Deep Ridge Research Articles

Spotsize converters integrated with deep ridge waveguide structure

Spotsize converters (SSCs) that can be integrated with a deep ridge waveguide have been developed. By obtaining low loss coupling of a deep ridge and buried waveguide, an SSC loss of < 2 dB has been realised. The 1 dB-down tolerances in the lateral and vertical directions are increased to ± 2.2 and 2.0 µm, respectively.

Spreading-rate dependence of the extent of mantle melting beneath ocean ridges

Abyssal peridotites and mid-ocean-ridge basalts (MORBs) are complementary products of the mantle melting and melt-extraction processes that create the ocean crust. Studies of abyssal peridotites1–4 and MORBs2 have showed that the extent of mantle melting is high beneath hotspot-influenced shallow ridges, and is low beneath deep ridges away from hotspots. These results have led to the recognition of a global correlation of MORB composition with ridge depth5, and to the notion that mantle temperature variation exerts the primary control on the extent of melting beneath ocean ridges2,5–8. This conclusion is, however, based largely on data from slow-spreading ridges in the Atlantic and Indian oceans. At the fast-spreading East Pacific Rise (EPR), there is little correlation between MORB chemistry and ridge depth9,10, an observation that has proved puzzling8–12. Here we show that abyssal peridotites from the EPR13–21 are extremely depleted in basaltic major-element components—significantly more so than peridotites from ridges away from hotspots in the Atlantic and Indian oceanss—indicating that the EPR peridotites are residues of the highest extents of melting. These abyssal peridotite data and existing MORB major-element data12 both suggest that the extent of mantle melting beneath normal ocean ridges increases with increasing spreading rate.

Polarisation-insensitive modulator and influence of propagation direction on bulk electroabsorption

The authors report measurements on electroabsorption in deep ridge waveguide structures. The polarisation sensitivity is found to depend not only on the detuning but also on the propagation direction. In an InGaAsP/InP double heterostructure, polarisation insensitivity is obtained over a large detuning range (80 nm) for propagation along the [-110] direction.

The generation of mid-ocean ridge basalts from the Hf and Nd isotope perspective

This paper presents new Hf and Nd isotope and trace element data for mid-ocean ridge basalts. The intention of this study was to investigate whether melt parameters derived from the isotopic systematics of MORB ( δ (Lu) (Hf) and δ (Sm) (Nd) ) support the variations in depth and degree of melting as inferred from the major elements and ridge depth; that is, the ‘local’ and ‘global’ trend [1]. Variation on a ‘local’ scale is defined as variation within a ridge segment, while the ‘global’ scale variation is defined as variation between ridge segments. Both on a ‘local’ and a ‘global’ scale, δ (Lu) (Hf) and δ (Sm) (Nd) show consistent variations with the major element melt parameters, Na 8 and Fe 8. In addition, the δ melt parameters vary consistently with ridge depth. Basalts from some of the deepest ridges, Australian-Antarctic Discordance and Mid-Cayman Rise, show evidence that a relatively large proportion of the basalt was generated in the presence of garnet. A melting model is derived using best available estimates for a large number of parameters that influence the chemistry of MORBs. With this melting model, the additional constraints of δ (Lu) (Hf) and δ (Sm) (Nd) further define the melting regime beneath the ocean ridges. The onset of melting for shallow ridges, like Kolbeinsey Ridge, starts deeper than for deep ridges, the aggregated melts from the Kolbeinsey Ridge sample a columnar shaped melting regime. Basalts from deep ridges represent a smaller degree of melting, which was generated in a triangular-shaped melting regime. The translation of δ (Lu) (Hf) and δ (Sm) (Nd) in absolute values for degree and depth of melting for individual ridge segments is hampered by uncertainties in the details of the heterogeneity of the MORB reservior.

Diffuse impact of the Mid‐Atlantic Ridge with the Romanche transform: an ultracold ridge‐transform intersection

