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1.
Indoor Air ; 27(5): 1001-1011, 2017 09.
Artículo en Inglés | MEDLINE | ID: mdl-28303599

RESUMEN

An INdoor air Detailed Chemical Model was developed to investigate the impact of ozone reactions with indoor surfaces (including occupants), on indoor air chemistry in simulated apartments subject to ambient air pollution. The results are consistent with experimental studies showing that approximately 80% of ozone indoors is lost through deposition to surfaces. The human body removes ozone most effectively from indoor air per square meter of surface, but the most significant surfaces for C6 -C10 aldehyde formation are soft furniture and painted walls owing to their large internal surfaces. Mixing ratios of between 8 and 11 ppb of C6 -C10 aldehydes are predicted to form in apartments in various locations in summer, the highest values are when ozone concentrations are enhanced outdoors. The most important aldehyde formed indoors is predicted to be nonanal (5-7 ppb), driven by oxidation-derived emissions from painted walls. In addition, ozone-derived emissions from human skin were estimated for a small bedroom at nighttime with concentrations of nonanal, decanal, and 4-oxopentanal predicted to be 0.5, 0.7, and 0.7 ppb, respectively. A detailed chemical analysis shows that ozone-derived surface aldehyde emissions from materials and people change chemical processing indoors, through enhanced formation of nitrated organic compounds and decreased levels of oxidants.


Asunto(s)
Contaminación del Aire Interior/análisis , Aldehídos/análisis , Modelos Químicos , Ozono/química , Monitoreo del Ambiente , Humanos , Estaciones del Año
4.
Environ Sci Technol ; 46(20): 11028-39, 2012 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-22963451

RESUMEN

Oxygenated volatile organic compounds (OVOCs) in the atmosphere are precursors to peroxy acetyl nitrate (PAN), affect the tropospheric ozone budget, and in the remote marine environment represent a significant sink of the hydroxyl radical (OH). The sparse observational database for these compounds, particularly in the tropics, contributes to a high uncertainty in their emissions and atmospheric significance. Here, we show measurements of acetone, methanol, and acetaldehyde in the tropical remote marine boundary layer made between October 2006 and September 2011 at the Cape Verde Atmospheric Observatory (CVAO) (16.85° N, 24.87° W). Mean mixing ratios of acetone, methanol, and acetaldehyde were 546 ± 295 pptv, 742 ± 419 pptv, and 428 ± 190 pptv, respectively, averaged from approximately hourly values over this five-year period. The CAM-Chem global chemical transport model reproduced annual average acetone concentrations well (21% overestimation) but underestimated levels by a factor of 2 in autumn and overestimated concentrations in winter. Annual average concentrations of acetaldehyde were underestimated by a factor of 10, rising to a factor of 40 in summer, and methanol was underestimated on average by a factor of 2, peaking to over a factor of 4 in spring. The model predicted summer minima in acetaldehyde and acetone, which were not apparent in the observations. CAM-Chem was adapted to include a two-way sea-air flux parametrization based on seawater measurements made in the Atlantic Ocean, and the resultant fluxes suggest that the tropical Atlantic region is a net sink for acetone but a net source for methanol and acetaldehyde. Inclusion of the ocean fluxes resulted in good model simulations of monthly averaged methanol levels although still with a 3-fold underestimation in acetaldehyde. Wintertime acetone levels were better simulated, but the observed autumn levels were more severely underestimated than in the standard model. We suggest that the latter may be caused by underestimated terrestrial biogenic African primary and/or secondary OVOC sources by the model. The model underestimation of acetaldehyde concentrations all year round implies a consistent significant missing source, potentially from secondary chemistry of higher alkanes produced biogenically from plants or from the ocean. We estimate that low model bias in OVOC abundances in the remote tropical marine atmosphere may result in up to 8% underestimation of the global methane lifetime due to missing model OH reactivity. Underestimation of acetaldehyde concentrations is responsible for the bulk (∼70%) of this missing reactivity.


