Ichnofossils, cracks or crystals? A test for biogenicity of stick-like structures from vera rubin ridge, mars

New images from Mars rover Curiosity display millimetric, elongate stick- like structures in the fluvio-lacustrine deposits of Vera Rubin Ridge, the depositional environment of which has been previously acknowledged as habitable. Morphology, size and topology of the structures are yet incompletely known and their biogenicity remains untested. Here we provide the first quantitative description of the Vera Rubin Ridge structures, showing that ichnofossils, i.e., the product of life-substrate interactions, are among their closest morphological analogues. Crystal growth and sedimentary cracking are plausible non-biological genetic processes for the structures, although crystals, desiccation and syneresis cracks do not typically present all the morphological and topological features of the Vera Rubin Ridge structures. Morphological analogy does not necessarily imply biogenicity but, given that none of the available observations falsifies the ichnofossil hypothesis, Vera Rubin Ridge and its sedimentary features are here recognized as a privileged target for astrobiological research

Aquifer architecture of the Quaternary alluvial succession of the southern lambro basin (Lombardy-Italy)

Aquifer stratigraphy of the sector of the Pleistocene - Holocene alluvial plain of Lombardy, run by the Lambro valley system south of Milan, has been reconstructed on the basis of geological mapping at 1:10.000 and subsurface interpretation and correlation of more than 150 among water wells, boreholes and deep excavations. The Middle (?) - Late Pleistocene sedimentary evolution of this sector includes four major progradation cycles of alluvial depositional systems that migrated from the alpine northern side towards the axial palaeo-Po depositional system. These cycles were governed by Pleistocene glacial cycles, in combination with ramp-folding of the San Colombano - Salerano apenninic anticlines and minor uplift of the alpine side. Every major cycle is soled by an erosion surface, and is shaped by minor fining upward sequences. Both major and minor sequences record at first the advance of coarse-grained units (distal braided alluvial fan or sandy braid plain) which fringe-out south-eastwards into meandering fluvial systems, and are replaced upwards by alluvial plain fines, which close the sequences. Physical stratigraphy and geomorphology, analysis of facies associations, characterisation of gravel composition, radiocarbon dating on 4 peat and plant relic samples and findings of transported artefacts allowed the correlation of the four cycles with the regional evolution. The Post Glacial meandering depositional systems of the deeply entrenched Lambro valley system (Unit 4, Holocene; Unit 5, historical), are cut into the braided stream to meandering depositional systems that developed during L.G.M. times, at present outside the Lambro valley (Unit 3, Late Pleistocene). These represent the uppermost aquifer unit, i.e. the phreatic - non saturated zone. The underlying Unit 2 (Late Pleistocene) can be correlated with the Besnate Allogroup, and therefore developed during the corresponding glaciations. It is formed by three stacked sequences, controlled by glacial cycles, which are deeply scoured into the lowermost succession that could be studied (Unit 1 Middle ? - Late Pleistocene ?). It represents the most important and permeable intermediate aquifer unit, that is only partly confined by the flood-plain fines of the uppermost sub-unit 2C

Gemcitabine plus vinorelbine in advanced non-small cell lung cancer: a phase II study of three different doses

Our aim was to study the activity and toxicity of the gemcitabine plus vinorelbine (Gem Vin) combination and to identify the optimal dose. Previously untreated patients aged < 70 years, with stage IV or IIIb (not candidates for radiotherapy) non-small cell lung cancer were eligible. Studied dose-levels of Gem Vin, administered on days 1 and 8 every 3 weeks, were (mg m–2): level I = 1000/25; level II = 1200/25; level III = 1000/30; level IV = 1200/30. A feasibility study was performed at each dose-level, followed by a single-stage phase II study. Dose-level IV was unfeasible because of grade 4 neutropenia. Overall, out of 126 patients enrolled in phase II studies, there were one complete and 32 partial responses (response rate 26%: 95% CI 18–34%). Response rates were 27.9%, 21.4% and 29.3% at levels I, II and III, respectively. The treatment was well tolerated. Toxicity was less frequent and severe at level I. Overall median survival was 33 weeks (95% CI 28–40). Descriptive quality of life analysis showed that patients with a worse baseline global health status score tended to drop out of the study earlier than those with a better score. Gem Vin is feasible at different doses. It is sufficiently active and well tolerated. A phase III study to compare the effect on quality of life of Gem Vin (level I) vs cisplatin-based chemotherapy is ongoing. © 2000 Cancer Research Campaig

Pemetrexed single agent chemotherapy in previously treated patients with locally advanced or metastatic non-small cell lung cancer

