bluuebunny/crossref_metadata_2025 huggingface dataset:
A methodology for merging multisensor precipitation estimates based on expectation‐maximization and scale‐recursive estimation
Authors: Gupta Rohit , Venugopal V. , Foufoula‐Georgiou Efi
Published: January 2006

Scale‐recursive estimation (SRE) is a Kalman‐filter‐based methodology, which can be used to produce optimal (in terms of bias and minimum variance) estimates of a field at any desired scale given uncertain and sparse observations at different scales. SRE requires the specification of the state equation, which describes the variability of the precipitation process across scales, and the observation equation, which relates the observations to the state. Typical models for describing the multiscale rainfall variability are the multiplicative cascade models. However, in order to convert them into the additive form needed by SRE, one needs to work in the log space, thus creating a problem in handling zero‐intermittency in a satisfactory way. In this paper, we propose an alternative approach, based on a data‐driven identification methodology, which operates directly on the data and does not require a prespecified multiscale model structure. Rather, system identification and estimation are performed simultaneously via a likelihood‐based expectation‐maximization (EM) procedure. The merits of the proposed approach versus approaches based on multiplicative cascade models are explored via several examples of synthetic and real precipitation fields. For practical application the proposed approach will need to be extended to include the temporal evolution of storms. This extension presents theoretical challenges, and until these are addressed, a simple alternative is explored of coupling the EM‐SRE approach with a spatial downscaling methodology to merge precipitation observations available at different spatial and temporal scales. An example application is presented motivated by its relevance to the Global Precipitation Measuring (GPM) mission.
The electronic spectrum of AgCl2: Ab initio benchmark versus density-functional theory calculations on the lowest ligand-field states including spin-orbit effects
Authors: Ramírez-Solís A. , Poteau R. , Daudey J. P.
Published: January 2006

The XΠg2, Σg+2, and Δg2 states of AgCl2 have been studied through benchmark ab initio complete active space self-consistent field plus second-order complete active space multireference Möller-Plesset algorithm (CASSCF+CASPT2) and complete active space self-consistent field plus averaged coupled pair functional (CASSCF+ACPF) and density-functional theory (DFT) calculations using especially developed basis sets to study the transition energies, geometries, vibrational frequencies, Mulliken charges, and spin densities. The spin-orbit (SO) effects were included through the effective Hamiltonian formalism using the ΛSΣ ACPF energies as diagonal elements. At the ACPF level, the ground state is Πg2 in contradiction with ligand-field theory, SCF, and large CASSCF; the adiabatic excitation energies for the Σg+2 and Δg2 states are 1640 and 18230cm−1, respectively. The inclusion of the SO effects leads to a pure Ω=3∕2(Πg2) ground state, a Ω=1∕2 (66%Πg2 and 34%Σg+2) A state, a Ω=1∕2 (34%Πg2 and 66%Σg+2) B state, a Ω=5∕2(Δg2)C state, and a Ω=3∕2(99%Δg2)D state. The X-A, X-B, X-C, and X-D transition energies are 485, 3715, 17 246, and 20110cm−1, respectively. The B97-2, B3LYP, and PBE0 functionals overestimate by ≈100% the XΠg2−Σg+2Te but provide a qualitative energetic ordering in good agreement with ACPF results. B3LYP with variable exchange leads to a 42% optimal Hartree-Fock exchange for transition energies but all equilibrium geometries get worsened. Asymptotic corrections to B3LYP do not provide improved values. The nature of the bonding in the XΠg2 state is very different from that of CuCl2 since the Mulliken charge on the metal is 1.1 while the spin density is only 0.35. DFT strongly delocalizes the spin density providing even smaller values of around 0.18 on Ag not only for the ground state, but also for the Σg+2 state.
On the photophysics of all-transpolyenes: Hexatriene versus octatetraene
Authors: Catalán J. , de Paz J. L. G.
Published: January 2006

The disparate photophysical behavior of trans-1,3,5-hexatriene (nonfluorescent) and trans-1,3,5,7-octatetraene (with two fluorescence emissions) in the gas phase is explained in terms of the tendency of their 1Bu excited states to rotate about their terminal carbon-carbon single bonds in order to adopt a quasiplanar molecular form of lower energy than the 1Bu state in the parent all-trans structure. The origin of their disparate photophysical behavior is that such a transformation is subject to a small energy barrier in octatetraene; the barrier produces two minima (two fluorescence emissions) in the corresponding potential-energy curve. Instead of an energy barrier, hexatriene gives a 1,3-diene species which falls to the ground state so rapidly that no emission is produced.
Tunnel magnetoresistance in La0.7Ca0.3MnO3∕PrBa2Cu3O7∕La0.7Ca0.3MnO3
Authors: Sefrioui Z. , Cros V. , Barthélémy A. , Peña V. , León C. , Santamaria J. , Varela M. , Pennycook S. J.
Published: January 2006

We report large tunneling magnetoresistance in La0.7Ca0.3MnO3(8nm)∕PrBa2Cu3O7(2.4nm)∕La0.7Ca0.3MnO3(50nm) junctions. The coherent growth of the cuprate on the manganite allows the deposition of ultrathin barriers which are continuous and flat over long lateral distances. Epitaxial strain causes the top layer to be a weaker ferromagnet without a significant decrease in the spin polarization.
Magnetic Resonance Lineshapes of Pr3+ in Double Nitrate Crystals
Authors: Culvahouse J. W. , Pfortmiller L. , Schinke D. P.
Published: January 2006

