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ABSTRACTSchools are ideal settings to promote adolescent physical activity (PA), yet school-based interventions have shown limited long-term impact. This position paper presents key issues surrounding school-based PA interventions. Collaborative conceptual thinking drawing on multi-author expertise and available evidence advanced our understanding and opinion. Key arguments: 1) the adoption of a systems approach, which maximizes partnership action and leverages policy, is crucial for understanding the complexities of implementing whole-school programs; 2) a reorientation to an assets perspective optimizes existing strengths and resources allowing greater emphasis on the full range of physical, cognitive, emotional and social benefits that PA provides, and 3) a move beyond traditional positivist research designs to advance our knowledge of what works better, for whom and in what context is needed for greater progress We provide suggestions, specifically advocating for systems approaches, as a realistic way to improve how we support PA in schools in the future.

Purpose: The aim of this study was to analyze the relationship between adiposity, cardiometabolic risk and cardiorespiratory fitness (CRF) according to different groups of adiponectin concentration. Methods: 255 adolescents of both sexes, aged 11–17 years old, participated. Anthropometric and biochemical parameters such as body mass, height, abdominal circumference (AC), waist circumference (WC), fat mass, fat-free mass, total cholesterol (TC), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c), triglycerides (TG), glucose, insulin, adiponectin, blood pressure, peak oxygen consumption (VO2peak) were measured. Body mass index (BMI), z-score BMI (BMI-z), triponderal mass index (TMI), waist-to-height ratio (WHtR), homeostasis model to assessment insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were calculated. Adiponectin was categorized: low adiponectin concentration (LAC  ≤ 5.18 µg/mL−1), intermediate (IAC = 5.18 and 7.63 µg/mL−1) and high (HAC ≥ 7.63 µg/ml−1). Results: LAC showed higher BMI, BMI-z and TMI than the other groups (p< 0.05) and higher AC, WC and WHtR that the HAC (p< 0.05). IAC showed lower values of TC, LDL-c and TG, and the LAC presented the highest values of insulin, HOMA-IR and QUICKI (p< 0.05) to the IAC and HAC. HAC presented the lower VO2peakthan the other groups (p< 0.01). BMI, TMI, glucose, insulin, HOMA-IR showed inverse, and QUICKI a direct and weak correlation with adiponectin (p< 0.05). No significant association was found between adiponectin and VO2peak(p> 0.05). Conclusion: The LAC group had higher means in the anthropometric variables and the worst results related to insulin resistance and sensitivity. Thus, adiponectin may play an important role in obesity and reduced concentration may be a factor in the development of obesity-associated morbidities.

Purpose: This study aimed to evaluate the effect and individual responsiveness after 12 (12wk) and 24 weeks (24wk) of physical exercise (PE) and nutritional guidance (NG) on metabolic syndrome (MetS) criteria and hepatic parameters in overweight adolescents. Methods: The study comprised 94 overweight adolescents, aged between 10 and 16 years old, from both sexes, allocated into groups: PE and NG (PENGG, n= 64) and control with NG (NGCG, n= 30). Variables were collected at baseline, 12wk, and 24wk. Weight, height, abdominal circumference (AC), blood pressure, and peak oxygen consumption (VO2peak), as well as insulin, triglycerides (TAG), high-density lipoprotein (HDL-c), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were evaluated. HOMA-IR and QUICKI were calculated. PE session consisted of 45 min of indoor cycling, 45 min of walking, and 20 min of stretching, three times a week. The NG consisted of three collective sessions in the first 12wk. Anova, effect size, and prevalence of responders were used for statistical analysis. Results: The PENGG12wk reduced anthropometric and metabolic measurements, while increased VO2peakand HDL-c. The PEG24wk promoted anthropometric, blood pressure, metabolic, and VO2peakimprovements, but participants without PE returned to pre-exercise status and presented worsening AST and ALT concentrations. Frequencies of respondents in PENGG12wk versus (vs) NGCG12wk were, respectively, AC (69.1% vs 17.6%, p< 0.01), HDL-c (87.2% vs 23.5%, p< 0.01), TAG (67.3% vs 41.7%, p= 0.05) and ALT (45.5% vs 5,9%; p= 0.003). Conclusion: Interventions with PE were effective to reduce MetS components in 12wk and maintenance in 24wk, showing anthropometric, metabolic, and VO2peakimprovements. Higher individual responses were observed in 12wk and in 24wk, important changes in overweight adolescent’s therapy. Level of evidence: Level I, evidence obtained from well-designed controlled trials randomization. Trial registration number and date of registration: Brazilian Registry of Clinical Trials (RBR-4v6h7b) and date of registration April 4th, 2020.

