Nearby Layers Research Articles

An unusual branching in single crystals of isotactic poly(4-methyl-1-pentene)

Single crystals of low M w poly(4-methyl-1-pentene) (P4MP1) in its form I display an unusual streaking of their diffraction pattern. The crystals also frequently give rise to composite diffraction patterns made of two patterns rotated by 37°. The streaking indicates a structural disorder, namely a shift of nearby layers along the a or b axis by one quarter of the unit-cell edge. The daughter crystals, rotated by 37°, are produced on the edges of the parent crystals via an epitaxial growth that is a direct consequence of the structural disorder.

Tunneling-assisted Poole-Frenkel conduction mechanism in HfO2 thin films

Tunneling-assisted Poole-Frenkel (TAPF) mechanism, which represents electron tunneling from a metal electrode to traps in a nearby insulator layer followed by detrapping of the electrons from the traps by virtue of a lowered potential well due to an applied electric field, is suggested in this study to precisely describe the electrical conduction behavior of a Pt∕HfO2∕Si capacitor. The current density versus the applied electric-field curves of the TAPF conduction show a similar electric-field dependency to that of the Poole-Frenkel (PF) conduction. However, unlike the PF mechanism, the activation energy of the leakage current density corresponds to the value of the Schottky barrier height (SBH) of a metal/insulator junction minus a lowered potential-well height by the applied electric field in the TAPF mechanism. In addition, the SBH of the Pt∕HfO2 junction is calculated considering a high space-charge density (>∼1018cm−3) in the HfO2 layer. The measured activation energy for the electrical conduction from an atomic-layer-deposited HfO2 film is compared to the value that is expected from this model.

Innervation of ectopic endometrium in a rat model of endometriosis.

Endometriosis (ENDO) is a disorder in which vascularized growths of endometrial tissue occur outside the uterus. Its symptoms include reduced fertility and severe pelvic pain. Mechanisms that maintain the ectopic growths and evoke symptoms are poorly understood. One factor not yet considered is that the ectopic growths develop their own innervation. Here, we tested the hypothesis that the growths develop both an autonomic and a sensory innervation. We used a rat model of surgically induced ENDO whose growths mimic those in women. Furthermore, similar to women with ENDO, such rats exhibit reduced fertility and increased pelvic nociception. The ENDO was induced by autotransplanting, on mesenteric cascade arteries, small pieces of uterus that formed vascularized cysts. The cysts and healthy uterus were harvested from proestrous rats and immunostained using the pan-neuronal marker PGP9.5 and specific markers for calcitonin gene-related peptide (CGRP) (sensory C and A delta fibers), substance P (SP) (sensory C and A delta fibers) and vesicular monoamine transporter (sympathetic fibers). Cysts (like the uterus) were robustly innervated, with many PGP9.5-stained neurites accompanying blood vessels and extending into nearby luminal epithelial layers. CGRP-, SP-, and vesicular monoamine transporter-immunostained neurites also were observed, with CGRP and SP neurites extending the furthest into the cyst lining. These results demonstrate that ectopic endometrial growths develop an autonomic and sensory innervation. This innervation could contribute not only to symptoms associated with ENDO but also to maintenance of the ectopic growths.

Analysis of Core Buckling Defects in Sheet Metal Coil Processing

The elastic stability of a wound coil comprising a central core and many layers of sheet metal is modeled and analyzed. A common failure mode resulting from unfavorable internal stresses—called v-buckling—is characterized by a section of the core buckling inward, possibly with several nearby sheet metal layers. In the present study, the core is modeled as a thin cylinder that is subjected to (i) the uniform external pressure generated by the coil’s wound-in stresses and (ii) a nonuniform elastic foundation around its circumference that represents core-coil contact or loss thereof. The model and an iterative numerical technique are used to predict the critical winding pressure along the core-coil interface and the core’s ensuing buckled shape. The role of geometric imperfection in the core, and the sensitivity of the buckling pressure to such initial defects, are also examined. Critical imperfection wavenumbers that facilitate the onset of significant deformations are identified with a view toward applying the results to improve quality and core inspection procedures. The predicted buckling pressure and the maximum radial stress developed in the coil, as based on a nonlinear stress model, are together used to determine factors of safety against core buckling over a range of manufacturing process parameters. Three case studies evaluate sensitivity with respect to process tension, core radius, and core thickness. The results are intended to guide the development of solutions to control the stability and quality of coils in sheet metal manufacturing.