The lineshapes for 10 concentrations of Pr3+ in double nitrate crystals have been measured. The data have been interpreted in terms of a distribution of zero-field splittings and a symmetrical broading. The effect of electric-field-induced transitions on the interpretation of the shapes is concisely described and the values of the electric field interaction constant are reported for La(C2H5SO4)3·9H2O, Y(C2H5SO4)3·9H2O, LaCl3, La2Mg3(NO3)12·24H2O, and La2Zn3(NO3)12·24H2O. From the concentration dependence of the Pr resonance lineshape, it is concluded that the major source of zero-field splitting is due to the misfitting of Pr and La ions in the lattice. In Pr2Mg3(NO3)12·24H2O, there is almost no asymmetrical broadening due to a distribution of Δ, but there is a large symmetrical broadening of about 0.095 cm−1. The origin of this symmetrical broadening appears to be an effective spin-spin interaction anomalously large for rare earth ions in the double nitrates.
Valence band offset of wurtzite InN∕AlN heterojunction determined by photoelectron spectroscopy
Authors: Wu C.-L. , Shen C.-H. , Gwo S.
Published: January 2006

The valence band offset (VBO) at the wurtzite-type, nitrogen-polarity InN∕AlN(0001¯) heterojunction has been determined by photoelectron spectroscopy to be 3.10±0.04eV. The heterojunction samples used for this study have an atomically abrupt 8:9 commensurate interface, at which every eight-unit cell of InN aligns exactly with every nine-unit cell of AlN. The commensurately matched InN∕AlN heterojunction system grown on Si(111) is particularly suitable for the determination of VBO since both InN and AlN epitaxial layers are completely relaxed and the strain-induced piezoelectric fields, which are difficult to be quantitatively determined, have a negligible effect.
Suppression of the pull-in instability for parallel-plate electrostatic actuators operated in dielectric liquids
Authors: Legrand B. , Rollier A.-S. , Collard D. , Buchaillot Lionel
Published: January 2006

We study electrostatic parallel-plate actuators operated in dielectric liquids. The stable operation zone of the actuators in common liquids is extended far beyond one-third of the initial gap, which is the typical limit of stability for such actuators operated in air. The pull-in effect can even be totally suppressed. In spite of higher dielectric constants in liquids than in air, which is expected to magnify the electrostatic forces, the required voltages to actuate are not significantly reduced and may even be larger. These results are discussed with regard to the dielectric constant of the liquids and to the electrical insulating layers of the parallel plates which appear to play a major role. Finally, the analytical approach is compared to experiments performed on fabricated devices.
Engineering the imaging properties of a metallic photonic-crystal slab lens
Authors: Feng Shuai , Li Zhi-Yuan , Feng Zhi-Fang , Cheng Bing-Ying , Zhang Dao-Zhong
Published: January 2006

Focusing properties of a two-dimensional metallic photonic crystal (PC) slab lens are studied through the finite-difference time-domain technique. The PC consists of a square lattice of metallic cylinders immersed in a dielectric background. A good-quality image can form in the opposite side of the slab in both the lowest and second higher transverse magnetic-polarized photonic bands, consistent with the analysis of equifrequency-surface contours. The all-angle negative refraction can be realized and controlled by simply adjusting the background material permittivity,.
Transistor performance of top rough surface of pentacene measured by laminated double insulated-gate supported on a poly(dimethylsiloxanes) base structure
Authors: Ling Mang-mang , Bao Zhenan , Li Dawen
Published: January 2006

We report the fabrication and electrical characterization of pentacene field-effect transistors with a laminated double insulated-gate using poly(dimethylsiloxanes) (PDMS) as their supporting structure. The ability of PDMS to conform to surfaces enables us to directly evaluate the device performance of the top rough surface of the pentacene active layer (the pentacene-air interface). The mobility measured for the top surface was only about 20% slightly lower than that of the bottom surface. Device stability under ambient conditions is evaluated. This device structure is useful for the characterization of electrical transport in both the top and bottom surface of a thin film simultaneously.
Photovoltaic Schottky ultraviolet detectors fabricated on boron-doped homoepitaxial diamond layer
Authors: Liao Meiyong , Koide Yasuo , Alvarez Jose
Published: January 2006

A photovoltaic diode using tungsten carbide (WC) Schottky contact for deep ultraviolet (DUV) light detection is developed using a lightly boron-doped homoepitaxial diamond layer. The photodiode shows a quick dc response time lower than an instrumental time constant of 0.3 s. The responsivity varies linearly with the DUV light intensity. A discrimination ratio of 105 between 210 nm and visible light is achieved at zero bias. The short-circuit photocurrent at 220 nm decreases with increasing the temperature from 300 to 373 K, whereas the Schottky barrier height under illumination remains unchanged. Numerical and experimental analyses reveal that the interface states between diamond and WC play a major role in reducing the zero-bias responsivity at elevated temperatures.
The macroinvertebrate fauna of an Australian dryland river: spatial and temporal patterns and environmental relationships
Authors: Marshall Jonathan C. , Sheldon Fran , Thoms Martin , Choy Satish
Published: January 2006

