Skates

in recent years, fatigue is a prominent failure mechanism for any vehicle's frame structure, and can lead to serious accidents, costly recalls, and poor product image for the vehicle's frame manufacturers. This paper deals with investigation of the fatigue behavior of the vehicle's frame and has carried out a design and modal analysis in SolidWorks. In this study, mode shapes and their natural frequencies of the wheel are obtained from the simulations. A method has been proposed to optimize the wheels and frame's material and design for an improved fatigue resistance.

In recent years, fatigue is a prominent failure mechanism for any vehicle’s frame structure, and can lead to serious accidents, costly recalls, and poor product image for the vehicle’s frame manufacturers. This paper deals with investigation of the fatigue behavior of the vehicle’s frame and has carried out a design and modal analysis in Solid Works. In this study, mode shapes and their natural frequencies of the wheel are obtained from the simulations. A method has been proposed to optimize the wheels and frame’s material and design for an improved fatigue resistance. Keywords – Design, Fatigue failure analysis, Modal Analysis Skate-cycle, Static Analysis.

El objetivo principal de la investigación es describir el sentido, los vínculos y los símbolos que se construyen en la práctica del Skateboarding en el marco de la vida cotidiana, en específico de un grupo de estudiantes de la Universidad de Antioquia. El modelo metodológico que fue empleado para el análisis del fenómeno consta de un enfoque Interaccionista Simbólico y fenomenológico, adscribiéndose al método cualitativo. La metodología utilizada fue la etnografía y la teoría fundamentada. Se presenta a modo de conclusión que: el Skateboarding es una práctica que desencadena múltiples intereses que dependen del fin con el que se realiza la acción, como también múltiples interacciones, y relaciones de sentido. Más que un deporte es un estilo de vida, por lo que se es abordado a partir de la vida cotidiana, y es allí, donde parte el sentido en el que giran sus vidas y el marco cultural y simbólico en el que se mueven. Dentro de ella se promueve la colectividad y la solidaridad, porque parte de unas vivencias y experiencias colectivas que lo incitan, es una manera contingente de ver la cuidad,  la realidad y crear un sentido de ellas.

This paper contains a collection of 1099 citations (685 articles and 414 conference abstracts) on topics related to extant and extinct Chondrichthyes (sharks, rays, and chimaeras) as well as a list of Chondrichthyan species and hosted parasites newly described in 2014. The list is the result of regular queries in numerous journals, books and online publications. It provides a complete list of publication citations as well as a database report containing rearranged subsets of the list sorted by the keyword statistics, extant and extinct genera and species descriptions from the years 2000 to 2014, list of descriptions of extinxt and extant species from 2014, parasitology, reproduction, distribution, diet, conservation, and taxonomy. The paper is intended to be consulted for information.

This paper contains a collection of 817 citations (no conference abstracts) on topics related to extant and extinct Chondrichthyes (sharks, rays, and chimaeras) as well as a list of Chondrichthyan species and hosted parasites newly described in 2017. The list is the result of regular queries in numerous journals, books and online publications. It provides a complete list of publication citations as well as a database report containing rearranged subsets of the list sorted by the keyword statistics, extant and extinct genera and species descriptions from the years 2000 to 2017, list of descriptions of extinct and extant species from 2017, parasitology, reproduction, distribution, diet, conservation, and taxonomy. The paper is intended to be consulted for information. In addition, we provide data information on the geographic and depth distribution of newly described species, i.e. the type specimens from the years 1990 to 2017 in a hot spot analysis. New in this year's POTY is the subheader "biodiversity" comprising a complete list of all valid chimaeriform, selachian and batoid species, as well as a list of the top 20 most researched chondrichthyan species.

