Flat Blocks Research Articles

Dentin resorption and cementum‐like tissue formation by bone morphogenetic protein application

Recent studies have shown that bone morphogenetic protein-2 (BMP-2) stimulates mineralization and osteoclast differentiation. Osteoclastic resorption by BMP-2 application may play an important role in the regulation of new cementum-like tissue formation on the dentin surfaces. Therefore, this study aimed to examine the effect of BMP-2 application on dentin resorption and cementum-like tissue formation at the dentin surfaces. Seventy-two flat dentin blocks were prepared from rat roots and treated with 24% EDTA. Each block was assigned to group 0, group 100, or group 400, and immersed correspondingly in 0, 100, or 400 microg/ml BMP-2. The dentin blocks were then implanted into palatal connective tissue of rats, and specimens were prepared 2, 4 and 8 wk after surgery for histologic and histomorphometric analyses. BMP-2 caused a dose-dependent increase in dentin resorption by osteoclastic cells. New cementum-like tissue was randomly formed on parts of the nonresorbed and resorbed dentin surfaces in groups 100 and 400. Dentin resorption in groups 100 and 400 was significantly greater than group 0 (p < 0.01). However, at 8 wk, new cementum-like tissue formed in 41.8% of group 100, as compared with 16.2% of group 400 (p < 0.05). Dentin resorption was stimulated by a high dose of BMP-2, and cementum-like tissue was induced by a low dose of BMP-2, effectively suggesting that BMP-2 application, at an appropriate dose, to a dentin surface may enhance periodontal regeneration.

A NOVEL INVESTIGATION OF THE OSCILLATORY FIELD OVER A TRANSPIRING SURFACE

The flowfield character is investigated inside a long rectangular chamber in the presence of time-harmonic pressure waves. The chamber is designed with multiple interchangeable sections for the purpose of controlling the length and therefore the system's natural frequency. Pressure waves are induced externally at variable frequencies by means of a Scotch-yoke mechanism theoretically capable of imparting pure oscillatory motions. In characterizing the internal flowfield, velocity measurements are acquired inside a principal test section that can accommodate flat blocks of solid carbon dioxide (i.e., dry ice). As solid CO2sublimates, a flow of gaseous carbon dioxide is generated at the bottom of the principal section and enters the chamber in the transverse direction. The resulting generalized Stokes layer formed above the transpiring surface exhibits several features associated with oscillatory flows over impermeable surfaces, including an overshoot in the velocity amplitude in the vicinity of the transpiring wall known as Richardson's annular effect. Quantitative pressure and velocity measurements are in agreement with theoretical predictions obtained from recent models of the oscillatory field over transpiring surfaces. The acoustic Reynolds number based on the Stokes layer thickness increases linearly with increasing Scotch-yoke frequency except in the neighborhood of the system's natural frequency. Near resonance, a sharp non-linear increase in the acoustic Reynolds number is noted. Furthermore, both acoustic pressure and velocity amplitudes increase with the driving frequency in a manner that is consistent with current theories. Since the sublimation rate of dry ice can be expressed in a similar mathematical form to the regression rate at the burning surface of solid propellants, this experiment constitutes a cold flow simulation of the internal flowfield in solid rocket motors.

Cytochemical and immunocytochemical methods for electron microscopic detection of glucose-6-phosphate dehydrogenase in brain areas

This paper reports on protocols for the cytochemical and immunocytochemical determination of the glucose-6-phosphate dehydrogenase (G6PD) in brain areas by electron microscopy (EM). The cytochemical assay consists of a pre-embedding staining of small and flat tissue blocks, which were first mildly fixed and then floated in a staining mixture based on the reduction of tetrazolium salts by NADPH. Tissue blocks were then washed, post-fixed in OsO 4, dehydrated through graded ethanol concentrations and embedded in resin. Ultrathin sections were then obtained and observed at the EM. The immunocytochemical technique was performed on completely fixed tissues of perfused animals. After the tissue embedding in resin, ultrathin sections were obtained and treated with a primary anti-erythrocyte G6PD antibody, produced and purified in our laboratory. The immunostaining was performed with secondary gold-conjugated antibody. Gold grains were well evident by EM analysis thus revealing the G6PD protein in the subcellular compartments. These protocols are useful to detect peculiar populations of neurons which express high levels of G6PD to sustain processes of neural plasticity in some brain areas. Themes: Development and regeneration Topics: Cell division and differentiation

Natural vibrations of prestressed flat composite blocks

A three-dimensional method for determination of natural vibration frequencies of prestressed flat composite blocks is proposed. Two approaches are used: analytic separation of variables and reduction of the three-dimensional problem to a two-dimensional one using the hypothesis method based on polynomial approximation of the required functions according to the structure thickness. The proposed hypothesis method provides generalized discrete- and continuous-structure approaches for mathematical modeling of layered structure deformation.

