A Tensor-Based Dictionary Learning Approach to Tomographic Image Reconstruction

We consider tomographic reconstruction using priors in the form of a dictionary learned from training images. The reconstruction has two stages: first we construct a tensor dictionary prior from our training data, and then we pose the reconstruction problem in terms of recovering the expansion coefficients in that dictionary. Our approach differs from past approaches in that a) we use a third-order tensor representation for our images and b) we recast the reconstruction problem using the tensor formulation. The dictionary learning problem is presented as a non-negative tensor factorization problem with sparsity constraints. The reconstruction problem is formulated in a convex optimization framework by looking for a solution with a sparse representation in the tensor dictionary. Numerical results show that our tensor formulation leads to very sparse representations of both the training images and the reconstructions due to the ability of representing repeated features compactly in the dictionary.Comment: 29 page

BN Nanotube Serving as a Gas Chemical Sensor for N₂O by Parallel Electric Field

Density functional theory calculations were performed to understand the electronic properties of C₂₄, B₁₂N₁₂, B₁₂P₁₂, and (6, 0) BNNT interacted with N₂O molecule in the presence and absence of an external electric field using the B3LYP method and 6-31G** basis set. The adsorption of N₂O from O-side on the surface of (6, 0) BNNT has high sensitivity in comparison with B₁₂N₁₂ nano-cage. The adsorption energy of N₂O (O-side) on the sidewalls of B₁₂N₁₂ and BNNT in the presence of an electric field are −21.01 and −15.48 kJ mol⁻¹, respectively. Our results suggest that in the presence of an electric field, the B₁₂N₁₂ nano-cage is the more energetically notable upon the N₂O adsorption than (6, 0) BNNT, C₂₄, and B₁₂P₁₂. Whereas, our results indicate that the electronic property of BNNT is more sensitive to N₂O molecule at the presence of an electric field than B₁₂N₁₂ nano-cage. It is anticipated that BNNT could be a favorable gas sensor for the detection of N₂O molecule. © 2016, Springer Science+Business Media New York

Binding energy of localized biexcitons in quantum wells

A variational calculation of the ground state energy of a biexciton in a GaAs/AlGaAs quantum well is presented. The well width fluctuations leading to trapping of the biexcitons are modeled by a parabolic potential. The results obtained for different well widths are compared with recent experimental data. Good agreement is obtained both for the biexciton binding energy and for the Haynes factor. We find that the structure of a biexciton is similar to the one of the H_2 molecule.Comment: 9 pages, 4 figure

Isolation, spectroscopic characterization, X-ray, theoretical studies as well as in vitro cytotoxicity of Samarcandin

Samarcandin 1, a natural sesquiterpene-coumarin, was isolated as well as elucidated from F. assa-foetida which has significant effect in Iranian traditional medicine because of its medicinal attitudes. The crystal structure of samarcandin was determined by single-crystal X-ray structure analysis. It is orthorhombic, with unit cell parameters a = 10.8204 (5) Å, b = 12.9894 (7) Å, c = 15.2467 (9) Å, V = 2142.9 (2) Å3, space group P212121 and four symmetry equivalent molecules in the unit cell. Samarcandin was isolated in order to study for its theoretical studies as well as its cellular toxicity as anti-cancer drug against two cancerous cells. In comparison with controls, our microscopic and MTT assay data showed that samarcandin suppresses cancer cell proliferation in a dose-dependent manner with IC50 = 11 μM and 13 for AGS and WEHI-164 cell lines, respectively. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) of the structure was computed by three functional methods and 6-311++G∗∗ standard basis set. The optimized molecular geometry and theoretical analysis agree closely to that obtained from the single crystal X-ray crystallography. To sum up, the good correlations between experimental and theoretical studies by UV, NMR, and IR spectra were found. © 2016 Elsevier Inc. All rights reserved

A DFT study of 5-fluorouracil adsorption on the pure and doped BN nanotubes

Abstract The electronic and adsorption properties of the pristine, Al-, Ga-, and Ge-doped BN nanotubes interacted with 5-fluorouracil molecule (5-FU) were theoretically investigated in the gas phase using the B3LYP density functional theory (DFT) calculations. It was found that the adsorption behavior of 5FU molecule on the pristine (8, 0) and (5, 5) BNNTs are electrostatic in nature. In contrast, the 5FU molecule (O-side) implies strong adsorption on the metal-doped BNNTs. Our results indicate that the Ga-doped presents high sensitivity and strong adsorption with the 5-FU molecule than the Al- and Ge-doped BNNTs. Therefore, it can be introduced as a carrier for drug delivery applications. © 2015 Elsevier Ltd

Socio-demographic and built environment determinants of car use among older adults in Iran

Internationally, an age-friendly built environment, including safe, affordable, and convenient transportation, has been identified as crucial in enhancing the quality of life for increasingly large numbers of elderly people. This study presents data on the urban travel and mobility patterns of older adults in Shiraz, Iran – a country where the population is ageing faster than the average of western societies. The relationship between car use and socio-demographic and built environment variables is investigated through Ordinary Least Squares and Geographically Weighted Regression models. These models show that the main determinants of car use among older adults are: employment status; household size; car ownership rate; trip purpose; property prices; and mixed land-uses. Also, the study reveals that car dependency is significant and more pronounced among wealthier individuals, who tend to be clustered in the northern section of the city. The population density and road network design characteristics do not affect car use among older adults, while a mix of land-uses tends to attenuate car dependency. Gender gaps in car use are much wider than in the West, and some level of spatial mismatch between travel needs and car access is observed in the southern section of the city. Clearly, Iranian cities must move away from the current car-centric development model

Comparison of effect of Zataria multiflora and Rosemarinus officinalis extracts on quality of minced frozen silver carp

The aim of the this study was to have a comparison between Zataria multiflora and Rosemarinus officinalis extracts on quality of minced frozen silver carp preserved in cold storage temperature -18°C for six months. In this research, one control and three treatments of minced silver carp were prepared as Tr1 (+ Zataria), Tr2 (+Rosemary) and Tr3 (mixed with Rosemary and Zataria) all in normal packaging. After quick freezing of samples in the spiral freezer they were preserved in cold storage temperature -18°C for six months. In this period, the changes of Peroxide Value, Total Volatile Nitrogen, Tio Barbituric Acid and Free Fatty Acids in all treatments were measured based on a predetermined schedule. The results of this investigation showed a significant effect of anti-oxidant in all treatments (p<.05) and it was concluded that Rosemary containing anti-oxidants maintains the best quality after six months of cold storage and corruption indices are not exceeded. Analysis of Peroxide Value, Total Volatile Nitrogen, Tio Barbituric Acid and Free Fatty Acids in different treatments during six months of reservation in freezing under the temperature of -18°C showed that the obtained results to the end of the reservation period for all treatments has increased and treatment containing Rosemary, with Peroxide Value 6.83±0.35meq.1000g^-1, Tio Barbituric Acid 2.1±0.1mgMAL.kg^-1 and Total Volatile Nitrogen with 19.16±0.28mg.100g ^-1 had the best quality of preservation compared with other treatments during the preservation period. Therefore, based on these results and statistical analyses, the effect of anti-oxidant and time in all treatments is significant (p<.05) and the treatments containing Rosemary had the best quality preservation status in -18°C and did not surpass perishing criteria during this period

Finite temperature Casimir effect in the presence of nonlinear dielectrics

Starting from a Lagrangian, electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained and their relation to coupling functions are determined. Finally, the Casimir energy and force in the presence of a nonlinear medium at finite temperature is calculated.Comment: 16 pages, 0 figure