bluuebunny/crossref_metadata_2025 huggingface dataset:
MP2 theory investigation on the halides of D6hC36:C36Xn (X=F,Cl,Br; n=2,4,6,12)
Authors: Hong Bo , Chang Ying-Fei , Qiu Yong-Qing , Sun Hao , Su Zhong-Min , Wang Rong-Shun
Published: April 2006

An investigation of C36Xn (X=F,Cl,Br; n=2,4,6,12) formed from the initial C36 fullerene with D6h symmetry has been performed using the MP2 theory. Their equilibrium structures, reaction energies, strain energies, lowest unoccupied molecular orbital-highest occupied molecular orbital (LUMO-HOMO) gap energies, and aromaticities have been studied. The calculation results showed that those addition reaction were highly exothermic and C36Xn were more stable than C36. Moreover, from the view of thermodynamics it should be possible to detect C36X6. The LUMO-HOMO gap energies of C36Xn were higher than D6hC36 and the redox characteristics of C36Xn were weaker comparing to D6hC36. The analyses of π-orbital axis vector indicated that the chemical reactivity of C36 was the result of the high strain, and the nucleus independent chemical shifts research showed that the stabilities of the C36X6 were correlative with the conjugation effect.
Time reversal of wideband microwaves
Authors: Lerosey G. , de Rosny J. , Tourin A. , Derode A. , Fink M.
Published: April 2006

In this letter, time reversal is applied to wideband electromagnetic waves in a reverberant room. To that end a multiantenna time reversal mirror (TRM) has been built. A 150MHz bandwidth pulse at a central frequency of 2.45GHz is radiated by a monopolar antenna, spread in time due to reverberation, recorded at the TRM, time reversed, and retransmitted. The time-reversed wave converges back to its source and focus in both time and space. The time compression is studied versus the number of antennas in the TRM and its bandwidth. The focal spot is also measured thanks to an eight-channel receiving array.
Nanoscale quantum dot infrared sensors with photonic crystal cavity
Authors: Posani K. T. , Tripathi V. , Annamalai S. , Weisse-Bernstein N. R. , Krishna S. , Perahia R. , Crisafulli O. , Painter O. J.
Published: April 2006

We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio (represented by the specific detectivity D*) by more than an order of magnitude. The conversion efficiency of the detector at Vb=−2.6V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility.
Nonlinear electron resonance heating in capacitive radio frequency discharges
Authors: Mussenbrock Thomas , Brinkmann Ralf Peter
Published: April 2006

Technological processing plasmas are frequently operated at relatively low gas pressure (<10Pa). A characteristic feature of this regime is that collisions of the electrons with the atoms or molecules of the neutral background are relatively rare, and the so-called collisional or Ohmic heating ceases to be an effective mechanism of energy deposition into the plasma. Experiments indicate that at low pressure an alternative mechanism of electron heating exists which can sustain the plasma. Despite 30years of intense research, the exact nature of this “anomalous” heating mechanism is still under discussion. The two standard models are known as “stochastic heating” and “pressure heating,” respectively. This work proposes a third explanation of anomalous electron heating and suggests that, in the last analysis, all three mechanisms may contribute to the observed effect.
Quantitative shadow technique for the investigation of magnetic domain wall widths
Authors: Pozzi G. , Beleggia M. , Schofield M. A. , Zhu Y.
Published: April 2006

Quantitative measurement of domain wall widths in a magnetic thin foil of Nd2Fe14B and a patterned Ni88Fe12 Permalloy element is obtained by the analysis of coherent shadow deformation of an electrostatic biprism in an electron microscope. Information related to the phase gradient in the direction perpendicular to the biprism is extracted by comparing the recorded shadow images with simulations computed according to the experimental electron optical configuration and by varying a single free parameter: the domain wall width. We demonstrate the feasibility of such experiments and the usefulness of the technique for characterization of magnetic features at different length scales.
Thin-film structures induced by electrostatic field and substrate kinetic constraint
Authors: Lu Wei , Kim Dongchoul
Published: April 2006

We present a three-dimensional dynamic model for the structural formation of thin polymer films on a substrate subjected to an electrostatic field. The simulations reveal the destabilization of a flat polymer-air interface and the formation of uniform pillars emerging out of the film. We show that this self-assembly process is not solely determined by energetics. The kinetic constraint of the substrate can play an important role.
Optical generation and detection of shock waves in sapphire at room temperature
Authors: van Capel P. J. S. , Dijkhuis J. I.
Published: April 2006

Using pump-probe spectroscopy, we study the propagation of laser-excited longitudinal, high-amplitude, coherent picosecond acoustic phonon wave packets in thin sapphire slabs at room temperature. We observe significant stretching of the wave packet up to several tens of picoseconds, accompanied by strong steepening of the wave fronts. The results demonstrate the supersonic and subsonic nature of propagation in viscous nonlinear media and more specifically the presence of acoustic frequencies in the wave packet as high as 500GHz. All experimental data are in excellent agreement with simulations based on Burgers’ equation.
Improved barrier properties of ultrathin Ru film with TaN interlayer for copper metallization
Authors: Qu Xin-Ping , Tan Jing-Jing , Zhou Mi , Chen Tao , Xie Qi , Ru Guo-Ping , Li Bing-Zong
Published: April 2006

