The Shell in the Lamellibranchia

1953 ◽  
Vol s3-94 (25) ◽  
pp. 57-70
Author(s):  
G. OWEN
Keyword(s):  
Radial Component ◽  
Transverse Component ◽  
Tangential Component ◽  
The Other ◽  
Transverse Diameter ◽  
Differential Growth ◽  
Anterior Portion ◽  
Normal Zone ◽  
Mantle Edge ◽  
Spiral Angle

1. In the Lamellibranchia, the direction of growth at any region of the valve margins may be resolved into: (a) a radial component radiating from the umbo and acting in the plane of the generating curve; (b) a transverse component acting at right angles to the plane of the generating curve; (c) a tangential component acting tangentially to, and in the plane of, the generating curve. The radial component is always present and affects the form of both valves while the transverse component may be reduced or absent in one valve. 2. The lamellibranch mantle/shell is orientated with reference to the normal axis. This normal axis follows that sector of the shell secreted by the normal zone of the mantle edge (i.e. where the effect of the transverse component is greatest) and passes through the umbo, the normal zone and the point at which the greatest transverse diameter of the shell intersects the surface of the valves. 3. The form of the shell valves should be considered with reference to: (a) the outline of the generating curve; (b) the spiral angle of the normal axis; (c) the form (i.e. planospiral or turbinate spiral) of the normal axis. 4. The ‘deflection’ anteriorly of the umbones and the splitting of the anterior portion of the ligament in many bivalves is a consequence of a tangential component affecting the form of the valves. 5. In both gastropods and lamellibranchs, the turbinate spiral shell is the resultant of two differential growth ratios. In the Gastropoda, however, both ratios act perpendicularly to the plane of the generating curve, while in the Lamellibranchia, one acts perpendicularly to this plane while the other acts in the plane of the generating curve.

An evolutionary and developmental approach toward understanding of growth variations of two closely related dwarfism of Galium verum

Biologia ◽  
2014 ◽  
Vol 69 (12) ◽  
Author(s):  
Keum Jeong ◽  
Jae-Hong Pak ◽  
Jeong Kim
Keyword(s):  
Cell Proliferation ◽  
Genetic Factors ◽  
Expression Patterns ◽  
Mrna Differential Display ◽  
Growth Patterns ◽  
The Other ◽  
Differential Growth ◽  
Developmental Approach ◽  
Differential Display Method ◽  
Low Activity

AbstractGalium L. is one of the largest and most widespread genus of Rubiaceae, consisting of more than 650 species worldwide. Galium verum var. asiaticum (G. verum a.) is a perennial herbaceous and widely distributed in in Korea peninsula. On the other hand, Galium verum var. asiaticum for. pusillum (G. verum a.p.) is endemic to Korea, inhabiting only on high land of Mt. Halla of Jeju. G. verum a.p. appears to be a dwarfism of G. verum a. We wondered what physiological, environmental, or genetic factors rendered those two taxa morphologically differentiated. We found that G. verum a.p. shows a low activity of the cell proliferation and was not associated with responsiveness contents of auxin and gibberellins. In order to search for genetic factors involved, we carried out an mRNA differential display method using the ACPs, and isolated several different expression genes between the two taxa. We chose one of those genes, which encoded RADIALIS-like proteins: GvaRADL1 from G. verum a. and GvapRADL1 from G. verum a.p. We discuss the relevancy of the genetic variations in regard to the differential expression patterns of those genes and the differential growth patterns of the two variants.

scholarly journals Relationship between Maxillary Arch Shape and Maxillary Labial Bone Dimensions: A Pilot Study

2021 ◽  
Author(s):  
Ahmad Assari ◽  
Shereen Shokry ◽  
Dana Al-Senan ◽  
Tasnim Alsbaih ◽  
Mada Alanazi ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Alveolar Bone ◽  
The Other ◽  
Cone Beam ◽  
Facial Bone ◽  
Anterior Portion ◽  
Significant Difference ◽  
Bone Dimensions ◽  
Maxillary Arch ◽  
Arch Shape

