Photoluminescent polymer-based smart window reinforced with electrospun glass nanofibres

Poly(vinyl chloride) (PVC) was reinforced with electrospun glass nanofibres (EGN) to develop photochromic and afterglow materials such as smart windows and anti-counterfeiting prints. A colourless electrospun glass nanofibres@poly(vinyl chloride) (EGN@PVC) sheet was prepared by physical integration of lanthanide-doped aluminate nanoparticles (LANP). The low concentrations of LANP in the photochromic and photoluminescent EGN@PVC hybrids displayed fluorescence emission with instant reversibility. EGN@PVC with the highest phosphor concentrations showed persistent phosphorescence emission with slow reversibility. Based on the results of the Commission Internationale de l'éclairage Laboratory and luminescence spectroscopy, the translucent EGN@PVC samples became green in the presence of ultraviolet illumination and greenish-yellow in the absence of light. According to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the morphological study of EGN and LANP showed diameters of 75–95 and 11–19 nm, respectively. The morphology of the EGN@PVC substrates was studied using SEM, X-ray fluorescence, and energy-dispersive X-ray spectroscopy. The mechanical characteristics of PVC were enhanced by reinforcement with EGN as a roughening agent. When comparing the scratching resistance of LANP-free substrate to photoluminescent EGN@PVC substrates, it was observed that the latter was much superior. The photoluminescence spectra were reported to have an emission peak at 519 nm when excited at 365 nm. These findings demonstrated that the luminous transparent EGN@PVC composites had improved superhydrophobic and UV-blocking characteristics.     

Se(VI) reduction by continuous-flow reactors packed with Shigella fergusonii strain TB42616 immobilized by Ca2+-alginate gel beads

Selenium at high levels may cause adverse health effects on human beings and endanger aquatic lives due to its toxicity. Se(VI) reduction in continuous-flow reactors packed with Shigella fergusonii strain TB42616 immobilized by Ca²⁺-alginate gel beads was investigated under various hydraulic retention times (HRT) and influent Se(VI) concentrations. Removal efficiency up to 98.8 % was achieved after 96 days operation under an HRT of 5 days and an influent Se(VI) concentration of 400 mg/L. The results showed that the overall selenium removal efficiency was affected by the HRT and the bed height of the reactor but not the influent Se(VI) concentration. The steady-state data were analyzed using a mathematical model and Monod-type kinetics. Biokinetic parameters of half-velocity constants and maximum specific reduction rates were optimized using steady-state data obtained under a range of HRTs (0.73–5.0 days) at a constant influent Se(VI) concentration of 50 mg/L. The model was validated using steady-state data obtained under influent Se(VI) concentrations ranging from 10 to 400 mg/L while maintaining the HRT at 5.0 days. The high correlation coefficients between model calculated Se(VI) and Se(IV) concentrations and the experimental data indicate that the model is robust to predict the performance of the continuous-flow bioreactor.     

褐飞虱对五种杀虫剂抗性的快速检测技术

【目的】建立褐飞虱Nilaparvata lugens对常用杀虫剂抗性的快速检测技术,实时掌握田间褐飞虱种群的抗药性水平,以指导褐飞虱防控合理用药。【方法】基于玻璃瓶药膜法,研制褐飞虱3龄若虫对吡虫啉、啶虫脒、醚菊酯、毒死蜱和异丙威5种杀虫剂抗性的快速检测试剂盒;利用试剂盒测定的死亡率与稻苗浸渍法测得的抗性倍数进行相关性分析,并验证利用试剂盒快速测定褐飞虱田间种群对5种杀虫剂 抗性水平的准确性。【结果】处理1 h时吡虫啉、啶虫脒、醚菊酯、毒死蜱和异丙威对褐飞虱室内敏感种群3龄若虫的LD₉₀分别为：30.96, 92.05, 117.24, 514.21和1.24 ng/cm²。在吡虫啉、啶虫脒、醚菊酯、毒死蜱和异丙威相应诊断剂量下,贵州省不同田间种群褐飞虱3龄若虫的校正死亡率分别在23.75%~78.75%, 25.00%~78.75%, 43.75%~88.75%, 36.25%~85.00%和18.75%~67.50%之间。相关性分析表明,上述田间种群褐飞虱3龄若虫的死亡率与稻苗浸渍法测定的抗性倍数呈显著负相关,相关系数在0.8751~0.9754之间。通过快速检测试剂盒获得的死亡率及相关性方程计算得到贵州安龙地区(AL)褐飞虱种群对吡虫啉、啶虫脒、醚菊酯、毒死蜱和异丙威的推测抗性倍数分别为7.23, 3.68, 4.14, 4.12和31.18,采用稻苗浸渍法测得上述5种杀虫剂的实测抗性倍数分别为6.33, 5.24, 3.71, 4.50和26.56,表明推测抗性倍数与实测的抗性倍数结果表现一致。【结论】该快速检测试剂盒可以通过测定褐飞虱田间种群的死亡率,快速评估褐飞虱田间种群对杀虫剂的抗性水平。     

