Toward a script theory of guidance in computer-supported collaborative learning

This article presents an outline of a script theory of guidance for computer-supported collaborative learning (CSCL). With its four types of components of internal and external scripts (play, scene, role, and scriptlet) and seven principles, this theory addresses the question how CSCL practices are shaped by dynamically re-configured internal collaboration scripts of the participating learners. Furthermore, it explains how internal collaboration scripts develop through participation in CSCL practices. It emphasizes the importance of active application of subject matter knowledge in CSCL practices, and it prioritizes transactive over non-transactive forms of knowledge application in order to facilitate learning. Further, the theory explains how external collaboration scripts modify CSCL practices and how they influence the development of internal collaboration scripts. The principles specify an optimal scaffolding level for external collaboration scripts and allow for the formulation of hypotheses about the fading of external collaboration scripts. Finally, the article points towards conceptual challenges and future research questions

Applications of satellite technology for regional organizations (Project ASTRO)

The direct arithmetic processing of adaptive delta modulation (ADM) encoded signals, conversion from ADM encoded signals to pulse code modulation (PCM) encoded signals, and conversion from PCM to ADM encoded signals are discussed. It is shown that signals which are ADM encoded can be arithmetically processed directly, without first decoding. Operating on the DM bit stream, and employing only standard digital hardware, the sum, difference and product can be obtained in PCM and ADM format

Novel FixL homologues in Chlamydomonas reinhardtii bind heme and O2

AbstractGenome inspection revealed nine putative heme-binding, FixL-homologous proteins in Chlamydomonas reinhardtii. The heme-binding domains from two of these proteins, FXL1 and FXL5 were cloned, expressed in Escherichia coli, purified and characterized. The recombinant FXL1 and FXL5 domains stained positively for heme, while mutations in the putative ligand-binding histidine FXL1-H200S and FXL5-H200S resulted in loss of heme binding. The FXL1 and FXL5 [Fe(II), bound O2] had Soret absorption maxima around 415nm, and weaker absorptions at longer wavelengths, in concurrence with the literature. Ligand-binding measurements showed that FXL1 and FXL5 bind O2 with moderate affinity, 135 and 222μM, respectively. This suggests that Chlamydomonas may use the FXL proteins in O2-sensing mechanisms analogous to that reported in nitrogen-fixing bacteria to regulate gene expression

Effect of Mill Type and Particle Size Variation on Growth Performance and Carcass Characteristics of Finishing Pigs

The objective of this experiment was to determine the effects of mill type used to grind corn and its particle size variation on diet flowability and subsequent finishing pig growth performance and carcass characteristics. A total of 200 pigs (DNA Line 241 × 600; initially 121.9 lb) were used in a 75-d growth trial. Pigs were randomly assigned to pens with either 5 barrows or 5 gilts per pen. Pens were then randomly allotted to 1 of 4 treatments balanced by weight and gender with 10 pens per treatment. Treatments were arranged as a 2 × 2 factorial with 2 mill types (3-high roller mill; RMS, Model 924 or a hammermill; Bliss, model 22115) and 2 particle size variations (standard vs. blended). Increasing corn particle size variation was accomplished by blending 30% 400 μm corn, 40% 600 μm corn, and 30% 800 μm corn. Standard treatments were accomplished by grinding corn to an average of 600 μm with either mill. On d 75, pigs were transported to a commercial packing plant for processing and determination of carcass characteristics. The average analyzed complete diet mean particle sizes and standard deviations were 497, 540, 503, and 520 μm and 2.70, 2.75. 3.35, and 3.35 for the roller mill standard, roller mill blended, hammermill standard, and hammermill blended treatments, respectively. Diet flowability was calculated using angle of repose (AoR), percent compressibility, and critical orifice diameter (COD) measurements to determine the composite flow index (CFI). The AOR were 34.2, 33.0, 35.4, and 36.2º; COD were 32.0, 31.3, 30.0, and 33.0 mm; compressibilitys were 18.7, 18.4, 17.0, and 15.7%; and CFI were 52.9, 55.4, 53.9, and 53.2 for the roller mill standard, roller mill blended, hammermill standard, and hammermill blended treatments, respectively. There were no interactions or main effects of mill type on growth performance or carcass characteristics. However, pigs fed the blended diets had marginally significant decreased (P \u3c 0.083) average daily gain (ADG) compared to those fed the standard diets. No differences were observed in total feed cost or cost per lb of gain between treatments. Pigs fed blended diets also had marginally decreased (P \u3c 0.059) gain value and income over feed costs (IOFC) compared to those fed diets that were not blended. In conclusion, mill type used to grind corn and increasing particle size variation did not impact flowability metrics of complete diets. Mill type used to grind corn did not influence performance of finishing pigs, while increasing particle size variation by blending various particle sizes of corn led to a marginal reduction in ADG, gain value, and IOFC

