Visualizing Oxidative Cellular Stress Induced by Nanoparticles in the Subcytotoxic Range Using Fluorescence Lifetime Imaging

Nanoparticles hold a great promise in biomedical science. However, due to their unique physical and chemical properties they can lead to overproduction of intracellular reactive oxygen species (ROS). As an important mechanism of nanotoxicity, there is a great need for sensitive and high‐throughput adaptable single‐cell ROS detection methods. Here, fluorescence lifetime imaging microscopy (FLIM) is employed for single‐cell ROS detection (FLIM‐ROX) providing increased sensitivity and enabling high‐throughput analysis in fixed and live cells. FLIM‐ROX owes its sensitivity to the discrimination of autofluorescence from the unique fluorescence lifetime of the ROS reporter dye. The effect of subcytotoxic amounts of cationic gold nanoparticles in J774A.1 cells and primary human macrophages on ROS generation is investigated. FLIM‐ROX measures very low ROS levels upon gold nanoparticle exposure, which is undetectable by the conventional method. It is demonstrated that cellular morphology changes, elevated senescence, and DNA damage link the resulting low‐level oxidative stress to cellular adverse effects and thus nanotoxicity. Multiphoton FLIM‐ROX enables the quantification of spatial ROS distribution in vivo, which is shown for skin tissue as a target for nanoparticle exposure. Thus, this innovative method allows identifying of low‐level ROS in vitro and in vivo and, subsequently, promotes understanding of ROS‐associated nanotoxicity.     

The interaction of human plasma low density lipoproteins with glycosamino-glycans: Influence of the chemical composition

Human plasma of 5 normolipemic individuals was incubated for 24 hr at 37 C in the presence or in the absence of lecithin: cholesterol acyltransferase (LCAT)-inhibitors. Plasma steored at 4 C served as a control. The low density lipoprotein (LDL) fractions of the samples were isolated and investigated with respected to changes in chemical composition and complexing activity with glycosamino glycans (GAG). Incubation of plasma in the presence of LCAT inhibitors caused a significant increase of LDL triglycerides at the expense of cholesteryl esters. Incubation with active LCAT not only changed the core but also the surface constituents (decrease in phospholipids and in free cholesterol). The amount of GAG bound per mg of LDL was not uniformly changed in samples incubated after LCAT inhibition. LDL isolated from plasma incubated in the presence of LCAT, on the other hand, showed a significant reduction in GAG binding. The ratio of free cholesterol: GAG in the complex was most significantly reduced in LCAT-modified LDL. There was in addition a highly significant correlation between the LDL:GAG ratio in the complex and the free cholesterol and phospholipid content of the LDL samples. It is concluded that alterations in surface lipid constitutents of LDL strongly after their interaction with sulfated polysaccharides, an effect which may be relevant also in vivo for the interaction of LDL with cell surfaces and intercellular matrices.     

Hardness results for approximate pure Horn CNF formulae minimization

We study the hardness of approximation of clause minimum and literal minimum representations of pure Horn functions in n Boolean variables. We show that unless P=NP, it is not possible to approximate in polynomial time the minimum number of clauses and the minimum number of literals of pure Horn CNF representations to within a factor of \(2^{\log^{1-o(1)} n}\) . This is the case even when the inputs are restricted to pure Horn 3-CNFs with O(n ^1+ε ) clauses, for some small positive constant ε. Furthermore, we show that even allowing sub-exponential time computation, it is still not possible to obtain constant factor approximations for such problems unless the Exponential Time Hypothesis turns out to be false.     

A?novel method for the quantitative analysis of the water content in lignocellulosic material

A novel method for the determination of the water content in wood has been developed and experimentally tested. Based on the reaction of trimethylchlorosilane with various wood constituents and water, the generation of a by-product (hexamethyldisiloxane) was pursued and quantified via gas-chromatography and the water content was subsequently calculated back. The experiments were carried out with preconditioned spruce wood meal (particle sizes ranging between 60 and 140 microns) using water free solvents and reagents in a water free reaction atmosphere. The results showed that the investigated samples incorporated around 10 wt. % of water after preconditioning for 48 h.     