This cross-sectional study investigated the association of physical fitness with cognitive function, functional capacity and quality of life among institutionalized older adults with dementia. One hundred and two older adults aged 78.0 ± 8.4 years, predominantly female (67.6%), with neurocognitive disorder due to Alzheimer’s disease (AD) (49.2%), vascular dementia (14.7%), Parkinson’s disease (2%), dementia with Lewy bodies (2%) or unspecified dementia (32.1%) participated in the present study. Regression analyses were used to examine associations between physical fitness components (Senior Fitness Test) and cognitive function (Mini-Mental State Examination), functional capacity (Katz Index of Independence in Activities of Daily Living) and Quality of Life (QoL)-Alzheimer's Disease scale. Univariate regression indicates that strength, flexibility, agility/dynamic balance and aerobic endurance are relevant for cognitive function, physical capacity and perceived QoL in institutionalized older people with dementia. After multiple regression analyses, adjusted for body mass index (BMI), results showed that aerobic endurance had a significant positive association with Total Katz Index. For both, caregiver perception of QoL-AD and global QoL-AD, BMI remained significantly and positively associated. Agility–dynamic balance presented a significant negative relation with global QoL-AD. Overall, our findings suggest that better physical fitness is important for cognition and autonomous functional capacity and that it has positive repercussions on the QoL in institutionalized older adults with dementia. Consequently, exercise-based therapeutic strategies aiming to improve physical fitness should be implemented.

To identify predictors of health-related quality of life (HRQoL) among former athletes.

Remission of acromegaly has been reported after somatostatin analogs withdrawal, but not after withdrawal of combination therapy with cabergoline, and only in case reports of patients controlled by cabergoline alone. To establish the remission rates (normal IGF-1 for age/sex: IGF-1 ≤ 1.00 xULN) after withdrawal of combined treatment with octreotide LAR and cabergoline and of cabergoline alone, we prospectively studied 16 patients with acromegaly controlled by those treatments in the preceding 2 years as part of a larger study on remission of acromegaly after withdrawal of different medical treatments. Among 97 patients with controlled acromegaly included in the entire study, only 16 patients had been on combination therapy (n= 12) or cabergoline alone (n= 4). At 8 weeks after treatment withdrawal, three patients (19%) were in remission (short-term remission). At 60 weeks (long-term remission), IGF-1 levels were still in the normal range in two patients (12.5%) and remained normal up to 108 weeks after treatment withdrawal (last visit). One patient had been treated with cabergoline alone and another one with combination of octreotide and cabergoline before treatment withdrawal. Remission of acromegaly after treatment withdrawal seems to be uncommon in patients controlled by cabergoline, either as monotherapy or in combination with octreotide. In the future, larger studies and/or meta-analysis will be necessary to accurately establish the remission rates of acromegaly after withdrawal of cabergoline with or without somatostatin analogs.

Background/Objective:Adipokines are involved in the etiology of diabetes, insulin resistance, and the development of atherosclerosis and other latent-onset complications. The objective of this meta-analysis was to determine the effectiveness of exercise interventions on adipokines in pediatric obesity.Subjects/Methods:A computerized search was made using three databases. The analysis was restricted to studies that examined the effect of exercise interventions on adipokines (adiponectin, leptin, resistin and visfatin) in pediatric obesity (6–18 years old). Fourteen randomized controlled trials (347 youths) were included. Weighted mean difference (WMD) and 95% confidence intervals were calculated.Results:Exercise was associated with a significant increase in adiponectin (WMD=0.882 μg ml−1, 95% CI, 0.271–1.493) but did not alter leptin and resistin level. Likewise, exercise intensity and change in body fat; as well as total exercise program duration, duration of the sessions, and change in body fat all significantly influenced the effect of exercise on adiponectin and leptin, respectively.Conclusions:Exercise seems to increase adiponectin levels in childhood obesity. Our results also suggested that exercise on its own, without the concomitant presence of changes in body composition levels, does not affect leptin levels.

