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The largest uncertainty in the historical radiative forcing of climate is caused by changes in aerosol particles due to anthropogenic activity. Sophisticated aerosol microphysics processes have been included in many [...]

The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions. 10.1126/science.1191056

Organonitrates (ON) are important products of gas-phase oxidation of volatile organic compounds in the troposphere; some models predict, and laboratory studies show, the formation of large, multifunctional ON with vapor pressures low enough to partition to the particle phase. Organosulfates (OS) have also been recently detected in secondary organic aerosol. Despite their potential importance, ON and OS remain a nearly unexplored aspect of atmospheric chemistry because few studies have quantified particulate ON or OS in ambient air. We report the response of a high-resolution time-of-flight aerosol mass spectrometer (AMS) to aerosol ON and OS standards and mixtures. We quantify the potentially substantial underestimation of organic aerosol O/C, commonly used as a metric for aging, and N/C. Most of the ON-nitrogen appears as N[O.sup.+.sub.x] ions in the AMS, which are typically dominated by inorganic nitrate. Minor organonitrogen ions are observed although their identity and intensity vary between standards. We evaluate the potential for using N[O.sup.+.sub.x] fragment ratios, organonitrogen ions, HN[O.sup.+.sub.3], ions, the ammonium balance of the nominally inorganic ions, and comparison to ion-chromatography instruments to constrain the concentrations of ON. for ambient datasets, and apply these techniques to a field study in Riverside, CA. OS manifests as separate organic and sulfate components in the AMS with minimal organosulfur fragments and little difference in fragmentation from inorganic sulfate. The low thermal stability of ON and OS likely causes similar detection difficulties for other aerosol mass spectrometers using vaporization and/or ionization techniques with similar or larger energy, which has likely led to an underappreciation of these species. atmospheric chemistry | organic aerosol | organic nitrate I organic sulfate | SOA doi/ 10.1073/pnas.0912340107

BACKGROUND: Lactose malabsorption (LM) is a very common problem with high prevalence in Southern Europe. The lactose tolerance test (LTT) is a basic probe, which is widespread in local hospitals, because it requires non-complex and inexpensive infrastructure. The aims of our study are to determine that a reduction in the duration of LTT does not affect its diagnostic accuracy to detect LM and to calculate the savings that this reduction may represent. METHODS: A prospective study of consecutive patients who underwent LTT for suspected LM was conducted. We analyzed and compared the clinical results and costs (extraction, analytical measurement, time spent by nursing staff, technicians and patients) of suppressing LTT points at 30 and 120 min. RESULTS: The study included 201 patients. Pathological LTT was found in 119 cases. Eliminating the measurement of glucose at 120 min did not alter the LTT interpretation in any patient; however, up to 18.4% of patients had a LTT misinterpretation when the 30 min point was suppressed. If the LTT 120 min measurement would have been suppressed, 41 334 euros could have been saved. CONCLUSIONS: Suppressing the 120 min LTT point does not imply any changes in clinical results and reduces patient's waiting time; it also benefits the health system by saving time, manpower and materials. European Journal of Clinical Nutrition (2014) 68, 106-108; doi: 10.1038/ejcn.2013.240; published online 27 November 2013 Keywords: lactose malabsorption; lactose tolerance test; lactose intolerance diagnosis, INTRODUCTION Lactose is a disaccharide (glucose and galactose) found in milk and in many everyday foods. For its absorption, it requires proper lactase enzyme activity found in the brush borders [...]

The coronavirus disease 2019 (COVID-19) pandemic has caused untold disruption throughout the world. Understanding the mechanisms for transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is key to preventing further spread, but there is confusion over the meaning of 'airborne' whenever transmission is discussed. Scientific ambivalence originates from evidence published many years ago which has generated mythological beliefs that obscure current thinking. This article collates and explores some of the most commonly held dogmas on airborne transmission in order to stimulate revision of the science in the light of current evidence. Six 'myths' are presented, explained and ultimately refuted on the basis of recently published papers and expert opinion from previous work related to similar viruses. There is little doubt that SARS-CoV-2 is transmitted via a range of airborne particle sizes subject to all the usual ventilation parameters and human behaviour. Experts from specialties encompassing aerosol studies, ventilation, engineering, physics, virology and clinical medicine have joined together to produce this review to consolidate the evidence for airborne transmission mechanisms, and offer justification for modern strategies for prevention and control of COVID-19 in health care and the community. [ABSTRACT FROM AUTHOR]

It is shown that the energy balance usually assumed for the derivation of the Abraham-Lorentz equation is incomplete because it does not take the change in the energy of the bound self-field into account. Starting from the energy balance implied by Poynting's theorem, a new derivation of the Abraham-Lorentz equation is presented. The energy balance is applied first to an extended charge distribution and then the point-charge limit is taken. This approach neither requires neglecting the so-called Schott energy term nor any further hypothesis. The calculations point to the dragged self-field as the origin of the 'radiation' damping term.

