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Air Spaces (air + space)
Selected AbstractsAttempts to Reduce and Eliminate Nuclear Weapons through the Nuclear Non -Proliferation Treaty and the Creation of Nuclear -Weapon -Free ZonesPEACE & CHANGE, Issue 4 2008Paul J. Magnarella Nuclear weapons remain the most dangerous weapons of mass destruction threatening our lives and planet. To date, the Nuclear Non-Proliferation Treaty (NPT) is the most comprehensive international agreement aimed at limiting these weapons. In response to some of NPT's shortcomings, a large number of nonnuclear weapon states have joined together to create nuclear-weapon-free zones (NWFZs). By doing so, they emphatically rejected nuclear weapons on their soil, in their territorial waters, and in their air space. In addition, they ask nuclear weapon states to solemnly promise not to use nuclear weapons against zone members and to do nothing to promote nuclear weapons in their zones. Currently, much of the Southern Hemisphere is covered by NWFZs. An NWFZ has been newly created in Central Asia, and the League of Arab States is considering one in the Middle East. [source] Blood samples collected under venous oxygen pressure from patients with sickle cell disease contain a significant number of a new type of reversibly sickled cells: Constancy of the percentage of sickled cells in individual patients during steady stateAMERICAN JOURNAL OF HEMATOLOGY, Issue 4 2005Toshio Asakura Abstract We found various levels of a new type of reversibly sickled cell (RSC) with blunt edges in 44 blood samples obtained from 32 steady-state patients with sickle cell disease (SCD) without exposure to air (UnExp-blood). Because these RSCs could be generated in vitro by partial oxygenation of once-deoxygenated SS cells to venous oxygen pressure, we named them "partially oxygenated sickled cells" (POSCs). These RSCs were classified into elongated and non-elongated RSCs, depending on the ratio of the short axis to long axis. The presence of these cells was previously unknown because the standard blood collection method oxygenates most of the POSCs to discocytes due to oxygen in the air space in the needle, syringe, and blood collection tube (Exp-blood). Although the shape of elongated POSCs is similar to that of irreversibly sickled cells (ISCs), POSCs revert to discocytes upon exposure to air. We found the following: (1) the percentage of total sickled cells (total POSCs + ISCs) in UnExp-blood (29.0 ± 14.5%) was significantly higher than the percentage of sickled cells (mainly ISCs) in Exp-blood (7.3 ± 5.7%); (2) the percentage of sickled cells in UnExp-blood was specific to individual patients during steady state, while it decreased at the onset of a vaso-occlusive event; and (3) the percentage of sickled cells in UnExp-blood varied widely among steady-state patients (4,56%). This new type of RSC may be used as an internal biomarker to evaluate the disease state of individual patients. Am. J. Hematol. 80:249,256, 2005. © 2005 Wiley-Liss, Inc. [source] On the measurement of growth with applications to the modelling and analysis of plant growthFUNCTIONAL ECOLOGY, Issue 2 2000Roderick M. L. Abstract 1.,In this paper, a theoretical framework for the analysis of growth is described. Growth is equated with change in volume (V) and the growth rate is given by the equation; dV/dt = (dm/dt)(1/,) , (d,/dt)(m/,2) where m is the mass and , the density. The volume is inclusive of internal air spaces. 2.,The second term of the growth equation (see above) can be ignored if density is constant over time. Data for humans (and presumably other large animals) show that while composition changes over time, the density is approximately constant at about that of water. In that case, the growth rate can be estimated from measures of the rate of change of mass. However, the density of plants is variable (c. 0·4,1·2 g cm,3) and measures of mass and density are necessary to analyse plant growth. 3.,To use the theory as the basis of plant growth models, it is necessary to develop simple methods for estimating the surface area of roots, stems and leaves assuming that the mass and volume are known. A literature review found that the surface area to volume ratios of leaves and roots generally increase with the mass concentration of water. Theoretical arguments are used to predict that in woody stems, the situation should be reversed such that the surface area to volume ratio increases with the mass concentration of dry matter. Those relationships should be very useful in the development of plant growth models. 