Unit Cross-sectional Area Research Articles

Relationship between fruit growth and peduncle cross-sectional area in durian ( Durio zibethinus Murray)

The relationship between fruit growth and peduncle cross-sectional area in the tropical tree Durio zibethinus Murray growing in an experimental field of Universiti Putra Malaysia (UPM), was examined. Fruit dry mass was allometrically related to the product of lateral and longitudinal fruit diameters by a power function, and the mass growth rate of the fruits was linearly related to the peduncle cross-sectional area. This linear relationship indicates that the specific fruit growth rate, defined as the fruit mass growth rate per unit cross-sectional area of peduncle, is constant. On the basis of previous findings of proportionality between the fruit growth rate and the rate of translocation of photosynthates into the fruit through the peduncle, it was concluded that fruit growth rate, translocation rate and peduncle cross-sectional area are proportional to each other.

New expressions for the radiation force function of spherical targets in stationary and quasi-stationary waves

A new expression for the radiation force function – which is the radiation force per unit energy density and unit cross-sectional surface area – for spheres in a stationary (or standing) and quasi-stationary wave is obtained based on the far-field acoustic scattering field. The radiation force function formulation has been simplified mathematically and improved into a more general form. Numerical results are presented for rigid and elastic spheres, air bubbles in water as well as liquid drops in air to illustrate the theory. It is demonstrated that expressions for the radiation force functions obtained from the far-field derivation approach are equivalent to those obtained from the near-field-based derivation.

Glutamate, water and ion transport through a charged nanosize pore

The transport of transmitter, ions and water through a positively-charged nanopore was investigated through computer simulations. The physics of the problem is described by a coupled set of Poisson–Nernst–Planck and Navier–Stokes equations in a computational domain consisting a cylindrical pore, whose radius ranged from 1 to 8 nm and which was flanked by two compartments representing the vesicular interior and extra-cellular space. The concentration of co-ions is suppressed and of counter-ions enhanced, especially near the pore wall owing to electrostatic interactions. Glutamate (i.e. the transmitter considered) is negatively charged and is simulated as a counter-ion. The electro-kinetically induced pressure due to the movement of ions is negative and very pronounced near the pore wall where the concentration and flux of counter-ions is very high. The water velocity peaks in the pore center, diminishes to zero at the pore wall, but is constant along the pore axis. The mean velocity of the water/fluid is proportional to the vesicular pressure and pore cross-sectional area. Interestingly it is inversely related to the vesicular glutamate concentration. The factors determining the glutamate flux are complex. The diffusive flux generally predominates for narrow pore, and convective flux may dominate for wide pore if the vesicular pressure is high. Surprisingly at low vesicular pressure the mean total glutamate flux per unit cross-sectional pore area is higher for narrow pores. Higher flux is probably due to the rise of glutamate concentration in the nanopore, which is much more pronounced for narrow nanopores, due to the maintenance of approximate neutrality of charges in the pore and on the pore wall. In conclusion intra-vesicular pressure helps ‘flushing-out’ the transmitter, but the induced pressure ‘drags-out’ the water into the extra-cellular space.

Application of LPW and SAI SAFNWC/MSG satellite products in pre-convective environments

The Spinning Enhanced Visible and Infrared Imagery (SEVIRI) instrument, on board the Meteosat Second Generation (MSG), is a radiometer with eight infrared (IR) spectral bands. Seven of these channels are used to retrieve Layer Precipitable Water (LPW) and Stability Analysis Imagery (SAI). Both products are the PGE07 and the PGE08 of SAFNWC (Satellite Application Facility on support to Nowcasting and Very Short-Range Forecasting). The authors at Instituto Nacional de Meteorología (INM) have developed the LPW and SAI algorithms, in the SAFNWC framework. Both products are retrieved using statistical retrieval based on neural networks. The main advantage of these algorithms versus physical retrieval algorithms is the independence from the Numerical Weather Prediction (NWP) models. The LPW provides information on the water vapor contained in a vertical column of unit cross-section area in three layers in the troposphere (low, middle and high) and in the total layer in cloud free areas. The SAI provides estimations of the atmospheric instability in cloud free areas, in particular the Lifted Index (LI). The stability and precipitable water obtained with both products are routinely generated every 15 min at a satellite horizontal resolution of 3 km in NADIR. A significant advantage of these MSG products, compared to traditional measurements such as radiosondes, is their ability to measure high resolution temporal and spatial variations of atmospheric stability and moisture in pre-convective environments. The main disadvantage is that they do not have the vertical resolution of radiosonde. The MSG moisture and stability time trend fields are especially useful during the period preceding the outbreak of convection due to the high resolution. Once the outbreak of convection occurs, the products calculated in the clear air pixels surrounding the convective system will allow to foresee the evolution of the convection.

