Deep Group Research Articles

Radial resection margin distinguishes between superficial versus deep resection in colorectal cancer: a retrospective study.

Randomized studies showed that robotic surgery was short-term useful and safe for cancer patients. We investigated whether robots improve deep resection margins or superficial resection margins for radial resection margins in terms of short-term results. From an institutional database, we selected all superficial groups (≤ 3mm) and deeper groups (≥ 4mm) with rectal cancer treated with resection for a year. We evaluated the short-term post-operative 90-day outcomes on a radial resection size-based margin differentiation, including the first bowel movement, length of hospital stay, sepsis, and harvested lymph node. The main results were grades III-IV on the Clavien-Dindo scale and complications. We found 120 patients who had oncologic resection of rectal cancer; 42 patients with a superficial radial resection margin of ≤ 3 mm, all the following outcomes improved: the harvested lymph node, proximal resection margin, TME, flatus time, liquid diet duration, anastomotic leakage, and sepsis. Among these advantages were a reduced risk of metastasis and an overall reduction in local recurrence.

Effect of Center-Pivot Irrigation Intensity on Groundwater Level Dynamics in the Agro-Pastoral Ecotone of Northern China

Groundwater-based irrigation is an effective buffer against water disconnects during droughts in areas of intensive agriculture. However, it is difficult to implement effective measures to sustainably utilize aquifers due to the unclear understanding of irrigation intensity in the agro-pastoral ecotone. To explore the influence of regional irrigation intensity on groundwater level (GL), we investigated the dynamics of Kernel density for irrigation well from 2000 and the changed GL (ΔGL in three groups) in a typical center-pivot irrigation (CPI) area (about 1,000 km2). The results showed that the implementation of CPI systems caused a rapid land-use change from natural grassland (NG) to cultivated pasture (CP). The observed ΔGL in deeper group (0.63 m yr−1, GL > 20 m) was significantly (p < 0.05) higher than that in shallower group (0.38 m yr−1, GL < 10 m) and medium group (0.43 m yr−1, 10 m < GL < 20 m). The predicted ΔGL and GL were significantly and positively correlated with the CPI well density (R2 = 0.447 and 0.429, p < 0.001), respectively, and showed a fitted plane function based on the variables (R2 = 0.655, p < 0.001). It indicted that the intensive cropping in the agro-pastoral ecotone profoundly changed regional irrigation intensity, resulting in a rapid response of the GL. To reduce the risk of increased irrigation costs and ensure sustainable availability of groundwater, it’s necessary to control the density of CPI systems in hotspot areas, and implement water-saving measures to balance water usage and recharge rates for sustainable groundwater management.

Assessment of Spatial Distribution and Temporal Variations of the Phreatic Groundwater Level Using Geostatistical Modelling: The Case of Oued Souf Valley—Southern East of Algeria

Since the beginning of the 1980s, several regions in the northern Sahara of Algeria have been confronting the rising groundwater. Among all these regions, Oued Souf Valley represented one of the most acute affected by this phenomenon. Due to the natural topography and the insufficient/weakness of water management and miscoordination between different sectors that are represented by intensive exploitation of deep groundwater reservoirs which returns to the shallow aquifer, absence of sewage and drainage network, leakage from drinking water supply system, the groundwater has raised to the surface or near to the surface, affecting the traditional cultural environment and urban areas and degrading all socio-economic aspects of the Oued Souf habitants. To preserve the Oued Souf environment, a vertical drainage system has been constructed. Consequently, in this research, an evaluation of the vertical drainage system performance and its impact on groundwater level stabilization has been performed by mapping the water table of the phreatic groundwater level using geostatistical modeling using ordinary kriging (OK) interpolation method, which has been applied to analyze the spatial and temporal structure of groundwater level fluctuation. Meanwhile, hierarchical cluster analysis (HCA) was applied for grouping the wells based on the groundwater fluctuations for 2008, 2009, 2014, 2016, 2018, and 2021. However, the vertical drainage system reflected a significant decline of groundwater from 2009 to 2018 due to the important drained volumes through it but another rising phenomenon might be threatening the region in the near future and this is what was indicated in the 2021 groundwater level data. Cluster analysis has generated four groups based on their fluctuation means that are increasing from the first group to the fourth group ascendingly. The first cluster grouped the drains that have a shallow depth (average mean of 5.91 mbgl) and declined over the clusters. The clusters are spatially combined with significant separation of the fourth cluster which represents the deepest group (12.89 mbgl). Based on this research, several factors are influencing the stability of the phreatic groundwater level and even the performance of the drainage system, the most important of which is the overexploitation from deep groundwater reservoirs such as complex terminal and continental intercalary (in drinking and irrigation) and even the illegal use of the phreatic groundwater with important quantities for irrigation and illegal industries.

