Heat flow and near-seafloor magnetic anomalies highlight hydrothermal circulation at Brothers volcano caldera, southern Kermadec arc, New Zealand

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 46(14), (2019): 8252-8260, doi: 10.1029/2019GL083517.Brothers volcano is the most hydrothermally active volcano along the Kermadec arc, with distinct hydrothermal fields located on the caldera walls and on the postcollapse volcanic cones. These sites display very different styles of hydrothermal activity in terms of temperature, gas content, fluid chemistry, and associated mineralization. Here we show the results of a systematic heat flow survey integrated with near‐seafloor magnetic data acquired using remotely operated vehicles and autonomous underwater vehicles. Large‐scale circulation is structurally controlled, with a deep (~1‐ to 2‐km depth) central recharge through the caldera floor and lateral discharge along the caldera walls and at the summits of the postcollapse cones. Shallow (~ 0.1‐0.2 km depth) circulation is characterized by small‐scale recharge zones located at a distance of ~ 0.1–0.2 km from the active vent sites.We thank the Captains and crews of the R/V Sonne, Thompson, and Tangaroa and the engineers from Wood Hole Oceanographic Institution and MARUM for the successful operation of ABE, Sentry, Quest 4000, and Jason. The heat flow data surveys were funded by NSF grant OCE‐1558356 (PI Susan Humphris) and a grant from the German Ministry for Education and Research BMBF, project no. 03G0253A (PI Andrea Koschinsky). Funding from the New Zealand Government (Ministry of Business, Innovation and Employment) helped enable this study. This paper was significantly improved by the comments from the Editor Rebecca Carey and from two unknown reviewers. The data used in this paper can be downloaded from the U.S. Lamont‐Doherty MGDS database.2020-01-1

Applicazione di metodi di potenziale in aree attive: uno studio sistematico e multiparametrico dell’Arcipelago di Panarea (Isole Eolie)

La caratteristica generale dei metodi gravimetrici, magnetici ed elettromagnetici, è quella di aver il pregio di integrare gli effetti di un fenomeno su un grande volume; anche in assenza di manifestazioni locali, come un terremoto o l’apertura di una frattura, le modificazioni del campo di stress o dello stato termodinamico, ad esempio all’interno di un edificio vulcanico, possono indurre variazioni della densità, della magnetizzazione e della resistività elettrica delle rocce. In questa ottica nel maggio 2005 è stata condotta una campagna nell’Arcipelago di Panarea, area di attuale interesse per fenomeni di attività esalativa (S.G.A.,1993; Italiano e Nuccio, 1991) attraverso uno studio microgravimetrico, magnetico e prelievo di campioni per analisi di suscettività magnetica e di densità. Lo scopo è quello di acquisire un gran numero di informazioni geofisiche differenti da affiancare alle attuali misurazioni geodetiche e di batimetria condotte dal gruppo INGV-CNT (Anzidei, 2000; Anzidei et al., 2003a) per produrre modelli dell’area sempre più vincolati e nello stesso tempo attraverso una ripetizione delle campagne nel tempo ottenere una visione 4D dei fenomeni finalizzati al monitoraggio dell’assetto dinamico dell’apparato di Panarea. Nel presente lavoro vengono presentati i risultati preliminari ottenuti dalla prima campagna di misure in cui sono state acquisite 53 stazioni microgravimetriche e magnetiche totali (di cui 6 sugli isolotti di Bottaro e Lisca Bianca) distribuite nel modo più omogeneo possibile compatibilmente con la logistica del territorio. Sono stati inoltre prelevati 14 campioni di rocce nelle principali litologie dell’isola su cui sono state eseguite misure di suscettività magnetica in laboratorio. Per le misure di gravità sono stati utilizzati Microgravimetri L&R modello Alliod 100x (di proprietà ENI) mentre per le misure di campo magnetico, un magnetometro portatile a protoni Scintrex. I risultati delle prime elaborazioni (fig.1) mostrano un’andamento qualitativo dei principali trends di anomalie in generale accordo tra loro. Nella carta residuata di anomalia di Bouguer, preliminarmente corretta per un valore di densità standard di 2.67 g/cm3 (in attesa di poter effettuare sui campioni delle misure di densità) ed ottenuta mediante sottrazione dall’anomalia in aria libera del contributo relativo alla topografia dell’isola mediante un Digital elevation terrain model, si nota una anomalia negativa localizzata nel fianco occidentale dell’isola (zona con quote più elevate) che sembra svilupparsi lungo gli affioramenti della formazione Punta Cardosi (PC2 e PC2a) costituita da colate di lava omogenee andesitiche e duomi di lava dacitici (Calanchi et al., 1999) di età più recente. La stessa formazione presenta i valori di suscettività più elevati misurati sull’isola, tra 3 e 4x10-2 SI (insieme alla formazione della fossa affiorante nella parte centro-orientale dell’isola tra il paese di San Pietro e Drauto) che si riflettono anche nella mappa di anomalia magnetica di campo totale, con un trend di anomalie con valori elevati in direzione circa Sud-Ovest. La fascia di anomalie distribuite lungo la costa risentono di un effetto spurio di bordo (limite del campionamento) e quindi per poterne meglio descriverne la forma sarebbe necessario poter condurre un rilievo marino circostante l’isola utile anche per collegare le misure acquisite sugli isolotti