One of the global targets for non-communicable diseases is to halt, by 2025, the rise in the age-standardised adult prevalence of diabetes at its 2010 levels. We aimed to estimate worldwide trends in diabetes, how likely it is for countries to achieve the global target, and how changes in prevalence, together with population growth and ageing, are affecting the number of adults with diabetes.

Diabetes has been defined on the basis of different biomarkers, including fasting plasma glucose (FPG), 2-h plasma glucose in an oral glucose tolerance test (2hOGTT), and HbA1c. We assessed the effect of different diagnostic definitions on both the population prevalence of diabetes and the classification of previously undiagnosed individuals as having diabetes versus not having diabetes in a pooled analysis of data from population-based health examination surveys in different regions.

Cohesive horizons are widespread along the Brazilian coastal tablelands and, despite their importance to soil management under intensive cultivation, their genesis remains, in many aspects, controversial. Studies diverge and indicate the participation of different mechanisms in the formation of these soil horizons. Although clay illuviation has been considered as one of the processes determining the formation of this soil attribute, recent studies suggest a limited participation of this soil process. The aim of the present study was to evaluate the relative contribution of argilluviation and sorting of sand to the genesis of cohesive horizons in an Ultisol toposequence from a toposequence from north-east Brazil. Soil samples were collected from cohesive and non-cohesive horizons from four soil profiles. We determined bulk soil density (BD), penetration resistance (PR), particle size distribution and the percentage of different sand fractions. The sand fractionation data were treated statistically to obtain different grain size parameters, such as mean grain size, sorting and kurtosis. An additional micromorphological study was performed on cohesive and non-cohesive horizons. The lowest BD and PR were recorded in non-cohesive horizons (1.53Mgm-3 and 0.74MPa, respectively), whereas significantly higher values of BD (1.66–1.80Mgm-3) and PR (2.61–7.71MPa) were observed in cohesive horizons. Thin sections of cohesive soil horizons showed a significant reduction in void sizes and interconnecting pores compared with non-cohesive soil horizons. The higher values of BD and PR observed in the cohesive horizons are apparently related to this poorly interconnected void network. Textural pedofeatures observable with optical microscopy, which indicate argilluviation, were only found in one cohesive horizon. Sand fractionation showed a predominance of medium and fine sand fractions and indicated the dominance of poorly selected sand in cohesive horizons, probably causing the higher BD and PR values. However, the presence of textural pedofeatures (clay coatings) in one of the cohesive horizons studied may indicate a combined contribution of sand heterogeneity and argilluviation in the genesis of these horizons. Overall, the results of the present study showed that subtle variations in the distribution of basic soil components (i.e. particle size fractions) may determine the formation of cohesive horizons and thus must be taken into account in future studies aiming to predict their spatial distribution and to establish more efficient management strategies.

