRI-VRF treatment in S3 (1.02). The Kcr and Kco equations as a function of growing degree days were developed and monthly average Kcr and Kco values were tabulated for practical applications. To the best of the authors’ knowledge, this research is the first that investigated and quantified the impact of VRI and VRF strategies under FRF, VRF and PP fertilizer management strategies on maize Kc values. The Kcr and Kco values quantified in this research can aid irrigators, state agencies and other water management and agricultural professionals for more accurate crop water use determinations under different irrigation and nitrogen management strategies and different soil types.

Different KCO and VA combinations exist for the same DLCO value in patients with diffuse parenchymal lung diseases.

BackgroundDLCO is the product of the CO transfer coefficient (KCO) by the “accessible” alveolar volume (VA). In theory, the same DLCO may result from various combinations of KCO and VA values, each of which reflect different injury sites and mechanisms. We sought to determine in this study the potential variability of both VA and KCO for fixed values of DLCO in diffuse parenchymal lung diseases (DPLD).MethodsTo this end, we designed a retrospective, cross-sectional study of three distinct types of DPLD and analysed pulmonary function test (PFT) datasets.ResultsWe show here that for the same value of DLCO (50 % predicted), KCO varied from 60 to 95 % predicted and VA from 55 to 85 % predicted in various types of DPLD idiopathic pulmonary fibrosis, sarcoidosis and connective tissue disease-associated DPLD, indicating distinct pathogenic mechanisms in these diseases. In addition, a comparison of VA with total lung capacity may help to evidence the distal airway obstruction sometimes associated with certain DPLD particularly sarcoidosis.ConclusionClinicians should take into account not only DLCO but also VA and KCO values when managing patients with DPLD.

Tidal Expiratory Flow Limitation at Rest as a Functional Marker of Pulmonary Emphysema in Moderate-to-Severe COPD

Background: Tidal expiratory flow limitation (EFL) is a step of paramount importance in the functional decline in COPD. Among mechanisms contributing to EFL, loss of airway-parenchymal interdependence could mostly be involved. Aim: To assess if EFL is a functional marker more frequently linked to prevalent pulmonary emphysema rather than to prevalent chronic bronchiolitis in COPD patients with moderate-to-severe airflow obstruction. Methods: Forty consecutive stable COPD patients with FEV1 between 59 and 30% of predicted were functionally evaluated by measuring spirometry, maximal flow-volume curve and lung diffusion capacity (DLCO) and coefficient of diffusion (KCO). EFL was assessed by the negative expiratory pressure (NEP) method both in sitting and supine position. Chronic dyspnea was also scored by modified Medical Research Council (mMRC) scale. Results: In sitting position 13 patients (33%) were flow limited (FL) and 27 were non-flow limited (NFL). Only FEV1/FVC, FEV1 and MEF25–75% were different between FL and NFL patients (p < 0.01). In supine position, however, among NFL patients in sitting position those who developed EFL, had significantly lower values of DLCO and KCO (p < 0.05) and higher mMRC score (p < 0.01), but similar values of FEV1 as compared to those who did not have EFL. Conclusions: In COPD EFL in sitting position is highly dependent by the severity of airflow obstruction. In contrast, the occurrence of EFL in supine position is associated with worse DLCO and KCO and greater chronic dyspnea, reflecting a prevalent emphysematous phenotype in moderate-to-severe COPD patients.

S21 Is There a Correlation Between Lung Function Values and Cardiopulmonary Exercise Outcome?

IntroductionCardiopulmonary Exercise testing (CPET) has become an important tool for perioperative assessment as it may identify patients at risk of postoperative cardiopulmonary complications. Older (1) recommended that an Anaerobic Threshold...

An analytical study of modal dispersion characteristics of helically clad crystal-cored optical fiber

The uniaxial crystal cored optical fiber, with optical axis parallel to the fiber axis, having helical cladding is proposed and a characteristic equation is derived. Employing helical boundary conditions, the characteristic equation is found and dispersion curves are drawn for different Kco (the ratio of longitudinal and transverse refractive index) values and for different modal order ν. The field components in the core region of the proposed fiber are found and a curve between effective-index vs. normalized frequency is drawn. Our studies show that the anisotropic parameter (Kco) influences the dispersion characteristics and modal cut-offs and the modal grouping occurs at different V number for different Kco values. It is also observed that the helix pitch angle ψ has no any pronounced effect on propagation characteristics of the proposed fiber.

