Irradiation of gold nanoparticles by x-rays: Monte Carlo simulation of dose enhancements and the spatial properties of the secondary electrons production.

PURPOSE: The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. METHODS: The effective range, deflection angle, dose deposition, energy, and interaction processes of electrons produced from the interaction of x-rays with a GNP were calculated by Monte Carlo simulations. The GEANT4 code was used to simulate and track electrons generated from a 2, 50, and 100 nm diameter GNP when it is irradiated with a 50 kVp, 250 kVp, cobalt-60, and 6 MV photon beam in water. RESULTS: When a GNP was present, depending on the beam energies used, secondary electron production was increased by 10- to 2000-fold compared to an absence of a GNP. Low-energy photon beams were much more efficient at interacting with the GNP by two to three orders of magnitude compared to MV energies and increased the deflection angle. GNPs with larger diameters also contributed more dose. The majority of the energy deposition was outside the GNP, rather than self-absorbed by the nanoparticle. The mean effective range of electron tracks for the beams tested ranged from approximately 3 microm to 1 mm. CONCLUSIONS: These simulated results yield important insights concerning the spatial distributions and elevated dose in GNP-enhanced radiotherapy. The authors conclude that the irradiation of GNP at lower photon energies will be more efficient for cell killing. This conclusion is consistent with published studies.

Effects of Tai Chi and Western exercise on physical and cognitive functioning in healthy community-dwelling older adults.

OBJECTIVE: To compare the effects of Tai Chi (TC, n = 37) and Western exercise (WE, n = 39) with an attention-control group (C, n = 56) on physical and cognitive functioning in healthy adults age 69 +/- 5.8 yr, in a 2-phase randomized trial. METHODS: TC and WE involved combined class and home-based protocols. Physical functioning included balance, strength, flexibility, and cardiorespiratory endurance. Cognitive functioning included semantic fluency and digit-span tests. Data were analyzed using intention-to-treat analysis. RESULTS: At 6 mo, WE had greater improvements in upper body flexibility (F = 4.67, p = .01) than TC and C. TC had greater improvements in balance (F = 3.36, p = .04) and a cognitive-function measure (F = 7.75, p < .001) than WE and C. The differential cognitive-function improvements observed in TC were maintained through 12 mo. CONCLUSION: The TC and WE interventions resulted in differential improvements in physical functioning among generally healthy older adults. TC led to improvement in an indicator of cognitive functioning that was maintained through 12 mo.

Relationships among values, achievement orientations, and attitudes in youth sport.

This research examines the value-expressive function of attitudes and achievement goal theory in predicting moral attitudes. In Study 1, the Youth Sport Values Questionnaire (YSVQ; Lee, Whitehead, & Balchin, 2000) was modified to measure moral, competence, and status values. In Study 2, structural equation modeling on data from 549 competitors (317 males, 232 females) aged 12-15 years showed that moral and competence values predicted prosocial attitudes, whereas moral (negatively) and status values (positively) predicted antisocial attitudes. Competence and status values predicted task and ego orientation, respectively, and task and ego orientation partially mediated the effect of competence values on prosocial attitudes and of status values on antisocial attitudes, respectively. The role of sport values is discussed, and new research directions are proposed.

Evidence-based surgery: creating the culture.

Hospitals and professional bodies require a culture that supports surgeons in their quest for knowledge, and provides the technological and educational environment in which they can promote evidence-based surgery. Surgeons must influence the development of their local information technology systems for data collection and outcome analysis, and deliver training programs that instill an attitude of continually seeking evidence. Identification of clinical problems and critical appraisal of the literature need to be taught. Management structures and relationships that facilitate a joint approach to delivering high-quality systematic clinical care should be developed. The culture that supports these aims is also one in which patients can rely on safely receiving up-to-date and effective treatments from well-trained and trusted surgeons.

Contribution of the submentalis muscle to feeding mechanics in the leopard frog, Rana pipiens.

This study investigated the functional contributions of the submentalis muscle to the coordination of feeding behavior in the leopard frog, Rana pipiens. Additionally, the anatomical origins of the motor neurons innervating this muscle are identified and described. The m. submentalis is a small muscle connecting the distal mandibular tips. Depending upon the anuran species studied, this muscle contributes to mandibular bending and the degree to which the tongue is protracted, or has little or no role in feeding biomechanics. High-speed videography was used to quantify feeding attempts before versus after bilateral denervation of the m. submentalis. Additionally, the terminal branch of the trigeminal nerve prior to innervating the m. submentalis was retrogradely labeled to identify the origins of motor neurons innervating the muscle. For the kinematic analyses, denervation of the submentalis resulted in significant increases in the time to maximum tongue protrusion, and the duration of tongue protrusion. Neither mandibular bending, nor tongue length variables differed significantly between normal conditions and deafferented conditions. However, when unsuccessful feeding attempts were quantified following the denervation, failed attempts were nearly always due to the tongue not reaching the prey. None of the unsuccessful feedings prior to denervation were due to inadequate tongue protrusion. Anatomical data show a much larger rostral-caudal distribution of the trigeminal motor neurons than previously described for anurans. These data suggest a larger role for the submentalis muscle in Rana than in previously studied anurans with long protrusible tongues, and suggests a feedback mechanism from the trigeminal nerve to the nerves coordinating tongue protraction and retraction.

Immediate breast reconstruction in the West Midlands: a survey of current practice.

Immediate reconstruction (IR) of the breast following mastectomy is not available to all appropriate patients. Previous studies have examined general surgeons attitudes toward reconstruction but have not assessed how these translate into surgical practice. We investigated the current rates of referral for, and availability of, IR across the West Midlands region.A postal questionnaire was sent to all breast surgery units in the region. Out of 20 units 19 responded. Units where IR was performed in-house were likely to have more breast surgeons (2.3 vs. 1.5, p=0.0106), and a higher annual workload (222 new cases vs. 174). Only two of 19 surgeons said they did not discuss IR with appropriate patients. Selection criteria in the other units included age, lack of co-morbidity, favourable pathology, smoking habit, and in one unit, only small-breasted women were offered IR. IR is performed in 13 of 19 units. Reconstructive procedures range from implants to deep inferior epigastric artery perforator (DIEP) flaps; the surgery is performed by breast and plastic surgeons together in seven units, breast surgeons alone in five and plastic surgeons alone in one. Six units do not carry out reconstruction. These units referred between two and 10 patients (average five) for IR in 2001. Units where some types of IR were available referred between three and 35 patients for surgery not performed in-house, and there was no relationship between complexity of surgery available in-house and referral rates. Reasons for low referral rates included: surgeons' attitudes; geographical isolation; long waiting times for plastic surgical opinion and for surgery; and loss of control of patients' management. Although surgeons' attitudes in the West Midlands are generally positive toward IR, availability and referral rates vary widely. Reconstructive surgeons should encourage referrals by increasing contact with general surgeons to overcome logistical problems and by ensuring appropriate systems for referral exist.