bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical space structure refinement of decagonal quasicrystal in rhombic Penrose tiling model
Authors: Wolny Janusz , Kozakowski Bartlomiej , Kuczera Pawel , Takakura Hiroyuki
Published: February 2009

For the first time, the refinement of a decagonal Al72Ni20Co8 quasicrystal was conducted in physical space. We used a structure factor obtained in statistical approach. As a reference lattice we took a rhombic Penrose tiling to which we applied overlapping rules of clusters. The resulting structure gives R-factor = 8.0% and R
w-factor = 6.1%. The density of the refined structure is very close to the experimental one.
Phonon-enhanced thermoelectric power of Y–Al–Ni–Co decagonal approximant
Authors: Dolinsek Janez , Smontara Ana , Barisic Osor S. , Gille Peter
Published: February 2009

We have investigated anisotropic electrical resistivity and thermoelectric power of the ypsilon-phase Al–Ni–Co (Y–Al–Ni–Co) decagonal approximant with composition Al76Co22Ni2. The crystalline-direction-dependent measurements were performed along three orthogonal directions a*, b and c of the Y–Al–Ni–Co unit cell, where (a, c) monoclinic atomic planes are stacked along the perpendicular b direction. Anisotropic electrical resistivity is low in all crystalline directions, appearing in the order ρ
a* > ρ
c > ρ
b and showing positive temperature coefficient typical of electron-phonon scattering mechanism. Thermopower shows electron-phonon enhancement effect. Anisotropic bare thermopower (in the absence of electron-phonon interactions) was extracted, appearing in the same order as the resistivity, ΙS
a*
bare/TΙ > Ι S
c
bare/T Ι > Ι S
b
bare/T Ι.
Optical transmission through generalized Thue-Morse superlattices
Authors: Yang Xiangbo , Chen Fuming , Xing Da
Published: February 2009

In this paper we study the transmission properties of light through generalized Thue-Morse (GTM (m, n)) aperiodic superlattices and obtain the formulae of the transmission coefficients (TCs) analytically at the central wavelength, which are confirmed by numerical simulations. It is found that: (1) all of the 1st generation systems are transparent to the substrates medium B; (2) GTM (m, 2 j) systems are transparent to the substrates medium B; (3) GTM (2i, 2j + 1) systems are translucent to the substrates medium B except the 1st generation; and (4) when i not equal j, transmission through GTM (2i + 1, 2j + 1) systems attenuates rapidly with the increase of generation number l and sequence parameters m, n. On the other hand, the positional correlations between the constituents of GTM (m, n) aperiodic superlattices responsible for the resonant states are also discussed. Based on the conclusions we study the properties of the amplitude of the electric field vector and find that they are different from those of periodic lattices and chaotic systems.
Anisotropic electrical and thermal conductivities of the Al76Co22Ni2 decagonal approximant
Authors: Smontara Ana , Stanic Denis , Smiljanic Igor , Dolinsek Janez , Gille Peter
Published: February 2009

The electrical (σ) and thermal conductivity (λ) of Al76Co22Ni2 decagonal approximant has been measured along three orthogonal directions a
*, b and cof the Al76Co22Ni2 unit cell, where (a, c) monoclinic atomic planes are stacked along the perpendicular b direction. Electrical conductivity is relatively high in all crystalline directions, appearing in the order σb
>> σc
> σa*
. Thermal conductivity appears in the same order λb
> λc
> λa*, so that b is the most conducting direction for both electricity and heat. The results are compared to the reported anisotropic electrical and thermal conductivity of the d-Al–Ni–Co decagonal quasicrystal.
Thermoelectric performance of Al–Pd–Mn quasicrystals: comparison with (1/1, 2/1-)AlPdMnSi approximants and improvement by Ga substitution for Al
Authors: Takagiwa Yoshiki , Kamimura Takahiko , Hosoi Sizuka , Kimura Kaoru
Published: February 2009

We report the thermoelectric properties of polygrain icosahedral Al–Pd–Mn quasicrystal and compare with those of (1/1, 2/1-)AlPdMnSi approximant crystals. To improve the dimensionless figure of merit (ZT), we substitute Ga for Al atoms in Al–Pd–Mn quasicrystal in accordance with the guiding principle of “weakly bonded rigid heavy clusters” (WBRHCs). Although the thermoelectric properties do not obey the WBRHCs principle, the maximum ZT increased by a factor of 1.4 from 0.18 for Al71Pd20Mn9 to 0.26 for Al68Ga3Pd20Mn9 quasicrystal.
Hydriding properties of Mg–Al–Zn quasicrystal powder produced by mechanical alloying
Authors: Bystrzycki Jerzy , Polanski Marek , Malka Iwona E. , Komuda Aneta
Published: February 2009

The stable quasicrystal belonging to the Bergman class based on Mg–Al–Zn (Mg44Al15Zn41) was prepared by the mechanical alloying of elemental powders. The phase structure, chemical composition and hydriding properties of the obtained quasicrystal were investigated by XRD, SEM, EDS, DSC and the volumetric Sievert method. Our results have shown that the Mg44Al15Zn41 quasicrystal is unstable while hydriding above 200 °C and decomposes irreversibly into different Mg–Zn based intermetallic compounds. While being hydrided at 200 °C, where the quasicrystal is stable, Mg44Al15Zn41 decomposes mainly into the MgZn2 based intermetallic compound with MgH2 but above 300 °C, where the 2/1 approximant is stable, Mg44Al15Zn41 transforms mainly into the Frank-Kasper phase with MgH2.
Magnetic behaviors of Ti50Zr33Ni17 quasicrystals measured by VSM
Authors: Lee Yunman , Jeon Jae-kyun , Shin Hyemin , Kim Jae-yong
Published: February 2009

