Influence of Particle Velocity on Adhesion of Cold-Sprayed Splats

In cold spray, innovative coating process, powder particles are accelerated by a supersonic gas flow above a certain critical velocity. Particles adhesion onto the substrate is influenced by particle impact velocity, which can change dramatically depending on particle position from the core of the jet. In the present work, an original experimental set-up was designed to discriminate the particles as a function of the levels of velocity to investigate the influence of this parameter on adhesion. Particles at given positions could therefore be observed using scanning electron microscope, which showed different morphologies as a function of impact velocity. High pressure and temperature at the interface during impact were calculated from numerical simulations using ABAQUS^®. Transmission electron microscope analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact velocity and corresponding adhesion strength which was obtained from LAser Shock Adhesion Test.     

Kinetische Parameteridentifikation und Modelldiskriminierung am Beispiel der nassen Oxidation von Thiosulfat

Coke technology involves polluted wastewater, which must be treated efficiently in order not to pollute the environment and to comply with legal regulations. This requires a thorough understanding of the process. Due to the large number of possible modifications, sulfur compounds occupy a special position and, thus, knowledge of the reaction pathways and kinetics is essential for the design of apparatuses. By means of parameter estimation and model discrimination, kinetics are determined on the basis of experimental data and reaction schemes of the wet oxidation of thiosulfate are evaluated in order to describe the concentration course of all species with sufficient accuracy.     

Development of transplantation vasculopathy and progression of donor-transmitted atherosclerosis: comparison by serial intravascular ultrasound imaging

BACKGROUND: Transplant coronary artery disease is a combination of atherosclerosis transmitted from the donor and new lesions of allograft vasculopathy. We sought to determine the morphological characteristics of allograft vasculopathy and differentiate it from donor-transmitted atherosclerosis with serial intravascular ultrasound. METHODS AND RESULTS: Intravascular ultrasound examination was performed in 93 patients at 27.2+/-15.0 and 369. 7+/-23.9 days after transplantation. The maximally and minimally diseased sites were selected in each segment as defined by Coronary Artery Surgery Study classification. For each matched site, maximal plaque thickness was measured. Lesions (maximum plaque thickness >/=0.5 mm) present at baseline examination were defined as donor lesions. On follow-up, lesions that developed at previously normal sites were defined as de novo lesions. The distribution and severity of donor and de novo lesions were similar in proximal, mid, and distal segments. The de novo lesions were less focal (43% vs 74%) and more circumferential (69% vs 45%) compared with the donor lesions, but there was significant morphological heterogeneity. Similar numbers of patients with and those without donor lesions developed de novo lesions. Moreover, progression of donor lesions was not associated with the presence or absence of de novo lesions. CONCLUSIONS: Differentiation between early allograft vasculopathy from conventional atherosclerosis by distribution and morphology of lesions alone is difficult. Serial intravascular ultrasound imaging with early baseline examination is necessary to make this distinction. This distinction is important because the progression of donor lesions and the development of de novo lesions are independent of each other.     

Bipyridine Modified Conjugated Carbon Aerogels as a Platform for the Electrocatalysis of Oxygen Reduction Reaction

Aerogels offer a great platform for heterogeneous electrocatalysis owing to their high surface area and porosity. Atomically dispersed transition metal ions can be imbedded in these platforms at ultra-high site density to make them catalytically active for various reactions. Herein, the synthesis of a new class of conjugated microporous organic aerogels that are used as covalent 3D frameworks for the electrocatalysis of oxygen reduction reaction (ORR) is reported. Modified aerogels functionalized with bipyridine ligands enable copper ion complexation in a single-step synthesis. The aerogels’ structures are fully characterized using a wide array of spectroscopic and microscopic methods, and heat-treated in order to make them electronically conductive. After heat treatment at 600 °C, the aerogels maintained their macrostructure and became active ORR catalysts in alkaline environment, showing high mass activity and ultra-high site density.     