Vertical jumping performance of bonobo (Pan paniscus) suggests superior muscle properties

Vertical jumping was used to assess muscle mechanical output in bonobos and comparisons were drawn to human jumping. Jump height, defined as the vertical displacement of the body centre of mass during the airborne phase, was determined for three bonobos of varying age and sex. All bonobos reached jump heights above 0.7 m, which greatly exceeds typical human maximal performance (0.3-0.4m). Jumps by one male bonobo (34 kg) and one human male (61.5 kg) were analysed using an inverse dynamics approach. Despite the difference in size, the mechanical output delivered by the bonobo and the human jumper during the push-off was similar: about 450 J, with a peak power output close to 3000 W. In the bonobo, most of the mechanical output was generated at the hips. To account for the mechanical output, the muscles actuating the bonobo's hips (directly and indirectly) must deliver muscle-mass-specific power and work output of 615 Wkg-1 and 92 Jkg-1, respectively. This was twice the output expected on the basis of muscle mass specific work and power in other jumping animals but seems physiologically possible. We suggest that the difference is due to a higher specific force (force per unit of cross-sectional area) in the bonobo.

Morfometria do miocárdio humano em indivíduos senis

To carry out a quantitative assessment in human myocardium cells of senile individuals, in right, left and septal ventricular regions. Five hearts from corpses of individuals without heart diseases, of both sexes, with age between 67 and 87 years old were used. The following parameters were assessed: myocyte unit cross section area (myoc. a(o)); myocyte unit perimeter length (myoc. l(o)); myocyte unit volume (myoc. v(o)); myocyte volumetric density (myoc. V(v)); number of myocytes per volume unit (Nmm 3myoc.). The t-test of Student was used in statistic analysis. The analysis of differences (p < 0.05) among right (RV), left (LV) and septal (S) ventricular regions of human heart showed that myoc. a(o) values were lower in RV (1.51 +/- 0.10 microm2) and in S (1.55 +/- 0.07 microm2) in relation to LV (1.84 +/- 0.24 microm2). Values of myoc. l(o) were also shown lower in S (5.11 +/- 0.46 microm) comparing to LV (6.2 +/- 0.97 microm). Likewise, myoc. v(o) and myoc. V(v) showed lower values in RV (88.75 +/- 25.37 microm3; 0.39 +/- 0.03%) in relation to LV (122.41 +/- 16.31 microm3; 0.41 +/- 0.01%). Results obtained show that there may be changes in dimensions of left ventricular wall myocyte cell during senescent stage. However, those differences are subtle and seem to mean the adjustment of tissue to functional changes that install along life.

The analysis of deformation size effects using multiple gauge length extensometry and the essential work of rupture concept

Size dependence of the load–displacement and stress–strain curves is a phenomenon widely reported in the literature and readily observed in experiments. The present paper introduces two developments in the analysis of ductile rupture, one in the area of experimental technique and interpretation, and one in the area of numerical modelling. Firstly, the new experimental technique is described of multiple gauge length optical extensometry (laser scanning) that provides a uniquely powerful means of collecting the data needed for the study of size effects, from a single tensile test on a ductile specimen. The interpretation procedures are presented based on the considerations about the nature of deformation and energy expenditure within different material volumes in a tensile specimen. Consequently, the property of the specimen can be defined and identified that relates to the energy consumption per unit cross-sectional area required to rupture the specimen entirely (the essential work of rupture). Another energetic measure is also obtained from the test that relates to the plastic work dissipation per unit volume in pre-peak deformed material. Secondly, the observed size effects and specific energy determination procedures are discussed in the context of non-local coupled plasticity-damage modelling. Conventional local numerical models of inelastic deformation fail to predict the sequence of deformation responses observed in the tensile test, namely, uniform deformation followed by strain localisation, necking and rupture. It is shown here that coupled non-local damage-plasticity modelling is capable of capturing the hardening–softening and global–local plasticity transitions, and hence the trends observed in ductile fracture. The predictions of the coupled non-local damage-plasticity modelling for different deformation regimes are shown to agree qualitatively with the experimentally observed behaviour. The two aspects of the proposed approach, experimental and modelling, are presented here together since they are intimately linked at the fundamental level. The implications of the proposed approach are discussed for the deformation analysis of plastically deforming and damageable materials and structures at various scales, from macroscopic to miniature.

