bluuebunny/crossref_metadata_2025 huggingface dataset:
Dolomitization of the Middle Devonian Winnipegosis carbonates in south‐central Saskatchewan, Canada
Authors: FU QILONG , QING HAIRUO , BERGMAN KATHERINE M.
Published: June 2006

The Middle Devonian Winnipegosis carbonate unit in south‐central Saskatchewan is partially to completely dolomitized. Two major types of replacive dolomite are distinguished. Microcrystalline to finely crystalline dolomite (type 1) displays nonplanar‐a to planar‐s textures, mimetically replaces the precursor limestone, accounts for about four‐fifths of dolomite phases volumetrically, and mainly occurs in the Winnipegosis mounds and the Lower Winnipegosis Member directly underlying the mounds. Medium crystalline dolomite (type 2) shows planar‐s to planar‐e textures, commonly occurs in the Lower Winnipegosis and Brightholme members, and decreases upward in abundance. The 87Sr/86Sr ratios of type 1 dolomite (0·70795 to 0·70807) fall within the estimated Sr‐isotopic range for Middle Devonian marine carbonates. Stratigraphic, petrographic and geochemical data constrain the formation of type 1 dolomite to hypersaline sea water in a near‐surface environment, after marine cementation and sub‐aerial diagenesis and prior to precipitation of the Middle Devonian Leofnard salts. Movement of dolomitizing fluids could be driven by density differences and elevation head. The shift to lower δ18O values of type 1 dolomite [−7·4 to −5·1‰ Vienna Pee Dee Belemnite (VPDB)] is interpreted as the result of recrystallization at elevated temperatures during burial. Type 2 dolomite has higher 87Sr/86Sr ratios (0·70809–0·70928), suggesting that the dolomite probably formed from basinal fluids with an increased richness in the radiogenic Sr isotope. In type 2 dolomite, Sr2+ concentrations are lower, and Fe2+ and Mn2+ concentrations are higher, compared with the associated limestone and type 1 dolomite. Type 2 dolomite is interpreted as having been formed from upward‐migrating basinal fluids during latest Devonian and Carboniferous period.
Is size-assortative mating important for rapid pigment differentiation in a freshwater isopod?
Authors: Hargeby A. , Erlandsson J.
Published: June 2006

Identifying mechanisms behind assortative mating is central to the understanding of ecological divergence and speciation. Recent studies show that populations of the freshwater isopod Asellus aquaticus can rapidly become locally differentiated when submerged Chara vegetation expands in lakes. In the novel Chara habitat, isopods have become lighter pigmented and smaller than in ancestral reed stands. In this study, we used a laboratory multiple-choice experiment to investigate assortative mating as a possible prezygotic reproductive barrier between Chara and reed isopods. Mating was assortative when Chara isopods were experimentally mixed with isopods from an adjacent reed site with large-size individuals, suggesting a partial prezygotic reproductive barrier. No deviation from random mating could, however, be detected when Chara isopods were mixed with smaller sized isopods from another reed site. In both experiments, assortative mating was apparently based on size, as Chara isopods were larger and reed isopods smaller in mixed pairs than in assortative pairs. Pigmentation did not have any clear influence on mating. We suggest that divergence in pigmentation evolved through natural selection in conjunction with size-assortative mating indirectly causing assortative mating between Chara and reed isopods. Size-assortative mating is likely a by-product of natural selection, but its importance may hypothetically be transient, if selection erodes the correlation between pigmentation and size over time.
HEDGING WITH ENERGY
Authors: Corielli Francesco
Published: June 2006

In the setting of diffusion models for price evolution, we suggest an easily implementable approximate evaluation formula for measuring the errors in option pricing and hedging due to volatility misspecification. The main tool we use in this paper is a (suitably modified) classical inequality for the L2 norm of the solution, and the derivatives of the solution, of a partial differential equation (the so‐called “energy” inequality). This result allows us to give bounds on the errors implied by the use of approximate models for option valuation and hedging and can be used to justify formally some “folk” belief about the robustness of the Black and Scholes model. Surprisingly enough, the result can also be applied to improve pricing and hedging with an approximate model. When statistical or a priori information is available on the “true” volatility, the error measure given by the energy inequality can be minimized w.r.t. the parameters of the approximating model. The method suggested in this paper can help in conjugating statistical estimation of the volatility function derived from flexible but computationally cumbersome statistical models, with the use of analytically tractable approximate models calibrated using error estimates.
A COMMENT ON MARKET FREE LUNCH AND FREE LUNCH
Authors: Klein Irene
Published: June 2006

Frittelli (2004) introduced a market free lunch depending on the preferences of the agents in the market. He characterized no arbitrage and no free lunch with vanishing risk in terms of no market free lunch (the difference comes from the class of utility functions determining the market free lunch). In this note we complete the list of characterizations and show directly (using the theory of Orlicz spaces) that no free lunch is equivalent to the absence of market free lunch with respect to monotone concave utility functions.
Family Background and the Propensity for Self‐Employment
Authors: HUNDLEY GREG
Published: June 2006