The Romanche is a long offset (∼950 km), slow slip (∼1.7 cm/yr) transform; thus a hot ridge axis should meet a ∼50‐m.y.‐old, thick and cold lithosphere at the ridge‐transform intersection (RTI). A strong thermal/topographic “transform cold edge effect” is therefore predicted. A morphobathymetric, seismic reflection and petrologic study of the eastern Romanche RTI shows that as the Mid‐Atlantic Ridge approaches the transform, a well‐formed axial rift valley disappears about 80 km from the RTI and is substituted by short en echelon, poorly developed axial ridge segments; they too disappear about 30 km from the edge of the transform valley. The predicted gradual deepening of the ridge axis toward the transform was not observed. An active nodal deep and an “inside corner high” are also absent. These observations, and the distribution of earthquake epicenters, suggest a poorly developed, diffuse RTI. An inactive rift valley ∼80 km west of the present RTI suggests ridge jumping within the last ∼4 m.y. The present poorly developed RTI may reflect the attempts of an embryonic spreading axis to become established and to propagate toward the transform. We infer from bottom rock sampling that the basaltic crust is patchy or absent and mantle‐derived serpentinized peridotites outcrop ubiquitously on the seafloor starting ∼30 km from the edge of the transform valley. The unusually deep (∼4 km below sea level) axial ridge segments, the lack of crust, and the chemistry of the peridotites suggest a prevalently amagmatic regime due to an ultracold upper mantle in this region. Absence of basaltic crust would favor massive serpentinization of a several kilometers thick peridotite column. Mass balance modeling suggests that the decrease of density and volume expansion resulting from serpentinization could explain the absence of the predicted deepening of the seafloor as it approaches the transform. These results suggest that the topographic effect of the transform edge thermal contrast may disappear at ultracold RTIs and that ultracold RTIs are magma starved, short lived, and unstable in time and space.

Extremely small polarization independent phased-array demultiplexers on InP

Compact, polarization insensitive phased-array wavelength demultiplexers are demonstrated with a deep ridge waveguide. Good agreement with the modeling is found for the birefringence and the refractive index. Zero birefringence is effectively obtained around 1.53 /spl mu/m. The guiding structure allows curvatures of 100 /spl mu/m; thus, the grating size of the 4- and 16-channel demultiplexers is reduced to 0.33/spl times/0.30 and 1.1/spl times/1.1 mm/sup 2/, with crosstalk below -16 and -14 dB respectively. These are the smallest demultiplexers reported to date.

Colorado Potato Beetle Control; Admire 2F Soil Application Depth, Big Lake, Mn, 1994

Abstract A small trial was established in an irrigated commercial field to determine efficacy of Admire 2F equivalent dosage with, and at varying distances above, the seed piece. Soils were sandy loams. A plot was a single 25 ft row. Treatments were arranged in an RCB design, replicated 4 times. The field was planted on 5 May, seed pieces uncovered on 11 May, re-covered to appropriate depth and treated with Admire 2F at a soil dosage of 1.3 fl ozl1000 row ft in 40 gal/ acre water. The original 6 deep ridge was then restored. Plant emergence began about 20 May but appeared uneven so % emergence data were recorded. The foliar treatment was delayed until slightly more than 15% larval defoliation was present. Foliar treatment dates were 29 June, 6, 13 & 20 July.

Resist planarization over topography using ion implantation

We present a novel application of ion implantation for obtaining planar films of resist on substrates with deep topography (≥1 μm). The motivation of this work comes from the fabrication of laterally coupled distributed feedback lasers, where lateral gratings need to be patterned adjacent to the sidewalls of a deep ridge waveguide. We demonstrate this process using both boron and phosphorous ion species implanted into polymethylmethacrylate (PMMA, 950 K) resist. The ion energies in our experiments ranged from a few tens of keV to approximately 1 MeV at a typical dose of 1013 cm−2. Experimental results show that the developed depth of the PMMA can be controlled very accurately. Furthermore, post-implant x-ray lithographic exposures show no deleterious effects of the implant on the PMMA characteristics. Lateral gratings (Λ=406 nm) were fabricated on 1.1-μm-high ridge waveguides in InP/InGaAlAs/InGaAsP by CH4/H2 reactive-ion etching. This process is equally applicable for other applications where lithography on substrates with significant topography is required.

Subsidence of the seafloor in the Atlantic and Pacific Oceans: Regional and large-scale variations

We present a deteiled survey of seafloor subsidence over the entire Atlantic Ocean and in the Pacific Ocean. We examine the evolution of depth as age increases within narrow (200 km wide) tectonic corridors elongate in the direction of spreading. Over the part of the young seafloor where the depth-age 1 2 relationship is valid, we estimate the subsidence rate by a least-squares adjustment. In the three oceanic regions (West Atlantic, East Atlantic and Pacific) the subsidence rate shows regional (1000–2000 km) and basin-scale fluctuations of the order of 100–150 m/m.y. 1 2 . We also note that in some regions subsidence rate and axial depth are correlated, with shallow ridges showing fast subsidence and deep ridges slow subsidence. On the basis of published models, we infer that regional variations in subsidence rate reflect temperature changes in the subaxial mantle of ∼ 100°C. Asymmetrical subsidence is observed in the Atlantic, especially in the South Atlantic. The age of departure from the depth-age 1 2 linear trend is highly variable, with values larger than 100 m.y. reported in several instances but very low values (20 m.y. or less) characterizing the central Pacific. Flattening predicted by the plate model occurs in some areas. In a number of cases however, quite distinct behaviour is observed, with a sudden depth increase where the depth-age 1 2 relationship breaks down, and a slow rise of the seafloor at older ages. Our results suggest that the subsidence behaviour of the seafloor is much more complex than global plate or half-space cooling models predict.

