Sprout inhibition in storage: Current status, new chemistries and natural compounds

A major component of managing potato quality in storage is effective sprout inhibition. Sprouting causes increased weight loss, reduced tuber quality and impedes air movement through the potato pile. The primary method to control sprouting in storage is with postharvest applications of isopropylN-(3-chlorophenyl) carbamate (chlorpropham; CIPC). CIPC inhibits sprout development by interfering with cell division. However, a recent Environmental Protection Agency mandate, from the requirements of the Food Quality Protection Act (FQPA) of 1996, resulted in a reduction in allowable CIPC residue on fresh potatoes in the United States from 50 ppm to 30 ppm. This mandate coincides with tolerance reductions or restrictions for use of CIPC in other parts of the world. CIPC is an effective sprout inhibitor although factors such as storage conditions, application technology, and cultivar can impact that effectiveness. Alternative sprout inhibitors to CIPC continue to be evaluated. Essential oils (e.g., caraway, peppermint, spearmint, clove) or their components (e.g., s-carvone, eugenol), and hydrogen peroxide-based materials, physically damage the developing sprout and suppress sprout elongation. However, repeated or continuous application of these compounds may be necessary for efficacy. Substituted naphthalenes (e.g., dimethyl naphthalene, diisopropyl naphthalene) may help reduce the amount of CIPC applied and/or our dependency on CIPC for sprout suppression in storage. The objective of this review is to summarize the current use of CIPC for potato sprout inhibition in storage and to review the status of current research on other postharvest applied compounds or materials that may be used as alternatives for CIPC.     

Combining local pressure and temperature measurements during bread baking: insights into crust properties and alveolar structure of crumb

Improvements in both the miniaturisation and heat compensation of pressure transducers made it possible to measure pressures as low as 5 kPa inside bread dough during baking (ΔT = 80 °C). Additional calibration was found to be necessary to decrease it below 0.18 kPa according to the variations in temperature encountered during baking. Two probes with both a thermocouple and a miniature pressure transducer were used to reveal pressure gradients inside bread dough during baking and post-cooling. During baking, increase in pressure (up to 1.1 kPa) was mainly attributed to the mechanical restrictions exerted on the dough by the stiffened surface layers. Pressure build-up due to the stiffening of bubble walls could not be detected. Various effects of the rupture in the bubble walls are reported. Sudden falls in pressure observed up to 70 °C were attributed to the bubble coalescence phenomenon. Evidence of an open porous structure was provided by the balance in pressure through the dough before the end of baking and the almost simultaneous lowering of pressure (−0.15 kPa) throughout the crumb during cooling. The slight lowering of pressure during post-cooling was also evidence of lower permeability of the crust compared to the crumb.     

Proliferation of epithelial cells on PDMS substrates with micropillars fabricated with different curvature characteristics

The present work studied the proliferation of epithelial cells when they were cultivated on substrates with micropillars fabricated with the same height but with different curvature characteristics. A special micro-fabrication method was employed to produce these micropillar substrates. Polyallyldiglycol carbonate (PADC) films were first irradiated by alpha particles and then chemically etched to reach or beyond the "transition" phase to form casts with micrometer-sized pits with the same depth, but with different size and shape. Polydimethylsiloxane (PDMS) replicas of these PADC films then gave the desired substrates with micropillars with the same height but with different curvature characteristics. The micropillars on the PDMS substrates were found to be capable of changing the response of HeLa cells in terms of the percentages of cells in the S-phase and the attached cell numbers after 3-day cell culture. This demonstrated that the proliferation of the HeLa cells could be changed through mechanosensing the substrate curvature.     

Microarray analysis of gene expression during the cell cycle

Microarrays have been applied to the determination of genome-wide expression patterns during the cell cycle of a number of different cells. Both eukaryotic and prokaryotic cells have been studied using whole-culture and selective synchronization methods. The published microarray data on yeast, mammalian, and bacterial cells have been uniformly interpreted as indicating that a large number of genes are expressed in a cell-cycle-dependent manner. These conclusions are reconsidered using explicit criteria for synchronization and precise criteria for identifying gene expression patterns during the cell cycle. The conclusions regarding cell-cycle-dependent gene expression based on microarray analysis are weakened by arguably problematic choices for synchronization methodology (e.g., whole-culture methods that do not synchronize cells) and questionable statistical rigor for identifying cell-cycle-dependent gene expression. Because of the uncertainties in synchrony methodology, as well as uncertainties in microarray analysis, one should be somewhat skeptical of claims that there are a large number of genes expressed in a cell-cycle-dependent manner.     

