Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forests

in Agricultural and Forest Meteorology (2010), 150(5), 655-664

The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time ... [more ▼]

The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time conditions, in an attempt to improve NEE estimates. Four towers were arranged in a square around a main tower, with the sides of the square about 100 m long. Equipped with 16 sonic anemometers and [CO2] sampling points, the towers were installed to measure vertical and horizontal advection of [CO2]. Vertical turbulent fluxes were measured by an eddy covariance system at the top of the main tower. The results showed that horizontal advection varied greatly from site to site and from one wind sector to another, the highest values being reached when there were large friction velocities and fairly unstable conditions. There was less variation in vertical advection, the highest values being reached when there were low friction velocities and stable conditions. The night-time NEE estimates deduced from the mass balance were found to be incompatible with biologically driven fluxes because (i) they varied strongly from one wind sector to another and this variation could not be explained in terms of a response of the biologic flux to climate, (ii) their order of magnitude was not realistic and (iii) they still showed a trend vs. friction velocity. From a critical analysis of the measurement and data treatment we concluded that the causes of the problem are related to the representativeness of the measurement (control volume size, sampling resolution) or the hypotheses underlying the derivation of the [CO2] mass balance (ignoring the horizontal turbulent flux divergence). This suggests that the improvement of eddy flux measurements by developing an advection completed [CO2] mass balance at night would be practically difficult. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

Direct and indirect costs attributable to osteoarthritis in active subjects

in Journal of Rheumatology (2006), 33(6), 1152-1158

OBJECTIVE: To estimate the direct and indirect costs of osteoarthritis (OA) in an active population, and to identify factors significantly influencing these expenditures. METHODS: A cohort of 3,440 ... [more ▼]

OBJECTIVE: To estimate the direct and indirect costs of osteoarthritis (OA) in an active population, and to identify factors significantly influencing these expenditures. METHODS: A cohort of 3,440 subjects employed by the Liege City Council was followed prospectively for 6 months. Subjects were asked to report monthly OA related health resource utilization (contacts with health professionals, medical examinations, drug consumption, etc.) and absence from work. Health related quality of life (HRQOL) was evaluated at baseline using the Medical Outcomes Study Short-form 36 (SF-36). Logistic regression analysis identified factors associated with the probability that the individual incurred costs, and multiple regression identified factors influencing the magnitude of these costs. RESULTS: A total of 1,811 subjects filled in at least one questionnaire (response rate 52%). The mean duration of followup was 3.46 months. Self-reported prevalence of OA was 34.1%. The mean total direct costs were 44.5 euros per OA patient-month. Contacts with health professionals, medical examinations, drugs, and hospital stays accounted for 23.7 euros, 8.7 euros, 6.7 euros, and 4.9 euros, respectively, per OA patient-month. The average number of sick-leave days was 0.8 per OA patient-month. From a payer's perspective, this loss of productivity represented a mean cost of 64.5 euros per OA patient-month. We also recorded 0.02 mean days off work per active subject-month due to informal care by relatives, yielding a mean cost of 1.8 euro per active subject-month for the employer. Poorer scores for most of the dimensions of the SF-36 at baseline were significantly associated with greater likelihood of incurring direct and indirect costs and with higher costs among subjects who reported costs. If we consider the overall cohort of active subjects, the burden of OA related to the direct and indirect costs was 15.2 euros and 23.8 euros, respectively, per active subject-month. CONCLUSION: Direct and indirect costs attributable to OA are substantial, with productivity related costs being predominant. Poorer HRQOL was a major determinant of these expenditures. [less ▲]

Direct and indirect pCO2 measurements in a wide range of pCO2 and salinity values

in Aquatic Geochemistry (2001), 7

Recent improvements in both Infra-red spectroscopy and equilibrator techniques have allowed to determine, for the first time, pCO2 using simultaneously and continuously both the direct and indirect ... [more ▼]

Recent improvements in both Infra-red spectroscopy and equilibrator techniques have allowed to determine, for the first time, pCO2 using simultaneously and continuously both the direct and indirect methods in an estuary where pCO2 values range from 500 to 8500 µatm and salinity from 0 to 30. Our results show that both methods are in excellent agreement in the whole estuary (r2 = 0.999, n = 1075, p < 0.0001). Thus, the NBS (US National Bureau of Standards) scale, although inadequate for seawater samples, is appropriate for estuarine waters and can be applied with confidence to calculate pCO2. [less ▲]

Direct and neurally mediated effects of halothane on pulmonary resistance in vivo.