Vertical changes in abundance, biomass and community structure of pelagic polychaetes down to 1000 m depths at Station K2 in the western subarctic Pacific Ocean covering the four seasons and day–night

Abstract Pelagic polychaetes are distributed from the sea surface to greater depths of the oceans worldwide, but little information is available regarding their ecology. This study investigated the vertical distribution of abundance, biomass and community structure of pelagic polychaetes at a single station in the western subarctic Pacific based on day–night vertical stratified samples collected from a 0 to 1000 m water column during four seasons covering 1 year. The polychaete abundance and biomass ranged from 0 to 757 ind. 1000 m−3 and 0–6.1 mg WW m−3, respectively. Ten pelagic polychaete species belonging to nine genera and six families were identified. From cluster analysis based on abundance, the polychaete community was divided into five communities. Each community occurred at different depth layers. Two surface groups seen at 0–200 m were dominated by two carnivorous species: Tomopteris septentrionalis and Typhloscolex muelleri. The deepest group, dominated by the particle feeder Pelagobia longicirrata, was seen at 500–1000 m. Two transition groups occurred in the intermediate depths. These vertical distributions of the pelagic polychaete communities were common throughout the season and day. Water mass, food availability and the oxygen minimum layer are put forth as environmental factors that affect the pelagic polychaete community.

Color information from linked color imaging is associated with invasion depth and vascular diameter in superficial esophageal squamous cell carcinoma.

Accurate diagnosis of invasion depth is important for reliable treatment of esophageal squamous cell carcinoma (ESCC), but it is limited to the muscularis mucosae to slight submucosal invasion (MM/SM1). The diagnostic accuracy of invasion depth is unsatisfactory and remains to be improved. We aimed to investigate the association between the color of the superficial ESCC and invasion depth using linked color imaging (LCI) under light-emitting diode (LED) light sources. Lesions diagnosed as superficial ESCC were observed using white light imaging and then by LCI. The color values were calculated using Commission Internationale de l'Eclariage - L*a*b* color space, and the color difference was calculated according to invasion depth. The vascular diameters and vascular angles of the intrapapillary capillary loops were pathologically analyzed. Their correlation with mucosal color was also investigated by LCI. In all, 52 lesions from 48 patients were analyzed. On the basis of invasion depth, the color difference between the normal mucosa and the lesion was larger in the MM/SM1 or deeper group than in the epithelium and the lamina propria mucosa (EP/LPM) group using LCI (P=0.025). The vascular diameter was positively correlated with the b* color value (correlation coefficient=0.302, P=0.033). Observation using LCI under LED light sources may improve the endoscopic diagnosis of the invasion depth of superficial ESCC. Further research is needed to validate its usefulness. (UMIN000024615).

Optical pumping and readout of bismuth hyperfine states in silicon for atomic clock applications.

The push for a semiconductor-based quantum information technology has renewed interest in the spin states and optical transitions of shallow donors in silicon, including the donor bound exciton transitions in the near-infrared and the Rydberg, or hydrogenic, transitions in the mid-infrared. The deepest group V donor in silicon, bismuth, has a large zero-field ground state hyperfine splitting, comparable to that of rubidium, upon which the now-ubiquitous rubidium atomic clock time standard is based. Here we show that the ground state hyperfine populations of bismuth can be read out using the mid-infrared Rydberg transitions, analogous to the optical readout of the rubidium ground state populations upon which rubidium clock technology is based. We further use these transitions to demonstrate strong population pumping by resonant excitation of the bound exciton transitions, suggesting several possible approaches to a solid-state atomic clock using bismuth in silicon, or eventually in enriched 28Si.