The properties of ultrathin ruthenium (∼5nm)∕TaN(∼5nm) bilayer as the copper diffusion barrier are studied. Cu, Ru, and TaN thin films are deposited by using the ion beam sputtering technique. The experimental results show that the thermal stability of the Cu∕Ru∕TaN∕Si structure is much more improved than that of the Cu∕Ru∕Si structure, which should be attributed to the insertion of the amorphous TaN interlayer. The microstructure evolution of the Cu∕Ru∕TaN∕Si structure during annealing is also discussed. The results show that the Ru∕TaN bilayer can be a very promising diffusion barrier in the future seedless Cu interconnect technology.
Roo-Guard® sound emitters are not effective at deterring tammar wallabies (Macropus eugenii) from a source of food
Authors: Muirhead Sarah , Blache Dominique , Wykes Boyd , Bencini Roberta
Published: April 2006

Auditory deterrents such as the Roo-Guard® sound emitters (Shu-Roo Australia Pty Ltd) have been used to keep kangaroos off crops and airstrips. We tested the efficacy of the Roo-Guard® Mk II sound emitter in deterring tammar wallabies (Macropus eugenii) from a known source of food on Garden Island, Western Australia, where up to 400 tammars are killed yearly by vehicles. The device was not effective in deterring the tammars from the food even when an alternative source of food was available. It was concluded that the Roo-Guards in their present form are not suitable to keep tammars off the roads of Garden Island.
Temporal dynamics of emergence and dispersal of garter snakes from a communal den in Manitoba
Authors: Shine R. , Langkilde T. , Wall M. , Mason R. T.
Published: April 2006

Although garter snakes at communal overwintering dens on the Canadian prairies have attracted considerable behavioural ecology research, previous studies have relied upon sampling of active animals to describe broad patterns of distribution and abundance of snakes within the den population. We conducted a mark–recapture study to directly quantify temporal and spatial variation in the phenotypic traits (sex, size, body condition) of snakes at the den itself, and those dispersing through woodland 50 m away. Captures of 909 snakes on the days they emerged, and 6653 snakes as they dispersed, revealed massive spatiotemporal heterogeneity in phenotypic traits among samples. Day-to-day variation in weather conditions affected numbers and sex ratios of emerging and dispersing snakes; for example, small females dispersed in greater numbers after unusually cold nights, when harassment by courting males was reduced. Most snakes stayed at the den only briefly (<5 days) prior to dispersal, so that sampling at the den itself (the only evidence available from most previous studies) underestimates the number of animals in the population, as well as the proportions of females, of small adult males and of juvenile animals. Overall, the heterogeneous and temporally dynamic distributions of phenotypic traits (such as sex and size) among our samples are predictable on the basis of the central roles of male–male competition and sexual conflict in the mating system of these snakes. Surprisingly, however, many of the snakes that overwinter at this den play no part in den-based breeding aggregations
The propensity of spotted-tailed quolls (Dasyurus maculatus) to encounter and consume non-toxic meat baits in a simulated canid-control program
Authors: Claridge Andrew W. , Murray Andy J. , Dawson James , Poore Rob , Mifsud Greg , Saxon Michael J.
Published: April 2006

Using a biomarker, we assessed the propensity of spotted-tailed quolls (Dasyurus maculatus) to encounter and consume non-toxic meat baits, ordinarily laced with the poison 1080 (sodium monofluoroacetate) and deployed for control of wild dogs (Canis lupus dingo, Canis familiaris and hybrids of the two) in southern Australia. In the first experiment, 60 unpoisoned meat baits injected with Rhodamine B were placed on the surface of the ground at 250-m intervals along two separate transects crossing an open woodland study area. One week after placement, a range of animals, including quolls, had removed all baits. Microscopic assay of whisker samples collected from live-captured quolls later revealed that 6 of 10 (60%) animals were positive for the biomarker, indicating that they had encountered and consumed baits. In the second experiment, conducted at the same site one year later, 150 similarly prepared meat baits were delivered aerially from a helicopter along the same transects, at a rate of one bait every 100 m. Eight of 17 quolls (47%) were found to have encountered and consumed at least one and up to five baits. Combined with previous studies, our results reaffirm that surface or aerial baiting operations for wild dogs may place local quoll populations at risk. However, further research is necessary to establish the relationship between this risk and actual mortality levels during such baiting operations since there are a number of factors that may influence the toxicity of baits for spotted-tailed quolls in a field situation as well as the danger those baits may pose.
Fine-scale habitat use by the southern emu-wren (Stipiturus malachurus)
Authors: Maguire Grainne S.
Published: April 2006