The bovine desmocollin family: a new gene and expression patterns reflecting epithelial cell proliferation and differentiation.

We have discovered a third bovine desmocollin gene, DSC3, and studied expression of all three desmocollin genes, DSC1, 2, and 3, by Northern blotting, RT-PCR and in situ hybridization. DSC1 is strongly expressed in epidermis and tongue papillae, showing a "skin"-type pattern resembling that previously described for keratins 1 and 10. Expression is absent from the epidermal basal layer but appears in the immediate suprabasal layers and continues uniformly to the lower granular layer. In tongue epithelium, expression is suprabasal and strictly localized to papillae, being absent from interpapillary regions. In other epithelial low level DSC1 expression is detectable only by RT-PCR. The distribution of Dsc1 glycoproteins, detected by an isoform-specific monoclonal antibody, closely reflects mRNA distribution in epidermis and tongue. DSC2 is ubiquitously expressed in epithelia and cardiac muscle. In stratified epithelia, expression appears immediately suprabasal, continuing weakly to the lower granular layer in epidermis and to just above half epithelial thickness in interpapillary tongue, oesophageal, and rumenal epithelia. DSC3 expression is restricted to the basal and immediately suprabasal layers in stratified epithelia. In deep rete ridges DSC expression strikingly resembles the distribution of stem, transit-amplifying, and terminally differentiating cells described by others. DSC3 expression is strongly basal, DSC2 is strong in 5-10 suprabasal layers, and then weakens to be superseded by strong DSC1. These results suggest that desmocollin isoform expression has important functional consequences in epithelial proliferation, stratification, and differentiation. The data also provide a standard for nomenclature of the desmocollins.

Constraints in the MORB Melting Regime Based on the Lu-Hf and Sm-Nd Systematics

Lu-Hf and Sm-Nd isotope systematics place the onset for MORB melting in the garnet field and are indicators for degree and depth of melting. In addition, recent results on U-Th partitioning indicates Th-disequilibria are also explained by placing the onset of melting in the garnet stability field. And, thirdly, Klein and Langmuir (1989) have shown that the normalized major element content of MORB also reveal information about the degree and the depth of melting. Especially Nas and Fes are important indicators whereby Nas is an indicator for the degree of melting and Fes is an indicator for the average depth of melting. We have taken the constrains derived f rom the 176Hf/177Hf, 143Nd/144Nd and 23~ systematics one step further and combined the constrains derived from the isotope systematics with those derived from major elements. The first set of four figures (Fig. 1.) shows the isotope data for two Atlantic Ridge segments with a clear 'local' trend. These two segments show positive correlations with both Fes and Nas and the isotope melting parameters, 8(Sm/~d) and 8(L,m0, indicating that the smaller degree melts have a larger portion of melt generated in the garnet stability field. This is consistent with previous explanations of incomplete mixing of the different malting columns in a triangular shaped melting regime. The high Nas, high 8(L.mO and high Fes melts represent a small degree of melting generated at relatively deep levels and this correspond to melts generated in of-axis melting columns. The low Nas, low Fes and low 8(L,/H0 are large degree of melts that were generated at relatively shallow level in he mantle which represents melts from an on-axis melting column. We also analyzed mid-ocean ridge basalts erupted at different ridge depth. Klei~ and Langmuir (1989) interpreted the 'global' trend and its correlation with ridge depth as follows: the deep ridge segments have high Nas and low Fes indicating a low degree of rdatively low pressure melting, while the shallow ridges represent a large degree of melting and a high average pressure during melting. The Mid-Cayman Rise and the American Antarctic Discordance are two of the de~pest parts of the ocean which both have high Nas and high Fes. However, both MCR and AAD

MBE regrowth of GaAs/AlGaAs structures on RIE patterned substrates

GaAs/AlGaAs heterostructures with excellent morphology and high luminescence yield were regrown by molecular beam epitaxy on nonplanar wafers patterned by reactive ion etching with SiCl 4 or CCl 2F 2. Faceted growth occurs on pattern edges, depending on adatom species, crystallographic planes, growth parameters and pattern sizes. While shallow etched structures ( <100 nm ) are planarized during regrowth, independent of their orientation, deep etched ridges or grooves ( >300 nm ) aligned in the [011]-direction are isolated from the surrounding surface by distinct trenches due to shadowing effects. Narrow ridges ( <1 μ m ) with widths smaller than the migration length of the Ga atoms exhibit very smooth ( 01 1 ) facets at the sides and (111) B-facets on the top. This growth behaviour is applied for the direct growth of isolated nanostructures. On the other hand, the planarizing regrowth on shallow etched wafers is used to build in a thin n-AlGaAs blocking layer in the p-AlGaAs contact layer of a vertical cavity surface emitting laser diode to reduce current spreading.

