bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Importance of Factors Contributing to Postfire Seedling Establishment in Maritime Chaparral
Authors: Tyler Claudia M.
Published: May 2006

Several mechanisms have been proposed to explain the postburn flush of seedlings in the chaparral; these include direct effects of fire, such as heating of the soil and seed bank, and indirect effects of fire, such as a temporary reduction in competition by shrubs or herbivory by mammals. I conducted an experiment in burned and adjacent unburned chaparral to assess the relative importance of these mechanisms to seedling emergence and mortality of four functional plant groups: shrubs, subshrubs, perennial herbs, and annual herbs. I assessed direct effects of burning by comparing experimental plots in a burned area to plots in adjacent, unburned chaparral that were cleared of shrubs. In the unburned chaparral, competition with shrubs was manipulated by removing aboveground vegetation; herbivory by large mammals was manipulated using fence exclosures. The direct effects of burning enhanced emergence of shrub and subshrub seedlings, but reduced emergence of annual herbs. Shrub removal alone did not affect seedling emergence, but did improve survivorship of annuals. Exclusion of mammalian herbivores improved the survivorship of annual herbs and all seedlings combined. No single factor explained the high abundance of perennial herbs in the burn area; my results suggest that the combined removal of shrubs and herbivores following fire enhanced their growth and establishment. Thus, both the direct and indirect effects of fire contributed to the high postburn recruitment of seedlings in maritime chaparral, but different mechanisms were responsible for the increase in specific plant groups.
Untangling Multiple Factors in Spatial Distributions: Lilies, Gophers, and Rocks
Authors: Thomson James D. , Weiblen George , Thomson Barbara A. , Alfaro Satie , Legendre Pierre
Published: May 2006

Despite broad consensus on the power of experiments, correlational studies are still important in ecology, and may become more so as spatial studies proliferate. Conventional correlation analysis, however, (1) fundamentally conflicts with the basic ecological concept of limiting factors, and (2) ignores spatial structure in data, which can produce spuriously high correlations. Especially for field data, bivariate scattergrams often show factor—ceiling" distributions wherein data points are widely scattered beneath an upper limit, due to the action of other factors. Although most ecological information in such a graph resides in the upper limit, standard correlation/regression does not characterize such limits. If other factors have been measured, path analysis may be useful, but otherwise, direct description of ecological ceilings is desirable. Objective methods for doing so are barely known to ecologists; we review recent proposals for statistical testing and data display. For correcting correlations for spatial patchiness of the variables, another new technique has been proposed by Clifford, Richardson, and Hemon: by reducing the effective sample size to account for the autocorrelation it allows significance tests. We discuss these issues with reference to counts of glacier lily (Erythronium grandiflorum) seedlings, vegetative plants, and flowering plants in a square grid of 256 contiguous $2 \times 2$ m quadrats in subalpine meadow in western Colorado. We also measured soil moisture, pocket gopher activity, and soil rockiness. All six variables showed significant patchiness (spatial autocorrelation) at similar scales. The abundance of flowering plants was positively correlated with rockiness and negatively correlated with moisture and gopher activity. Although limited seed dispersal suggests that seedlings should be spatially associated with flowering plants, no such correlation existed: indeed, examination of the bivariate scatterplot suggests a negative association, in the particular and restricted sense that seedlings are abundant only in quadrats where flowering is low. We hypothesize that seed germination is higher in less rocky areas of deeper, moister soil than in the rocky areas where most seeds land, but that seedlings seldom reach maturity unless they are in a rocky refuge from predation. Results from path analysis are consistent with this hypothesis. Such an ecological situation should weaken natural selection on characters enhancing seed dispersal.
Population Size, Pollinator Limitation, and Seed Set in the Self‐ Incompatible Herb Lythrum Salicaria
Authors: Agren Jon
Published: May 2006

In reward—producing animal—pollinated plants, small populations are likely to be less attractive to pollinators than large populations. The likelihood of pollinator limitation of seed production should therefore increase with decreasing population size. I documented the number of flowering plants and plant fecundity in 18 populations of the self—incompatible, tristylous herb Lythrum salicaria within an archipelago in northern Sweden in two consecutive years. To test the hypothesis that a positive correlation between population size and seed set is due to a higher degree of pollinator limitation in small than in large populations, I performed supplemental hand—pollinations in eight (1993) and 13 (1994) of the study populations. To test the hypothesis that common mating types are more likely than rare types to experience inadequate pollination, I compared the natural level of seed production and the effect of supplemental pollination in different style morphs in the five populations in which $\geq 10$ plants per morph were included in the experiment. There was no significant correlation between population size and plant size in terms of number of floral shoots or number of flower—producing leaf nodes per shoot. However, there was a positive relationship between population size and seed production per flower and between population size and total seed number per plant. In contrast, there was no significant correlation between population size and seed production of flowers that had received supplemental pollination. In both years, the difference in mean seed production per flower between hand—pollinated flowers and controls decreased with increasing population size. In two of five populations, the effect of supplemental pollination differed significantly among morphs. Seed production was more likely to be pollinator limited in long—styled than in short—styled plants, but this difference could not be attributed to a preponderance of the long—styled morph in the studied populations. Results of the supplemental hand—pollinations indicate that the positive correlation between population size and seed production is a function of insufficient pollen transfer in small populations. Additional demographic studies are needed to determine to what extent the reduced level of seed production in small populations limits the growth of young populations, and to what extent it may threaten the local persistence of L. salicaria.
Trophic Generalists vs. Trophic Specialists: Implications for Food Web Dynamics in Post‐Fire Streams
Authors: Mihuc Timothy B. , Minshall G. Wayne
Published: May 2006

