Hot vs. cold water steeping of different teas: Do they affect antioxidant activity?

A new popular way of making tea, especially in Taiwan, is to steep leaves in cold water. Here we investigate whether antioxidant activity of teas may be affected by hot or cold water steeping and if this correlates with their polyphenol content and metal-chelating activity. A set of five loose tea samples, consisting of unblended and blended teas, was analysed following their infusion in either hot water (90 °C, 7 min) or cold water (room temperature, 2 h). Antioxidant activity, measured as hydrogen-donating ability, using the ABTS· and DMPD assays, showed no significant differences among hot or cold teas, except in the case of white tea, where significantly higher values were obtained after cold water steeping, a recurrent finding in this study. The antioxidant activity of the teas correlates well with their total phenolic content and metal-chelating activity. Cold teas were, however, generally better inhibitors of in vitro LDL conjugated diene formation and of loss in tryptophan fluorescence. The results of this study contribute to gaining further knowledge on how the potential health benefits of this popular beverage may be maximised by the different methods of preparation.     

A survey of applications of second-order sliding mode control to mechanical systems

The effective application of sliding mode control to mechanical systems is not straightforward because of the sensitivity of these systems to chattering. Higher-order sliding modes can counteract this phenomenon by confining the switching control to the higher derivatives of the mechanical control variable, so that the latter results are continuous. Generally, this approach requires the availability of a number of time derivatives of the sliding variable, and, in the presence of noise, this requirement could be a practical limitation. A class of second-order sliding mode controllers, guaranteeing finite-time convergence for systems with relative degree two between the sliding variable and the switching control, could be helpful both in reducing the number of differentiator stages in the controller and in dealing with unmodelled actuator dynamics. In this paper different second-order sliding mode controllers, previously presented in the literature, are shown to belong to the above cited class, and some challenging control problems involving mechanical systems are addressed and solved. Simulations and experimental results are provided throughout the paper.     

Cell proliferation’ differentiation’ and apoptosis are modified by n−3 polyunsaturated fatty acids in normal colonic mucosa

Supplementation with low doses of eicosapentaenoic (EPA) or docosahexaenoic (DHA) acid was used here to investigate changes in epithelial proliferation’ differentiation’ and apoptosis in normal rat colonic mucosa. ACI/T rats received by oral administration low doses of purified EPA or DHA ethyl esters (1g/kg body weight) and colonic mucosa was analyzed for cell proliferation’ differentiation’ and apoptosis. n−3 Polyunsaturated fatty acid incorporation into membrane phospholipids was investigated as reflections of fatty acid metabolism. Both EPA and DHA suppressed colonocyle proliferation and increased the numbers of differentiating and apoptotic cells without modification of the crypt morphology and the number of cells per crypt columns. A significant incorporation of the supplemented fatty acids into total phospholipids was observed. This enrichment was accompanied by a decreased content in arachidonic acid. The observation that EPA and DHA do not alter crypt morphology although they modify cell turnover in normal colonic mucosa suggests a possible use of these fatty acids as dietary chemopreventive agents.     

Dual‐Acting Drugs: an in vitro Study of Nonimidazole Histamine H3 Receptor Antagonists Combining Anticholinesterase Activity

Dual‐acting compounds that combine H₃ antagonism with anticholinesterase properties are currently emerging as a novel and promising therapeutic approach in the treatment of multifactorial disorders primarily characterized by cholinergic deficits such as Alzheimer's disease. A series of novel nonimidazole H₃ ligands was developed from the chemical manipulation of 1,1′‐octa‐, ‐nona‐, and ‐decamethylene‐bis‐piperidines—H₃ antagonists that had been the subject of previous investigations. These compounds were evaluated for in vitro binding affinity, antagonistic potency, and selectivity at rodent and human histamine H₃ receptors, inhibitory activity at rat brain cholinesterase, and in vivo CNS access and cholinomimetic effects. Within the present series, the tetrahydroaminoacridine hybrid 18 stands out as one of the most attractive molecules, synergistically combining nanomolar and selective H₃ antagonism with remarkable anticholinesterase activity. From this original starting point, it is hoped that future investigations will lead to dual‐acting compounds that can selectively enhance central cholinergic neurotransmission and thus facilitate the treatment of cognitive disorders.     

Structure and Morphology of PDI8‐CN2 for n‐Type Thin‐Film Transistors

A multiscale investigation of N,N′‐bis(n‐octyl)‐x:y, dicyanoperylene‐3,4:9,10‐bis(dicarboximide), PDI8‐CN2, shows the same molecular arrangement in the bulk and in thin films sublimated on SiO₂/Si wafers. Non‐conventional powder diffraction methods and theoretical calculations concur to provide a coherent picture of the crystalline structure. X‐ray diffraction (XRD) and atomic force microscopy (AFM) analyses of films of different thickness deposited at different substrate temperatures indicate the existence of two temperature‐dependent deposition regimes: a low‐temperature (room temperature) regime and a high‐temperature (80–120 °C) one, each characterized by different growth mechanisms. These mechanisms eventually result in different morphological and structural features of the films, which appear to be highly correlated with the trend of the electrical parameters that are measured in PDI8‐CN2‐based field‐effect transistors.     