Waterholes within the dryland Cooper Creek, Lake Eyre Basin, Australia, are connected only during floods and are typically isolated for long periods. Spatial changes in the macroinvertebrate assemblages of 15 of these waterholes belonging to four regions were explored and these changes were related to environmental aspects of the waterholes measured at four spatial scales: floodplain, waterhole, within waterhole and sample habitat. To explore temporal patterns, one region was sampled on four occasions differing in time since connection. Spatial patterns were characterised by ‘differentiation by distance’ whereby samples collected closer to each other in the landscape were more similar in assemblage composition than those collected further apart. Thus, there were significant differences between the assemblages of the four regions. Although there was a correlation between macroinvertebrate spatial patterns and a combination of local habitat, geomorphology and water chemistry attributes, it appears unlikely that these variables were responsible for the faunal differentiation by distance. Temporal variability was larger than spatial variability and temporal assemblage patterns were best explained by the ‘connectivity potential’ of waterholes, reflecting the position of individual waterholes within the broader channel network and long-term connectivity relationships, rather than the actual time since hydrological connection.
Can flow velocity regulate epixylic biofilm structure in a regulated floodplain river?
Authors: Ryder Darren S. , Watts Robyn J. , Nye Errol , Burns Adrienne
Published: January 2006

Scour is one of the most important regulators of biofilm structure and function, especially in floodplain rivers where low gradients and flood frequencies limit potential for scouring. In this study, we experimentally examined the effects of flow velocity on the biomass and taxonomic composition of epixylic biofilms from floodplain reaches of the Murrumbidgee River, south-eastern Australia. Six blocks from each combination of colonisation period (30 or 70 days) and condition (wet or dried), were individually exposed to no velocity (control), or velocities of 0.3 m s−1 (low), 0.55 m s−1 (intermediate), or 1 m s−1 (high) in a laboratory flume. Biofilms exposed to all the experimental velocities had significantly lower dry mass (F3,94; P < 0.001), ash-free dry mass (F3,94; P < 0.001) and chlorophyll a (F3,94; P < 0.001) than the control. Losses of ash-free dry mass (F1,94; P < 0.05) and chlorophyll a (F1,94; P < 0.001) were significantly higher from wet biofilms exposed to each velocity than from dried biofilms. All velocities resulted in a substantial reduction in taxonomic richness among all treatments, with filamentous chlorophytes completely removed by velocities of 0.55 m s−1. These results indicate the potential to delineate thresholds for the response of biofilm biomass and algal taxa to flow velocity in floodplain rivers based on knowledge of antecedent conditions regulating biofilm development. This information significantly improves our understanding of the potential for ecological change using environmental flow releases in low-gradient floodplain rivers.
The International Society for Complementary Medicine Research (ISCMR): the Way Forward
Authors: Lewith George T , Verhoef Marja J
Published: January 2006

This article describes the birth and development of the International Society for Complementary Medicine Research (ISCMR) from its inception in 2003. The society′s main function is to facilitate the development of CAM research internationally and to use its networks, website, newsflashes and newsletters to communicate with its members and bring CAM researchers together from all over the world.
Targeted deletion of a cis-regulatory region reveals differential gene dosage requirements for Pdx1 in foregut organ differentiation and pancreas formation
Authors: Fujitani Yoshio , Fujitani Shuko , Boyer Daniel F. , Gannon Maureen , Kawaguchi Yoshiya , Ray Michael , Shiota Masakazu , Stein Roland W. , Magnuson Mark A. , Wright Christopher V.E.
Published: January 2006

Pdx1 (IPF-1 in humans, which is altered in MODY-4) is essential for pancreas development and mature β-cell function. Pdx1 is expressed dynamically within the developing foregut, but how its expression characteristics are linked to the various steps of organ specification, differentiation, and function is unknown. Deletion of a conserved enhancer region (Area I-II-III) from Pdx1 produced a hypomorphic allele (Pdx1ΔI-II-III) with altered timing and level of expression, which was studied in combination with wild-type and protein-null alleles. Lineage labeling in homozygous Area I-II-III deletion mutants (Pdx1ΔI-II-III/ΔI-II-III) revealed lack of ventral pancreatic bud specification and early-onset hypoplasia in the dorsal bud. Acinar tissue formed in the hypoplastic dorsal bud, but endocrine maturation was greatly impaired. While Pdx1-/- (protein-null) mice have nonpancreatic abnormalities (e.g., distorted pylorus, absent Brunner's glands), these structures formed normally in Pdx1ΔI-II-III/ΔI-II-III and Pdx1ΔI-II-III/- mice. Surprisingly, heterozygous (Pdx1+/ΔI-II-III) mice had abnormal islets and a more severe prediabetic condition than Pdx1+/- mice. These findings provide in vivo evidence of the differential requirements for the level of Pdx1 gene activity in the specification and differentiation of the various organs of the posterior foregut, as well as in pancreas and gut endocrine cell differentiation.
Extension of chronological life span in yeast by decreased TOR pathway signaling
Authors: Powers R. Wilson , Kaeberlein Matt , Caldwell Seth D. , Kennedy Brian K. , Fields Stanley
Published: January 2006