Fine-scale variation in habitat structure and composition is likely to influence habitat use by avian species with limited flight capabilities. I investigated proportional use of available habitat and microhabitat by the southern emu-wren (Stipiturus malachurus), a threatened, flight-limited passerine, at three sites in Victoria, in relation to vegetation structure and composition. Emu-wrens appeared to discriminate between habitats with regard to structural rather than floristic characteristics. Habitats with dense vertical foliage of shrubs, grasses and sedges/rushes between ground level and 100 cm, and dense horizontal cover of medium to tall shrubs, were used most frequently. However, when availability of habitat was taken into account, habitat use was negatively correlated with the vertical density of low shrub foliage and species richness. Within habitats, emu-wrens more frequently used plant species that had a dense canopy cover (26 ± 2% of total cover, crown diameter 93 ± 5 cm), high foliage density between 50 and 100 cm, and average heights of ~1 m. Plant species in which the birds nested comprised ~14% of total canopy cover and were densest between ground level and 50 cm. Canopy cover, vegetation height and vertical foliage density were consistently important variables correlated with emu-wren habitat use at multiple fine-scales. This study provides valuable information for conservation management of the species; in particular, the restoration of degraded habitats.
Absence of the transcription factor CCAAT enhancer binding protein α results in loss of myeloid identity in bcr/abl-induced malignancy
Authors: Wagner Katharina , Zhang Pu , Rosenbauer Frank , Drescher Bettina , Kobayashi Susumu , Radomska Hanna S. , Kutok Jeffery L. , Gilliland D. Gary , Krauter Jürgen , Tenen Daniel G.
Published: April 2006

The lineage-determining transcription factor CCAAT enhancer binding protein α (C/EBPα) is required for myeloid differentiation. Decreased function or expression of C/EBPα is often found in human acute myeloid leukemia. However, the precise impact of C/EBPα deficiency on the maturation arrest in leukemogenesis is not well understood. To address this question, we used a murine transplantation model of a bcr/abl-induced myeloproliferative disease. The expression of bcr/abl in C/EBPα
pos
fetal liver cells led to a chronic myeloid leukemia-like disease. Surprisingly, bcr/abl-expressing C/EBPα
−/−
fetal liver cells failed to induce a myeloid disease in transplanted mice, but caused a fatal, transplantable erythroleukemia instead. Accordingly, increased expression of the transcription factors SCL and GATA-1 in hematopoietic precursor cells of C/EBPα
−/−
fetal livers was found. The mechanism for the lineage shift from myeloid to erythroid leukemia was studied in a bcr/abl-positive cell line. Consistent with findings of the transplant model, expression of C/EBPα and GATA-1 was inversely correlated. Id1, an inhibitor of erythroid differentiation, was identified as a critical direct target of C/EBPα. Down-regulation of Id1 by RNA interference impaired C/EBPα-induced granulocytic differentiation. Taken together, our study provides evidence that myeloid lineage identity of malignant hematopoietic progenitor cells requires the residual expression of C/EBPα.
A Dirichlet process model for detecting positive selection in protein-coding DNA sequences
Authors: Huelsenbeck John P. , Jain Sonia , Frost Simon W. D. , Pond Sergei L. Kosakovsky
Published: April 2006

Most methods for detecting Darwinian natural selection at the molecular level rely on estimating the rates or numbers of nonsynonymous and synonymous changes in an alignment of protein-coding DNA sequences. In some of these methods, the nonsynonymous rate of substitution is allowed to vary across the sequence, permitting the identification of single amino acid positions that are under positive natural selection. However, it is unclear which probability distribution should be used to describe how the nonsynonymous rate of substitution varies across the sequence. One widely used solution is to model variation in the nonsynonymous rate across the sequence as a mixture of several discrete or continuous probability distributions. Unfortunately, there is little population genetics theory to inform us of the appropriate probability distribution for among-site variation in the nonsynonymous rate of substitution. Here, we describe an approach to modeling variation in the nonsynonymous rate of substitution by using a Dirichlet process mixture model. The Dirichlet process allows there to be a countably infinite number of nonsynonymous rate classes and is very flexible in accommodating different potential distributions for the nonsynonymous rate of substitution. We implemented the model in a fully Bayesian approach, with all parameters of the model considered as random variables.
Global traffic and disease vector dispersal
Authors: Tatem Andrew J. , Hay Simon I. , Rogers David J.
Published: April 2006

The expansion of global air travel and seaborne trade overcomes geographic barriers to insect disease vectors, enabling them to move great distances in short periods of time. Here we apply a coupled human–environment framework to describe the historical spread ofAedes albopictus, a competent mosquito vector of 22 arboviruses in the laboratory. We contrast this dispersal with the relatively unchanged distribution ofAnopheles gambiaeand examine possible future movements of this malaria vector. We use a comprehensive database of international ship and aircraft traffic movements, combined with climatic information, to remap the global transportation network in terms of disease vector suitability and accessibility. The expansion of the range ofAe. albopictusproved to be surprisingly predictable using this combination of climate and traffic data. Traffic volumes were more than twice as high on shipping routes running from the historical distribution ofAe. albopictusto ports where it has established in comparison with routes to climatically similar ports where it has yet to invade. In contrast,An. gambiaehas rarely spread from Africa, which we suggest is partly due to the low volume of sea traffic from the continent and, until very recently, a European destination for most flights.
Evidence for C–H cleavage by an iron–superoxide complex in the glycol cleavage reaction catalyzed by
myo
-inositol oxygenase
Authors: Xing Gang , Diao Yinghui , Hoffart Lee M. , Barr Eric W. , Prabhu K. Sandeep , Arner Ryan J. , Reddy C. Channa , Krebs Carsten , Bollinger J. Martin
Published: April 2006

myo

-Inositol oxygenase (MIOX) activates O
2
at a mixed-valent nonheme diiron(II/III) cluster to effect oxidation of its cyclohexan-(1,2,3,4,5,6-hexa)-ol substrate [

