bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoreductive Self-Assembly from [MoVI7O24]6− to Anti-Tumoral [H2MoV12O28(OH)12(MoVIO3)4]6− in Aqueous Media
Authors: Yamase Toshihiro , Ishikawa Eri
Published: August 2008

The long-term photolysis of [iPrNH3]6[Mo7O24]·3H2O in aqueous solutions at pH 5–6 is found to provide the formation of anti-tumoral [H2MoV12O28(OH)12(MoVIO3)4]6− species (1a), the core of which is a well-known ε-isomer ({ε-MoV12}) of the Keggin anion showing edge-shared MoVO6 octahedra in the arrangement of six diamagnetic MoV2-pairs with a MoV–MoV bond distance of 2.6 Å. To obtain structural insight of 1a in aqueous solutions from a viewpoint of the pharmaceutical mechanism, 95Mo NMR, electronic absorption, IR, and electrospray ionization mass (ESI-MS) spectrometries of 1a are investigated and indicate that the {ε-MoV12} core remains intact at pH 5–9 and that a detachment of the MoVIO3 unit from 1a proceeds at high pH level with an accompanying increase in the electronic transition of the MoV2 pairs. Highly positive and negative potentials (0.8–0.9 and −1.1– −1.2 V) of oxidation and reduction current peaks for the MoV2 pairs of 1a assist the structural stability of the ε-Keggin {MoV12} framework in aerobic solutions. A plausible mechanism of the photoreductive self-assembly of [MoVI7O24]6− to 1a through two- and four-electron reduction species, [MoV2Mo5O22(OH)2]6− ({MoV2MoVI5}) and [MoV4Mo3O20(OH)4]6− ({MoV4MoVI3}), is proposed in terms of the formation of a half molecule ([HMoV6O18(OH)6(MoVIO3)2]11−) of 1a, which is suggested by ESI-MS spectrometry of the photolytes.
Three-Dimensional Manganese Octacyanoniobate-Based Pyroelectric Ferrimagnet
Authors: Kosaka Wataru , Hashimoto Kazuhito , Ohkoshi Shin-ichi
Published: August 2008

A novel pyroelectric ferrimagnet, [{MnII(pyrazine)(H2O)2}{MnII(H2O)2}{NbIV(CN)8}]·4H2O, is synthesized. The crystal consists of an NbIV–CN–MnII linked three-dimensional network, which has an electric polarization along the b axis. This compound exhibits ferrimagnetism with a Curie temperature of 48 K due to the antiparallel ordering of magnetic spins on NbIV (S=1⁄2) and those on MnII (S=5⁄2).
Regioselective Synthesis of Antipodal β-Tetrabrominated meso-Tetraarylporphyrins
Authors: Bhyrappa Puttaiah , Velkannan Veerapandian , Karunanithi Karuppaiah , Varghese Babu , Harikrishna
Published: August 2008

A series of meso-tetraarylporphyrins bearing electron-donor or electron-withdrawing substituents at the meso-phenyl groups were examined for antipodal β-pyrrole tetrabromination using different brominating agents. Porphyrins bearing electron-donor substituents undergo bromination at moderate temperatures with N-bromosuccinimide as the brominating agent while the electron-deficient porphyrins require liq. Br2 at room temperature. The brominated porphyrins were isolated in moderate to very good yields. Synthesized compounds were characterized by electronic absorption, 1H NMR, and mass spectroscopic methods. Regioselectivity of an electron-deficient porphyrin, 2,3,12,13-tetrabromo-5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin was examined by single-crystal X-ray structure analysis and showed antipodal β-pyrrole bromo substitution.
Facile Preparation of Polytopic Azoles: Synthesis, Characterization, and X-ray Powder Diffraction Studies of 1,4-Bis(pyrazol-4-yl)- and 1,4-Bis(tetrazol-5-yl)benzene
Authors: Maspero Angelo , Galli Simona , Masciocchi Norberto , Palmisano Giovanni
Published: August 2008

Two polytopic azoles, 1,4-bis(pyrazol-4-yl)benzene and 1,4-bis(tetrazol-5-yl)benzene, were prepared in sizable amounts by high yield syntheses employing, in mild conditions, cheap reactants and, whenever possible, aqueous solutions. The two species were characterized by 1H and 13C NMR spectroscopy and by thermal analyses, the latter evidencing their high chemical and thermal stability. X-ray powder diffraction methods disclosed their non isomorphous crystal structures, in which individual molecules interact via hydrogen bonds to form two-dimensional sheets.
XAFS Analysis of Ti and Ni Dissolution from Pure Ti, Ni–Ti Alloy, and SUS304 in Soft Tissues
Authors: Uo Motohiro , Asakura Kiyotaka , Tamura Kazuchika , Totsuka Yasunori , Abe Shigeaki , Akasaka Tsukasa , Watari Fumio
Published: August 2008

