Tides and their seminal impact on the geology, geography, history, and socio-economics of the Bay of Fundy, eastern Canada

Tides are an ever-present reality in many coastal regions of the world, and their causes and influence have long been matters of intrigue. In few places do tides play a greater role in the economics and character of a region and its people than around the shores of the Bay of Fundy in eastern Canada. Indeed, the Bay of Fundy presents a wonderful natural laboratory for the study of tides and their effects. However, to understand these phenomena more fully, some large perspectives are called for on the general physics of the tides and their operation on an oceanic scale. The geologic history of the region too provides key insights into how and why the most dramatic tides in the world have come to be in the Bay of Fundy. Tidal characteristics along the eastern Canadian seaboard result from a combination of diurnal (daily) and semidiurnal (twice daily) tides, the latter mostly dominant. Tidal ranges in the upper Bay of Fundy commonly exceed 15 m, in large part a consequence of tectonic forces that initiated the Bay during the Triassic. The existence and position of the Bay is principally determined by a half-graben, the Fundy Basin, which was established at the onset of the opening of the Atlantic Ocean. Due to the proportions of the Bay of Fundy, differences in tidal range through the Gulf of Maine-Bay of Fundy-Georges Bank system are governed by near resonance with the forcing North Atlantic tides. Although Fundy tide curves are sinusoidal, tide prediction calls for consideration of distinct diurnal inequalities. Overlapping of the cycles of spring and perigean tides every 206 days results in an annual progression of 1.5 months in the periods of especially high tides. Depending on the year, these strong tides can occur at all seasons. The strongest Fundy tides occur when the three elements – anomalistic, synodical, and tropical monthly cycles – peak simultaneously. The closest match occurs at intervals of 18.03 years, a cycle known as the Saros. Tidal movements at Herring Cove, in Fundy National Park, illustrate the annual expected tidal variations. Vigorous quasi-equilibrium conditions characterize interactions between land and sea in macrotidal regions like the Bay of Fundy. Ephemeral on the scale of geologic time, estuaries progressively infill with sediments as relative sea level rises, forcing fringing salt marshes to grow to successively higher levels. Although closely linked to a regime of tides with large amplitude and strong tidal currents, Fundy salt marshes rarely experience overflow. Established about 1.2 m lower than the highest astronomical tide, only very large tides are able to cover the marshes with a significant depth of water. Peak tides arrive in sets at periods of 7 months, 4.53 years, and 18.03 years. For months on end no tidal flooding of the high marshes occurs. Most salt marshes are raised to the level of the average tide of the 18-year cycle. The exact locations of coastal zone water levels such as mean high water and mean low water is a recurring problem and the subject of much litigation. Marigrams constructed for selected river estuaries illustrate how the estuarine tidal wave is reshaped over its course, to form bores, and varies in its sediment-carrying and erosional capacity as a result of changing water surface gradients. Changing seasons bring about dramatic changes in the character of the estuaries, especially so as ice conditions develop during the second half of the 206-day cycle when the difference in height between Neap tide and Spring tide is increasing, the optimal time for overflow in any season. Maximum ice hazard, including build-up of "ice walls" in Fundy estuaries, occurs one or two months before perigean and spring tides combine to form the largest tide of the cycle. Although "ice walls" and associated phenomena pose hazards for man-made constructions, important natural purposes are served which need to be considered in coastal development and management schemes. Tides play a major role in erosion and in complex interactions among Fundy physical, biological, and chemical processes. Recent observations on mud flat grain size alterations, over deepening areas of the sea bed, and changes in the benthic community indicate changing environmental conditions in the Bay, caused possibly by increased hydrodynamic energy in the system. Résumé Les marées constituent une réalité omniprésente dans de nombreuses régions côtières du monde, et leurs causes et leur influence intriguent depuis longtemps. Il existe peu d'endroits où les marées jouent un rôle plus marquant au sein de l'économie et du caractère d'une région et de ses habitats que dans le secteur du rivage de la baie de Fundy, dans l'Est du Canada. La baie de Fundy représente effectivement un merveilleux laboratoire naturel pour l'étude des marées et de leurs effets. Il faut toutefois, pour mieux comprendre ces