Modelling of sediment transport and bed deformation in rivers with continuous bends

Peer reviewedPostprin

Mean Transverse Energy of Ultrananocrystalline Diamond Photocathode

Nitrogen incorporated ultrananocrystalline diamond ((N)UNCD) could be an enabling material platform for photocathode applications due to its high emissivity. While the quantum efficiency (QE) of UNCD was reported by many groups, no experimental measurements of the intrinsic emittance/mean transverse energy (MTE) have been reported. Here, MTE measurement results for an (N)UNCD photocathode in the photon energy range of 4.41 to 5.26 eV are described. The MTE demonstrates no noticeable dependence on the photon energy, with an average value of 266 meV. This spectral behavior is shown to not to be dependent upon physical or chemical surface roughness and inconsistent with low electron effective mass emission from graphitic grain boundaries, but may be associated with emission from spatially-confined states in the graphite regions between the diamond grains. The combined effect of fast-growing QE and constant MTE with respect to the excess laser energy may pave the way to bright UNCD photocathodes.Comment: 4 pages, 4 figure

Translation and validation of the Chinese version of the Self-awareness Scale for Nurses

BackgroundLevels of self-awareness may affect the decision-making ability of clinical nurses and may also be related to mental health. Therefore, it is crucial to develop tools to identify nurses’ level of self-awareness. The purpose of this study was to investigate the reliability and validity of a short scale among Chinese nurses and to explore the factors associated with nurses’ self-awareness.MethodsA total of 957 participants were recruited, 549 participants were used for reliability tests and 408 subjects were used for impact factor studies. They completed the General Information Questionnaire, the Self-Awareness Scale for Nurses, and the Psychological Distress Scale. Exploratory factor analysis, confirmatory factor analysis, Cronbach’s alpha, and retest reliability were used to investigate the psychometric properties of the Self-Awareness Scale for Nurses. Multiple regression analyses were used in this study to investigate the relationship between nurses’ self-awareness and the independent variables.ResultsA 4-factor model of the Chinese version of the Self-Awareness Scale for Nurses was validated. The overall Cronbach’s alpha value for the Chinese version of the Self-Awareness Scale for Nurses was 0.873. Cronbach’s alpha values for each subscale ranged from 0.808 to 0.979. Significant predictors of each dimension of the Self-awareness and the total score of the scale were age and work experience.ConclusionThe Chinese version of the Self-Awareness Scale for Nurses is a valid and reliable scale

Few-femtosecond Electron Beam with THz-frequency Wakefield-driven Compression

We propose and demonstrate a novel method to produce few-femtosecond electron beam with relatively low timing jitter. In this method a relativistic electron beam is compressed from about 150 fs (rms) to about 7 fs (rms, upper limit) with the wakefield at THz frequency produced by a leading drive beam in a dielectric tube. By imprinting the energy chirp in a passive way, we demonstrate through laser-driven THz streaking technique that no additional timing jitter with respect to an external laser is introduced in this bunch compression process, a prominent advantage over the conventional method using radio-frequency bunchers. We expect that this passive bunching technique may enable new opportunities in many ultrashort-beam based advanced applications such as ultrafast electron diffraction and plasma wakefield acceleration.Comment: 5 pages, 4 figure

Overestimation of thermal emittance in solenoid scans due to coupled transverse motion

The solenoid scan is a widely used method for the in-situ measurement of the thermal emittance in a photocathode gun. The popularity of this method is due to its simplicity and convenience since all rf photocathode guns are equipped with an emittance compensation solenoid. This paper shows that the solenoid scan measurement overestimates the thermal emittance in the ordinary measurement configuration due to a weak quadrupole field (present in either the rf gun or gun solenoid) followed by a rotation in the solenoid. This coupled transverse dynamics aberration introduces a correlation between the beam's horizontal and vertical motion leading to an increase in the measured 2D transverse emittance, thus the overestimation of the thermal emittance. This effect was systematically studied using both analytic expressions and numerical simulations. These studies were experimentally verified using an L-band 1.6-cell rf photocathode gun with a cesium telluride cathode, which shows a thermal emittance overestimation of 35% with a rms laser spot size of 2.7 mm. The paper concludes by showing that the accuracy of the solenoid scan can be improved by using a quadrupole magnet corrector, consisting of a pair of normal and skew quadrupole magnets.Comment: 12 pages, 13 figure