Selection bias: neighbourhood controls and controls selected from those presenting to a Health Unit in a case control study of efficacy of BCG revaccination.

BACKGROUND: In most case control studies the hardest decision is the choice of the control group, as in the ideal control group the proportion exposed is the same as in the population that produced the cases. METHODS: A comparison of two control groups in a case control study of the efficacy of BCG revaccination. One group was selected from subjects presenting to the heath unit the case attended for routine prevention and care; the second group was selected from the neighbourhood of cases. All Health Units from which controls were selected offered BCG revaccination. Efficacy estimated in a randomized control trial of BCG revaccination was used to establish that the neighbourhood control group was the one that gave unbiased results. RESULTS: The proportion of controls with scars indicating BCG revaccination was higher among the control group selected from Health Unit attenders than among neighbourhood controls. This excess was not removed after control for social variables and history of exposure to tuberculosis, and appears to have resulted from the fact that people attending the Health Unit were more likely to have been revaccinated than neighbourhood controls, although we can not exclude an effect of other unmeasured variables. CONCLUSION: In this study, controls selected from people presenting to a Health Unit overrepresented exposure to BCG revaccination. Had the results from the HU attenders control group been accepted this would have resulted in overestimation of vaccine efficacy. When the exposure of interest is offered in a health facility, selection of controls from attenders at the facility may result in over representation of exposure in controls and selection bias

Eficácia dos exercícios para ombro nas complicações loco-regionais em mulheres submetidas a radioterapia para câncer de mama: ensaio clínico

OBJECTIVE: To investigate the effect of shoulder exercises during radiotherapy in relation to prevention of locoregional physical complications: limitation of range of motion (ROM) and functional capacity, arm circumference and scar tissue adhesion. METHODS: Sixty-six women without shoulder ROM impairment following breast cancer surgery that included complete axillary dissection were allocated to one of two groups: 32 in the physical therapy group (PG) (52.7±10.2 years), who underwent an exercise program; and 34 in the control group (CG) (48±10.1 years). Shoulder ROM, upper-limb circumference and functional capacity and scar tissue adhesion were evaluated at the beginning and end of radiotherapy and six months after completing radiotherapy. RESULTS: The PG showed improvements in flexion and abduction ROM between the first and third evaluations (flexion from 164.77°±8.9° to 167.98°±9.5° and abduction from 168.56°±10.0° to 175.62°±10.2°), which was not observed in the CG (flexion from 167.06±06° to 165.16°±9.2° and abduction from 169.71°±10.1° to 169.53°±12.8°). There was a statistically significant increase in ROM in the PG in relation to the CG (flexion, p=0.02; and abduction, p=0.004). The circumference and functional capacity were similar between the groups and the frequency of scar tissue adhesion in the CG was twice that observed in the PG (48% versus 24%, p=0.04). CONCLUSIONS: These results suggest that shoulder exercises favor maintenance of flexion and abduction ROM of the shoulder and minimize the incidence of scar tissue adhesion in women undergoing radiotherapy for breast cancer treatment.OBJETIVO: Verificar o efeito da realização de exercícios para o ombro durante a radioterapia na prevenção de complicações físicas loco-regionais: limitação da amplitude de movimento (ADM) e da capacidade funcional, circunferência do braço e aderência cicatricial. MÉTODOS: Sessenta e seis mulheres sem comprometimento de ADM de ombro no pós-operatório de cirurgia para câncer de mama com dissecção axilar completa foram alocadas em dois grupos, sendo 32 no grupo de fisioterapia (GF) (52,7±10,2 anos), o qual foi submetido a um programa de exercícios, e 34 no grupo controle (GC) (48±10,1 anos). A ADM do ombro, a circunferência e capacidade funcional dos membros superiores e a aderência cicatricial foram avaliados no início e no final da radioterapia e seis meses após seu término. RESULTADOS: O GF apresentou melhora da ADM de flexão e abdução entre a primeira e terceira avaliação (Flexão: de 164,77°±8,9° para 167,98°±9,5° e Abdução: 168,56°±10° para 175,62°±10,2°), o que não se observou no GC (Flexão: 167,06°±6° para 165,16°±9,2° e Abdução: 169,71°±10,1° para 169,53°±12,8°), demonstrando uma melhora significativa do GF em relação do GC (Flexão: p=0,02 e Abdução: p=0,004). A circunferência e a capacidade funcional foram similares entre os grupos e a frequência de aderência cicatricial no GC foi o dobro daquela observada no GF (48% e 24%, p=0,04). CONCLUSÕES: Esses resultados sugerem que exercícios para o ombro favorecem a manutenção da ADM de flexão e abdução de ombro e minimizam a incidência de aderência cicatricial em mulheres submetidas à radioterapia para tratamento por câncer de mama.13614

