An evaluation study for improving gap flow simulations in coastal areas on Portugal

Winds inferred by Synthetic Aperture Radar (SAR) satellites are a very important source of spatial wind field behavior along coastal areas particularly on small coastal areas that are temporary affected by strong flow disturbances mainly driven from land to the ocean. Gap flow circulations, among others, are an example of such wind phenomena disturbances which are not yet described by regional atmospheric models nor by CFD modeling. Such situations could compromise both offshore wind resource and park deployment studies on places affected by the presence of these phenomena types. A possible way to overcome this situation is the usage of SAR images assimilated into regional atmospheric models using certain type of assimilation techniques. In this work, a real case occurred in a coastal area in Portugal will be taken into account. A strong gap flow occurred during the beginning of the night 9 December 2010 was captured by a SAR image which was assimilated into the model. Some validation meteorological stations were used for validation purposes taken into account scenarios performed with and without wind SAR assimilation. Spatial results lead to the conclusion that the assimilation of SAR images improves the wind pattern results which reflects how SAR assimilation into the mesoscale models are important for simulating the coastal wind flow patterns

Effects of hydrogen uptake and yttrium doping on the oxidation of zirconium-yttrium alloys

Zirconium-based fuel cladding used in nuclear reactors is susceptible to significant hydrogen uptake during normal operating conditions. This results in the formation of zirconium hydride. The nucleation of a brittle hydride phase results in a degradation of cladding mechanical properties in the long term as plate-like hydrides provide pathways for the propagation of cracks in the cladding. These hydride structures can be modified to reduce the possibility of cracking by alloying yttrium into the zirconium. Yttrium acts as a hydrogen getter, and provides dispersed nucleation sites and nodular hydrides. Using yttrium has two drawbacks: increased hydrogen uptake and increased oxidation kinetics. Hydrogen uptake in zirconium-based cladding under simulated reactor water chemistry has been observed to be dependent upon the alloying elements commonly used in cladding material. An inverse relationship between power-law exponent of the weight gain and the hydrogen uptake has been observed. The space-charge-theory of oxidation has been used to explain the link between the kinetics and hydrogen uptake. Allowing for local charge imbalance to occur in the oxide creates an electric field. At thicker oxides, once the electric field becomes large enough, it will limit the electron flux resulting in a smaller power-law exponent. Alloying elements dope the oxide, either increasing or decreasing the net space charge in the oxide, and therefore changing the oxidation kinetics. Hydrogen serves as an additional charged species which can compensate for a limited electron flux, and at smaller values for the power-law exponent, greater hydrogen uptake occurs to compensate for this limited flux. This doctoral research investigates how increased hydrogen uptake due to yttrium, as well as yttrium doping of the oxide, affects the high temperatures steam oxidation kinetics of zirconium through systematic experimental work coupled with a computational study of oxygen, electron, and hydrogen diffusion. Experiments focused on the oxidation of 0.01-1 wt% yttrium in pure zirconium samples and the characterization of the resultant oxides and hydrides. A thermogravimetric analysis instrument was used to collect active weight gain during oxidation in both steam and oxygen/argon environments at temperatures ranging from 500C to 1100C. Synchrotron diffraction of the steam-exposed samples provided information about the hydrogen uptake through the intensity of the zirconium hydride phase, as well as identification of oxides formed. Powder diffraction samples were fabricated from oxidized samples to provide a stress free environment to study the effect of yttrium concentration on the oxides. Additional cross-sectional optical microscopy was performed to confirm the zirconium hydride phase evolution as a function of yttrium concentration. It was observed that without hydrogen, the addition of yttrium decreased the power-law exponent, n, from 0.39 to 0.31 at 500C due to an increase in the space charge. The rate constant, k, increased from 0.16(g/(m^2*t^n)) to 0.51(g/(m^2*t^n)) due to the generation of oxygen vacancies. In steam, significant hydrogen uptake occurred at 500C and 700C. Both the amount of hydrogen absorbed, and the oxidation power-law exponent increased (0.39 to 0.44) with increasing yttrium. These results are a departure from what has been previously observed. The powder diffraction data indicated that the amount of yttrium doping of the zirconia was directly related to both the temperature and concentration of yttrium in solid solution in the starting zirconium. To better understand the oxidation kinetics fit from the weight gain data, the Poisson-Nernst-Planck (PNP) system of differential equations was solved using Multiphysics Object Oriented Simulation Environment (MOOSE); the PNP system describes a space charge controlled oxidation model. These computations were performed by solving the steady state solution for increasing oxide thicknesses. It was found that the oxygen vacancy flux as a function of oxide thickness followed a power-law function allowing for the oxidation kinetics to be calculated from the oxide thickness-dependent flux equations. The resulting model was initially tested on an oxide with only electron/oxygen vacancy diffusion to compare with previous work, and then hydrogen was added as an additional charged species. The effect of changing the hydrogen diffusivity or hydrogen concentration at the steam/oxide interface was modeled. It was found that changing the diffusivity and concentration did not have a large effect on the oxidation kinetics; the hydrogen flux initially increased, however, the space charge effect countered the effects of the perturbations. Implementing a simple, flat chemical potential to simulate hydrogen gettering resulted in an increase in both the power-law exponent, n, from 0.4 to 0.47, and in the hydrogen uptake. Driving hydrogen into the system created a new current, necessitating increased hydrogen and oxygen vacancy fluxes to compensate. This resulted in an increase in the oxygen diffusion into the oxide and an increase in n. By increasing this chemical potential, which simulated an increase in the yttrium concentration, both the hydrogen uptake and power-law exponent increased. An additional result from the modeling was the observation that the value of the rate constant, k, changed inversely with that of the power-law exponent n. Several important conclusions can be drawn from this work. First, using yttrium as an alloying element will increase the steam oxidation rate of zirconium at intermediate temperatures (500C to 900C), and result in an increased hydrogen uptake. Fortunately, the effects of yttrium on the oxidation kinetics at high temperatures which would be experienced in accidents are either nonexistent or beneficial. Second, hydrogen uptake driven-oxidation instead of oxidation-driven hydrogen uptake was observed. This serves as additional confirmation of the space charge oxidation model can be used to describe the oxidation kinetics of zirconium

