Edge-to-edge Research Articles

Self-assembling endohedrally doped CdS nanoclusters: new porous solid phases of CdS

Hollow CdS nanoclusters were predicted to trap alkali metals and halogen atoms inside their cavity. Furthermore, electron affinities (EA) of endohedrally halogen doped clusters and ionization potentials (IE) of endohedrally alkali doped clusters were predicted to be very similar. This makes them suitable to build cluster-assembled materials, in the same vein as do related ZnO, ZnS and MgO nanoclusters, which yield porous solid materials. With this aim in mind, we have focused on the assembly of bare Cd(i)S(i) and endohedral K@Cd(i)S(i)-X@Cd(i)S(i) (i = 12, 16, X = Cl, Br) clusters in order to obtain solids with tailored semiconducting and structural properties. Since these hollow nanoclusters possess square and hexagonal faces, three different orientations have to be considered, namely, edge-to-edge (E-E), square-to-square (S-S) and hexagon-to-hexagon (H-H). These three orientations lead to distinct zeolite-like nanoporous bulk CdS solid phases denoted as SOD, LTA and FAU. These solids are low-density crystalline nanoporous materials that might be useful in a wide range of applications ranging from molecular sieves for heterogeneous catalysis to gas storage templates.

Optimized guidance of percutaneous edge-to edge repair of the mitral valve using real-time 3-D transesophageal echocardiography

Percutaneous edge-to-edge repair with the MitraClip device has been shown to allow effective treatment of mitral regurgitation. It is mainly guided by transesophageal echocardiography while fluoroscopic guidance is of less importance. The impact of real-time three-dimensional transesophageal echocardiography (RT 3-D TEE) for guidance of this complex interventional procedure has not been evaluated. In 28 high-surgical risk patients with moderate or severe mitral regurgitation (mean age 67±10years; 15 male), 2-D and RT 3-D TEE were used for the guidance of percutaneous edge-to-edge mitral valve repair using the MitraClip device. We performed a structured analysis to compare information and guidance capacity provided by RT 3-D TEE compared to 2-D TEE. RT 3-D TEE was found to provide advantages in 9 of 11 steps of the percutaneous mitral repair procedure. The advantages related to optimized definition of the transseptal puncture site, improved guidance of the clip delivery system towards the mitral valve, precise positioning of the clip delivery system simultaneously in anterior-posterior and lateral-medial direction above the mitral valve considering mitral valve scallops A2 and P2 and valvular regurgitation jet position, adjustment of the opened clip-arms perpendicular to the commissural line, visualization of the clip position relative to the valvular orifice and of the remaining regurgitant jet after clip closure from atrial as well as ventricular views providing double orifice images and thereby allowing confirmation or rejection of clip position in medial-lateral direction. RT 3-D TEE was inferior to 2-D TEE for leaflet grasping and analysis of leaflet insertion. In complex interventional edge-to-edge repair with the MitraClip device requiring optimal spatial information RT 3-D TEE allows improved guidance of the procedure. RT 3-D TEE guidance compared with 2-D TEE guidance alone resulted in greater operator confidence to adequately perform the procedure.

Control of Mode of Crystal Networking During Monolayer Assembly of Microcrystals on Water

A series of hydrocarbon (HC)-coated cubic zeolite microcrystals (1.7 microm) was prepared. The HCs were n-octyl, n-dodecyl, methyl n-undecanoate, n-octadecyl, and n-heptadecafluorodecyl. The measured water contact angles (theta) of the corresponding HC-coated glass plates were 64, 77, 82, 102, and 105 degrees, respectively, indicating that the hydrophobicity of the surface-tethered hydrophobic chain (HC) increased in the above order. The HC-coated zeolite microcrystals readily formed closely packed monolayers at the air-water interface through interdigitation of surface-tethered HCs, and on glass plates after transferring onto glass plates by dip coating. Interestingly, while the mode of networking was face-to-face (FTF) contacting with n-octyl or n-dodecyl (theta < or =77 degrees) as HC, it changed to edge-to-edge (ETE) contacting mode with n-octadecyl or n-heptadecafluorodecyl (theta > or = 102 degrees) as HC. With methyl n-undecanoate (theta = 82 degrees) as HC, both modes appeared in the monolayers, with about equal populations. The resulting monolayers of cubic zeolite microcrystals with their three-fold axes oriented perpendicular to substrates would be useful for application of the zeolite monolayers for advanced materials.

