Reaction Between Ethylene and Acetate Species on Clean and Oxygen-Covered Pd(100): Implications for the Vinyl Acetate Monomer Formation Pathway

Abstract  

The reaction between gas-phase ethylene and adsorbed acetate species on Pd(100)-p(2 × 2)-O and Pd(100)-c(2 × 2)-O surfaces is studied using infrared spectroscopy. It is found that acetate species are removed more rapidly by gas-phase ethylene on oxygen-covered Pd(100) than on Pd(111). However, in contrast to reaction on Pd(111), where vinyl acetate monomer (VAM) formation is detected by infrared spectroscopy, only CO is found on oxygen-covered Pd(100) surfaces. In the case of Pd(111), it has been shown that VAM is stabilized on the crowded, ethylidyne-covered surface. Since ethylidyne species do not form on Pd(100), any VAM that is formed can thermally decompose. The reaction shows an isotope effect when C₂D₄ is substituted for C₂H₄, indicating the hydrogen is involved in the rate-limiting step. Based on the surface chemistry found for VAM on a Au/Pd(111) alloy, where 30 to 40% ML of gold inhibits VAM decomposition, it is suggested that the VAM formation rate will increase on (100) alloy surfaces, while it will decrease at higher gold coverages since acetate formation is inhibited.     

Studies on the activation of hydrogen peroxide for color removal in the presence of a new Cu(II)-polyampholyte heterogeneous catalyst

In this work we describe the application of a new non-soluble and non-porous complex with copper ion based on ethylene glycol diglycidyl ether (EGDE), methacrylic acid (MAA) and 2-methylimidazole (2MI) in the decolorization of an azo dye Methyl Orange (MO) as a model pollutant at room temperature.The complex with copper ion was studied by ESR and SEM and was tested as a heterogeneous catalyst for H₂O₂ activation. A possible mechanism of interaction involves the production of hydroxyl radicals (confirmed by ESR), dioxygen and water.The Cu(II)-polyampholyte/H₂O₂ system acted efficiently in the color removal of MO. The adsorption and oxidative degradation of the azo-based dye followed pseudo-first-order kinetic profiles, and the rate constant for degradation had a second-order dependence on copper ion content in the mixture.A removal of MO higher than 90% was achieved in 20 min at pH 7.0, combining 0.8 mM of complexed copper ions in the mixture with 24 mM hydrogen peroxide.The dye adsorbed on the polyampholyte following a L4-type isotherm with 4.9 μmol g⁻¹ maximum loading capacity and 3.1 μM dissociation constant for the first monolayer.     

The Human Microbiomes in Pancreatic Cancer: Towards Evidence-Based Manipulation Strategies?

Recent pieces of evidence have emerged on the relevance of microorganisms in modulating responses to anticancer treatments and reshaping the tumor-immune microenvironment. On the one hand, many studies have addressed the role of the gut microbiota, providing interesting correlative findings with respect to etiopathogenesis and treatment responses. On the other hand, intra-tumoral bacteria are being recognized as intrinsic and essential components of the cancer microenvironment, able to promote a plethora of tumor-related aspects from cancer growth to resistance to chemotherapy. These elements will be probably more and more valuable in the coming years in early diagnosis and risk stratification. Furthermore, microbial-targeted intervention strategies may be used as adjuvants to current therapies to improve therapeutic responses and overall survival. This review focuses on new insights and therapeutic approaches that are dawning against pancreatic cancer: a neoplasm that arises in a central metabolic “hub” interfaced between the gut and the host.     

