Change in the North Atlantic circulation associated with the mid-Pleistocene transition

The southwestern Iberian margin is highly sensitive to changes in the distribution of North Atlantic currents and to the position of oceanic fronts. In this work, the evolution of oceanographic parameters from 812 to 530 ka (MIS20-MIS14) is studied based on the analysis of planktonic foraminifer assemblages from site IODP-U1385 (37 degrees 34.285' N, 10 degrees 7.562' W; 2585m b.s.l.). By comparing the obtained results with published records from other North Atlantic sites between 41 and 55 degrees N, basin-wide paleoceano-graphic conditions are reconstructed. Variations of assemblages dwelling in different water masses indicate a major change in the general North Atlantic circulation during MIS16, coinciding with the definite establishment of the 100 ky cyclicity associated with the mid-Pleistocene transition. At the surface, this change consisted in the redistribution of water masses, with the subsequent thermal variation, and occurred linked to the northwestward migration of the Arctic Front (AF), and the increase in the North Atlantic Deep Water (NADW) formation with respect to previous glacials. During glacials prior to MIS16, the NADW formation was very weak, which drastically slowed down the surface circulation; the AF was at a southerly position and the North Atlantic Current (NAC) diverted southeastwards, developing steep south-north, and east-west, thermal gradients and blocking the arrival of warm water, with associated moisture, to high latitudes. During MIS16, the increase in the meridional overturning circulation, in combination with the northwestward AF shift, allowed the arrival of the NAC to subpolar latitudes, multiplying the moisture availability for ice-sheet growth, which could have worked as a positive feedback to prolong the glacials towards 100 ky cycles.info:eu-repo/semantics/publishedVersio

Morphology, biostratigraphy, and evolution of PliocenePleistocene diatoms Proboscia barboi..

Proboscia barboi and Proboscia curvirostris are two important diatom biostratigraphic markers from the high latitudes of the North Pacific and North Atlantic Oceans, dating back to the Pliocene-Pleistocene time. This study analyzes the biostratigraphic events and describes the morphology of P. barboi and P. curvirostris, particularly the morphologic variations of the latter species, based on observations of samples of Core U1340A from the IODP Expedition 323 in the Bering Sea. In Site U1340, the First Occurrence of P. curvirostris is observed at 1.52Ma and its First Common Occurrence at 1.39Ma, where morphologic variations were found abundantly. The Last Occurrence of P. curvirostris was found at 0.33Ma, while P. barboi's Last Occurrence is found at 0.67Ma. Based on the morphological similarity and known biostratigraphic distribution, previous authors have assumed that P. curvirostris descends from P. barboi, although this hypothesis is still in debate. At 1.39Ma P. curvirostris shows an increased size and thickness, which is typical of P. barboi, and some specimens display an incipient structure characteristic of P. curvirostris - the secondary spine. This morphology is intermediate between the two species and suggests an evolutionary transition from P. barboi to P. curvirostris. However, P. curvirostris already existed since 1.9Ma in the subarctic indicating that its speciation happened much earlier than 1.39Ma. Furthermore, since P. barboi co-occurs with P. curvirostris in the North Pacific, this evolutionary process was cladogenetic. Besides being evidence for a phylogenetic relationship, the abundant occurrence of intermediate forms at 1.39Ma may constitute a bioevent for a short time interval in the Bering Sea.info:eu-repo/semantics/publishedVersio

