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Machine learning (ML) is effective to establish the complicated trilateral relationship among structures, properties, and photovoltaic performance, which is fundamental issue in developing novel materials for improving power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, we constructed the database of 397 donor–acceptor pairs of OSCs with photovoltaic parameters and descriptor sets, which include donor–acceptor weight ratio within the active layer of the OSCs, root mean square of roughness, and 1024-bit Morgan molecular fingerprint for donor (Fp-D) and acceptor (Fp-A). The ML models random forest (RF), adaptive boosting (AdaBoost), extra trees regression, and gradient boosting regression trees were trained based on the descriptor set. The metrics determination coefficient (R2), Pearson correlation coefficient (r), root mean square error, and mean absolute error were selected to evaluate ML model performances. The results showed that the RF model exhibits the highest accuracy and stability for PCE prediction among these four ML models. Moreover, based on the decomposition of non-fullerene acceptors L8-BO, BTP-ec9, AQx-2, and IEICO, 20 acceptor molecules with symmetric A–D–A and A–π–D–π–A architectures were designed. The photovoltaic parameters of the designed acceptors were predicted using the trained RF model, and the virtual screening of designed acceptors was conducted based on the predicted PCE. The results indicate that six designed acceptors can reach the predicted PCE higher than 12% when P3HT was adopted as a donor. While PM6 was applied as a donor, five designed acceptors can achieve the predicted PCE higher than 16%. [ABSTRACT FROM AUTHOR]

The complicated trilateral relationships among molecular structures, properties, and photovoltaic performances of electron donor and acceptor materials hinder the rapid improvement of power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, the database of 310 donor and non‐fullerene acceptor pairs is constructed and 39 molecular structure descriptors are selected. Four kinds of machine learning (ML) algorithms random forest (RF), extra trees regression, gradient boosting regression trees, and adaptive boosting are applied to predict photovoltaic parameters. The coefficient of determination, Pearson correlation coefficient, mean absolute error, and root mean square error are adopted to evaluate ML performance. The results show that the RF model exhibits the best prediction accuracy. The Gini important analysis suggests the fused ring and aromatic heterocycles are critical fragments in determining PCE. The molecular unit sets are constructed by cutting each donor and acceptor molecules in database. The 31 752 D‐π‐A‐π type donor molecules and 5 455 164 A‐π‐D‐π‐A type acceptor molecules are designed by recombination of molecular units, and 173 212 367 328 donor–acceptor pairs are generated by combining the newly designed donor and acceptor molecules. Based on the predicted PCE using the trained RF model, 42 donor–acceptor pairs exhibit the predicted PCE > 16%, in which the highest PCE is 16.24%. [ABSTRACT FROM AUTHOR]

The selection of electron donors and nonfullerene acceptors (NFAs) in organic solar cells (OSCs) is crucial for improving photovoltaic performance. Machine learning (ML) has brought a breakthrough solution. Herein, 292 donor‐NFA pairs with experimental OSC parameters from the reported articles are collected. The ML descriptors include device processing parameters, molecular properties, and molecular structure. The five ML regression models, random forest (RF), extra tree regression, gradient boosting regression tree, adaptive boosting, and artificial neural network (ANN) are trained. GridSearchCV is used for hyperparameter optimization of ML regression models. The SHapley Additive exPlanation approach is employed to analyze descriptor importance. Among the trained five ML models, the RF model shows superior performance, achieving Pearson's correlation coefficient (r) of 0.81 on the test set. Based on the donors and NFAs in constructed dataset, the 9779 donor–NFA pairs for OSCs are generated by randomly combining donor and acceptor molecules. The trained RF model is utilized to predict the power conversion efficiency (PCE) of new donor–acceptor pairs for OSCs. The results indicate that the OSC composed of PBDB‐TF as donor and L8‐BO as acceptor can achieve the remarkable PCE of 17.9%. [ABSTRACT FROM AUTHOR]