A MEMS-based thermal infrared emitter for an integrated NDIR spectrometer

A novel micromachined thermal infrared emitter using a heavily boron doped silicon slab as radiating element is presented. The fabrication process has been designed to allow the integration of such infrared emitters with an array of thermopile infrared detectors, with the aim of achieving an integrated non-dispersive infrared microspectrometer. A first set of infrared emitters with a common size for the doped silicon radiating slab (1,100?×?300?×?8?μm³) has been successfully fabricated and characterized. The working temperature of the Joule-heated radiating slabs has been controlled by means of DC and pulsed electrical signals, achieving temperatures well beyond 700°C. The thermal time constant measured in pulsed operation, around 50?ms, is adequate to enable the direct electrical modulation of the emitted radiation up to a frequency of 5?Hz while maintaining the full modulation depth. The temperature distribution in the radiating elements has been analyzed using two different thermal imaging methods.     

Comparative advantage: the impact of ISO 14001 environmental certification on exports

Relative to the enormous acceptance of the ISO 9000 quality standard, the ISO 14001 environmental management certification has been met with only moderate enthusiasm among industrial facilities. The literature on corporate motivation for ISO 14001 participation is relatively modest considering the enormous number of publications reviewing other aspects of its adoption and implementation. It would seem that the present "marketing" package supporting ISO environmental commitments does not seem to offer sufficiently persuasive incentives for increased sales, either domestically or internationally. While researchers assume that a higher export rate of companies is positively associated with higher ISO participation rates, there have been very few empirical studies that support this inference, and conclusions have not been based on data taken from importing countries orfrom a systematic evaluation of expressed corporate preference for products sold by ISO 14001 certified companies. The present study reports the results of a survey to firms in six countries that are Israel's leading trade partners, importing chemicals, textiles, and produce. The survey results confirm that while the international market still considers price and quality as the paramount factors in selection of suppliers, environmental management systems (EMS) are an important feature that is frequently taken into consideration. EMS certification appears to signify a supplier who is managing the business well and exhibiting ethical responsibility. The European market proved to be more environmentally conscious than those in other industrialized parts of the world. EMS offer a particularly valuable advantage for producers wishing to reach European markets. As policy-makers seek to expand the voluntary adoption of EMS, a clear advantage for exporters should be highlighted among national industries.     

Differential scanning calorimetry evaluation of oxidation stability of docosahexaenoic acid in microalgae cells and their extracts

The aim of this work was to evaluate the oxidative stability of docosahexaenoic acid (DHA) from Aurantiochytrium limacinum SR21 microalgae cells and in their lipidic extract by differential scanning calorimetry (DSC). Besides, freezing was evaluated as a strategy for microalgal DHA long‐term conservation by analysing changes in their thermal properties. As a first approach, mixtures of the most representative A. limacinum SR21‐fatty acids were evaluated in model systems. DHA and palmitic acid were the major polyunsaturated and saturated fatty acids produced by the microalgae cells, respectively. Changes in DHA/palmitic acid ratio in model systems, in cells and their lipidic extracts, were detected by DSC through shifts in the oxidation onset temperature (OOT) values. However, OOT values of cells and lipidic extracts could be also influenced by cellular compartmentalisation, carotenoids and other components presence. Freezing was not a good strategy for DHA long‐term conservation, as revealed by OOT values and thermal properties, which reflected the extensive changes that occurred during storage.     

Indoor persistent organic pollutants in agricultural areas from Argentina

Persistent Organic Pollutants (POPs) are anthropogenic chemicals extensively used in the past for industrial and agricultural purposes, characterized by their lipophilicity, ubiquity, volatility and environmental persistence. By other hand, chlorpyrifos is the most widely used current pesticide (CUPs) being the main insecticide used for crops in Argentina. The aim of this work was to assess levels of POPs and CUPs in different fractions of airborne particles collected indoor in agricultural areas from Argentina. Particles higher than 2.5 µm were trapped in polyurethane foams (PUF) while particles smaller than 1 µm and volatile compounds were adsorbed on activated charcoal. Compounds were analyzed by gas chromatograph with electron capture detector (GC-ECD). Endosulfans, chlordanes, PCBs, and HCHs were detected in all PUF samples, while endosulfans, chlorpyrifos, PCBs, and HCHs were the most abundant in smaller particles. Majority of pesticides showed higher concentrations during the summer season (1397.7 vs 832.5 pg/m³). Even adding up all measured organic compounds, no sample reaches the threshold limit value for indoor pesticides levels (0.1 pg/m³), neither in the large or small particle fraction. However, the fact that chronic exposure to POPs has been linked to several diseases raises concern for human health.     