Asunto(s)
Acetaldehído/análisis , Acetona/análisis , Contaminantes Atmosféricos/análisis , Contaminación del Aire/estadística & datos numéricos , Metanol/análisis , Compuestos Orgánicos Volátiles/análisis , Océano Atlántico , Atmósfera/química , Cabo Verde , Monitoreo del Ambiente , Ozono/química , Estaciones del Año , Clima Tropical
5.
Proc Natl Acad Sci U S A ; 106(44): 18447-51, 2009 Nov 03.
Artículo en Inglés | MEDLINE | ID: mdl-19841269

RESUMEN

More than half the world's rainforest has been lost to agriculture since the Industrial Revolution. Among the most widespread tropical crops is oil palm (Elaeis guineensis): global production now exceeds 35 million tonnes per year. In Malaysia, for example, 13% of land area is now oil palm plantation, compared with 1% in 1974. There are enormous pressures to increase palm oil production for food, domestic products, and, especially, biofuels. Greater use of palm oil for biofuel production is predicated on the assumption that palm oil is an "environmentally friendly" fuel feedstock. Here we show, using measurements and models, that oil palm plantations in Malaysia directly emit more oxides of nitrogen and volatile organic compounds than rainforest. These compounds lead to the production of ground-level ozone (O(3)), an air pollutant that damages human health, plants, and materials, reduces crop productivity, and has effects on the Earth's climate. Our measurements show that, at present, O(3) concentrations do not differ significantly over rainforest and adjacent oil palm plantation landscapes. However, our model calculations predict that if concentrations of oxides of nitrogen in Borneo are allowed to reach those currently seen over rural North America and Europe, ground-level O(3) concentrations will reach 100 parts per billion (10(9)) volume (ppbv) and exceed levels known to be harmful to human health. Our study provides an early warning of the urgent need to develop policies that manage nitrogen emissions if the detrimental effects of palm oil production on air quality and climate are to be avoided.


Asunto(s)
Agricultura , Contaminación del Aire/análisis , Arecaceae/fisiología , Nitrógeno/análisis , Ozono/análisis , Aceites de Plantas/análisis , Clima Tropical , Aeronaves , Butadienos/análisis , Geografía , Hemiterpenos/análisis , Monoterpenos/análisis , Óxido Nítrico/análisis , Dióxido de Nitrógeno/análisis , Aceite de Palma , Pentanos/análisis , Ácido Peracético/análogos & derivados , Ácido Peracético/análisis , Factores de Tiempo
6.
Food Chem ; 129(3): 1258-64, 2011 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-25212365

RESUMEN

The objective of this study was to determine the effects of roasting time on volatile components of Pistacia terebinthus L., a fruit growing wild in Turkey. The whole fruit samples were pan roasted for 0, 5, 10, 15, 20 and 25min at 200°C. Volatile compounds were isolated and identified using the direct thermal desorption (DTD) method coupled with comprehensive gas chromatography - time of flight mass spectrometry (GCxGC-TOF/MS). The major components of the fresh hull of P. terebinthus were α-pinene (10.37%), limonene (8.93%), ß-pinene (5.53%), 2-carene (4.47%) and γ-muurolene (4.29%). Eighty-three constituents were characterised from the volatiles of fresh whole P. terebinthus fruits obtained by direct thermal desorption with α-pinene (9.62%), limonene (5.54%), γ-cadinane (5.48%), ß-pinene (5.46%), ß-caryophyllene (5.24%) being the major constituents. The type and the number of constituents characterised were observed to change with differing roasting times. Limonene (5.56%), α-pinene (4.84%), 5-methylfurfural (4.78%), 5-hydroxymethylfurfural (5-HMF, 3.89%), dimethylmetoxyfuranone (3.67%) and 3-methyl-2(5H)furanone (3.12%) were identified as the major components among the 104 compounds characterised in the volatiles of P. terebinthus, roasted for 25min. In addition, volatiles of fully roasted P. terebinthus fruits contained furans and furanones (15.42%), pyridines (4.45%) and benzene derivatives (3.81%) as the major groups.

7.
Science ; 232(4752): 863-5, 1986 May 16.
Artículo en Inglés | MEDLINE | ID: mdl-17755969

RESUMEN

Darwin hypothesized that flower constancy in insects that feed on nectar results from the need to learn how to extract nectar from a flower of a given species. In laboratory tests, Pieris rapae, the cabbage butterfly, showed flower constancy by continuing to visit flower species with which it had experience. The time required by individuals to find the source of nectar in flowers decreased with successive attempts, the performance following a learning curve. Learning to extract nectar from a second species interfered with the ability to extract nectar from the first. Insects that switch species thus experience a cost in time to learn. These results support recent suggestions on the importance of learning in animal foraging.