Chronological life span (CLS) in Saccharomyces cerevisiae, defined as the time cells in a stationary phase culture remain viable, has been proposed as a model for the aging of post-mitotic tissues in mammals. We developed a high-throughput assay to determine CLS for ∼4800 single-gene deletion strains of yeast, and identified long-lived strains carrying mutations in the conserved TOR pathway. TOR signaling regulates multiple cellular processes in response to nutrients, especially amino acids, raising the possibility that decreased TOR signaling mediates life span extension by calorie restriction. In support of this possibility, removal of either asparagine or glutamate from the media significantly increased stationary phase survival. Pharmacological inhibition of TOR signaling by methionine sulfoximine or rapamycin also increased CLS. Decreased TOR activity also promoted increased accumulation of storage carbohydrates and enhanced stress resistance and nuclear relocalization of the stress-related transcription factor Msn2. We propose that up-regulation of a highly conserved response to starvation-induced stress is important for life span extension by decreased TOR signaling in yeast and higher eukaryotes.
Regulated Pumilio-2 binding controls RINGO/Spy mRNA translation and CPEB activation
Authors: Padmanabhan Kiran , Richter Joel D.
Published: January 2006

CPEB is a sequence-specific RNA-binding protein that controls the polyadenylation-induced translation of mos and cyclin B1 mRNAs in maturing Xenopus oocytes. CPEB activity requires not only the phosphorylation of S174, but also the synthesis of a heretofore-unknown upstream effector molecule. We show that the synthesis of RINGO/Spy, an atypical activator of cyclin-dependent kinases (cdks), is necessary for CPEB-directed polyadenylation. Deletion analysis and mRNA reporter assays show that a cis element in the RINGO/Spy 3′UTR is necessary for translational repression in immature (G2-arrested) oocytes. The repression is mediated by 3′UTR Pumilio-Binding Elements (PBEs), and by its binding protein Pumilio 2 (Pum2). Pum2 also interacts with the Xenopus homolog of human Deleted for Azoospermia-like (DAZL) and the embryonic poly(A)-binding protein (ePAB). Following the induction of maturation, Pum2 dissociates not only from RINGO/Spy mRNA, but from XDAZL and ePAB as well; as a consequence, RINGO/Spy mRNA is translated. These results demonstrate that a reversible Pum2 interaction controls RINGO/Spy mRNA translation and, as a result, CPEB-mediated cytoplasmic polyadenylation.
TLSMDweb server for the generation of multi-group TLS models
Authors: Painter Jay , Merritt Ethan A.
Published: January 2006

TheTLSMDweb server extracts information about dynamic properties of a protein based on information derived from a single-crystal structure. It does so by analyzing the spatial distribution of individual atomic thermal parameters present in an input structural model. The server partitions the protein structure into multiple, contiguous chain segments, each segment corresponding to one group in a multi-group description of the protein's overall dynamic motion. For each polypeptide chain of the input protein, the analysis generates the optimal partition into two segments, three segments, … up to 20 segments. Each such partition is optimal in the sense that it is the best approximation of the overall spatial distribution of input thermal parameters in terms ofNchain segments, each acting as a rigid group undergoing TLS (translation/libration/screw) motion. This multi-group TLS model may be used as a starting point for further crystallographic refinement, or as the basis for analyzing inter-domain and other large-scale motions implied by the crystal structure.
Use of the dynamic vapor sorption meter to measure skin hydration properties, in vitro
Authors: Kilpatrick‐Liverman LaTonya , Polefka Thomas G.
Published: January 2006

Background: Maintaining an adequate skin moisture balance is important for retaining soft, pliable, healthy‐looking skin. This report describes the use of the dynamic vapor sorption (DVS) meter to quantify water content of skin in vitro under a variety of conditions. It is the only instrument that couples an ultra‐sensitive Cahn microbalance (resolution=0.1 μg) with an environmental system where both humidity and temperature are controlled. This feature is important since the skin's water content is influenced by changes in the relative humidity.

Method: In every experiment, the temperature was held constant at 25°C, and the starting relative humidity (RH) was set to 0% RH. The RH was programmed to step in 10% increments ending at 90% RH. The RH was incremented to the next level only when the mass change was less than 0.005%/min.

Results: A hysteresis was observed for all skin sorption/desorption experiments completed. Glycerin and the sodium salt of pyrrolidone carboxylic acid (NaPCA) both enhanced the % water content of skin. NaPCA was a more effective humectant at high relative humidities (above 60% RH); while glycerin performed better at humidities below 40% RH. Washing the skin with sodium lauryl sulfate (SLS) reduced the skin's ability to absorb water more so than washing with Tween 80, a milder surfactant. Vaseline® petroleum jelly enhanced the water‐retention properties of untreated skin.

Conclusions: The DVS can effectively be used to study the sorption and desorption properties of skin. We have shown that the amount of water absorbed is influenced by the RH, the presence of humectants and/or occlusive agents, and surfactant harshness.
The difference between the constitutive and facultative skin color does not reflect skin phototype in Asian skin
Authors: Choe Y. B. , Jang S. J. , Jo S. J. , Ahn K. J. , Youn J. I.
Published: January 2006

Background/purpose: The assessment of the sensitivity of human skin to ultraviolet (UV) radiation is important in the area of phototherapy, photodermatoses, photo‐aging, photo‐carcinogenesis, and photo‐protection. Some reports have shown that quantitatively measured skin color is a good indicator for predicting UV sensitivity to human skin in Caucasians. In this study, our aim was to define the correlation between skin color and the skin phototype assessed by the Fitzpatrick method in Asian brown skin.