CALCULATION PROCEDURE FOR FLOODING IN PACKED COLUMNS USING A CHANNEL MODEL

The combined effect of a channel-based approach for dry pressure drop and the Buchanan equation for wet pressure drop in packed beds has been numerically evaluated within the flooding region. The flooding point is an important design parameter since it establishes the maximum hydrodynamic capacity at which a packed column can operate. Upon analyzing the aforementioned approach, it was found that the usual practice of fixing a “reasonable” wet pressure drop at the flooding point (e.g., 1025 Pa/m) may not yield the correct flooding velocity of the gas, particularly at higher liquid loads. In fact, numerical evaluations of the aforementioned model showed a rather “retrograde” non-monotonic behavior of pressure drop with respect to the f factor of the gas near flooding at different liquid loads. A calculation procedure was therefore devised in this work to correctly compute the flooding point for a given liquid load when using the aforementioned modeling approach. Interestingly, it was found that the correct flooding velocity can be directly computed from liquid holdup below the gas loading point. To illustrate the use of the procedure, maximum capacity calculations were performed for a well-known random packing, a conventional structured packing, and a novel catalytic structured packing.     

Photodegradation of fluoroquinolones in surface water and antimicrobial activity of the photoproducts

The widespread presence of fluoroquinolone antibiotics (FQs) in natural ecosystems is a health hazard for humans and other living organisms. The role of sunlight in degrading FQs present in environmental waters has been studied. In particular, the photodegradation of four largely employed FQs, viz. Ciprofloxacin (CIP), Danofloxacin (DAN), Levofloxacin (LEV) and Moxifloxacin (MOX) has been studied in not tampered river water. Degradation rates have been investigated at ppb levels (20-50 μg L⁻¹) under solar light, and the results have been commented critically. The products distribution has been studied by HPLC-ESI-MS/MS analysis and structures have been attributed on the basis of their mass fragmentation spectra.Importantly from the environmental point of view, the (potentially toxic) FQ nucleus remained intact over the early stages of the degradation. Indeed, the photoproducts were proved to possess residual antibacterial activity, as shown from in vitro antibacterial activity tests against different well characterized human and environmental bacterial strains, carried out on the above FQs, as well as for Enrofloxacin (ENR) and Marbofloxacin (MAR).     

Risk of viral acute gastrointestinal illness from nondisinfected drinking water distribution systems

Acute gastrointestinal illness (AGI) resulting from pathogens directly entering the piping of drinking water distribution systems is insufficiently understood. Here, we estimate AGI incidence from virus intrusions into the distribution systems of 14 nondisinfecting, groundwater-source, community water systems. Water samples for virus quantification were collected monthly at wells and households during four 12-week periods in 2006-2007. Ultraviolet (UV) disinfection was installed on the communities' wellheads during one study year; UV was absent the other year. UV was intended to eliminate virus contributions from the wells and without residual disinfectant present in these systems, any increase in virus concentration downstream at household taps represented virus contributions from the distribution system (Approach 1). During no-UV periods, distribution system viruses were estimated by the difference between well water and household tap virus concentrations (Approach 2). For both approaches, a Monte Carlo risk assessment framework was used to estimate AGI risk from distribution systems using study-specific exposure-response relationships. Depending on the exposure-response relationship selected, AGI risk from the distribution systems was 0.0180-0.0661 and 0.001-0.1047 episodes/person-year estimated by Approaches 1 and 2, respectively. These values represented 0.1-4.9% of AGI risk from all exposure routes, and 1.6-67.8% of risk related to drinking water exposure. Virus intrusions into nondisinfected drinking water distribution systems can contribute to sporadic AGI.     

Stereochemical Outcome of the Biocatalysed Reduction of Activated Tetrasubstituted Olefins by Old Yellow Enzymes 1–3

The ene‐reductase‐mediated reactions of (E)‐ and (Z)‐stereoisomers of tetrasubstituted activated alkenes were performed by means of isolated old yellow enzymes (OYEs) 1–3. The comprehension of the resulting data required a careful analysis of the stereochemical course of this kind of reaction. The investigation of the bioreduction of tetrasubstituted alkenes allowed us to appreciate the contribution of several factors (configuration of the starting alkene, mechanism of hydrogen addition, substrate binding mode) to the overall stereochemistry of the reaction.     

Single electron tunneling in large scale nanojunction arrays with bisferrocene-nanoparticle hybrids

We report on the fabrication and single electron tunneling behaviour of large scale arrays of nanogap electrodes bridged by bisferrocene-gold nanoparticle hybrids (BFc-AuNP). Coulomb staircase was observed in the low temperature current-voltage curves measured on the junctions with asymmetric tunnel barriers. On the other hand, junctions with symmetric tunneling barrier exhibited mere nonlinear current voltage characteristics without discrete staircase. The experimental results agreed well with simulations based on the orthodox theory. The junction resistance showed thermally activated conduction behaviour at higher temperature. The overall voltage and temperature dependent results show that the transport behaviour of the large arrays of single particle devices obtained by a facile optical lithography and chemical etching process corresponds with the behaviour of single particle devices fabricated by other techniques like e-beam lithography and mechanical breaking methods.