Undisturbed State Research Articles

Removal of extracellular sodium prevents anoxia-induced injury in freshly dissociated rat CA1 hippocampal neurons

Anoxia is believed to cause nerve injury and death in part, by inducing sustained, elevated levels of intracellular Ca 2+. The increased concentration of intracellular Ca 2+ is capable, by itself, of inducing nerve injury and death, even without the added stress of anoxia. However, we have recently shown that an increased level of intracellular Ca 2+ is not necessary for anoxia-induce CA1 nerve injury. Since we have observed that extracellular Na + decreases during anoxia, we studied the role of extracellular Na + in anoxia-induced nerve injury. Removal of extracellular Na + and its replacement with the impermeant cation N-methyl- d-glucamine (NMDG +) completely protected freshly dissociated CA1 neurons during and after severe anoxia, for up to 90 min. Intracellular Ca 2+ decreased during anoxia, recovering during reoxygenation. Propidium iodide was excluded from the neurons for as long as Na + was absent. Addition of Na + (by replacing NMDG +) following anoxia resulted in rapid bleb formation, swelling and intracellular Ca 2+ rise. Removal of Na + before the rupture of blebs caused either shrinkage or pinching off of blebs so that the neuron apparently returned to its previous undisturbed state. We conclude that: (1) replacement of Na o + with NMDG + totally prevents anoxia-induced nerve injury as manifested by morphological changes, e.g., swelling, bleb formation and membrane injury; (2) upon re-exposure to Na o + following anoxia in the absence of Na o +, neurons swell and bleb; (3) the appearance of blebs following anoxic exposure in the absence of Na o + is reversible and Na o + dependent. (4) Bleb formation itself is not necessarily immediately lethal to the neuron.

A continuous monitoring system for blood glucose measurements in conscious animals without surgery

AbstractThe hypoglycemic activity of insulin delivered via the various routes is commonly determined by measuring glucose levels in the whole blood samples taken intermittently at frequent intervals. This procedure is usually performed in the anaesthetized animals, however, the glucose levels determined could be higher than those in the conscious animals. Furthermore, the animals are usually excited by direct contact with the investigator during the frequent blood sampling in conscious state, which could cause the glucose level to be higher than at undisturbed state. To overcome these problems, a continuous blood glucose monitoring system was developed by connecting the sensor chamber of a glucose analyzer (YSI Industrial Analyzer model 27), which utilizes glucose oxidase for glucose measurement, to a peristaltic pump with a specially designed mixing chamber and a data acquisition station. By using this system, the hyper-/hypoglycemic activity of glucagon/insulin formulations in the conscious animals, aft...

Strong dynamical effects in the Kβ2 and Lγ2,3 X-ray emission spectra of lanthanum

The Kβ1,3 (K å M3,2), Kβ2I,II (K å N3,2), and the Lγ2,3 (L1 å N2,3) X-ray emission spectra from lanthanum have been measured, using high resolution crystal spectrometers. For the first time we observe an undisturbed 4p32 hole state together with a 4p12 hole state that is spread over an extended energy range. In comparison with theoretical calculations we show that in this case the quasi-particle picture only breaks down for the 4p12 core hole, due to very strong dynamical dipolar fluctuation and associated decay processes of the 4p12 core hole.

