Developing Elementary Science Concepts by an Individualized Approach

In developing a concept of the universe at the elementary level many learning aids are utilized. Visual presentations, direct observations, experimentations and critical reading accompanied by discussions serve to enhance a child\u27s understanding of a concept. Moreover, it is apparent that all elementary school children do not arrive at the same level of understanding of scientific phenomena. There are many children who do not respond effectively to experimentation and critical reading and thus must rely on direct observations and visual presentation in arriving at a lower level of conceptual development. Other children who are more sophisticated may understand the orderliness of scientific phenomena and display knowledge of the vastness and complexities of our universe. Branley (1), Sheckles (13), and Vinacke (14) have pointed out that differentiation and gradual progression take place in concept development as one matures. Further credence is given to this belief by Russell (12) who states that concept development seems to move along a continuum from simple to complex, from concrete to abstract, from undifferentiated to differentiated, from discrete to organized, from egocentric to more social

Crystal structure of the wide-spectrum binuclear zinc β-lactamase from Bacteroides fragilis

AbstractBackground: The metallo-β-lactamase from Bacteroides fragilis hydrolyzes a wide range of β-lactam antibiotics, and is not clinically susceptible to any known β-lactamase inhibitors. B. fragilis is associated with post-surgery hospital infections, and there has been a recent report of plasmid-mediated dissemination of the enzyme. Effective inhibitors are therefore urgently needed. Knowledge of the three-dimensional structure will aid in the drug design effort.Results The crystal structure of the enzyme has been determined by using multiwavelength anomalous diffraction at the zinc absorption edge and refined to 1.85 Å resolution. The structure is a four-layer α/β/β/α molecule. The active site, found at the edge of the β sandwich, contains a binuclear zinc center with several novel features. One zinc is tetrahedrally coordinated, the other has a trigonal bipyramidal coordination; a water/hydroxide molecule serves as a ligand for both metals. The residues that coordinate the two zincs are invariant in all metallo-β-lactamases that have been sequenced, except for two conservative replacements. Despite the existence of the pattern for binuclear zinc binding, the reported structure of the Bacillus cereus enzyme contains only a single zinc.Conclusion Structural analysis indicates that affinity for the penta-coordinated zinc can be modulated by neighboring residues, perhaps explaining the absence of the second zinc in the B. cereus structure. Models of bound substrates suggest that the active-site channel can accommodate a wide variety of β-lactams. We propose that the zinc cluster prepares an hydroxide, probably the hydroxide that ligates both zincs, for nucleophilic attack on the carbonyl carbon atom of the β-lactam. The resulting negatively charged tetrahedral intermediate implicated in catalysis is stabilized by an oxyanion hole formed by the side chain of the invariant Asn193 and the tetrahedral zinc

Chaotic and pseudochaotic attractors of perturbed fractional oscillator

We consider a nonlinear oscillator with fractional derivative of the order alpha. Perturbed by a periodic force, the system exhibits chaotic motion called fractional chaotic attractor (FCA). The FCA is compared to the ``regular'' chaotic attractor. The properties of the FCA are discussed and the ``pseudochaotic'' case is demonstrated.Comment: 20 pages, 7 figure

Turing machines can be efficiently simulated by the General Purpose Analog Computer

The Church-Turing thesis states that any sufficiently powerful computational model which captures the notion of algorithm is computationally equivalent to the Turing machine. This equivalence usually holds both at a computability level and at a computational complexity level modulo polynomial reductions. However, the situation is less clear in what concerns models of computation using real numbers, and no analog of the Church-Turing thesis exists for this case. Recently it was shown that some models of computation with real numbers were equivalent from a computability perspective. In particular it was shown that Shannon's General Purpose Analog Computer (GPAC) is equivalent to Computable Analysis. However, little is known about what happens at a computational complexity level. In this paper we shed some light on the connections between this two models, from a computational complexity level, by showing that, modulo polynomial reductions, computations of Turing machines can be simulated by GPACs, without the need of using more (space) resources than those used in the original Turing computation, as long as we are talking about bounded computations. In other words, computations done by the GPAC are as space-efficient as computations done in the context of Computable Analysis

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences

The Meat of the Matter: The Effect of Science-based Information on Consumer Perception of Grass-fed Beef

In the United States, there is a growing disconnect between consumers and their food source, leading to a lack of knowledge and trust in the agricultural food system. Urbanization has moved people away from farms, ranches, and food production; and the information consumers seek about their food is filtered through mass and social media. Portrayals of information about food production, specifically beef, from outside the agriculture industry often present polarizing and conflicting information about beef production and its implications for the health and well-being of humans, livestock, and the environment. This adds to consumer confusion and influences purchasing behaviors. Using a quasi-experimental pretest-posttest 2x2 factorial design, we sought to explore consumer (n = 60) perceptions, consumption, and purchasing behaviors of grass-fed beef and determine the effects of four information treatments on overall perception. Descriptive results showed consumers do not have a shared definition pertaining to grass- and grain-fed beef, citing the internet as their most referenced source for information about food and grass-fed beef. Results from a t-test indicated that exposing consumers to an information treatment had a significant effect on environmental impacts, cost, quality/nutrition, and overall perception of grass-fed beef. A between-subjects factorial ANOVA revealed there was no significant difference in perception based on treatment type. Efforts to raise awareness about beef production, on-farm practices, and links between food and grower could be warranted to help enhance the trust and credibility of the industry and bridge the gap between producers and consumers

