959 research outputs found
Interface control of ferroelectricity in LaNiO3-BaTiO3 superlattices
LaNiO-BaTiO superlattices with different types of interfaces are
studied from first-principles density-functional theory. It is revealed that
the ferroelectricity in the superlattice with (NiO)/(BaO)
interfaces is enhanced from that of the superlattice with
(LaO)/(TiO) interfaces. The origin lies at the polar discontinuity
at the interface, which makes the holes localized within the
(NiO)/(BaO) interface, but drives a penetration of electrons into
BaTiO component near (LaO)/(TiO) interface. Our calculations
demonstrate an effective avenue to the robust ferroelectricity in BaTiO
ultrathin films.Comment: 14 pages, 6 figure
The Age-Redshift Relationship of Old Passive Galaxies
We use 32 age measurements of passively evolving galaxies as a function of
redshift to test and compare the standard model (CDM) with the Universe. We show that the latter fits the data with a reduced
for a Hubble constant km
. By comparison, the optimal flat CDM
model, with two free parameters (including and km ), fits the age-\emph{z} data with a reduced .
Based solely on their values, both models appear to account
for the data very well, though the optimized CDM parameters are only
marginally consistent with those of the concordance model ( and km ). Fitting the age-
data with the latter results in a reduced . However,
because of the different number of free parameters in these models, selection
tools, such as the Akaike, Kullback and Bayes Information Criteria, favour
over CDM with a likelihood of
versus . These results are suggestive, though not yet
compelling, given the current limited galaxy age- sample. We carry out Monte
Carlo simulations based on these current age measurements to estimate how large
the sample would have to be in order to rule out either model at a confidence level. We find that if the real cosmology is CDM, a
sample of galaxy ages would be sufficient to rule out
at this level of accuracy, while galaxy ages would be required to
rule out CDM if the real Universe were instead .Comment: 36 pages, 13 figures, 1 table; accepted for publication in The
Astronomical Journal. arXiv admin note: text overlap with arXiv:1405.238
Surface enhanced Raman scattering of Ag or Au nanoparticle-decorated reduced graphene oxide for detection of aromatic molecules
We report a method for fabrication of an efficient surface enhanced Raman scattering (SERS) substrate by combination of metallic nanostructures and graphene, which shows dramatic Raman enhancement and efficient adsorption of aromatic molecules. As an example, the fabricated Ag or Au nanoparticle (NP)-decorated reduced graphene oxide (rGO) on Si substrate is used as an efficient SERS substrate to detect the adsorbed aromatic molecules with a low detection limit at nM level. Systematic studies on the effects of NP size and substrate morphology on Raman enhancement are presented. This method might be useful for the future application in detection of biomolecules, such as DNA and protein
Performance of Track-to-Track Association Algorithms Based on Mahalanobis Distance
In multi-sensor tracking system, the track-to-track association problem is to determine whether a set of local tracks from different sensor systems are represent the same target. This problem is usually formulated as a binary hypothesis test, and the most common statistics is defined as the squared Mahalanobis distance (SMD) between the kinematic state estimates of two tracks. In this paper, three types of SMD algorithms are investigated, i.e., the SMD algorithm, the cumulative SMD algorithm, and the Discrete Wavelet Transform (DWT) algorithm which can be regarded as a generalized SMD ratio algorithm. The first one can be looked as singlescan algorithm, and the rest two are multiscan approaches. From another viewpoint, the first two are time domain algorithms, and the last one is a transform domain algorithm. The probability distribution functions of statistics defined by these algorithms have been discussed under the assumption that the estimates errors are independent across time. The Operating Characteristic Function is used to describe association performance. It shows that the multiscan algorithm performs better than the singlescan algorithm. As to multiscan algorithms, the DWT algorithm is superior to time domain algorithm. But better algorithm is more sensitive to the residual bias because the statistic based on SMD of target state estimates is directly contaminated by the bias
Characterization of a newly isolated green microalga Scenedesmus sp. as a potential source of biodiesel
An oil-producing microalga SP-01 belonging to the genus Scenedesmus was shown to be able to grow on a media containing 5 to 30 g L-1 NaCl. Under mixotrophic condition, the maximum cell dry weight of 3.1 g L-1 and specific growth rate of 0.034 h-1 were obtained at 0.5 g L-1 NaNO3 and 6 g L-1 acetate. The effects of salinity on the biomass, lipid, and carotenoid productions of the alga SP-01 in mixotrophic mode were investigated. The biomass productivity increased with increasing NaNO3 concentrations, and addition of NaCl resulted in a higher biomass while NaNO3 was present. The maximum lipid content was obtained while no NaNO3 and NaCl was added, and the lipid content decreased with increasing NaNO3 concentrations or addition of NaCl. The maximum lipid productivities of 67.44 to 68.44 mg L-1day-1 were obtained while NaNO3 and NaCl were not added or while 20 g L-1 NaCl and 0.13 g L-1 NaNO3 were added. The algal lipid was mainly composed of C16 and C18 fatty acids accounting for more than 90% of total fatty acids. Furthermore, lutein and astaxanthin were the main carotenoids.Key words: Halotolerant, microalga, Scenedesmus sp., mixotrophic culture, lipid, carotenoid
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