Friction and wear in railway ballast stone interfaces

Particle friction in railway ballast influences strongly the behaviour of ballasted tracks. New challenges posed on railway infrastructure increase the requirement for simulations, which need the friction coefficient as an input parameter. Measured friction coefficients of ballast stone contacts were found only in two studies, both under constant loads. In this work, two types of ballast were investigated in cyclic friction tests with incremental increase of the applied load after several cycles. Before each load increase, 3D-scans of some ballast stones allowed to calculate the contact area. Estimating the stress in the contact, the stress-dependency of the friction coefficient and wear were investigated. These experimental observations are discussed regarding their impact for friction modelling in the simulation of railway ballast

Krakow clean fossil fuels and energy efficiency program. Phase 1 report

Krakow is one of the largest and oldest cities in Poland. It is situated in the south of the country on the banks of the Vistula River. From the 11th until the 17th centuries, it was the capital of Poland. Today, Krakow is a city of 750,000 residents, one of the largest centers of higher education, an important industrial center, and is of particular importance because of the number and kinds of historic buildings and sites. For this reason, Krakow was included by the UNESCO in the list of the world`s cultural heritages. For about three decades, significant air pollution has been one of Krakow`s most serious problems. Because the city is situated in the Vistula River valley, it is poorly ventilated and experiences a high concentration of air pollutants. The quality of air in Krakow is affected mainly by industry (Sendzimir Steelworks, energy industry, chemical plants), influx from the Silesian industrial region (power plants, metallurgy), transboundary pollution (Ostrava - Czech Republic), and local sources of low pollution, i.e. more than 1,000 boiler houses using solid fuels and more than 100,000 coal-fired home stoves. These local sources, with low stacks and almost no pollution-control equipment, are responsible for about 35-40% of the air pollution. This report presents phase I results of a program to reduce pollution in krakow. Phase I was to gather information on emissions and costs, and to verify assumptions on existing heating methods and alternatives

2-[2-(2-Pyrid­yl)eth­yl]isoindolinium perchlorate

In the title salt, C15H17N2 +·ClO4 −, the isoindoline N atom is protonated and an intra­molecular N—H⋯N hydrogen bond occurs. In the crystal, N—H⋯O and numerous weak C—H⋯O inter­actions occur between the cation and anion. The O atoms of the perchlorate anion are disordered over four sets of sites with occupancies of 0.438 (4), 0.270 (9), 0.155 (8) and 0.138 (5)

Accomplishments of the American-Polish Program for Elimination of Low Emissions in Krakow

Since 1990 the US Department of Energy (DOE) has been involved in a program aimed at reducing air pollution caused by small, coal-fired sources in Poland. The activity is focused on the city of Cracow, Poland with the intention that results will be applicable and extendable to the entire region. The effort under this program has been focused into 5 main areas of interest as follows: (1) energy conservation and extension of central station district heating; (2) replacement of coal- and coke-fired boilers with natural gas-fired boilers; (3) replacement of coal-fired home stoves with electric heating appliances; (4) reduction of emissions from stoker-fired boiler houses; and (5) reduction of emissions from coal-fired home heating stoves

1-(2-Bromo­benz­yl)-3-isopropyl­benz­imid­azolin-2-one

In the structure of the title compound, C17H17BrN2O, the central phenyl and imidazol-2-one rings are coplanar (dihedral angle between planes of 0.73 (11)°). The angles subtended by the substituents on the N atoms of the imidazol-2-one ring range from 109.71 (14)° to 128.53 (15) due to steric hindrance of these substituents with the phenyl H atoms. The carbonyl O and Br both make two weak C—H⋯O and C—H⋯Br inter­actions with two adjacent mol­ecules, thus forming an three-dimensional array

2-Bromo-N′-[(Z)-2-bromo­benzyl­idene]-5-methoxy­benzohydrazide

In the title compound, C15H12Br2N2O2, the mol­ecule adopts an E conformation about the C=N double bond and a transoid conformation about the central N—N bond, with a C(=O)—N—N—C(H) dihedral angle of 169.4 (4)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, leading to C(4) chains. The packing also features slipped π–π stacking inter­actions, with a centroid–centroid separation of 3.838 (3) Å and a slippage of 1.19 Å