CO and O2 Binding to Pseudo-tetradentate Ligand−Copper(I) Complexes with a Variable N-Donor Moiety: Kinetic/Thermodynamic Investigation Reveals Ligand-Induced Changes in Reaction Mechanism

The kinetics, thermodynamics, and coordination dynamics are reported for O(2) and CO 1:1 binding to a series of pseudo-tetradentate ligand-copper(I) complexes ((D)LCu(I)) to give Cu(I)/O(2) and Cu(I)/CO product species. Members of the (D)LCu(I) series possess an identical tridentate core structure where the cuprous ion binds to the bispicolylamine (L) fragment. (D)L also contains a fourth variable N-donor moiety {D = benzyl (Bz); pyridyl (Py); imidazolyl (Im); dimethylamino (NMe(2)); (tert-butylphenyl)pyridyl (TBP); quinolyl (Q)}. The structural characteristics of (D)LCu(I)-CO and (D)LCu(I) are detailed, with X-ray crystal structures reported for (TBP)LCu(I)-CO, (Bz)LCu(I)-CO, and (Q)LCu(I). Infrared studies (solution and solid-state) confirm that (D)LCu(I)-CO possess the same four-coordinate core structure in solution with the variable D moiety "dangling", i.e., not coordinated to the copper(I) ion. Other trends observed for the present series appear to derive from the degree to which the D-group interacts with the cuprous ion center. Electrochemical studies reveal close similarities of behavior for (Im)LCu(I) and (NMe(2))LCu(I) (as well as for (TBP)LCu(I) and (Q)LCu(I)), which relate to the O(2) binding kinetics and thermodynamics. Equilibrium CO binding data (K(CO), ΔH°, ΔS°) were obtained by conducting UV-visible spectrophotometric CO titrations, while CO binding kinetics and thermodynamics (k(CO), ΔH(double dagger), ΔS(double dagger)) were measured through variable-temperature (193-293 K) transient absorbance laser flash photolysis experiments, λ(ex) = 355 nm. Carbon monoxide dissociation rate constants (k(-CO)) and corresponding activation parameters (ΔH(double dagger), ΔS(double dagger)) have also been obtained. CO binding to (D)LCu(I) follows an associative mechanism, with the increased donation from D leading to higher k(CO) values. Unlike observations from previous work, the K(CO) values increased as the k(CO) and k(-CO) values declined; the latter decreased at a faster rate. By using the "flash-and-trap" method (λ(ex) = 355 nm, 188-218 K), the kinetics and thermodynamics (k(O(2)), ΔH(double dagger), ΔS(double dagger)) for O(2) binding to (NMe(2))LCu(I) and (Im)LCu(I) were measured and compared to those for (Py)LCu(I). A surprising change in the O(2) binding mechanism was deduced from the thermodynamic ΔS(double dagger) values observed, associative for (Py)LCu(I) but dissociative for (NMe(2))LCu(I) and (Im)LCu(I); these results are interpreted as arising from a difference in the timing of electron transfer from copper(I) to O(2) as this molecule coordinates and a tetrahydrofuran (THF) solvent molecule dissociates. The change in mechanism was not simply related to alterations in (D)LCu(II/I) geometries or the order in which O(2) and THF coordinate. The equilibrium O(2) binding constant (K(O(2)), ΔH°, ΔS°) and O(2) dissociation rate constants (k(-O(2)), ΔH(double dagger), ΔS(double dagger)) were also determined. Overall the results demonstrate that subtle changes in the coordination environment, as occur over time through evolution in nature or through controlled ligand design in synthetic systems, dictate to a critically detailed level the observed chemistry in terms of reaction kinetics, structure, and reactivity, and thus function. Results reported here are also compared to relevant copper and/or iron biological systems and analogous synthetic ligand-copper systems.

