Holonomic quantum gates: A semiconductor-based implementation

We propose an implementation of holonomic (geometrical) quantum gates by means of semiconductor nanostructures. Our quantum hardware consists of semiconductor macroatoms driven by sequences of ultrafast laser pulses ({\it all optical control}). Our logical bits are Coulomb-correlated electron-hole pairs (excitons) in a four-level scheme selectively addressed by laser pulses with different polarization. A universal set of single and two-qubit gates is generated by adiabatic change of the Rabi frequencies of the lasers and by exploiting the dipole coupling between excitons.Comment: 10 Pages LaTeX, 10 Figures include

Controls on natural gas migration in the western Nile Delta fan

The aim of this study is to combine petrophysical and geochemical data in order to reconstruct the migration history and pathways of mixed microbial-thermogenic gases drilled on the Nile Delta fan, offshore Egypt. While general interest lies in understanding migration routes, rates and mechanisms special attention is dedicated to understanding (1) the origin of gas in both reservoir and non-reservoir units using chemical and isotopic fingerprints and (2) whether a free gas phase supports relatively rapid leakage via bulk flow in non-reservoir units, both above and below commercial accumulations. The Pilocene section in this study is a classic slope environment comprising channels, mud-rich turbidites, mass transport complexes and hemipelagites. Data from seismic and drilled wells suggest that the channel and levee reservoirs are rarely full to spill, implying either a lack of charge and leakage rates which precludes complete filling of the structures. The provided data set enables a quantitative assessment of gas distribution and its genetic fingerprint in the context of both stratigraphic position and lithology. Data is reported from 25 wells, each provided with a conventional wireline log suite and some with borehole images and high-quality core images. Gas concentration data, plus compositional and isotope data are available for isotubes and headspace gas for both reservoir and non-reservoir units. Small-to-medium scale linear and non-linear depth shifts between different techniques (core recovery, core logging, wireline logging) in conjunction with scale and resolution issues demanded logical/stochastic depth synchronisation and well as harmonisation of signal resolution (typically up-scaling). Accordingly, great care was taken to depth-match core, log and gas data. In general, there is evidence of leaking thermogenic and partly biodegraded gas from the reservoirs under investigation, while some microbial methane appears to be retained in the cap rock. Careful assessment of the maturity of the thermogenic gas charge suggests that in a given structure, maturities are similar throughout the sampled section of underseal, reservoir and top seal. Furthermore, compositional temperature stratification suggests a balance between influx of fresh gas and microbial metabolism rates, supporting the concept of a dynamic charge-leak scenario that is sustaining hydrocarbon fermenting microbial communities in the deep biosphere. It was found that microbial recycling of hydrocarbons at depth enables the identification of diffusive gas mixing pathways in the combined analysis of methane and ethane compositional and isotopic data. The proposed diffusion pattern supports the idea of a widely present coupling between both methanogenic and biodegrading microbial communities that exhibit strong carbon isotopic dis-balances at gas-water contacts (GWC) where nutrient supply is in favour of the biodegrading metabolism. Although the hypothesis of coupled diffusive/microbial gas overprints complies with (1) various literature reports that microbial attack on free gas phases is hindered by restricted physical access and (2) segregative isotope fractionation as a consequence of differences on methane and ethane diffusivity, it is conditional to the nature of gas mixing patterns along borehole trajectories in the context of lithology and pore fluid saturations. Undoubtedly, the ubiquitous presence of microbial gas has consequences for vertical net leakage. As classic empirical wireline models for hydrocarbon saturation (i.e. free gas phase volumetrics) are not suited for clay-dominated cap rock sections, an alternative approach presented in this study is based on total gas (TG) modelling from nuclear logs and its solubility in the formation of brine. The calibrated saturation model is scale-independent and implies that free gas occurs on the most of the clay-dominated non-reservoir sections. However, model resolution is not sufficient to capture the suspected filamentary network of free gas phase within the mudrock pore space that enables relatively rapid leakage via Darcy flow. In an unique attempt to validate manual and thereby subjective lithofacies allocations to core images a subset of rock sample properties such as grain size fractions and porosity were successfully modelled using quantitative core image properties. However, model validity appears to be restricted to clay-rich lithofacies due to both an absence of calibration data for sands and occurrence of abnormally dark sandstone units. Further, an artificial neural network (ANN) was trained to propagate the calibrated core fancies along the entire wireline logged borehole section to set the lithological context for a detailed fluid flow analysis. Reproducibility of input (core) facies by output (wireline) facies is similar to the reproducibility by fellow geoscientists but could not be significantly improved to 60-80% of reliability by reduction of facies types. The study shows that a combination of geochemical data with lithological and petro-physical information generates detailed insights into rates, mechanisms, and pathways of two phase flow through the deep biosphere of gas-charged basins. Vertical, geologically rapid flow through mud-rich sequences is a viable migration route for gas if the influence of cap rock bypass systems (permeable faults, sandstone intrusions, mud volcanoes etc.) is restricted. It was found that an adequate quantification of both thermogenic gas fraction and diffusive gas mixing fingerprints is crucial to identity stratigraphic intervals that are not dominated by advective leakage through the pore space and are consequently bypassed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Dysfunctional autophagy induced by the pro-apoptotic natural compound climacostol in tumour cells

