bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Log‐Linear Smoothing to Improve Small‐Sample DIF Estimation
Authors: Puhan Gautam , Moses Timothy P. , Yu Lei , Dorans Neil J.
Published: February 2009

This study examined the extent to which log‐linear smoothing could improve the accuracy of differential item functioning (DIF) estimates in small samples of examinees. Examinee responses from a certification test were analyzed using White examinees in the reference group and African American examinees in the focal group. Using a simulation approach, separate DIF estimates for seven small‐sample‐size conditions were obtained using unsmoothed (U) and smoothed (S) score distributions. These small sample U and S DIF estimates were compared to a criterion (i.e., DIF estimates obtained using the unsmoothed total data) to assess their degree of variability (random error) and accuracy (bias). Results indicate that for most studied items smoothing the raw score distributions reduced random error and bias of the DIF estimates, especially in the small‐sample‐size conditions. Implications of these results for operational testing programs are discussed.
A Conditional Exposure Control Method for Multidimensional Adaptive Testing
Authors: Finkelman Matthew , Nering Michael L. , Roussos Louis A.
Published: February 2009

In computerized adaptive testing (CAT), ensuring the security of test items is a crucial practical consideration. A common approach to reducing item theft is to define maximum item exposure rates, i.e., to limit the proportion of examinees to whom a given item can be administered. Numerous methods for controlling exposure rates have been proposed for tests employing the unidimensional 3‐PL model. The present article explores the issues associated with controlling exposure rates when a multidimensional item response theory (MIRT) model is utilized and exposure rates must be controlled conditional upon ability. This situation is complicated by the exponentially increasing number of possible ability values in multiple dimensions. The article introduces a new procedure, called the generalized Stocking‐Lewis method, that controls the exposure rate for students of comparable ability as well as with respect to the overall population. A realistic simulation set compares the new method with three other approaches: Kullback‐Leibler information with no exposure control, Kullback‐Leibler information with unconditional Sympson‐Hetter exposure control, and random item selection.
A Comparison of Bridging Methods in the Analysis of NAEP Trends with the New Race Subgroup Definitions
Authors: Meyer J. Patrick , Setzer J. Carl
Published: February 2009

Recent changes to federal guidelines for the collection of data on race and ethnicity allow respondents to select multiple race categories. Redefining race subgroups in this manner poses problems for research spanning both sets of definitions. NAEP long‐term trends have used the single‐race subgroup definitions for over thirty years. Little is known about the effects of redefining race subgroups on these trends. Bridging methods for reconciling the single and multiple race definitions have been developed. These methods treat single‐race subgroup membership as unknown or missing. A simulation study was conducted to determine the effectiveness of four bridging methods: multiple imputation logistic regression, multiple imputation probabilistic whole assignment, deterministic whole assignment—smallest group, and deterministic whole assignment—largest group. Only the first of these methods incorporates covariate information about examinees into the bridging procedure. The other three methods only use information contained in the race item response. The simulation took into account the percentage of biracial examinees and the missing data mechanism. Results indicated that the multiple imputation logistic regression was often the best performing method. Given that all K‐12 and higher education institutions will be required to use the multiple‐race definitions by 2009, implications for No Child Left Behind and other federally mandated reporting are discussed.
Tracer Method to Determine Residence Time in a Permeable Reactive Barrier
Authors: Bartlett T.R. , Morrison S.J.
Published: February 2009

A method is presented to evaluate ground water residence time in a zero‐valent iron (ZVI) permeable reactive barrier (PRB) using radon‐222 (222Rn) as a radioactive tracer. Residence time is a useful indicator of PRB hydraulic performance, with application to estimating the volumetric rate of ground water flow through a PRB, identifying flow heterogeneity, and characterizing flow conditions over time as a PRB matures. The tracer method relies on monitoring the decay of naturally occurring aqueous 222Rn as ground water flows through a PRB. Application of the method at a PRB site near Monticello, Utah, shows that after 8 years of operation, residence times in the ZVI range from 80 to 486 h and correlate well with chemical parameters (pH, Ca, SO4, and Fe) that indicate the relative residence time. Residence times in this case study are determined directly from the first‐order decay equation because we show no significant emanation of 222Rn within the PRB and no measurable loss of 222Rn other than by radioactive decay.
First-in-Human Trial Participants: Not a Vulnerable Population, but Vulnerable Nonetheless
Authors: Dresser Rebecca
Published: February 2009

Translational science is a 21st century mission. Government officials and industry leaders are making huge investments in an attempt to transform more basic science discoveries into therapeutic applications. Scientists and policymakers express great excitement about the medical advances that could come with the current bench-to-bedside campaign.

A key step in translational science is the move from animal and other preclinical studies to initial human testing. Researchers ability to predict human effects is limited, and first-in-human (FIH) tests present significant uncertainty. Participants in this form of research face risks and can experience serious, even lethal, harm. Well-known incidents involving Jolee Mohr and Jesse Gelsinger, as well as subjects in the 2006 study of the investigational agent TGN1412, show the dangers that can arise in early human research.