Microbial carbon monoxide uptake in the St. Lawrence estuarine system

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 389:17-29 (2009) - DOI: https://doi.org/10.3354/meps08175 Microbial carbon monoxide uptake in the St. Lawrence estuarine system Huixiang Xie1,*, Yong Zhang1,2, Karine Lemarchand1, Patrick Poulin1 1Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Present address: Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Sciences, 17 Chunhui Road, Laishan District, 264003 Yantai, PR China ABSTRACT: Microbial uptake of carbon monoxide (CO) in the Gulf of St. Lawrence and the estuary of the St. Lawrence River, Canada, typically followed first-order kinetics at ambient CO concentrations, [CO], but saturation kinetics occasionally occurred in spring. The first-order uptake rate constant, Kco, decreased from the upper estuary (8.48 d–1) to the lower estuary (3.94 d–1) and the gulf (1.32 d–1). Kco inversely varied with tide and decreased from its highest value in summer (7.52 d–1) to intermediate values in spring (5.15 d–1) and autumn (4.12 d–1), and to its lowest value in winter (1.09 d–1). Maximum Kco values always occurred in a turbidity maximum zone near the head of the estuary. An empirical model was proposed to account for the effect of particle-associated bacteria on Kco. Temperature dependence of Kco obeyed Arrhenius behavior with the activation energy being lower in the upper estuary (21.5 kJ mol–1) than in the lower estuary and gulf (32.7 kJ mol–1). The combination of bacterial abundance and temperature can serve as an all-season predictive tool for Kco. CO uptake rate versus [CO] plots show typical Michaelis-Menten kinetics or inhibition behavior at elevated [CO]. Km was low and relatively invariable: 3.2 nmol l–1 [CO] in autumn and 4.9 nmol l–1 [CO] in winter. CO specific affinity in autumn (1.25 l (mg of cell)–1 h–1) more than doubled that observed in winter (0.51 l (mg of cell)–1 h–1). This study demonstrated strong seasonal variations in microbial CO uptake and complex influences of various biotic and abiotic variables on this process. KEY WORDS: Carbon monoxide · Microbial uptake · Seasonal variation · Temperature dependence · Bacteria · Suspended particles · Estuarine waters · Gulf of St. Lawrence Full text in pdf format PreviousNextCite this article as: Xie H, Zhang Y, Lemarchand K, Poulin P (2009) Microbial carbon monoxide uptake in the St. Lawrence estuarine system. Mar Ecol Prog Ser 389:17-29. https://doi.org/10.3354/meps08175Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 389. Online publication date: September 04, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

A Supramolecular Receptor of Diatomic Molecules (O2, CO, NO) in Aqueous Solution

A per-O-methylated beta-cyclodextrin dimer, Py2CD, was conveniently prepared via two steps: the Williamson reaction of 3,5-bis(bromomethyl)pyridine and beta-cyclodextrin (beta-CD) yielding 2A,2'A-O-[3,5-pyridinediylbis(methylene)bis-beta-cyclodextrin (bisCD) followed by the O-methylation of all the hydroxy groups of the bisCD. Py2CD formed a very stable 1:1 complex (Fe(III)PCD) with [5,10,15,20-tetrakis(p-sulfonatophenyl)porphinato]iron(III) (Fe(III)TPPS) in aqueous solution. Fe(III)PCD was reduced with Na2S2O4 to afford the Fe (II)TPPS/Py2CD complex (Fe(II)PCD). Dioxygen was bound to Fe(II)PCD, the P(1/2)(O2) values being 42.4 +/- 1.6 and 176 +/- 3 Torr at 3 and 25 degrees C, respectively. The k(on)(O2) and k(off)(O2) values for the dioxygen binding were determined to be 1.3 x 10(7) M(-1) s(-1) and 3.8 x 10(3) s(-1), respectively, at 25 degrees C. Although the dioxygen adduct was not very stable (K(O2) = k(on)(O2)/k(off)(O2) = 3.4 x 10(3) M(-1)), no autoxidation of the dioxygen adduct of Fe(II)PCD to Fe(III)PCD was observed. These results suggest that the encapsulation of Fe (II)TPPS by Py2CD strictly inhibits not only the extrusion of dioxygen from the cyclodextrin cage but also the penetration of a water molecule into the cage. The carbon monoxide affinity of Fe(II)PCD was much higher than the dioxygen affinity; the P(1/2)(CO), k(on)(CO), k(off)(CO), and K(CO) values being (1.6 +/- 0.2) x 10(-2) Torr, 2.4 x 10(6) M(-1) s(-1), 4.8 x 10(-2) s(-1), and 5.0 x 10(7) M(-1), respectively, at 25 degrees C. Fe(II)PCD also bound nitric oxide. The rate of the dissociation of NO from (NO)Fe(II)PCD ((5.58 +/- 0.42) x 10(-5) s(-1)) was in good agreement with the maximum rate ((5.12 +/- 0.18) x 10(-5) s(-1)) of the oxidation of (NO)Fe(II)PCD to Fe(III)PCD and NO3(-), suggesting that the autoxidation of (NO)Fe(II)PCD proceeds through the ligand exchange between NO and O2 followed by the rapid reaction of (O2)Fe(II)PCD with released NO, affording Fe(II)PCD and the NO3(-) anion inside the cyclodextrin cage.