The modification of fused rings in the central backbone, side chains, and end groups of the non‐fullerene acceptor (NFA) for organic solar cells (OSCs) can modulate properties and photovoltaic performance. In order to investigate the effect of fused rings and side chains on photovoltaic performance, PBDB‐T is selected as electron donor and IDTIC, IDIC, IDIC‐PhC6, IDIC‐C4Ph, 4TIC, ITIC‐OE, IDTTIC, ITC6‐IC, ITIC, and C8‐ITIC are selected as NFAs. Based on quantum chemistry calculations, the geometries, electronic structures, excitation properties, excited‐state lifetimes, and electrostatic potentials (ESPs) of the monomer and the PBDB‐T:NFA complexes are studied, and the rate constants of charge transfer (CT), exciton dissociation (ED) and charge recombination (CR) processes are analyzed. The results show that the increase of fused‐ring in NFA's backbone by substituting phenyl or thienyl with bithiophene can elevate the highest occupied molecular orbital energies, reduce the gap of frontier molecular orbital energies, induce red‐shift of absorption spectrum, increase CT energy, improve CT and ED rates. This work provides a detailed understanding of tuning optoelectronic properties and photovoltaic performance by modifying NFA's side chains and extending backbones. [ABSTRACT FROM AUTHOR]

Developing non-fullerene acceptors (NFAs) by modifying the backbone, side chains and end groups is the most important strategy to improve the power conversion efficiency of organic solar cells (OSCs). Among numerous developed NFAs, Y6 and its derivatives are famous NFAs in the OSC field due to their good performance. Herein, in order to understand the mechanism of tuning the photovoltaic performance by modifying the Y6's center backbone, π-spacer and side-chains, we selected the PM6:Y6 OSC as a reference and systematically studied PM6:AQx-2, PM6:Y6-T, PM6:Y6-2T, PM6:Y6-O, PM6:Y6-1O and PM6:Y6-2O OSC systems based on extensive quantum chemistry calculations. The results indicate that introducing quinoxaline to substitute thiadiazole in the backbone induces a blue-shift of absorption spectra, reduces the charge transfer (CT) distance (Δd) and average electrostatic potential (ESP), and increases the singlet–triplet energy gap (ΔEST), CT excitation energy and the number of CT states in low-lying excitations. Inserting thienyl and dithiophenyl as π spacers generates a red-shift of absorption spectra, enlarges Δd and average ESP, and reduces ΔEST and the number of CT states. Introducing furo[3,2-b]furan for substituting one thieno[3,2-b]thiophene unit in the Y6's backbone causes a red-shift of absorption spectra and increases ΔEST, Δd and average ESP as well as CT excitation energy. Introducing alkoxyl as a side chain results in a blue-shift of absorption spectra, and increases ΔEST, Δd, average ESP, CT excitation energy and the number of CT states. The rate constants calculated using Marcus theory suggest that all the molecular modifications of Y6 reduce the exciton dissociation and charge recombination rates at the heterojunction interface, while introducing furo[3,2-b]furan and alkoxyl enlarges CT rates. [ABSTRACT FROM AUTHOR]

Understanding organic photovoltaic (OPV) work principles and the materials' optoelectronic properties is fundamental for developing novel heterojunction materials with the aim of improving power conversion efficiency (PCE) of organic solar cells. Here, in order to understand the PCE performance (>13%) of OPV device composed of the non-fullerene acceptor fusing naphtho[1,2-b:5,6-b′]dithiophene with two thieno[3,2-b]thiophene (IDCIC) and the polymer donor fluorobenzotriazole (FTAZ), with the aid of extensive quantum chemistry calculations, we investigated the geometries, molecular orbitals, excitations, electrostatic potentials, transferred charges and charge transfer distances of FTAZ, IDCIC and their complexes with face-on configurations, which was constructed as heterojunction interface model. The results indicate that, the prominent OPV performance of FTAZ:IDCIC heterojunction is caused by co-planarity between the donor and acceptor fragments in IDCIC, the the charge transfer (CT) and hybrid excitations of FTAZ and IDCIC, the complementary optical absorptions in visible region, and the large electrostatic potential difference between FTAZ and IDCIC. The electronic structures and excitations of FTAZ/IDCIC complexes suggest that exciton dissociation can fulfill through the decay of local excitation exciton in acceptor by means of hole transfer, which is quite different from the OPVs based on fullerenes acceptor. The rates of exciton dissociation, charge recombination and CT processes, which were evaluated by Marcus theory, support the efficient exciton dissociation that is also responsible for good photovoltaic performance. [ABSTRACT FROM AUTHOR]

