EC62-818 Estimating the Value of Corn or Grain Sorghum Silage

Extension Circular 62-818 is estimating the value of corn or grain sorghum silage

Characterisation of Australian opals

University of Technology, Sydney. Faculty of Science.Australia is the world's largest producer of precious opals, contributing more than $1 billion per annum to the GDP. However, to date little fundamental research has been carried out on banded opals, which are potentially the most valuable of all opal varieties. Opal is also Australia's national gemstone; yet for such an important resource, it is surprising that the mechanisms of opal formation remain in dispute, in particular for banded opals. The focus of this study is to understand the formation of opal by investigating the chemistry and microstructure of banded and nonbanded opals. Opals from several regions of Australia (Coober Pedy, Lightning Ridge, Andamooka and Tintenbar), in addition to opals from Mexico, were thus investigated in detail using a range of techniques. Evaluation of the trace element chemistry of opals was carried out by employing a combination of experimental techniques, including Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICPMS) and Secondary Ion Mass Spectrometry (SIMS). Darker-coloured bands contained significantly higher concentrations of certain transition elements (Ti, V, Co, Ni, Cu, Zn and Y) and rare-earth elements (La, Ce) than the lighter-coloured bands. The concentrations of other elements (Mg, Ca, Al, Fe and Mn) were in most cases found to be similar between bands. Some elements (Ti, Cr, Cu, Zn, Co and Zr) were found to be distributed more heterogeneously than others (Na, Ca, Mg, K, Al and Fe). Based on this evidence, a solution depletion model was proposed to explain the formation of banded opals, involving the charge-neutralisation of silica colloids by highly-charged transition metal cations. The microstructural characteristics of several Australian opal-AG (amorphous, gel-like opal) specimens were studied using a number of experimental techniques such as porosity measurement, thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). An initial expansion followed by contraction was observed in TMA. The temperature at which this 'transition' occurred ranged from 200 to 400°C and was found to be region dependent. TGA revealed that the temperature range, from 215 to 350°C, over which the maximum rate of dehydration occurred, was again region dependent, consistent with the TMA data. A dehydroxylation-sintering mechanism was proposed to account for these results. Porosity measurement yielded a greater degree of porosity in the opaque white samples than the transparent ones; the additional voids consequently scatter light internally, rendering the opal opaque. 29Si NMR and 27 Al NMR experiments were undertaken to characterise the relative disorder, silanol content and the coordination state of Al within opal-AG and opal-CT (cristobalite-tridymite opal). The comparison of 29Si NMR spectra demonstrated that opal-CT samples contained a higher proportion of both geminal (Q2) and vicinal silanol groups (Q3) than opal-AG. This result was attributed to the large internal surface area of opal-CT compared to that of opal-AG. Since Al was found to exist in a tetrahedral coordination within the opal structure, incorporation of Al occurred through substitution of Si during the period of colloidal growth. As the concentration of Al in banded opals was similar, the colloids within each band are considered to have formed at similar times

Multiple views of L1 writing score reliability

This paper provides an in-depth investigation of the reliability of scores on the Manoa Writing Placement Examination (MWPE) based on a reanalysis of the scores of 6875 students who took MWPE during a four year period. Classical test theory analyses indicated that the MWPE scores were reasonably consistent across semesters (with a slight overall rise in scores over the four years), and that they produced traditional reliability estimates ranging from .51 to .74. The standard error of measurement was also examined in relationship to placement decision making. Generalizability theory was used to examine the relative importance of the numbers of topics and ratings to the consistency of scores. The results indicate that consistency would be increased more effectively by increasing the number of topics than by increasing the number of ratings. In addition, phi(lambda) indexes and signal-to-noise ratios were calculated to estimate score dependability at various decision points. The discussion focuses on the relative usefulness of these various approaches to reliability in practical test use, development, and interpretations