The trophic ecology of 11 benthic macroinvertebrate taxa found in Cache Creek, Yellowstone National Park (YNP) was studied to determine if burned organic matter is an important resource and how resource utilization patterns may be altered in post—fire streams. Laboratory food quality experiments were conducted to determine the growth response of each species when grown on several resource types: burned organic matter, periphyton, unburned coarse particulate material (CPM), and unburned fine particulate material (FPM). The central hypothesis of this research was that benthic macroinvertebrates cannot use burned organic matter as a resource. A secondary hypothesis was that some benthic macroinvertebrates are facultative in trophic function, with the ability to use both allochthonous and autochthonous resources for growth. Of the 11 taxa studied, only one (Paraleptophlebia heteronea) could grow on burned organic matter as a resource, indicating that post—fire food webs probably do not exhibit major shifts in resource utilization to burned material. Two species were generalist detrivores (P. heteronea, Ameletus cooki) able to use both natural FPM and CPM resources. Two species were specialist detritivores (Oligophlebodes sigma, Ephemerella infrequens) growing only on unburned CPM resources, and two (Cinygmula mimus, Epeorus albertae) were specialist herbivores utilizing only periphyton. Five species were generalist herbivore—detritivores (Baetis bicaudatus, Drunella doddsi, D. coloradensis, D. spinifera, Zapada columbiana), exhibiting growth on both detritus and periphyton resources. Based on the experimental results, trophic generalists are common food web components in Yellowstone streams. Two of the most abundant benthic macroinvertebrates during post—fire recovery, B. bicaudatus and Z. columbiana, were trophic generalists, indicating that some generalists may be disturbance adapted. In this study, published functional feeding group classification did not indicate obligate resource utilization (growth on only one resource type) for most taxa studied. Comparison of a food web for Cache Creek based on functional feeding group classification and one based on the results of this study indicates that the inclusion of generalists in the web results in a more realistic approximation of food web relationships such as the link—species scaling law. Our results suggest that future research should include spatial and temporal aspects of resource switching and generalist resource utilization by individual lotic primary consumers.
Tactile coactivation resets age‐related decline of human tactile discrimination
Authors: Dinse Hubert R. , Kleibel Nadine , Kalisch Tobias , Ragert Patrick , Wilimzig Claudia , Tegenthoff Martin
Published: May 2006

Objective

For young subjects, it is well‐documented that training and practice improve sensorimotor performance. However, little is known about how the typically observed age‐related decline of sensorimotor abilities can be ameliorated by sensory stimulation.

Methods

As an alternative approach to training, we have introduced a tactile coactivation protocol involving Hebbian synaptic plasticity to improve tactile performance on a short timescale of a few hours.

Results

By applying coactivation on the index finger to drive perceptual learning, we demonstrate that in the elderly, aged 65 to 89 years, the age‐related impairment of tactile two‐point discrimination can be mitigated substantially. In elderly adults, tactile‐acuity thresholds increased to 3.5mm compared with 1.5mm found in young adults, whereas 50‐year‐old subjects showed intermediate performance. As a result of coactivation, discrimination thresholds of the 80‐year‐old adults came to match those typically found at an age of 50, demonstrating that age‐related decline in tactile performance is not irreversible, but rather subject to considerable restoration by specific stimulation protocols.

Interpretation

Because the preservation of sufficient tactile acuity into advanced age is an important prerequisite for the maintenance of autonomous living, we believe that the concept of coactivation might turn out to be beneficial in preserving everyday sensorimotor competence in the elderly through new forms of therapeutic interventions. Ann Neurol 2006.
Differential twin concordance for multiple sclerosis by latitude of birthplace
Authors: Islam Talat , Gauderman W. James , Cozen Wendy , Hamilton Ann S. , Burnett Margaret E. , Mack Thomas M.
Published: May 2006

Objective

To address the inconsistency in the reported concordance of multiple sclerosis (MS) among twins by zygosity, sex, and latitude.

Methods

Four hundred eighteen medically documented monozygotic (MZ) and 380 same‐sex dizygotic (DZ) pairs were ascertained from 1980 to 1992 and followed. The study population was representative of twins with multiple sclerosis. Twins from Canada and adjacent US states (at or above 41–42° N) were considered “northern,” and ancestry was dichotomized from descent from high‐risk populations. Diagnosis before median age 29.3 years was considered “early.”

Results

The MZ/DZ concordance ratio was 2.9 (95% confidence interval [CI], 1.0–8.9) among men and 2.6 (95% CI, 1.5–4.5) among women. The average age at northern diagnosis was independent of ancestry and 2 years earlier for both MZ (p < 0.02) and DZ (p < 0.01) patients. Among DZ twins, concordance was independent of all characteristics. Among MZ twins, concordance was 1.9 times (95% CI, 1.2–3.2) greater among northern twins, 1.9 (95% CI, 1.1–3.6) times greater among twins with high‐risk ancestry, and 2.1 (95% CI, 1.2–3.6) times greater if diagnosis was early. Ancestry and early diagnosis made independent significant contributions to the differential concordance by latitude.