Frother-related research at McGill University

Over the past ten years the Mineral Processing group at McGill University has developed techniques to determine gas dispersion properties (gas superficial velocity, gas holdup, bubble size and bubble surface area flux) in flotation machines. This work is finding application in metallurgical diagnostics and cell characterization. The picture, however, will remain incomplete until the impact of chemistry on bubble production, and hence on gas dispersion, is understood. This has prompted investigations into frothers. There are two areas addressed in this communication: frother analysis and frother characterization. Coincident with the centenary, for 100 years there was no convenient frother analysis procedure. A colorimetric technique originally developed for alcohols had been applied to MIBC (Parkhomovski, V.L., Petrunyak, D.G., Paas, L., 1976. Determination of methylisobutylcarbinol in waste waters of concentration plants. Obogashchenie Rud 21 (2), 44–45). Using this as a starting point, the technique was successfully extended to a wide range of commercial frothers and shown to be robust against most common ‘contaminants’. The technique is readily used on-site and some observations from plant surveys are described. Characterization of frothers has taken two routes, determining water carrying rate and investigating properties of thin bubble films. Second only to transporting particles the recovery of water by bubbles has the most influence on metallurgy. The question posed was whether this ‘water carrying’ property could be related to frother type. In a specially designed column the volume rate of water to the overflow per unit cross-sectional area (‘carrying rate’, J wo) and gas holdup ( ε g) at controlled froth depths were measured. The J wo– ε g relationship proved approximately linear and dependent on frother type, with four frother ‘families’ being identified. Bubble thin films have been studied for soaps and the techniques were adapted for frothers. From infrared analysis it became apparent that the frother molecule, while itself not seen, had an impact on organizing water molecules, apparently forming a film of bound water on the bubble surface. Exploiting the interference pattern generated in UV/Vis the film thickness ( d) was determined; for MIBC d was less than 160 nm while for DF250 d was ∼600 nm. Taking a representative frother from the four families identified above, the water carrying rate at a given gas holdup increased with film thickness. Possible implications of the findings on the role of frother in bubble production are explored.

Analysis of Essential Work of Rupture using Non-local Damage-plasticity Modelling

We consider the non-local damage plasticity modelling of the essential work of rupture (EWR), i.e. the specific energy required to cause failure within a specimen, resulting in its separation into two parts. The more usual concept of essential work of fracture (EWF) is a measure of the specific energy, per unit cross sectional area, consumed during the propagation of cracks across a series of double edge-notched tensile (DENT) specimens. Recently, a novel framework has been proposed allowing the determination of a related quantity, the essential work of necking and tearing from a single tensile test on an unnotched dogbone specimen of ductile metal. Simultaneous multiple gauge length extensometry forms a crucial component of the experimental approach, and allows capture of such phenomena as strain localisation, post-critical deformation behaviour, damage non-locality, elastic snap-back, and size effects. In this study the rupture test is simulated using a non-local damage-plasticity model using finite elements. The results are interpreted in terms of essential and non-essential work of rupture.

Determination of essential work of necking and tearing from a single tensile test

The energy (or work) characterizing the resistance of a structure to ductile fracture is important for many applications, from structural design to impact protection. Essential work of fracture (EWF) is one such measure traditionally associated with the specific energy, per unit cross sectional area, consumed during ductile fracture in a double edge notched tensile (DENT) specimen. This energy is referred to as ’essential’ in order to distinguish it from the non-essential energy consumed on distributed plastic deformation accompanying fracture, but not required for material separation. The present article describes how the essential work of tearing can be determined from a single tensile test on an unnotched specimen. Tensile tests were performed on unnotched dog-bone (DB) tensile specimens carrying large numbers of markers, with continuous measurement of elongation between any two markers using a laser scanning extensometer. From such single test it is then possible to obtain multiple load-elongation curves for a large number of tensile specimens. This data is analyzed by separating contributions to specimen elongation made by distributed (pre-softening) and localized (post-softening) plastic deformation. Essential and non-essential work of necking and tearing is determined for an aluminum alloy subjected to different heat treatments, and results compared with those obtained from conventional DENT tests.

