Dispersion-convolution model for simulating peaks in a flow injection system

A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance or a period of time, the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position, height and area (tp*, h* and At*) from a recorder. An empirical temporal shift (Phi*) can be further approximated by Phi*=D*/u2, which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q)=delta0+delta1Q+delta2Q2. The optimal dispersion occurs at a pumping rate of Qopt=sqrt[delta0/delta2]. This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis.     

Quantifying the intrinsic effects of two point mutation models of pro-pro-pro triamino acid diamide. A first-principle computational study

Stabilities and conformational properties of two Pro --> Thr point mutation models were computed at the B3LYP/6-31G(d) level of theory for the parent triamino acid diamide Pro-Pro-Pro (HCO-Pro-Pro-Pro-NH2). Geometrical parameters for the amino acid sequences, used in the molecular orbital computations for Pro-Pro-Thr and Pro-Thr-Pro, were retrieved from the Protein Data Bank. Thermodynamic functions (S, H, G) were computed for the fully optimized geometries. To assess the stabilization energetics of these mutant models, relative to the parent Pro-Pro-Pro reference conformer epsilon(L) epsilon(L) gamma(L), isodesmic reactions were constructed to calculate DeltaS, DeltaH, and DeltaG. The importance of intramolecular hydrogen bonds involving the -OH group of the Thr side chain, which emerged after the point mutations, was also examined to determine the internal stabilization of these peptide models. This study describes an approach to analyzing a point mutation at the center of a peptide chain and compares its stability to that of a point mutation at a terminal end in a small peptide model.     

Transition state infrared spectra for the trans-->cis isomerization of a simple peptide model

Trans-->cis isomerization of N-methylacetylamide (MeCO-NHMe) has been studied at the G3MP2B3 level of theory and the vibration spectrum has been calculated as a function of the torsional mode of motion along the peptide bond. Noticeable spectral differences have been observed for the transition state interconnecting the cis and trans isomers.     

A cross-sectional scanning tunneling microscopy study of IrO2 rutile single crystals

Rutile iridium dioxide (IrO₂) surfaces were studied by cross-sectional scanning tunneling microscopy (XSTM). Atomically flat surfaces prepared by in situ ultra high vacuum cleaving of crystalline platelets of thicknesses <50 μm were successfully demonstrated. In addition to (1 1 0) surface, several vicinal planes, e.g., (1 2 0), (1 3 0) and , were also examined. The cleaved planes are close to bulk-terminated surfaces with predominant [0 0 1]-oriented bridge oxygen rows. Unlike TiO₂, bright oxygen rows are imaged and oxygen defects appear as dim species. Our studies show that XSTM is a viable technique to study oxide surfaces that are otherwise difficult to prepare.     

Junceols D-H, new polyoxygenated briaranes from sea whip gorgonian coral Junceella juncea (Ellisellidae)

Chemical investigations on the sea whip gorgonian coral Junceella juncea have led to the isolation of five new 8-hydroxybriarane diterpenoids, junceols D-H (1-5). The structures of briaranes 1-5 were determined on the basis of spectroscopic methods and the methylenecyclohexane rings were found to exist in boat form in these new diterpenoids. Junceols D (1) and F-H (3-5) exhibited cytotoxicity toward CCRF-CEM and DLD-1 tumor cells and junceols E-H (2-5) displayed weak inhibitory effects on superoxide anion generation by human neutrophils.     

A unified nonlinear formulation for plate and shell theories

A general geometrically exact nonlinear theory for the dynamics of laminated plates and shells under-going large-rotation and small-strain vibrations in three-dimensional space is presented. The theory fully accounts for geometric nonlinearities by using the new concepts of local displacements and local engineering stress and strain measures, a new interpretation and manipulation of the virtual local rotations, an exact coordinate transformation, and the extended Hamilton principle. Moreover, the model accounts for shear coupling effects, continuity of interlaminar shear stresses, free shear-stress conditions on the bonding surfaces, and extensionality. Because the only differences among different plates and shells are the initial curvatures of the coordinates used in the modeling and all possible initial curvatures are included in the formulation, the theory is valid for any plate or shell geometry and contains most of the existing nonlinear and shear-deformable plate and shell theories as special cases. Five fully nonlinear partial-differential equations and corresponding boundary and corner conditions are obtained, which describe the extension-extension-bending-shear-shear vibrations of general laminated two-dimensional structures and display linear elastic and nonlinear geometric coupling among all motions. Moreover, the energy and Newtonian formulations are completely correlated in the theory.     

