261 research outputs found
Single-valley high-mobility (110) AlAs quantum wells with anisotropic mass
We studied a doping series of (110)-oriented AlAs quantum wells (QWs) and
observed transport evidence of single anisotropic-mass valley occupancy for the
electrons in a 150 \AA wide QW. Our calculations of strain and quantum
confinement for these samples predict single anisotropic-mass valley occupancy
for well widths greater than 53 \AA. Below this, double-valley occupation
is predicted such that the longitudinal mass axes are collinear. We observed
mobility anisotropy in the electronic transport along the crystallographic
directions in the ratio of 2.8, attributed to the mass anisotropy as well as
anisotropic scattering of the electrons in the X-valley of AlAs
Response of stratospheric water vapor and ozone to the unusual timing of El Niño and the QBO disruption in 2015–2016
The stratospheric circulation determines the transport and lifetime of key trace gases in a changing climate, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño–Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 2015–2016. Here, we quantify the impact of the alignment of these two phenomena in 2015–2016 on lower stratospheric water vapor and ozone from satellite observations. We show that the warm ENSO event substantially increased water vapor and decreased ozone in the tropical lower stratosphere. The QBO disruption significantly decreased global lower stratospheric water vapor and tropical ozone from early spring to late autumn. Thus, this QBO disruption reversed the lower stratosphere moistening triggered by the alignment of the warm ENSO event with westerly QBO in early boreal winter. Our results suggest that the interplay of ENSO events and QBO phases will be crucial for the distributions of radiatively active trace gases in a changing future climate, when increasing El Niño-like conditions and a decreasing lower stratospheric QBO amplitude are expected
Polyphenol oxidases exhibit promiscuous proteolytic activity
Tyrosinases are an industrially significant class of polyphenol oxidase. Here, two tyrosinases are shown to cleave a specific peptide bond in a carboxylesterase, yielding a truncated product with higher catalytic activity than the full-length enzyme
Unique crystal structure of a novel surfactant protein from the foam nest of the frog Leptodactylus vastus.
Made available in DSpace on 2018-06-26T01:01:48Z (GMT). No. of bitstreams: 1
cavalcante2014.pdf: 808321 bytes, checksum: a927306da964e003eaa8404a49991b26 (MD5)
Previous issue date: 2015-01-19bitstream/item/115835/1/cavalcante2014.pd
The TropD software package (v1): standardized methods for calculating tropical-width diagnostics
Observational and modeling studies suggest that Earth's tropical belt has
widened over the late 20th century and will continue to widen throughout the
21st century. Yet, estimates of tropical-width variations differ significantly
across studies. This uncertainty, to an unknown degree, is partly due to the
large variety of methods used in studies of the tropical width. Here, methods
for eight commonly used metrics of the tropical width are implemented in the
Tropical-width Diagnostics (TropD) code package in the MATLAB programming
language. To consolidate the various methods, the operations used in each of
the implemented methods are reduced to two basic calculations: finding the
latitude of a zero crossing and finding the latitude of a maximum. A
detailed description of the methods implemented in the code and of the code
syntax is provided, followed by a method sensitivity analysis for each of the
metrics. The analysis provides information on how to reduce the
methodological component of the uncertainty associated with fundamental
aspects of the calculations, such as monthly vs. seasonal averaging biases,
grid dependence, sensitivity to noise, and sensitivity to threshold criteria.</p
Critical Behaviour of Non-Equilibrium Phase Transitions to Magnetically Ordered States
We describe non-equilibrium phase transitions in arrays of dynamical systems
with cubic nonlinearity driven by multiplicative Gaussian white noise.