Autophagy occurs at a basal level in all eukaryotic cells and may support cell survival or activate death pathways. Due to its pathophysiologic significance, the autophagic machinery is a promising target for the development of multiple approaches for anti-neoplastic agents. We have recently described the cytotoxic and pro-apoptotic mechanisms, targeting the tumour suppressor p53, of climacostol, a natural product of the ciliated protozoan Climacostomum virens. We report here on how climacostol regulates autophagy and the involvement of p53-dependent mechanisms. Using both in vitro and in vivo techniques, we show that climacostol potently and selectively impairs autophagy in multiple tumour cells that are committed to die by apoptosis. In particular, in B16-F10 mouse melanomas climacostol exerts a marked and sustained accumulation of autophagosomes as the result of dysfunctional autophagic degradation. We also provide mechanistic insights showing that climacostol affects autophagosome turnover via p53-AMPK axis, although the mTOR pathway unrelated to p53 levels plays a role. In particular, climacostol activated p53 inducing the upregulation of p53 protein levels in the nuclei through effects on p53 stability at translational level, as for instance the phosphorylation at Ser15 site. Noteworthy, AMPK\u3b1 activation was the major responsible of climacostol-induced autophagy disruption in the absence of a key role regulating cell death, thus indicating that climacostol effects on autophagy and apoptosis are two separate events, which may act independently on life/death decisions of the cell. Since the activation of p53 system is at the molecular crossroad regulating both the anti-autophagic action of climacostol and its role in the apoptosis induction, it might be important to explore the dual targeting of autophagy and apoptosis with agents acting on p53 for the selective killing of tumours. These findings also suggest the efficacy of ciliate bioactive molecules to identify novel lead compounds in drug discovery and development

