Second Phase Of Activity Research Articles

Deciphering the Africa-Arabia breakup: Insights from U-Pb dating along the Carmel-Gilboa fault system and its triple junction with the Dead Sea transform

The Carmel–Gilboa fault system (CGFS) runs sub-parallel to the Azraq–Sirhan Garben (ASG) and the Red Sea Rift. Although the system currently forms a triple junction with the Dead Sea transform (DST), its initiation is considered to be associated with NE–SW extensional regime during the Africa-Arabia breakup in the late Oligocene to early Miocene. The role of the CGFS in the breakup process is not fully understood. In addition, the exact timing of initiation and potential reactivation during the onset of the DST plate boundary is not well constrained. This work sheds light on these events by establishing a long-term record of deformation along the CGFS and its intersection with the DST. This study presents 17 U-Pb ages of syn-tectonic calcite (n=14, ∼33.2 to 2.3 Ma) collected along the CGFS. These ages suggest that the earliest faulting phase along the CGFS took place between ∼25 to ∼21 Ma - coinciding with the initiation of the Red Sea Rift. The second phase of activity along the CGFS commenced at ∼16 Ma. This phase supports northward propagation of the DST from the Gulf of Elat to the southern tip of the Lebanese restraining bend from ∼18 to ∼14 Ma. The new U-Pb ages along the CGFS together with ages from the DST constrain the propagation rate of the DST to ∼105 mm/year, roughly 20 times faster than the current left-lateral offset along this active plate boundary (∼5 mm/year). The trigger for two simultaneous rifts, located 500 km apart and the distributed extension along the northern Red Sea is most probably related to the relative mechanical strength of oceanic vs. continental lithosphere, which also controls the eventual establishment of the DST and the failure of the rifting process along the CGFS-Azraq-Sirhan rift system.

Rivers and Lakes in Western Arabia Terra: The Fluvial Catchment of the ExoMars 2022 Rover Landing Site

AbstractOxia Planum, the landing site for the ExoMars rover mission, is a shallow basin on the southern margin of Chryse Planitia that hosts remnants of fan‐shaped sedimentary deposits associated with the ancient channel system Coogoon Vallis. This indicates runoff from a catchment in Arabia Terra has transported sediment into the landing site. To explore this fluvial system we created a model catchment for Oxia Planum and, using 6 m/pixel ConTeXt camera orbital remote sensing image data, we digitized the fluvial and lacustrine landforms in Western Arabia Terra in and around this catchment. We find: (a) The catchment has a minimum area of ∼2.1 × 105 km2 and has been episodically deformed by tectonic activity; (b) There were at least two phases of fluvial activity. The first created a mature landscape associated with Coogoon Vallis, which may have deposited alluvial or deltaic deposits in the Oxia Basin. After a substantial hiatus, a second phase of activity incised U‐section channels into the pre‐existing landscape and channel systems; and (c) Evidence for numerous possible paleolake deposits within the catchment. These are not well connected to the fluvial system and were probably sustained by groundwater activity contemporaneous with both phases of fluvial activity. This groundwater might have modified the mineralogy of Oxia Planum. Oxia Planum probably experienced an alluvial or distal deltaic/lacustrine depositional environment during the mid Noachian, which was later overprinted by a younger phase of fluvial activity.

Using mobile big data to support emergency preparedness and address economically vulnerable communities during the COVID-19 pandemic in Nigeria

