A Relay Level Set Method for Automatic Image Segmentation

This paper presents a new image segmentation method that applies an edge-based level set method in a relay fashion. The proposed method segments an image in a series of nested subregions that are automatically created by shrinking the stabilized curves in their previous subregions. The final result is obtained by combining all boundaries detected in these subregions. The proposed method has the following three advantages: 1) It can be automatically executed without human-computer interactions; 2) it applies the edge-based level set method with relay fashion to detect all boundaries; and 3) it automatically obtains a full segmentation without specifying the number of relays in advance. The comparison experiments illustrate that the proposed method performs better than the representative level set methods, and it can obtain similar or better results compared with other popular segmentation algorithms.

Synthesis and Properties of Carbazole Main Chain Copolymers with Oxadiazole Pendant toward Bipolar Polymer Host: Tuning the HOMO/LUMO Level and Triplet Energy

Three new carbazole copolymers, poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-3,6-diyl)s (P1), poly(9-(2,5-diarene-[1,3,4]oxadiazole)-2, 7-carbazole-alt-9-(2-ethylhexyl)-3, 6-carbazole-diyl)s (P2), and poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-2,7-diyl)s (P3), were synthesized by the Suzuki coupling reaction

Energy-Level and Molecular Engineering of Organic D-pi-A Sensitizers in Dye-Sensitized Solar Cells

A series of organic D-pi-A sensitizers composed of different triarylamine donors in conjugation with the thienothiophene unit and cyanoacrylic acid as an acceptor has been synthesized at a moderate yield. Through tuning the number of methoxy substituents on the triphenylamine donor, we have gradually red-shifted the absorption of sensitizers to enhance device efficiencies.

Probing Charge Transport of Ruthenium-Complex-Based Molecular Wires at the Single-Molecule Level

A ruthenium(II) bis(sigma-arylacetylide)-complex-based molecular wire functionalized with thiolacetyl alligator clips at both ends (OPERu) was used to fabricate gold substrate-molecular wire-conductive tip junctions. To elucidate the ruthenium-complex-enhanced charge transport, we conducted a single-molecule level investigation using the technique-combination method, where electronic delay constant, single-molecular conductance, and barrier height were obtained by scanning tunneling microscopy (STM) apparent height measurements, STM break junction measurements, and conductive probe-atomic force microscopy (CP-AFM) measurements, respectively.

Application of a New Cyclic Guanidinium Ionic Liquid on Dye-Sensitized Solar Cells (DSCs)

A new cyclic guanidinium ionic liquid OGI (1,3-dimethyl-2-N ''-methyl-N ''-octylimidazoguanidinium iodide) has been used as a quasi-solid-state electrolyte for dye-sensitized solar cells (DSCs), and 6.38% conversion efficiency was achieved at AM 1.5 simulated sunlight (9.81 mW cm(-2)). Further gelation with SiO2 nanoparticles afforded the solid-state electrolyte, which presented overall conversion efficiency of 5.85%. The diffusion properties of these OGI-based electrolytes were investigated. In the meantime, the optimal structure and ion-pairing interaction in OGI have been proposed by density functional theoretical calculation (DFT) at the B3LYP/6-21G(d,p) level.

Tuning the Energy Level of Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells

Cost-effective organic sensitizers will play a pivotal role in the future large-scale production and application of dye-sensitized solar cells. Here we report two new organic D-pi-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2'-bis(3,4-ethylenedioxythiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts. On the basis of the 3-f{5'-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2'-bis(3,4-ethylenedioxythiophene)-5-yl}2-cyanoacrylic acid dye, we have set a new efficiency record of 7.6% for solvent-free dye-sensitized solar cells based on metal-free organic sensitizers. Importantly, the cell exhibits an excellent stability, keeping over 92% of its initial efficiency after 1000 h accelerated tests under full sunlight soaking at 60 degrees C. This achievement will considerably encourage further design and exploration of metal-free organic dyes for higher performance dye-sensitized solar cells.

SOLVENT AND SUBSTITUENT EFFECTS ON THE INTRAMOLECULAR AMIDE HYDROLYSIS OF N-METHYLMALEAMIC ACID

Intramolecular amide hydrolysis of N-methylmaleamic acid is revisited at the B3LYP/6-311G(2df,p)//B3LYP/6-31G(d,p)+ZVPE level, including solvent effects at the CPCM-B3LYP/6-311G(2df,p)//Onsager-B3LYP/6-31G(d,p)+ZPVE level. The concerted reaction mechanism is energetically favorable over stepwise reaction mechanisms in both the gas phase and solution. The calculated reaction barriers are significantly lower in solution than in the gas phase. In addition, it is concluded that the substituents of the four N-methylmaleamic acid derivatives considered herein have a significant effect on the gas-phase reaction barriers but a smaller, or little, effect on the barriers in solution.

