Seeded stimulated X-ray emission at 5.9 keV.

X-ray free-electron lasers (XFELs) provide intense pulses that can generate stimulated X-ray emission, a phenomenon that has been observed and studied in materials ranging from neon to copper. Two schemes have been employed: amplified spontaneous emission (ASE) and seeded stimulated emission (SSE), where a second color XFEL pulse provides the seed. Both phenomena are currently explored for coherent X-ray laser sources and spectroscopy. Here, we report measurements of ASE and SSE of the 5.9 keV Mn Kα1 fluorescence line from a 3.9 molar NaMnO4 solution, pumped with 7 femtosecond FWHM XFEL pulses at 6.6 keV. We observed ASE at a pump pulse intensity of 1.7 × 1019 W/cm2, consistent with earlier findings. We observed SSE at dramatically reduced pump pulse intensities down to 1.1 × 1017 W/cm2. These intensities are well within the range of many existing XFEL instruments, which supports the experimental feasibility of SSE as a tool to generate coherent X-ray pulses, spectroscopic studies of transition metal complexes, and other applications.

Does Practice Type Determine the Complexity of Patients Encountered for Orthognathic Surgery?

PURPOSE: This study sought to determine whether the type of oral and maxillofacial surgery (OMS) practice dictated the complexity of patients encountered for orthognathic surgery and to determine whether there were meaningful differences in comorbidities between patient groups. MATERIALS AND METHODS: This was a retrospective cohort study of orthognathic surgical patients operated on by surgeons at an academic medical center (AMC; OMS department at the University of Alabama-Birmingham) compared with a private practice (PP) group that also operated at the AMC auxiliary facility. Surgical procedures included in this study were Le Fort osteotomy, bilateral sagittal split osteotomy, genioplasty, and combinations of these procedures. An experienced surgeon scrutinized the medical records of the AMC and PP groups for age, gender, medical history, American Society of Anesthesiologists (ASA) classification, and indications for surgical procedures. These data were statistically compared for differences in patient complexity. RESULTS: The average age of patients in the 2 groups was similar (AMC, 29 yr; PP, 27 yr). Many more females were treated in the PP setting (male-to-female ratio, 1.06:1 in the AMC group and 1:1.6 in the PP group). The AMC group had a larger percentage of patients with medical comorbidities, a larger proportion of patients with ASA class 2 or 3, and a larger proportion of patients who underwent procedures for reasons other than malocclusion or cosmetic purposes, and these proportions were statistically relevant. Average length of surgery and average length of stay were longer in the AMC group. CONCLUSION: This retrospective cohort study suggests that OMS departments in AMCs tend to treat orthognathic surgical patients with increased comorbidities and systemic illnesses and operate on a larger percentage of patients with concomitant dentofacial issues versus more routine dentofacial skeletal and occlusion deformities.

Influence of connection geometry on dynamic micromotion at the implant-abutment interface.

The aim of this study was to evaluate dynamic micromotion at the implant-abutment interface for 3 different implant neck designs. Five samples each from 3 implant types with different neck designs were subjected to 1 x 10(6) cycles under simulated oral conditions. Load magnitudes varied from 10 to 250 N at 15 Hz. The results revealed a significant main effect for type of implant (P < .0001). The main effect for level of cycles proved to be nonsignificant (P = .9999), as did the interaction between type of implant and level of cycles (P = .9989). Differences in neck design among the 3 implant types resulted in differences in micromotion at the implant-abutment interface under simulated oral conditions.