Empirical analysis shows that men with self‐employed fathers and higher parental incomes are more likely to be self‐employed, the impact of paternal self‐employment is leveraged by higher family income, and self‐employment is more likely when the father worked in an occupation with task requirements similar to those of an independent business. The idea that the paternal self‐employment effect is attributable to sons following their fathers into occupations inherently more or less conducive to self‐employment is not supported.
The Determinants of Stock Option Compensation: Evidence from Finland
Authors: JONES DEREK C. , KALMI PANU , MÄKINEN MIKKO
Published: June 2006

A new, long, and rich panel data set consisting of all Finnish publicly traded firms is used to study how firm characteristics and stock market developments influence the adoption and targeting of stock option compensation. Stock option adoption is found to be a procyclical phenomenon. Findings from firm‐level econometric analysis often corroborate those based on U.S. data, but important differences also emerge. Findings include: (i) firms with higher market value per employee are more likely to use stock option compensation; (ii) share returns from the past year affect the adoption of targeted stock options, but not broad‐based plans; (iii) our results are consistent with the hypothesis that selective and broad‐based plans arise as solutions to differing monitoring difficulties. Broad‐based schemes are observed when production is human capital‐intensive and employee performance is hard to monitor, while selective schemes are adopted when ownership is dispersed and therefore owners may have weak incentives to monitor management.
Gastrointestinal tract of the brown kiwi (Apteryx mantelli)
Authors: Potter M. A. , Lentle R. G. , Minson C. J. , Birtles M. J. , Thomas D. , Hendriks W. H.
Published: June 2006

The caeca of the brown kiwiApteryx mantelliincreased in length isometrically with body mass, but wall mass and thus mucosal thickness increased allometrically. Kiwi caeca are sacculate, with greater thickness of mucosa in the proximal portions. The caecal mucosa is similar to the small intestinal mucosa, with well‐developed mucosal folds, villi, and crypts of Lieberkühn or intestinal glands. The solid matter in caecal digesta contained disproportionately large quantities of material that was not retained by a 75 μm sieve. The per cent of incombustible material (total ash) within the caeca digesta did not differ significantly from those within adjacent small intestinal or rectal segments. The fine particles within the caeca were not composed of fine crystalline uric acid; chemical analyses showed only low levels of uric acid in caecal digesta. These findings indicate that the caeca of this flightless insectivorous ratite are a site for the sequestration and fermentative digestion of fine particulate material, such as plant fibre, fragmented chitin or uric acid crystals.
The functional significance of multiple nest‐building in the Australian Reed Warbler Acrocephalus australis
Authors: BERG MATHEW L. , BEINTEMA NIENKE H. , WELBERGEN JUSTIN A. , KOMDEUR JAN
Published: June 2006

The vast majority of bird species build a nest in which to breed. Some species build more than one nest, but the function of most multiple nest‐building remains unclear. Here we describe the unusual nest‐building behaviour of the Australian Reed Warbler Acrocephalus australis, and test experimentally the hypotheses that multiple nest‐building is related to individual condition or territory quality, and plays a role in mate assessment. Australian Reed Warblers built two types of nest structures: ‘type I’ nests, which were used for eggs and nestlings, and ‘type II’ nests, which were structurally distinct from type I nests, did not support eggs, nestlings or adults and were not essential for successful breeding. The number of type II nests built in each territory varied. Type II nests were only built before breeding had commenced in a territory and females were not observed participating in their construction, supporting a role in female mate choice. Birds provided with supplementary food built significantly more type II nests than control birds. However, supplementary‐fed birds did not have greater pairing success, and the addition of further type II nests to territories did not increase the pairing rate or type II nest construction in those territories. There was no relationship between the presence of type II nests and either reproductive success or likelihood of nest predation. We discuss the implications of these results in light of previous suggestions regarding the function of multiple nest‐building in birds.
An ecomorphological study of the raptorial digital tendon locking mechanism
Authors: EINODER LUKE , RICHARDSON ALASTAIR
Published: June 2006

Extensive adaptive radiation in hindlimb design among raptors is well known. However, the degree of variation in the structure and expression of the digital tendon locking mechanism (TLM) and its adaptive significance have received little attention. This comparative morphological study of 12 raptor and three non‐raptor species revealed a distinct raptorial design, characterized by a distally located TLM that is densely packed with locking elements of increased robustness and height. Although the Falconiformes and Strigiformes converged upon this pattern, unique design features were identified among the nocturnal birds of prey. Variation in TLM structure was often consistent with phylogeny, although interfamily similarities were revealed among a number of species with the same dietary habit. The evolutionary factors that may have led to the observed variation, as well as the biomechanical implications of varying designs, are discussed.
The effect of migration strategy and food availability on White StorkCiconia ciconiabreeding success
Authors: MASSEMIN‐CHALLET SYLVIE , GENDNER JEAN‐PAUL , SAMTMANN SÉBASTIEN , PICHEGRU LORIEN , WULGUÉ ANITA , LE MAHO YVON
Published: June 2006

