Outflow Currents Research Articles

고등학교 과학 교과서 인공위성 해수면온도 영상 오류 분석과 예비교사들의 반응

해수면온도는 급변하는 기후를 이해하는 가장 중요한 해양 변수 중의 하나이므로 과학 교과서에는 정확하고 오류없는 해수면온도 영상이 제시되어야 한다. 그러나 고등학교 교과서에 제시된 해수면온도 영상들은 다양한 원인에서 비롯된 많은 오류들을 가지고 있었다. 본 연구는 제 7차 교육과정에 근거한 24종의 고등학교 과학 교과서, 지구과학 I, 지구과학 II 교과서의 36개의 인공위성 해수면온도 영상을 17개 항목에 대하여 분석하였다. 해수면온도 영상 처리 과정에서 생긴 구름 제거, 육지 마스킹, 색상표, 위치 정보, 시간 표시와 관련된 오류와 인공위성에 대한 기본적인 표현 오류를 조사하였다. 예비교사 25명에게 문제가 있는 대표적인 인공위성 영상들을 제시하고 설문을 실시하고 반응을 분석하였다. 그 결과 대부분의 예비교사들은 해수면온도 영상 처리 과정에서 발생할 수 있는 오류에 대하여 인지하지 못하였으며, 해빙, 강수 유입, 한류와 같은 실제 해양현상과 연관지어 해수면온도를 이해하려는 경향을 보였다. 따라서 교과서 해수면온도 영상은 본 연구에서 제시한 세부 항목들을 고려하여 정확하게 처리되어야 한다. Sea Surface Temperature (SST) is one of the most important oceanic variables to understand rapidly-changing climate, so that accurate and error-free SST images should be presented in school science textbooks. However, satelliteobserved SST images in the high-school textbooks presented some errors caused by various reasons. This study analyzed 36 satellite images for SST presented in 24 kinds of high-school textbooks (earth science I and II textbooks on the basis of the 7th National Curriculum) for 17 items. This study investigated errors in image processing such as cloud removal, land masking, color bar, geological and time information, and some erroneous expressions related to the fundamental information of satellites. Twenty five pre-service teachers filled out a survey about several problematic satellite images, and their responses were analyzed. As a result, most of the pre-service teachers did not recognize the errors associated with image processing and tended to comprehend the SST errors as real oceanographic phenomena such as sea ice, river outflow, or cold current. Therefore, satellite SST images in the textbooks should be accurately presented by including detailed items suggested in this study.

Spatial distribution of phytoplankton in the White Sea in the late summer period with regard to the water structure and dynamics

The species composition and biomass of the phytoplankton, as well as the hydrophysical and hydrochemical characteristics of the water masses, were estimated for different areas of the White Sea at 24 stations for the period of August 26 to September 3, 2007. The micronutrient concentrations were lower compared to the average long-term values for the summer period. The total biomass of phytoplankton (Bt) varied from 87 to 1914 mg C/m2. For most of the studied sites, Bt was low; dinoflagellates were the most abundant species. Diatoms dominated in the areas of elevated hydrodynamic activity, i.e., in the Gorlo (vertical mixing of the water layers), in intrusions of the Gorlo water masses into the basin of the White Sea, and in the peripheral areas of the Dvina outflow current. The Bt was also the highest in the listed areas.

Spin separation via a three-terminal Aharonov–Bohm interferometers

We propose a three-terminal ring-type device which contains a single-level quantum dot (QD) to extract or separate the spin-up and the spin-down electrons that are injected into the QD from a middle lead, into the left and the right leads, respectively. This scheme is based on the Rashba spin-orbit interaction (RSOI) in the bridge between the left and the right leads and is free from magnetic field or magnetic material. We find that both the spin directions and the magnitude of the outflow currents in the left and the right leads can be tuned by the RSOI strength and the structure parameters.

グリーン関数法によるパッケージされたＬＳＩの電流分布推定に関する検討

In this study, we focused on high frequency currents on LSI. We estimated the high-frequency current distribution on a packaged LSI using the Green's Function method, in which the distribution of current is estimated by a two-dimensional magnetic field as an inverse problem. We used a packaged IC mounted on the PCB and estimated the current distribution on the packaged IC. As a result, we could observe the high-frequency current distribution on the packaged IC and the in- and outflow currents of the packaged IC as emission sources.