Ti, a Ni–Ti alloy, and stainless steel (SUS304) were implanted in rat soft tissues for 6 months. The chemical states of the component elements contained in the tissues surrounding those metallic implants were analyzed by fluorescence X-ray absorption fine structure (XAFS). Titanium oxide and a nickel aquo complex, which would be caused by the erosion of Ti and Ni, were detected in the surrounding tissues. The concentrations of Ti and Ni in the tissues were 1–3 and 300 ppm, respectively. Thus, the dissolved conditions and concentrations of those practical metallic materials in vivo were successfully confirmed.
Quenching and Recovery of Fluorescence of Azobenzenes by Acid–Base Reactions
Authors: Yoshino Junro , Kano Naokazu , Kawashima Takayuki
Published: August 2008

2-[Bis(pentafluorophenyl)boryl]-4′-(dimethylamino)azobenzene was synthesized as a hybrid of the intensely fluorescent 2-borylazobenzene and the pH-responsive 4-(dimethylamino)azobenzene. Quenching and recovery of fluorescence of this azobenzene were reversibly performed by addition of trifluoroacetic acid and triethylamine, respectively. The reason of fluorescence quenching was investigated by theoretical calculations.
Efficient Entry to the Pyrroloquinoline Core of Martinella Alkaloids via Novel Base-catalyzed Mukaiyama–Mannich Reaction
Authors: Ikeda Shuhei , Shibuya Masatoshi , Kanoh Naoki , Iwabuchi Yoshiharu
Published: August 2008

An efficient enantiocontrolled entry to Martinella alkaloids was achieved based on the unexpected discovery that a catalytic amount of KH/dicyclohexyl-18-crown-6 induced an intramolecular Mukaiyama–Mannich reaction of imine 3, leading to a cascade sequence involving a novel silyl group migration to furnish the pyrroloquinoline core 6.
Drastic Enhancement of Cycle Lifetime of Electrochromic Devices Using Polysilsesquioxane as an Anchoring Agent
Authors: Imae Ichiro , Takenaka Youichi , Tokita Daisuke , Ooyama Yousuke , Komaguchi Kenji , Harima Yutaka
Published: August 2008

Polysilsesquioxanes were obtained by hydrolysis of viologens having one or two triethoxysilyl groups, followed by their polycondensation, and anchored on the surface of an ITO electrode. The electrochromic properties of the polysilsesquioxanes were investigated and its component was optimized to enhance the cycle lifetime.
Heptanuclear Nickel(II) Wheel with Eight Redox Active Ferrocenyl Groups
Authors: Mitsumoto Kiyotaka , Nihei Masayuki , Shiga Takuya , Oshio Hiroki
Published: August 2008

The reaction of Ni(ClO4)2·6H2O with 3-ferrocenyl-5-(2-pyridyl)pyrazole (Hfcpp) and Et3N in acetonitrile yielded a pentadecanuclear heterometallic complex of [Ni7(fcpp)8(OH)4](ClO4)2·6CH3CN (1). Complex 1 has a heptanuclear wheel core composed of seven NiII ions, and eight ferrocenyl groups are attached to the core through pyrazolyl groups. Magnetic susceptibility measurements for 1 revealed that overall antiferromagnetic interactions are operative within the heptanuclear core.
Extraction of Electrons from H2 with a NiIRuI Catalyst
Authors: Matsumoto Takahiro , Kure Bunsho , Ogo Seiji
Published: August 2008

The mechanism of extraction of electrons from H2 catalyzed by hydrogenases has proven challenging to elucidate. Catalytic extraction of electrons from H2 has been achieved by use of a low-valent NiIRuI complex [NiI(μ-SR)2RuI(η6-C6Me6)]{(μ-SR)2 = N,N′-dimethyl-N,N′-bis(2-mercaptoethyl)-1,3-propanediamine} as the active catalyst with evolution of H2 under ambient conditions. The electrons extracted from H2 have been used for a catalytic reduction of Cu2+ to Cu0 with the NiRu complexes.
Resolving the Global Imbalance: The Dollar and the U.S. Saving Rate
Authors: Feldstein Martin
Published: August 2008

The massive deficit in the U.S. trade and current accounts is one of the most striking features of the current global economy and, to some observers, one of the most worrying. Although the current account deficit finally began to shrink in 2007, it remained at more than 5 percent of GDP—more than $700 billion. While some observers claim that the U.S. economy can continue to have trade deficits of this magnitude for years—some would say for decades—into the future, I believe that such enormous deficits cannot continue and will decline significantly in the coming years. This paper discusses the reasons for that decline and the changes that are needed in the U.S. saving rate and in the value of the dollar to bring it about. Reducing the U.S. current account deficit does not require action by the U.S. government or by the governments of America's trading partners. Market forces alone will cause the U.S. trade deficit to decline further. In practice, however, changes in government policies at home and abroad may lead to faster reductions in the U.S. trade deficit. More important, the response of the U.S. and foreign governments and central banks will determine the way in which the global economy as a whole adjusts to the decline in the U.S. trade deficit. Reductions in the U.S. current account deficit will of course imply lower aggregate trade surpluses in the rest of the world. Taken by itself, a reduction in any country's trade surplus will reduce aggregate demand and therefore employment in that country. I will therefore look at what other countries—China, Japan, and European countries—can do to avoid the adverse consequences of the inevitable decline of the U.S. trade deficit.
Forensic Finance
Authors: Ritter Jay R
Published: August 2008

