Establishing good initial quantum efficiency (QE) and reliable in-situ cleaning for copper cathode in the RF gun is of critical importance for the RF gun operations. Recent studies on the SLAC RF gun ...test bed indicated that the pre-cleaning (plasma cleaning) in the test chamber followed by copper cathode exposure to air for cathode change leads to a very low initial QE in the RF gun, and also demonstrated that without the pre-cleaning good initial QE >4×10−5 can be routinely achieved in the RF gun with the cathodes of QE <1×10−7 measured in the test chamber. QE can decay over the time in the RF gun. The in-situ laser cleaning technique for copper cathodes in the RF gun is established and refined in comparison to previous cleaning at the linac coherent light source, resulting in an improved QE and emittance evolutions. The physics of the laser cleaning process is discussed. It is believed that the reflectivity change is one of the major factors for the QE boost with the laser cleaning.
It has been proposed that scleroderma in particular or connective-tissue diseases in general may be caused by exposure to silicone-containing materials used for breast augmentation. We performed a ...historical cohort study to estimate the point prevalence of this potential complication sometimes referred to as "human adjuvant disease." Three-hundred and seventy-eight patients who underwent augmentation mammaplasty with silicone-containing envelope-type prostheses from 1970 through 1981 were surveyed. Regional musculoskeletal syndromes, fibrositis, or osteoarthritis occurred in a third (38 of 125) of our responders. No patient developed an inflammatory systemic rheumatic disease during the period of observation (mean 6.8 years for the 125 subjects). Using calculations based on risk for development of rheumatic disease, it does not appear likely that augmentation mammaplasty is a significant or major inducer of inflammatory connective-tissue diseases in general. However, the number of patients surveyed was small, and our results must be considered preliminary. We could not exclude a specific risk for the development of scleroderma.
Transitions between different charge density wave (CDW) states in quasi-two-dimensional materials may be accompanied also by changes in the inter-layer stacking of the CDW. Using MeV ultrafast ...electron diffraction, the out-of-plane stacking order dynamics in the quasi-two-dimensional dichalcogenide 1
-TaS
is investigated for the first time. From the intensity of the CDW satellites aligned around the commensurate
= 1/6 characteristic stacking order, it is found out that this phase disappears with a 0.3 ps time constant. Simultaneously, in the same experiment, the emergence of the incommensurate phase, with a slightly slower 2.0 ps time constant, is determined from the intensity of the CDW satellites aligned around the incommensurate
= 1/3 characteristic stacking order. These results might be of relevance in understanding the metallic character of the laser-induced metastable "hidden" state recently discovered in this compound.
Transitions between different charge density wave (CDW) states in quasi-two-dimensional materials may be accompanied also by changes in the inter-layer stacking of the CDW. Using MeV ultrafast ...electron diffraction, the out-of-plane stacking order dynamics in the quasi-two-dimensional dichalcogenide 1T-TaS2 is investigated for the first time. From the intensity of the CDW satellites aligned around the commensurate l = 1/6 characteristic stacking order, it is found out that this phase disappears with a 0.3 ps time constant. Simultaneously, in the same experiment, the emergence of the incommensurate phase, with a slightly slower 2.0 ps time constant, is determined from the intensity of the CDW satellites aligned around the incommensurate l = 1/3 characteristic stacking order. These results might be of relevance in understanding the metallic character of the laser-induced metastable “hidden” state recently discovered in this compound.
The direct excision of glabellar frown lines is a method that is not new, but neither has it been well evaluated. This paper describes the method, discusses the reason for the problem, and suggests ...why this method should have long-lasting results. Several examples of the scars are demonstrated. In selected patients, this may be a reasonable alternative to the myriad surgical possibilities in our quest for a solution to this problem.
We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient ...Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.
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