42 research outputs found
Lattice model for cold and warm swelling of polymers in water
We define a lattice model for the interaction of a polymer with water. We
solve the model in a suitable approximation. In the case of a non-polar
homopolymer, for reasonable values of the parameters, the polymer is found in a
non-compact conformation at low temperature; as the temperature grows, there is
a sharp transition towards a compact state, then, at higher temperatures, the
polymer swells again. This behaviour closely reminds that of proteins, that are
unfolded at both low and high temperatures.Comment: REVTeX, 5 pages, 2 EPS figure
The NY-Ă lesund TurbulencE Fiber Optic eXperiment (NYTEFOX): investigating the Arctic boundary layer, Svalbard
The NY-Ă
lesund TurbulencE Fiber Optic eXperiment (NYTEFOX) was a field experiment at the
Ny-Ă
lesund Arctic site (78.9⊠N, 11.9⊠E) and yielded a unique meteorological data set. These data describe the
distribution of heat, airflows, and exchange in the Arctic boundary layer for a period of 14 d from 26 February
to 10 March 2020. NYTEFOX is the first field experiment to investigate the heterogeneity of airflow and its
transport of temperature, wind, and kinetic energy in the Arctic environment using the fiber-optic distributed
sensing (FODS) technique for horizontal and vertical observations. FODS air temperature and wind speed were
observed at a spatial resolution of 0.127 m and a temporal resolution of 9 s along a 700 m horizontal array at
1 m above ground level (a.g.l.) and along three 7 m vertical profiles. Ancillary data were collected from three
sonic anemometers and an acoustic profiler (minisodar; sodar is an acronym for âsound detection and rangingâ)
yielding turbulent flow statistics and vertical profiles in the lowest 300 m a.g.l., respectively. The observations
from this field campaign are publicly available on Zenodo (https://doi.org/10.5281/zenodo.4756836, Huss et al.,
2021) and supplement the meteorological data set operationally collected by the Baseline Surface Radiation
Network (BSRN) at Ny-Ă
lesund, Svalbard
Stochastic dynamics of model proteins on a directed graph
A method for reconstructing the energy landscape of simple polypeptidic
chains is described. We show that we can construct an equivalent representation
of the energy landscape by a suitable directed graph. Its topological and
dynamical features are shown to yield an effective estimate of the time scales
associated with the folding and with the equilibration processes. This
conclusion is drawn by comparing molecular dynamics simulations at constant
temperature with the dynamics on the graph, defined by a temperature dependent
Markov process. The main advantage of the graph representation is that its
dynamics can be naturally renormalized by collecting nodes into "hubs", while
redefining their connectivity. We show that both topological and dynamical
properties are preserved by the renormalization procedure. Moreover, we obtain
clear indications that the heteropolymers exhibit common topological
properties, at variance with the homopolymer, whose peculiar graph structure
stems from its spatial homogeneity. In order to obtain a clear distinction
between a "fast folder" and a "slow folder" in the heteropolymers one has to
look at kinetic features of the directed graph. We find that the average time
needed to the fast folder for reaching its native configuration is two orders
of magnitude smaller than its equilibration time, while for the bad folder
these time scales are comparable. Accordingly, we can conclude that the
strategy described in this paper can be successfully applied also to more
realistic models, by studying their renormalized dynamics on the directed
graph, rather than performing lengthy molecular dynamics simulations.Comment: 15 pages, 12 figure
MĂ©todo GPM-RAM para avaliação dos riscos ambientais e para saĂșde causados pelo uso de agroquĂmicos.