Elastic moduli of living epithelial pancreatic cancer cells and their skeletonized keratin intermediate filament network

In simple epithelia, such as living epithelial pancreatic cancer cells (Panc-1), unusual amounts of keratin filaments can be found, which makes these cells an ideal model system to study the role of keratin for cell mechanical properties. In this work, the elastic moduli of Panc-1 cells and their extracted in-situ subcellular keratin intermediate filament network are determined and compared with each other. For this, the living adherent cells and their extracted keratin network were probed with local quasistatic indentation testing during large deformations using the Atomic Force Microscope (AFM). We determined the elastic modulus of the skeletonized but structurally intact keratin network to be in the order of 10 Pa, while the living cell elastic modulus ranged from 100 to 500 Pa. By removing microfilaments, microtubules, membranes and soluble cytoplasmic components during keratin network extraction, we excluded effects caused by crosslinking with other filamentous fibers and from the viscosity of the cytoplasm. Thus, the determined elastic modulus equals the actual elastic modulus inherent to such a keratin filamentous network. In our assessment of the effective mechanical contribution of the architecturally intact, skeletonized keratin network to living cell mechanics, we come to the conclusion that it plays only a very limited role. Evidently, the quantitative dominance of keratin in these cells does not reflect a strong influence on determining the cell's elastic modulus. Instead, keratin like other filamentous structures in the cell's scaffolding, e.g., F-actin and microtubuli, is one part of a greater whole.     

Dough processing in a Couette-type device with varying eccentricity: Effect on glutenin macro-polymer properties and dough micro-structure

Dough mixing involves a combination of different deformation flows, e.g. shear and elongation. The complicated nature of mixing process makes it difficult to understand dough processing at a mechanistic level. A new Couette device allowed the effects of shear flow on the physical properties of glutenin macro-polymer (GMP) and micro-structure formation of the dough to be studied. Steady shear deformation using concentric Couette-type flow did not decrease GMP content or size of glutenin particles. Confocal scanning laser microscopy revealed the formation of interconnected gluten domains indicating the development of a gluten network. In an eccentric Couette configuration the results depended on the degree of eccentricity. A higher degree of eccentricity and a longer processing time led to considerable reduction in GMP content and size of glutenin particles. The micro-structural change in the narrow gap regions of the eccentric cell occurred early in processing, leading to a break up of large protein domains, and a microscopically more homogeneous dough. Transient high shear flow led to elongation and break up of the macroscopic gluten network. In low shear regions of the eccentric cell (wider gap settings), reformation or aggregation of protein domains was observed. Thus, the gluten aggregation–break up mechanisms are strongly influenced by the local flow profile in a conventional mixer. The impact of different types of shear flow must be taken into account in the design of dough mixers.     

小麦颖果发育和萌发过程中盾片的结构特征

为了进一步明确小麦颖果发育和萌发过程中盾片的结构特征,以扬麦13为材料,采用超薄切片、显微和超微观察及Image-pro Plus软件图像分析等技术,研究了小麦盾片在颖果发育及萌发过程中的结构变化。结果表明,花后16d,颖果靠近胚乳的胚周缘细胞由外到内分别分化为盾片上皮细胞和盾片薄壁细胞。在颖果发育过程中,盾片上皮细胞形态由不规则形转变为细长形,数目逐渐增加,面积逐渐减小。盾片上皮细胞中淀粉粒不断降解,颈部盾片上皮细胞呈细长形,而底部细胞呈多边形和椭圆形。盾片薄壁细胞淀粉粒不断增多,体积变大。花后16~20d细胞液泡化,积累脂质体和植酸钙镁颗粒,细胞核中核染色质明显降解。在萌发过程中,盾片上皮细胞由不规则形和多边形向圆形转变,细胞的数目先减少后增加,面积先增加后呈减小趋势。薄壁细胞内淀粉体不断变形、塌陷并逐渐降解,蛋白体发生解体,而脂质体先降解而后又重新合成。由以上结果说明,小麦盾片具有吸收转运养分、贮藏养分及保护胚等功能。     

