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The Force Concept Inventory is a multiple-choice test and is one of the most popular and most analyzed concept inventories. It is used to investigate student understanding of Newtonian mechanics. A structured approach to data analysis can transform it in a "diagnostic" instrument that can validate inferences about student thinking. In this paper, we show how cluster analysis methods can be used to investigate patterns of student conceptual understanding and supply useful details about the relationships among student concepts and misconceptions. The answers given to the FCI questionnaire by a sample of freshman engineering have been analyzed. The analysis takes into account the decomposition of the force concept into the conceptual dimensions suggested by the FCI authors and successive studies. Our approach identifies latent structures within the student response patterns and groups students characterized by similar correct answers, as well as by non-correct answers. These response patterns give us new insights into the relationships between the student force concepts and their ability to analyze motions. Our results show that cluster analysis proved to be a useful tool to identify latent structures within the student conceptual understanding. Such structures can supply diagnostic insights for classroom pedagogy and teaching approaches.

Purpose. The primary aim of this study was to asses the internal and external match demands of young beach soccer players during an official match. The secondary aim was to evaluate how these demands compared to those of 11-a-side soccer Materials and methods. The study involved 24 young soccer players under the age of 17 (all outfield players). Performance assessments were performed on a sand field (35 x 28 m) with beach soccer ball, over three 12-min periods. Internal physiological indicators (heart rate, RPE) and external indicators (total distance, distance/per minute, peak speed, ecc) were collected during and after the match. Results. The internal load values obtained show that the beach soccer competition imposes high cardio-vascular intensity on the young soccer player: about 70% of the distance covered results in a HR value between 80% and 100% of HRmax, with an average HR of about 95% of HRmax. The playing time for each player was 17.11±4.23 minutes. The total distance covered and the distance achieved per minute of play were 1733.21±280.76 meters and 83.95±6.29 meters, respectively. The equivalent distance was 1957.98±320.29 meters. The peak speed reached by the young soccer players was 20.01±0.97 km/h while the average speed observed was 5.12±0.52 km/h. The distance measured in moderate- and high-intensity running was significantly lower than the value of low-intensity running (p<0.05). The metabolic power intervals showed that the young soccer players ran 1480.46 ± 236.48 meters at low power, 199.45 ± 49.56 meters at high power, 46.13 ± 14.25 at very high power, and 7.43 ± 6.57 meters at maximum power. The values at high power (p<0.05), very high power (p<0.05) and maximum power (p<0.001) were significantly lower than those at low power. Conclusions. The performance profile of the young beach soccer player imposes high heart rate values and modest mechanical load during official competition. The performance profile is very different from that of the young 11-a-side soccer player. Beach soccer can be considered a sport that complements the physical condition of the 11-a-side soccer player. [ABSTRACT FROM AUTHOR]

Pronounced warming negatively impacts ecosystem resilience in modern oceans. To offer a long‐term geological perspective of the calcareous plankton response to global warming, we present an integrated record, from two Tethyan sections (northeastern Italy), of the planktic foraminiferal and calcareous nannofossil response to the Eocene Thermal Maximum 2 hyperthermal (ETM2, ∼54 Ma). Our study reveals pronounced changes in assemblage composition and a striking dwarfing of planktic foraminiferal tests of up to 40% during the event, impacting both surface and deeper dwellers. The increased abundance of small placoliths among calcareous nannofossils is interpreted as community size reduction. Literature and our foraminiferal size data from Sites 1263 and 1209 (Atlantic and Pacific Oceans) highlights that the pronounced dwarfism is restricted to the Tethyan area. The ETM2 is characterized by warm sea surface temperatures as indicated by our δ18O data, but this warming is of global extent and cannot explain the unique dwarfism. Excluding evolutionary modifications, other potential drivers of dwarfism (eutrophication, deoxygenation, metabolic adaptation) cannot explain the exceptional dwarfism by themselves. The smallest sizes are in close temporal association with peaks in volcanic derived Hg/Th‐Hg/Rb recorded just before and at the ETM2 which could not have been brought into our sections through weathering. In contrast, size reductions are absent below and above the ETM2 at Hg peaks where δ18O data do not show warm conditions. We speculate that the local input of toxic metals from submarine volcanic emissions could have acted synergistically to warming, causing the unique dwarfism. Key Points: Calcareous plankton size in the Tethys during the Eocene Thermal Maximum 2 (ETM2) reveals marked dwarfismPronounced dwarfism was restricted to the Tethyan area, highlighting the importance of local signals in interpreting hyperthermalsCalcareous plankton were highly unstable across the ETM2 but ultimately resilient [ABSTRACT FROM AUTHOR]

In this paper we discuss a pedagogical approach aimed at pointing out the role played by the Boltzmann factor in describing phenomena usually perceived as regulated by different mechanisms of functioning. Experimental results regarding some aspects of a chemical reaction and of the viscous flow of some liquids are analysed and described in terms of macroscopic variables whose temperature dependence is proportional to the Boltzmann factor. A description of a workshop implementing the approach in the framework of an undergraduate course for engineering education and some preliminary results about its pedagogical relevance are then reported. (Contains 1 footnote, 1 table and 7 figures.)

