685 research outputs found
Changes in co-existence mechanisms along a long-term soil chronosequence revealed by functional trait diversity
1. Functional trait diversity can reveal mechanisms of species co-existence in plant communities. Few studies have tested whether functional diversity for foliar traits related to resource use strategy increases or decreases with declining soil phosphorus (P) in forest communities.
2. We quantified tree basal area and four foliar functional traits (i.e. nitrogen (N), phosphorus (P), thickness and tissue density) for all woody species along the c. 120 kyr Franz Josef soil chronosequence in cool temperate rainforest, where strong shifts occur in light and soil nutrient availability (i.e. total soil P declines from 805 to 100 mg g–1). We combined the abundance and trait data in functional diversity indices to quantify trait convergence and divergence, in an effort to determine whether mechanisms of co-existence change with soil fertility.
3. Relationships between species trait means and total soil N and P were examined using multiple regression, with and without weighting of species abundances. We used Rao’s quadratic entropy to quantify functional diversity at the plot scale, then compared this with random expectation, using a null model that randomizes abundances across species within plots. Taxonomic diversity was measured using Simpson’s Diversity. Relationships between functional and taxonomic diversity and total soil P were examined using jackknife linear regression.
4. Leaf N and P declined and leaf thickness and density increased monotonically with declining total soil P along the sequence; these relationships were unaffected by abundance-weighting of species in the analyses. Inclusion of total soil N did not improve predictions of trait means. All measures of diversity calculated from presence/absence data were unrelated to total soil N and P. There was no evidence for a relationship between Rao values using quantitative abundances and total soil P. However, there was a strongly positive relationship between Rao, expressed relative to random expectation, and total soil P, indicating trait convergence of dominant species as soil P declined.
5. Synthesis: Our results demonstrate that at high fertility dominant species differ in resource use strategy, but as soil fertility declines over the long-term, dominant species increasingly converge on a resource-retentive strategy. This suggests that differentiation in resource use strategy is required for co-existence at high fertility but not in low fertility ecosystems
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An Orbital Basis Set for Double Photoionization of Atoms and Molecules.
The ab initio theoretical treatment of one-photon double photoionization processes has been limited to atoms and diatomic molecules by the challenges posed by large grid-based representations of the double ionized continuum wave function. To provide a path for extensions to polyatomics, an energy-adapted orbital basis approach is demonstrated that reduces the dimensions of such representations and simultaneously allows larger time steps in time-dependent computational descriptions of double ionization. Additionally, an algorithm that exploits the diagonal nature of the two-electron integrals in the grid basis and dramatically accelerates the transformation between grid and orbital representations is presented. Excellent agreement between the present results and benchmark theoretical calculations is found for H- and Be atoms, as well as the hydrogen molecule, including for the triply differential cross sections that relate the angular distribution and energy sharing of all of the particles in the molecular frame
CMOS-compatible multi-band plasmonic TE-pass polarizer
A CMOS-compatible plasmonic TE-pass polarizer capable of working in the O, E,S, C, L, and U bands is numerically analyzed. The device is based on an integrated hybrid plasmonic waveguide (HPW) with a segmented metal design. The segmented metal will avoid the propagation of the TM mode, confined in the slot of the HPW, while the TE fundamental mode will pass. The TE mode is not affected by the metal segmentation since it is confined in the core of the HPW. The concept of the segmented metal can be exploited in a plasmonic circuit with HPWs as the connecting waveguides between parts of the circuit and in a silicon photonics circuit with strip or slab waveguides connecting the different parts of the circuit. Using 3D FDTD simulations, it is shown that for a length of 5.5 μm the polarization extinction ratios are better than 20 dB and the insertion losses are less than 1.7dB over all the optical communication bands
Association of Preoperative Copeptin Levels with Risk of All-Cause Mortality in a Prospective Cohort of Adult Cardiac Surgery Patients.