Polyester fiber production using virgin and recycled PET

In this study, the design and construction of an extrusion equipment with spinning fiber devices has been developed to produce polyester fiber from virgin and recycled polyethylene terephthalate (PET). Several operating parameters (i.e., pressure, temperature, feed flow rate, extrusion speed and extruder design) have been analyzed to identify the best process conditions. In particular, this study has focused on a detailed analysis for the processing of recycled raw material for polyester textile fiber applications considering the variability of the process and identifying alternatives to minimize the impact on the quality parameters such as the fiber diameter and mechanical specifications. The experimental results were compared with the values calculated using a theoretical model, which has been developed for these particular cases. The mathematical analysis of the mass flow showed a very good agreement with respect to the experimental data, where there was a percentage difference < 3 %. It was found that the fiber diameter is a function of intrinsic viscosity (VI) or melt flow index (MFI). Finally, the mechanical properties of the fibers were evaluated and results indicated that the fiber with higher average molecular weight showed higher tenacity and lower Young’s modulus values.     

A Comparative Study on the Flocculation of Silica and China Clay with Chitosan and Synthetic Polyelectrolytes

Flocculation is still one of the most important and efficient processes for water treatment. However, most industrial processes, such as in water treatment plants, still use huge amounts of synthetic polyelectrolytes for the flocculation process. Here we compare the flocculation of two different suspended particles, i.e., silica particles and china clay, with the biopolymer chitosan and two common strong synthetic polyelectrolytes. As a flocculant, chitosan featured a minimum uptake rate of 0.05 mg/g for silica and 1.8 mg/g for china clay. Polydiallyldimethylammonium chloride (PDADMAC) for comparison possessed a minimum uptake rate of 0.05 mg/g for silica and 2.2 mg/g for china clay. Chitosan as an environmentally friendly biopolymer competes with the synthetic polyelectrolytes and thus represents a beneficial economic alternative to synthetic flocculants.     

Fibroblast adhesion on unidirectional polymeric nanofilms

Nanotextured polymeric surfaces with inclined rods reveal highly anisotropic properties concerning wetting and adhesion. In this work, we report on the interaction of fibroblast cells with these highly anisotropic materials. The authors quantified removal of adherent cells from such surfaces by a laminar flow. The critical shear force needed for cell removal from the surface depends on the inclination direction. Based on electron microscopy cross sections we deduce that interactions of cellular filopodia extending into the nanotextured surface are causing the direction depending removal.     

Development of molecular simulation methods to accurately represent protein-surface interactions: The effect of pressure and its determination for a system with constrained atoms

When performing molecular dynamics simulations for a system with constrained (fixed) atoms, traditional isobaric algorithms (e.g., NPT simulation) often cannot be used. In addition, the calculation of the internal pressure of a system with fixed atoms may be highly inaccurate due to the nonphysical nature of the atomic constraints and difficulties in accurately defining the volume occupied by the unconstrained atoms in the system. The inability to properly set and control pressure can result in substantial problems for the accurate simulation of condensed-phase systems if the behavior of the system (e.g., peptide/protein adsorption) is sensitive to pressure. To address this issue, the authors have developed an approach to accurately determine the internal pressure for a system with constrained atoms. As the first step in this method, a periodically extendable portion of the mobile phase of the constrained system (e.g., the solvent atoms) is used to create a separate unconstrained system for which the pressure can be accurately calculated. This model system is then used to create a pressure calibration plot for an intensive local effective virial parameter for a small volume cross section or "slab" of the system. Using this calibration plot, the pressure of the constrained system can then be determined by calculating the virial parameter for a similarly sized slab of mobile atoms. In this article, the authors present the development of this method and demonstrate its application using the CHARMM molecular simulation program to characterize the adsorption behavior of a peptide in explicit water on a hydrophobic surface whose lattice spacing is maintained with atomic constraints. The free energy of adsorption for this system is shown to be dramatically influenced by pressure, thus emphasizing the importance of properly maintaining the pressure of the system for the accurate simulation of protein-surface interactions.     

Injection molding of vertebral fixed cage implant

A vertebral cage is a hollow medical device which is used in spine surgery. By implanting the cage into the spine column, it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they detract the biocompatibility. Currently PEEK (polyether ether ketone) is applied to various implants because it has good properties like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g., injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simulation program, MOLDFLOW, several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress analysis with ABAQUS, and shrinkage and residual stress fields are predicted. With these results, optimum process conditions are determined.     