myo

-inositol (MI)] by four electrons to
d
-glucuronate. Abstraction of hydrogen from C
1
by a formally (superoxo)diiron(III/III) intermediate was previously proposed. Use of deuterium-labeled substrate, 1,2,3,4,5,6-[
2
H]
6
-MI (D
6
-MI), has now permitted initial characterization of the C–H-cleaving intermediate. The MIOX·1,2,3,4,5,6-[
2
H]
6
-MI complex reacts rapidly and reversibly with O
2
to form an intermediate, G, with a g = (2.05, 1.98, 1.90) EPR signal. The rhombic g-tensor and observed hyperfine coupling to
57
Fe are rationalized in terms of a (superoxo)diiron(III/III) structure with coordination of the superoxide to a single iron. G decays to H, the intermediate previously detected in the reaction with unlabeled substrate. This step is associated with a kinetic isotope effect of ≥5, showing that the superoxide-level complex does indeed cleave a C–H(D) bond of MI.
Bone marrow-derived cells fuse with normal and transformed intestinal stem cells
Authors: Rizvi Adnan Z. , Swain John R. , Davies Paige S. , Bailey Alexis S. , Decker Adria D. , Willenbring Holger , Grompe Markus , Fleming William H. , Wong Melissa H.
Published: April 2006

Transplanted adult bone marrow-derived cells (BMDCs) have been shown to adopt the phenotype and function of several nonhematopoietic cell lineages and promote tumorigenesis. Beyond its cancer enhancing potential, cell fusion has recently emerged as an explanation of how BMDCs regenerate diseased heptocytes, contribute to Purkinje neurons and skeletal and cardiac muscle cells, and participate in skin and heart regeneration. Although bone marrow-derived epithelial cells also have been observed in the intestine, fusion as a mechanism has not been investigated. Here, we show that transplanted BMDCs fuse with both normal and neoplastic intestinal epithelium. Long-term repopulation by donor-derived cells was detected in all principal intestinal epithelial lineages including enterocytes, goblet cells, Paneth cells, and enteroendocrine cells, suggesting that the fusion partners of the BMDCs are long-lived intestinal progenitors or stem cells. Fusion of BMDCs with neoplastic epithelium did not result in tumor initiation. Our findings suggest an unexpected role for BMDCs in both regeneration and tumorigenesis of the intestine.
The molecular basis for differential dioxin sensitivity in birds: Role of the aryl hydrocarbon receptor
Authors: Karchner Sibel I. , Franks Diana G. , Kennedy Sean W. , Hahn Mark E.
Published: April 2006

2,3,7,8-Tetrachlorodibenzo-
p
-dioxin (TCDD) and related halogenated aromatic hydrocarbons (HAHs) are highly toxic to most vertebrate animals, but there are dramatic differences in sensitivity among species and strains. Aquatic birds including the common tern (
Sterna hirundo
) are highly exposed to HAHs in the environment, but are up to 250-fold less sensitive to these compounds than the typical avian model, the domestic chicken (
Gallus gallus
). The mechanism of HAH toxicity involves altered gene expression subsequent to activation of the aryl hydrocarbon receptor (AHR), a basic helix–loop–helix-PAS transcription factor. AHR polymorphisms underlie mouse strain differences in sensitivity to HAHs and polynuclear aromatic hydrocarbons, but the role of the AHR in species differences in HAH sensitivity is not well understood. Here, we show that although chicken and tern AHRs both exhibit specific binding of [
3
H]TCDD, the tern AHR has a lower binding affinity and exhibits a reduced ability to support TCDD-dependent transactivation as compared to AHRs from chicken or mouse. We further show through use of chimeric AHR proteins and site-directed mutagenesis that the difference between the chicken and tern AHRs resides in the ligand-binding domain and that two amino acids (Val-325 and Ala-381) are responsible for the reduced activity of the tern AHR. Other avian species with reduced sensitivity to HAHs also possess these residues. These studies provide a molecular understanding of species differences in sensitivity to dioxin-like compounds and suggest an approach to using the AHR as a marker of dioxin susceptibility in wildlife.
Signaling mediated by the dopamine D2 receptor potentiates circadian regulation by CLOCK:BMAL1
Authors: Yujnovsky Irene , Hirayama Jun , Doi Masao , Borrelli Emiliana , Sassone-Corsi Paolo
Published: April 2006

Environmental cues modulate a variety of intracellular pathways whose signaling is integrated by the molecular mechanism that constitutes the circadian clock. Although the essential gears of the circadian machinery have been elucidated, very little is known about the signaling systems regulating it. Here, we report that signaling mediated by the dopamine D2 receptor (D2R) enhances the transcriptional capacity of the CLOCK:BMAL1 complex. This effect involves the mitogen-activated protein kinase transduction cascade and is associated with a D2R-induced increase in the recruiting and phosphorylation of the transcriptional coactivator cAMP-responsive element-binding protein (CREB) binding protein. Importantly, CLOCK:BMAL1-dependent activation and light-inducibility of
mPer1
gene transcription is drastically dampened in retinas of D2R-null mice. Because dopamine is the major catecholamine in the retina, central for the neural adaptation to light, our findings establish a physiological link among photic input, dopamine signaling, and the molecular clock machinery.
Nanomechanical measurements of the sequence-dependent folding landscapes of single nucleic acid hairpins
Authors: Woodside Michael T. , Behnke-Parks William M. , Larizadeh Kevan , Travers Kevin , Herschlag Daniel , Block Steven M.
Published: April 2006