An EFL Readability Index

This surdy explores readability and its relationship to the cloze passage performance of EFL students. Fifty reading passages were randomly selected from an American public library and made into 30-item cloze passages by deleting every 12th word. Thc subjects were 2298 EFL students from 18 university level institutions in Japan. Each student was randomly selected to take one of the 30-item cloze passages. Any differences between the cloze passages were therefore assumed to be due to other than sampling difierences. The result was a set of 50 cloze passages the means of which sewed as the dependent variable: EFL Difficulty. Each passage was then analyzed for two sets of independent variables chosen to investigate how well they predict the EFL Difficulty: the first set was made up of various first language readability indices (including the Flesch, Flesch-Kincaid, Fry, Gunning, Fog, and modified Gunning-Fog indices); the second set was made up of quantifiable linguistic characteristics of the passages (e.g., the percent of function words number of syllabuses per sentence, number of words per paragraph, frequencies of words in the passages, and nany others). Correlational, factor and multiple-regression analyses indicated that the first language readability indices were only weakly related to EFL Difficulty (23 to 30 percent). However, the analysis of linguistic characteristics indicated clear groupings among the variables. In addition, four of the linguistic characteristics (number of syllables per sentence, the average frequency of lexical items elsewhere in the passage, percent of words with seven or more letters, and percent of function words) when combined were more highly related to EFL Difficulty (55 percent). These results are discussed in terms of their implications for the development of an EFL readability index

Charged Particle Motion in a Highly Ionized Plasma

A recently introduced method utilizing dimensional continuation is employed to compute the energy loss rate for a non-relativistic particle moving through a highly ionized plasma. No restriction is made on the charge, mass, or speed of this particle. It is, however, assumed that the plasma is not strongly coupled in the sense that the dimensionless plasma coupling parameter g=e^2\kappa_D/ 4\pi T is small, where \kappa_D is the Debye wave number of the plasma. To leading and next-to-leading order in this coupling, dE/dx is of the generic form g^2 \ln[C g^2]. The precise numerical coefficient out in front of the logarithm is well known. We compute the constant C under the logarithm exactly for arbitrary particle speeds. Our exact results differ from approximations given in the literature. The differences are in the range of 20% for cases relevant to inertial confinement fusion experiments. The same method is also employed to compute the rate of momentum loss for a projectile moving in a plasma, and the rate at which two plasmas at different temperatures come into thermal equilibrium. Again these calculations are done precisely to the order given above. The loss rates of energy and momentum uniquely define a Fokker-Planck equation that describes particle motion in the plasma. The coefficients determined in this way are thus well-defined, contain no arbitrary parameters or cutoffs, and are accurate to the order described. This Fokker-Planck equation describes the longitudinal straggling and the transverse diffusion of a beam of particles. It should be emphasized that our work does not involve a model, but rather it is a precisely defined evaluation of the leading terms in a well-defined perturbation theory.Comment: Comments: Published in Phys. Rep. 410/4 (2005) 237; RevTeX, 111 Pages, 17 Figures; Transcription error corrected in temperature equilibration rate (3.61) and (12.44) which replaces \gamma-2 by \gamma-

The Washback Effect of Language Tests

Because the first definition at the top of this paper (from Shohamy et al, 1996) is both adequate and parsimonious, it is very attractive. However, that definition does not explicitly include the link between washback and validity. Hence the working definition of washback that I will use in this paper is a slightly expanded version ofthe one provided by Shohamy et al. (1996): the connections between language testing and learning, and the consequences of those connections. I will continue to explore the concept of backwash by addressing a number of questions: Does washback exist? What factors affect the impact of washback? What are the negative aspects of washback? How can we promote positive washback? What directions might future research on washback effect take

What Makes a Cloze Item Difficult?

This pilot study explores the link between linguistic characteristics of doze test items and individual item difficulty estimates. Five reading passages were randomJy selected from a public library, developed into 30-item doze tests and randomJy administered to 179 Japanese EFL students. Each of the 150 resulting items was analyzed for item facility and for various linguistic characteristics. Multiple-regression analysis indicates that linguistic characteristics, in various combinations, can account for large proportions of the variation in doze item facility. These results are discussed in terms of their implications for language testing research and plans for future research on a larger scale