Small Oval Research Articles

360° deterministic magnetization rotation in a three-ellipse magnetoelectric heterostructure

A magnetic dipole-coupled magnetoelectric heterostructure comprised of three closely spaced ellipse shapes was designed and shown to be capable of achieving deterministic in-plane magnetization rotation. The design approach used a combination of conventional micromagnetic simulations to obtain preliminary configurations followed by simulations using a fully strain-coupled, time domain micromagnetic code for a detailed assessment of performance. The conventional micromagnetic code has short run times and was used to refine the ellipse shape and orientation, but it does not accurately capture the effects of the strain gradients present in the piezoelectric and magnetostrictive layers that contribute to magnetization reorientation. The fully coupled code was used to assess the effects of strain and magnetic field gradients on precessional switching in the side ellipses and on the resulting dipole-field driven magnetization reorientation in the center ellipse. The work led to a geometry with a CoFeB ellipse (125 nm × 95 nm × 4 nm) positioned between two smaller CoFeB ellipses (75 nm × 50 nm × 4 nm) on a 500 nm PZT-5H film substrate clamped at its bottom surface. The smaller ellipses were oriented at 45° and positioned at 70° and 250° about the central ellipse due to the film deposition on a thick substrate. A 7.3 V pulse applied to the PZT for 0.22 ns produced 180° switching of the magnetization in the outer ellipses that then drove switching in the center ellipse through dipole-dipole coupling. Full 360° deterministic rotation was achieved with a second pulse. The temporal response of the resulting design is discussed.

Hypertrophy of the transverse ligament caused by os odontoideum: a case report

Os odontoideum is a small oval or round shaped bone fragment observed as the most common congenital anomaly of the odontoid process. Since it causes a slowly increasing mobility or instability in the atlanto-axial joint, sudden death, tetraplegia, chronic neck pain, headache, torticollis and myelopathy may develop. The spinal canal widens initially at the craniocervical junction and symptoms can occur at a very late stage. In this case, clinical complaints emerged after the age of 35. There was no other neurological finding and no history of recent trauma in this case presenting with severe neck pain. This case report shows how ligaments, the supporting connective tissue elements, can be thickened to maintain stability when the stability of the cervical spine is impaired. Since it may cause sudden death even when asymptomatic, it is important to recognize this pathology and to distinguish os odontoideum from odontoid fractures in trauma patients.