Prospects of application of Mo–V-phosphoric heteropolyacid solutions as bifunctional catalysts for syntheses of anthraquinones and their substituted derivatives

The acid-catalyzed condensation of 1,3-butadienes with p-quinones and oxidation of the obtained adducts can be carried out as one-pot process in the presence of aqueous solutions of Mo–V–P-heteropolyacids (HPA) of the general composition H_aP_zMo_yV_xO_b. These solutions act as bifunctional catalysts, since they simultaneously behave as strong Brönsted acids and fairly strong reversible oxidants. The condensation of 1,4-naphthoquinone (NQ) with 1,3-butadiene in solutions of high-vanadium HPA of the empirical compositions H₁₅P₄Mo₁₈V₇O₈₉ and H₁₇P₃Mo₁₆V₁₀O₈₉ in the presence of water-miscible organic solvents (acetone, 1,4-dioxane) affords 9,10-anthraquinone in a yield of ~70% and purity up to 97% at a complete conversion of NQ. Under similar conditions, the reactions of NQ and substituted 1,3-butadienes afford substituted anthraquinones in the yields up to 90% and purity up to 99%. The catalysts are regenerated with oxygen in an individual step and can be reused.     

Electronic Properties and Field‐Effect Transistors of Thiophene‐Based Donor–Acceptor Conjugated Copolymers

Summary: The thiophene‐quinoxaline donor–acceptor conjugated copolymer poly[(thiophene‐2,5‐diyl‐alt‐(2,3‐diheptylquinoxaline‐5,8‐diyl)] (PTHQx) was explored as a semiconductor in thin‐film organic field‐effect transistors (OFETs). A hole mobility of 3.6 × 10⁻³ cm² · V⁻¹ · s⁻¹ and an on/off current ratio of 6 × 10⁵ were observed in p‐channel OFETs made from spin‐coated PTHQx thin films. The electronic structures of PTHQx and a related thiophene‐thienopyrazine donor–acceptor copolymer were calculated by density functional theory. Atomic force microscopy of PTHQx thin films showed a polycrystalline grain morphology that varied with the substrate.

Output (left) and transfer (right) characteristics of a PTHQx (structure shown) organic field‐effect transistor.     

Induction of G2/M Cell Cycle Arrest via p38/p21Waf1/Cip1-Dependent Signaling Pathway Activation by Bavachinin in Non-Small-Cell Lung Cancer Cells

Lung cancer is the most commonly diagnosed malignant cancer in the world. Non-small-cell lung cancer (NSCLC) is the major category of lung cancer. Although effective therapies have been administered, for improving the NSCLC patient’s survival, the incident rate is still high. Therefore, searching for a good strategy for preventing NSCLC is urgent. Traditional Chinese medicine (TCM) are brilliant materials for cancer chemoprevention, because of their high biological safety and low cost. Bavachinin, which is an active flavanone of Proralea corylifolia L., possesses anti-inflammation, anti-angiogenesis, and anti-cancer activities. The present study’s aim was to evaluate the anti-cancer activity of bavachinin on NSCLC, and its regulating molecular mechanisms. The results exhibited that a dose-dependent decrease in the cell viability and colony formation capacity of three NSCLC cell lines, by bavachinin, were through G2/M cell cycle arrest induction. Meanwhile, the expression of the G2/M cell cycle regulators, such as cyclin B, p-cdc2^Y15, p-cdc2^T161, and p-wee1, was suppressed. With the dramatic up-regulation of the cyclin-dependent kinase inhibitor, p21^Waf1/Cip1, the expression and association of p21^Waf1/Cip1 with the cyclin B/cdc2 complex was observed. Silencing the p21^Waf1/Cip1 expression significantly rescued bavachinin-induced G2/M cell accumulation. Furthermore, the expression of p21^Waf1/Cip1 mRNA was up-regulated in bavachinin-treated NSCLC cells. In addition, MAPK and AKT signaling were activated in bavachinin-added NSCLC cells. Interestingly, bavachinin-induced p21^Waf1/Cip1 expression was repressed after restraint p38 MAPK activation. The inhibition of p38 MAPK activation reversed bavachinin-induced p21^Waf1/Cip1 mRNA expression and G2/M cell cycle arrest. Collectively, bavachinin-induced G2/M cell cycle arrest was through the p38 MAPK-mediated p21^Waf1/Cip1-dependent signaling pathway in the NSCLC cells.     

Total Synthesis of 16-Acetoxy-6,7-didehydroferruginyl Methyl Ether

16-hydroxy-6,7-didehydroferruginol1wasisolatedfromtherootofSalviaapianabyAnonioG.etal.ItisinterestingtomedicinalandsyntheticstatusofC16inthismolecular.Basedonourknowledge,nosyntheticwayhadbeenconductedtothisc0mpoundandtofurtherexploretherelati0nshipbetWeenstructureandbioactivities,weherereportanefficientsyntheticroutet0thel6-acet0xy-6,7-didehydroferruginylmethylether2.citral3gavethe(a)-cyclocitraI4.Condensati0nof4with(4-methoxybenZyl)-triphenylphosph0niumchIoride5(preparedformp-anisicacidvi…