AbstractWith the declaration of the coronavirus disease 2019 (COVID-19) pandemic in Nigeria in 2020, the Nigeria Governors’ Forum (NGF) instigated a collaboration with MTN Nigeria to develop data-driven insights, using mobile big data (MBD) and other data sources, to shape the planning and response to the pandemic. First, a model was developed to predict the worst-case scenario for infections in each state. This was used to support state-level health committees to make local resource planning decisions. Next, as containment interventions resulted in subsistence/daily paid workers losing their income and ability to buy essential food supplies, NGF and MTN agreed a second phase of activity, to develop insights to understand the population clusters at greatest socioeconomic risk from the impact of the pandemic. This insight was used to promote available financial relief to the economically vulnerable population clusters in Lagos state via the HelpNow crowdfunding initiative. This article discusses how anonymized and aggregated mobile network data (MBD), combined with other data sources, were used to create valuable insights and inform the government, and private business, response to the pandemic in Nigeria. Finally, we discuss lessons learnt. Firstly, how a collaboration with, and support from, the regulator enabled MTN to deliver critical insights at a national scale. Secondly, how the Nigeria Data Protection Regulation and the GSMA COVID-19 Privacy Guidelines provided an initial framework to open the discussion and define the approach. Thirdly, why stakeholder management is critical to the understanding, and application, of insights. Fourthly, how existing relationships ease new project collaborations. Finally, how MTN is developing future preparedness by creating a team that is focused on developing data-driven insights for social good.

Eruptive history of La Poruña scoria cone, Central Andes, Northern Chile

New stratigraphic, lithological and petrographic analyses of La Poruna scoria cone (21° 53′ S-68° 30′ W, Central Andes, northern Chile) allow the reconstruction of the eruptive sequence of this monogenetic cone. Petrographic and lithological characteristics allow us to identify three main lithostratigraphic units at La Poruna scoria cone. The first unit consists of agglutinated lapilli, spatter beds, and clastogenic lavas that are related to the construction of the cone. The other two units are associated with a lava flow field and consist of flow of andesitic composition, which differ both in their degree of weathering and in their development of channel, surface, and internal structures (e.g., levees, ogives, and joints). With these lithostratigraphic analyses, we interpret that the construction of La Poruna occurred during four main eruption phases involving Strombolian, Hawaiian, and transitional eruptive styles. Furthermore, differences in the degree of erosion, alteration, and weathering of the lithostratigraphic units in the lava field of La Poruna suggest that this flow field was formed during two eruptive events. The excellent outcrop conditions and preservation state of the volcanic products of La Poruna allow new stratigraphic insights that advance the wider and more general understanding and the dynamics of this important type of volcanism and the potential hazards of a scoria cone eruption. The polycyclic style of the eruption needs to be included in the hazards assessment of these centers type, especially when the cone is associated with structures that can be reactivated. This process could correspond to a second phase of activity, involving ash fall, bomb, and lava emission.

Large-scale gravity-driven phenomena in the Crotone Basin, southern Italy

The aim of this study is to better define the scale, timing and driving mechanisms of a seaward-gliding landmass currently affecting the Crotone Basin, a forearc basin on the Ionian side of Calabria (southern Italy). An integrated approach of seismic, well and field data, together with literature information, have revealed that the slide includes an onshore updip extensional domain compatible with the presence of a curved seaward-dipping fault system to the NW, which is connected southward to an offshore downdip compressional domain through a buried detachment surface lying at a Messinian halite layer. The landmass, which involves Messinian-Pleistocene deposits, has started to slide since the Zanclean, and experienced a paroxysmal episode between late Zanclean and early Piacenzian linked to transpressional tectonics. After a phase of inactivity during the Calabrian, the gravitational collapse underwent a second reactivation since middle Pleistocene due to regional uplift, which seems to be restricted to the offshore sector, the Crotone peninsula and probably the eastern coastal area. • A better definition of the scale, timing and driving mechanisms of the Crotone Megalandslide is provided. • A first phase of activity started during the Zanclean and ended during the Gelasian, and involved the whole basin. • A second phase of activity persists since the middle Pleistocene and involved only the Crotone peninsula and the offshore area.