Typy morfogenetyczne wsi w środkowej Polsce

Historico-geographical analysis of the layouts of villages in central Poland made it possible to distinguish the morphogenetic types of rural settlements characteristic of the specified historical periods. On the basis of the historical topographic maps, it is also possible to describe the features of spatial distribution of the morphogenetic types of villages for the investigated area. Central Poland presents a very diversified morphogenetic picture of villages, which results from a great number of complex historical and socio-economic processes, as well as from varied geographical conditions. Four main historical periods were distinguished, during which the following characteristic morphogenetic types of villages were established: 1. irregular medieval villages which did not undergo regulation in the Middle Ages; 2. regular medieval villages located on German Law; 3. newer settlements founded in the Modern Period (e.g. manorial layouts and villages connected with the so-called oleder settlement and Frederician colonization); 4. villages formed in the process of regulation and parcellation in 19th c. The villages form Early Middle Ages developed in an evolutionary way, were not regulated, and adapted well to the local topographic position. Among the villages with irregular habitats from this period the following types can be singled out: road villages, little green villages (small oval) and circular villages; cross-road villages and multi-road villages. The land was divided into numerous small fields, irregular in shape. The layout of fields in these villages takes the form of blocks, block-strips and irregular small fields. Two distinct processes were taking place in the Middle Ages: foundation of the new villages on the so-called in cruda radice , and regulation of the villages already existing according to the German law. These villages were built mostly on the Church land of the cloisters and bishops, as well as on land belonging at that time to the Duke. The generally accepted types of villages founded on the German law are: large regular street villages and regular green villages (with oval or rectangular square). Regular field patterns in those villages were organized in the open-field patternadapted to the three-field rotation system. Within the group of villages of later origin, established between the 16th c. and the 1th half of 19th c., the following types were distinguished: manors and marshy row villages (the so-called oleder or Frederician colonies and other colonies – the so-called forest settlements). In Modern Period one can identify mostly the manor-peasant village with a complex of manor buildings and peasant homesteads. Manor and peasant fields intermingled and were cultivated by means of the three-field system. Rarely can one observe manor villages which included only the manor complex with crofters’ small holdings and where fields were consolidated into large blocks. In the 18th c. planned villages were built again, which was connected with the Frederician and the so-called oleder colonization. Marshy row villages located on clearings can be distinguished, which represented a different spatial pattern with regard to the economic functions of their population. Agricultural colonies were mostly regular street villages, densely built-up. The pattern of the fields took the form of regular, schematic, broad stripes, belonging to separate owners. The 19th c. marks the turning point in the development of the forms of rural settlement. The ancient spatial settings of villages have changed mostly in connection with the transformation of the socio-economic life of the countryside, in particular the enfranchisement of peasants, the parcellation of manors and field consolidation, the disappearance of the threefield rotation system, and the introduction of new techniques of cultivation. In the manor- peasant village one can observe the process of separation of manor and peasant land. In the context of parceling-out it is possible to distinguish row villages with fields in the form of ownership stripes, perpendicular to the road and dispersed settlement with block system of fields. The irregular layouts of villages from the Middle Ages were formed mostly in the peripheries of central Poland, in the valleys of the Warta, Bzura and Pilica rivers. Compact settlement regions of regular villages, founded during the medieval colonization, have been identified in the area of former ecclesiastical or royal estates where proprietors were interested in location of villages based on the German law. Manors developed mainly inside the villages, and they did not form separate settlement units and morphogenetic zones. Forest colonies and marshy row villages appear as small enclaves throughout the whole investigated area, especially in the central part of region, because they were mostly founded on clearings, areas not cultivated before, on poor soils and in forests.

Clinicopathological features and risk factors of lymph node metastasis of gastrointestinal neuroendocrine neoplasms in 467 patients