4.,Measures of plant dry mass and estimates of the rate of change in dry mass are shown to be very difficult to interpret because of differences in the mass concentration of dry matter between individuals and over time. 5.,It is concluded that measures of mass and density will be necessary before plant growth analysis can achieve its full potential. A framework for extending the theory to include the forces necessary for growth to occur is described. [source] Histological and ultrastructural aspects of the nasal complex in the harbour porpoise, Phocoena phocoenaJOURNAL OF MORPHOLOGY, Issue 11 2009Susanne Prahl Abstract During the evolution of odontocetes, the nasal complex was modified into a complicated system of passages and diverticulae. It is generally accepted that these are essential structures for nasal sound production. However, the mechanism of sound generation and the functional significance of the epicranial nasal complex are not fully understood. We have studied the epicranial structures of harbor porpoises (Phocoena phocoena) using light and electron microscopy with special consideration of the nasal diverticulae, the phonic lips and dorsal bursae, the proposed center of nasal sound generation. The lining of the epicranial respiratory tract with associated diverticulae is consistently composed of a stratified squamous epithelium with incomplete keratinization and irregular pigmentation. It consists of a stratum basale and a stratum spinosum that transforms apically into a stratum externum. The epithelium of the phonic lips comprises 70,80 layers of extremely flattened cells, i.e., four times more layers than in the remaining epicranial air spaces. This alignment and the increased number of desmosomes surrounding each cell indicate a conspicuous rigid quality of the epithelium. The area surrounding the phonic lips and adjacent fat bodies exhibits a high density of mechanoreceptors, possibly perceiving pressure differentials and vibrations. Mechanoreceptors with few layers and with perineural capsules directly subepithelial of the phonic lips can be distinguished from larger, multi-layered mechanoreceptors without perineural capsules in the periphery of the dorsal bursae. A blade-like elastin body at the caudal wall of the epicranial respiratory tract may act as antagonist of the musculature that moves the blowhole ligament. Bursal cartilages exist in the developmental stages from fetus through juvenile and could not be verified in adults. These histological results support the hypothesis of nasal sound generation for the harbor porpoise and display specific adaptations of the echolocating system in this species. J. Morphol. 2009. © 2009 Wiley-Liss, Inc. [source] SIMULTANEOUS INSTRUMENTAL MEASUREMENT OF FIRMNESS AND JUICINESS OF APPLE TISSUE DISCSJOURNAL OF TEXTURE STUDIES, Issue 3 2003F. ROGER HARKER Discs of apple tissue were compressed to 75% of their original height. Throughout compression, the force-distance curve was collected and the electrical impedance of the discs was measured at two frequencies of alternating current,1 kHz and 1 MHz. Electrical impedance was separated into its resistive and reactive components, and at these particular frequencies changes in resistance predominated. Measurements at 1 kHz indicate the resistance of extracellular regions of the discs (ruptured cells as well as those regions external to the plasma membrane), while measurements at 1 MHz indicate the resistance of the entire disc (combined intracellular and extracellular regions). Juice was released from the discs as a result of damage to cells and the extrusion of cellular fluid into intercellular air spaces. This resulted in a decline in electrical resistance at 1 kHz, but little change to the resistance at 1 MHz. Changes in juice release as determined by electrical measurement were related to the mechanical properties of the discs. Generally, the release of juice occurred after the inflection point on the force-distance curves, but much earlier than mechanical failure (indicated by maximum force). The extent of tissue damage was determined from the relative decrease in resistance at 1 kHz, and was found to vary among apple cultivars and in response to fruit ripening. [source] Collecting, shipping, storing, and imaging snow crystals and ice grains with low-temperature scanning electron microscopy ,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2003Eric F. Erbe Abstract Methods to collect, transport, and store samples of snow and ice have been developed that enable detailed observations of these samples with a technique known as low-temperature scanning electron microscopy (LTSEM). This technique increases the resolution and ease with which samples of snow and ice can be observed, studied, and photographed. Samples are easily collected in the field and have been shipped to the electron microscopy laboratory by common air carrier from distances as far as 5,000 miles. Delicate specimens of snow crystals and