Students' Understanding of Direct Current Resistive Electrical Circuits

Research has shown that both high school and university students' reasoning patterns regarding direct current resistive electric circuits often differ from the currently accepted explanations. At present, there are no standard diagnostic examinations in electric circuits. Two versions of a diagnostic instrument called Determining and Interpreting Resistive Electric circuits Concepts Tests (DIRECT) were developed, each consisting of 29 questions. The information provided by the exam provides classroom instructors a means with which to evaluate the progress and conceptual difficulties of their students and their instructional methods. It can be used to evaluate curricular packages and/or other supplemental materials for their effectiveness in overcoming students' conceptual difficulties. The analyses indicate that students, especially females, tend to hold multiple misconceptions, even after instruction. During interviews, the idea that the battery is a constant source of current was used most often in answering the questions. Students tended to focus on current in solving the problems and to confuse terms, often assigning the properties of current to voltage and/or resistance. Results indicated that students do not have a clear understanding of the underlying mechanisms of electric circuit phenomena. On the other hand, students were able to translate easily from a "realistic" representation of a circuit to the corresponding schematic diagram.Comment: This article has been accepted for publication in the American Journal of Physics - Physics Education Research Supplement. No known publication date as ye

A Comparison of Two Formulas of Topical Menthol on Vascular Responses and Perceived Intensity Prior to and following a Bout of Maximum Voluntary Muscular Contractions (MVMCs)

The purpose of this study was to compare the vascular responses in the brachial artery and perceived intensity of two different formulas of topical menthol gels prior to and following a bout of maximum voluntary muscular contractions (MVMCs). 18 adults completed the same protocol on different days using blinded topical menthol gels (Old Formula and New Formula). Heart rate, brachial artery blood flow (ml/min), vessel diameter and reported intensity of sensation were measured at baseline (T1), at 5 min after application of the gel to the upper arm (T2), and immediately following five MVMCs hand grips (T3). The New Formula exhibited a significant decline in blood flow (−22.6%) between T1 and T2 which was not different than the nonsignificant declines under the Old Formula 1 (−21.8%). Both formulas resulted in a significant increase in perceived intensity of sensation between T1 and T2. Blood flow increased significantly with the New Formula (488%) between T2 and T3 and nonsignificantly with the Old Formula (355%)

Conjugated linoleic acid reduces permeability and fluidity of adipose plasma membranes from obese Zucker rats

NOTICE: this is the author’s version of a work that was accepted for publication in Biochemical and Biophysical Research Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochemical and Biophysical Research Communications. July 2010; 398 (2): 199-204.Conjugated linoleic acid (CLA) is a dietary fatty acid frequently used as a body fat reducing agent whose effects upon cell membranes and cellular function remain unknown. Obese Zucker rats were fed atherogenic diets containing saturated fats of vegetable or animal origin with or without 1% CLA, as a mixture of cis(c)9,trans(t)11 and t10,c12 isomers. Plasma membrane vesicles obtained from visceral adi- pose tissue were used to assess the effectiveness of dietary fat and CLA membrane incorporation and its outcome on fluidity and permeability to water and glycerol. A significant decrease in adipose membrane fluidity was correlated with the changes observed in permeability, which seem to be caused by the incor- poration of the t10,c12 CLA isomer into membrane phospholipids. These results indicate that CLA supple- mentation in obese Zucker rats fed saturated and cholesterol rich diets reduces the fluidity and permeability of adipose membranes, therefore not supporting CLA as a body fat reducing agent through membrane fluidification in obese fat consumers

Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T

Background: Arsenic (As) is a natural metalloid, widely used in anthropogenic activities, that can exist in different oxidation states. Throughout the world, there are several environments contaminated with high amounts of arsenic where many organisms can survive. The most stable arsenical species are arsenate and arsenite that can be subject to chemically and microbiologically oxidation, reduction and methylation reactions. Organisms surviving in arsenic contaminated environments can have a diversity of mechanisms to resist to the harmful effects of arsenical compounds. Results: The highly metal resistant Ochrobactrum tritici SCII24 was able to grow in media with arsenite (50 mM), arsenate (up to 200 mM) and antimonite (10 mM). This strain contains two arsenic and antimony resistance operons (ars1 and ars2), which were cloned and sequenced. Sequence analysis indicated that ars1 operon contains five genes encoding the following proteins: ArsR, ArsD, ArsA, CBS-domain-containing protein and ArsB. The ars2 operon is composed of six genes that encode two other ArsR, two ArsC (belonging to different families of arsenate reductases), one ACR3 and one ArsH-like protein. The involvement of ars operons in arsenic resistance was confirmed by cloning both of them in an Escherichia coli ars-mutant. The ars1 operon conferred resistance to arsenite and antimonite on E. coli cells, whereas the ars2 operon was also responsible for resistance to arsenite and arsenate. Although arsH was not required for arsenate resistance, this gene seems to be important to confer high levels of arsenite resistance. None of ars1 genes were detected in the other type strains of genus Ochrobactrum, but sequences homologous with ars2 operon were identified in some strains. Conclusion: A new strategy for bacterial arsenic resistance is described in this work. Two operons involved in arsenic resistance, one giving resistance to arsenite and antimonite and the other giving resistance to arsenate were found in the same bacterial strain