Interpretation

Multiple sclerosis is similarly heritable by sex, and the apparent variation in MZ concordance by latitude is influenced by environmental and genetic factors. Ann Neurol 2006
Documents and queries as random variables: History and implications
Authors: Bodoff David , Wong Samuel Po‐Shing
Published: May 2006

The view of documents and/or queries as random variables is gaining importance in the theory of information retrieval. We argue that traditional probabilistic models consider documents and queries as random variables, but that newer models such as language modeling and our unified model take this one step further. The additional step is called error in predictors. Such models consider that we don't observe the document and query random variables that are modeled to predict relevance probabilistically. Rather, there are additional random variables, which are the observed documents and queries. We discuss some important implications of this idea for parameter estimation, relevance prediction, and even test‐collection construction. By clarifying the positions of various probabilistic models on this question, and presenting in one place many of its implications, this article aims to deepen our common understanding of the theories behind traditional probabilistic models, and to strengthen the theoretical basis for further development of more recent approaches such as language modeling.
Genomic DNA of leukemic patients: Target for clinical diagnosis of MLL rearrangements
Authors: Meyer Claus , Kowarz Eric , Schneider Björn , Oehm Clarissa , Klingebiel Thomas , Dingermann Theo , Marschalek Rolf
Published: May 2006

Genomic DNA is the optimal resource to analyze questions concerning genetic changes that are related to oncogenesis. This article tries to summarize recent efforts to analyze chromosomal changes that trigger the development of human acute myeloid and lymphoblastic leukemias. The aim of this study was to establish an universal method that enables the identification and characterization of chromosomal translocations of the human MLL gene at the genomic nucleotide level. Chromosomal translocations of the MLL gene are the result of illegitimate recombination events in hematopoietic stem or precursor cells, strictly associated with the onset of highly malignant leukemic diseases. The applied technology was able to identify specific fusion alleles that were generated by chromosomal translocations, chromosomal deletions, chromosomal inversions and partial tandem duplications. Moreover, it allowed us to investigate even highly complex genetic changes by applying systematic breakpoint analyses. On the basis of these analyses, patient‐specific molecular markers were established that turned out to be a very good source for monitoring minimal residual disease (MRD). MRD analyses control the efficiency and efficacy of current treatment protocols and have become a very sensitive molecular tool to monitor therapeutic success or failure in individual leukemia patients.
Measurement of two caspase activities simultaneously in living cells by a novel dual FRET fluorescent indicator probe
Authors: Wu Xiaoli , Simone James , Hewgill Derek , Siegel Richard , Lipsky Peter E. , He Liusheng
Published: May 2006

Background:

A number of fluorescent caspase substrates and FRET‐based indicators have been developed to study the in vivo activation of caspases, a conserved family of proteases critical in inflammatory, and apoptosis signaling pathways. To date, all substrates have measured only one caspase activity. Here, we describe a FRET‐based probe for simultaneously measuring two distinct caspase activities in living cells.

Methods:

This probe consists of a CFP‐YFP‐mRFP fusion protein containing a caspase‐3‐cleavage motif, DEVD, between CFP and YFP, and a caspase‐6‐cleavage site, VEID, between YFP and mRFP. DEVDase and VEIDase activities could be assessed simultaneously by monitoring diminished FRET mediated by cleavage of either or both of these protease cleavage sites using flow cytometry.

Results:

DEVDase and VEIDase activities were completely inhibited by the pan‐caspase inhibitor z‐VAD‐fmk and enhanced by DNA‐damaging drugs or by anti‐Fas stimulation. DEVD and VEID cleavage specificities were validated by using caspase‐3‐deficient MCF7‐Fas cells and a caspase‐6‐specific inhibitor. Kinetic analysis with the FRET probe revealed that caspase‐3 activation consistently preceded caspase‐6 by ∼30 min following induction of apoptosis.

Conclusions:

We have developed a novel FRET‐based probe for simultaneous detection of two caspase activities in living cells using flow cytometry. Simultaneous detection of two caspase activities using this probe has clearly provided information of the ordering of caspase‐3 and ‐6 in the apoptotic pathway. © 2006 International Society for Analytical Cytology
A Theoretical Rationale for the Formation, Structure and Spin State of Pentacyanochromate(II)
Authors: Deeth Robert J.
Published: May 2006

The pentacyanochromate(II) complex is unusual in two respects. Firstly, it is one of the few homoleptic cyanide species with a high‐spin ground state. Secondly, it was synthesised during an attempt to make the hexacoordinate complex. A combination of qualitative ligand field theory and quantitative density functional theory including solvation effects is applied to rationalise these observations. The spin state depends on the d orbital energy differences and how the promotion energy, PE, associated with a change in spin state compares to the d–d spin pairing energy, SPE. The calculations show that PE > SPE for octahedral [CrII(CN)6]4–, hence it has a spin triplet S = 1 ground state, while PE < SPE for [CrII(CN)5]3–, hence it is high spin with S = 2. The hexacyanide is stabilised in aqueous solution by solvation. In less polar solvents such as acetonitrile, the unfavourable electrostatic interactions dominate and the reaction stops at the pentacyano complex. In both complexes, the cyanide behaves as a strong‐field ligand and is both a good σ donor and π acceptor.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Asymmetric Mannich‐Type Reaction of a Chiral N‐(tert‐Butylsulfinyl) Ketimine with Imines: Application to the Synthesis of Chiral 1,3‐Diamines
Authors: Zhao Cui‐Hua , Liu Li , Wang Dong , Chen Yong‐Jun
Published: May 2006