Exploring Identities of Extension Faculty and Educators as Science Communicators

This research explored the relationship between University of Idaho (UI) Extension educators and faculty’s social identity as science communicators and their most-used communication type. This non-experimental, sequential, mixed-method study with a qualitative priority utilized surveys and interviews to gather data. This paper will focus on the qualitative and mixing components of the study. We used stratified purposive sampling based on location and most used communication type to select participants for interviews and conducted interviews to understand their social identities as science communicators. We identified five main themes: continual development, technology, research dissemination, evaluation for motivation, and community relationships. We employed a cross-case comparison to find relationships between themes and communication type. Science communication identity and communication types have distinct relationships with science communication identity being seen as an adaptable and flexible title. Participants reported diverse motivations for communicating science, but all emphasized their roles in sharing reliable, research-based information with constituents. Participants discussed the value of skill-building and expressed interest in additional training to become more effective science communicators and better meet the needs of the communities they serve. Additional research to understand the constituent perspective is warranted to explore how professionals are using science communication practices to align with the communication preferences of their audiences to achieve intended outcomes. Replicating this study with Extension professionals in other states would provide insight into a national understanding and application of science communication in Extension

Neutral Hydrogen in the Interacting Magellanic Spirals NGC 4618/4625

Asymmetry is a common trait in spiral galaxies and is particularly frequent among Magellanic spirals. To explore how morphological and kinematic asymmetry are affected by companion galaxies, we analyze neutral hydrogen observations of the interacting Magellanic spirals NGC 4618 and 4625. The analysis of the H I distribution revealed that about 10% of the total H I mass of NGC 4618 resides in a looping tidal structure that appears to wrap all the way around the galaxy. Through calculations based on derived H I profiles, we show that NGC 4618 and 4625 are no more asymmetric than non-interacting Magellanic spirals analyzed by Wilcots & Prescott (2004). We also derive rotation curves for the approaching and receding sides of each galaxy. By fitting the mean curves with an isothermal halo model, we calculate dynamical masses of 4.7 times 10^{9} M_sun and 9.8 times 10^{9} M_sun out to 6.7 kpc, for NGC 4618 and 4625 respectively. While the rotation curves had systematically higher velocities on the receding side of each galaxy, the effect was no more pronounced than in studies of non-interacting spirals (Swaters et. al. 1999). The degree of interaction-driven asymmetry in both galaxies is indistinguishable from the intrinsic degree of asymmetry of lopsided galaxies.Comment: 20 pages, 11 figures, accepted for publication in the Astronomical Journa

A Vegetation and Fire History of Lake Titicaca since the Last Glacial Maximum

Fine-resolution fossil pollen and charcoal analyses reconstruct a vegetation and fire history in the area surrounding Lake Titicaca (3810 m, Peru/Bolivia) since ca. 27,500 cal yr BP (hereafter BP). Time control was based on 26 accelerator mass spectrometer (AMS) radiocarbon dates. Seventeen AMS dates and 155 pollen and charcoal samples between ca. 17,500 BP and ca. 3,100 BP allow a centennial-scale reconstruction of deglacial and early- to mid-Holocene events. Local and regional fire signals were based on the separation of two charcoal size fractions, ≥180 μm and 179–65 μm. Charcoal abundance correlated closely with the proportion of woody taxa present in the pollen spectra. Little or no pollen was detected in the sedimentary record prior to ca. 21,000 BP. Very cold climatic conditions prevailed, with temperatures suggested to be at least 5–8°C cooler than present. Increases in pollen concentration suggest initial warming at ca. 21,000 BP with a more significant transition toward deglaciation ca. 17,700 BP. Between 17,700 BP and 13,700 BP, puna brava is progressively replaced by puna and sub-puna elements. The most significant changes between the Pleistocene and the Holocene floras were largely complete by 13,700 BP, providing an effective onset of near-modern conditions markedly earlier than in other Andean records. Fire first occurs in the catchment at ca. 17,700 BP and becomes progressively more important as fuel loads increase. No evidence is found of a rapid cooling and warming coincident with the Younger Dryas chron. A dry event between ca. 9,000 BP and 3,100 BP, with a peak between 6,000 and 4,000 BP, is inferred from changes in the composition of aquatics, and the marsh community as pollen of Cyperaceae is replaced by Poaceae, Apiaceae, Plantago and the shrub Polylepis. Human disturbance of the landscape is evident in the pollen spectra after ca. 3,100 BP with the appearance of weed species