Molecular stacking modes that determine morphology of bulk‐heterojunctions are important because of their effects on photovoltaic performance of organic solar cells (OSCs). Here, in order to investigate how molecular stacking pattern in OSCs heterojunction impact on electronic structures and properties, and then influence photovoltaic performance, this work selected D18:Y6 OSC as a representative system. On the basis of semi‐empirical quantum chemistry and density functional theory calculations, we studied the geometries, electronic structures and excitation properties, as well as electron and hole couplings of D18 and Y6 molecules, Y6 dimers, D18/Y6 and D18/Y6‐dimer complexes which are heterojunction interface models. The results indicate that the molecular stacking effects on open‐circuit voltage (VOC) can be attributed to the influences on charge transfer (CT) excitation energies because molecular stacking modes at donor/acceptor heterojunction interface can significantly change excitation energies. Furthermore, the molecular stacking modes can cause drastically different electron and hole couplings, and then affect charge transfer/transport rates. Hence, the molecular stacking effects on short‐circuit current density (JSC) can be understood from the effects on electron and hole couplings. The molecular stacking modes that are favorable to improving VOC and JSC of D18:Y6 OSC were also discussed. [ABSTRACT FROM AUTHOR]

Molecular descriptors are critical for determining the accuracy of machine learning (ML) study on organic photovoltaics (OPV). To unravel the complex relationship between molecular properties and device performance, on the basis of 510 donor‐acceptor pairs in OPV active layer, the open‐circuit voltage loss (VOC‐loss), dielectric constants of donor and acceptor (ε‐D and ε‐A) were firstly implemented into property descriptor set that includes 41 quantities totally. Then, the five ML algorithms were applied to compare the property descriptor sets with and without VOC‐loss, ε‐D and ε‐A (coded as new and old sets) in the prediction of photovoltaic parameters. The ML results of Pearson's correlation coefficient and the slope of regression lines indicate the performances of new molecular descriptor set are prevailing to that of old set. Furthermore, the Gini important analysis indicates that the ε‐D, ε‐A and VOC‐loss are very important parameters for determining device performance. Higher dielectric constants and lower VOC‐loss will be more beneficial to the performance of OPV devices. [ABSTRACT FROM AUTHOR]

Modifying the backbone, side chains and end groups of non-fullerene acceptors (NFAs) in organic photovoltaics (OPVs) can tune their properties and impact performance. Hence, understanding how different functional groups influence properties and performances is critical for developing novel NFAs for OPVs. Herein, to investigate the effects of introducing methyl groups and substituting dicyano with O, based upon extensive quantum chemistry calculations, we selected a PM6:IT-4F heterojunction as the reference system and studied the geometries, electronic structures, excitation properties, and electrostatic potentials (ESPs) of PM6, IT-4F, IM-4F, and IO-4F as well as PM6:IT-4F, PM6:IM-4F, and PM6:IO-4F complexes as interface models. The rate constants of the charge transfer (CT), exciton dissociation (ED), and charge recombination processes at the heterojunction interface were also calculated. The results indicated that the superior performance of PM6:IM-4F and PM6:IT-4F systems could be ascribed to the redshift of optical absorptions that assure more photon harvest, larger ESP difference between PM6 and NFAs, and larger excitation energy difference between NFA's local excitation and CT that is favorable for efficient ED. However, the larger open-circuit voltage of PM6:IO-4F OPV results from the substitution of dicyano with O, causing a significant increase in the lowest unoccupied molecular orbital and CT excitation energies of PM6:NFA complexes, whereas the smallest short-circuit current density is mainly related to less CT excitations, blue-shift optical absorption that is not complementary with that of PM6, inefficient ED, and the smaller ESP difference between PM6 and IO-4F. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of formamidinium CH(NH2)2+ (FA) doped double perovskite Cs2AgBiBr6 with corresponding formula Cs1.875FA0.125AgBiBr6 were investigated based on electronic structures and supercell models. The dopant formation energies, tolerance and octahedral factors support the doped structures are stable. FA dopant increases band gap about 0.15 eV without introducing dopant states in gap, but also increases the reduced effective masses, exciton binding energies, and elastic constants. However, it decreases exciton energies and charge carrier mobilities. Though the energy barriers among the different FA orientations in Cs1.875FA0.125AgBiBr6 are quite small (<30 meV), FA orientations in doped systems can remarkably impact on electron and hole mobilities. [ABSTRACT FROM AUTHOR]