Carbon Monoxide Coordination and Reversible Photodissociation in Copper(I) Pyridylalkylamine Compounds

Systematic studies of CO coordination and photodissociation have been carried out for a series of copper(I) carbonyl compounds possessing tripodal tetradentate ligands, [CuI(L)(CO)]B(C6F5)4 (L = Me2N-TMPA (1Me2N), MeO-TMPA (1MeO), H-TMPA (1H), PMEA (2pmea), PMAP (2pmap), BQPA (3bqpa). Detailed structural, electrochemical, and infrared characterization has been accomplished. In addition, various experimental techniques were utilized to determine equilibrium binding constants (KCO), association (kCO), and dissociation (k-CO) rate constants, as well as the thermodynamic (DeltaH degrees , DeltaS degrees ) and activation parameters (DeltaH, DeltaS) that regulate these processes. With increased ligand-electron-donating ability, greater pi back-bonding results in stronger Cu-CO bonds, leading to KCO values on the order 1Me2N-CO > 1MeO-CO > 1H-CO. With systematic synthetic expansion of the five-membered chelate rings like 1R to six-membered chelate rings like 2R, the stability of the CO adduct decreases, 1H-CO > 2pmea-CO > 2pmap-CO. The CO-binding properties of 3bqpa did not follow trends observed for the other compounds, presumably because of its bulkier ligand framework. Through solid- and solution-state analyses, we concluded that the photolabile carbonyl species in solution possess a tridentate coordination mode, forming strictly five-membered chelate rings to the copper ion with one dangling arm of the tripodal ligand. Carbon monoxide reversibly photodissociated from complexes 1Me2N-CO, 1MeO-CO, 1H-CO, and 3bqpa-CO in coordinating (CH3CN) and weakly coordinating (THF) solvent but not from 2pmea-CO and 2pmap-CO. Comparisons to O2-binding data available for these copper complexes as well as to small molecule (O2, CO, NO) reactions with hemes and copper proteins are discussed.

Crop Coefficients for Microsprinkler-Irrigated, Clean-Cultivated, Mature Citrus in an Arid Climate

Crop evapotranspiration (ETc) was measured over a clean-cultivated, mature navel orange orchard with microsprinkler irrigation located near Lindsay, California. Hourly mean latent heat flux density was determined as the residual of the energy balance equation with measured net radiation, soil heat flux density and sensible heat flux density estimated using the surface renewal method. The ETc was compared with ETo calculated using hourly weather data and the ASCE-EWRI Penman-Monteith equation. Following pruning and topping of the trees in the spring of 2001, the Kco values slowly increased as the canopy developed in the following season. An average Kco=0.82 was observed. In the following year, the mean summertime value increased to about Kco=0.95, and in 2003 and 2004, the summertime value averaged near Kco=1.00, which is somewhat higher than observed for drip irrigated trees in southwestern Arizona and considerably higher than reported in the widely used Food and Agricultural Organization of the United Nations publications that were based on infrequent surface irrigation.

Variation in Phenanthrene Sorption Coefficients with Soil Organic Matter Fractionation: The Result of Structure or Conformation?

Sorption of phenanthrene to varying soil types was investigated to better understand sorption processes. Humic acid and humin fractions were isolated from each soil sample, and sorption coefficients were measured by batch equilibration. Samples were characterized by carbon analysis and 13C cross polarization magic angle spinning (CP/ MAS) nuclear magnetic resonance (NMR) spectroscopy. Measured organic carbon-normalized sorption coefficients (Koc) of the fractions were greater in all cases when compared to the soils. The humin fractions exhibited greater Koc values than did source samples, suggesting that fractionation may reorganize organic matter in humin resulting in an increased availability of and/or more favorable sorption domains. Mass balance calculations revealed that the sum of sorption to the fractions is greater than sorption to the whole sample. The greatest difference between sorption values was found to occur with the mineral soils, suggesting that clay minerals influence the physical conformation of soil organic matter (SOM) and availability of sorption domains. The mass balance, sorption data, and a lack of consistent trends between observed Kco values and solid-state 13C NMR data suggest that the physical conformation of SOM and chemical characteristics both play important roles in sorption processes.

