ALBERT

Notizen: A novel miniature superconducting quantum interference device magnetometer with direct readout electronics has been developed. A high flux-to-voltage transfer factor of up to 2500 μV/Φ0 is achieved without additional positive feedback (Φ0 is the flux quantum). A flux resolution of 8×10−7 Φ0/Hz1/2, corresponding to a magnetic moment sensitivity of approximately 2×10−20 A m2/Hz1/2, has been measured. This magnetometer can be used to study the dynamic magnetization properties (including nuclear magnetic resonance and magnetic resonance imaging) of micron and submicron size particles and for high-resolution surface magnetometry. © 1997 American Institute of Physics.

Notizen: The Chicago mineral-carbonate oxygen isotope fractionation curves have been combined with mineral-water fractionation data for jadeite, zoisite and rutile and new data for grossular-water to provide a set of self-consistent mineral-pair calibrations. The A coefficients in the equation 1000 In α=A× 106T-2 of the new mineral-pair fractionations areJadeite Zoisite Grossular RutileQuartz 1.69 2.00 3.03 5.02Jadeite 0.31 1.34 3.33Zoisite 1.03 3.02Grossular 1.99The isotopic fractionation properties of natural pyralspite garnet [(Ca, Fe, Mg, Mn)3Al2Si3O12] can be approximated by those of the grossular end-member. Appropriate substitutions also yield coefficients for the solid-solution minerals: sodic pyroxene and epidote, e.g. A quartz-sodic pyroxene= 2.75 - 1.06Xjd, A quartz-epidote= 2.00 + 0.75Xpswhere XJd and XPs are the mole fractions of the jadeite and pistacite components, respectively.The new data set is particularly suitable for the geothermometry of metamorphic rocks. δ18O data from minerals of the high-pressure metamorphic rocks of the Sesia Zone of Italy and Cyclades Complex of Greece yield well-constrained mean temperatures of 572 and 478d̀ C, respectively. Type III blueschist metabasalts of the Franciscan Formation of California give mean quartz-garnet temperatures of 354d̀ C.

Notizen: Abstract Petrological, oxygen isotope and 40Ar/39Ar studies were used to constrain the Tertiary metamorphic evolution of the lower tectonic unit of the Cyclades on Tinos. Polyphase high-pressure metamorphism reached pressures in excess of 15 kbar, based on measurements of the Si content in potassic white mica. Temperatures of 450–500° C at the thermal peak of high-pressure metamorphism were estimated from critical metamorphic assemblages, the validity of which is confirmed by a quartz–magnetite oxygen isotope temperature of 470° C. Some 40Ar/39Ar spectra of white mica give plateau ages of 44–40 Ma that are considered to represent dynamic recrystallization under peak or slightly post-peak high-pressure metamorphic conditions. Early stages in the prograde high-pressure evolution may be documented by older apparent ages in the high-temperature steps of some spectra.Eclogite to epidote blueschist facies mineralogies were partially or totally replaced by retrograde greenschist facies assemblages during exhumation. Oxygen isotope thermometry of four quartz–magnetite pairs from greenschist samples gives temperatures of 440–470° C which cannot be distinguished from those deduced for the high-pressure event. The exhumation and overprint is documented by decreasing ages of 32–28 Ma in some greenschists and late-stage blueschist rocks, and ages of 30–20 Ma in the lower temperature steps of the Ar release patterns of blueschist micas. Almost flat parts of Ar–Ar release spectra of some greenschist micas gave ages of 23–21 Ma which are assumed to represent incomplete resetting caused by a renewed prograde phase of greenschist metamorphism.Oxygen isotope compositions of blueschist and greenschist facies minerals show no evidence for the infiltration of a δ18O-enriched fluid. Rather, the compositions indicate that fluid to rock ratios were very low, the isotopic compositions being primarily controlled by those of the protolith rocks. We assume that the fundamental control catalysing the transformation of blueschists into greenschists and the associated resetting of their isotopic systems was the selective infiltration of metamorphic fluid. A quartz–magnetite sample from a contact metamorphic skarn, taken near the Miocene monzogranite of Tinos, gave an oxygen isotope temperature of 555° C and calculated water composition of 9.1%. The value of δ18O obtained from this water is consistent with a primary magmatic fluid, but is lower than that of fluids associated with the greenschist overprint, which indicates that the latter event cannot be directly related to the monozogranite intrusion.