Biomechanics of a Motor Pattern and its Sports Application

Man is capable of acquiring an ever increasing number of motor responses and in this way to improve his relationship with the environment. Obviously, if it was necessary to create a new motor organization for each new situation, the human motor behaviour would be chaotic for the sheer number of motor responses which would have to be available for ready utilization. Indeed, it is easier for the central nervous system to adjust to new environmental conditions and to different goals by compounding new motor programs from previously learnt subroutines. These subroutines -the motor patterns -evolve during the performer's life through general learning and specific training processes. The pattern approach to the motor organization is not new. Broer (1966) relates the shape of the movement with the skill goal and gives a set of examples with different goals but for which the shape is conserved. Wickstrom (1977) calls these shapes «Movement patterns». Obviously, similar limb kinematic relationships correspond to similar kinetic relationships, a fact already pointed out by Higgins (1972) when he states that each motor skill consists of three -motor, muscular and movement components. According to Wickstrom the development of each skill is an extensive process focused successively upon three major steps: the minimal form, the mature form and the sport skill form. The core of the mature form is the fundamental motor pattern. The sport skill is adapted to special requirements by the rules or by the strategy of each sport. From a mechanical point of view the human body «is» an articulated link system which simultaneously behaves as a rigid one when it resorts to external support to achieve the mechanical energy flows envolved in a desired performance. The efficiency of such a performance is determined by the mechanical work of the limbs but its final effect can be deduced from the knowledge of the center of mass kinematics and of the force exerted on the support. The motor organization may thus be conceived as integrating two simultaneous mechanical behaviours: an articulated link system relatively to the limb movements and a rigid system relatively to the external environment. Indeed if the human body behaved strictly as a «rigid system» it would have the tendency to rotate about the center of the support by an amount which would be proportional to the energy it possessed. In reality this does not occur and, instead, the system performs a set of intersegmental movements in accordance with the goal proposed for the desired skill and the result of this «articulated» behaviour is transferred to that of the «rigid» mode. Two complementary approaches to the biomechanical study of human motor patterns are thus available: the evaluation of the internal work performed by the limbs and the dynamical analysis of the center of mass of the «rigid body» system

THE DYNAMIC SUPPORT STRUCTURE AND THE FOOT STABILITY RELATED TO RUNNING SPEED

Introduction - The alterations of the dynamic support structure in running, related to the horizontal speed increase, has been studied by several authors; Cavanagh (1989)studies the displacement of the support center and the pressure distributions; Nigg et all (1981) analyses the active and passive loader Bates (1983) study the critical variables defining the support dynamic. Simultaneously, the study of the rearfoot mobility around the horizontal axes of the subtalar joint during ground contact has been gaining in importance (Nigg et all, 1978). The above mentioned subjects are integrated in the present study for a more complete knowledge of the foot contact. Relations between the increase of running speed and respectively the variables defining the rearfoot mobility and the critical variable6 of the ground reaction forces are establish. Methods - Six sprinter of Portuguese national level carried out each of them 6 performances, barefoot, at three different speeds (Vl=3.3 7 me-I+/-0.56 ; V2=4. 37me"+/-0.37 e V,55 -44 me-I+/-0.31). The kinetic data were obtained on a force platform (Kistler 9281B, sampling frequency 1000 Hz) connected t6 the computer via A/D card (DT 2801A Data Translation). The runners speed was controlled by means of photoelectric censors that synchronized the collection of the kinetic and video images. The kinematic data was processed according to the methodology proposed by Nigg et all (1978). Results and Discussion - The obtained kinetic results are similar to those contained in the corresponding bibliographic references , in form patterns as well as in quantitative results (Cavanagh,1989 ; Nigg et a11,1981; Batee et all, 1983). Regarding the rearfoot mobility the displacement/time curves are similar to the ones presented by Nigg et all (1978) as far as barefoot runners are concerned. Significant statistical correlations (correlation coefficient, Bravais-Pearson) were ascertained showing that the running speed increase ie related to : (1) decrease of ground contact time (r=-0.96, P-ZO.01) , (2) increase of anteriorposterior speed variation (aVy) (r50.77,