Depending on the sign of the spatial coupling we observe transitions to
ferromagnetic or antiferromagnetic ordered states. We discuss the phase
diagram, the order of the transitions, and the critical behaviour. For global
coupling we show analytically that the critical exponent of the magnetization
exhibits a transition from the value 1/2 to a non-universal behaviour depending
on the ratio of noise strength to the magnitude of the spatial coupling.Comment: 4 pages, 5 figure
Mind the Costs: Rescaling and Multi-Level Environmental Governance in Venice Lagoon
Competences over environmental matters are distributed across agencies at different scales on a national-to-local continuum. This article adopts a transaction costs economics perspective in order to explore the question whether, in the light of a particular problem, the scale at which a certain competence is attributed can be reconsidered. Specifically, it tests whether a presumption of least-cost operation concerning an agency at a given scale can hold. By doing so, it investigates whether the rescaling of certain tasks, aiming at solving a scale-related problem, is likely to produce an increase in costs for day-to-day agency operations as compared to the status quo. The article explores such a perspective for the case of Venice Lagoon. The negative aspects of the present arrangement concerning fishery management and morphological remediation are directly linked to the scale of the agencies involved. The analysis suggests that scales have been chosen correctly, at least from the point of view of the costs incurred to the agencies involved. Consequently, a rescaling of those agencies does not represent a viable option
Nonequilibrium wetting
When a nonequilibrium growing interface in the presence of a wall is
considered a nonequilibrium wetting transition may take place. This transition
can be studied trough Langevin equations or discrete growth models. In the
first case, the Kardar-Parisi-Zhang equation, which defines a very robust
universality class for nonequilibrium moving interfaces, with a soft-wall
potential is considered. While in the second, microscopic models, in the
corresponding universality class, with evaporation and deposition of particles
in the presence of hard-wall are studied. Equilibrium wetting is related to a
particular case of the problem, it corresponds to the Edwards-Wilkinson
equation with a potential in the continuum approach or to the fulfillment of
detailed balance in the microscopic models. In this review we present the
analytical and numerical methods used to investigate the problem and the very
rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure
Recommended from our members
The extratropical upper troposphere and lower stratosphere
The extratropical upper troposphere and lower stratosphere (Ex-UTLS) is a transition region between the stratosphere and the troposphere. The Ex-UTLS includes the tropopause, a strong static stability gradient and dynamic barrier to transport. The barrier is reflected in tracer profiles. This region exhibits complex dynamical, radiative, and chemical characteristics that place stringent spatial and temporal requirements on observing and modeling systems. The Ex-UTLS couples the stratosphere to the troposphere through chemical constituent transport (of, e.g., ozone), by dynamically linking the stratospheric circulation with tropospheric wave patterns, and via radiative processes tied to optically thick clouds and clear-sky gradients of radiatively active gases. A comprehensive picture of the Ex-UTLS is presented that brings together different definitions of the tropopause, focusing on observed dynamical and chemical structure and their coupling. This integral view recognizes that thermal gradients and dynamic barriers are necessarily linked, that these barriers inhibit mixing and give rise to specific trace gas distributions, and that there are radiative feedbacks that help maintain this structure. The impacts of 21st century anthropogenic changes to the atmosphere due to ozone recovery and climate change will be felt in the Ex-UTLS, and recent simulations of these effects are summarized and placed in context
Long-term prognostic significance of HER-2/neu in untreated node-negative breast cancer depends on the method of testing
INTRODUCTION: The prognostic significance of HER-2/neu in breast cancer is a matter of controversy. We have performed a study in 101 node-negative breast cancer patients with long-term follow-up not treated in the adjuvant setting, and analysed the prognostic significance of immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH), both separately and in combination, in comparison with traditional prognostic factors. METHODS: Overexpression was classified semiquantitatively according to a score (0 to 3+) (HER-2_SCO). FISH was used to analyse HER2/neu amplification (HER-2_AMP). Patients classified 2+ by IHC were examined with FISH for amplification (HER-2_ALG). Patients with 3+ overexpression as well as amplification of HER-2/neu were positive for the combined variable HER2_COM. These variables were compared with tumour size, histological grade and hormone receptor status. RESULTS: HER-2_SCO was 3+ in 20% of all tumours. HER-2_ALG was positive in 22% and amplification (HER-2_AMP) was found in 17% of all tumours. Eleven percent of the tumours showed simultaneous 3+ overexpression and amplification. Only histological grade (relative risk [RR] 3.22, 95% confidence interval [CI] 1.73–5.99, P = 0.0002) and HER-2_AMP (RR 2.47, 95% CI 1.12–5.48, P = 0.026) were significant for disease-free survival in multivariate analysis. For overall survival, both histological grade (RR 3.89, 95% CI 1.77–8.55, P = 0.0007) and HER-2_AMP (RR 3.08, 95% CI 1.24–7.66, P = 0.016) retained their independent significance. CONCLUSION: The prognostic significance of HER-2/neu in node-negative breast cancer depends on the method of testing: only the amplification of HER-2/neu is an independent prognostic factor for the long-term prognosis of untreated node-negative breast cancer
- …