8,310 research outputs found
Forbidden oxygen lines at various nucleocentric distances in comets
To study the formation of the [OI] lines - i.e., 5577 A (the green line),
6300 A and 6364 A (the two red lines) - in the coma of comets and to determine
the parent species of the oxygen atoms using the green to red-doublet emission
intensity ratio (G/R ratio) and the lines velocity widths. We acquired at the
ESO VLT high-resolution spectroscopic observations of comets C/2002 T7
(LINEAR), 73P-C/Schwassmann-Wachmann 3, 8P/Tuttle, and, 103P/Hartley 2 when
they were close to the Earth (< 0.6 au). Using the observed spectra, we
determined the intensities and the widths of the three [OI] lines. We have
spatially extracted the spectra in order to achieve the best possible
resolution of about 1-2", i.e., nucleocentric projected distances of 100 to 400
km depending on the geocentric distance of the comet. We have decontaminated
the [OI] green line from C2 lines blends. It is found that the observed G/R
ratio on all four comets varies as a function of nucleocentric projected
distance. This is mainly due to the collisional quenching of O(1S) and O(1D) by
water molecules in the inner coma. The observed green emission line width is
about 2.5 km/s and decreases as the distance from the nucleus increases which
can be explained by the varying contribution of CO2 to the O(1S) production in
the innermost coma. The photodissociation of CO2 molecules seems to produce
O(1S) closer to the nucleus while the water molecule forms all the O(1S) and
O(1D) atoms beyond 1000 km. Thus we conclude that the main parent species
producing O(1S) and O(1D) in the inner coma is not always the same. The
observations have been interpreted in the framework of the
coupled-chemistry-emission model of Bhardwaj & Raghuram (2012) and the upper
limits of CO2 relative abundances are derived from the observed G/R ratios.
Measuring the [OI] lines could indeed provide a new way to determine the CO2
relative abundance in comets.Comment: accepted for publication in A&A, the abstract is shortene
The effect of fly ash, β-cyclodextrin and fly ash-β-cyclodextrin composites on concrete workability and strength
Abstract: To increase the use of fly ash (FA) as a pozzolanic material in concrete, a composite was formed with an interaction of FA with β-cyclodextrin (β-CD). Further research was carried out in this article to study the effects of replacing cement with FA (30% and 50% by mass), β-CD (0.025%, 0.05% and 0.1%) and FA-β-CD composite on the workability and strength of concrete. Workability was assessed by means of the slump test and strengths were assessed using the compressive and split tensile strength tests. Higher combined contents of FA and β- CD resulted in increased workability of concrete of up to approximately 550 %. Furthermore, the inclusion of β-CD generally increased both the compressive and tensile strengths of the concretes not containing FA by up to 10 %. When combined with FA, the β-CD resulted in increased compressive strengths of up to 63 % and tensile strengths of up to 28 %, compared to the relevant pozzolanic concretes which did not include β-CD. The study contributed to the knowledge of FA performance using cyclodextrin and promoted the continued inclusion of FA in concrete, which in turn should reduce the environmental pollution resulting from FA
Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study
An efficient way to precisely pattern particles on solid surfaces is to
dispense and evaporate colloidal drops, as for bioassays. The dried deposits
often exhibit complex structures exemplified by the coffee ring pattern, where
most particles have accumulated at the periphery of the deposit. In this work,
the formation of deposits during the drying of nanoliter colloidal drops on a
flat substrate is investigated numerically and experimentally. A finite-element
numerical model is developed that solves the Navier-Stokes, heat and mass
transport equations in a Lagrangian framework. The diffusion of vapor in the
atmosphere is solved numerically, providing an exact boundary condition for the
evaporative flux at the droplet-air interface. Laplace stresses and thermal
Marangoni stresses are accounted for. The particle concentration is tracked by
solving a continuum advection-diffusion equation. Wetting line motion and the
interaction of the free surface of the drop with the growing deposit are
modeled based on criteria on wetting angles. Numerical results for evaporation
times and flow field are in very good agreement with published experimental and
theoretical results. We also performed transient visualization experiments of
water and isopropanol drops loaded with polystyrene microsphere evaporating on
respectively glass and polydimethylsiloxane substrates. Measured evaporation
times, deposit shape and sizes, and flow fields are in very good agreement with
the numerical results. Different flow patterns caused by the competition of
Marangoni loops and radial flow are shown to determine the deposit shape to be
either a ring-like pattern or a homogeneous bump
Study of incidence and outcome of acute inversion of uterus