Reknit Revolution: Knitwear Design for the Domestic Circular Economy

An ongoing initiative seeks to encourage hand knitters to expand their practices to encompass reknitting: the reworking of existing knitted items using knit-based skills, techniques and knowledge. Reknitting offers potential benefits in terms of promoting repair and re-use by individual users within the domestic sphere, thereby contributing to the “domestic circular economy”. Although reknitting was a common element of hand knitting practice in the past, the knowledge of how to open, alter, unravel and reknit has largely been lost. This gap in practice presents a fertile challenge for contemporary knitted textile design. A first phase of activity saw the initial development and testing of reknitting techniques suitable for the garments in our wardrobes today. This project demonstrated that it is possible to engage knitters with reknitting, but that support is needed to overcome barriers to participation and shift perceptions of what is both possible and desirable. Three interconnected elements of support are discussed: inspiration, information and confirmation. A second phase of activity, centered around an exhibition in a public gallery, aimed to communicate the techniques to a wider knitting community. Exhibits included physical garments, a large-scale infographic and a film; adaptable instructions were developed and published on a companion website. Through analysis of these exhibits and instructions, categories within each of the three elements of support were identified to create a more detailed taxonomy of support for domestic reknitting practice. Reflection on the progress of this initiative indicates the direction for future activity: raising broader awareness of reknitting, primarily via online channels, and structuring opportunities for participation to build a mutually supportive community of practice. It is anticipated that the taxonomy of support could be applied to other initiatives seeking to promote domestic circular economy activity.

The clinical course of juvenile idiopathic arthritis-associated uveitis in childhood and puberty

AimThe long-term course of juvenile idiopathic arthritis (JIA)-associated uveitis is not known yet. This study investigates the course and activity of JIA-associated uveitis in childhood and puberty.DesignRetrospective study of the...

Modelling the enzymatic activity of two lipases isoenzymes commonly used in the food industryModelado de la actividad enzimática de dos isoenzimas lipasas comúnmente utilizadas en la industria alimentaria

An in-depth analysis of the kinetics of two lipases isoenzymes (Lip1 and Lip2) in triacetin hydrolysis in absence and in presence of hexane was carried out. The addition of hexane led to an increase in enzymatic activities of both enzymes for all triacetin concentrations, and the kinetic data described a hyperbola which was consistent with the classical Michaelis–Menten model. Without hexane, the time-course of the triacetin hydrolysis by Lip1 and Lip2 did not follow a Michaelian behaviour. In this case, a first phase of low enzymatic activity (at triacetin concentrations from 0 to 250 mM) was followed by a rapid increase in velocity at triacetin concentrations ≥250 mM. The Michaelis–Menten model was unable to describe the first phase due to the linear (nonhyperbolic) relationship between the velocity and the triacetin concentration, meanwhile the logistic model provided a satisfactory description of the experimental data corresponding to the second phase of activity. En este trabajo se llevó a cabo un profundo análisis de la cinética de dos isoenzimas lipasas (Lip1 y Lip2) en la hidrólisis de triacetina, en ausencia y en presencia de hexano. La adición de hexano a la mezcla de reacción incrementó las actividades enzimáticas de ambas enzimas para todas las concentraciones de triacetina, obteniéndose una relación hiperbólica compatible con el modelo clásico de Michaelis-Menten. En ausencia de hexano, la actividad de Lip1 y Lip2 no mostró un comportamiento Michaeliano, observándose una fase inicial de baja velocidad a concentraciones de triacetina entre 0–250 mM, seguida de un rápido incremento en la actividad enzimática ([triacetina] ≥ 250 mM). El modelo de Michaelis-Menten no pudo ser utilizado para describir la primera fase debido al incremento lineal (no hiperbólico) de la velocidad con la concentración de triacetina, mientras el modelo logístico describió adecuadamente la cinética de hidrólisis en la segunda fase.