Spatial changes in the vertical distribution of calanoid copepods down to great depths in the North Pacific.

Despite its ecological importance, little information is available regarding the spatial and vertical changes in the calanoid copepod community over large geographical regions. This study investigated the spatial and vertical patterns in calanoid copepod abundance and community structure using zooplankton samples collected between depths of 0 and 2,615 m across the North Pacific from 0° to 56°N. A total of 211 calanoid copepod species belonging to 66 genera and 24 families were identified. Calanoid copepod abundance decreased with increasing depth, and few latitudinal differences were detected. Across the entire region, species diversity peaked near 500 to 2,000 m in depth. The calanoid copepod community was separated into seven groups with distinct spatial and vertical distributions. For all groups, the number of species was low (28 to 37 species) in the subarctic region (north of 40°N) and high (116 to 121 species) in the subtropical-tropical region. The deepest group in the subtropical-tropical region was composed of cosmopolitan species, and this group was also observed in deep water in the subarctic region. Indeep water, most of the calanoid copepod community consisted of cosmopolitan species, while an endemiccommunity was observed in the subarctic region. Because the food of deep-sea calanoid copepods originates fromthe surface layer, sufficient and excess flux in the eutrophic subarctic region may be responsible for maintaining the endemic species in the region.

Decoherence mechanisms of209Bi donor electron spins in isotopically pure28Si

Bismuth (209Bi) is the deepest Group V donor in silicon and possesses the most extreme characteristics such as a 9/2 nuclear spin and a 1.5 GHz hyperfine coupling. These lead to several potential advantages for a Si:Bi donor electron spin qubit compared to the more common phosphorus donor. Previous studies on Si:Bi have been performed using natural silicon where linewidths and electron spin coherence times are limited by the presence of 29Si impurities. Here we describe electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) studies on 209Bi in isotopically pure 28Si. ESR and ENDOR linewidths, transition probabilities and coherence times are understood in terms of the spin Hamiltonian parameters showing a dependence on field and mI of the 209Bi nuclear spin. We explore various decoherence mechanisms applicable to the donor electron spin, measuring coherence times up to 700 ms at 1.7 K at X-band, comparable with 28Si:P. The coherence times we measure follow closely the calculated field-sensitivity of the transition frequency, providing a strong motivation to explore 'clock' transitions where coherence lifetimes could be further enhanced.

Decreasing Urea∶Trimethylamine N-Oxide Ratios with Depth in Chondrichthyes: A Physiological Depth Limit?

In marine osmoconformers, cells use organic osmolytes to maintain osmotic balance with seawater. High levels of urea are utilized in chondrichthyans (sharks, rays, skates, and chimaeras) for this purpose. Because of urea's perturbing nature, cells also accumulate counteracting methylamines, such as trimethylamine N-oxide (TMAO), at about a 2∶1 urea∶methylamine ratio, the most thermodynamically favorable mixture for protein stabilization, in shallow species. However, previous work on deep-sea teleosts (15 species) and chondrichthyans (three species) found an increase in muscle TMAO content and a decrease in urea content in chondrichthyans with depth. We hypothesized that TMAO counteracts protein destabilization resulting from hydrostatic pressure, as is demonstrated in vitro. Chondrichthyans are almost absent below 3,000 m, and we hypothesized that a limitation in urea excretion and/or TMAO retention might play a role. To test this, we measured the content of major organic osmolytes in white muscle of 13 chondrichthyan species caught with along-contour trawls at depths of 50-3,000 m; the deepest species caught was from 2,165 m. Urea and TMAO contents changed significantly with depth, with urea∶TMAO declining from 2.96 in the shallowest (50-90 m) groups to 0.67 in the deepest (1,911-2,165 m) groups. Urea content was 291-371 mmol/kg in the shallowest group and 170-189 mmol/kg in the deepest group, declining linearly with depth and showing no plateau. TMAO content was 85-168 mmol/kg in the shallowest group and 250-289 mmol/kg in the deepest groups. With data from a previous study for a skate at 2,850 m included, a second-order polynomial fit suggested a plateau at the greatest depths. When data for skates (Rajidae) were analyzed separately, a sigmoidal fit was suggested. Thus, the deepest chondrichthyans may be unable to accumulate sufficient TMAO to counteract pressure; however, deeper-living specimens are needed to fully test this hypothesis.

