Deep sea navigation techniques

Accurate navigation forms an essential part of all research at sea and the deep ocean imposes it's own unique problems. This chapter discusses several of the techniques in current use on the research vessels of the Natural Environment Research Council (NERC), concentrating on those systems which provide global navigation facilities, as opposed to the more localised, coastal aids. Whilst most of the systems rely on surface propagation of radio waves, the use of acoustics and sea-bed mapping instruments constitute accurate alternatives for some sub-sea applications.     

用电子束CT作冠状动脉血管造影

本文介绍用电子束ＣＴ作冠状动脉可视化造影的方法,说明本项成就的特征和在应用这项技术的局限性,并指出这种技术在临床上,可能成为新无创伤性的诊断工具。     

Locational components of urban and regional public policy in postwar Vietnam: The case of Ho Chi Minh city (Saigon)

Ho Chi Minh city is a primate city in which wartime dislocations have resulted in severely overcrowded conditions as well as a shrunken economic base. The new government has opted for a policy based on the rapid decanting of a large proportion of the urban population by encouraging internal migration to New Economic Zones in the hinterlands. This policy is based on a hierarchial administrative structure with agricultural productivity as its prime goal. A Green Belt policy has been articulated that uses the New Economic Zones as building blocks. The Green Belts constrain urban growth as well as provide foodstuff for the remaining urban residents. The ultimate objective of the overall policy is a balanced urban and regional environment that is in tune with Vietnam's agricultural economy.     

Induced Temperature Gradients to Examine Groundwater Flowpaths in Open Boreholes

Techniques for characterizing the hydraulic properties and groundwater flow processes of aquifers are essential to design hydrogeologic conceptual models. In this study, rapid time series temperature profiles within open‐groundwater wells in fractured rock were measured using fiber optic distributed temperature sensing (FO‐DTS). To identify zones of active groundwater flow, two continuous electrical heating cables were installed alongside a FO‐DTS cable to heat the column of water within the well and to create a temperature difference between the ambient temperature of the groundwater in the aquifer and that within the well. Additional tests were performed to examine the effects of pumping on hydraulic fracture interconnectivity around the well and to identify zones of increased groundwater flow. High‐ and low‐resolution FO‐DTS cable configurations were examined to test the sensitivities of the technique and compared with downhole video footage and geophysical logging to confirm the zones of active groundwater flow. Two examples are presented to demonstrate the usefulness of this new technique for rapid characterization of fracture zones in open boreholes. The combination of the FO‐DTS and heating cable has excellent scope as a rapid appraisal tool for borehole construction design and improving hydrogeologic conceptual models.     

Monte guardia sequence: a late-pleistocene eruptive cycle on Lipari (Italy)

This paper documents a complex sequence of interbedded lapilli-fall, base-surge, and pyroclastic-flow deposits, here named the Monte Guardia sequence, that erupted from volcanic centers in the southern part of Lipari (Aeolian Island Arc). Radiocarbon data from ash-flow tuffs above and below this sequence bracket its eruption between 22,600 and 16,800 years ago. Geologic evidence, however, suggests that this single eruptive cycle had a more restricted duration of years to tens-of-years. The basis for our interpretations comes from data measured at 38 detailed sections located throughout the island. The Monte Guardia sequence rests on a series of lower rhyolitic endogenous domes in the southern part of Lipari and it covers the oldest lavas, lahars, and pyroclastic flows in the north. Only in the northeast part of the island is it covered by younger deposits which there consist of lapilli tuffs and lavas of the Monte Pilato rhyolitic cycle. The deposit ranges in thickness from more than 60 m surrounding the vents in the south to less than a few decimeters at 10 km distance in the north. Throughout most of the island the Monte Guardia sequence overlies a thin andesitic lapilli-fall layer which is a key bed for correlation. This lapilli tuff probably erupted from a volcanic center on another island of the Aeolian Arc (possibly Salina). The principal activity of the Monte Guardia sequence started with an explosion that formed a continuous breccia blanket covering most of the island. Some pumiceous blocks within this breccia are composed of alternating bands of acidic and andesitic composition suggesting that the initiation of pyroclastic activity could have been triggered by magma mixing. Typical Monte Guardia sequence consists of explosive products that grade from magmatic (pumice-fall) to phreatomagmatic (base-surge) character. The eruptive cycle is characterized by a number of energy decreasing megarhythms that start with a lapilli-fall bed and end with a base-surge set that progresses through sand-wave, massive, and planar beds. Isopach maps of the fall and surge deposits indicate that both types were directed to the northwest by prevailing winds. Existing topographic relief was an additional factor that affected the emplacement of surge products. At the end of the cycle andesitic pyroclastic flows and rhyolitic endogenous domes were emplaced above the Monte Guardia deposits near the vent.     

Joint inversion of long‐offset and central‐loop transient electromagnetic data: Application to a mud volcano exploration in Perekishkul,Azerbaijan

