Ridge Angle Research Articles

Fluctuating asymmetry in dermatoglyphics of non-insulin-dependent diabetes mellitus in Bangalore-based population

Background: The aetiology of NIDDM is believed to be as a consequence of genetic and environmental factors that impair metabolism. While little can be done on the genetic component, much can be done as a preventive measure in NIDDM. Because nothing much can be done prenatally, researchers have resorted to studying physical variables like dermatoglyphics (DGs). Dermatoglyphic patterns form on the finger pad and the palm prenatally and remain unchanged throughout life, thus these features may serve as markers for fetal origin of adult disease like NIDDM. Thus the concept of fluctuating asymmetry (FA) which has been defined as random differences between the right (R) and left (L) sides of a morphological trait has gained prominence in diseases like schizophrenia. When the distribution of R-L differences in a population sample approximates a normal curve with a mean approximately equal to zero, the variance of distributions of R-L difference is a measure of FA. Studies have shown that genetic factors may also have a link to FA in finger and a-b ridge counts. No studies have been reported on FA in NIDDM. FA derived from quantitative parameters in DGs of NIDDM may throw light on fetal origins of an adult disease. Hence this study has been undertaken. Aim: The present study aims at deriving FA from quantitative parameters in DGs of NIDDM compared to controls in the Bangalore based population. Materials and Methods: Bilateral rolled finger and palm prints of 150 NIDDM patients (Males - 75, Females - 75) were compared to 120 controls (Males - 60, females -60) from Bangalore based population. FA measures derived from quantitative parameters (finger ridge counts, a-b ridge counts, main line index and palmar angles) were analysed. Results: Comparisons were made in all parameters between homologous fingers of both hands using Pearson's product moment correlation coefficients (r). The difference in correlation coefficients between cases and controls was calculated using Fisher's Z transformation. 1-r2 an estimate of error variance thus measures FA. FA measures were significantly higher in NIDDM males for the 5th finger (FA=2.04) and for the palmar angle 'dat' (FA=2.24); for the NIDDM female a high FA was found in the 2nd finger (FA=2.17) compared to controls. CONCLUSION: Overall measures of the above ridge counts and angles and their derived measures of FA were prominent features of NIDDM in this sample.

Mechanisms of elevated temperature fatigue crack growth in Zr–Ti–Cu–Ni–Be bulk metallic glass

Zr-based bulk metallic glasses (BMGs) are surprisingly susceptible to cyclic fatigue processes. In the present study, the sub- T g elevated temperature fatigue crack growth behavior was examined. The fatigue threshold, Δ K TH, was found to increase from ∼1.1 to ∼1.4 MPa m 1/2 as testing temperature was increased from 100 to 220 °C. Low levels of fatigue crack closure were apparent and not associated with threshold behavior. Regular arrays of micron-sized elongated ridges formed parallel to the crack growth direction in the near-threshold fatigue crack-growth regime at elevated temperatures. A model for ridge formation based upon the planar stability of a Mode I crack was proposed. Ridge wavelengths and amplitudes were accurately predicted with respect to changes in applied stress intensity and temperature, and ridge angles were calculated on the basis of a Mohr–Coulomb yield criterion.

Direct numerical simulation of heat transfer over riblets

Riblets are well-known as a passive mean for drag reduction in turbulent flow conditions, but their effectiveness for heat transfer is quite controversial. In this paper we present the numerical results for fully developed laminar and turbulent flow and heat transfer in a channel with triangular riblets. The turbulent study is performed by means of direct numerical simulation at a Reynolds number Re τ =180 based on the wall-shear velocity, for a fluid with a Prandtl number Pr=0.71. Four different ribbed channels are considered, under a constant heat flux boundary condition, and correspond to ridge angle α=45° and 60°, and riblet spacing s +=20 and s +=40. The results obtained, for the flow and turbulent quantities, are in good agreement with past experimental and numerical studies, and correctly reproduce drag reduction over the smaller s +=20 riblets and drag increase over the larger s +=40 riblets. The predicted heat transfer efficiency of riblets do not agree with some experimental results, and is below that of a flat plate for all the configurations. The conditions for heat transfer enhancement are discussed.