Trabectedin and Plitidepsin: Drugs from the Sea that Strike the Tumor Microenvironment

The prevailing paradigm states that cancer cells acquire multiple genetic mutations in oncogenes or tumor suppressor genes whose respective activation/up-regulation or loss of function serve to impart aberrant properties, such as hyperproliferation or inhibition of cell death. However, a tumor is now considered as an organ-like structure, a complex system composed of multiple cell types (e.g., tumor cells, inflammatory cells, endothelial cells, fibroblasts, etc.) all embedded in an inflammatory stroma. All these components influence each other in a complex and dynamic cross-talk, leading to tumor cell survival and progression. As the microenvironment has such a crucial role in tumor pathophysiology, it represents an attractive target for cancer therapy. In this review, we describe the mechanism of action of trabectedin and plitidepsin as an example of how these specific drugs of marine origin elicit their antitumor activity not only by targeting tumor cells but also the tumor microenvironment.     

Ecological and Industrial Implications of Dynamic Seaweed-Associated Microbiota Interactions

Seaweeds are broadly distributed and represent an important source of secondary metabolites (e.g., halogenated compounds, polyphenols) eliciting various pharmacological activities and playing a relevant ecological role in the anti-epibiosis. Importantly, host (as known as basibiont such as algae)–microbe (as known as epibiont such as bacteria) interaction (as known as halobiont) is a driving force for coevolution in the marine environment. Nevertheless, halobionts may be fundamental (harmless) or detrimental (harmful) to the functioning of the host. In addition to biotic factors, abiotic factors (e.g., pH, salinity, temperature, nutrients) regulate halobionts. Spatiotemporal and functional exploration of such dynamic interactions appear crucial. Indeed, environmental stress in a constantly changing ocean may disturb complex mutualistic relations, through mechanisms involving host chemical defense strategies (e.g., secretion of secondary metabolites and antifouling chemicals by quorum sensing). It is worth mentioning that many of bioactive compounds, such as terpenoids, previously attributed to macroalgae are in fact produced or metabolized by their associated microorganisms (e.g., bacteria, fungi, viruses, parasites). Eventually, recent metagenomics analyses suggest that microbes may have acquired seaweed associated genes because of increased seaweed in diets. This article retrospectively reviews pertinent studies on the spatiotemporal and functional seaweed-associated microbiota interactions which can lead to the production of bioactive compounds with high antifouling, theranostic, and biotechnological potential.     

蔗茎机械强度精准评价及机制解析

倒伏是限制我国糖料蔗生产的核心问题之一.茎秆机械强度是决定蔗茎抗倒伏性能的重要性状,由于缺乏精准评价甘蔗机械强度的有效方法,甘蔗抗倒伏研究进展严重受阻.本研究针对甘蔗倒伏、折断的问题,分别建立一套基于穿刺力和折断力的蔗茎力学表型测定方法,对117份甘蔗品系蔗茎机械强度精准评价,并对茎秆抗倒伏差异品种('桂糖 42号'和...     

Fabrication of nanofibers with ultrahigh production by a facile high pressure air-jet atomized electrospinning

A novel method named as high pressure air-jet atomized electrospinning was proposed to prepare nanofibers with ultrahigh production. The spinning solution with lower concentration and viscosity was cutted into micron-sized droplets by a 700 mesh filter in the front of nozzle and then was crushed and atomized into massive smaller droplets, which were drawn into nanofibers directly under the electric force and airflow force. Flow field under different air pressure was simulated to study its effect on the formation of nanofibers. The airflow showed the minimum pressure and maximum velocity at a location 2 cm away from the spray nozzle, where small droplets cutted were crushed and atomized into massive smaller droplets by the converging airflow. The velocity and distribution region of the airflow increased with increasing air pressure. It showed a smaller diameter of 150 nm and ultrahigh production of 75.6 g/h for nanofibers prepared based on this novel method at the air pressure of 0.8 MPa. The production of nanofibers almost reached thousands of times of that from conventional needle electrospinning.     