[1] New detailed morphotectonic analyses of a well exposed flight of marine terraces along the Ionian coast of southern Italy has been carried out. The area represents a key transect for investigating the middle-late Quaternary evolution of the Southern Apennines chain-foredeep-foreland geodynamic system. A major result of the research is the reconstruction of a virtually complete 3D geometry of the marine surfaces along a coastal sector of ca. 70 km, which (1) documents the occurrence of 18 paleo-shorelines and (2) provides evidence for a strong regional uplift affecting the investigated area. Following a systematic critical review of literature relating to geochronological data, integrated with a morphogenetic model based on the interaction between tectonic uplift and eustatic sea level changes, the different terraces are correlated to as many highstand sea level peaks, dating the highest/ oldest terrace to ca. 600 ka (MIS 15). The vertical and horizontal distribution of the terraces show a general convergence of the paleo-shorelines toward NNE, which indicates a decreasing trend in differential uplift in that direction ranging from almost 2 mm/a in the southwestern sector to about 0.2 mm/a in the northeastern sector. Detailed mapping and 3D reconstruction also emphasize the partitioning of the area into three distinct sectors characterized by different tilting rates. This behavior is likely caused by the combined role and activity of three major tectonic structures working at different scales and rates including (1) the reactivation of an out-of-sequence thrust, (2) sliding along the basal detachment of the external Apennines wedge and (3) a lithospheric-scale duplexing (crustal or deeper). As a major conclusion, within the external sector of the Southern Apennines chain and its fore-deep, regional shortening and a contractional tectonic regime persisted throughout the whole Quaternary and it is probably still active. Citation: Caputo, R., M. Bianca, and R. D'Onofrio (2010), Ionian marine terraces of southern Italy: Insights into the Quaternary tectonic evolution of the area, Tectonics, 29, TC4005, doi: 10.1029/2009TC002625.

Wave front propagation with nontrivial bottom topography is studied within the formalism of hyperbolic long wave models. Evolution of nonsmooth initial data is examined, and, in particular, the splitting of singular points and their short time behavior is described. In the opposite limit of longer times, the local analysis of wave fronts is used to estimate the gradient catastrophe formation and how this is influenced by the topography. The limiting cases when the free surface intersects the bottom boundary, belonging to the so‐called "physical" and "nonphysical" vacuum classes, are examined. Solutions expressed by power series in the spatial variable lead to a hierarchy of ordinary differential equations for the time‐dependent series coefficients, which are shown to reveal basic differences between the two vacuum cases: for nonphysical vacuums, the equations of the hierarchy are recursive and linear past the first two pairs, whereas for physical vacuums, the hierarchy is nonrecursive, fully coupled, and nonlinear. The former case may admit solutions that are free of singularities for nonzero time intervals, whereas the latter is shown to develop nonstandard velocity shocks instantaneously. Polynomial bottom topographies simplify the hierarchy, as they contribute only a finite number of inhomogeneous forcing terms to the equations in the recursion relations. However, we show that truncation to finite‐dimensional systems and polynomial solutions is in general only possible for the case of a quadratic bottom profile. In this case, the system's evolution can reduce to, and is completely described by, a low‐dimensional dynamical system for the time‐dependent coefficients. This system encapsulates all the nonlinear properties of the solution for general power series initial data, and, in particular, governs the loss of regularity in finite times at the dry point. For the special case of parabolic bottom topographies, an exact, self‐similar solution class is introduced and studied to illustrate via closed‐form expressions the general results. [ABSTRACT FROM AUTHOR]

A small insect can stand or walk on water surface, drops of mercury do not spread on a solid surface, and a meniscus is formed at the free surface of a liquid contained in a thin vessel. These phenomena can be seen as macroscopic manifestations of molecular interactions and can be explained macroscopically in terms of surface tension. In this study, we deal with an approach to surface tension from a mechanical point of view, presenting a simple mesoscopic mechanical model of surface tension and the results of its implementation in numerical fluid dynamics simulations. Particularly, phenomena like droplet formation without gravity and with gravity when it can drop from a narrow hole like a trickling tap, the formation of a meniscus at the free surface of a liquid contained in a vessel, the behavior of a small piece of solid on a liquid surface, and a sessile droplet are studied. Student and teachers can study the behavior of a liquid due to the surface tension by using the numeric simulations as a "tool" for analyzing several different situations. [ABSTRACT FROM AUTHOR]