Quasicrystals made with Ti, Zr and Ni are good candidate materials studying the magnetic properties of aperiodic structure because the role of Ni in stabilization of the quasicrystal phase is important. Various magnetic states in quasicrystals have been reported including diamagnetism, paramagnetism, spin glass, ferromagnetism and ferrimagnetism. We prepared Ti–Zr–Ni quasicrystals by rapid quenching method. The magnetization (M) of Ti50Zr33Ni17 quasicrystal was measured as a function of applied magnetic field (H) and a temperature by using a vibrating sample magnetometer (VSM). When the magnetic fields of higher than 2000 G were applied, the magnetization values were decreased as increasing temperature. The field-cooling (FC) and zero-field-cooling (ZFC) magnetization of the samples were also measured and showed no significant difference in magnetization behavior. Our combined results demonstrated that the rapidly quenched Ti–Zr–Ni quasicrystals exhibit paramagnetic properties with no hint of a measurable magnetic hysteresis. It is shown that Ti50Zr33Ni17 quasicrystals demonstrate papramagnetic characteristic to the maximum applied magnetic field of 10 000 Oe. Interestingly, magnetization fluctuation was noticed in the regions of high magnetic field and at low temperature (25–300 K).
Al4(Cr, Fe): single crystal growth by the Czochralski method and structural investigation with neutrons at FRM II
Authors: Bauer Birgitta , Pedersen Björn , Gille Peter
Published: February 2009

A single crystal of Al4(Cr,Fe) with composition Al78Cr19Fe3 grown by the Czochralski method was studied by neutron diffraction for the first time. As a preliminary result the neutron diffraction experiment suggests a body-centered orthorhombic space group Immm with a = 1.24985(3) nm, b = 1.25500(3) nm and c = 3.0512(2) nm as found by Deng et al. (Pearson symbol: oI366-59.56) [1] using single crystal X-ray diffraction. Additionally, more or less diffuse maxima at positions with k = n/2 (n = odd) are clearly observable.
Phason disorder effects in the Penrose tiling antiferromagnet
Authors: Szallas Attila , Jagannathan Anuradha
Published: February 2009

We discuss the ground state of a disordered two dimensional Heisenberg antiferromagnet. The starting structure is taken to be a perfectly deterministic quasiperiodic tiling, and the type of disorder we consider is geometric, involving frozen phason flips of a randomly selected subset of sites. We consider S = 1/2 quantum spins placed on the vertices of the tiling, and interacting with the nearest neighbor spins with a uniform exchange interaction J. We calculate the energy spectrum, ground state energy and real space local magnetization values as a function of degree of disorder. We find that quantum fluctuations are enhanced by disorder. The real space staggered magnetization loses its symmetry properties and the average staggered magnetization decreases compared to the case of the perfect Penrose tiling. We explain our results in terms of a simple Heisenberg star cluster model that takes into account the changes of local environments due to phason flips.
Structural defects in Al–Ni–Rh and Al–Pd–Fe crystalline approximant phases
Authors: Sun Wei , Wang Jun-Ping , Zhang Ze
Published: February 2009

Structural defects of high density have been observed to exist in the as-cast crystalline approximants Al–Ni–Rh ξ and Al–Pd–Fe ε
16 which contain columnar atom clusters as the most fundamental building blocks. By means of high-resolution electron microscopy (HREM), the structural and distributional features of these defects have been revealed. It is clearly shown that, accommodating structural defects of high density in the Al–Ni–Rh ξ-phase can lead to the formation of a unique mixed structure in which nearly regular arrangement of structural defects can be established. On the basis of HREM observations, long-range structural features of the defective ξ- and ε
16-structures have been discussed in terms of the characteristic arrays of columnar atom clusters.
Effect of atom substitution on the low-temperature phase transitions in Cd- and Zn-based 1/1 cubic approximants
Authors: Yamada Tsunetomo , Tamura Ryuji
Published: February 2009

Effect of atom substitution on the low-temperature phase transitions in binary Cd6Ca and Zn6Sc 1/1 cubic approximants were investigated by means of electrical resistivity and X-ray diffraction. By adding thirdelements such as Yb, Cu and Fe to the binary approximants, it is concluded that Yb is substituted to the icosahedron site in both Cd6Ca and Zn6Sc, and Cu and Fe are substituted to the Zn sites in Zn6Sc. Upon the substitutions of the third elements, the temperature of the resistivity anomaly decreases without an exception and the anomaly disappears above a certain level of substitutions. Moreover, it is found that the chemical disorder introduced in the 2nd shell of the icosahedral cluster plays a crucial role in the suppression of the ordering of the Zn tetrahedron. On the other hand, the chemical disorder introduced in the 3rd icosahedron shell affects the transition temperature (T

c
) rather weakly. Finally, the variation of T

c
has been found to depend on the difference of the atomic radius between the host and the guest elements and the distortion of the outer shells is considered to be mainly responsible for the suppression of the ordering of the tetrahedra.
Synthesis and superstructure of Al—Ir, Al—Ir—Pd crystalline approximants and their electrical resistivities
Authors: Oishi Atsushi , Nishimoto Kazue , Tamura Ryuji
Published: February 2009