Effects of blanching conditions on the mechanical properties of french fry strips

Control of the various processing operations is crucial for achieving optimal texture in french fries. This, in turn, requires precise measurement of the effect of each processing operation on the mechanical properties of the fries. A puncture test was used to measure the effects of blanching and freezing on peak force of french fry strips. Potatoes (cv. Russet Burbank) were grown at two locations in Manitoba in 1994 and 1995. Two blanching treatments (a 1-stage process, and a 2-stage process with a low-temperature long-time step) were followed by blast freezing. Strip position within the tuber was found to be a major source of variation for mechanical properties. Because peak force varied widely within and between tubers, it was necessary to compare the efficacy of the two blanching regimes using a pair of strips taken from as close a position as possible in the tuber. For both locations and crop years, blanched french fry strips taken from the pith of the tuber (referred to as inner strips), exhibited higher peak force than outer strips taken from the cortex. The 2-stage blanching process decreased the variation seen in the mechanical properties of different potato strips. Overall, strips blanched by the 2-stage process had significantly higher peak force than strips blanched by a single blanching process. The effect of blanching was evident in the mechanical properties of strips even after freezing and thawing. Microstructural analysis revealed that cells in the outer strips had a “balloon-like” appearance due to the degree of starch swelling pressure generated by swollen granules. For inner strips, this “balloon-like” appearance was less evident. Such appearance is in support of the starch swelling pressure hypothesis. The research shows that measurement of the effect of processing can be achieved by comparing treatments on adjacent strips in order to minimize variation between strips, and that a 2-stage blanching treatment can ameliorate texture differences between strips taken from different parts of the tuber.     

Parenchyma cell growth in potato tubers II. Cell divisions vs. cell enlargement

Initial swelling and early tuber enlargement are the result of cell enlargement at a rate surpassing addition of new storage cells. New phloem strands are added by procambial activity. New storage cells are formed marginal to the phloem strands. Frequency of divisions in these new cells rapidly decreases. Tubers in which mitotic processes are compapratively restricted in early stages of development are slow growers; i.e., cell enlargement proceeds with fewer cells present. Tubers in which more phloem strands and associated cells have been added in early growth are rapid growers and contain more enlarging cells. Reduction in mitotic rate concurrently with increased cell enlargement progresses radially from each phloem strand in young tubers. Cell divisions are rare in all young storage tissues by the time a tuber has attained a size of 30 to 40 g, except in the immediate sites of “eye” buds. Some cell divisions are nececssary for phloem strands to keep pace with tuber enlargement, and also for formation of phellogen. Volumetric increase in these highly localized areas accounts for a small percentage of the increase in tuber volume resulting from enlargement of cells.     

Investigation of Parameters for Preparing Nanofiber Yarn via a Stepped Airflow-assisted Electrospinning

Electrospinning is a simple and cost-effective method to prepare fiber with nanometer scale. More importantly, 3D flexible nanofiber yarns that fabricated by electrospinning have shown excellent application prospects in smart textiles, wearable sensors, energy storage devices, tissue engineering, and so on. However, current methods for preparing electrospinning nanofiber yarns had some limitations, including low yarn yield and poor yarn structure. In this paper, a stepped airflow-assisted electrospinning method was designed to prepare continuously twisted nanofiber yarn through introducing stepped airflow into traditional electrospinning system. The stepped airflow could not only help to improve nanofiber yield, but also good for controlling the formed nanofibers to be deposited in a small area. In addition, the experimental methods of single factor variables were used to study the effects of stepped airflow pressure, applied voltage, spinning distance, solution flow rate, air pumping volume and friction roller speed on nanofiber yarn yield, nanofiber diameter, yarn twist and mechanical property. The results showed that prepared nanofiber yarns exhibited perfect morphologies and the yield of nanofiber yarn could reach to a maximum of 4.207 g/h. The breaking strength and elongation at break of the prepared yarn could reach to 23.52 MPa and 30.61 %, respectively.     

Application of electrostatic force microscopy on characterizing an electrically charged fiber

The application of Electrostatic Force Microscopy (EFM) was studied in analyzing the corona-charged polypropylene fiber. Electrostatic force gradient images were obtained from the phase shifts with the varied bias voltages applied to the EFM cantilever by the noncontact scans. A mathematical expression to model the EFM phase shifts as a function of the applied tip bias voltages was introduced. EFM analysis was used to test the hypothesis that the solvent-induced efficiency deterioration of electret filter media originates from charge deterioration. EFM investigation produced evidence that exposure to isopropanol in the liquid phase affected the electrostatic charges on fibers. Exposure to organic solvents in liquid phase is thought to increase chain and charge mobility in polypropylene fibers, thereby reducing the electrostatic charge and the particle capture ability.