The Soret effect and isotopic fractionation in high-temperature silicate melts.

Diffusion in condensed phases is a ubiquitous but poorly understood phenomenon. For example, chemical diffusion, which is the transport of matter associated with chemical concentration gradients (Fick's law), is treated as a separate process from thermal transport (the Soret effect), which is mass transport induced by temperature gradients. In the past few years, large variations in the proportions of isotopes of Mg, Ca, Fe, Si and O found in silicate melts subject to thermal gradients have been found, but no physical mechanism has been proposed. Here we present a model of diffusion in natural condensed systems that explains both the chemical and isotopic fractionation of Mg, Ca and Fe in high-temperature geochemical melts. Despite the high temperatures associated with these melts (T>1,000 °C), we find that consideration of the quantum-mechanical zero-point energy of diffusing species is essential for understanding diffusion at the isotopic level. Our model explains thermal and chemical mass transport as manifestations of the same underlying diffusion mechanism. This work promises to provide insights into mass-transport phenomena (diffusion and evaporation) and associated isotopic fractionations in a wide range of natural condensed systems, including the atmospheric water cycle, geological and geochemical systems and the early Solar System. This work might also be relevant to studies of mass transport in biological and nanotechnological condensed systems.

Determination of polycyclic aromatic hydrocarbons in soy isoflavone nutraceutical products by gas chromatography coupled to triple quadrupole tandem mass spectrometry.

Thirteen polycyclic aromatic hydrocarbons have been determined in soy-based nutraceutical products. First, an optimization of extraction procedure was performed, and a solid-liquid extraction assisted by sonication and a dilute and shoot procedure were compared, selecting the dilute and shoot approach for the extraction of target compounds, utilizing a mixture of acetone/n-hexane (1:1 v/v) as extractant solvent. After this, a clean-up step was needed bearing in mind the complexity of these matrices. Dispersive solid-phase extraction, using a mixture of C18 and Zr-Sep+ (25 mg/mL each) was used. The separation was achieved by gas chromatography and detection with triple quadrupole tandem mass spectrometry. For quantification purposes, matrix-matched calibration was used. The validation was applied at three concentration levels (20, 100 and 250 µg/kg), obtaining recoveries between 70 and 120% and precision values equal to or lower than 23%. Limits of detection and quantification were below 8 and 20 µg/kg, respectively. The method was applied in 11 samples, detecting five polycyclic aromatic hydrocarbons at concentrations ranging from 4.1 to 18.5 µg/kg.

Ultrafast and nanoscale plasmonic phenomena in exfoliated graphene revealed by infrared pump-probe nanoscopy.

Pump-probe spectroscopy is central for exploring ultrafast dynamics of fundamental excitations, collective modes, and energy transfer processes. Typically carried out using conventional diffraction-limited optics, pump-probe experiments inherently average over local chemical, compositional, and electronic inhomogeneities. Here, we circumvent this deficiency and introduce pump-probe infrared spectroscopy with ∼ 20 nm spatial resolution, far below the diffraction limit, which is accomplished using a scattering scanning near-field optical microscope (s-SNOM). This technique allows us to investigate exfoliated graphene single-layers on SiO2 at technologically significant mid-infrared (MIR) frequencies where the local optical conductivity becomes experimentally accessible through the excitation of surface plasmons via the s-SNOM tip. Optical pumping at near-infrared (NIR) frequencies prompts distinct changes in the plasmonic behavior on 200 fs time scales. The origin of the pump-induced, enhanced plasmonic response is identified as an increase in the effective electron temperature up to several thousand Kelvin, as deduced directly from the Drude weight associated with the plasmonic resonances.

Multiresidue method for the fast determination of pesticides in nutraceutical products (Camellia sinensis) by GC coupled to triple quadrupole MS.

A method based on QuEChERS (quick, easy, cheap, effective, rugged, and safe) has been developed and validated for the determination and quantification of more than 140 pesticides in nutraceutical products obtained from green tea (Camellia sinensis). Extraction was performed with acidified acetonitrile (acetic acid 1%, v/v) and a clean-up step using primary secondary amine (50 mg), graphitized black carbon (100 mg) and magnesium sulfate (200 mg) was needed. Pesticide determination was achieved utilizing GC coupled to triple quadrupole MS/MS using the selective-reaction monitoring mode. The total run time was 23 min. Pesticides were quantified using matrix-matched calibration. Recoveries ranged from 70 to 120% and relative SD was lower than 25% at 10, 50, and 100 µg/kg. LOQs were lower than 10 µg/kg. 148 pesticides were validated. The validated method was applied to commercial nutraceutical products, detecting 4,4-dichlorobenzophenone (28 µg/kg), o,p'-dicofol (38 µg/kg) and p,p-dicofol (44 µg/kg) in a few samples.

