1,989 research outputs found
The Yellow Coral Dendrophyllia cornigera in a Warming Ocean
Ocean warming is expected to impinge detrimentally on marine ecosystems worldwide up to impose extreme environmental conditions capable to potentially jeopardize the good ecological status of scleractinian coral reefs at shallow and bathyal depths. The integration of literature records with newly acquired remotely operated vehicle (ROV) data provides an overview of the geographic distribution of the temperate coral Dendrophyllia cornigera spanning the eastern Atlantic Ocean to the whole Mediterranean Sea. In addition, we extracted temperature values at each occurrence site to define the natural range of this coral, known to maintain its physiological processes at 16\ub0C. Our results document a living temperature range between 3c7\ub0C and 17\ub0C, suggesting that the natural thermal tolerance of this eurybathic coral may represent an advantage for its survival in a progressively warming ocean
Instruções técnicas para o cultivo comercial de hortaliças em Rondônia.
Instrucoes tecnicas dirigidas a extensionistas, baseadas em trabalhos de pesquisa e unidades de observacoes, conduzidas no periodo de 1984/86, pela EMBRAPA-UEPAE Porto Velho, em varios locais do Estado. Apresentam-se meios de superar algumas limitacoes tecnicas e contribui com o crescimento da atividade olericola e Rondonia. Inclui informacoes sobre propagacao, epoca de plantio e regioes aptas para o cultivo, preparo do solo, calagem, adubacao e adubacao organica, doencas e pragas, nematoides e rotacao de culturas.bitstream/item/55039/1/Circ.Tec.110001.pd
The Ages and Abundances of the M87 Globular Clusters
A subset of 150 globular clusters in M87 has been selected on the basis of
S/N ratio for abundance and age determinations from the sample of Paper I.
Indices measuring the strength of the strongest spectral features were
determined for the M87 GCs and from new data for twelve galactic GCs. Combining
the new and existing data for the galactic GCs and comparing the colors
and the line indices gives qualitative indications for the ages and abundances
of the GCs. Quantitative results are obtained by applying the Worthey (1994)
models for the integrated light of stellar systems of a single age, calibrated
by observations of galactic GCs, to deduce abundances and ages for the objects
in our sample.
We find that the M87 GCs span a wide range in metallicity, from very metal
poor to somewhat above solar metallicity. The mean [Fe/H] of -0.95 dex is
higher than that of the galactic GC system, and there is a metal rich tail that
reaches to higher [Fe/H] than one finds among the galactic GCs. The mean
metallicity of the M87 GC system is about a factor of four lower than that of
the M87 stellar halo at a fixed projected radius . The metallicity inferred
from the X-ray studies is similar to that of the M87 stellar halo, not to that
of GCs. We infer the relative abundances of Na, Mg, and Fe in the M87 GCs from
the strength of their spectral features. The behavior of these elements between
the metal rich and metal poor M87 GCs is similar to that shown by the galactic
GCs and by halo stars in the Galaxy. The pattern of chemical evolution in these
disparate old stellar systems is indistinguishable. We obtain a median age for
the M87 GC system of 13 Gyr, similar to that of the galactic GCs, with a small
dispersion about this value.Comment: 56 pages with included postscript figures; added derived M87 GC
metallicities to Table 2, a statistical analysis of possible bimodality, an
appendix on the metallicity calibration of U-R and the Washington system, and
other smaller changes. Accepted for publication in ApJ. (See paper for
complete version of the Abstract.