This paper contains a collection of 786 citations (no conference abstracts) on topics related to extant and extinct Chondrichthyes (sharks, rays, and chimaeras) as well as a list of Chondrichthyan species and hosted parasites newly described in 2015. The list is the result of regular queries in numerous journals, books and online publications. It provides a complete list of publication citations as well as a database report containing rearranged subsets of the list sorted by the keyword statistics, extant and extinct genera and species descriptions from the years 2000 to 2015, list of descriptions of extinct and extant species from 2015, parasitology, reproduction, distribution, diet, conservation, and taxonomy. The paper is intended to be consulted for information. In addition, we provide information on the geographic and depth distribution of newly described species, i.e. the type specimens from the year 1990- 2015 in a hot spot analysis.

This is the second version of the database report “Host-Parasite List” and “Parasite-Host List” of cartilaginous fishes (Chondrichthyes: Elasmobranchii, Holocephali). The two lists result from the analysis of 1,078 research articles reporting on host-parasite relations in diverse species of sharks, rays, and chimaeras. The list contains 6,891 records in total. This edition contains 2,036 different species of parasites recovered from 495 species of elasmobranchs. All information about the parasites are also available at http://shark-references.com/species/host-parasites-list/A or http://shark-references.com/species/parasite-hosts-list/A  (weekly update).

In this study, a diverse fauna of fossil elasmobranch teeth from the Early Miocene (Middle Burdigalian) is analysed. The fossil diversity strongly resembles extant deep-water shark and ray assemblages. The fossils were collected from the Upper Marine Molasse of the lower Ottnangian in the Neuhofener Beds location, Mitterdorf, Germany. The collection site is a clay pit in between the Lower Bavarian villages Fürstenzell and Schmidham. The sample revealed 14 shark and four ray species. We present the first record of fossils assigned to taxa Nanocetorhinus tuberculatus, Deania and Apristurus from Germany. In addition, we describe a hitherto unknown genus and species of shark, Pseudoapristurus nonstriatus gen. et sp. nov., based on fossil teeth. The documented diversity is compared to both extant and fossil records of neoselachian deep-water diversities, and it is evident that this Miocene fauna is very similar in composition to indo-pacific deep-water assemblages. Zusammenfassung Aus der Oberen Meeresmolasse (Neuhofener Schichten, unteres Ottnangium) Niederbayerns (Tongrube zwischen Fürstenzell und Schmidham) wird eine artenreiche Tiefwasser-Elasmobranchierfauna beschrieben. Insgesamt werden 14 Hai-und vier Rochenarten nachgewiesen. Erstnachweise für Deutschland werden von Nanocetorhinus tuberculatus, Apristurus sp. und Deania sp. erbracht. Zusätz-lich wird eine bisher unbekannte Neoselachier Gattung und Art (Pseudoapristurus nonstriatus nov. gen. et sp.) anhand von Zahnfossilien beschrieben. Ein Vergleich der hier dokumentierten Diversität mit verschiedenen anderen rezenten und fossilen Neoselachier Vergesell-schaftungen zeigt, dass die vorliegende Fauna große Übereinstimmungen mit rezenter indo-pazifischer Tiefseediversität aufweist.

Inspired by the relatively simple morphological blueprint provided by batoid fish such as stingrays and skates, we created a biohybrid system that enables an artificial animal—a tissue-engineered ray—to swim and phototactically follow a light cue. By patterning dissociated rat cardiomyocytes on an elastomeric body enclosing a microfabricated gold skeleton, we replicated fish morphology at Embedded Image scale and captured basic fin deflection patterns of batoid fish. Optogenetics allows for phototactic guidance, steering, and turning maneuvers. Optical stimulation induced sequential muscle activation via serpentine-patterned muscle circuits, leading to coordinated undulatory swimming. The speed and direction of the ray was controlled by modulating light frequency and by independently eliciting right and left fins, allowing the biohybrid machine to maneuver through an obstacle course.

By Rune Edberg and Johnny Karlsson // 679 bone skates from two important sites in the Stockholm area were examined. Cattle bones dominate in Birka (8th to 10th centuries AD), while horse bones are more numerous in Sigtuna (10th to 13th centuries AD). The average length of the
skates is c. 20 cm in Birka and c. 22 cm in Sigtuna. It seems that in Birka, bone skating
was practiced mostly by children. In Sigtuna it also became popular among adolescents and perhaps young adults. Ethnological analogies strongly support the interpretation of bone skates as toys and sporting equipment.