During popular prime-time television shows, forensic investigators use specialized but wide-ranging scientific knowledge of chemical trace evidence, bacteria, DNA, teeth, insects, and other specialties to collect and sift evidence of possible crimes. In economics and finance, forensic investigators apply their own specialized knowledge of prices, quantities, timing, and market institutions—and sometimes discover or substantiate evidence that is used by regulatory or criminal enforcement agencies. In this article, I will discuss four recent topics in forensic finance, all of which have attracted media attention: 1) the late trading of mutual funds, 2) stock option backdating, 3) the allocation of underpriced initial public offerings to corporate executives, and 4) changes in the records of stock analyst recommendations. In most of these cases, once certain practices or patterns have been publicized, financial industry practice has changed.
A Pragmatic Approach to Capital Account Liberalization
Authors: Prasad Eswar S , Rajan Raghuram G
Published: August 2008

In the mid-1990s, mainstream economists of nearly all stripes commonly recommended capital account liberalization—that is, allowing a free flow of funds in and out of a country's economy—as an essential step in the process of economic development. But then came the East Asian financial crisis of 1997–98, in which even seemingly healthy and well-managed economies like those of South Korea were engulfed by massive capital outflows and tremendous currency volatility, and capital account liberalization became quite controversial in the economics profession. A decade later, now that time has quelled passions and intervening research can shed more light on the debate, it appears that both the costs and benefits of capital account liberalization may have been misunderstood in that earlier debate. Now it appears that the main benefits of capital account liberalization for emerging markets are indirect, more related to their role in building other institutions than to the increased financing provided by capital inflows. And these indirect benefits are important enough that countries should look for creative approaches to capital account liberalization that would help attain these benefits while reducing the risks. Countries don't have much choice but to plan for capital account liberalization because capital accounts are de facto becoming more open over time, whatever governments may do to try to control them.
Probability and Uncertainty in Economic Modeling
Authors: Gilboa Itzhak , Postlewaite Andrew W , Schmeidler David
Published: August 2008

Economic modeling assumes, for the most part, that agents are Bayesian, that is, that they entertain probabilistic beliefs, objective or subjective, regarding any event in question. We argue that the formation of such beliefs calls for a deeper examination and for explicit modeling. Models of belief formation may enhance our understanding of the probabilistic beliefs when these exist, and may also help us characterize situations in which entertaining such beliefs is neither realistic nor necessarily rational.
Secrets of the Academy: The Drivers of University Endowment Success
Authors: Lerner Josh , Schoar Antoinette , Wang Jialan
Published: August 2008

University endowments have received much attention recently for their superior investment returns compared with other institutional investors. This study documents trends in college and university endowment returns and investments in the United States between 1992 and 2005 using data on over a thousand schools. Such endowments have generally performed well over this time period, with a median growth rate of 7.4 percent per year and median return of 6.9 percent. This sector has been dominated both in size and performance by the endowments of elite universities such as the Ivy League schools. The top 20 endowments grew more than 9 percent annually on a real basis between 1992 and 2005. As of 2007, the two largest endowments, belonging to Harvard and Yale, have grown to $35 billion and $22 billion in size, respectively. Much of the growth in endowment size has been driven by investment performance. As we will show in the paper, the top endowments posted impressive returns in 2005, averaging a net real return of 12.3 percent, compared to 4.4 percent posted by the S&P 500 index in the same year. We investigate the underlying drivers of these high returns and show that performance is related to the size of endowment, the quality of the student body, and the use of alternative investments. We caution ordinary investors that mimicking the strategies of the top endowments would not necessarily result in similar returns.
Parental Education and Parental Time with Children
Authors: Guryan Jonathan , Hurst Erik , Kearney Melissa
Published: August 2008

This paper examines parental time allocated to the care of one's children. Using data from the recent American Time Use Surveys, we highlight some interesting cross-sectional patterns in time spent by American parents as they care for their children: we find that higher-educated parents spend more time with their children; for example, mothers with a college education or greater spend roughly 4.5 hours more per week in child care than mothers with a high school degree or less. This relationship is striking, given that higher-educated parents also spend more time working outside the home. This robust relationship holds across all subgroups examined, including both nonworking and working mothers and working fathers. It also holds across all four subcategories of child care: basic, educational, recreational, and travel related to child care. From an economic perspective, this positive education gradient in child care (and a similar positive gradient found for income) can be viewed as surprising, given that the opportunity cost of time is higher for higher-educated, high-wage adults. In sharp contrast, the amount of time allocated to home production and to leisure falls sharply as education and income rise. We conclude that child care is best modeled as being distinct from typical home production or leisure activities, and thinking about it differently suggests important questions for economists to explore. Finally, using data from a sample of 14 countries, we explore whether the same patterns holds across countries and within other countries.
Will the Stork Return to Europe and Japan? Understanding Fertility within Developed Nations
Authors: Feyrer James , Sacerdote Bruce , Stern Ariel Dora
Published: August 2008