The bench-to-bedside campaign will need many volunteers to participate in early human testing. Investigators and regulators must not allow the policy enthusiasm for translational science to overshadow the commitment to protect human subjects. Participants in exploratory research are diverse and as a group lack characteristics usually associated with vulnerable populations, such as impaired decisional ability or economic or educational disadvantage.
Vulnerable Brains: Research Ethics and Neurosurgical Patients
Authors: Ford Paul J.
Published: February 2009

The vulnerability of patients receiving significantly innovative neurosurgical procedures, either as research or as non-standard therapy, presents particularly potent challenges for those attempting to substantially advance clinical Neurosurgical practice in the most ethically and efficacious manner. This beginning formulation has built into it several important notions about research participation, balancing values, and clinical advancement in the context of neurological illness. For the time being, allow vulnerability to act as a placeholder for circumstances or states of being wherein the established checks and balances of power and interest are no longer sufficient in promoting the just treatment of persons. Further, the phrase to substantially advance Neurosurgical practice encompasses radical innovation as well as significant research into new procedures. Finally, few of these explorations involve true randomized placebo controlled trials, but rather they enroll patients rightfully hoping for some benefit by means of undergoing the procedure.

When a neurosurgeon asks me, as an ethicist, to meet with a patient who has medically refractory disease and no good standard therapy options remaining, he is asking for help concerning whether to offer, as a last chance, an unproven therapy as either innovation or research.
iPLEDGE Allegiance to the Pill: Evaluation of Year 1 of a Birth Defect Prevention and Monitoring System
Authors: Schonfeld Toby L. , Amoura N. Jean , Kratochvil Christopher J.
Published: February 2009

Following the widespread occurrence of birth defects from the use of thalidomide to treat nausea during pregnancy in the 1960s and 1970s, the Food and Drug Administration (FDA) became particularly vigilant about the use of therapeutic agents during pregnancy and in women of childbearing potential. The FDA developed a list that categorizes an agent according to the known (and potential unknown) risks to a fetus. The drug thalidomide falls into Category X: agents that have demonstrated clear risk of fetal abnormalities and whose risks outweigh the benefits of use during pregnancy.

Another Category X drug is isotretinoin, commonly known by its trade name Accutane. Isotretinoin is an oral medication prescribed for severe recalcitrant, nodular acne in patients who are unresponsive to conventional therapy. Isotretinoin has been available since 1982, and it remains the only effective treatment for this condition.
Currents in Contemporary Ethics
Authors: Harrell Heather
Published: February 2009

The Human Papillomavirus (HPV) vaccine burst onto the market and the legislative scene nearly simultaneously. Marketed as an amazing medical breakthrough, the vaccine GARDASIL prevents infection with four strains of Human Papillomavirus in nave populations; these four strains are responsible for 70% of cervical cancers and 90% of genital warts. Although most agreed that the vaccine was a wonderful medical advancement with the potential to save women's lives, there was strong disagreement about and a vocal public response to legislative attempts to require girls to receive HPV vaccines for school attendance.

The strong public response to HPV vaccine mandates partially stemmed from the sense that this vaccine is different from previously mandated vaccines because it attempts to prevent disease whose sole route of transmission is through sexual contact. Most other diseases covered by mandated vaccines are spread through the air, with little an individual can do in altering their behavior to prevent infection.
The Causative Alternation
Authors: Schäfer Florian
Published: February 2009

This article discusses the transitivity alternation between lexical causative verbs and their anticausative (inchoative) counterparts. It provides an overview of the semantic, syntactic and morphological properties of verbs undergoing the causative alternation, thereby identifying their cross‐linguistically stable core as well as the areas of variation among languages. The main theoretical lines of analysis proposed in the literature are introduced by an exemplary discussion of accounts within lexical and syntactic frameworks of word formation. The article serves as an introduction to the research on the causative alternation as it presents important results achieved in the earlier literature, but also touches upon more recent findings and their theoretical interpretation. Finally, it addresses the aspects that still await a conclusive analysis.
Coupling Between the Retinal Thermal Isomerization and the Glu194 Residue of Bacteriorhodopsin†
Authors: Lazarova Tzvetana , Querol Enric , Padrós Esteve
Published: February 2009

Glu194 is a residue located at the end of F helix on the extracellular side of the light‐induced proton pump bacteriorhodopsin (BR). Currently, it is well recognized that Glu194 and Glu204 residues, along with water clusters, constitute the proton release group of BR. Here we report that the replacement of Glu194 for Gln affects not only the photocycle of the protein but also has tremendous effect on the all‐trans to 13‐cis thermal isomerization. We studied the pH dependence of the dark adaptation of the E194Q mutant and performed HPLC analysis of the isomer compositions of the light‐ and partially dark‐adapted states of the mutant at several pH values. Our data confirmed that E194Q exhibits extremely slow dark adaptation over a wide range of pH. HPLC data showed that a significantly larger concentration of all‐trans isomer was present in the samples of the E194Q mutant even after prolonged dark adaptation. After 14 days in the dark the 13‐cis to all‐trans ratio was 1:3 in the mutant, compared to 2:1 in the wild type. These data clearly indicate the involvement of Glu194 in control of the rate of all‐trans to 13‐cis thermal isomerization.
Genetic Aspects of the Manto‐type Copper Deposits Based on Geochemical Studies of North Chilean Deposits
Authors: Kojima Shoji , Trista‐Aguilera Dania , Hayashi Ken‐ichiro
Published: February 2009