<p>Abstract</p> <p>Background</p> <p>The main objective of this study was to evaluate the safety of second-line pemetrexed in Stage IIIB or IV NSCLC.</p> <p>Methods</p> <p>Overall, 95 patients received pemetrexed 500 mg/m²i.v. over Day 1 of a 21-day cycle. Patients also received oral dexamethasone, oral folic acid and i.m. vitamin B12 supplementation to reduce toxicity. NCI CTC 2.0 was used to rate toxicity. All the adverse events were graded in terms of severity and relation to study treatment. Dose was reduced in case of toxicity and treatment was delayed for up to 42 days from Day 1 of any cycle to allow recovering from study drug-related toxicities. Tumor response was measured using the RECIST criteria.</p> <p>Results</p> <p>Patients received a median number of 4 cycles and 97.8% of the planned dose. Overall, 75 patients (78.9% of treated) reported at least one adverse event: 34 (35.8%) had grade 3 as worst grade and only 5 (5.2%) had grade 4. Drug-related events occurred in 57.9% of patients. Neutropenia (8.4%) and leukopenia (6.3 %) were the most common grade 3/4 hematological toxicities. Grade 3 anemia and thrombocytopenia were reported in 3.2% and 2.1% of patients, respectively. Diarrhea (6.3%), fatigue (3.2%) and dyspnea (3.2%) were the most common grade 3/4 non-hematological toxicities. The most common drug-related toxicities (any grade) were pyrexia (11.6%), vomiting, nausea, diarrhea and asthenia (9.5%) and fatigue (8.4%). Tumor Response Rate (CR/PR) in treated patients was 9.2%. The survival at 4.5 months (median follow-up) was 79% and the median PFS was 3.1 months. Twenty patients (21.1%) died mainly because of disease progression.</p> <p>Conclusion</p> <p>Patients with locally advanced or metastatic NSCLC could benefit from second-line pemetrexed, with a low incidence of hematological and non-hematological toxicities.</p

Validation of Hurst statistics : a predictive tool to discriminate turbiditic sub-environments in a confined basin

Turbidite sequences within confined basins constitute important hydrocarbon reservoirs worldwide; for this reason the discrimination of sedimentary sub-environments based on an objective statistical method is of interest for pure and applied science. We investigated the potential use of the Hurst test (Chen & Hiscott 1999) as a statistical tool to discriminate sub-environments within geologically complex turbiditic units that fill a confined basin with well exposed facies transitions and onlaps, at the scale of several stacked reservoirs (Cengio and Bric la Croce - Castelnuovo Turbidite Systems in the Tertiary Piedmont Basin, Oligocene, Northern Italy). In vertical stratigraphic sections, the Hurst test determines the degree of clustering of low and high values of sedimentological variables like bed-thickness, grain-size and sand/mud ratio that are dependent on sub-environments of deposition. We applied the Hurst test to depocentral and marginal sub-areas across the basin (parallel and perpendicular to the main palaeo-current direction), documenting a different clustering of thick and thin beds, and of high and low values of the sand/mud ratio, in the depocentre-distal sector with respect to the onlap areas. A new field (onlap sub-environment) could thus be added to the Chen & Hiscott (1999) classification diagram of turbidite settings based on the Hurst index. The Hurst phenomenon i.e. clustering of high and low values of the selected variables, was also able to distinguish between proximal and distal (depocentral) lobe settings, and to recognize the fingerprint of the different depositional lobes (fully confined aggrading, prograding, backstepping). The map of turbidite sub-environments obtained by interpolation of the Hurst index is quite comparable to the field-observed facies map, providing impressive robust validation of the Hurst statistics. This method seems to represent a very promising predictive tool for subsurface studies of turbiditic oil fields based on core and log analyses

Quantification of the degree of confinement of a turbidite-filled basin : a statistical approach based on bed thickness distribution