Facility for validating technologies for the autonomous space rendezvous and docking to uncooperative targets
We present the latest advancements in the air-bearing facility installed at La Sapienza’s GN Lab in the School of Aerospace Engineering. This facility has been utilized in recent times to validate robust control laws for simultaneous attitude control and vibration active damping. The instrumentation and testbed have been restructured and enhanced to enable simulations of close proximity operations. Relative pose determination, accomplished through visual navigation as either an auxiliary or standalone system, is the first building block. Leveraging the acquired knowledge, optimal guidance and control algorithms can be tested for contactless operations (e.g. on-orbit inspection), as well as berthing and docking tasks
Efficient Digital Signal Processing Techniques and Architectures for On-Board Processors
In this paper, we present a number of algorithmic and architectural DSP solutions to be incorporated in digital OBPs for communication satellites to boost the system performance primarily in terms of reducing their power consumption. More specifically this article addresses (1) Infinite impulse response (IIR) implementation of digital filters, (2) Efficiency savings in channeliser FFT twiddle storage and multiplications and their reconfigurable implementation (3) Companding of interconnect data, and (4) Critically sampled/reduced over-sampling channelisation. The applicability and efficiency of these approaches were evaluated in detail during our European Space Agency (ESA) funded research project entitled "Efficient Techniques for On-Board Processing”, undertaken by Airbus Defence and Space and the Applied DSP and VLSI Research Group at the University of Westminster. The results demonstrated noteworthy improvements both in terms of power dissipation, and furthermore in the reduction of circuit complexity for future digital OBPs, which will be shown at the summary of results section
On board Processor and Processing Strategies for Next Generation Reconfigurable Satellite Payloads
Today, the increasing demand in higher data rates necessitates new methods as well as higher flexibility for satellite telecommunication payloads in order to address a variety of applications and customers. This paper presents one of these processing strategies that is applicable to today’s processing satellite payloads aiming to meet those demands. For this purpose, a two-tier filter bank is designed as part of a digital onboard processor, which first divides the spectrum at the output of the ADC into a number of sub-bands extracting all the stacked channels in the digital domain. Following the analysis section of the first tier of operations, the extracted channels go under a secondary channelisation process to obtain much finer granularity of 31.25 kHz or 50 kHz depending on the communication standard used for data transmission. The implementation of the channeliser was delivered on a bit-true simulation model and the input and the output of the channelisers were compared and evaluated both in the time and frequency domains
The Design of Low Complexity Low Power Pipelined Short Length Winograd Fourier Transforms
In this paper a novel pipelining approach applicable to Winograd Fourier transforms is presented. The novel approach makes use of reconfigurable multiplier blocks to implement the real multipliers required for the transform as well as sharing the hardware resources among additions. The additions are realized using modified forms of butterfly circuits. The novel approach is tested on a 5-point Winograd Fourier transform and the circuit area and power dissipation of the design are estimated using an in-house power estimation tool and compared to the state-of-the- art approaches
Endoscopic Submucosal Dissection of Gastric Neoplastic Lesions. An Italian, Multicenter Study
Endoscopic submucosal dissection (ESD) allows removing neoplastic lesions on gastric
mucosa, including early gastric cancer (EGC) and dysplasia. Data on ESD from Western countries
are still scanty. We report results of ESD procedures performed in Italy. Data of consecutive patients
who underwent ESD for gastric neoplastic removal were analyzed. The en bloc resection rate and
the R0 resection rates for all neoplastic lesions were calculated, as well as the curative rate (i.e., no
need for surgical treatment) for EGC. The incidence of complications, the one‐month mortality, and
the recurrence rate at one‐year follow‐up were computed. A total of 296 patients with 299 gastric
lesions (80 EGC) were treated. The en bloc resection was successful for 292 (97.6%) and the R0 was
achieved in 266 (89%) out of all lesions. In the EGC group, the ESD was eventually curative in 72.5%
(58/80) following procedure. A complication occurred in 30 (10.1%) patients. Endoscopic treatment
was successful in all 3 perforations, whereas it failed in 2 out of 27 bleeding patients who were
treated with radiological embolization (1 case) or surgery (1 case). No procedure‐related deaths at
one‐month follow‐up were observed. Lesion recurrence occurred in 16 (6.2%) patients (6 EGC and
10 dysplasia). In conclusion, the rate of both en bloc and R0 gastric lesions removal was very high in
Italy. However, the curative rate for EGC needs to be improved. Complications were acceptably low
and amenable at endoscopy
Optical and electrical behavior of synthetic melanin thin films spray-coated
AbstractWe investigated the optical and the electrical conductivity properties of synthetic melanin thin films spray-coated on glass. These films showed a broadband monotonic increase of the absorption coefficient, decreasing the wavelength in the Visible-NIR range. Conductivity as a function of the temperature evidenced a semiconductor like character and a hysteretic behaviour after thermal annealing up to 475 K. Thermal activation energies extrapolated by resistance curves have been explained by using the framework of a band-model as for an amorphous semiconductor
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