Recent studies on mineralogy, geochronology, fluid inclusion and stable isotope (Pb, Os, S, C, O, Sr) characteristics were reviewed to determine constraints for genetic models of the Chilean manto‐type copper deposits. The Chilean manto‐type deposits are divided into the two geologic categories of the northern areas (Arica–Iquique, Tocopilla–Taltal) and the central areas (Copiapó, La Serena, Santiago). The former is distributed in the coastal range composed of Jurassic andesite‐dominated volcano‐sedimentary piles and younger plutonic intrusions, and yields chalcocite (‐digenite) and bornite as the principal hypogene copper sulfides. The latter is hosted mostly in Lower Cretaceous volcano‐sedimentary sequences, and has chalcopyrite‐rich mineral associations. The fluid inclusion data indicate that the primary copper mineralization was commonly generated in the temperature range 150–360°C under low‐pressure conditions near the boiling curve, mediated with relatively saline brines. Generally, homogeneous Pb and S isotope compositions for primary copper minerals imply direct magma source or leaching of igneous rocks. Pb and Os isotope data published for some deposits, however, suggest that ore‐forming metals were derived mainly from the volcano‐sedimentary host rocks. The noticeably negative isotope ratios of primary sulfide sulfur and hydrothermal calcite carbon of some central area deposits indicate influx of sedimentary rock components, and the high 87Sr/86Sr initial ratios of hydrothermal calcite from the Tocopilla–Taltal area deposits imply contribution of the contemporaneous seawater or marine carbonates. These isotopic constraints imply a formation mechanism in which the Chilean manto‐type copper deposits formed epigenetically in the process of hydrothermal interaction of non‐magmatic surface‐derived brine with the volcano‐sedimentary host rocks, which is inferred to have been induced by a deep‐seated plutonic complex as the possible heat source.
Occurrence of Uraniferous Iron Grains at Gabal Gattar, El Missikat and El Erediya Granites in Eastern Desert of Egypt
Authors: Raslan Mohamed F.
Published: February 2009

Uraniferous iron grains occur in some radioactive granite plutons in the Eastern Desert of Egypt. Modal analysis of these grains indicates that weight abundance of uraniferous grains amounts to 17.50%, 18.00% and 26.00% of the total accessory heavy minerals of the uranium‐mineralized samples of Gabal Gattar, El Missikat and El Erediya, respectively. These grains are mainly restricted to shear zones associated with strong hematitization, and occur either as fracture fillings or as interstitial grains among the main rock‐forming minerals. Uraniferous iron grains are mainly composed of uranophane and β‐uranophane coated and stained with limonite. These grains represent the main radioactive minerals in addition to the bright canary yellow to yellow uranophane and β‐uranophane mineral grains. The data obtained on scanning electron microscopy and electron microprobe analysis confirm the abundance of iron in the darker colored varieties with respect to the light colored varieties. This mode of occurrence of the uranium minerals requires special consideration during mineral processing by physical means.
Isolation and characterization of new microsatellite markers for rose bitterlings, Rhodeus ocellatus
Authors: SHIRAI Y. , IKEDA S. , TAJIMA S.
Published: February 2009

The Japanese rose bitterling (Rhodeus ocellatus kurumeus) is facing imminent extinction because of hybridization and competition from an invasive alien subspecies (Rhodeus ocellatus ocellatus). Eleven new microsatellite markers for the two subspecies were developed using dinucleotide repeat specific polymerase chain reaction. The number of alleles per locus and the heterozygosity in R. o. kurumeus were lower than those in R. o. ocellatus. Most of these microsatellite markers were successfully cross‐amplified in three Acheilognathinae species.
Characterization of single nucleotide polymorphism markers for the green sea turtle (Chelonia mydas)
Authors: RODEN SUZANNE E. , DUTTON PETER H. , MORIN PHILLIP A.
Published: February 2009

We present data on 29 new single nucleotide polymorphism assays for the green sea turtle, Chelonia mydas. DNA extracts from 39 green turtles were used for two methods of single nucleotide polymorphism discovery. The first approach employed an amplified fragment length polymorphism technique. The second technique screened a microsatellite library. Allele‐specific amplification assays were developed for high‐throughput single nucleotide polymorphism genotyping and tested on two Pacific C. mydas nesting populations. Observed heterozygosities ranged from 0 to 0.95 for a Hawaiian population and from 0 to 0.85 for a Galapagos population. Each of the populations had one locus out of Hardy–Weinberg equilibrium, SSCM2b and SSCM5 for Hawaii and Galapagos, respectively. No loci showed significant genotypic linkage disequilibrium across an expanded set of four Pacific nesting populations. However, two loci, SSCM4 and SSCM10b showed linkage disequilibrium across three populations indicating possible association.
A combination of techniques proves useful in the development of nuclear markers in the newt genus Triturus
Authors: ESPREGUEIRA THEMUDO G. , BABIK W. , ARNTZEN J. W.
Published: February 2009