Abstract OBJECTIVE: To determine whether there is any relationship between the thickness of the labial alveolar bone wall in the anterior portion of the maxilla and arch shape.MATERIALS AND METHODS: Thirty patients (age, 12–53 years) were selected from archived cone beam computed tomography (CBCT) cases. All maxillary front teeth were present in all the cases. The distance between the cementoenamel junction (CEJ) and the facial bone crest and the thickness of the labial alveolar bone wall at distances of 1, 3, and 5 mm apical to the facial bone crest were measured.RESULTS: The distance between the CEJ and the facial bone crest ranged from 2.24 mm and 3.08 mm. No significant differences were found between the thickness of the bone wall at 1, 3, and 5 mm apical to the crest. A significant difference was found between the U-shaped arch on one side and the V-shaped and square-shaped arches on the other side. The U-shaped arch and labial bone wall thickness were correlated at the 1-mm distance (F = (8, 276) = 3.24, p = 0.002). U-shaped and V-shaped arches were common in women, whereas square-shaped arches were common in men (χ2 = 105.5, p = 0.000).CONCLUSION: Our study is the first to associate arch shape and labial alveolar bone wall thickness.CLINICAL RELEVANCE: The association between the U-shaped arch and bone wall thickness may constitute a new indicator for the tendency of the labial alveolar bone to resorb after extraction and placement of endo-osseous implants.

Morphological variation in the genus Juliomys (Rodentia: Cricetidae: Sigmodontinae) and taxonomic status of Juliomys anoblepas (Winge 1887) from the Quaternary of Southeast Brazil

Zootaxa ◽  
2020 ◽  
Vol 4861 (3) ◽  
pp. 429-443
Author(s):  
CAROLINA PIRES ◽  
MARCELO WEKSLER ◽  
CIBELE R. BONVICINO
Keyword(s):  
Principal Component Analysis ◽  
Morphological Variation ◽  
Morphological Analysis ◽  
Principal Component ◽  
Taxonomic Status ◽  
Morphological Characters ◽  
The Other ◽  
Anterior Portion ◽  
Living Species ◽  
Qualitative Characters

The region of Lagoa Santa, Minas Gerais, Brazil, is one of the most important karstic areas of the Brazilian Quaternary due to the faunistic diversity of living and extinct forms. Among them, some taxa remain poorly studied, as is the case of Calomys anoblepas Winge 1887. Despite the recent allocation of the taxon within Juliomys, its description and morphological analysis are condensed, based on comparative few specimens and on few informative characters. In this study, we investigate characters proposed to distinguish species of Juliomys, and reevaluate the taxonomic status of the fossil Juliomys anoblepas. We analyzed 80 cranio-dental morphological characters in 233 specimens represented by the four species currently recognized: J. pictipes (Osgood 1933), J. rimofrons Oliveira & Bonvicino 2002, J. ossitenuis Costa, Pavan, Leite & Fagundes 2007, and J. ximenezi Christoff, Vieira, Oliveira, Gonçalves, Valiati & Tomasi 2016. We also performed principal component analysis on eight craniodental measurements available for the J. anoblepas hypodigm. The review of morphological systems and the evaluation of the characters used in the literature revealed that there are no diagnostic characters in the anterior portion of the skull and in the molar series of Juliomys, being difficult to differentiate the fossil from the other living species. Only six qualitative characters were variable and applicable to the hypodigm of J. anoblepas. Characters are polymorphic, invariable, or the fossil is not sufficiently complete to determinate its states. The taxon could not be morphometrically differentiated from J. pictipes and J. ossitenuis. Based on the results presented herein, we consider J. anoblepas as a nomen dubium and restrict its name to the taxon’s hypodigm. 

Performance of Fractional-Slot Winding PM Machines due to Un-even Coil Turns and Asymmetric Design of Stator Teeth

2015 ◽  
Vol 6 (4) ◽  
pp. 853
Author(s):  
Mohd Luqman Mohd Jamil ◽  
Syed Muhammad S. A. Al-Habshi ◽  
Md Nazri Othman ◽  
Tole Sutikno
Keyword(s):  
Finite Element Analysis ◽  
Magnetic Force ◽  
Radial Component ◽  
Tangential Component ◽  
Slight Reduction ◽  
Element Analysis ◽  
Electromagnetic Performance ◽  
Asymmetric Winding ◽  
Number Combination ◽  
Fractional Slot

PM machines in which slot number and pole number combination differs by one have to be configured with asymmetric winding pattern in order to maximize it back-emf performance. However, this asymmetric winding configuration inherently results an unwanted Unabalanced Magnetic Force (UMF). Investigations of electromagnetic performance of fractional-slot asymmetric winding PM machines using 2-D Finite-Element Analysis are presented. The investigations are mainly driven by the effort of minimizing the UMF. By employing techniques such as non-uniform number of coil turns in every tooth and asymmetric design of stator tooth, the UMF are expected can be minimized. The investigations show that the radial component of UMF has greater effect than the tangential component on the UMF itself. In all proposed techniques, a slight reduction of machine torque performance is inevitable.

scholarly journals Theoretical and experimental study on a finite size vector sensor array with a cylindrically symmetric carrier