In the mid 1970s, the breeding populations of the migrant White StorkCiconia ciconiawere close to extinction in the northeastern region of France (Alsace). A re‐introduction project was implemented, resulting in the year‐round settlement of some individuals in the region, which rely on additional food supplied by humans during the winter. Today, both resident and migrant birds breed in the same areas and take food from rubbish dumps and humans (farmers). The effects of these anthropogenic influences, altering Stork behaviour, on Stork reproductive success are not known. The aim of this study was to test the influence of bird status (resident vs. migrant) and food availability (control nests vs. nests that benefit from high food supply) on reproductive success. In control nests, the mean laying date was earlier in resident than in migrant White Storks. There was also a clear seasonal decline in clutch size. For all nests, the numbers of eggs and hatchlings were higher in resident birds than in migrants, which can be attributed to the earlier breeding of resident Storks. The large broods of resident birds showed a high mortality rate, leading to the same fledgling success (fledglings/hatchlings) and number of fledglings as in migrants. Fledgling success and the number of fledglings were higher for nests close to a reliable food supply. In summary, although resident birds can breed earlier and produce more eggs than migrants, we found no advantage in terms of number of fledglings. The higher mortality rate of chicks found in pairs with a large brood could be caused by the deterioration of their habitat. Thus, the year‐round settlement of Storks may not present a biological advantage if the quality of their habitat is not guaranteed by the conservation of their grasslands.
Effects of neonatal nutrition on adult reproduction in a passerine bird
Authors: BLOUNT JONATHAN D. , METCALFE NEIL B. , ARNOLD KATHRYN E. , SURAI PETER F. , MONAGHAN PAT
Published: June 2006

Effects of neonatal nutrition on adult reproductive performance have been little studied. In Zebra FinchesTaeniopygia guttata, poor neonatal nutrition is known to be associated with reduced blood antioxidant levels in adulthood, which could impair reproductive performance. Here, we compare the effects of standard‐quality (SQ) or lower‐quality (LQ) neonatal nutrition on components of fecundity. Compared with controls, LQ birds took longer to initiate egg‐laying, and then laid eggs at a slower rate. LQ birds did not, however, show reduced clutch mass or size, or yolk antioxidant levels (retinol; α‐ or γ‐tocopherol; carotenoids). Zebra Finches breed opportunistically, often only once in their short lifetime. Therefore, the timing but also the number and quality of eggs are critical fitness‐related traits. Our results indicate that LQ birds had impaired reproductive capacity, suggesting resource accumulation constraints. Maximizing egg number and quality appears to have been more important than rapid egg production.
Cognitive training in Alzheimer's disease: a meta‐analysis of the literature
Authors: Sitzer D. I. , Twamley E. W. , Jeste D. V.
Published: June 2006

Objective: To systematically review the literature and summarize the effect of cognitive training (CT) for Alzheimer's disease (AD) patients on multiple functional domains.

Method: Effect sizes (Cohen'sd) were calculated for 17 controlled studies identified through a comprehensive literature review.

Results: An overall effect size of 0.47 was observed for all CT strategies across all measured outcomes. Mean effect sizes were higher for restorative (0.54) than for compensatory (0.36) strategies. Domain‐specific effect sizes ranged from 2.16 (verbal and visual learning) to −0.38 (visuospatial functioning). Data are also presented on the relative impact of restorative and compensatory strategies for each domain of functioning.

Conclusion: CT evidenced promise in the treatment of AD, with primarily medium effect sizes for learning, memory, executive functioning, activities of daily living, general cognitive problems, depression, and self‐rated general functioning. Restorative strategies demonstrated the greatest overall effect on functioning. Several limitations of the published literature are discussed.
Melatonin protects against hydrogen peroxide‐induced cell death signaling in SH‐SY5Y cultured cells: involvement of nuclear factor kappa B, Bax and Bcl‐2
Authors: Chetsawang Banthit , Putthaprasart Chorkaew , Phansuwan‐Pujito Pansiri , Govitrapong Piyarat
Published: June 2006

Abstract:  Oxidative stress is defined as a disturbance in the prooxidant–antioxidant balance, leading to potential cell damage. Reactive oxygen species such as superoxide radicals, hydroxyl radicals and hydrogen peroxide may act also as secondary intermediaries in intracellular signaling leading to cell death. The neuroprotective effect of melatonin has been observed both in vivo and in vitro. The objective of this research, therefore, was to better understand the cellular mechanisms of neuronal cell degeneration induced via oxidative stress and the protective roles of melatonin on this cell death. In the present study, the effects of melatonin on H2O2‐induced neuronal cell degeneration in human dopaminergic neuroblastoma SH‐SY5Y cultured cells were investigated. The results showed that H2O2 significantly decreased cell viability and melatonin reversed the toxic effects of H2O2. An inhibition of caspase enzyme activity by Ac‐DEVD‐CHO, a caspase‐3 inhibitor, significantly increased cell viability in H2O2‐treated cells. The phosphorylation of transcription factors, nuclear factor kappa B (NF‐κB) was increased in H2O2‐treated cells and this effect was abolished by melatonin. Translocation of phosphorylated NF‐κB to perinuclear and nuclear sites, estimated using immunofluorescence, occurred to a greater extent in H2O2‐treated cells than in untreated control cells and again this effect was abolished by melatonin. In addition, induction of Bcl‐2 and Bax proteins was demonstrated in SH‐SY5Y cultured cells treated with H2O2, whereas the induction of Bax but not Bcl‐2 was diminished by melatonin. In light of these finding, it is possible that the antioxidative stress effect of melatonin associated with inhibition of Bax expression, may offer a means of treating neuronal degeneration and disease.
Self‐efficacy, symptoms and physical activity in patients with an anterior cruciate ligament injury: a prospective study
Authors: Thomeé P. , Währborg P. , Börjesson M. , Thomeé R. , Eriksson B. I. , Karlsson J.
Published: June 2006