Steam oxidation of FeCrAl coated Zircaloy-2

A NEITZCH Jupiter 441 simultaneous thermal analysis with a water vapor furnace was installed and calibrated for temperature and di fferential scanning calorimetry (DSC). Bare and FeCrAl coated Zircaloy-2 nuclear fuel cladding and FeCrAl coated single crystal Yttria stabilized Zirconia (YSZ) samples were oxidized in an argon/steam environment at 700 C and 1100 C. FeCrAl coated Zircaloy-2 was also heated to 1200 C in an inert environment. Real-time thermo gravimetric analysis (TGA) and DSC data was taken during the steam oxidation. Glancing angle and 2 theta-omega X-ray di raction (XRD) scans were taken of the samples pre- and post- exposure. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Auger electron spectroscopy (AES) depth profiling was performed. The TGA showed that the coated Zircaloy-2 samples experienced significantly less weight gain as compared to the bare Zircaloy-2 samples, indicating a slower rate of oxidation. AES and XRD showed that at 700 C this decrease was due to the formation of a protective alpha -alumina layer. Chromium segregated below the alumina layer to form a secondary layer. Finally it was observed that iron di fused into the base Zircaloy-2. At 1100 C a eutectic interaction between the zirconium and iron on the Zr exists and is postulated to have caused the evaporation of the coating and loss of protection. The FeCrAl on YSZ samples did not exhibit this phenomenon, however a spinel oxide was formed at 1100 C as opposed to alpha-alumina

INGX (inhibitor of growth family, X-linked, pseudogene)