The species-area relationship is one of the most commonly studied issues in ecology and several explanatory models have been proposed for the question. Most papers on the relationships between taxa and area adopt the species-level approach. By contrast, our approach exports these concepts to other organizational levels of biodiversity and analyses the community-area relationships in the Betic mountain ranges at 4 levels of syntaxonomical hierarchy. Our approach also aims at studying the diversity of communities in the same way as taxonomical diversity is studied. To evaluate the matching of data to the different models, we used the regression coefficient (R2) and the corrected version of Akaike's information criterion (AICc). The highest altitude of asierrawas taken as a surrogate of habitat diversity. “Syntaxonomical diversity” was evaluated in a similar way to the taxonomical diversity of Clarke & Warwick.We have studied 94 associations (belonging to 42 alliances, 36 orders and 25 classes). The calculated indexes reveal higher regression coefficient between richness in syntaxa and the parameter under study (area and highest altitude) in a semi-log model than in a log-log model. Although the best correlation is obtained considering both variables, the patterns of richness exhibit a higher correspondence with altitude than with area. Results confirm very high regression coefficient between richness in syntaxa and in the quantity of the endemic flora present in each sierra. The higher the syntaxonomical level concerned, the higher the regression coefficient.The richness of the syntaxa exhibits patterns similar to those of the endemic flora: the most important sites are siliceous Sierra Nevada, Sierra de Las Nieves and Sierra de Gádor. There are important implications for conservation biology. These results show that approaches based on species and those based on communities are compatible for the preservation of biodiversity.

This article revisits the Navier–Stokes equations for the flow between two cylinders with a small thickness of lubricating oil. An effective parameterization of the geometry is proposed, allowing a more detailed description of the problem and its adaptation to other contexts. Simplifications based on the lubrication theory are carried out, resulting in an elliptical partial differential equation, whose solution is the pressure field between the cylinders, approximated by the centered finite difference method. To illustrate the effectiveness of the proposed approach, the model is applied to hydrodynamic bearings, for which the pressure field, the fluid forces applied to the shaft, the static equilibrium position and the stiffness and damping coefficients are calculated. Three cases are presented: (1) a cylindrical bearing, (2) an elliptical bearing, and (3) a worn bearing. Their results are evaluated and a comparative analysis is carried out showing the effectiveness of the proposed approach. The modeling exposed in this text, as well as all its simulations, were developed to integrate Ross-Rotordynamics, an open library on Pythonfor rotodynamic analysis, available on the GitHubplatform.

The main objective of this work is to develop an eco-friendly, single-step natural dyeing and antibacterial finishing process for wool. Non-treated and low-pressure oxygen-plasma-treated wool fabrics were dyed with the antibacterial natural dyes Ellagic acid, Laccaic acid A and Lawsone. Low-pressure plasma treatments were carried out on wool to improve its affinity for natural dyes and to avoid the use of metallic mordants. Laccaic acid A and Lawsone showed better affinity for wool fibres than Ellagic acid. Further, bacteriological tests were carried out to quantify the bactericidal character of the dyed fabrics. We observed that the plasma treatments resulted in improved exhaustion of all the antibacterial natural dyes on wool fabrics. However, the antibacterial character for non-treated fabrics was found to be slightly better than those for plasma-treated fabrics. This could be attributed to the enhanced dye penetration into the bulk of the fibres as a result of plasma treatments, unlike the more superficial dyeing achieved in the case of non-treated wool. Additionally, the free radicals formed on the wool surface by the plasma treatment may modify the functional groups on the dye structure, thus reducing its antibacterial activity. [ABSTRACT FROM AUTHOR]

