Geochemical evidence concerning sources and petrologic evolution of Faial Island,Central Azores

Volcanic rocks that make up Faial Island, Central Azores, consist of four volcano-stratigraphic units, with ages between 730 ka and the present. Lavas range from alkali basalts to trachyandesites and belong to the alkaline-sodic series. The oldest unit is the Ribeirinha Volcanic Complex, generally characterized by low MgO contents. The Cedros Volcanic Complex is composed of basalts to benmoreites with low MgO contents. The Almoxarife Formation represents fissure flows, containing MgO contents similar to to slightly higher than those of the underlying Cedros Volcanic Complex. The youngest unit, the Capelo Formation, consists of mafic rocks with MgO values higher than those of the other units. Bulk-rock major and trace element trends suggest that differentiation of the three earliest units were dominated by fractional crystallization of plagioclase ± clinopyroxene ± olivine ± titanomagnetite. Capelo bulk-rock compositions are the most primitive, and are related to a period when volcanic activity was fed by deep magmatic chambers, and melts ascended more rapidly. Comparison among geochemical patterns of the trace elements suggests a strong similarity between the lavas from Faial and Pico islands. Corvo Island volcanism contrasts with the geochemistry of Faial and Pico lavas, reflecting its strong K and Rb depletion, and Th, U, Ta, Nb, La, and Ce enrichment. Absence of the Daly gap in the Faial volcanics is attributed to early crystallization of Ti-Fe oxides. The probable source of the Faial magma coincides with the MORB-FOZO array, which implies the presence of ancient recycled oceanic crust in the mantle source. Ratios of incompatible trace elements suggest the similarity of Corvo volcanic rocks with magmas derived from HIMU sources, whereas the Faial and Pico volcanic rocks could have been produced from sources very close to EMII-type OIB.     

White dwarf + red dwarf binary systems and the period gap of cataclysmic variables

Cataclysmic variables (CV) and pre-cataclysmic binaries (PCB) are discussed. The main difference between them (accretion or its absence) is shown to be a consequence of the evolutionary process and the properties of their progenitors. Both types of system have a bimodal distribution of their periods, but the extrema are in counterphase. Luminosity-effective temperature diagrams for the primary components are used to show that both systems have approximately the same age, which conflicts with the notion of PCBs as precursors of CVs. Calculations of the maximum distance between components for which the system remains stable show that CVs have passed this limit, while PCBs maintain their stability during this evolution. It is suggested that, after ejecting a common shell, future CVs immediately become semi-detached systems. It this is so, then there must be cataclysmic variables which are the central stars of planetary nebulae. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 427–439 (August 2007).     

A comparative slope stability analysis of sheet pile supported I-wall in New Orleans,Louisiana with sheet pile penetrating into sand layer

Computer modelling and stability analyses of the New Orleans I-walls with and without the consideration of gap formation has drawn significant attention of the engineering community during the post Katrina period. In addition, when the sheet pile penetrates into sand layer, seepage becomes an integral part of the stability analysis. Basic guidelines have been developed for the analysis of this problem by other researchers and documented by the U.S. Army Corps of Engineers (USACE). However, the inherent complexity of the problem and uncertainties associated with the choice of analysis methods warrant for further investigation of this problem in detail so that more useful insights can be gained. In this paper, a comprehensive analysis of this complex coupled problem of seepage and stability of a typical New Orleans I-wall is presented using different limit equilibrium methods of slope stability analysis. Useful comparisons are made between the analyses results and methodologies. The authors believe that the findings of this study will enhance the understanding of the behaviour of the I-wall sheet pile system subjected to seepage forces, when different limit equilibrium methods of analyses are invoked.     

On the Lack of Asteroids in the Hecuba Gap

The lack of asteroids in the 2/1-resonance is explained by the global stochasticity of the solutions in the Sun-Jupiter-Saturn-asteroid model. The explanation is based on data obtained with Laskar's frequency map analysis and on simulations showing the decisive influence of Jupiter's orbit perturbations related to the "Great Inequality". This revised version was published online in July 2006 with corrections to the Cover Date.     