Bed thickness distribution within turbidite systems is related to basin geometry and to magnitude and duration of depositional events. Cumulative distribution of turbidite bed thicknesses is often interpreted in terms of a power-law. Alternatively, these distributions have been described by a lognormal mixture model. Changes in the power-law exponent can be related to the rheological properties of the gravity-driven flows and to the geometry of the basin. This study attempts to quantify the degree of confinement of well-exposed turbidite units of the Oligocene Cengio and Bric la Croce - Castelnuovo Turbidite Systems (Tertiary Piedmont Basin, Italy). Focus is on the behaviour of bed thickness distribution. The succession is suitable for this study because it represents the infill of a progressively widening basin, during quiescence of intrabasinal tectonics. In this basin the cumulative frequency distribution of turbidite bed thickness follows a segmented power-law relationship. The deviation from the trend observed for the thickest beds is associated with a deficiency of beds in a certain thickness range. This behaviour suggests existence of a thickness threshold that segregates the deposits of the fully confined flows that could deposit thick aggrading beds, with minor downcurrent flow transitions, from the rest of the bed-thickness population. This threshold decreases from the lowermost (and most confined) to the uppermost units of the Cengio Turbidite System (CTS). No thresholds were identified for the uppermost Bric la Croce - Castelnuovo Turbidite Systems (BCTS) that spread over a wider basin than the CTS, suggesting unconfined deposition. The BCTS was presumably larger than the area that could be covered by the turbidity currents. When integrated with data on sedimentology and basin morphology (well-log and seismic data), bed thickness statistics can provide a general guidance about interpretation of depositional settings, degree of confinement, erosion/amalgamation and bypass of turbidites, improving and assisting the development of reservoir models

Evoluzione del Bacino del Cellino : geometria ed analisi di facies dei pricipali corpi sabbiosi (avanfossa Periadriatica pliocenica, Italia centrale)