Nucleic acid hairpins provide a powerful model system for probing the formation of secondary structure. We report a systematic study of the kinetics and thermodynamics of the folding transition for individual DNA hairpins of varying stem length, loop length, and stem GC content. Folding was induced mechanically in a high-resolution optical trap using a unique force clamp arrangement with fast response times. We measured 20 different hairpin sequences with quasi-random stem sequences that were 6–30 bp long, polythymidine loops that were 3–30 nt long, and stem GC content that ranged from 0% to 100%. For all hairpins studied, folding and unfolding were characterized by a single transition. From the force dependence of these rates, we determined the position and height of the energy barrier, finding that the transition state for duplex formation involves the formation of 1–2 bp next to the loop. By measuring unfolding energies spanning one order of magnitude, transition rates covering six orders of magnitude, and hairpin opening distances with subnanometer precision, our results define the essential features of the energy landscape for folding. We find quantitative agreement over the entire range of measurements with a hybrid landscape model that combines thermodynamic nearest-neighbor free energies and nanomechanical DNA stretching energies.
Phenotypically distinct B cell development pathways map to the three B cell lineages in the mouse
Authors: Tung James W. , Mrazek Matthew D. , Yang Yang , Herzenberg Leonard A. , Herzenberg Leonore A.
Published: April 2006

A recent article by Montecino-Rodriguezet al.[Montecino-Rodriguez, E., Leathers, H. & Dorshkind, K. (2006)Nat. Immunol.7, 293–301] has distinguished the early progenitors for B-1 cells, which principally develop in neonates, from early progenitors for B-2 cells, which principally develop in adult bone marrow. Here we introduce syndecan-1 (CD138) and MHC class II (I-A) as markers of early B cell development [Hardy, R. R., Carmack, C. E., Shinton, S. A., Kemp, J. D. & Hayakawa, K. (1991)J. Exp. Med.173, 1213–1225; Hardy fractionsB–D] and show that the expression of these markers distinguishes the predominant B cell development pathway in neonates from the corresponding predominant pathway in adults (both progenitors are present but differently represented in each case). We show that pre-B cells (Hardy fractionD) in the predominant adult pathway express high levels of CD138 and intermediate levels of I-A, whereas the corresponding pre-B cells in the pathway that predominates in neonates do not express either of these markers. As expected, because most of the pre-B cells in adults express CD138, we find that sorted CD138+adult pre-B cells differentiate to IgM+B cellsin vitro. Sorted CD138−pre-B cells from neonates, the majority subset at this age, also mature to IgM+cells (without passing through a CD138+stage). Importantly, our studies here confirm the differential representation of adult and neonatal progenitor populations and further demonstrate that CD138 expression subdivides the adult CD19+, B220–6B2−/lowpopulation shown to contain B-1 progenitors in a way consistent with the predominance of B-1b progenitors in adults. Thus, CD138 expression provides a key route to distinguishing early B cell development pathway for what now are clearly three B cell lineages.
Optimal vortex formation as an index of cardiac health
Authors: Gharib Morteza , Rambod Edmond , Kheradvar Arash , Sahn David J. , Dabiri John O.
Published: April 2006

Heart disease remains a leading cause of death worldwide. Previous research has indicated that the dynamics of the cardiac left ventricle (LV) during diastolic filling may play a critical role in dictating overall cardiac health. Hence, numerous studies have aimed to predict and evaluate global cardiac health based on quantitative parameters describing LV function. However, the inherent complexity of LV diastole, in its electrical, muscular, and hemodynamic processes, has prevented the development of tools to accurately predict and diagnose heart failure at early stages, when corrective measures are most effective. In this work, it is demonstrated that major aspects of cardiac function are reflected uniquely and sensitively in the optimization of vortex formation in the blood flow during early diastole, as measured by a dimensionless numerical index. This index of optimal vortex formation correlates well with existing measures of cardiac health such as the LV ejection fraction. However, unlike existing measures, this previously undescribed index does not require patient-specific information to determine numerical index values corresponding to normal function. A study of normal and pathological cardiac health in human subjects demonstrates the ability of this global index to distinguish disease states by a straightforward analysis of noninvasive LV measurements.
An impending water crisis in Canada's western prairie provinces
Authors: Schindler D. W. , Donahue W. F.
Published: April 2006

Canada is usually considered to be a country with abundant freshwater, but in its western prairie provinces (WPP), an area 1/5 the size of Europe, freshwater is scarce. European settlement of the WPP did not begin until the late 19th and early 20th centuries. Fortuitously, the period since European settlement appears to have been the wettest century of the past two millennia. The frequent, long periods of drought that characterized earlier centuries of the past two millennia were largely absent in the 20th century. Here, we show that climate warming and human modifications to catchments have already significantly reduced the flows of major rivers of the WPP during the summer months, when human demand and in-stream flow needs are greatest. We predict that in the near future climate warming, via its effects on glaciers, snowpacks, and evaporation, will combine with cyclic drought and rapidly increasing human activity in the WPP to cause a crisis in water quantity and quality with far-reaching implications.
Tropical drying trends in global warming models and observations
Authors: Neelin J. D. , Münnich M. , Su H. , Meyerson J. E. , Holloway C. E.
Published: April 2006

