bluuebunny/crossref_metadata_2025 huggingface dataset:
Light-emitting defects and epitaxy in alkali-ion-implanted α quartz
Authors: Keinonen J. , Gąsiorek S. , Sahoo P. K. , Dhar S. , Lieb K. P.
Published: June 2006

Light-emitting centers in alkali-ion-implanted α quartz have been investigated with respect to the solid phase epitaxial growth of the ion irradiation induced amorphous zone. Cathodoluminescence was studied under the conditions of chemical epitaxy in annealing the samples, implanted with 2.5×1016 50keV Na ions/cm2 or 175keV Rb ions/cm2, in O218 atmosphere in the temperature range of 673–1173K. In addition to the known intrinsic subbands at 2.40, 2.79, and 4.30eV, which previously were associated with specific defects in the silica matrix, a strong violet band at 3.65eV and a band at 3.25eV have been identified. Both are intimately correlated with the presence of the implanted alkali atoms and recrystallization process. With respect to the 3.25eV band reported in the literature, they are discussed to be correlated with the presence of nanoclusters in Si-enriched, and Ge- and Sn-implanted SiO2 structures.
Adsorption of colloidal particles to curved interfaces
Authors: Komura S. , Hirose Y. , Nonomura Y.
Published: June 2006

As a simple model for a Pickering emulsion droplet, we consider the adsorption of spherical particles to a spherical liquid-liquid interface in order to investigate the curvature effect on the particle adsorption. By taking into account both the surface and the volume energies due to the presence of a particle, we show that the equilibrium contact angle is determined by the classical Young’s equation although the adsorption energy depends on the curvature. We also calculate the partitioning of the colloidal particles among the two liquids and the interface. The distribution of colloidal particles is expressed in terms of the interfacial curvature as well as the relative wettability of the particle.
Guided three-dimensional molecular self-assembly on silicon substrates
Authors: Chang Chia-Ching , Sun Kien Wen , Kan Lou-Sing , Kuan Chieh-Hsiung
Published: June 2006

We demonstrate three-dimensional (3D) self-assemble growth of the metallothionein (Mn,Cd-MT-2) molecules on patterned semiconductor substrates. The MT molecules deposited on the patterned substrates were found to grow into 3D rod or ring-type nanostructures, depending on the shape of patterned nanostructures on the substrates. Dense arrays of 3D molecular nanorods or rings with an area density close to 1010cm−2 were demonstrated with a pore size of 20nm and a pitch size of 100nm. Those engineered molecular nanostructures provide an excellent opportunity for biological applications, sensing sources of nanodevices, biochemical reactions on surfaces, and even single molecule studies.
Reliability of strain-balanced Ga0.331In0.669As∕Al0.659In0.341As∕InP quantum-cascade lasers under continuous-wave room-temperature operation
Authors: Evans A. , Razeghi M.
Published: June 2006

The reliability of high power strain-balanced Ga0.331In0.669As∕Al0.659In0.341As∕InP intersubband quantum cascade lasers (QCLs) emitting at a wavelength of 4.6μm has been studied. Constant current aging is reported for two randomly selected high-reflectivity-coated QCLs with an output power over 100mW. QCLs are tested under continuous-wave operation at a heat sink temperature of 298K(25°C) corresponding to an internal temperature of 378K (105°C). Over 4000h of continuous testing is reported without any decrease in output power.
Effect of oxygen plasma treatment on reduction of contact resistivity at pentacene/Au interface
Authors: Kim Woong-Kwon , Lee Jong-Lam
Published: June 2006

We report the reduction of contact resistivity between Au and pentacene by O2 plasma treatment. Contact resistance dramatically reduced from 5.65to0.22MΩcm by the treatment. O2 plasma treatment transformed Au to AuOx, increasing the surface energy from 45.1to71.5mJ∕m2. Molecular adsorption geometry of pentacene on AuOx changed from a planar structure to an upright type, improving crystallinity and molecular packing. Thus, defects and traps at the interface were reduced, decreasing the contact resistance between Au and pentacene.
Improved ultraviolet emission from reduced defect gallium nitride homojunctions grown on step-free 4H-SiC mesas
Authors: Caldwell Joshua D. , Mastro Michael A. , Hobart Karl D. , Glembocki Orest J. , Eddy Charles R. , Bassim Nabil D. , Holm R. T. , Henry Richard L. , Twigg Mark E. , Kub Fritz , Neudeck Phillip G. , Trunek Andrew J. , Powell J. Anthony
Published: June 2006

We previously reported 100-fold reductions in III-N heterofilm threading dislocation density achieved via growth on top of (0001) 4H-SiC mesas completely free of atomic scale steps. This letter compares the electroluminescent (EL) output of GaN pn junctions grown on top of 4H-SiC mesas with and without such steps. An average of 49% enhancement of the ultraviolet luminescence (380nm) was observed in step-free mesas over comparable “stepped” counterparts. Despite the intense EL from the step-free devices, significant leakage was observed through the periphery of the device, possibly due to the lack of GaN junction isolation processing.
Fabrication and characterization of the piezoelectric microtransformer based on microelectromechanical systems
Authors: Kim Seong Kon , Seo Young Ho
Published: June 2006