in Anesthesiology (1990), 72(6), 1057-63

It has been suggested that halothane inhibits contraction of airway smooth muscle in vivo mainly by reducing reflex activity in nerves innervating the muscle with only minimal direct effects on the muscle ... [more ▼]

It has been suggested that halothane inhibits contraction of airway smooth muscle in vivo mainly by reducing reflex activity in nerves innervating the muscle with only minimal direct effects on the muscle itself. To examine possible mechanisms of action of halothane at clinically relevant concentrations the authors studied the effect of halothane on increases in pulmonary resistance (RL) produced by either vagus nerve stimulation (VNS, which caused neurally mediated constriction) or the inhalation of nebulized acetylcholine (ACh, which directly stimulated the smooth muscle cell) in nine mongrel dogs. The frequency of bilateral VNS and the dose of nebulized ACh were adjusted to produce approximately equal increases in RL. Halothane reduced the response to both types of stimulation in a dose-dependent fashion. At halothane concentrations greater than or equal to 0.4 MAC, the VNS response was significantly less than the ACh response. When tetrodotoxin was given to block neural activity, the ACh response was unchanged, confirming that neural activation did not contribute significantly to smooth muscle contraction in response to ACh. The authors conclude that in addition to neurally mediated effects, halothane at clinically used concentrations has significant direct effects on airway smooth muscle stimulated by ACh. The relative importance of each factor in vivo should depend on the stimulus that causes contraction of airway smooth muscle. [less ▲]

Direct CO2 advection measurements and the night flux problem

in Agricultural and Forest Meteorology (2010), 150(5), 651-654

Direct costs of hip fractures in patients over 60 years of age in Belgium.

in PharmacoEconomics (1999), 15(5), 507-514

OBJECTIVE: Osteoporosis-related costs are now considered a major burden for health authorities in most developed countries. An accurate and exhaustive evaluation of these costs would be a major ... [more ▼]

OBJECTIVE: Osteoporosis-related costs are now considered a major burden for health authorities in most developed countries. An accurate and exhaustive evaluation of these costs would be a major contribution to health economic studies evaluating the efficiency of screening and prevention strategies. Osteoporosis is the most frequent underlying cause of femoral neck fractures in the elderly; these fractures weigh heavily on healthcare budgets. However, in Belgium, very few data on the financial burden of hip fractures are available and no updated estimates have been made. The goal of this paper is to estimate the direct medical expenditures associated with hip fractures in Belgium in 1996. DESIGN AND SETTING: This 1-year population-based cross-sectional study is conducted from the social security perspective. The target population in this study are men and women aged 60 years and over. PATIENTS AND PARTICIPANTS: We selected patients who had been hospitalised for a hip fracture during the year 1996 who were also affiliated with a registered social security organisation (covering 25% of the Belgian population). The sample constituted 2374 patients. INTERVENTIONS: For each of these patients, we collected an exhaustive and detailed list of healthcare resource use as well as nursing home admissions following the hip fracture event. Cost items investigated in the analysis were inpatient hospital costs and outpatient costs. Mean annual costs per case recorded in the sample were then extrapolated to the whole country on the basis of an exhaustive list of diagnoses having lead to all countrywide hospitalisations (1,700,000 hospital stays/year). MAIN OUTCOME MEASURES AND RESULTS: The mean hospital inpatient costs for hip fracture were evaluated at 332,148 Belgian francs (BeF) [$US8977] per case and BeF4,367,746,200 ($US118,047,194) for the whole country (10 million inhabitants). Patients with a hip fracture experienced an annual BeF27,825 ($US752) extra outpatient cost during the year following this fracture event, after correcting for costs related to additional comorbidity already present before the hip fracture. Finally, after a proximal femoral neck fracture, the rate of nursing home admission was higher, both for men and women at any age compared with age- and gender-matched population. CONCLUSIONS: With a total cost (acute hospital and outpatient costs) of BeF4,667,894,950 ($US126,159,323) per year in Belgium, proximal femoral neck fracture should be considered a major health economic problem and appropriate measures to prevent this disease should be rapidly undertaken. [less ▲]

Direct differentiation of time integrators for multibody systems with absolute rotations

in Proceedings of the ECCOMAS Thematic Conference - Multibody Dynamics 2007 (2007)

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct ... [more ▼]

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct differentiation technique leads to a significant reduction in the computational cost of the sensitivities while keeping a good accuracy. In particular, this paper focuses on the optimization of multibody systems with large rotations. In this framework, two versions of the generalized-alpha time integration scheme are considered: the first one is based on a parameterized treatment of the rotations, whereas the second one is formulated in a geometric setting. We show that the sensitivity analysis is much simpler and computationally more efficient in the second case than in the first case. The performance of both algorithms is compared for a numerical example. [less ▲]