Hamiltonian dynamics of the two-dimensional lattice phi^4 model
The Hamiltonian dynamics of the classical model on a two-dimensional
square lattice is investigated by means of numerical simulations. The
macroscopic observables are computed as time averages. The results clearly
reveal the presence of the continuous phase transition at a finite energy
density and are consistent both qualitatively and quantitatively with the
predictions of equilibrium statistical mechanics. The Hamiltonian microscopic
dynamics also exhibits critical slowing down close to the transition. Moreover,
the relationship between chaos and the phase transition is considered, and
interpreted in the light of a geometrization of dynamics.Comment: REVTeX, 24 pages with 20 PostScript figure
Pre-Flight Calibration of the Mars 2020 Rover Mastcam Zoom (Mastcam-Z) Multispectral, Stereoscopic Imager
The NASA Perseverance rover Mast Camera Zoom (Mastcam-Z) system is a pair of zoomable, focusable, multi-spectral, and color charge-coupled device (CCD) cameras mounted on top of a 1.7 m Remote Sensing Mast, along with associated electronics and two calibration targets. The cameras contain identical optical assemblies that can range in focal length from 26 mm (25.5âĂ19.1â FOV) to 110 mm (6.2âĂ4.2â FOV) and will acquire data at pixel scales of 148-540 ÎŒm at a range of 2 m and 7.4-27 cm at 1 km. The cameras are mounted on the roverâs mast with a stereo baseline of 24.3±0.1 cm and a toe-in angle of 1.17±0.03â (per camera). Each camera uses a Kodak KAI-2020 CCD with 1600Ă1200 active pixels and an 8 position filter wheel that contains an IR-cutoff filter for color imaging through the detectorsâ Bayer-pattern filters, a neutral density (ND) solar filter for imaging the sun, and 6 narrow-band geology filters (16 total filters). An associated Digital Electronics Assembly provides command data interfaces to the rover, 11-to-8 bit companding, and JPEG compression capabilities. Herein, we describe pre-flight calibration of the Mastcam-Z instrument and characterize its radiometric and geometric behavior. Between April 26thth and May 9thth, 2019, âŒ45,000 images were acquired during stand-alone calibration at Malin Space Science Systems (MSSS) in San Diego, CA. Additional data were acquired during Assembly Test and Launch Operations (ATLO) at the Jet Propulsion Laboratory and Kennedy Space Center. Results of the radiometric calibration validate a 5% absolute radiometric accuracy when using camera state parameters investigated during testing. When observing using camera state parameters not interrogated during calibration (e.g., non-canonical zoom positions), we conservatively estimate the absolute uncertainty to be 0.2 design requirement. We discuss lessons learned from calibration and suggest tactical strategies that will optimize the quality of science data acquired during operation at Mars. While most results matched expectations, some surprises were discovered, such as a strong wavelength and temperature dependence on the radiometric coefficients and a scene-dependent dynamic component to the zero-exposure bias frames. Calibration results and derived accuracies were validated using a Geoboard target consisting of well-characterized geologic samples
Internet of Things in Sustainable Energy Systems
Our planet has abundant renewable and conventional energy resources but technological capability and capacity gaps coupled with water-energy needs limit the benefits of these resources to citizens. Through IoT technology solutions and state-of-the-art IoT sensing and communications approaches, the sustainable energy-related research and innovation can bring a revolution in this area. Moreover, by the leveraging current infrastructure, including renewable energy technologies, microgrids, and power-to-gas (P2G) hydrogen systems, the Internet of Things in sustainable energy systems can address challenges in energy security to the community, with a minimal trade-off to environment and culture. In this chapter, the IoT in sustainable energy systems approaches, methodologies, scenarios, and tools is presented with a detailed discussion of different sensing and communications techniques. This IoT approach in energy systems is envisioned to enhance the bidirectional interchange of network services in grid by using Internet of Things in grid that will result in enhanced system resilience, reliable data flow, and connectivity optimization. Moreover, the sustainable energy IoT research challenges and innovation opportunities are also discussed to address the complex energy needs of our community and promote a strong energy sector economy
The Novel Deacetylase Inhibitor AR-42 Demonstrates Pre-Clinical Activity in B-Cell Malignancies In Vitro and In Vivo
While deacetylase (DAC) inhibitors show promise for the treatment of B-cell malignancies, those introduced to date are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have shown suboptimal activity or unacceptable toxicities. We therefore investigated the novel DAC inhibitor AR-42 to determine its efficacy in B-cell malignancies.In mantle cell lymphoma (JeKo-1), Burkitt's lymphoma (Raji), and acute lymphoblastic leukemia (697) cell lines, the 48-hr IC(50) (50% growth inhibitory concentration) of AR-42 is 0.61 microM or less. In chronic lymphocytic leukemia (CLL) patient cells, the 48-hr LC(50) (concentration lethal to 50%) of AR-42 is 0.76 microM. AR-42 produces dose- and time-dependent acetylation both of histones and tubulin, and induces caspase-dependent apoptosis that is not reduced in the presence of stromal cells. AR-42 also sensitizes CLL cells to TNF-Related Apoptosis Inducing Ligand (TRAIL), potentially through reduction of c-FLIP. AR-42 significantly reduced leukocyte counts and/or prolonged survival in three separate mouse models of B-cell malignancy without evidence of toxicity.Together, these data demonstrate that AR-42 has in vitro and in vivo efficacy at tolerable doses. These results strongly support upcoming phase I testing of AR-42 in B-cell malignancies