To increase the number of markers available for study of phylogeny and phylogeography in the newt genus Triturus, we developed and tested 59 primer pairs using three different techniques. Primers were obtained from published sources, by designing exon‐primed intron‐crossing primers and from randomly cloned anonymous nuclear DNA fragments. Successful polymerase chain reaction products were cloned and sequenced. Five fragments were successfully amplified and sequenced for six species of Triturus: intron 7 of the β‐fibrinogen gene (βfibint7), third intron of the calreticulin gene (CalintC), the 11th intron of the α‐subunit of the platelet derived growth factor receptor (PDGFRα) and two anonymous markers (Cri1 and Cri4). The average percentage species divergence across all the markers is low (c. 3%), compared to what has been found in mitochondrial DNA (25–30%).
Identifying gastropod spawn from DNA barcodes: possible but not yet practicable
Authors: PUILLANDRE N , STRONG E. E. , BOUCHET P. , BOISSELIER M.‐C. , COULOUX A. , SAMADI S
Published: February 2009

Identifying life stages of species with complex life histories is problematic as species are often only known and/or described from a single stage. DNA barcoding has been touted as an important tool for linking life‐history stages of the same species. To test the current efficacy of DNA barcodes for identifying unknown mollusk life stages, 24 marine gastropod egg capsules were collected off the Philippines in deep water and sequenced for partial fragments of the COI, 16S and 12S mitochondrial genes. Two egg capsules of known shallow‐water Mediterranean species were used to calibrate the method. These sequences were compared to those available in GenBank and the Barcode of Life Database (BOLD). Using COI sequences alone, only a single Mediterranean egg capsule was identified to species, and a single Philippine egg capsule was identified tentatively to genus; all other COI sequences recovered matches between 76% and 90% with sequences from BOLD and GenBank. Similarity‐based identification using all three markers confirmed the Mediterranean specimens’ identifications. A phylogenetic approach was also implemented to confirm similarity‐based identifications and provide a higher‐taxonomic identification when species‐level identifications were not possible. Comparison of available GenBank sequences to the diversity curve of a well‐sampled coral reef habitat in New Caledonia highlights the poor taxonomic coverage achieved at present in existing genetic databases, emphasizing the need to develop DNA barcoding projects for megadiverse and often taxonomically challenging groups such as mollusks, to fully realize its potential as an identification and discovery tool.
Development of 11 polymorphic microsatellite markers in a macrophyte of conservation concern, Vallisneria americana Michaux (Hydrocharitaceae)
Authors: BURNETT JR ROBERT K. , LLOYD MICHAEL W. , ENGELHARDT KATHARINA A. M. , NEEL MAILE C.
Published: February 2009

Vallisneria americana Michaux (wild celery) is currently a target of submersed aquatic vegetation restoration efforts in the Chesapeake Bay watershed. To aid these efforts, we have developed 11 polymorphic microsatellite markers to assess the distribution and degree of genetic diversity in both restored and naturally occurring populations in the Chesapeake Bay. In 59 individuals from two populations, we detected two to 10 total alleles per locus. Observed heterozygosity ranged from 0.125 to 0.929, and two loci exhibited significant deviations from Hardy–Weinberg equilibrium in at least one of the populations assayed.
Microsatellite loci from the endemic Southern Ocean octopus Adelieledone polymorpha (Robson, 1930)
Authors: STRUGNELL JAN M. , ALLCOCK A. LOUISE , WATTS PHILLIP C.
Published: February 2009

To determine the pattern of spatial genetic structure in the endemic Southern Ocean octopus Adelieledone polymorpha, microsatellite loci were isolated from partial genomic libraries enriched for repetitive DNA motifs. Seven dinucleotide and two trinucleotide microsatellite loci were isolated successfully and levels of polymorphism were quantified in 34 individuals sampled from the Southern Ocean near South Georgia. No pairs of microsatellite loci were linked significantly; however, one locus deviated (P < 0.05) from Hardy–Weinberg equilibrium. Overall, the nine loci produced between five and 16 alleles, with observed and expected heterozygosities varying between 0.22 and 0.86 and between 0.21 and 0.94 respectively. This is the first description of microsatellite loci from an octopus endemic to the Southern Ocean, and these genetic markers are being used to quantify spatial structure within A. polymorpha.
Characterization and cross‐amplification of 13 microsatellite loci in the northern pine processionary moth, Thaumetopoea pinivora (Lepidoptera: Notodontidae)
Authors: CASSEL‐LUNDHAGEN ANNA , RONNÅS CECILIA , FRAUENFELDER NATHALIE
Published: February 2009