Training to deeper compression depth reduces shallow compressions after six months in a manikin model

Introduction Studies show that students, trained to perform compressions between 40 and 50 mm deep, often do not achieve sufficient depth at retention testing. We hypothesized that training to achieve depths >50 mm would decrease the proportion of students with depth <40 mm after 6 months, compared to students trained to a depth interval of 40–50 mm. Methods A basic life support (BLS) self-learning station was attended by 190 third year medicine students. They were first offered the possibility to refresh their skills, following the instructions of a 15 min abbreviated Mini Anne™ video (Laerdal, Norway) using a full size torso and a face shield. This was followed by further training using Resusci Anne Skills Station™ software (Laerdal, Norway). Voice feedback was provided according to randomisation to a standard group (SG) 40–50 mm and a deeper group (DG) >50 mm. Quality of compressions was tested after 6 months. Results The SG and DG groups consisted of 90 (67% female) and 100 (58% female) participants respectively. At the end of training, all students reached the target depth without overlap between groups. After 6 months, the proportion of students achieving a depth <40 mm was 26/89 (29%) in the SG vs. 12/89 (14%) in the DG ( P = 0.01). The proportion of students with a depth >50 mm was 5/89 (6%) for the SG and 44/89 (49%) in the DG ( P < 0.001). Conclusions The educational strategy to train students to a deeper depth, reduced shallow compressions 6 months after training.

Hyperfine Structure and Nuclear Hyperpolarization Observed in the Bound Exciton Luminescence of Bi Donors in Natural Si

As the deepest group-V donor in Si, Bi has by far the largest hyperfine interaction and also a large I = 9/2 nuclear spin. At zero field this splits the donor ground state into states having total spin 5 and 4, which are fully resolved in the photoluminescence spectrum of Bi donor bound excitons. Under a magnetic field, the 60 expected allowed transitions cannot be individually resolved, but the effects of the nuclear spin distribution, -9/2 < or = I(z) < or = 9/2, are clearly observed. A strong hyperpolarization of the nuclear spin towards I(z) = -9/2 is observed to result from the nonresonant optical excitation. This is very similar to the recently reported optical hyperpolarization of P donors observed by EPR at higher magnetic fields. We introduce a new model to explain this effect, and predict that it may be very fast.

Source-side shear wave splitting and upper mantle flow in the Romanian Carpathians and surroundings

We present shear wave splitting measurements from 5 earthquakes that occurred in the Vrancea seismic zone of the Carpathian Arc. S waves from these events, all with magnitudes > 5.4 M w and deeper than 88 km, were recorded at broadband stations of the Global Seismic Network, and the Geoscope and Geofon Networks, and used by us to measure shear wave splitting corrected for sub-station splitting and anisotropy. In order to carry out these corrections we used published shear wave splitting parameters, thus isolating contributions to observed splitting from the Vrancea source region and upper mantle surrounding the Carpathian Arc. The resulting 32 good observations of source-side shear wave splitting, along with 54 null splitting observations (which yield two potential splitting directions) clearly show that upper mantle anisotropy is strongly variable in the region of the tightly curved Carpathian Arc: shear waves taking off from Vrancea along paths that sample the East and Southern Carpathians have fast anisotropy axes parallel to these ranges, whereas those leaving the source region to traverse the upper mantle beneath the Transylvanian Basin (i.e., mantle wedge side) trend NE–SW. Shear waves sampling the East European and Scythian Platforms are separable into two groups, one characterized by fast shear trends to the NE–SW, and a second, deeper group, with trends to NW–SE; also, the majority of null splits occur along paths leaving Vrancea in these NE–E azimuths. We interpret these results to indicate the presence of at least three distinct upper mantle volumes in the Carpathians region: the upper mantle beneath the Carpathian Arc is strongly anisotropic with fabrics parallel to the local arc strike; the Transylvanian Basin upper mantle fabrics trend NE–SW; and the anisotropy beneath the westernmost East European Platform may be characterized by a shallow NW–SE trending fabric concentrated in the cratonic lithosphere of the East European Platform, and a second, deeper fabric with E–W trend marking asthenospheric flow beneath the craton's base. This more complex anisotropy beneath the western edge of the East European Platform would account for both the variability of observed splitting of waves that sample this volume, and also the strong prevalence of nulls observed along eastward-departing azimuths.