Self‐efficacy belief may be of major importance for the outcome of rehabilitation after sports‐related injuries. A new instrument, the Knee Self‐Efficacy Scale (K‐SES), was used to evaluate the role of perceived self‐efficacy in patients with an anterior cruciate ligament (ACL) injury. The purpose of this prospective exploratory study was to describe the patients' perceived self‐efficacy at various times post‐injury and surgery, respectively, for responsiveness of the K‐SES and to correlate the K‐SES score with the patients' subjective symptoms. The purpose was also to describe the influence of gender, age and physical activity on the patients' perceived self‐efficacy. Thirty recently injured patients with an ACL‐deficient knee and 33 patients who had undergone ACL reconstruction reported their physical activity level and their perceived self‐efficacy on four test occasions during a 1‐year period. The patients' subjective knee symptoms were documented on two of the test occasions. A significant increase in the K‐SES score was seen after injury as well as after surgery, during the course of rehabilitation. Pre‐operatively, men's perceived self‐efficacy was significantly (P=0.013) higher compared with women's self‐efficacy. Patients with a high baseline (pre‐injury) physical activity level (Tegner 7–10) perceived their self‐efficacy as being significantly (P=0.005) higher pre‐operatively compared with patients with a low baseline activity level (Tegner 3–6). “Younger” (age 17–29), recently injured patients, perceived their self‐efficacy as being significantly (P=0.034) higher compared with “older” patients (age 30–54). At the 12‐month test, 15 of 30 patients with an ACL‐deficient knee and 15 of 33 patients who had undergone ACL reconstruction reported that they had returned or nearly returned to their baseline physical activity level. The subjective knee outcome score, as measured by the Knee Injury and Osteoarthritis Outcome Score (KOOS), improved significantly (P<0.01) during rehabilitation, apart from the KOOS subscale of “pain” (P=0.077) for patients who had undergone ACL reconstruction. There was a “low” to “strong” correlation (rs=0.0–0.7) between the K‐SES and the five subscales in the KOOS. We conclude from the present study that K‐SES has good responsiveness with significantly increased self‐efficacy during the rehabilitation process for patients with an ACL‐deficient knee as well as for patients who had undergone ACL reconstruction. The improvement in perceived self‐efficacy could, however, only be partly explained by the improvement in subjective symptoms. Furthermore, self‐efficacy differed significantly with gender, age and physical activity level early in the rehabilitation process.
The Role of Functional Parameters for Topographical Characterization of Bone‐Anchored Implants
Authors: Arvidsson Anna , Sater Bashar A. , Wennerberg Ann
Published: June 2006

Background  The surface topographical characterization of bone‐anchored implants has been recommended to be based on amplitude, spatial, and hybrid parameters. There are also functional parameters that have the potential to describe characteristics important for a specific application.

Purpose  The aim of the present study was to evaluate if parameters that have been described as functional in engineering applications are also relevant in the topographical characterization of bone‐anchored implants.

Materials and Methods  The surface topography of threaded titanium implants with different surface roughness (Sa, Sds, and Sdr) was analyzed with an optical interferometer, and five candidating functional parameters (Sbi, Sci, Svi, Sm, and Sc) were calculated. Examples of the same parameters for five commercially available dental implants were also calculated.

Results  The highest core fluid retention index (Sci) was displayed by the turned implants, followed by fixtures blasted with 250‐ and 25‐μm particles, respectively. Fixtures blasted with 75‐μm Al2O3 particles displayed the lowest Sci value. This is the inverse order of the bone biological ranking based on earlier in vivo studies with the experimental surfaces included in the present study.

Conclusion  A low core fluid retention index (Sci) seems favorable for bone‐anchored implants. Therefore, it is suggested to include Sci to the set of topographical parameters for bone‐anchored implants to possibly predict the biological outcome.
Intrusion of Molars with Implants as Anchorage: A Report of Two Cases
Authors: Kato Satoshi , Kato Michiko
Published: June 2006

Background  Osseointegrated implants do not move in response to orthodontic loads.

Purpose  The aim of this study was to describe a method to intrude supra‐erupted molars using prosthetic implants as anchorage.

Materials and Methods  A 51‐year‐old female and a 36‐year‐old male were treated with adjacent implants for orthodontic anchorage for supra‐erupted teeth in the maxilla (16, 17) and in the mandible (46, 47), respectively. In both cases, the force of intrusion applied was 300 g.

Results  The therapy was completed without complications or abnormalities of the intruded teeth or anchorage implants. Intrusion required 13 months in the first case and 19 months in the latter.