The Effects of Filter Type and Warm-Up Time on Pellet Durability Index Using the Holmen NHP100 Portable Pellet Tester

The Holmen NHP100 (TekPro Ltd, Norfolk, UK) is a portable forced air pellet tester commonly used by the feed industry to determine the pellet durability index (PDI). The objective of this study was to determine the effect of filter type and machine warm-up time on PDI. A corn-soybean meal-based grower diet was conditioned at 185°F for 30 sec and subsequently pelleted using a laboratory pellet mill (Model CL5 California Pellet Mill Co., Crawfordsville, IN) equipped with a 0.16- × 0.5-in die. Production rate was 120 lb/h. Once cool, pellets were analyzed for PDI using the NHP100 with a 60-sec run time. Air temperature and pressure within the NHP100 were recorded throughout the experiment. Treatments were arranged in a 3 × 8 factorial with varying filters (none, factory tissue filter, or commercial paper towel filter) and machine warm-up time (0, 3, 6, 9, 12, 15, 18, or 21 min). There were three replicates per treatment. Pellets were sifted before and after analysis for separation of fines and pellets using a U.S. #6 standard sieve. There was a filter × warm-up time interaction (P ≤ 0.05) for air temperature. The air temperature without warm-up time (0 min) was greater with the factory filter and paper towel compared to no filter. Air temperature remained similar regardless of filter type as the warm-up time increased from 6 to 21 min There was a filter × warm-up time interaction (P ≤ 0.05) for air pressure. At 0 min warm-up time, there were no differences in air pressure between none, factory and paper towel filters. At 3 to 21 min warm-up time, air pressure remained similar between factory and paper towel filters, while no filter was greater than the paper towel filter. There was a filter × warm-up time interaction (P ≤ 0.05) for PDI. For no filter, increasing warm-up time from 0 to 6 min increased PDI with no further increase from 6 to 21 min. However, there were no differences in PDI with increasing warm-up time when using the factory filter or paper towel. Using the factory filter or paper towel had similar PDI, but resulted in greater PDI compared to no filter. In conclusion, warm-up time did not influence air temperature, pressure, or PDI when using a filter. Therefore, it is suggested to use a filter when conducting PDI analysis using the Holmen NHP 100

Evaluation of Pellet Binders on Pellet Durability Index of a High-Fat Swine Diet

The objective of this study was to evaluate the addition of different pellet binders on pellet quality of a grower swine diet by measuring pellet durability index (PDI). Dietary treatments consisted of a corn-soybean meal-based control diet with 20% dried distillers grains with solubles and 4% choice white grease, the control diet with 0.6% lignosulfonate (AMERI-BOND 2X; LignoTech USA Inc.; Rothschild, WI), or the control diet with increasing levels of a pasta by-product (2.5, 5.0, or 10.0%; International Ingredients, St. Louis, MO). Pellet binders were added to the control diet in the place of corn to create dietary treatments. Each treatment was pelleted in 333 lb batches at 3 separate periods to provide 3 replications per treatment. Pelleting run was considered the experimental unit and time of processing served as the blocking factor. Order of pelleting dietary treatments was randomized within each time period. Corn was ground to approximately 600 μm. Diets were pelleted via steam conditioning (10- × 55-in. Wenger twin staff conditioner, Model 150) and using a 30-horsepower pellet mill (1012-2 HD Master Model, California Pellet Mill) with a 5/32- × 1-in. pellet die. During each processing run, pellet samples were collected throughout the run and immediately placed in an experimental counter-flow cooler for 10 minutes. After cooling, samples were analyzed for pellet durability index using the Holmen NHP 100 (TekPro Ltd, Norfolk, UK) for 30 seconds. There was no evidence (P \u3e 0.172) of difference for the effect of treatment on conditioner temperature, hot pellet temperature, or production rate. The average conditioner temperature, hot pellet temperature, and production rate were 185.9°F, 188.2°F, and 1,364 lb/h, respectively. The diet containing lignosulfate improved (P \u3c 0.001) PDI compared to the control diet. Increasing pasta by-product from 2.5 to 10% increased the PDI (P \u3c 0.01) compared with the control diet. Diets containing 2.5% pasta by-product had lower PDI compared to those with lignosulfonate, diets with 5% pasta by-product and lignosulfonate had similar PDI, and diets containing 10% pasta by-product had increased PDI compared to the lignosulfonate treatment. In conclusion, adding pellet binders to the high fat finisher diets improved PDI by 7.4 to 10.7%. Adding 5% pasta by-product improved PDI similar to that of lignosulfonate and adding 10% pasta by-product further improved PDI compared to lignosulfonate