Methods: A total of 180 medical students with similar life styles were included in this study. Their skin phototype was classified according to the system introduced by Fitzpatrick. Then, using a Minolta Spectrophotometer CM‐2002®, their skin color was determined on the buttocks and forehead. The buttock color was taken as the constitutive skin color, and the forehead color as the facultative skin color. Using these measured values, we compared the skin color with the skin phototype to find their correlation. Also, we investigated whether the difference between the constitutive and facultative skin colors of each individual had a relationship with his or her skin phototype.

Results: The constitutive skin color became darker with increasing skin phototype, and this change was statistically significant. As for the facultative skin color, it also became darker with increasing skin phototype, but was less well correlated with the skin phototype than the constitutive skin color. However, the difference between the constitutive and facultative skin colors did not show consistent results in predicting the skin phototype.

Conclusion: In this study, we found that the constitutive skin color can be a good indicator of the skin phototype. However, the difference between the constitutive and facultative skin colors of each individual does not give any meaningful information for the assessment of his or her skin phototype in Asian skin.
Habitat and resource use by larval and juvenile fishes in an arid‐land river (Rio Grande, New Mexico)
Authors: PEASE ALLISON A. , JUSTINE DAVIS J. , EDWARDS MELANIE S. , TURNER THOMAS F.
Published: January 2006

1. Studies of mesic temperate and tropical rivers suggest an important role for floodplain habitats as nursery areas for larval and juvenile fishes. In arid‐land rivers the extent and duration of flooding is diminished and habitats and resources used by larval fishes are poorly known. Our study documented habitat and resource use of larval fishes in the Rio Grande, New Mexico, an arid‐land river.

2. Spatial and temporal distribution of larval and juvenile fishes and their inferred microhabitat preferences were studied during spring, summer and autumn, 2003. Stable carbon (13C : 12C) and nitrogen (15N : 14N) isotope ratios were measured to identify nutrient sources and characterise trophic positions of young‐of‐year fishes in this system.

3. Some fishes recruited during high flows (in spring), whereas others recruited during low‐flow periods in late summer. Regardless of the timing of reproduction, microhabitats with lower current velocity and higher temperature appeared to serve as vital nursery grounds for Rio Grande fishes. Ephemeral backwaters and disconnected side channels held the highest abundance and diversity of larvae and juveniles.

4. Stable isotope analyses revealed that fish larvae obtained carbon predominately from algal production in early summer, but used organic carbon derived from emergent macrophytes as river discharge decreased in mid‐summer. This shift may have been facilitated by microinvertebrate prey that grazed down edible algae and then switched to macrophytes in mid‐summer. Nitrogen isotope ratios did not differ among species or early life stages, suggesting that larval and juvenile fishes use similar food resources, especially when restricted to isolated pools in summer.
Characterization of the heme synthesis enzyme coproporphyrinogen oxidase (CPO) in zebrafish erythrogenesis
Authors: Hanaoka Ryuki , Katayama Shiori , Dawid Igor B. , Kawahara Atsuo
Published: January 2006

Hemoglobin consists of heme and globin proteins and is essential for oxygen transport in all vertebrates. Although biochemical features of heme synthesis enzymes have been well characterized, the function of these enzymes in early embryogenesis is not fully understood. We found that the sixth heme synthesis enzyme, coproporphyrinogen oxidase (CPO), is predominantly expressed in the intermediate cell mass (ICM) that is a major site of zebrafish primitive hematopoiesis. Knockdown of zebrafish CPO using anti‐sense morpholinos (CPO‐MO) leads to a significant suppression of hemoglobin production without apparent reduction of blood cells. Injection of human CPO RNA, but not a mutant CPO RNA that is similar to a mutant responsible for a hereditary coproporphyria (HCP), restores hemoglobin production in the CPO‐MO‐injected embryos. Furthermore, expression of CPO in the ICM is severely suppressed in both vlad tepes/gata1 mutants and in biklf‐MO‐injected embryos. In contrast, over‐expression of biklf and gata1 significantly induces ectopic CPO expression. The function of CPO in heme biosynthesis is apparently conserved between zebrafish and human, suggesting that CPO‐MO‐injected zebrafish embryos might be a useful in vivo assay system to measure the biological activity of human CPO mutations.
Effect of natural atmospheric CO2 fertilization suggested by open‐grown white spruce in a dry environment
Authors: GEOFF WANG G. , CHHIN SOPHAN , BAUERLE WILLIAM L.
Published: January 2006