Effect of steam injection into two nearby layers

Equations describing heat transfer between two layers undergoing simultaneous heat injection are developed. Results are presented for realistic examples. Analyses of the results show that the interaction between adjacent layers may be significant. In particular, the growth of the steam zone in one layer may be significantly improved by injection in other layers even when the layers are reasonably far apart. Calculated steam zone volumes and oil production by steam injection may be undervalued if heat transfer between layers is not taken into account. This may result in overlooking field development opportunities.

The Effect of Heat Transfer Between Nearby Layers on the Volume of the Steam Zones

Summary The work of Mandl and Volek1 is extended analytically to include the effect on the volume of the steam zone in one layer owing to heat transfer from a second layer undergoing steam injection. The contribution of the heat transfer delays the onset of heat convection across the advancing condensation front (the critical time) and significantly increases the volume of the steam zone even where 30 or more feet separate the layers. The increase in the heat content of the steam zone (or volume) increases with increasing ratio of the sensible to latent heat of the injected steam, and is larger than the increase in the total heat content. The interpretation for this behavior is that heat transfer delays the rate of condensation of the steam vapor, this being more important at poor steam qualities. Results of the simple approach presented here have been confirmed qualitatively through numerical simulation.

SOUND RADIATION FROM A PLATE INTO A POROUS MEDIUM

A nearby layer of porous sound-absorbing material has previously been shown to be capable of greatly increasing the acoustic power radiated from a vibrating flat plate, and consequently of enhancing the structural damping in the plate. In this paper, a previously published model for sound radiation from a plate of infinite extent, radiating into a semi-infinite region of absorbent, is extended to allow for a finite air gap between absorbent and plate, as well as a finite absorbent thickness. Limited parametric studies are presented here for typical cases, and model predictions are compared to finite-plate predictions and to measured data. It is concluded that the infinite-plate model can be a useful design tool, presenting minimal computational demands.

The Effect of Heat Transfer To A Nearby Layer on Heat Efficiency

Summary This paper provides an analytic solution in Laplace space for the heat distribution in two nearby layers undergoing heat injection at variable rates. The heat content in the layers undergoing thermal injection, divided by the cumulative net-injected heat, is known as the heat efficiency. In this treatment, the thermal properties of the layers, the thickness of the layers undergoing heat injection, and the intervening layer can have any values. The overburden and underburden are semi-infinite. Examples are given for two sets of thermal properties and three values of the intervening layer's thickness. Only a constant rate of heat injection is considered in the examples. Results indicate that significant thermal interaction occurs at an intervening layer thickness as great as 45 ft, with the effect being faster and more pronounced the thinner the intervening layer.

P-T Paths, H2O recycling, and depth of crystallisation for crustal melts

The P-T (pressure-temperature) paths taken by the high-grade metamorphic rocks during orogenesis govern which melting and crystallisation reactions are encountered and hence the location and amount of melt. Small differences in rock fertility, water amount and migmatite deformability influence the amount and distribution of anatectic partial melt on an outcrop scale. Layer-scale migration of H2O in response to gradients in μH2O controls when melting in one layer occurs while partial melt in a nearby layer crystallises. Suprasolidus decompression - dehydration reactions (SDDR) can occur patchily at mid-crustal depths generating feldspathic segregations with alumino-silicates, and releasing H2O. Quite different mineralogies and textures are diagnostic of the possible crystallisation reactions at different crustal depths. Local mineralogical variations in anatectites can reveal whether melting occurred in response to decompression through a melting reaction or to access of H2O. This is particularly important to help decide whether anatexis required a localised heat supply or an influx of H2O.

