Regions Of Low Activity Research Articles

Serotonin and morphogenesis. Transient expression of serotonin uptake and binding protein during craniofacial morphogenesis in the mouse.

This study describes the timecourse of expression of low-affinity serotonin uptake sites in the developing craniofacial region of the mouse embryo. Whole mouse embryos were incubated in the presence of various serotonergic compounds followed by immunocytochemical localization of serotonin (5-HT) and its binding protein. In the gestational day 9 embryo (3-5 somites), 5-HT uptake was observed in the myocardium of the heart, the visceral yolk sac and foregut. A specific and transient pattern of 5-HT uptake was observed in the hindbrain neuroepithelium from day 9.5-11, where it was localized in rhombomeres 2-5 in the day 9.5 embryo. By day 10, when rhombomeres were no longer evident, uptake was present in the dorso-lateral neuroepithelium surrounding the fourth ventricle (rhombic lip; cerebellar anlage). Uptake of 5-HT was initially observed in the surface epithelium of the craniofacial region at day 10 (20-25 somites) and was greatly increased at day 11. The invaginating lens, nasal placode epithelium and otocyst also took up 5-HT at day 11. During these stages a 45 kD serotonin-binding protein (SBP) was expressed in craniofacial mesenchyme, and became progressively restricted to regions subjacent to epithelial uptake sites. These staining patterns were shown to be specific for 5-HT and SBP by their absence in embryos stained using preabsorbed antisera. The timecourse of these patterns are correlated with critical events in craniofacial morphogenesis including (1) onset of inductive epithelial-mesenchymal interactions, (2) invagination and fusion of placodal structures, (3) presence of rhombomeres, and (4) regions of low proliferative activity.

Estimation of Velocity from Argos-tracked Surface Drifters during OCEAN STORMS

Abstract Modern surface drifters tracked by Argos are an attractive method for measuring the spatial structure of near-surface currents. This note discusses the accuracy to which velocity can be estimated from such data, assuming perfect drifters. The analysis concentrates on data from OCEAN STORMS centered at 47.5°N in the eastern North Pacific, a region of low mesoscale activity. The irregular, but nearly diurnally repeating, pattern of fixes leads to leakage between near-inertial (1.48 cpd) and subinertial (0.5 cpd) frequencies. Total spectral leakage for a naive spline interpolant of the fixes is about 2×10−3 in energy, or 5% in amplitude. Other interpolants can produce an order of magnitude more leakage. An algorithm that controls these errors is described. Only an inertial peak and frequencies well below 0.5 cpd can be resolved. The remaining noise can be described as the sum of a random fix error of 600 m rms and unresolved subinertial velocities with an rms displacement of about 550 m. The errors ...

Central auditory metabolic activity induced by intense noise exposure

Neural activity in the central auditory system was mapped by measuring 2-deoxyglucose (2-DG) uptake during a one hour exposure to a two-octave (1414–5656 Hz) band of noise. Gerbils were exposed to 100, 110 or 120 dB SPL, intensities which can produce only temporary (100 dB) or both temporary and permanent (120 dB) hearing loss. Exposure to 100 dB SPL evoked high levels of neural activity throughout responsive regions of auditory nuclei. At 110 dB SPL, a central region of low neural activity was surrounded by areas exhibiting increased activity. At 120 dB SPL, neural activity was low in almost all areas of auditory nuclei. To study the effects of permanent hearing loss on auditory neuronal activity, other animals were given 2-DG during exposure to 65 dB SPL broad band noise as a test stimulus, two months after exposure to the noise band at 110 dB SPL. Central auditory nuclei showed a tonotopic region of low neural activity corresponding to an approximately 3 kHz pure tone, surrounded by regions of evoked activity. The deficits in evoked metabolic activity observed both during and long after noise exposure appear to exceed those predicted from the degree of temporary and permanent threshold shift produced by the same noise exposures.

Method to estimate intensity occurrence probabilities in low seismic activity regions : Egozcue, J J; Barbat, A; Canas, J A; Miquel, J; Earthq Engng Struct DynamV20, N1, Jan 1991, P43–60

Method to estimate intensity occurrence probabilities in low seismic activity regions : Egozcue, J J; Barbat, A; Canas, J A; Miquel, J; Earthq Engng Struct DynamV20, N1, Jan 1991, P43–60

Attenuation compensation of cone beam SPECT images using maximum likelihood reconstruction

Attenuation compensation for cone beam single-photon emission computed tomography (SPECT) imaging is performed by cone beam maximum likelihood reconstruction with attenuation included in the transition matrix. Since the transition matrix is too large to be stored in conventional computers, the E-M maximum likelihood estimator is implemented with a ray-tracing algorithm, efficiently recalculating each matrix element as needed. The method was applied and tested in both uniform and nonuniform density phantoms. Test projections sets were obtained from Monte Carlo simulations and experiments using a commercially available cone beam collimator. For representative regions of interest. reconstruction of a uniform sphere is accurate to within 3% throughout, in comparison to a reference image simulated and reconstructed without attenuation. High- and low-activity regions in a uniform density are reconstructed accurately, except that low-activity regions in a more active background have a small error. This error is explainable by the nonnegativity constraints of the E-M estimator and the image statistical noise.

