Synthesis,self‐assembly and drug‐loading capacity of well‐defined drug‐conjugated amphiphilic A2B2 type miktoarm star copolymers based on poly(ε‐caprolactone) and poly(ethylene glycol)

Well‐defined drug‐conjugated amphiphilic A₂B₂ miktoarm star copolymers [(PCL)₂‐(PEG)₂‐D] were prepared by the combination of controlled ring‐opening polymerization (CROP) and “click” reaction strategy. First, bromide functionalized poly(ε‐caprolactone) (PCL‐Br) with double hydroxyl end groups was synthesized by the CROP of ε‐caprolactone using 2,2‐bis(bromomethyl)propane‐1,3‐diol as a difunctional initiator in the presence of Sn(Oct)₂ at 110 °C. Next, the bromide groups of PCL‐Br were quantitatively converted to azide form by NaN₃ to give PCL‐N₃. Subsequently, the end hydroxyl groups of PCL‐N₃ were capped with ibuprofen as a model drug at room temperature. Finally, copper(I)‐catalyzed cycloaddition reaction between ibuprofen‐conjugated PCL‐N₃ and slightly excess alkyne‐terminated poly(ethylene glycol) (A‐PEG) led to ibuprofen‐conjugated A₂B₂ miktoarm star copolymer [(PCL)₂‐(PEG)₂‐D]. The excess A‐PEG was removed by dialysis. ¹H NMR, FTIR and SEC analyzes confirmed the expected miktoarm star architecture. These amphiphilic miktoarm star copolymers could self‐assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In addition, the drug‐loading capacity of these drug‐conjugated miktoarm star copolymers as well as their nondrug‐conjugated analogs were also investigated in detail. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Research on a Rice Counting Algorithm Based on an Improved MCNN and a Density Map

The thousand grain weight is an index of size, fullness and quality in crop seed detection and is an important basis for field yield prediction. To detect the thousand grain weight of rice requires the accurate counting of rice. We collected a total of 5670 images of three different types of rice seeds with different qualities to construct a model. Considering the different shapes of different types of rice, this study used an adaptive Gaussian kernel to convolve with the rice coordinate function to obtain a more accurate density map, which was used as an important basis for determining the results of subsequent experiments. A Multi-Column Convolutional Neural Network was used to extract the features of different sizes of rice, and the features were fused by the fusion network to learn the mapping relationship from the original map features to the density map features. An advanced prior step was added to the original algorithm to estimate the density level of the image, which weakened the effect of the rice adhesion condition on the counting results. Extensive comparison experiments show that the proposed method is more accurate than the original MCNN algorithm.     

铁氰化钴修饰石墨烯平面电极对过氧化氢的传感作用

利用高分子支撑法将气相沉积(CVD)石墨烯从铜基底上转移到聚对苯二甲酸乙二醇酯(PET)基底上,制备出石墨烯平面电极(GPE), 通过循环伏安法将铁氰化钴(CoHCF)纳米颗沉积到GPE上,得到铁氰化钴修饰石墨烯平面电极(CoHCF/GPE).研究表明,此电极对过氧化氢具有良好的传感作用,从而构建一种新型无酶过氧化氢传感器.此传感器在过氧化氢浓度为5.0-1200 μmol/L范围内,响应电流与浓度呈现良好的线性关系,检出限为7.1 nmol/L (S/N=3),响应时间约为2 s,具有稳定性好、抗干扰能力强、制备简单等优点.     

A Practical System for High-Throughput Screening of Mutants of <Emphasis Type="Italic">Bacillus fastidiosus</Emphasis> Uricase

For high-throughput screening (HTS) of Bacillus fastidiosus uricase mutants, a practical system was proposed. By error-prone PCR with final 1.5 mM MnCl₂, two focused libraries of mutants for A1-V158 and V150-D212 were generated separately. After induced expression of individual clones in 48-well microplates, Escherichia coli cells (BL21) were lyzed by 1.0 M Tris-HCl at pH 9.0 in 96-well microplates at 25 °C for 7.5 ~ 10.5 h; uricase reaction was continuously monitored with 0.15 mM uric acid in 96-well plates by absorbance at 298 nm to estimate V _m/K _m by kinetic analysis of reaction curve for comparison. V _m/K _m was resistant to initial uric acid levels with an upper limit 3-fold over that of initial rates. By receiver-operator-characteristic analysis of the recognition of the one of higher activity in uricase pair whose specific activity ratio was 1.8 or 3.3, the area-under-the-curve was comparable to that with cell lysates prepared by sonication treatment. A cutoff for the maximum Youden index was thus developed to recognize positive mutants of 1-fold higher activity. Indeed, mutant L171I/Y182F/Y187F/A193S of higher activity but lower thermostability at pH 7.4 and mutant V144A of higher activity and consistent thermostability were discovered. Therefore, the proposed system was practical for HTS of uricase mutants.     