Human keratinocyte growth factor effects in a porcine model of epidermal wound healing.

Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor (FGF) family (hence the alternative designation FGF-7). It is produced by stromal cells, but acts as a mitogen for epithelial cells. We examined the effects of topically applied KGF on healing of wounds in a porcine model. In partial-thickness wounds, KGF stimulated the rate of reepithelialization (p < 0.0002), associated with a thickening of the epidermis (p < 0.0001). Epidermis from KGF-treated full-thickness wound sites was significantly thicker (0.31 +/- 0.22 mm) compared with mirror image control sites (0.18 +/- 0.12 mm) (p < 0.0001). Moreover, the majority (77%) of KGF-treated wounds exhibited epidermis with a deep rete ridge pattern as compared with control sites. These effects were observed as early as 14 d and persisted for at least 4 wk. KGF treatment also increased the number of serrated basal cells associated with increased deposition of collagen fibers in the superficial dermis adjacent to the acanthotic epidermis. Electron microscopy revealed better developed hemidesmosomes associated with thicker bundles of tonofilaments in the serrated cells. The pattern of epidermal thickening observed in KGF-treated wounds resembled psoriasis. Psoriasis is a disease associated with epidermal thickening, parakeratosis as well as hyperproliferation that extends beyond the basal layer. In striking contrast to psoriasis, KGF-treated wounds exhibited normal orthokeratotic maturation, and proliferation was localized to the basal cells. Our present findings have significant implications concerning the role of KGF as a paracrine modulator of epidermal proliferation and differentiation.

Ridges and grooves on the bony surfaces of osteoarthritic joints

Osteoarthritis (OA) is associated with disruption of the articular cartilage and remodeling of subchondral bone. However, the macroscopic changes seen on the surface of the underlying bone have received little attention. Deep parallel ridges and grooves of the subchondral, eburnated bone have been observed in palaeopathological skeletons with OA. The same phenomenon has been seen in contemporary bones treated to remove soft tissues. Four such specimens were examined in detail and the characteristics of the ridges were documented by reflex microscopy. The depth and peak-to-peak distance of the grooves varied considerably. In each case there was matching of ridges and grooves on the two articulating surfaces of the joint, which fitted together like cog-wheels. This previously undocumented aspect of the pathology of OA may have significance to the function and outcome of an osteoarthritic joint, raises questions on the nature and control of subchrondal bone changes in OA.

Early tectonic extension between the Agulhas Bank and the Falkland Plateau due to the rotation of the Lafonia microplate

Along the Southeast African continental margin, a deep sedimentary basin and marginal ridge bordering the Agulhas Fracture Zone formed coevally with South American counterparts underlying the Falkland Plateau. Extension in both the Southern Outeniqua and the Falkland basin is related to large-angle ( ∼ 100°) rotation of the Lafonia (Falkland Islands) block in Middle-Late Jurassic times, during attempted propagation of the proto-Indian Ocean across the active circum-Pacific margin of Gondwanaland. In the Early Cretaceous, the Jurassic microplate boundaries were partly reactivated, and partly transected by a right-lateral shear along the ∼ 1200 km long Falkland-Agulhas transform fault. Preceded by substantial vorticity of the surrounding crustal blocks, this boundary segment separating the South American and African plates was probably generated by complex geodynamic interactions between oceanic plate subduction, continental to back-arc rift propagation, and the impingement of deep mantle plumes on the lithosphere.