Genetic relationships between Nereimyra punctata and N. woodsholea (Hesionidae, Polychaeta)

We present a COI-based parsimony analysis of the relationships between the shallow water, pigmented hesionid polychaete Nereimyra punctata, and a deep-water, unpigmented form with sympatric distribution in Norway and Sweden. Apart from the pigmentation differences, the two forms exhibit no observed morphological differences. The terminals are represented by four specimens each of the two forms from the Trondheimsfjord in Norway, and four each of the two forms from northern Bohuslan in Sweden, plus members of the two hesionids Heteropodarke and Ophiodromus as outgroups. In addition, the analysis includes a topotype of the morphologically similar and unpigmented Nereimyra woodsholea from the Middle Atlantic Bight off the US east coast. The equally weighted matrix includes 132 informative characters. All most-parsimonious trees unequivocally indicate that specimens belonging to the same form (pigmented or unpigmented) from different areas are cladistically closer related to each other than different forms from the same areas. Nereimyra woodsholea is nested within the unpigmented deeper group of the Norwegian and Swedish specimens, thus indicating that this name should be applied to the deep-water form in Norway and Sweden.

Ecology of bathyal polychaete fauna at an Arctic–Atlantic boundary (Faroe–Shetland Channel, North-east Atlantic)

By reference to a series of 15 sampling stations spanning the West Shetland Slope (150–1000 m; Faroe–Shetland Channel, North-east Atlantic) we examined the potential environmental controls on the standing stock, diversity and composition of the polychaete fauna. In contrast to the majority of studied bathyal environments, the Faroe–Shetland Channel has a highly complex and dynamic hydrographic regime, particularly notable for extreme thermal variability at mid-slope depths (i.e. 7°C range at ca. 500 m). Contrary to general expectation, polychaete biomass increased (rather than decreased) with depth. Species diversity exhibited a parabolic pattern with depth, maximum diversity occurring at depths of 350–550 m, rather shallower than observed in other bathyal studies, and possibly linked with a maximum in habitat temperature range. Multivariate analyses of faunal composition suggested a separation of the sampling stations into a shallower and a deeper group, with temperature exerting a major control on polychaete species distributions. The decline in diversity below 600 m (i.e. the descending limb of the parabolic relationship) may be a result of historically limited immigration/recolonization of the thermally isolated Arctic deep-water basins that feed the cold-water flow through the Faroe–Shetland Channel. The bathymetric distribution of polychaetes and other benthos in this region appears to be intimately linked with the thermal regime, having a long-term impact (geological timescales) on the deep-water species pool and leading to local enhancement of diversity where cold- and warm-water masses meet and mix.

Relocation of seismicity preceding the 1984 eruption of Mauna Loa Volcano, Hawaii: Delineation of a possible failed rift

Waveform cross-correlation based repicking of P arrival times and subsequent relocation of 187 earthquakes that occurred near the summit of Mauna Loa, Hawaii, prior to the March 1984 eruption has illuminated a previously obscured structure beneath the northwestern flank. Simultaneous inversion for hypocenters and velocity model parameters using the refined arrival times resulted in well-constrained relative earthquake locations with very low arrival time misfits (average RMS 0.041 s). Pre-eruption seismicity from this time period occurred in two groups: a shallow group located near Mauna Loa’s summit, at depths of 1–3 km, and a deeper group (5–10 km) located 4–6 km northwest of the summit. After relocation, we found that most of the northwest flank earthquakes occurred along a 3-km-long planar feature striking about 60° West of North in a thin band about 1 km thick. There is a temporal migration of epicenters from the northwestern edge of the zone migrating towards the summit. Focal mechanisms in this zone reveal a change in faulting from strike-slip in the southeast to a mix of strike-slip and normal faulting in the northwest. This feature we interpret to be related to a rift zone that was stunted by the buttressing of the adjacent volcanoes Hualalai and Mauna Kea. Previous gravity and magnetic studies provide supporting evidence for the existence of a rift zone. There was only a modest increase in clustering of the summit events. After relocation, hypocenters that were previously located within a diffuse zone (4.5 km) were reduced to a 2.5-km-wide zone. They extend from a depth of 6 km to about sea level, trending toward the summit. The focal mechanisms from the summit events are mix of faulting types without a consistent pattern.