Secondary instability of a gas-fluidized bed

It is known that stationary fluid with density that varies sinusoidally with small amplitude and wavenumber k in the vertical direction is unstable to disturbances that are sinusoidal in a horizontal direction with wavenumber α. Small values of α/k are the most unstable in the sense that a neutral disturbance exists at sufficiently small α/k however small the Rayleigh number may be. The non-uniformity of density in the undisturbed state may be regarded as being a consequence of non-uniformity of concentration of extremely small solid particles in fluid. The paper is concerned with the corresponding instability of such a non-uniform dispersion when the particle size is not so small that the fall speed relative to the fluid is negligible. In the undisturbed state, which is an outcome of the well-known primary instability of a uniform fluidized bed with particle volume fraction Φ 0 , the sinusoidal distribution of concentration propagates vertically, and in the steady state relative to this kinematic wave particles fall with speed V(=|ΦdU/dΦ| Φ0 ), where U(Φ) is the mean speed of fall particles, relative to zero-volume-flux axes, in a uniform dispersion with volume fraction Φ. This particle convection with speed V transports particle volume and momentum and tends to even out variations of a disturbance in the vertical direction and thereby to suppress a disturbance, especially one with small α/k. Analysis of the behaviour of a disturbance is based on the equation of motion of the mixture of particles and fluid and an assumption that the disturbance velocities of the particles and the fluid are equal (as is suggested by the relatively small relaxation time of particles). The method of solution used in the associated pure-fluid problem is also applicable, and values of the Rayleigh number as a function of α/k for a neutral disturbance and a given value of the new non-dimensional parameter involving V are found. Particle convection with only modest values of V stabilizes all disturbances for which α/k 1. It appears that under practical conditions disturbances with α/k above unity are unstable, although ignorance of the values of parameters characterizing a fluidized bed hinders quantitative conclusions

Effects of Weathering on Stability of Natural Slopes in North-Central Kumamoto

ABSTRACT Through chemical process weathering, unwelded tuff pyroclastic flow deposits from Aso volcano have been altered to allophane and halloysite in geological time. As a result, natural slopes in areas abundant in Weathered soils of unwelded tuff are prone to catastrophic failure in periods of heavy rainfall. Mineralogical, chemical and electron microscopy study of soil samples from unfailed slope and actual case of failed slopes have shown that the main clay mineral of these soils is halloysite. The results from strength tests have proved that the complex interaction between weathering and leaching processes transforms the soil grain structure into a collapsible structure considerably weak in a saturated state. The collapsible structure is identifyable from the low density in undisturbed state and hence, the low density criterion may be used as an indicator on the loss of strength that may result from field saturation during heavy rainfall. Besides, leaching accelerates internal erosion in the natural slopes, and hence risk of failure by the seepage forces.

Latitudinal gradients in the structure of macrobenthic communities: a comparison of Arctic, temperate and tropical sites

As part of a programme to re-assess the existence of latitudinal gradients in the diversity of the macrobenthic infauna of soft sediments, samples were taken from Sassenfjord, Spitzbergen. Abundancebiomass curves showed the shallowest sites to be moderately disturbed, possibly as a result of glacial run-off from the Gipselva. These clearly differed from a site at 123 m which appeared to be in an undisturbed state. A comparison of the diversity profile of the latter site (78 °N) with those of physically similar sites in the North Sea (55 °N) and off the coast of Java (7 °S), sampled by identical methods, shows no real difference in diversity.

On the cold start problem in transient simulations with coupled atmosphere-ocean models

Finite computer resources force compromises in the design of transient numerical experiments with coupled atmosphere-ocean general circulation models which, in the case of global warming simulations, normally preclude a full integration from the undisturbed pre-industrial state. The start of the integration at a later time from a climate state which, in contrast to the true climate, is initially in equilibrium then induces a cold start error. Using linear response theory a general expression for the cold start error is derived. The theory is applied to the Hamburg CO2 scenario simulations. An attempt to estimate the global-mean-temperature response function of the coupled model from the response of the model to a CO2 doubling was unsuccessful because of the non-linearity of the system. However, an alternative derivation, based on the transient simulation itself, yielded a cold start error which explained the initial retardation of the Hamburg global warming curve relative to the IPCC results obtained with a simple box-diffusion-upwelling model. In the case of the sea level the behaviour of the model is apparently more linear. The cold start error estimations based on a CO2 doubling experiment and on an experiment with gradually increasing CO2 (scenario A) are very similar and explain about two thirds of the coupled model retardation relative to the IPCC results.