Chemically ordered Al2.7Ir and Al64.5Ir22Pd13.5 1/0 approximants are prepared by two different methods and characterized by X-ray diffraction and transmission electron microscopy. Al2.7Ir possesses a primitive cubic lattice with a = 15.345(6), whereas Al64.5Ir22Pd13.5 has a face-centered cubic lattice with a = 15.497(9). Examination of the samples prepared by two different methods reveals that the texture of the samples prepared by spark plasma sintering is more homogeneous than those prepared by arc melting. Electrical resistivities of both the compounds exhibit metallic characters, i.e., a positive temperature coefficient of the resistivity (TCR) with a high resistivity value. The results suggest that the TCR may not always be negative for 1/0 approximants with 15 to 16 periodicity but the high residual resistivities are common to all the approximants, which is presumably attributed to the common structural unit, an icosahedral cluster of about 7.7.
Origin of magnetic moments in i-Al–Pd–Mn quasicrystal
Authors: Krajci Marian , Hafner Jürgen
Published: February 2009

Using ab-initio density-functional methods in the generalized gradient approximation we have investigated the origin of magnetic moments on Mn atoms in icosahedral (i) Al–Pd–Mn quasicrystals. Two major mechanisms contribute to the formation of magnetic moments on Mn atoms located at special sites – loosely packed environments of the Mn atoms and the interaction of the Mn atoms with nearest-neighbor Pd atoms leading to a shift of the Mn d-band to lower binding energies and an increased partial density of states at the Fermi level. Mn–Pd nearest neighbors exist only at special sites located at intersections of the pseudo-Mackay and the Bergman clusters building the icosahedral structure. A change in the chemical decoration of these sites can lead to a complete disappearance of magnetism in i-Al–Pd–Mn. Total energy calculations show that the models with a chemical ordering disfavoring moment formation on Mn atoms are also lowest in energy.
Synthesis and TEM study of Ag–In–(Eu, Ce) ternary approximants
Authors: Nishimoto Kazue , Muraki Miki , Tamura Ryuji
Published: February 2009

Ternary Ag–In–(Eu, Ce) 1/1 approximants are synthesized and their structures are studied by transmission electron microscopy (TEM). For both the approximants, superlattice spots are clearly observed at room temperature, and the superstructures of the Ag–In–(Eu, Ce) approximants are found to be similar to those of Cd25Eu4 and Cd37Ce6, respectively. The Ag–In–Eu 1/1 approximant has a double unit cell with space group Fd-3 while the Ag–In–Ce 1/1 approximant has a normal unit cell with space group Pn-3, both at room temperature. The results suggest that the tetrahedron at the center of the icosahedral cluster is ordered in the Ag–In–(Eu, Ce) approximants in the same manner as the corresponding binary approximants Cd6(Eu, Ce). Furthermore, TEM observations at high temperatures reveal that the Ag–In–(Eu, Ce) approximants undergo a phase transition to a bcc lattice at an elevated temperature. The transitions are understood as a consequence of disordering of the tetrahedron located at the center of the icosahedral cluster.
Magnetic behavior of Fe and Tm in Zn–Fe–Sc–Tm icosahedral quasicrystals
Authors: Kashimoto Shiro , Masuda Chihiro , Ishimasa Tsutomu
Published: February 2009

The magnetic properties of p-type Zn77Fe7Sc16–x
Tm
x
(x = 0, 1, 2, 4 and 6) icosahedral quasicrystals have been investigated. The magnetic susceptibility of these samples obeys Curie-Weiss paramagnetism in 72–300 K. The estimated Curie constants indicated that 3d Fe magnetic moments also exist besides 4f Tm in these quasicrystals. In the lower temperature region, spin glass-like behavior was observed for all samples with freezing temperature 7.0–9.5 K. For samples with higher concentration of Tm, namely x = 2, 4 and 6, the magnetic susceptibility increase as temperature decrease below the freezing temperature. This behavior indicates weak antiferromagnetic interaction between 4f Tm magnetic moments.
The influence of thermal annealing on structural order in the μ-Al4Mn complex intermetallic
Authors: Jagodic Marko , Jaglicic Zvonko , Grushko Benjamin , Balanetskyy Sergiy , Dolinsek Janez
Published: February 2009

The influence of cooling rate on structural order in the complex hexagonal μ-Al4Mn phase was investigated. As higher magnetizations are detected in more disordered samples, the short-scale disorder was studied indirectly by magnetic measurements. The magnetizations of as-grown samples and samples subjected to different thermal treatments were compared. It was found that water-quenching increases the disorder in the crystal structure regardless of previous thermal history. Qualitatively the same results were obtained for the quasicrystalline i-Al—Pd—Mn phase where the changes in magnetic properties and consequently in the degree of structural order for different thermal treatments were even more pronounced.
Evaluation of phason elastic constants from HRTEM image of a dislocation in icosahedral quasicrystal
Authors: Edagawa Keiichi , Kamimura Takahiko , So Yeong-Gi
Published: February 2009

A method is proposed for quantitative evaluation of the ratio of the two phason elastic constants K
2/K
1 in icosahedral quasicrystals from a high-resolution transmission electron microscopy (HRTEM) image of a dislocation. Here, the Hytch´s method originally proposed for quantitative evaluation of displacement fields in crystals is generalized to quasicrystals. The generalized Hytch´s method gives phason displacement fields around a dislocation in icosahedral quasicrystals, from which K
2/K
1 can be evaluated. This method is demonstrated using a simulated HRTEM image of a dislocation in an icosahedral quasicrystal.
Infantile Hemangiomas and Retinopathy of Prematurity: Possible Association
Authors: Praveen Vijayakumar , Vidavalur Ramesh , Rosenkrantz Ted S. , Hussain Naveed
Published: February 2009

OBJECTIVE. The goal was to study the clinical association between infantile hemangiomas and retinopathy of prematurity in preterm infants.

