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BackgroundGlobal health has stimulated a lot of students and has attracted the interest of many faculties, thereby initiating the establishment of many academic programs on global health research and education. global health education reflects the increasing attention toward social accountability in medical education.ObjectiveThis study aims to identify gaps in the studies on global health education.DesignA critical literature review of empirical studies was conducted using Boolean search techniques.ResultsA total of 238 articles, including 16 reviews, were identified. There had been a boom in the numbers of studies on global health education since 2010. Four gaps were summarized. First, 94.6% of all studies on global health education were conducted in North American and European countries, of which 65.6% were carried out in the United States, followed by Canada (14.3%) and the United Kingdom (9.2%). Only seven studies (2.9%) were conducted in Asian countries, five (2.1%) in Oceania, and two (0.8%) in South American/Caribbean countries. A total of 154 studies (64.4%) were qualitative studies and 64 studies (26.8%) were quantitative studies. Second, elective courses and training or programs were the most frequently used approach for global health education. Third, there was a gap in the standardization of global health education. Finally, it was mainly targeted at medical students, residents, and doctors. It had not granted the demands for global health education of all students majoring in medicine-related studies.ConclusionsGlobal health education would be a potentially influential tool for achieving health equity, reducing health disparities, and also for future professional careers. It is the time to build and expand education in global health, especially among developing countries. Global health education should be integrated into primary medical education. Interdisciplinary approaches and interprofessional collaboration were recommended. Collaboration and support from developed countries in global health education should be advocated to narrow the gap and to create further mutual benefits.

Streaking of photoelectrons with optical lasers has been widely used for temporal characterization of attosecond extreme ultraviolet pulses. Recently, this technique has been adapted to characterize femtosecond x-ray pulses in free-electron lasers with the streaking imprinted by farinfrared and Terahertz (THz) pulses. Here, we report successful implementation of THz streaking for time-stamping of an ultrashort relativistic electron beam of which the energy is several orders of magnitude higher than photoelectrons. Such ability is especially important for MeV ultrafast electron diffraction (UED) applications where electron beams with a few femtosecond pulse width may be obtained with longitudinal compression while the arrival time may fluctuate at a much larger time scale. Using this laser-driven THz streaking technique, the arrival time of an ultrashort electron beam with 6 fs (rms) pulse width has been determined with 1.5 fs (rms) accuracy. Furthermore, we have proposed and demonstrated a non-invasive method for correction of the timing jitter with femtosecond accuracy through measurement of the compressed beam energy, which may allow one to advance UED towards sub-10 fs frontier far beyond the ∼100 fs (rms) jitter.

The production of ultra-bright electron bunches using ionization injection triggered by two transversely colliding laser pulses inside a beam-driven plasma wake is examined via three-dimensional (3D) particle-in-cell (PIC) simulations. The relatively low intensity lasers are polarized along the wake axis and overlap with the wake for a very short time. The result is that the residual momentum of the ionized electrons in the transverse plane of the wake is much reduced and the injection is localized along the propagation axis of the wake. This minimizes both the initial thermal emittance and the emittance growth due to transverse phase mixing. 3D PIC simulations show that ultra-short (∼8 fs) high-current (0.4 kA) electron bunches with a normalized emittance of 8.5 and 6 nm in the two planes respectively and a brightness greater than 1.7 × 10 19 A · rad −2 · m −2 can be obtained for realistic parameters. The demonstration of the Linac Coherent Light Source (LCLS) as an X-ray free electron laser (X-FEL) [1] has given impetus to research on the fifth-generation light sources [2]. The goal is to make X-FELs smaller and cheaper while decreasing their wavelength and increasing their coherence and intensity. The FEL performance is partially determined by the brightness of the electron beam that traverses the undulator. The brightness is defined as B n = 2I/ǫ 2 n where I is the beam current and ǫ n is the normalized emittance of the beam. In order to make the length of the undulator needed to drive the SASE-FEL [3] into saturation, shorter, high current (∼kA), multi GeV electron beams with ǫ n ∼ 10nm will be needed. These emittances are an order of magnitude smaller than those from state-of-the-art photoinjector RF guns [4]. In this letter, we show the generation of ultrabright electron bunches using ionization injection triggered by two transversely overlapping laser pulses inside a beam-driven wake in plasma. In our scheme, the relatively low intensity lasers are polarized along the wake axis and overlap with the wake for a very short time. Particle-in-cell (PIC) simulations using OSIRIS [5] show that this geometry reduces the residual momentum of the ionized electrons in the transverse plane and localizes them along the propagation axis of the wake leading to an electron beam with a brightness greater than 10 19