ANALYSIS OF THE HANDS SUPPORT IN EXTRA-PLUMMET CLIMBING SKILL

INTRODUCTION-The purpose of this study is to compare the hands support behaviour in two different extra-plummet climbing skills (as performed in climbing walls with angles between horizontal below 90°). These two extra-plummet climbing skills can be distinguished by basic body positions. Taking the pressure centre of hands support as reference the body balance is considered a stable balance because the hands have a higher positions than the feet. (Jodar, 1993). Therefore the level of body stability in these two skills, depends, basically, on the performers capacity of maintaining body contact with the wall by means of the hand grip. (Vert>ier, 1991). The capacity to maintain the hand's grip is the result of the relationship between friction force and the tangential forces applied by the c1imber on contact surface. The two studied skills have different basic body positions: in skill A tha basic body position is "body are" and in skill B the basic body position is "body suspense”. Taking the mathematical expression of friction force into account, the access to the behaviour of the friction force can be achieved through normal force (Hammil & Knutzen, 1995). Thus, the hand's support stability is accomplished by the quotient of each tangential and normal force appfied by the climber on contact with the surface. The registration of force values (Fx is the force acting in parallel direction to the sagittal plan, Fy is the force acting in parallel direction to the frontal plan and Fz is the normal force) in both skills and was achieved through the Kistler platform, model 9281 Sand appropriate software, fixed horizontally on an artificial climbing wall. RESULTS-The sample was composed of eight experimented c1imbers whose ages ranged from twenty-two to forty years old. Every subject performed five valid executions in both skills. In skill A, the arithmetical mean of Fx/Fz was 0,372, CV=0,352, and the arithmetical mean of Fy/Fz was 0,009, CV=6,83. In skili S, the arithmetical mean of Fx/Fz was 0,25, CV=0,311, and the arithmetical mean of Fy/Fz was 0,017, CV=1,089. The statistical method T of Pairs was applied to evaluate the differences between Fx/Fz data in both skills and also to evaluate the differences between Fy/Fz data in the same skills. CONCLUSIONS-The results give evidence that the values of Fy/Fz do not differ between the studied skills, but the value of Fx/Fz in skill S was significantly different from skill A. Therefore skill B has a greater potential to be used in further climbing skills, because it uses a smaller percentage (~25%) of normal force than skill A (~37,2%). REFERENCES• Hamill, Joseph; Knutzen, Kathleen M. (1995). Biomechanical Basis of Human Mouvement. Williams & Wilkins. Philadelphia. USA. 403-405. J6dar, Xavier Aguado (1993) Eficacia Y Teeniea Deportiva. INDE. Barcelona. Epana. 178-186. Verdier, Jean-Pierre (1991). Initiation et Perfectionement ä Esca/ade. Amphora. Paris. Franee. 29-36

KINEMATIC ANALYSIS OF BASKETBALL SHOOTING. PRELIMINARY RESULTS

INTRODUCTION-Basketball shooting is the most important skill of the game Its teaching methodology is based on permanent adjustment of theoretical sentences of performance and individual characteristics. Development of basketball players needs talent but also technical qualities which is the reason why youngsters must know the basic principles of technique However, ball size, basket height and court dimensions are three variables which can affect the learning process of basketball shooting (Skleryk , 1985). The purpose of the present study is to analyse the effect of ball size on some mechanical parameters of free throw shooting, as performed by eight fourteen-year-old basketball players Two ball sizes were used regular size ball (613 gr weight, 74 cm perimeter) and adapted size ball (608 gr weight, 76.5 cm perimeter). Two video cameras were utilized to recover the videographic material on frontal and lateral views of shooters Three free throws of each player were digitalized and analysed with BIOSIST Based on Satern (1989), six mechanical parameters related to shooter segment were analysed on ball release (shoulder angle, elbow angle, wrist angle, hand height, linear hand velocity and hand angle) The determination of maximum elbow flexion occurring during shooting was another goal. Also, displacement of the centre of gravity and its relationship with support surface was investigated RESULTS-Mean and standard deviation of each parameter per trial digitalized were selected. Higher values of height and angle release were obtained with adapted size ball. It appears that the regular ball needs an increase of linear hand velocity in shooting Differences between intersegmental angles reveal a general tendency for the shooter to employ more force in regular-ball than in adapted-size-ball. Results show a higher flexion of elbow and a higher release elbow angle when the player shoots with a larger ball. Release angle wrist appears less with regular ball which indicates that more work is produced by the shooting hand with adapted-size-ball. Displacement of centre of gravity on the vertical plan was the most significant difference. The difference between initial instant of shooting and the ball release instant is 0.16 (+/-0 12) m with smaller ball and only 0.07 (+/-0.03) m with a larger ball. CONCLUSIONS-Despite the small differences in the quantitative results, this probably indicates that young players transfer lesser energy on regular-ball than on adapted-size-ball. This leads up to the hypothesis that the adaptation of ball size to particular characteristics of each age scale will create better conditions for young players to learn the correct principles of shooting technique REFERENCES Satern,M.;et al. (1989); The Effect of Ball Size and Basket Height on the Mechanics of Free Throw; J. Mov. SI.; 16; 123-137