Conclusion  The present method makes it possible to secure enough space for prosthodontic therapy at edentulous segments and perform highly reliable implant therapy.
Abutment Rotational Displacement of External Hexagon Implant System Under Lateral Cyclic Loading
Authors: Khraisat Ameen , Baqain Zaid H , Smadi Leena , Nomura Shuichi , Miyakawa Osamu , Elnasser Ziad
Published: June 2006

Purpose  This in vitro study investigated the effect of lateral cyclic loading with different load positions and periods on abutment rotational displacement (RD) of external hexagon implant system.

Materials and Methods  Four groups of five implant assemblies each were used. Each assembly consisted of Brånemark System® Mk IV implant (Nobel Biocare AB, Göteborg, Sweden), CeraOne® abutment (Nobel Biocare AB), and a cement‐retained casting. A cyclic load of 50 N was applied centrally and perpendicular to the long axis of the implant for groups A and B for 0.25 and 0.50 × 106 cycles, respectively, while for groups C and D, the same load was applied at 4‐mm distance eccentrically for 0.25 and 0.50 × 106 cycles, respectively. The displacement was evaluated by hand drawing a longitudinal line across the implant‐abutment interface. Before and after loading, the lateral distance between two reference points on the abutment and implant was measured under high resolution (×200) and the difference formed the RD value. The data were analyzed with one‐way analysis of variance and compared with Tukey test (α=0.05).

Results  Group D had the highest mean of RD value (55.00 ± 1.871 μm), while group A had the lowest (2.800 ± 0.837 μm). Groups A and B had a high statistically significant difference in RD values, as compared to groups C or D (p < .001). Moreover, group C had statistically significant difference from group D (p=.011). Conversely, no statistical significance was obtained when group A was compared with group B.

Conclusion  Within the limits of this in vitro study, the RD of the external hexagon joint components occurred significantly under eccentric lateral loading when compared to centric loading. The displacement increased significantly with longer period of eccentric lateral loading.
Sialylation of urinary prothrombin fragment 1 is implicated as a contributory factor in the risk of calcium oxalate kidney stone formation
Authors: Webber Dawn , Radcliffe Catherine M. , Royle Louise , Tobiasen Gemma , Merry Anthony H. , Rodgers Allen L. , Sturrock Edward D. , Wormald Mark R. , Harvey David J. , Dwek Raymond A. , Rudd Pauline M.
Published: June 2006

Urinary glycoproteins are important inhibitors of calcium oxalate crystallization and adhesion of crystals to renal cells, both of which are key mechanisms in kidney stone formation. This has been attributed to glycosylation of the proteins. In South Africa, the black population rarely form stones (incidence < 1%) compared with the white population (incidence 12–15%). A previous study involving urinary prothrombin fragment 1 from both populations demonstrated superior inhibitory activity associated with the protein from the black group. In the present study, we compared N‐linked and O‐linked oligosaccharides released from urinary prothrombin fragment 1 isolated from the urine of healthy and stone‐forming subjects in both populations to elucidate the relationship between glycosylation and calcium oxalate stone pathogenesis. The O‐glycans of both control groups and the N‐glycans of the black control samples were significantly more sialylated than those of the white stone‐formers. This demonstrates a possible association between low‐percentage sialylation and kidney stone disease and provides a potential diagnostic method for a predisposition to kidney stones that could lead to the implementation of a preventative regimen. These results indicate that sialylated glycoforms of urinary prothrombin fragment 1 afford protection against calcium oxalate stone formation, possibly by coating the surface of calcium oxalate crystals. This provides a rationale for the established roles of urinary prothrombin fragment 1, namely reducing the potential for crystal aggregation and inhibiting crystal–cell adhesion by masking the interaction of the calcium ions on the crystal surface with the renal cell surface along the nephron.
In vivo heteromer formation. Expression of soluble βA4‐crystallin requires coexpression of a heteromeric partner
Authors: Marín‐Vinader Laura , Onnekink Carla , van Genesen Siebe T. , Slingsby Christine , Lubsen Nicolette H.
Published: June 2006

The β‐crystallins are a family of long‐lived, abundant structural proteins that are coexpressed in the vertebrate lens. As β‐crystallins form heteromers, a process that involves transient exposure of hydrophobic interfaces, we have examined whether in vivoβ‐crystallin assembly is enhanced by protein chaperones, either small heat shock proteins, Hsp27 or αB‐crystallin, or Hsp70. We show here that βA4‐crystallin is abundantly expressed in HeLa cells, but rapidly degraded, irrespective of the presence of Hsp27, αB‐crystallin or Hsp70. Degradation is even enhanced by Hsp70. Coexpression of βA4‐crystallin with βB2‐crystallin yielded abundant soluble βA4–βB2‐crystallin heteromers; βB1‐crystallin was much less effective in solubilizing βA4‐crystallin. As βB2‐crystallin competed for βA4‐crystallin with Hsp70 and the proteasomal degradation pathway, βB2‐crystallin probably captures an unstable βA4‐crystallin intermediate. We suggest that the proper folding of βA4‐crystallin is not mediated by general chaperones but requires a heteromeric partner, which then also acts as a dedicated chaperone towards βA4‐crystallin.
An Empirical Investigation Demonstrating the Multidimensional DIF Paradigm: A Cognitive Explanation for DIF
Authors: Walker Cindy M. , Beretvas S. Natasha
Published: June 2006