Studying Daphnia feeding behavior as a black box: a novel electrochemical approach

We present a novel approach for examining the complex feeding behavior of a filter feeder at a previously unexploited scale. A Daphnia lives in a viscous environment and thus creates a feeding current with a distinct laminar inflow and a repetitive pulsed outflow. We propose that by treating the feeding apparatus as a black box, and using the pulsed outflow current as a surrogate to the inside working of the apparatus, we can calculate feeding rate in near real time. The structure of the outflow is interpreted as a direct representation of the organism’s response to its environment. Therefore, we examine how the work performed by an organism’s feeding apparatus is altered according to environmental factors and metabolic demands. Our approach is an integration of optical (Schlieren system) and electrochemical (chronoamperometry) techniques that allow for real time visualization and temporal analysis of flow systems, respectively. As electrochemistry requires a tracer chemical, we employed low dopamine concentrations (≤ 1mM), and tested the effect of dopamine on the heart rate and swimming of Daphnia. It appears that dopamine free in solution at concentrations below 10 mM has no adverse effects on the organism, and all observed differences in Daphnia feeding behavior were due to environmental or metabolic factors. The feeding nature of daphnids in the presence or absence of food, and differences between the sexes is reported. Our results indicate that in the absence of food a Daphnia has a strict and repetitive feeding behavior with short delays between pumping actions. However, in the presence of food this behavior becomes complex, with increased delays between pumps, perhaps designed to maximize feeding efficiency. Our observations demonstrate that males have a higher appendage beat frequency than females under identical conditions. We hypothesize that the difference may be dictated by metabolic demand, as a male spends more time actively seeking a mate. The application of electrochemistry to the study of Daphnia feeding behavior is an improvement over current methods for its near real time quantification of behavioral response, its versatile application under varying environmental conditions and its extreme sensitivity to changes in the organism’s feeding behavior. This technique is a valuable addition to the current tools available for studying Daphnia feeding behavior and will allow us to learn more about the interactions of an organism with its environment.

Mediterranean outflow strengthening during northern hemisphere coolings: A salt source for the glacial Atlantic?

High-resolution grain size and magnetic susceptibility records from the eastern Gulf of Cadiz (site MD99-2339; 1170 m water depth) reveal contourites formed by the Mediterranean Outflow (MOW) during the last 47 kyr BP. Oscillations in the MOW's intensity occurred in phase with Greenland temperature variations with a stronger outflow during northern hemisphere coolings such as Dansgaard-Oeschger stadials, Heinrich events, and the Younger Dryas. Benthic δ 13C data implies the Western Mediterranean Deep Water as one of the main sources feeding the outflow current, while differential changes in the properties of the Mediterranean source and entrained North Atlantic Central Water largely control the MOW's strength. Detailed studies for Heinrich events 1, 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern Gulf of Cadiz, while incursions of icebergs and subpolar surface water were not favorable for the MOW's intensification. As the MOW was strong when the Atlantic's thermohaline circulation (THC) was weakened, the heat and salt injected by the MOW into the intermediate North Atlantic waters might have preconditioned the THC to switch from the stadial to the interstadial mode.

Electric currents streaming out of stressed igneous rocks – A step towards understanding pre-earthquake low frequency EM emissions

Transient electric currents that flow in the Earth’s crust are necessary to account for many non-seismic pre-earthquake signals, in particular for low frequency electromagnetic (EM) emissions. We show that, when we apply stresses to one end of a block of igneous rocks, two currents flow out of the stressed rock volume. One current is carried by electrons and it flows out through a Cu electrode directly attached to the stressed rock volume. The other current is carried by p-holes, i.e., defect electrons on the oxygen anion sublattice, and it flows out through at least 1 m of unstressed rock to meet the electrons that arrive through the outer electric circuit. The two outflow currents are part of a battery current. They are coupled via their respective electric fields and fluctuate. Applying the insight gained from these laboratory experiments to the field, where large volume of rocks must be subjected to ever increasing stress, leads us to suggest transient, fluctuating currents of considerable magnitude that would build up in the Earth’s crust prior to major earthquakes.