Abstracts Background and objective The study was performed to determine whether catch-up growth is associated with the development of insulin resistance and to explore serum endocrine markers associated with the metabolism of adipose tissue in a Chinese population born small for gestational age(SGA) Subjects and methods We recruited 56 children born SGA with catch-up growth and 55 born without catch-up growth, who were further grouped into groups I (with BMI catch-up) and II (without BMI catch-up) respectively, as well as 52 children born appropriate for gestational age (AGA) with normal height. Their serum fasting insulin, fasting glucose, insulin-like growth factor-1, adiponectin, IGFBP-1, triglyceride concentrations, and the homeostasis assessment model for insulin resistance (HOMA-IR) were evaluated. Results (1) The HOMA-IR values in SGA-I with catch-up growth group were significantly higher than those in SGA-II with catch-up growth, SGA-I without catch-up growth and AGA children respectively. (2) The serum adiponectin levels of individuals in the SGA-I without catch-up growth and SGA-II with catch-up growth groups were significantly lower than those from the SGA-II without catch-up growth group. There was no difference in triglyceride or IGFBP-1 levels among the groups. (3) The degree of HOMA-IR was positively correlated with age, current BMI and △height SDS in SGA children. Conclusion The development of insulin resistance and lower levels of adiponectin were closely correlated with higher BMI and the postnatal height catch-up growth in SGA children.

Molecular engineering of electron donors and acceptors for organic bulk heterojunction solar cells is critical to develop novel materials with improved power conversion efficiency. Here, the non-fullerene acceptors (NFAs) BTPT-4F and BTPTT-4F combined with an electron donor, P2F-EHp, were taken as a representative system to theoretically study the effects of the fusion of thienyl into the backbone of NFAs. On the basis of extensive quantum chemistry calculations, it was found that fusing thienyl into the backbone elevated the highest occupied molecular orbital (HOMO) energy, reduced the gap between the HOMO and the lowest unoccupied molecular orbital, decreased the dipole moment, enhanced the light absorbance and generated red-shifts in the absorption bands. The data for the P2F-EHp/BTPT-4F and P2F-EHp/BTPTT-4F complexes indicate that fusing thienyl into the backbone of the electron acceptor modifies the excitation character of the donor/acceptor complexes, increases the charge transfer (CT) excitation energy and the number of local excitation and CT hybridized low-lying excited states, amplifies the CT rate, reduces the exciton dissociation rate, and dramatically suppresses the charge recombination (CR) rate, leading to better performance of BTPTT-4F. However, the poorer performance of BTPT- 4F can mainly be attributed to its larger dipole moment and faster CR rate. [ABSTRACT FROM AUTHOR]