Deprotonation of the chiral N‐(tert‐butylsulfinyl) ketimine 1 followed by trapping with imines 2 afforded the β‐aminoimines 3 as the Mannich‐type products in high diastereoselectivities (99:1 dr). As versatile synthons chiral β‐amino imines 3 could be transformed into enantiomeric β‐amino ketone and chiral syn‐ or anti‐1,3‐diamines with high diastereomeric excess by hydrolysis or reduction, respectively. Moreover, the nucleophilic addition of organometallicreagents to chiral β‐amino imines 3 could provide 1,1,3‐trisubstituted 1,3‐diamines with high diastereoselectivities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Joint data detection and estimation of time‐varying multipath rayleigh fading channels in asynchronous DS‐CDMA systems with long spreading sequences
Authors: Xiao Pei , Ström Erik G.
Published: May 2006

In this paper, we present a joint approach to data detection and channel estimation for the asynchronous direct‐sequence code‐division multiple access (DS‐CDMA) systems employing orthogonal signaling formats and long scrambling codes. Our emphasis is placed on different channel estimation algorithms since the performance of a communication system depends largely on its ability to retrieve an accurate measurement of the underlying channel. We investigate channel estimation algorithms under different conditions. The estimated channel information is used to enable coherent data detection to combat the detrimental effect of the multiuser interference and the multipath propagation of the transmitted signal. In the considered multiuser detector, we mainly use interference cancellation techniques, which are suitable for long‐code CDMA systems. Interference cancellation and channel estimation using soft estimates of the transmitted signal is also proposed in this paper. Different channel estimation schemes are evaluated and compared in terms of mean square error (MSE) of channel estimation and bit error rate (BER) performance. Based on our analysis and numerical results, some recommendations are made on how to choose appropriate channel estimators in practical systems. Copyright © 2006 AEIT
Distribution and magnitude of type I error of model‐based multipoint lod scores: implications for multipoint mod scores
Authors: Xing Chao , Elston Robert C.
Published: May 2006

The multipoint lod score and mod score methods have been advocated for their superior power in detecting linkage. However, little has been done to determine the distribution of multipoint lod scores or to examine the properties of mod scores. In this paper we study the distribution of multipoint lod scores both analytically and by simulation. We also study by simulation the distribution of maximum multipoint lod scores when maximized over different penetrance models. The multipoint lod score is approximately normally distributed with mean and variance that depend on marker informativity, marker density, specified genetic model, number of pedigrees, pedigree structure, and pattern of affection status. When the multipoint lod scores are maximized over a set of assumed penetrances models, an excess of false positive indications of linkage appear under dominant analysis models with low penetrances and under recessive analysis models with high penetrances. Therefore, caution should be taken in interpreting results when employing multipoint lod score and mod score approaches, in particular when inferring the level of linkage significance and the mode of inheritance of a trait. Genet. Epidemiol. 2006. © 2006 Wiley‐Liss, Inc.
Progressive increase of frontostriatal brain activation from childhood to adulthood during event‐related tasks of cognitive control
Authors: Rubia Katya , Smith Anna B. , Woolley James , Nosarti Chiara , Heyman Isobel , Taylor Eric , Brammer Mick
Published: May 2006

Higher cognitive inhibitory and attention functions have been shown to develop throughout adolescence, presumably concurrent with anatomical brain maturational changes. The relatively scarce developmental functional imaging literature on cognitive control, however, has been inconsistent with respect to the neurofunctional substrates of this cognitive development, finding either increased or decreased executive prefrontal function in the progression from childhood to adulthood. Such inconsistencies may be due to small subject numbers or confounds from age‐related performance differences in block design functional MRI (fMRI). In this study, rapid, randomized, mixed‐trial event‐related fMRI was used to investigate developmental differences of the neural networks mediating a range of motor and cognitive inhibition functions in a sizeable number of adolescents and adults. Functional brain activation was compared between adolescents and adults during three different executive tasks measuring selective motor response inhibition (Go/no‐go task), cognitive interference inhibition (Simon task), and attentional set shifting (Switch task). Adults compared with children showed increased brain activation in task‐specific frontostriatal networks, including right orbital and mesial prefrontal cortex and caudate during the Go/no‐go task, right mesial and inferior prefrontal cortex, parietal lobe, and putamen during the Switch task and left dorsolateral and inferior frontotemporoparietal regions and putamen during the Simon task. Whole‐brain regression analyses with age across all subjects showed progressive age‐related changes in similar and extended clusters of task‐specific frontostriatal, frontotemporal, and frontoparietal networks. The findings suggest progressive maturation of task‐specific frontostriatal and frontocortical networks for cognitive control functions in the transition from childhood to mid‐adulthood. Hum Brain Mapp, 2006. © 2006 Wiley‐Liss, Inc.
Synthesis of new pterocarpans and rapid O‐alkylation under microwave irradiation
Authors: Evangelista E. A. , Couri M. R. C. , Raslan D. S. , Alves R. B.
Published: May 2006