Anthropogenic changes in tropical rainfall are evaluated in a multimodel ensemble of global warming simulations. Major discrepancies on the spatial distribution of these precipitation changes remain in the latest-generation models analyzed here. Despite this uncertainty, we find a number of measures, both global and local, on which reasonable agreement is obtained, notably for the regions of drying trend (negative precipitation anomalies). Models agree on the overall amplitude of the precipitation decreases that occur at the margins of the convective zones, with percent error bars of magnitude similar to those for the tropical warming. Similar agreement is found on a precipitation climate sensitivity defined here and on differential moisture increase inside and outside convection zones, a step in a hypothesized causal path leading to precipitation changes. A measure of local intermodel agreement on significant trends indicates consistent predictions for particular regions. Observed rainfall trends in several data sets show a significant summer drying trend in a main region of intermodel agreement: the Caribbean/Central-American region.
Partnering between monomers of cyclooxygenase-2 homodimers
Authors: Yuan Chong , Rieke Caroline Jill , Rimon Gilad , Wingerd Byron A. , Smith William L.
Published: April 2006

Prostaglandin endoperoxide H synthases (PGHSs) 1 and 2 convert arachidonic acid to prostaglandin H
2
in the committed step of prostanoid biosynthesis. These enzymes are pharmacological targets of nonsteroidal antiinflammatory drugs and cyclooxygenase (COX) 2 inhibitors. Although PGHSs function as homodimers and each monomer has its own COX and peroxidase active sites, the question of whether there is cross-talk between monomers has remained unresolved. Here we describe two heterodimers in which a native subunit of human PGHS-2 has been coupled to a subunit having a defect within the COX active site at some distance from the dimer interface. Native/G533A PGHS-2, a heterodimer with a COX-inactive subunit, had the same specific COX activity as the native homodimer. Native/R120Q PGHS-2, a heterodimer in which both subunits can oxygenate arachidonic acid but in which the R120Q subunit cannot bind the COX inhibitor flurbiprofen, was inhibited by flurbiprofen to about the same extent as native PGHS-2. These results imply that native PGHS-2 exhibits half-of-sites reactivity. Isothermal titration calorimetry established that only one monomer of the native PGHS-2 homodimer binds flurbiprofen tightly. In short, binding of ligand to the COX site of one monomer alters its companion monomer so that it is unable to bind substrate or inhibitor. We conclude that PGHS monomers comprising a dimer, although identical in the resting enzyme, differ from one another during catalysis. The nonfunctioning subunit may provide structural support enabling its partner monomer to catalyze the COX reaction. This subunit complementarity may prove to be characteristic of other dimeric enzymes having tightly associated monomers.
Total zinc absorption in young women, but not fractional zinc absorption, differs between vegetarian and meat-based diets with equal phytic acid content
Authors: Kristensen Mette Bach , Hels Ole , Morberg Catrine M. , Marving Jens , Büge Susanne , Tetens Inge
Published: April 2006

Zn bioavailability is often lower in vegetarian diets mainly due to low Zn and high phytic acid contents. The objective of the present study was to determine the fractional and total absorption of Zn from a vegetarian diet in comparison with meat diets with equal concentrations of phytic acid. A randomized crossover design, comprising three whole-day diet periods of 5 d each, with a vegetarian diet or diets containing Polish-produced meat or Danish-produced meat, was conducted. Twelve healthy female subjects completed the study. All diets had a high content of phytic acid (1250μlmol/d) and in the meat diets the main meals contained 60 g pork meat. All main meals were extrinsically labelled with the radioactive isotope65Zn and absorption of Zn was measured in a whole-body counter. The mean Zn content of the whole-day diet was: Polish meat diet 9·9 (SE 0·14) mg, Danish meat diet 9·4 (SE 0·19) mg and vegetarian diet 7·5 (SE 0·18) mg. No difference was observed in the fractional absorption of Zn (Polish meat diet: 27 (SE 1·2) %, Danish meat diet: 27 (SE 1·9)% and vegetarian diet: 23 (SE 2·6) %). A significantly lower amount of total Zn was absorbed from the vegetarian diet (mean Zn absorption of Polish meat diet: 2·7 (SE 0·12) mg/d (P<,0·001), Danish meat diet: 2·6 (SE 0·17) mg/d (P=/4 0·006) and vegetarian diet: 1·8 (SE 0·20) mg/d). In conclusion, the vegetarian diet compared with the meat-based diets resulted in lower amounts of absorbed Zn due to a higher content of Zn in the meat diets, but no difference was observed in the fractional absorption of Zn.
Effects of a policosanol supplement on serum lipid concentrations in hypercholesterolaemic and heterozygous familial hypercholesterolaemic subjects
Authors: Greyling A. , De Witt C , Oosthuizen W , Jerling J. C.
Published: April 2006