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

State of the climate in 2018

In 2018, the dominant greenhouse gases released into Earth’s atmosphere—carbon dioxide, methane, and nitrous oxide—continued their increase. The annual global average carbon dioxide concentration at Earth’s surface was 407.4 ± 0.1 ppm, the highest in the modern instrumental record and in ice core records dating back 800 000 years. Combined, greenhouse gases and several halogenated gases contribute just over 3 W m−2 to radiative forcing and represent a nearly 43% increase since 1990. Carbon dioxide is responsible for about 65% of this radiative forcing. With a weak La Niña in early 2018 transitioning to a weak El Niño by the year’s end, the global surface (land and ocean) temperature was the fourth highest on record, with only 2015 through 2017 being warmer. Several European countries reported record high annual temperatures. There were also more high, and fewer low, temperature extremes than in nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava in March, while South Korea set its record high of 41.0°C in August in Hongcheon. Nawabshah, Pakistan, recorded its highest temperature of 50.2°C, which may be a new daily world record for April. Globally, the annual lower troposphere temperature was third to seventh highest, depending on the dataset analyzed. The lower stratospheric temperature was approximately fifth lowest. The 2018 Arctic land surface temperature was 1.2°C above the 1981–2010 average, tying for third highest in the 118-year record, following 2016 and 2017. June’s Arctic snow cover extent was almost half of what it was 35 years ago. Across Greenland, however, regional summer temperatures were generally below or near average. Additionally, a satellite survey of 47 glaciers in Greenland indicated a net increase in area for the first time since records began in 1999. Increasing permafrost temperatures were reported at most observation sites in the Arctic, with the overall increase of 0.1°–0.2°C between 2017 and 2018 being comparable to the highest rate of warming ever observed in the region. On 17 March, Arctic sea ice extent marked the second smallest annual maximum in the 38-year record, larger than only 2017. The minimum extent in 2018 was reached on 19 September and again on 23 September, tying 2008 and 2010 for the sixth lowest extent on record. The 23 September date tied 1997 as the latest sea ice minimum date on record. First-year ice now dominates the ice cover, comprising 77% of the March 2018 ice pack compared to 55% during the 1980s. Because thinner, younger ice is more vulnerable to melting out in summer, this shift in sea ice age has contributed to the decreasing trend in minimum ice extent. Regionally, Bering Sea ice extent was at record lows for almost the entire 2017/18 ice season. For the Antarctic continent as a whole, 2018 was warmer than average. On the highest points of the Antarctic Plateau, the automatic weather station Relay (74°S) broke or tied six monthly temperature records throughout the year, with August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea sector contributed to a low melt season overall for 2017/18. High SSTs contributed to low summer sea ice extent in the Ross and Weddell Seas in 2018, underpinning the second lowest Antarctic summer minimum sea ice extent on record. Despite conducive conditions for its formation, the ozone hole at its maximum extent in September was near the 2000–18 mean, likely due to an ongoing slow decline in stratospheric chlorine monoxide concentration. Across the oceans, globally averaged SST decreased slightly since the record El Niño year of 2016 but was still far above the climatological mean. On average, SST is increasing at a rate of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared largest in the tropical Indian Ocean and smallest in the North Pacific. The deeper ocean continues to warm year after year. For the seventh consecutive year, global annual mean sea level became the highest in the 26-year record, rising to 81 mm above the 1993 average. As anticipated in a warming climate, the hydrological cycle over the ocean is accelerating: dry regions are becoming drier and wet regions rainier. Closer to the equator, 95 named tropical storms were observed during 2018, well above the 1981–2010 average of 82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s landfall intensity of 140 kt was the fourth strongest for any continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and $25 billion (U.S. dollars) in damages. In the western North Pacific, Super Typhoon Mangkhut led to 160 fatalities and$6 billion (U.S. dollars) in damages across the Philippines, Hong Kong, Macau, mainland China, Guam, and the Northern Mariana Islands. Tropical Storm Son-Tinh was responsible for 170 fatalities in Vietnam and Laos. Nearly all the islands of Micronesia experienced at least moderate impacts from various tropical cyclones. Across land, many areas around the globe received copious precipitation, notable at different time scales. Rodrigues and Réunion Island near southern Africa each reported their third wettest year on record. In Hawaii, 1262 mm precipitation at Waipā Gardens (Kauai) on 14–15 April set a new U.S. record for 24-h precipitation. In Brazil, the city of Belo Horizonte received nearly 75 mm of rain in just 20 minutes, nearly half its monthly average. Globally, fire activity during 2018 was the lowest since the start of the record in 1997, with a combined burned area of about 500 million hectares. This reinforced the long-term downward trend in fire emissions driven by changes in land use in frequently burning savannas. However, wildfires burned 3.5 million hectares across the United States, well above the 2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded $40 billion (U.S. dollars)