Lo studio dell\u2019evoluzione del Bacino del Cellino durante il Pliocene inferiore permette di interpretare, sulla base di nuove osservazioni sedimentologiche, il riempimento torbiditico dell\u2019avanfossa Periadriatica nel settore Abruzzese. In una prima fase (Pliocene basale) il bacino si apre verso sud permettendo la sedimentazione di spessi strati di conglomerato (conglomerati di Pietranico) con provenienza meridionale dal vicino Massiccio della Maiella. La presenza di indicatori di corrente alla base degli strati, la natura dei clasti e il loro sviluppo dimostrano la loro origine meridionale. Nello stesso tempo, un\u2019estensione flessurale si verifica nella zona di cerniera della placca Adriatica in sottoscorrimento (downbending), originando faglie longitudinali dirette N-S, parallele alla direzione delle strutture appenniniche. Il depocentro, suddiviso in graben paralleli, raggiunge la sua massima profondit\ue0 e diventa l\u2019area di accumulo di torbiditi questa volta con provenienza settentrionale, cos\uec come avviene di norma nell\u2019avanfossa Periadriatica. All\u2019inizio le correnti torbiditiche hanno volumi limitati e composizione molto argillosa (fase di starvazione), ma rapidamente il tasso di sedimentazione cresce con uno sviluppo di una sequenza di tipo \u201ccoarsening and thickening upward\u201d. In questo momento iniziano ad accumularsi spessi strati sabbiosi intercalati a torbiditi sottilmente stratificate. Il bacino assume una nuova forma, con la chiusura a sud dovuta al sollevamento di una struttura trasversale al bacino stesso (Alto del Cigno). La dimensione del bacino pu\uf2 essere stimata in almeno 150 km nella direzione parallela all\u2019asse del bacino e 30 \u2013 40 km nella direzione perpendicolare (Carruba et al., 2006). Il grande volume delle correnti di torbida permette la sedimentazione di strati che si depositano nell\u2019intero bacino: le correlazioni strato a strato, effettuate grazie all\u2019utilizzo di dati di pozzo (log elettrici) mostrano un ottimo grado di correlazione senza apprezzabili variazioni di natura e di spessore degli strati (Fig.1). I flussi torbiditici sono probabilmente molto diluiti e quindi in grado di muoversi per lunghe distanze e quindi estendersi per l\u2019intera area del bacino; nel Bacino del Cellino questa caratteristica (e cio\ue8 la presenza di strati con estensione bacinale) \ue8 peculiare della porzione inferiore della successione stratigrafica (membri E \u2013 D \u2013 C della Formazione di Cellino). Contrariamente a quanto avviene per i suddetti membri, i megastrati del soprastante membro B mostrano (come si pu\uf2 dedurre dalle correlazioni di sottosuolo) una estensione laterale limitata ad alcune aree del bacino e sensibili variazioni di spessore. Il membro A, che chiude la Formazione di Cellino, \ue8 costituito principalmente da torbiditi sottilmente stratificate con rari megastrati di estensione areale limitata e di difficile correlazione. Mentre in passato si \ue8 studiata attentamente la geometria di questi megastrati a scala bacinale sulla base di dati di sottosuolo, nel presente studio ci siamo focalizzati su un\u2019accurata analisi di facies partendo da dati raccolti in affioramento. Ci\uf2 ha permesso di effettuare nuove considerazioni sui meccanismi di trasporto e deposizione. In particolare \ue8 stato osservato quanto segue: 1) membri E - D - C La porzione inferiore della Formazione di Cellino (Fig.2) \ue8 costituita da megastrati tabulari con alla base arenarie molto spesse e massicce. La loro organizzazione interna indica la presenza correnti \u201csostenute\u201d che durano a lungo nel tempo (sustained turbidity current; Kneller and Branney, 1995) e depositano importanti spessori di sedimento in aggradazione. Le seguenti caratteristiche interne posso indicare flussi \u201csostenuti\u201d: (i) strati torbiditici con spessori e volume enormi, (ii) presenza di una porzione massiva basale molto spessa (0.5 \u2013 6 m), (iii) frequenti ripetizioni verticali di intervalli deposizionali massivi e a laminazione parallela e incrociata, associate a sottili superfici di erosione, (iv) porzione sommitale pelitica molto spessa (1 \u2013 10 m) oppure rappresentata da torbiditi sottili, (v) profilo granulometrico dello strato non ben sviluppato ma che in generale indica una diminuzione della granulometria verso l\u2019alto, (vi) abbondante materia organica, (vii) importanti strutture dovute a fuga d\u2019acqua. La presenza dello spesso intervallo massivo alla base pu\uf2 essere spiegata come il risultato di una progressiva aggradazione e assenza di trazione. La frequente ripetizione verticale di strutture sedimentarie (intervalli massivi e intervalli laminati) e la presenza di superfici erosive all\u2019interno dei megastrati riflettono le variazioni nel tempo della velocit\ue0 del flusso all\u2019interno della stessa corrente (flussi quasi-stazionari). La porzione superiore gradata (da sabbie fini a silt) dei megastrati rappresenta la fase finale della corrente, quando si assiste ad una sua progressiva diminuzione della velocit\ue0 nel tempo. Assumendo uno scenario caratterizzato dalla presenza di flussi torbiditici quasi-stazionari (e cio\ue8 che durano a lungo nel tempo), risulta pi\uf9 semplice spiegare la presenza dei numerosi megastrati che caratterizzano la porzione inferiore della Formazione di Cellino. In quest\u2019ottica, i fattori che determinano lo spessore degli strati sarebbero il confinamento del bacino, il tasso e la durata dell\u2019evento deposizionale che, come spiegato precedentemente, pu\uf2 perdurare fino a quando la corrente \ue8 in grado di mantenere (sostenere) un flusso di sedimento verso le aree deposizionali del bacino. 2) membro B Una riattivazione dell\u2019attivit\ue0 tettonica da origine a una nuova morfologia del bacino che si caratterizza per un generale sollevamento dell\u2019area settentrionale e conseguente approfondimento delle regioni meridionali del bacino, dovuto ad una migrazione verso sud del depocentro dell\u2019avanfossa. Nella porzione inferiore di questo membro i megastrati diventano meno frequenti e tendono ad assottigliarsi verso sud (flussi depletivi sensu Kneller and Branney, 1995), mentre nella porzione superiore del membro B I flussi tendono ad oltrepassare le aree sopracorrente e a depositarsi nelle porzioni pi\uf9 meridionali del bacino (flussi accumulativi sensu Kneller and Branney, 1995). L\u2019efficienza di trasporto \ue8 ancora molto alta: i megastrati si caratterizzano per la presenza di sequenze di Bouma troncate alla base ma con un intervallo pelitico a tetto molto sviluppato. 3) membro A Durante la deposizione del membro A il sollevamento delle aree settentrionali aumenta: come ben documentato dai dati di pozzo (es. le superfici erosionali e i depositi di riempimento di canale nei pozzi Bellante) si sviluppano superfici erosionali associate alla presenza di canali profondamente incisi che progradano verso i quadranti meridionali del bacino. Questa progradazione verso sud, associata ad un generale assottigliamento degli strati, \ue8 ben osservabile sul terreno lungo il torrente Fino e i suoi affluenti. I nostri dati suggeriscono che l\u2019evoluzione sedimentaria del bacino del Cellino \ue8 da ricollegarsi all\u2019interazione di diversi fattori di controllo, interni ed esterni al bacino, che sono caratteristici di molti bacini di avanfossa. In particolare, i megastrati del membro E potrebbero essere dovuti a flussi catastrofici e/o franamenti di sedimento da una scarpata durante un abbassamento relativo del livello marino indotte da un\u2019intensa fase di sollevamento tettonico delle aree marginali del bacino stesso