phénomènes, des perspectives élargies des caractéristiques physiques générales des marées et de leur fonctionnement à l'échelle océanique. Le passé géologique de la région fournit lui aussi des indices précieux sur la façon dont les marées les plus spectaculaires du globe sont apparues dans la baie de Fundy et sur les raisons de leur présence. Les caractéristiques des marées le long du littoral de l'Est du Canada découlent d'une combinaison de marées diurnes (quotidiennes) et semi-diurnes (biquotidiennes), parmi laquelle ces dernières prédominent principalement. Les amplitudes des marées dans la partie supérieure de la baie de Fundy dépassent communément 15 mètres, en grande partie en raison des forces tectoniques qui ont sculpté la baie au cours du Trias. L'existence et l'emplacement de la baie sont principalement déterminés par un semi-graben, le bassin de Fundy, dont l'établissement remonte au début de l'ouverture de l'océan Atlantique. Vu les proportions de la baie de Fundy, les différences d'amplitude des marées à l'intérieur du système du golfe du Maine, de la baie de Fundy et du Banc Georges sont régies par une quasi-résonance avec les marées de contrainte de l'Atlantique Nord. Même si les courbes des marées de Fundy sont sinusoïdales, les prévisions des marées nécessitent la considération d'inégalités diurnes distinctes. Le chevauchement des cycles des marées de vives-eaux et des marées de périgée tous les 206 jours entraîne une progression annuelle de 1,5 mois des périodes de marées particulièrement élevées. Selon l'année, ces marées de grande envergure peuvent survenir toutes les saisons. Les marées les plus fortes de Fundy apparaissent lorsque les trois éléments – les cycles mensuels anomalistique, synodique et tropique – culminent simultanément. Le jumelage le plus proche survient à des intervalles de 18,3 ans en vertu d'un cycle appelé le cycle Saros. Les mouvements des marées de l'anse Herring dans le parc national Fundy illustrent les variations annuelles des marées anticipées. Les interactions entre la terre et la mer dans les régions macrotidales comme la baie de Fundy sont caractérisées par des conditions de quasi-équilibre intenses. Des estuaires, éphémères à l'échelle des temps géologiques, se remplissent progressivement de sédiments au fur et à mesure que s'élève le niveau relatif de la mer, ce qui force les marais salés en bordure à passer à des niveaux successivement supérieurs. Même si les marais salés de Fundy sont étroitement liés à un régime de marées de grande amplitude et de courants périodiques puissants, ils débordent rarement. Comme ces marais sont établis à environ 1,2 mètre de moins que les marées astronomiques les plus élevées, seules les très grandes marées peuvent les recouvrir d'une couche d'eau d'une profondeur substantielle. Les marées les plus importantes se présentent en série à des périodes de sept mois, 4,53 ans et 18,03 ans. Aucune inondation des marais élevés due aux marées ne survient pendant des mois et des mois. La majorité des marais salés s'élèvent au niveau moyen du cycle de 18 ans. Les emplacements exacts des niveaux d'eau des zones côtières, comme le niveau moyen des hautes-eaux et le niveau moyen des basses-eaux, ne cessent de poser des problèmes et font l'objet de beaucoup de litiges. Les courbes de marées établies dans le cas de certains estuaires de rivières illustrent de quelle façon les vagues des marées estuariennes se transforment le long de leur trajet pour former des mascarets et dans quelle mesure varient leur capacité de transport de sédiments et capacité d'érosion par suite des variations des pentes de la ligne d'eau. Les saisons qui se succèdent entraînent des changements spectaculaires du caractère des estuaires, en particulier lorsque des glaces apparaissent au cours de la seconde moitié du cycle de 206 jours, quand la différence de hauteur entre la marée de mortes-eaux et la marée de vives-eaux s'accroît, moment optimal de débordement au cours de n'importe quelle saison. Le danger maximal de glaces, notamment l'apparition de « murs de glace » dans les estuaires de Fundy, survient un ou deux mois avant que les marées de périgée et de vives-eaux se combinent pour former la marée la plus importante du cycle. Même si les « murs de glace » et les phénomènes connexes posent des dangers aux constructions érigées, ils servent des fins naturelles importantes qu'il faut considérer dans les programmes d'aménagement et de mise en valeur des côtes. Les marées jouent un rôle marquant dans l'érosion et dans les interactions complexes au sein des processus physiques, biologiques et chimiques de Fundy. Les observations récentes des modifications des grosseurs des grains des vasières, les secteurs d'approfondissement marqué du plancher océanique et les changements survenus dans la communauté benthique révèlent que les conditions du milieu de la baie changent, possiblement en raison de l'énergie hydrodynamique accrue à l'intérieur du système. [Traduit par la rédaction

