Linking denitrification and infiltration rates during managed groundwater recharge

We quantify relations between rates of in situ denitrification and saturated infiltration through shallow, sandy soils during managed groundwater recharge. We used thermal methods to determine time series of point-specific flow rates, and chemical and isotopic methods to assess denitrification progress. Zero order denitrification rates between 3 and 300 μmol L(-1) d(-1) were measured during infiltration. Denitrification was not detected at times and locations where the infiltration rate exceeded a threshold of 0.7 ± 0.2 m d(-1). Pore water profiles of oxygen and nitrate concentration indicated a deepening of the redoxocline at high flow rates, which reduced the thickness of the zone favorable for denitrification. Denitrification rates were positively correlated with infiltration rates below the infiltration threshold, suggesting that for a given set of sediment characteristics, there is an optimal infiltration rate for achieving maximum nitrate load reduction and improvements to water supply during managed groundwater recharge. The extent to which results from this study may be extended to other managed and natural hydrologic settings remains to be determined, but the approach taken in this study should be broadly applicable, and provides a quantitative link between shallow hydrologic and biogeochemical processes.     

Polymeric proanthocyanidins in skins and seeds of 37 Vitis vinifera L. cultivars: a methodological comparative study

Abstract: The polymeric proanthocyanidins (PAs) composition of skins and seeds from different Vitis vinifera L. cv. was evaluated, sampling 37 cultivar, preserved in the grapevine collection of Grinzane Cavour (Piedmont, Italy). PAs were quantified using both spectrophotometric (n‐butanol and vanillin assay) and chromatographic (high‐performance liquid chromatography [HPLC]) methods, and the evaluation of their antioxidant activity was performed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging assay. Results of PAs quantification with the different methods were significantly correlated. A strong correlation pointed out between anthocyans and PAs content (particularly regarding HPLC method; r = 0.9359, P = 0), and the antioxidant activity was not dependent on the polymeric PAs content, but negatively correlated with the degree of polymerization (r =–0.6102, P = 1 × 10^?4). The hierarchical clustering on principal components analysis allowed grouping the samples in 3 different clusters, observing a direct association between the cluster classification and the anthocyans/PAs content.     

Adaptive growth responses of Listeria monocytogenes to acid and osmotic shifts above and across the growth boundaries

The effect of acid and osmotic shifts on the growth of Listeria monocytogenes was evaluated at 10°C. Two types of shifts were tested: (i) within the range of pH and water activity (a(w)) levels that allow growth of L. monocytogenes and (ii) after habituation at no-growth conditions back to growth-permitting conditions. A L. monocytogenes cheese isolate, with high survival capacity during cheesemaking, was inoculated (10(2) CFU/ml) in tryptic soy broth supplemented with 0.6% yeast extract at six pH levels (5.1 to 7.2; adjusted with lactic acid) and 0.5% NaCl (a(w) 0.995), or four a(w) levels (0.995 to 0.93, adjusted with 0.5 to 10.5% NaCl) at pH 7.2 and grown to early stationary phase. L. monocytogenes was then shifted (at 10(2) CFU/ml) to each of the aforementioned growth-permitting pH and a(w) levels and incubated at 10°C. Shifts from no-growth to growth-permitting conditions were carried out by transferring L. monocytogenes habituated at pH 4.9 or a(w) 0.90 (12.5% NaCl) for 1, 5, and 10 days to all pH and a(w) levels permitting growth. Reducing a(w) or pH at different levels in the range of 0.995 to 0.93 and 7.2 to 5.1, respectively, decreased the maximum specific growth rate of L. monocytogenes. The lag time of the organism increased with all osmotic downshifts, as well as by the reduction of pH to 5.1. Conversely, any type of shift within pH 5.5 to 7.2 did not markedly affect the lag times of L. monocytogenes. The longer the cells were incubated at no-growth a(w) (0.90), the faster they initiated growth subsequently, suggesting adaptation to osmotic stress. Conversely, extended habituation at pH 4.9 had the opposite effect on subsequent growth of L. monocytogenes, possibly due to cell injury. These results suggest that there is an adaptation or injury rate induced at conditions inhibiting the growth of the pathogen. Thus, quantifying adaptation phenomena under growth-limiting environments, such as in fermented dairy and meat products or products preserved in brine, is essential for reliable growth simulations of L monocytogenes during transportation and storage of foods.     

Towards a better understanding of the pectin structure-function relationship in broccoli during processing: Part I—macroscopic and molecular analyses

To investigate the structure-function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. The macroscopic attributes of broccoli were linked to the chemical structure of broccoli pectin. By enhancing the cross-linking of pectic polymers, both LTB and HP reduced the texture loss that occurred during thermal processing of broccoli. During these pretreatments, homogalacturonan was de-esterified by pectin methylesterase, which led to changes in pectin solubility. When LTB or HP was combined with Ca²⁺ infusion, changes in the structure of pectin occurred, however not always reflected at the macroscopic level. The degree of esterification of pectin in Ca²⁺-soaked broccoli samples was lower compared to non-Ca²⁺-soaked samples and, in addition, a higher amount of ionically cross-linked pectin was retrieved.     