Solution to the Boltzmann equation for layered systems for current perpendicular to the planes

Present theories of giant magnetoresistance (GMR) for current perpendicular to the planes (CPP) are based on an extremely restricted solution to the Boltzmann equation that assumes a single free electron band structure for all layers and all spin channels. Within this model only the scattering rate changes from one layer to the next. This model leads to the remarkable result that the resistance of a layered material is simply the sum of the resistances of each layer. We present a solution to the Boltzmann equation for CPP for the case in which the electronic structure can be different for different layers. The problem of matching boundary conditions between layers is much more complicated than in the current in the planes (CIP) geometry because it is necessary to include the scattering-in term of the Boltzmann equation even for the case of isotropic scattering. This term couples different values of the momentum parallel to the planes. When the electronic structure is different in different layers there is an interface resistance even in the absence of intermixing of the layers. The size of this interface resistance is affected by the electronic structure, scattering rates, and thicknesses of nearby layers. For Co–Cu, the calculated interface resistance and its spin asymmetry is comparable to that measured at low temperature in sputtered samples.

Paschen and Brackett Lines in Be stars

AbstractThe activities detected in Be stars indicate that the formation of the circumstellar envelope and its structure cannot be studied independently of the phenomena taking place in the outermost layers of the central stars. Assuming that related to the stellar activity there is an expanding atmospheric region with temperatures Te > Teff followed by an envelope with a decreasing temperature, we calculated hydrogen line profiles for different velocity fields and different positions of temperature maxima relative to the underlying photosphere. Results show that the Hα line is not very sensitive to changes introduced to the stellar atmosphere and to the nearby circumstellar layers. Moreover, the Hα emission line profiles look like those produced by disc-like circumstellar envelopes seen pole-on, although the model for the circumstellar envelope is spherical. However, the first members of the Paschen and Brackett series are strongly sensitive to any changes introduced in the photospheric and exophotospheric layers. We conclude that the study of these lines may then be valuable to obtain new insight on the activity of central stars and on the phenomena involved in circumstellar envelope formation in Be stars.

Optical imaging of neural activity in a rat hippocampal slice in an ischemia-like condition

We visualized neural activity evoked by stimulating Schaffer collaterals in the CA1 regions in a rat hippocampal slice preparation, and anlayzed the effect of exposure to an ischemia-like condition at room temperature. We recorded also field potentials from the nearby pyramidal cell layer. Optical signals revealed propagation of action potentials in the molecular/radiatum layers in both directions from the stimulated site, followed by activation of pyramidal/oriens layers, and at the later phase spread to more lateral regions. In an ischemia-like condition in which oxygen and glucose were removed from the perfusing fluid, population spikes and/or slow potentials gradually reduced and disappeared, while optical signals remained only at the stimulation locus. When the perfusate solution was switched to the normal fluid within 10 min population spikes and the optical signals restored to the control level after 15-30 min. These observations demonstrated that generation of neural activities in Schaffer collaterals are the most resistive, but that synaptic transmissions are very sensitive to ischemia-like condition.

Uniform growth of compound-semiconductor film over 10 inch circle by controlling entrance effects by diffusion mixing between 3 layered flows

Entrance effects at platen edge of a wafer holder bring about a predominantly high growth rate in a horizontal reactor of high flow rate of metal organic vapor phase epitaxy (MOVPE) of compound-semiconductors. To solve this problem, we have developed a horizontal reactor with 3 layered flow injections. In this reactor, metal-alkyl source gases diffuse through a nearby flow layer while flowing down stream. By adjusting the thickness and flow rate of the diffusion layer, we can control an amount of metal-alkyl molecules that reach the substrate surface at the entrance region. This method also brings about a freedom of choice in a growth conditions that sometimes contradict with each other such as doping, composition and thickness. As a results, ±1% thickness uniformity of GaAs, AlGaAs and InGaP, and ±1% doping uniformity of Si as well as ±2% doping uniformity of Zn have been obtained.