Effects of supra‐physiological changes in human ovarian hormone levels on maximum force production of the first dorsal interosseus muscle

The purpose of this study was to investigate the effects of supra-physiological changes in ovarian hormone levels on maximum force production in two conditions, one physiological (pregnancy) and one pseudo-physiological (in vitro fertilization (IVF) treatment). Forty IVF patients were tested at four distinct stages of treatment and 35 women were tested during each trimester of pregnancy and following parturition. Maximum voluntary isometric force per unit cross-sectional area of the first dorsal interosseus muscle was measured. Plasma concentrations of total and bioavailable oestradiol and testosterone were measured, in addition to the total concentrations of progesterone and human chorionic gonadotropin. Despite significant changes in the concentrations of total progesterone, 17beta-oestradiol, bioavailable oestradiol and testosterone between phases, strength did not change significantly throughout IVF treatment (1.30+/-0.29, 1.16+/-0.38, 1.20+/-0.29 and 1.26+/-0.34 N mm-2, respectively, in the 4 phases of IVF treatment). Force production was significantly higher during the second trimester of pregnancy than following childbirth (1.33+/-0.20 N mm-2 at week 12 of pregnancy, 1.51+/-0.42 N mm-2 at week 20, 1.15+/-0.26 N mm-2 at week 36 and 0.94+/-0.31 N mm-2 at week 6 postnatal) but was not significantly correlated with any of the hormones measured. These data suggest that extreme changes in the concentrations of reproductive hormones do not affect the maximum force-generating capacity of young women.

Permeability of hydrophilic and hydrophobic Shirasu-porous-glass (SPG) membranes to pure liquids and its microstructure

Morphological properties of hydrophilic and hydrophobic Shirasu-porous-glass (SPG) membranes were investigated over a wide range of mean pore sizes (0.252–20.3 μm) by liquid permeability measurements, scanning electron microscopy and Hg porosimetry. Hydrophobic modification of membrane surface was made by surface coating with silicone resin. The results are discussed using the non-uniform capillary bundle model of membrane permeability. The mean pore tortuosity of 1.28 was kept constant over the whole range of mean pore sizes investigated. The SEM images confirmed that the geometry of pore network was similar for all SPG membranes, irrespective of their mean pore size. The span of pore size distribution ranged from 0.28 to 0.68 and the number of pores per unit cross-sectional membrane area from 10 9 to 10 13 m −2. The membrane resistance was unchanged after surface treatment with silicone resin, which means that the pores were not plugged by the resin, even in the submicron range of mean pore sizes.

Decreased plasma membrane targeting of NMDA-NR1 receptor subunit in dendrites of medial nucleus tractus solitarius neurons in rats self-administering morphine.

Opioid abuse is associated with repeated administration and escalation of dose that can result in profound adaptations in homeostatic processes. Potential cellular mechanisms and neural sites mediating opiate-dependent adaptations may involve NMDA-dependent synaptic plasticity within brain areas participating in behaviors related to consumption of natural reinforcers, as well as affective-autonomic integration, notably the medial nucleus tractus solitarius (mNTS). NMDA-dependent synaptic plasticity may be mediated by changes in the intracellular and surface targeting of NMDA receptors, particularly in postsynaptic sites including spines or small distal dendrites. High-resolution immunogold electron microscopic immunocytochemistry combined with morphometry were used to measure changes in targeting of the NMDA-NR1 (NR1) receptor subunit between intracellular and plasmalemmal sites in dendrites of neurons of the intermediate mNTS of rats self-administering escalating doses of morphine (EMSA). In control and EMSA rats, the density of plasmalemmal and cytosolic gold particles was inversely related to profile size. Collapsed across all NR1-labeled dendrites, rats self-administering morphine had a lower number of plasmalemmal gold particles per unit surface area (7.1 +/- 0.8 vs. 14.4 +/- 1 per 100 microm), but had a higher number of intracellular gold particles per unit cross-sectional area (169 +/- 6.1 vs. 148 +/- 5.1 per 100 microm2) compared to saline self-administering rats. Morphometric analysis showed that the decrease in plasma membrane labeling of NR1 was most robust in small dendritic profiles (<1 microm), where there was a reciprocal increase in the density of intracellular particles. These results indicate that the plasmalemmal distribution of the essential NR1 subunits in distal sites may prominently contribute to NMDA receptor-dependent modulation of neural circuitry regulating homeostatic processes, and targeting of these proteins can be prominently affected by morphine self-administration.