ice grains survive the shipment procedures and have been stored for as long as 3 years without undergoing any structural changes. The samples are not subjected to the melting or sublimation artifacts. LTSEM allows individual crystals to be observed for several hours with no detectable changes. Furthermore, the instrument permits recording of photographs containing the parallax information necessary for three-dimensional imaging of the true shapes of snowflakes, snow crystals, snow clusters, ice grains, and interspersed air spaces. This study presents detailed descriptions of the procedures that have been used successfully in the field and the laboratory to collect, ship, store, and image snow crystals and ice grains. Microsc. Res. Tech. 62:19,32, 2003. Published 2003 Wiley-Liss, Inc. [source] Stomatal responses to humidity and temperature in darknessPLANT CELL & ENVIRONMENT, Issue 7 2010KEITH A. MOTT ABSTRACT Stomatal responses to leaf temperature (Tl) and to the mole fractions of water vapour in the ambient air (wa) and the leaf intercellular air spaces (wi) were determined in darkness to remove the potential effects of changes in photosynthesis and intercellular CO2 concentration. Both the steady-state and kinetic responses of stomatal conductance (gs) to wa in darkness were found to be indistinguishable from those in the light. gs showed a steep response to the difference (,w) between wa and wi when wa was varied. The response was much less steep when wi was varied. Although stomatal apertures responded steeply to Tl when ,w was held constant at 17 mmol mol,1, the response was much less steep when ,w was held constant at about zero. Similar results were obtained in the light for ,w = 15 mmol mol,1 and ,w , 0 mmol mol,1. These results are discussed in the context of mechanisms for the stomatal response to humidity. [source] Mesophyll conductance to CO2: current knowledge and future prospectsPLANT CELL & ENVIRONMENT, Issue 5 2008JAUME FLEXAS ABSTRACT During photosynthesis, CO2 moves from the atmosphere (Ca) surrounding the leaf to the sub-stomatal internal cavities (Ci) through stomata, and from there to the site of carboxylation inside the chloroplast stroma (Cc) through the leaf mesophyll. The latter CO2 diffusion component is called mesophyll conductance (gm), and can be divided in at least three components, that is, conductance through intercellular air spaces (gias), through cell wall (gw) and through the liquid phase inside cells (gliq). A large body of evidence has accumulated in the past two decades indicating that gm is sufficiently small as to significantly decrease Cc relative to Ci, therefore limiting photosynthesis. Moreover, gm is not constant, and it changes among species and in response to environmental factors. In addition, there is now evidence that gliq and, in some cases, gw, are the main determinants of gm. Mesophyll conductance is very dynamic, changing in response to environmental variables as rapid or even faster than stomatal conductance (i.e. within seconds to minutes). A revision of current knowledge on gm is presented. Firstly, a historical perspective is given, highlighting the founding works and methods, followed by a re-examination of the range of variation of gm among plant species and functional groups, and a revision of the responses of gm to different external (biotic and abiotic) and internal (developmental, structural and metabolic) factors. The possible physiological bases for gm, including aquaporins and carbonic anhydrases, are discussed. Possible ecological implications for variable gm are indicated, and the errors induced by neglecting gm when interpreting photosynthesis and carbon isotope discrimination models are highlighted. Finally, a series of research priorities for the near future are proposed. [source] Slow development of leaf photosynthesis in an evergreen broad-leaved tree, Castanopsis sieboldii: relationships between leaf anatomical characteristics and photosynthetic ratePLANT CELL & ENVIRONMENT, Issue 3 2001S.-I. Miyazawa ABSTRACT Changes in net photosynthetic rate on a leaf area basis and anatomical properties during leaf development were studied in an evergreen broad-leaved tree, Castanopsis sieboldii and an annual herb, Phaseolus vulgaris. In C. sieboldii, surface area of mesophyll cells facing the intercellular air spaces on a leaf area basis (Smes) was already considerable at the time of full leaf area expansion (FLE). However, surface area of chloroplasts facing the intercellular air spaces on a leaf area basis (Sc), and chlorophyll and Rubisco contents on a leaf area basis increased to attain their maximal values 15,40 d after FLE. In contrast, in P. vulgaris, chloroplast number on a leaf area basis, Sc and Smes at 10 d before FLE were two to three times greater