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Plinian eruptions are characterized by high intensity and an overall steady character, and result in a stable convective column. The main processes controlling the dynamics of such steady and stable plume systems have been extensively investigated. Conversely, sub-Plinian eruptions are unsteady, as recorded by the large variability of the products and deposits. Our knowledge of the processes creating this unsteadiness on various timescales remains limited, and still requires more observations as well as theoretical and experimental investigation. Here, we focus on the sub-Plinian eruption of the Greenish Pumice (GP, 19,265 ± 105 BP), Mt. Somma-Vesuvius (Italy). On the basis of coupled geochemical and textural analyses of samples from the well-established stratigraphy of the GP deposits, we investigate volatiles (H2O, CO2, F, Cl) to better constrain the unsteady sub-Plinian eruptive style. This allows us to carry out a detailed study of the degassing processes in relation to the eruption dynamics. We find that degassing by open-system processes generally dominates throughout the entire eruption, but alternates with episodes of closed-system degassing. The fluctuating degassing regimes, responsible for the variable magma ascent rate within the conduit, are also responsible for the eruptive column instability. Volatile behavior is well correlated with textural heterogeneities of the eruptive products. Both reflect higher conduit heterogeneity than for Plinian eruptions, where we find a higher horizontal gradient in magma ascent velocity due to a smaller conduit diameter.

This data report focuses on Holes U1394B, U1395B, and U1396C located offshore Montserrat. These holes were drilled during Integrated Ocean Drilling Program Expedition 340 and contain deposits associated with the growth and decay of the volcanic island of Montserrat. Hole U1394B dates to ~353 ka and is composed of 17 bioclastic turbidites, 24 mixed turbidites, 55 volcaniclastic turbidites, and 32 tephra fall layers within a background stratigraphy of hemipelagic marine mud. Hole U1395B dates to older than 1 Ma and contains 18 bioclastic turbidites, 27 mixed turbidites, 43 volcaniclastic turbidites, and 52 tephra fall layers. The uppermost 7 m of Hole U1396C covers ~1 My of stratigraphy and contains 1 bioclastic turbidite, 1 mixed turbidite, 9 volcaniclastic turbidites, and 13 tephra fall layers. Tephra fall and some volcaniclastic deposits are associated with episodes of island building, whereas bioclastic turbidites, mixed turbidites, and some volcaniclastic turbidites are associated with large landslide events from Montserrat.

The aragonite shell-bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing pCO2 and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250 000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the Limacina Dissolution Index (LDX), fluctuations in pteropod calcification through the most recent glacial/interglacial cycles are documented. By comparison to the oxygen isotope record (global ice volume), we show that pteropod calcification is closely linked to global changes in pCO2 and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification.

We present palaeomagnetic data obtained from large clasts collected in non-welded pyroclastic deposits from Montagne Pelee volcano (Martinique Island, West Indies). These deposits, dated by the 14C method from 5000 yr BP to the present, comprise block- and ash-flows, ash- and pumice-flows and pumice fallouts. Alternating fields treatment was as a routine chosen to demagnetise large samples for which the magnetisation was measured with a specially designed inductometer. The mean directions obtained from block- and ash-flow deposits of the 1902 and 1929 eruptions are in good agreement with the expected geomagnetic directions at these times in Martinique. The so-called P1 eruption (∼1345 AD), which is characterised by a rarely observed transition from a Peleean to a Plinian eruptive style, allows a direct comparison of the palaeomagnetic directions obtained from the three types of pyroclastic deposits. All deposits provide identical mean directions, which further demonstrates the suitability of the non-welded pyroclastic deposits for geomagnetic secular variation study with a very good accuracy and precision. The possibility of using pyroclastic deposits is promising for obtaining a wider distribution of sampling sites, which may better allow us to constrain our knowledge on the geomagnetic secular variation. We find that large geomagnetic changes occurred in Martinique during the last millennium, while the variations appear more limited prior to this period.

Onshore-offshore geophysical studies conducted on Martinique have identified major flank collapse events of Montagne Pelee that generated large submarine mass wasting deposits. Here, we evaluate the preconditioning factors involved in the deformation and failure of marine sediments related to volcano-flank collapse events. We use core logging, sedimentological and geotechnical data of the upper 200 m of core at sites U1397, U1398, U1399 and U1400 drilled during the Integrated Ocean Drilling Program (IODP) expedition 340, west of Martinique. We find that the low hydraulic conductivity of hemipelagic sediment causes low rates of dewatering of turbidites and tephra layers allowing excess pore fluid pressures to persist at depth. Overpressure generation was likely enhanced during major flank collapses, leading to low shear strength and subsequent deformation of large volumes of marine sediments, as found at Site U1400.