2019 ◽  
Vol 283 ◽  
pp. 07008
Author(s):  
Junyuan Guo ◽  
Shi-e Yang ◽  
Hongjuan Chen ◽  
Shengchun Piao ◽  
Longhao Qiu
Keyword(s):  
Finite Size ◽  
Low Frequency ◽  
Doa Estimation ◽  
Radial Component ◽  
Tangential Component ◽  
Low Frequencies ◽  
Cylindrically Symmetric ◽  
Noise Characteristics ◽  
Vector Sensor ◽  
Array Gain

In this work, a finite size acoustic vector sensor (AVS) array is designed and its performance is theoretically and experimentally studied. The two-dimensional AVS array is comprised of five vector sensors and configured as a cross, and the array carrier is a cylindrically symmetric structure. Theoretical analysis and simulation indicate that the proposed method considering structure scattering can widen the working bandwidth. Furthermore, the utilization of vector sensor enables a significant white noise gain improvement at low frequencies, which makes the array more robust and easier to realize. Experiments have been done to study the array performance from several aspects including sensor noise characteristics, the beampattern, the direction-of-arrival (DOA) estimation ability and the array gain. From the change of the sensor directivity patterns or the amplitude distortion of the noise field, we can clearly observe the scattering field intensity. Moreover, it shows that the influence of the structure scattering on the tangential component of the vector field is symmetric, while that of the radial component is asymmetric. Experimental results also demonstrate that, with the proposed method, the 2nd and the 3rd order beamformers can be obtained which could be further used for the estimation of target DOA. In addition, an array gain of at least 6 dB is obtained capable of detection of weak signals. Our results indicate that the proposed array with a physical size less than one meter, although affected by nearby scatterers, can effectively break the Rayleigh limit and realize the remote detection in low-frequency regime.

DIFFERENTIAL GROWTH AND COMPETITIVE ABILITY OF Amaranthus retroflexus, A. powellii AND A. hybridus

1984 ◽  
Vol 64 (3) ◽  
pp. 715-724 ◽  
Author(s):  
SUSAN E. WEAVER
Keyword(s):  
Competitive Ability ◽  
Dry Weight ◽  
Amaranthus Retroflexus ◽  
The Other ◽  
Constant Density ◽  
Differential Growth ◽  
Amaranthus Hybridus ◽  
Temperature Regimes ◽  
Germination And Growth ◽  
Amaranthus Powellii

The frequency of occurrence of Amaranthus powellii and A. hybridus relative to that of A. retroflexus in agricultural fields in southwestern Ontario is increasing. Rates of germination and growth and development of the three species were compared at 28/22 °C and 22/14 °C in the growth chamber. Amaranthus powellii exhibited a faster rate of germination and greater early growth with respect to height and leaf number than either of the other species under both temperature regimes. Amaranthus hybridus had a greater root dry weight, took 3 wk longer to reach maturity and produced more seeds than either of the other species. In the field, when sown in pure stands and mixtures at constant density but varying proportions, A. powellii showed a greater competitive ability than A. retroflexus or A. hybridus with respect to number of plants, aboveground fresh weight, and number of seeds produced per square metre.Key words: Pigweed, germination, seed production, competition

scholarly journals NEW DYROSAURID REMAINS (CROCODYLIFORMES, MESOEUCROCODYLIA) FROM THE PALEOCENE OF THE PARAÍBA BASIN, NE BRAZIL

2018 ◽  
Author(s):  
Mariana Sena
Keyword(s):  
The Other ◽  
Northeastern Brazil ◽  
Anterior Portion ◽  
Mandibular Symphysis ◽  
New Material ◽  
The Right

The fossil crocodyliforms from the Paraíba Basin in Northeastern Brazil are represented by two species, Hyposaurus derbianus,(uncertain age) and Guarinisuchus munizi, from the Paleocene Maria Farinha Formation. Herein we present new material of a dyrosauridalso collected in deposits of the Maria Farinha Formation, representing cranial, axial and appendicular remains. The specimens are housedat Centro Acadêmico de Vitória, Universidade Federal de Pernambuco (CAV–UFPE) and at Universidade Federal Rural de Pernambuco(UFRPE). The most important contribution of this find is a well-preserved mandibular specimen (CAV 0056-V) with 16 alveoli on the leftside and 13 on the right side. Nine complete or partial tooth crowns are preserved, in positions 1–5. The teeth are conical and homodont withvertical striations. The largest teeth are located at positions d1 and d4. The biggest occlusion pits are located between positions d2 and d3. Theseventh alveoli are reduced and close to the eighth alveoli. The mandible, CAV 0056-V, possesses three foramina in the anterior portion ofthe dentaries and the mandibular symphysis extends to the posterior margins of the d11–d12 dentary alveoli. Based on the features presentedin the mandible and the other fossils recovered, we attribute these materials to Dyrosauridae, particularly, to Guarinisuchus cf. G. munizi.

