Increasing prevalence of extreme summer temperatures in the U.S.

Human-caused climate change can affect weather and climate extremes, as well as mean climate properties. Analysis of observations and climate model results shows that previously rare (5th percentile) summertime average temperatures are presently occurring with greatly increased frequency in some regions of the 48 contiguous United States. Broad agreement between observations and a mean of results based upon 16 global climate models suggests that this result is more consistent with the consequences of increasing greenhouse gas concentrations than with the effects of natural climate variability. This conclusion is further supported by a statistical analysis based on resampling of observations and model output. The same climate models project that the prevalence of previously extreme summer temperatures will continue to increase, occurring in well over 50% of summers by mid-century.     

云南天文台三孔较差视宁度监视仪的建立

较详细地讲述了云南天文台三孔较差视宁度监视仪的情况,然而,与一般天文理论和天文技术的专题研究不一样,天文仪器的研制有如说是研究,还不如说是归纳;它不是分析一个具体的尚未解决的难题,而是把许多已知的理论和技术综合起来,构成一台具体的仪器。所以,本文把许多至少是表面上互不相关的理论和技术问题归纳到一篇论文中。仪器是有许多模块组成的,为了看起来逻辑性较强,我们将仪器分模块叙述,全文遵循如下顺序：１在第一篇中,回顾世界各天文台视宁度测量设备的发展史和云南天文台的宁静度测量发展史;２在第二篇中,介绍：１）云南天文台三孔较差视宁度研制任务的来源,仪器的整体状况;２）介绍云南天文台三孔较差视宁度仪的硬件系统;３）介绍云南天文台三孔较差视宁度仪的软件系统;若大模块中有多个小模块,在每一个大模块中,又遵循下述顺序：１）本模块的总体功能;２）构成该模块的基本技术;３）这些基本技术如何构成整体和完成预定功能。３在第三篇中,介绍我们所作的与视宁度测量有关的一些实验和实验结果。     

Olive tree phenology and climate variations in the Mediterranean area over the last two decades

The flowering characteristics of plant species of economic interest and the influence of climate on them are of great importance considering the implications for fruit setting and the final harvest: Olive is one of the typical species of the Mediterranean habitat. We have investigated the timing of olive full flowering during the anthesis period and flowering intensity over a period of 20 years (1990–2009), in three major cultivation areas of the Mediterranean basin: Italy, Spain and Tunisia. The importance of these characteristics from a bioclimatic point of view is considered. The biological behaviour was studied to determine its main relationships with temperature and water availability, considering also the different sub-periods and the bio-climatic variations during the study period. The flowering dates and pollen emissions show different behaviours for the Spanish monitoring area in comparison with the other two olive cultivation areas. In the Italian and Tunisian areas, the flowering period over the last decade has become earlier by about 5 and 7 days, respectively, in comparison to the previous decade. Moreover, pollen emissions have decreased in Perugia (Italy) and Zarzis (Tunisia) over the period of 2000–2009, while in Cordoba (Spain), they showed their highest values from 2005 to 2009. The climate analysis has shown an increase in temperature, which results in an increase in the growing degree days for the growth of the olive flower structures, particularly in the more northern areas monitored. Although the olive tree is a parsimonious water consumer that is well adapted to xeric conditions, the increase in the potential evapotranspiration index over the last decade in the Italian and Tunisian olive areas might create problems for olive groves without irrigation, with a negative influence on the flowering intensity. Overall, in all of these Mediterranean monitoring areas, the summer water deficit is an increasingly more important parameter in comparison to the winter parameters, which confirms that the winter period is not as limiting as the summer period for olive tree cultivation in these Mediterranean areas.     