Change of biota after construction of “high crest” submerged breakwater

A submerged breakwater, its crest nearly coincided with the H.W.L., was constructed off Hagino, the Iburi Coast in Hokkaido. Echo-freindly units were used for this “high crest” submerged breakwater. The new units have large empty spaces to allow sunlight to go through onto the rock mound. A study on organisms attaching themselves and macrobenthos in the surroundings was performed over a period of 3 years. Kelp (Laminaria angustata) forests formed on the insidewalls of both units and the rock mound. The standing crop was 10-25 times that found on flat crest blocks (used as a control). This distinction was due to the complex unit structure and the variation in depth substrata. As the sand particle size on the landward side of the breakwater increased slightly with every year, macrobenthos such as annelida became more abundant. In addition, rock fish were seen to frequent the breakwater. The “high crest” submerged breakwater using the new units functioned not only protected the coast, but also acted as a rocky ecosystem and feeding point on the sandy bottom.

Surface morphology and backscattering of ice-ridge sails in the Baltic Sea

Abstract The triangular shape of an ice-ridge sail in the Baltic Sea was studied statistically. The dimensions and orientation of individual ice blocks were measured in several ridges. All measurements were carried out from the standpoint of backscattering research. The results confirm that given geometrical properties of the two sides of ice ridges are in general not equal. A slight negative correlation was found between the slope angle and width of the sail. All three orientations and all three size parameters of ice blocks on both sides of the ridges studied can be considered as normally distributed. A log-normal distribution, however, fits slightly better the dimensions of the orientationally best rectangular approximations of the polygonal main facets of flat ice blocks. Three-dimensional modelling of ice ridges is essential, since the total side-facet area visible is typically at least as large as the total main-facet area. Calculated incidence-angle distrubutions show that the broad distributions of orientations and dimensions make different redges appear very similar on radar images.

Surface morphology and backscattering of ice-ridge sails in the Baltic Sea

AbstractThe triangular shape of an ice-ridge sail in the Baltic Sea was studied statistically. The dimensions and orientation of individual ice blocks were measured in several ridges. All measurements were carried out from the standpoint of backscattering research. The results confirm that given geometrical properties of the two sides of ice ridges are in general not equal. A slight negative correlation was found between the slope angle and width of the sail. All three orientations and all three size parameters of ice blocks on both sides of the ridges studied can be considered as normally distributed. A log-normal distribution, however, fits slightly better the dimensions of the orientationally best rectangular approximations of the polygonal main facets of flat ice blocks. Three-dimensional modelling of ice ridges is essential, since the total side-facet area visible is typically at least as large as the total main-facet area. Calculated incidence-angle distrubutions show that the broad distributions of orientations and dimensions make different redges appear very similar on radar images.

Precast Concrete Blocks for High‐Velocity Flow Applications

Precast concrete blocks can be used as erosion protection to a surface subjected to high‐velocity water, for example a dam spillway.The paper describes model testing carried out on flat and wedge‐shaped blocks in a purpose‐designed facility at the University of Salford, where an open channel discharge intensity of 0.5 m2/s can be accelerated to a velocity of 7.5 m/s.The failure modes of tied and untied flat concrete blocks have been investigated under different laying and bedding conditions. The model results are compared to the findings from prototype studies. Results from experiments on wedge‐shaped blocks of a Soviet design are also presented and confirm the Russian experience that the wedge shape is inherently stable at large discharges, a block of 100‐m thickness being stable under a discharge intensity of 20 m2/s.

Numerical two-dimensional analysis of a ring DF-CO2 continuous chemical laser taking into account reagent mixing

This paper uses a two-dimensional approach and takes into account viscosity, diffusion, and heat conduction to study the effect of a finite rate of mixing on the specific energy indicators of DF-CO/sub 2/ lasers with flat and cylindrical nozzle blocks. Numerous calculations show that the use of a narrow-channel model is entirely justified. To obtain more subtle information, associated with the distrubution of the gasdynamic parameters in the lasing zone more complicated models based on the complete system of Navier-stokes equations are used. However, the real flow pattern evidently depends substantially on the initial parameters of the chemically active jets being mixed, whose correct determination is in itself by no means a trivial problem.

Efficient and multiplierless design of FIR filters with very sharp cutoff via maximally flat building blocks

A new design technique for linear-phase FIR filters, based on maximally flat buildiing blocks, is presented. The design technique does not involve iterative approximations and is, therefore, fast. It gives rise to filters that have a monotone stopband response, as required in some applications. The technique is partially based on an interpolative scheme. Implementation of the obtained filter designs requires a much smaller number of multiplications than maximally flat (MAXFLAT) FIR filters designed by the conventional approach. A technique based on FIR spectral transformations to design new multiplierless FIR filter structures is then advanced, and multiplierless implementations for sharp cutoff specifications are included.

Initial colonization, erosion and accretion of coral substrate

Blocks cut from Porites lutea were laid on the fore reef slope, reef flat and a lagoonal patch reef at Lizard Island, in the Northern Great Barrier Reef, and replicates removed from each environment at intervals of three months over a period of one and a half years. Variations in bioeroders and bioaccretors were noted. Microfaunas are far more numerous than macrofaunas as block colonizers; the principal borers are polychaete worms, whereas encrusters are molluscs, bryozoans, serpulids and solitary corals. The reef slope is more readily colonised by microfauna pioneer communities than are the other areas. All the environments exhibit a change from cirratulids to either sabellids or spionids (polydorids) over the length of the experiment. Accretion occurred on all blocks during the experiment, with significant differences detectable between environments; both reef slope and reef flat blocks showed weight increases of 9–10% whereas blocks from the patch reef showed increases of 15%. Annual erosion rates produced by polychaete worms are 0.694 kg m-2 year-1 (reef front), 0.843 kg m-2 year-1 (reef flat) and 1.788 kg m-2 year-1 (patch reef).