Mid-Holocene gullying indicating extreme hydroclimatic events in the centre of the Russian Plain

At the Satino site in the center of the Russian Plain, major events of the Holocene erosion history are concentrated on sides of river valleys incised into smooth moraine landscape. Valley sides are dissected by Pleistocene gullies. Extraordinary for the Holocene was formation of four new permanent gullies. Three of them had appeared in the Late Atlantic – Early Subboreal time. One gully permitted direct dating of the fan base, which gave estimation of its appearance between 4.3-4.6 ka BP (cal). Two other gullies were constrained within the two intervals 5.2-5.5 and 5.9-6.2 ka BP (cal), based on assumed correlation with extreme runoff events dated over the area. After a long break of erosion, two of the gullies had exhibited the second phase of activity between 3.0-3.7 ka BP (cal). As in the Bronze Age no settlements are known in the study area and surroundings; human reinforcement of erosion was minor if any. The four intervals of extraordinary linear erosion on valley sides coincided with extremely high runoff events in streams of various sizes, which left prominent geomorphic and sedimentological features: meander arcs, coarse-grained alluvium, buried floodplain soils, etc. Altogether, this is considered to indicate a highly irregular climatic pattern in the area in the interval of 3.0-6.2 ka BP (cal) with several phases containing a series of extreme downpours, which had no analogs throughout the Holocene.

A CD28 superagonistic antibody elicits 2 functionally distinct waves of T cell activation in rats

Administration of the CD28 superagonistic antibody JJ316 is an efficient means to treat autoimmune diseases in rats, but the humanized antibody TGN1412 caused devastating side effects in healthy volunteers during a clinical trial. Here we show that JJ316 treatment of rats induced a dramatic redistribution of T lymphocytes from the periphery to the secondary lymphoid organs, resulting in severe T lymphopenia. Live imaging of secondary lymphoid organs revealed that JJ316 administration almost instantaneously (<2 minutes) arrested T cells in situ. This reduction in T cell motility was accompanied by profound cytoskeletal rearrangements and increased cell size. In addition, surface expression of lymphocyte function-associated antigen-1 was enhanced, endothelial differentiation sphingolipid G protein-coupled receptor 1 and L selectin levels were downregulated, and the cells lost their responsiveness to sphingosine 1-phosphate-directed migration. These proadhesive alterations were accompanied by signs of strong activation, including upregulation of CD25, CD69, CD134, and proinflammatory mediators. However, this did not lead to a cytokine storm similar to the clinical trial. While most of the early changes disappeared within 48 hours, we observed that CD4+CD25+FoxP3+ regulatory T cells experienced a second phase of activation, which resulted in massive cell enlargement, extensive polarization, and increased motility. These data suggest that CD28 superagonists elicit 2 qualitatively distinct waves of activation.

Distinct Roles of Nitrate and Nitrite in Regulation of Expression of the Nitrate Transport Genes in the Moss Physcomitrella patens

Five NRT2 genes and three Nar2 genes, encoding putative high-affinity nitrate transporters, and the respective cDNAs were identified and characterized in Physcomitrella patens. The deduced moss NRT2 and NAR2 proteins were more similar to the corresponding proteins of higher plants than to those of the green alga Chlamydomonas reinhardtii. Expression of all the genes was inhibited by ammonium added to the medium. The regulation by ammonium was abolished by an inhibitor of glutamine synthetase, but the effect of this inhibitor was counteracted by an inhibitor of glutamate synthase. Negative correlation was observed between the glutamine content of protonemata and the transcript levels of PpNRT2 and PpNar2. These results indicated that glutamine is the signal for repression of the genes. All the genes except PpNRT2;5 showed transient expression stimulated by nitrate but not by nitrite, peaking at 2-4 h after the medium was deprived of ammonium. When the glutamine synthetase inhibitor was used to inhibit assimilation of the ammonium generated intracellularly from nitrate or nitrite, the second phase of activation of genes became manifest at approximately 8 h after the medium was deprived of ammonium. Surprisingly, both nitrate and nitrite stimulated gene expression at this stage. PpNRT2;5 was distinct from the other genes in that its expression is sharply induced by nitrite, is strictly dependent on nitrite or nitrate, and is much less susceptible to the feedback regulation, retaining a constant level in nitrate-containing medium. These results indicated that P. patens has multiple mechanisms for sensing nitrate and nitrite.