Evidence of neutron leakage at the Fukushima nuclear plant from measurements of radioactive 35S in California.

A recent earthquake and the subsequent tsunami have extensively damaged the Fukushima nuclear power plant, releasing harmful radiation into the environment. Despite the obvious implication for human health and the surrounding ecology, there are no quantitative estimates of the neutron flux leakage during the weeks following the earthquake. Here, using measurements of radioactive (35)S contained in sulfate aerosols and SO(2) gas at a coastal site in La Jolla, California, we show that nearly 4 × 10(11) neutrons per m(2) leaked at the Fukushima nuclear power plant before March 20, 2011. A significantly higher (35)SO(2-)(4) activity as measured on March 28 is in accord with neutrons escaping the reactor core and being absorbed by the coolant seawater (35)Cl to produce (35)S by a (n, p) reaction. Once produced, (35)S oxidizes to (35)SO(2) and (35)SO(2-)(4) and was then transported to Southern California due to the presence of strong prevailing westerly winds at this time. Based on a moving box model, we show that the observed activity enhancement in (35)SO(2-)(4) is compatible with long-range transport of the radiation plume from Fukushima. Our model predicts that (35)SO(2-)(4), the concentration in the marine boundary layer at Fukushima, was approximately 2 × 10(5) atoms per m(3), which is approximately 365 times above expected natural concentrations. These measurements and model calculations imply that approximately 0.7% of the total radioactive sulfate present at the marine boundary layer at Fukushima reached Southern California as a result of the trans-Pacific transport.

Intestinal intussusception as a postoperative complication of gastric bypass.

The gold standard for bariatric surgery is the laparoscopic gastric bypass, which consists in forming a small gastric pouch and a Roux-en-Y anastomosis. We present the case of a 41-year-old female who underwent a laparoscopic gastric bypass 8 years prior to her admission to the emergency room, where she arrived complaining of severe and colicky epigastric abdominal pain. The abdominal computed tomography showed a jejuno-jejunal intussusception, for which the patient underwent urgent exploratory laparotomy with intussusception reduction. Intestinal intussusception is a possible postoperative complication of a Roux-en-Y gastric bypass.

El Método de referencia en la cirugía bariátrica es el bypass gástrico laparoscópico, que consiste en la creación de una bolsa gástrica pequeña, anastomosada al tracto digestivo mediante una Y de Roux. Presentamos el caso de una mujer de 41 años con el antecedente de un bypass gástrico laparoscópico realizado 8 años antes, quien ingresó al servicio de urgencias refiriendo dolor abdominal grave. La tomografía computarizada abdominal evidenció una intususcepción a nivel de la anastomosis yeyuno-yeyuno, por lo que se realizó una laparotomía exploradora con reducción de la intususcepción. Se debe considerar la intususcepción intestinal como complicación posoperatoria de bypass gástrico.

Spontaneous pneumoperitoneum in the absence of visceral perforation in a patient with systemic sclerosis: a case report.

We present the case of a 44 year old woman with systemic sclerosis who presented with intense abdominal pain without signs of peritonitis. An abdominal computed tomography showed generalized intestinal dilation, intestinal pneumatosis and an extensive pneumoperitoneum. A diagnostic laparoscopy was performed but no perforation nor gastrointestinal leakage were found. Spontaneous pneumoperitoneum in patients with systemic sclerosis without visceral perforation is an extremely rare complication. Physicians must have a low threshold of suspicion for this entity when a patient with systemic sclerosis presents with spontaneous pneumoperitoneum in the absence of peritoneal signs.

Presentamos el caso de una mujer de 44 años con diagnóstico de esclerosis sistémica, quien presentó dolor abdominal intenso sin datos de irritación peritoneal. Una tomografía computarizada de abdomen mostró dilatación generalizada de asas intestinales, neumatosis intestinal y neumoperitoneo extenso, por lo cual se realizó una laparoscopía diagnóstica, sin encontrar sitio de perforación. El neumoperitoneo espontáneo en pacientes con esclerodermia sin evidencia de perforación visceral es una complicación extremadamente rara. El médico deberá mantener un alto índice de sospecha para esta condición ante un paciente con esclerosis sistémica que se presente con un neumoperitoneo espontáneo sin datos de irritación peritoneal.