Evaluation of the influence of kyphosis and scoliosis on intervertebral disc extrusion in French bulldogs

Although thoracic vertebral malformations with kyphosis and scoliosis are often considered incidental findings on diagnostic imaging studies of screw-tailed brachycephalic breeds, they have been suggested to interfere with spinal biomechanics and intervertebral disc degeneration. It is however unknown if an abnormal spinal curvature also predisposes dogs to develop clinically relevant intervertebral disc herniations. The aim of this study was to evaluate if the occurrence of thoracic vertebral malformations, kyphosis or scoliosis would be associated with a higher prevalence of cervical or thoracolumbar intervertebral disc extrusion in French bulldogs

Resonance Raman scattering studies in Br-2-adsorbed double-wall carbon nanotubes

ArticlePhysical Review B. 73(23):235413 (2006)journal articl

Suboptimal Debridement Quality Produced by the Single-file F2 Protaper Technique in Oval-shaped Canals

Abstract Introduction: The aim of this study was to determine whether the debridement quality of the single-file F2 ProTaper instrumentation technique is comparable to a full conventional ProTaper sequence in both round and oval-shaped root canals. Methods: Fifty-four recently extracted vital lower incisors were instrumented with either a full range of ProTaper Universal instruments in rotary motion (group 1) or with the single-file F2 ProTaper technique in reciprocating motion (group 2). Teeth were previously classified as round or oval-shaped by means of bidirectional radiographs, resulting in 24 round canals, 24 oval canals, and 12 controls. After instrumentation, the roots were demineralized, and the apical 3 mm was multi-sliced and processed for histologic examination. The percentage of residual pulp tissue (PRPT) was calculated with the aid of image analysis software. Univariate analysis of variance was used to verify the variables influencing PRPT. Results: Both canal shape and technique significantly influenced PRPT (P < .05). Oval-shaped canals displayed much more PRPT than round canals in both techniques (P < .05). The difference in PRPT between the techniques depended on the root canal shape, since a significant interaction between canal shape and technique was observed (P < .05). Group 1 displayed considerably less PRPT in oval canals than group 2 (P < .05), whereas in round canals no significant difference was found between the 2 techniques (P > .05). Conclusions: The single-file F2 ProTaper technique displayed similar PRPT to the full range of ProTaper instruments in round canals. However, the debridement quality of the single-file F2 ProTaper technique was suboptimal in oval canals

Gauge symmetry and W-algebra in higher derivative systems

The problem of gauge symmetry in higher derivative Lagrangian systems is discussed from a Hamiltonian point of view. The number of independent gauge parameters is shown to be in general {\it{less}} than the number of independent primary first class constraints, thereby distinguishing it from conventional first order systems. Different models have been considered as illustrative examples. In particular we show a direct connection between the gauge symmetry and the W-algebra for the rigid relativistic particle.Comment: 1+22 pages, 1 figure, LaTeX, v2; title changed, considerably expanded version with new results, to appear in JHE

Emergent quantum confinement at topological insulator surfaces

Bismuth-chalchogenides are model examples of three-dimensional topological insulators. Their ideal bulk-truncated surface hosts a single spin-helical surface state, which is the simplest possible surface electronic structure allowed by their non-trivial $\mathbb{Z}_2$ topology. They are therefore widely regarded ideal templates to realize the predicted exotic phenomena and applications of this topological surface state. However, real surfaces of such compounds, even if kept in ultra-high vacuum, rapidly develop a much more complex electronic structure whose origin and properties have proved controversial. Here, we demonstrate that a conceptually simple model, implementing a semiconductor-like band bending in a parameter-free tight-binding supercell calculation, can quantitatively explain the entire measured hierarchy of electronic states. In combination with circular dichroism in angle-resolved photoemission (ARPES) experiments, we further uncover a rich three-dimensional spin texture of this surface electronic system, resulting from the non-trivial topology of the bulk band structure. Moreover, our study reveals how the full surface-bulk connectivity in topological insulators is modified by quantum confinement.Comment: 9 pages, including supplementary information, 4+4 figures. A high resolution version is available at http://www.st-andrews.ac.uk/~pdk6/pub_files/TI_quant_conf_high_res.pd