Experimental Study on Purification of Diesel Particulate Matter by Non-thermal Plasma Technology

In order to investigate the effects of non-thermal plasma (NTP) on diesel particulate matter (PM), an engine test bench was built up. An engine exhaust particle sizer (EEPS) was introduced to analyze the emission concentration and size distribution of PM and a thermo-gravimetric analyzer was used to analyze the effects of NTP on the composition of the particulate matter in the exhaust gas. The results show that the size distribution interval of the particle mass concentration falls behind that of the quantity concentration under various loads. When the diesel engine operating speed is 2400 rpm and the load is 25%, after NTP, the proportions of the nucleation mode particles and the accumulative mode particles exhibit a small fluctuation while the proportion of ultrafine particles decreases by 10% due to their large quantity concentration. Under the dual effect of DPF and NTP, the particle quantity concentration decreases by 98%. In order to investigate the effect of NTP on the composition of the PM, a thermo-gravimetric analysis of the particles obtained before and after NTP was carried out. The results show that the proportion of volatile matter falls by 16.05% and solid carbon accounts for an increase of 7.29%. NTP has the ability to improve reduction activity of particles and make particles easier to be oxidized at a lower temperature.     

Polarization holographic optical recording based on a new photochromic diarylethene compound

A new unsymmetrical photochromic diarylethene, namely1-[2-methyl-5-(p-N,N-dimethylaminophenyl)-3-thienyl]-2-[2-methyl-5-(3-methoxylphenyl)-3-thienyl] perfluorocyclopentene (1a), was synthesized. The compound showed good photochromism, high sensitivity and remarkable fatigue-resistance both in solution and in poly(methyl methacrylate) (PMMA) matrix with UV/Vis light irradiation. The absorption maximum of its closed-ring isomer was observed at 624 nm in PMMA amorphous film. It is a nice match for the wavelength of the recording laser (633 nm). Using this target compound as recording medium, four types of polarization holographic optical recordings were performed successfully using a He-Ne laser. The results showed that only the orthogonal circular polarization recording could obtain a hologram with high diffraction efficiency and high signal-to noise-ratio. With multiplexing recording technology, three types of polarization multiplexing holographic optical recordings, including angular multiplexing, polarization multiplexing, and angular plus polarization multiplexing holographic recording, were also carried out perfectly based on its photoinduced anisotropic phenomenon accompanying the photochromic reaction by photoirradiation. The results demonstrate that the multiplexing recording technology is an effective method to improve recording capacity when using diarylethene 1 as recording medium.     

A comparison of positive and negative ion collision‐induced dissociation for model heptapeptides with one basic residue

The effects of the identity and position of basic residues on peptide dissociation were explored in the positive and negative modes. Low‐energy collision‐induced dissociation (CID) was performed on singly protonated and deprotonated heptapeptides of the type: XAAAAAA, AAAXAAA, AAAAAXA and AAAAAAX, where X is arginine (R), lysine (K) or histidine (H) residues and A is alanine. For [M + H]⁺, the CID spectra are dominated by cleavages adjacent to the basic residues and the majority of the product ions contain the basic residues. The order of a basic residue's influence on fragmentation of [M + H]⁺ is arginine > histidine ≈ lysine, which is also the order of decreasing gas‐phase basicity for these amino acids. These results are consistent with the side chains of basic residues being positive ion charge sites and with the more basic arginine residues having a higher retention (i.e. sequestering) of the positive charge. In contrast, for [M ? H]^? the identity and position of basic residues has almost no effect on backbone fragmentation. This is consistent with basic residues not being negative mode charge sites. For these peptides, more complete series of backbone fragments, which are important in the sequencing of unknowns, can be found in the negative mode. Spectra at both polarities contain C‐terminal y‐ions, but y_n″⁺ has two more hydrogens than the corresponding y_n^?. Another major difference is the production of the N‐terminal backbone series b_n⁺ in the positive mode and c_n^? in the negative mode. Thus, comparison of positive and negative ion spectra with an emphasis on searching for pairs of ions that differ by 2 Da (y_n″⁺ vs y_n^?) and by 15 Da (b_n⁺ vs c_n^?) may be a useful method for determining whether a product ion is generated from the C‐terminal or the N‐terminal end of a peptide. In addition, a characteristic elimination of NH?C?NH from arginine residues is observed for deprotonated peptides. Copyright © 2010 John Wiley & Sons, Ltd.     

基于像散与理想光源成像原理的高亮度半导体激光器光纤耦合设计方法

运用像散原理和理想光源成像原理,讨论了半导体激光器消像散设计.提出了一种基于消像散的高亮度半导体激光器光纤耦合系统的设计方法.以波长为808 nm,输出功率为10 W的半导体激光器的光纤耦合为例,给出了详细的计算方法和设计步骤.结果表明:采用该方法将半导体激光器光束耦合入数值孔径为0.22,芯径为50 μm的光纤中,耦...     

Different sound decay patterns and energy feedback in coupled volumes

Different non-exponential decays such as the concave and the convex double sloped decays in the coupled rooms provide distinct sound qualities. These are commonly considered to occur in the less reverberant sub-room and the more reverberant sub-room, respectively. However, numerical simulations and experiments in this paper show that the demarcation line is not located along the physical boundaries (e.g., the partition and the coupling aperture), but in the more reverberant sub-room. The sound field with the concave double sloped decay penetrates into the auxiliary sub-room to an extent which is influenced by the difference between the two natural reverberations of the sub-rooms. Furthermore the sound energy flows in different regions are investigated, demonstrating how energy feedback leads to the concave double sloped decay.