A conceptual map about alternating current circuits

Teachers are deeply concerned on how to be more effective in our task of teaching. We must organize the contents of our specific area providing them with a logical configuration, for which we must know the mental structure of the students that we have in the classroom. We must shape this mental structure, in a progressive manner, so that they can assimilate the contents that we are trying to transfer, to make the learning as meaningful as possible. In the generative learning model, the links before the stimulus delivered by the teacher and the information stored in the mind of the learner requires an important effort by the student, who should build new conceptual meanings. That effort, which is extremely necessary for a good learning, sometimes is the missing ingredient so that the teaching-learning process can be properly assimilated. In electrical circuits, which we know are perfectly controlled and described by Ohm's law and Kirchhoff's two rules, there are two concepts that correspond to the following physical quantities: voltage and electrical resistance. These two concepts are integrated and linked when the concept of current is presented. This concept is not subordinated to the previous ones, it has the same degree of inclusiveness and gives rise to substantial relations between the three concepts, materializing it into a law: The Ohm, which allows us to relate and to calculate any of the three physical magnitudes, two of them known. The alternate current, in which both the voltage and the current are reversed dozens of times per second, plays an important role in many aspects of our modern life, because it is universally used. Its main feature is that its maximum voltage is easily modifiable through the use of transformers, which greatly facilitates its transfer with very few losses. In this paper, we present a conceptual map so that it is used as a new tool to analyze in a logical manner the underlying structure in the alternate current circuits, with the objective of providing the students from Sciences and Engineering majors with another option to try, amongst all, to achieve a significant learning of this important part of physics.

(Table T1) Physical properties of minicores from ODP Leg 193 sites, PACMANUS field

Permeability of the ocean crust is one of the most crucial parameters for constraining submarine fluid flow systems. Active hydrothermal fields are dynamic areas where fluid flow strongly affects the geochemistry and biology of the surrounding environment. There have been few permeability measurements in these regions, especially in felsic-hosted hydrothermal systems. We present a data set of 38 permeability and porosity measurements from the PACMANUS hydrothermal field, an actively venting, felsic hydrothermal field in the eastern Manus Basin. Permeability was measured using a complex transient method on 2.54-cm minicores. Permeability varies greatly between the samples, spanning over five orders of magnitude. Permeability decreases with both depth and decreasing porosity. When the alteration intensity of individual samples is considered, relationships between depth and porosity and permeability become more clearly defined. For incompletely altered samples (defined as >5% fresh rock), permeability and porosity are constant with depth. For completely altered samples (defined as <5% fresh rock), permeability and porosity decrease with depth. On average, the permeability values from the PACMANUS hydrothermal field are greater than those in other submarine environments using similar core-scale laboratory measurements; the average permeability, 4.5 x 10-16 m**2, is two to four orders of magnitude greater than in other areas. Although the core-scale permeability is higher than in other seafloor environments, it is still too low to obtain the fluid velocities observed in the PACMANUS hydrothermal field based on simplified analytical calculations. It is likely that core-scale permeability measurements are not representative of bulk rock permeability of the hydrothermal system overall, and that the latter is predominantly fracture controlled.

(Table T2) Integrated intensity (peak area) of matrix minerals of ODP Hole 173-1068A

Mass-wasting deposits characterize the Upper Jurassic(?) to Lower Cretaceous sedimentary record of the Iberia Abyssal Plain. These deposits include olistostromes at Site 897, olistostromes and/or possible rock-fall deposits at Site 899, a breccia succession at Site 1068, slumped and fractured deposits at Site 1069, and a breccia succession at Site 1070. Whereas the exact origin of these deposits is uncertain, the regional common occurrence of middle to upper Mesozoic mass-wasting deposits suggests that they record the early rifting evolution of the west Iberia margin. This data report presents both qualitative and semiquantitative results from XRD analyses of the breccia matrix at Site 1068. In this study the matrix is defined as the fine-grained particles (as viewed through a binocular microscope) plus cement. Results are based on analytical methods that aimed to isolate the desired matrix from larger clast contamination prior to XRD analyses. In addition, the breccia was sampled at a higher resolution than was conducted aboard ship, producing a more complete description of downcore matrix mineralogical changes. The data presented here may be used to (1) further justify the subunit designation of Unit IV made aboard ship, (2) help determine to what degree the matrix and the larger clasts (studied in thin section aboard ship; Shipboard Scientific Party, 1998, doi:10.2973/odp.proc.ir.173.106.1998) are compositionally distinct, (3) help identify the extent of hydrothermal fluid migration in the breccia, and (4) support the proposed shipboard hypothesis that the Site 1068 breccia succession resulted from multiple mass-wasting.