Beautifying the City: 1960s Artistic Mosaics by Italian Canadians in Toronto

Italian Canadian craftsmen deserve recognition for their contribution to the aesthetics of Toronto's architectural environment through their role in the production of mosaic artworks. After an early period in the 1930s (which witnessed the ROM and Foster Memorial projects) there was a second phase of activity in the 1960s, in part as a result of the efforts of the entrepreneur Remo De Carli. Major works in churches (e.g. Our Lady of Sorrows Church), business establishments, banquet halls, and private homes were designed by Italian-trained artists in Canada, especially Vittorio Corsaletti, Luigi Nasato, and Vincenzo Vanin.

Functional role of JNK in neuritogenesis of PC12-N1 cells

JNKs, also known as SAPKs, are activated in response to a wide variety of factors including growth factors, cytokines, UV radiation, and heat shock. In the rat pheochromocytoma PC12 cells, the JNK signaling pathway mediates diverse functions such as differentiation and apoptosis. We have previously shown that activated JNK is required for later stages of neuritogeneis induced by NGF in a variant PC12 cell line (N1). Here, the functional role of JNK in N1 cells is further investigated. We show that NGF treatment, which induces extensive neurite branching and cell soma enlargement in the N1 cells, stimulates a biphasic activation of JNK. The first phase of activation is rapid and transient, beginning at 15 min after NGF exposure and lasting approximately 45 min. The second phase of activation is sustained, beginning at 9–12 h of NGF treatment and lasting for at least 24 h. Similar biphasic pattern of JNK activation is also observed in the parental PC12 cells. Using the specific JNK inhibitor SP600125, we show that the biphasic activation is necessary for neurite outgrowth and branching, and that inhibition of either phase suppresses neuritogenesis in the N1 cells. These results suggest that dynamic JNK activation may play a key role in neurite outgrowth during neuronal development.

Direct Activation of Platelets by Tissue Factor Is Amplified by FVIIa and Potentiated by Serotonin: Influence of Shear Rate.

Although exposure of tissue factor (TF) at sites of disrupted atherosclerotic plaques plays a critical role in platelet-triggered ischemic complications, a direct interaction of TF with platelets has not been yet demonstrated. We have investigated the effects of TF on platelets under different shear rate conditions. Exposure of isolated washed platelets to TF derived from human placenta resulted in reversible aggregation (35-50% max at 1 min) using standard platelet aggregometry. This response was αIIb-β3 dependent and occurred in the presence of residual concentrations of calcium. TF-induced reversible aggregation was enhanced and made irreversible to 90–100% by the addition of FVIIa (5μg/ml). This second phase of activation was blocked by the presence of serine-protease inhibitors. A combination of ultrastructural and flow cytometry studies revealed that although TF induced shape change and moderate expression of P-selectin an ANV positive phospholipids, internal contraction and full platelet degranulation only occurred after addition of FVIIa. All these transformations occurred together with tyrosine phosphorylation of proteins. Platelets adhered, spread and aggregated onto synthetic membranes coated exclusively with TF that had been exposed to circulating blood. Addition of FVIIa caused a 50% enhancement on platelet interactions and a two-fold increase in fibrin deposition. Serotonin enhanced overall TF induced platelet interactions under the different experimental approaches. A selective serotonin reuptake inhibitor (citalopram) reduced the intensity and extent of the effects of TF in the two experimental settings used in our investigations. Our results are consistent with a direct role of TF on platelet-triggered ischemic complications. We demonstrate that a lipidated from of TF activates isolated platelets in suspension. In studies conducted with flowing whole blood we show that TF firmly attached to a surface acts itself as an adhesive substrate, and promotes formation of aggregates. These TF-platelet interactions are enhanced through serotoninergic mechanism and markedly potentiated in the presence of FVIIa. The possible synergism between FVIIa and serotoninergic mechanisms may well contribute to the development of severe ischemic complications triggered on ruptured atherosclerotic plaques.