Evidence of an atmospheric CO2‐fertilization effect on radial growth rates was uncovered for open‐grown white spruce in a mixed‐grass prairie of southwestern Manitoba, Canada. Consistent upward trends of the residuals from dendroclimatic models indicated a decreased ability for climatic parameters to predict radial growth. Despite that a similar amount (61%) of the total variation in radial growth index was explained by climate for both young and old trees, residuals from young trees for the period of 1955–1999 demonstrated a stronger upward trend (R2=0.551, P<0.0001) than old trees for the period of 1900–1996 (R2=0.020, P=0.167). Similar to young trees, the residuals from the early growth period (1900–1929) of old trees also demonstrated a stronger upward trend (R2=0.480, P<0.0001) than the period of 1900–1996. Likewise, a comparable period (1970–1999) of young trees also demonstrated a stronger upward trend (R2=0.619, P<0.0001) than the early growth period (1900–1929) of old trees. In addition, postdrought growth response was much stronger for young trees (1970–1999) compared with old trees at the same development stage (1900–1929) (P=0.011) or within the same time period (1970–1999) (P=0.014). There was no difference (P=0.221) in drought recovery between the early (1900–1929) period and the late (1970–1999) period within old trees. Together, our results suggest that (1) open‐grown white spruce trees improved their growth with time at the early developmental stage, and (2) at the same developmental stage, a greater growth response occurred in the late period when atmospheric CO2 concentration, and the rate of atmospheric CO2 increase were both relatively high. While it is impossible to rule out other factors, these results are consistent with expectations for CO2‐fertilization effects.
Tree growth and soil acidification in response to 30 years of experimental nitrogen loading on boreal forest
Authors: HÖGBERG PETER , FAN HOUBAO , QUIST MAUD , BINKLEY DAN , TAMM CARL OLOF
Published: January 2006

Relations among nitrogen load, soil acidification and forest growth have been evaluated based on short‐term (<15 years) experiments, or on surveys across gradients of N deposition that may also include variations in edaphic conditions and other pollutants, which confound the interpretation of effects of N per se. We report effects on trees and soils in a uniquely long‐term (30 years) experiment with annual N loading on an un‐polluted boreal forest. Ammonium nitrate was added to replicated (N=3) 0.09 ha plots at two doses, N1 and N2, 34 and 68 kg N ha−1 yr−1, respectively. A third treatment, N3, 108 kg N ha−1 yr−1, was terminated after 20 years, allowing assessment of recovery during 10 years. Tree growth initially responded positively to all N treatments, but the longer term response was highly rate dependent with no gain in N3, a gain of 50 m3 ha−1 stemwood in N2 and a gain of 100 m3 ha−1 stemwood in excess of the control (N0) in N1. High N treatments caused losses of up to 70% of exchangeable base cations (Ca2+, Mg2+, K+) in the mineral soil, along with decreases in pH and increases in exchangeable Al3+. In contrast, the organic mor‐layer (forest floor) in the N‐treated plots had similar amounts per hectare of exchangeable base cations as in the N0 treatment. Magnesium was even higher in the mor of N‐treated plots, providing evidence of up‐lift by the trees from the mineral soil. Tree growth did not correlate with the soil Ca/Al ratio (a suggested predictor of effects of soil acidity on tree growth). A boron deficiency occurred on N‐treated plots, but was corrected at an early stage. Extractable NH4+ and NO3−were high in mor and mineral soils of on‐going N treatments, while NH4+ was elevated in the mor only in N3 plots. Ten years after termination of N addition in the N3 treatment, the pH had increased significantly in the mineral soil; there were also tendencies of higher soil base status and concentrations of base cations in the foliage. Our data suggest the recovery of soil chemical properties, notably pH, may be quicker after removal of the N‐load than predicted. Our long‐term experiment demonstrated the fundamental importance of the rate of N application relative to the total amount of N applied, in particular with regard to tree growth and C sequestration. Hence, experiments adding high doses of N over short periods do not mimic the long‐term effects of N deposition at lower rates.
Bias and variance in model results associated with spatial scaling of measurements for parameterization in regional assessments
Authors: OGLE STEPHEN M. , BREIDT F. JAY , PAUSTIAN KEITH
Published: January 2006

Models are central to global change analyses, but they are often parameterized using data that represent only a portion of heterogeneity in a region. This creates uncertainty in the results and constrains the reliability of model inferences. Our objective was to evaluate the uncertainty associated with differential scaling of parameterization data to model soil organic carbon stock changes as a function of US agricultural land use and management. Specifically, we compared analyses in which model parameters were derived from field experimental data that were scaled to the entire US vs. the same data scaled to climate regions within the country. We evaluated the effect of differential scaling on both bias and variance in model results.

Model results had less variance by scaling data to the entire country because of a larger sample size for deriving individual parameter values, although there was a relatively large bias associated with this parameterization, estimated at 2.7 Tg C yr−1. Even with the large bias, resulting confidence intervals from the two parameterizations had considerable overlap for the estimated national rate of SOC change (i.e. 77% overlap in those intervals). Consequently, the results were relatively similar when focusing on the uncertainty rather than solely on the mean estimate. In contrast, large biases created less overlap in confidence intervals for the change rates within individual climate regions, compared with the national estimates. For example, the overlap in resulting intervals from the two parameterizations was only 32% for the warm temperate moist region, with a corresponding bias of 3.1 Tg C yr−1.