In this letter, the design, fabrication, and characterization of a novel piezoelectric microtransformer with bar geometry are presented. The piezoelectric microtransformers were fabricated using PZT thin films and microelectromechanical system technologies. The dimensions of these devices are 1000×400×5.8μm3 (length×width×thickness). The dynamic displacement of around 9.2±0.064μm was observed at 10Vac. The dynamic displacement varied almost linearly with voltage. When driven at the input voltage of 3Vac, the output voltage of the piezoelectric microtransformer was 6.4Vac at the resonant frequency (Fr), 8.006kHz and load resistance (RL), 1MΩ. The average voltage gain (step-up ratio) was approximately 2.13.
Enhanced second harmonic generation from nanoscale double-hole arrays in a gold film
Authors: Lesuffleur Antoine , Kumar L. Kiran Swaroop , Gordon Reuven
Published: June 2006

We present enhanced second harmonic generation (SHG) from arrays with a basis of overlapping double holes. The arrays were created by focused-ion beam milling through a gold film, and the measurements were performed in the transmission geometry. By fixing the array periodicity and varying the spacing between the holes, the SHG was enhanced by an order of magnitude for the single case where the apexes of the double-hole structure were nearly touching. Numerical calculations showed a local electric field enhancement that agrees with the SHG observations. This work shows the potential of double-hole structures for nonlinear optics at the nanoscale.
Role of alloy fluctuations in photoluminescence dynamics of AlGaN epilayers
Authors: Kuokstis E. , Sun W. H. , Shatalov M. , Yang J. W. , Asif Khan M.
Published: June 2006

The near-band-edge (NBE) photoluminescence (PL) of AlGaN layers with different Al content was analyzed in a wide range of excitation intensities and temperatures. The PL peculiarities indicated that tails of density of states are formed in AlGaN alloys due to the fluctuation of the alloy composition. The model involving recombination through one type of nonradiative center is proposed. The dependence of NBE PL integrated intensity on excitation power for AlGaN is weaker than that for GaN, which is attributed to carrier localization in alloys with compositional fluctuations and, thus, reduction of probability of nonradiative recombination.
Application of the interface capacitance model to thin-film relaxors and ferroelectrics
Authors: Tyunina M. , Levoska J.
Published: June 2006

The interface capacitance model is briefly revised. It is emphasized that this is a device model related to the boundary condition for polarization and unable to explain the thickness evolution of the ferroelectric properties. The model can be applied to extract the properties of the film from those measured in the capacitor. The interface parameters are found to be temperature independent. The coupling of the film with the interface and the electrode is shown to result in the measured frequency dependent permittivity totally different from that of the film.
The influence of season, agricultural management, and soil properties on gross nitrogen transformations and bacterial community structure
Authors: Cookson W. R. , Marschner P. , Clark I. M. , Milton N. , Smirk M. N. , Murphy D. V. , Osman M. , Stockdale E. A. , Hirsch P. R.
Published: June 2006

The aim of this study was to assess the influence of season, farm management (organic, biodynamic, integrated, and conventional), and soil chemical, physical, and biological properties on gross nitrogen (N) fluxes and bacterial community structure in the semi-arid region of Western Australia. Moisture availability was the dominant factor mediating microbial activity and carbon (C) and N cycling under this climate. In general, microbial biomass N, dissolved organic N, and potentially mineralisable N were greater in organic and biodynamic than integrated and conventional soil. Our results indicate that greater silt and clay content in organic and biodynamic soil may also partly explain these differences in soil N pools, rather than management alone. Although plant-available N (NH4+ + NO3–) was greater in conventional soil, this was largely the result of higher NO3– production. Multiple linear modelling indicated that soil temperature, moisture, soil textural classes, pH, electrical conductivity (EC), and C and N pools were important in predicting gross N fluxes. Redundancy analysis revealed that bacterial community structure, assessed by denaturing gradient gel electrophoresis of 16S rDNA, was correlated with C and N pools and fluxes, confirming links between bacterial structure and function. Bacterial community structure was also correlated with soil textural classes and soil temperature but not soil moisture. These results indicate that across this semi-arid landscape, soil bacterial communities are relatively resistant to water stress.
Suppression of Rhizoctonia solani AG-8 induced disease on wheat by the interaction between Pantoea, Exiguobacterium, and Microbacteria
Authors: Barnett Stephen J. , Roget David K. , Ryder Maarten H.
Published: June 2006

Rhizoctonia solani AG-8 is a major wheat root pathogen; however, soils can become suppressive to the expression of disease under intensive cropping with retention of crop residues. This is in part due to the action of soil microorganisms. A step-wise approach was used to determine which microorganisms contributed to suppression of R. solani induced disease in a disease-suppressive soil. Using wheat-soil-pathogen bioassays it was determined that the interaction between 3 phylogenetically diverse groups of bacteria, Pantoea agglomerans, Exiguobacterium acetylicum, and Microbacteria (family Microbacteriaceae), was a major contributor to disease suppression. Inoculation of a sterilised soil with the combination of these groups resulted in greatly increased seedling shoot dry weight and reduced infection compared with diseased control plants with no bacterial inoculation, or inoculated with individual types of bacteria. These groups, however, did not reduce levels of pathogen DNA, although inoculation with suppressive soil (at 10% w/w) did reduce pathogen DNA. Root associated P. agglomerans and E. acetylicum promoted the growth of infected wheat plants and soil associated Microbacteria reduced root infection by R. solani.
Nitrogen mineralisation in relation to previous crops and pastures
Authors: Angus J. F. , Bolger T. P. , Kirkegaard J. A. , Peoples M. B.
Published: June 2006