Almost all Rajiformes are viviparous without placentas, and their embryos are nourished by yolk sacks accompanied in
some cases by uterine milk. However, there are few studies of biological aspects of the species in this group in Colombia.
This study aimed to analyze some reproductive aspects of Narcine bancroftii (Griffith y Smith, 1834), Diplobatis guamachensis
Martin, 1957, and Rhinobatos percellens (Walbaum, 1792), captured as bycatch of the shrimp trawling fishery in
two zones (north and south) of the Colombian Caribbean during the second semester of 2004. Samples were caught from
the same fleet’s fishing tasks, and corresponded to one-fifth of the homogenized discard, taken randomly from one of the
four nets in the ship. Individuals of the three species were brought to the laboratory for further morphometry measurements,
taxonomic identification and determination of the maturity state. The maturity state differentiation was based on claspers
development and sperm presence for males, and in the size and development of the ovaries, eggs, and embryos for females.
Females of N. bancroftii showed immaturity and spawned states, while the males were mature. The individuals of D.
guamachensis were represented by maturity females with embryos, and maturity males, whereas those of R. percellens were
characterized as maturity females with embryos and spawned states, and maturity males. The presence of uterine milk in
individuals of N. bancroftii, and embryos in D. guamachensis were the first known reports in the literature for this country.

ABSTRACT: Eight species of marine and freshwater leeches are reported from Puerto Rico, five of which are new to the Puerto Rican fauna. Additional observations of leeches from
other Caribbean islands are reported, along with a key to the nine known species of the Caribbean region, excluding Trinidad. Leeches of the Caribbean

The authors of this paper are serious avocational students of paleontology. We are pleased to present their work on vertebrate fossils found in Delaware, a subject that has not before been adequately investigated. Edward M. Lauginiger of Wilmington, Delaware teaches

In this study 14 species of marine leeches (Piscicolidae) are reported. These are divided geographically into  northern and southern species, and ecologically into brackish water and high salinity species. Notice is made of Cape Hatteras as a divide between northern and southern species.

In recent years, fatigue is a prominent failure mechanism for any vehicle's frame Structure, and it can lead to serious accidents, costly recalls, and poor product image for the vehicle's frame manufacturers. This paper deals with investigation of the fatigue behaviour of the vehicle's chassis and has carried out a design and optimization in Solid Works. In the first part of the study, the static loads acting on the connecting rod, after that the work is carried out for safe design. Based on the observations of the static Finite Element Analysis (FEA) and the load analysis results, the load for the optimization study was selected. The results were also used to determine degree of stress, and the fatigue model to be used for analysing the fatigue strength. Outputs include fatigue life, damage, factor of safety, fatigue sensitivity. A method has been proposed to optimize the wheels and frame's material and design for an improved fatigue resistance. 1. INTRODUCTION The ability to optimize and improvement in design has created substantial amount of growing engineering requirements. This paper analyses the design of a Skate cycle – A hub less personal vehicle used for recreational activities. The analyses is done utilizing finite element analysis using number of calculated forces and contact forces representing what a Skate cycle would undergo under normal use, on both sets of wheels. The analysis for this piece was done by using SolidWorks for modelling and design analysis. Proper stress levels, a very complex problem in highly redundant structures, are calculated using versatile computer matrix methods to solve for detailed internal loads. Modern FEM models of personal vehicle components include many degrees-of-freedom and are used to determine the required thicknesses to avoid any excessive stress levels, deflections or strain. The main goal of detailed design is to reduce or eliminate the stress concentrations, any hidden undetectable cracks or a single failure leading to overall component failure. Every vehicle should be able to provide comfort in the terms of the ride and smooth handling. But along with this, the components should have a good fatigue life. Fatigue is a phenomenon with respect to variable loading or cyclic loading resulting in straining of the material. Fatigue is one of the major issues in automobile components. It must be able to withstand numerous cycles before failing or not fail during the service period of the automobile. Fatigue cracks are most commonly found in areas where there is a change in geometry eg., holes, notches or sudden changes in section, cause stress concentration. This paper presents modal analysis, stress and strain analysis and fatigue analysis to the Skate-cycle modelled using Solidworks software.