Policosanol is a mixture of higher aliphatic primary alcohols that is extracted from purified sugar cane wax or a variety of other plant sources, and has been shown to have beneficial effects on serum lipid concentrations. The objective of this study was to investigate the effects of a policosanol supplement (Octa-60) on lipid profiles of hypercholesterolaemic and heterozygous familial hypercholesterolaemic subjects. Nineteen hypercholesterolaemic and familial hypercholesterolaemic subjects completed this randomised, placebo-controlled, double-blind study. The subjects received either a daily dose of 20 mg policosanol or placebo for 12 weeks. After a wash-out period of 4 weeks, the interventions were crossed over. Lipid levels were measured at baseline and at the end of each intervention period. No significant differences in total cholesterol and LDL-cholesterol from baseline to end or between policosanol and placebo were seen in the hypercholesterolaemic or familial hypercholesterolaemic groups. There were small reductions in total cholesterol and LDL-cholesterol from baseline to end in the hypercholesterolaemic group, but these changes did not differ significantly from the changes with the placebo, indicating that the observed decrease in cholesterol in the policosanol group was not due to the specific effect of policosanol treatment. The differences in response may be ascribed to the differences in composition of the higher aliphatic primary alcohols in the previously used products, compared with the local policosanol supplement. An intake of 20 mg/d policosanol for 12 weeks had no significant effect on serum lipid levels in hypercholesterolaemic and heterozygous familial hypercholesterolaemic patients when compared with placebo intake.
Absorption and metabolism of red orange juice anthocyanins in rats
Authors: Felgines Catherine , Talavéra Séverine , Texier Odile , Besson Catherine , Fogliano Vincenzo , Lamaison Jean-Louis , Fauci Luca la , Galvano Giacomo , Rémésy Christian , Galvano Fabio
Published: April 2006

Anthocyanins are natural pigments that could be involved in various health effects. Red oranges are an important dietary source of anthocyanins, including cyanidin 3-glucoside (Cy 3-glc) and an acylated derivative, cyanidin 3-(600-malonyl)-glucoside (Cy 3-malglc). The aim of this study was to evaluate the absorption and metabolism of red orange anthocyanins in rats fed an anthocyanin-enriched diet for 12 d (approximately 2·8 μmol anthocyanins/d). Furthermore, the absorption of these anthocyanins was studied in both the stomach and intestine using in situ models in rats. Anthocyanin metabolites were identified and quantified by HPLC–electrospray ionization tandem MS and HPLC–diode array detection, respectively. The red orange anthocyanins, Cy 3-glc and Cy 3-malglc, as well as their respective methylated derivatives, were recovered in urine after red orange juice intake. The 24 h urinary excretion of total anthocyanins was low (0·081 (SEM 0·009) % of the ingested amount). However, a high proportion (about 20 %) of red orange anthocyanins was absorbed from the stomach. More Cy 3- malglc than Cy 3-glc was absorbed in the intestine. This study thus indicated that red orange juice anthocyanins were rapidly absorbed from both stomach and small intestine, and then excreted in the urine as intact and methylated forms. Moreover, the absorption and metabolism of acylated anthocyanins and non-acylated anthocyanins were similar.
Uptake of triacylglycerol-rich lipoproteins of differing triacylglycerol molecular species and unsaponifiable content by liver cells
Authors: Perona Javier S. , Avella Michael , Botham Kathleen M. , Ruiz-Gutierrez Valentina
Published: April 2006

The fatty acid composition of dietary oils can modulate the incorporation of triacylglycerol-rich lipoproteins (TRL) into hepatocytes, thus affecting the atherogenicity of these particles. However, nothing is known about the effect of the unsaponifiable fraction of the oils. In the present study, we evaluated the influence of these components on the uptake of TRL by rat primary hepatocytes. TRL were isolated from human serum after the intake of meals enriched in high-oleic sunflower oil (HOSO), virgin olive oil (VOO) or VOO enriched in its own unsaponifiable fraction (EVO). HOSO and HOSO-TRL differed from VOO and EVO and their corresponding TRL in the composition of triacylglycerol molecular species and of the unsaponifiable fraction. Furthermore, the increase in the unsaponifiable fraction of VOO led to changes in the triacylglycerol molecular species in the EVO-TRL. On incubation with hepatocytes, HOSO-TRL were taken up at a faster rate than VOO-TRL or EVO-TRL. In addition, in comparison to VOO-TRL, HOSO-TRL increased the expression of mRNA for the LDL receptor-related protein receptor, which plays an important role in the internalisation of remnant lipoproteins. EVO-TRL also increased LDL receptor-related protein mRNA expression in comparison with VOO-TRL, but this change was not accompanied by a rise in the uptake rate, suggesting that the unsaponifiable fraction of VOO may inhibit LDL receptor-related protein expression or activity post-transcriptionally. In conclusion, TRL from dietary oils with differing triacylglycerol molecular species and unsaponifiable fraction content are taken up by liver cells at different rates, and this may be important in the atherogenicity of these particles.
Methodological approaches to study dietary patterns in relation to risk of coronary heart disease and stroke
Authors: Schulze Matthias B. , Hoffmann Kurt
Published: April 2006

Dietary pattern analysis, which reflects the complexity of dietary intake, has received considerable attention by nutritional epidemiology. For a long time, two general approaches have been used to define these summary variables in observational studies. The exploratory approach is based only on the data of the study, whereas the hypothesis-oriented approach constructs pattern variables based on scientific evidence available before the study. Recently, a new statistical method, reduced rank regression, was applied to nutritional epidemiology that is exploratory by nature, but can use scientific evidence by focusing on disease-related dietary components or biomarkers. Several studies, both observational and clinical, suggest that dietary patterns may predict the risk of CHD and stroke. In the present review, we describe the results of these studies and the available evidence regarding the relationships between dietary patterns and risk of CVD and we discuss limitations and strengths of the statistical methods used toextract dietary patterns.
Phylloquinone (vitamin K1) intakes and serum undercarboxylated osteocalcin levels in Irish postmenopausal women
Authors: Collins Aoife , Cashman Kevin D. , Kiely Máiréad
Published: April 2006