Equilibration and Circulation of Red Sea Outflow Water in the Western Gulf of Aden*

Abstract Hydrographic, direct velocity, and subsurface float observations from the 2001 Red Sea Outflow Experiment (REDSOX) are analyzed to investigate the gravitational and dynamical adjustment of the Red Sea Outflow Water (RSOW) where it is injected into the open ocean in the western Gulf of Aden. During the winter REDSOX cruise, when outflow transport was large, several intermediate-depth salinity maxima (product waters) were formed from various bathymetrically confined branches of the outflow plume, ranging in depth from 400 to 800 m and in potential density from 27.0 to 27.5 σθ, a result of different mixing intensity along each branch. The outflow product waters were not dense enough to sink to the seafloor during either the summer or winter REDSOX cruises, but analysis of previous hydrographic and mooring data and results from a one-dimensional plume model suggest that they may be so during wintertime surges of strong outflow currents, or about 20% of the time during winter. Once vertically equilibrated in the Gulf of Aden, the shallowest RSOW was strongly influenced by mesoscale eddies that swept it farther into the gulf. The deeper RSOW was initially more confined by the walls of the Tadjura Rift, but eventually it escaped from the rift and was advected mainly southward along the continental slope. There was no evidence of a continuous boundary undercurrent of RSOW similar to the Mediterranean Undercurrent in the Gulf of Cadiz. This is explained by considering 1) the variability in outflow transport and 2) several different criteria for separation of a jet at a sharp corner, which indicate that the outflow currents should separate from the boundary where they are injected into the gulf.

The degree of potassium channel blockade and the risk of torsade de pointes: the truth, nothing but the truth, but not the whole truth

This editorial refers to ‘Anti-HERG activity and the risk of drug-induced arrhythmias and sudden death’† by M.L. De Bruin et al. , on page 590 Several anti-arrhythmic drugs, as well as medications not intended for cardiac indications, block a specific potassium channel named IKr (the rapid delayed rectifying potassium current). In the case of the anti-arrhythmic drugs, IKr channels are purposely targeted. By blocking potassium outflow currents, the anti-arrhythmic drugs prolong the action potential. This action (depicted in the electrocardiogram as prolongation of the QT interval) can be advantageous given that prolongation of the action potential also lengthens the refractory period, thereby suppressing common arrhythmias. Unfortunately, by a mechanism explained elsewhere,1 IKr blockade may lead to excessive QT prolongation and trigger a polymorphic ventricular tachyarrhythmia (torsade de pointes) that may degenerate into ventricular fibrillation. Furthermore, because of its unique three-dimensional characteristics,2 IKr channels are very easily blocked by the small molecules of numerous non-cardiac drugs. The result is that otherwise harmless and valuable drugs, like the non-sedative antihistamines and the quinolone-antibiotics, become potentially lethal pro-arrhythmic medications.3 An important study by De Bruin et al .4 suggests that a strong correlation exists between the strength of IKr blockade caused by a given drug and its pro-arrhythmic potential. The concept that stronger IKr blockers will lead not only to more QT prolongation but also to higher arrhythmic risk is so logical that the reader will be left wondering why this study was ever conducted, let alone published. In reality, however, this concept has been difficult to prove.5 Amiodarone, ranolazine, and verapamil illustrate that the correlation between IKr … *Corresponding author. Tel: +972 524266859; fax: +972 36974416. E-mail address : saviskin{at}tasmc.health.gov.il

Dispersal of suspended sediments in the turbid and highly stratified Red River plume

The Red River, annually transporting 100 million tons of sediment, flows into a shallow shelf sea where it rapidly deposits most of its sediment on a prograding delta front. Oceanographic cruises were carried out in February–March and July–August 2000 to determine the vertical structure of the Ba Lat river plume and sediment transport patterns on the delta front. The surface waters in the coastal zone were strongly stratified with a low density and high sediment concentration during the larger part of the wet season, caused by low mixing rates of river plumes with ambient water. The river plume is advected to the south by a well-developed coastal current which originates from the river plumes that enter the Gulf of Tonkin North of the Ba Lat and are deflected southward by the Coriolis force. Sediment predominantly leaves the surface plume by settling from suspension and less by mixing of fresh and marine water. A one-dimensional model for plume deposition valid for fair weather conditions indicates that most sediment is deposited within 10 km and southward of the river mouth. Of prime importance for this depositional pattern is the phase relation between river outflow and tidal currents, in combination with the southward surface flow; alongshore advection is very low during outflow of the turbid river plume. The agreement of modeled plume sedimentation patterns with long-term bathymetric changes strongly suggests that fair weather depositional processes determine delta front development. This may be related to the fact that reworking of sediment mainly occurs several months after the peak deposition period; in the meantime sediment compaction and consolidation have increased the shear strength of deposited sediments.