Review on INGX, with data on DNA/RNA, on the protein encoded and where the gene is implicated

The Ten Martini Problem

We prove the conjecture (known as the ``Ten Martini Problem'' after Kac and Simon) that the spectrum of the almost Mathieu operator is a Cantor set for all non-zero values of the coupling and all irrational frequencies.Comment: 31 pages, no figure

Quantum Hall - insulator transitions in lattice models with strong disorder

We report results of numerical studies of the integer quantum Hall effect in a tight binding model on a two-dimensional square lattice with non-interacting electrons, in the presence of a random potential as well as a uniform magnetic field applied perpendicular to the lattice. We consider field magnitudes such that the area per flux quantum is commensurate with the lattice structure. Topological properties of the single electron wave functions are used to identify current carrying states that are responsible for the quantized Hall conductance. We study the interplay between the magnetic field and the disorder, and find a universal pattern with which the current carrying states are destroyed by increasing disorder strength, and the system driven into an insulating state. We also discuss how to interpolate results of lattice models to the continuum limit. The relationship to previous theoretical and experimental studies of quantum Hall-insulator transitions in strongly disordered systems at low magnetic fields is discussed.Comment: 20 pages, 6 figure

An In Vivo CRISPR Screening Platform for Prioritizing Therapeutic Targets in AML

CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in cancer, including acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because most of these screens have been performed in vitro using established cell lines, evaluating the physiologic relevance of these targets is critical. We have established a CRISPR screening approach using orthotopic xenograft models to validate and prioritize AML-enriched dependencies in vivo, including in CRISPR-competent AML patient-derived xenograft (PDX) models tractable for genome editing. Our integrated pipeline has revealed several targets with translational value, including SLC5A3 as a metabolic vulnerability for AML addicted to exogenous myo-inositol and MARCH5 as a critical guardian to prevent apoptosis in AML. MARCH5 repression enhanced the efficacy of BCL2 inhibitors such as venetoclax, further highlighting the clinical potential of targeting MARCH5 in AML. Our study provides a valuable strategy for discovery and prioritization of new candidate AML therapeutic targets. SIGNIFICANCE: There is an unmet need to improve the clinical outcome of AML. We developed an integrated in vivo screening approach to prioritize and validate AML dependencies with high translational potential. We identified SLC5A3 as a metabolic vulnerability and MARCH5 as a critical apoptosis regulator in AML, both of which represent novel therapeutic opportunities.This article is highlighted in the In This Issue feature, p. 275

Observing Sea States

Sea state information is needed for many applications, ranging from safety at sea and on the coast, for which real time data are essential, to planning and design needs for infrastructure that require long time series. The definition of the wave climate and its possible evolution requires high resolution data, and knowledge on possible drift in the observing system. Sea state is also an important climate variable that enters in air-sea fluxes parameterizations. Finally, sea state patterns can reveal the intensity of storms and associated climate patterns at large scales, and the intensity of currents at small scales. A synthesis of user requirements leads to requests for spatial resolution at kilometer scales, and estimations of trends of a few centimeters per decade. Such requirements cannot be met by observations alone in the foreseeable future, and numerical wave models can be combined with in situ and remote sensing data to achieve the required resolution. As today's models are far from perfect, observations are critical in providing forcing data, namely winds, currents and ice, and validation data, in particular for frequency and direction information, and extreme wave heights. In situ and satellite observations are particularly critical for the correction and calibration of significant wave heights to ensure the stability of model time series. A number of developments are underway for extending the capabilities of satellites and in situ observing systems. These include the generalization of directional measurements, an easier exchange of moored buoy data, the measurement of waves on drifting buoys, the evolution of satellite altimeter technology, and the measurement of directional wave spectra from satellite radar instruments. For each of these observing systems, the stability of the data is a very important issue. The combination of the different data sources, including numerical models, can help better fulfill the needs of users