Gas permeability changes of rocksalt subjected to thermo-mechanical stresses

Abstract Permeabilities lower than 10 -17 M 2 cannot be measured using classical methods. To overcome this problem, the pulse decay method may be applied. In this method the evolution of a pressure pulse applied on the upstream side of the sample at 1 = 0 is recorded. An apparatus has been constructed to measure ultra-low permeabilities of rocks under thermo-mechanical stresses; intrinsic permeabilities between 10 -15 and 10 -22 m 2 can be measured. Several thermo-mechanical tests, including permeability determinations have been carried out on samples from saline lithofacies of the Bresse basin (France). The initial permeabilities are more representative of the condition of the test sample than of the undisturbed state of the formation. Nevertheless, the permeability changes observed during these tests seem to be directly connected to the nature and structure of the material sustains under changes of temperature and stress. During isotropic deformation tests, the response of permeability to pressure varies depending on the specific lithological characteristics of the samples. Deformation tests under deviatoric stress with constant confining pressure and temperature show that, for all the lithofacies, the permeability decreases continuously. This can be attributed to creep deformation of the halite.

Boundary Effects on Osmophoresis: motion of a vesicle in an arbitrary direction with respect to a plane wall

The problem of the osmophoretic motion of a spherical vesicle in the presence of a nearby plane wall is analyzed in the quasi-steady limit of negligible Reynolds and Peclet numbers. The solute concentration gradient in the surrounding fluid is uniform in the undisturbed state and is oriented at an arbitrary angle relative to the plane wall. The solution of conservative equations for the solute species and fluid momentum applicable to the system is constructed by superposing solutions of the corresponding problems of motion normal to the plane and motion parallel to it. Using the spherical bipolar coordinate system, the translational and angular velocities of the osmophoretic vesicle are solved for various cases. Interestingly, the osmophoretic mobility of the vesicle increases monotonically as it approaches the wall. The interaction between the boundary and the vesicle can be very strong when the gap thickness gets close to zero. The direction of motion of the vesicle is, in general, different from that of the solute concentration gradient. The plane wall exerts the greatest influence on the vesicle in the case of parallel osmophoresis, and the weakest in the case of motion normal to it. In addition to the translational migration, the osmophoretic vesicle rotates at the same time in the direction opposite to that which would occur if the spherical particle sedimented parallel to a plane wall. The ratio of rotational-to-translational speeds of the sphere is, in general, much larger for osmophoresis than for sedimentation.

Confocal study of microaggregates in 2.5 billion year-old sediments

Light microscopy conducted on samples of Archean sediments reveals microaggregates (Fig. 1) which are suggestive of a biotic origin. These aggregates, typically 15 μm wide and 50 μm long, are thought to be the mineral remains of colonies of microorganisms that lived 2.5 billion years ago. Confocal microscopy is used to study the structures of these microaggregates in 3-D.Samples under study are from the lowest section drill core taken from the Dales Gorge Member of the Brockman Iron-Formation (Hamersley Basin) in Western Australia. These sediments are well preserved and escaped metamorphic conditions typically experienced by older rocks of this type. Two types of samples were prepared for study under the microscope: thin sections (~40 μm) for transmitted light microscopy to study the general rock texture and to locate the features of interest, and thick sections (3 mm) for confocal microscopy to determine the 3-D structure of the aggregates in their undisturbed state.

Distribution of Seven Native and Two Exotic Plants in a Tallgrass Prairie in Southeastern Wisconsin: The Importance of Human Disturbance