We aimed to investigate the association of preoperative copeptin, a new cardiovascular biomarker, with short- and long-term mortality in a cohort of adult patients undergoing cardiac surgery, including its potential as a prognostic marker for clinical outcome. Preoperative blood samples of the Bern Perioperative Biobank, a prospective cohort of adults undergoing cardiac surgery during 2019, were analyzed. The primary and secondary outcome measures were 30-day and 1-year all-cause mortality. Optimal copeptin thresholds were calculated with the Youden Index. Associations of copeptin levels with the two outcomes were examined with multivariable logistic regression models; their discriminatory capacity was assessed with the area under the receiver operating characteristic (AUROC). A total of 519 patients (78.4% male, median age 67 y (IQR: 60-73 y)) were included, with a median preoperative copeptin level of 7.6 pmol/L (IQR: 4.7-13.2 pmol/L). We identified an optimal threshold of 15.9 pmol/l (95%-CI: 7.7 to 46.5 pmol/L) for 30-day mortality and 15.9 pmol/L (95%-CI: 9.0 to 21.3 pmol/L) for 1-year all-cause mortality. Regression models featured an AUROC of 0.79 (95%-CI: 0.56 to 0.95) for adjusted log-transformed preoperative copeptin for 30-day mortality and an AUROC of 0.76 (95%-CI: 0.64 to 0.88) for 1-year mortality. In patients undergoing cardiac surgery, the baseline levels of copeptin emerged as a strong marker for 1-year all-cause death. Preoperative copeptin levels might possibly identify patients at risk for a complicated, long-term postoperative course, and therefore requiring a more rigorous postoperative observation and follow-up
Propriedades psicométricas da Escala de Medida do Estado Atual (MOCS) em pacientes mexicanos com câncer
Background: Cancer is a public health problem, and stress is one of the psychosocial variables associated to this disease, which calls for the need to have a reliable scale to measures stress in the Hispanic population with cancer. Objective: To determine the psychometric properties of the Measurement of Current Status (MOCS) Scale in Mexican cancer patients. Method: Study design: Cross-sectional, non-experimental instrumental. A total of 197 patients aged 18-81 years, at any clinical stage, receiving cancer treatment or follow-up were included. Instruments: MOCS and emotional distress thermometer. Statistical analysis: Confirmatory factor analysis was performed to evaluate the fit of the model to the data using the maximum likelihood estimation and cut-off points. Results: Two models were obtained. The first, self-perceived current state, had an alpha of .90 with an explained variance of 74.2 %; the second, non-specific effect, with an alpha of .61 and an explained variance of 74.3 %. The confirmatory factor analysis showed that both models had indexes suggesting stability and acceptable adjustment. Scores are shown by interquartile ranges for each model. Conclusions: The Mexican version of the MOCS is reliable and valid; with a confirmatory factor structure similar to the original version. Therefore, we support its use in the clinical and research setting with cancer patients.Antecedentes: El cáncer es un problema de salud pública, una de las variables psicosociales en relación con esta enfermedad es el estrés, por tanto es necesario tener una escala que mida el estrés en población hispana con cáncer. Objetivo: Determinar las propiedades psicométricas de la Escala de Medida del Estado Actual (MOCS, por sus igla en inglés) en pacientes mexicanos con cáncer. Método: Estudio transversal, instrumental no experimental. Participaron 197 pacientes de 18 a 81 años, de cualquier etapa clínica, en tratamiento o seguimiento del cáncer. Instrumentos: MOCS y termómetro de malestar emocional. Análisis estadísticos: análisis factorial confirmatorio para evaluar el ajuste del modelo a los datos mediante el método de máxima verosimilitud y puntos de corte. Resultados: Se obtuvieron dos modelos, el primero, estado actual autopercibido, con un alfa de .90 varianza explicada de 74.2 %, el segundo, efectos inespecíficos, con un alfa de .61 varianza explicada de 74.3 %. El análisis factorial confirmatorio mostró que ambos modelos tuvieron índices que sugieren estabilidad, ajuste aceptable, se muestran puntajes mediante rangos intercuartílicos para cada modelo. Conclusiones: la versión mexicana del MOCS tiene confiabilidad y validez, su estructura factorial confirmatoria es similar a la versión original. Se recomienda su uso en la práctica clínica e investigación en pacientes con cáncer.Antecedentes: O câncer é um problema de saúde pública, uma das variáveis psicossociais relacionadas a essa doença é o estresse, portanto, é necessário ter uma escala que meça o estresse na população hispânica com câncer. Objetivo: Determinar as propriedades psicométricas da Escala de Medição do Estado Atual (MOCS) em pacientes mexicanos com câncer. Método: Desenho do estudo: transversal, instrumental, não experimental. Participaram 197 pacientes com idades entre 18 e 81 anos, em qualquer estágio clínico, em