Differential Item Functioning (DIF) is traditionally used to identify different item performance patterns between intact groups, most commonly involving race or sex comparisons. This study advocates expanding the utility of DIF as a step in construct validation. Rather than grouping examinees based on cultural differences, the reference and focal groups are chosen from two extremes along a distinct cognitive dimension that is hypothesized to supplement the dominant latent trait being measured. Specifically, this study investigates DIF between proficient and non‐proficient fourth‐ and seventh‐grade writers on open‐ended mathematics test items that require students to communicate about mathematics. It is suggested that the occurrence of DIF in this situation actually enhances, rather than detracts from, the construct validity of the test because, according to the National Council of Teachers of Mathematics (NCTM), mathematical communication is an important component of mathematical ability, the dominant construct being assessed. However, the presence of DIF influences the validity of inferences that can be made from test scores and suggests that two scores should be reported, one for general mathematical ability and one for mathematical communication. The fact that currently only one test score is reported, a simple composite of scores on multiple‐choice and open‐ended items, may lead to incorrect decisions being made about examinees.
Identifying Sources of Differential Item and Bundle Functioning on Translated Achievement Tests: A Confirmatory Analysis
Authors: Gierl Mark J. , Khaliq Shameem Nyla
Published: June 2006

Increasingly, tests are being translated and adapted into different languages. Differential item functioning (DIF) analyses are often used to identify non‐equivalent items across language groups. However, few studies have focused on understanding why some translated items produce DIF. The purpose of the current study is to identify sources of differential item and bundle functioning on translated achievement tests using substantive and statistical analyses. A substantive analysis of existing DIF items was conducted by an 11‐member committee of testing specialists. In their review, four sources of translation DIF were identified. Two certified translators used these four sources to categorize a new set of DIF items from Grade 6 and 9 Mathematics and Social Studies Achievement Tests. Each item was associated with a specific source of translation DIF and each item was anticipated to favor a specific group of examinees. Then, a statistical analysis was conducted on the items in each category using SIBTEST. The translators sorted the mathematics DIF items into three sources, and they correctly predicted the group that would be favored for seven of the eight items or bundles of items across two grade levels. The translators sorted the social studies DIF items into four sources, and they correctly predicted the group that would be favored for eight of the 13 items or bundles of items across two grade levels. The majority of items in mathematics and social studies were associated with differences in the words, expressions, or sentence structure of items that are not inherent to the language and/or culture. By combining substantive and statistical DIF analyses, researchers can study the sources of DIF and create a body of confirmed DIF hypotheses that may be used to develop guidelines and test construction principles for reducing DIF on translated tests.
A Comparative Study of On‐line Pretest Item—Calibration/Scaling Methods in Computerized Adaptive Testing
Authors: Ban Jae‐Chun , Hanson Bradley A. , Wang Tianyou , Yi Qing , Harris Deborah J.
Published: June 2006

The purpose of this study was to compare and evaluate five on‐line pretest item‐calibration/scaling methods in computerized adaptive testing (CAT): marginal maximum likelihood estimate with one EM cycle (OEM), marginal maximum likelihood estimate with multiple EM cycles (MEM), Stocking's Method A, Stocking's Method B, and BILOG/Prior. The five methods were evaluated in terms of item‐parameter recovery, using three different sample sizes (300, 1000 and 3000). The MEM method appeared to be the best choice among these, because it produced the smallest parameter‐estimation errors for all sample size conditions. MEM and OEM are mathematically similar, although the OEM method produced larger errors. MEM also was preferable to OEM, unless the amount of time involved in iterative computation is a concern. Stocking's Method B also worked very well, but it required anchor items that either would increase test lengths or require larger sample sizes depending on test administration design. Until more appropriate ways of handling sparse data are devised, the BILOG/Prior method may not be a reasonable choice for small sample sizes. Stocking's Method A had the largest weighted total error, as well as a theoretical weakness (i.e., treating estimated ability as true ability); thus, there appeared to be little reason to use it.
Differences Between Self‐Adapted and Computerized Adaptive Tests: A Meta‐Analysis
Authors: Pitkin Angela K. , Vispoel Walter P.
Published: June 2006

Self‐adapted testing has been described as a variation of computerized adaptive testing that reduces test anxiety and thereby enhances test performance. The purpose of this study was to gain a better understanding of these proposed effects of self‐adapted tests (SATs); meta‐analysis procedures were used to estimate differences between SATs and computerized adaptive tests (CATs) in proficiency estimates and post‐test anxiety levels across studies in which these two types of tests have been compared. After controlling for measurement error, the results showed that SATs yielded proficiency estimates that were 0.12 standard deviation units higher and post‐test anxiety levels that were 0.19 standard deviation units lower than those yielded by CATs. We speculate about possible reasons for these differences and discuss advantages and disadvantages of using SATs in operational settings.
Grades and Test Scores: Accounting for Observed Differences
Authors: Willingham Warren W. , Pollack Judith M. , Lewis Charles
Published: June 2006