Isolation and Identification of Bacillus spp. and Related Genera from Different Starchy Foods

ABSTRACT: Samples of butternut squash, potatoes, rice, and wheat flour were analyzed. Bacillus spp. and related species belonging to Paenibacillus and Brevibacillus genera were found in 96% of the samples. In butternut squash, predominant species were Bacillus pumilus and Paenibacillus polymyxa together with other Bacillus spp. species (B. cereus, B. licheniformis, B. sphaericus, and B. subtilis). In all the potato samples, Bacillus species were detected (B. cereus, B. mycoides, and B. licheniformis). Also, Bacillus spp. were detected in 100% of the unhusked rice samples, while incidence in white rice samples was 83%. In total rice samples, B. pumilus, Brevibacillus brevis, and Paenibacillus macerans were the main species and B. cereus, P. polymyxa, B. subtilis, and Brevibacillus laterosporus had the lower percentage. The most important species found in wheat flour was P. polymyxa with colony forming units per gram of about 10². As the identified species were potentially causatives of foodborne diseases, attention should be given to sanitary and temperature conditions as critical factors that influence the safety and shelf life of these products. Practical Application: Foodborne illness produce by B. cereus have been associated with a wide variety of food. In addition, some other Bacillus species have been related to foodborne disease in humans. Information about the virulence mechanisms of other Bacillus spp. is scanty and their risk is underestimated. Identifying the group of food and the food processes in which Bacillus cereus or other Bacillus spp. would be hazardous for human health is vital for the prevention of foodborne outbreak. In this study, we determined the incidence of Bacillus spp. and related genera in some food items of agriculture origin from Argentina. This research is relevant to identify the presence of potentially pathogen Bacillus species and related genera in this type of food.     

Isolation and characterization of the flour and starch of plantain bananas (Musa paradisiaca)

Plantain bananas of the variety “Terra” (Musa paradisiaca) may have industrial value due to their high starch content. In this research, the flour and starch of such unripe fruit were isolated and their chemical, physicochemical, and structural characteristics were determined. Banana flour and starch had a dry basis yield of 50.6 and 28.5%, and an average granule size of 31.7 and 47.3 µm, respectively. Both raw materials revealed a C‐type pattern and high gelatinization temperatures. The peak viscosity was greater for flour (378.0 RVU) than for starch (252.6 RVU), although the final viscosity was lower. At temperatures above 65°C, the swelling power of banana flour was lower than that of starch, while the solubility of flour was greater than that of starch at all temperatures. Furthermore, the presence of other components in banana flour influenced its physicochemical properties. In general, the flour and starch processed from unripe bananas have numerous possible uses as ingredients in food systems and for other industrial purposes.     

Adsorption isotherms of pinhão (Araucaria angustifolia seeds) starch and thermodynamic analysis

The seeds of Araucaria angustifolia, commonly known as pinhão, are widely consumed in both Southern and Southeastern Brazil due to their high nutritious value comprised basically by starch. The literature on the technological aspects of this seed is still very scarce. Moisture adsorption isotherms of pinhão starch were determined at 10, 20, 30 and 40 °C using the gravimetric method. Results show that the Peleg model most appropriately represents the experimental data. Other models (Chung–Pfost, GAB, Henderson, BET and Chirife) also were found to adjust well. The isosteric heat of sorption (differential enthalpy) was calculated by using the moisture adsorption isotherm and decreased as moisture content increased. The enthalpy–entropy compensation theory was applied to adsorption isotherms and the isokinetic temperature for pinhão starch was calculated by plotting the differential enthalpy versus differential entropy. It was found that the adsorption process investigated was enthalpy-controlled and spontaneous.