滇西施甸地区晚泛非运动的地层学和岩石学响应

保山地块的寒武系露头少,研究范围有限。长期以来,地学界对寒武系与奥陶系之间的接触关系存在较大争议,有人认为是整合接触,有人认为是假整合接触,囿于过去的工作精度,目前尚无定论。近年来,在保山施甸地区开展1∶5万区调工作时发现,区内普遍缺失早奥陶世沉积,仅在施甸半坡一带有中奥陶统,在大寨一带,中上奥陶统蒲缥组直接平行不整合在上寒武统保山组之上,结合晚寒武世—早奥陶世业已存在的岩浆活动,认为这是晚泛非运动的远程响应。     

上海市商务办公楼租金差异及其影响因素

上海房地产市场在国家房产新政下出现了较大的转折,商务办公楼市场升温。本文从总体上分析了上海部分区域商务办公楼的平均租金差异,并选择商务办公楼比较集中的南京路、延安路和淮海路三条线路作为典型调查区段,共采集24个样本区域、66幢甲级商务办公楼、492个具体样本资料,运用多元线性回归分析方法,揭示了上海市商务办公楼租金差异与地理区位、服务设施、交通条件、平均层数、平均停车位及绿化景观6个影响因子的相互作用关系。回归分析结果表明:服务设施和停车位是影响上海市商务办公楼租金差异的主要因子;其次为绿化景观、地理区位和交通条件;而平均层数的影响甚微。最后针对上海商务办公楼多中心化趋势,就有关问题进行了分析和讨论。     

西双版纳热带次生林林窗辐射特征初步研究

利用西双版纳不同季节热带次生林林窗、林内及旷地不同波长太阳辐射的实测资料,比较分析了热带次生林窗不同波长辐射特征。分析得出：热带次生林窗中央与北侧林冠下的不同波长太阳辐射量值在中午前后迅速达到最大后又急速下降的现象明显;林窗内不同波长太阳辐射日总量值均大于林内,小于旷地;林窗中央和北侧林冠下相比较。一般是北侧林冠下的各辐射要素总量值高于林窗中央;林窗区域的总辐射日总量在干热季最高,雨季和雨季后期次之,雾凉季时最小;林窗中央和北侧林冠下的红外辐射及可见光在总辐射中所占份额随季节的变化而不同,充分显示了林窗辐射环境的异质性;与旷地和林内相比,林窗内各测点的红外辐射在总辐射中所占份额高于旷地却低于林内,而可见光占总辐射的比值情况正好相反。     

Contrasting mineral isograd sequences in metabasites of the Cape Smith Belt, northern Québec, Canada: three new bathograds for mafic rocks

Regional-scale mapping of index-mineral isograds in mafic units of the early Proterozoic Cape Smith Thrust Belt (northern Québec) has revealed contrasting pressure-temperature regimes associated with two distinct structural domains. In the southern domain, crustal thickening was accomplished by early, piggy-back thrust faults. Isograds cross-cut the thrusts, indicating that thermal-peak mineral growth outlasted deformation associated with early imbrication. Mineral zones are: (1) actinolite (Act) + albite (Alb); (2) hornblende (Hbl) + Act + Alb; (3) Hbl + Act + oligoclase (Oli); (4) Hbl + Oli; and (5) garnet (Grt) or clinopyroxene + Hbl + Oli-andesine. The oligoclase isograd occurs at higher grade than the hornblende isograd, a sequence typical of medium-pressure terranes (5–7 kbar). An Hbl-Alb bathograd. calibrated from mixed-volatile equilibria in the NCMASH-CO₂ model system, suggests minimum pressures of about 5.4 kbar. Metamorphism in the northern domain was a consequence of re-imbrication, by means of out-of-sequence thrust faults active during and after peak metamorphic conditions. Mineral growth was coeval with thrusting, as documented by the syn-kinematic garnet porphyroblasts. Compared to the southern domain, a different sequence of isograds in mafic rocks shows that the albite-oligoclase transition takes place in the garnet zone. Based on thermobarometry in garnet-hornblende rocks, the oligoclase isograd occurs in a temperature range of 525–600°C, typical of high-pressure terranes (7–10 kbar). Calibrated bathograds for the Hbl-Ms-Alb and Grt-Alb bathozonal assemblages, respectively in the KNCMASH-CO₂ and NCMASH model systems, indicate minimum pressures in the northern domain of 6.7 and 8.5 kbar. Higher-pressure series for this domain are explained by out-of-sequence thrusts exposing deeper crustal levels. For similar structural levels, only minor amounts of syn-deformational uplift (1–2 kbar and 50–75°C) are recorded in metabasites of this domain, compared to results in adjacent metapelites of the area (essentially isothermal uplift of 3–5 kbar). RESUME La bande du Cap Smith (nord du Québec) est une ceinture de chevauchement d'ǎge protérozoique inférieur, dominée par des roches mafiques. La cartographie d'isogrades à minéraux indicateurs dans les unités mafiques de la ceinture a révelé deux régimes contrastes de pression–température, chacun associéà des épisodes distincts d'épaississement crustal. Dans le domaine sud, des failles de chevauchement en-série sont responsables pour l'empilement tectonique. Les isogrades recoupent les failles, indiquant que l'apogée thermale a suivi l'emplacement initial des nappes de charriage. Les zones minérales sont: (1) actinote (Act) + albite (Alb); 2) hornblende (Hbl) + Act + Alb; (3) Hbl + Act + oligoclase (Oli); 4) Hbl + Oli; et (5) grenat (Grt) où clinopyroxene + Hbl + Oli-andésine. L'isograde d'oligoclase apparaǐt à plus haute température que l'isograde d'hornblende, une séquence typique des terrains de pressions moyennes. Un bathograde Hbl–Alb, calibréà partir d'équilibre mixte de volatiles dans le système NCMASH–CO₂, suggère des pressions minimales d'environ 5.4 kbar. Le métamorphisme dans le domaine nord de la ceinture a été le résultat d'une réimbrication, causé par des chevauchements hors-série actifs pendant et après l'apogée thermale. La croissance minérale fǔt synchrone au chevauchement, documentée par des porphyroblastes de grenat syn-cinénatique. Comparé au domaine sud, une différente séquence d'isogrades dans les métabasaltes montre que la transition albite–oligoclase se situé dans la zone à grenat. Par la thermobarométrie dans les roches à grenat–hornblende l'isograde d'oligoclase se situe dans un écart de température de 525–600°C, typique des terrains de hautes pressions (7–10 kbar). Des bathogrades calibrés pour les assemblages bathozonales Hbl–Ms–Alb et Grt–Alb, rcspectivement dans les systèmes KNCMASH–CO₂ et NCMASH, indique des pression minimales pour le domaine nord de 6.7 et 8.5 kbar. Une zonégraphie à plus haute pression pour ce domaine est expliquée par des chevauchements hors-série exposant des niveaux plus inférieurs de la croǔte imbriqué. Pour des niveaux structuraux similaries, des soulèvements syn-métamorphiques mineurs sont enregistrés dans les métabasaltes (1–2 kbar et 50–75°C), comparés aux métapélites adjacentes avec un soulèvement (essentially isothermal uplift of 3–5 kbar.     

