Concept of Formation Length in Radiation Theory

The features of electromagnetic processes are considered which connected with finite size of space region in which final particles (photon, electron-positron pair) are formed. The longitudinal dimension of the region is known as the formation length. If some external agent is acting on an electron while traveling this distance the emission process can be disrupted. There are different agents: multiple scattering of projectile, polarization of a medium, action of external fields, etc. The theory of radiation under influence of the multiple scattering, the Landau-Pomeranchuk-Migdal (LPM) effect, is presented. The probability of radiation is calculated with an accuracy up to "next to leading logarithm" and with the Coulomb corrections taken into account. The integral characteristics of bremsstrahlung are given, it is shown that the effective radiation length increases due to the LPM effect at high energy. The LPM effect for pair creation is also presented. The multiple scattering influences also on radiative corrections in a medium (and an external field too) including the anomalous magnetic moment of an electron and the polarization tensor as well as coherent scattering of a photon in a Coulomb field. The polarization of a medium alters the radiation probability in soft part of spectrum. Specific features of radiation from a target of finite thickness include: the boundary photon emission, interference effects for thin target, multi-photon radiation. The experimental study of LPM effect is described. For electron-positron colliding beams following items are discussed: the separation of coherent and incoherent mechanisms of radiation, the beam-size effect in bremsstrahlung, coherent radiation and mechanisms of electron-positron creation.Comment: Revised review paper, 96 pages, 28 figures. Description of SLAC E-146 experiment removed, discussion of CERN SPS experiment adde

Clinical review: Early patient mobilization in the ICU

Early mobilization (EM) of ICU patients is a physiologically logical intervention to attenuate critical illness-associated muscle weakness. However, its long-term value remains controversial. We performed a detailed analytical review of the literature using multiple relevant key terms in order to provide a comprehensive assessment of current knowledge on EM in critically ill patients. We found that the term EM remains undefined and encompasses a range of heterogeneous interventions that have been used alone or in combination. Nonetheless, several studies suggest that different forms of EM may be both safe and feasible in ICU patients, including those receiving mechanical ventilation. Unfortunately, these studies of EM are mostly single center in design, have limited external validity and have highly variable control treatments. In addition, new technology to facilitate EM such as cycle ergometry, transcutaneous electrical muscle stimulation and video therapy are increasingly being used to achieve such EM despite limited evidence of efficacy. We conclude that although preliminary low-level evidence suggests that EM in the ICU is safe, feasible and may yield clinical benefits, EM is also labor-intensive and requires appropriate staffing models and equipment. More research is thus required to identify current standard practice, optimal EM techniques and appropriate outcome measures before EM can be introduced into the routine care of critically ill patients

Undergraduate training in breaking bad news: A continuation study exploring the patient perspective.

This paper reports on the continuation of an initial study that demonstrated the effectiveness, as rated by experts, of an undergraduate training in breaking bad news (BBN) using simulated patient (SP) and individual feedback. The current study aimed to further explore whether such an individualized training approach also has positive effects from the perspective of the patient, using the analogue patient (AP) methodology. A subsample of 180 videotaped interviews with SPs were selected from the existing data set (N = 332), consisting of 60 pre- and post-training interviews of students benefiting from the individualized approach (intervention group) and 60 post-training interviews of students having small-group SP training and collective supervision (comparison group). Sixty-eight APs-healthy untrained observers-were asked to view the videotaped interviews while "putting themselves in the patient's shoes" and evaluate satisfaction, trust, liking, and the competence of medical students. The intervention group students improved significantly from pre- to post-training on several dimensions evaluated by the APs: patient satisfaction, trust in the student, liking of the student, and perceived medical competence. Increased AP satisfaction was related to different changes in students' communication behavior between pre- and post-training: increase in positive talk, emotional responsiveness, biomedical and psychosocial information, and biomedical counseling. There was no significant between-group difference at post-training. AP evaluation showed significant improvement between pre- and post-training. This result provides additional and complementary evidence of the positive effects of individualized training in BBN from the AP perspective, a proxy of (real) patients

Individual Supervision to Enhance Reflexivity and the Practice of Patient-Centered Care: Experience at the Undergraduate Level.