Herein, it is described five new pterocarpans. Pterocarpans 8 and 9 were synthesized by classical [3 + 2] cycloaddition reaction of 2H‐chromene 7a and 7b with 2‐methoxy‐1,4‐benzoquinone. Pterocarpan 8 was O‐alkylated in the absence of solvents using a domestic microwave oven as a heat source and a classical O‐alkylation method with traditional heating. In this way three more new pterocarpans were obtained. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:239–244, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20175
Synthesis of new bridgehead heterocycles: Pyrimido[3′,2′:3,4]‐1,2,4‐triazino[5,6‐b]indoles
Authors: Bhagat Sunita , Jain Manish , Pandey Mukesh K. , Pragati  , Saxena Anjali , Jain Subhash C.
Published: May 2006

A new bridgehead nitrogen hetero‐ cycle viz. 11‐carboethoxy‐9‐oxo‐pyrimido[3′2′:3,4]‐1,2,4‐triazino[5,6‐b]indole 3 has been synthesized from 3‐azido‐5H‐1,2,4‐triazino[5,6‐b]indole 2 by its reaction with diethyl fumerate. The intermediate 2 was obtained by treating 3‐hydrazino‐5H‐1,2,4‐triazino[5,6‐b]indole with NaNO2 in presence of polyphosphoric acid. A plausible mechanism for the formation of 3 has been formulated and discussed. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:272–276, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20199
Highly functionalized dihydrofuran derivatives: Synthesis by diastereoselective intramolecular Wittig reaction
Authors: Azizian Javad , Karimi Ali Reza , Soleimani Ebrahim , Mohammadi Ali A. , Mohammadizadeh Mohammad R.
Published: May 2006

3a,8a‐Dihydroxy‐1,3,3a,8a‐tetrahydro‐ indeno[1,2‐d]imidazole‐2,8‐dione 3 reacts with dialkyl acetylenedicarboxylates in the presence of triphenylphosphine to produce some novel interesting dihydrofuran derivatives diastereoselectively. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:277–279, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20202
Utilization of α‐halocarbonyl compounds in the synthesis of thiazole, thiadiazole, and thiophene derivatives
Authors: Abdel‐latif Ehab , Bondock Samir
Published: May 2006

The behavior of ethyl 2‐phenylthiocarb‐ amoyl acetate 1 toward a variety of several α‐halo‐ carbonyl compounds was investigated. Thus, reaction of 1 with α‐bromoketones, hydrazonoyl bromides, and 2‐chloro‐N‐arylacetamides afforded the corresponding dihydrothiazole, 1,3,4‐thiadiazole, and thiophene derivatives, respectively. The synthesis of thiazolidin‐4‐one 11, thiazolidin‐5‐one 12, and some azo derivatives of thiazolidin‐5‐one were described. 5‐Arylazothiazoles 17 and 19 were synthesized by condensation of hydrazonoyl bromides 3 with different thiourea derivatives. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:299–305, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20206
Synthesis of N‐lactosylated thiourea and benzothiazolyl thiourea
Authors: Tale Prashant V. , Deshmukh Shirish P.
Published: May 2006

Several N‐lactosylated aryl thioureas and benzothiazolyl thioureas have been prepared by the condensation of hepta‐O‐acetyl‐β‐D‐lactosyl isothiocyanate with aryl amines and 2‐aminobenzothiazole/substituted benzothiazoles. Hepta‐O‐acetyl‐β‐D‐lactosyl isothiocyanate was prepared by the interaction of hepta‐O‐acetyl‐α‐D‐lactosyl bromide and lead thiocyanate. The structures of these new N‐lactosides have been established on the basis of IR, NMR, and mass spectral studies. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:306–309, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20207
Chiral activated alkenes induced asymmetric Baylis–Hillman reaction in Me3N/H2O/solvent medium
Authors: He Ke , Zhou Zhenghong , Zhao Guofeng , Tang Chuchi
Published: May 2006

Chiral‐activated alkenes, L‐menthyl acrylate and (+)‐N‐α‐phenylethyl acrylamide, induced asymmetric Baylis–Hillman reaction of aromatic aldehydes was realized at 25°C for 7 days in Me3N/H2O/solvent homogeneous medium. The corresponding Baylis–Hillman adducts were obtained in good chemical yield with moderate to excellent diastereoselectivity (up to 99% de). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:317–321, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20209
Maternal anxiety at amniocentesis and plasma cortisol
Authors: Sarkar P. , Bergman K. , Fisk N.M. , Glover V.
Published: May 2006

Objectives

To assess whether anticipation of amniocentesis is linked with maternal anxiety, and whether this anxiety is associated with increased maternal plasma cortisol.

Methods

Two hundred and fifty‐four women awaiting a morning amniocentesis for karyotyping (gestation range 15–37 weeks, median 17 weeks) completed Spielberger state and trait anxiety inventory (STAI) questionnaires, and provided blood samples immediately before the procedure for cortisol assay. Six hundred and five women at mean gestation of 20 weeks, attending the same hospital for routine ultrasound but not for amniocentesis, also completed Spielberger STAI questionnaires and served as a comparison group for the anxiety ratings.