We seek to explain the differences in fertility rates across high-income countries by focusing on the interaction between the increasing status of women in the workforce and their status in the household, particularly with regards to child care and home production. We observe three distinct phases in women's status generated by the gradual increase in women's workforce opportunities. In the earliest phase, characteristic of the 1950s and 1960s in the United States, women earn low wages relative to men and are expected to shoulder all of the child care at home. As a result, most women specialize in home production and raising children. In an intermediate stage, women have improved (but not equal) labor market opportunities, but their household status lags. Women in this stage are still expected to do the majority of child care and household production. Increasing access to market work increases the opportunity cost of having children, and fertility falls. Female labor force participation increases. Working women in this phase of development have the strongest disincentives to having additional children since the entire burden of child care falls on them. In the final phase of development, women's labor market opportunities begin to equal those of men. In addition, the increased household bargaining power that comes from more equal wages results in much higher (if not gender-equal) male participation in household production. Female labor force participation is higher than in the intermediate phase. The increased participation of men in the household also reduces the disincentives for women to have additional children, and fertility rates rise compared to the intermediate phase. The intermediate, low-fertility phase might describe Japan, Italy, and Spain in the present day, while the Scandinavian countries, the Netherlands, and the modern-day United States may be entering the final phase. After presenting the empirical evidence, we predict that high-income countries with the lowest fertility rates are likely to see an increase in fertility in the coming decades.
Education and the Age Profile of Literacy into Adulthood
Authors: Cascio Elizabeth , Clark Damon , Gordon Nora
Published: August 2008

American teenagers perform considerably worse on international assessments of achievement than do teenagers in other high-income countries. This observation has been a source of great concern since the first international tests were administered in the 1960s. But does this skill gap persist into adulthood? We examine this question using the first international assessment of adult literacy, conducted in the 1990s. We find that, consistent with other assessments of the school-age population, U.S. teenagers perform relatively poorly, ranking behind teenagers in the twelve other rich countries surveyed. However, by their late twenties, Americans compare much more favorably to their counterparts abroad: U.S. adults aged 26–30 assessed at the same time using the same test ranked seventh in the same group of countries, and the gap with countries still ahead was much diminished. The historical advantage that the United States has enjoyed in college graduation appears to be an important reason why, between the teen years and the late twenties, American literacy rates appear to catch up with those in other high-income countries. The educational systems of countries with high university graduation rates appear to share two features: comprehensive secondary schools—in which all students have the option of taking courses to prepare for university—and a highly accessible university sector. For most of the twentieth century, the United States led the developed world in participation and completion of higher education. In recent years, however, other high-income countries—many of which established comprehensive secondary schooling in decades prior—have substantially expanded access to university education. These changes should have striking consequences for the distribution of skill across countries in the years to come
The Lengthening of Childhood
Authors: Deming David , Dynarski Susan
Published: August 2008

Over the past 40 years, the age at which children enter first grade has slowly drifted upward. In the fall of 1968, 96 percent of six-year-old children were enrolled in first grade or above. By 2005, the proportion had dropped to 84 percent, mainly because a substantial share of six-year-olds were still in kindergarten. About a third of the increase in age at school entry can be explained by legal changes. Almost every state has increased the age at which children are allowed to start primary school. The other two-thirds of the increase in the age at school entry reflects the individual decisions of parents and teachers who choose to keep children out of kindergarten or first grade even when they are legally eligible to attend. This practice is sometimes called “red-shirting,” a phrase originally used to describe the practice of holding college athletes out of play until they have grown larger and stronger. Red-shirting is referred to as “the gift of time” in education circles, reflecting a perception that children who have been allowed to mature for another year will benefit more from their schooling. As we will discuss, little evidence supports this perception. It is indeed true that in any grade, older children tend to perform better academically than the younger children. In the early grades there is a strong, positive relationship between a child's age in months and his performance relative to his peers. But there is little evidence that being older than your classmates has any long-term, positive effect on adult outcomes such as IQ, earnings, or educational attainment. By contrast, there is substantial evidence that entering school later reduces educational attainment (by increasing high school dropout rates) and depresses lifetime earnings (by delaying entry into the labor market).
Global Imbalances: Globalization, Demography, and Sustainability
Authors: Cooper Richard N
Published: August 2008

The current account deficit of the United States has been large in recent years, both in absolute size and relative to GDP. In 2006, it reached $811 billion, 6.1 percent of GDP. It has become a dominant feature of the world economy; if you sum up the current account deficits of all nations that are running deficits in the world economy, the U.S. deficit accounts for about 70 percent of the total. This paper looks beyond the national income accounting relationships to offer a more complex view of the U.S. imbalance. I argue that the generally rising U.S. trade deficit over the last 10–15 years is a natural outcome of two important forces in the world economy—globalization of financial markets and demographic change—and therefore that the U.S. current account deficit is likely to remain large for at least a decade. In a globalized market, the United States has a comparative advantage in producing marketable securities and in exchanging low-risk debt for higher-risk equity. It is not surprising that savers around the world want to put a growing portion of their savings into the U.S. economy. I argue that serious efforts to reduce the U.S. deficit, even collaborative efforts with other countries, may well precipitate a financial crisis and an economic downturn every bit as severe as the one that many fear could result from a disorderly market adjustment to the trade deficit.
Cauda equina syndrome: a serious trap for the urological surgeon
Authors: Notley Richard G
Published: August 2008