Objetivo. Interpretar los sentidos y significados que subyacen en las relaciones que los practicantes de parkour y skateboard tejen dentro de su práctica y con los demás habitantes de la ciudad. Metodología. Este es un estudio fenomenológico que recurre a entrevistas de discusión y entrevistas semiestructuradas realizadas a grupos e individuos que hacen parte de las prácticas. Resultados. Los resultados indican que las relaciones intersubjetivas en la práctica se caracterizan por su horizontalidad, en ellas los saberes y experiencias valen por su carácter formativo y amistoso y no por la jerarquía. Dentro de las practicas la interrelación de los sujetos está circunscrita a la solidaridad, la responsabilidad, la motivación y cuidado del otro. Conclusión. Los procesos de subjetivación e intersubjetividad se alimentan del sí mismo de los otros, traceurs y skaters proyectan no solo sus propias subjetividades, sino que reflejan algunas formas de aquellos con los que confrontan.

Six bottom trawl surveys carried out in the southeastern Gulf of St. Lawrence between September 1986 and September 1987 indicated a marked seasonal cycle in distribution and relative abundance of demersal fish. Atlantic cod (Gadus morhua), white hake (Urophycis tenuis) and American plaice (Hippoglossoides platessoides) exhibited the greatest movement, migrating out of the shallow water of the southeastern Gulf in winter and returning in spring. Yellowtail flounder (Limanda jerruginea) and winter flounder (Pseudopleuronectes americanus) undertook limited movements with a portion of the population remaining in shallow water year round. Longhorn sculpin (Myoxocephalus octodecemspinosus) moved to slightly deeper water in winter but remained in the water shallower than 100 m where the bottom temperature reached OoC or below. Thorny skate (Raja radiata) exhibited a winter migration to the warmer waters of the southern slopes of the Laurentian Channel and returned to the shallows of the southeastern Gulf in summer. There was also an indication of at least a partial movement of this species out of the Laurentian Channel to the Atlantic. Winter skate (Raja ocellata) moved to slightly deeper water in winter, although not as far as the Laurentian Channel, and then dispersed back to the shallows in summer. Smooth skate (Raja senta) exhibited no seasonal movement and remained in the relatively warm, stable, deeper water of the Laurentian Channel and Cape Breton Trough.

Six recensements au chalut de fond effectues dans Ie sud-est du golfe du Saint-Laurent entre septembre 1986 et septembre 1987 ont revele un cycle saisonnier marque dans la distribution ainsi que dans I'abondance relative des poissons demersaux. La morue franche (Gadus morhua), la merluche (Urophycis tenuis) et la plie canadienne (Hippogiossoides platessoides) se deplac;ent Ie plus, quittant les eaux peu profondes du sud-est du Golfe en hiver et y retournant au printemps. La limande it queue jaune (Limanda jerruginea) et la plie rouge (Pseudopieuronectes americanus) se deplac;ent assez peu puisqu'une partie de la population demeure en eaux peu profondes tout I'annee. Le chaboisseau it dix-huit epines (Myoxocephaius octodecemspinosus) migre vers des eaux legerement plus profon-des en hiver, mais il demeure it une profondeur de moins de 100 m ou la temperature de fond atteint OoC ou moins. La raie radiee (Raja radiata) migre en hiver vers les eaux plus chaudes des pentes sud du Chenal Laurentien et revient dans les bas-fonds du sud-est du golfe du Saint-Laurent en ete. II semble aussi qu'une partie de la population de cette espece quitte Ie Chenal Laurentien pour se rendre jusque dans l' Atlantique. La raie tachetee (Raja ocellata) migre vers des eaux legerement plus profondes en hiver, sans toutefois se rendre jusqu'au Chenal Laurentien et elle se disperse it nou-veau sur les bas-fonds en ete. La raie lisse (Raja senta) ne montre aucun mouvement saisonnier et demeure dans les eaux plus profondes et relativement stables et chaudes du Chenal Laurentien et de la fosse du Cap-Breton.

