228 research outputs found
Parallel genetic algorithm and parallel simulated annealing algorithm for the closest string problem
In this paper, we design genetic algorithm and simulated
annealing algorithm and their parallel versions to solve the Closest String
problem. Our implementation and experiments show usefulness of the
parallel GA and SA algorithms
PVM algorithms for some problems in bioinformatics
We design and analyze implementation aspects of a PVM
version of the well known Smith-Waterman algorithm, and then we consider
other problems important for bioinformatics, such as finding longest
common substring, finding repeated substrings and finding palindromes
Modeling of Exoplanet Atmospheres
Spectrally characterizing exoplanet atmospheres will be one of the fastest moving astronomical disciplines in the years to come. Especially the upcoming James Webb Space Telescope
(JWST) will provide spectral measurements from the near- to mid-infrared of unprecedented precision. With other next generation instruments on the horizon, it is crucial to possess the tools necessary for interpretating observations. To this end I wrote the petitCODE, which solves for the self-consistent atmospheric structures of exoplanets, assuming chemical and radiative-convective equilibrium. The code includes scattering, and models clouds. The code outputs the planet’s observable emission and transmission spectra. In addition, I constructed a spectral retrieval code, which derives the full posterior probability distribution of atmospheric parameters from observations. I used petitCODE to systematically study the atmospheres of hot jupiters and found, e.g., that their structures depend strongly on the type of their host stars. Moreover, I found that C/O ratios around unity can lead to atmospheric inversions. Next, I produced synthetic observations of prime exoplanet targets for JWST, and studied how well we will be able to distinguish various atmospheric scenarios. Finally, I verified the implementation of my retrieval code using mock JWST observations
Visualization 1.mp4
The evolution of phase over time (ground truth, wrapped, 2D unwrapped and 3D unwrapped) is demonstrated in the video (Visualization 1)
Sequential and parallel algorithms for sequence analysis problems in bioinformatics
The study of biological and genetic information, mostly DNA data, is an extremely important subject which can provide critical information in many areas, such as understanding human diseases or discovering new drugs. A huge number of computing algorithms are developed and available now to help with the study of these, and in order to solve these problems more efficiently and accurately, much attention has been paid in recent decades to developing new and better algorithms. [continues]
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visualization 2.mp4
The changes of cell morphology over time during the detachment process
Facile Surface Modification of Ubiquitous Stainless Steel Led to Competent Electrocatalysts for Overall Water Splitting
Competent and low-cost
electrocatalysts play a crucial role in
the wide deployment of electrocatalytic water splitting for clean
H<sub>2</sub> production. Herein, for the first time, we report that
readily available stainless steel can be transformed to competent
electrocatalysts for both H<sub>2</sub> and O<sub>2</sub> evolution
reactions (HER and OER, respectively) after facile surface modification.
Specifically, our sulfurized stainless steel foil (SSFS) could achieve
a catalytic current density of 10 mA cm<sup>–2</sup> at overpotentials
of 136 and 262 mV for HER and OER, respectively, in 1.0 M KOH. When
SSFS served as the electrocatalysts for both the cathode and the anode,
an overall water splitting current density of 10 mA cm<sup>–2</sup> was obtained at 1.64 V with robust durability. Such a superior performance
can rival those of many recently reported water splitting catalysts
that consist of expensive elements, contain high-cost supports, or
require sophisticated synthesis. In addition, excellent water splitting
activity was also achieved by SSFS in neutral media, largely expanding
its working conditions. Finally, we further demonstrated that analogous
phosphorization and nitridation treatments also could substantially
enhance the electrocatalytic performance of stainless steel for water
splitting, suggesting the great versatility of our surface modification
strategy
