How indirect supportive digital help during and after solving physics problems can improve problem-solving abilities

This study investigates the effectiveness of computer-delivered hints in relation to problem-solving abilities in two alternative indirect instruction schemes. In one instruction scheme, hints are available to students immediately after they are given a new problem to solve as well as after they have completed the problem. In the other scheme, hints are only available as worked out problems after students have finished their solution. The instruction schemes are supplied by means of a web-based program, Physhint, which supports the development of strategic knowledge [Pol, H. J., Harskamp, E. G., & Suhre, C. J. M. (2008). The effect of the timing of instructional support in a computer-supported problem-solving program for students in secondary physics education. Computers in Human Behavior, 24, 1156–1178]. This program supports novice problem solvers while undertaking physics problems concerned with forces by providing hints structured in accordance with Schoenfeld’s episodes [Schoenfeld, A. H. (1992). Learning to think mathematically: Problem solving, metacognition, and sense making in mathematics. In D. A. Grouws (Ed.), Handbook of research on mathematics teaching (pp. 224–270). New York: McMillan Publishing].     

Minimum sodium nitrite levels for pinking of various cooked meats as related to use of direct or indirect-dried soy isolates in poultry rolls

The relationship between sodium nitrite level and pinking was investigated in cooked meats, as measured by panel color score, acetone extraction of NO-hemochrome, and instrumental redness values. Beef was less susceptible than poultry breast meat to nitrite-induced pinking. Minimum sodium nitrite level for pinking was 14, 4, 2, and 1 ppm for beef round, pork shoulder, turkey breast, and chicken breast, respectively. By regression analysis, minimum ppm nitrite for pinking=0.092 (ppm total pigment)+0.53 (R(2)=0.99). High levels of nitrate (>250 ppm as sodium nitrate) and nitrite (>45 ppm as sodium nitrite) were found in direct-dried (DD) soy isolates. Chicken breast rolls formulated with >2% DD soy were pink, but control rolls with 156 ppm sodium nitrate were not pink. Thus, it was concluded that nitrite was the primary pinking agent in DD soy. Indirect-dried (ID) soy isolates contained <11 ppm sodium nitrite, which was insufficient for pinking in poultry rolls.     

Synthesis and surface activity of nonionic surfactants containing fluorocarbon hydrophobes

Nonionic surfactants having polydisperse polyoxyethylene chains and highly fluorinated hydrophobes were synthesized via a complex reaction route and their adsorption at water/air interfaces studied. They exhibit high surface activity and decrease both effectively and efficiently the surface tension of their aqueous solutions. The effect of the length of the polyoxyethylene chain upon surfactant surface activity is relatively low. Lower values of surface tension, below 30 mN m^?1, are obtained for surfactants having a low degree of ethoxylation. Surfactants having two terminal highly fluorinated hydrophobes are less surface active than analogues with one terminal hydrophobe.     

Particle velocities in a gas fluidized bed

A force acts on the walls of a fluidized bed container due to the collisions of the particles with these walls. A method is described for measuring this force, here called the particle pressure to distinguish it from the gas pressure. Using a model similar to the elementary kinetic theory of gases, an equation has been derived for calculating the average particle velocity from this particle pressure. Comparison shows the calculated velocities to be in fair agreement with reported measurements made photographically and with scintillation counters.     

Stability of supercurrents in flat films of tin

Using pulsed, 80-nsec-currents the stability of supercurrents in flat films of tin with compensating current return has been investigated. It is found that the voltage along the film rises with timet approximately asV=b+a[t/2(t–c)) ^1/2], whereb represents the (almost instantaneous) flux-flow voltage in a perpendicular field and the time constantt is an exponentially decreasing function ofJ(1+420/d)/[1–(T/T _c ⁴][1–H/H_c]. HereJ is the current density in the film of thicknessd in Å,T/T _c is the reduced temperature, andH /H_c is the reduced magnetic field. It is suggested that this instability is of the type investigated by Kramer and by Fink and Presson for currents in a superconducting surface sheath. At lower temperatures a second instability is found which is distinctly different from the one dominant at the higher temperatures.Supported in part by the National Science Foundation, in part by the Cryogenics Center through a Grant from the DOD Themis Program.     

Triggered Correlation

This paper shows to what extent an average-response computer can be utilized for computing a cross-correlation function. This type of computer needs synchronization pulses, and the simplest methods of computation are those in which these pulses are directly derived from one of the signals (triggered correlation). The first method is to generate a synchronization pulse whenever the signal crosses a pre-set threshold in any direction. In this case, the computer output function is shown to be proportional to the true correlation function, for Gaussian signals. In a second method, synchronization pulses are produced when the signal crosses the threshold in a specified (e.g., positive) direction. Then the computer output is found to be contaminated by a systematic error, which, in turn, depends on the derivative of the correlation function. These two methods are described in detail, both with respect to the results and to the accuracy obtainable. Several other, less important, methods are only briefly described.     