8.
Science ; 165(3895): 808-9, 1969 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-5804723

RESUMEN

Choleragenic toxin was separated from vascular permeability factor by ion-exchange chromatography of supernatants of dialyzed peptone cultures of Vibrio cholerae. The choleragenic toxin eluted from columns of QAE-Sephadex with low-ionicity systems is free of permeability factor activity. Further elution of these columns with 0.5M NaCl removes both the permeability factor and residual choleragenic toxin. When this latter material is chromatographed on columns of carboxymethyl-Sephadex, the permeability factor toxin is eluted by 0.02M phosphate buffer and is free of choleragenic activity. Therefore, choleragenic and permeability factor activities of the type 2 cholera toxins are different and can be separated by these procedures.


Asunto(s)
Toxinas Biológicas/aislamiento & purificación , Vibriosis/etiología , Vibrio/clasificación , Animales , Cromatografía por Intercambio Iónico , Inyecciones Intravenosas , Permeabilidad , Conejos
9.
J Biomed Mater Res A ; 82(2): 363-72, 2007 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-17295226

RESUMEN

Surface chemistry of CoCr particles is demonstrated to be fundamental to the process of phagocytosis by fibroblast cells in vitro. Particles preincubated in serum for 5 days and washed in water before addition to cell cultures were phagocytosed less readily than were particles preincubated in minimal essential medium (MEM) for 1 h and washed in water. This was explained by the coating of calcium phosphate and protein on the serum-immersed particles investigated by time-of-flight secondary ion mass spectroscopy. The cells incubated with the serum-immersed particles had a reduced mitotic index when compared with the MEM-immersed particles, indicating that the phagocytosed particles were causing cell cycle arrest. The release of soluble ions measured by electrothermal atomic absorption spectroscopy within the first hour of particle immersion in MEM was identified as the most likely cause for the DNA damage measured by single cell gel electrophoresis ("Comet" assay). Cryofocused ion beam SEM with a spatial resolution of 8 nm was used to cross section cells, to investigate the location of the phagocytosed particles, some of which were found within the nuclear membrane. This paper demonstrated that consideration of the surface chemistry is essential to understand the processes of the effects of orthopedic wear debris.


Asunto(s)
Materiales Biocompatibles/química , Materiales Biocompatibles/toxicidad , Aleaciones de Cromo/química , Aleaciones de Cromo/toxicidad , Daño del ADN , Fagocitosis , Ciclo Celular/efectos de los fármacos , Células Cultivadas , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/fisiología , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Falla de Prótesis , Espectrometría de Masa de Ion Secundario , Propiedades de Superficie
10.
J Orthop Res ; 24(8): 1587-96, 2006 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-16779825

RESUMEN

Physical wear of orthopedic implants is inevitable. CoCr alloy samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, foetal bovine serum (FBS), synovial fluid, albumin in phosphate-buffered saline (PBS), EDTA in PBS, and water were studied using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The difference in the corrosive nature of human serum, water, albumin in PBS and synovial fluid after 5 days of immersion was highlighted by the oxide layer, which was respectively 15, 3.5, 1.5, and 1.5 nm thick. The thickness of an additional calcium phosphate deposit from human serum and synovial fluid was 40 and 2 nm, respectively. Co and Cr ions migrated from the bulk metal surface and were trapped in this deposit by the phosphate anion. This may account for the composition of wear debris from CoCr orthopedic implants, which is known to consist predominantly of hydroxy-phosphate compounds. Known components of synovial fluid including proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP), have been identified as possible causes for the lack of significant calcium phosphate deposition in this environment. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition.


