Large Prisms Research Articles

Original papers: A combination horizontal/vertical prism bar A precisely calibrated tool for use in front of one eye

The authors used an optical bench to investigate calibration and errors from improper positioning of prism bars manufactured by R.O. Gulden and Luneau. They urged Gulden to redesign its prism bars to be used back-to-back in front of one eye. The horizontal bar is held with its flat face posteriorly within a channel on the flat face of the vertical bar; the interface is positioned perpendicular to the direction of the fixation object, which demands that the horizontal prism bar be calibrated in the frontal plane position and the vertical bar in the Prentice position. Analysis of calibration demonstrated that Gulden's new combination horizontal/vertical prism bar can be used without significant error (within + 0.5δ of labelled values). Gulden's old vertical prism bar is also calibrated in the Prentice position. Luneau's horizontal and vertical prism bars are calibrated close to the frontal plane position (within +1.0δ and +0.4δ respectively). Improper positioning demonstrated an increasing error with larger prisms. Luneau's 25δ segment measured 27.8δ in the Prentice position, the 40δ segment 67.5δ. The 25δ segment of Gulden's new and old vertical prism bars measured 23.25δ in the frontal plane position. Gulden's vertical prism bars should always be held with the flat surface toward the examiner. Luneau's horizontal and vertical prism bars should be held one in front of each eye when used simultaneously; thus, neither eye is looking directly at the fixation object and defining primary and secondary deviations is not possible. The combination horizontal/vertical prism bar is manufactured by Gulden Ophthalmics, 225 Cadwalader Avenue, Elkins Park, PA 19117-2097. The Luneau prism bars are manufactured by Luneau Ophtalmologie, B.P. 252, 28005 Chartres Cedex, France. The authors have no proprietary or financial interest in these products or in the companies involved.

Evidence from fluid seeps atop serpentine seamounts in the Mariana forearc: Clues for emplacement of the seamounts and their relationship to forearc tectonics

The Mariana forearc is a non-accretionary forearc with numerous seamounts. Dredge hauls from these seamounts are composed primarily of serpentinite, indicating a non-volcanic origin. In addition, dredged carbonate samples reveal (1) the presence of aragonite in water depths greater than the aragonite compensation depth, (2) unusual porosity and cement types, (3) light carbon and heavy oxygen isotopic compositions, and (4) an unusual trace element geochemistry of aragonite and calcite. These mineralogic, petrologic, and geochemical characteristics formed the basis of a prediction that methane-bearing fluids are venting from these seamounts. Subsequent to this prediction, submersible dives on a Mariana forearc seamount found and sampled chimneys seeping cool water that contains dissolved methane. The serpentine substrate beneath the chimneys appears to form from cold gravitational flows of serpentine material. Fluid inclusion contents of chimney samples also show an earlier history of methane, as well as longer chain hydrocarbons, aromatics and acetate ions. Drilling into the flank and the summit of this seamount by the Ocean Drilling Program during Leg 125 confirmed the presence of methane, other light alkanes, and organic acids in the present-day interstitial pore fluid of the cores. The presence of aromatic compounds and organic acids, if derived from the maturation of organic compounds, indicates a thermogenic origin for these volatiles. Strontium isotopic ratios of the aragonitic chimney samples and of the present-day interstitial waters range from present-day seawater values to significantly lower values. The strontium isotopic ratios of the pore waters within the seamount trend toward a relatively less radiogenic composition with increasing depth below the seafloor. This strontium isotopic signature is probably not the consequence of near-surface processes, but more likely a contribution from an igneous source deeper in the lithosphere. The lack of a large accretionary prism in the Mariana forearc removes the complication of fluid contribution from dewatering of the prism by compression during convergence, as in the Oregon-Washington or Barbados margins. The organic compounds in the fluid inclusions and interstitial pore fluids, as well as the isotopic and the geochemical composition of the carbonates and the dissolved constituents, suggest that fluids are derived from dewatering, compression, and dehydration of subducted sediments and the subducting plate. Furthermore, the composition of the fluid is influenced by thermal maturation of organics in subducted sediments as well as by a contribution from a deep igneous source.