Ascorbic acid: a review of its chemistry and reactivity in relation to a wine environment

Extensive reviews of research are available on the use of ascorbic acid, and its consequent degradation pathways, in physiological conditions or food matrices. However, very little information can be found for wine-related systems. This review highlights the relevant chemistry and reactivity of ascorbic acid with a focus on its behavior and potential behavior in a wine environment. The review describes the use of ascorbic acid as a complementary antioxidant preservative to sulfur dioxide along with the metal-catalyzed and radical-dependent manner by which it achieves this role. The relevant degradation products of ascorbic acid in aerobic and anaerobic conditions are presented as well as the interaction of these degradation products with sulfur dioxide and other wine-relevant sulfur compounds. Limitations in existing knowledge, especially regarding the crossover between the antioxidant and pro-oxidant roles of ascorbic acid, are identified.     

Greenhouse gas emissions reduction by use of wind and solar energies for hydrogen and electricity production: Economic factors

This study addresses economic aspects of introducing renewable technologies in place of fossil fuel ones to mitigate greenhouse gas emissions. Unlike for traditional fossil fuel technologies, greenhouse gas emissions from renewable technologies are associated mainly with plant construction and the magnitudes are significantly lower. The prospects are shown to be good for producing the environmentally clean fuel hydrogen via water electrolysis driven by renewable energy sources. Nonetheless, the cost of wind- and solar-based electricity is still higher than that of electricity generated in a natural gas power plant. With present costs of wind and solar electricity, it is shown that, when electricity from renewable sources replaces electricity from natural gas, the cost of greenhouse gas emissions abatement is about four times less than if hydrogen from renewable sources replaces hydrogen produced from natural gas. When renewable-based hydrogen is used in a fuel cell vehicle instead of gasoline in a IC engine vehicle, the cost of greenhouse gas emissions reduction approaches the same value as for renewable-based electricity only if the fuel cell vehicle efficiency exceeds significantly (i.e., by about two times) that of an internal combustion vehicle. It is also shown that when 6000 wind turbines (Kenetech KVS-33) with a capacity of 350 kW and a capacity factor of 24% replace a 500-MW gas-fired power plant with an efficiency of 40%, annual greenhouse gas emissions are reduced by 2.3 megatons. The incremental additional annual cost is about $280 million (US). The results provide a useful approach to an optimal strategy for greenhouse gas emissions mitigation.     

Influence of thermal ageing on the stability of polymer bulk heterojunction solar cells

A new approach is presented in order to improve the thermal stability of polymer: [6-6]-phenyl C₆₁ butyric acid methyl ester (PCBM) bulk heterojunction solar cells. The central idea in this approach is the use of a polymer with high glass transition temperature (T_g), well above the normal operating temperatures of the devices. In this paper, a PPV-derivative with a T_g of 150 °C was used as an electron donor and the thermal stability of the obtained solar cells was compared with solar cells based on the reference material poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) with a T_g of 45 °C. The use of the material with higher glass transition temperature resulted in a significant improvement of the thermal stability of the photovoltaic parameters. Furthermore, a systematic transmission electron microscope (TEM) study demonstrates that the better thermal stability of performance coincides with a more stable active layer morphology. Both improvements are attributed to the reduced free movement of the electron donor material (PCBM) within the active layer of the solar cell.     

Building an index of activity of inhabitants from their activity on the residential electrical power line

In the framework of context awareness within the home, our team is currently assessing the unobtrusive detection of inhabitants' activity through the monitoring of their use and consumption of electricity. The objective is to develop a system for the remote monitoring of large populations of elderly people living independently at home. To be readily deployable on the field, such a system must be minimally intrusive both for the home environment and for the field professionals (paramedics and social workers) visiting the patients at home. We carried out two successive field experiments to evaluate and to improve our system designed to deliver a single index of daily activity. The first experiment involved 13 elderly persons over a nine-month period (84,240 h data recorded) and the second one 12 elderly over six months (51,840 h). We evaluated both the relevance of the index and the acceptability of the system as a whole. We discovered that electrical activity is a kind of unique "signature" of each person's activity. Moreover, this profile provides unexpected information on the health status of the subject. We confirmed that the system was unobtrusive and well accepted both by the subjects and by the professionals involved. Our unique index of activity, and its trend over time, can provide timely information to the professionals on the patient.     

Highly Stretchable Conducting SIBS‐P3HT Fibers

Poly(styrene‐β‐isobutylene‐β‐styrene)‐poly(3‐hexylthiophene) (SIBS‐P3HT) conducting composite fibers are successfully produced using a continuous flow approach. Composite fibers are stiffer than SIBS fibers and able to withstand strains of up 975% before breaking. These composite fibers exhibit interesting reversible mechanical and electrical characteristics, which are applied to demonstrate their strain gauging capabilities. This will facilitate their potential applications in strain sensing or elastic electrodes. Here, the fabrication and characterization of highly stretchable electrically conducting SIBS‐P3HT fibers using a solvent/non‐solvent wet‐spinning technique is reported. This fabrication method combines the processability of conducting SIBS‐P3HT blends with wet‐spinning, resulting in fibers that could be easily spun up to several meters long. The resulting composite fiber materials exhibit an increased stiffness (higher Young’s modulus) but lower ductility compared to SIBS fibers. The fibers’ reversible mechanical and electrical characteristics are applied to demonstrate their strain gauging capabilities.