In this paper, I review the evidence associated with two hypotheses, both ultimately derived from sexual selection theory, put forth to explain social sexual segregation in human juveniles. More ...proximately, I posit that segregation is motivated by sex differences in body size, physical activity and competitiveness. The first hypothesis, the energetic/behavioural hypothesis, suggests that difference in energetics is a way in which males differentiate themselves from females and develop muscle and brain systems implicated in reproductive roles. The second hypothesis, the social roles hypothesis, suggests that segregation is related to learning male and female reproductive roles. The reviewed evidence supports the view that there are differences in energetics in male and female groups. With development, the vigorous behaviours shown by males take the form of specific social roles, related to dominance and competitiveness for males and maternal roles for females.
In 2017, LHC incorporated in operation an anti-leveling procedure of adapting the crossing angle of the colliding beams in steps to increase the integrated luminosity. In this paper, we present the ...Dynamic Aperture simulations that were employed to identify the operational margins, and therefore define the leveling steps. The results are complemented by observations from nominal operation, as well as projections for the 2018 run. Additional leveling techniques, investigated in dedicated machine studies are also discussed.
We performed extended simulations of HL-LHC dynamic aperture in the presence of beam-beam effects in the weak-strong approximation, evaluating the contributions of parameters such as: bunch ...intensity, crossing angle, chromaticity, current in the Landau octupoles and multipole errors. From the beam dynamics point of view, the main difference between the LHC (until 2017) and the HL-LHC is the deployment of the achromatic telescopic squeezing (ATS) optics, allowing not only for a smaller β* reach, but also modifying the phase advances between the lattice correctors (sextupoles, octupoles) and the main IPs, and increasing the peak β functions in the arcs. These correctors become therefore more efficient for the chromatic correction, but also a mitigation of the beam-beam long range interactions using the Landau octupoles is enabled, resulting in a possible reduction of the normalised crossing angle. The limits have been investigated in a tracking simulation campaign aimed at exploring the operational space for the HL-LHC and two possible options for luminosity levelling.
The goal of residency programs is to provide an educational venue with graduated responsibility and increasing levels of independence as preparation for entering the unsupervised practice of ...medicine. Surgical programs are required to both cultivate and convey skills pursuant to three fundamental domains: a sufficient fund of knowledge, technical competence in surgical procedures, and a degree of professionalism to enable ethical independent practice. Never before has the expectation that residency programs provide graduated responsibility in preparation for entering the unsupervised practice of medicine been so clearly articulated as it has by Nasca in the recent Accreditation Council for Graduate Medical Education (ACGME) work-hour guideline revisions. The Royal College of Physicians and Surgeons has provided similar guidance in Canada. Yet, as we progress further into the second decade of work-hour restrictions, it is unclear that we have adequately defined or can recognize the critical end points essential to trainee competency. What is clear is that we must achieve these end points in a manner different from that prior to the introduction of work-hour restrictions. We present the current state of thinking from North America and contrast this with the evolving medical educational process in the United Kingdom.
Abstract
We report the experimental activity on the plasma-discharge capillary tubes suitable for plasma-based accelerators (PBAs) carried out at the SPARC LAB (sources for plasma accelerators and ...compton with laser and beam) test-facility. A high-voltage discharge is produced inside a Hydrogen-filled capillary tube. Through spectroscopic techniques, the density of the plasma thus produced is monitored either spatially or temporally through the line Stark broadening profiles.
Adequate irrigation of open musculoskeletal injuries is considered the standard of care to decrease bacterial load and other contaminants. While the benefit of debris removal compared with the risk ...of further seeding by high-pressure lavage has been studied, the effects of irrigation on muscle have been infrequently reported. Our aim in the present study was to assess relative damage to muscle by pulsatile lavage compared with bulb-syringe irrigation.
In an animal model of heterotopic ossification, 24 Sprague-Dawley rats underwent hindlimb blast amputation via detonation of a submerged explosive, with subsequent through-the-knee surgical amputation proximal to the zone of injury. All wounds were irrigated and underwent primary closure. In 12 of the animals, pulsatile lavage (20 psi 138 kPa) was used as the irrigation method, and in the other 12 animals, bulb-syringe irrigation was performed. A third group of 6 rats did not undergo the blast procedure but instead underwent surgical incision into the left thigh muscle followed by pulsatile lavage. Serial radiographs of the animals were made to monitor the formation of soft-tissue radiopaque lesions until euthanasia at 6 months. Image-guided muscle biopsies were performed at 8 weeks and 6 months (at euthanasia) on representative animals from each group. Histological analysis was performed with hematoxylin and eosin, alizarin red, and von Kossa staining on interval biopsy and postmortem specimens.
All animals managed with pulsatile lavage, with or without blast injury, developed soft-tissue radiopaque lesions, whereas no animal that had bulb-syringe irrigation developed these lesions (p = 0.001). Five of the 12 animals that underwent blast amputation with pulsatile lavage experienced wound complications, whereas no animal in the other 2 groups experienced wound complications (p = 0.014). Radiopaque lesions appeared approximately 10 days postoperatively, increased in density until approximately 16 weeks, then demonstrated signs of variable regression. Histological analysis of interval biopsy and postmortem specimens demonstrated tissue damage with inflammatory cells, cell death, and dystrophic calcification.
Pulsatile lavage of musculoskeletal wounds can cause irreversible insult to tissue, resulting in myonecrosis and dystrophic calcification.
The benefits and offsetting harm of pulsatile lavage (20 psi) should be considered before its routine use in the management of musculoskeletal wounds.