Thirteen polymorphic microsatellite loci were developed for the northern pine processionary moth (Thaumetopoea pinivora) and tested for cross‐amplification in seven other species within the Thaumetopoea family. Number of alleles ranged from two to 10 when at least 28 individuals from one population were screened and one locus, Thapin06, appears to be sex linked. Expected heterozygosity ranged from 0.094 to 0.856 and observed heterozygosity ranged from 0.097 to 0.806. Amplification success varied between sister species, with two up to seven loci being successfully amplified. The described loci will be valuable for studying the population genetic structure and dispersal behaviour of this forest pest.
Isolation and characterization of nine microsatellite loci in an ant‐tended treehopper Publilia concava
Authors: CHHATRE VIKRAM , MORALES MANUEL A. , ABBOT PATRICK
Published: February 2009

Publilia concava is an eastern North American membracid commonly occurring in large but spatially patchy aggregations, primarily on the host plant Solidago altissima. Like other myrmecophiles, P. concava provides sugary excretions to ants in return for the various protective, competitive or even sanitary benefits that ants provide. We developed nine microsatellite loci from P. concava. Mean per locus allele number was 6.78, and observed heterozygosities ranged from 0.03 to 0.850. One locus exhibited significant heterozygote deficit, possibly due to the presence of null alleles. These markers provide important tools for future spatial ecological studies in this model system for the study of mutualism.
Griscelli syndrome: a model system to study vesicular trafficking
Authors: Van Gele Mireille , Dynoodt Peter , Lambert Jo
Published: February 2009

Griscelli syndrome (GS) is a rare autosomal recessive disorder caused by mutations in either the myosin VA (GS1), RAB27A (GS2) or melanophilin (GS3) genes. The three GS subtypes are commonly characterized by pigment dilution of the skin and hair, due to defects involving melanosome transport in melanocytes. Here, we review how detailed studies concerning GS have contributed to a better understanding of the molecular mechanisms involved in vesicle transport and membrane trafficking processes. Additionally, we demonstrate that the identification and biological analysis of novel disease‐causing mutations highlighted the functional importance of the RAB27A‐MLPH‐MYO5A tripartite complex in intracellular melanosome transport. As the small GTPase Rab27a is able to interact with multiple effectors, including Slp2‐a and Myrip, we report on their presumed role in melanosome transport. Furthermore, we summarize data suggesting that RAB27B and RAB27A are functionally redundant and hereby provide further insight into the pathogenesis of GS2. Finally, we discuss how the gathered knowledge about the RAB27A‐MLPH‐MYO5A tripartite complex can be translated into a possible therapeutic application to reduce (hyper)pigmentation of the skin.
Changes in soil organic carbon under biofuel crops
Authors: ANDERSON‐TEIXEIRA KRISTINA J. , DAVIS SARAH C. , MASTERS MICHAEL D. , DELUCIA EVAN H.
Published: February 2009

One potentially significant impact of growing biofuel crops will be the sequestration or release of carbon (C) in soil. Soil organic carbon (SOC) represents an important C sink in the lifecycle C balances of biofuels and strongly influences soil quality. We assembled and analyzed published estimates of SOC change following conversion of natural or agricultural land to biofuel crops of corn with residue harvest, sugarcane, Miscanthus x giganteus, switchgrass, or restored prairie. We estimated SOC losses associated with land conversion and rates of change in SOC over time by regressing net change in SOC relative to a control against age since establishment year. Conversion of uncultivated land to biofuel agriculture resulted in significant SOC losses – an effect that was most pronounced when native land was converted to sugarcane agriculture. Corn residue harvest (at 25–100% removal) consistently resulted in SOC losses averaging 3–8 Mg ha−1 in the top 30 cm, whereas SOC accumulated under all four perennial grasses, with SOC accumulation rates averaging <1 Mg ha−1 yr−1 in the top 30 cm. More intensive harvests led to decreased C gains or increased C losses – an effect that was particularly clear for residue harvest in corn. Direct or indirect conversion of previously uncultivated land for biofuel agriculture will result in SOC losses that counteract the benefits of fossil fuel displacement. Additionally, SOC losses under corn residue harvest imply that its potential to offset C emissions may be overestimated, whereas SOC sequestration under perennial grasses represents an additional benefit that has rarely been accounted for in life cycle analyses of biofuels.
Putting Thoughts to Work: Concepts, Systematicity, and Stimulus‐Independence*
Authors: CAMP ELISABETH
Published: February 2009

I argue that we can reconcile two seemingly incompatible traditions for thinking about concepts. On the one hand, many cognitive scientists assume that the systematic redeployment of representational abilities suffices for having concepts. On the other hand, a long philosophical tradition maintains that language is necessary for genuinely conceptual thought. I argue that on a theoretically useful and empirically plausible concept of ‘concept’, it is necessary and sufficient for conceptual thought that a thinker be able to entertain many of the potential thoughts produced by recombining her representational abilities apart from a direct confrontation with the states of affairs being represented. Such representational abilities support a cognitive engagement with the world that is flexible, abstract, and active.
Cooperative Advertising and Pricing in a Dynamic Stochastic Supply Chain: Feedback Stackelberg Strategies
Authors: He Xiuli , Prasad Ashutosh , Sethi Suresh P.
Published: February 2009