Dephasing in matter-wave interferometry

We review different attempts to show the decoherence process in double-slit-like experiments both for charged particles (electrons) and neutral particles with permanent dipole moments. Interference is studied when electrons or atomic systems are coupled to classical or quantum electromagnetic fields. The interaction between the particles and time-dependent fields induces a time-varying Aharonov phase. Averaging over the phase generates a suppression of fringe visibility in the interference pattern. We show that, for suitable experimental conditions, the loss of contrast for dipoles can be almost as large as the corresponding one for coherent electrons and therefore, be observed. We analyze different trajectories in order to show the dependence of the decoherence factor with the velocity of the particles.Comment: 9 pages, 1 eps-figure. To appear in J. Phys. A: Math. Ge

Ventajas y desventajas del uso del concreto autorreparable en Colombia

Concrete is one of the most widely used building materials in the world. It is economical, fire-resistant, and malleable, which allows it to adapt to a wide variety of constructions. For this reason, techniques and processes are being sought every day to improve this material so that someday it will not require any type of maintenance and will have a long useful life. Self-repairing concrete or bio-concrete is a material created in the 21st century that can seal the cracks in it, thanks to the fact that it contains certain types of bacteria that allow closing those openings. An investigation is carried out on the impact that the application of self-repairing concrete in Colombia would have in the different fields of construction, using the favorable and unfavorable characteristics that this concrete has, and the results that have been obtained with its use in other countries.El concreto es uno de los materiales de construcción más utilizado alrededor del mundo. Es económico, resistente al fuego y maleable, lo que le permite adaptarse a gran variedad de construcciones. Por ello, día a día se buscan técnicas y procesos que perfeccionen dicho material de manera que algún día no sea necesario realizarle algún tipo de mantenimiento y tenga una vida útil amplia. El concreto autorreparable o bio-concreto es un material creado en el siglo XXI que tiene la capacidad de sellar las gritas que en él hayan, gracias a que contiene cierto tipo de bacterias que permiten cerrar esas aberturas. Se realiza una investigación sobre el impacto que tendría la aplicación del hormigón autorreparable en Colombia en los distintos campos de la construcción, por medio de las características favorables y desfavorables que tiene este concreto, y los resultados que se han obtenido con su uso en otros países

The editorial expression of l'Architecture Vivante: from persuasive systems to critical editing

[EN] L' Architecture Vivante was a French magazine that pioneered in disseminating the productions of the architectural avant-gardes of the early twentieth century. Today with the passage of time, it has become a relevant historical and cultural document. Its editorial expression is the outcome of different semantic variables that came together, although not without conflict. These include the meanings emanating from the editorial decisions made by Jean Badovici, the implicitness in the semantic frameworks that were characteristic of Ediciones Morancé s editorial design, and the contributions of the published oeuvres. Following the methodology used in cultural studies, we will examine these variables as part of a broad cultural context and interpret them from a standpoint of controversy with the reorganization of mass production processes and the integration of marketing in design, aimed at adapting cultural productions to a consumption situation. The analysis will show that, although L Architecture Vivante aligns itself to some extent with the discursive constructs and editorial encodings that sought to determine and contain the meaning of those searches, it also challenges them, in a way that it still preserves a critical value today.[ES] L' Architecture Vivante fue una revista francesa que divulgó tempranamente la producción de las vanguardias arquitectónicas de comienzos del siglo XX, convertida hoy en un relevante documento histórico-cultural. En su expresión editorial convergen, no sin conflicto, distintas variables semánticas: los significados que emanan de las decisiones editoriales de Jean Badovici, los implícitos en los marcos semánticos característicos del diseño editorial de Ediciones Morancé y los aportados por las obras publicadas. Siguiendo la metodología de los estudios culturales, situaremos estas variables en un contexto cultural amplio, leyéndolas en polémica con las políticas de reorganización de los procesos productivos en masa y la integración del marketing en el diseño para adaptar las producciones culturales a una situación de consumo. Se mostrará que, si bien L' Architecture Vivante se alinea en cierta medida con los constructos discursivos y codificaciones editoriales que trataron de fijar y contener el significado de aquellas búsquedas, también los desafía, conservando aún hoy una valencia crítica.Álvarez Benítez, PV. (2022). La expresión editorial de l'Architecture Vivante: de los sistemas persuasivos a la edición crítica. EGA Expresión Gráfica Arquitectónica. 27(44):174-187. https://doi.org/10.4995/ega.2022.15558OJS174187274