Post-caldera activity in the Alban Hills volcanic district (Italy): 40Ar/39Ar geochronology and insights into magma evolution

We present 24 40Ar/39Ar ages for the youngest volcanic products from the Alban Hills volcanic district (Rome). Combined with petrological data on these products, we have attempted to define the chronology of the most recent phase of activity and to investigate the magma evolution of this volcanic district. The early, mainly explosive activity of the Alban Hills spanned the interval from 561±1 to 351±3 ka. After approximately 50-kyr of dormancy, a mainly effusive phase of activity took place, accompanied by the strombolian activity of a small central edifice (Monte delle Faete). This second phase of activity spanned the interval 308±2 to 250±1 ka. After another dormancy period of approximately 50-kyr, a new, hydromagmatic phase of activity started at 200 ka at several centers located to the southwest of the Monte delle Faete edifice. After an initial recurrence period of approximately 50-kyr, which also characterized this new phase of activity, the longest dormancy period (approximately 80-kyr) in the history of the volcanic district preceded the start of the activity of the Albano and Giuturna centers at 70±1 ka. Results of our study suggest a quasi-continuous magmatic activity feeding hydromagmatic centers with a new acme of volcanism since around 70 ka. Based on data presented in this paper, we argue that the Alban Hills should not be considered an extinct volcanic district and a detailed re-assessment of the volcanic hazard for the area of Rome is in order.

Tumor Necrosis Factor-regulated Biphasic Activation of NF-κB Is Required for Cytokine-induced Loss of Skeletal Muscle Gene Products

NF-kappaB activation is classically defined as a transient response initiated by the degradation of IkappaB inhibitor proteins leading to nuclear import of NF-kappaB and culminating with the resynthesis of IkappaBalpha and subsequent inactivation of the transcription factor. Although this type of regulation is considered the paradigm for NF-kappaB activation, other regulatory profiles are known to exist. By far the most common of these is chronic or persistent activation of NF-kappaB. In comparison, regulation of NF-kappaB in a biphasic manner represents a profile that is scarcely documented and whose biological significance remains poorly understood. Here we show using differentiated skeletal muscle cells, that tumor necrosis factor (TNF) induces NF-kappaB activation in a biphasic manner. Unlike the first transient phase, which is terminated within 1 h of cytokine addition, the second phase persists for an additional 24-36 h. Biphasic activation is mediated at both the levels of NF-kappaB DNA binding and transactivation function, and both phases are dependent on the IKK/26 S proteasome pathway. We find that regulation of the first transient phase is mediated by the degradation and subsequent resynthesis of IkappaBalpha, as well as by a TNF-induced expression of A20. Second phase activity correlates with persistent down-regulation of both IkappaBalpha and IkappaBbeta proteins, derived from a continuous TNF signal. Finally, we demonstrate that inhibition of NF-kappaB prior to initiation of the second phase of activity inhibits cytokine-mediated loss of muscle proteins. We propose that the biphasic activation of NF-kappaB in response to TNF may play a key regulatory role in skeletal muscle wasting associated with cachexia.

Geology, Geochemistry, and Mineralogy of the Worthington Offset Dike: A Genetic Model for Offset Dike Mineralization in the Sudbury Igneous Complex