Cooperative (co‐op) advertising is an important instrument for aligning manufacturer and retailer decisions in supply chains. In this, the manufacturer announces a co‐op advertising policy, i.e., a participation rate that specifies the percentage of the retailer's advertising expenditure that it will provide. In addition, it also announces the wholesale price. In response, the retailer chooses its optimal advertising and pricing policies. We model this supply chain problem as a stochastic Stackelberg differential game whose dynamics follows Sethi's stochastic sales‐advertising model. We obtain the condition when offering co‐op advertising is optimal for the manufacturer. We provide in feedback form the optimal advertising and pricing policies for the manufacturer and the retailer. We contrast the results with the advertising and price decisions of the vertically integrated channel, and suggest a method for coordinating the channel.
Lifetime Buy Decisions with Multiple Obsolete Parts
Authors: Bradley James R. , Guerrero Héctor H.
Published: February 2009

L ife‐cycle mismatch occurs when the life cycles of parts end before the life cycles of the products in which those parts are used. Lifetime buys are one tactic for mitigating the effect of part obsolescence, where a quantity of parts is purchased for the remaining life of a product. We extend prior work that determines optimal lifetime buy quantities for one product with one obsolete part by providing an analytic solution and two simple heuristic policies for the optimal lifetime buy quantities when many parts become obsolete over a product's life cycle. We determine which of our two heuristics is most accurate for different product life cycles, which yields a metaheuristic with increased accuracy. That analysis also reveals critical perspectives in making lifetime buy decisions with nonstationary life‐cycle demand patterns.
Sub-100 μm SnAg Solder Bumping Technology and the Bump Reliability
Authors: Lin Xiaoqin , Luo Le
Published: February 2009

Lead-free solder bumping and its related interconnection and reliability are becoming one of the important issues in today’s electronic packaging industry. In this paper, alloy electroplating was used as SnAg solder bumping process. Multiple reflow was preformed on as-plated solder bumps. Scanning electron microscopy and energy dispersive X-ray analysis were used to investigate the intermetallic compound and microvoids of cross-sectioned solder bump. Shear test was used to evaluate the reliabilities of the SnAg bumps. The 13×13 area-array Sn/3.0Ag solder bumps of 70 μm in height and 90 μm in diameter were fabricated with a smooth and shiny surface and with a uniform distribution of Ag. During multireflow, the scalloped Cu6Sn5 phase grows by a ripening process. Volume shrinkage was the main reason for the formation of microvoids during multireflow. The average shear strength of solder bumps on TiW/Cu under bump metallurgy (UBM) increased with reflow times. The electroplating process is suitable for mass production of well-controlled geometry and uniformity of SnAg solder bumps. Microvoids have trivial negative impacts on the solder bonds. The combination of TiW/Cu UBM and SnAg solder is reliable.
Correlating Drop Impact Simulations With Drop Impact Testing Using High-Speed Camera Measurements
Authors: Zaal J. J. M. , van Driel W. D. , Kessels F. J. H. G. , Zhang G. Q.
Published: February 2009

The increased use of mobile appliances such as mobile phones and navigation systems in today’s society has resulted in an increase in reliability issues related to drop performance. Mobile appliances are dropped several times during their lifespan and the product is required to survive common drop accidents. A widely accepted method to assess the drop reliability of microelectronics on board-level is the drop impact test. This test has been standardized by international councils such as Joint Electron Device Engineering Council and is widely adopted throughout the industry. In this research the solder loading is investigated by combining high-speed camera measurements of several drop impact tests with verified finite element models. These simulation models are developed in order to gain an insight on the loading pattern of solder joints based on interconnect layout, drop conditions, and product specifications prior to physical prototyping. Deflections and frequencies during drop testing are measured using a high-speed camera setup. The high-speed camera experiments are performed on two levels: machine level (rebounds with and without a catcher) and product level (with different levels of energy and different pulse times). Parametric (dynamic and quasistatic) 3D models are developed to predict the drop impact performance. The experimental results are used to verify and enhance the simulation models, e.g., by tuning the damping parameters. As a result, the verified models can be used to determine the location of the critical solder joint and to obtain estimates of the solder lifetime performance.
Thermal Stresses Due to Laser Welding in Bridge-Wire Initiators
Authors: Maughan Michael R. , Stephens Robert R. , Blackketter Donald M. , Rink Karl K.
Published: February 2009