Vertical interincisal trespass assessment in children with speech disorders

Through a transversal epidemiological study, conducted with 333 Brazilian children, males (157) and females (176), aged 3 to 6 years old, enrolled in a public preschool, this study aimed to evaluate the prevalence of the different types of vertical interincisal trespass (VIT) and the relationship between these occlusal aspects and anterior lisping and/or anterior tongue thrust in the articulation of the lingua-alveolar phonemes /t/, /d/, /n/ and /l/. All children involved were submitted to a VIT examination and to a speech evaluation. Statistical significance was analyzed through the Qui-square test, at a significance level of 0.05 (95% confidence limit). The quantitative analysis of the data demonstrated the following prevalences: 1 - the different types of VIT: 48.3% for normal overbite (NO), 22.5% for deep overbite (DO), 9.3% for edge to edge (ETE) and 19.8% for open bite (OB); 2 - interdental lisping in relation to the different types of VIT: 42% for NO, 12.5% for DO, 12.5% for ETE, 32.9% for OB; and 3 - children with anterior tongue thrust in the articulation of lingua-alveolar phonemes in relation to the different types of VIT: 42.1% for NO, 14% for DO, 10.5% for ETE, 33.3% for OB. The results demonstrated that there was a significant relationship between open bite and anterior lisping and/or anterior tongue thrust in the articulation of the lingua-alveolar phonemes /t/, /d/, /n/ and /l/; and that there was a significant relationship between deep overbite and the absence of anterior lisping and anterior tongue thrust in the articulation of the lingua-alveolar phonemes.

Laterotrusive Occlusal Schemes and Jaw Posture Tasks Effects On Supra- and Infrahyoid EMG Activity in the Lateral Decubitus Position

The purpose of this study was to determine the effect of canine guidance and group function on supra- and infrahyoid EMG activity in the lateral decubitus position at different jaw posture tasks. The sample included 40 healthy subjects with natural dentition and bilateral molar support, 20 with bilateral canine guidance and 20 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left supra- and infrahyoid muscles for EMG recordings. In the lateral decubitus position, EMG activity was recorded in subjects with canine guidance or group function, during the following jaw posture tasks: A. maximal clenching in the edge-to edge lateral contact position; B. grinding from intercuspal position to edge-to-edge lateral contact position, and C. grinding from edge-to-edge lateral contact position to intercuspal position. Supra- and infrahyoid EMG activity was not significantly different with canine guidance or group function (mixed model with unstructured covariance matrix). Overall comparison of suprahyoid or infrahyoid EMG activity among the three jaw posture tasks studied showed a significantly higher activity during jaw posture task A (clenching) than jaw posture tasks B and C (grinding). Suprahyoid EMG activity was significantly higher during jaw posture task C than B, whereas infrahyoid EMG activity did not present a significant difference between jaw posture tasks C and B. These EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding. The neurophysiological mechanisms involved are discussed.

Muscular adaptation to gradual advancement of the mandible.

Muscular activity of the superficial masseter muscle and anterior portion of the temporal muscle before, during, and after treatment, with gradual advancement of the mandible, was evaluated by assessing the average integrated electromyogram (EMG) with the mandible in retruded position (RP) and incisal edge-to-edge (EE) position on 23 consecutive subjects with skeletal Class II malocclusion. Toward the end of active treatment and follow-up, the RP position and EE position coincided. At any given registration, the EMG activity of the masseter muscle was at least twice (P < .001) that of the anterior portion of the temporal muscle. The EMG activity in RP for the anterior portion of the temporal muscle was not affected significantly, whereas the EMG activity at EE position decreased significantly (P < .05) during the initial treatment, but, thereafter, it increased continuously. The difference in EMG activity between six months of follow-up and pretreatment level reached statistical significance (P < .05). For the masseter muscle, the EMG activity at both RP and EE position was reduced about 20% during the initial treatment but returned to the pretreatment level during active treatment and exceeded pretreatment level by approximately 30% to 50% at two and six months of follow-up, respectively. In conclusion, it seemed that gradual advancement affected the anterior portion of the temporal muscle to a minor extent, whereas the effect on the masseter muscle was significant.

Hydrophobic attraction may contribute to aqueous flocculation of clays

SEM observations of low solid content vitrified clay suspensions reveal that clay platelets build porous three-dimensional networks with platelets contacting each other mostly by their edges. To explain this behaviour, which must require long range edge-to-edge (EE) attractive forces, a hydrophobic-like interaction has been proposed. This interaction may be induced by the presence of nano-bubbles existing on the edges of clay crystals which may cause clay particles to flocculate. The following indirect evidence for such hydrophobic behaviour is presented. First, a clay platelet is shown attached to an oil drop by its edge; second, clay flocs were attracted by a vertically placed Teflon strip but not to the hydrophilic mica basal surface; third, a much thicker porous sediment occurred in CO2-saturated water solution compared with vacuum degassed water.

