3,188 research outputs found
Nuclear quantum effects in ab initio dynamics: theory and experiments for lithium imide
Owing to their small mass, hydrogen atoms exhibit strong quantum behavior
even at room temperature. Including these effects in first principles
calculations is challenging, because of the huge computational effort required
by conventional techniques. Here we present the first ab-initio application of
a recently-developed stochastic scheme, which allows to approximate nuclear
quantum effects inexpensively. The proton momentum distribution of lithium
imide, a material of interest for hydrogen storage, was experimentally measured
by inelastic neutron scattering experiments and compared with the outcome of
quantum thermostatted ab initio dynamics. We obtain favorable agreement between
theory and experiments for this purely quantum mechanical property, thereby
demonstrating that it is possible to improve the modelling of complex
hydrogen-containing materials without additional computational effort
Electroless plating of NiP and Cu on polylactic acid and polyethylene terephthalate glycol-modified for 3D printed flexible substrates
Electroless nickel and copper metallization of 3Dprinted polymers like polylactic acid and polyethylene terephthalate glycol modified is presented. The plating process is tested on suitable samples, which reproduce the characteristic morphologies used in 3D printing of objects. An alkaline etching is used for both polymers in order to modify the surface properties and to enhance the adhesion and uniformity of the metallic coating. In the case of polylactic acid, a plasma treatment is applied as well to further improve adhesion of the metallic coating. For the activation of the surface, a tin free process involving an immersion in a palladium solution and subsequent reduction to form metallic nuclei is employed. Electrolytes are formulated and selected to operate in temperature ranges comparable with the glass transition temperatures of the polymers. Adherent and uniform layers of NiP (3-4% P wt) and Cu can be easily obtained for esthetic and functional applications, also on flexible substrates
Shocked and Scorched: The Tail of a Tadpole in an Interstellar Pond
We report multi-wavelength observations of the far-infrared source IRAS
20324+4057, including high-resolution optical imaging with HST, and
ground-based near-infrared, millimeter-wave and radio observations. These data
show an extended, limb-brightened, tadpole-shaped nebula with a bright,
compact, cometary nebula located inside the tadpole head. Our molecular line
observations indicate that the Tadpole is predominantly molecular, with a total
gas mass exceeding 3.7 Msun. Our radio continuum imaging, and archival Spitzer
IRAC images, show the presence of additional tadpole-shaped objects in the
vicinity of IRAS 20324+4057 that share a common E-W head-tail orientation: we
propose that these structures are small, dense molecular cores that originated
in the Cygnus cloud and are now being (i) photoevaporated by the ultraviolet
radiation field of the Cyg OB2 No. 8 cluster located to the North-West, and
(ii) shaped by ram pressure of a distant wind source or sources located to the
West, blowing ablated and photoevaporated material from their heads eastwards.
The ripples in the tail of the Tadpole are interpreted in terms of
instabilities at the interface between the ambient wind and the dense medium of
the former.Comment: (accepted by the Astrophysical Journal
Report on advances for pediatricians in 2018: allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery.
This review reported notable advances in pediatrics that have been published in 2018. We have highlighted progresses in allergy, cardiology, critical care, endocrinology, hereditary metabolic diseases, gastroenterology, infectious diseases, neonatology, nutrition, respiratory tract disorders and surgery. Many studies have informed on epidemiologic observations. Promising outcomes in prevention, diagnosis and treatment have been reported. We think that advances realized in 2018 can now be utilized to ameliorate patient car
Ochroconis gallopava bronchitis mimicking haemoptysis in a patient with bronchiectasis.
Ochroconis gallopava is an anamorphic mould characterized by slow growth rate and production of a maroon pigment, which has been isolated worldwide from soil, thermal springs, decaying vegetation, and chicken litter. It has been reported to cause localized, mostly pulmonary, and systemic infection in severely immunocompromised patients. We describe the case of a 76-year-old woman known for ulcerative colitis-related bronchiectasis treated with low dose oral steroids, who developed a fungal bronchitis with dark, bloody-like, sputum which was initially misinterpreted as haemoptysis. A filamentary mould grew on sputum culture, and was identified by DNA analysis as Ochroconis gallopava. We observed a significant clinical improvement after 6 weeks of itraconazole therapy
Observations on the Formation of Massive Stars by Accretion
Observations of the H66a recombination line from the ionized gas in the
cluster of newly formed massive stars, G10.6-0.4, show that most of the
continuum emission derives from the dense gas in an ionized accretion flow that
forms an ionized disk or torus around a group of stars in the center of the
cluster. The inward motion observed in the accretion flow suggests that despite
the equivalent luminosity and ionizing radiation of several O stars, neither
radiation pressure nor thermal pressure has reversed the accretion flow. The
observations indicate why the radiation pressure of the stars and the thermal
pressure of the HII region are not effective in reversing the accretion flow.
The observed rate of the accretion flow, 0.001 solar masses/yr, is sufficient
to form massive stars within the time scale imposed by their short main
sequence lifetimes. A simple model of disk accretion relates quenched HII
regions, trapped hypercompact HII regions, and photo-evaporating disks in an
evolutionary sequence
Evolution of carbon fluxes during initial soil formation along the forefield of Damma glacier, Switzerland
Soil carbon (C) fluxes, soil respiration and dissolved organic carbon (DOC) leaching were explored along the young Damma glacier forefield chronosequence (7-128years) over a three-year period. To gain insight into the sources of soil CO2 effluxes, radiocarbon signatures of respired CO2 were measured and a vegetation-clipping experiment was performed. Our results showed a clear increase in soil CO2 effluxes with increasing site age from 9±1 to 160±67gCO2-Cm−2year−1, which was linked to soil C accumulation and development of vegetation cover. Seasonal variations of soil respiration were mainly driven by temperature; between 62 and 70% of annual CO2 effluxes were respired during the 4-month long summer season. Sources of soil CO2 effluxes changed along the glacier forefield. For most recently deglaciated sites, radiocarbon-based age estimates indicated ancient C to be the dominant source of soil-respired CO2. At intermediate site age (58-78years), the contribution of new plant-fixed C via rhizosphere respiration amounted up to 90%, while with further soil formation, heterotrophically respired C probably from accumulated ‘older' soil organic carbon (SOC) became increasingly important. In comparison with soil respiration, DOC leaching at 10cm depth was small, but increased similarly from 0.4±0.02 to 7.4±1.6gDOCm−2year−1 over the chronosequence. A strong rise of the ratio of SOC to secondary iron and aluminium oxides strongly suggests that increasing DOC leaching with site age results from a faster increase of the DOC source, SOC, than of the DOC sink, reactive mineral surfaces. Overall, C losses from soil by soil respiration and DOC leaching increased from 9±1 to 70±17 and further to 168±68gCm−2year−1 at the <10, 58-78, and 110-128year old sites. By comparison, total ecosystem C stocks increased from 0.2 to 1.1 and to 3.1kgCm−2 from the young to intermediate and old sites. Therefore, the ecosystem evolved from a dominance of C accumulation in the initial phase to a high throughput system. We suggest that the relatively strong increase in soil C stocks compared to C fluxes is a characteristic feature of initial soil formation on freshly exposed rock
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