Non-local F(R)-mimetic gravity     

Ratbay Myrzakulov  Lorenzo Sebastiani 《Astrophysics and Space Science》2016,361(6):188

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k-essence in Horndeski models     

Shynaray Myrzakul  Ratbay Myrzakulov  Lorenzo Sebastiani 《Astrophysics and Space Science》2016,361(8):254

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Hypsometric Analysis of Headwater Rock Basins in the Dolomites (Eastern Alps) Using High‐Resolution Topography          下载免费PDF全文

Lorenzo Marchi  Marco Cavalli  Sebastiano Trevisani 《Geografiska Annaler: Series A, Physical Geography》2015,97(2):317-335

Hypsometric curves and integrals are effective tools for rapid quantitative assessments of topography. High‐resolution digital terrain models derived from airborne LiDAR data have been analysed to study the hypsometry of small headwater rock basins (drainage areas up to 0.13 km²) in three study areas in the Dolomites (Eastern Alps) that have similar lithologies and climatic conditions. Hypsometric curves in the studied rocky headwaters display a variety of shapes and present remarkable differences between neighbouring basins. Hypsometric integrals show generally high values in the three study areas (>0.42, mean values between 0.51 and 0.65). The extent of the scree slopes located at the foot of rock basins in the three study areas is larger in the area with lower hypsometric integrals and indicates consistency between the development of basin erosion, which is shown by the hypsometric integral, and debris yield, represented by the extent of scree slope. No clear relations were observed between the hypsometric integrals and basin area and shape. When extending the analysis to larger basins, which encompass rocky headwaters and downslope soil‐mantled slopes, a negative correlation is found between the hypsometric integral and catchment area, suggesting that the scale independency of the hypsometric integral occurs essentially in headwater rock basins. Geomorphometric indices (residual relief and surface roughness) have contributed to interpreting the variability of surface morphology, which is related to the geo‐structural complexity of the catchments.  相似文献   

Interspecific introgression and changes in population structure in a flatfish species complex after the Prestige accident     

V. Crego-Prieto  D. Danancher  D. Campo  J. Perez  E. Garcia-Vazquez  A. Roca 《Marine pollution bulletin》2013

Oil spills cause aggressive impacts on marine ecosystems affecting immense areas and the species inhabiting them. If wastes are not cleaned up properly, the remnants may affect local populations for a long time. This work focuses on the long-term impacts of the Prestige spillage that occurred off Galician coast (Spain) in November 2002. Model species were two sympatric flatfish, the megrims Lepidorhombus whiffiagonis and Lepidorhombus boscii. Samples obtained before and nine years after the Prestige accident from affected and unaffected areas were genotyped for six hypervariable nuclear markers and for the mitochondrial D-loop sequence. The results revealed a high proportion of post-F1 interspecific hybrids in the area affected, and also increased intraspecific population differentiation likely due to such localized introgression of foreign genes. These changes suggest the appearance of a hybrid zone following the accident and emphasize the need of paying special attention to potential evolutionary impacts of oil spills.  相似文献   

Trends and variability of ocean waves under RCP8.5 emission scenario in the Mediterranean Sea     

De Leo  Francesco  Besio  Giovanni  Mentaschi  Lorenzo 《Ocean Dynamics》2021,71(1):97-117

Ocean Dynamics - Wind-generated ocean waves are key inputs for several studies and applications, both near the coast (coastal vulnerability assessment, coastal structures design, harbor...  相似文献   

MarcoPolo-R near earth asteroid sample return mission   总被引：3，自引：0，他引：3  

Maria Antonietta Barucci  A. F. Cheng  P. Michel  L. A. M. Benner  R. P. Binzel  P. A. Bland  H. B?hnhardt  J. R. Brucato  A. Campo Bagatin  P. Cerroni  E. Dotto  A. Fitzsimmons  I. A. Franchi  S. F. Green  L.-M. Lara  J. Licandro  B. Marty  K. Muinonen  A. Nathues  J. Oberst  A. S. Rivkin  F. Robert  R. Saladino  J. M. Trigo-Rodriguez  S. Ulamec  M. Zolensky 《Experimental Astronomy》2012,33(2-3):645-684

MarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) proposed in collaboration with NASA. It will rendezvous with a primitive NEA, scientifically characterize it at multiple scales, and return a unique sample to Earth unaltered by the atmospheric entry process or terrestrial weathering. MarcoPolo-R will return bulk samples (up to 2?kg) from an organic-rich binary asteroid to Earth for laboratory analyses, allowing us to: explore the origin of planetary materials and initial stages of habitable planet formation; identify and characterize the organics and volatiles in a primitive asteroid; understand the unique geomorphology, dynamics and evolution of a binary NEA. This project is based on the previous Marco Polo mission study, which was selected for the Assessment Phase of the first round of Cosmic Vision. Its scientific rationale was highly ranked by ESA committees and it was not selected only because the estimated cost was higher than the allotted amount for an M class mission. The cost of MarcoPolo-R will be reduced to within the ESA medium mission budget by collaboration with APL (John Hopkins University) and JPL in the NASA program for coordination with ESA’s Cosmic Vision Call. The baseline target is a binary asteroid (175706) 1996 FG3, which offers a very efficient operational and technical mission profile. A binary target also provides enhanced science return. The choice of this target will allow new investigations to be performed more easily than at a single object, and also enables investigations of the fascinating geology and geophysics of asteroids that are impossible at a single object. Several launch windows have been identified in the time-span 2020–2024. A number of other possible primitive single targets of high scientific interest have been identified covering a wide range of possible launch dates. The baseline mission scenario of MarcoPolo-R to 1996 FG3 is as follows: a single primary spacecraft provided by ESA, carrying the Earth Re-entry Capsule, sample acquisition and transfer system provided by NASA, will be launched by a Soyuz-Fregat rocket from Kourou into GTO and using two space segment stages. Two similar missions with two launch windows, in 2021 and 2022 and for both sample return in 2029 (with mission duration of 7 and 8?years), have been defined. Earlier or later launches, in 2020 or 2024, also offer good opportunities. All manoeuvres are carried out by a chemical propulsion system. MarcoPolo-R takes advantage of three industrial studies completed as part of the previous Marco Polo mission (see ESA/SRE (2009)3, Marco Polo Yellow Book) and of the expertise of the consortium led by Dr. A.F. Cheng (PI of the NASA NEAR Shoemaker mission) of the JHU-APL, including JPL, NASA ARC, NASA LaRC, and MIT.  相似文献   

SEDIMENT YIELD CONDITIONED BY GLACIATION IN A RURAL AGRICULTURAL BASIN OF SOUTHERN ONTARIO,CANADA     

Susan H. Campo  Joseph R. Desloges 《自然地理学》2013,34(6):495-515

A sediment budget is constructed for the South Saugeen River, a sixth-order stream basin in southwestern Ontario. Input from eroding glacial embankments accounts for up to 68% of the fine (<63 μm) sediment outputs from the basin. Sediment derived from eroding alluvial banks in the main river contributes approximately 22% of sediment outputs and is approximately equivalent in magnitude to sediments stored in the floodplain. The remaining 10% is derived from sheet and rill erosion of uplands that have been modified by agriculture. However, specification of an appropriate sediment delivery ratio from individual fields to the low-order tributaries remains problematic. Small reservoirs confined by mill dams constructed around the time of land settlement in 1860 store about 3% of the basin sediment inputs. The results demonstrate the importance of downstream, non-alluvial (glacial) sediment sources and can be linked to the model of increasing specific sediment yields with drainage area found in several other river systems of Canada. The high frequency of tall glacial banks in several entrenched river valleys entering the Great Lakes in southern Ontario indicates that the model of dominantly agricultural sediment inputs needs to be adjusted for this region. [Key words: sediment budget, glacial conditioning, reservoir sedimentation, bank erosion, agricultural erosion, southern Ontario, Canada.]  相似文献   

Resolution of GPR bowtie antennas: An experimental approach     

Fernando I. Rial  Manuel Pereira  Henrique Lorenzo  Pedro Arias  Alexandre Novo 《Journal of Applied Geophysics》2009,67(4):367