The physical chemistry of mass-independent isotope effects and their observation in nature.

Historically, the physical chemistry of isotope effects and precise measurements in samples from nature have provided information on processes that could not have been obtained otherwise. With the discovery of a mass-independent isotopic fractionation during the formation of ozone, a new physical chemical basis for isotope effects required development. Combined theoretical and experimental developments have broadened this understanding and extended the range of chemical systems where these unique effects occur. Simultaneously, the application of mass-independent isotopic measurements to an extensive range of both terrestrial and extraterrestrial systems has furthered the understanding of events such as solar system origin and evolution and planetary atmospheric chemistry, present and past.

Optimized low-level liquid scintillation spectroscopy of 35S for atmospheric and biogeochemical chemistry applications.

Anthropogenic activities, dominated by emissions of sulfur dioxide (SO(2)), have perturbed the global sulfur (S) cycle. Uncertainties in timescales of S transport and chemistry in the atmosphere lead to uncertainties in the predicted impact of S emissions. Measurements of cosmogenic (35)S may potentially be used to resolve existing uncertainties in the photochemical and chemical transformation of S in the environment. The lack of a simple, effective, and highly sensitive technique to measure (35)S activity in samples with low activities may explain the scarcity of published measurements. We present a set of new sample handling and measurement procedures optimized for the measurement of (35)S in natural samples with activities as low as 0.20 dpm above background (2sigma, integration time = 2 hr). We also report simultaneous measurements of aerosol (35SO4 ) and gas phase (35SO2) collected at inland and coastal locations; the range of observed activities corresponds to SO(2) residence lifetimes of 0.2 +/- 0.04 (coastal) - 22.3 d +/- 0.04 (inland). These optimized techniques offer the potential for resolving atmospheric processes that occur on 6-12-hour timescales as well as resolving transport phenomena such as stratospheric mixing into the troposphere.

Ruptura esplénica después de terapia anticoagulante en un paciente con antecedente de COVID-19: reporte de caso.

We present the case of a 75-year-old man with a history of COVID-19 and splenic infarct treated with enoxaparin, who presented with intense abdominal pain and tomographic findings of free peri-splenic fluid and a hyperdense image in the spleen. An emergency laparotomy was performed, with findings of a splenic rupture at the vascular hilum. Spontaneous splenic rupture is a rare and fatal entity that should be suspected in a patient with history of COVID-19 who presents with acute abdominal pain after the administration of heparin.

Presentamos el caso de un varón de 75 años con antecedente de COVID-19 e infarto esplénico tratado con enoxaparina, quien inició con dolor abdominal intenso y hallazgos tomográficos de líquido libre periesplénico, así como una imagen hiperdensa en el bazo. Fue sometido a laparotomía de urgencia, encontrando una ruptura esplénica a nivel del hilio vascular. La ruptura esplénica espontánea es una condición rara y potencialmente fatal, por lo que se deberá tener un alto índice de sospecha ante un paciente con antecedente de COVID-19 que inicie con dolor abdominal agudo posterior a la administración de heparina.

Infrared nanoscopy of dirac plasmons at the graphene-SiO2 interface.

We report on infrared (IR) nanoscopy of 2D plasmon excitations of Dirac fermions in graphene. This is achieved by confining mid-IR radiation at the apex of a nanoscale tip: an approach yielding 2 orders of magnitude increase in the value of in-plane component of incident wavevector q compared to free space propagation. At these high wavevectors, the Dirac plasmon is found to dramatically enhance the near-field interaction with mid-IR surface phonons of SiO(2) substrate. Our data augmented by detailed modeling establish graphene as a new medium supporting plasmonic effects that can be controlled by gate voltage.

Engineering an incubation environment that mimics in situ conditions for in vitro coastal microbiome studies.

Coastal environments are dynamic and can vary widely on short- or long-term scales depending on location and weather. Incubation equipment that reflects these changes through programmable gradient light and temperature cycles would permit more precise in vitro coastal microbiome studies. Here we present an open-source incubation environment that mimics in situ conditions for in vitro coastal microbiome studies using a modified shaking water bath that has fully customizable temperature and light gradients that can also mimic real-time field conditions. We compared coastal microbial community profiles incubated in situ and in our build mimicking field conditions over 48 h. Analyses of congruence indicated significant overlap (p > 0.2) between microbial communities incubated in situ and in vitro at each time point.