The Worthington offset dike extends for approximately 15 km away from the southwestern margin of the 1.85 Ga Igneous Complex. The dike is zoned with respect to inclusion and sulfide contents. Marginal chilled quartz diorite is transitional into medium-grained quartz diorite. These rocks are sulfide undersaturated, contain small inclusions from the wall rocks, and are preserved along much of the dike. Locally, the dike contains a core of inclusion-rich quartz diorite, which can be choked with inclusions surrounded by semimassive to massive sulfide. The more heavily mineralized inclusion-rich quartz diorite contains 10 to 75 percent amphibolite inclusions, which are petrologically and geochemically similar to the immediately adjacent country-rock amphibolites, locally termed Sudbury gabbros. The semimassive to massive sulfide zones form subvertical pipes, much like the deposits of the Copper Cliff offset dike, and these are associated with locations where the Worthington dike widens from 20 to 30 m to 50 to 80 m. The average metal tenors of the sulfide with > = 5% sulfur are calculated to be 7 percent Ni and 13 percent Cu. Thus the dike ores have a much higher Cu/Ni ratio than orebodies within the contact sublayer (Cu/Ni ~ 1). The medium-grained inclusion-poor quartz diorite and inclusion-rich quartz diorite differ in Ni, Cu, Pt, and Pd abundances, but they have similar major and lithophile trace element abundance levels despite having different inclusion and sulfide contents. Assimilation of inclusions has therefore not significantly changed the composition of the silicate matrix of the inclusion-rich quartz diorite. The composition of the inclusion-poor quartz diorite is a close approximation to average crust and also to the bulk composition of the Igneous Complex rocks. Regional differences in offset geochemistry exist between the North and South Range offset dikes, but we believe that the formation of the inclusion-poor quartz diorite and inclusion-rich quartz diorite silicate magmas predated significant silicate differentiation or silicate gravitational segregation of the melt sheet and that the differences may record primary silicate heterogeneity of the melt sheet. These differences may have developed in response to the different proportions of Archean granitoids relative to Proterozoic sediments and volcanics that contributed to the melt sheet on the North and South Ranges of the Igneous Complex. The first quartz diorite melt was sulfide undersaturated and devoid of amphibolite inclusions. The introduction of this melt took place during or shortly after the generation of the melt sheet and represented a very rapid introduction of quartz diorite magma into radial and concentric dikes with local incorporation of metasedimentary inclusions. The second phase of activity involved the introduction of a sulfide-bearing melt into portions of the quartz diorite melt that were not completely crystallized at the center of the offset dike; this produced the inclusion-rich quartz diorite. The main control on the location of injection of the sulfide-bearing melt appears to be widened domains of the partially crystallized quartz diorite dike that often correspond to contacts between different country-rock types and sulfides, especially where there are gabbro country rocks and/or local development of breccia. The injection of sulfide-enriched melt is interpreted to have taken place along steeply oriented pipes through these heavily brecciated country rocks; this appears to explain why there is a contact relationship between inclusion-rich quartz diorite and inclusion-poor quartz diorite, and also explains the presence of fragments of inclusion-poor quartz diorite and country-rock amphibolites in the inclusion-rich quartz diorite. The introduction of sulfides into these pipes is interpreted to have taken place from the overlying melt sheet and it is suggested that the high Cu/Ni ratios and platinum-group element tenors of these sulfides, compared to contact-style sulfides, indicate that these were some of the earliest sulfides to segregate from the overlying melt sheet. The type and style of brecciation developed in the country rocks along different offset dikes controlled the continuity of the quartz diorite and the location of the orebodies. Intersections of the quartz diorite with domains of breccia appear to have been important in the Copper Cliff offset dike and the development of mineralization may be a response to the presence of favorable channels through which magmatic sulfides were introduced into the dike from the overlying melt sheet. We propose that the quantity of sulfide in a dike is related to the thickness of the overlying melt sheet. The melt sheet thickness was presumably greatest at the Copper Cliff and Frood-Stobie offset dikes, the Worthington offset dike is located below a thinner melt sheet, and the Manchester and Foy offset dikes developed beneath very thin portions of the melt sheet.

Interleukin-1β Induces Chronic Activation and de Novo Synthesis of Neutral Ceramidase in Renal Mesangial Cells