METHODS. A retrospective study of preterm neonates weighing ≤1250 g at birth who were born during a 5-year period (November 1, 2000, to October 31, 2005) at John Dempsey Hospital was performed by using a prospectively collected, neonatal database. Data were collected on demographic features (gestational age, birth weight, and gender) and prenatal/postnatal steroid use. In the physical examination at discharge, all infants were checked for infantile hemangiomas, and the size and number of lesions were noted. The highest stage of retinopathy of prematurity diagnosed at any time before discharge also was noted. Analyses were performed to identify associated risk factors.

RESULTS. Of 406 neonates admitted with birth weights of ≤1250 g, 351 (86.4%) survived. Of the survivors, 49 (13.9%) had infantile hemangiomas at discharge. Infantile hemangiomas were present for 16.8% of neonates with retinopathy of prematurity, compared with 6.7% of those without retinopathy of prematurity. Multiple infantile hemangiomas were present in 14 (28.5%) of 49 neonates, whereas 18 (42.8%) of 42 neonates had infantile hemangiomas that were ≥1 cm in size. Univariate analyses showed lower gestational age, lower birth weight, and postnatal steroid use to be predictors of retinopathy of prematurity, whereas prenatal steroid use, race, and gender were not significantly related. In multivariate logistic regression analyses controlling for gestational age and postnatal steroid use, infantile hemangiomas were found to be independently associated with any stage of retinopathy of prematurity. Neither the number nor the size of infantile hemangiomas showed any association with the severity of retinopathy of prematurity.

CONCLUSIONS. Infantile hemangiomas are associated with the development of retinopathy of prematurity in infants weighing ≤1250 g. The biological significance of this association may yield clues to the management of retinopathy of prematurity.
Unfractionated Heparin Therapy in Infants and Children
Authors: Newall Fiona , Johnston Linda , Ignjatovic Vera , Monagle Paul
Published: February 2009

Unfractionated heparin is frequently used in tertiary pediatric centers for the prophylaxis and treatment of thromboembolic disease. Recent evidence suggests that the clinical outcomes of unfractionated heparin therapy in children are poor, as determined by target-range achievement and adverse-event rates. These reports of poor outcomes may be related to an age-dependent mechanism of action of unfractionated heparin. Furthermore, several published studies have indicated that unfractionated heparin–monitoring assays currently in clinical use have significant limitations that likely affect the safety and efficacy of anticoagulant management. This review summarizes the growing body of evidence suggesting that pediatric-specific recommendations for unfractionated heparin therapy management are required to improve clinical outcomes related to this commonly prescribed medication.
Kétnyelvűség a Hettita Birodalomban
Authors: Simon Zsolt
Published: February 2009

E
tanulmány a hettita—luvi kétnyelvűség főképp H. Cr. Melchert, E. Rieken és Th.
van den Hout által nemrégiben kifejlesztett elméletének kritikai áttekintése. A
késő bronzkori Anatólia nyelvi térké-__
A Bar Kochba-felkelés
Authors: Grüll Tibor
Published: February 2009

A
második zsidó háborúnak is nevezett Bar Kochba-felkelés nem rendelkezik olyan
krónikással, mint Flavius Josephus, aki nemcsak aktív részese és szemtanúja
volt az első zsidó háború (66—73/74) eseményeinek, hanem lehetősége is nyílt
annak áthagyományozására. Néhány késői római és keresztény __
Egy Jeromos-idézet Szent Gellértnél - és a bogumilok
Authors: Déri Balázs
Published: February 2009

A
tanulmány kimutatja, hogy egy többsoros szakasz Szent Gellért csanádi püspök
exegetikai munkájában (
Gerardi Moresenae ecclesiae seu Csanadiensis episcopi
Deliberatio supra hymnum trium puerorum,
__
Thyroid stimulating autoantibody M22 mimics TSH binding to the TSH receptor leucine rich domain: a comparative structural study of protein–protein interactions
Authors: Núñez Miguel R , Sanders J , Chirgadze D Y , Furmaniak J , Rees Smith B
Published: February 2009

