Comparative toxicity of nanoparticulate ZnO, bulk ZnO, and ZnCl2 to a freshwater microalga (Pseudokirchneriella subcapitata): the importance of particle solubility

Metal oxide nanoparticles are finding increasing application in various commercial products, leading to concerns for their environmental fate and potential toxicity. It is generally assumed that nanoparticles will persist as small particles in aquatic systems and that their bioavailability could be significantly greater than that of larger particles. The current study using nanoparticulate ZnO (ca. 30 nm) has shown that this is not always so. Particle characterization using transmission electron microscopy and dynamic light scattering techniques showed that particle aggregation is significant in a freshwater system, resulting in flocs ranging from several hundred nanometers to several microns. Chemical investigations using equilibrium dialysis demonstrated rapid dissolution of ZnO nanoparticles in a freshwater medium (pH 7.6), with a saturation solubility in the milligram per liter range, similar to that of bulk ZnO. Toxicity experiments using the freshwater alga Pseudokirchneriella subcapitata revealed comparable toxicity for nanoparticulate ZnO, bulk ZnO, and ZnCl2, with a 72-h IC50 value near 60 microg Zn/ L, attributable solely to dissolved zinc. Care therefore needs to be taken in toxicity testing in ascribing toxicity to nanoparticles per se when the effects may be related, at least in part, to simple solubility.     

Analysis of a novel class of predictive microbial growth models and application to coculture growth

In this paper, a novel class of microbial growth models is analysed. In contrast with the currently used logistic type models (e.g., the model of Baranyi and Roberts [Baranyi, J., Roberts, T.A., 1994. A dynamic approach to predicting bacterial growth in food. International Journal of Food Microbiology 23, 277–294]), the novel model class, presented in Van Impe et al. (Van Impe, J.F., Poschet, F., Geeraerd, A.H., Vereecken, K.M., 2004. Towards a novel class of predictive microbial growth models. International Journal of Food Microbiology, this issue), explicitly incorporates nutrient exhaustion and/or metabolic waste product effects inducing stationary phase behaviour. As such, these novel model types can be extended in a natural way towards microbial interactions in cocultures and microbial growth in structured foods. Two illustrative case studies of the novel model types are thoroughly analysed and compared to the widely used model of Baranyi and Roberts. In a first case study, the stationary phase is assumed to be solely resulting from toxic product inhibition and is described as a function of the pH-evolution. In the second case study, substrate exhaustion is the sole cause of the stationary phase. Finally, a more complex case study of a so-called P-model is presented, dealing with a coculture inhibition of Listeria innocua mediated by lactic acid production of Lactococcus lactis.     

Diagnostic Performance of 1→3-β-d-Glucan in Neonatal and Pediatric Patients with Candidemia

Fungal sepsis is one of the major problems in neonatal and pediatric care unit settings. The availability of new diagnostic techniques could allow medical practitioners to rapidly identify septic patients and to improve their outcome. The aim of this study was to evaluate the performance of the 1→3-β-d-glucan (BDG), individually and in comparison with the Candida mannan (CM) antigen, in ten preterm infants and five onco-haematological pediatric patients with Candida bloodstream infections already proven by positive culture. The serum levels of BDG were >80 pg/mL on the same day as a positive blood culture in all examined patients, while CM antigen was negative in the patients with C. parapsilosis fungemia and in one further case due to C. albicans. These results suggest that a regular monitoring of serum circulating antigens (i.e., 1→3-β-d-glucan) combined with other microbiological and clinical information, may allow earlier and accurate diagnosis. However, further studies are necessary to confirm its usefulness in routine clinical practice.     

Electrosynthesis and characterization of gold nanoparticles for electronic capacitance sensing of pollutants

In the present study, gold/surfactant core/shell colloidal nanoparticles with a controlled morphology and chemical composition have been obtained via the so-called sacrificial anode technique, carried out in galvanostatic mode. As synthesized Au-NPs had an average core diameter comprised between 4 and 8 nm, as a function of the electrochemical process experimental conditions. The UV–Vis characterization of gold nanocolloids showed clear spectroscopic size effects, affecting both the position and width of the nanoparticle surface plasmon resonance peak.The nanomaterial surface spectroscopic characterization showed the presence of two chemical states, namely nanostructured Au(0) (its abundance being higher than 90%) and Au(I). Au-NPs were then deposited on the top of a capacitive field effect sensor and subjected to a mild thermal annealing aiming at removing the excess of stabilizing surfactant molecules. Au-NP sensors were tested towards some gases found in automotive gas exhausts. The sensing device showed the largest response towards NO_x, and much smaller – if any – responses towards interferent species such as NH₃, H₂, CO, and hydrocarbons.     

Sigma‐2 Receptor Agonists as Possible Antitumor Agents in Resistant Tumors: Hints for Collateral Sensitivity

With the aim of contributing to the development of novel antitumor agents, high‐affinity σ₂ receptor agonists were developed, with 6,7‐dimethoxy‐2‐[4‐[1‐(4‐fluorophenyl)‐1H‐indol‐3‐yl]butyl]‐1,2,3,4‐tetrahydroisoquinoline ( 15 ) and 9‐[4‐(6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinolin‐2‐yl)butyl]‐9H‐carbazole ( 25 ) showing exceptional selectivity for the σ₂ subtype. Most of the compounds displayed notable antiproliferative activity in human MCF7 breast adenocarcinoma cells, with similar activity in the corresponding doxorubicin‐resistant MCF7adr cell line. Surprisingly, a few compounds, including 25 , displayed enhanced activity in MCF7adr cells over parent cells, recalling the phenomenon of collateral sensitivity, which is under study for the treatment of drug‐resistant tumors. All of the compounds showed interaction with P‐glycoprotein (P‐gp), and 15 and 25 , with the greatest activity, were able to revert P‐gp‐mediated resistance and reestablish the antitumor effect of doxorubicin in MCF7adr cells. We therefore identified a series of σ₂ receptor agonists endowed with intriguing antitumor properties; these compounds deserve further investigation for the development of alternate strategies against multidrug‐ resistant cancers.     