Energy-conserving, angular momentum changing collisions between protons and highly excited Rydberg hydrogen atoms are important for precise understanding of atomic recombination at the photon decoupling era and the elemental abundance after primordial nucleosynthesis. Early approaches to ℓ-changing collisions used perturbation theory only for dipole-allowed (Δℓ = ±1) transitions. An exact non-perturbative quantum mechanical treatment is possible, but it comes at a computational cost for highly excited Rydberg states. In this paper, we show how to obtain a semiclassical limit that is accurate and simple, and develop further physical insights afforded by the non-perturbative quantum mechanical treatment. [ABSTRACT FROM AUTHOR]

We identify a novel connection between a recently introduced pseudo-Riemannian framework for optimal mass transport and the geometry of Monge-Ampère equations. We show this correspondence by application to an example from geophysical fluid dynamics. [ABSTRACT FROM AUTHOR]

The Early Eocene Climatic Optimum (EECO) records the highest prolonged global temperatures over the past 70 Ma. Understanding the causes and timing of Eocene climate change remains a major challenge in Cenozoic paleoceanography, which includes the biotic response to climate variability and the changes among planktic foraminifer5 al assemblages across the EECO. The symbiont bearing and shallow dwelling genera Morozovella and Acarinina were important calcifiers in the tropical-subtropical early Paleogene oceans but almost completely disappeared at about 38 Ma, near the Bartonian/ Priabonian boundary. We show here that morozovellids record a first critical step across the EECO through a major permanent decline in relative abundance from the Tethyan Possagno section and ODP Site 1051 in the western subtropical North Atlantic. Possible causes may include increased eutrophication, weak water column stratification, changes in ocean chemistry, loss of symbiosis and possible complex interaction with other microfossil groups. Relative abundances of planktic foraminiferal taxa at Possagno parallel negative shifts in both δ13C and δ18O of bulk sediment from Chron C24r to basal Chron C20r. The post-EECO stable isotopic excursions towards lighter values are of modest intensity. Significant though ephemeral modifications in the planktic foraminiferal communities occur during these minor isotopic excursions. These modifications are marked by pronounced increases in relative abundance of acarininids, in a manner similar to their behaviour during pre-EECO hyperthermals in the Tethyan settings, which suggest a pronounced biotic sensitivity to climate change of planktic foraminifera even during the post-EECO interval. [ABSTRACT FROM AUTHOR]

Energy-changing electron-hydrogen atom collisions are crucial to regulating the energy balance in astrophysical and laboratory plasmas and are relevant to the formation of stellar atmospheres, recombination in H II clouds, primordial recombination, three-body recombination, and heating in ultracold and fusion plasmas. Computational modeling of electron-hydrogen collision has been attempted through quantum mechanical scattering state-to-state calculations of transitions involving low-lying energy levels in hydrogen (with principal quantum number n < 7) and at large principal quantum numbers using classical trajectory techniques. Analytical expressions are proposed that interpolate the current quantum mechanical and classical trajectory results for electron-hydrogen scattering in the entire range of energy levels for nearly the entire temperature range of interest in astrophysical environments. An asymptotic expression for the Born cross section is interpolated with a modified expression previously derived for electron-hydrogen scattering in the Rydberg regime using classical trajectory Monte Carlo simulations. The derived formula is compared to existing numerical data for transitions involving low principal quantum numbers, and the dependence of the deviations on temperature is discussed. [ABSTRACT FROM AUTHOR]

Collisions between electrically charged particles and neutral atoms are central for understanding the dynamics of neutral gases and plasmas in a variety of physical situations of terrestrial and astronomical interest. Specifically, redistribution of angular momentum states within the degenerate shell of highly excited Rydberg atoms occurs efficiently in distant collisions with ions. This process is crucial in establishing the validity of the local thermal equilibrium assumption and may also play a role in determining a precise ionization fraction in primordial recombination. We provide an accurate expression for the non-perturbative rate coefficient of collisions between protons and H(nl) ending in a final state H(nl'), with n being the principal quantum number and l, l' the initial and final angular momentum quantum numbers, respectively. The validity of this result is confirmed by results of classical trajectory Monte Carlo simulations. Previous results, obtained by Pengelly and Seaton only for dipole-allowed transitions l ͛ l ± 1, overestimate the l-changing collisional rate coefficients approximately by a factor of six, and the physical origin of this overestimation is discussed. [ABSTRACT FROM AUTHOR]

We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6Li and bosonic 87Rb. This combination of alkali metals has the potential to reach deeper Fermi degeneracy with respect to other mixtures since it allows for improved heat capacity matching which optimizes sympathetic cooling efficiency. Atomic beams of the two species are independently produced and then decelerated by Zeeman slowers. The slowed atoms are collected into a magneto-optical trap and then transferred into a quadrupole magnetic trap. An ultracold Fermi gas with temperature in the 10−3 T F range should be attainable through selective confinement of the two species via a properly detuned laser beam focused in the center of the magnetic trap. [ABSTRACT FROM AUTHOR]