North and South Hemispheric Solar Activity for Cycles 21 – 23: Asymmetry and Conditional Volatility of Plage Region Areas     

E. Gonçalves  N. Mendes-Lopes  I. Dorotovič  J. M. Fernandes  A. Garcia 《Solar physics》2014,289(6):2283-2296

We study the dynamic evolution of the time series describing the plage regions areas observed daily at the Observatório Astronómico da Universidade de Coimbra, in each one of the solar hemispheres during solar cycles 21?–?23. The classical ARMA model has proven to be insufficient to describe the time variations seen in the data because of the strong conditional variability. We found that the data are well fitted by ARMA mixed with power-δ TGARCH error models. The power index δ is non-integer; this property has recently been introduced in the literature on time-series analyses and indicates the presence of strong volatility and long memory in the data series. We also detected dynamic asymmetry in the plage region areas observed in the two hemispheres when two different temporal models were obtained to fit them. The finding of a dynamic asymmetry is also supported by the dynamic evolution of the daily difference (north–south) time series, which is significantly different from white noise. This statistical modeling of time series, taking into account new and different characteristics of the solar activity, will be very useful in subsequent forecast developments.  相似文献   

The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205     

Stephen M. Elardo  Charles K. Shearer Jr.  Amy L. Fagan  Lars E. Borg  Amy M. Gaffney  Paul V. Burger  Clive R. Neal  Vera A. Fernandes  Francis M. McCubbin 《Meteoritics & planetary science》2014,49(2):261-291

Northwest Africa (NWA) 4734 is an unbrecciated basaltic lunar meteorite that is nearly identical in chemical composition to basaltic lunar meteorites NWA 032 and LaPaz Icefield (LAP) 02205. We have conducted a geochemical, petrologic, mineralogic, and Sm‐Nd, Rb‐Sr, and Ar‐Ar isotopic study of these meteorites to constrain their petrologic relationships and the origin of young mare basalts. NWA 4734 is a low‐Ti mare basalt with a low Mg* (36.5) and elevated abundances of incompatible trace elements (e.g., 2.00 ppm Th). The Sm‐Nd isotope system dates NWA 4734 with an isochron age of 3024 ± 27 Ma, an initial ε_Nd of +0.88 ± 0.20, and a source region ¹⁴⁷Sm/¹⁴⁴Nd of 0.201 ± 0.001. The crystallization age of NWA 4734 is concordant with those of LAP 02205 and NWA 032. NWA 4734 and LAP 02205 have very similar bulk compositions, mineral compositions, textures, and ages. Their source region ¹⁴⁷Sm/¹⁴⁴Nd values indicate that they are derived from similar, but distinct, source materials. They probably do not sample the same lava flow, but rather are similarly sourced, but isotopically distinct, lavas that probably originate from the same volcanic complex. They may have experienced slightly different assimilation histories in route to eruption, but can be source‐crater paired. NWA 032 remains enigmatic, as its source region ¹⁴⁷Sm/¹⁴⁴Nd definitively precludes a simple relationship with NWA 4734 and LAP 02205, despite a similar bulk composition. Their high Ti/Sm, low (La/Yb)_N, and Cl‐poor apatite compositions rule out the direct involvement of KREEP. Rather, they are consistent with low‐degree partial melting of late‐formed LMO cumulates, and indicate that the geochemical characteristics attributed to urKREEP are not unique to that reservoir. These and other basaltic meteorites indicate that the youngest mare basalts originate from multiple sources, and suggest that KREEP is not a prerequisite for the most recent known melting in the Moon.  相似文献   

Investigating the correlation between monthly average temperatures and tithe proxy data from the Low Countries     

A. M. J. de Kraker  R. Fernandes 《Climatic change》2013,118(2):291-306

The likely intensification of extreme droughts from climate change in many regions across the United States has increased interest amongst researchers and water managers to understand not only the magnitude of drought impacts and their consequences on water resources, but also what they can do to prevent, respond to, and adapt to these impacts. Building and mobilizing ‘adaptive capacity’ can help in this pursuit. Researchers anticipate that drought preparedness measures will increase adaptive capacity, but there has been minimal testing of this and other assumptions about the governance and institutional determinants of adaptive capacity. This paper draws from recent extreme droughts in Arizona and Georgia to empirically assess adaptive capacity across spatial and temporal scales. It combines quantitative and qualitative methodologies to identify a handful of heuristics for increasing adaptive capacity of water management to extreme droughts and climate change, and also highlights potential tradeoffs in building and mobilizing adaptive capacity across space and time.  相似文献   

Can industrial pollution cause intersexuality in the amphipod, Echinogammarus marinus?     