Assessing Antisite Defect and Impurity Concentrations in Bi2Te3 Based Thin Films by High‐Accuracy Chemical Analysis

In Bi₂Te₃‐based materials charge‐carrier densities are determined by antisite defects and controlling these defects is a key issue for thermoelectric and topological insulator materials. Bi‐Te thin films with high‐quality thermoelectric properties are deposited using a nano‐alloying approach by molecular beam epitaxy (MBE) and sputtering. The in‐plane transport properties are measured at room temperature as a function of charge‐carrier density. High‐accuracy chemical analysis by wavelength‐dispersive X‐ray spectrometry (WDX) is applied for the first time to these Bi₂Te₃‐based thin films. The acquisition conditions for WDX spectrometry are established using Monte Carlo simulations for the electron trajectories, which guarantees a high lateral resolution and rules out stray radiation generated in the substrate of the films. In contrast to energy‐dispersive X‐ray spectrometry (EDX), which is usually applied, WDX offers unprecedented accuracy for measuring antisite defect concentrations and thus has a high impact on improving the quality of thin films. The charge‐carrier densities are calculated from the WDX results according to the point‐defect model of Miller and Li and the thermopower and electrical conductivity are calculated for different charge‐carrier densities by solving the linearized Boltzmann transport equation. A good quantitative agreement is found for the dependence of the thermopower on stoichiometry, whereas the electrical conductivity is sensitively affected by contaminants.     

Innovative composite films of chitosan, methylcellulose, and nanoparticles

Plastic is readily available and inexpensive, so it is becoming the main material for packaging. Unfortunately plastics do not biodegrade and, if reduced in small pieces, contaminate soil and waterways. In the present work, natural films composed of chitosan, methylcellulose, and silica (SiO(2)) nanoparticles (NPs) were developed as new packaging materials. The effect of the incorporation of NPs into the polymeric film matrix was evaluated. An excellent improvement of the mechanical properties was obtained for nanostructured films with a composition of CH:MC 50:50 and NPs 1% w/v that make these materials able to replace plastics and derivatives, reducing environmental pollution.     

Presence and significance of Bacillus cereus in dehydrated potato products

Dehydrated potato contains Bacillus cereus at a prevalences of 10 to 40% and at numbers usually less than 10(3) CFU g(-1). B. cereus in dehydrated potato is likely to be present as spores that are able to survive drying of the raw vegetable and may represent a significant inoculum in the reconstituted (rehydrated) product where conditions favor germination of, and outgrowth from, spores. Holding rehydrated mashed potato alone, or as part of another product (e.g., potato-topped pie), at temperatures above 10 degrees C and below 60 degrees C may allow growth of vegetative B. cereus. Levels exceeding 10(4) CFU g(-1) are considered hazardous to human health and may be reached within a few hours if stored inappropriately between these temperatures. Foods incorporating mashed potato prepared from dehydrated potato flakes have been implicated in B. cereus foodborne illness. This review is a summary of the information available concerning the prevalence and numbers of B. cereus in dehydrated potato flakes and the rate at which growth might occur in the rehydrated product.     

Power Consumption Optimization Strategy for Wireless Networks

In this paper, we focus on the optimization of the total power utilization in a communication network. The utility function used in this paper aims for the maximization of joint network capacity in an interference limited environment. This paper outlines the various approaches currently being used in order to reduce the total power consumption in a multi cellular network. We present an algorithm for power optimization under no interference and in presence of interference conditions, targeting to maximize the network capacity. The convergence of the algorithm is guaranteed if the interference is not too large.     

Diamond wire sawing in ornamental basalt quarries: technical,economic and environmental considerations

The market interest in ornamental rocks commercially referred to as “stones” has grown significantly in recent years, particularly regarding basalt. This has resulted in the widespread use of diamond wire equipped with sintered diamond beads for precision sawing in basalt quarries, especially those located in the industrialized countries; it also has the advantage of preventing rock damages. Diamond wire has been widely used in up-line cutting and other sawing works in both marble and granite quarries for decades; therefore, performance data about the use of this tool on these two different types of rocks are widely documented in academic literature. However, for basalt sawing, information pertaining to the use of diamond wire is unavailable due to various reasons, but mostly because of to its relatively recent introduction in the basalt quarries and also to the historical low market demand for processed basalt in the past. This study offers a possible solution to this lack of information and provides a technical, economic and environmental assessment of diamond wire used in quarrying basalt for ornamental purposes. After an overview on the state of the art of diamond wire and on the final use of processed basalt, the study describes the experimental plan and the results. These show a tool yield much higher than those measured when diamond wire is used on other silicate dimension stones (e.g. granites). Moreover, the composition of basalt sawdust (sludge) has been analysed in the laboratory and has indicated the absence of polluting materials related to tool wear; therefore, basalt sludge, which is made of water and micronized basalt, can be used as a secondary raw material for the environmental restoration of the area or for any other purpose. Further research on other lithotypes is also proposed.