Genealogical concordance,comparative species delimitation,and the specific status of the Caspian pipefish Syngnathus caspius (Teleostei: Syngnathidae)

To evaluate the specific validity of the Caspian pipefish Syngnathus caspius, we used a comparative molecular species delimitation method on a COI barcode library of Syngnathus, as well as principles of genealogical concordance. Comparative species delimitation allowed us to delineate putative species without a priori assignment of individuals to nominal species, while genealogical concordance extended our species delimitation results to multiple genes, multiple codistributed species, and comparisons with biogeographic evidence. All species delimitation analyses including two topology‐based, one network‐based, and one distance‐based analysis showed genetically isolated lineages of pipefish in the Black and Caspian Sea, corresponding to S. abaster and S. caspius, respectively. Mean evolutionary divergence between the two lineages (0.029) was within the range separating species of Syngnathus (0.024–0.217). The interclade/intraclade ratio of variation was comparable to the operational criterion of divergence between clades greater or equal to 10 × the level within clades to recognize separate species. Our argument on taxonomic validity of S. caspius is also supported by the principles of genealogical concordance as a conceptual basis for recognition of biological species. As a second objective, using a limited number of S. caspius specimens from two semi‐confined water bodies along the Caspian Sea south coastal zone (i.e., Anzali Wetland in the west and Gorgan Bay in the east), we searched for a possible matrilineal structure. The retrieved phylogeographic pattern was characterized by a shallow genealogy and lineage distributions varied, most probably caused by low to modest contemporary gene flow between populations of S. caspius across the southern Caspian Sea that are linked tightly through history.     

Band-limited functions on a bounded spherical domain: the Slepian problem on the sphere

The Slepian problem consists of determining a sequence of functions that constitute an orthonormal basis of a subset of ℝ (or ℝ²) concentrating the maximum information in the subspace of square integrable functions with a band-limited spectrum. The same problem can be stated and solved on the sphere. The relation between the new basis and the ordinary spherical harmonic basis can be explicitly written and numerically studied. The new base functions are orthogonal on both the subspace and the whole sphere. Numerical tests show the applicability of the Slepian approach with regard to solvability and stability in the case of polar data gaps, even in the presence of aliasing. This tool turns out to be a natural solution to the polar gap problem in satellite geodesy. It enables capture of the maximum amount of information from non-polar gravity field missions. Received: 10 June 1998 / Accepted: 20 May 1999