Results

Mean state and trait anxiety scores (± SD) in the comparison group of 605 women at mean gestation of 20 weeks were 36.1 ± 10.2 (range 20–70) and 35.6 ± 8.9 (range 20–73), respectively. The mean state anxiety score (±SD) of 49.8 ± 14.0 (range 20–77) of the amniocentesis group was considerably higher than the comparison group (p < 0.001), although the mean trait anxiety score in the amniocentesis group was similar at 36.4 ± 8.6 (range 21–60). The state, but not trait, anxiety correlated with plasma cortisol (r = 0.176, p = 0.005). Maternal cortisol in the amniocentesis group increased with gestational age (r = 0.310, p < 0.001), whereas state anxiety scores showed no significant change with increase in gestational age (r = − 0.042, ns). Multivariate analysis demonstrated that maternal state anxiety was positively correlated with plasma cortisol independent of gestation and time of collection.

Conclusion

Women awaiting amniocentesis experience a high state anxiety associated with modestly increased plasma cortisol. Copyright © 2006 John Wiley & Sons, Ltd.
Theoretical study of cation doping effect on the electronic conductivity of Li4Ti5O12
Authors: Liu Daotan , Ouyang Chuying , Shu Jie , Jiang Jun , Wang Zhaoxiang , Chen Liquan
Published: May 2006

The electronic band structures of pristine and Cr‐, Fe‐, Ni‐ or Mg‐doped Li4Ti5O12 have been calculated by first‐principles local‐density calculations. Analysis is carried out for the band gaps and density of states of these materials. It is shown that Cr or Mg doping can improve the electronic conduction of Li4Ti5O12, but Ni or Fe doping does not have such an effect. The mechanism for the improved electronic conduction is also proposed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐dimensional electron gas in cubic Alx Ga1–xN/GaN heterostructures
Authors: Potthast S. , Schörmann J. , Fernandez J. , As D. J. , Lischka K. , Nagasawa H. , Abe M.
Published: May 2006

We report on the optical and electrical properties of cubic AlxGa1–xN/GaN heterostructures. The optical properties were investigated by photoluminescence measurements. A luminescence band at 3.250 eV was observed with our cubic AlxGa1–xN/GaN heterostructures. The emission lies between the excitonic emission of c‐GaN at 3.276 eV and the donor‐acceptor transition at about 3.135 eV. With increasing excitation power we find a characteristic blue shift of 4.5 meV/decade. To confirm the existence of a two‐dimensional electron gas the transition energy versus externally applied voltage has been investigated. A 1.3 meV/V shift was measured and quantitatively verified by a self consistent solution of the Schrödinger and Poisson equation. The electrical properties were determined by capacity‐voltage (CV)‐measurements. The measured carrier profile is in excellent agreement with theoretical simulations and showed a sheet carrier concentration up to n = 1.6 × 1012 cm–2 at the AlxGa1–xN/GaN interface. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Planning and analysis of three‐arm non‐inferiority trials with binary endpoints
Authors: Kieser Meinhard , Friede Tim
Published: May 2006

Three‐arm trials including an experimental treatment, an active control and a placebo group are frequently preferred for the assessment of non‐inferiority. In contrast to two‐arm non‐inferiority studies, these designs allow a direct proof of efficacy of a new treatment by comparison with placebo. As a further advantage, the test problem for establishing non‐inferiority can be formulated in such a way that rejection of the null hypothesis assures that a pre‐defined portion of the (unknown) effect the reference shows versus placebo is preserved by the treatment under investigation. We present statistical methods for this study design and the situation of a binary outcome variable. Asymptotic test procedures are given and their actual type I error rates are calculated. Approximate sample size formulae are derived and their accuracy is discussed. Furthermore, the question of optimal allocation of the total sample size is considered. Power properties of the testing strategy including a pre‐test for assay sensitivity are presented. The derived methods are illustrated by application to a clinical trial in depression. Copyright © 2006 John Wiley & Sons, Ltd.
Chronic itch and pain—Similarities and differences
Authors: Ständer Sonja , Schmelz Martin
Published: May 2006

Both, pruritus and pain are aversive, but clearly distinct sensations originating in the peripheral and central nervous system. During the last years, many interactions between itch and pain in acute transmission and sensitization processes have been identified. It is common experience that the itch sensation can be reduced by the painful sensations caused by scratching. Vice versa analgesia may reduce this inhibition and thus enhance itch. This phenomenon is particularly relevant to spinally administered μ‐opioid receptor agonists, which induce segmental analgesia often combined with segmental pruritus. The peripheral and central sensitization to pain and to itch exhibits striking similarities. Classical inflammatory mediators such as bradykinin have been shown to sensitize nociceptors for both itch and pain. Also regulation of gene expression induced by trophic factors, such as NGF, plays a major role in persistently increased neuronal sensitivity for itch and pain. Finally, itch and pain exhibit corresponding patterns of central sensitization. The knowledge of antagonistic interaction, but also of similar sensitization processes has major implication for antipruritic therapeutic approaches.
Undetectable levels of N6‐methyl adenine in mouse DNA: Cloning and analysis of PRED28, a gene coding for a putative mammalian DNA adenine methyltransferase
Authors: Ratel David , Ravanat Jean-Luc , Charles Marie-Pierre , Platet Nadine , Breuillaud Lionel , Lunardi Joël , Berger François , Wion Didier
Published: May 2006