Most of the nitrogen (N) used by Australian crops is mineralised from the residues of previous crops and pastures. Net N mineralisation was studied in 2 field experiments in southern NSW, one comparing different residue-management and tillage systems during continuous cropping and the other comparing residues of annual and perennial pastures in a pasture–crop system. After 14 years of continuous cropping, soil total N concentration had decreased by 50%. Neither stubble retention nor direct drilling affected potential N mineralisation or the decrease in total N. However, soil mineral N in the field was greater after direct drilling than cultivation and greater after stubble retention than stubble burning. There were 2 reasons for the discrepancy. One was because retained stubble conserved soil water, leading to periods of increased mineralisation. The other was that direct drilling and stubble retention reduced growth and N uptake by crops. In contrast to the similar rates of potential mineralisation under different tillage and stubble systems, there were significant differences following different pasture species. In a 5-year study of a pasture–crop system we measured net mineralisation following annual pasture based on subterranean clover and perennial pasture based on lucerne and/or the grasses phalaris and cocksfoot. Mineralisation generally decreased with number of years after pasture removal. Previous lucerne pastures led to slow net mineralisation in the first year after removal, apparently because of immobilisation by high C : N residues. Mineralisation in soil containing perennial grass residues was the highest measured. This high rate may be due to redistribution of N to the topsoil by roots of perennial grasses. The comparison of continuous crop and pasture–crop systems showed that the decline in soil N supply was not prevented by direct drilling and stubble conservation, but N mineralisation was increased by pastures, particularly those containing perennial grasses.
Brassica crops stimulate soil mineral N accumulation
Authors: Ryan M. H. , Kirkegaard J. A. , Angus J. F.
Published: June 2006

The impact of Brassica crops and their tissues on accumulation of mineral N in soil was examined in the field and in laboratory incubation experiments. Mineral N accumulation over the summer fallow increased by an additional 39–49 kg/ha in the top 0.10 m of soil following brassicas compared with wheat at 2 sites. At a third site there was no increase in the top 0.10 m, but this was possibly due to leaching, as a 21–39 kg/ha increase was detected over the 1.50 m profile. The accumulation of mineral N in soil collected after harvest of canola crops and incubated in the laboratory was double that of soil collected after non-Brassica crops. This outcome was not evident in soil collected when crops were flowering, only occurred in the top 0.05 m of soil, and did not persist beyond week 3 of the incubation. In further laboratory incubations using tissues from wheat and a range of brassicas matched for C : N ratio but differing in glucosinolate concentration, Brassica root tissues initially immobilised, and later released, mineral N at a greater rate than wheat root tissues. These results suggest that enhanced accumulation of mineral N following Brassica crops compared with cereal crops is unlikely to be due to biofumigation of the soil microbial community. Shifts in the composition of the soil microbial community and differences in the chemical constituents of root tissues and in above-ground crop residue inputs may instead be responsible.
Earthworm population dynamics under conservation tillage systems in south-eastern Australia
Authors: Chan K. Y. , Heenan D. P.
Published: June 2006

Changes in earthworm abundance, biomass, and diversity were monitored under a range of tillage and stubble management practices in a wheat/alternative crop rotation over 5 years on a Sodosol (Alfisol) in southern New South Wales, Australia. There were 3 tillage and 2 stubble management practices in a completely randomised block design with 3 replications. The 3 tillage treatments were no-tillage (NT), 1 tillage pass (1T), and 3 tillage passes (3T). Stubble management practices were stubble retained (sr) and stubble burnt (sb). Positive responses of earthworm abundance and biomass to stubble retention (>2-fold increase) were evident in the second year and to both stubble and tillage in the third year. In the latter, abundance in NT/sr was 6.6 times that found under 3T/sb (239 v. 36/m2). Higher earthworm abundance in NT/sr compared with 3T/sb prevailed for the remaining duration of the experiment. However, a drastic decline in total population (to a mean of 31/m2) was observed in the fourth year in all the treatments and this was followed by further decline to a mean abundance of 4/m2 in the fifth year. The drastic decline in abundance was also accompanied by a shift in earthworm species composition. The earthworm population was originally dominated by the exotic Lumbrid, Aporrectodea trapezoides (Lumbricidae) (~100% in composition), but by the fifth year, Microscolex dubious (Acanthodrilidae) was the dominant species, making up 75% of the earthworm population in NT/sr. Improvement in soil quality as detected in the fifth year under a conservation tillage system compared with a conventional system included higher transmitting macropores, higher labile carbon, and water-stable aggregation. The reason for the decline in earthworm abundance was not clear but was unlikely related to changes in soil quality, wheat yield, and rainfall. Instead, we suggest that it was related to the changes in insecticide applications during the course of the experiment. The study highlights the importance of judicious use of chemicals in farming systems if earthworm presence is to be encouraged.
Nanog binds to Smad1 and blocks bone morphogenetic protein-induced differentiation of embryonic stem cells
Authors: Suzuki Atsushi , Raya Ángel , Kawakami Yasuhiko , Morita Masanobu , Matsui Takaaki , Nakashima Kinichi , Gage Fred H. , Rodríguez-Esteban Concepción , Izpisúa Belmonte Juan Carlos
Published: June 2006