Observed tidal currents outside Block Island Sound: Offshore decay and effects of estuarine outflow

An array of moored profiling current meters on the inner continental shelf 15–65 m deep is used to investigate tidal currents outside the Block Island Sound and Long Island Sound estuarine system. The M2 constituent dominates due to near‐resonant semi‐diurnal estuarine response. Vertical‐mean M2 currents rotate clockwise in time in ellipses elongated toward the estuary mouth with little sensitivity to complex local bathymetry; semi‐major axes decay sharply offshore (55 to 20 cm/s over 10 km) in agreement with the nearly inverse‐square radius dependence of a kinematic theory. Estimated tidal volume exchange out of Block Island Sound to the south is 2.9 × 105 m3/s. Observed vertical structure of M2 ellipses in the deepest 10–20 m (amplitude decay, ellipse flattening, major axis turning clockwise, phase advance) is generally captured well by optimally fit frictional solutions despite the fact that they omit bathymetry and include stratification only indirectly through its influence on eddy viscosity. In the upper water column, vertical structure varies seasonally: Mid‐depth ellipses enlarge in spring; near‐surface ellipses are larger (smaller) than optimal‐fit solutions in fall/winter (spring). Observed seasonal‐average estuarine outflow includes surface‐intensified Coriolis‐deflected mean flow that strengthens and spreads farther offshore in spring. Richardson numbers based on moored hydrographic profiler records suggest spring stratification suppresses deep eddy viscosities, which in frictional solutions can explain mid‐depth ellipse enlargement. An inviscid theory for mean‐flow modifications due to ambient vorticity of estuarine outflow currents is shown to be the most plausible explanation for observed seasonal changes in near‐surface tidal ellipses.

Interannual variability and sensitivity study of the ocean circulation and thermohaline structure in Prince William Sound, Alaska

The interannual variability and sensitivity of ocean circulation and the thermocline structure of Prince William Sound, Alaska were examined using a 3D circulation model. A 4-year (1995–1998) simulation compared well with field observations of circulation and monthly mean sea surface temperature at NOAA Station 46060. Seasonal circulation regimes were characterized by an anticyclonic gyre in the central sound in January–April, and a strong cyclonic gyre in the central sound in September to December, while summer was the transition period of the two circulation regimes. The size, position and strength of the gyres and thermohaline depth in the central sound showed small interannual variability. Freshwater displayed a very strong seasonal cycle in the sound with minimum in April–May and maximum in October with a spatial distribution of more in the northwest sound and less in the other areas. The simulated freshwater thickness in the whole sound showed up to 20% interannual variability related to wind. The numerical oil spill drift experiments also showed a large interannual variability of possible oil spill trajectories. Sensitivity studies showed the relative importance of each model forcing: (1) wind has more impact on the surface circulation and mixed layer depth. Without wind, the surface current became weaker and the thermocline became shallower; (2) tidal current is a major current in the sound and important to surface and bottom mixing. Without tide, the thermocline depth became shallower; (3) the magnitude of the Alaska coastal current (ACC) inflow determined the outflow current through Montague Strait. Doubled ACC inflow could change the cyclonic circulation pattern in October in case of normal or less ACC inflow into a northward jet with a small accompanying anticyclonic gyre and strongly flush the west sound in addition to the central sound. Also, double ACC inflow would increase the mix-layer depth significantly; and (4) the surface T, S restoring is critical to maintain T, S seasonal cycle and surface circulation patterns. Salinity was the most important factor determining the central sound circulation patterns.