Observations at convergent margins concerning sediment subduction, subduction erosion, and the growth of continental crust

At ocean margins where two plates converge, the oceanic plate sinks or is subducted beneath an upper one topped by a layer of terrestrial crust. This crust is constructed of continental or island arc material. The subduction process either builds juvenile masses of terrestrial crust through arc volcanism or new areas of crust through the piling up of accretionary masses (prisms) of sedimentary deposits and fragments of thicker crustal bodies scraped off the subducting lower plate. At convergent margins, terrestrial material can also bypass the accretionary prism as a result of sediment subduction, and terrestrial matter can be removed from the upper plate by processes of subduction erosion. Sediment subduction occurs where sediment remains attached to the subducting oceanic plate and underthrusts the seaward position of the upper plate's resistive buttress (backstop) of consolidated sediment and rock. Sediment subduction occurs at two types of convergent margins: type 1 margins where accretionary prisms form and type 2 margins where little net accretion takes place. At type 2 margins (∼19,000 km in global length), effectively all incoming sediment is subducted beneath the massif of basement or framework rocks forming the landward trench slope. At accreting or type 1 margins, sediment subduction begins at the seaward position of an active buttress of consolidated accretionary material that accumulated in front of a starting or core buttress of framework rocks. Where small‐to‐medium‐sized prisms have formed (∼16,300 km), approximately 20% of the incoming sediment is skimmed off a detachment surface or decollement and frontally accreted to the active buttress. The remaining 80% subducts beneath the buttress and may either underplate older parts of the frontal body or bypass the prism entirely and underthrust the leading edge of the margin's rock framework. At margins bordered by large prisms (∼8,200 km), roughly 70% of the incoming trench floor section is subducted beneath the frontal accretionary body and its active buttress. In rounded figures the contemporary rate of solid‐volume sediment subduction at convergent ocean margins (∼43,500 km) is calculated to be 1.5 km³/yr. Correcting type 1 margins for high rates of terrigenous seafloor sedimentation during the past 30 m.y. or so sets the long‐term rate of sediment subduction at 1.0 km³/yr. The bulk of the subducted material is derived directly or indirectly from continental denudation. Interstitial water currently expulsed from accreted and deeply subducted sediment and recycled to the ocean basins is estimated at 0.9 km³/yr. The thinning and truncation caused by subduction erosion of the margin's framework rock and overlying sedimentary deposits have been demonstrated at many convergent margins but only off northern Japan, central Peru, and northern Chile has sufficient information been collected to determine average or long‐term rates, which range from 25 to 50 km³/m.y. per kilometer of margin. A conservative long‐term rate applicable to many sectors of convergent margins is 30 km³/km/m.y. If applied to the length of type 2 margins, subduction erosion removes and transports approximately 0.6 km³/yr of upper plate material to greater depths. At various places, subduction erosion also affects sectors of type 1 margins bordered by small‐ to medium‐sized accretionary prisms (for example, Japan and Peru), thus increasing the global rate by possibly 0.5 km³/yr to a total of 1.1 km³/yr. Little information is available to assess subduction erosion at margins bordered by large accretionary prisms. Mass balance calculations allow assessments to be made of the amount of subducted sediment that bypasses the prism and underthrusts the margin's rock framework. This subcrustally subducted sediment is estimated at 0.7 km³/yr. Combined with the range of terrestrial matter removed from the margin's rock framework by subduction erosion, the global volume of subcrustally subducted material is estimated to range from 1.3 to 1.8 km³/yr. Subcrustally subducted material is either returned to the terrestrial crust by arc‐related igneous processes or crustal underplating or is lost from the crust by mantle absorption. Geochemical and isotopic data support the notion that upper mantle melting returns only a small percent of the subducted material to the terrestrial crust as arc igneous rocks. Limited areal exposures of terrestrial rocks metamorphosed at deep (>20–30 km) subcrustal pressures and temperatures imply that only a small fraction of subducted material is reattached via deep crustal underplating. Possibly, therefore much of the subducted terrestrial material is recycled to the mantle at a rate near 1.6 km³/yr, which is effectively equivalent to the commonly estimated rate at which the mantle adds juvenile igneous material to the Earth's layer of terrestrial rock.