The TSH receptor (TSHR) ligands M22 (a thyroid stimulating human monoclonal antibody) and TSH, bind to the concave surface of the leucine rich repeats domain (LRD) of the TSHR and here, we show that M22 mimics closely the binding of TSH. We compared interactions produced by M22 with the TSHR in the M22–TSHR crystal structure (2.55 Å resolution) and produced by TSH with the TSHR in a TSH–TSHR comparative model. The crystal structure of the TSHR and a comparative model of TSH based on the crystal structure of FSH were used as components to build the TSH–TSHR model. This model was built based on the FSH–FSH receptor structure (2.9 Å) and then the structure of the TSHR in the model was replaced by the TSHR crystal structure. The analysis shows that M22 light chain mimics the TSHβ chain in its interaction with TSHR LRD, while M22 heavy chain mimics the interactions of the TSHα chain. The M22–TSHR complex contains a greater number of hydrogen bonds and salt bridges and fewer hydrophobic interactions than the TSH–TSHR complex, consistent with a higher M22 binding affinity. Furthermore, the surface area formed by TSHR residues N208, Q235, R255, and N256 has been identified as a candidate target region for small molecules which might selectively block binding of autoantibodies to the TSHR.
Landscape diversity enhances biological control of an introduced crop pest in the north‐central USA
Authors: Gardiner M. M. , Landis D. A. , Gratton C. , DiFonzo C. D. , O'Neal M. , Chacon J. M. , Wayo M. T. , Schmidt N. P. , Mueller E. E. , Heimpel G. E.
Published: February 2009

Arthropod predators and parasitoids provide valuable ecosystem services in agricultural crops by suppressing populations of insect herbivores. Many natural enemies are influenced by non‐crop habitat surrounding agricultural fields, and understanding if, and at what scales, land use patterns influence natural enemies is essential to predicting how landscape alters biological control services. Here we focus on biological control of soybean aphid, Aphis glycines Matumura, a specialist crop pest recently introduced to the north‐central United States. We measured the amount of biological control service supplied to soybean in 26 replicate fields across Michigan, Wisconsin, Iowa, and Minnesota across two years (2005–2006). We measured the impact of natural enemies by experimentally excluding or allowing access to soybean aphid infested plants and comparing aphid population growth over 14 days. We also monitored aphid and natural enemy populations at large in each field. Predators, principally coccinellid beetles, dominated the natural enemy community of soybean in both years. In the absence of aphid predators, A. glycines increased significantly, with 5.3‐fold higher aphid populations on plants in exclusion cages vs. the open field after 14 days. We calculated a biological control services index (BSI) based on relative suppression of aphid populations and related it to landscape diversity and composition at multiple spatial scales surrounding each site. We found that BSI values increased with landscape diversity, measured as Simpson's D. Landscapes dominated by corn and soybean fields provided less biocontrol service to soybean compared with landscapes with an abundance of crop and non‐crop habitats. The abundance of Coccinellidae was related to landscape composition, with beetles being more abundant in landscapes with an abundance of forest and grassland compared with landscapes dominated by agricultural crops. Landscape diversity and composition at a scale of 1.5 km surrounding the focal field explained the greatest proportion of the variation in BSI and Coccinellidae abundance. This study indicates that natural enemies provide a regionally important ecosystem service by suppressing a key soybean pest, reducing the need for insecticide applications. Furthermore, it suggests that management to maintain or enhance landscape diversity has the potential to stabilize or increase biocontrol services.
Incorporating ecological and evolutionary processes into continental‐scale conservation planning
Authors: Klein Carissa , Wilson Kerrie , Watts Matthew , Stein Janet , Berry Sandra , Carwardine Josie , Smith Mark Stafford , Mackey Brendan , Possingham Hugh
Published: February 2009

Systematic conservation planning research has focused on designing systems of conservation areas that efficiently protect a comprehensive and representative set of species and habitats. Recently, there has been an emphasis on improving the adequacy of conservation area design to promote the persistence and future generation of biodiversity. Few studies have explored incorporating ecological and evolutionary processes into conservation planning assessments. Biodiversity in Australia is maintained and generated by numerous ecological and evolutionary processes at various spatial and temporal scales. We accommodated ecological and evolutionary processes in four ways: (1) using sub‐catchments as planning units to facilitate the protection of the integrity and function of ecosystem processes occurring on a sub‐catchment scale; (2) targeting one type of ecological refugia, drought refugia, which are critical for the persistence of many species during widespread drought; (3) targeting one type of evolutionary refugia which are important for maintaining and generating unique biota during long‐term climatic changes; and (4) preferentially grouping priority areas along vegetated waterways to account for the importance of connected waterways and associated riparian areas in maintaining processes. We identified drought refugia, areas of relatively high and regular herbage production in arid and semiarid Australia, from estimates of gross primary productivity derived from satellite data. In this paper, we combined the novel incorporation of these processes with a more traditional framework of efficiently representing a comprehensive sample of biodiversity to identify spatial priorities across Australia. We explored the trade‐offs between economic costs, representation targets, and connectivity. Priority areas that considered ecological and evolutionary processes were more connected along vegetated waterways and were identified for a small increase in economic cost. Priority areas for conservation investment are more likely to have long‐term benefits to biodiversity if ecological and evolutionary processes are considered in their identification.
Rapid decomposition of maize detritus in agricultural headwater streams
Authors: Griffiths Natalie A. , Tank Jennifer L. , Royer Todd V. , Rosi-Marshall Emma J. , Whiles Matt R. , Chambers Catherine P. , Frauendorf Therese C. , Evans-White Michelle A.
Published: February 2009