Microscale pumping technologies for microchannel cooling systems

A review of the state of the art in micropumping technologies for driving fluid through microchannels is presented with a particular emphasis on small-scale cooling applications. An extensive variety of micropumping techniques developed over the past fifteen years in the literature is reviewed. The physical principles, engineering limitations, and advantages of approximately twenty different kinds of micropumps are reviewed. The available micropumping techniques are compared quantitatively, primarily in terms of the maximum achievable flow rate per unit cross-sectional area of the microchannel and the maximum achievable back pressure. A concise table is developed to facilitate the convenient comparison of the micropumps based on different criteria including their miniaturization potential, size (in-plane and out-of-plane), actuation voltage and power required per unit flow rate, ease and cost of fabrication, minimum and maximum frequency of operation, and suitability for electronics cooling. Some important performance characteristics of the micropumps, which are likely to be decisive for specific applications, are also discussed. The current state of the art in micropump design and fabrication is also comprehensively reviewed. There are 171 references cited in this review article.

Nitric oxide and other novel therapies for pulmonary hypertension.

Pulmonary hypertension is an uncommon, yet devastating, syndrome with a complex underlying pathobiology. Hypoxia, inflammation, and increased shear stress appear to be the primary pathogenic events; however, mechanisms by which these processes lead to pulmonary hypertension remain incompletely understood. The ultimate increase in pulmonary vascular resistance is attributed to remodelling of the walls of resistance vessels, which can lead to encroachment on and reduction of the vascular lumen. The number of blood vessels per unit of cross-sectional area in the hypertensive lung is also reduced, which can contribute to increased vascular resistance. Regardless of its etiology, endothelial dysfunction underlies pulmonary hypertension, one manifestation of which is the attenuated production of bioactive nitric oxide. Nitric oxide administration can exert beneficial effects at various stages of the disease. Here we review the known pathobiology of pulmonary hypertension, with a principal focus on endothelial nitric oxide, and also summarize the data on nitric oxide replacement therapy and other novel therapies that relate to nitric oxide as one approach to treatment.

Poster 46: Immunohistochemical evidence of immature myosin expression in aged rat skeletal muscle

Objective: To evaluate 2 hindlimb skeletal muscles in young and aged rats for presence of immature myosin heavy chain (MHC) isoforms. Design: Randomized controlled trial. Setting: Basic science laboratory. Animals: Fisher 344 Brown Norway F1 hybrid rats, ages 12 and 36 months. Interventions: The soleus and extensor digitorum longus (EDL) muscles of young (12mo old) and aged (36mo old) sedentary rats were excised, quick frozen, and stained immunohistochemically for the developmental MHC isoform. Muscle cross-sections were then evaluated for the number of developmental positive fibers per unit area. Main Outcome Measures: Number of muscle fibers per unit cross-sectional area expressing developmental MHC. Results: The soleus muscles of the aged rats showed significantly greater numbers of developmental MHC positive cells when compared with the soleus of the 12-month-old rats. The EDL of the 36-month-old rats exhibited noticeably greater numbers of developmental MHC positive cells than in the young animals in half of the muscles studied. Conclusions: There is evidence of skeletal muscle regeneration occurring in the soleus of the aged rats in the midst of the fiber atrophy that accompanies aging. Such changes in the EDL also occur, but appear to be less common. The muscle specific differences observed in the expression of developmental MHC with age may be influenced by the fiber type and function differences of this muscle as compared with the soleus. Evaluation of the coexpression of the developmental MHC with the mature MHCs (slow, fast) is currently under investigation.