Scaling Behavior of the Rheological Properties of Montmorillonite Suspensions: Correlation between Interparticle Interaction and Degree of Flocculation

In this work we investigate some aspects of the rheological behavior of sodium montmorillonite (NaMt) suspensions in the pH range 3 to 9, of NaCl concentrations between 10−3 and 10−1 M, and of solid concentrations between 5 and 11% w/v. Three kinds of experiments were performed: steady-state viscometry, oscillatory test, and creep recovery. The physical quantities of interest were the yield stress σy of the suspensions, the elastic rigidity modulus G′, and the instantaneous elastic compliance. Furthermore, G′ was obtained from oscillatory tests in three different experiments: determination of the viscoelastic linear region, oscillograms, and the gelation process. All quantities were found to scale with the concentration of solids, C, according to a power law of the form Y=kyCn. The exponents n were found to change from ∼3 to ∼6 when the pH was increased from 3 to 9 (at constant ionic strength 10−2 M), although values as high as 10 were estimated when the NaCl concentration was reduced to 1 mM. Such values of n correlate well with the characteristics of the edge-to-face (E-F), edge-to-edge (E-E), and face-to-face (F-F) interparticle interactions. The minimum values of n correspond to maximum E-F attractions, whereas the largest n are associated with strong F-F repulsions.

Microstructure of kaolinite sediments made with unaged FeCl3

Fine kaolinite suspensions were prepared with unaged FeCl3 to perform sedimentation tests in this study. The microstructure of kaolinite sediments was examined by scanning electron microscopy after CO2 supercritical drying. The interaction between clay particles and FeCl3 in an aqueous medium was investigated by means of electrophoresis and analytical transmission electron microscopy. Clay particles were connected in three basic modes — edge to edge (EE), edge to face (EF) and face to face (FF). Clay particles with different connection modes formed aggregates or flocs in sediments. The flocs not only exhibited a fractal structure themselves, but also formed sediments with fractal characteristics. This study determined the formation conditions of different clay particle connection modes, aggregates or fractal flocs in the presence of unaged FeCl3 in an aqueous medium.

Surface relief effects associated with the formation of grain boundary allotriomorph in an Fe–C alloy

Surface relief effects associated with the formation of grain boundary allotriomorph (GBA) in an Fe–C alloy have been first studied by scanning tunneling microscopy (STM). It was discovered that the GBAs which exhibit the surface relief are only developed into one austenite grain, which means the interface between the austenite and the GBA which exhibits surface relief is partially coherent, and the interface between the austenite and the GBA nucleated at the same grain boundary but developed into the adjacent austenite grain may be incoherent. The maximum shape deformation of surface relief due to GBA precipitation is ca. 0.39, which is consistent with that of Widmanstätten ferrite plates. Accompanying the formation of Widmanstätten sawteeth, surface relief is produced, which is composed of reliefs associated with several sideplates. By STM the boundaries between GBAs are clear, which indicates that they are resulted from edge-to-edge (ETE) or face-to-face (FTF) sympathetic nucleation. Super ledges ( ca. 300 nm high) were observed on the broad face of GBA. All these results can be rationally interpreted by the sympathetic nucleation-ledgewise growth mechanism.

Homogenization of Harmonic Vector Fields on Riemannian Manifolds with Complicated Microstructure

We study the asymptotic behaviour of harmonic vector fields with givenfluxes or periods on special manifolds consisting of one or several copiesof the Euclidean space, with a large number of small holes attached edge toedge by means of thin tubes (wormholes) when the number of holes tends toinfinity. We obtain the homogenized equations describing the leading term ofthe asymptotics.

前方運動時における下顎頭の回転と移動の様相に関する研究

This study was designed to clarify the standards for functional evaluation of the anterior guidance. The rotation and translation of the mandibular head in protrusive movement were measured with a simplified condylar movement recorder using the dual axis graphic system.At the edge-to-edge position, a significant correlation was noted between the sagittal condylarguide inclination and the incisal guide inclination, but the rotation of the mandibular head inprotrusive movement was variable because of curves of the condylar path and incisal path. Thechanging aspects of the rotation of the mandibular head could be classified into three types.Nevertheless, changes in the rotation of the mandibular head did not go beyond a certain range, suggesting that there are some limitations on the change in the rotation of the mandibular head.From the above, it was concluded that there is something characteristic about the rotation of themandibular head from the intercuspal position to edge-to edge contact position in protrusivemovement. This suggests that it is important for us to understand the phases of rotation andtranslation of the mandibular head in the evaluation of the function of anterior guidance.