ES cells represent a valuable model for investigating early embryo development and hold promise for future regenerative medicine strategies. The self-renewal of pluripotent mouse ES cells has been shown to require extrinsic stimulation by the bone morphogenetic protein (BMP) and leukemia inhibitory factor signaling pathways and the expression of the transcription factors Oct4 and Nanog. However, the network of interactions among extrinsic and intrinsic determinants of ES cell pluripotency is currently poorly understood. Here, we show that
Nanog
expression is up-regulated in mouse ES cells by the binding of T (Brachyury) and STAT3 to an enhancer element in the mouse
Nanog
gene. We further show that Nanog blocks BMP-induced mesoderm differentiation of ES cells by physically interacting with Smad1 and interfering with the recruitment of coactivators to the active Smad transcriptional complexes. Taken together, our findings illustrate the existence of ES cell-specific regulatory networks that underlie the maintenance of ES cell pluripotency and provide mechanistic insights into the role of Nanog in this process.
CD4+T cells and CXC chemokines modulate the pathogenesis ofStaphylococcus aureuswound infections
Authors: McLoughlin Rachel M. , Solinga Robert M. , Rich Jeremy , Zaleski Kathleen J. , Cocchiaro Jordan L. , Risley Allison , Tzianabos Arthur O. , Lee Jean C.
Published: June 2006

T cells are critical for the formation of intraabdominal abscesses byStaphylococcus aureus. We hypothesized that T cells modulate the development of experimental staphylococcal infections by controlling polymorphonuclear leukocyte (PMN) trafficking. In models of staphylococcal s.c. abscess formation, hindpaw infection, and surgical wound infection,S. aureusmultiplied in the tissues of WT C57BL/6J mice and elicited a marked inflammatory response. CD4+αβ T cells homed to the surgical wound infection site of WT animals. In contrast, significantly fewerS. aureuswere recovered from the tissues of mice deficient in αβ T cells, and the inflammatory response was considerably diminished compared with that of WT animals. αβ T cell receptor (−/−) mice had significantly lower concentrations of PMN-specific CXC chemokines in wound tissue than did WT mice. The severity of the wound infection was enhanced by administration of a CXC chemokine and abrogated by antibodies that blocked the CXC receptor. An acapsular mutant was less virulent than the parentalS. aureusstrain in both the s.c. abscess and the surgical wound infection models in WT mice. These data reveal an important and underappreciated role for CD4+αβ T cells inS. aureusinfections in controlling local CXC chemokine production, neutrophil recruitment to the site of infection, and subsequent bacterial replication.
Just one cross appears capable of dramatically altering the population biology of a eukaryotic pathogen like
Toxoplasma gondii
Authors: Boyle Jon P. , Rajasekar Badri , Saeij Jeroen P. J. , Ajioka James W. , Berriman Matthew , Paulsen Ian , Roos David S. , Sibley L. David , White Michael W. , Boothroyd John C.
Published: June 2006

Toxoplasma gondii
, an obligate intracellular protozoan of the phylum Apicomplexa, is estimated to infect over a billion people worldwide as well as a great many other mammalian and avian hosts. Despite this ubiquity, the vast majority of human infections in Europe and North America are thought to be due to only three genotypes. Using a genome-wide analysis of single-nucleotide polymorphisms, we have constructed a genealogy for these three lines. The data indicate that types I and III are second- and first-generation offspring, respectively, of a cross between a type II strain and one of two ancestral strains. An extant
T. gondii
strain (P89) appears to be the modern descendant of the non-type II parent of type III, making the full genealogy of the type III clonotype known. The simplicity of this family tree demonstrates that even a single cross can lead to the emergence and dominance of a new clonal genotype that completely alters the population biology of a sexual pathogen.
On the origin and robustness of power-law species–area relationships in ecology
Authors: García Martín Héctor , Goldenfeld Nigel
Published: June 2006

We present an explanation for the widely reported power-law species–area relationship (SAR), which relates the area occupied by a biome to the number of species that it supports. We argue that power-law SARs are a robust consequence of a skewed species abundance distribution resembling a lognormal with higher rarity, together with the observation that individuals of a given species tend to cluster. We show that the precise form of the SAR transcends the specific details of organism interactions, enabling us to characterize its broad trends across taxa.
Base pair motions control the rates and distance dependencies of reductive and oxidative DNA charge transfer
Authors: Valis Linda , Wang Qiang , Raytchev Milen , Buchvarov Ivan , Wagenknecht Hans-Achim , Fiebig Torsten
Published: June 2006