Proteolytic release and crystallization of the RNase H domain of human immunodeficiency virus type 1 reverse transcriptase

The RNase H domain of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase was released from recombinant DHFR-RNase H fusion protein by the action of HIV-1 protease and crystallized as large trigonal prisms that diffract x-rays to at least 2.4-A resolution. The protease cleavage occurred 18 residues away from the Phe440-Tyr441 site reported to be processed during maturation of the reverse transcriptase heterodimer. Mutagenesis of the protease-sensitive region (residues 430-440), which is part of the crystallized domain, indicates that any alteration of the wild-type sequence results in increased proteolysis of the p66 subunit. A model of asymmetric processing in HIV-1 reserve transcriptase which involves partial unfolding of the RNase H domain is proposed based on these results and the recently reported three-dimensional structure of this domain.

Animalizing Effect of A23187 on Sea Urchin Embryos: (sea urchin/animalization/vegetalization/A23187/tetracaine).

Pulse treatment of sea urchin embryos with 3 μM A23187 for 2 hr starting at a stage in initial 10 hr period of development at 20°C, followed by a culture in normal sea water up to the pluteus corresponding stage (45 hr after fertilization), yielded many large exogastrulae with thin embryo walls. The pulse treatment starting at a time between 10 and 13 hr after fertilization yielded considerable number of large prisms and gastrulae having thin embryo walls. Probably, the pulse treatment exerts stimulating effects on ectodermal cell determination in whole span of pre-hatching period to produce animalized embryos. On the other hand, pulse treatment with A23187 in pre-hatching period exerts stage-specific effects on gut formation. Embryos, thus treated for 2 hr starting at stages between 3 and 5 hr after fertilization, produced quite small exoguts but those treated at stages between 7 and 8 hr formed well developed and long exoguts. In embryos treated at the other stages than above, guts or exoguts were almost the same in their size to those in normal ones. These effects of A23187 on morphogenesis were canceled by procaine, tetracaine and ruthenium red. Probably, artificial Ca2+ signal induced by A23187 alters the determination of cell fates, programmed in pre-hatching period.

Fluids in accretionary prisms

Subduction zones are the most dynamic tectonic environments on the face of Earth. Most subduction zones are submarine and at many, large accretionary prisms are formed of sediments scraped from the subducting oceanic lithosphere. These prisms grow in a water‐saturated environment; consequently, their tectonic, thermal and chemical evolution is strongly influenced by fluids, and the role of the aqueous phase must be considered in any study in this realm.In view of widespread and growing interest, the North Atlantic Treaty Organization and National Science Foundation sponsored the workshop “The Role of Fluids in Sediment Accretion, Deformation, Diagenesis and Metamorphism at Subduction Zones,” which convened September 19–23, 1988, at Il Ciocco, Tuscany, Italy. This meeting assembled 60 geologists, geochemists and geophysicists representing eight countries whose interests spanned both marine and continental environments.

Regional Factors Affecting Petroleum Potential of the Aleutian Accretionary Prism: ABSTRACT

Two first-order factors influencing the petroleum potential of large accretionary prisms are (1) their structural contact (backstop) with the margin's bedrock framework, and (2) that beneath a master decollement, the volume of the sediment that has underthrust the prism and passed through the petroleum-generation window (PGW). In the Aleutian prism, the backstop contact slopes landward because the accretionary body has underrun and elevated the seaward edge of the ridge's arc massif. Within the thickened landward part of the prism, the overlying lid of the underrun bedrock slab and its mantle of thick (2-4 km) forearc deposits has served to constrain vertical fluid movements and enhance the thermal environment and circumstances that favor the generation of hydrocarbons and their channelized migration toward higher structural levels. The thickness of the underthrusting or subdecollement section commonly is greater than 1.0 km. Most of this sequence of fine-grained sediment is transported below the landward-dipping slab or forearc basement to depths in excess of 8 km. A substantial mass is transported farther landward and deeper, and is subducted beneath the base of the arc massif. Deeply underthrust and subducted sedimentary deposits thus are transported through the PGW - a circumstance that should sustain the continuousmore » generation of petroleum from deep within and below the accreted pile. During the past 5-6 m.y., more than 50% of the 1 to 3-m-thick sedimentary section entering the subduction zone (at roughly 80 km/m.y.) has been subducted and, therefore, passed through the PGW. Evidently, since the late Miocene, larger volumes of hydrocarbons have been produced and possibly entrapped in high-level structures within either the accretionary complex or the forearc section mantling the underthrust basement slab.« less

Trajectories of reaches to prismatically-displaced targets: evidence for ?automatic? visuomotor recalibration