This article reports on what is at work during individual supervision of medical students in the context of teaching breaking bad news (BBN). Surprisingly, there is a relative lack of research and report on the topic of supervision, even though it is regularly used in medical training. Building on our research and teaching experience on BBN at the undergraduate level, as well as interviews of supervisors, the following key elements have been identified: learning objectives (e.g., raising student awareness of structural elements of the interview, emotion (patients and students) handling), pedagogical approach (being centered on student's needs and supportive to promote already existing competences), essentials (e.g., discussing skills and examples from the clinical practice), and enhancing reflexivity while discussing specific issues (e.g., confusion between the needs of the patient and those of the student). Individual supervision has been identified as crucial and most satisfactory by students to provide guidance and to foster a reflexive stance enabling them to critically apprehend their communication style. Ultimately, the challenge is to teach medical students to not only connect with the patient but also with themselves

Prospective study of 310 patients: can early CT predict the severity of acute pancreatitis?

Background: This study was designed to determine the most important early CT parameters predictive of acute pancreatitis severity. Methods: Three hundred and seventy-one consecutive patients with acute abdominal pain and hyperamylasemia were enrolled. Three hundred and ten of the 371 patients met our inclusion criteria. Acute pancreatitis severity was evaluated using the 1992 Atlanta criteria. Different CT parameters were reported from the admission abdominal CT by two radiologists blinded from any clinical parameter, but the patients' age and gender. These variables were fitted in a binary logistic regression model. Results: Acute pancreatitis was mild in 80% cases, severe in 20% cases and lethal in 12.69% cases. The following CT parameters were significantly associated with the severity of acute pancreatitis: the objective size of the pancreas (P=0.001), the peripancreatic fat abnormalities (P=0.001) and the extent of necrosis (P=0.007). Moreover, the age of the patient revealed itself a highly significant (P=0.001) indicator of disease severity. The association of the four CT criteria eventually showed a sensitivity of 73% and a specificity of 81% to predict acute pancreatitis severity. Conclusion: Although these criteria correlated with disease severity, our study identified that morphological CT criteria cannot be used to triage patients with severe and mild acute pancreatiti

Study protocol for the ETMED-L project: longitudinal study of mental health and interpersonal competence of medical students in a Swiss university using a comprehensive framework of empathy.

Physician interpersonal competence is crucial for patient care. How interpersonal competence develops during undergraduate medical education is thus a key issue. Literature on the topic consists predominantly of studies on empathy showing a trend of decline over the course of medical school. However, most existing studies have focused on narrow measures of empathy. The first aim of this project is to study medical students' interpersonal competence with a comprehensive framework of empathy that includes self-reported cognitive and affective empathy, performance-based assessments of emotion recognition accuracy, and a behavioural dimension of empathy. The second aim of the present project is to investigate the evolution of mental health during medical school and its putative link to the studied components of interpersonal competence. Indeed, studies documented a high prevalence of mental health issues among medical students that could potentially impact their interpersonal competence. Finally, this project will enable to test the impact of mental health and interpersonal competence on clinical skills as evaluated by experts and simulated patients. This project consists of an observational longitudinal study with an open cohort design. Each year during the four consecutive years of the project, every medical student (curriculum years 1-6) of the University of Lausanne in Switzerland will be asked to complete an online questionnaire including several interpersonal competence and mental health measures. Clinical skills assessments from examinations and training courses with simulated patients will also be included. Linear mixed models will be used to explore the longitudinal evolutions of the studied components of interpersonal competence and mental health as well as their reciprocal relationship and their link to clinical skills. The project has received ethical approval from the competent authorities. Findings will be disseminated through internal, regional, national and international conferences, news and peer-reviewed journals