In 1999, Wan
et al
. [
Proc. Natl. Acad. Sci. USA
96, 6014–6019] published a pioneering paper that established the entanglement between DNA base pair motions and the transfer time of the charge carrier. The DNA assemblies contained an ethidium covalently bound via a flexible alkyl chain to the 5′ hydroxyl group of the DNA backbone. Although covalently attached, the loose way in which the ethidium was linked to DNA allowed for large degrees of conformational freedom and thus raised some concern with respect to conformational inhomogeneity. In this letter, we report studies on a different set of ethidium DNA conjugates. In contrast to the “Caltech systems,” these conjugates contain ethidium tightly incorporated (as a base pair surrogate) into the DNA base stack, opposite to an abasic site analog. Despite the tight binding, we found that charge transfer from the photoexcited ethidium base pair surrogate across two or more base pairs is several orders of magnitude slower than in case of the DNA systems bearing the tethered ethidium. To further broaden the scope of this account, we compared (oxidative) electron hole transfer and (reductive) electron transfer using the same ethidium chromophore as a charge donor in combination with two different charge acceptors. We found that both electron and hole transfer are characterized by similar rates and distance dependencies. The results demonstrate the importance of nuclear motions and conformational flexibility and underline the presence of a base gating mechanism, which appears to be generic to electronic transfer processes through π-stacked nucleic acids.
Distinct structural and mechanical properties of the nuclear lamina in Hutchinson–Gilford progeria syndrome
Authors: Dahl Kris Noel , Scaffidi Paola , Islam Mohammad F. , Yodh Arjun G. , Wilson Katherine L. , Misteli Tom
Published: June 2006

The nuclear lamina is a network of structural filaments, the A and B type lamins, located at the nuclear envelope and throughout the nucleus. Lamin filaments provide the nucleus with mechanical stability and support many basic activities, including gene regulation. Mutations in
LMNA
, the gene encoding A type lamins, cause numerous human diseases, including the segmental premature aging disease Hutchinson–Gilford progeria syndrome (HGPS). Here we show that structural and mechanical properties of the lamina are altered in HGPS cells. We demonstrate by live-cell imaging and biochemical analysis that lamins A and C become trapped at the nuclear periphery in HGPS patient cells. Using micropipette aspiration, we show that the lamina in HGPS cells has a significantly reduced ability to rearrange under mechanical stress. Based on polarization microscopy results, we suggest that the lamins are disordered in the healthy nuclei, whereas the lamins in HGPS nuclei form orientationally ordered microdomains. The reduced deformability of the HGPS nuclear lamina possibly could be due to the inability of these orientationally ordered microdomains to dissipate mechanical stress. Surprisingly, intact HGPS cells exhibited a degree of resistance to acute mechanical stress similar to that of cells from healthy individuals. Thus, in contrast to the nuclear fragility seen in
lmna
null cells, the lamina network in HGPS cells has unique mechanical properties that might contribute to disease phenotypes by affecting responses to mechanical force and misregulation of mechanosensitive gene expression.
The solid-state architecture of a metallosupramolecular polyelectrolyte
Authors: Kolb Ute , Büscher Karsten , Helm Christiane A. , Lindner Anne , Thünemann Andreas F. , Menzel Michael , Higuchi Masayoshi , Kurth Dirk G.
Published: June 2006

Self-assembly of Fe(II) and the ditopic ligand 1,4-bis(2,2′:6′,2″-terpyridine-4′-yl)benzene results in equilibrium structures in solutions, so-called metallosupramolecular coordination polyelectrolytes (MEPEs). It is exceedingly difficult to characterize such macromolecular assemblies, because of the dynamic nature. Therefore, hardly any structural information is available for this type of material. Here, we show that from dilute solutions, where small aggregates predominate, it is possible to grow nanoscopic crystals at an interface. A near atomic resolution structure of MEPE is obtained by investigating the nanoscopic crystals with electron diffraction in combination with molecular modeling. The analysis reveals a primitive monoclinic unit cell (
P
2
1
/
c
space group,
a
= 10.4 Å,
b
= 10.7 Å,
c
= 34.0 Å, α = γ = 90°, β = 95°, ρ = 1.26 g/cm
3
, and
Z
= 4). The MEPE forms linear rods, which are organized into sheets. Four sheets intersect the unit cell, while adjacent sheets are rotated by 90° with respect to each other. The pseudooctahedral coordination geometry of the Fe(II) centers is confirmed by Mössbauer spectroscopy. The combination of diffraction and molecular modeling presented here may be of general utility to address problems in structural materials science.
Island radiation on a continental scale: Exceptional rates of plant diversification after uplift of the Andes
Authors: Hughes Colin , Eastwood Ruth
Published: June 2006

Species radiations provide unique insights into evolutionary processes underlying species diversification and patterns of biodiversity. To compare plant diversification over a similar time period to the recent cichlid fish radiations, which are an order of magnitude faster than documented bird, arthropod, and plant radiations, we focus on the high-altitude flora of the Andes, which is the most species-rich of any tropical mountains. Because of the recent uplift of the northern Andes, the upland environments where much of this rich endemic flora is found have been available for colonization only since the late Pliocene or Pleistocene, 2–4 million years (Myr) ago. Using DNA sequence data we identify a monophyletic group within the genusLupinusrepresenting 81 species endemic to the Andes. The age of this clade is estimated to be 1.18–1.76 Myr, implying a diversification rate of 2.49–3.72 species per Myr. This exceeds previous estimates for plants, providing the most spectacular example of explosive plant species diversification documented to date. Furthermore, it suggests that the high cichlid diversification rates are not unique. Lack of key innovations associated with the AndeanLupinusclade suggests that diversification was driven by ecological opportunities afforded by the emergence of island-like habitats after Andean uplift. Data from other genera indicate that lupines are one of a set of similarly rapid Andean plant radiations, continental in scale and island-like in stimulus, suggesting that the high-elevation Andean flora provides a system that rivals other groups, including cichlids, for understanding rapid species diversification.
Snail family genes are required for left–right asymmetry determination, but not neural crest formation, in mice
Authors: Murray Stephen A. , Gridley Thomas
Published: June 2006