The origin, classification and modelling of sand banks and ridges

Sand banks and elongated sand ridges occur in many coastal and shelf seas where there is abundant sand and where the currents are strong enough to move sediment, but they have a wide variety of forms. Their generation requires a source of mobile sediment, either from the local sea bed, or from coast erosion. Most appear to have been created during the post-glacial rise in sea level, but they have been subsequently modified by changing currents and waves, thus losing their relict characteristics. A descriptive classification scheme is developed to unify the approaches of marine geologists and physical oceanographers, which emphasizes the formation and present hydrodynamic setting in their long-term development. Open shelf linear ridges (Type 1) are up to 80 km long, average 13 km wide and are tens of metres in height. They are oriented at an angle to the flow, are asymmetrical and appear to migrate in the direction of their steep face. They appear to be in near equilibrium with the flow. These contrast with linear ridges formed in mouths of wide estuaries, which are aligned with the flow, and which migrate away from their steeper face (Type2A). In narrow-mouthed estuaries and inlets, tidal currents are strong only close to the mouth and waves are more dominant. The banks then form close to the mouth as ebb and flood deltas (Type 2Bi). When the coast is retreating, the ebb delta forms a primary source of sand to the nearshore region, which can become modified by storm flows into `shore attached ridges’ at angles to the coastline (Type 2Bii). Tidal eddies produced by headlands can create `banner banks’ (Type 3A), but when the headland is retreating alternating or `en-echelon’ ridges can be formed which can become isolated from the coast as it recedes (Type 3B). Coastal retreat and rising sea level can then cause the ridges to become moribund. Thus the majority of ridges rely on sea level rise for their origin. Theoretical and modelling studies of the shorter term response to present hydrodynamic forcing are generally confined to Types 1 ridges and 3A banks. The most promising work considers the coupled system of hydrodynamics, sediment transport and morphology on Type 1 ridges, and predicts features such as the ridge spacing and angle to the flow. Type 3A sand banks are clearly related to the flow patterns produced by the headlands, and the models can reproduce the eddy structures and sand bank extents. Nevertheless, the vital role of shoreline processes has not been fully incorporated into the models, and there is little modelling of ebb tidal deltas or other Type 2 banks. There thus appears to be a wide scope for modelling the generation, evolution and stability of sank banks under the scenario of rising sea level and coastal retreat.

Grain Orientation Effect During Single Asperity Plowing of Two-Dimensionally Polycrystalline Aluminum Alloys

Results are presented from a series of atomic force microscope (AFM) experiments, wherein a sharp diamond indentor with a sub-micron tip radius. was directed to plow along specific crystallographic directions on selected alloy aluminum surfaces. A set of four. two-dimensionally polycrystalline aluminum alloys was chosen for this work. viz.. Al-99.99wt%. Al-0.2wt%Mg. Al-l.Owt%Mn. and Al-0.5wt%Cu. Crystallographic orientations of the surface grains upon which plowing was conducted were determined a priori through orientation imaging microscopy (OIM). Two sets of plow tracks were generated in four crystallographic directions. each set containing four plow tracks generated at four different normal indentor forces. The plow tracks were subsequently imaged to provide measurements of the plow track depths. ridge heights, and ridge angles relative to the nominal (undisturbed) surface plane. This data was then input to a model of single asperity plowing based on the upper bound theorem of plasticity for isotropic. non-strain hardening materials. The model provided estimates of surface flow strength as a function of depth of cut for each of the crystallographic directions. Experimental measurements of the friction (or plowing) force and depth of cut variations with normal indentor force are also presented.

Factors affecting the sensitivity of electrostatic ultrasonic transducers

The sensitivity of an electrostatic transducer determines the range of pulse-echo detection. Maximum sensitivity can be achieved by increasing the bias voltage within certain limits and by using a light membrane. The tension of the membrane was not found to affect the transducer's sensitivity. By using a uniformly grooved backplate the acoustic properties of the transducer can be optimized. The different sensitivity factors of the electrostatic ultrasonic transducer were confirmed with experimental results. High sensitivity can be achieved by using well manufactured backplates with shallow grooves and a small ridge angle.

The effect of variation of residual ridge angle on partial denture abutment tooth movement.