The present study examined the kinematics of unrestricted reaches to prismatically-displaced targets. The kinematic analysis allowed us (1) to document how and where in the reach adjustments were made to compensate for the prismatic displacement. (2) to detail the changes that occur in the characteristics of reaches during the course of adaptation to the prisms, and (3) to look at the effects of providing information (or not) to the subject about the presence and nature of the prismatic distortion. The experiment differed from classic studies of prism adaptation in that subjects were permitted full visual feedback of their moving limb at all times, and entire reaching movements were recorded in addition to terminal errors. Experimental subjects were tested either with large-displacement prisms of the sort typically used in such experiments (20 diopters) or with small-displacement prisms (5 diopters) the properties of which went undetected in uninformed subjects. By using small displacements, it was possible to examine the process of visuomotor recalibration directly, free of contamination by "conscious" correction strategies. There were no differences in the terminal accuracies of the reaches made by subjects in any of the conditions. The availability of visual feedback allowed subjects to place their finger accurately on the target, despite the fact that in some cases their vision was displaced by as much as 11.4 degrees to the right. When the entire reach was examined, however, it was found that the amount of curvature in the path increased when large or small diopter prisms were unexpectedly introduced, with the subjects showing large deviations to the right. This rightward deviation was corrected in the final approach with a larger terminal correction. On some occasions, nonetheless, corrections were observed very early in the course of the reaching movement and appeared to be part of a natural process of trajectory fine-tuning. Uninformed subjects exposed to either large or small prismatic displacements also showed evidence of adaptation through an increased number of on-line corrections which compensated for a tendency to reach into the side of space opposite to the direction of the displacement (a "negative after-effect" in the path of the reach). Moreover, when questioned after the experiment, it became clear that uninformed subjects exposed to small prismatic displacements had apparently failed to detect any visual displacement whatsoever. Taken together, these results suggest that visuomotor recalibration can take place "automatically" without feedback from terminal errors and without the use of conscious strategies.(ABSTRACT TRUNCATED AT 400 WORDS)

Variation in ebb-delta morphologies along the West and East Frisian Islands, The Netherlands and Germany

Ebb-delta morphologies in the West and East Frisian Islands differ mainly in terms of the direction and the degree of asymmetry of the ebb-deltas. In the East Frisian Islands, the ebb-tidal deltas and their main ebb channels are asymmetrically directed downdrift (to the east). In the West Frisian Islands, they are asymmetrically directed updrift (to the west), except for a few of the small ebb-tidal deltas which are asymmetrically directed downdrift. Earlier theories for the East Frisian Islands considered wind-driven waves coming dominantly from the west to be the main cause of the downdrift asymmetry of the ebb-tidal deltas. Theories for the West Frisian Islands related the updrift-directed ebb-tidal deltas to tidal currents. None of these theories can explain the morphological variation in the ebb-tidal deltas for both the West and East Frisian Islands. Observation of the ebb-delta morphologies of the West and East Frisian Islands in relation to tidal and wave regimes shows that the above-mentioned difference in the ebb-delta morphologies is due to the varying importance of the tidal prism and the wave-induced longshore drift for the different inlets. The difference is especially pronounced between the large and the small ebb-tidal deltas because their tidal prisms are different. The inlets with a large tidal prism have large ebb-tidal deltas and they are dominated by tidal currents. Interaction of marine shore-parallel tidal currents with onshore-offshore inlet tidal currents, which is enhanced by the ebb-delta shoals, causes the large ebb-tidal deltas and their main ebb channels to be asymmetrically directed updrift (to the west). The inlets with a small tidal prism have small ebb-tidal deltas and they are dominated by waves. Eastward-moving deep-water wave and wave-induced longshore drift drive the small ebb-tidal deltas asymmetrically downdrift (to the east). The general model proposed not only explains the varying morphologies of the ebb-tidal deltas of the West and East Frisian Islands, but is also applicable to other ebb-tidal deltas.

ChemInform Abstract: Polymeric and Monomeric Forms of Metalphosphinates.

AbstractDiphenylphosphinic acid reacts with Mn(ClO4)2·6 H2O in a solvent mixture of DMF/DMSO/acetone/NaOMe to yield long colorless needles of the polymeric compounds (I) and large colorless prisms of the monomeric complex (IIa).