These findings demonstrate that there is a greater risk of making erroneous inferences because of large biases if models are parameterized with broader scale information, such as an entire country, and then used to address impacts at a finer spatial scale, such as sub‐regions within a country. In addition, the study demonstrates a trade‐off between variance and bias in model results that depends on the scaling of data for model parameterization.
Functional and transcriptional profiling of MUTZ‐3, a myeloid cell line acting as a model for dendritic cells
Authors: Larsson Kristina , Lindstedt Malin , Borrebaeck Carl A. K.
Published: January 2006

The incidence of allergy is steadily increasing, but the molecular mechanisms involved in the allergic immune response are still not fully understood. In particular, further investigations focusing on dendritic cells, which are central in orchestrating the immune response, are needed. The objective of this study was to investigate the ability of myeloid leukaemia‐derived cell lines, such as KG‐1, THP‐1 and MUTZ‐3, to serve as in vitro models for dendritic cells. The ability of these cell lines to mature into functional dendritic cells, expressing costimulatory molecules, was assessed by functional and transcriptional profiling and compared with that of monocyte‐derived dendritic cells, which are now used as a standard source of dendritic cells. High‐density microarray analysis was utilized to study the transcriptional activity and kinetics of activation of the differentiated MUTZ‐3 cell line, in response to a cocktail of inflammatory cytokines. The data obtained clearly demonstrate that MUTZ‐3 cells have the ability to induce antigen‐independent proliferation in CD4+ CD45RA+ T cells, whereas KG‐1 and THP‐1 only induced a marginal response. Furthermore, MUTZ‐3 displayed the phenotypic and transcriptional profiles of immature dendritic cells, after differentiation with granulocyte–macrophage colony‐stimulating factor and interleukin‐4. Upon activation with inflammatory cytokines, MUTZ‐3 matured phenotypically and exhibited a gene induction similar to that of monocyte‐derived dendritic cells. This delineation of the cellular and transcriptional activity of MUTZ‐3, in response to maturational stimuli, demonstrates the significance of this cell line as a model for functional studies of inflammatory responses.
Deletion is neither sufficient nor necessary for the induction of peripheral tolerance in mature CD8+ T cells
Authors: Lees Jason R. , Charbonneau Bridget , Swanson Axel K. , Jensen Robert , Zhang JianFeng , Matusik Robert , Ratliff Timothy L.
Published: January 2006

Previous reports have demonstrated clonal deletion of CD8+ T cells during peripheral tolerance induction to tissue antigens. However, direct evidence demonstrating a causal connection between deletion and tolerance has not been reported because of model limitations in which the tissue antigens were expressed in vital organs. Thus, studies were initiated in a mouse model where expression of a membrane‐bound ovalbumin fusion protein (mOVA) was driven by a prostate specific androgen regulated probasin promotor, providing restricted expression in a non‐vital organ where antigen levels can be abrogated through androgen deprivation. Adoptive transfer of mOVA specific CD8+ T cells (OT‐I) was used to assess the development of peripheral tolerance. Proliferation of OT‐I cells was observed, as was partial deletion of transferred OT‐I cells. Although deletion occurred, the long‐term persistence of a stable level of OT‐I cells was observed. Importantly, the persistent OT‐I cells lost antigen responsiveness within 3 weeks of transfer. Castration resulted in loss of high‐level prostate mOVA expression, with a resultant abrogation of tolerance induction, but surprisingly did not affect the deletion rate of OT‐I cells. In contrast, abrogation of deletion through the adoptive transfer of OT‐I cells from third generation CD95‐deficient mice had no effect on tolerance induction. These data demonstrate the necessity for continued expression of tissue antigen throughout the establishment of peripheral tolerance. Furthermore, these findings demonstrate that deletion is neither sufficient nor required for CD8+ T‐cell tolerance to tissue antigens, suggesting that regulatory events independent of deletion are necessary for peripheral tolerance induction to prostate antigens.
Gonochorism vs. hermaphroditism: relationship between life history and fitness in three species of Ophryotrocha (Polychaeta: Dorvilleidae) with different forms of sexuality
Authors: PREVEDELLI DANIELA , N'SIALA GLORIA MASSAMBA , SIMONINI ROBERTO
Published: January 2006

The relationships between life history, fitness and sexuality, together with their ecological and evolutionary significance, has been analysed comparing the main life‐history traits and demography in three closely related species belonging to the genus Ophryotrocha. The species are: the gonochoristic O. labronica, the simultaneous hermaphrodite O. diadema and the protandrous hermaphrodite O. puerilis.

Survivorship and reproductive data were collected weekly and were used to construct life tables and population projection matrices for each species and compare life‐history characteristics. Elasticity, life‐table response and decomposition analyses were performed to examine the relative contribution of fecundity and survivorship to differences in λ between species.

The gonochoristic and hermaphroditic species differ in all the main life‐history parameters and also in demographic characteristics. In particular the value of λ, used commonly to express fitness, is markedly higher in the gonochoristic species while in terms of fitness simultaneous and sequential hermaphroditism are very similar. In the genus Ophryotrocha gonochorism currently represents the most widespread condition, being characteristic of the majority of the known species in the genus.

Given the demographic advantage ensured by gonochorism, it remains be understood why some species have retained simultaneous hermaphroditism and one has evolved a sequential type hermaphroditism; the most probable hypothesis is correlated with the density of the species in natural habitats.
Unrealistic animal movement rates as behavioural bouts: a reply
Authors: JOHNSON CHRIS J. , PARKER KATHERINE L. , HEARD DOUGLAS C. , GILLINGHAM MICHAEL P.
Published: January 2006

Johnson et al. (Journal of Animal Ecology, 2002, 71, 225–235) proposed a technique for stratifying the movements of ungulates into small‐ and large‐scale behaviours. They identified movement paths for woodland caribou and fitted a nonlinear curve to the log‐frequency of movement rates. They assumed that slow small‐scale movements were correlated with foraging activities in patches and faster large‐scale movements occurred when caribou moved between patches.

