Exarachellos: Dírhames en la Barcelona del siglo X

Around the year 1000, in addition to local currency, dirhams from al-Andalus circulated in Barcelona, which were called caceminos in documents. This name imitated the Arabic designation darāhim qāsimiyya, reminiscent of Córdoba’s famous mint master, Qāsim ibn Ḫālid. Furthermore, three local documents testify to the use of silver coins called exarachellos. Based on philological considerations, this word can be deciphered as a nickname of the dirham, formed from the Arabic word for shine (al-šaraq) and the Romanic diminutive ending -ello. In allusion to their silvery shine, the dirhams in al-Andalus could have been referred to as *al-šaraq-ellos (“little shiners”), a nickname later transmitted to Barcelona in the course of close bilateral contacts.Alrededor del año mil en Barcelona circulaban, aparte de la moneda local, dírhames de al-Andalus que fueron llamados caceminos en los documentos. Este nombre imitaba la denominación árabe darāhim qāsimiyya que recordaba el famoso director de la Moneda de Córdoba, Qāsim ibn Ḫālid. Además de esto, tres documentos locales atestiguan el uso de monedas de plata llamadas exarachellos. A base de consideraciones filológicas, esta palabra puede ser descifrada como un apodo del dírham formado a raíz de la palabra árabe para brillo (al-šaraq) complementada por la desinencia románica del diminutivo -ello. En alusión a su brillo argénteo, los dírhames en al-Andalus podrían haber sido llamados *al-šaraq-ellos (‘piezas brillantes’), un apodo trasmitido posteriormente a Barcelona a través de contactos bilaterales estrechos

Untersuchungen zum massenspektrometrischen Fragmentierungsverhalten von Steroiden

Die Isolierung und Strukturbestimmung komplexer Naturstoffe wie der Steroide hat die Chemie vor allem in den ersten Jahrzehnten des 20. Jahrhunderts geprägt, seit den 1950er und 1960er Jahren wurde ihr massenspektrometrisches Verhalten näher untersucht, vor allem aufgrund ihrer Präsenz und Wichtigkeit sowohl in den "life sciences" als auch als elementare Pharmazeutika. Die Einführung moderner Ionisierungsmethoden wie der Elektro-Spray-Ionisation (ESI) öffnete neue Wege zur Untersuchung biologischer Proben, während ein detaillierteres Wissen der Fragmentierungspfade solcher Substanzen durch die Fourier-Transform-Cyclotron-Massenspektrometrie zugänglich wurde, was zu überraschenden Einsichten in das Fragmentierungsverhalten der Estradiol- und Estriolbenzylether führte

An application of tomographic PIV to investigate the spray-induced turbulence in a direct-injection engine

Fuel sprays produce high-velocity, jet-like flows that impart turbulence onto the ambient flow field. The spray-induced turbulence augments fuel-air mixing, which has a primary role in controlling pollutant formation and cyclic variability in engines. This paper presents tomographic particle image velocimetry (TPIV) measurements to analyse the 3D spray-induced turbulence during the intake stroke of a direct-injection engine. The spray produces a strong spray-induced jet in the far field, which travels through the cylinder and imparts turbulence onto the surrounding flow. Planar high-speed PIV measurements at 4.8 kHz are combined with TPIV at 3.3 Hz to evaluate spray particle distributions and validate TPIV measurements in the particle-laden flow. An uncertainty analysis is performed to assess the uncertainty associated with vorticity and strain rate components. TPIV analyses quantify the spatial domain of the turbulence in relation to the SIJ and describe how turbulent flow features such as turbulent kinetic energy, strain rate and vorticity evolve into the surrounding flow field. Access to the full tensors facilitate the evaluation of turbulence for individual spray events. TPIV images reveal the presence of strong shear layers (visualized by high S magnitudes) and pockets of elevated vorticity along the immediate boundary of the SIJ. Values are extracted from spatial domains extending in 1mm increments from the SIJ. Turbulence levels are greatest within the 0-1mm region from the SIJ boarder and dissipate with radial distance. Individual strain rate and vorticity components are analyzed in detail to describe the relationship between local strain rates and 3D vortical structures produced within strong shear layers of the SIJ. Analyses are intended to understand the flow features responsible for rapid fuel-air mixing and provide valuable data for the development of numerical models

Investigation of an IC Engine Intake Flow Based on Highly Resolved LES and PIV

To reduce emissions and fuel consumption, the current generation of gasoline engines uses technologies such as direct injection, downsizing and supercharging. All of them require a strong vortical in-cylinder charge motion, usually described as “tumble”, to improve fuel-air mixing and enhance flame propagation. The tumble development strongly depends on the flow field during the intake stroke. This flow field is dominated by the intake jet, which has to be captured well in the simulation. This work investigates the intake jet on a steady-state flow bench, especially in the vicinity of the intake valve. At first, the general flow dynamics of the intake jet for three different valve lifts and three different mass flows were investigated experimentally. For the smallest valve lift (3 mm), flow-field measurements using Particle Image Velocimetry (PIV) show that the orientation of the intake jet significantly depends on the air flow rate, attaching to the pent roof for low flow rates. This phenomenon is less pronounced for higher valve lifts. An intermediate valve lift and flow rate were chosen for further investigations by scale-resolving simulations. Three different meshes (coarse, medium and fine) and two turbulence models (Sigma and Detached Eddy Simulation-Shear Stress Transport (DES-SST)) are applied to consider their effect on the numerical results. An ad-hoc post-processing methodology based on the ensemble-averaged velocity field is presented capturing the jet centerline’s mean velocity and velocity fluctuations as well as its orientation, curvature and penetration depth. The simulation results are compared to each other as well as to measurements by PIV