Low phylloquinone (vitamin K1) intakes have been associated with low bone mineral density in older adults. Phylloquinone intakes and serum undercarboxylated osteocalcin (ucOC) levels were assessed in ninety-seven apparently healthy, free-living Irish women aged 50–75 years. Phylloquinone intakes were estimated using a detailed dietary history, which measured habitual food intakes from a typical 14 d period, and recently published food composition data for phylloquinone. Fasting serum ucOC was measured using an enzyme immunoassay. The median daily intake of phylloquinone in the group from all sources was 108·8 mg and from food sources only was 106·6 mg, indicating that approximately 99% of the phylloquinone came from food. Vegetables and vegetable dishes contributed 67% of the total phylloquinone intake, but further analysis showed that broccoli, cabbage and lettuce were the primary sources, making a total contribution of 44 %. Twenty per cent of the women had a phylloquinone intake below the UK recommendation of 1μg/kg body weight per day and 34% failed to meet the US Adequate Intake value of 90mg/day. Mean serum ucOC levels in the women were 6·2 (SD 1·7) ng/ml and were predicted by phylloquinone intake (β— 22·20, generated from log-transformed phylloquinone intake data; P=4 0·04). On the basis of comparisons with both UK recommendations and US A equate Intakes for phylloquinone, the habitual intakes of phylloquinone in a high proportion of Irish postmenopausal women may not be adequate.
Differences in the relationship between BMI and percentage body fat between Japanese and Australian-Caucasian young men
Authors: Kagawa Masaharu , Kerr Deborah , Uchida Hayato , Binns Colin W
Published: April 2006

This cross-sectional study aimed to determine ethnic and environmental influences on the relationship between BMI and percentage body fat, using a sample of 144 Japanese and 140 Australian-Caucasian men living in Australia, and eighty-eight Japanese men living in Japan. Body composition was assessed by anthropometry using standard international methods (International Society for the Advancement of Kinanthropometry protocol). Body density was predicted using Durnin and Womersley's (1974) equation, and percentage body fat was calculated from Siri's (1961) equation.Significant (P<0·05) ethnic differences in stature, body mass and BMI were observed between Japanese and Australian men, but no ethnic differences were observed in their percentage body fat and height-corrected sum of skinfold thicknesses. No differences were found in the BMI–percentage body fat relationship between the Japanese subjects living in Australia and in Japan. Significant (P<0·05) ethnic differences in the BMI–percentage body fat relationship observed from a comparison between pooled Japanese men(aged 18–40 years, BMI range 16·6–32·8kg/m2) andAustralians (aged 18–39 years, BMI range 16·1–31·4kg/m2) suggest that Japanese men are likely to havea greater percentage body fat than Australian men at any given BMI value.From the analyses, the Japanese men were estimated to have an equivalent amount of body fat to the Australian men at BMI values that were about 1·5 units lower than those of the Australians (23·5kg/m2 and 28·2kg/m2, respectively).It was concluded that Japanese men have greater body fat deposition than Australian-Caucasians at the same BMI value. Japanese men may therefore require lower BMI cut-off points to identify obese individuals compared with Australian-Caucasian men.
NMR-based metabonomic studies reveal changes in the biochemical profile of
plasma and urine from pigs fed high-fibre rye bread
Authors: Bertram Hanne C. , Knudsen Knud E. Bach , Serena Anja , Malmendal Anders , Nielsen Niels Chr. , Fretté Xavier C. , Andersen Henrik J.
Published: April 2006

This study presents an NMR-based metabonomic approach to elucidate the overall endogenous biochemical effects of a wholegrain diet. Two diets with similar levels of dietary fibre and macronutrients, but with contrasting levels of wholegrain ingredients, were prepared from wholegrain rye (wholegrain diet (WGD)) and non-wholegrain wheat (non-wholegrain diet (NWD)) and fed to four pigs in a crossover design. Plasma samples were collected after 7 d on each diet, and 1H NMR spectra were acquired on these. Partial least squares regression discriminant analysis (PLSDA) on spectra obtained for plasma samples revealed that the spectral region at 3·25 parts per million dominates the differentiation between the two diets, as the WGD is associated with higher spectral intensity in this region. Spiking experiments and LC–MS analyses of the plasma verified that this spectral difference could be ascribed to a significantly higher content of betaine in WGD plasma samples compared with NWD samples. In an identical study with the same diets, urine samples were collected, and1H NMR spectra were acquired on these. PLS-DA on spectra obtained for urine samples revealed changes in the intensities of spectral regions, which could be ascribed to differences in the content of betaine and creatine/creatinine between the two diets, and LC–MS analyses verified a significantly lower content of creatinine in WGD urine samples compared with NWD urine samples. In conclusion, using an explorative approach, the present studies disclosed biochemical effects of a wholegrain diet on plasma betaine content and excretion of betaine and creatinine.