Using a laboratory model simulating a free-end saddle partial denture situation, the effect of variation of the angulation of the crest of the residual alveolar ridge to the horizontal on movement of the abutment tooth and saddle was observed. It was found that the inclination of the residual ridge affected the direction and magnitude of abutment tooth movement. The direction of abutment tooth movement was not related to the position of the occlusal rest. However, the magnitude of saddle and abutment tooth movement is affected by the design of the clasp used.

Diffraction of harmonic acoustic radiation by the apex of a ridge

In general, there are three components in the acoustic field propagating over a ridge: an arrival via a direct path, which does not interact with the ridge, a component diffracted by the apex of the ridge, and a component reflected from the boundary of the ridge. All three contributions are included in a new, exact solution of the Helmholtz equation for the three‐dimensional, harmonic field from a point source over a ridge formed by two intersecting, pressure‐release planes. The solution is obtained by the application of three integral transforms to the Helmholtz equation, followed by the corresponding inverse transforms. It is valid for any ridge angle θ0, including the special case of a knife edge (θ0 = 360°) and a plane (θ0 = 180°). In the latter case, which is the Lloyd's mirror problem, there is no diffraction; only the direct and reflected components contribute to the field, which is highly variable because of strong spatial interference. Diffraction by the knife edge is exemplified by the leakage of energy over the barrier, and by the presence of spatial interference in regions where there is no reflected component. Similar phenomena appear with other ridge geometries, where it is usually possible to assess whether interference effects are due predominantly to diffraction or reflection.

Sickle cell gnathopathy: Radiologic assessment

To provide objective evaluation of sickle cell gnathopathy, lateral skull radiographs of fifty patients with sickle cell anemia and twenty-five controls, matched for age and sex, were evaluated with respect to hard palate length and palate—alveolar ridge (PAR) angle. These measurements were compared to the angle formed between sella, nasion, and a point just below the anterior nasal spine of the maxilla (SNA angle), which is widely used in evaluation of the midfacial skeletal profile. The maxillary protrusion was found to be due to an increase in the PAR angle, as there was significant difference in this measurement between the two groups while there was no difference in the hard palate and SNA angle measurements. In keeping with prior explanations, marrow hyperplasia is the cause of maxillary overgrowth. Although often detected clinically, sickle cell gnathopathy can be evaluated radiographically simply and accurately by measurement of the PAR angle.

総義歯床基底面の機能的形態に関する研究

In order to make analysis of functional form of full denture, plaster models of 49 edentulous patients were used and denture basal surface was measured by the electroless plating method and projected basal surface by photographs. Alveolar ridge form of the mandibular first molar region which is the main bearing area was expressed numerically and analyzed. Changes in biting force with a decrease in denture basal surface in four subjects were measured by the strain-gauge method and denture basal surface which enables full dentures to function sufficiently was studied. The results were as follows : 1. The basal surface area was 49.9±10.6 cm^2 for the maxilla and 30.1±7.7 cm^2 for the mandlble. The projected basal surface area was 22.6±2.8 cm^2 for the maxilla, 6.0±1.4 cm^2 for the maxillary buccal region, 16.7±1.9 cm^2 for the palatal region, 11.8±2.1 cm^2 for the mandible, 5.7±1.3 cm^2 for the mandibular buccal region, and 6.1±1.3 cm^2 for the mandibular lingual region. The surface area of the lateral retention region which is the difference between the basal surface area and projected basal surface area was 27.3±8.7 cm^2 for the maxilla and 18.3±6.8 cm^2 for the mandible. A highly significant difference was observed between the maxilla and mandible. No significant correlation was observed in the basal surface area between the maxilla and mandible. In projected basal surface, however, significant correlation was observed and the projected basal surface area of the palatal region showed a value three times those of the other parts measured. 2. In the mandibular alveolar ridge form, no difference was observed in every measured item between the left side and right side. However, the buccal height was 4.0±3.2 mm for the left side and 4.0±3.0 mm for the right side, and the lingual height was 5.7±3.1 mm for the left side and 5.3±2.8 mm for the right side. A significant difference in the alveolar ridge height was observed between the buccal and lingual sides for each lateral side. The buccal width was 6.5±1.9 mm for the left side and 6.8±2.0 mm for the right side, the lingual width was 6.5±1.8 mm for the left side and 6.6±1.6 mm for the right side, and the sum of buccal and lingual widths was 13.0±2.5 mm for the left side and 13.3±2.4 mm for the right side. No significant difference in the alveolar width was observed between the buccal and lingual sides for each lateral side. The buccal alveolar ridge angle was 28.6±17.7° for the left side and 28.0±17.5° for the right side. The lingual alveolar ridge angle was 39.3±17.0° for the left side and 37.6±16.0° for the right side. A highly significant difference in the alveolar ridge angle was observed between the buccal and lingual sides for each lateral side and the lingual side was more acutely inclined. 3. The relation between the projected basal surface area and biting force was examined in four full denture patients. The patients complained of poor retention of the bite plate when the maxillary palatal plate was reduced by 20∿45% of the projected basal surface area. The biting force at this point was reduced by 22% or less. Every patient complained of pain when the mandibular lingual region of the plate was reduced by 10∿20% of its projected surface area and further removal could not be made. The biting force at this point was reduced by 20% reduction of the buccal region of the plate by 20∿30% caused a reduction in the biting force by 50%. Based on the forgoings, it appears to be necessary to increase basal surface area, as much as possible, of the mandibular lingual side to relieve pain and of the mandibular buccal side to prevent decrease in biting force.