High-definition endoscopy with digital chromoendoscopy for histologic prediction of distal colorectal polyps

Background: Distal diminutive colorectal polyps are common and accurate endoscopic prediction of hyperplastic or adenomatous polyp histology could reduce procedural time, costs and potential risks associated with the resection. Within this study we assessed whether digital chromoendoscopy can accurately predict the histology of distal diminutive colorectal polyps according to the ASGE PIVI statement. Methods: In this prospective cohort study, 224 consecutive patients undergoing screening or surveillance colonoscopy were included. Real time histology of 121 diminutive distal colorectal polyps was evaluated using high-definition endoscopy with digital chromoendoscopy and the accuracy of predicting histology with digital chromoendoscopy was assessed. Results: The overall accuracy of digital chromoendoscopy for prediction of adenomatous polyp histology was 90.1 %. Sensitivity, specificity, positive and negative predictive values were 93.3, 88.7, 88.7, and 93.2 %, respectively. In high-confidence predictions, the accuracy increased to 96.3 % while sensitivity, specificity, positive and negative predictive values were calculated as 98.1, 94.4, 94.5, and 98.1 %, respectively. Surveillance intervals with digital chromoendoscopy were correctly predicted with >90 % accuracy. Conclusions: High-definition endoscopy in combination with digital chromoendoscopy allowed real-time in vivo prediction of distal colorectal polyp histology and is accurate enough to leave distal colorectal polyps in place without resection or to resect and discard them without pathologic assessment. This approach has the potential to reduce costs and risks associated with the redundant removal of diminutive colorectal polyps

Ex vivo experimental study on the Thulium laser system : new horizons for interventional endoscopy (with videos)

BACKGROUND AND STUDY AIMS: The Thulium laser system (TLS) is an emerging interventional tool adopted in many surgical specialties. Its 2.0-\u3bcm wavelength allows precise coagulation (0.2\u200a-\u200a0.4\u200amm in depth) and cutting, limiting the possibilities of collateral injuries. We tested the impact of the TLS for gastric endoscopic submucosal dissection (ESD) and per oral endoscopic myotomy (POEM) ex vivo in pigs. MATERIALS AND METHODS: Ex vivo porcine stomach and esophagus models underwent 2 POEMs, and 3 ESDs (mean diameter 3.5\u200acm) with TLS using a 272-\ub5m and a 365-\ub5m thick optical fibers. Both continuous and pulsed laser emission were evaluated. Subsequent histopathological analysis was performed by an expert GI pathologist on the whole porcine models. RESULTS: Complete POEMs and gastric ESDs were successfully performed in all cases in 30 to 70 and 15 to 20 minutes. Both optical fibers were equally effective and precise. The best power output for mucosal incision was 25 to 30\u200aW during ESD and 25\u200aW for POEM using continuous laser emission. During submucosal dissection and tunneling the favorite power output was 20\u200aW and 15 to 20\u200aW, respectively, operating in continuous mode. No transmural perforation occurred throughout the operations and histopathology confirmed the absence of accidental muscular layer damage. CONCLUSIONS: The TLS stands out as a precise and manageable instrument in ex vivo models. This technique appears to be a promising tool for advanced interventional endoscopy

Interpretation of gravity and magnetic anomalies at Lake Rotomahana: geological and hydrothermal implications