Long wave radiation regime in vegetation-parameterisations for climate research

An analytical and mathematical model that describes the long wave radiation regime inside a vegetation canopy was developed. The model assumptions are: leaves are the only vegetation elements and are arranged in horizontally infinite layers: they are evenly spread in the layers; having random azimuthal direction and defined zenithal direction. Leaves absorb all thermal radiation, do not scatter any and emit isotropic radiation. An adaptation of the `View factor' concept describes radiation exchanges between leaves and leaf layers. The model calculated the amount of irradiance incident on a single tilted leaf from a flat surface (like the ground). It was found that for an isothermal and infinite emitting surface, with both sides of the leaf absorbing identically, the leaf's tilt angle does not influence the amount of irradiance impinging on it. Then the amount of radiation exchanged by two leaves in nearby layers and the irradiance reaching the leaf from a nearby leaf layer are evaluated. Next, the `layer attenuation coefficient', and the `emission coefficient of a leaf layer' are calculated. Finally, the plane parallel radiation transfer equation of thermal fluxes radiance in vegetation canopy is presented. It was concluded that for an infinite, homogeneous and isothermal leaf canopy with erect leaves, outside irradiance penetrates into deeper layers and less thermal radiation is released to the surroundings, than for the plane leaf canopy case. From this point of view an erect leaf canopy is better suited to cold climates.

Optical spectroscopy of II–VI (magnetic) semiconductor quantum dots

We have probed the magnetooptical properties of II–VI semiconductor quantum dots at low temperatures ( T=5 K) in magnetic fields up to 6T. A layer of coherently strained CdSe dots of diameters 5–20nm is introduced into heterostructures containing either a Zn 0.8Cd 0.2Se quantum well or a barrier layer of MnSe. In the quantum well structure, carriers are localized in strain fields due to the nearby quantum dot layer. The effective g-factors g ∗ of excitons in the localized states are ∼−1.5. In contrast, g ∗∼6 –7 for carriers localized in CdSe islands coupled to an adjacent MnSe barrier. The enhancement of the g-factor in this case is due to the overlap of the tails of the localized wave functions with Mn ++ ions in the barrier.

Volume loss and metasomatism during cleavage formation in carbonate rocks

Controversy exists regarding the amount of volume loss associated with cleavage development. A combination of geometrical and geochemical techniques provides evidence for contemporaneous passive concentration (volume loss) and metasomatism leading to the formation of cleavage in carbonate lithologies and emphasizes the relationship between observational scales and textural heterogeneity. Comparison of protoliths and weakly- to strongly-cleaved rocks along steep, layer-parallel strain gradients within the Doublespring duplex, Lost River Range, Idaho enables quantitative assessments of geometric transformation and elemental mass transfer accompanying progressive deformation. Geometric finite strain analysis documents shortening in the Z direction at low strains ( ε̄ s<0.15) and in both the Z and Y directions at higher strains ( ε̄ s>0.15). Unbalanced shortening in Z and Y with extension in X results in volume loss. Geometrically derived volume strain estimates at the 1–4 cm 3 scale indicate volumetric dilations of from −2% to −12% in uncleaved to weakly-cleaved rocks, and from −20% to −50% in strongly- to very strongly-cleaved rocks. Small-scale significant volume losses and gains contrast with the estimated volume loss of <3% associated with duplex formation at the 100 km 3–1 km 3 scale due to the localization of strain within thin deformation zones. Sampling scale is also a factor in evaluating the major and trace element and O and C isotope compositions of the variably deformed rocks. Samples collected at the 4–15 cm 3 scale reflect mixtures of chemically and mineralogically distinct selvage and microlithon domains. Microdrilling of samples at scales of a few cubic millimeters to 1 cm 3 affords examination of chemical and isotopic differences among individual selvages and microlithons. The data for microdrilled samples demonstrate depletion of Ca and 18O and enrichment of K, Al, Si, Ti, Fe, Na, Mg and P in selvages relative to microlithons and nearby undeformed carbonate layers. The enrichments of some elements (Mg, P, Na and possibly Fe) are more compatible with a passive concentration mechanism, whereas the concentrations of other elements, particularly K, Al, Si and Ti, require significant metasomatic addition during deformation. Shifts in O-isotope compositions of deformed samples relative to the protolith δ 18O values unequivocally demonstrate open-system behavior during deformation. Trends of deformed samples toward lower δ 18O with increasing strain and the δ 18O values of veins are compatible with infiltration by H 2O-rich fluids with relatively low δ 18O V-SMOW (near 0‰). The formation of disjunctive cleavage at the Doublespring duplex occurred by passive concentration resulting from calcite dissolution and related volume loss, and neo-crystallization of illite+kaolinite+quartz±anatase in selvages as a result of metasomatic additions. Chemical and geometric strain softening within selvages likely led to enhanced and preferential fluid flow in selvages.