Objective To investigate the clinicopathological features and risk factors of lymph node metastasis of gastrointestinal neuroendocrine neoplasms (GI-NENs). Methods The retrospective case-control study was conducted. The clinicopathological data of 467 patients with GI-NENs who were admitted to the Fourth Hospital of Hebei Medical University from January 2006 to December 2015 were collected. Observation indicators: (1) occurrence sites and pathological classification of GI-NENs; (2) pathological characteristics of surgical specimens of GI-NENs; (3) univariate analysis and multivariate analysis affecting lymph node metastasis of GI-NENs: sex, age, tumor location, tumor diameter, pathological classification, pathological stage and tumor invasive depth. The univariate analysis and multivariate analysis were respectively done using the chi-square test and Logistic regression model. Results (1) Occurrence sites and pathological classification of GI-NENs: of 467 patients with GI-NENs, tumors of 304, 15, 7, 14 and 127 patients were located at stomach, duodenum, small intestine, colon and rectum, respectively. Tumor diameter was 0.3-12.0 cm, with an average diameter of 2.2 cm. Of 467 patients with GI-NENs, G1 and G2 of neuroendocrine tumors (NETs), G3 of neumendocfine carcinomas (NECs) and mixed adenoneuroendocfine carcinomas (MANECs) were respectively detected in 209, 64, 146 and 48 patients. Lymph node metastasis rate of GI-NENs was 31.48%(147/467). (2) Pathological characteristics of surgical specimens of GI-NENs: NETs were high-differentiated NENs. Cells of NETs were solid and nest-, trabeculum- and tubular-shaped, and consisted of small or medium cells, with moderate amount or massive cytoplasms, round or oval nucleus, particle-shaped chromatin, unobvious nucleolus and positive endocrine markers. There were abundant of small blood vessels and surrounding fibrous stroma in peripheral tumor cell nests. NECs were low-differentiated NENs and included small cell carcinoma and large cell NEC. Cells of small cell carcinoma were small round or oval and looked similar to lymphocytes, with few amount cytoplasms, fine granular-shaped or hyperchromatic nucleus and common mitosis figures. Cells of large cell NEC were large and greater than 3 lymphocytes, arrayed in organoid- or chrysanthemum-shape, with massive cytoplasms, coarse particle-shaped chromatin, obvious nucleus, clear mitosis figures and large laminar-shaped necrosis. There were different positive expressions of endocrine markers between small cell carcinoma and large cell NEC. MANECs had the characteristics of glandular cavity formation of traditional adenocarcinoma and NENs. Results of immuno-histochemical staining in 467 patients showed that Ki-67 of 467 patients was positive; CD56 in 379 of 428 with CD56 test was positive; synaptophysin (Syn) in 416 of 422 with Syn test was positive; cytokeratin (CK) in 354 of 396 with CK test was positive; chromogranin (CgA)in 264 of 388 with CgA test was positive; neuron specific enolase (NSE) in 287 of 346 with NSE test was positive. (3) Univariate analysis and multivariate analysis affecting lymph node metastasis of GI-NENs: results of univariate analysis showed that sex, tumor location, tumor diameter, pathological classification, pathological satge and tumor invasive depth were related factors affecting lymph node metastasis of patients with GI-NENs (χ2=20.654, 18.182, 26.788, 184.709, 163.738, 195.391, P<0.05). Results of multivariate analysis showed that pathological classification and pathological stage were independent influenced factors affecting lymph node metastasis of patients with GI-NENs (HR=2.129, 7.171, 95% confidence interval: 1.273-3.561, -2.327-22.098, P<0.05). Conclusions GI-NENs are mostly located on the stomach and rectum. Results of immunohistochemical staining could help diagnosis of GI-NENs. Pathological classification and pathological stage are independent influenced factors affecting lymph node metastasis of patients with GI-NENs. Key words: Neuroendocrine neoplasms; Gastrointestinal tract; Pathology; Lymph node metastasis

An innovative approach to NC programming for accurate five-axis flank milling of spiral bevel or hypoid gears

To transfer power, a pair of spiral bevel or hypoid gears engages. From beginning to end of two tooth surfaces engaging with each other: for their rigid property, they contact at different points; and for their plastic property, they contact at small ellipses around the points. On each surface, the contact line (or called as contact path) by connecting these points and the contact area by joining these ellipses are critical to driving performance. Therefore, to machine these surfaces, it is important to machine the contact line and area with higher accuracy than other areas. Five-axis flank milling is efficient and is widely used in industry. However, tool paths for flank milling the gears, which are generated with the existing methods, can cause overcuts on the contact area with large machining errors. To overcome this problem, an innovative approach to NC programming for accurate and efficient five-axis flank milling of spiral bevel or hypoid gears is proposed. First, the necessary conditions of the cutter envelope surface tangent with the designed surface along a designed line are derived to address the overcut problem of five-axis milling. Second, the tooth surface including the contact line and area are represented using their machining and meshing models. Third, according to the tooth surface model, an optimization method based on the necessary conditions is proposed to plan the cutter location and orientation for flank milling the tooth surface. By using these planned tool paths, the overcut problem is eliminated and the machining errors of contact area are reduced. The proposed approach can significantly promote flank milling in the gear manufacturing industry.

Synthesis and antiviral activity of 1-(1,3-disubstitutedimidazolidyn-2-ylidene)-3-ethoxycarbonylmethylurea derivatives

Novel 1-(1,3-disubstituted-imidazolidyn-2-ylidene)-3-ethoxycarbonylmethylurea derivatives (3a–3j) were obtained from appropriate 1-aryl-3-arylsulfonyl-1H-imidazolidine-2-imines (1a–1j) and ethyl isocyanatoacetate (2), which were subjected to condensation. Seven compounds were tested for their antiviral activity against HSV-1 and CVB3 viruses. Among the tested compounds, 3c was found to be active against HSV-1, proving that 4-methoxy substituent as R and 4-methyl substituent as R1 are most beneficial for activity against this virus. Furthermore, 3e and 3g were active against CVB3, which demonstrated that both 4-methyl and 4-chloro substitution is tolerated as R1, whereas 4-chloro and 2-methoxy substituents are best as R. It was also shown that the active compounds are characterized by relatively big surface area, small ovality, and greatest HOMO and LUMO energies in comparison to the rest of the compounds.