Although the alteration of DNA methylation due to abiotic stresses, such as exposure to the toxic metal cadmium (Cd), has been often observed in plants, little is known about whether such epigenetic changes are linked to the ability of plants to adapt to stress. Herein, we report a close linkage between DNA methylation and the adaptational responses in Arabidopsis plants under Cd stress. Exposure to Cd significantly inhibited the expression of three DNA demethylase genes ROS1/DML2/DML3 (RDD) and elevated DNA methylation at the genome‐wide level in Col‐0 roots. Furthermore, the profile of DNA methylation in Cd‐exposed Col‐0 roots was similar to that in the roots of rdd triple mutants, which lack RDD, indicating that Cd‐induced DNA methylation is associated with the inhibition of RDD. Interestingly, the elevation in DNA methylation in rdd conferred a higher tolerance against Cd stress and improved cellular Fe nutrition in the root tissues. In addition, lowering the Fe supply abolished improved Cd tolerance due to the lack of RDD in rdd. Together, these data suggest that the inhibition of RDD‐mediated DNA demethylation in the roots by Cd would in turn enhance plant tolerance to Cd stress by improving Fe nutrition through a feedback mechanism. Cadmium stress resulted in an increase in global genome‐wide DNA methylation by inhibiting the DNA demethylases ROS1/DML2/DML3 in roots of Arabidopsis plants, which improved the iron nutrition in roots, thus, resulting in an improvement of Cd tolerance in the plants. [ABSTRACT FROM AUTHOR]

Identification of the mechanisms that control lead (Pb) concentration in plants is a prerequisite for minimizing dietary uptake of Pb from contaminated crops. This study examines how nitrate uptake by roots affects Pb uptake and reveals a new resistance strategy for plants to cope with Pb contamination. We investigated the interaction between nitrate transporter (NRT)-mediated NO3– uptake and exposure to Pb in Arabidopsis using NRT-related mutants. Exposure to Pb specifically stimulated NRT1.1-mediated nitrate uptake. Loss of function of NRT1.1 in nrt1.1 -knockout mutants resulted in greater Pb toxicity and higher Pb accumulation in nitrate-sufficient growth medium, whereas no difference was seen between wild-type plants and null-mutants for NRT1.2 , NRT2.1 , NRT2.2 , NRT2.4 , and NRT2.5. These results indicate that only NRT1.1-mediated NO3− uptake alleviated Pb toxicity in the plants. Further examination indicated that rhizosphere acidification, which favors Pb entry to roots by increasing its availability, is prevented when NRT1.1 is functional and both NO3– and NH4+ are present in the medium. [ABSTRACT FROM AUTHOR]

The investigation of adsorption properties of anchor group on photo-anode is foundation in the optimization of dye sensitizers (DS) for solar cells. α-cyanoacrylic acid (CAA) is the typical anchor moiety coupled electronic acceptor in DS. To understand the interaction between rutile TiO 2 photo-anode and DS based upon CAA in dye sensitized solar cells, the atomic configurations, energies and electronic properties of CAA adsorbed on rutile TiO 2 (1 1 0) surface were studied by using density functional theory calculations. The results indicate CAA prefers to dissociatively adsorb on rutile TiO 2 (1 1 0) surface as bidentate configuration in which the O atoms of CAA bind with two adjacent surface five-coordinate Ti atoms along [0 0 1] direction, and the H atom in hydroxyl of CAA adhere to the nearest neighbor surface O atom at bridge site, generating a hydroxyl species. The corresponding adsorption energy is 1.480 eV. The analysis of geometrical parameters, density of states and electron density suggests the bonds between rutile TiO 2 (1 1 0) surface and CAA are formed. The density of states and orbital character at the gamma-point in reciprocal space support that the adsorption of CAA on the surface provides feasible mode for photo-induced electron injection. [ABSTRACT FROM AUTHOR]

( MgO ) 9 with a rocksalt structure, a magic number cluster of ( MgO ) n , exhibits high stability. In this study, the hydrogen storage properties of ( MgO ) 9 under an external electric field are explored by DFT calculation. The results reveal that H 2 can be adsorbed on single Mg/O atoms. Because the ( MgO ) 9 and H 2 are effectively polarized by the external electric field, the adsorption strength of H 2 at certain adsorption sites is substantially enhanced. The adsorption energies of H 2 on three-coordinated Mg/O atoms increase from −0.071/−0.056 eV in the absence of an electric field to −0.186/−0.237 eV under a field intensity of 0.025 a.u. Under the field, ( MgO ) 9 can adsorb a maximum of 18 H 2 molecules, and the corresponding mass density of hydrogen storage reaches 9.1 wt%. Our results suggest that subjecting the ( MgO ) 9 to an external electric field is a potential hydrogen storage method. In this paper, the interaction mechanism between H 2 and ( MgO ) 9 under the external electric field is also investigated through an electronic structure analysis. [ABSTRACT FROM AUTHOR]