Ford AT  Fernandes TF  Robinson CD  Davies IM  Read PA 《Marine pollution bulletin》2006,53(1-4):100-106

Following recent studies, in which intersex and/or reproductive abnormalities have been observed in a number of crustaceans in association with pollution, the prevalence of intersexuality in the amphipod, Echinogammarus marinus was monitored at sites receiving industrial discharges for one year in 2002/2003. Based upon reports of intersexuality occurring in amphipods due to feminising microsporidian parasites, the occurrence, and role of microsporidian parasites in causing intersex was investigated through histological examination. Results demonstrate a significantly higher prevalence of intersex organisms was found at sites receiving industrial discharges throughout the year when compared to a reference site, with the phenotype of intersex (intersex male and intersex female) varying in its dominance between impacted sites. Intersex specimens were significantly more likely to be infected with microsporidian parasites at sites receiving discharges than reference sites, however relatively few specimens (normal or intersex) were infected at reference sites suggesting parasitism is not the only cause of intersex. The direct/indirect role of pollution in the observed intersexuality is discussed.  相似文献   

Application of Laser‐Induced Breakdown Spectroscopy and Hyperspectral Images for Direct Evaluation of Chemical Elemental Profiles of Coprolites          下载免费PDF全文

Marco Aurélio Sperança  Francisco Wendel Batista de Aquino  Marcelo Adorna Fernandes  Alejandro Lopez‐Castillo  Renato Lajarim Carneiro  Edenir Rodrigues Pereira‐Filho 《Geostandards and Geoanalytical Research》2017,41(2):273-282

This study demonstrates the application of laser‐induced breakdown spectroscopy (LIBS) and hyperspectral imaging to the investigation of coprolite and fossil samples. Solid samples from the Permian (seven coprolites and one fossil), Cretaceous (one coprolite) and Oligo‐Miocene (two coprolites) periods were directly analysed, and emission spectra from 186 to 1042 nm were obtained in several areas covering coprolite/fossil and rock material. Initial exploratory analyses were performed using principal component analysis with the data set normalised by the norm (Euclidean norm = 1). After identification and selection of emission lines of eleven elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, P and Si), the signals were normalised again by the relative intensity of the selected element. Phosphorus was identified mainly in the coprolites, while K and Na were primarily found in the rock material. In several cases, there was a positive correlation between Ca and P. A sample from the Oligo‐Miocene series was also analysed using inductively coupled plasma‐optical emission spectrometry (ICP‐OES) (rock and coprolites were analysed separately). Based on the quantitative results from ICP‐OES, it was confirmed that the tendency was the same as that observed with the results obtained from LIBS directly in the solid sample.  相似文献   

Paleoenvironmental dynamics in central-eastern Brazil during the last 23 000 years: tropical peatland record in the Cerrado biome     

Camila Rodrigues Costa  Cynthia Fernandes Pinto da Luz  Ingrid Horák-Terra  Plínio Barbosa de Camargo  Uidemar Morais Barral  Carlos Victor Mendonça-Filho  Thamyres Sabrina Gonçalves  Alexandre Christófaro Silva 《第四纪科学杂志》2023,38(1):61-75

The Cerrado biome is the second largest in Brazil, but the evolution of the Cerrado during the late Quaternary is not yet fully known. This study identifies paleoenvironmental changes during the last 23 000 years, based on a tropical mountain peatland record, in the Serra do Espinhaço Meridional in central-eastern Brazil. A multi-proxy approach was used that involved palynological analysis, stable isotopes (δ¹³C, δ¹⁵N), geochemistry, radiocarbon dating and multivariate statistics derived from a peatland core from Rio Preto (Minas Gerais state). The study reveals a very humid and cold climate during the late Pleistocene, with an increase in temperature and decrease in humidity at the Pleistocene–Holocene transition. During this period there was strong instability in the landscape (episodes of erosion). At the beginning of the Holocene there was a reduction in humidity with greater landscape stability. The current sub-humid climatic conditions seem to have been established in the mid-/late Holocene, with periods of landscape instability. Our findings agree with other Cerrado records that contradict previously established hypotheses, such as the Amazonian Refuge and the Pleistocene Arc.  相似文献   

Glacial oscillations during the Bølling–Allerød Interstadial–Younger Dryas transition in the Ruda Valley,Central Pyrenees     

M. Fernandes  M. Oliva  G. Vieira  D. Palacios  J. M. Fernndez-Fernndez  J. Garcia-oteyza  I. Schimmelpfennig  Aster Team  D. Antoniades 《第四纪科学杂志》2022,37(1):42-58

The Upper Garonne Basin included the largest glacial system in the Pyrenees during the last glacial cycle. Within the long-term glacial retreat during Termination-1 (T-1), glacier fluctuations left geomorphic evidence in the area. However, the chronology of T-1 glacial oscillations on the northern slopes of the Central Pyrenees is still poorly constrained. Here, we introduce new geomorphological observations and a 12-sample dataset of ¹⁰Be cosmic-ray exposure ages from the Ruda Valley. This U-shaped valley, surrounded by peaks exceeding 2800 m a.s.l., includes a sequence of moraines and polished surfaces that enabled a reconstruction of the chronology of the last deglaciation. Following the maximum ice extent, warmer conditions prevailing at ~15–14 ka, during the Bølling–Allerød (B–A) Interstadial, favoured glacial retreat in the Ruda Valley. Within the B–A, glaciers experienced two phases of advance/stillstand with moraine formation at 13.5 and 13.0 ka. During the early Younger Dryas (YD), glacial retreat exposed the highest surfaces of the Saboredo Cirque (~2300–2350 m) at 12.7 ka. Small glaciers persisted only inside the highest cirques (~2470 m), such as in Sendrosa Cirque, with moraines stabilising at 12.6 ka. The results of this work present the most complete chronology for Pyrenean glacial oscillations from the B–A to the YD.  相似文献