KINEMATICS IN BASKETBALL SHOOTING - THE INFLUENCES OF BASKET HEIGHT AND BALL SIZE

INTRODUCTION The majority of coaches identify shooting as the most important skill of basketball. This does not preclude the importance of other skills - dribbling, passing or footwork - but only assume that all offensive actions have shooting as their final objective. Coaches have many preocupations about the direction of team's development. Some of them revolve around the effort of teaching and developing the basic skills of offence. At the same time young players must, from an early age, practice their skills in a regular context, in similar conditions to the adult basketball game. In these more demanding conditions the successful execution of basic skills of offence actions, have the tendency to become more difficult for young players. The purpose of the present study was to analyse the effects of basket height and ball size on some mechanical parameters of shooting technique. METHODS Ten thirteen years old right-handed basketball players were the subjects in this study. A total of 11 3 shoots were digitised and analysed in a bidimensional software program named BIOSIST. Two kind of kinematics parameters were considered: instant kinematics parameters, determinate on the instant of ball release, and behaviour kinematics parameters, which are relative to shooting time. Two heights of basket and two sizes of ball were used. RESULTS Results point to significant differences in linear velocity of shooting hand and height of same segment on ball release, when regular and adapted conditions of basket height were compared. Ball size seemed to have more influence on displacement of centre of mass, particularly on its horizontal path during shooting time. Despite the small differences obtained on intersegmental angles, for both conditions of basket and ball, the adapted form of these variables promotes a better quality of execution for the players. CONCLUSION More significant than ball size, the tendency of results reveals that the adaptation of basket height could create an execution in which its characteristics are similar to theoretical models used by coaches. REFERENCES Ferreira, A.P.; Fernandes, 0.; Abrantes, J. (1996); Kinematic Analysis of Basketball Shooting. Prellimhar Results; in, 14th International Symposium on Biomechanics in Sports. Ed. by Joiio M.C.S. Abrantes; Edi~dies F.M.H., Universidade Tdcnica de Lisboa; pp. 47 1-474

Influencia de la Laguna de Aveiro en los contenidos de metales pesados en la plataforma continental adyacente (Portugal)

A chemical analysis of Al, Ca, Fe, Mg, Cu, Pb, Zn, Cr, Co, Ni and Cd was carried out in 22 surface sediment samples of the continental shelf and upper slope between Espinho and Aveiro (Portugal). To reduce the disturbing effects of grain size, all samples were size-normalized by wet sieving (<63 µm). The fine fraction was digested with concentrated acids and analyzed by flame atomic absorption spectrometry. The Al and heavy metal concentrations displayed a similar distribution pattern, decreasing seaward. Exceptions to this general pattern are Ca, Mg and Pb distributions. The Ca contents are related to carbonated biogenic particles that are very abundant in the outer shelf. Multivariate statistical analysis was applied to all data to assess the behaviour and sources of each element analyzed. The results from factor analysis showed that terrigenous supply (from Aveiro Lagoon flow, coastal erosion and littoral drift), grain size (clay) sorting and anthropogenic influences from Aveiro Lagoon are the major factors controlling spatial variations of chemical elements in the continental shelf between Espinho and Aveiro. Unusually high contents of Pb were found in the middle shelf off Furadouro, but we could not determine the possible source of this contamination.Se realizaron análisis químicos de Al, Ca, Fe, Mg, Pb, Zn, Cr, Co, Ni y Cd en 22 muestras de sedimento superficial de la plataforma y vertiente continental entre Espinho y Aveiro (Portugal). Para reducir el efecto de la granulometría del sedimento, se normalizó el tamaño de las muestras mediante tamizado (<63 µm). Se procedió a la digestión de la fracción fina con ácidos concentrados y se analizó mediante espectrometría de absorción atómica con llama. Las concentraciones de Al y metales pesados muestran un patrón de distribución similar, disminuyendo hacia la vertiente. Las excepciones a este patrón general son las distribuciones de Ca, Mg y Pb. El contenido de Ca está relacionado con las partículas biogénicas carbonatadas que son muy abundantes en la plataforma externa. Con el objetivo de determinar el comportamiento y el origen de cada uno de los elementos analizados, se aplicaron técnicas de análisis estadístico multivariante. Los resultados obtenidos muestran que los principales factores que controlan las variaciones espaciales de los elementos químicos en la plataforma continental entre Espinho y Aveiro son los sedimentos terrígenos procedentes de la Laguna de Aveiro, de la erosión costera y de la deriva litoral; el tamaño de grano (tamaño arcillas); y la influencia antropogénica en la Laguna de Aveiro. En la plataforma media, a la altura de Furadouro, se encontraron valores elevados de Pb, aunque no hemos podido determinar la posible fuente de esta contaminación