Background: Acute inversion of uterus also called as puerperal inversion of uterus is a rare, but life-threatening complication of third stage of labour. Severe uterine atony, mismanagement of third stage of labour, adherent placenta are some of the common factors associated with the occurrence of acute inversion of uterus. Early recognition and prompt treatment are important to save life of the woman.Methods: A retrospective cross-sectional record-based study was carried out to find out the incidence, presentation and outcome of cases of acute inversion of uterus admitted to Pravara Rural Hospital Loni for a period of three years (October 2015 to September 2018).Results: During the study period, there were 27,134 deliveries including 8,834 caesarean sections. There were six cases of acute inversion of uterus in the hospital during study period. The incidence of acute inversion of uterus was 0.22 per one thousand deliveries (0.27 per thousand vaginal deliveries and 0.11per one thousand caesarean sections). Three cases were referred from outside hospital and three cases had delivered at Pravara Rural Hospital. Five cases had delivered vaginally, where as one case had undergone caesarean section. There were two maternal deaths and four survivals among six cases of inversion of uterus. Severe anaemia, irreversible hypovolemic shock and multi-organ failure were causes of maternal deaths.Conclusions: Prompt recognition of uterine inversion and its immediate reposition under anaesthesia was a key for successful management. Delay in recognition and transfer of cases resulted in haemorrhagic and neurogenic shock, leading to death of a women. Institutional deliveries with practice of principles of active management of third stage of labour (AMTSL) and improvement in emergency obstetric care services at peripheral hospitals, avoiding delays at all levels will help to reduce the incidence, morbidity and mortality associated with acute inversion of uterus
The propensity of molecules to spatially align in intense light fields
The propensity of molecules to spatially align along the polarization vector
of intense, pulsed light fields is related to readily-accessible parameters
(molecular polarizabilities, moment of inertia, peak intensity of the light and
its pulse duration). Predictions can now be made of which molecules can be
spatially aligned, and under what circumstances, upon irradiation by intense
light. Accounting for both enhanced ionization and hyperpolarizability, it is
shown that {\it all} molecules can be aligned, even those with the smallest
static polarizability, when subjected to the shortest available laser pulses
(of sufficient intensity).Comment: 8 pages, 4 figures, to be submitted to PR
From discovery to scale-up: alpha-lipoic acid : nicotinamide co-crystals in a continuous oscillatory baffled crystalliser
The crystalline nutritional supplement alpha-lipoic acid degrades rapidly on exposure to temperatures above its melting point 65 degrees C and to light. A small-scale experimental co-crystal screen has produced three novel co-crystals of alpha-lipoic acid that each display enhanced thermal stability and differences in aqueous solubilities compared to alpha-lipoic acid. In each case, the initial screening procedure produced tens of milligrams of material enabling initial identification, characterisation and crystal structure determination. The structure of the alpha-lipoic acid : nicotinamide co-crystal was determined by single crystal X-ray diffraction and used for subsequent phase identification. Scale-up of the co-crystallisation process of alpha-lipoic acid with nicotinamide was then investigated in a continuous oscillatory baffled crystalliser. Over 1 kg of solid co-crystals was produced using a continuous crystallisation process in a continuous oscillatory baffled crystalliser at a throughput of 350 g h-1 yielding a purity of 99% demonstrating this as an effective route to rapid scale-up of a novel co-crystal system
From discovery to scale-up: alpha-lipoic acid : nicotinamide co-crystals in a continuous oscillatory baffled crystalliser
The crystalline nutritional supplement alpha-lipoic acid degrades rapidly on exposure to temperatures above its melting point 65 degrees C and to light. A small-scale experimental co-crystal screen has produced three novel co-crystals of alpha-lipoic acid that each display enhanced thermal stability and differences in aqueous solubilities compared to alpha-lipoic acid. In each case, the initial screening procedure produced tens of milligrams of material enabling initial identification, characterisation and crystal structure determination. The structure of the alpha-lipoic acid : nicotinamide co-crystal was determined by single crystal X-ray diffraction and used for subsequent phase identification. Scale-up of the co-crystallisation process of alpha-lipoic acid with nicotinamide was then investigated in a continuous oscillatory baffled crystalliser. Over 1 kg of solid co-crystals was produced using a continuous crystallisation process in a continuous oscillatory baffled crystalliser at a throughput of 350 g h-1 yielding a purity of 99% demonstrating this as an effective route to rapid scale-up of a novel co-crystal system
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