The aragonite shell–bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing pCO2 and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250,000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the Limacina Dissolution Index (LDX), fluctuations in pteropod dissolution through the most recent glacial/interglacial cycles is documented. By comparison to the oxygen isotope record (global sea ice volume), we show that pteropod dissolution is closely linked to global changes in pCO2 and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification.

A PowerPC system-on-a-chip processor which integrates high speed state of the art 800 MHz PowerPC, DDRII-667 memory controller, RAID assist logic, and three PCI-X DDR266 interfaces with a rich mix of conventional peripherals is described. The PowerPC, with on-chip L2 cache enabled, executes up to 1600 DMIPS. The RAID assist logic is capable of transferring 2 Gbytes/sec. The state of the art PowerPC, the high bandwidth data pipes, and the RAID assist logic make the SOC an ideal solution for RAID controller applications. Active power consumption is as low as 6W with a 1.5 volt supply. The SOC has been implemented in a 0.13 /spl mu/m, 1.5 V nominal-supply, bulk CMOS process.

Full-swing BiCMOS logic circuits for complementary MOS/bipolar technologies are described. The circuits utilize a complementary emitter-follower driver configuration for efficient driving, switched base-emitter shutting to achieve full swing, and CMOS diodes for base-to-base clamping. The performance of the circuits has been demonstrated in a BiCMOS technology featuring 0.8- mu m design rules and a single-poly (poly-emitter) npn-BJT (bipolar junction transistor) with an f/sub T/ of 15 GHz. Using an n-well-base substrate-pnp-BJT (f/sub T/ approximately=500 MHz), a gate delay (fan-in=2, fan-out=1) of 232 ps was obtained with a 3.6-V supply. Low-voltage operation has been demonstrated down to 1.4 V. >

BiCMOS associates high-speed circuits with the low power requirements of CMOS. Traditional BiCMOS circuits are mainly CMOS-based with bipolar buffers to improve driving capability and speed. Increased performance can be obtained with BiCMOS technology if CMOS/BiCMOS circuits are merged with an ECL (emitter-coupled logic) low swing circuit. Mixing of logic is possible if very-high-speed level translators for levels conversion are designed. The benefits of such an approach in 0.5- mu m BiCMOS technology have been estimated for the proposed ECL-to-CMOS-level convertor circuits. >

Six saponins were isolated from leaves and stems of Opilia celtidifolia and their structures established. These saponins are described for the first time in this plant. One of them is a new saponin: 3- O -[α- l -rhamnopyranosyl(l → 3) β- d -glucuronopyranosyl]-28- O -β- d -glucopyranosyl-hederagenin.

When pyroclastic deposits settle at high temperature in a terrestrial magnetic field they memorize their setting temperature. This temperature varies from one type of deposit to the other, from ambient temperature for some airfall ashes up to hundreds of degrees centigrade for nuees ardentes or pumice flows. These temperatures also vary significantly with distance from the eruptive vent. At old events, it is often very difficult first to establish the nature of the deposit because of crystallizations or cements created by diagenesis, and then to locate the eroded eruptive centers. The exact assessment of the setting temperature allows one, on the one hand, to find both the nature and the emplacement process of the deposit and, on the other hand, to find the location of the eruptive centers, by working out a temperature map. The methods used up to now are all based on the analysis of objects buried in the flow, or on that of the surrounding rocks. Where burnt wood or heated objects are concerned, this analysis may be chemical or based on fossil thermoremanent magnetization in the case of potteries or rocks. Such objects are not always to be found, so the method proposed here uses samples drawn from the deposit itself. The principle, derived from Thellier's method, compares the natural magnetization lost during heating to the loss of total thermoremanent magnetization acquired during cooling in a known field. This method essentially differs from that of Thellier by a direct reading of the magnetization left at any high temperature. This process, which requires only two heatings, enables one to avoid any difficulty linked to magnetic interactions and to lessen the effect of mineralogical transformations.

Seven flavonol 3- O-glycosides were isolated from the flowers of CALENDULA OFFICINALIS L. Their structures were elucidated as isorhamnetin 3- O-glucoside, rutinoside, neohesperidoside, 2 (G)-rhamnosylrutinoside, quercetin glucoside, neohesperidoside, and 2 (G)-rhamnosylrutinoside by paper and thin layer chromatography, UV, (13)C-NMR, and mass spectroscopy. The interglycosidic linkages of isorhamnetin 3- O-neohesperidoside, 2 (G)-rhamnosylrutinoside, quercetin 3- O-neohesperidoside and structural determination of quercetin 2 (G)-rhamnosylrutinoside are described for the first time in CALENDULA OFFICINALIS.