Discovery and measurement of an isotopically distinct source of sulfate in Earth's atmosphere.

Sulfate (SO(4)) and its precursors are significant components of the atmosphere, with both natural and anthropogenic sources. Recently, our triple-isotope ((16)O, (17)O, (18)O) measurements of atmospheric sulfate have provided specific insights into the oxidation pathways leading to sulfate, with important implications for models of the sulfur cycle and global climate change. Using similar isotopic measurements of aerosol sulfate in a polluted marine boundary layer (MBL) and primary sulfate (p-SO(4)) sampled directly from a ship stack, we quantify the amount of p-SO(4) found in the atmosphere from ships. We find that ships contribute between 10% and 44% of the non-sea-salt sulfate found in fine [diameter (D) < 1.5 microm) particulate matter in coastal Southern California. These fractions are surprising, given that p-SO(4) constitutes approximately 2-7% of total sulfur emissions from combustion sources [Seinfed JH, Pandis SN (2006) Atmospheric Chemistry and Physics (Wiley-Interscience, New York)]. Our findings also suggest that the interaction of SO(2) from ship emissions with coarse hydrated sea salt particles may lead to the rapid removal of SO(2) in the MBL. When combined with the longer residence time of p-SO(4) emissions in the MBL, these findings suggest that the importance of p-SO(4) emissions in marine environments may be underappreciated in global chemical models. Given the expected increase of international shipping in the years to come, these findings have clear implications for public health, air quality, international maritime law, and atmospheric chemistry.

Independent lineage of lymphocytic choriomeningitis virus in wood mice (Apodemus sylvaticus), Spain.

To clarify the presence of lymphocytic choriomeningitis virus (LCMV) in Spain, we examined blood and tissue specimens from 866 small mammals. LCMV RNA was detected in 3 of 694 wood mice (Apodemus sylvaticus). Phylogenetic analyses suggest that the strains constitute a new evolutionary lineage. LCMV antibodies were detected in 4 of 10 rodent species tested.

Multi-class methodology to determine pesticides and mycotoxins in green tea and royal jelly supplements by liquid chromatography coupled to Orbitrap high resolution mass spectrometry.

A multi-class methodology was developed to determine pesticides and mycotoxins in food supplements. The extraction was performed using acetonitrile acidified with formic acid (1%, v/v). Different clean-up sorbents were tested, and the best results were obtained using C18 and zirconium oxide for green tea and royal jelly, respectively. The compounds were determined using ultra high performance liquid chromatography (UHPLC) coupled to Exactive-Orbitrap high resolution mass spectrometry (HRMS). The recovery rates obtained were between 70% and 120% for most of the compounds studied with a relative standard deviation <25%, at three different concentration levels. The calculated limits of quantification (LOQ) were <10 µg/kg. The method was applied to green tea (10) and royal jelly (8) samples. Nine (eight of green tea and one of royal jelly) samples were found to be positive for pesticides at concentrations ranging from 10.6 (cinosulfuron) to 47.9 µg/kg (paclobutrazol). The aflatoxin B1 (5.4 µg/kg) was also found in one of the green tea samples.

Contribution of respiratory syncytial virus, influenza and parainfluenza viruses to acute respiratory infections in San Luis Potosí, Mexico.

BACKGROUND: Respiratory viruses are the main pathogens associated with acute respiratory illness (ARI) in children. OBJECTIVE: To establish the relationship between the presence of respiratory syncytial virus (RSV), influenza and parainfluenza viruses in the community and the number of ARI and pneumonia cases reported to the State Health Services Epidemiology Department (SHSED) in San Luis Potosí, México. METHODS: We compared the weekly number of ARI and pneumonia episodes in children younger than 5 years of age reported to the SHSED for weeks in which the different respiratory viruses were detected in the community. Excess respiratory infection episodes compared with nonepidemic periods were calculated for each of the viruses. RESULTS: From July 2003 through June 2004, there were 236,597 ARI episodes and 2350 pneumonia cases reported to the SHSED. Distinct epidemic periods for parainfluenza type 1 and influenza were observed, whereas RSV and parainfluenza type 3 epidemic periods showed some overlap. The weekly number of excess ARI was greatest when influenza circulated in the community, whereas excess pneumonia cases were greatest when RSV was prevalent. Overall RSV was associated to the largest number of excess ARI and pneumonia cases reported to the SHSED. CONCLUSIONS: RSV detection is associated to the greatest number of ARI and pneumonia episodes in the state of San Luis Potosí. Influenza epidemics are associated to a significant number of ARI visits. Appropriate surveillance systems will be required to assess the impact of influenza immunization and other preventive measures on the number of ARI and pneumonia cases in our community.