Analysis of methods of determining the compressive strength of rocks

1. The diversity of the methods of compression testing of rocks and the appearance of a great number of new ones indicates that they do not completely satisfy the requirements occurring in connection with practical activity in the area of the mining industry and construction. 2. The development and improvement of methods of determining the compressive strength of rocks under laboratory, field, and production conditions are continuing. 3. State standardization of methods of physical testing of rocks, including methods of determining the uniaxial compressive strength, has been being carried out during the past 10 years. 4. Methods of crushing large rock prisms should be used when constructing especially important objects. In this case it is necessary to fulfill the requirements following from the basic principles of mathematical statistics (to take into account variation of the indices, to select the necessary number of repeated determinations, to fulfill identity of the conditions of repeated determinations, etc.). 5. When determining the compressive strength on large prisms it is necessary to simultaneously determine the compressive strength of rocks by one or two methods on small samples (GOST 21153.2-75 and GOST 21153.4-75). 6. It is necessary to more deeply and widely conduct special experimental and theoretical investigatons to establish the regularities of the distribution of stresses in rock samples being tested and effect on rock strength of various natural factors on a scale of the rock mass (moisture content, jointing, stratification, etc.) to obtain well-founded recommendations for the reliable establishment of rock strength from the results of determining rock strength under laboratory or field conditions on small samples.

The drawing prism

Artists using conventional computer graphic input devices cannot produce the same visual effects which they can with traditional tools and media. The drawing prism is a new device which allows people to draw or paint directly into a frame buffer, using brushes, their hands, or a variety of other objects. These objects can be manipulated to achieve continuously adjustable line qualities and textures, in the same ways that artists have traditionally used their hands and tools.The device uses one face of a large transparent prisms as a drawing surface. A video camera views that surface from an angle such that it can only image the points of optical contact between drawing tools and the surface. These images are digitized and processed in real time so as to build up a drawing as the tools are moved along the surface. A layer of transparent liquid helps tools make optical contact with the drawing surface. Any light colored object can thus be used as a drawing tool.Details of the current implementation are provided along with suggestions for improving its resolution. Combinations of visual effects previously restricted to either traditional media or computer graphics are described and illustrated.

Crystallization of α 1-acid glycoprotein

Crystals of α 1-acid glycoprotein have been grown reproducibly from delipidated protein in the presence of chlorpromazine. The crystals are large hexagonal prisms of space group either P622 or P6 222 and the unit cell dimensions are a = b = 101 Å and C = 201 Å. The unit cell is very highly hydrated and is nearly 80% solvent. It contains one molecule of protein per asymmetric unit. The crystals diffract only to low resolution, presumably reflecting the extensive hydration and accompanying disorder.

Ophthalmic Prisms: Measurement Errors and How to Minimize Them

Variable results of strabismus surgery may be due in part to errors in prism measurement. The amount of deviation neutralized by an ophthalmic prism is variable depending on how the prism is held. For example, a 40Δ glass prism with the posterior face held in the frontal plane gives only 32Δ of effect. Glass prisms are calibrated for use in the Prentice position. Plastic prisms are calibrated for use in the frontal plane position. Surprisingly large errors in prism measurement are produced when adding a small prism to a large prism. For example, adding a 5Δ glass prism to a 40Δ glass prism gives not 45Δ of effect, but 59Δ. This error can be minimized but not eliminated by holding one prism in front of each eye. The error can also be calculated so that the appropriate correction can be made.

Antler orogeny and foreland basin: A model

The Antler orogeny occurred in Mississippian time at a passive margin of the sialic North American continent in Nevada and probably in Idaho. Its principal events were the emplacement of an extensive allochthon of oceanic rocks on the continental shelf, subsidence of an elongate foreland basin, and maintenance of highlands in the interior region of the allochthon during and after subsidence of the foreland basin. The orogeny was apparently not accompanied by thermal phenomena or large crustal shortening. We follow earlier models by assuming that the orogeny was initiated by collision of an arc system with North America. Our proposal holds that a large accretionary prism of the probably far-traveled arc system was underthrust by the continental slope and outer shelf and became the Roberts Mountains allochthon. The Antler magmatic arc, now unexposed, thermally contracted after collision and was largely or entirely subducted in a later (Triassic) arc-continent collision. The Antler foreland basin was created by vertical loading and downflexing of the continental shelf by the allochthon, and sediment from subaerial regions of the allochthon ultimately filled and broadened the foreland basin. Quantitative models using the theory of a loaded thin elastic plate above a dense fluid provide reasonable agreement between calculated widths, depths, and asymmetry of plate deflections and the Antler foreland basin. Models predict that a flexural bulge of low amplitude migrated continentward ahead of the foreland basin during arc-continent closure. Certain stratigraphic phenomena in pre-foreland basin strata of central Nevada may record the passage of the bulge.