The Hamilton-Jacobi equation for the one-dimensional damped oscillator is analyzed, and different ways of obtaining the solution are shown. The technique of the Poisson brackets is also applied to such a dissipative system.

Proposes a photodetector capable of multi-spectral channel operation. Employment of a quantum dot plane ability to capture an optical spectrum; Development of a resonant-tunneling structure to perform spectrally sensitive read-out; Details on realistic simulations of the optical channel capabilities.

Investigates the resonant tunneling of electrons in AlSb-GaSb-AlSb and AlSb-InGaSb-AlSb double barrier heterostructures. Dependence of current voltage on barrier and well thickness; Observation of second negative differential resistance region with anomalous temperature dependence; Estimation of the band alignment in strained GaSb/InGaSb system.

Abstract: We analyze detailed atmospheric gas/aerosol composition data acquired during the 2008 NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) airborne campaign performed at high northern latitudes in spring (ARCTAS-A) and summer (ARCTAS-B) and in California in summer (ARCTAS-CARB). Biomass burning influences were widespread throughout the ARCTAS campaign. MODIS data from 2000 to 2009 indicated that 2008 had the second largest fire counts over Siberia and a more normal Canadian boreal forest fire season. Near surface arctic air in spring contained strong anthropogenic signatures indicated by high sulfate. In both spring and summer most of the pollution plumes transported to the Arctic region were from Europe and Asia and were present in the mid to upper troposphere and contained a mix of forest fire and urban influences. The gas/aerosol composition of the high latitude troposphere was strongly perturbed at all altitudes in both spring and summer. The reactive nitrogen budget was balanced with PAN as the dominant component. Mean ozone concentrations in the high latitude troposphere were only minimally perturbed (<5ppb), although many individual pollution plumes sampled in the mid to upper troposphere, and mixed with urban influences, contained elevated ozone (ΔO3/ΔCO=0.11±0.09v/v). Emission and optical characteristics of boreal and California wild fires were quantified and found to be broadly comparable. Greenhouse gas emission estimates derived from ARCTAS-CARB data for the South Coast Air Basin of California show good agreement with state inventories for CO2 and N2O but indicate substantially larger emissions of CH4. Simulations by multiple models of transport and chemistry were found to be broadly consistent with observations with a tendency towards under prediction at high latitudes. [ABSTRACT FROM AUTHOR]

High-resolution size-resolved mass concentration of organic and inorganic species present in/on sub-micron particles measured during the PACIFIC 2001 field study in the Lower Fraser Valley (LFV) are presented. The measurements of major particulate species (organics, sulfate, nitrate and ammonium) were made in situ and in real time at three different sites representing urban (Slocan Park), semi-rural (Sumas) and rural (Langley) areas, using two Aerodyne aerosol mass spectrometers (AMSs). The total non-refractory PM1.0 mass concentrations at the three sites were found to range from 0.12 to 24.50μgm-3, with an average concentration of 4.76μgm-3. A large variability in aerosol composition was observed in the LFV, depending on meteorological conditions. Generally, during southwesterly wind conditions, inorganic species accounted for 50% of total mass loadings in the LFV, while during stagnant conditions organic species made up the majority of the particle mass. The organic aerosol species exhibit a bimodal size distribution, while the inorganic species are in most cases confined to the accumulation mode centered around 400nm. Background sulfate levels of ∼1μgm-3 were observed in the LFV during the entire campaign. Transport is found to be an important factor controlling the composition of sulfate in the LFV. Several photochemical events leading to the observation of substantial increases of sulfate in the LFV were also identified. Many of these events involve sulfate-dominated growth of small particles and appear to occur on a regional scale within the LFV. [Copyright &y& Elsevier]