The Internal Structure of a Rectangular Frame: Position, Orientation, and Direction

Previous research has shown that the structure of a rectangular frame strongly influences perceived goodness-of-fit for a small circular probe positioned within it (Palmer and Guidi, 2011). The center is consistently rated as the best position, followed by positions along the global vertical, global horizontal, and local diagonal symmetry axes. Here we report how goodness-of-fit within a surrounding frame is influenced by the relation between with the orientational and directional structure of the probe and that of the frame. In Experiment 1, fit ratings of short line segments and small ovals (each with two symmetry axes) at 35 positions and four orientations within the frame revealed strong orientational effects, especially when the probe’s and frame’s axes of symmetry were aligned. Experiment 2 extended the paradigm using triangular probes (with a single symmetry axis) at 15 positions and eight pointing directions. The results showed high fit ratings when the probe was aligned with global and local symmetry axes of the frame, and directional increments when the probes pointed upward, rightward, and into the frame. Experiment 3 confirmed the upward, rightward, and inward directional effects of Experiment 2 using a more sensitive Two-Alternative Forced Choice (2AFC) task. Experiment 4 showed that orientational effects were more strongly driven by alignment with the rectangle’s sides than with gravitational or retinal reference frames, especially when the probe was near the sides and vertices of the frame. The relevance of these findings to the empirical study of aesthetic response to images within rectangular frames is discussed.

Azimuthal spin wave modes in an elliptical nanomagnet with single vortex configuration

In comparison with uniformly magnetized states, vortex structures demonstrate a rich frequency spectrum of spin-wave (SW) excitations. However, a detailed theoretical description of the magnetic modes is generally still a challenge due to the difficulty of analytic calculation, except for the well-defined symmetric circular states. In contrast, the method of micromagnetic simulations combined with Fourier analysis is shown to be very powerful for gaining insight into the nature of magnetic excitation modes. Vortex excitation modes have been reported to be directly influenced by the geometric symmetry of the elements and/or the nature of the initial perturbation of pulse field. In order to understand how the reduced symmetry affects the vortex SW modes, we perform the micromagnetic simulations on vortex modes excited in a submicron-sized thin ellipse. In order to excite the spin-wave modes, a short in-plane Gaussian field pulse is applied along the short axis direction. After the pulse, the off-centered vortex core moves following an elliptical trajectory around its equilibrium position. Simulations provide the time evolution of the local magnetizations (at each discretization point) and dynamics of the spatially averaged magnetization. To determine the mode frequencies, the spectrum is obtained from the average magnetization through Fourier transformation from time domain the frequency domain. By means of Fourier analysis, a variety of azimuthal SW modes can be observed in the excitation spectrum. The ellipse in single vortex state has a twofold rotational symmetry with a rotation of πup around the z-axis (out-of plane) and can be described by the C2 group. The observed azimuthal modes can be divided into two categories according to their symmetry. Two modes occur alternately with increasing azimuthal number, indicating that the magnetic excitation modes remain to keep the symmetry of the ellipse structure. Their frequencies are found to increase linearly with the azimuthal index number. An increase of the SW frequency with increasing number of nodal planes is rather well known, which results from the competition between exchange and dipolar energy terms. According to the temporal evolution of the ellipse's spatially averaged energy densities, our micromagnetic simulation shows that the average exchange energy is significantly higher than the magnetostatic energy, suggesting that the exchange interaction plays a more important role in the excitation modes. The exchange energy density is mainly focused on the core origin while the largest contribution of the magnetostatic energy is distributed near the long axis. Thus, we can conclude that the exchange interaction provides the principal contribution to the vortex energy in such small ellipses with a single vortex state, resulting in the increasing frequency versus the azimuthal number, that is observed.