Fast Optimal Design of Semiconductor Devices

This paper presents a new approach to the design of semiconductor devices, which leads to fast optimization methods whose numerical effort is of the same order as a single forward simulation of the underlying model, the stationary drift-diffusion system. The design goal we investigate is to increase the outflow current on a contact for fixed applied voltage; the natural design variable is the doping profile. By reinterpreting the doping profile as a state variable and the electrostatic potential as the new design variable, we obtain a simpler optimization problem, whose Karush--Kuhn--Tucker conditions partially decouple. This property allows us to construct efficient iterative optimization algorithms, which avoid solving the fully coupled drift-diffusion system, and need only solves of the continuity equations and their adjoints. The efficiency and success of the new approach is demonstrated in several numerical examples.

A Three-Dimensional Simulation of the Formation of Anticyclonic Lenses (Meddies) by the Instability of an Intermediate Depth Boundary Current

The evolution of a buoyancy-driven intermediate water current along an idealized continental slope is investigated using a three-dimensional primitive equation ocean model. The outflow current, originating in a marginal sea, flows northward along a linear sloping bottom where it undergoes considerable mixing. For a parameter range resembling the Mediterranean outflow, the flow becomes hydrodynamically unstable. The intruding, relatively dense outflow water interacts with the overlaying slope water by inducing vortex compression and stretching. The phase relation between the upper-layer and lower-layer perturbations indicates that baroclinic instability is the driving mechanism in the initial destabilization. As the disturbances grow to large amplitude, dipoles are formed and move away from the boundary current in a westward direction. While the amplifying anticyclones wrap around the intruding low potential vorticity water, the cyclones usually entrain ambient water and decrease in strength. Isolated anticyclones finally separate from the boundary current and develop a southward translation component. In some cases dipolar structures remain intact and propagate to the west. In the slope water strong cyclones and somewhat weaker anticyclones are formed periodically and travel in the direction of the bottom flow. The upper-layer flow shows surface expressions of the middepth lenses that develop as meddies. These penetrate into the ambient slope water and gain a barotropic velocity component. The adjustment process is discussed in terms of potential vorticity conservation. The instability mechanism discussed here does not require any topographic irregularities. Sensitivity experiments, however, suggest that canyons or capes introduce an additional source of vorticity and may lead to the observed localization of spawning events.

The Cadiz margin study off Spain: an introduction

The Cadiz continental margin of the northeastern Gulf of Cadiz off Spain was selected for a multidisciplinary project because of the interplay of complex tectonic history between the Iberian and African plates, sediment supply from multiple sources, and unique Mediterranean Gateway inflow and outflow currents. The nature of this complex margin, particularly during the last 5 million years, was investigated with emphasis on tectonic history, stratigraphic sequences, marine circulation, contourite depositional facies, geotechnical properties, geologic hazards, and human influences such as dispersal of river contaminants. This study provides an integrated view of the tectonic, sediment supply and oceanographic factors that control depositional processes and growth patterns of the Cadiz and similar modern and ancient continental margins.

Influence of the Atlantic inflow and Mediterranean outflow currents on Late Quaternary sedimentary facies of the Gulf of Cadiz continental margin