Why do grades and test scores often differ? A framework of possible differences is proposed in this article. An approximation of the framework was tested with data on 8,454 high school seniors from the National Education Longitudinal Study. Individual and group differences in grade versus test performance were substantially reduced by focusing the two measures on similar academic subjects, correcting for grading variations and unreliability, and adding teacher ratings and other information about students. Concurrent prediction of high school average was thus increased from 0.62 to 0.90; differential prediction in eight subgroups was reduced to 0.02 letter‐grades. Grading variation was a major source of discrepancy between grades and test scores. Other major sources were teacher ratings and Scholastic Engagement, a promising organizing principle for understanding student achievement. Engagement was defined by three types of observable behavior: employing school skills, demonstrating initiative, and avoiding competing activities. While groups varied in average achievement, group performance was generally similar on grades and tests. Major factors in achievement were similarly constituted and similarly related from group to group. Differences between grades and tests give these measures complementary strengths in high‐stakes assessment. If artifactual differences between the two measures are not corrected, common statistical estimates of validity and fairness are unduly conservative.
The Effects of a Student Sampling Plan on Estimates of the Standard Errors for Student Passing Rates
Authors: Lee Guemin , Fitzpatrick Anne R.
Published: June 2006

Examined in this study were three procedures for estimating the standard errors of school passing rates using a generalizability theory model. Also examined was how these procedures behaved for student samples that differed in size. The procedures differed in terms of their assumptions about the populations from which students were sampled, and it was found that student sample size generally had a notable effect on the size of the standard error estimates they produced. Also the three procedures produced markedly different standard error estimates when student sample size was small.
Guess Where: The Position of Correct Answers in Multiple‐Choice Test Items as a Psychometric Variable
Authors: Attali Yigal , Bar‐Hillel Maya
Published: June 2006

In this article, the authors show that test makers and test takers have a strong and systematic tendency for hiding correct answers—or, respectively, for seeking them—in middle positions. In single, isolated questions, both prefer middle positions to extreme ones in a ratio of up to 3 or 4 to 1. Because test makers routinely, deliberately, and excessively balance the answer key of operational tests, middle bias almost, though not quite, disappears in those keys. Examinees taking real tests also produce answer sequences that are more balanced than their single question tendencies but less balanced than the correct key. In a typical four‐choice test, about 55% of erroneous answers are in the two central positions. The authors show that this bias is large enough to have real psychometric consequences, as questions with middle correct answers are easier and less discriminating than questions with extreme correct answers, a fact of which some implications are explored.
Comparison of Answer Copying Indices with Real Data
Authors: Wollack James A.
Published: June 2006

This study investigated the Type I error rate and power of four copying indices, K‐index (Holland, 1996), Scrutiny! (Assessment Systems Corporation, 1993), g2 (Frary, Tideman, & Watts, 1977), and ω (Wollack, 1997) using real test data from 20,000 examinees over a 2‐year period. The data were divided into three different test lengths (20, 40, and 80 items) and nine different sample sizes (ranging from 50 to 20,000). Four different amounts of answer copying were simulated (10%, 20%, 30%, and 40% of the items) within each condition. The ω index demonstrated the best Type I error control and power in all conditions and at all α levels. Scrutiny! and the K‐index were uniformly conservative, and both had poor power to detect true copiers at the small α levels typically used in answer copying detection, whereas g2 was generally too liberal, particularly at small α levels. Some comments on the proper uses of copying indices are provided.
The Attribute Hierarchy Method for Cognitive Assessment: A Variation on Tatsuoka's Rule‐Space Approach
Authors: Leighton Jacqueline P. , Gierl Mark J. , Hunka Stephen M.
Published: June 2006

A cognitive item response theory model called the attribute hierarchy method (AHM) is introduced and illustrated. This method represents a variation of Tatsuoka's rule‐space approach. The AHM is designed explicitly to link cognitive theory and psychometric practice to facilitate the development and analyses of educational and psychological tests. The following are described: cognitive properties of the AHM; psychometric properties of the AHM, as well as a demonstration of how the AHM differs from Tatsuoka's rule‐space approach; and application of the AHM to the domain of syllogistic reasoning to illustrate how this approach can be used to evaluate the cognitive competencies required in a higher‐level thinking task. Future directions for research are also outlined.
Hierarchical Logistic Regression in Course Placement
Authors: Schulz E. Matthew , Betebenner Damian , Ahn Meeyeon
Published: June 2006

Whether hierarchical logistic regression can reduce the sample size requirement for estimating optimal cutoff scores in a course placement service where predictive validity is measured by a threshold utility function is explored. Data from courses with varying class size were randomly partitioned into two halves per course. Non‐hierarchical and hierarchical analyses were performed on each half. Compared to their nonhierarchical counterparts, hierarchically estimated cutoff scores from different halves were more stable and predicted course outcomes in the other half more accurately. These differences were most pronounced with small samples. Sample size requirements for developing cutoff scores for course placement can be substantially reduced if hierarchical logistic regression is used.
The Use of Hierarchical Generalized Linear Model for Item Dimensionality Assessment
Authors: Beretvas S. Natasha , Williams Natasha J.
Published: June 2006