景观水体周丛生纤毛虫群落结构及其与环境因子的关系

为了解载玻片法获取的周丛生纤毛虫群落可否用于监测景观水体,于2015年利用载玻片采样法对上海东南角的一处景观水体的周丛生纤毛虫的群落结构进行了周年调查,并对其与环境因子之间的相关性进行了研究。共检出12目51种周丛生纤毛虫。周丛生纤毛虫的年平均密度为127.29个/cm~2,2月密度最低,为24.27个/cm~2,5月密度最高,为248.57个/cm~2;其群落结构应对水体环境的变化呈现显著的季节性变动。多元统计分析表明,总磷浓度和水温(T)均是影响周丛生纤毛虫群落结构的主要环境因子。作为周丛生纤毛虫最主要的类群,缘毛目纤毛虫的密度与透明度(SD)和电导率(Spc)呈显著正相关,与T呈极显著正相关;丁丁目、毛口目和侧口目纤毛虫的密度与SD呈显著负相关,其中丁丁目纤毛虫的密度与T呈极显著负相关;此外,丁丁目纤毛虫的密度与总氮(TN)浓度呈极显著正相关。冗余分析显示,优势种钟形钟虫、钟虫sp.2、聚缩虫sp.1、亨氏累枝虫、沟钟虫和螅状独缩虫的密度与环境因子具有较好相关性。研究表明,载玻片法采集的周丛生纤毛虫能很好的反映水质变化,该方法可以作为景观水体水质监测方法的一个补充。     

Gravettian tear-drop-shaped beads

The two regions southwestern Germany and southwestern France have yielded Gravettian personal ornaments in form of tear-drop-shaped beads. We present updated numbers of these artefacts, because during the recent excavations since 2002 in Hohle Fels cave near the city of Ulm, Southwest Germany, additional beads were found. The present paper proposes for the first time a typo-technological study of the tear-drop-shaped beads.     

Increased neem extract content enhances drying survival of co-encapsulated Saccharomyces cerevisiae and decreases relative release of azadirachtin

Plant extracts from the neem tree can be applied as a bioinsecticidal compound in ‘attract-and-kill’ co-formulations to control soil-dwelling insect pests. Since insects are attracted to the bioinsecticide, the attract-and-kill approach benefits from a reduced dose of insecticide needed. Here, we demonstrate that a powdery neem seed kernel extract in combination with corn starch significantly enhances the drying survival of co-encapsulated CO₂-releasing Saccharomyces cerevisiae. Additionally, an increased content of the neem extract was shown to slow down the relative release of azadirachtin A. Both findings are of high relevance for the development of formulations in the field of biological pest control.     

Pilot-scale process for magnetic bead purification of antibodies directly from non-clarified CHO cell culture

High capacity magnetic protein A agarose beads, LOABeads PrtA, were used in the development of a new process for affinity purification of monoclonal antibodies (mAbs) from non-clarified CHO cell broth using a pilot-scale magnetic separator. The LOABeads had a maximum binding capacity of 65 mg/mL and an adsorption capacity of 25–42 mg IgG/mL bead in suspension for an IgG concentration of 1 to 8 g/L. Pilot-scale separation was initially tested in a mAb capture step from 26 L clarified harvest. Small-scale experiments showed that similar mAb adsorptions were obtained in cell broth containing 40 × 10⁶ cells/mL as in clarified supernatant. Two pilot-scale purification runs were then performed on non-clarified cell broth from fed-batch runs of 16 L, where a rapid mAb adsorption ≥96.6% was observed after 1 h. This process using 1 L of magnetic beads had an overall mAb yield of 86% and 16 times concentration factor. After this single protein A capture step, the mAb purity was similar to the one obtained by column chromatography, while the host cell protein content was very low, <10 ppm. Our results showed that this magnetic bead mAb purification process, using a dedicated pilot-scale separation device, was a highly efficient single step, which directly connected the culture to the downstream process without cell clarification. Purification of mAb directly from non-clarified cell broth without cell separation can provide significant savings in terms of resources, operation time, and equipment, compared to legacy procedure of cell separation followed by column chromatography step. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2775, 2019.     