Cauda equina syndrome, that is the symptoms and signs of cauda equina compression, does not often present to the urological surgeon. However, when it does it may pose a major problem in diagnosis and management, simply because the average urological surgeon may never have seen the condition before. Therefore the likelihood of correct diagnosis may be low and the litigation risk correspondingly high. This paper outlines the anatomy, the disparate presenting symptoms and the necessity for urgent management of this rare problem, which may produce such devastating disabilities.
The Manchester Patient Safety Framework: sharing the learning
Authors: Parker Dianne , Lawrie Matthew , Carthey Jane , Coultous Mike
Published: August 2008

This article describes the Manchester Patient Safety Framework (MaPSaF) and summarizes some early experiences with using it to help healthcare organizations and teams reflect on their progress in developing a mature patient safety culture.
Life expectancy estimation in cerebral palsy – a paediatrician's approach
Authors: Miles Richard
Published: August 2008

Paediatricians involved in providing reports for cerebral palsy litigation are often asked to give an opinion on life expectancy and this article outlines the approach taken by one paediatrician.

The article describes how statistical data is available, particulary from America, to guide the clinician and the Court. This data acts as the starting point. The two factors that affect life expectancy most of all in the data are mobility and feeding ability, hence tables and survival curves are provided within the publications cited so that additional years of survival can be assessed for individuals in the different functional groups. The article describes how it is the clinicians' role to assess the individual's functional capabilities and any relevant clinical issues and ‘interpret’ the data accordingly.
Calculating life expectation, periodical payments and developments since Royal Victoria Infirmary & Associated Hospitals NHS Trust v B (A Child)
Authors: QC Elizabeth-Anne Gumbel
Published: August 2008

The importance of calculating life expectation in catastrophic injury claims, the impact of periodical payments and the limited extent to which the calculation of life expectation can be avoided, the needed for statistical evidence, the use of table 28 and the 6th edition of the Ogden tables.
Experimental Estimation of Mutation Rates in a Wheat Population With a Gene Genealogy Approach
Authors: Raquin Anne-Laure , Depaulis Frantz , Lambert Amaury , Galic Nathalie , Brabant Philippe , Goldringer Isabelle
Published: August 2008

Microsatellite markers are extensively used to evaluate genetic diversity in natural or experimental evolving populations. Their high degree of polymorphism reflects their high mutation rates. Estimates of the mutation rates are therefore necessary when characterizing diversity in populations. As a complement to the classical experimental designs, we propose to use experimental populations, where the initial state is entirely known and some intermediate states have been thoroughly surveyed, thus providing a short timescale estimation together with a large number of cumulated meioses. In this article, we derived four original gene genealogy-based methods to assess mutation rates with limited bias due to relevant model assumptions incorporating the initial state, the number of new alleles, and the genetic effective population size. We studied the evolution of genetic diversity at 21 microsatellite markers, after 15 generations in an experimental wheat population. Compared to the parents, 23 new alleles were found in generation 15 at 9 of the 21 loci studied. We provide evidence that they arose by mutation. Corresponding estimates of the mutation rates ranged from 0 to 4.97 × 10−3 per generation (i.e., year). Sequences of several alleles revealed that length polymorphism was only due to variation in the core of the microsatellite. Among different microsatellite characteristics, both the motif repeat number and an independent estimation of the Nei diversity were correlated with the novel diversity. Despite a reduced genetic effective size, global diversity at microsatellite markers increased in this population, suggesting that microsatellite diversity should be used with caution as an indicator in biodiversity conservation issues.
Exchangeable Models of Complex Inherited Diseases
Authors: Slatkin Montgomery
Published: August 2008

A model of unlinked diallelic loci affecting the risk of a complex inherited disease is explored. The loci are equivalent in their effect on disease risk and are in Hardy–Weinberg and linkage equilibrium. The goal is to determine what assumptions about dependence of disease risk on genotype are consistent with data for diseases such as schizophrenia, bipolar disorder, autism, and multiple sclerosis that are relatively common (0.1–2% prevalence) and that have high concordance rates for monozygotic twins (30–50%) and high risks to first-degree relatives of affected individuals (risk ratios exceeding 4). These observations are consistent with a variety of models, including generalized additive, multiplicative, and threshold models, provided that disease risk increases rapidly for a narrow range of numbers of causative alleles. If causative alleles are in relatively high frequency, then the combined effects of numerous causative loci are necessary to substantially elevate disease risk.
Localization of the Genetic Determinants of Meiosis Suppression in Daphnia pulex
Authors: Lynch Michael , Seyfert Amanda , Eads Brian , Williams Emily
Published: August 2008

Although ∼1 in 10,000 animal species is capable of parthenogenetic reproduction, the evolutionary causes and consequences of such transitions remain uncertain. The microcrustacean Daphnia pulex provides a potentially powerful tool for investigating these issues because lineages that are obligately asexual in terms of female function can nevertheless transmit meiosis-suppressing genes to sexual populations via haploid sperm produced by environmentally induced males. The application of association mapping to a wide geographic collection of D. pulex clones suggests that sex-limited meiosis suppression in D. pulex has spread westward from a northeastern glacial refugium, conveyed by a dominant epistatic interaction among the products of at least four unlinked loci, with one entire chromosome being inherited through males in a nearly nonrecombining fashion. With the enormous set of genomic tools now available for D. pulex, these results set the stage for the determination of the functional underpinnings of the conversion of meiosis to a mitotic-like mode of inheritance.
A Complex Genetic Basis to X-Linked Hybrid Male Sterility Between Two Species of House Mice
Authors: Good Jeffrey M , Dean Matthew D , Nachman Michael W
Published: August 2008