Flux flow velocity in superconducting films by measurement of passage time

The velocity of flux tubes in thin superconducting films has been determined by measuring the time for their passing across the film. A legion of flux tubes has been pulsed in on the left side of a film carrying a current large enough to break the pinning. The arrival of the flux tubes on the right side is observed with a pick-up coil. Flow velocities of 3 to 50×10⁴ cm/sec have been observed with current densities up to 10⁵ A/cm².Supported in part by the National Science Foundation, in part by the Cryogenics Center through a grant from the DOD Themis program.     

Analysis of time-series MODIS 250 m vegetation index data for crop classification in the U.S. Central Great Plains

The global environmental change research community requires improved and up-to-date land use/land cover (LULC) datasets at regional to global scales to support a variety of science and policy applications. Considerable strides have been made to improve large-area LULC datasets, but little emphasis has been placed on thematically detailed crop mapping, despite the considerable influence of management activities in the cropland sector on various environmental processes and the economy. Time-series MODIS 250 m Vegetation Index (VI) datasets hold considerable promise for large-area crop mapping in an agriculturally intensive region such as the U.S. Central Great Plains, given their global coverage, intermediate spatial resolution, high temporal resolution (16-day composite period), and cost-free status. However, the specific spectral-temporal information contained in these data has yet to be thoroughly explored and their applicability for large-area crop-related LULC classification is relatively unknown. The objective of this research was to investigate the general applicability of the time-series MODIS 250 m Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) datasets for crop-related LULC classification in this region. A combination of graphical and statistical analyses were performed on a 12-month time-series of MODIS EVI and NDVI data from more than 2000 cropped field sites across the U.S. state of Kansas. Both MODIS VI datasets were found to have sufficient spatial, spectral, and temporal resolutions to detect unique multi-temporal signatures for each of the region's major crop types (alfalfa, corn, sorghum, soybeans, and winter wheat) and management practices (double crop, fallow, and irrigation). Each crop's multi-temporal VI signature was consistent with its general phenological characteristics and most crop classes were spectrally separable at some point during the growing season. Regional intra-class VI signature variations were found for some crops across Kansas that reflected the state's climate and planting time differences. The multi-temporal EVI and NDVI data tracked similar seasonal responses for all crops and were highly correlated across the growing season. However, differences between EVI and NDVI responses were most pronounced during the senescence phase of the growing season.     

A comparison of MODIS 250-m EVI and NDVI data for crop mapping: a case study for southwest Kansas

Multi-temporal vegetation index (VI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are becoming widely used for large-area crop classification. Most crop-mapping studies have applied enhanced vegetation index (EVI) data from MODIS instead of the more traditional normalized difference vegetation index (NDVI) data because of atmospheric and background corrections incorporated into EVI's calculation and the index's sensitivity over high biomass areas. However, the actual differences in the classification results using EVI versus NDVI have not been thoroughly explored. This study evaluated time-series MODIS 250-m EVI and NDVI for crop-related land use/land cover (LULC) classification in the US Central Great Plains. EVI- and NDVI-derived maps classifying general crop types, summer crop types and irrigated/non-irrigated crops were produced for southwest Kansas. Qualitative and quantitative assessments were conducted to determine the thematic accuracy of the maps and summarize their classification differences. For the three crop maps, MODIS EVI and NDVI data produced equivalent classification results. High thematic accuracies were achieved with both indices (generally ranging from 85% to 90%) and classified cropping patterns were consistent with those reported for the study area (> 0.95 correlation between the classified and USDA-reported crop areas). Differences in thematic accuracy (< 3% difference), spatially depicted patterns (> 90% pixel-level thematic agreement) and classified crop areas between the series of EVI- and NDVI-derived maps were negligible. Most thematic disagreements were restricted to single pixels or small clumps of pixels in transitional areas between cover types. Analysis of MODIS composite period usage in the classification models also revealed that both VIs performed equally well when periods from a specific growing season phase (green, peak or senescence) were heavily utilized to generate a specific crop map.     

The Cognitive Interview: A meta-analytic review and study space analysis of the past 25 years.

The Cognitive Interview (CI) is a well-established protocol for interviewing witnesses. The current article presents a study space analysis of laboratory studies of the CI together with an empirical meta-analysis summarizing the past 25 years of research. The study space comprises 57 published articles (65 experiments) on the CI, providing an assessment of the boundary conditions underlying the analysis and application of this interview protocol. The current meta-analysis includes 46 published articles, including 20 articles published since the last meta-analysis conducted a decade earlier (K?hnken, Milne, Memon, & Bull, 1999). Reassuringly for practitioners, the findings of the original meta-analysis were replicated with a large and significant increase in correct details and a small increase in errors. In addition we found that there were no differences in the rate at which details are confabulated. Importantly, the effect sizes were unaffected by the inclusion of recent studies using modified versions of the CI. The CI appeared to benefit older adult witnesses even more than younger adults. We highlight trends and gaps in research and discuss how our findings can inform policy and training decisions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)