We study a model for the lateral propagation of a combustion front through a porous medium with two parallel layers having different properties. The reaction involves oxygen and a solid fuel. In each layer, the model consists of a nonlinear reaction–diffusion–convection system, derived from balance equations and Darcy’s law. Under an incompressibility assumption, we obtain a simple model whose variables are temperature and unburned fuel concentration in each layer. The model includes heat transfer between the layers. We find a family of traveling wave solutions, depending on the heat transfer coefficient and other system parameters, that connect a burned state behind the combustion front to an unburned state ahead of it. These traveling waves are strong: they correspond to connecting orbits of a system of five ordinary differential equations that lie in the unstable manifold of a hyperbolic saddle and the stable manifold of a nonhyperbolic equilibrium. We argue that for physically relevant initial conditions, traveling waves that correspond to connecting orbits that approach the nonhyperbolic equilibrium along its center direction do not occur. When the heat transfer coefficient is small, we prove that strong traveling waves exist for a small range of system parameters, near parameter values where the two layers individually admit strong traveling waves with the same speed. When the heat transfer coefficient is large, we prove that strong traveling waves exist for a very large range of parameters. For small heat transfer, combustion typically does not occur simultaneously in the two layers; for large heat transfer, it does. The proofs use geometric singular perturbation theory. We give a numerical method to solve the nonlinear problem, and we present numerical simulations that indicate that the traveling waves we have found are in fact the dominant feature of solutions.We study a model for the lateral propagation of a combustion front through a porous medium with two parallel layers having different properties. The reaction involves oxygen and a solid fuel. In each layer, the model consists of a nonlinear reaction–diffusion–convection system, derived from balance equations and Darcy’s law. Under an incompressibility assumption, we obtain a simple model whose variables are temperature and unburned fuel concentration in each layer. The model includes heat transfer between the layers. We find a family of traveling wave solutions, depending on the heat transfer coefficient and other system parameters, that connect a burned state behind the combustion front to an unburned state ahead of it. These traveling waves are strong: they correspond to connecting orbits of a system of five ordinary differential equations that lie in the unstable manifold of a hyperbolic saddle and the stable manifold of a nonhyperbolic equilibrium. We argue that for physically relevant initial conditions, traveling waves that correspond to connecting orbits that approach the nonhyperbolic equilibrium along its center direction do not occur. When the heat transfer coefficient is small, we prove that strong traveling waves exist for a small range of system parameters, near parameter values where the two layers individually admit strong traveling waves with the same speed. When the heat transfer coefficient is large, we prove that strong traveling waves exist for a very large range of parameters. For small heat transfer, combustion typically does not occur simultaneously in the two layers; for large heat transfer, it does. The proofs use geometric singular perturbation theory. We give a numerical method to solve the nonlinear problem, and we present numerical simulations that indicate that the traveling waves we have found are in fact the dominant feature of solutions.

A procedure, combining molecular simulation, Raman spectroscopy, and standard nitrogen adsorption, is developed for structural characterization of single-walled carbon nanotube (SWNT) samples. Grand canonical Monte Carlo simulations of nitrogen adsorption are performed on the external and internal adsorption sites of homogeneous arrays of SWNTs of diameters previously determined by Raman spectroscopy of the sample. The results show the importance of the peripheral grooves of a nanotube bundle at low relative pressure and the insensitivity of nanotube diameter toward adsorption on the external surface of the bundle at higher pressures. Simulations also reveal that samples containing thin nanotubes have less internal adsorption capacity that saturates at lower pressure than those comprising large diameter nanotubes. The fraction of open-ended nanotubes in a sample can be estimated by scaling the simulated internal adsorption inside nanotubes to obtain a near perfect fit between simulated and experimental isotherms. This procedure allows extrapolation of adsorption properties to conditions in which all nanotubes in the sample are open-ended.

Mixing by chaotic advection is studied in a new 3‐D flow geometry. It consists of two confocal elliptic cylinders whose inner and outer boundaries glide circumferentially so that the geometry does not vary with time. Dye advection experiments have been performed and compared to numerical streak lines calculated using the analytical solution of Stokes' equations in elliptical cylindrical coordinates. Experiments show that particle trajectories remain for all practical purposes inside tubes defined by the potential mixing zone during the whole process. For the case where the elliptic cylinders turn time periodically in opposite directions, we examine the effect of the modulation frequency of the boundary displacement protocol by defining appropriate dimensionless control parameters and then numerically monitoring the advection of a passive scalar. It is shown that for a given average axial velocity, there is an optimum modulation frequency that maximizes the mixing enhancement due to chaotic advection.

The enzymatic hydrolysis of the meso-diester cis-cyclohex-4-ene-1,2-dicarboxylate to the monoester methyl-hydrogen(1S,2R)-cyclohex-4-ene-1,2-dicarboxylate using pig liver esterase has been studied both experimentally and theoretically. A chiral monoester product of high pharmaceutical interest is obtained with an enantiomeric excess of 97%. The enzymatic conversion of the meso-diester compound highly soluble in organic solvents to the desired monoester highly soluble in aqueous phase was studied in a two-phase contactor under controlled hydrodynamic conditions and interfacial contact area. A comprehensive mathematical model comprising mass transfer and simultaneous enzymatic conversion was developed. This model proved to be a simple and useful tool, making it possible to simulate the process under different conditions and to optimize the most relevant operating parameters, without resorting to exhaustive laboratory studies.