Geochemistry of Ordovician black shales at Meductic, southern Miramichi Highlands, New Brunswick

The geochemistry of black shales is useful for identifying geological events such as anoxia, for predicting the proximity of submarine hydrothermal springs and associated mineral deposits, and for indicating the existence of mineral deposits in precursor terrains. In the Miramichi Highlands of New Brunswick, large massive sulfide deposits occur in a mid-Ordovician (Llanvirnian) sequence of felsic volcanic and sedimentary rocks of the Tetagouche Group, disconformably overlying relatively monotonous quartzose wacke and grey-green shale of the Miramichi Group. Black shales commonly occur at the boundary between the Miramichi and Tetagouche groups, and in some areas such as at Meductic in the southern Miramichi Highlands, they display high heavy metal values in common with Scandinavian-Caledonide black shales. Like the massive sulphide deposits, the Meductic metalliferous black shales were deposited in a back-arc basin associated with an island-arc system formed during the closing of the proto-Atlantic Ocean and the onset of the Taconian orogeny. The average Meductic black shale, as deduced from the Bright Eye Brook Formation at the base of the Tetagouche Group, shows high values of V and Ba, moderate enrichment in Nb, Th, Pb, Ti, and Crf and depletion in Sr, Cu and Ni compared to black shale USGS standard SDO-1. Total organic carbon is well above the minimum value for a carbonaceous shale, the highest value (2.35%) corresponding to highest V (3016 ppm) and highest Ba (16,173 ppm). CaO, Fe2O3 and MnO contents are low, and SiO2, K2O and P2O5 contents are relatively high compared to the standard. Chondrite-normalized REE patterns show elevated LREE, fairly flat HREE signatures, a negative Eu anomaly and a slightly positive Cc anomaly. These features are characteristic of marine volcanological detrital input rather than a hydrothermal regime. Correlation of high V with Ba indicates that conditions were favourable for deposition of both metals. It is postulated that early deposition in an oxic environment (higher than normal MnO) was succeeded by gradual stagnation (increasing levels of V). Concomitant enrichment in Ba under anoxic conditions was linked to a regime of elevated heat flow. This scenario is compatible with the record of sea level fluctuations during the early Palaeozoic. RÉSUMÉ L'analyse géochimique des schistes noirs permet de deceler des phénomènes géologiques comme l'anoxie, qui annonce la proximité de sources hydrothermales sous-marines et de gites minéraux connexes et qui révèle l'existence de gttes minéraux dans des terrains précurseurs. Dans les hautes terres de Miramichi, au Nouveau-Brunswick, on relève des gisements de sulfures massifs importants dans une séquence de l'Ordovicien moyen (Llanvirnien) de roches sédimentaires et volcanofelsiques du groupe de Tetagouche qui recouvrent de fa÷on discordante des wackes quartzeuses relativement monotones et des schistes gris-vert du groupe de Miramichi. On trouve couramment des schistes noirs le long de la frontière séparant les groupes de Miramichi et de Tetagouche; de plus, dans certains secteurs, comme eclui de Meductic, dans le sud des hautes terres de Miramichi, les schistes noirs affichent, en commun avec des schistes noirs scandinaviens-calédoniens, des valeurs élevées de métaux lourds. À l'instar des gisements de sulfures massifs, les schistes noirs métalliferes de Meductic se sont déposés dans des bassins arrière-arcs associés a un système d'arcs insulaires formé lors de la fermeture de l'ocean proto-atlantique et au début de l'orogenèse taconique. Les schistes noirs de Meductic moyens, d'après ce qu'on en déduit de la Formation de Bright Eye Brook à labase du groupe de Tetagouche, affichent des valeurs élevéens de V et de Ba, un enrichissement moyen en Nb, Th,Pb, Ti et Cr, ainsi qu'une réduction de Sr, de Cu et de Ni, comparativement à la norme SDO-1 du USGS. Lecarbone organique total se situé bien au-dessus de la valcur minimale d'un schiste charbonneux, la valeur la plus élevée (2,35 %) correspondant aux teneurs les plus élevées en V (3 016 mg/kg) et en Ba (16 173 mg/kg). Lesteneurs en CaO, Fe2O3 et en MnO sont basses et celles en SiO2, K2O et P2O5 sont relativement élevées comparativementaux teneurs normales. Les modeles d'ETR réduits en chondrites affichent des quantités élevées d'éléments deterres rares legers, des signatures d'éléments de terres rares lourds passablement uniformes, une anomalie négatived'Eu et une anomalie légèrement positive de Ce. Ces traits sont caractéristiques d'un apport détritique volcanologiquemarin ptutôt que d'un régime hydrothermal. La corrélation de valeurs élevées de V et de B revéle que les conditions étaient propices à la sédimentation des deux métaux. On suppose qu'une sédimentation précoce dans unmilieu oxique (présence de MnO supérieure à la normale) a été suivie par une stagnation graduelle (nivcaux croissants de V). On a relié l'enrichissement concomitant en Ba dans des conditions anoxiques à un régime deflux thermique élevé. Ce scénario est compatible avec les fluctuations du niveau de la mer enregistrées au coursdu Paléozoique inférieur. [Traduit par la réedaction