In ongoing research at the University of Idaho, potential failure mechanisms of airbag initiators are being investigated. Cracking of the cylindrical glass-to-metal seal (GTMS) present in these devices has been observed. These cracks could be a path for moist gas to diffuse into the initiator, potentially leading to bridge-wire degradation and late-fire or no-fire initiator failure. Previous research has shown that cracking may be caused by thermal stresses induced by the GTMS formation process. The goal of this research was to determine if welding of the output-can onto the initiator header could produce stresses in the glass great enough to cause cracking. A finite element analysis solution was chosen to model the transient heat transfer and temperature distribution in the initiator assembly during the welding process. The thermal stresses were calculated with a mechanical analysis once the temperature distribution was determined. Compressive stresses induced by pressing the header assembly into the output-can as part of the manufacturing process were also investigated with a closed-form mechanics of materials solution. The welding thermal stress model initially predicted radial stresses greater than the tangential stresses. This conflicts with observed radial cracks, which would be induced by tangential stresses. Subsequent investigations with an interface region stiffness model showed that when the stiffness of the bond at the pin-glass and glass-header interfaces is decreased, the maximum radial stress is greatly reduced and that the maximum tangential stress stays relatively constant. These predicted stresses were still in excess of the range of glass strengths reported in literature. However, superposition of the compressive stresses due to the press-fit and residual stresses created when the GTMS is formed with these thermal stresses results in the total radial and tangential stresses being on the same order as the reported strengths. It was determined that when initiators are overheated during welding, radial stresses due to thermal expansion cause the bond to fail and separation to occur over a portion of the pin-glass interface. Tangential stresses developed for the same reason are sufficient enough to cause radial cracking, where the bond is still intact.
Thermal Solution Maps: A Strategy for Thermal Design of Three-Dimensional Packages
Authors: Rayasam M. , Chaparala S. , Farnam D. , Sammakia B. G. , Subbarayan G.
Published: February 2009

Three-dimensional (3D) packages are of considerable interest at the present time as a means for heterogeneous high-performance integration of disparate digital, analog, optical, and MEMS technologies. However, their design is challenged by several issues, including the appropriate choice of thermal solution to be used in the 3D stack. Suboptimal placement of heat sources/sinks leads to hot spots, which are detrimental to package reliability. The broad goals of this study are to determine the appropriate cost and reliability-constrained heat-sinking solutions through an optimal placement of spatially distributed energy transporting elements. The heat-sinking solutions considered in this study include microchannels, and thermal vias. We conduct a microchannel analysis to develop a reduced model of the heat and mass transfer characteristics of the microchannel. We also develop optimization techniques and tools for thermal solution design of three-dimensional packages. We use a nonuniform “real-life” microprocessor power map for the illustration of the procedure. We subsequently obtain the optimal size and location of the thermal vias and microchannels in a 3D stack by minimizing a proposed multi-objective criteria. Finally, we develop and illustrate the notion of design maps that would guide the designers in the selection of appropriate thermal solution technologies for 3D packages.
Two-Dimensional Navier–Stokes Turbulence in Bounded Domains
Authors: Clercx H. J. H. , van Heijst G. J. F.
Published: February 2009

In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the past 10 years. The scope of this review concerns the self-organization of two-dimensional Navier–Stokes turbulence, the quasi-stationary final states in domains with no-slip boundaries, the role of the lateral no-slip walls on two-dimensional turbulence, and their role on the possible destabilization of domain-sized vortices. The overview of the laboratory experiments on quasi-two-dimensional turbulence is restricted to include only those carried out in thin electromagnetically forced shallow fluid layers and in stratified fluids. The effects of the quasi-two-dimensional character of the turbulence in the laboratory experiments will be discussed briefly. As a supplement, the main results from numerical simulations of forced and decaying two-dimensional turbulence in rectangular and circular domains, thus explicitly taking into account the lateral sidewalls, will be summarized and compared with the experimental observations.
Noise suppression in scatter correction for cone‐beam CT
Authors: Zhu Lei , Wang Jing , Xing Lei
Published: February 2009

Scatter correction is crucial to the quality of reconstructed images in x‐ray cone‐beam computed tomography (CBCT). Most of existing scatter correction methods assume smooth scatter distributions. The high‐frequency scatter noise remains in the projection images even after a perfect scatter correction. In this paper, using a clinical CBCT system and a measurement‐based scatter correction, the authors show that a scatter correction alone does not provide satisfactory image quality and the loss of the contrast‐to‐noise ratio (CNR) of the scatter corrected image may overwrite the benefit of scatter removal. To circumvent the problem and truly gain from scatter correction, an effective scatter noise suppression method must be in place. They analyze the noise properties in the projections after scatter correction and propose to use a penalized weighted least‐squares (PWLS) algorithm to reduce the noise in the reconstructed images. Experimental results on an evaluation phantom (Catphan©600) show that the proposed algorithm further reduces the reconstruction error in a scatter corrected image from 10.6% to 1.7% and increases the CNR by a factor of 3.6. Significant image quality improvement is also shown in the results on an anthropomorphic phantom, in which the global noise level is reduced and the local streaking artifacts around bones are suppressed.
Biological equivalent dose studies for dose escalation in the stereotactic synchrotron radiation therapy clinical trials
Authors: Prezado Y. , Fois G. , Edouard M. , Nemoz C. , Renier M. , Requardt H. , Estève F. , Adam J. F. , Elleaume H. , Bravin A.
Published: February 2009