Al hematites prepared by homogeneous precipitation of oxinates: material characterization and determination of the Morin transition

A novel method for synthesis of aluminium hematites, based upon the homogeneous precipitation of Fe and Al oxinates in various proportions, is presented. The precursor precipitates are heated in air at 700?°C. X-ray diffraction, thermal analyses, BET, FTIR, optical reflection analysis, TEM and Mössbauer spectroscopy at room temperature and 80?K of the resulting products indicate that single-phase hematites are formed with structural Al substitution of up to 10 at%. Interestingly, the particle size (>100?nm) is not substantially reduced by the Al content. Although it remains difficult to obtain a homogeneously distributed Al substitution in the final hematite, this processing line offers a unique opportunity to separate the effects of grain size and Al substitution on the Morin transition temperature (T _M) of Al hematite. From the comparison between the present hematites and a series of Al-substituted hematites with lepidocrocite as precursor, it could be shown that the effect on T _M, associated with a change of a factor 10 in grain size, is about 1/3 of the effect caused by a change of 10 in the degree of substitution. Finally, it is suggested that proper thermal treatments under different conditions of the same precursors are likely to produce spinel phases.     

A search for soft X-ray emission from stellar sources

With the soft X-ray detector (0.2–0.284 keV) aboard the Astronomical Netherlands Satellite (ANS) we have searched for X-ray emission from hot star coronae and peculiar stars. On Sirius ( CMa) and Capella ( Aur) X-ray emission has been measured at 6 and 5 level, respectively, above background. In all other cases the search revealed no evidence for soft X-ray emission. Upper limits to the luminosities of about 25 star coronae (main-sequence stars, (sub)giants, and supergiants) and of 4 peculiar stars ( Sco, Lyr, P Cyg, and Car) have been obtained.Paper presented at the COSPAR/IAU Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Dating of Quaternary Sediments from Western Borneo, Using Optically Stimulated Luminescence

Optically Stimulated Luminescence (OSL) dates from five sites in western Kalimantan are compared with ¹⁴C and thermo-luminescence dates from other sediments in the region. There is now strong evidence that the Old Alluvium of Peninsular Malaysia is of late Pleistocene age and that it can be correlated with the White Sand Complexes of western Borneo. This contrasts with the late Pliocene to mid Pleistocene ages for Old Alluvium, based primarily on stratigraphic deductions, put forward by geoscientists examining the regional tin deposits. This study shows that the upper parts, at least, of the western Borneo White Sand Complexes were deposited mid-way through the last glaciation (76 ka), with extensive terminal Pleistocene re-deposition (11.2-9.8 ka) and at least two gully erosion events during the Holocene (5.8-3.8 ka and 0.48 ka).     

Eruption episodes and magma recharge events in andesitic systems: Mt Taranaki,New Zealand

Eruption episodes, where a series of eruption events are generically related, can include the eruption of a wide spectrum of volcanic activity over decadal periods. This paper concentrates on the opening phases of an eruption episode which occurred approximately 1800 yrs BP from Mt Taranaki, New Zealand. These events spanned the eruption of differing bulk compositions and styles from two distinct vent locations; an andesitic sub-plinian eruption from the summit vent and a scoria cone-building eruption of basaltic magma from a satellite vent. Compositional profiles and zoning textures of plagioclase, amphibole and clinopyroxene phenocrysts from the opening andesitic event show evidence of magma mixing and subsequent crystallisation just prior to the initiation of the eruption episode. Titanomagnetite grain morphology and Ti variation suggest that the magma mixing event occurred within a few days to weeks before the eruption acting as a trigger for it. We present a magmatic model which is constrained by the petrological observations and eruptions of the episode. In this model magma differentiation at depth causes its rise and recharging of a mid-crustal magma storage area at 5–7 km. Although the recharging magma differed slightly in oxygen fugacity and temperature, it was compositionally and physically similar enough to the residing andesitic magma to allow efficient mixing. The petrological characteristics described here can be readily observed and enable identification of mixing events in other recent eruption episodes.     