An efficient method for combining the Adsorption Potential and Ideal Adsorbed Solution theories in simulation models of multicomponent adsorption columns is presented. The main advantage of this dual-theory approach is that it reduces the number of equilibrium measurements required to predict the breakthrough profiles. The validity of the dual-theory equilibrium procedure is illustrated by embedding it in a dynamic-column breakthrough model of adsorption of ternary mixtures of methane, ethane, and propane on activated carbon. The resulting dynamic model was found to be computationally efficient, and good agreement was obtained between the predicted and experimental breakthrough curves. It is shown that the two theories can be coupled in such a way as to provide a simple and practically useful method of correlating multicomponent adsorption equilibrium in dynamic process modeling studies.

The use of isotope dilution analysis (IDA) with inductively coupled plasma–mass spectrometry (ICP–MS) for the determination of oxidized metallothionein (MT) by a Cd-saturation method is investigated. The method developed here is a modification of an earlier methodology which used a radioactive Cd isotope (¹⁰⁹Cd). While retaining the many advantages of this previous approach, the procedure presented here uses stable isotope ratio measurements (¹¹⁴Cd/¹¹¹Cd) for the determination of MT. Experimental parameters governing the instrumental precision and accuracy for isotope ratio measurements of Cd by ICP–MS were characterized. Systematic errors, including mass bias, detector dead time, and spectroscopic interferences, could be easily corrected. The isotope dilution ICP–MS method was validated by the determination of very low levels of cadmium in biological certified reference materials (NIST SRM 2670 freeze-dried urine, IAEA H-8 horse kidney, and BCR TP-25 lichens). Finally, the IDA procedure was evaluated for the determination of oxidized MT by a Cd-saturation method previously developed using radioactive ¹⁰⁹Cd. The final procedure was applied to the quantification of MT in Long–Evans Cinnamon rat liver cytosol samples and the results were compared with data obtained for the same samples using the reference ¹⁰⁹Cd methodology. A good agreement between the analytical values obtained by both methods was observed. Copyright 2000 Academic Press.

A detailed examination of the performance of a double focusing (DF) sector field ICP-MS (Element, Finnigan MAT) for the ID-ICP-MS determination of cadmium in biological and environmental samples is described and compared with a quadrupole-based instrument (HP4500, Hewlett Packard). Experimental parameters governing the instrumental precision and accuracy for isotope ratio measurements of cadmium in the DF-ICP-MS are first characterized. Systematic errors, including dead time, mass bias effects and spectroscopic interferences, can be easily corrected in the two instruments studied. Detector dead time has only to be taken into account using the DF-ICP-MS. Typical isotope ratio precisions of 0.2-0.3% can be obtained routinely with both instruments. However, the precision of the measurements in the DF-ICP-MS can be improved (<0.1%) by increasing the number of scans. Moreover, for very low cadmium concentrations the DF-ICP-MS at low resolution setting (R=300) can provide better isotope ratio precision than the quadrupole ICP-MS because of its higher sensitivity. Both ICP-MS instruments were successfully applied to the determination of very low levels of cadmium by ID-ICP-MS (by both conventional and on-line ID modes) in biological and environmental certified reference materials, including Freeze-Dried Urine NIST SRM-2670, Horse Kidney IAEA H-8, Lichens BCR TP-25, Marine Sediment PACS-1 and Riverine Water SLRS-3. Combined uncertainty associated with the determinations is addressed.