An unusual case of large, destructive stafne bone cavity with computed tomography findings

Stafne bone cavity (SBC) is an asymptomatic lingual bone depression that usually described as a small oval homogenous radiolucency in the posterior mandibular region. The radiographic appearance and location of the SBC are characteristic and easily identified. The diagnosis can be confirmed by computed tomography (CT) scans, magnetic resonance (MR) imaging or sialography. This report describes a case of SBC in a 61-year-old male asymptomatic patient, presenting as a radiolucency in the left mandibular body with loss of buccal and lingual cortical plates on three-dimensional CT scan.

Continent‐Wide Maps ofLgCodaQfor North America and Their Relationship to Crustal Structure and Evolution

Abstract We have obtained tomographic maps of Lg coda Q and its frequency dependence at 1 Hz for all of North America assuming that all of our coda Q data can be described by a power law. Our map of Q 0 displays highest values (700–1000) throughout a large region that coincides with the Canadian Shield and exhibits sharp changes in Q 0 across much of the boundary separating the high values of the shield from lower values outside it. A second high Q region appears as a small oval of high Q 0 values (650–700) overlying much of the Ozark uplift in the central United States. A band of low values (200–350) covers most of Central America and Mexico and extends northward from California into western Canada before broadening in Alaska. A north–south‐trending band of high η values, extending from northern Canada to the gulf coast, separates the North American Cordillera from stable portions of central North America. We compared our Q 0 and η determinations with those found in five earlier studies in two regions of the United States. In the present study, in each region these values agree with values found in the earlier studies when earthquake–station distances are greater than 300 km but differ when distances are less than that. The similarity of our Q 0 measurements to previous direct Lg and Lg coda measurements and the inverse correlation we find of Q 0 with upper mantle temperatures suggest that we may predominantly be measuring intrinsic Q 0 . We propose a mechanism for explaining why scattering dominates over intrinsic attenuation for Lg and Lg coda propagation at short distances but can be secondary to intrinsic attenuation at long distances. It can be nicely described using a ray characterization for Lg and understanding that at short distances many near‐vertical traveling rays are multiply reflected in the crust and much energy is lost to the mantle. At greater distances (say 300 km), virtually all of the reflected waves exceed the critical angle and so cannot easily be lost to the mantle.

Generalized method for calculating the durability of sliding bearings with technological out-of-roundness of details

This article presents the generalized cumulative model of wear kinetics for the sliding bearing elements in the case of single area and single-and-double area contact for different phases of rotating a shaft with a small contour ovality and a bushing with a circular contour. As a result of the performed numerical analysis, the regularities of the change in the initial maximum contact pressure due to shaft rotation and shaft changes due to wear are described, as well as the durability of the bearing and the linear wear of the bushing and shaft depending on the size of ovality are discussed in the work. The contact pressures are considerably higher in the zones of double-area contact than in the zones of single-area contact. The shaft ovality increases the bearing durability and reduces the hob wear. The results are presented graphically by means of charts.

Simulation and Mathematical Modeling on Bending of Pipe Subjected to Internal Pressure

This Paper Aims from the Simulation Tests to Highlight the Influence of the Diameter and Material Quality, Reflected by the Flow Limit of the Pipe and the Quality and Technological Parameters at the Bending under Pressure of the Pipes. from Literature, those Quality Parameters which Characterize a Correct Bending are: the Ovality of the Transversal Section, the Variation of the Wall Thickness or Eccentricity, the Lack of Whetstones, the Resistance in Function of the Bent Pipe. Pipe Material Characteristics Influence the Quality Parameters of the under Pressure Modeling Process, in the Sense that at the Materials with Small Flow Limit, Ovality or Variation of the Wall Thickness are Small. at Pipes under Pressure Modeling, Ovalities and Variation of the Wall Thickness are in Permissible Limits Valid Recommended for Domains without Special Precision Restrictions.