Estimation of Evapotranspiration of Different-Sized Navel-Orange Tree Orchards Using Energy Balance

Crop evapotranspiration (ETc) and crop coefficient (Kco) values of four clean-cultivated navel-orange orchards that were irrigated with microsprinklers, having different canopy features (e.g., age, height, and canopy cover) were evaluated. Half-hourly values of latent heat flux density were estimated as the residual of the energy balance equation using measured net radiation (Rn), soil heat flux density (G), and sensible heat flux density (H) estimated using the surface renewal method. Hourly means of latent heat flux density (LE) were calculated and were divided by the latent heat of vaporization (L) to obtain ETc. Crop coefficients were determined by calculating the ratio Kco=ETc∕ETo, with reference evapotranspiration (ETo) determined using the hourly Penman–Monteith equation for short canopies. The estimated Kco values ranged from 0.45 to 0.93 for canopy covers having between 3.5 and 70% ground shading. The Kco values were compared with Kc values from FAO 24 (reported by Doorenbos and Pruitt in 1975) and FAO 56 (reported by Allen et al. in 1998) and with Kc values from research papers that estimated reference ET from pan evaporation data using the FAO 24 method. The observed Kco values were slightly higher than Kc values for clean-cultivated orchards with high-frequency drip irrigation in Arizona and were slightly lower than for nontilled orchards in Florida. The Kco values were considerably higher than Kc values from FAO 24 and FAO 56 and were higher than Kc values from border-irrigated orchards near Valencia, Spain.

Activation parameters for the reactive intermediates relevant to carbonylation catalysts based on cobalt carbonyls.

Time-resolved spectroscopic techniques have been used to prepare and to interrogate transient species that are models for reactive intermediates in cobalt-catalyzed hydroformylation. Flash photolysis of acetylcobalt carbonyl complexes of the type RC(O)Co(CO)3(PR'3) (A; R = CH3, CD3, or C2H5; R' = Ph or nBu) leads to CO photodissociation to give the "unsaturated" intermediate [RC(O)Co(CO)2(PR'3)] (I), which decays by two competitive pathways, alkyl migration to the cobalt to give RCo(CO)3PR'3 (M) and reaction with CO to re-form A. With the perdeuterioacetyl complex (R = CD3, R' = Ph), rate constants both of CO trapping (kco) and of methyl migration (kM) were just slightly smaller than those of the perprotio analogue (kh/kd = 1.04 +/- 0.01 and 1.07 +/- 0.09, respectively). Thus, any stabilization of the "vacant" coordination site of I by agostic interactions with the acetyl methyl group appears to be kinetically insignificant, consistent with the previous conclusion (Inorg. Chem. 2000, 39, 3098-3106) that this site is stabilized by an eta 2-coordinated carbonyl. Changing the phosphine ligand has a greater influence on the kinetics of I. The species generated by the flash photolysis of the trialkyl phosphine complex CH3C(O)Co-(CO)3(P(nBu3)) exhibited a much larger kM than was the case for the PPh3 analogue, although there was little difference in the kco values. Similarly, kM proved to be sensitive to the nature of R as demonstrated by the slower alkyl migration (at 298 K) for the intermediate formed by CO photodissociation from the propionyl complex C2H5C(O)Co(CO)3PPh3 relative to the acetyl analogue. Nonetheless, all these intermediates displayed analogous time-resolved infrared spectra and general kinetics behavior in benzene solution (implying common mechanisms for decay), so it is concluded that all are present as the eta 2-chelated acyl structure under these conditions.