Asunto(s)
Fosfatos de Calcio/química , Aleaciones de Cromo/química , Sangre Fetal/química , Falla de Prótesis , Líquido Sinovial/química , Albúminas/química , Animales , Tampones (Química) , Bovinos , Corrosión , Ácido Edético/química , Humanos , Técnicas In Vitro , Cloruro de Sodio , Espectrometría de Masa de Ion Secundario , Espectrometría por Rayos X , Estrés Mecánico , Agua/química
11.
Sci Total Environ ; 360(1-3): 5-25, 2006 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-16289266

RESUMEN

The PUMA (Pollution of the Urban Midlands Atmosphere) Consortium project involved intensive measurement campaigns in the Summer of 1999 and Winter of 1999/2000, respectively, in which a wide variety of air pollutants were measured in the UK West Midlands conurbation including detailed speciation of VOCs and major component analysis of aerosol. Measurements of the OH and HO2 free radicals by the FAGE technique demonstrated that winter concentrations of OH were approximately half of those measured during the summer despite a factor of 15 reduction in production through the photolysis of ozone. Detailed box modelling of the fast reaction chemistry revealed the decomposition of Criegee intermediates formed from ozone-alkene reactions to be responsible for the majority of the formation of hydroxyl in both the summer and winter campaigns, in contrast to earlier rural measurements in which ozone photolysis was predominant. The main sinks for hydroxyl are reactions with NO2, alkenes and oxygenates. Concentrations of the more stable hydrocarbons were found to be relatively invariant across the conurbation, but the impacts of photochemistry were evident through analyses of formaldehyde which showed the majority to be photochemical in origin as opposed to emitted from road traffic. Measurements on the upwind and downwind boundaries of the conurbation revealed substantial enhancements in NOx as a result of emissions within the conurbation, especially during westerly winds which carried relatively clean air. Using calcium as a tracer for crustal particles, it proved possible to reconstruct aerosol mass from the major chemical components with a fairly high degree of success. The organic to elemental carbon ratios showed a far greater influence of photochemistry in summer than winter, presumably resulting mainly from the greater availability of biogenic precursors during the summer campaign. Two urban airshed models were developed and applied to the conurbation, one Eulerian, the other Lagrangian. Both were able to give a good simulation of concentrations of both primary and secondary pollutants at urban background locations.


Asunto(s)
Contaminantes Atmosféricos/análisis , Contaminación del Aire/análisis , Modelos Teóricos , Acetona/análisis , Aerosoles/análisis , Monóxido de Carbono/análisis , Monitoreo del Ambiente , Formaldehído/análisis , Radicales Libres/análisis , Hidrocarburos/análisis , Óxidos de Nitrógeno/análisis , Ozono/análisis , Tamaño de la Partícula , Ácido Peracético/análogos & derivados , Ácido Peracético/análisis , Fotoquímica , Reproducibilidad de los Resultados , Reino Unido
12.
J Biomed Mater Res A ; 75(2): 365-73, 2005 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-16088901

RESUMEN

Physical wear of orthopedic implants is inevitable. CoCr metal samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, fetal bovine serum (FBS), synovial fluid, and water were studied using time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The differences in the corrosive nature of human serum, FBS, synovial fluid, and water after 5 days immersion were highlighted by the oxide/hydroxide layer, which was, respectively, 25, 10, 1.5, and 3-3.5 nm thick. The thickness of calcium phosphate deposit from human serum, FBS, and synovial fluid was, respectively, 30, 20, and 2 nm. Co and Cr ions migrated from the bulk metal surface and were trapped in the serum deposits, where chromium existed as oxides, hydroxides, and phosphates, whereas the cobalt chemistry was dominated only by phosphates and hydroxides. This may account for the composition of wear debris from CoCr orthopedic implants, which are predominantly hydroxyphosphate compounds. From the literature, proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP) have been identified as possible causes for the insignificant deposit of calcium phosphate from synovial fluid. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition and therefore contribute to osteolysis.


Asunto(s)
Materiales Biocompatibles/química , Fosfatos de Calcio/química , Aleaciones de Cromo/química , Cobalto/química , Falla de Prótesis , Animales , Bovinos , Corrosión , Electroquímica , Humanos , Ensayo de Materiales , Prótesis e Implantes , Suero/química , Propiedades de Superficie
13.
J Biomed Mater Res A ; 73(4): 456-67, 2005 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-15900610