Three methylated bases, 5‐methylcytosine, N4‐methylcytosine and N6‐methyladenine (m6A), can be found in DNA. However, to date, only 5‐methylcytosine has been detected in mammalian genomes. To reinvestigate the presence of m6A in mammalian DNA, we used a highly sensitive method capable of detecting one N6‐methyldeoxyadenosine per million nucleosides. Our results suggest that the total mouse genome contains, if any, less than 103 m6A. Experiments were next performed on PRED28, a putative mammalian N6‐DNA methyltransferase. The murine PRED28 encodes two alternatively spliced RNA. However, although recombinant PRED28 proteins are found in the nucleus, no evidence for an adenine‐methyltransferase activity was detected.
A transgenic rice seed accumulating an anti‐hypertensive peptide reduces the blood pressure of spontaneously hypertensive rats
Authors: Yang Lijun , Tada Yoshifumi , Yamamoto Masayuki P. , Zhao Hui , Yoshikawa Masaaki , Takaiwa Fumio
Published: May 2006

RPLKPW is a potent anti‐hypertensive peptide designed according to the structure of ovokinin(2–7) (RADHPF). In this study, we generated transgenic rice plants that accumulate the RPLKPW peptide as a fusion protein with the rice storage protein glutelin. The engineered peptide is expressed under the control of endosperm‐specific glutelin promoters and specifically accumulates in seeds. Oral administration of either the RPLKPW‐glutelin fraction or transgenic rice seeds to spontaneously hypertensive rats (SHRs) significantly reduced systolic blood pressures. These results suggest the possible application of transgenic rice seed as a nutraceutical delivery system and specifically for administration of active peptides in hypertension.
Interaction of pro‐apoptotic protein HGTD‐P with heat shock protein 90 is required for induction of mitochondrial apoptotic cascades
Authors: Kim Jee-Youn , Kim Su-Mi , Ko Jeong-Hun , Yim Ji-Hye , Park Jin-Hae , Park Jae-Hoon
Published: May 2006

HGTD‐P is a hypoxia‐responsive pro‐apoptotic protein that transmits hypoxic signals directly to mitochondria. When overexpressed, HGTD‐P induces cell death via typical mitochondrial apoptotic cascades. However, much is unknown about post‐transcriptional modification and signaling networks of HGTD‐P in association with cell death‐regulating proteins. We performed yeast two‐hybrid screening to identify the molecules involved in HGTD‐P‐mediated cell death pathways. In this study, we show that heat shock protein 90 physically interacts with HGTD‐P and that suppression of Hsp90 activity by low concentrations of geldanamycin reduced HGTD‐P‐induced mitochondrial catastrophe through inhibition of mitochondrial translocation of HGTD‐P.
Determinanten der Motivation und der Bereitschaft zur Teilnahme an Fragebogenstudien
Authors: Konradt Udo , Fary Yasmin
Published: May 2006

Zusammenfassung. In dieser Studie wurden Prädiktoren zur Vorhersage der Motivation zur Teilnahme an Fragebogenstudien erfasst. Darüber hinaus wurden die Prädiktoren verwendet, um die Beteiligung an einer geplanten weiteren Untersuchung vorherzusagen. 457 Teilnehmer nahmen an einer selbst-administrierten schriftlichen Befragung teil und beantworteten Fragen zu personenbezogenen Variablen (u.a. Fähigkeiten und Einstellungen) sowie situativen Variablen (u.a. zeitlicher Aufwand, monetärer Anreiz, persönliche Ansprache, Art der Quelle). Als Kriterium wurde die Beteiligung an einer geplanten schriftlichen Befragung verwendet. Die Ergebnisse zeigen, dass eher jüngere Personen, Personen mit höherer Bildung sowie Personen, die beruflichen Umgang mit Fragebögen besitzen, eher bereit sind, an einer Fragebogenstudie teilzunehmen. Als bedeutsame Einstellungsvariablen erwiesen sich die Privatsphäre, eine akademische Quelle der Befragung und ein persönliches Interesse am Fragebogenthema. In Bezug auf die Beteiligung zeigten sich das Alter, das Bildungsniveau, das persönliche Interesse, eine indirekte Form der Ansprache sowie der Wert, der Fragebögen insgesamt zugemessen wird, als signifikante Prädiktoren. Der Zusammenhang zwischen den Einstellungsvariablen und der Beteiligung wurde von der Teilnahmemotivation vollständig mediiert.
Auroral poleward boundary intensifications (PBIs): Their two‐dimensional structure and associated dynamics in the plasma sheet
Authors: Zesta E. , Lyons L. , Wang C.‐P. , Donovan E. , Frey H. , Nagai T.
Published: May 2006