tratamento ou acompanhamento do câncer. Instrumentos: MOCS e Termômetro de desconforto emocional. Análises estatísticas: análise fatorial confirmatória para avaliar o ajuste do modelo aos dados por meio do método de máxima verossimilhança e pontos de corte. Resultados: Foram obtidos dois modelos, o primeiro estado atual autopercebido com um alfa de 0,90 variância explicada de 74,2 %, o segundo efeito inespecífico com um alfa de 0,61 variância explicada de 74,3 %; a análise fatorial confirmatória mostrou que ambos os modelos tiveram índices que sugerem estabilidade, ajuste aceitável e são demonstradas pontuações por meio de intervalos interquartis para cada modelo. Conclusões: a versão mexicana do MOCS tem confiabilidade e validade; sua estrutura fatorial confirmatória é semelhante à versão original. É recomendado para prática clínica e pesquisa em pacientes com câncer
La(, ) cross sections constrained with statistical decay properties of La nuclei
The nuclear level densities and -ray strength functions of
La were measured using the La(He, ),
La(He, He) and La(d, p) reactions. The
particle- coincidences were recorded with the silicon particle
telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these
experimental results, the low-energy enhancement in the A140 region is
discussed. The La( cross sections were calculated
at - and -process temperatures using the experimentally measured nuclear
level densities and -ray strength functions. Good agreement is found
between La( calculated cross sections and previous
measurements
Optical and thermal analysis of the light-heat conversion process employing an antenna-based hybrid plasmonic waveguide for HAMR
We investigate a tapered, hybrid plasmonic waveguide which has previously
been proposed as an optically efficient near-field transducer (NFT), or
component thereof, in several devices which aim to exploit nanofocused light.
We numerically analyze how light is transported through the waveguide and
ultimately focused via effective-mode coupling and taper optimization. Crucial
dimensional parameters in this optimization process are identified that are not
only necessary to achieve maximum optical throughput, but also optimum thermal
performance with specific application towards heat-assisted magnetic recording
(HAMR). It is shown that existing devices constructed on similar waveguides may
benefit from a heat spreader to avoid deformation of the plasmonic element
which we achieve with no cost to the optical efficiency. For HAMR, our design
is able to surpass many industry requirements in regard to both optical and
thermal efficiency using pertinent figure of merits like 8.5% optical
efficiency.Comment: 14 pages, 7 figures, and 3 tables. Published version: see
https://doi.org/10.1364/OE.26.001752. Related works: see
https://doi.org/10.1364/oe.22.011236, https://doi.org/10.1364/oe.26.030292,
and https://doi.org/10.1063/5.0044490. Keywords: Integrated Optics;
Components; Integrated Optics Devices; Surface Plasmons; Plasmonic
Optical and thermal analysis of the light-heat conversion process employing an antenna-based hybrid plasmonic waveguide for HAMR
We investigate a tapered, hybrid plasmonic waveguide which has previously been proposed as an optically efficient near-field transducer (NFT), or component thereof, in several devices which aim to exploit nanofocused light. We numerically analyze how light is transported through the waveguide and ultimately focused via effective-mode coupling and taper optimization. Crucial dimensional parameters in this optimization process are identified that are not only necessary to achieve maximum optical throughput, but also optimum thermal performance with specific application towards heat-assisted magnetic recording (HAMR). It is shown that existing devices constructed on similar waveguides may benefit from a heat spreader to avoid deformation of the plasmonic element which we achieve with no cost to the optical efficiency. For HAMR, our design is able to surpass many industry requirements in regard to both optical and thermal efficiency using pertinent figure of merits like 8.5% optical efficiency
NH3-SCR catalysts for heavy-duty diesel vehicles: Preparation of CHA-type zeolites with low-cost templates
Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This “ab-initio” analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHA-type material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.This work has been supported by Umicore and by the Spanish Government-MCIU through RTI2018-101033-B-I00 (MCIU/AEI/FEDER, UE) and PID2020-112590GB-C21 (AEI/FEDER, UE). T.W. acknowledges financial support by the Swedish Research Council (Grant No. 2019-05465). E.B. acknowledges the Spanish Government-MCIU for a FPI scholarship (PRE2019-088360). P.F. thanks ITQ for a contract. The Electron Microscopy Service of the UPV is acknowledged for their help in sample characterization. The computations were performed on the Tirant III cluster of the Servei d'Informàtica of the University of Valencia
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