On the statistics of multipath fading using a direct sequence CDMA signal at 2 GHz,in microcellular and indoor environment

This paper describes the results of field tests consisting of received signal variations and multipath returns seen by a mobile receiver using direct-sequence (DS) code-division multiple-access (CDMA) waveforms. The experimental data for outdoor (microcellular environment) reveals that the instantaneous received power lost due to fading (sometimes called the fade margin) increases dramatically as the signaling bandwidth decreases below 11 MHz. It also shows that for most outdoor locations the significant multipath was confined primarily to 1s of excess delay with average delay of less than 200 ns. A broader-band CDMA system, having a bandwidth exceeding 10 MHz, could resolve the multipath components and could use a RAKE receiver to further reduce the transmitted power. However, a narrower-band CDMA system could not resolve these multipath components and thereby would suffer signal fading which would have to be compensated by 15 dB or more signal amplification. As a result, a narrower-band CDMA system would interfere with its other users and reduce its user capacity if no other forms of diversity are used. Our results also reveal that at some locations, returns with delays of more than 1s can be seen by the receiver with enough energy that could be collected using a RAKE receiver. However, these locations were found to be confined to a very low probability of existence within a prescribed cell (3-mile radius).     

The Vibration Behavior of Sub‐Micrometer Gas Vesicles in Response to Acoustic Excitation Determined via Laser Doppler Vibrometry

The ability to monitor sub‐micrometer gas vesicles' (GVs) vibration behavior to nonlinear buckling and collapse using laser Doppler vibrometry is reported, providing a precise noncontact technique for monitoring the motion of sub‐micrometer objects. The fundamental and first harmonic resonance frequencies of the vesicles are found to be 1.024 and 1.710 GHz, respectively. An interparticle resonance is furthermore identified at ≈300 MHz, inversely dependent upon the agglomerated GV size of around 615 nm. Most importantly, the vesicles amplify and broaden input acoustic signals at far lower frequencies—for example, 7 MHz—associated with medical and industrial applications, and they are found to transition from a linear to nonlinear response at 150 kPa and to collapse at 350 kPa or greater.     

Who is sleepier on the night shift? The influence of bio-psycho-social factors on subjective sleepiness of female nurses during the night shift

Sleepiness is a common complaint during the night shift and may impair performance. The current study aims to identify bio-psycho-social factors associated with subjective sleepiness during the night shift. Ninety-two female nurses working rotating shifts completed a sociodemographic questionnaire, the Munich ChronoType Questionaire for shift workers, the Pittsburg Sleep Quality Index, and the Pre-sleep Arousal Scale. Subjective sleepiness was measured hourly during two night shifts using the Karolinska Sleepiness Scale, and activity monitors assessed sleep duration 24-h before each shift. Findings showed that increased sleepiness was associated with increased age in nurses with early chronotypes and with more children. High cognitive pre-sleep arousal, but not sleep, was associated with increased sleepiness, especially in late chronotypes. The impact of bio-psycho-social factors on night shift sleepiness is complex, and depends on mutual interactions between these factors. Nurses most prone to increased sleepiness must develop personal strategies for maintaining vigilance on the night shift.

Practitioner Summary: This study aims to identify bio-psycho-social factors associated with subjective sleepiness of female nurses during the night shift. Increasing sleepiness was associated with increased age in nurses with early chronotypes and with more children. Increased cognitive pre-sleep arousal, but not sleep, was associated with increased sleepiness, especially in late chronotypes.     

Applied current density in the section of a type-II superconductor

A thermodynamic treatment suggests that the applied current density is located in the surface sheet in order to create a null magnetic local field inside the bulk superconductor according to the London penetration law, until there is no dissipation in the sample. A direct investigation of this evidence is performed by measuring the field created by the current near the surface of square- or rectangular-section samples. This field is known by the measurement of the flux variation in small pickup coils while the current is turned on and off. The main experimental result shows that the critical current intensity does not flow in a uniform distribution inside the sample section and so denies a physical meaning to the notion of critical current density.Laboratoire associé au C.N.R.S., 24 rue Lhomond, 75231 Paris Cedex 05.