Accuracy of Evaluation of the Service Life of a Plain Bearing According to the Generalized Cumulative Model of Wear

By using the generalized cumulative model of wear and a developed rapid method for the investigation of the kinetics of tribocontact interaction in a plain bearing with small ovality of the shaft, we evaluate the accuracy of evaluation of the service life. We study single-zone and single–double–single-zone contact interactions of the shaft with the bush. The obtained results are thoroughly analyzed and the influence of the parameters of the interval-block main scheme and modified computational scheme on the accuracy of evaluation of the service life of the bearing is estimated. We establish the regularities of decrease in the accuracy of the solution depending on the sizes of the blocks of interaction cycles with constant conditions and on the interval of discretization of the contour of the shaft. The schemes of calculations optimal from the engineering point of view and their parameters are indicated.

Small shape deviations causes complex dynamics in large electric generators

We prove that combinations of small eccentricity, ovality and/or triangularity in the rotor and stator can produce complex whirling motions of an unbalanced rotor in large synchronous generators. It is concluded which structures of shape deviations that are more harmful, in the sense of producing complex whirling motions, than others. For each such structure, we derive simplified equations of motions from which we conclude analytically the relation between shape deviations and mass unbalance that yield non-smooth whirling motions. Finally we discuss validity of our results in the sense of modeling of the unbalanced magnetic pull force.

Spontaneous progression of cutaneous angiomatosis to an infiltrative sarcoma-like tumour in a bull

CASE HISTORY: A 5-month-old valuable Red Holstein bull presented with a cutaneous mass on the fetlock of the right hind limb. The mass was removed and histologically diagnosed as a benign angiomatosis. Four months later, the mass reoccurred on the same leg.PATHOLOGICAL FINDINGS: The first excision biopsy consisted of numerous blood vessels of different diameters and wall thicknesses. Often, the smaller vessels were oriented around a larger, vein-like vessel. The endothelial cells were elongated with small oval to elongated nuclei with dense chromatin. Following recurrence, the mass showed clear signs of infiltrative growth, including solid bundles of cells, increased polymorphism and round to oval nuclei with coarse chromatin and distinctive nucleoli. The neoplastic cells were immunohistochemically positive for von Willebrand Factor (vWF).DIAGNOSIS: Angiomatosis with focal progression to an infiltrative growing sarcoma-like tumour.CLINICAL RELEVANCE: This case represents the progression of a benign vascular proliferation, often considered as a reactive process, into a more aggressively behaving neoplasm. The clinical behaviour and histopathological morphology were strikingly similar to previous cases described in human and veterinary medicine.

Three new earthworm species of the genus Amynthas (Clitellata: Megascolecidae) from Mt. Chiak National Park, Korea.

Earthworm specimens collected from Mt. Chiak, National Park, Korea were found to represent three new species of megascolecid earthworms: Amynthas chiakensis sp. nov., Amynthas gyeongriae sp. nov., and Amynthas wonjuensis sp. nov. Amynthas chiakensis sp. nov. has two pairs of spermathecae in VII and VIII, small transverse oval male porophores each with C-shaped small patches of genital papillae, 0.22-0.31 circumference apart. Amynthas gyeongriae sp. nov. has spermathecae in VI-VIII, male field with large circular-shaped raised pads and seminal grooves, with pores 0.16-0.28 circumference apart. Amynthas wonjuensis sp. nov. has spermathecae in VI and VII, male pores superficial in XVIII on small oval-shaped white porophores lateral to large roughly circular raised genital papillae, 0.15 circumference apart.