Synchrotron radiation is an innovative tool for the treatment of brain tumors. In the stereotactic synchrotron radiation therapy (SSRT) technique a radiation dose enhancement specific to the tumor is obtained. The tumor is loaded with a high atomic number element and it is irradiated in stereotactic conditions from several entrance angles. The aim of this work was to assess dosimetric properties of the SSRT for preparing clinical trials at the European Synchrotron Radiation Facility (ESRF). To estimate the possible risks, the doses received by the tumor and healthy tissues in the future clinical conditions have been calculated by using Monte Carlo simulations (PENELOPE code). The dose enhancement factors have been determined for different iodine concentrations in the tumor, several tumor positions, tumor sizes, and different beam sizes. A scheme for the dose escalation in the various phases of the clinical trials has been proposed. The biological equivalent doses and the normalized total doses received by the skull have been calculated in order to assure that the tolerance values are not reached.
Radiotherapy margin design with particular consideration of high curvature CTVs
Authors: Herschtal Alan , Kron Tomas , Fox Chris
Published: February 2009

In applying 3D conformal radiation therapy to a tumor clinical target volume (CTV), a margin is added around the CTV to account for any sources of error in the application of treatment which may result in misalignment between the CTV and the dose distribution actually delivered. The volume enclosed within the CTV plus the margin is known as the PTV, or planning target volume. The larger the errors are anticipated to be, the wider the margin will need to be to accommodate those errors. Based on the approach of van Herk et al. [“The probability of correct target dosage: Dose‐population histograms for deriving treatment margins in radiotherapy,” Int. J. Radiat. Oncol. Biol., Phys. 47(4), 1121–1135 (2000)] this paper develops the mathematical theory behind the calculation of the margin width required to ensure that the entire CTV receives sufficiently high dose with sufficiently high probability. The margin recipe developed not only considers the magnitude of the errors but also includes a term to adjust for curved CTV surfaces. In doing so, the accuracy of the margin recipe is enhanced yet remains mathematically concise enough to be readily implemented in the clinical setting. The results are particularly relevant for clinical situations in which the uncertainties in treatment are large relative to the size of the CTV.
The delta envelope: A technique for dose distribution comparison
Authors: Blanpain Baptiste , Mercier David
Published: February 2009

The index is a tool that compares a dose distribution with a reference distribution by combining dose‐difference and distance‐to‐agreement criteria. It has been widely used for ten years despite its high computational cost. This cost is due to both a search process for each reference point and the necessity to remove overestimations caused by the discrete nature of dose grids. The method proposed in this paper is much faster since it avoids both these problems. It consists in computing the envelope formed by the ellipsoids around the points of the reference distribution. This envelope provides dose‐difference tolerances that are then used to create new indices, called the indices, that provide useful information to interpret the deviations. Applied to both 1D and 2D test cases and compared to the index, the indices proved to be very accurate and intuitive. Their computational efficiency was evaluated on a 3D case: the envelope can be computed in on a grid. Moreover it can be precomputed if the reference dose is known in advance. Then the indices are obtained in less than .
Clinic based transfer of the calibration coefficient using a linear accelerator
Authors: Abdel‐Rahman W. , Evans M. D. C. , Serré L. , McCaffrey J. P. , Podgorsak E. B. , Seuntjens J. P.
Published: February 2009

Ionization chambers used for reference dosimetry require a local secondary standard ionization chamber with a absorbed dose to water calibration coefficient traceable to a national primary standards dosimetry laboratory or an accredited secondary dosimetry calibration laboratory. Clinic based (in‐house) transfer of this coefficient to tertiary reference ionization chambers has traditionally been accomplished with chamber cross calibration in water using a beam; however, access to teletherapy machines has become increasingly limited for clinic based physicists. In this work, the accuracy of alternative methods of transferring the calibration coefficient using 6 and 18 MV photon beams from a linear accelerator in lieu of has been investigated for five different setups and four commonly used chamber types.
Electromagnetic tracking in the clinical environment
Authors: Yaniv Ziv , Wilson Emmanuel , Lindisch David , Cleary Kevin
Published: February 2009

When choosing an electromagnetic tracking system (EMTS) for image‐guided procedures several factors must be taken into consideration. Among others these include the system's refresh rate, the number of sensors that need to be tracked, the size of the navigated region, the system interaction with the environment, whether the sensors can be embedded into the tools and provide the desired transformation data, and tracking accuracy and robustness. To date, the only factors that have been studied extensively are the accuracy and the susceptibility of EMTSs to distortions caused by ferromagnetic materials. In this paper the authors shift the focus from analysis of system accuracy and stability to the broader set of factors influencing the utility of EMTS in the clinical environment. The authors provide an analysis based on all of the factors specified above, as assessed in three clinical environments. They evaluate two commercial tracking systems, the Aurora system from Northern Digital Inc., and the 3D Guidance system with three different field generators from Ascension Technology Corp. The authors show that these systems are applicable to specific procedures and specific environments, but that currently, no single system configuration provides a comprehensive solution across procedures and environments.