TEM analysis of pillared and delaminated hectorite catalysts

When a dispersion of clay particles flocculates in water, the plates may associate as face-to-face (FF), edge-to-edge (EE), or edge-to-face (EF). The FF association forms thicker particles whereas EF and EE interactions generate large three-dimensional aggregates which was described as having a house-of-card structure. These two modes of particle association can be observed also in solids. In fact, by ion-exchanging the charge compensating cations in layer-lattice clay minerals such as montmorillonite or hectorite with large organic or inorganic cations, multilayered FF aggregates are formed called pillared clays. Clay particle aggregates containing EF and EE linkages are called delaminated clays. Delaminated clays are a new family of catalysts first prepared by reacting a synthetic hectorite with polyoxocations of aluminum. In these materials, 001 X-ray reflections are absent due to a lack of long range FF stacking of the clay silicate layers. Short range FF layer ordering is believed to be responsible for the zeolite-like selectivity in cracking gas oil. Delaminated clays are characterized by EE and EF connections which form a macrospace of the type found in amorphous alumino-silicate supports. In contrast, pillared clays, are characterized by regularly spaced FF layers of clay platelets propped apart by inorganic oxide clusters. Tokarzmore » and Shabtai have shown transmission electron micrographs (TEM) of Ce/sup +3/-montmorillonite before and after pillaring. It is the purpose of this note to present TEM and electron diffraction data that will further characterize the structure of delaminated clay catalysts.« less

Electrical properties and the surface characteristics and structure of clays. II. Kaolinite—a nonswelling clay

The conductivity and permittivity of sodium kaolinite are measured with respect to frequency (10–10 5 Hz), concentration (0.1 to 100 g solid per 100 ml sample), and temperature (293–318°K). The Stern/Gouy model of the colloid double layer is applied, together with the Schwarz theory for polarization due to bound surface ions. The total surface change on kaolinite, as in the preceding paper on swelling clays, is quantitatively accounted for by the combined conductivity and permittivity results. An edge-to-edge (EE) and edge-to-face (EF) associated structure made up of face-to-face (FF) aggregates of multilayer clay platelets is indicated, with microscopic dimensions similar to the individual particle sizes, though much smaller than is suggested by the macroscopic sedimentation rates. The macroscopic structure is probably closer to a microporous “honeycomb” than a macroporous “capillary” system. The conductivity results and mechanisms are applied to electrophoresis and electroosmosis, and the permittivity results and mechanisms are correlated with dielectrophoresis. The problem of electrokinetic dewatering in both swelling and nonswelling clays is discussed, referring to the results of the accompanying paper on swelling clays.

Electrical properties and the surface characteristics and structure of clays. I. Swelling clays

The conductivity and permittivity of montmorillonite and laponite are measured with respect to frequency (10–10 5 Hz), concentration (0–24%), temperature (288–315°K), and purity. The Stern/Gouy model of the colloid double layer is applied. Conduction involves ions in the diffuse part of the double layer and seems to resemble the macroscopic three-dimensional volume conductivity of simple electrolytes, rather than a surface migration along the clay platelets. Surface polarization occurs in the Stern part of the double layer—a microscopic migration of relatively bound, immobile counterions to produce a surface capacitance. The latter relaxes via diffusion of the counterions under the gradient of chemical potential (concentration) that accompanies the polarization by the electric field, and so gives rise to a dielectric loss. This loss is equivalent to a surface conductance. The total surface charge on the clays, represented by the cation exchange capacity, is quantitatively accounted for by the combined conductivity and permittivity results. An edge-toedge (EE) and edge-to-face (EF) associated structure of single layer clay platelets is favored, with observed microscopic dimensions in accord with light scattering studies and with theoretical models. The macroscopic structure seems closer to a microporous “honeycomb” than a macroporous “capillary” system.

The 'Sawdust Sand'; an Eocene sediment of floccule origin

The Sawdust Sand of the Eocene-Wilcox in western Tennessee is an unconsolidated sediment composed largely of aggregate grains. The aggregate grains and cross-stratification give the Sawdust Sand the appearance of medium to coarse, well-sorted sands. When disaggregated the sands become poorly sorted, silty and clayey, very fine sands, indicating a break-down of the aggregate particles. Two general types of aggregates are present: those composed chiefly of clay mineral particles in a three dimensional array of face to face (FF), edge to edge (EE) and edge to face (EF) configurations; and those where silt and fine sand-sized quartz and feldspar are included in the clay mineral particle network. The aggregates have clay mineral compositions of kaolinite-montmorillonite or kaolinite and the two mineralogical suites are stratigraphically segregated. The fabrics and textures of the aggregate grains, their mineralogical associations and their primary stratification lead to the conclusion that the aggregate grains in the Sawdust Sand are relict floccules.