Objective: To investigate possible correlations between apelin-12 levels and obesity in children in China and associations between apelin-12 and obesity-related markers, including lipids, insulin sensitivity and insulin resistance index (HOMA-IR). Methods: Forty-eight obese and forty non-obese age- and gender-matched Chinese children were enrolled between June 2008 and June 2009. Mean age was 10.42±2.03 and 10.86±2.23 years in obesity and control groups, respectively. Main outcome measures were apelin-12, BMI, lipids, glucose and insulin. HOMA-IR was calculated for all subjects. Results: All obesity group subjects had significantly higher total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), insulin levels and HOMA-IR (all P<0.05). In separate analyses, obese girls had significantly higher LDL-C, insulin and HOMA-IR than controls, and obese boys had significantly higher TC, TG, insulin and HOMA-IR than controls (all P<0.05). Apelin-12 levels were significantly higher in obese girls compared to controls (P = 0.024), and correlated positively with TG in all obese subjects. Among obese girls, apelin-12 levels correlated positively with TG, insulin and HOMA-IR after adjusting for age and BMI. In all boys (obese and controls) apelin-12 was positively associated with fasting plasma glucose (FPG). No significant correlations were found in either group between apelin-12 levels and other characteristics after adjusting for age, sex, and BMI. Conclusions: Apelin-12 levels are significantly higher in obese vs. non-obese girls in China and correlate significantly with obesity-related markers insulin, HOMA-IR, and TG. Increased apelin-12 levels may be involved in the pathological mechanism of childhood obesity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Selecting DFT functional is important to calculate the excited state properties. [•] The excited states with not-effective charger transfer character result into smaller Jsc . [•] The designed Ru-complexes may have good performance in DSCs. [Copyright &y& Elsevier]

Fanconi-Bickel syndrome (FBS) is a rare inherited disease caused by mutations in the glucose transporter 2 gene, SLC2A2. We reported the first two Chinese cases of FBS. Both cases presented typical clinical features of hepatomegaly, hypophosphatemic rickets, severely stunted growth, fasting hypoglycemia along with postprandial hyperglycemia, and proximal renal tubular dysfunction with disproportionately severe glucosuria. Genetic analysis of SLC2A2 gene revealed novel compound heterozygous mutations in both patients. The characteristics of being born as small for gestational age and apparent liver dysfunction in our cases have been seldom discussed in the literature. It seems FBS patients in general have lower birth weight than normal, but further data collection is still needed. Symptomatic treatments were effective, but the serum transaminase of patient 2 remained moderately increased, and he patient needed further follow-up. The present study will supplement the up-to-date clinical characteristic spectrum for FBS. [ABSTRACT FROM AUTHOR]

Background: Adrenocortical tumors (ACTs) are rare in children. Because of the rarity and various manifestations of ACTs, patients of ACTs are not easily diagnosed. Some patients were misdiagnosed before surgery. Objective: Identify the clinical, laboratorial, imaging and histopathological characteristics of adrenocortical tumors in children. Compare adrenalcortical adenoma with carcinoma. Methods: A retrospective review of 34 identified patients who were younger than 15 years old with histologic confirmation of adrenocortical carcinoma (ACC) or adenomas from 1991 to 2010. Results: In these 34 patients, 19 were adrenocortical adenoma (ACA) and 15 were ACC. The median age at diagnosis was 3.33 years (range, 0-16 years), and 70.6% of the patients were younger than five years. Girls slightly predominated over boys (1.4:1). For endocrine abnormality, 14 patients had isolated precocious puberty, five patients had isolated Cushing syndrome, 10 patients had precocious puberty plus Cushing syndrome, and five patients did not have any symptoms. The most frequent findings in laboratory tests were disturbance of the normal circadian rhythm of cortisol secretion (93.8%), followed by elevated serum level of testosterone (89.7%). Only 3.8% of ultrasound diagnosis and 12.1% of computed tomography (CT) diagnosis were consistent with pathologic diagnosis. Conclusion: Different from those in adult, the most frequent presentation in children with ACTs is peripheral precocious puberty with or without Cushing syndrome, and isolated Cushing' syndrome. Few present with non-functional local mass. Laboratory tests usually reveal the discordantly elevated serum levels of sexual corticosteroid hormones, change of diurnal rhythm of cortisol or increase of morning cortisol. The differentiation of malignant from benign tumor cannot merely depend on imaging. Final diagnosis relies on comprehensive evaluation of clinical manifestations, laboratory data, imaging and pathology. [ABSTRACT FROM AUTHOR]