Estimation of capillary density in human skeletal muscle based on maximal oxygen consumption rates.

A previously developed Krogh-type theoretical model was used to estimate capillary density in human skeletal muscle based on published measurements of oxygen consumption, arterial partial pressure of oxygen, and blood flow during maximal exercise. The model assumes that oxygen consumption in maximal exercise is limited by the ability of capillaries to deliver oxygen to tissue and is therefore strongly dependent on capillary density, defined as the number of capillaries per unit cross-sectional area of muscle. Based on an analysis of oxygen transport processes occurring at the microvascular level, the model allows estimation of the minimum number of straight, evenly spaced capillaries required to achieve a given oxygen consumption rate. Estimated capillary density values were determined from measurements of maximal oxygen consumption during knee extensor exercise and during whole body cycling, and they range from 459 to 1,468 capillaries/mm2. Measured capillary densities, obtained with either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects, are generally lower, ranging from 123 to 515 capillaries/mm2. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction and muscle biopsy samples typically are strongly contracted. The results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle.

DO CHANGES IN THE CONCENTRATION OF REPRODUCTIVE HORMONES DURING PREGNANCY INFLUENCE MAXIMUM FORCE PRODUCTION?

We have previously reported that acute, supra-physiological changes in the concentration of reproductive hormones do not affect muscle strength in females. PURPOSE To investigate the effect of chronic, significant changes in the concentration of human chorionic gonadotropin (hCG), oestradiol, progesterone and testosterone on muscle strength during pregnancy. METHODS Maximum voluntary isometric force per unit cross-sectional area (MVIF/CSA) of the first dorsal interosseus (FDI) muscle was examined during each trimester (12, 20 and 36 weeks) of pregnancy and post-natal (PN) in 35 females using a cross sectional research design. Maximum strength was measured using a custom-built finger dynamometer and percutaneous electrical stimulation. Cross-sectional area was determined using a real-time ultrasound system. Concentrations of reproductive hormones were measured using the Enzyme Linked Fluorescent Assay technique. RESULTS Concentrations of progesterone, oestradiol and testosterone increased significantly throughout pregnancy and were significantly reduced post-partum (Figure 1). The concentration of hCG peaked during the first trimester and declined thereafter. Post hoc analysis revealed significant differences in MVIF/CSA of the FDI muscle between weeks 12 and PN (p = 0.05) and 20 and PN (p = 0.01).Figure: No Caption AvailableCONCLUSION Post-natal strength was significantly lower than strength during the first two trimesters of pregnancy. However, it is unlikely that changes in strength during pregnancy are sex hormone dependent as strength was not significantly different between the 3rd trimester and 6 weeks post-partum when the difference in reproduction status was greatest.

903 ABS 系と PC/ABS 系ポリマーアロイのモルフォロジが機械特性に及ぼす影響

The purpose of this study is to investigate the influence that morphologies of ABS series and PC/ABS series of polymer alloy exerts its mechanical properties. Morphology characteristic values approximated to the ellipse, such as a diameter and area of rubber phase and ABS series phase, were measured. The effects of morphology characteristic values and fatigue crack growth rate on tensile properties were discussed. It was found that there were correlation between percentage reduction of area, young's modulus and yield stress in tensile properties and rubber area per unit cross-section area and no correlation between tensile properties and fatigue crack growth rate.

DRAG COEFFICIENTS OF AGRICULTURAL GRAINS IN VERTICAL PNEUMATIC CONVEYING

A study was made of drag coefficients in vertical pneumatic conveying of agricultural grains. From experimentsconducted on rough rice and milled rice, it was found that the values of drag coefficient computed using the basic relationshipfor slip velocity of a single particle in an air stream were closely related to the solid flow rate per unit crosssectional areaof the conveying pipe and solidtoair ratio. Generalized equations were developed for estimation of drag coefficient in termsof particle equivalent diameter, solid flow rate per unit crosssectional area of pipe, and solidtoair ratio. The equationswere also verified for another agricultural grain, namely corn. The closeness between experimental and predicted valuesvalidated the equations for general use for grain particles ranging in size approximately from 3 to 7mm mean diameter.