The primary influence on medical students' career choice is their third-year clerkship. However, orthopaedics is not a required rotation in the curriculum of most medical schools. Our goals were to ...identify factors that motivate students to choose an orthopaedic career and to compare these with the factors that influence students to choose nonorthopaedic disciplines.
Fourth-year medical students and orthopaedic residents at the postgraduate year (PGY)-1 level at eight orthopaedic training programs in the United States were surveyed to determine the reasons that they chose orthopaedics instead of other medical or surgical fields.
Of the 622 individuals who responded to our survey, 125 were entering orthopaedics and 497 were not. Although career choice in both groups was most heavily influenced by third and fourth-year clinical rotations and faculty contacts, orthopaedics-bound respondents were more likely than non-orthopaedics-bound respondents to be strongly influenced by experiences and people prior to medical school. Orthopaedics-bound respondents were less likely to report a faculty member as the most important person influencing career choice. Fifty-one percent (sixty-three) of 124 students who selected orthopaedics had already decided to pursue this field prior to their third-year rotation. Patient care was chosen by 71% (347) of 490 non-orthopaedics-bound respondents and 75% (ninety-four) of 125 orthopaedics-bound respondents as the most important factor for pursuing a particular field. Income was not selected as the deciding factor by respondents in either group.
Although faculty contacts and third-year clinical rotations played an important role in student selection of specialty training, they were less influential for those choosing an orthopaedic career than for those choosing other disciplines. Many students choosing orthopaedics made this decision prior to medical school. We believe that increased exposure to positive clinical role models and experiences during medical school would enhance medical students' options for choosing orthopaedic surgery as a career. Anticipated income did not play a deciding role in career selection.
Methods of identifying aggressive/bullying and victimized youngsters in a middle school sample were compared. First, the authors compared teachers' and research associates' ratings of students' ...aggression and found that the 2 measures were significantly correlated. Second, direct observations of youngsters' aggression and victimization were compared with indirect, diary measures kept by youngsters of the same behaviors. The measures were not interrelated, but the diary measures were related to the peer and self-report measures, whereas the direct observations were related to peer and teacher measures. Third, the authors compared the ability of different peer and self-report measures to identify youngsters at different levels of aggression and victimization severity. All measures were associated, even at low levels of severity. Results are discussed in terms of different instruments that provide information on public and private behavior.
External beam irradiation is an accepted treatment for skeletal malignancies. Radiation acts on both cancerous and normal cells and, depending on the balance of these effects, may promote or impair ...bone healing after pathologic fracture. Previous studies suggest an adverse effect of radiation on endochondral ossification, but the existence of differential effects of radiation on the two distinct bone healing pathways is unknown.
The purpose of this study was to investigate the differential effects of external beam irradiation on endochondral compared with intramembranous ossification with intramedullary nail and plate fixation of fractures inducing the two respective osseous healing pathways through assessment of (1) bone biology by histomorphometric analysis of cartilage area and micro-CT volumetric assessment of the calcified callus; and (2) mechanical properties of the healing fracture by four-point bending failure analysis of bending stiffness and strength.
Thirty-six male Sprague-Dawley rats underwent bilateral iatrogenic femur fracture: one side was repaired with an intramedullary nail and the other with compression plating. Three days postoperatively, half (n = 18) received 8-Gray external beam irradiation to each fracture. Rodents were euthanized at 1, 2, and 4 weeks postoperatively (n = 3/group) for quantitative histomorphometry of cartilage area and micro-CT assessment of callus volume. The remaining rodents were euthanized at 3 months (n = 9/group) and subjected to four-point bending tests to assess stiffness and maximum strength.
Nailed femurs that were irradiated exhibited a reduction in cartilage area at both 2 weeks (1.08 ± 1.13 mm versus 37.32 ± 19.88 mm; 95% confidence interval CI of the difference, 4.32-68.16 mm; p = 0.034) and 4 weeks (4.60 ± 3.97 mm versus 39.10 ± 16.28 mm; 95% CI of the difference, 7.64-61.36 mm; p = 0.023) compared with nonirradiated fractures. There was also a decrease in the volume ratio of calcified callus at 4 weeks (0.35 ± 0.08 versus 0.51 ± 0.05; 95% CI of the difference, 0.01-0.31; p = 0.042) compared with nonirradiated fractures. By contrast, there was no difference in cartilage area or calcified callus between irradiated and nonirradiated plated femurs. The stiffness (128.84 ± 76.60 N/mm versus 26.99 ± 26.07 N/mm; 95% CI of the difference, 44.67-159.03 N/mm; p = 0.012) and maximum strength (41.44 ± 22.06 N versus 23.75 ± 11.00 N; 95% CI of the difference, 0.27-35.11 N; p = 0.047) of irradiated plated femurs was greater than the irradiated nailed femurs. However, for nonirradiated femurs, the maximum strength of nailed fractures (36.05 ± 17.34 N versus 15.63 ± 5.19 N; 95% CI of the difference, 3.96-36.88 N; p = 0.022) was greater than plated fractures, and there was no difference in stiffness between the nailed and plated fractures.
In this model, external beam irradiation was found to preferentially inhibit endochondral over intramembranous ossification with the greatest impairment in healing of radiated fractures repaired with intramedullary nails compared with those fixed with plates. Future work with larger sample sizes might focus on further elucidating the observed differences in mechanical properties.
This work suggests that there may be a rationale for compression plating rather than intramedullary nailing of long bone fractures in select circumstances where bony union is desirable, adjunctive radiation treatment is required, and bone stock is sufficient for plate and screw fixation.
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