Reduction spheroids from the Upper Carboniferous Hopewell Group, Dorchester Cape, New Brunswick: notes on geochemistry, mineralogy and genesis

The bajada-playa sequence of terrestrial Upper Carboniferous redbeds of the Hopewell Group at Dorchester Cape, New Brunswick, hosts innumerable reduction spheroids in fine- to coarse-grained clastic sedimentary rocks, paleosols and caliche beds. The spheroids are grey-green, typically 2 to 3 cm in diameter, and may contain a dark, mineralized central core and less commonly one or more mineralized rings, concentric about the core. They decrease progressively in average diameter from 2.75 cm at the base to 0.85 cm at the top of an overall upward-fining 250 m thick measured stratigraphic section. Conditions controlling the genesis of the spheroids were established shortly after sedimentation. Development was subtly controlled by groundwater flow patterns and by various sedimentary structures. The enclosing redbeds provide an adequate source for the metals contained in the mineralized spheroids. Low-temperature chloride complexes originating from evaporative fluids concentrated during redbed formation are believed to have been responsible for transport of the metals to reduction sites. Precipitation probably occurred as a result of a change in redox potential governed by electrical self-potentials of various detrital and early diagenetic grains, particularly pyritc and/or Fe-Ti oxides. Electron microprobc analyses reveal Cu, Ag, Fe, Ti, U, V and REE enrichments in reduction spheroid cores. Mineralized rings arc less enriched in these elements but contain slightly greater concentrations of Ti-oxide minerals. Minerals observed other than bulk redbed constituents include: chatcocite, covellitc, cuprite, pyritc, il-menite, rutile, mottramite, roscoelite, xenotime, monazite, native copper, azurite and native silver with trace amounts of alloyed Hg. RÉSUMÉ La séquence de bajadas-playas des formations rouges terrestres du Carbonifere supérieur du groupe de Hopewell à Dorchester Cape, Nouveau-Brunswick, abrite d'innombrables sphéroides de réduction dans des couches de caliche, dc paléosol et de sédiments clastiques à grain fin à gros. Les sphéroides sont de couleur gris-vert, its ont généralement 2 à 3 cm de diamètre et ils peuvent renfermer un noyau central minéralisé de teinte foncée de même que, moins couramment, un ou plusieurs anneaux minéralisés concentriques au noyau. Leur diamètre moyen diminuc graduellement, passant de 2,75 cm à la base a 0,85 cm au sommet d'une section stratigraphique à affinement généralement ascendant d'une épaisseur mesurée de 250 m. Les conditions ay ant régi l'origine des sphéroldes ont été établies peu après la sédimentation. Leur développement a été subtilement gouverné par les configurations d'écoulement des eaux souterraines ct par diverses structures sédimentaires. Les formations rouges encaissantes constituent une source adéquate des métaux que ren ferment les sphéroldes minéraliseés. On croit que les complexes chlorurés de basse température provenant des fluides volatils concentrés pendant la constitution des formations rouges ont causé le transport des métaux à des points de réduction. Des précipitations sont probablement survenucs par suite d'un changement du potentiel d'oxydor&Juction gouverné par les polarisations spontanées éiectriques de divers grains diagénétiques détritiques ct anciens, en particulier de la pyrite ou des oxydes de fer-titane. Les analyses par microsonde éiectronique révèlent des enrichissements de Cu, d'Ag, de Fe, de Ti, d'U, de V et d'éléments des terres rares dans les noyaux des sphéroldes de réduction. Les anneaux minéralisés renferment des proportions moindres de certains de ces éléments, mais des concentrations légèrement plus fortes d'oxyde dc titane. Outre les composants bruts des couches rouges, les minéraux observes comprennent de la chalcocyte, de la covellite, de la cuprite, de la pyritc, de l'ilménite, du rutile, de la mottramite, de la roscoélite, du xénotime, du monazite, du cuivrc natif, de l’azurite et de l’argent natif avec des quantités infimes de mcrcure allie. [Traduit par la rédaction