Headwater streams draining agricultural landscapes receive maize leaves (Zea mays L.) via wind and surface runoff, yet the contribution of maize detritus to organic‐matter processing in agricultural streams is largely unknown. We quantified decomposition and microbial respiration rates on conventional (non‐Bt) and genetically engineered (Bt) maize in three low‐order agricultural streams in northwestern Indiana, USA. We also examined how substrate quality and in‐stream nutrient concentrations influenced microbial respiration on maize by comparing respiration on maize and red maple leaves (Acer rubrum) in three nutrient‐rich agricultural streams and three low‐nutrient forested streams. We found significantly higher rates of microbial respiration on maize vs. red maple leaves and higher rates in agricultural vs. forested streams. Thus both the elevated nutrient status of agricultural streams and the lability of maize detritus (e.g., low carbon‐to‐nitrogen ratio and low lignin content) result in a rapid incorporation of maize leaves into the aquatic microbial food web. We found that Bt maize had a faster decomposition rate than non‐Bt maize, while microbial respiration rates did not differ between Bt and non‐Bt maize. Decomposition rates were not negatively affected by genetic engineering, perhaps because the Bt toxin does not adversely affect the aquatic microbial assemblage involved in maize decomposition. Additionally, shredding caddisflies, which are known to have suppressed growth rates when fed Bt maize, were depauperate in these agricultural streams, and likely did not play a major role in maize decomposition. Overall, the conversion of native vegetation to row‐crop agriculture appears to have altered the quantity, quality, and predictability of allochthonous carbon inputs to headwater streams, with unexplored effects on stream ecosystem structure and function.
Grazers, browsers, and fire influence the extent and spatial pattern of tree cover in the Serengeti
Authors: Holdo Ricardo M. , Holt Robert D. , Fryxell John M.
Published: February 2009

Vertebrate herbivores and fire are known to be important drivers of vegetation dynamics in African savannas. It is of particular importance to understand how changes in herbivore population density, especially of elephants, and fire frequency will affect the amount of tree cover in savanna ecosystems, given the critical importance of tree cover for biodiversity, ecosystem function, and human welfare. We developed a spatially realistic simulation model of vegetation, fire, and dominant herbivore dynamics, tailored to the Serengeti ecosystem of east Africa. The model includes key processes such as tree–grass competition, fire, and resource‐based density dependence and adaptive movement by herbivores. We used the model to project the ecosystem 100 years into the future from its present state under different fire, browsing (determined by elephant population density), and grazing (with and without wildebeest present) regimes. The model produced the following key results: (1) elephants and fire exert synergistic negative effects on woody cover; when grazers are excluded, the impact of fire and the strength of the elephant–fire interaction increase; (2) at present population densities of 0.15 elephants/km2, the total amount of woody cover is predicted to remain stable in the absence of fire, but the mature tree population is predicted to decline regardless of the fire regime; without grazers present to mitigate the effects of fire, the size structure of the tree population will become dominated by seedlings and mature trees; (3) spatial heterogeneity in tree cover varies unimodally with elephant population density; fire increases heterogeneity in the presence of grazers and decreases it in their absence; (4) the marked rainfall gradient in the Serengeti directly affects the pattern of tree cover in the absence of fire; with fire, the woody cover is determined by the grazing patterns of the migratory wildebeest, which are partly rainfall driven. Our results show that, in open migratory ecosystems such as the Serengeti, grazers can modulate the impact of fire and the strength of the interaction between fire and browsers by altering fuel loads and responding to the distribution of grass across the landscape, and thus exert strong effects on spatial patterns of tree cover.
Untangling the biological contributions to soil stability in semiarid shrublands
Authors: Chaudhary V. Bala , Bowker Matthew A. , O'Dell Thomas E. , Grace James B. , Redman Andrea E. , Rillig Matthias C. , Johnson Nancy C.
Published: February 2009

Communities of plants, biological soil crusts (BSCs), and arbuscular mycorrhizal (AM) fungi are known to influence soil stability individually, but their relative contributions, interactions, and combined effects are not well understood, particularly in arid and semiarid ecosystems. In a landscape‐scale field study we quantified plant, BSC, and AM fungal communities at 216 locations along a gradient of soil stability levels in southern Utah, USA. We used multivariate modeling to examine the relative influences of plants, BSCs, and AM fungi on surface and subsurface stability in a semiarid shrubland landscape. Models were found to be congruent with the data and explained 35% of the variation in surface stability and 54% of the variation in subsurface stability. The results support several tentative conclusions. While BSCs, plants, and AM fungi all contribute to surface stability, only plants and AM fungi contribute to subsurface stability. In both surface and subsurface models, the strongest contributions to soil stability are made by biological components of the system. Biological soil crust cover was found to have the strongest direct effect on surface soil stability (0.60; controlling for other factors). Surprisingly, AM fungi appeared to influence surface soil stability (0.37), even though they are not generally considered to exist in the top few millimeters of the soil. In the subsurface model, plant cover appeared to have the strongest direct influence on soil stability (0.42); in both models, results indicate that plant cover influences soil stability both directly (controlling for other factors) and indirectly through influences on other organisms. Soil organic matter was not found to have a direct contribution to surface or subsurface stability in this system. The relative influence of AM fungi on soil stability in these semiarid shrublands was similar to that reported for a mesic tallgrass prairie. Estimates of effects that BSCs, plants, and AM fungi have on soil stability in these models are used to suggest the relative amounts of resources that erosion control practitioners should devote to promoting these communities. This study highlights the need for system approaches in combating erosion, soil degradation, and arid‐land desertification.
Leaf chemical and spectral diversity in Australian tropical forests
Authors: Asner Gregory P. , Martin Roberta E. , Ford Andrew J. , Metcalfe Daniel J. , Liddell Michael J.
Published: February 2009

Leaf chemical and spectral properties of 162 canopy species were measured at 11 tropical forest sites along a 6024 mm precipitation/yr and 8.7°C climate gradient in Queensland, Australia. We found that variations in foliar nitrogen, phosphorus, chlorophyll a and b, and carotenoid concentrations, as well as specific leaf area (SLA), were expressed more strongly among species within a site than along the entire climate gradient. Integrated chemical signatures consisting of all leaf properties did not aggregate well at the genus or family levels. Leaf chemical diversity was maximal in the lowland tropical forest sites with the highest temperatures and moderate precipitation levels. Cooler and wetter montane tropical forests contained species with measurably lower variation in their chemical signatures. Foliar optical properties measured from 400 to 2500 nm were also highly diverse at the species level, and were well correlated with an ensemble of leaf chemical properties and SLA (r2 = 0.54–0.83).