The late Quaternary pattern of sedimentary facies on the Spanish Gulf of Cadiz continental shelf results from an interaction between a number of controlling factors that are dominated by the Atlantic inflow currents flowing southeastward across the Cadiz shelf toward the Strait of Gibraltar. An inner shelf shoreface sand facies formed by shoaling waves is modified by the inflow currents to form a belt of sand dunes at 10–20 m that extends deeper and obliquely down paleo-valleys as a result of southward down-valley flow. A mid-shelf Holocene mud facies progrades offshore from river mouth sources, but Atlantic inflow currents cause extensive progradation along shelf toward the southeast. Increased inflow current speeds near the Strait of Gibraltar and the strong Mediterranean outflow currents there result in lack of mud deposition and development of a reworked transgressive sand dune facies across the entire southernmost shelf. At the outer shelf edge and underlying the mid-shelf mud and inner shelf sand facies is a late Pleistocene to Holocene transgressive sand sheet formed by the eustatic shoreline advance. The late Quaternary pattern of contourite deposits on the Spanish Gulf of Cadiz continental slope results from an interaction between linear diapiric ridges that are oblique to slope contours and the Mediterranean outflow current flowing northwestward parallel to the slope contours and down valleys between the ridges. Coincident with the northwestward decrease in outflow current speeds from the Strait there is the following northwestward gradation of contourite sediment facies: (1) upper slope sand to silt bed facies, (2) sand dune facies on the upstream mid-slope terrace, (3) large mud wave facies on the lower slope, (4) sediment drift facies banked against the diapiric ridges, and (5) valley facies between the ridges. The southeastern sediment drift facies closest to Gibraltar contains medium–fine sand beds interbedded with mud. The adjacent valley floor facies is composed of gravelly, shelly coarse to medium sand lags and large sand dunes on the valley margins. By comparison, the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand. Because of the complex pattern of contour-parallel and valley-perpendicular flow paths of the Mediterranean outflow current, the larger-scale bedforms and coarser-grained sediment of valley facies trend perpendicular to the smaller-scale bedforms and finer-grained contourite deposits of adjacent sediment drift facies. Radiocarbon ages verify that the inner shelf shoreface sand facies (sedimentation rate 7.1 cm/kyr), mid-shelf mud facies (maximum rate 234 cm/kyr) and surface sandy contourite layer of 0.2–1.2 m thickness on the Cadiz slope (1–12 cm/kyr) have deposited during Holocene time when high sea level results in maximum water depth over the Gibraltar sill and full development of the Atlantic inflow and Mediterranean outflow currents. The transgressive sand sheet of the shelf, and the mud layer underlying the surface contourite sand sheet of the slope, correlate, respectively, with the late Pleistocene sea level lowstand and apparent weak Mediterranean outflow current.

Interaction of tectonic and depositional processes that control the evolution of the Iberian Gulf of Cadiz margin

This study provides an integrated view of the growth patterns and factors that controlled the evolution of the Gulf of Cadiz continental margin based on studies of the tectonic, sedimentologic and oceanographic history of the area. Seven sedimentary regimes are identified, but there are more extensive descriptions of the late Cenozoic regimes because of the larger data base. The regimes of the Mesozoic passive margin include carbonate platforms, which become mixed calcareous–terrigenous deposits during the Late Cretaceous–early Tertiary. The Oligocene and Early Miocene terrigenous regimes developed, in contrast, over the active and transcurrent margins near the African–Iberian plate boundary. The top of the Gulf of Cadiz olistostrome, emplaced in the Late Miocene, is used as a key horizon to define the `post-orogenic' depositional regimes. The Late Miocene progradational margin regime is characterized by a large terrigenous sediment supply to the margin and coincides with the closing of the Miocene Atlantic–Mediterranean gateways. The terrigenous drift depositional regime of the Early Pliocene resulted from the occurrence of high eustatic sea level and the characteristics of the Mediterranean outflow currents that developed after the opening of the Strait of Gibraltar. The Late Pliocene and Quaternary regimes are dominated by sequences of deposits related to cycles of high and low sea levels. Deposition of shelf-margin deltas and slope wedges correlate with regressive and low sea level regimes caused by eustasy and subsidence. During the highstand regimes of the Holocene, inner shelf prograding deltas and deep-water sediment drifts were developed under the influence of the Atlantic inflow and Mediterranean outflow currents, respectively. A modern human cultural regime began 2000 years ago with the Roman occupation of Iberia; human cultural effects on sedimentary regimes may have equalled natural factors such as climate change. Interplay of tectonic and oceanographic controls dominated the evolution of the Cadiz margin during the Cenozoic. Depositional sequences formed where the tectonic setting provided the accommodation space and the shape of the deposits has been greatly influenced by the strong unidirectional Atlantic inflow currents on the shelf and Mediterranean outflow currents on the slope. The entire cycle of the inflow and outflow deposition along the margin has been controlled first by the tectonic evolution of the Betic and Rif gateways, which become closed during the Late Miocene, and after the Messinian by the opening of the Strait of Gibraltar. Strong current development during eustatic sea level highstands of the Pliocene and Quaternary has controlled deposition because of maximum sill depths at Gibraltar for water circulation. Lowstand sea levels slowed circulation and resulted in mud drapes over the slope and regressive stratigraphic sequences over the shelf. More recently, the human industrial revolution has caused heavy metal contamination of sediment and water over the Cadiz margin. Human activity also has affected sedimentation rates because of deforestation that caused increased depositional rates near undammed rivers and decreased rates where rivers have been dammed. Future research efforts will need to focus on: (1) the effect of increased Mediterranean outflow caused by river damming plus global warming and the increased outflow as a potential trigger for new ice ages; (2) assessments of geologic hazards for planning man-made shoreline structures, developing offshore petroleum resources and maintaining undersea communications cables; and (3) confirmation of the general geologic history of the Cadiz margin.