Snail family genes encode zinc finger transcriptional repressors that are key regulators of epithelial–mesenchymal transitions in vertebrates, including the transitions that generate the mesoderm and neural crest. Here, we show that, contrary to observations in frog and avian embryos, the Snail family genes Snail (
Snai1
) and Slug (
Snai2
) are not required for formation and delamination of the neural crest in mice. However, embryos with conditional inactivation of
Snai1
function exhibit defects in left–right asymmetry determination. This work demonstrates that although some aspects of Snail family gene function, such as a role in left–right asymmetry determination, appear to be evolutionarily conserved, their role in neural crest cell formation and delamination is not.
Physical training and metabolic supplementation reduce spontaneous atherosclerotic plaque rupture and prolong survival in hypercholesterolemic mice
Authors: Napoli Claudio , Williams-Ignarro Sharon , de Nigris Filomena , Lerman Lilach O. , D’Armiento Francesco P. , Crimi Ettore , Byrns Russell E. , Casamassimi Amelia , Lanza Alessandro , Gombos Fernando , Sica Vincenzo , Ignarro Louis J.
Published: June 2006

Moderate physical exercise (PE) combined with metabolic treatment (MT) (antioxidants and
l
-arginine) are well known to reduce atherosclerotic lesion formation in hypercholesterolemic mice. However, the long-term beneficial effects on unstable atheroma remain poorly understood. We started early PE training in large groups of 6-week-old hypercholesterolemic mice (by graduated swimming) alone or in combination with nutritional supplementation (1.0% vitamin E added to the chow and 0.05% vitamin C and 6%
l
-arginine added to the drinking water). Inactive controls did not receive PE. The spontaneous development of atherosclerotic plaque rupture (associated with advanced atherosclerosis) and survival rates were evaluated. Moderate PE elicited an increase in plasma levels of nitric oxide. Early combined treatment with PE and MT in the hypercholesterolemic mice significantly reduced lesions (also detected noninvasively at 10 months) and spontaneous atherosclerotic plaque rupture and prolonged survival more effectively than each intervention alone. Thus, early concerted actions of MT and PE improve the natural history of atherosclerotic lesions and reduce the plaque instability in hypercholesterolemic mice.
Therapy of ovarian cancers with targeted cytotoxic analogs of bombesin, somatostatin, and luteinizing hormone-releasing hormone and their combinations
Authors: Buchholz Stefan , Keller Gunhild , Schally Andrew V. , Halmos Gabor , Hohla Florian , Heinrich Elmar , Koester Frank , Baker Benjamin , Engel Jörg B.
Published: June 2006

The aim of this study was to investigate the effect of treatment of experimental ovarian cancers with targeted cytotoxic analogs as single compounds and in combination. Targeted cytotoxic analogs of bombesin (AN-215), somatostatin (AN-238), and luteinizing hormone-releasing hormone (AN-207) consisted of 2-pyrrolinodoxorubicin (AN-201) linked to the respective peptide carrier. AN-238 at 200 nmol/kg significantly inhibited growth of UCI-107, ES-2 and OV-1063 ovarian cancers. AN-215 alone at 200 nmol/kg and its combination with AN-238 at one-half of the dose were also able to inhibit the growth of UCI-107 tumors. A combination of AN-238 with AN-207at 50% of the dose strongly suppressed the proliferation of ES-2 and OV-1063 ovarian tumors. Cytotoxic radical AN-201 was toxic and had no significant effect on tumor growth. In contrast, the toxicity of the conjugated peptide analogs was low. Because ovarian cancers tend to acquire chemoresistance, we used real-time PCR to measure the mRNA expression of multidrug resistance protein 1, multidrug resistance-related protein 1, and breast cancer resistance protein after treatment. Low or no induction of multidrug resistance protein 1, multidrug resistance-related protein, and breast cancer resistance protein occurred after treatment with AN-238, AN-215, and the combination of AN-238 with AN-207 or AN-215. These results demonstrate that a therapy with cytotoxic analogs such as single agents and combinations is effective and nontoxic. Our work suggests that cytotoxic peptide analogs of luteinizing hormone-releasing hormone, somatostatin, and bombesin could be used for the therapy of ovarian cancers, considering the lack of induction of chemoresistance.
Effective gene therapy in an authentic model of Tay-Sachs-related diseases
Authors: Cachón-González M. Begoña , Wang Susan Z. , Lynch Andrew , Ziegler Robin , Cheng Seng H. , Cox Timothy M.
Published: June 2006