A method to estimate intensity occurrence probabilities in low seismic activity regions

AbstractThe estimation of site intensity occurrence probabilities in low seismic activity regions has been studied from different points of view. However, no method has been definitively established because several problems arise when macroseismic historical data are incomplete and the active zones are not well determined. The purpose of this paper is to present a method that estimates site occurrence probabilities and at the same time measures the uncertainties inherent in these probabilities in low activity regions. The region to be studied is divided into very broad seismic zones. An exponential intensity probability law is adjusted for each zone and the degree of uncertainty in the assumed incompleteness of the catalogue is evaluated for each intensity. These probabilities are used to establish what may be termed ‘prior site occurrence models’. A Bayesian method is used to improve ‘prior models’ and to obtain the ‘posterior site occurrence models’. Epicentre locations are used to recover spatial information lost in the prior broad zoning. This Bayesian correction permits the use of specific attenuation for different events and may take into account, by means of conservative criteria, epicentre location errors. Following Bayesian methods, probabilities are assumed to be random variables and their distribution may be used to estimate the degree of uncertainty arising from (a) the statistical variance of estimators, (b) catalogue incompleteness and (c) mismatch of data to prior assumptions such as Poisson distribution for events and exponential distribution for intensities. The results are maps of probability and uncertainty for each intensity. These maps exhibit better spatial definition than those obtained by means of simple, broad zones. Some results for Catalonia (NE of Iberian Peninsula) are shown.

Measurements of light atmospheric hydrocarbons over the Atlantic in regions of low biological activity

More than 200 in situ measurements of several selected nonmethane hydrocarbons (NMHCs) were made in the remote marine atmosphere over the Atlantic between 40°S and 50°N. Ethane, the by far longest lived of the NMHCs, showed southern hemispheric mixing ratios around 280 ppt, comparable in magnitude to most other previous measurements. The mixing ratios of ethene, propene, propane, and i‐ and n‐butane in the southern hemisphere were in the range of 10–30 ppt. For i‐pentane and n‐pentane the atmospheric mixing ratios in the southern hemisphere were below the detection limit of 15–20 ppt. These values are rather low compared to other published measurements in the marine atmosphere. This is due to the remoteness of the measuring locations and the very low biological activity in the surrounding ocean areas. For all alkanes the latitudinal profiles exhibit a considerable decrease from north to south. The relative hydrocarbon patterns show that the alkanes in the northern hemisphere are primarily due to long‐range transport from continental or coastal areas. In general the transport times exceed several days. Consequently, the observed northern hemispheric ethene and propene mixing ratios must be, with few exceptions, primarily the result of oceanic emissions. The average difference of these compounds by a factor of 2 between the southern and the northern hemisphere can be explained by change of the phytoplankton concentration in ocean water. There is little or no indication for the existence of significant diurnal cycles for these two alkenes.

Comparison of [99mTc]HMPAO SPECT with [18F]Fluoromethane PET in Cerebrovascular Disease

Positron emission tomography (PET) of [18F]fluoromethane (FM) and single-photon emission tomography (SPECT) of [99mTc]hexamethylpropyleneamine oxime (HMPAO) were performed under identical conditions within 2 h in 22 patients suffering from cerebrovascular disease (8 ischemic infarction, 2 intracerebral hemorrhages, 7 transient ischemic attacks, and 5 multi-infarct syndrome). While gross pathological changes could be seen in the images of either procedure, focal abnormalities corresponding to transient ischemic deficits or to lesions in multi-infarct syndrome and areas of functional deactivation were sometimes missed on SPECT images. Overall, HMPAO SPECT images showed less contrast between high and low activity regions than the FM PET images, and differences between lesions and contralateral regions were less pronounced (6.4 vs 13.3% difference). Regional cerebral blood flow (rCBF) was calculated from FM PET studies in 14 large territorial regions and the pathological lesion, and the regional values relative to mean flow were compared to the relative HMPAO uptake in an identical set of regions defined on the SPECT images. Among individual patients, the Spearman rank-correlation coefficient between relative rCBF and HMPAO uptake varied between 0.48 and 0.89, with a mean of 0.70. While an underestimation of high flow with SPECT--which was demonstrated in a curvilinear relationship between all relative regional PET and SPECT values--could be corrected by linearization taking into account HMPAO efflux from the brain before metabolic trapping, correspondence of SPECT data with PET rCBF values was not improved since this procedure also increased the variance in high flow areas. In the cerebellum, however, a high HMPAO uptake in SPECT always overestimated CBF in relation to forebrain values; this finding might be due to high capillary density in the cerebellum. The differences observed between SPECT and PET data may be explained by technical and physical properties of the methods and by the incomplete first-pass extraction of HMPAO. Additionally, HMPAO or its metabolites may leak through a damaged blood-brain barrier (as observed in one infarct and in the surrounding of hemorrhages), impairing the contrast between lesion and normal tissue. The presented data indicate that the quantification of rCBF by HMPAO SPECT is limited.