Pulmonary diffusing capacity in chronic dialysis patients

Patients with end-stage renal disease treated by hemodialysis with bioincompatible membranes are exposed during the dialysis period to acute effects on lung microcirculation, which may result in pulmonary fibrosis and diffusion defects in long-standing dialysis. To investigate the occurrence of these possible chronic pulmonary alterations, we determined lung function in patients with chronic renal failure not undergoing hemodialysis and in patients who had been receiving regular hemodialysis both for short and long periods of time. Forty-three patients divided into three groups were studied: 17 patients before dialysis with a mean (SD) creatinine clearance of 14.1 (6.8) ml/minl 1.73 m2, 10 patients receiving regular hemodialysis for a period of less than 12 months (mean 6.4 ± 3.5 months), and 16 patients receiving regular hemodialysis for more than 5 years (mean 8.3 ± 3.6 years). First-use bioincompatible cellulosic dialysis membranes were used in all the cases. The following parameters were recorded: forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), total lung capacity (TLC), residual volume (RV), carbon monoxide transfer factor (TLCO), accesible lung volume (VA), carbon monoxide transfer factor/accesible lung volume (KCO— that is, TLCO/VA), and arterial blood gases. Patients receiving regular hemodialysis for more than 5 years showed significantly lower values of TLCO and KCO than patients before dialysis and patients receiving regular hemodialysis for less than 12 months. Seventy-five percent of patients on long-term hemodialysis had markedly reduced TLCO or KCO values (below 80% of the reference value) as compared with 17% of patients before dialysis and 10% of patients dialyzed for less than 12 months (P<0.001). Differences among groups for the remaining parameters were not observed. In conclusion, patients undergoing long-term regular hemodialysis with a bioincompatible membrane showed a selective reduction in pulmonary diffusing capacity possibly due to chronic pulmonary fibrosis.

Room-Temperature Reactions of the Intermediate(s) Generated by Flash Photolysis of (η5-C5H5)Fe(CO)2CH3

The transient formed by the photolysis of the methyl complex CpFe(CO)2CH3 (M, Cp = (η5-C5H5)) has been studied by FTIR spectroscopy in methylcyclohexane solution at 77 K and by time-resolved infrared detection in ambient-temperature solutions in cyclohexane and tetrahydrofuran. The transient IR spectrum of the intermediate IM displays a single νco absorption band and can be characterized as a monocarbonyl. In 295 K solution, the reaction of IM with CO occurs with second-order kinetics (rate = kco[IM][CO]) with kco values of (6.3 ± 0.2) × 108 and (3.4 ± 0.4) × 106 M-1 s-1 in cyclohexane and THF, respectively. On the basis of these data, IM is concluded to be the solvento complex CpFe(CO)(Sol)CH3.

Abnormalities of the lungs and thoracic cage in the Ehlers-Danlos syndrome.

Twenty patients with the Ehlers-Danlos syndrome, (10 type I, six type II, and four type IV) were studied to assess the frequency of respiratory abnormalities in this condition. Five patients (25%) had had at least one episode of haemoptysis, but none had any defect of coagulation. There was a high frequency of recurrent sinusitis, notably in those with the type I syndrome. Two patients had bullous lung disease, one of whom (type IV) had had three pneumothoraces and subsequent pleurodesis; he also had tracheomegaly (the Mounier-Kuhn abnormality). Minor skeletal abnormalities such as pectus excavatum were common, particularly in patients with type IV disease. Three patients had the straight back syndrome. There were no consistent spirometric or lung volume abnormalities, but eight patients (40%) had a raised gas transfer coefficient (Kco), possibly due to an increased intrapulmonary vascular volume. Two other patients had very low values of Kco that were unexplained.

Deactivation of Vibrationally Excited Carbon Dioxide (001) by Collisions with Carbon Monoxide

The rate constants associated with the deactivation of vibrationally excited CO2*(001) by collisions with CO have been experimentally determined from 300 to 900°K by a laser fluorescence method. These reactions involving CO considered were CO2*(001)+CO⇆ lim k2k1CO2+CO*(υ = 1), CO2*(001)+CO→ lim kCOCO2(ν1, ν2)+CO, CO*(υ = 1)+CO2→ lim k4CO+CO2(ν1, ν2), where CO2(ν1, ν2) is an unidentified product state. Within experimental error the rate constant k1 increases linearly with temperature T(°K) from a value of 5.7 × 103 torr−1·sec−1 at room temperature to a value of 11.2 × 103 torr−1·sec−1 at 900°K. From 500 to 900°K the rate constant kCO(torr−1·seconds−1) varies with temperature as log10kCO = A − BT−1/3, with A = 6.61 and B = 31.6. From 300 to 500°K the measured values of kCO are greater than those corresponding to the cited relation. The rate constant k4 was found to be negligible compared to kCO. The probability per collision of vibrational energy transfer from CO2*(001) to CO(υ = 0) was computed by a theory involving long range forces. The calculated probabilities, using only multipolar interaction and only exponential repulsive interaction, are in equally good agreement with the probabilities deduced from measurement of R1, the transfer rate constant in the exothermic direction.