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Misorientation texture development during grain growth. Part I: Simulation and experiment

Grain growth in two and three dimensions with anisotropic interfacial properties was simulated using the Monte Carlo method. The relative effects of grain boundary energy and mobility anisotropy on number- and area-weighted misorientation distribution functions (MDFs) were compared. Results indicate that energy anisotropy has a measurable effect on misorientation texture development, while mobility anisotropy does not. Qualitatively similar results are obtained in all simulations regardless of dimensionality or crystal symmetry. Microstructures with random orientation texture appear to evolve steady-state MDFs, while those with a preferred orientation do not. Experimentally measured number- and area-weighted MDFs in polycrystalline magnesia are shown to be comparable to those measured in our simulations.     

Increasing concrete durability with high-reactivity metakaolin

High-reactivity metakaolin (HRM) is a manufactured pozzolan produced by thermal processing of purified kaolinitic clay. Field performance and laboratory research of concrete containing HRM have demonstrated its value for bridge decks, bridge deck overlays, industrial flooring, high-strength concrete and masonry products. This paper discusses laboratory evaluations to assess the long-term performance of concrete containing HRM produced in North America for resistance to chloride penetration and reduction in expansion due to alkali-silica reactivity. Bulk diffusion testing indicated that HRM substantially reduced chloride ion penetration in concrete with w/cm of 0.30 or 0.40. Reductions in diffusion coefficients compared to control specimens were of the order of 50% and 60% for concrete with 8% and 12% HRM, respectively. Also, the performance of the concrete containing 8% or 12% cement replacement with HRM showed improved performance versus merely reducing the w/c from 0.4 to 0.3. Such reductions can be expected to have a substantial impact on the service life of reinforced concrete in chloride environments. Expansion tests on concrete prisms containing reactive aggregates showed that 15% HRM can prevent deleterious expansion due to alkali-silica reactivity (ASR). The mechanism of control is likely linked to the substantial reduction in pore solution alkalinity seen in pastes containing 20% HRM in comparison to the control specimen which contained no supplementary cementing materials. However, the reduction was not large enough to depassivate steel reinforcement.     

Blushing and physiological arousability in social phobia.

Blushing is the most prominent symptom of social phobia, and fear perception of visible anxiety symptoms is an important component of cognitive behavioral models of social phobia. However, it is not clear how physiological and psychological aspects of blushing and other somatic symptoms are linked in this disorder. The authors tested whether social situations trigger different facial blood volume changes (blushing) between social phobic persons with and without primary complaint of blushing and control participants. Thirty social phobic persons, 15 of whom were especially concerned about blushing, and 14 control participants were assessed while watching an embarrassing videotape, holding a conversation, and giving a talk. Only when watching the video did social phobic persons blush more than controls blushed. Social phobic persons who complained of blushing did not blush more intensely than social phobic persons without blushing complaints but had higher heart rates, possibly reflecting higher arousability of this subgroup. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bearingless Segment Motor With Five Stator Elements—Design and Optimization

Bearingless motors and active magnetic bearings work completely contactless and wearless. With these properties, hermetically sealed and lubricant-free rotating systems for various applications can be designed. It is possible to stabilize three degrees of freedom by reluctance forces when a permanent-magnet excited rotor disc is used. Hence, only the remaining three degrees of freedom are actively controlled. A subtype of this constructional design called bearingless slice motor is the bearingless segment motor. This paper comprises the design process of a bearingless segment motor with five equal stator elements and concentrated windings. Finite-element simulations are applied to maximize the bearing forces and the motor torque per ampere and minimize the reluctance forces. However, the mathematical model of the system is nonlinear, therefore, an appropriate nonlinear control scheme has to be applied to put the system into operation. The introduction of a prototype, together with first measurements, completes the paper.