Abstract.: Systemic mastocytosis (SM) is an abnormal proliferation of mast cells, located in different structures: skin, bone marrow, spleen, liver and lymph nodes. Magnetic resonance imaging was prospectively performed in ten patients diagnosed by bone marrow biopsy in order to describe the different patterns of bone marrow involvement. Coronal T1-weighted spin-echo images were obtained in vertebral, pelvic, humeral and femoral bones. Depending on the extension of the cell infiltration, three patterns of bone marrow involvement were used: normal/no involvement (N), non-homogeneous (NH) and homogeneous (H). All ten patients presented bone infiltration. The patterns observed were: spine (50 % NH, 50 % H), pelvis (70 % NH), humerus 100(NH) and femur 40 % (NH). T1-weighted MR imaging is a sensitive technique for detecting marrow abnormalities in patients with systemic mastocytosis. There is no correlation between percentage of mast cells in bone marrow biopsy and extent or pattern of bone marrow involvement.

The new taxonMoehringia intricata subsp.giennensis, from the calcareous mountains of the south-eastern Iberian Peninsula is described. A comparative morphological study with regard to the most closely related taxa, contributes information of leaf anatomy, seed and pollen morphology, ecology and distribution.

Natural convection in a porous medium bounded by two horizontal cylinders is studied by solving the two-dimensional Boussinesq equations numerically. An accurate second-order finite difference scheme using an alternating direction method and successive underrelaxation is applied to a very fine grid. For a radius ratio above 1.7 and for Rayleigh numbers above a critical value, a closed hysteresis loop (indicating two possible solutions depending on initial conditions) is observed. For a radius ratio below 1.7 and as the Rayleigh number is increased, the number of cells in the annulus increases without bifurcation, and no hysteresis behavior is observed. Multicellular regimes and hysteresis loops have also been reported for fluid layers of same geometry but several differences between these two cases exist.

Acid catalyzed isomerization of 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (4) yields 1-aryl-4-(D-galacto-pentitol-1-yl)imidazoles (8) which can be also obtained by reductive desulphuration of 1-aryl-2-benzylthio-4-(D-galacto-pentitol-1-yl)imidazoles (6). Compounds (4) were obtained by desulphuration with Raney nickel from 1-aryl-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-imidazolidine-2-thiones (1) or 1-aryl-2-benzylthio-(1,2-dideoxy-D-glycero-β-L-gluco-heptofuranose) [1,2-d]-2-imidazolines (2).

1-Methyl- and 1-aryl-(1,2-dideoxy-D-glyofurano)[2,1-d]-imidazolidine-2-thiones having the configurations β-D-glycero-L-gluco (4), β-D-glycero-D-ido (5 - 8), α-D glycerol-D-galacto (9 - 10) and β-D-glycero-D-talo (11, 12) are prepared by reaction of 2-amino-2-deoxy-aldoses with methyl and aryl isothiocyanates. 1-Aryl-(1,2-dideoxy-β-D-glycero-L-gluco-heptofurano)[2,1-d]imidazolidine-2-thiones (1 - 3) have been converted into 1-aryl-4-(D-galacto-pentitol-1-yl)-4-imidazo-line-2-thiones (24 - 26) by acid catalysed isomerization.

Experimental parameters governing the instrumental precision and accuracy for isotope ratio measurements of cadmium in ICP-MS, including sampling time, mass bias, detector dead-time and spectroscopic interferences, were first characterised. The precision achieved for the isotope ratio determination of Cd was around 0.2% (RSD forn=5) both for 111:112 and 111:114 ratios. Two alternative flow approaches for the determination of ultratrace concentrations of cadmium by isotope dilution (ID) were explored and compared with the more conventional ID methodology: first, on-line mixing of the sample solution with the spike solution just before the ICP-MS nebuliser using a peristaltic pump and, second, the generation of volatile cadmium species using sodium tetraethylborate by merging zones flow injection ICP-MS. The three approaches were successfully applied to the determination of ultratrace levels of cadmium in biological and environmental certified reference materials (NIST SRM 2670 Freeze-Dried Urine, IAEA H-8 Horse Kidney, BCR TP-25 Lichens, PACS-1 Marine Sediment and SLRS-3 Riverine Water). The on-line ID method proved to be the most convenient for the determination of cadmium in such samples because it is fast, provides similar results to those of conventional ID and requires less sample preparation.