Tay-Sachs disease is a prototypic neurodegenerative disease. Lysosomal storage of GM2 ganglioside in Tay-Sachs and the related disorder, Sandhoff disease, is caused by deficiency of β-hexosaminidase A, a heterodimeric protein. Tay-Sachs-related diseases (GM2 gangliosidoses) are incurable, but gene therapy has the potential for widespread correction of the underlying lysosomal defect by means of the secretion-recapture cellular pathway for enzymatic complementation. Sandhoff mice, lacking the β-subunit of hexosaminidase, manifest many signs of classical human Tay-Sachs disease and, with an acute course, die before 20 weeks of age. We treated Sandhoff mice by stereotaxic intracranial inoculation of recombinant adeno-associated viral vectors encoding the complementing human β-hexosaminidase α and β subunit genes and elements, including an HIV tat sequence, to enhance protein expression and distribution. Animals survived for >1 year with sustained, widespread, and abundant enzyme delivery in the nervous system. Onset of the disease was delayed with preservation of motor function; inflammation and GM2 ganglioside storage in the brain and spinal cord was reduced. Gene delivery of β-hexosaminidase A by using adeno-associated viral vectors has realistic potential for treating the human Tay-Sachs-related diseases.
TrkB binds and tyrosine-phosphorylates Tiam1, leading to activation of Rac1 and induction of changes in cellular morphology
Authors: Miyamoto Yuki , Yamauchi Junji , Tanoue Akito , Wu Chengbiao , Mobley William C.
Published: June 2006

Small GTPases of the Rho family play key roles in the formation of neuronal axons and dendrites by transducing signals from guidance cues, such as neurotrophins, to the actin cytoskeleton. However, there is little insight into the mechanism by which neurotrophins regulate Rho GTPases. Here, we show the crucial role of the ubiquitous Rac1-specific guanine nucleotide exchange factor, Tiam1 (T lymphoma invasion and metastasis 1), in transducing a neurotrophin-mediated change in cell shape. We demonstrate that BDNF, acting through TrkB, directly binds and specifically activates Tiam1 by phosphorylating Tyr-829, leading to Rac1 activation and lamellipodia formation in Cos-7 cells and increased neurite outgrowth from cortical neurons. A point mutation in Tiam1, Tyr-829 to Phe-829, blocked these BDNF-induced changes in cellular morphology. The findings are evidence of a previously uncharacterized mechanism for the activation of Tiam1 and of a role for this effector in neurotrophin-mediated signal transduction leading to changes in cellular morphology.
Identification of novel antimicrobials using a live-animal infection model
Authors: Moy Terence I. , Ball Anthony R. , Anklesaria Zafia , Casadei Gabriele , Lewis Kim , Ausubel Frederick M.
Published: June 2006

The alarming increase of antibiotic-resistant bacterial pathogens points to the need for novel therapeutic approaches to combat infection. To discover novel antimicrobials, we devised a screen to identify compounds that promoted the survival of the model laboratory nematode
Caenorhabditis elegans
infected with the human opportunistic pathogen
Enterococcus faecalis
.
E. faecalis
colonizes the nematode intestinal tract, forming a persistent lethal infection. Infected nematodes were rescued by antibiotic treatment in a dose-dependent manner, and antibiotic treatment markedly reduced the number of bacteria colonizing the nematode intestine. To facilitate high throughput screening of compound libraries, we adapted a previously developed agar-based
C. elegans
-
E. faecalis
infection assay so that it could be carried out in liquid medium in standard 96-well microtiter plates. We used this simple infection system to screen 6,000 synthetic compounds and 1,136 natural product extracts. We identified 16 compounds and 9 extracts that promoted nematode survival. Some of the compounds and extracts inhibited
E. faecalis
growth
in vitro
, but, in contrast to traditional antibiotics, the
in vivo
effective dose of many of these compounds was significantly lower than the minimum inhibitory concentration needed to prevent the growth of
E. faecalis
in vitro
. Moreover, many of the compounds and extracts had little or no affect on
in vitro
bacterial growth. Our findings indicate that the whole-animal
C. elegans
screen identifies not only traditional antibiotics, but also compounds that target bacterial virulence or stimulate host defense.
Monocyte accumulation in mouse atherogenesis is progressive and proportional to extent of disease
Authors: Swirski Filip K. , Pittet Mikael J. , Kircher Moritz F. , Aikawa Elena , Jaffer Farouc A. , Libby Peter , Weissleder Ralph
Published: June 2006

Monocytes participate importantly in the pathogenesis of atherosclerosis, but their spatial and temporal recruitment from circulation remains uncertain. This study tests the hypothesis that monocyte accumulation in atheroma correlates with the extent of disease by using a sensitive and simple quantitative assay that allows tracking of highly enriched populations of blood monocytes. A two-step isolation method yielded viable and functionally intact highly enriched peripheral blood monocyte populations (>90%). Recipient mice received syngeneic monocytes labeled in two ways: by transgenically expressing EGFP or with a radioactive tracer [
111
In]oxine. After 5 days, more labeled cells accumulated in the aorta, principally the aortic root and ascending aorta, of 10-wk-old ApoE
−/−
compared with 10-wk-old C57BL/6 mice (223 ± 3 vs. 87 ± 22 cells per aorta). Considerably more monocytes accumulated in 20-wk-old ApoE
−/−
mice on either chow (314 ± 41 cells) or high-cholesterol diet (395 ± 53 cells). Fifty-week-old ApoE
−/−
mice accumulated even more monocytes in the aortic root, ascending aorta, and thoracic aorta after both chow (503 ± 67 cells) or high-cholesterol diet (648 ± 81 cells). Labeled monocyte content in the aorta consistently correlated with lesion surface area. These data indicate that monocytes accumulate continuously during atheroma formation, accumulation increases in proportion to lesion size, and recruitment is augmented with hypercholesterolemia. These results provide insights into mechanisms of atherogenesis and have implications for the duration of therapies directed at leukocyte recruitment.
State welfare in Egypt since adjustment: Hegemonic control with a minimalist role
Authors: Tadros Mariz
Published: June 2006