THE USEFULNESS OF ENDOSCOPIC ULTRASONOGRAPHY (EUS) IN THE DIAGNOSIS OF THE DEPTH OF INVASION OF GASTRIC CANCER

The usefulness of preoperative examinations with endoscopic ultrasonography (EUS) in determining operative procedure and ranges of lymph node dissection was examined in 135 patients with gastric cancer. The patients received EUS examinations in order to measure the depth of cancer invasion before undergoing gastrectomies. The EUS results were then compared with the findings of the histological examinations of the resected specimens; the depth of cancer invasion and the degree of lymph node metastasis. The correct diagnosing rates of m-, sm-, mp-cancer groups and ss-cancer or deeper group were 68.1%, 42.4%, 50.0% and 93.3%, respectively, with an overall accuracy of 68.9%. In an analysis of misdiagnosed cases, there were more overdiagnosed cases than underdiagnosed ones. The cases diagnosed as M and SM by the EUS examination had low potential of lymphnode metastasis; and no cases were observed with n2 or more distant lymphnode metastasis. It is suggested that positive adoption of conservative surgery with Dl-level lymph node dissection would be appropriate for patients with EUS diagnosis of M or SM.

Low-temperature adaptation of deep-sea bacteria isolated from the Japan Trench

Growth responses for bacteria culturable at 4 °C, isolated randomly from three different habitats comprising surface seawater, deep-sea water (5000 to 6000 m) and deep-sea sediments (ca. 2200 to 6000 m), were tested for growth at temperatures from 4 to 30 °C. All 67 isolates grew well at 4 and 20 °C, indicating that they were psychrotrophic. Compared with the surface seawater, psychrotrophic bacterial groups from the deep-sea were rich in bacteria with higher growth yield at 4 °C and lower doubling time at 30 °C. According to Ratkowsky's square root analysis, the deep-sea water group was characterized by lower predicted minimum growth temperature (mean Tmin = 266.2 K) than the surface-water group (269.9 K), while the lowest Tmin was measured in the deep-sea sediment group (263.9 K). Lower Tmin was also found in a deeper group among the sediment bacterial group. These data suggest that most of deep-sea bacterial isolates consist of members possessing higher adaptability to low-temperature environments. Psychrotrophs from deep-sea water also demonstrated an abundance of Gram-negative bacteria which were tentatively identified as belonging to the genus Moraxella, while psychrotrophs from surface water were more diverse. Bacillus spp. and Gram-positive coryneform bacteria dominated in deep-sea sediments, decreasing with increasing depth. Restriction fragment length polymorphism analysis of PCR-amplified 16S rDNA of Moraxella-like bacteria showed that deep-sea strains were different from surface strains and from the four known species tested belonging to the Moraxella–Psychrobacter group.

Regional coda Q in Costa Rica, Central America

Regional seismic apparent attenuation was estimated for Costa Rica, Central America, by using a time domain single scattering model of the shear wave coda decay of local earthquakes. The sensitivity of coda Q (Qc) measurements with respect to geological differences in the crust is demonstrated in eight sub-regions with a large variety of tectonic and geologic properties. The Qc estimations were performed for 96 selected local earthquakes recorded at 13 sites during a period of three months. In order to model the scattering as a weak process and to avoid short distance nonlinear effects, we made use of the S-wave coda data only from events within a hypocentral distance of 12 to 106 km with a lapse time between 9 and 53 s. Seismograms were also divided into groups with three different focal depths d, namely d<21 km, 21 km<d<43 km and 43 km<d<94 km. As in many other investigations, the Qc values are frequency dependent in the range 1–9 Hz, and are approximated by a least-squares fit to the power law Qc(f) = Q0(f/f0)n. The estimated parameters of the power-law dependence of Qc for the whole region, including all depths and possible wave paths, are Q0 = 91 (± 8.4) and n = 0.72 (±0.071). Differences in the parameter of Qc for different depths intervals are small, ranging from Q0 = 90 (±0.7) and n = 0.70 (±0.006) for the uppermost group, with focal depths less than 21 km, to Q0 = 97 (±0.7) and n = 0.79 (±0.005) for the deepest group with focal depths larger than 43 km. The regional differences in Qc for the eight sub-regions are significantly larger when compared with the differences between the three focal depth groups. An attempt is made to interpret the variation of Qc in terms of spatial variations in the geologic and tectonic properties of the crust. Other authors have found that the frequency exponent n might be larger in active tectonic areas and smaller in more stable regions. In the northern region of the Pacific coast we obtain a value of n = 0.52 (±0.011), which might indicate a lower level of tectonic activity when compared with n = 0.85 (±0.015) and 0.83 (±0.031), respectively, for the central and southern sub-regions along the Pacific coast. The latter two sub-regions are located closer to the active area near the Cocos ridge. We obtain the frequency exponent n = 0.72 (±0.052) along a major shear zone in central Costa Rica characterized by high volcanic activity and large geologic complexity. Values of n along the Panamean border are 0.62 (±0.029) in the north and 0.86 (±0.009) and 0.83 (±0.031) in two regions adjacent to the subduction zone and the Cocos Ridge, respectively.