Since target reflections directly depend on the emitted pulse characteristics, a key factor for carrying out a successful GPR survey is to know as much as possible about the transmission features of the antennas used. This information is very important in order to choose the right antennas and set the appropriate configuration parameters for a specific survey. With this in mind this paper deals with the development of a set of laboratory experiments on the resolution capabilities of three bowtie antennas at frequencies of 500, 800 and 1000 MHz. Results from these measurements give a first estimation of the resolution of the antennas under test, showing the advantage of performing experiments rather than relying only on theoretical assumptions. The results are also expressed in terms of the central wavelength for each antenna and compared with some theoretical estimations proposed in the specialized bibliography.  相似文献   

Linkages between the North Pacific Oscillation and central tropical Pacific SSTs at low frequencies   总被引：2，自引：1，他引：1  

Jason C. Furtado  Emanuele Di Lorenzo  Bruce T. Anderson  Niklas Schneider 《Climate Dynamics》2012,39(12):2833-2846

The North Pacific Oscillation (NPO) recently (re-)emerged in the literature as a key atmospheric mode in Northern Hemisphere climate variability, especially in the Pacific sector. Defined as a dipole of sea level pressure (SLP) between, roughly, Alaska and Hawaii, the NPO is connected with downstream weather conditions over North America, serves as the atmospheric forcing pattern of the North Pacific Gyre Oscillation (NPGO), and is a potential mechanism linking extratropical atmospheric variability to El Ni?o events in the tropical Pacific. This paper explores further the forcing dynamics of the NPO and, in particular, that of its individual poles. Using observational data and experiments with a simple atmospheric general circulation model (AGCM), we illustrate that the southern pole of the NPO (i.e., the one near Hawaii) contains significant power at low frequencies (7–10?years), while the northern pole (i.e., the one near Alaska) has no dominant frequencies. When examining the low-frequency content of the NPO and its poles separately, we discover that low-frequency variations (periods >7?years) of the NPO (particularly its subtropical node) are intimately tied to variability in central equatorial Pacific sea surface temperatures (SSTs) associated with the El Ni?o-Modoki/Central Pacific Warming (CPW) phenomenon. This result suggests that fluctuations in subtropical North Pacific SLP are important to monitor for Pacific low-frequency climate change. Using the simple AGCM, we also illustrate that variability in central tropical Pacific SSTs drives a significant fraction of variability of the southern node of the NPO. Taken together, the results highlight important links between secondary modes (i.e., CPW-NPO-NPGO) in Pacific decadal variability, akin to already established relationships between the primary modes of Pacific climate variability (i.e., canonical El Ni?o, the Aleutian Low, and the Pacific Decadal Oscillation).  相似文献   

Calibrating adaptive antenna arrays for high-integrity GPS     

David S. De Lorenzo  Sherman C. Lo  Per K. Enge  Jason Rife 《GPS Solutions》2012,16(2):221-230

A major challenge in using GPS guidance for aircraft final approach and landing is to reject interference that can jam reception of the GPS signals. Antenna arrays, which use space–time adaptive processing (STAP), significantly improve the signal to interference plus noise ratio, but at the possible expense of distorting the received signals, leading to timing biases that may degrade navigation performance. Rather than a sophisticated calibration approach to remove biases introduced by STAP, this paper demonstrates that a relatively compact calibration strategy can substantially reduce navigation biases, even under elevated interference conditions. Consequently, this paper develops an antenna bias calibration strategy for two classes of adaptive array algorithm and validates this method using both simulated and experimental data with operational hardware in the loop. A proof-of-concept system and an operational prototype are described, which implement the adaptive antenna algorithms and deterministic corrections. This investigation demonstrates that systems with adaptive antenna arrays can approach the accuracy and integrity requirements for automatic aircraft landing, and in particular for sea-based landing on board aircraft carriers, while simultaneously providing significant attenuation of interference. Evidence suggests that achieving these goals is possible with minimal restrictions on system hardware configuration—specifically, limitations on the permissible level of antenna anisotropy and the use of sufficient analog-to-digital converter resolution.  相似文献