KINEMATICAL AND DYNAMICAL ANALYSIS OF LONG JUMP TAKE-OFF: A FOUR CASES STUDY

INTRODUCTION-The take-off is one of. the most important phases of the long jump. Once there is no available knowledge on kinematic vs. dynamic relationships on the take-of, the purposes of this study were: (i) to analyse the biomechanical variations that occur at take-off; (ii) to establish relationships between kinematic and dynamic variables; (iii) to verify which of the moments of the take-off is more important to the production of the vertical velocity as well as the best result. METHODS~ Subjects for this 4-casesstudy research were well trained jumpers. Each athlete performed 6 trials, all videotaped (JVC-SVHS) in the sagitai plane for kinematical analysis (50 Hz). Simultaneously, dynamic analysis was performed through a Kistler 9218 B force plate (250 Hz). The kinematic parameters studied were: (i) resulting velocity of the center mass (VCM); (ii) horizontal velocity of the center mass (Vx); (iii) vertical velocity of the center mass (Vy); (iv) horizontal velocity of the lead leg knee (VeIK); (v) horizontal velocity of the touchdown foot (VeITd); (vi) loss of horizontal velocity (LVx); (vii) gain of vertical velocity (GVy); (viii) center mass / heel angle in the instants of touchdown and take-off (AngCM-he); (ix) knee angle (AngK); (x) support time (ST); (xi) touchdown distance (TdD); (xii) take-off angle (AngT). The described velocities and angles were determined in the following instants: (i) touchdown; (ii) maximum knee flexion and (iii) take off. The dynamical parameters studied were: fi) vertical impulse (Iz): (ii) maximum vertical force (Fzmax): (iii) time course to achieve maximum vertical force (lH/Fz max); (iv) passive impulse (lzPass}: (v) time course of the passive impulse (lHPass); (vi) active impulse (lzAct); (vii) time course of the active impulse (ßTAct); (viii) horizontal anterior posterior impulse (Iy); (ix) horizontal lateral impulse (Ix) RESULTS-The main results of this study showed that, in all cases, the major loss of the Vx and the major gain of the Vy were observed between the touchdown and the maximum knee flexion We also noticed that the knee of the lead leg has its maximum velocity at the moment of the maximum knee flexion for all subjects. This variables contribute significantly, in all cases, to the increase of the AngK in the take-off instant (psO.05), which is theoretically advantageous to the performance. One other finding was that when the values for AngCM-he in the touchdown and take-off instants were out of the theoretical limits defined by Fischer (1975), a reduced performance was observed. The observation of results also showed: (i) a increased Fzmax was always related with a higher jump length, with a higher % IZPass / IzAct, with a reduction both on ßTAct and ST, despite the correlation analysis did not always provide significant r values. CONCLUSIONS-Long jumpers should pay a special attention to the phase between the touchdown and the maximum knee flexion, where the main production of Vy occurs. There, a reduclion on ST during the take-off should be searched. Attention should also be paid to the values of the AngCM-he during the touchdown. REFERENCES Fischer, R. (1975). Weitsprung. Biomechanische untersuchungen am schweizerischen weitsprungkader mittels filmanalyse und messugen mir der mehrkomponenrenmessplattform. Diplamarbeil in biomechanik, ETH, Zurich