Two-photon microscopy-guided femtosecond-laser photoablation of avian cardiogenesis: Noninvasive creation of localized heart defects

Yalçın, Hüseyin Çağatay (Dogus Author)Embryonic heart formation is driven by complex feedback between genetic and hemodynamic stimuli. Clinical congenital heart defects (CHD), however, often manifest as localized microtissue malformations with no underlying genetic mutation, suggesting that altered hemodynamics during embryonic development may play a role. An investigation of this relationship has been impaired by a lack of experimental tools that can create locally targeted cardiac perturbations. Here we have developed noninvasive optical techniques that can modulate avian cardiogenesis to dissect relationships between alterations in mechanical signaling and CHD. We used two-photon excited fluorescence microscopy to monitor cushion and ventricular dynamics and femtosecond pulsed laser photoablation to target micrometer-sized volumes inside the beating chick hearts. We selectively photoablated a small (∼100 μm radius) region of the superior atrioventricular (AV) cushion in Hamburger-Hamilton 24 chick embryos. We quantified via ultrasound that the disruption causes AV regurgitation, which resulted in a venous pooling of blood and severe arterial constriction. At 48 h postablation, quantitative X-ray microcomputed tomography imaging demonstrated stunted ventricular growth and pronounced left atrial dilation. A histological analysis demonstrated that the laser ablation produced defects localized to the superior AV cushion: a small quasispherical region of cushion tissue was completely obliterated, and the area adjacent to the myocardial wall was less cellularized. Both cushions and myocardium were significantly smaller than sham-operated controls. Our results highlight that two-photon excited fluorescence coupled with femtosecond pulsed laser photoablation should be considered a powerful tool for studying hemodynamic signaling in cardiac morphogenesis through the creation of localized microscale defects that may mimic clinical CHD

The Influence of Environment on the Star Formation Rates of Galaxies

We have used a sample of 15749 galaxies taken from the Las Campanas Redshift Survey to investigate the effects of environment on the rate of star formation (SFR) in galaxies. The size and homogeneity of this data set allows us to sample, for the first time, the entire range of galactic environment, from the voids to the clusters, in a uniform manner, thus, we could decouple the local galaxy density from the membership in associations. This decoupling is very crucial for constraining the physical processes responsible for the environmental dependencies of SFR. On the other hand, the use of an automatically-measured concentration index (C), rather than Hubble type, allows us to cleanly separate the morphological component from the SFR vs. environment relationship. We find that cluster galaxies exhibit lower SFR for the same C than field galaxies, while a further division of clusters by `richness' reveals a new possible excitation of `starbursts' in poor clusters. Meanwhile, a more general environmental investigation reveals that the SFR of a given C shows a continuous correlation with the local density. Interestingly, this trend is also observed both inside and outside of clusters, implying that physical processes responsible for this correlation might not be intrinsic to the cluster environment. On the other hand, galaxies with differing levels of SFR appear to respond differently to the local density. Low levels of SFR are more sensitive to environment inside than outside of clusters. In contrast, high levels of SFR, identified as ``starbursts'', are as sensitive to local density in the field as in clusters. We conclude that at least two separate processes are responsible for the environmental sensitivity of the SFR.Comment: 25 pages, 10 figures, submitted to Ap

(Acetonitrile)[bis­(2-pyridylmeth­yl)amine]bis­(perchlorato)copper(II)

In the title compound, [Cu(ClO4)2(C12H13N3)(C2H3N)], the CuII atom is six-coordinate in a Jahn–Teller distorted octahedral geometry, with coordination by the tridentate chelating ligand, an acetonitrile mol­ecule, and two axial perchlorate anions. The tridentate ligand bis­(2-pyridylmeth­yl)amine chelates meridionally and equatorially while an acetonitrile mol­ecule is coordinated at the fourth equatorial site. The two perchlorate anions are disordered with site occupancy factors of 0.72/0.28. The amine H is involved in intra­molecular hydrogen bonding to the perchlorate O atoms and there are extensive but weak inter­molecular C—H⋯O inter­actions