This article argues that Egypt's implementation of an economic reform and structural adjustment programme since 1991 has not led to a reduction of its hegemony over certain welfare services. Yet its role in the provision of free health and educational services has been drastically curtailed. This is evident if the pre- and post adjustment situations are analysed in terms of the poor's access to education and health services. The introduction of cost recovery measures has negatively impacted on the poor and increased their vulnerability to exploitation by exposing them to a wide range of ‘hidden’ and informal fees. Further, the introduction of special policies designed to mitigate the rising costs of education and health care are not being implemented due to a set of institutional and political reasons. The consequences of the increasing privatisation of educational and health services on the poor are examined by looking at the detail of those living in the densely populated community of Bulaq el Dakrour in Cairo.
America, China & the Scramble for Africa's Oil
Authors: Klare Michael , Volman Daniel
Published: June 2006

After decades of Cold War, when Africa was simply viewed as a convenient pawn on the global chessboard, and a further decade of benign neglect in the 1990s, the African continent has now become a vital arena of strategic and geopolitical competition for not only the United States, but also for China, India, and other new emerging powers. The main reason for this is quite simple: Africa is the final frontier as far as the world's supplies of energy are concerned with global competition for both oil and natural gas (particularly the latter) becoming just as intense – if not even more so – than the former.

The factors behind the growing attention to African energy supplies are well known; so we will only summarise them here.1 World oil production is only just meeting world demand and old fields are being drained faster than new production can be brought on line. Supplies will be tight for the foreseeable future, so any new source of supply is significant. Most importers are also trying to reduce their dependence on Middle Eastern oil. In the next 10-15 years, most of the new oil entering the world market is going to be coming from African fields because it is only in Africa – and to a lesser extent in the volatile Central Asia region – that substantial new fields have been found and brought into production.
Association between fruit and vegetable consumption and birth weight: A prospective study among 43,585 Danish women
Authors: Mikkelsen Tina B. , Osler Merete , Orozova-Bekkevold Ivanka , Knudsen Vibeke K. , Olsen Sjurdur F.
Published: June 2006

Objective: To examine whether fruit and vegetable consumption in pregnancy is associated with birth weight in a Western population. Design: Prospective cohort study based on telephone interviews, a food frequency questionnaire (FFQ), and extractions of birth characteristics from national health registries. Subjects and setting: The 43,585 Danish women from the Danish National Birth Cohort who had completed the FFQ in mid-pregnancy and on whom information about birth outcome was available. The exposures were frequency of green leafy vegetable (GLV) intake and quantified intake of fruit, fruit and vegetables, and fruit and vegetables and juice. The outcomes were birth weight and z-score for expected birth weight adjusted for sex and gestation week. Information on maternal height, weight, smoking, and other potential confounders was obtained through telephone interviews. Results: Significant associations were found for all exposures to fruit and vegetable intake with birth weight and most with z-score. The strongest association was found for fruit intake in which case birth weight increased by 10.7 g (95% CI 7.3—14.2) per quintile. All associations were stronger among lean women (BMI<20, n=7,169), whose children's birth weight increased by 14.6 g (95% CI 6.4—22.9) per quintile increase in fruit intake. For GLV the results were more inconclusive. When adjusted for confounders, but not for energy, the association between GLV and birth weight was significant, but the same was not the case for z-score. Conclusion: Fruit and vegetable consumption in pregnancy is positively associated with birth weight in well-nourished Danish women, especially among lean women.
Hip fractures among the elderly in a Swedish urban setting: Different perspectives on the significance of country of birth
Authors: Furugren Lena , Laflamme Lucie
Published: June 2006

Objectives: The study investigates the significance of country of birth for hip fractures among the elderly in a Swedish urban setting. Design: Cross-sectional register-based study. Methods: All people aged 65 or above hospitalized because of hip fracture in Stockholm County over the years 1993—95 were identified in the County's Hospital Discharge Register. Information was obtained from Sweden's National Population Register on the countries of birth of the people affected (reference year: 1994). The foreign-born were grouped in two ways: according to the geographic location of their country of birth, and to the level of development of that country (as measured by the UN's Human Development Index). Age-standardized odds ratios were computed for men and women separately, with the Swedish-born elderly as reference group. Results: Many of the foreign-born groups registered significantly lower odds of hip fracture than their Swedish-born counterparts, regardless of whether countries of birth were grouped geographically or according to level of development. This applied to both men and women. Conclusions: As a whole, the Swedish elderly population has one of the highest prevalences of hip fracture in the world. When country of origin is accounted for, the foreign-born elderly are significantly less vulnerable than native Swedes. This contrasts remarkably with other health outcomes.