Abstract: The stable structures of (AgBr) n (n ⩽6) are optimized by using density functional method, and the basis set effect is also investigated. Our initial structures are the stable structures of (AgX) n (X=Cl, Br, I, n ⩽6) obtained from the results of genetic algorithm. It is found that the most stable structures of (AgBr) n are planar rings for n ⩽4 and three-dimensional structures for n >4, with (AgBr)3 the most stable one. For the ground state structures of (AgBr) n , the chemical bonds are studied and electronic structures also explored. [ABSTRACT FROM AUTHOR]

The geometry, electronic structure, polarizability and hyperpolarizability of dye sensitizer 3,4-bis[1-(carboxymethyl)-3-indolyl]-1H-pyrrole-2,5-dione (BIMCOOH) were studied using density functional theory (DFT) with hybrid functional B3LYP, and the electronic absorption spectra were investigated using semi-empirical quantum chemical method ZINDO-1 and time-dependent DFT (TDDFT). The results of natural bond orbital suggest that the natural charges of the dione, indole, and acetic groups are about –0.15e, –0.29e, and 0.44e, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant and hyperpolarizability are 305.4, 188.3, and 1155.4 a.u., respectively. The electronic absorption spectral features in visible and near-UV region were assigned to the π→π* transition due to the qualitative agreement between the experiment and the TDDFT calculations, and the transitions of the excited states 9–11 related to photoinduced intramolecular charge transfer processes. The analysis of electronic structure and UV-Vis absorption indicates that the indole groups primarily contributed sensitization of photo-to-currency conversion processes, and the interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer BIMCOOH are electron injection processes from excited states of the dyes to the semiconductor conduction band. [ABSTRACT FROM AUTHOR]

During the study of anti-HIV-1 active components of the aqueous extracts of the roots of Salvia yunnanensis, three new derivatives of polyphenols, namely: methyl salvianolate A (2), ethyl salvianolate A (3) and cis-lithospermic acid (5) were isolated along with two known polyphenols, salvianolic acid A (1) and lithospermic acid (4) their structures were elucidated on the basis of NMR and MS spectral analyses. The anti-HIV-1 activities of the 5 polyphenols were tested for the inhibition of P24 antigen in HIV-1 infected MT-4 cell cultures and HIV-1 replicative enzymes in vitro. [ABSTRACT FROM AUTHOR]

A new polyphenol, designated as salvianolic acid N, was isolated from the aqueous extracts of the roots of Salvia yunnanensis. Its chemical structure was elucidated as 3-(3,4-dihydroxylphenyl)-2-{(E)-3-(1,8,9-trihydroxyl-dibenzo[b,f]oxpin-3-yl)acryloxloxy}propanoic acid (1) on the basis of NMR and MS spectral analyses. The new polyphenol inhibited both HIV-1 IN in vitro and also reduced HIV-1 p24 antigen in MT-4 cell lines. [ABSTRACT FROM AUTHOR]

Abstract: Genetic algorithm was combined with the semi-empirical quantum chemical PM3 method (GA+PM3) to scan the potential energy surface of cluster. The resulting isomers found by the GA+PM3 approach were then further optimized at the first principle level using Density Functional Theory (DFT) to obtain the optimal geometry and electronic structure for each cluster. This methodology was applied to investigate Si6N8 clusters. The electric charges and bond properties, along with the IR and Raman frequencies, polarizabilities and hyperpolarizabilities, of Si6N8 clusters were analyzed in detail. [Copyright &y& Elsevier]