Auroral poleward boundary intensifications (PBIs) are typically seen both in ground meridian scanning photometers (MSP) and in ground and spacecraft auroral images. They appear as a localized increase in intensity at or near the magnetic separatrix. This increase is often seen to extend equatorward through the ionospheric mapping of the plasma sheet. PBIs are associated with plasma sheet flow bursts and are thus important for the remote monitoring of plasma sheet dynamics. From the study of simultaneous ground MSP observations, IMAGE FUV auroral images, and Geotail plasma sheet data, we find that PBIs correlate well with plasma sheet fast flows observed within the local time sector of the PBIs and that there can be several PBIs over the longitudinal range of fast flows in the tail. We infer that every north‐south PBI is the ionospheric signature of a fast flow channel in the plasma sheet and that many fast flow channels exist simultaneously over a width of the plasma sheet that can comprise the whole width of the plasma sheet or only a part of it. Also, we find that there is a local time dependence on the type of PBI structure. Most PBIs are narrow auroral structures that are not strictly north‐south oriented. Instead, PBIs are tilted counterclockwise away from the north‐south direction, leading to a preferred orientation that is approximately aligned with a line going from 0300 magnetic local time (MLT) to 1700 MLT. This results in PBIs that are closer to north‐south (NS) structures in the postmidnight sector and closer to east‐west (EW) near the dusk sector. In the premidnight sector (2200–0000 MLT), PBIs start as EW arcs and then tilt and become primarily NS structures. We further found for one event that the PBI fast flows have a large Vy component resulting in tail convection that is both earthward and dawnward in the region of Geotail. We suggest that the continuous and strongly positive interplanetary magnetic field (IMF) By may order the two‐dimensional convection as observed, thus offering a possible explanation for the alignment direction of PBIs in the ionosphere under the assumption that fast flow channels align themselves with the background convection. However, the projection of the PBI structures into the tail using the T96 model suggests that all PBIs, both EW and NS, map to radially stretched channels in the tail that do not have a significant dawnward component. Future work is needed to clarify this apparent contradiction. Finally, frequency analysis indicates that the PBI/bursty bulk flow (BBF) period is characterized by oscillations in the velocity and magnetic field with frequencies of ∼0.6 mHz and ∼1.3–1.5 mHz. This oscillation in velocity is superposed on the background strong convection.
Modeling organic carbon burial during sea level rise with reference to the Cretaceous
Authors: Bjerrum C. J. , Bendtsen J. , Legarth J. J. F.
Published: May 2006

After three decades of research on the correlation between sea level and various proxies, there has been very little quantification of the first‐order influence of sea level change on nutrient inventory, marine productivity, and burial of organic carbon. We present a model aimed at quantifying the burial of organic carbon as a function of sea level rise. The biogeochemical model explicitly considers the mean surface area distribution of the Earth as a function of elevation. Also included is dissolved inorganic phosphate (DIP) liberated from coastal sediments during transgression. We quantify how sea level rise of magnitudes inferred for the mid‐Cretaceous influences the phosphorus cycle and burial of organic carbon. The burial efficiency is greater on the shelf. Therefore, in the model, the larger shelf area under high sea level results in more efficient burial of marine organic carbon for a given DIP concentration and associated new production of organic matter (NP). With a Late Cretaceous model shelf area the residence time of DIP decreases by 60% relative to the present‐day reference. Thus, in the final steady state, DIP and NP in the open ocean are reduced compared to today when the biologically reactive phosphorus (Preac) fluxes to the ocean from land are held constant. The lower new production reduces the oxygen demand for respiration and results in a significant oxygenation of the global ocean. Finally, the global organic carbon burial decreases by 30% relative to today in the model. This decrease results from feedbacks between the flux of organic carbon to the seafloor and the ratio of organic carbon to Preac in buried sediments. In contrast, during sea level rise, coastal erosion may increase the Preac flux to the ocean by up to ∼20% relative to today and cause a temporary increase in DIP concentration in the ocean. The resulting increase in organic carbon burial is equivalent to a carbon isotope event of +0.5 to 1‰. Larger carbon isotope events can be triggered by sea level rise only when the ocean is sufficiently close to anoxia in the oxygen minimum zone just prior to the sea level rise.
U‐Pb dating of zircon by LA‐ICP‐MS
Authors: Chang Zhaoshan , Vervoort Jeffery D. , McClelland William C. , Knaack Charles
Published: May 2006

In this study we used LA‐ICP‐MS (laser ablation–inductively coupled plasma–mass spectrometry) to determine U‐Pb ages of 5 zircon samples of known age (∼1800 Ma to ∼50 Ma) in order to determine the reproducibility, precision, and accuracy of this geochronologic technique. This work was performed using a ThermoFinnigan Element2 magnetic sector double‐focusing ICP‐MS coupled with a New Wave Research UP‐213 laser system. The laser ablation pit sizes ranged from 30 to 40 μm in diameter. Laser‐induced time‐dependent fractionation is corrected by normalizing measured ratios in both standards and samples to the beginning of the analysis using the intercept method. Static fractionation, including those caused during laser ablation and due to instrumental discrimination, is corrected using external zircon standards. Total uncertainty for each laser analysis of an unknown is combined quadratically from the uncertainty in the measured isotope ratios of the unknown and the uncertainty in the fractionation factors calculated from the measurement of standards. For individual analyses we estimate that the accuracy and precision are better than 4% at the 2 sigma level, with the largest contribution in uncertainty from the measurement of the standards. Accuracy of age determinations in this study is on the order of 1% on the basis of comparing the weighted average of the LA‐ICP‐MS determinations to the TIMS ages. Due to unresolved contributions to uncertainty from the lack of a common Pb correction and from potential matrix effects between standards and unknowns, however, this estimate cannot be universally applied to all unknowns. Nevertheless, the results of this study provide an example of the type of precision and accuracy that may be possible with this technique under ideal conditions. In summary, the laser ablation technique, using a magnetic sector ICP‐MS, can be used for the U‐Pb dating of zircons with a wide range of ages and is a useful complement to the established TIMS and SHRIMP techniques. This technique is especially well suited to reconnaissance geochronologic and detrital zircon studies.