Periodontal study on the form of plunger ridge. (1) (author's transl)

This stdy was observed on the correlation between the extensive angle, height of the plunger cusp and ridge in the maxillary molars of the periodontal patients. On experimental methods, one hundred and two periodontal patients from thirty five to forty five ages. and from which one hundred and forty-four plaster model blocks included upper first and second molar were selected for this stdy. The examination of differences on the extensive angle, cusp and ridge height were calculated between the distal buccal cusp of the fist molar and menial buccal cusp of the the second molar. The results were obtained as follow:(1) The mean angle of the extensive angle was 61.6±15.9°, and there was a tendency of almost in 40.1° to 80°(2) The mean difference of cusp height was in 1.195±0.786mm, and also the ridge height was in 1.0±0.670mm.(3) No significant correlations were found between the extensive angle and height of cusp or ridge.(4) If the extensive angle was confined in 40.1°-80°, the smaller the extensive angle, the alveolar bone a resorption in relation to it on the X-ray photograph.

Laboratory simulation of the herringbone pattern associated with lunar secondary crater chains

V-shaped ridge components of the herringbone pattern associated with lunar secondary crater chains have been simulated by simultaneous and nearly simultaneous impact of two projectiles near one another. The impact velocities and angles of the projectiles were similar to those of the fragments that produced secondary craters found at various ranges from large lunar craters. Variables found to affect the included angles of the V-shaped ridges are: relative time of impact of the projectiles, impact angle, relative projectile mass, and azimuth angle of the crater chain relative to the projection of the flight line onto the target surface. The functional relationships between the forms of the ridges and many of these variables are similar to those observed for lunar V-shaped ridges. Comparison of the magnitudes of the ridge angles of both laboratory crater pairs and secondary crater chains of the crater Copernicus implies that material was ejected from Copernicus at angles in excess of 60°, measured from the normal, to form many of Copernicus' satellitic craters. Moreover, other independent calculations presented indicate that many of the fragments that produced secondary craters also ricocheted to produce tertiary craters. Application of the study to identification of isolated secondary craters and to the determination of the origin of large lunar craters is discussed.

Pendulum analogues to illustrate the particle motion in spiral ridge accelerators

The essential features of the motion of a particle in an azimuthally varying magnetic field of `spiral ridge' form may be described by a pair of non-linear coupled equations of simple form. These reduce to the uncoupled linear radial and vertical betatron equations when the azimuthally varying component of field is zero. In this paper two pendulum analogues are described, which obey the same equations of motion as the particles. The first of these represents the radial motion only and consists of a torsional pendulum with a magnetic moment which interacts with a rotating magnetic field; the second, which represents both radial and vertical motion, consists of a compound pendulum supported by two sets of pivots at right angles, with a magnetic bob which interacts with a travelling magnetic field. The first of these analogues was used to make an extensive survey of the maximum stable amplitude of the motion as the parameters corresponding to ridge angle, azimuthal field modulation depth and radial field index were varied. No quantitative measurement was made with the second model, but the effect of ridges in stabilizing the vertical motion was demonstrated.