than the steady-state levels attained at around FLE. In C. sieboldii, the internal CO2 transfer conductance (gi) slightly increased for 10 d after FLE but then decreased toward the later stages. Limitation of photosynthesis by gi was only about 10% at FLE, but then increased to about 30% at around 40 d after FLE. The large limitation after FLE by gi was probably due to the decrease in CO2 concentration in the chloroplast caused by the increases in thickness of mesophyll cell walls and in Rubisco content per chloroplast surface area. These results clearly showed that: (1) in C. sieboldii, chloroplast development proceeded more slowly than mesophyll cell expansion and continued well after FLE, whereas in P. vulgaris these processes proceeded synchronously and were completed by FLE; (2) after FLE, photosynthesis in leaves of C. sieboldii was markedly limited by gi. From these results, it is suggested that, in the evergreen broad-leaved trees, mechanical protection of mesophyll cells has priority over the efficient CO2 transfer and quick construction of the chloroplasts. [source] Comparative floral anatomy of PontederiaceaeBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2004AMY STRANGE Floral anatomy is described in eight species (representing five genera) of Pontederiaceae, and floral ontogeny is described in Pontederia cordata. The results are assessed in the context of recent phylogenetic work on Pontederiaceae, which indicates that the unilocular ovary condition has been achieved by two different, non-homologous routes in Pontederiaceae: via loss of interlocular septa in Heteranthera and Hydrothrix, and via pseudomonomery in Pontederia, which has a single fertile carpel. Absence of septal nectaries has evolved more than once in Pontederiaceae, at least in Heterantha and Monochoria, probably due to a transfer of the insect reward from nectar to pollen in these taxa. The presence of an elliptical or linear unvascularized appendage on the abaxial outer stamen in Monochoria is also probably correlated with enantiostyly. In Pontederia, air spaces in the ovary wall are modified into canals, each with a ring of apparently secretory epithelial cells. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 144, 395,408. [source] SP-D and regulation of the pulmonary innate immune system in allergic airway changesCLINICAL & EXPERIMENTAL ALLERGY, Issue 4 2010L. R. Forbes Summary The airway mucosal surfaces are constantly exposed to inhaled particles that can be potentially toxic, infectious or allergenic and should elicit inflammatory changes. The proximal and distal air spaces, however, are normally infection and inflammation free due to a specialized interplay between cellular and molecular components of the pulmonary innate immune system. Surfactant protein D (SP-D) is an epithelial-cell-derived immune modulator that belongs to the small family of structurally related Ca2+ -dependent C-type collagen-like lectins. While collectins can be detected in mucosal surfaces of various organs, SP-A and SP-D (the ,lung collectins') are constitutively expressed in the lung at high concentrations. Both proteins are considered important players of the pulmonary immune responses. Under normal conditions however, SP-A-/- mice display no pathological features in the lung. SP-D-/- mice, on the other hand, show chronic inflammatory alterations indicating a special importance of this molecule in regulating immune homeostasis and the function of the innate immune cells. Recent studies in our laboratory and others implied significant associations between changes in SP-D levels and the presence of airway inflammation both in animal models and patients raising a potential usefulness of this molecule as a disease biomarker. Research on wild-type and mutant recombinant molecules in vivo and in vitro showed that SP-D binds carbohydrates, lipids and nucleic acids with a broad spectrum specificity and initiates phagocytosis of inhaled pathogens as well as apoptotic cells. Investigations on gene-deficient and conditional over expressor mice in addition, provided evidence that SP-D directly modulates macrophage and dendritic cell function as well as T cell-dependent inflammatory events. Thus, SP-D has a unique, dual functional capacity to induce pathogen elimination on the one hand and control of pro-inflammatory mechanisms on the other, suggesting a potential suitability for therapeutic prevention and treatment of chronic airway inflammation without compromising the host defence function of the airways. This paper will review recent findings on the mechanisms of immune-protective function of SP-D in the lung. Cite this as: L. R. Forbes and A. Haczku, Clinical & Experimental Allergy, 2010 (40) 547,562. 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