Evaporation behaviour of metallic aerosol condensates

SUMMARYThe particles in sediment from condensation aerosols of zinc and cadmium were exposed to hot, inert gas or radiant heat to investigate the structure revealed by evaporation. The smallest prisms retained their shape but the larger ones evaporated back to the dendritic form characteristic of an earlier stage in their development. It is concluded that large prisms grow with a flawed structure because of strain present in the dendritic skeleton.On spheres, the curved surface surrounding the basal flat tends to become smoother on evaporation of the vapour‐grown layer texture although deep pits develop eventually. The texture opposite the flat, where the growth helix emerges from the solidifying melt, is more persistent. The basal flat remains flat, indicating that the high degree of crystalline perfection achieved in the slowly‐growing basal raft is retained after solidification.

Direct spectrographic analysis of granitic and basaltic type rocks and soils for Cs, Li and Rb

A direct emission spectrographic method for the determination of Cs, Li and Rb in granitic and basaltic type of rocks and soils is described here. KCl is used as a buffer and graphite as a diluent. Hilger Large Glass Prism spectrograph is used to photograph the spectra of the samples, synthetic standards and standard reference materials, all excited in a 3 A d.c. arc for 90 s. Reproducibility and accuracy of the method are around ±10%. Using this method, a Certified Reference Material (Soil-5), prepared by International Atomic Energy Agency, is analysed for Cs, Li and Rb and results are reported.

Microtropia - heterophoria

In 31 cases of microtropia combined with large angle esophoria, prism treatment and surgery to eliminates the phoria component were performed. In 19 cases a stable microsotropia remained after elimination of the phoria component. In 12 cases unstable microtropia was found, i.e., the microtropia disappeared after treatment. In these cases, microtropia may be secondary to the heterophoria. The treatment of the esophoria component in cases of microtropia/esophoria with refraction or bifocal correction, prisms and surgery is as much indicated as in simple esophoria.

Variation of sediment geotechnical properties between the greater antilles outer ridge and the nares abyssal plain

Abstract It is clear from morphology alone that distinctly different dynamic and sedimentary processes can be expected to be associated with the Greater Antilles Outer Ridge relative to those of the adjacent Nares Abyssal Plain. This difference is further substantiated by seismic reflection data which show the ridge to be a very large prism of acoustically transparent sediment in contrast to the stratified deposits of the abyssal plain. An examination of the geotechnical properties of the near‐surface (0 to 2.4m) deposits of the two areas also reveals distinct differences in their sedimentological characteristics. The outer ridge sediments, of more or less homogenous clay‐size material, display much higher water contents, porosities, sensitivities, plasticity, and organic carbon contents in contrast to the abyssal plain deposits which are much less homogenous owing to the presence of turbidite sequences. The turbidites themselves are uniquely contrasted to the other abyssal plain sediments by their higher...

A case study on infiltration into dry clay soil I. Morphological observations

Infiltration patterns of water into four dry clay soils with different macrostructures were determined in the field as a function of application rate ( i = 4−80 mm/h) and applied quantity ( q = 2.5−40 mm), using methylene blue as a tracer. Stains on the walls of large vertical pores (dominantly planar voids) occurred as small vertical bands and were observed and counted to a depth of 1 m after excavation of the 0.5 m 2 plots. Deep infiltration through large pores, as demonstrated by occurrence of stained bands, could be manipulated by varying application rates and applied quantities. The number of stained bands was always very low, occupying at the most an estimated 2% of the available vertical surface area of large prisms, and (for each stained band) a horizontal cross-sectional area of 60 cm 2 or more. Infiltration was deeper, at comparable flow regimes, in two soils with strongly developed prisms, as compared with two soils with moderately developed prisms. Deep infiltration occurred along vertical prism faces where grass roots were also concentrated.