Method of Moment Determination of Current Distribution on Elements of Yagi-Uda Array

2017 ◽  
Vol 2 (9) ◽  
pp. 23-29
Author(s):  
Raji A. Abimbola
Keyword(s):  
Integral Equation ◽  
Method Of Moments ◽  
Current Distribution ◽  
Tangential Component ◽  
The Other ◽  
Induced Current ◽  
Method Of Moment ◽  
Current Distributions ◽  
Complex Coefficients

Presented in this paper is the numerical solution to the current distributions on two forms of Yagi-Uda antenna designs. One form consists of twelve elements while the other consists of fourteen elements. Employing method of moments technique in which the unknown current is expanded in terms of known expansion function and complex coefficients which are to be determined. It is demonstrated that, when the integral equation that expresses tangential component of an impressed field in terms of induced current on the elements of Yagi-Uda array is reduced into matrix form, the current distribution of interest becomes known. The profiles for the current distributions on elements of those arrays represented in graphical forms reveal that, the currents are symmetrical about the length of the element in each case. It is found that the highest magnitude of the current exists on the driven element. Furthermore, the characteristic profiles of the currents on elements of those arrays exhibit sinusoidal type of waveform and are largely similar when the frequencies of operation are 200MHz and 665MHz, respectively.

Peculiarities of marine eddy manifestation in the structure of surfactant slick band

2021 ◽  
Author(s):  
Olga Shomina ◽  
Tatiana Tarasova ◽  
Olga Danilicheva ◽  
Ivan Kapustin
Keyword(s):  
Water Surface ◽  
Remote Sensing Data ◽  
Radial Component ◽  
Tangential Component ◽  
Length Scale ◽  
Russian Science ◽  
Radial Velocity Component ◽  
Radar Images ◽  
Wind Velocities ◽  
Spiral Shape

<p>Slick structures on the sea surface can mark processes occurring in upper ocean and atmosphere. Spiral shape of slicks observed in optical and radar images of water surface is traditionally interpreted through the manifestation of marine eddy which length scale is supposed to be equal to the scale of spiral. This assumption implies that wind has no effect on the kinematics of forming slick band, which, according to our estimation, is incorrect even at moderate wind velocities. This approach can cause misinterpretation of remote sensing data when estimating the characteristics of observed marine eddies. This study is devoted to the investigation of conditions necessary for the formation of slick spiral and to some peculiarities of its shape and scale.</p><p>The system of equations for the description of kinematics of Lagrangian particle (element of water surface covered with surface active substance) in the fields of axisymmetric eddy with non-zero radial velocity component and homogeneous wind was obtained. It is demonstrated that the spiral center is not collocated with the center of the eddy; the distance between them can achieve the eddy length scale. It is shown that the displacement of the spiral center and the direction of the main axis is quasi perpendicular to the wind direction when radial component of the eddy is small compared to the tangential component. The presence of the threshold wind velocity corresponding to the breakdown of the spiral structure is demonstrated analytically. The possibilities of correct retrieval of length scales and character velocities of observed sub mesoscale marine eddies are discussed.</p><p>The research was funded by the Russian Science Foundation (Project RSF 18-77-10066).</p>

III —The Cruciform Muscle of Lamellibranchs

1935 ◽  
Vol 54 ◽  
pp. 17-30 ◽  
Author(s):  
Alastair Graham
Keyword(s):  
Adductor Muscle ◽  
Point Of View ◽  
The Other ◽  
Similar Process ◽  
Muscle Fibres ◽  
Directed Attention ◽  
Posterior Portion ◽  
Adductor Muscles ◽  
Mantle Edge

In 1900 von Ihering directed attention to the presence in certain Lamellibranchs of a special muscle lying in the posterior portion of the ventral mantle edge, close to the inner end of the inhalent siphon. This muscle consisted of two strands, each running diagonally from an origin on one valve to be inserted on the other, and crossing one another in the mid-ventral line so as to form a muscular apparatus with the appearance of a St Andrew's cross. He regarded this cruciform muscle as a specially differentiated group of fibres belonging to the pallial edge, acting as an accessory adductor muscle, a point of view in which he has been followed by all subsequent observers. To this von Ihering added the speculation that it had been by some similar process of specialisation of marginal pallial muscle fibres that the two other true adductor muscles of Lamellibranchs had originated.

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