Electrically measuring viscoelastic parameters of adherent cell layers under controlled magnetic forces

Electrical cell-substrate impedance sensing (ECIS) was used to measure the time-dependence and frequency-dependence of impedance for current flowing underneath and between cells. Osteosarcoma cells with a topology similar to a short cylinder (coin-like) surmounted by a dome were used in this study. Application of a small step increase in net vertical stress to the cells (4 and 7 dyn/cm²), via magnetic beads bound to the dorsal (upper) surface, causes an increase in cell body height and an increase in cell-cell separation, as well as stretching of the cell-substrate adhesion bonds. This results in a fast drop in measured resistance (less than 2 s), followed by a slower change with a time constant of 60–150 s. This time constant is about 1.5 times longer at 22 °C than that at 37 °C; it also increases with applied stress. Our frequency scan data, as well as our data for the time course of resistance and capacitance, show that the fast change is associated with both the under-the-cells and between-the-cells resistance. The slower change in resistance mainly reflects the between-the-cells resistance. To obtain viscoelastic parameters from our data we use a simple viscoelastic model comprising viscous and elastic elements (i.e., a dashpot and two springs) for the cell body, and an elastic element (a spring) for the cell-substrate adhesion system. Our results show that the spring constants and the viscosity of the cell body components of this viscoelastic model decrease as the temperature increases, whereas the elastic modulus of cell-substrate adhesion increases with temperature. At 37 °C, for the cell body we obtain a value of about 10⁵ P for the viscous element of the viscoelastic model, and a spring constant expressed in units of an elastic modulus of about 10⁴ dyn/cm² for the spring in series with the viscous element, with another spring with a modulus of about 2×10³ dyn/cm² in parallel with these. In comparable units, we have a modulus for the cell-substrate adhesion system of about 3×10³ dyn/cm². Received: 23 March 1998 / Revised version: 23 June 1998 / Accepted: 1 July 1998     

Molecular weight effects on the glass transition of gelatin/cosolute mixtures

The structural properties of four gelatin fractions in mixture with sucrose and glucose syrup have been investigated extensively using small deformation dynamic oscillation. The total level of solids was 80%, the number average molecular weight of the protein ranged from 29.2 to 68 kD, and the temperatures were between 60 and -60 degrees C. Remarkably, the nature of the time and temperature dependence on the viscoelastic functions of all samples could be reduced to master curves using horizontal shift factors. The construction of master curves indicates a common mechanism of structure formation, which, in accordance with the synthetic polymer literature, comprises the rubbery zone, glass transition region, and glassy state. Application of Ferry's free-volume formalism and Rouse theory suggests that there is no change in the thermodynamic state of materials during vitrification, with changes in molecular weight simply introducing shifts in the time scale and temperature range of contributions to viscoelasticity. The thermorheological simplicity allowed development of the concept of "rheological" Tg. This was defined as the point between free-volume phenomena of the polymeric backbone occurring in the glass transition region and an energetic barrier to rotation required for local chain rearrangements in the glassy state. Mechanical relaxation and retardation distribution functions were calculated, thus obtaining values for the effective friction coefficient per monomer unit of the protein. It appears that the local friction coefficient is governed by a linear relationship between fractional free volume and the decreasing molecular weight of the protein, which introduces additional voids due to molecular ends.     

Hydrodynamic characteristics of immobilized cell beads in a liquid-solid fluidized-bed bioreactor

This study examined the hydrodynamic characteristics of a liquid-solid fluidized-bed bioreactor using elastic particles (PVA gel beads) of various diameters as carriers. The drag coefficient-Reynolds number, velocity-voidage, and expansion index-Reynolds number relationships observed during fluidization of PVA gel beads in a fluidized bed in our experiments were compared with the published results. Predictions made from previous correlations were examined with our new experimental findings, revealing the inadequacy of most of these correlations. Thus, new correlations describing the above-mentioned relationships are suggested. The drag coefficient of immobilized cell beads is larger than that of free cell ones at the same Reynolds number because the surface of the immobilized cell beads is rougher. For multiparticle systems, the correction factor, f(epsilon), is a function of the falling gel bead properties (Reynolds number) as well as the fluidized gel bead properties (Archimedes number), and depend strongly on the bed voidage (epsilon). A new simple relation was developed to predict easily the epsilon value from 0.5-0.9 at 4,986 < A(r) < 40,745 or 34 < Re(t) < 186. For all the immobilized cell beads used in this study, the prediction error of the bed voidage was less than 5% at epsilon > 0.5. The prediction equations in this study can be further applied to analyzing the hydrodynamic characteristics of a fluidized-bed reactor using similar entrapped elastic particles as carriers.