A Direct Dopaminergic Control of Aromatase Activity in the Quail Preoptic Area

in Journal of Steroid Biochemistry & Molecular Biology (1997), 63(1-3, Sep-Oct), 99-113

In the quail preoptic area (POA) anatomical and pharmacological data suggest that catecholamines may be implicated in the control of testosterone (T) aromatization into estrogens. The biochemical ... [more ▼]

In the quail preoptic area (POA) anatomical and pharmacological data suggest that catecholamines may be implicated in the control of testosterone (T) aromatization into estrogens. The biochemical mechanism(s) mediating this control of the enzyme activity is (are) however unexplored. The present studies were carried out to investigate whether the catecholamines, dopamine (DA) and norepinephrine (NE) are able to directly affect aromatase activity (AA) measured during in vitro incubations of POA homogenates. AA was quantified in the POA-hypothalamus of adult male Japanese quail by measuring the tritiated water production from [1beta-3H]-androstenedione. Enzyme activity was linear as a function of the incubation time and of the protein content of homogenates. It exhibited a typical Michaelis-Menten kinetics, with an apparent Km of 2.8 nM and a Vmax of 266.6 fmol h(-1) mg wet weight(-1). AA was then measured at a substrate concentration of 25 nM in the presence of catecholamines and some of their receptor agonists or antagonists, at two concentrations, 10(-3) and 10(-6) M. Norepinephrine and prazosin (alpha1-adrenergic antagonist) had no or very limited effects on AA at both concentrations. In contrast, DA and some D1 and/or D2 receptor agonists (apomorphine[D1/D2], SKF-38393 [D1] and RU-24213 [D2]) depressed AA by 40 to 70% at the 10(-3) M concentration. One D2 receptor antagonist also produced a major inhibition of AA (sulpiride) while other antagonists either had no significant effect or only produced moderate decreases in enzyme activity (SCH-23390 [D1], spiperone [D2], pimozide [D2]) as did two DA indirect agonists, amfonelic acid and nomifensine. The inhibitory effect of the agonists was not antagonized by the less active antagonists, SCH-23390 [D1] or spiperone [D2]. Taken together these results suggest that the inhibitory effects do not involve specific binding of DA or its agonists/antagonists to dopaminergic receptors mediating changes in cAMP concentration. This conclusion is also supported by the observation that addition of dibutyryl cAMP did not change brain AA. It appears more likely that DA and dopaminergic drugs inhibit AA by a direct effect on the enzyme, as suggested by the competitive nature of DA and SKF-38393 inhibition of AA (Ki's of 59 and 84 microM, respectively). The functional significance of this effect should still be demonstrated but this mechanism may represent an important physiological pathway through which neurotransmitters could rapidly affect steroid-dependent processes such as the neural synthesis of estrogens. This would provide a mean by which environmental stimuli could affect reproductive behavior and physiology. [less ▲]

A direct enzyme-linked immunosorbent assay (Elisa) for antibodies to enterobacterial score glycolipid and lipid A. Results in Healthy Subjects and in Patients Infected by Gram-Negative Bacteria

in Medical Microbiology & Immunology (1987), 176(5), 257-271

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of ... [more ▼]

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of healthy blood donors, whereas anti-lipid A activities were found in 13% of individuals only. The anti-CGL and anti-lipid A activities were examined in patients in a surgical intensive care unit, selected on the basis of a definite risk of infectious complications due to Gram-negative bacteria. Of the patients who developed such infections, the rate of favourable outcome was significantly higher in patients with either stable positive or increasing anti-CGL activities than in patients found to be negative. Our results provide clear evidence that anti-CGL antibodies contribute to host defence against various Gram-negative bacteria. [less ▲]

Direct evidence for ferroelectric polar distortion in ultrathin lead titanate perovskite films

in Physical Review b (2006), 73(9),

X-ray photoelectron diffraction is used to directly probe the intracell polar atomic distortion and tetragonality associated with ferroelectricity in ultrathin epitaxial PbTiO3 films. Our measurements ... [more ▼]

X-ray photoelectron diffraction is used to directly probe the intracell polar atomic distortion and tetragonality associated with ferroelectricity in ultrathin epitaxial PbTiO3 films. Our measurements, combined with ab initio calculations, unambiguously demonstrate noncentrosymmetry in films a few unit cells thick, imply that films as thin as three unit cells still preserve a ferroelectric polar distortion, and also show that there is no thick paraelectric dead layer at the surface. [less ▲]