Seafloor manifestations of fluid seepage at the top of a 2000-metre-deep ridge in the eastern Nankai accretionary wedge: Long-lived venting and tectonic implications

The results of the 1989 Kaiko-Nankai diving cruise to the eastern Nankai accretionary wedge show that a narrow corridor on the top of a 2000 m deep ridge is characterized by concentrated surface manifestations of fluid seepage and chaotic outcrop orientations, suggesting active faulting along a right-lateral shear zone.Modern biological indicators of fluid venting include bivalve vesicomyid species and vestimentiferan tube worms. Ancient manifestations of fluid venting consist of similar vesicomyid species found in 20 and 150 ka concretions. This suggests relatively constant biotypes. Carbonate deposits including fossil cemented shells were observed near active sites, either as “paving stones” (diffuse seepage and cementation) cut by channels or as pinnacles (local seepage and cementation). Despite its proximity (less than 15 km), a nearby 3800 m deep site, where substantial fluid discharge occurs, seems to be completely separate from the 2000 m deep ridge site. The 3800 m deep site differs from its shallower counterpart in terms of its seafloor manifestations and the composition of its fluids.The sediment at the top of the ridge ranges in age around500 ± 300 ka, which attests that the transition from a depositional to an erosional stage was younger than 800 ka but older than 200 Ka. This transition can be due to either the incorporation of this unit from the trench fill into the accretionary wedge front or the uplift of a slope basin. The first hypothesis leads to a 2.5 cm/yr minimum progradation rate associated with a 2.5 mm/yr minimum uplift rate from the paleotrench to the present ridge. The second hypothesis implies a recent uplift of a “piggy-back” basin at a minimum rate of 1 mm/yr.

Regional variations in subsidence rate of oceanic plates: a global analysis

A global analysis of the dependence of seafloor depth on crustal age has been performed for each large oceanic plate independently. Each plate has been divided into regions bounded by major tectonic features. A total of 32 regions have been considered. Bathymetry corrected for sediment loading has been plotted as a function of crustal age for each region. Except for three regions (western Pacific between 10°S and 40°N, North American plate between 24°N and 38°N and African plate between 10°N and 24°N) where ocean floor older than 80–100 Ma flattens with age, in other regions, depth increases linearly with age 1/2. Subsidence rate over each region has been computed by linear regression. Large variations (up to a factor 2) are reported from one region to another. Asymmetrical subsidence is also observed in a number of areas. However, the largest asymmetries are less than the regional variations in subsidence rate occurring on individual plates. Regional variations in subsidence rate appear linearly related to regional variations in ridge crest topography, shallow ridge subsiding quickly and deep ridge subsiding slowly. Hence seafloor depth subsides at a rate modulated by the value of the initial (axial) depth. This observation suggests that regional variations in subsidence rate reflect the thermal regime of the mantle beneath mid-ocean ridges rather than lateral temperature variations inside the asthenosphere involving small-scale convection.

Ridged cavity backed slot antenna with dielectric loading

A reduced size cavity backed slot antenna, consisting of a transverse slot in the flat broadwall of a deep single ridge waveguide cavity is described. Partial dielectric loading achieves significant further reduction in electrical size. Moderate dielectric loss increases bandwidth (and significantly reduces antenna gain).

Topographic Scattering of Equatorial Kelvin Waves

Abstract We develop a linear, reduced-gravity model with two active layers above a deep, resting layer to examine the scattering of equatorial Kelvin waves from meridional submarine ridges. Model ridges, idealized as infinitely long in the meridional direction and infinitesimally thin in the zonal direction, completely obstruct flow in the lower active layer. The equatorial long-wave approximation is made, which restricts the class of motions considered to nondispersive Kelvin and Rossby waves in each of two internal modes. Thus, coastal and topographically trapped phenomena are filtered out, but variability far from the ridge is accurately modeled. The scattering of Kelvin wave energy depends on two parameters, r = H0/H1 and γ = (ρ1 − ρ0)/(ρ2 − ρ1), where H0 and H1 are the equilibrium thicknesses of the upper and lower active layers, respectively, and ρ0≲ρ1≲ρ2 are the layer densities. Incident first internal mode Kelvin waves are little affected by a deep ridge (i.e., for large r) and strongly reflected ...

Structural Framework and Sand Genesis of Wilcox Group, Travis Ward Field, Jim Hogg County, Texas: ABSTRACT

ABSTRACT Since its discovery in 1983, operators have drilled eight deep Wilcox wells in Travis Ward field, of which four produce from deep sands; three, which appear capable of production, have been junked and abandoned, and one produces from the Hinnant Sand at the top of the Wilcox. Also, five of eight Queen City wells have been completed; three are considered commercial. Wilcox reserve estimates range from 60 to 200 BCF. To date, Wilcox and Queen City production is related to normal faulting associated with a deep salt and/or shale ridge within the Rio Grande Interior Salt Basin. Growth of the ridge has resulted in the Wilcox being as much as 2000 feet structurally high to the areas immediately north and south of Travis Ward field. Knowledge of the ancestral development of ridge closure prior to faulting may be critical to successful completions at Travis Ward field. Ridge-associated sea floor topography, shelf currents, sediment source proximity, and rate of sedimentation have combined for local development of high quality clean reservoir sands.