Interfacial Stresses for Bonded Rubber Blocks in Compression and Shear

When a rubber block is compressed between two rigid surfaces, to which it is bonded, both compressive and shear stresses are set up at the interfaces. These interfacial stresses have been measured for small compressions of four relatively-thin, flat rubber blocks of square and circular cross section. Maximum compressive stresses, nearly twice the average value, were developed in the center of the bonded surfaces. Shear stresses were found to increase continuously from zero at the center to maximum values at the edges. No evidence was detected of a singularity at the edges. For all of the blocks examined, the observed stress distributions agreed satisfactorily with theoretical predictions based on incompressibility of the rubber and a simple superposition of two deformation states. Measurements were also made of the shear stress distribution associated with an overall shear displacement of the block.

New products

The Logitech Precision Lapping System, centered on the LP 30 Production Lapping Machine, provides a unified automatic method whereby finished rock sections of high quality may be produced at a considerably enhanced production rate. The LP 30 machine has a reported capacity for lapping at three work stations and provides facilities for automatic feed of abrasive, variable speed control, and vacuum supply for vacuum chuck location of specimens. Conditioning‐retaining rings and flat pressure blocks are used for primary thinning and flat lapping of unmounted rock slices. The lapped slices, typically of 2‐mm thickness, are cemented to glass microscope slides of uniform lapped thickness by means of a special bonding jig so that the cement layer thickness is effectively zero.

New product

The Logitech concern of Scotland has developed an automatic system that will enable technicians to treble their output of 30‐micron rock sections for geological research. The system revolves around a Logitech Model LP 30 production lapping machine with a capacity for lapping at three work stations providing facilities for automatic feed of abrasives, variable speed control and vacuum supply for vacuum chuck location of specimens. Three sets of conditioning/retaining rings and flat pressure blocks are used for primary thinning and flat lapping of unmounted rock slices. The lapped slices, typically of 2mm thickness, are cemented to glass microscope slides of uniform lapped thickness by means of a special bonding jig so that the cement layer thickness is of the order of one micron.

Creative mathematics at Nueva

That's the most beautiful description of infinity I have ever thought about,” exclaimed deep-thinking Benjie. For a nineyear-old to consider infinity and express his appreciation was a real mountaintop. With a box of base-three blocks before him, he had seen that three units make a long, three longs a flat, and three flats a block; then, in the same way, three blocks would make a long block, three long blocks a flat block, and three flat blocks a block block. The last question on the activity card was, “Does this process ever end?” At that point Benjie nudged me to say, “If I had all the wood in the world, it would not be enough to finish the process, and that is why it describes infinity.”

Brovst, en kystboplads fra ældre stenalder

Brovst, en kystboplads fra ældre stenalder

Plate Sliding Type Automatic One Side Welding in Assembly Stage of Hull Construction

Intending to apply an assembly-line-production, a mass production medium, to the assembly of flat blocks, it is essential for the plate joining work which is the beginning of the whole production to be applicable to the assembly-line-production.The conventional plates joining method is such that the right side of the plates is initially welded and the reverse side is also welded after turning them over. But the busy crane program in many cases prevents a smooth progress of work since the crane is not provided exclusively for this process. So, if such welding method, capable of welding two plates together in one process from the right side to the extreme reverse side, is available, it can eliminate such extra works as turnover and welding reverse side and can creates a smoother flow of material. Of various methods of automatic one side welding, the one we have developed is “Plate sliding type automatic one side welding” that the steel plates to be welded slide themselves through the welding point of a fixed welding machine, under neath which there is a piece of copper plate to keep pushing up the reverse side of the plates being welded.By this process, the plates are welded together from the extreme right side to the extreme reverse side.This particular welding method has required us so much study in the process of development especially regarding welding method itself and the holding copper plate system because of the fact that it is different in many respects from ordinary welding methods which hold steel plates to be welded still. As a result of our thorough study, we have successfully developed an automatic one side welding method capable of welding to the extreme reverse side of the plate in one process capable of handling plates, 10 mm to 40 mm in thickness and 10 m to 20 m in length. This new method is now being applied to our hull assembly work in factory.

Arabiens arkæologi

Arabiens arkæologi

A Metallographic Study of Diffusion Interfaces

By sintering wires to flat metallic blocks, diffusion interfaces were obtained between the following pairs of metals: Cu-Ni, Au-Ag, Cu-Ag, Cu-Fe, Fe-Ni, Cu-Zn, Ni-Zn, and 70/30 brass-Cu. The interfaces were subsequently investigated metallographically. Grooves were observed in the lower melting point component in the vicinity of the sintered interfaces. This is attributed to the faster diffusion rate in the lower melting point metal.