Localization of enkephalin immunoreactivity in the spinal cord of the long‐tailed ray Himantura fai

Enkephalin-like immunoreactivity (ENK-LI) was found throughout the spinal cord of the long-tailed ray Himantura fai. The densest ENK-LI was in the superficial portion of lamina A of the dorsal horn. Lamina B and the deeper parts of lamina A contained radially oriented, labelled fibres. Laminae C, D, and E contained many longitudinally orientated fascicles which were surrounded by a reticulum of transversely orientated, labelled fibres, some of which projected into the ventral and lateral funiculi. Labelled fibres were found in the dorsal commissure and around the central canal, but the later did not cross the midline. One-third of all enkephalinergic cells were found throughout laminae A and B, while two-thirds were located in the medial half of C, D, and E. Occasionally a labelled cell was located in the lateral funiculus. The ventral horn (laminae F and G) contained many enkephalinergic fibres but no labelled nuclei. A few dorsal column axons contained ENK-LI. In the lateral funiculus there were two groups of labelled axons, a superficial, dorsolateral group, and a deeper group, occupying a crescent-shaped region. The ventral funiculus also contained many labelled axons. The central projection of the dorsal root passed through the substantia gelatinosa and divided into rostrally and caudally projecting fascicles within lamina C. The root, and these fascicles, both lacked ENK-LI. In contrast, the fascicles in laminae D and E did contain enkephalinergic fibres. The origin of the various fibre systems and the role of enkephalin in the regulation of sensory processing and motor output are discussed. © 1996 Wiley-Liss, Inc.

Localization of enkephalin immunoreactivity in the spinal cord of the long-tailed ray Himantura fai.

Enkephalin-like immunoreactivity (ENK-LI) was found throughout the spinal cord of the long-tailed ray Himantura fai. The densest ENK-LI was in the superficial portion of lamina A of the dorsal horn. Lamina B and the deeper parts of lamina A contained radially oriented, labelled fibres. Laminae C, D, and E contained many longitudinally oriented fascicles which were surrounded by a reticulum of transversely oriented, labelled fibres, some of which projected into the ventral and lateral funiculi. Labelled fibres were found in the dorsal commissure and around the central canal, but the later did not cross the midline. One-third of all enkephalinergic cells were found throughout laminae A and B, while two-thirds were located in the medial half of C, D, and E. Occasionally a labelled cell was located in the lateral funiculus. The ventral horn (laminae F and G) contained many enkephalinergic fibres but no labelled nuclei. A few dorsal column axons contained ENK-LI. In the lateral funiculus there were two groups of labelled axons, a superficial, dorsolateral group, and a deeper group, occupying a crescent-shaped region. The ventral funiculus also contained many labelled axons. The central projection of the dorsal root passed through the substantia gelatinosa and divided into rostrally and caudally projecting fascicles within lamina C. The root, and these fascicles, both lacked ENK-LI. In contrast, the fascicles in laminae D and E did contain enkephalinergic fibres. The origin of the various fibre systems and the role of enkephalin in the regulation of sensory processing and motor output are discussed.