Selection of a dtpa chelate conjugate for monoclonal antibody targeting to a human colonic tumor in nude mice

Our previous studies with a 90Y-labelled antibody against carcinoembryonic antigen (CEA) conjugated to the cyclic anhydride-DTPA (CA-DTPA) indicated that the accretion of 90Y in the bone may limit the application of 90Y-labelled antibodies for therapy. In this report, we have compared the tumor targeting of CA-DTPA-conjugated antibody to antibody conjugated with 4 isothiocyanatobenzyl (ITC-Bz) derivatives of DTPA in nude mice bearing a human colonic tumor xenograft. In biodistribution studies using an 111In-labelled anti-CEA murine monoclonal antibody (MAb), the CA-DTPA-conjugated MAb showed lower tumor uptake, faster blood clearance, and higher accretion in the liver than any of the 4 ITC-Bz-DTPA-conjugated MAbs. There were smaller differences among the 4 ITC-Bz-DTPA conjugates. Whole-body autoradiography of animals given 90Y-MAb prepared with the CA-DTPA or the ITC-Bz-DTPA showed less radioactivity in the bone with the ITC-Bz-DTPA-MAb than the CA-DTPA-MAb. 90Y uptake in the bone corresponded with regions of low proliferative activity as defined by 3H-labelled thymidine, suggesting that the 90Y was in the cortex rather than the marrow. These studies clearly show an advantage of the ITC-Bz-DTPA derivatives for 90Y and 111In labelling of MAbs.

Seismic hazard assessments for two test areas ? ?Southern Italy? and ?Belgium?The Netherlands?Germany?

Within the activity of the ESC Subcommission 8 ‘Engineering Seismology’, Project TERESA, seismic hazard calculations have been performed for two areas of a different earthquake activity. Fundamental seismological data (earthquake catalogues, macroseismic observations and maps) and some additional geological information were analyzed and processed to prepare inputs for hazard computations. Great attention has been paid to verifying the reliability of the input data. Seismic hazards obtained for five sites of the region of high seismic activity (Sannio-Matese, southern Italy) and six sites of the region of low seismic activity (Brabant Massif and northern Rhine, Belgium—The Netherlands—Germany) are presented and discussed.

Earthquake recurrence and risk assessment in circum-Pacific seismic gaps

THE development of the concept of seismic gaps, regions of low earthquake activity where large events are expected, has been one of the notable achievements of seismology and plate tectonics. Its application to long-term earthquake hazard assessment continues to be an active field of seismological research. Here I have surveyed well documented case histories of repeated rupture of the same segment of circum-Pacific plate boundary and characterized their general features. I find that variability in fault slip and spatial extent of great earthquakes rupturing the same plate boundary segment is typical rather than exceptional but sequences of major events fill identified seismic gaps with remarkable order. Earthquakes are concentrated late in the seismic cycle and occur with increasing size and magnitude. Furthermore, earthquake rup-ture starts near zones of concentrated moment release, suggesting that high-slip regions control the timing of recurrent events. The absence of major earthquakes early in the seismic cycle indicates a more complex behaviour for lower-slip regions, which may explain the observed cycle-to-cycle diversity of gap-filling sequences.

Seismic hazard assessment in TERESA test areas based on a Bayesian technique

A method based on Bayesian techniques has been applied to evaluate the seismic hazard in the two test areas selected by the participants in the ESC/SC8-TERESA project: Sannio-Matese in Italy and the northern Rhine region (BGN). A prior site occurrence model (prior SOM) is obtain from a seismicity distribution modeled in wide seismic sources. The posterior occurrence model (posterior SOM) is calculated after a Bayesian correction which, basically, recovers the spatial information of the epicenter distribution and considers attenuation and location errors, not using source zones. The uncertainties of the occurrence probabilities are evaluated in both models. The results are displayed in terms of probability and variation coefficient contour maps for a chosen intensity level, and with plots of mean return period versus intensity in selected test sites, including the 90% probability intervals. It turns out that the posterior SOM gives a better resolution in the probability estimate, decreasing its uncertainty, especially in low seismic activity regions.