A probabilistic diversity model amplified the leaf chemical differences among species, revealing that lowland tropical forests maintain a chemical diversity per unit richness far greater than that of higher elevation forests in Australia. Modeled patterns in spectral diversity and species richness paralleled those of chemical diversity, demonstrating a linkage between the taxonomic and remotely sensed properties of tropical forest canopies. We conclude that species are the taxonomic unit causing chemical variance in Australian tropical forest canopies, and thus ecological and remote sensing studies should consider the role that species play in defining the functional properties of these forests.
Lacandon Maya ecosystem management: sustainable design for subsistence and environmental restoration
Authors: Diemont Stewart A. W. , Martin Jay F.
Published: February 2009

Indigenous groups have designed and managed their ecosystems for generations, resulting in biodiversity protection while producing for their family's needs. Here we describe the agroecosystem of the Lacandon Maya, an indigenous group who live in Chiapas, Mexico. The Lacandon practice a form of swidden agriculture that conserves the surrounding rain forest ecosystem while cycling the majority of their land through five successional stages. These stages include an herbaceous stage, two shrub stages, and two forest stages. A portion of their land is kept in primary forest. This study presents the Lacandon traditional ecological knowledge (TEK) for agroforestry and quantitatively describes the plant community and the associated soil ecology of each successional stage. Also documented is the knowledge of the Lacandon regarding the immediate use of plant species and plant species useful for soil fertility enhancement. Woody plant diversity increases during the successional stages of the Lacandon system, and by the beginning of the first forest stage, the diversity is similar to that of the primary forest. In all stages, Lacandon use 60% of the available plant species for food, medicine, and raw materials. Approximately 45% of the woody plant species present in each fallow stage were thought by the Lacandon to enhance soil fertility. Total soil nitrogen and soil organic matter increased with successional stage and with time from intentional burn. Nutrient and soil nematode dynamics in shrub stages related to the presence of introduced and managed plants, indicating engineered soil enhancement by the Lacandon. The effects on biodiversity and soil ecology coupled with productivity for agricultural subsistence indicate that Lacandon TEK may offer tools for environmental conservation that would provide for a family's basic needs while maintaining a biodiverse rain forest ecosystem. Tools such as these may offer options for regional restoration and conservation efforts such as the Mesoamerican Biological Corridor in Mexico and Central America, where attainment of environmental goals must include methods to provide resources to local inhabitants.
Grass strip corridors in agricultural landscapes enhance nest‐site colonization by solitary wasps
Authors: Holzschuh Andrea , Steffan-Dewenter Ingolf , Tscharntke Teja
Published: February 2009

Corridors that connect otherwise isolated habitats have often been proposed as a management strategy to mitigate negative effects of habitat fragmentation. Non‐crop corridors may have the potential to enhance the connectivity for arthropod predators in cropland landscapes, especially for species that require multiple habitats, such as cavity‐nesting wasps which use wooded habitat for nesting and grassland habitat for foraging. However, the effects of corridors in nonexperimental landscapes have been rarely examined. We studied the species richness and abundance of cavity‐nesting wasps and their parasitoids in standardized trap nests located in three habitat types (forest edge, hedge, grass strip) and in three grass‐strip types (connected to a forest edge, slightly isolated, highly isolated from a forest edge).

Species richness and the abundance of wasps (Hymenoptera: Sphecidae, Eumenidae, Pompilidae) were highest at forest edges, which provide natural nesting sites, and lowest in grass strips, with few natural nesting sites. Wasp abundance in grass strips connected to forest edges was 270% higher than in slightly isolated grass strips and 600% higher than in highly isolated grass strips. The abundance of caterpillar‐hunting eumenid wasps was 600% higher in connected grass strips than in slightly and highly isolated grass strips. Species richness of wasps was enhanced by 180% in connected grass strips compared to highly isolated grass strips. Parasitism rates were not directly influenced by habitat or grass‐strip type, but increased with increasing parasitoid diversity that was higher at forest edges than in grass strips.