Gene expression profiling of human myeloid leukemic MV4-11 cells treated with 5-Aza-2’-deoxycytidine

The pyrimidine analog, 5-aza-2’-deoxycytidine (5-aza-dC) is a DNA methyltransferase inhibitor that triggers DNA demethylation leading to the reactivation of epigenetically silenced tumor suppressor genes. To understand the shift in gene expression which mediates the beneficial 5-aza-dC effects in leukemia, we have treated human myeloid derived leukemic cells with 5-aza-dC. Target genes were identified first in MV4-11 cells using a genome-wide gene expression profiling assay to detect differences in treated and untreated cells. From this analysis six genes were identified (HOXA4, HOXD4, HOXA8, HOXD12, CD9 and RGS2) as being significantly different expressed after treatment. To validate microarray data, we performed quantitative PCR on these genes from multiple leukemic cells. The results suggest that these genes are epigenetically regulated indicating that dysregulation of HOXA4, HOXD4, HOXA8, HOXD12, CD9 and RGS2 expression may play an important role in establishing the malignant phenotype in AML

Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site's former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services

The Chandra Source Catalog

The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~ 30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1 sigma uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of <~ 1 false source per field for a 100 ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively.Comment: To appear in The Astrophysical Journal Supplement Series, 53 pages, 27 figure

Bioinformatics-Based Identification of Expanded Repeats: A Non-reference Intronic Pentamer Expansion in RFC1 Causes CANVAS

Genomic technologies such as next-generation sequencing (NGS) are revolutionizing molecular diagnostics and clinical medicine. However, these approaches have proven inefficient at identifying pathogenic repeat expansions. Here, we apply a collection of bioinformatics tools that can be utilized to identify either known or novel expanded repeat sequences in NGS data. We performed genetic studies of a cohort of 35 individuals from 22 families with a clinical diagnosis of cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS). Analysis of whole-genome sequence (WGS) data with five independent algorithms identified a recessively inherited intronic repeat expansion [(AAGGG)exp] in the gene encoding Replication Factor C1 (RFC1). This motif, not reported in the reference sequence, localized to an Alu element and replaced the reference (AAAAG)11 short tandem repeat. Genetic analyses confirmed the pathogenic expansion in 18 of 22 CANVAS-affected families and identified a core ancestral haplotype, estimated to have arisen in Europe more than twenty-five thousand years ago. WGS of the four RFC1-negative CANVAS-affected families identified plausible variants in three, with genomic re-diagnosis of SCA3, spastic ataxia of the Charlevoix-Saguenay type, and SCA45. This study identified the genetic basis of CANVAS and demonstrated that these improved bioinformatics tools increase the diagnostic utility of WGS to determine the genetic basis of a heterogeneous group of clinically overlapping neurogenetic disorders

