[Lake algae chemotaxonomy technology based on fluorescence excitation emission matrix and parallel factor analysis].

An in vivo three-dimensional fluorescence method for the determination of algae community structure was developed by parallel factor (PARAFAC) analysis and CHEMTAX. The PARAFAC model was applied to fluorescence excitation-emission matrix (EEM) of 23 algae species and 12 fluorescent components were identified according to the residual sum of squares and specificity of the composition profiles of fluorescent. Based on the 12 fluorescent components, the algae species at different growth stages were correctly classified at the division level using Bayesian discriminant analysis (BDA). Then the reference fluorescent component ratio matrix was constructed for CHEMTAX, and the EEM-PARAFAC-CHEMTAX method was developed to differentiate taxonomic groups of algae. When the fluorometric method was used for 531 single-species samples, the average correct discrimination ratio (CDR) was 99.1% and the correct discrimination ratios (CDRs) were 100% at the division level except Chlorophyta, the CDR of which was 97.5%. The CDRs for 95 mixtures were above 98.5% for the dominant algae species and above 90.5% for the subdominant algae species, with average relative contents of 69.7% and 26.4%, respectively. This technique would be of great aid when low-cost and rapid analysis is needed for samples in a large batch.

Interactions between polyacrylonitrile and solvents: density functional theory study and two-dimensional infrared correlation analysis.

Polyacrylonitrile (PAN) is a semicrystalline polymer with high polarity and is usually processed from solutions. Selected solvents for processing influence both the structure and properties of PAN products. We describe the interactions between PAN and various solvents by theoretical calculation based on density functional theories (DFT), and by experimental methods of Fourier transform infrared (FTIR) spectra and two-dimensional infrared (2D-IR) correlation analysis. The selected solvents include dimethyl sulfone (DMSO2), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), propylene carbonate (PC), N,N-dimethyl formamide (DMF), and N,N-dimethyl acetamide (DMAc). Calculation results show that the PAN model monomer (PAN') interacts with each solvent through dipole-dipole interaction and formed PAN'-solvent complexes. Each complex displays an antiparallel alignment of interacting pair between the C≡N group of PAN' and the polar group of solvent molecule (S═O or C═O group). The calculated binding energies (ΔE) reveal that PAN' preferentially interacts with solvent in the order of DMSO2 > DMSO > EC > PC > DMF > DMAc. Red shifts of vibration frequencies are observed for C≡N, S═O, and C═O stretching bands. The C≡N stretching band shifts from 2245 cm(-1) in PAN to 2240, 2242, and 2241 cm(-1) in PAN-DMSO, PAN-EC, and PAN-DMF mixtures, respectively, indicating the existence of PAN-solvent interactions. Moreover, 2D-IR correlation analysis shows that as the PAN content increases, DMSO molecules vary prior to PAN-DMSO complexes, and change earlier than PAN bulk. However, PAN-EC and PAN-DMF mixtures follow the order of PAN bulk > PAN-solvent complexes > solvent molecules. This combination of theoretical simulation and experimental characterization is useful in selection of solvents for PAN or even other polar polymers and can provide an insight into the physical behavior of PAN-solvent complexes.

3-Diazo-N-[(2S)-1-hy-droxy-propan-2-yl]-2-oxopropanamide.

In the title compound, C(6)H(9)N(3)O(3), the 3-diazo-2-oxopropan-amide section of the mol-ecule is nearly planar, with a maximum deviation of 0.025 (1) Šfrom the mean plane of its constituent atoms. The diazo C=N=N angle is 178.0 (3)°. In the crystal, pairs of inter-molecular O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into infinite double chains along the [100] direction. The double chains are additionally stabilized by weak C-H⋯O contacts with C⋯O distances of 3.039 (3) Å. Neighboring double chains in turn inter-act with each other through π-π stacking inter-actions [centroid-centroid distance of the 3-diazo-2-oxopropanamide units = 3.66 (6) Å] to form infinite stacks along the b axis. Mol-ecules from neighboring stacks inter-digitate with each other in the c-axis direction, thus leading to an inter-woven three-dimensional network held together by O-H⋯O, N-H⋯O and C-H⋯O inter-actions and π-π stacking.

[The expression pattern and possible function of microRNA-34a in neurons].

Using Northern blotting, ISH and FISH, we demonstrated miR-34a expresses with aging in the brain of rhesus monkey and rat. Correspondingly, the same trend was found in the primary cultures of cortical neurons. Moreover, we found that induction of miR-34a led to neuronal apoptosis by targeting BCL-2. Our study suggests that miR-34a may play critical roles in neuronal development and ageing.

[The quantified analysis of fresh mutton tenderness using PLS methods and Fourier transform near-infrared spectroscopy].

Ninety eight representative fresh mutton samples from Neimeng, Ningxia, Gansu, Xinjiang province were selected for this study, the nondestructive measurement of the fresh mutton tenderness by Fourier transform near infrared (FT-NIR) spectroscopy was discussed. Partial least squares(PLS) algorithm was used to build the model between the shear force value of the fresh mutton tenderness measured by the texture machine and the FT-NIR spectra. The influence of different processing method of spectra, factors and wave regions on the determination coefficients (r2), root mean square error of cross validation (RMSECV) and root mean square error of prediction (RMSEP) was studied. The result showed that the shear force value of ninety eight representative fresh mutton samples was 1.673-6.631 kg, and the shear force value above 75% samples was 2-5 kg, almost covering the fresh mutton tenderness of our country's sheep, the r2 of the calibration could reach 86.2% and the RMSECV was up to 0. 445 in the wave number range 11 995-5 446 cm(-1) and 4 601-4 246 cm(-1) with vector normalization when the PLS factors was ten. The correlation coefficient(R), RMSEP and average bias between value measured by the texture machine and predicted value of model based on validation samples were 0.87, 0.524 and 0.385 respectively. The result indicates that FT-NIR spectroscopy is capable of predicting tenderness value of fresh mutton.