To assess item dimensionality, the following two approaches are described and compared: hierarchical generalized linear model (HGLM) and multidimensional item response theory (MIRT) model. Two generating models are used to simulate dichotomous responses to a 17‐item test: the unidimensional and compensatory two‐dimensional (C2D) models. For C2D data, seven items are modeled to load on the first and second factors, θ1 and θ2, with the remaining 10 items modeled unidimensionally emulating a mathematics test with seven items requiring an additional reading ability dimension. For both types of generated data, the multidimensionality of item responses is investigated using HGLM and MIRT. Comparison of HGLM and MIRT's results are possible through a transformation of items' difficulty estimates into probabilities of a correct response for a hypothetical examinee at the mean on θ and θ2. HGLM and MIRT performed similarly. The benefits of HGLM for item dimensionality analyses are discussed.
Tax evasion and the Proceeds of Crime Act 2002
Authors: Alldridge Peter , Mumford Ann
Published: June 2006

Pursuit of the proceeds of crime has always been central to the criminal justice agenda of Tony Blair‧s Labour Party. In response to Blair‧s moral imperatives and to wider global forces, legislation has been put in place that targets, in various ways, the proceeds of crime. These efforts reached at least a temporary culmination in the Proceeds of Crime Act 2002. The mechanisms directed against property are backed by widespread reporting obligations, set out in the Money Laundering Regulations 2003, implementing the Amending EU Directive. The increased rate of seizures and growing rate of confiscation under the Proceeds of Crime Act 2002 and a number of decided cases under the Act are evidence of the courts ‘doing their bit’. A large industry is now in place for the delivery of the legal and other services the need for which was generated by the Proceeds of Crime Act 2002.
Evaluating tribunal adjudication: administrative justice and asylum appeals
Authors: Thomas Robert
Published: June 2006

This article examines the development, operation and reform of the tribunal system responsible for determining appeals against the refusal of refugee status by the Home Office. Consideration of this particular appellate system is situated within a broader discussion of the criteria and values against which tribunal adjudication systems may be evaluated, By examining asylum appeals, light is shed on the theory and practice of administrative justice with regard to: the problematic nature of ensuring accuracy in tribunal decision-making; the tensions under which appeal procedures operate; the importance of onward appeal rights; and the role of tribunals in policy implementation. The article argues that recent reform of the asylum appeal process, including the introduction of a single tier of appeal, the Asylum and Immigration Tribunal, by the Asylum and Immigration (Treatment of Claimants, etc) Act 2004 and restrictions on legal aid, has been motivated by political considerations and may increase the dificulties in operating an effective appeal process.
State of fear: Britain's ‘compensation culture’ reviewed
Authors: Williams Kevin
Published: June 2006

Assertions that Britain is (or is in danger of becoming) a‘ blame and sue’ society are nowadays so frequently repeated in the media and elsewhere that they have all but become received wisdom. Whether they express a dangerous reality or a passing moral panic deserves serious consideration because of their potential to influence legislative and judicial agendas. This article examines what is meant by the phrase ‘compensation culture’, evaluates the recent evidence concerning it, and attempts to assess whether the concerns expressed are justified.
Justice and the representative parties rule: an overriding interest?
Authors: Seymour Jillaine
Published: June 2006

The recent spate of cases successfully relying on CPR 19.6 has failed to clarify the content of the ‘same interest’ required by the rule. Interpretation of ‘same interest’ must give effect to the overriding objective set out in CPR 1.1(1), which provides that cases must be dealt with ‘justly’ and ‘fairly’. In line with the aspirations of the new Civil Procedure Rules, the overriding objective emphasises improving access to justice and reducing the costs of litigation. A number of recent decisions permitting reliance on CPR 19.6 make particular reference to the rule's potential to achieve these goals. However, reducing costs is only one goal of civil procedure and it is argued that whether a procedure, or its use in particular circumstances, is just or fair depends on balancing those purposes and principles of civil procedural law which it supports against those which it inhibits. This article demonstrates how balanced reference to the principles of procedure supports a test for ‘same interest’ based on finding ‘a common question of law or fact’.
The Role of πσ* Excited States in the Photodissociation of Heteroaromatic Molecules
Authors: Ashfold M. N. R. , Cronin B. , Devine A. L. , Dixon R. N. , Nix M. G. D.
Published: June 2006

High-resolution measurements of the kinetic energies of hydrogen atom fragments formed during ultraviolet photolysis of imidazole, pyrrole, and phenol in the gas phase confirm that N(O)–H bond fission is an important nonradiative decay process from their respective
1
πσ* excited states. The measurements also reveal that the respective cofragments (imidazolyl, pyrrolyl, and phenoxyl) are formed in very limited subsets of their available vibrational states. Identification of these product states yields uniquely detailed insights into the vibronic couplings involved in the photoinduced evolution from parent molecule to ultimate fragments.