Nams (Journal of Animal Ecology, 2006, 75, 298–302) reviewed the assumptions and tested the technique presented by Johnson et al. (2002). Simulated animal movements resulted in rates inconsistent with the data of Johnson et al. (2002) and the distribution necessary to fit the nonlinear curve. Nams (2006) challenged animal movement as suitable for the technique and concluded that sampling interval would confound results.

We evaluated Nams's (2006) criticisms with movement data collected for caribou, moose and mountain goat. All three species demonstrated the required distribution of movement rates and sampling interval had little influence on the criterion used to identify scales of movement for a range of woodland caribou data. In addition, we tested the sensitivity of the curve‐fitting model to the width of the frequency interval for the log‐frequency plot of movement rates. We noted bias in the rate criterion, but the scalar relationship was consistent among interval widths.

The discrepancy in movement data presented by Nams (2006) and Johnson et al. (2002) is likely the result of different movement processes. The movements of simulated animals did not encompass the full range of behaviours typically observed for ungulates. Our analyses and those of Nams (2006) provide little evidence to universally reject the nonlinear curve‐fitting model and the results of Johnson et al. (2002). However, we caution against blind application of the technique, as not all movement processes are suitable and the scale of movement must be consistent with the scale of the behaviour.
Nutritional value of cannibalism and the role of starvation and nutrient imbalance for cannibalistic tendencies in a generalist predator
Authors: MAYNTZ DAVID , TOFT SØREN
Published: January 2006

Cannibalism is considered an adaptive foraging strategy for animals of various trophic positions, including carnivores. However, previous studies on wolf spiders have questioned the high nutritional value of cannibalism. We therefore analysed two different aspects of nutritional quality of conspecifics in the wolf spider Pardosa prativaga: their value for survival, growth and development; and the growth efficiency of feeding on conspecifics. We also measured the propensity for cannibalistic attacks and the consumption rate of conspecifics in an experiment where hunger level and nutrient balance were manipulated. In all experiments, cannibalism was compared with predation on fruit flies as control prey.

The growth experiment gave ambiguous results regarding the nutritional quality of conspecifics. Spiders on pure cannibalistic diets split into two distinct groups, one performing much better and the other much worse than spiders on fruit fly diets. We discuss the possibility that the population is dimorphic in its cannibalistic propensity, with the latter group of individuals showing a high level of inhibition against cannibalistic attacks in spite of a high nutritional value of cannibalism.

The food utilization experiment confirmed the high nutritional quality of conspecifics, as cannibalistic spiders had the same growth rate as spiders fed insect prey in spite of a much lower consumption rate.

Inhibition against cannibalistic attacks was demonstrated in medium‐sized juveniles: only half of the spiders attacked a prescribed victim of 50% the size of their opponents, and the latency for those that did attack was more than half an hour, compared with a few minutes for spiders fed fruit flies.

Nutrient‐imbalanced spiders utilized an alternative insect diet less efficiently than balanced spiders, whereas no difference was present in efficiency of utilizing conspecifics. This result indicates that spiders can remedy at least part of a nutrient imbalance through cannibalism.

As spiders can escape nutritional imbalance as well as restore energy reserves through cannibalism, we predicted both nutrient imbalance and hunger to stimulate cannibalism. This prediction was confirmed only with respect to hunger. Nutrient‐imbalanced spiders had reduced cannibalistic consumption, perhaps due to lowered predatory aggressiveness as a result of bad condition.
Evaluating the performance of species richness estimators: sensitivity to sample grain size
Authors: HORTAL JOAQUÍN , BORGES PAULO A. V. , GASPAR CLARA
Published: January 2006

Fifteen species richness estimators (three asymptotic based on species accumulation curves, 11 nonparametric, and one based in the species–area relationship) were compared by examining their performance in estimating the total species richness of epigean arthropods in the Azorean Laurisilva forests. Data obtained with standardized sampling of 78 transects in natural forest remnants of five islands were aggregated in seven different grains (i.e. ways of defining a single sample): islands, natural areas, transects, pairs of traps, traps, database records and individuals to assess the effect of using different sampling units on species richness estimations.

Estimated species richness scores depended both on the estimator considered and on the grain size used to aggregate data. However, several estimators (ACE, Chao1, Jackknife1 and 2 and Bootstrap) were precise in spite of grain variations. Weibull and several recent estimators [proposed by Rosenzweig et al. (Conservation Biology, 2003, 17, 864–874), and Ugland et al. (Journal of Animal Ecology, 2003, 72, 888–897)] performed poorly.

Estimations developed using the smaller grain sizes (pair of traps, traps, records and individuals) presented similar scores in a number of estimators (the above‐mentioned plus ICE, Chao2, Michaelis–Menten, Negative Exponential and Clench). The estimations from those four sample sizes were also highly correlated.

Contrary to other studies, we conclude that most species richness estimators may be useful in biodiversity studies. Owing to their inherent formulas, several nonparametric and asymptotic estimators present insensitivity to differences in the way the samples are aggregated. Thus, they could be used to compare species richness scores obtained from different sampling strategies. Our results also point out that species richness estimations coming from small grain sizes can be directly compared and other estimators could give more precise results in those cases. We propose a decision framework based on our results and on the literature to assess which estimator should be used to compare species richness scores of different sites, depending on the grain size of the original data, and of the kind of data available (species occurrence or abundance data).