The X chromosome plays a central role in the evolution of reproductive isolation, but few studies have examined the genetic basis of X-linked incompatibilities during the early stages of speciation. We report the results of a large experiment focused on the reciprocal introgression of the X chromosome between two species of house mice, Mus musculus and M. domesticus. Introgression of the M. musculus X chromosome into a wild-derived M. domesticus genetic background produced male-limited sterility, qualitatively consistent with previous experiments using classic inbred strains to represent M. domesticus. The genetic basis of sterility involved a minimum of four X-linked factors. The phenotypic effects of major sterility QTL were largely additive and resulted in complete sterility when combined. No sterility factors were uncovered on the M. domesticus X chromosome. Overall, these results revealed a complex and asymmetric genetic basis to X-linked hybrid male sterility during the early stages of speciation in mice. Combined with data from previous studies, we identify one relatively narrow interval on the M. musculus X chromosome involved in hybrid male sterility. Only a handful of spermatogenic genes are within this region, including one of the most rapidly evolving genes on the mouse X chromosome.
Cut Thy Neighbor: Cyclic Birth and Death of Recombination Hotspots via Genetic Conflict
Authors: Friberg Urban , Rice William R
Published: August 2008

Most recombination takes place in numerous, localized regions called hotspots. However, empirical evidence indicates that nascent hotspots are susceptible to removal due to biased gene conversion, so it is paradoxical that they should be so widespread. Previous modeling work has shown that hotspots can evolve due to genetic drift overpowering their intrinsic disadvantage. Here we synthesize recent theoretical and empirical results to show how natural selection can favor hotspots. We propose that hotspots are part of a cycle of antagonistic coevolution between two tightly linked chromosomal regions: an inducer region that initiates recombination during meiosis by cutting within a nearby region of DNA and the cut region itself, which can evolve to be resistant to cutting. Antagonistic coevolution between inducers and their cut sites is driven by recurrent episodes of Hill–Robertson interference, genetic hitchhiking, and biased gene conversion.
Defective Break-Induced Replication Leads to Half-Crossovers inSaccharomyces cerevisiae
Authors: Deem Angela , Barker Krista , VanHulle Kelly , Downing Brandon , Vayl Alexandra , Malkova Anna
Published: August 2008

Break-induced replication (BIR) is an important process of DNA metabolism that has been implicated in the restart of collapsed replication forks, as well as in various chromosomal instabilities, including loss of heterozygosity, translocations, and alternative telomere lengthening. Therefore, knowledge of how BIR is carried out and regulated is important for better understanding the maintenance of genomic stability in eukaryotes. Here we present a new yeast experimental system that enables the genetic control of BIR to be investigated. Analysis of mutations selected on the basis of their sensitivity to various DNA-damaging agents demonstrated that deletion of POL32, which encodes a third, nonessential subunit of polymerase δ, significantly reduced the efficiency of BIR, although some POL32-independent BIR was still observed. Importantly, the BIR defect in pol32Δ cells was associated with the formation of half-crossovers. We propose that these half-crossovers resulted from aberrant processing of BIR intermediates. Furthermore, we suggest that the half-crossovers observed in our system are analogous to nonreciprocal translocations (NRTs) described in mammalian tumor cells and, thus, our system could represent an opportunity to further study the NRT mechanism in yeast.
Bayesian Quantitative Trait Loci Mapping for Multiple Traits
Authors: Banerjee Samprit , Yandell Brian S , Yi Nengjun
Published: August 2008

Most quantitative trait loci (QTL) mapping experiments typically collect phenotypic data on multiple correlated complex traits. However, there is a lack of a comprehensive genomewide mapping strategy for correlated traits in the literature. We develop Bayesian multiple-QTL mapping methods for correlated continuous traits using two multivariate models: one that assumes the same genetic model for all traits, the traditional multivariate model, and the other known as the seemingly unrelated regression (SUR) model that allows different genetic models for different traits. We develop computationally efficient Markov chain Monte Carlo (MCMC) algorithms for performing joint analysis. We conduct extensive simulation studies to assess the performance of the proposed methods and to compare with the conventional single-trait model. Our methods have been implemented in the freely available package R/qtlbim (http://www.qtlbim.org), which greatly facilitates the general usage of the Bayesian methodology for unraveling the genetic architecture of complex traits.
Legume Anchor Markers Link Syntenic Regions Between Phaseolus vulgaris, Lotus japonicus, Medicago truncatula and Arachis
Authors: Hougaard Birgit Kristine , Madsen Lene Heegaard , Sandal Niels , de Carvalho Moretzsohn Marcio , Fredslund Jakob , Schauser Leif , Nielsen Anna Marie , Rohde Trine , Sato Shusei , Tabata Satoshi , Bertioli David John , Stougaard Jens
Published: August 2008