Primary spinal epidural rhabdomyosarcoma: a case report and review of the literature

Primary intraspinal sarcomas are very rare in children. Rhabdomyosarcoma (RMS) is a highly aggressive and rapidly growing sarcoma with skeletal origin that occasionally appears in the spinal epidural space. We report a 13-year-old girl who presented with back pain, progressive paraparesis, and urinary retention. She had muscular weakness in her lower extremities and absent deep tendon reflex. An epidural dumbbell-shape mass at T11-T12 level was observed on MRI. The patient underwent T12 hemilaminectomy, partial T11 hemilaminectomy, and right facetectomy. A large, firm, dark-red vascular epidural tumor was found compressing the cord. The tumor which extended to intracanal and foraminal parts was removed completely. Histopathological examination revealed undifferentiated small round and oval tumoral cells. Immunohistochemical staining was positive for vimentin, desmin, and myogenin. The final diagnosis was alveolar RMS. She received radiotherapy and chemotherapy by vincristine, actinomycin-D, doxorubicin, and ifosfamide. The patient was in good condition with no tumor recurrence or metastasis at the 1-year follow-up.

A case of Congenital Fistula from An Accessory Parotid Gland: Diagnosis and Treatment

The author reports a case of congenital fistula from an accessory parotid gland and describes its diagnosis and treatment. The patient was referred to the author's clinic for evaluation of a continuous serous discharge from a small orifice in the left cheek near the angle of the mouth. A left preauricular appendix was also noted. Fistulography detected an aberrant duct leading to an accessory parotid gland. The main parotid gland and its duct were normal. The anomalous duct was dissected in continuity with a small ellipse of skin and sutured to the buccal mucosa. The patient's recovery was uneventful. The author also discusses the embryologic origin of this rare anomaly.

Amphicutis stygobita, a new genus and new species of brittle star (Echinodermata: Ophiuroidea: Ophiurida: Amphilepididae) found in Bernier Cave, an anchialine cave on San Salvador Island, Bahamas

Amphicutis stygobita is a new genus and new species of ophiuroid found in Bernier Cave, an anchialine cave on San Salvador Island, Bahamas. The species is small (disk diameter 3–4 mm) with short arms (2–2.5X disk diameter). Dorsal disk features include imbricated scales, and oval radial shields separated by a column of scales. Ventral disk features include imbricated scales, genital scales flat and thin, no bursal sacs, second tentacle pore of oral frame outside mouth slit, oral shields small ovals similar in appearance to disk scales, two to three oral papillae per jaw side with the proximal papillae usually in the infradental position, and ventral tooth at the apex of each jaw broadly rounded. The arms are the most distinctive feature. Dorsal arm plates are small diamond-oval shaped and separated from one another by a gap equal to the arm plate length. Ventral arm plates are small figure-8 shaped and separated from one another by a gap equal to the arm plate length. Lateral arm plates meet medially on dorsal and ventral sides and make up most of an arm segment. Each lateral arm plate bears two arm spines. Disk and arms are often formed by soft tissue outlining plates and scales, but lacking significant calcification. A raised skin persists after calcification, from which the genus name derives. The species is named for its aquatic cave-dwelling habit, apparently endemic to a single cave, and may be unique among ophiuroids in being restricted to a cave environment.

Quasistatic contact problem for cylindrical joints with minor cutting of the contours of the bodies

We solve a quasistatic contact problem of interaction of cylindrical elements with minor cutting of their contours. We study joints in which single-area or mixed (single-and-double-area) types of contact are realized. The basic regularities of changes in the maximum contact pressure caused by the rotation of a disk with certain degree of ovality in a hole with different types of cutting are established. It is well known that, in the process of manufacturing, all parts of typical cylindrical joints (plain bearings, guides, hinges, etc.) inevitably acquire a certain degree of nonroundness of the contours (ovality, trihedrality, tetrahedrality, etc.). The influence of the indicated nonroundness on the level and distribution of contact pres- sures in different joints with symmetric relative positions of contacting bodies leading to single-area or double- area contact was studied in a series of works (1-4, 8). The solution of the quasistatic problem was obtained in (5-7) for the case where a shaft with small ovality (ellipticity) rotates in an oval hole (bush), which leads to cy- clic changes in the maximum contact pressure. In the present work, we solve the quasistatic problem for joints in which the bush is characterized by the presence of cutting of complex shape.