Mud volcanism is commonly observed in Azerbaijan and the surrounding South Caspian Basin. This natural phenomenon is very similar to magmatic volcanoes but differs in one considerable aspect: Magmatic volcanoes are generally the result of ascending molten rock within the Earth's crust, whereas mud volcanoes are characterised by expelling mixtures of water, mud, and gas. The majority of mud volcanoes have been observed on ocean floors or in deep sedimentary basins, such as those found in Azerbaijan. Furthermore, their occurrences in Azerbaijan are generally closely associated with hydrocarbon reservoirs and are therefore of immense economic and geological interest. The broadside long‐offset transient electromagnetic method and the central‐loop transient electromagnetic method were applied to study the inner structure of such mud volcanoes and to determine the depth of a resistive geological formation that is predicted to contain the majority of the hydrocarbon reservoirs in the survey area. One‐dimensional joint inversion of central‐loop and long‐offset transient electromagnetic data was performed using the inversion schemes of Occam and Marquardt. By using the joint inversion models, a subsurface resistivity structure ranging from the surface to a depth of approximately 7 km was determined. Along a profile running perpendicular to the assumed strike direction, lateral resistivity variations could only be determined in the shallow depth range using the transient electromagnetic data. An attempt to resolve further two‐dimensional/three‐dimensional resistivity structures, representing possible mud migration paths at large depths using the long‐offset transient electromagnetic data, failed. Moreover, the joint inversion models led to ambiguous results regarding the depth and resistivity of the hydrocarbon target formation due to poor resolution at great depths (>5 km). Thus, 1D/2D modelling studies were subsequently performed to investigate the influence of the resistive terminating half‐space on the measured long‐offset transient electromagnetic data. The 1D joint inversion models were utilised as starting models for both the 1D and 2D modelling studies. The results tend to show that a resistive terminating half‐space, implying the presence of the target formation, is the favourable geological setting. Furthermore, the 2D modelling study aimed to fit all measured long‐offset transient electromagnetic Ex transients along the profile simultaneously. Consequently, 3125 2D forward calculations were necessary to determine the best‐fit resistivity model. The results are consistent with the 1D inversion, indicating that the data are best described by a resistive terminating half‐space, although the resistivity and depth cannot be determined clearly.     

Statistische Bearbeitung einer einjährigen Grobaerosol-Messreihe

Zusammenfassung Die Ergebnisse von Untersuchungen über das Grobaerosol (Partikelgröße über 0.5 ) in einer Großstadt (Hamburg), wurden mit Hilfe modernster statistischer Verfahren eingehend bearbeitet. Eine ursprünglich durchgeführte grobe Bearbeitung, wie sie heute noch von den meisten Meteorologen vorgenommen wird, ergab praktisch nur eine Abhängigkeit von den Jahreszeiten (Heizperiode) und von den Inversionslagen.Mit Hilfe moderner statistischer Methoden war es u. a. möglich, statistisch gesicherte Abhängigkeiten der Partikelzahlen und Partikelgrößen von der Windrichtung, der Partikelzahlen von der Windstärke und der Partikelzahlen von den Luftkörpern, aufzudecken. Auch ein statistisch gesicherter Zusammenhang zwischen der Sichtweite und der Partikelzahl des Grobaerosols konnte festgestellt werden.Diese Untersuchungen zeigen deutlich die Vorteile und die Notwendigkeit der Bearbeitung von Meßreihen mit den neuen Verfahren der mathematischen Statistik.     

Les gisements d'émeraude de la Cordillère Orientale de la Colombie: Nouvelles données métallogéniques

Emerald deposits of Colombia are confined to lower Cretaceous shales of the Eastern Cordillera. The tectonic pattern of the deposits is related to deep reverse and large regional fault systems. Hydrofracturing is the main factor controlling emerald mineralization. It permitted to the hydrothermal solutions to permeate through fractures but also along stratification planes forming in this case stratabound mineralizations. Emerald occurs in calcite veins, veinlets, pockets and brecciated zones associated mainly with pyrite, quartz, parisite, codazzite and fluorite. Emerald mineralization belongs to an epigenetic hydrothermal process. The alternance of arenite-shale formations in the Cretaceous probably played an important role in the accumulation of solutions and in the propagation of the hydrothermal channels. The origin of emerald involves chemical elements mobilized by the fluids in the Cr-V-Fe-Al-Si-bearing black shales. The source of beryllium remains a problem and is discussed in the paper.     

The Urban Heat Island Effect at Fairbanks, Alaska

Summary  Using climatic data from Fairbanks and rurally situated Eielson Air Force Base in Interior Alaska, the growth of the Fairbanks heat island was studied for the time period 1949 – 1997. The climate records were examined to distinguish between a general warming trend and the changes due to an increasing heat island effect. Over the 49-year period, the population of Fairbanks grew by more than 500%, while the population of Eielson remained relatively constant. The mean annual heat island observed at the Fairbanks International Airport grew by 0.4 °C, with the winter months experiencing a more significant increase of 1.0 °C. Primary focus was directed toward long-term heat island characterization based on season, wind speed, cloud cover, and time of day. In all cases, the minima temperatures were affected more than maxima and periods of calm or low wind speeds, clear winter sky conditions, and nighttime exhibited the largest heat island effects. Received August 17, 1998 Revised March 26, 1999     

Continental crust in Gorny Altai: nature and composition of protoliths

The history of the Vendian–Early Paleozoic formation of protoliths of continental crust in the Gorny Altai segment of the Central Asian fold belt is considered, and their composition, isotopic characteristics, and formation mechanisms are estimated. We have established two stages of crust-forming processes in Gorny Altai: Early and Late Caledonian, with the different structures of formed geoblocks and nature and compositions of crustal protoliths. At the Early Caledonian stage, fragments of oceanic lithosphere of basic composition (MORB, OIT, OIB) (T_Nd(DM-2st) = 0.65–1.1 Ga) formed, as well as island arcs with andesite-basaltic and andesitic protoliths with low contents of incompatible elements (T_Nd(DM-2st) = 0.7–0.9 Ga). At the Late Caledonian stage, the redistribution of the substance of these blocks and the external supply of material led to the formation of heterogeneous crust of turbidite basins with an oceanic basement and andesite-dacitic upper-crustal protoliths (T_Nd(DM-2st) varies from 0.8–0.9 Ga in the framing of the volcanic arc of Altaids to 1.4–1.6 Ga at the boundary of the Altai–Mongolian microcontinent).