RESUMEN

The corrosion and dissolution of high- and low-carbon CoCrMo alloys, as used in orthopedic joint replacements, were studied by immersing samples in phosphate-buffered saline (PBS), water, and synovial fluid at 37 degrees C for up to 35 days. Bulk properties were analyzed with a fine ion beam microscope. Surface analyses by X-ray photoelectron spectroscopy and Auger electron spectroscopy showed surprisingly that synovial fluid produced a thin oxide/hydroxide layer. Release of ions into solution from the alloy also followed an unexpected pattern where synovial fluid, of all the samples, had the highest Cr concentration but the lowest Co concentration. The presence of carbide inclusions in the alloy did not affect the corrosion or the dissolution mechanisms, although the carbides were a significant feature on the metal surface. Only one mechanism was recognized as controlling the thickness of the oxide/hydroxide interface. The analysis of the dissolved metal showed two mechanisms at work: (1) a protein film caused ligand-induced dissolution, increasing the Cr concentration in synovial fluid, and was explained by the equilibrium constants; (2) corrosion at the interface increased the Co in PBS. The effect of prepassivating the samples (ASTM F-86-01) did not always have the desired effect of reducing dissolution. The release of Cr into PBS increased after prepassivation. The metal-synovial fluid interface did not contain calcium phosphate as a deposit, typically found where samples are exposed to calcium rich bodily fluids.


Asunto(s)
Ortopedia/métodos , Cloruro de Sodio/farmacología , Líquido Sinovial/metabolismo , Vitalio/farmacología , Agua/farmacología , Materiales Biocompatibles , Tampones (Química) , Calcio/química , Fosfatos de Calcio/química , Carbono/química , Cromo/química , Calor , Humanos , Hidróxidos/química , Iones , Ensayo de Materiales , Modelos Químicos , Fosfatos/farmacología , Prótesis e Implantes , Espectrometría por Rayos X , Propiedades de Superficie , Temperatura , Termodinámica , Factores de Tiempo
14.
J Bone Joint Surg Br ; 87(10): 1439-44, 2005 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-16189324

RESUMEN

Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty. All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions. Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.


Asunto(s)
Daño del ADN , Prótesis Articulares , Metales/toxicidad , Líquido Sinovial/química , Anciano , Anciano de 80 o más Años , Artroplastia de Reemplazo , Células Cultivadas , Aleaciones de Cromo , Fibroblastos/efectos de los fármacos , Humanos , Ensayo de Materiales/métodos , Persona de Mediana Edad , Diseño de Prótesis , Acero Inoxidable/toxicidad
15.
Am J Med ; 71(5): 841-5, 1981 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-7304657

RESUMEN

The efficacy of single-dose (cefaclor, 2 g orally) and multidose (cefaclor, 250 mg orally three times a day for 10 days) antibiotic regimens in the therapy of acute uncomplicated urinary tract infections (UTI) in nonpregnant women were compared. The patient's clinical status and results of urine cultures were compared in retrospect with the results of the antibody-coated bacteria (ACB) test and C-reactive protein (CRP) test in order to determine if either test would predict the patient's response. Overall, 10 of 30 patients (33 percent) and 18 of 22 patients (81 percent) given single doses and multidoses, respectively, had negative urine cultures four weeks after completion of therapy. A negative urine culture at four weeks correlated with a negative ACB test utilizing the less inclusive criteria for negativity (less than 5 bacteria with fluorescence in 5 minutes of search) but not with a negative ACB test utilizing the more inclusive criteria (less than 10 percent bacteria with fluorescence) or with a negative CRP test. The cure rate in the ACB-negative single-dose group (7 of 9 patients) utilizing the less inclusive criteria for negativity was similar to the cure rate in the ACB-negative multidose group (8 of 10 patients). This study suggests that the ACB test, if properly standardized, might permit identification of a population of patients with UTI who would respond to single-dose cefaclor therapy.