A combined numerical and experimental study of the 3D tumble structure and piston boundary layer development during the intake stroke of a gasoline engine

Due to its positive effect on flame propagation in the case of a well-defined breakdown, the formation of a large-scale tumble motion is an important goal in engine development. Cycle-to-cycle variations (CCV) in the tumble position and strength however lead to a fluctuating tumble breakdown in space and time and therefore to combustion variations, indicated by CCV of the peak pressure. This work aims at a detailed investigation of the large-scale tumble motion and its interaction with the piston boundary layer during the intake stroke in a state-of-the-art gasoline engine. To allow the validation of the flow near the piston surface obtained by simulation, a new measurement technique called “Flying PIV” is applied. A detailed comparison between experimental and simulation results is carried out as well as an analysis of the obtained flow field. The large-scale tumble motion is investigated based on numerical data of multiple highly resolved intake strokes obtained using scale-resolving simulations. A method to detect the tumble center position within a 3D flow field, as an extension of previously developed 2D and 3D algorithms, is presented and applied. It is then used to investigate the phase-averaged tumble structure, its characteristics in terms of angular velocity and the CCV between the individual intake strokes. Finally, an analysis is presented of the piston boundary layer and how it is influenced by the tumble motion during the final phase of the intake stroke

A PIV-Guided Large-Eddy Simulation of In-Cylinder Flows

A combination of Large-Eddy Simulation (LES) and Particle Image Velocimetry (PIV) was utilized to investigate the three-dimensional in-cylinder flow within an optically accessible Direct Injection Spark Ignition (DISI) engine at motored engine operation. The PIV measurements were used to guide the meshing procedure by identifying the regions were refinements and improvements were needed. From the iteratively optimized meshes LES results are shown from two selected meshes, an intermediate coarse mesh and the final optimized mesh, and compared to PIV measurements. The evolution of the intake flow and the tumble in the central tumble plane during compression are presented and discussed. Exploitation of the LES results allowed showing the influence of out-of-plane velocities along the cylinder liner impacting the formation of the tumble flow. The optimized mesh was then used to investigate the influence of the spark plug on the in-cylinder flow. For the studied engine the spark plug had a significant impact on the evolution of the tumble flow during compression. Finally 35 engine cycles were simulated using the optimized mesh with the spark plug in place. Velocity distributions in a region below the spark plug are shown and compared with PIV results. The two-sample Kolmogorov-Smirnov test revealed a strong similarity between the velocity distributions obtained by PIV and LES, thus validating the potential of LES for investigating cycle-to-cycle variability

Development and application of bivariate 2D-EMD for the analysis of instantaneous flow structures and cycle-to-cycle variations of in-cylinder flow

International audienceThe bivariate two dimensional empirical mode decomposition (Bivariate 2D-EMD) is extended to estimate the turbulent fluctuations and to identify cycle-to-cycle variations (CCV) of in-cylinder flow. The Bivariate 2D-EMD is an adaptive approach that is not restricted by statistical convergence criterion, hence it can be used for analyzing the nonlinear and non-stationary phenomena. The methodology is applied to a high-speed PIV dataset that measures the velocity field within the tumble symmetry plane of an optically accessible engine. The instantaneous velocity field is decomposed into a finite number of 2D spatial modes. Based on energy considerations, the in-cylinder flow large-scale organized motion is separated from turbulent fluctuations. This study is focused on the second half of the compression stroke. For most of the cycles, the maximum of turbulent fluctuations is located between 50 and 30 crank angle degrees before top dead center (TDC). In regards to the phase-averaged velocity field, the contribution of CCV to the fluctuating kinetic energy is approximately 55% near TDC

Invasive Group B Streptococcus Disease With Recurrence and in Multiples: Towards a Better Understanding of GBS Late-Onset Sepsis.

Group B Streptococcus (GBS) is a common intestinal colonizer during the neonatal period, but also may cause late-onset sepsis or meningitis in up to 0.5% of otherwise healthy colonized infants after day 3 of life. Transmission routes and risk factors of this late-onset form of invasive GBS disease (iGBS) are not fully understood. Cases of iGBS with recurrence (n=25) and those occurring in parallel in twins/triplets (n=32) from the UK and Ireland (national surveillance study 2014/15) and from Germany and Switzerland (retrospective case collection) were analyzed to unravel shared (in affected multiples) or fixed (in recurrent disease) risk factors for GBS disease. The risk of iGBS among infants from multiple births was high (17%), if one infant had already developed GBS disease. The interval of onset of iGBS between siblings was 4.5 days and in recurrent cases 12.5 days. Disturbances of the individual microbiome, including persistence of infectious foci are suggested e.g. by high usage of perinatal antibiotics in mothers of affected multiples, and by the association of an increased risk of recurrence with a short term of antibiotics [aOR 4.2 (1.3-14.2), P=0.02]. Identical GBS serotypes in both recurrent infections and concurrently infected multiples might indicate a failed microbiome integration of GBS strains that are generally regarded as commensals in healthy infants. The dynamics of recurrent GBS infections or concurrent infections in multiples suggest individual patterns of exposure and fluctuations in host immunity, causing failure of natural niche occupation