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Journal of Volcanology and Geothermal Research 314 (2016): 84-94, doi:10.1016/j.jvolgeores.2015.07.002.We investigate the geological and hydrothermal setting at Lake Rotomahana, using recently collected potential-field data, integrated with pre-existing regional gravity and aeromagnetic compilations. The lake is located on the southwest margin of the Okataina Volcanic Center (Haroharo caldera) and had well-known, pre-1886 Tarawera eruption hydrothermal manifestations (the famous Pink and White Terraces). Its present physiography was set by the caldera collapse during the 1886 eruption, together with the appearance of surface activities at the Waimangu Valley. Gravity models suggest subsidence associated with the Haroharo caldera is wider than the previously mapped extent of the caldera margins. Magnetic anomalies closely correlate with heat-flux data and surface hydrothermal manifestations and indicate that the west and northwestern shore of Lake Rotomahana are characterized by a large, well-developed hydrothermal field. The field extends beyond the lake area with deep connections to the Waimangu area to the south. On the south, the contact between hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high heat-flux and bubble plumes which suggest hydrothermal activity occurring west of Patiti Island. The absence of a well-defined demagnetization anomaly at this location suggests a very young age for the underlying geothermal system which was likely generated by the 1886 Tarawera eruption. Locally confined intense magnetic anomalies on the north shore of Lake Rotomahana are interpreted as basalts dikes with high magnetization. Some appear to have been emplaced before the 1886 Tarawera eruption. A dike located in proximity of the southwest lake shore may be related to the structural lineament controlling the development of the Patiti geothermal system, and could have been originated from the 1886 Tarawera eruption.Science funding provided by GNS Science Strategic Development Fund

Birth of an ocean in the Red Sea: Initial pangs

We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub- axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly $2.2 and$2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element com- position suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with man- tle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwell- ing form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading

Studio multiparametrico dell’arcipelago di Panarea (Isole Eolie): primi risultati dei rilievi geodetici, geofisici e geologici

La recente crisi esalativa di Panarea ha indotto ad effettuare uno studio sistematico dell’area con tecniche GPS, batimetrie ad alta risoluzione, rilievi gravimetrici e di suscettività magnetica, rilievi geologici sottomarini e terrestri. I rilievi batimetrici hanno permesso di individuare la posizione e la estensione dei centri esalativi principali e il campo di fratturazione; quelli gravimetrici e di suscettività magnetica mostrano anomalie nel fianco occidentale di Panarea (formazione Punta Cardosi). I dati GPS, acquisiti sia sulla rete locale che nelle stazioni continue di Lisca Bianca e Panarea, mostrano una deformazione dell’area che è in accordo con il trend del campo di fratturazione attivo stimato dai rilievi geologici sottomarini e terrestri

Ice-templated hybrid graphene oxide—graphene nanoplatelet lamellar architectures: tuning mechanical and electrical properties

From IOP Publishing via Jisc Publications RouterHistory: received 2020-10-21, oa-requested 2021-01-07, rev-recd 2021-01-12, accepted 2021-01-25, epub 2021-02-23, open-access 2021-02-23, ppub 2021-05-14Publication status: PublishedFunder: Morgan Advanced Materials and RAEngFunder: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES)Funder: Heilongjiang Huasheng Graphite Co., People’s Republic of ChinaAbstract: The traditional freeze-casting route for processing graphene-based aerogels is generally restricted to aqueously dispersed flakes of graphene oxide (GO) and post-processing reduction treatments, which brings restrictions to the aerogels electrical properties. In this work, we report a versatile aqueous processing route that uses the ability of GO todisperse graphene nanoplatelets (GNP) to produce rGO-GNP lamellar aerogels via unidirectional freeze-casting. In order to optimise the properties of the aerogel, GO-GNP dispersions were partially reduced by L-ascorbic acid prior to freeze-casting to tune the carbon and oxygen (C/O) ratio. The aerogels were then heat treated after casting to fully reduce the GO. The chemical reduction time was found to control the microstructure of the resulting aeorgels and thus to tune their electrical and mechanical properties. An rGO-GNP lamellar aerogel with density of 20.8 ± 0.8 mg cm−3 reducing using a reduction of 60 min achieved an electrical conductivity of 42.3 S m−1. On the other hand, an optimal reduction time of 35 min led to an aerogel with compressive modulus of 0.51 ±0.06 MPa at a density of 23.2 ± 0.7 mg cm−3, revealing a compromise between the tuning of electrical and mechanical properties. We show the present processing route can also be easily applied to produce lamellar aerogels on other graphene-based materials such as electrochemically exfoliated graphene