-Invasion by exotic plant species is a serious threat to the integrity of natural communities. The distribution of an exotic species depends upon environmental conditions, the structure of the native community, patterns of disturbance and ecological features of the species itself. This study identifies (1) associations between two exotic and seven native species in a tallgrass prairie in southeastern Wisconsin and (2) factors underlying the distribution of these species, with special regard to the effects of human disturbance. The distribution of two exotic species, Melilotus alba (white sweetclover) and Daucus carota (Queen Anne's lace), and seven native species, Potentilla arguta (prairie cinquefoil), Pedicularis canadensis (Canada lousewort), Dodecatheon meadia (Mead's shooting star), Equisetum laevigatum (scouring rush), Pycnanthemum virginianum (Virginia mountain mint), Phlox glaberrima (smooth phlox) and Solidago graminifolia (bushy goldenrod), were studied in 100, 4 m2 quadrats on five transects. Plant densities and soil characteristics were recorded for each quadrat and analyzed using nonparametric comparison of means and Spearman correlation analysis. Densities of the two exotic species were positively correlated with each other and negatively correlated with those of five of the seven natives. Most species exhibited a clear segregation between disturbed and undisturbed transects; Melilotus and Daucus dominated the disturbed transects, and native species dominated the undisturbed transects. Edaphic conditions appear to be the most important factor driving this habitat segregation between exotics and natives. Our finding is instructive for prairie restoration, because it suggests that in some cases, soil restoration may be desirable even if it results in additional mechanical disturbance. Although the prairie in its undisturbed state seems to resist invasion of these two exotic species, Daucus is able to escape disturbed microhabitats more extensively than is Melilotus.

Scientific Method and Prose Style in the Early Royal Society

This article discusses two conflicts occurring during the first decade of the Royal Society (1660–1670). One conflict concerned the proper method of scientific experimentation, the other the proper writing style for communicating scientific knowledge. Following the method proposed by taxonomists, language would be a vehicle for representing the order of reality in its undisturbed state. Following the method proposed by conjecturalists, language would be a means for constructing a theory and arguing for its validity. Members of the Society were divided over these crucial questions, as evident in scientific documents of the period as well as in Thomas Sprat's History of the Royal Society. Parallels to this division are present in contemporary issues in technical writing, and this article closes by discussing some implications for teaching, practice, and theory.

The response of a turbulent boundary layer to artificial disturbances

With periodic fluid injection through small slots, a turbulent boundary layer is artificially disturbed on scales that are of the order of those of the natural quasi-periodic events. The periodic phase-average of the streamwise fluid velocity is determined from hot-film measurements, and used to find the coherent velocity component as defined by the triple decomposition. It appears that, when a disturbance is active, the generated flow pattern is very similar to the one caused by the interaction of a crossflow and a jet. However, when it is terminated, the turbulent boundary layer returns to its undisturbed state.

A Continuous Monitoring system for Blood Glucose Measurements in conscious Animals without Surgery

AbstractThe hypoglycemic activity of insulin delivered via the various routes is commonly determined by measuring glucose levels in the whole blood samples taken intermittently at frequent intervals. This procedure is usually performed in the anaesthetized animals, however, the glucose levels determined could be higher than those in the conscious animals. Furthermore, the animals are usually excited by direct contact with the investigator during the frequent blood sampling in conscious state, which could cause the glucose level to be higher than at undisturbed state. To overcome these problems, a continuous blood glucose monitoring system was developed by connecting the sensor chamber of a glucose analyzer (YSI Industrial Analyzer model 27), which utilizes glucose oxidase for glucose measurement, to a peristaltic pump with a specially designed mixing chamber and a data acquisition station. By using this system, the hyper-/hypoglycemic activity of glucagon/insulin formulations in the conscious animals, aft...

Microaggregations of Oceanic Plankton Observed by Towed Video Microscopy

Oceanic plankton have been hypothesized to occur in micropatches (<10 meters) that can have a large impact on marine ecosystem dynamics. Towed video microscopy was used to unobtrusively determine distributions of oceanic plankton over a continuum of scales from microns to hundreds of meters. Distinct, taxa-specific aggregations measuring less than 20 centimeters were found for copepods but not for nonmotile (cyanobacterial colonies) or asexual (doliolid phorozooids) forms, which suggests that these small patches are related to mating. Significant patchiness was also found on larger scales and was correlated among taxa, indicating physical control. These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.