Bone skates
Skates now associate with metal skid attached to the elegant shoes. Few people remember how they looked a few decades ago, and few people know what our ancestors used skates, such as a few hundred years ago, or even longer…
On archaeological sites on the northern, eastern and central Europe, ranging from those dating from the Bronze Age to modern times, are found, made from animal bones, runners - bone skates. They are characterized by long-smoothing one surface (slid), articular surface machined one quadrant-shaped "bow", trimming the other end of the bone, which (in place of anatomical hole) portion of specimens have drilled the hole, used skid attached to the foot. Holes were made sometimes on the sides of the monument.
So looking objects used to move around the ice.
The oldest found skates are about 5 thousand. years, were made of animal bones, tied straps to the foot. Wooden skates with metal reinforcement appeared in the fourteenth century Skates made entirely of iron was introduced in the seventeenth century.
Ice skating has long been a means of transport in Europen countries with long, cold winters. For the eighteenth century, skating has become not only a way of movement, but also well-received sports. European colonists introduced quickly skating in the North America.
Fully preserved early medieval bone skate from the church of Saint Andrew in Kraków undoubtedly served to slide / move the fluid movements on the ice without lifting your feet. Thus perfectly fulfill the function of skid. However, presented below excerpt from the drilled hole, which facilitate attachment to her feet, it's skate that allows lifting the foot, and therefore the holding of long walks on the ice and snow and fun on the ice.

Łyżwy kościane
Łyżwy kojarzą się obecnie z metalową płozą przytwierdzoną do eleganckich butów. Mało kto pamięta jak wyglądały kilkadziesiąt lat temu, a mało kto wie, jakich łyżew używali nasi przodkowie, np. kilkaset lat temu lub jeszcze dawniej…
Na stanowiskach archeologicznych północnej, wschodniej i środkowej Europy, poczynając od tych datowanych na epokę brązu aż po czasy nowożytne, znajdowane są, wykonane z kości zwierzęcych, płozy – łyżwy kościane. Charakteryzują się one wygładzeniem jednej powierzchni długiej (ślizgu), obrobieniem jednej powierzchni stawowej w kształcie półokrągłego „dziobu”, przycięciem drugiego końca kości, na którym (w miejscu anatomicznego otworu) część okazów posiada nawiercony otwór, służący przymocowaniu płozy do stopy. Otwory wykonywano czasami także na bocznych powierzchniach zabytków.
Tak wyglądające przedmioty wykorzystywano do poruszania się po lodzie.
Najstarsze znalezione łyżwy mają ok. 5 tys. lat, były zrobione z kości zwierzęcych, przywiązywane rzemieniami do stóp. Łyżwy drewniane z metalowym usztywnieniem pojawiły się w XIV w. Łyżwy zrobione całkowicie z żelaza wprowadzono w XVII wieku.
Łyżwiarstwo przez długi czas było środkiem lokomocji w europejskich krajach z długimi, mroźnymi zimami. Do XVIII wieku łyżwiarstwo stało się już nie tylko sposobem przemieszczania się, lecz również dobrze przyjętym sportem. Europejscy koloniści szybko wprowadzili łyżwiarstwo w Ameryce Północnej.



Zachowana w całości wczesnośredniowieczna kościana łyżwa z kościoła św. Andrzeja służyła niewątpliwie do ślizgania/przesuwania się po lodzie płynnymi ruchami bez podnoszenia stóp. Spełniała dzięki temu znakomicie funkcję płozy. Natomiast prezentowany poniżej fragment z nawierconym otworem, który ułatwiał przytwierdzenie do jej stopy, to już łyżwa umożliwiająca unoszenie stóp, a więc także odbywanie dłuższych wędrówek po lodzie i śniegu czy zabawy na ślizgawce.