Novel Applications of Rapid Thermal Chemical Vapor Deposition for Nanoscale MOSFET’s

ABSTRACTIn this paper we examine several applications of Rapid Thermal Chemical Vapor Deposition (RTCVD) for the fabrication of sub-100 rum MOSFET's. Vertical dual-gated MOSFET’s are used as a test vehicle to implement FET's of very short channel length. To realize such devices, the ability of epitaxial Si1-x-y, GexCy layers for suppressing the thermal diffusion, transient enhanced diffusion, and oxidation enhanced diffusion of boron both in the Si1-x-y, GexCy and in nearby Si layers is very useful Novel gate electrodes deposited by RTCVD also showed the ability to greatly reduce boron penetration in ptype polycrystalline gates for p-channel FET’s.

Multipole expansion for inclusions in a lamellar phase

Inclusions in a bulk smectic phase distort the ordering of nearby layers. We argue that a multipole expansion for this distortion represents a powerful technique for understanding the linear interactions between inclusions with arbitrary boundary conditions. The fields for the first few higher-order moments are derived and some specific examples are discussed. Our results show the importance of the orientation and/or configuration of the inclusions.

Defects in colloidal crystal

Colloidal crystal of polystyrene spheres of 0·53 µm diameter dispersed in water is prepared in a quartz container. Optical microscope, video camera and image processor are used to investigate the defects, their dynamics and the effect of shear in this colloidal crystal. Six layers of the crystal from the surface of the container are imaged sequentially, one after another, and the crystal is reconstructed. FCC structure with (111) planes parallel to the container surface is stable at high volume fraction whereas, at low volume fraction (100) planes also coexist. Vacancies, dislocations, grain boundaries, voids and particle aggregates are identified. The vibration of aggregates is sluggish as compared to that of a single particle. The nearest layer of particles to the container surface is better ordered than those in the interior layers. The container wall provides a stabilizing potential to the nearby layers of particles. The 2-D crystalline-like characteristics of the nearby layers are probed. The colloidal crystal is shear-melted by shaking the container. On resting it, the crystal-flow slows down. The flow is constrained to be parallel to the container surface and occurs along the layer in quantum jumps. During the flow, both (111) and (100) planes coexist in the layer. Flow at low rates anneals the defects created by the shear-melting.

Be redistribution in InGaAs and InP grown by gas source molecular beam epitaxy

The redistribution of Be during the growth of InGaAs and InGaAs/InP heterostructures by gas source molecular beam epitaxy has been studied using secondary ion mass spectrometry. Be deposition to the InP layer grown next to the highly Be-doped InGaAs layer has been shown to cause significant Be segregation. Although the growth temperature and AsH 3 flux dependence of Be redistribution in InGaAs layers can be explained by the substitutional-interstitial (S-I) diffusion mechanism, no enhancement of Be redistribution in InGaAs is observed by n + doping in nearby layers, inconsistent with previous results of Zn diffusion. The temperature dependence of Be profiles in InP layers follows the S-I diffusion mechanism, however the PH 3 flow rate dependence is inconsistent with the model.