A study of isomeric diglycosyl flavonoids by SORI CID of Fourier transform ion cyclotron mass Spectrometry in negative ion mode

High-resolution Sustained off resonance irradiation (SORI) CID was employed to distinguish four pairs of isomeric diglycosyl flavonoids in the negative mode using the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). All of these isomers can be distinguished via MS/MS data. For these diglycosyl flavones and flavanones, the deprotonated alpha 1-->6 linkage diglycosyl flavonoids produce fewer fragments than the alpha 1-->2 linkage type compounds and the Retro-Diels-Alder (RDA) reaction in MS/MS only takes place when the aglycone is a flavanone and glycosylated with an alpha 1-->2 intersaccharide linkage disaccharide. The deprotonation sites after collisional activation are discussed according to the high mass accuracy and high-resolution data of tandem spectrometry. Some of these high-resolution SORI CID product ions from alpha 1-->2 linkage diglycosyl flavonoids involve multibond cleavages; the possible mechanism is discussed based on the computer modeling using Gaussian 03 program package at the B3LYP/6-31G level of theory. Unambiguous elementary composition data provides fragmentation information that has not been reported previously.

Tuning the energy level and photophysical and electroluminescent properties of heavy metal complexes by controlling the ligation of the metal with the carbon of the carbazole unit

Four novel Ir-III and Pt-II complexes with cyclometalated ligands bearing a carbazole framework are prepared and characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Single-crystal X-ray diffraction studies of complexes 1, 3, and 4 reveal that the 3- or 2-position C atom of the carbazole unit coordinates to the metal center. The difference in the ligation position results in significant shifts in the emission spectra with the changes in wavelength being 84 nm for the Ir complexes and 63 nm for the Pt complexes. The electrochemical behavior and photophysical properties of the complexes are investigated, and correlate well with the results of density functional theory (DFT) calculations. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ(3)/LiF/Al can attain very high efficiencies.

Evaluation of different culture conditions for high-level soluble expression of human cyclin A(2) with pET vector in BL21 (DE3) and spectroscopic characterization of its inclusion body structure

In this paper, we evaluated various parameters of culture condition affecting high-level soluble expression of human cyclin A, in Escherichia coli BL21(DE3), and demonstrated that the highest protein yield was obtained using TB(no glycerol) + 0.5% glucose medium at 25 degrees C. By single immobilized metal ion affinity chromatography, we got highly purified human cyclin A(2) with a yield ranged from 20 to 30 mg/L. By amyloid-diagnostic dye ThT binding and Fourier transform infrared spectroscopy, we observed a significant decrease in alpha-helix content and an increase in beta-sheet structure in cyclin A(2) inclusion body in comparison to its native protein, and confirmed the resemblance of the internal organization of cyclin A(2) inclusion body and amyloid fibrils.

Electronic structures of hafnium dimer and trimer by density functional theory

Equilibrium geometries, vibrational frequencies and dissociation energies of hafnium dimer and trimer were studied by density functional methods B3LYP, BLYP, B3PW91, BHLYP, BP86, B3P86, mPW1PW91 and PBE1PBE. The results indicate that singlet is the ground state both for hafnium dimer and for trimer. For hafnium dimer, the calculated bond distance is less sensitive to the methods used. Except at BHLYP level, the calculated vibrational frequency is comparable to the experimental value. For hafnium trimer, equilateral triangle with D-3h symmetry is slightly favored compared with isosceles triangle with C-2v, symmetry except at BHLYP level. This conclusion is in agreement with experiment in which the ground state of Hf-3 is fluxional and low-spin or closed shell is preferred.

Substitution effect of nitrogen atoms with carbon atoms in porphyrin on the electronic structure and excited states properties

Density functional theory (DFT) electronic structure calculations were carried out to predict the structures and the absorption and emission spectra for porphyrin and a series of carbaporphyrins-carbaporphyrin, adj-dicarbaporphyrin, opp-dicarbaporphyrin, tricarbaporphyrin and tetracarbaporphyrin. The ground- and excited-state geometries were optimized at the B3LYP/6-31g(d) and CIS/6-31g(d) level, respectively. The optimized ground-state geometry and absorption spectra of porphyrin, calculated by DFT and time-dependent DFT (TDDFT), are comparable with the available experimental values. Based on the optimized excited-state geometries obtained by CIS/6-31g(d) method, the emission properties are calculated using TDDFT method at the B3LYP/6-31g(d) level. The effects of the substitution of nitrogen atoms with carbon atoms at the center positions of porphyrin are discussed. The results indicate that the two-pyrrole nitrogens are important to the chemical and physical properties for porphyrin.