Statistical Characterization of the Chandra Source Catalog

The first release of the Chandra Source Catalog (CSC) contains ~95,000 X-ray sources in a total area of ~0.75% of the entire sky, using data from ~3,900 separate ACIS observations of a multitude of different types of X-ray sources. In order to maximize the scientific benefit of such a large, heterogeneous data-set, careful characterization of the statistical properties of the catalog, i.e., completeness, sensitivity, false source rate, and accuracy of source properties, is required. Characterization efforts of other, large Chandra catalogs, such as the ChaMP Point Source Catalog (Kim et al. 2007) or the 2 Mega-second Deep Field Surveys (Alexander et al. 2003), while informative, cannot serve this purpose, since the CSC analysis procedures are significantly different and the range of allowable data is much less restrictive. We describe here the characterization process for the CSC. This process includes both a comparison of real CSC results with those of other, deeper Chandra catalogs of the same targets and extensive simulations of blank-sky and point source populations.Comment: To be published in the Astrophysical Journal Supplement Series (Fig. 52 replaced with a version which astro-ph can convert to PDF without issues.

Long Term Transcriptional Reactivation of Epigenetically Silenced Genes in Colorectal Cancer Cells Requires DNA Hypomethylation and Histone Acetylation

Epigenetic regulation of genes involves the coordination of DNA methylation and histone modifications to maintain transcriptional status. These two features are frequently disrupted in malignancy such that critical genes succumb to inactivation. 5-aza-2′-deoxycytidine (5-aza-dC) is an agent which inhibits DNA methyltransferase, and holds great potential as a treatment for cancer, yet the extent of its effectiveness varies greatly between tumour types. Previous evidence suggests expression status after 5-aza-dC exposure cannot be explained by the DNA methylation status alone. Aim: We sought to identify chromatin changes involved with short and long term gene reactivation following 5-aza-dC exposure. Two colorectal cancer cell lines, HCT116 and SW480, were treated with 5-aza-dC and then grown in drug-free media to allow DNA re-methylation. DNA methylation and chromatin modifications were assessed with bisulfite sequencing and Chromatin Immuno-Precipitation analysis. Results: Increased H3 acetylation, H3K4 tri-methylation and loss of H3K27 tri-methylation were associated with reactivation. Hypermethylated genes that did not show increased acetylation were transiently expressed with 5-aza-dC treatment before reverting to an inactive state. Three reactivated genes, CDO1, HSPC105 and MAGEA3, were still expressed 10 days post 5-aza-dC treatment and displayed localised hypomethylation at the transcriptional start site, and also an increased enrichment of histone H3 acetylation. Conclusions: These observations suggest that hypomethylation alone is insufficient to reactivate silenced genes and that increased Histone H3 acetylation in unison with localised hypomethylation allows long term reversion of these epigenetically silenced genes. This study suggests that combined DNA methyltransferase and histone deacetylase inhibitors may aid long term reactivation of silenced genes

Toxicity of lunar dust

The formation, composition and physical properties of lunar dust are incompletely characterised with regard to human health. While the physical and chemical determinants of dust toxicity for materials such as asbestos, quartz, volcanic ashes and urban particulate matter have been the focus of substantial research efforts, lunar dust properties, and therefore lunar dust toxicity may differ substantially. In this contribution, past and ongoing work on dust toxicity is reviewed, and major knowledge gaps that prevent an accurate assessment of lunar dust toxicity are identified. Finally, a range of studies using ground-based, low-gravity, and in situ measurements is recommended to address the identified knowledge gaps. Because none of the curated lunar samples exist in a pristine state that preserves the surface reactive chemical aspects thought to be present on the lunar surface, studies using this material carry with them considerable uncertainty in terms of fidelity. As a consequence, in situ data on lunar dust properties will be required to provide ground truth for ground-based studies quantifying the toxicity of dust exposure and the associated health risks during future manned lunar missions.Comment: 62 pages, 9 figures, 2 tables, accepted for publication in Planetary and Space Scienc