The lipid signaling molecule ceramide is formed by the action of acid and neutral sphingomyelinases and degraded by acid and neutral ceramidases. Short-term stimulation of mesangial cells with the pro-inflammatory cytokine interleukin-1beta (IL-1beta) leads to a rapid and transient increase in neutral sphingomyelinase activity (Kaszkin, M., Huwiler, A., Scholz, K., van den Bosch, H., and Pfeilschifter, J. (1998) FEBS Lett. 440, 163-166). In this study, we report on a second delayed peak of activation occurring after hours of IL-1beta treatment. This second phase of activation was first detectable after 2 h of treatment and steadily increased over the next 2 h, reaching maximal values after 4 h. In parallel, a pronounced increase in neutral ceramidase activity was observed, accounting for a constant or even decreased level of ceramide after long-term IL-1beta treatment, despite continuous sphingomyelinase activation. The increase in neutral ceramidase activity was due to expressional up-regulation, as detected by an increase in mRNA levels and enhanced de novo protein synthesis. The increase in neutral ceramidase protein levels and activity could be blocked dose- dependently by the p38 MAPK inhibitor SB 202190, whereas the classical MAPK pathway inhibitor U0126 and the protein kinase C inhibitor Ro 318220 were ineffective. Moreover, cotreatment of cells for 24 h with IL-1beta and SB 202190 led to an increase in ceramide formation. Interestingly, IL-1beta-stimulated neutral ceramidase activation was not reduced in mesangial cells isolated from mice deficient in MAPK-activated protein kinase-2, which is a downstream substrate of p38 MAPK, thus suggesting that the p38 MAPK-mediated induction of neutral ceramidase occurs independently of the MAPK-activated protein kinase-2 pathway. In summary, our results suggest a biphasic regulation of sphingomyelin hydrolysis in cytokine-treated mesangial cells with delayed de novo synthesis of neutral ceramidase counteracting sphingomyelinase activity and apoptosis. Neutral ceramidase may thus represent a novel cytoprotective enzyme for mesangial cells exposed to inflammatory stress conditions.

Seismicity and Velocity Structure of Loihi Seamount from the 1996 Earthquake Swarm

The largest earthquake swarm yet recorded on Loihi submarine volcano took place in July and August of 1996. The swarm consisted of two phases of seismic activity and was associated with the formation of a pit crater and additional faulting of Loihi's summit platform. The first phase of activity was comprised of predomi- nantly high-frequency events scattered over the southern flanks of the volcano. Fol- lowing a day of seismic quiescence, the second phase of activity began, consisting of lower-frequency earthquakes with strong T-phases. The phase 2 events took place beneath Loihi's summit, presumably marking the formation of the pit crater, Pele's Pit. Data obtained by an ocean-bottom seismometer (OBS) on Loihi during the swarm help constrain a new velocity model for Loihi. The relocated earthquakes, combined with other characteristics of the swarm, enabled us to develop a model for the events leading up to the formation of Pele's Pit that includes (1) a prolonged eruption, (2) a tectonic event beneath Loihi's south flank, and (3) the drainage of a shallow magma chamber.

Root and microbial involvement in the kinetics of 14C-partitioning to rhizosphere respiration after a pulse labelling of maize assimilates

In a previous study, we examined the kinetics of radioactivity evolution from rhizosphere respiration after the pulse labelling of maize shoots with 14CO2 (Nguyen et al., 1999). The specific activity of rhizosphere respiration demonstrated two peaks of 14CO2 production. The first one occurred a few hours after the pulse of 14CO2 and was followed by a second peak, which took place during the night following the labelling. In the present work, we demonstrate that the second phase of activity occurred in both sterile and non sterile plant–soil systems. This was inconsistent with the results obtained for wheat by Warembourg and Billes (1979) who observed the second peak solely in the case of non-sterile cultures. These authors suggested that this second phase of 14CO2 production was related to microbial mineralisation of labelled complex compounds. Their synthesis and breakdown into smaller molecules delayed their utilisation by micro-organisms. However, in the present work, we also demonstrate that the second phase of activity was closely related to photoperiod. When plants were transferred from a 16 h to 20 h photoperiod, the second mineralisation of labelled rhizosphere compounds occurred sooner after the initiation of the dark period and it was strongly attenuated. Therefore, we suggest that the second phase of activity resulted from the utilisation by roots and by micro-organisms of stored 14C-compounds, which accumulated during the previous light period.