Laboratory study of gas permeability changes in rock salt during deformation

Gas permeability and porosity measurements have been made during hydrostatic and triaxial quasi-static, stress-rate controlled compression tests. The permeability and porosity of the as-received samples decrease significantly as a result of hydrostatic loading. These changes are largely irreversible, and are believed to “heal” or return the rock to a condition comparable to its undisturbed state. The permeability can increase more than 5 orders of magnitude over the initial (healed) state as the samples are deformed during deviatoric loading. The gas permeability and porosity changes are consistent with a flow model based on the equivalent channel concept. A model of microcrack initiation and growth based on the frictional sliding crack suggests the flow paths initially develop along grain boundaries and then along axial intragranular tensile cracks. Post-test visual observations support the model predictions.

Vaca Muerta mesosiderite strewnfield

Abstract A field investigation is presented of the strewnfield of the mesosiderite Vaca Muerta, originally found in 1861. The area, 11.5 km long, 2.1 km wide, is located about 60 km southeast of Taltal, Chile, in the Atacama Desert. It has yielded 80 meteorites with a total mass exceeding 3782 kg. Most fragments were found in an undisturbed state, but some had been broken by prospectors. The present studies, in connection with historical records, indicate that the original mass of Vaca Muerta exceeded 6 metric tons. One impact feature, somewhat modified by man, consists of a 10.5‐m diameter, 1.7‐m deep hole, without an uplifted rim. Small masses were scattered up to 85 m from the hole.

The equatorial neutral thermospheric response to geomagnetic

Thermospheric temperature and neutral density measurements from Dynamics Explorer 2 (DE 2) have been used to study the time‐dependent response of the equatorial thermosphere to geomagnetic forcing. Data taken following the onsets of several different isolated geomagnetic storms have been used in a superposed‐epoch scheme to investigate the characteristic response of the density and temperature structure of the equatorial thermosphère at ∼350 lcm altitude in the rooming and evening local‐time sectors. The principal post‐storm‐onset features that have been observed are as follows: 1) Two travelling waves, one generated at northern high latitudes and one at southern high latitudes, pass through the equatorial thermosphere, with wave crests crossing the equator at a time lag of 3–6 hours after the storm onset. The maximum neutral density perturbations associated with these waves are ∼15–25% for atomic oxygen and ∼30–40% for molecular nitrogen. 2) Following the passage of these travelling waves, the densities and temperatures in the evening sector return relatively rapidly to their undisturbed state, whereas those in the morning sector have significant variations at longer lag times. In particular, significant increases in neutral density and temperature occur in the morning sector about 12 hours after the onset of the storm. The N2 density enhancements are seen earliest in the summer hemisphere, while the O density enhancements are seen earliest in the winter hemisphere.

A general scheme for the derivation of evolution equations describing mixed nonlinearity

We examine hyperbolic, quasilinear systems in which the usual quadratic nonlinearity coefficient may be positive or negative depending on the undisturbed state of the medium. A general multiple-scales technique is developed which is capable of determining the evolution equations governing small disturbances to a state which lies close to that where the quadratic nonlinearity coefficient vanishes. The resultant equation contains both quadratic and cubic nonlinearity and describes the mixed nonlinearity inherent in such systems. Extensions to weakly dissipative or weakly dispersive systems are provided as are examples illustrating applications to electromagnetics and solid and fluid mechanics.

Stability of couette flow between free cylinders with allowance for self-gravitation

The free two-dimensional motion of a gravitating system consisting of two unfixed rotating cylinders and the incompressible fluid between them is considered. The undisturbed state of the system is determined by the viscous Couette flow between the coaxial cylinders. The stability of the central position of the cylinders is investigated within the framework of the equations of an inviscid fluid in a rotating coordinate system in which the flow is assumed to be potential. The critical values of the parameters and the spectral characteristics of the system are found. The qualitative form of the neutral curves obtained is determined by the value of the unique parameter of the problem ρr, which is equal to the ratio of the density of the inner cylinder to the density of the fluid. It is noted that if ρr→ 1, then however small the values of the angular velocities of the cylinders, generally speaking, they cannot be neglected in calculating the natural vibrations of the system. It is shown that if ρr > 1, then in the absence of gravitation the radial play between the cylinder axes leads to the growth of disturbances in the region stable with respect to the Rayleigh criterion.