We have previously described a bioinformatics pipeline identifying comparative anchor-tagged sequence (CATS) loci, combined with design of intron-spanning primers. The derived anchor markers defining the linkage position of homologous genes are essential for evaluating genome conservation among related species and facilitate transfer of genetic and genome information between species. Here we validate this global approach in the common bean and in the AA genome complement of the allotetraploid peanut. We present the successful conversion of ∼50% of the bioinformatics-defined primers into legume anchor markers in bean and diploid Arachis species. One hundred and four new loci representing single-copy genes were added to the existing bean map. These new legume anchor-marker loci enabled the alignment of genetic linkage maps through corresponding genes and provided an estimate of the extent of synteny and collinearity. Extensive macrosynteny between Lotus and bean was uncovered on 8 of the 11 bean chromosomes and large blocks of macrosynteny were also found between bean and Medicago. This suggests that anchor markers can facilitate a better understanding of the genes and genetics of important traits in crops with largely uncharacterized genomes using genetic and genome information from related model plants.
An Empirical Test for Branch-Specific Positive Selection
Authors: Nickel Gabrielle C , Tefft David L , Goglin Karrie , Adams Mark D
Published: August 2008

The use of phylogenetic analysis to predict positive selection specific to human genes is complicated by the very close evolutionary relationship with our nearest extant primate relatives, chimpanzees. To assess the power and limitations inherent in use of maximum-likelihood (ML) analysis of codon substitution patterns in such recently diverged species, a series of simulations was performed to assess the impact of several parameters of the evolutionary model on prediction of human-specific positive selection, including branch length and dN/dS ratio. Parameters were varied across a range of values observed in alignments of 175 transcription factor (TF) genes that were sequenced in 12 primate species. The ML method largely lacks the power to detect positive selection that has occurred since the most recent common ancestor between humans and chimpanzees. An alternative null model was developed on the basis of gene-specific evaluation of the empirical distribution of ML results, using simulated neutrally evolving sequences. This empirical test provides greater sensitivity to detect lineage-specific positive selection in the context of recent evolutionary divergence.
Avaliação do ciclo e produção da planta-filha em função do manejo da planta-mãe em diferentes épocas do ano em bananeira Prata-Anã
Authors: Flori José Egídio , Scarpare Filho João Alexio , Resende Geraldo Milanez de
Published: August 2008

Objetivou-se, neste trabalho, avaliar o efeito do manejo da planta-mãe e da época de seleção das plantas-filha de bananeira 'Prata-Anã´ (Musa spp.) na produção e no período de desenvolvimento da planta-filha. Utilizou-se um bananal comercial com cinco anos de idade, plantado no espaçamento de 3,5 m x 2,0 m. O delineamento foi inteiramente casualizado no esquema de parcelas subdivididas, com três repetições. Os tratamentos nas parcelas foram: manejo 1 (M1) - família conduzida sem a planta-mãe, a qual foi retirada logo após a sua floração; manejo 2 (M2) - família conduzida com planta-mãe (manejo convencional). As subparcelas corresponderam a doze épocas de seleção das plantas-filha, selecionadas no estádio de chifrão, iniciando em fev./02 e finalizando em jan./03. As características avaliadas foram: a) período de desenvolvimento da planta-filha (período em dias entre a data de seleção da planta-filha e a sua colheita); b) massa do cacho das plantas-filha. Diante dos resultados obtidos concluiu-se: o manejo da planta-mãe não influenciou a massa do cacho da planta-filha; o manejo da planta-mãe alterou o período de desenvolvimento da planta-filha, sendo esse menor naquelas conduzidas sem a planta-mãe (M1); a época de seleção influenciou a massa do cacho e o período de desenvolvimento da planta-filha.
Urease activity in aged copper and zinc-spiked soils: Relationship to CaCl2-extractable metals and Cu2+ activity
Authors: Kim Bojeong , McBride Murray B , Hay Anthony G
Published: August 2008

In the present study, the utilization of dilute CaCl2 extraction and free metal ion activity was tested for its ability to predict urease activity in soils that was measured by a simple and rapid urease assay. Two soil series (an Arkport sandy loam and a Hudson silty clay loam) were spiked with Cu and Zn, both singly and in combination, and then field aged for over a year prior to use. For both the metal-spiked Arkport and Hudson soils, much of the inhibition in measured urease activity was explained by increased CaCl2-extractable Cu, with a lesser effect from increased Zn extractability. A positive but weak interaction between Cu and Zn suggested by regression analysis indicates the toxicity of Cu-Zn mixtures to soil urease is slightly less than additive (antagonistic). Copper extractability using CaCl2 was able to predict urease activity in only one of the tested soils. By contrast, measurements of Cu2+ activity were predictive of reduced urease activity in both soils (R2adj = 0.726, p < 0.0001), indicating that Cu2+ activity is a more useful predictor of urease inhibition in soils than CaCl2-extractable Cu. The present study also highlighted the importance that clay mineral content had on controlling the availability of added metals in soils over time since a greater aging effect on Cu toxicity was found for the fine-textured Hudson than the coarse-textured Arkport soil.
Time-Dependent transcriptional profiles of genes of the hypothalamic-pituitary-gonadal axis in medaka (Oryzias latipes) exposed to fadrozole and 17β-trenbolone
Authors: Zhang Xiaowei , Hecker Markus , Park June-Woo , Tompsett Amber R , Jones Paul D , Newsted John , Au Doris W. T , Kong Richard , Wu Rudolf S. S , Giesy John P
Published: August 2008