Scale-free energy dissipation and dynamic phase transition in stochastic sandpiles

We study numerically scaling properties of the distribution of cumulative energy dissipated in an avalanche and the dynamic phase transition in a stochastic directed cellular automaton [B. Tadi\'c and D. Dhar, Phys. Rev. Lett. {\bf 79}, 1519 (1997)] in d=1+1 dimensions. In the critical steady state occurring for the probability of toppling $p\ge p^\star$= 0.70548, the dissipated energy distribution exhibits scaling behavior with new scaling exponents $\tau_E $ and D_E for slope and cut-off energy, respectively, indicating that the sandpile surface is a fractal. In contrast to avalanche exponents, the energy exponents appear to be p- dependent in the region $p^\star \le p <1$, however the product $(\tau_E-1)D_E$ remains universal. We estimate the roughness exponent of the transverse section of the pile as $\chi =0.44\pm 0.04$. Critical exponents characterizing the dynamic phase transition at $p^\star $ are obtained by direct simulation and scaling analysis of the survival probability distribution and the average outflow current. The transition belongs to a new universality class with the critical exponents $\nu_\| =\gamma =1.22 \pm 0.02$, $\beta =0.56\pm 0.02$ and $\nu_\bot = 0.761 \pm 0.029$, with apparent violation of hyperscaling. Generalized hyperscaling relation leads to $\beta + \beta ^\prime = (d-1)\nu_\bot $, where $\beta ^\prime = 0.195 \pm 0.012$ is the exponent governed by the ultimate survival probability.

Phosphorus transportation processes in Gehu Lake (Ⅰ):phosphorus balance and processes predictions

在滆湖磷的来源途径调查和磷迁移过程模型建立的基础上,计算了磷的平衡及磷浓度的变化趋势。结果表明,滆湖磷的年入湖量为270t,年出湖量为174.5t,滞留系数为0.35。在适当控制和合理利用磷资源的情况下,滆湖水体将继续维持目前的中营养水平;反之,隔湖磷浓度将逐年上升,湖水富营养化的进程将会大大加快。;On the basis of phosphorus source investigation and transportation modelling, the phosphorus balance ivS studied and the phosphorus concentration dynamics predicted. In Gehu Lake, the total input for phosphorus ivS 270t/a, and output 174.5t/a, with a deposit coefficient of 35%. The main input ways are inflow current, cage aquaculture and feeding. The main output ways are outflow current, harvest of fish and harvest of aquatic plants. The models of phosphorus transportation processes show that Gehu Lake will remain mesotrophic under the maintenance of macrophyte biomass. Otherwise the phosphorus concentration would be raised, and algea will become dominent to make the lake eutrophic.

Initiation of a Solitary Wave Family in the Demise of a Nocturnal Thunderstorm Density Current

Abstract This paper describes the characteristics and evolving nature of a vigorous thunderstorm density current very early in the morning of 9 May 1981 in Oklahoma. Because the ambient lower atmosphere was stratified, interesting interactions between the outflow current and the ambient environment resulted. The leading portion of the current was modulated by at least three gravity wavelike perturbations of horizontal spacing 12 km which initially coexisted with it. However, as the current evolved, it initiated an undular borelike disturbance which propagated ahead into the stable boundary layer, carrying cold outflow air in large amplitude rolls. Eventually the wave family left the decelerating outflow air in its wake. This borelike disturbance resembles the Australian “morning glory” phenomenon and appears to represent an early stage in the development of a solitary wave family. The observations resemble other reported morning glories and solitary waves as well their laboratory and numerically simulated...