We conclude that grass‐strip corridors enhance the colonization of nesting sites, presumably by facilitating wasp movements. In agricultural landscapes, where nesting sites are limited and food availability changes frequently, rapid colonization of nests may enhance population viability. Higher wasp abundance in connected nesting sites may be directly linked to higher biocontrol of pest caterpillars within the foraging range around nests. Although grass strips can reduce the negative effects of habitat fragmentation, non‐crop habitats such as forest habitats and hedges providing nesting sites are required within the home range of wasps to allow reproduction in agricultural landscapes.
Aspects of the Relationship between Drug Dose and Drug Effect
Authors: Peper Abraham
Published: February 2009

It is generally assumed that there exists a well-defined relationship between drug dose and drug effect and that this can be expressed by a dose-response curve. This paper argues that there is no such clear relation and that the dose-response curve provides only limited information about the drug effect. It is demonstrated that tolerance development during the measurement of the dose-response curve may cause major distortion of the curve and it is argued that the curve may only be used to indicate the response to the first administration of a drug, before tolerance has developed. The precise effect of a drug on an individual depends on the dynamic relation between several variables, particularly the level of tolerance, the dose anticipated by the organism and the actual drug dose. Simulations with a previously published mathematical model of drug tolerance demonstrate that the effect of a dose smaller than the dose the organism has developed tolerance to is difficult to predict and may be opposite to the action of the usual dose.
The Perception of Smile Attractiveness
Authors: de Deus Tupinambá Rodrigues Caroline , Magnani Romeu , Machado Maria Salete Candido , Oliveira Osmir Batista
Published: February 2009

Objectives: To evaluate the attractiveness of a smile according to variations from esthetic norms, photographic framing, and the order of the presentation of photographs.

Materials and Methods: A photograph of an individual was selected and digitally manipulated to create the following smiles: an ideal control smile (I), a smile with diastema (D1), a smile with midline deviation (LM3), a smile with deviation from the long axes of the lateral incisors (10D), and a smile with an inverted smile arc (LSRV). The manipulated photographs were developed in framings of the face and of the mouth and evaluated by 20 laypeople. For half the evaluators, the presentation started with facial photographs and, for the other half, the presentation began with the mouth shots. Evaluators were asked to rank the photographs from the least to the most attractive; then, each photograph was awarded a mark (scale of 0.0 to 10.0).

Results: In both presentations, the smiles I, LM3, 10D, and LSRV received favorable ratings, whereas the D1 smile got poor ratings. The photographic framings used (face vs mouth) and the order of presentation of the photographs did not influence the rankings.

Conclusion: The absence of variations from beauty norms of a smile has a positive impact on its esthetic perception, but variations from the norms do not necessarily result in reduced attractiveness.
Alveolar Bone Loss around Incisors in Surgical Skeletal Class III Patients
Authors: Kim Yoonji , Park Je Uk , Kook Yoon-Ah
Published: February 2009

Objective: To test the hypothesis that there is no difference in the vertical alveolar bone levels and alveolar bone thickness around the maxillary and mandibular central incisors in surgically treated skeletal Class III malocclusion patients.

Materials and Methods: The study sample comprised 20 Korean patients with skeletal Class III malocclusion with anterior crossbite and openbite (9 male, 11 female, mean ages 24.1). Three-dimensional cone beam computed tomography images were taken at least 1 month before the orthognathic surgery, and sagittal slices chosen at the labio-lingually widest point of the maxillary and mandibular right central incisor were evaluated. Measurement of the amount of vertical alveolar bone levels and alveolar bone thickness of the labial and lingual plate at the root apex was made using the SimPlant Pro 12.0 program.

Results: The mandibular incisors showed reduced vertical alveolar bone levels than the maxillary incisors, especially on the lingual side. The alveolar bone thickness was significantly greater on the lingual side in the maxillary incisors, whereas the mandibular incisors exhibited an opposite result (P < .05). The percentage of vertical bone loss to root length showed a statistically significant difference between the upper labial and lower labial alveolar bone and also between the upper lingual and lower lingual alveolar bone, showing more bone loss in the lower incisors (P < .001).

Conclusions: The hypothesis is rejected. For the skeletal Class III patients undergoing orthognathic surgery, special care should be taken to prevent or not aggravate preexisting alveolar bone loss in the anterior teeth, especially in the mandible.
An In Vivo 3D Micro-CT Evaluation of Tooth Movement After the Application of Different Force Magnitudes in Rat Molar
Authors: Gonzales Carmen , Hotokezaka Hitoshi , Arai Yoshinori , Ninomiya Tadashi , Tominaga Junya , Jang Insan , Hotokezaka Yuka , Tanaka Motohiro , Yoshida Noriaki
Published: February 2009

Objective: To investigate the precise longitudinal change in the periodontal ligament (PDL) space width and three-dimensional tooth movement with continuous-force magnitudes in living rats.

Materials and Methods: Using nickel-titanium closed-coil springs for 28 days, 10-, 25-, 50-, and 100-g mesial force was applied to the maxillary left first molars. Micro-CT was taken in the same rat at 0, 1, 2, 3, 10, 14, and 28 days. The width of the PDL was measured in the pressure and tension sides from 0 to 3 days. Angular and linear measurements were used to evaluate molar position at day 0, 10, 14, and 28. The finite element model (FEM) was constructed to evaluate the initial stress distribution, molar displacement, and center of rotation of the molar.

Results: The initial evaluation of PDL width showed no statistical differences among different force magnitudes. Tooth movement was registered 1 hour after force application and gradually increased with time. From day 10, greater tooth movement was observed when 10 g of force was applied. The FEM showed that the center of rotation in the molar is located in the center of five roots at the apical third of the molar roots.

Conclusion: The rat's molar movement mainly consists of mesial tipping, extrusion of distal roots, intrusion of mesial root, palatal inclination, and mesial rotation. Although the initial tooth movement after the application of different force magnitudes until day 3 was not remarkably different, 10 g of force produced more tooth movement compared with heavier forces at day 28.