Media 1: Real-time 3D and 4D Fourier domain Doppler optical coherence tomography based on dual graphics processing units
Originally published in Biomedical Optics Express on 01 September 2012 (boe-3-9-2162
Efficient H<sub>2</sub> Evolution Coupled with Oxidative Refining of Alcohols via A Hierarchically Porous Nickel Bifunctional Electrocatalyst
Water
electrolysis to produce H<sub>2</sub> and O<sub>2</sub> with
renewable energy input has been generally viewed as an attractive
route to meet future global energy demands. However, the sluggish
O<sub>2</sub> evolution reaction usually requires high overpotential
and may yield reactive oxygen species (ROS) that can degrade the electrolyzer
membrane and hence shorten the device lifetime. In addition, the potential
gas crossover may result in an explosive H<sub>2</sub>/O<sub>2</sub> mixture and hence safety risks. To address these issues, we herein
report a general electrolysis strategy for the simultaneous H<sub>2</sub> production and alcohol oxidative upgrading (e.g., benzyl
alcohol, 4-nitrobenzyl alcohol, 4-methylbenzyl alcohol, ethanol, and
5-hydroxymethylfurfural), in which the thermodynamics of the latter
is much easier than that of water oxidation. A facile and environmentally
friendly template-free electrodeposition was used to obtain a 3D hierarchically
porous nickel-based electrocatalyst (hp-Ni) for such an integrated
electrolysis, requiring a voltage of ∼220 mV smaller than that
of water splitting to achieve 50 mA cm<sup>–2</sup> together
with robust stability, high Faradaic efficiencies, and no formation
of ROS, as well as production of valuable products at both the cathode
(H<sub>2</sub>) and anode (alcohol oxidation products). More importantly,
we demonstrated that these diverse alcohol oxidations over hp-Ni exhibited
similar onset potentials which were largely determined by the desirable
oxidation potential of hp-Ni, irrespective of the different intrinsic
thermodynamics of these alcohol oxidation reactions. This result provides
a new direction for the rational design of heterogeneous transition-metal-based
electrocatalysts with lower oxidation potential for more highly efficient
electrocatalytic alcohol oxidation
A General Strategy for Decoupled Hydrogen Production from Water Splitting by Integrating Oxidative Biomass Valorization
Conventional
water electrolyzers produce H<sub>2</sub> and O<sub>2</sub> simultaneously,
such that additional gas separation steps
are needed to prevent H<sub>2</sub>/O<sub>2</sub> mixing. The sluggish
anodic O<sub>2</sub> evolution reaction (OER) always results in low
overall energy conversion efficiency and the product of OER, O<sub>2</sub>, is not of significant value. In addition, the potential
formation of reactive oxygen species (ROS) may lead to degradation
of cell membranes and thus premature device failure. Herein we report
a general concept of integrating oxidative biomass upgrading reactions
with decoupled H<sub>2</sub> generation from water splitting. Five
representative biomass substrates, ethanol, benzyl alcohol, furfural,
furfuryl alcohol, and 5-hydroxymethylfurfural (HMF), were selected
for oxidative upgrading catalyzed by a hierarchically porous Ni<sub>3</sub>S<sub>2</sub>/Ni foam bifunctional electrocatalyst (Ni<sub>3</sub>S<sub>2</sub>/NF). All the five organics can be oxidized to
value-added liquid products at much lower overpotentials than that
of OER. In particular, the electrocatalytic oxidation of HMF to the
value-added 2,5-furandicarboxylic acid (FDCA) was further studied
in detail. Benefiting from the more favorable thermodynamics of HMF
oxidation than that of OER, the cell voltage for integrated H<sub>2</sub> production and HMF oxidation was significantly reduced by
∼200 mV relative to pure water splitting to achieve 100 mA
cm<sup>–2</sup>, while the oxidation product (FDCA) at the
anode was much more valuable than O<sub>2</sub>. When utilized as
electrocatalysts for both cathode and anode, Ni<sub>3</sub>S<sub>2</sub>/NF demonstrated outstanding durability and nearly unity Faradaic
efficiencies for both H<sub>2</sub> and FDCA production. Overall,
such an integration of oxidative biomass valorization and HER via
earth-abundant electrocatalysts not only avoids the generation of
explosive H<sub>2</sub>/O<sub>2</sub> mixture and ROS, but also yields
products of high value at both electrodes with lower voltage input,
maximizing the energy conversion efficiency
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