Notizen: Basic and ultrabasic blocks within ophiolitic mélanges of the Cycladic Blueschist Unit in southern Evia provide a detailed insight into its ocean floor igneous and hydrothermal evolution, as well as the regional poly-metamorphism occurring during Alpine orogenesis. The upper structural levels (Mt. Ochi exposures) are dominated by metamorphosed wehrlites, gabbros and highly light rare earth element (LREE)-enriched pillow basalts, whereas the underlying Tsaki mélange consists of basic protoliths with much less fractionated REE patterns as well as mantle harzburgites. Most of the metabasites show Nb anomalies, indicative of derivation from a subduction-affected mantle. The igneous bodies were juxtaposed and incorporated into the enclosing sedimentary sequences prior to high-pressure/low-temperature (HP/LT) metamorphism (M1). Glaucophane, epidote, sodic clinopyroxene and high-Si phengite constitute the Eocene M1 assemblage, which is estimated to have formed at 〉11 kbar and 400–450 °C. High δ18O values of M1 minerals in Ochi metagabbros indicate that the formation of the high-pressure assemblage was controlled by infiltration of fluids from the dehydrating host sediments. Cooling during decompression is indicated by an overprinting (M2, Early Miocene) pumpellyite–actinolite facies assemblage in metabasic rocks, calculated to have developed at P〈8 kbar and T 〈350 °C. Possible mechanisms for such cooling include: exhumation from shallower burial levels relative to the eclogites of the NW Cyclades, accretion of colder rocks from below and extensional unroofing by low-angle normal faults and detachments. The occurrence of sodic augite in the M2 assemblage of Tsaki metagabbros indicates that rocks at the base of the Blueschist Unit cooled faster or longer than their higher level Ochi counterparts. This suggests that differential cooling of the blueschists was enhanced by the underthrusting of colder rock units.

Notizen: The Ordnance Survey's approach to the revision of the 1: 2500 scale series is discussed, with particular emphasis on the variety of photogrammetric methods which are used. The special problems of re-casting existing maps onto the National Grid projection, without losing the value of the existing detail, are outlined whilst emphasising the need to complete the revision with maximum speed to an adequate accuracy for a minimum cost.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On expose les méthodes de l′ Ordnance Survey en matière de révision des levés au 1: 2500; on examine le problème de l'adaptation des levés existants au système cartographique national, sans qu'il y ait perte de richesse.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Es wird ein Versuch des Ordnance Survey zur Laufendhaltung der Karte 1: 2500 beschrieben, wobei die verschiedenen photogrammetrischen Verfahren, die angewendet wurden, besonders betont werden. Die speziellen Probleme der Einpassung bestehender Karten in das Nationale Gitternetz ohne den Verlust der vorhandenen Details werden skizziert, wobei hervorgehoben wird, dass die Revision mit maximaler Geschwindigkeit ohne Genauigkeitsverlust bei minimalen Kosten durchgeführt werden muss.

Notizen: Conventional ion plating theory assumes that the metal vapor arrives at the substrate in monatomic form. Our results suggest this is not the case, and that a large proportion of the metal arrives as clusters. This is based on measurements of the cathode fall distance before and during titanium deposition in a thermionically supported argon glow discharge. The results have been used to evaluate the charge-to-mass ratio of the metal species in accordance with the Child–Langmuir equation. This predicts that some titanium is present as atomic clusters which contain at least tens of atoms per unit charge. Also we show that at least 90% of the ion current arriving at the substrate is carried by the metallic species.

Notizen: The features of the Intergraph InterMap digital photogrammetric workstation are described. The flexibility of the photogrammetric and image processing capabilities of InterMap allows the system to be fully integrated into a number of fields of special application without the need for a photogrammetric operator, but data handling should still be controlled by a photogrammetric expert. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On d'crit dans cet article les l'ments caracteristiques de la station de photogramétrie numérique InterMap d'Intergraph. Si la souplesse des possibilityés offertes par InterMap dans les traitements ďimages ou de photogramétrie permet au systéme de s'intégrer pleinement dans un large domaine ďapplication spéciales sans recourir a'ľaide ďun opérateurphotogrammétre, il n‘en reste pas moins que la manipulation des donnees doit rester sous le contrôle ďun spécialiste de la photogramétrie. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Beschreibung der Charakteristika der digitalen photogrammetrischen Arbeitsstation Inter Map von Intergraph. Die Flexibilität der photogrammetrischen und Bildverarbeitungs-komponenten gestattet die voile Integration des Systems bei einer Anzahl von Sonderanwendungen, ohne daβ dazu ein photogrammetrischer Auswerter erforderlich ist, jedoch sollte die Datenbehandlung weiterhin von einem photogrammetrischen Experten gesteuert werden.

Notizen: The potential impact of climate change by the year 2050 on British grazing livestock systems is assessed through the use of simulation models of farming systems. The submodels, consisting of grass production, livestock feeding, livestock thermal balance, the thermal balance of naturally ventilated buildings and a stochastic weather generator, are described. These are integrated to form system models for sheep, beef calves and dairy cows. They are applied to scenarios representing eastern (dry) lowlands, western (wet) lowlands and uplands. The results show that such systems should be able to adapt to the expected climatic changes. There is likely to be a small increase in grass production, possibly allowing an increase in total productivity in some cases.

Notizen: The potential impact of climate change by the year 2050 on intensive livestock systems in Britain is assessed through the use of simulation models of farming systems. The submodels comprise livestock feeding, livestock thermal balance and the thermal balance of controlled environment buildings and a stochastic weather generator. These are integrated to form system models for growing pigs and broiler chickens. They are applied to scenarios typical of SE England, which is the warmest region of the country and represents the worst case. For both species the frequency of severe heat stress is substantially increased, with a consequent risk of mortality. To offset this, it would be necessary to reduce stocking densities considerably, or to invest in improved ventilation or cooling equipment. Other effects on production are likely to be small.