Practical limitations of superresolution imaging due to conventional sample preparation revealed by a direct comparison of CLSM,SIM and dSTORM

We evaluate the suitability of conventional sample preparation and labelling methods for two superresolution techniques, structured illumination microscopy and direct stochastic optical reconstruction microscopy, by a comparison to established confocal laser scanning microscopy. We show that SIM is compatible with standard fixation procedures and immunofluorescence labelling protocols and improves resolution by a factor of two compared to confocal laser scanning microscopy. With direct stochastic optical reconstruction microscopy, fluorophores can theoretically be localized with much higher precision. However, in practice, with indirect immunofluorescence labelling density can be insufficient due to the bulky probes to reveal biological structures with high resolution. Fine structures like single actin fibres are in fact resolved with direct stochastic optical reconstruction microscopy when using small affinity probes, but require proper adjustment of the fixation protocol. Finally, by a direct comparison of immunofluorescent and genetic labelling with fluorescent proteins, we show that target morphology in direct stochastic optical reconstruction microscopy data sets can differ significantly depending on the labelling method and the molecular environment of the target.     

Oxidative Changes of Heat-Sterilized Meat in Trays

We studied oxidative changes of ground pork meat filled into plastic or aluminum trays, sterilized at 121 or 131°C and stored up to 56 days at 20 or 37°C in the dark or exposed to light, respectively. Sterilization temperature did not influence either thiobarbituric acid reactive substances (TBARS) of the samples or ethane concentrations in headspace of trays. An increase of storage temperature from 20 to 37°C increased TBARS and ethane concentrations regardless of filling method and packaging material. No changes in double-bond indices were observed. Nitrogen flushing in combination with light protection reduced lipid oxidation up to 85–95%     

金属镍高温氧化机理及稀土元素效应研究

对纯镍及其表面离子注钇试样在1000℃空气中的恒温氧化和循环氧化行为进行了研究。用扫描电镜(SEM)和透射电镜(TEM)对氧化膜的表面形貌及结构进行了观测。此外，用声发射(AE)技术研究了氧化膜／基体界面上缺陷的分布情况，并用激光拉曼(Raman)谱对注钇引起的膜内应力变化进行了测量。结果表明：离子注钇降低了NiO氧化膜的生长速率，提高了镍的抗氧化性能；离子注钇减小了表面NiO的晶粒尺寸，降低了膜内压应力水平；离子注钇还减小了氧化膜／基体界面缺陷的平均尺寸和数目，因而极大地提高了镍表面NiO氧化膜的粘附性和保护性。     

Localized photodamage of the human erythrocyte membrane causes an invagination as a precursor of photohaemolysis

Fluorescence excitation can result in the formation of reactive oxygen species and free radicals damaging to live cells. In the case of erythrocytes, reaction of these reactive oxygen species with membrane components causes large‐scale morphological changes followed by cell haemolysis. In an effort to understand the origin of these morphological changes, we have studied the consequences of localized photodamage on the erythrocyte membrane. For this, we irradiated a small area of the cell membrane using a focused laser beam in the presence of an external photosensitizer. We observed the rapid formation of an invagination (approximately 1 μm deep) at the laser focus, long before photohaemolysis occurred. We measured the rate of invagination formation and the rate of cell haemolysis, using a combination of fluorescence contrast imaging (to detect the membrane position) with fluorescence correlation spectroscopy (to measure photosensitizer concentration). We found that the kinetics of both processes depend in a similar manner on light energy flux, fluorophore concentration and the presence of oxygen scavenger. This leads us to the conclusion that the observed invagination is due to the photooxidation of membrane‐associated proteins, representing a precursor of cellular photohaemolysis. We then discuss two different molecular mechanisms (conformational change of the protein band 3 and detachment of the spectrin cytoskeleton from the lipid membrane) that may explain how the photodamage of membrane‐associated proteins can lead to a deformation of the lipid bilayer.     

INFLUENCE OF RARE EARTH DOPING ON MECHANICAL PROPERTY AND MICRO-STRUCTURE OF CHROMIA OXIDE FILM

The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine the Cr2O3 oxide film＇s morphology after oxidation. Acoustic emission （AE） method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects.     

EFFECTS OF CULTURAL CONDITIONS ON THE SYNTHESIS OF SALMONELLA TOXIN

The influence of culture age, pH, aeration, and temperature on Salmonella toxin production was investigated using fermentor cultures containing casamino acids-yeast extract as a growth medium. About 75% or more of total Salmonella toxin was synthesized and released when the cultures were harvested during stationary phase of growth. Increased production and release of the toxin was also observed when the cultures were regulated at pH 6.0, 7. 0, or under alkaline control. The optimal temperature for the synthesis of Salmonella toxin was at 37°C; increased aeration of the cultures (500 rpm) appeared to enhance Samonella toxin production.     

THE INFLUENCE OF NUTRITIONAL FACTORS ON SYNTHESIS OF SALMONELLA TOXIN

The nutritional requirements for the synthesis of a cholera toxin-like toxin from Salmonella enteritidis serotype braenderup were examined. Toxin levels of both culture filtrates and sonicates were determined by the modified Chinese hamster ovary (CHO) floating cell assay. With few exceptions, most amino acids which contained charged polar R groups were stimulatory for Salmonella toxin synthesis. Glycerol enhanced toxin production to the largest extent; however, glucose was a poor carbon source suggesting that Salmonella toxin elaboration may be subject to catabolite repression. Biotin and Mn⁺⁺ were shown to increase the synthesis as well as release of this toxin. An ideal defined medium, supplemented with all the nutritional factors shown to stimulate toxin synthesis, was formulated. The amount of Salmonella toxin produced in this supplemented medium was about 82% of the total toxin elaborated when cultured in Casamino acids plus yeast extract.     

Retrieval sequencing for unit-load automated storage and retrieval systems with multiple openings

Automated storage and retrieval systems (AS/RS) have made a dramatic impact on material handling and inventory control in warehouses and product systems. A unit-load AS/RS is generic and other AS/RS represent its variations. In this paper, we study a problem of sequencing retrieval requests in a unit-load AS/RS. In a unit-load AS/RS, there are usually multiple openings and a unit-load can be stored in any opening. Given a list of retrieval requests and the locations of openings, this problem seeks a sequence of dual cycles that minimizes total travel time taken by a storage/retrieval machine. Previous researchers believed that this problem is computationally intractable and provided greedy-style heuristic algorithms. In this paper, we present an algorithm that combines the Hungarian method and the ranking algorithm for the assignment problem with tour-checking and tour-breaking algorithms. We show that this algorithm finds either a verified optimal or near-optimal solution quickly for moderate size problems. Using this algorithm, we also evaluate the effectiveness of the existing simple heuristics. Computational results are reported.