The charge of natural gas adsorption storage systems is studied numerically, With emphasis given to the impact on its dynamics of intraparticle diffusional resistances to mass transport. Besides adsorption kinetics and thermal effects, the simulation model takes into account both mass transport inside the adsorbent and hydrodynamics of flow through the packed bed. Numerical results are presented for change with methane of a 50 liter cylindrical reservoir, filled with hypothetical adsorbents with diffusional time constants in the range 10−3s1D/Rp2≤ ∞. and with the adsorption equilibrium curve of a commercially available activated carbon with a good adsorptive storage capacity. An attempt is made to assemble the charge histories for different values ofD/Rp2, in a single cure by using a modilied time scale.

A two-dimensional model is developed to describe the hydrodynamics, heat transfer and adsorption phenomena associated with the adsorptive storage of natural gas (NG) in cylindrical reservoirs. Intraparticle and film resistances to both heat and mass transfer are neglected. In the momentum equation, Ergun's law is considered locally valid and is extended to two dimensions. These assumptions are fully justified in the paper. Numerical results are presented concerning the pressurization and blowdown of an ultra-lightweight 50 litre cylinder, commercially available for the storage of compressed NG, if it were filled with an activated carbon having a good adsorptive storage capacity. A simple formula is also proposed to predict the filling times for fast charges. The predicted temperature changes in the packed-bed are in good agreement with those reported in the literature for an experimental charge/discharge.

The generation of a volatile Bi compound by its reaction in aqueous solution with sodium tetraethylborate(iii) has been achieved using a flow injection (FI) system with injection of Bi and NaBEt₄ solutions in a ‘merging zones’ mode. This vapour generation (VG) system has been successfully interfaced with an atomic absorption spectrometric (AAS) detector for the determination of low levels of the metal. A detection limit of 0.8 μg l⁻¹ (0.56 ng) of Bi was obtained after optimization of the chemical and instrumental parameters. This volatile species generation with AAS detection showed a precision of ±2.9% at the 40 μg l⁻¹ level of Bi and a sample throughput of about 100 samples h⁻¹ was observed. Interference studies were carried out for many potentially interfering elements. The proposed FI–VG-AAS method proved to be very selective for the determination of Bi and so it has been successfully applied to the determination of ultratraces of Bi in human urine after simple 1+1 dilution without any other preteatment; the detection limit in real urine samples was 1.6 μg l⁻¹. Bismuth recoveries of 100% were found in spiked urine samples and also excellent agreement was achieved between results obtained by FI–VG-AAS and those obtained by ICP-MS for real urine samples. Finally, the proposed procedure was applied to the study of urinary clearance of Bi in three different people after intake, at therapeutic doses, of colloidal Bi subcitrate (CBS).

Abstract.: There is a large individual variation in human spinal cord and canal size, even in patients of different series studied by the same modality, and no authorized standard method has been established. A comparative study of sagittal diameters of the cervical spinal cord and canal using myelography and MRI is presented. The purposes of this paper are (a) to establish the correction factor (CF) needed for quantitative comparison of the two imaging modalities, and (b) to determine the different factors that may modify the measurement of these diameters. We studied 45 patients with clinical findings compatible with cervical spondilotic myelopathy. In our experience, the CF for accurate correlation of MRI and myelography measurements is 1.32 and depends almost entirely on the radiographic geometry of the myelographic procedure. In addition, there is a variability in the group of MRI results due to imprecision of the pressure-pad measuring/input device of the instrument itself and the sequence performed.

Autoradiograms of total lipid extracts from Streptococcus faecalisATCC 9790, harvested in the stationary phase from a medium containing 32P-orthophosphate, showed six major spots. The corresponding compounds were identified as diphosphatidylglycerol (possibly with a penta acyl structure); phosphatidylglycerol; a provisionally identified mixture of alanylphosphatidylglycerol and of the 2′-lysyl-derivative of phosphatidylglycerol; the 3′-lysyl-derivative of phosphatidylglycerol, probably together with some arginylphosphatidylglycerol; a diglucosyl derivative of phosphatidylglycerol; and a compound which was tentatively identified as the 2′,3′-dilysyl derivative of phosphatidylglycerol.