Both the anabolic androgen 17β-trenbolone (TRB) and the aromatase inhibitor fadrozole (FAD) can cause decreased plasma concentrations of estrogen (E2) and reduce fecundity of fish. However, the underlying mechanisms and the molecular pathways involved are largely unknown. The present study was designed to assess time-dependent effects of FAD and TRB on the transcriptional responses of the hypothalamic-pituitary-gonadal (HPG) axis of Japanese medaka (Oryzias latipes). Fourteen-week-old Japanese medaka were exposed to 50 μg FAD/L or 2 μg TRB/L in a 7-d static renewal test, and the expression profiles of 36 HPG axis genes were measured by means of a medaka HPG real-time reverse-transcription polymerase chain reaction array after 8 h, 32 h, or 7 d of exposure. Exposure to TRB or FAD caused lesser fecundity of Japanese medaka and down-regulated transcription of vitellogenin and choriogenin (CHG) gene expression in the liver of females. Exposure to FAD for 8 h resulted in an 8-fold and 71-fold down-regulation of expression of estrogen receptor α and choriogenin L (CHG L), respectively, in female liver. 17β-Trenbolone caused similar down-regulation of these genes, but the effects were not observed until 32 h of exposure. These results support the hypothesis that FAD reduces plasma E2 more quickly by inhibiting aromatase enzyme activity than does TRB, which inhibits the production of the E2 precursor testosterone. Exposure to FAD and TRB resulted in rapid (after 8 h) down-regulation of luteinizing hormone receptor and low-density-lipoprotein receptor in the testis to compensate for excessive androgen levels. Overall, the molecular responses observed in the present study differentiate the mechanisms of the reduced fecundity by TRB and FAD.
Effect of Cirsium arvense L. on soil physical properties and crop growth
Authors: REINTAM E. , TRÜKMANN K. , KUHT J.
Published: August 2008

The re-cultivation of abandoned areas creates weed control problems. The main problems in these areas are perennial weeds, such as Cirsium arvense L. but this perennial deep-rooted plant may have a beneficial effect on the physical properties of compacted soil. In order to study the effect of C. arvenses root system on soil properties, the field experiment and a survey of arable fields were conducted in Estonia. The soil bulk density and penetration resistance were measured from soils covered by C. arvense or spring barley (Hordeum vulgare L.) on compacted and un-compacted soil. The results showed significantly lower penetration resistance and bulk density underneath C. arvense than under barley in both the field experiment and a field survey on arable soils. The shoot mass of C. arvense was less affected than the shoot mass of barley by soil compaction and was caused by C. arvenses better ability to develop its root system in compacted soil. Wheat yield, on soils affected by C. arvense, was increased by 28% on loose soil and 37% on compacted soil. It may be concluded that in areas affected by deep-rooted weed species, such C. arvense, the soils physical properties will improve at least in the first two years.;
Interlopers and Field Change: The Entry of U.S. News into the Field of Legal Education
Authors: Sauder Michael
Published: August 2008

This article analyzes a process by which established organizational fields change through the incorporation of new field-level actors. Drawing on 137 in-depth interviews with U.S. law school administrators and faculty, the paper demonstrates how the U.S. News & World Report rankings of law schools gained a foothold in the field of legal education, how the dynamics of the field helped entrench the field position of USN and its rankings despite spirited opposition from key actors, and how these same dynamics explain how a seemingly minor change—the addition of a single actor to the roster of existing field actors—transformed many aspects of this field. A close examination of this new model of field change enhances field theory by underscoring how field characteristics, such as the interconnections among actors and the web of mutual influence that these imply, themselves can facilitate change. Substantively, this research provides insight into the way that those who measure, credential, or certify key field actors and activities can achieve pervasive influence over the fields they evaluate.
Local and Non-local Pre-founding Experience and New Organizational Form Penetration: The Case of the Israeli Wine Industry
Authors: Simons Tal , Roberts Peter W.
Published: August 2008

This paper presents a theory of how new organizational forms penetrate local populations. We theorize that founders with pre-founding industry experience in non-local populations are more likely to adopt locally novel forms. Pre-founding experience within local and non-local industry populations should also allow organizations to reach larger size and produce superior quality products, both of which contribute to the persistence of the novel organizational form. We evaluate these predictions in an analysis of the transformation of the population of Israeli wineries between 1983 and 2004, when five existing organizations witnessed the arrival of 138 new wineries. This explosion in numbers coincided with a shift from kosher toward non-kosher wine production, the new organizational form. Although the four largest Israeli wineries in 1982 were kosher, roughly 75 percent of the new entrants were established as non-kosher producers. We analyze how founders' pre-founding experiences helped the novel non-kosher form penetrate the local population. The results show that non-local wine industry experience prior to founding increased the odds that a new entrant would select the non-kosher organizational form. At the same time, both local and non-local pre-founding experience improved the size and product-quality outcomes achieved by the non-kosher entrants. This had an additional effect on form penetration by improving the impact and longevity of the novel-form producers.