Ducted whistler propagation outside the plasmapause

A study has been made of the conditions under which lightning whistlers are observed after propagating along geomagnetic field aligned paths or “ducts” located outside the plasmapause. The study was based in part upon results previously obtained from Antarctic whistler recordings in 1963 and in part upon new data from 45 days of observations at Siple Station, Antarctica (L ≃ 4.3) in 1977 and in 1982. Propagation beyond the plasmapause was found, as expected, to be rare in comparison to propagation within the nearby outer plasmasphere. However, detectable propagation beyond the plasmapause near dawn was found to occur on at least one path on roughly one half of the days studied. The path equatorial radii of propagation tended to cluster in two locations, one at the plasmapause outer edge, and the other in a belt separated from the plasmapause by a region of low activity of order 0.5 RE in extent. The outer edge of the belt was at L ≃ 5.5–6. The probability of whistler detection at any L value outside the plasmapause up to ≃ 6–7 was found to increase with local time across the dayside of the Earth; maximum activity was observed after noon. Whistler activity beyond the plasmapause was least common in the 1800–2400 MLT sector. Spatial variations in lightning source activity may be responsible for large variations with longitude in whistler activity outside the plasmapause and for the many cases in which only a small fraction of whistlers within a given period exhibit evidence of plasmatrough propagation. Ionospheric processes, such as wave damping, defocusing in the mid‐latitude trough, scattering by 10 to 100‐m irregularities, and focusing within 50 to 100‐km blobs, can explain many features of the observed spatial distribution of whistler paths beyond the plasmapause and also the relatively low amplitude of the associated whistlers as compared to plasmasphere events. The large differences in whistler activity between afternoon and premidnight appear to be due to spatial differences in perturbing magnetospheric electric field activity and in electron density in the plasma trough region. The experimental findings serve to make a relatively sharp distinction between the plasmasphere and the region beyond from both the propagation and wave‐particle‐interaction points of view.

Estimate of Electromagnetic Quantities in Space from Ground Magnetic Records

Magnetic field records at the earth's surface contain the effects of a variety of different source currents flowing in outer space. During the last decade, several computational techniques for the use of magnetometer data have been proposed to obtain the global pattern of the electric fields and currents and Joule heating in the ionosphere. The numerical algorithm has now been enormously improved, such that simultaneous more direct or in situ measurements by satellites and radars can be incorporated into the scheme. In particular, owing to recent progress in satellite-viewed auroral images, it is possible to estimate "instantaneous" patterns of the ionospheric electrodynamic quantities over the entire polar region with a time resolution of several minutes. This report demonstrates that, contrary to our conventional views, large ionospheric currents can flow in regions of low auroral activity.

Stopping Rule for the MLE Algorithm Based on Statistical Hypothesis Testing

It is known that when the maximum likelihood estimator (MLE) algorithm passes a certain point, it produces images that begin to deteriorate. We propose a quantitative criterion with a simple probabilistic interpretation that allows the user to stop the algorithm just before this effect begins. The MLE algorithm searches for the image that has the maximum probability to generate the projection data. The underlying assumption of the algorithm is a Poisson distribution of the data. Therefore, the best image, according to the MLE algorithm, is the one that results in projection means which are as close to the data as possible. It is shown that this goal conflicts with the assumption that the data are Poisson-distributed. We test a statistical hypothesis whereby the projection data could have been generated by the image produced after each iteration. The acceptance or rejection of the hypothesis is based on a parameter that decreases as the images improve and increases as they deteriorate. We show that the best MLE images, which pass the test, result in somewhat lower noise in regions of high activity than the filtered back-projection results and much improved images in low activity regions. The applicability of the proposed stopping rule to other iterative schemes is discussed.