Preparation and Characterization of Azadirachtin Alginate-Biosorbent Based Formulations: Water Release Kinetics and Photodegradation Study.

The botanical insecticide azadirachtin was incorporated in alginate-based granules to obtain controlled release formulations (CRFs). The basic formulation [sodium alginate (1.47%) - azadirachtin (0.28%) - water] was modified by the addition of biosorbents, obtaining homogeneous hybrid hydrogels with high azadirachtin entrapment efficiency. The effect on azadirachtin release rate caused by the incorporation of biosorbents such as lignin, humic acid, and olive pomace in alginate formulation was studied by immersion of the granules in water under static conditions. The addition of the biosorbents to the basic alginate formulation reduces the rate of release because the lignin-based formulation produces a slower release. Photodegradation experiments showed the potential of the prepared formulations in protecting azadirachtin against simulated sunlight, thus improving its stability. The results showed that formulation prepared with lignin provided extended protection. Therefore, this study provides a new procedure to encapsulate the botanical insecticide azadirachtin, improving its delivery and photostability.

Multifamily determination of pesticide residues in soya-based nutraceutical products by GC/MS-MS.

An analytical method based on a modified QuEChERS extraction coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was evaluated for the determination of 177 pesticides in soya-based nutraceutical products. The QuEChERS method was optimised and different extraction solvents and clean-up approaches were tested, obtaining the most efficient conditions with a mixture of sorbents (PSA, C18, GBC and Zr-Sep(+)). Recoveries were evaluated at 10, 50 and 100 µg/kg and ranged between 70% and 120%. Precision was expressed as relative standard deviation (RSD), and it was evaluated for more than 160 pesticides as intra and inter-day precision, with values always below 20% and 25%, respectively. Limits of detection (LODs) ranged from 0.1 to 10 µg/kg, whereas limits of quantification (LOQs) from 0.5 to 20 µg/kg. The applicability of the method was proved by analysing soya-based nutraceuticals. Two pesticides were found in these samples, malathion and pyriproxyfen, at 11.1 and 1.5 µg/kg respectively.

Application of QuEChERS based method for the determination of pesticides in nutraceutical products (Camellia sinensis) by liquid chromatography coupled to triple quadrupole tandem mass spectrometry.

A QuEChERS (quick, easy, cheap, effective, rugged, and safe) based method has been evaluated and validated for the determination and quantification of approximately 100 LC-amenable pesticides in nutraceutical products obtained from green tea (Camellia sinensis). Extraction was performed with acidified acetonitrile (acetic acid 1% (v/v)), and additional clean-up steps were not necessary. Pesticides determination was achieved using ultra high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). Total running time was 11 min. Pesticides were quantified using matrix-matched calibration. Recoveries ranged from 70% to 117% and relative standard deviation (RSD) was lower than 20% at concentration levels of 25, 50 and 100 µg/kg for intra-day precision and equal or lower than 25% for inter-day precision. Limits of quantification (LOQ) were equal or lower than 25 µg/kg. The validated method was applied to commercial nutraceutical products, detecting acetamiprid (56 µg/kg) and carbendazim (13 µg/kg) in two samples.

Occurrence of pesticide residues and transformation products in different types of dietary supplements.

The purpose of this study was to evaluate the presence of pesticide residues and transformation products in dietary supplement products. Thirty-two samples were analysed to determine 177 pesticides by gas chromatography-tandem mass spectrometry (GC-MS/MS) and 333 pesticides by liquid chromatography-high-resolution mass spectrometry (LC-HRMS). Pesticides were extracted from different kinds of dietary supplements by the use of a modified QuEChERS extraction method. Six samples contained pesticide residues at concentration up to 92.7 µg kg(-1), but only butralin exceeded the maximum residue limits set for raw material. In addition to target compounds, LC-HRMS enables the simultaneous detection of non-target pesticides. In this case, transformation products of pesticides were detected in the analysed samples using HRMS analyser (Exactive-Orbitrap). These compounds were not included in the original method, and they were monitored as post-target compounds, knowing their molecular formula and exact mass. Mass accuracy was always < 2 ppm, corresponding to a maximum mass error. The positive findings endorse the idea that a deeper and continuous investigation of pesticide residues and transformation products in dietary supplement products is necessary in order to guaranty consumer's safety.