Thermal and topographic tests of Europa chaos formation models from Galileo E15 observations

Stereo topography of an area near Tyre impact crater, Europa, reveals chaos regions characterised by marginal cliffs and domical topography, rising to 100-200 m above the background plains. The regions contain blocks which have both rotated and tilted. We tested two models of chaos formation: a hybrid diapir model, in which chaos topography is caused by thermal or compositional buoyancy, and block motion occurs due to the presence of near-surface (1-3 km) melt; and a melt-through model, in which chaos regions are caused by melting and refreezing of the ice shell. None of the hybrid diapir models tested generate any melt within 1-3 km of the surface, owing to the low surface temperature. A model of ocean refreezing following melt-through gives effective elastic thicknesses and ice shell thicknesses of 0.1-0.3 and 0.5-2 km, respectively. However, for such low shell thicknesses the refreezing model requires implausibly large lateral density contrasts (50-100 kg m⁻³) to explain the elevation of the centres of the chaos regions. Although a global equilibrium ice shell thickness of ≈2 km is possible if Europa's mantle resembles that of Io, it is unclear whether local melt-through events are energetically possible. Thus, neither of the models tested here gives a completely satisfactory explanation for the formation of chaos regions. We suggest that surface extrusion of warm ice may be an important component of chaos terrain formation, and demonstrate that such extrusion is possible for likely ice parameters.     

Metamorphic veining and mass transfer in a chemically closed system: a case study in Alpine metabauxites (western Vanoise)

In western Vanoise (French Alps), karstic pockets of Triassic‐to‐Jurassic metabauxites embedded in carbonate rocks and containing several generations of metamorphic veins were studied. During blueschist facies metamorphism, a cumulative amount of ～13 vol% of water is inferred to have been produced locally by successive dehydration reactions, and part of this fluid remained in the bauxitic lenses during most of the metamorphic cycle. Field and geochemical evidence show that these rocks have been isolated from large‐scale fluid flow (closed‐system behaviour). It is proposed that the internally derived fluid has promoted the opening of fluid‐filled open spaces (as attested by the euhedral habits of vein minerals) and served as medium for mass transfer from rock to vein. Indeed, the vein infill is obviously the result of chemical interactions, at the millimetre‐to‐centimetre scale, between the rock minerals and the locally produced aqueous fluid. Two vein types can be distinguished based on mineralogical and textural features: (i) some veins are filled with newly formed products of either prograde (chloritoid) or retrograde (chlorite) metamorphic reactions; in this case, fluid‐filled open spaces seem to offer energetically favourable nucleation/growth sites; (ii) the second vein type is infilled with cookeite or pyrophyllite, that were present in the host rock prior to the vein formation. In this closed chemical system, the components for the vein infill minerals have been transferred from rock to vein through the fluid, in a dissolution–transport–precipitation process, possibly stress‐assisted. These different vein generations all contain Al‐rich mineral infills, suggesting that Al was a mobile element (cm scale) during metamorphism. In these HP rocks, fluid flow may have been restricted, and if so mass transfer occurred by diffusion in an almost stagnant fluid. Metamorphic veins can be seen as witnesses of fluid and mass redistribution that partly accommodate the rock deformation (lateral segregation).     

Investigation of Failure Mechanisms and Migration of Organic Chemicals at Wilsonville, Illinois

Ground water contamination was discovered in 1981 in a monitoring well at the Earthline disposal facility near Wilsonville, Illinois. Organic chemicals had migrated at a rate 100 to 1000 times greater than predicted when the site received its permit to operate in 1978. Postulated failure mechanisms included migration through previously unmapped permeable zones, subsidence of an underground mine, organic-chemical and clay-mineral interactions, acid-mine drainage and clay interactions, trench-cover settlement, and erosion.
In this investigation, the Illinois State Geological Survey found the primary reason for the rapid migration: the presence of previously undetermined fractures and joints in glacial till. The inaccurate predictions of hydraulic conductivity were based on laboratory-determined values that did not adequately measure the effects of fractures and joints on the transit time calculations. Field-measured hydraulic conductivity values were generally 10 to 1000 times greater than their laboratory-measured counterparts, thus largely accounting for the discrepancy between predicted and actual migration rates in the transit time calculations. The problem was compounded, however, by the burial of liquid wastes and by trench covers that allowed excess surface runoff to enter the trenches. Organic-chemical and clay-mineral interactions may also have exacerbated the problem in areas where liquid organic wastes were buried.