Asunto(s)
Cefaclor/uso terapéutico , Cefalexina/análogos & derivados , Infecciones Urinarias/tratamiento farmacológico , Adulto , Prueba en la Orina con Bacterias Revestidas de Anticuerpos , Proteína C-Reactiva , Cefaclor/administración & dosificación , Cefaclor/efectos adversos , Estudios de Evaluación como Asunto , Femenino , Humanos
16.
J Med Microbiol ; 16(1): 75-82, 1983 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-6218305

RESUMEN

We examined the susceptibility of various anaerobes to four beta-lactamase susceptible (ampicillin, amoxycillin, cyclacillin, and penicillin G) and two beta-lactamase resistant (moxalactam, and N-F-thienamycin) beta-lactam antibiotics and measured beta-lactamase production. Members of the Bacteroides groups were most resistant to the six antibiotics. N-F-thienamycin was the most effective antimicrobial agent against all the test strains, moxalactam the next most effective, and penicillin G the least. Beta-lactamase production was mainly confined to Bacteroides species. Cephalosporinase was the most common beta-lactamase produced; penicillinase was detected less often. About two thirds of the penicillin-resistant isolates produced cephalosporinase. N-F-thienamycin and moxalactam were the most active agents against those anaerobes that were resistant to many beta-lactam antibiotics.


Asunto(s)
Antibacterianos/farmacología , Bacterias/efectos de los fármacos , beta-Lactamasas/biosíntesis , Amoxicilina/farmacología , Ampicilina/farmacología , Bacterias/enzimología , Bacteroides/efectos de los fármacos , Cefamicinas/farmacología , Ciclacilina/farmacología , Pruebas de Sensibilidad Microbiana , Moxalactam , Tienamicinas/farmacología
17.
Science ; 221(4611): 604, 1983 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-17787713
18.
Oecologia ; 70(1): 132-135, 1986 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-28311298

RESUMEN

Previous work has shown that host choice by acridids (grasshoppers and locusts) is sensitive to alterations in host quality. In particular, reduced plant water content has been found to increase palatability of certain plant species. To determine if this phenomenon is general, and to gain preliminary information on causes, turgid and wilted plant material of forty-one species was tested using nymphs of the desert locust, Schistocerca gregaria. Twelve plant species (29%) had increased and five (12%) had decreased palatability (as measured by meal size) when wilted. Among fifteen families tested, the increases occurred in six, the decreases in three. The greatest change occurred in Taraxacum officinale; further tests on this plant revealed the increase to be continuous, rising with decreasing water content. The behavioral observations combined with the pattern of the results across plant species suggest that changes are due to alterations in specific deterrents or stimulants, rather than to decreased water content or increased concentrations of amino acids and/or sugars. The implications of these results for understanding drought-associated population outbreaks are discussed.

19.
Food Chem ; 135(4): 2215-20, 2012 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-22980793

RESUMEN

The grilling of meat may generate dangerous levels of mutagenic and carcinogenic nitrosamines (NAs). Meat and vegetable samples underwent a two-step solid-phase extraction before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The GCxGC-NCD method showed high selectivity, sensitivity and equimolarity in its response to six specific NAs. NA contamination of charcoal-grilled lamb at various stages of cooking and with various fat contents and also charcoal-grilled vegetables were investigated. The grilling of lamb on unready charcoal resulted in the formation of considerable quantities of NAs. Grilling lamb on properly prepared, ready charcoal resulted in an increase in total concentrations of six NAs from 0 to 4.51 µg kg(-1) over a period of 16 min. Increasing the fat content of the grilled lamb from 5% to 20% caused a modest increase in total concentrations of the six investigated NAs from 4.51 to 5.30 µg kg(-1).


Asunto(s)
Cromatografía de Gases/métodos , Mediciones Luminiscentes/métodos , Carne/análisis , Nitrosaminas/análisis , Verduras/química , Compuestos Orgánicos Volátiles/análisis , Animales , Culinaria , Ovinos
20.
Philos Trans R Soc Lond B Biol Sci ; 366(1582): 3177-95, 2011 Nov 27.
Artículo en Inglés | MEDLINE | ID: mdl-22006961

RESUMEN

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.


Asunto(s)
Agricultura , Atmósfera/química , Árboles/química , Aerosoles/química , Contaminantes Atmosféricos/química , Aeronaves , Derivados de Alilbenceno , Anisoles/química , Arecaceae/química , Arecaceae/fisiología , Atmósfera/análisis , Borneo , Butadienos/química , Carbono/química , Hemiterpenos/química , Radical Hidroxilo/química , Industrias , Malasia , Monoterpenos/química , Óxidos de Nitrógeno/química , Ozono/química , Pentanos/química , Fotoquímica , Árboles/fisiología , Compuestos Orgánicos Volátiles/química
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