Neuropeptide Y, somatostatin, and reduced nicotinamide adenine dinucleotide phosphate diaphorase in the human striatum: A combined immunocytochemical and enzyme histochemical study

Neuropeptide Y and somatostatin immunoreactive neurons and processes were examined in human striatum using both immunofluorescence and avidin-biotin immunoperoxidase methods. Reduced nicotinamide adenine dinucleotide phosphate diaphorase activity was histochemically determined by the reduction of nitro blue tetrazolium. Immunofluorescence using a monoclonal anti-somatostatin antibody and a polyclonal anti-neuropeptide Y antibody, followed by diaphorase histochemistry, showed that these three neurochemical markers are co-localized in a single population of medium-sized aspiny intrinsic neurons. Cells were evenly distributed in clusters throughout the striatum, but fiber density was higher in the nucleus accumbens and ventromedial regions of the caudate and putamen. Double-stained reduced nicotinamide adenine dinucleotide phosphate diaphorase-acetylcholinesterase sections demonstrated that these neurons are located in zones of high acetylcholinesterase activity, often at the interface of these zones with regions of low enzyme activity. These biochemically distinctive neurons are uniquely situated to modulate activity between striatal compartments. Our findings provide new information about the modular organization of the striatum and extend these observations in human brain.

Cytochrome oxidase activity in the rat caudate nucleus: light and electron microscopic observations.

Cytochrome oxidase (CO) activity was examined in the neostriatum of normal adult rats at the light and electron microscopic level. At the light microscopic level a heterogeneous distribution of CO activity was observed and was characterized by patches of high activity ranging in size from 200 to 800 microns surrounded or adjacent to regions of lower activity. The most dorsomedial and ventromedial regions of the caudate nucleus appeared to be consistently high in activity in all animals. At the ultrastructural level CO reaction product was localized to the membranes and intracristal spaces of mitochondria. The most reactive mitochondria (those containing the denest precipitates of reaction product) were found within the dendrites of spiny neurons in all caudate regions. In areas of high CO activity the mitochondria within bundles of myelinated fibers and in many axon terminals were also highly reactive whereas those in neuronal somata, primary dendrites, and glial cells and processes exhibited relatively little activity. Quantitative study showed that mitochondria within dendrites accounted for most of the CO activity in caudate neuropil. The mitochondria within dendrites and axon terminals were more reactive in regions of high CO activity than in regions of low CO activity. No differences in the density of synapses or in the proportions of axospinous and axodendritic synapses were observed between CO-rich and CO-poor areas. Heterogeneity in the distribution of CO activity in the caudate nucleus may be related to the "patchy" pattern of localization previously observed for some neostriatal afferents, enzymes, transmitters, peptides, and receptor ligands.(ABSTRACT TRUNCATED AT 250 WORDS)

1984年長野県西部地震による震央付近の大加速度

Many boulders were thrown off out of their former sockets by the Western Nagano Prefecture Earthquake of September 14, 1984. Anomalous high accelerations of 5-30g, in the frequency range of 5-10Hz, are estimated from the displacement of these thrown out boulders.Almost all of the thrown out boulders were found on the tops, ridges and suddles of the mountains covered with the volcanic ash. The amplification effects by topography and soil sediment of the surface are estimated from the observation of the aftershocks recorded on the mountain-top, -foot and rock. The spectral ratios of seismic waves with the frequencies of 5-10Hz, namely mountain-top/-foot and soil/rock, are 2-7 and 2-10, respectively.The accelerations on the basement rock are obtained dividing the accelerations estimated on the mountain-tops. The high accelerations exceeding 1g distribute within a small area with a length of 3km and a width of 1km. This small area corresponds to the large dislocation portion of the assumed fault and the low active region of aftershocks.

How bioturbation supports manganese nodules at the sediment-water interface

Theoretical considerations suggest that oceanic manganese nodules are supported at the sediment-water interface by bioturbation. Bioturbation can cause a horizontal Stokes transport from regions of high biological activity to regions of low biological activity. Less sediment motion might be expected beneath a nodule than in the surrounding sediment because a nodule is a barrier to the foraging activities of macrobenthic organisms and also because there is probably less food directly beneath the nodule than in the surrounding sediment. Sediment velocities, calculated from particle mixing coefficient of pelagic sediment, appear to be sufficient to prevent nodules from being buried.

A case for submergence of magnetic flux in a solar active region

In NOAA Active Region 2372 (April 1980), 4 x 10 to the 20th maxwells of magnetic flux concentrated in an area 30 arcsec across disappeared overnight. Vector magnetograms show that all components of the magnetic field weakened together. If the field had weakened through diffusion or fluid flow, 90 percent of the original flux would still have been detected by the magnetograph within a suitably enlarged area. In fact there was a threefold decrease in detected flux. Evidently, magnetic field was removed from the photosphere. Since the disappearing flux was located in a region of low magnetic shear and low activity in H-alpha and Ly-alpha, it is unlikely that the field dissipated through reconnection. It is argued that the most likely possibility is that flux submerged. The observations suggest that even during the growth phase of active regions, submergence is a strong process comparable in magnitude to emergence.