1,667 research outputs found
Parallel functional and stoichiometric trait shifts in South American and African forest communities with elevation
The Amazon and Congo basins are the two largest continuous blocks of tropical forest with a central role for global biogeochemical cycles and ecology. However, both biomes differ in structure and species richness and composition. Understanding future directions of the response of both biomes to environmental change is paramount. We used one elevational gradient on both continents to investigate functional and stoichiometric trait shifts of tropical forest in South America and Africa. We measured community-weighted functional canopy traits and canopy and topsoil delta N-15 signatures. We found that the functional forest composition response along both transects was parallel, with a shift towards more nitrogen-conservative species at higher elevations. Moreover, canopy and topsoil delta N-15 signals decreased with increasing altitude, suggesting a more conservative N cycle at higher elevations. This cross-continental study provides empirical indications that both South American and African tropical forest show a parallel response with altitude, driven by nitrogen availability along the elevational gradients, which in turn induces a shift in the functional forest composition. More standardized research, and more research on other elevational gradients is needed to confirm our observations
Pressure effects on collective density fluctuations in water and protein solutions
Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure. Our results show significant differences between the pressure and density dependence of collective dynamics in bulk water and in concentrated protein solutions. Pressure-induced changes in the tetrahedral order of the water HB network have direct consequences for the high-frequency sound velocity and damping coefficients, which we find to be a sensitive probe for changes in the HB network structure as well as the wetting of biomolecular surfaces
Scarf\u27s Procedure for Integer Programming and a Dual Simplex Algorithm
Herbert Scarf has recently introduced an algorithm for integer programs based on the concept of primitive sets. We show that as the choice variables become continuous, this algorithm converges to a dual simplex algorithm. This result is robust in the sense that even before the limit is reached, the simplex path is contained in the primitive sets which define Scarf’s path to the solution of the integer program
Test engineering education in Europe: the EuNICE-Test project
The paper deals with a European experience of education in industrial test of ICs and SoCs using remote testing facilities. The project addresses the problem of the shortage in microelectronics engineers aware with the new challenge of testing mixed-signal SoCs far multimedia/telecom market. It aims at providing test training facilities at a European scale in both initial and continuing education contexts. This is done by allowing the academic and industrial partners of the consortium to train engineers using the common test resources center (CRTC) hosted by LIRMM (Laboratoire d'Informatique, de Robotique et de Microelectronique de Montpellier, France). CRTC test tools include up-to-date/high-tech testers that are fully representative of real industrial testers as used on production testfloors. At the end of the project, it is aimed at reaching a cruising speed of about 16 trainees per year per center. Each trainee will have attend at least one one-week training using the remote test facilities of CRTC
Measuring the cosmic ray acceleration efficiency of a supernova remnant
Cosmic rays are the most energetic particles arriving at earth. Although most
of them are thought to be accelerated by supernova remnants, the details of the
acceleration process and its efficiency are not well determined. Here we show
that the pressure induced by cosmic rays exceeds the thermal pressure behind
the northeast shock of the supernova remnant RCW 86, where the X-ray emission
is dominated by synchrotron radiation from ultra-relativistic electrons. We
determined the cosmic-ray content from the thermal Doppler broadening measured
with optical spectroscopy, combined with a proper-motion study in X- rays. The
measured post-shock proton temperature in combination with the shock velocity
does not agree with standard shock heating, implying that >50% of the
post-shock pressure is produced by cosmic rays.Comment: Published in Science express, 10 pages, 5 figures and 2 table
Synoptic study of the SMC SNRs using XMM-Newton
We present a detailed X-ray spectral analysis of 13 supernova remnants (SNR)
in the Small Magellanic Cloud (SMC). We apply both single-temperature
non-equilibrium ionisation models and models based on the Sedov similarity
solution, where applicable. We also present detailed X-ray images of individual
SNRs, which reveal a range of different morphological features. Eight remnants,
viz DEM S 32, IKT 2, HFPK 419, IKT 6, IKT 16, IKT 18 and IKT 23, are consistent
with being in their Sedov evolutionary phase. IKT 6 and IKT 23 both have a
clear shell like morphology with oxygen-rich X-ray emitting material in the
centre. We draw attention to similarities between these two remnants and the
well studied, oxygen-rich remnant IKT 22 (SNR 0102-72.3) and propose that they
are more evolved versions of IKT 22. IKT 4, IKT 5, DEM S 128 and IKT 5 are
evolved remnants which are in, or in the process of entering, the radiative
cooling stage. We argue that the X-ray emission from these four remnants is
most likely from the ejecta remains of type Ia SNe. Our modeling allow us to
derive estimates for physical parameters, such as densities, ages, masses and
initial explosion energies. Our results indicate that the average SMC hydrogen
density is a factor of ~6 lower as compared to the Large Magellanic Cloud. This
has obvious implications for the evolution and luminosities of the SMC SNRs. We
also estimate the average SMC gas phase abundances for the elements O, Ne, Mg,
Si and Fe.Comment: submitted to A&
Heroes or Villains? Recasting Middle Management Roles, Processes, and Behaviours
Middle management ranks are once again being questioned by scholars and practitioners alike. This introduction to the special issue represents a timely reference point for consolidating, reviving, and guiding the next wave of researchers seeking to engage this debate. We review the foundations and recent advances in middle management research and develop an organizing framework in terms of middle management's organizational roles, coordination processes, and agentic behaviours. We also identify how new ways of organizing, technology, and middle manager needs are changing to shape each of these themes. The collection of works we synthesize in this introduction offer theoretical advances and empirical evidence on how these changes affect middle management roles, processes, and behaviours. We conclude by mapping out promising research avenues for future research in middle management
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