Elucidating the combined effects of increasing temperature and ocean acidification on performance of fishes is central to our understanding of how species will respond to global climate change. Measuring the metabolic costs associated with intense and short activities, such as those required to escape predators, is key to quantifying changes in performance and estimating the potential effects of environmental stressors on survival. In this study, juvenile little skate Leucoraja erinacea from two neighboring locations (Gulf of Maine, or northern location, and Georges Bank, or southern location) were developmentally acclimatized and reared at current and projected temperatures (15, 18 or 20°C) and acidification conditions (pH 8.1 or 7.7), and their escape performance was tested by employing a chasing protocol. The results from this study suggest countergradient variation in growth between skates from the two locations, while the optimum for escape performance was at a lower temperature in individuals from the northern latitudes, which could be related to adaptation to the local thermal environment. Aerobic performance and scope declined in skates from the northern latitudes under simulated ocean warming and acidification conditions. Overall, the southern skates showed lower sensitivity to these climatic stressors. This study demonstrates that even mobile organisms from neighboring locations can exhibit substantial differences in energetic costs of exercise and that skates from the northern part of the geographic range may be more sensitive to the directional increase in temperature and acidification expected by the end of the century.

LING SIMPLE RESEARCH ON COLD SPELL:
SECTION 1,
P1. THE DUTCH ICE SKATING FEAST, P2. THE ELEVEN CITIES TOUR, P3. THE TOUR AND ITS SCIENCE, P4. THE TOUR AND THE SUNSPOTS, P5. RADIATING OR WINDY SUN, P6. ECLIPSE FOR VERIFICATION, P7. ECLIPSE MEASUREMENTS, P8. WILSON’s CLOUD CHAMBER, P9. WILSON CLOUD @ BIKINI, P10. LOCK DOWN TEMPERATURE RAISE
SECTION 2.
P1. THE 14C ISOTOPE @EROSOL, P2. 14C ISOTOPE BEHAVIOR, P3. 14C ABSORBING, NOT DECAYING, P4. CLIMATE "RESEARCH" SAY, P5. THE MAUNDERS SEEM RIGHT !, P6. BIKINI 14C-@EROSOL "VULCAN" 1946, P7. BIKINI 14C-@EROSOL & EL NIÑO, P8. 14C @EROSOL BIKINI TO EUROPE, P9. TODAYS 14C-@EROSOL PROBLEM, P10. PREDICTIONS & CLIMATE CHANGE
SECTION 3.
P1 SNOW RAIN & FOG, P2 LOTS OF SNOW IN W-EUROPE, P3 FINALLY EVEN IN THE PERCHE, P4 SNOW MEASUREMENTS IN S. EUROPE, P5 BUT TERRIBLE RAIN IN S-EUROPE, P6 IN STEAD OF SNOW: RAIN, P7 THE LINK TO THE CCN’s IS FOG, P8 THE METEO BEHAVIOR OF FOG, P9 THE COLD WAR STILL WITH US?, P10 THE CLEAN CAR AN A-BOMB?
SECTION 4.
P1 ELECTROSPHERE, P2 INFO FROM BEARNAIRDINE B.,P3 SAHARA DUST CHARACTERISTICS, P4 CRYOCONITE PARTICLES?, P5 FRENCH CESIUM-137?, P6 DUST SPREADING MECHANISMES, P7 THE SOLAR WIND => PLASMA, P8 HOW THE EARTH IS CHARGED (-), P9 NOT THEORY ONLY: A POLAR….,P10 THERE ARE MORE THINGS IN HEAVEN….
SECTION 5.
P1 GLOBAL @EROSOL TRANSPORT, P2 MOSCOU GETS MORE THEN USUAL, P3 EUROPE’s COLD SPELL, P4 SAHARA DUST & THE EVERGIVEN, P5 VOLCANIC ERUPTION, P6 FROM AFRICA TO THE AMAZONAS, P7 A COLD WAVE HITS EVEN TEXAS,P8 FROM ANALOG TO BINARY WEATHER, P9 VIRUS & DENTROCHRONOLOGY
P10 ….. IN HEAVEN AND EARTH…..