When should we stop mammography screening for breast cancer in elderly women?

There is insufficient evidence to recommend for or against routine screening mammography beyond the age of 69 years. The best candidates to stop screening are elderly women who have significant comorbidities, poor functional status, low bone mineral density (BMD), little interest in preventive care, or an unwillingness to accept the potential harm of screening. (Grade of Recommendation: C, based on retrospective cohort studies.

Верификация измерений фазовращателей отражательной антенной решетки

Introduction.  Large-size phased antenna arrays (PAA) frequently incorporate optical excitation schemes, whose main elements include the feed and the reflective aperture. In turn, the reflective aperture consists of several tens of thousands of radiators and phase shifters. Major distortions of the radiation pattern in reflective arrays occur due to phase errors, leading to a decrease in the gain and an increase in the side lobes of the radiation pattern. In the millimeter wavelength range, ferrite phase shifters can have an initial phase from 0 to 360 °, thus requiring measurements of the array elements following their assembly.Aim.  To develop a method for evaluating errors in measurements of the parameters of phase shifters incorporated in an antenna array by comparing theoretical and experimental data.Materials and methods.  A convenient method for determining the parameters of phase shifters is probing, in which a movable probe is connected in series with each array element. In cases where a PAA element represents a single structure consisting of a ferrite segment and a dielectric radiator, measurements are carried out using a probe in the form of a segment of a round waveguide moving towards the radiator. In order to evaluate the measurement error of such a scheme, a mechanically controlled reference phase shifter was used.Results. Measurement errors for the probe structure used were calculated based on the assumption of the phase error arising from the vector addition of the controlled and uncontrolled reflected signals at the input of the PAA element, in the section of the reference plane at the input of the probe. In addition, the S-parameters of the superposition section were calculated. The extrema of the error function were used to determine the maximum errors in measuring the phase and amplitude.Conclusion. The performed analysis confirmed the validity of the proposed method for measuring the parameters of phase shifters using a waveguide probe. The measurement error of the PAA elements according to the proposed scheme was found to be about 3 o, which is commensurate with that of recording devices.Введение. В больших фазированных антенных решетках (ФАР) широко используются оптические схемы возбуждения, основными элементами которых  являются облучатель и отражательная апертура, состоящая из нескольких десятков тысяч излучателей и фазовращателей.  В отражательных ФАР основные искажения диаграммы направленности происходят за счет фазовых ошибок, приводящих к снижению усиления и росту боковых лепестков. В миллиметровом диапазоне длин волн ферритовые фазовращатели могут иметь начальную фазу от 0 до 360°, поэтому после сборки в решетку необходимо проводить их фазовые измерения.Цель исследования. Создание способа оценки погрешности измерений параметров фазовращателей в составе антенной решетки на основе  сопоставления теоретических положений с экспериментальными данными.Материалы и методы. Удобным способом определения параметров фазовращателей является использование метода летающего пробника (flying probe), при котором подвижный пробник последовательно соединяется с каждым элементом решетки. Если элемент ФАР представляет собой единую конструкцию из ферритового отрезка и диэлектрического излучателя, то измерения проводят с помощью отрезка круглого волновода, надвигающегося на излучатель. Для проверки погрешности этой схемы измерений используется ме-ханически управляемый фазовращатель.Результаты. Рассчитаны погрешности измерений конструкции с подвижным пробником, исходя из предположения о фазовой ошибке, возникающей из-за векторного сложения управляемого и неуправляемого отраженных сигналов на входе элемента ФАР. Измерены S-параметры стыковочной секции. По экстремумам функции ошибки определены максимальные погрешности измерения фазы и амплитуды.Заключение. Проведенный анализ показал правомерность выбранного метода оценки погрешности измерений параметров фазовращателей в составе решетки, что определяет перспективы его дальнейшего использования. Погрешность измерений элементов ФАР по предложенной схеме составила около 3°, что соизмеримо с погрешностью регистрирующего прибора

Определение минимального шага сканирования луча фазированной антенной решетки

Introduction. Electronically scanned antennas (ESA) appeared about a century ago. Although the methods of their design and production have been sufficiently studied, some individual parameters are yet to be revealed. One of such parameters is the minimum step of movement, along with a related parameter – the accuracy of beam alignment in a given direction. From the electrodynamic problem of radiation, it is obvious that the step is associated with the number of radiators and the accuracy of phase adjustment in analogue phase shifters, or with the quantization step in the case of using phase shifters with a discrete step.Aim. To discover a connection between the design parameters of ESA and the step of beam steering; to investigate the dependence between the step and the parameters of the phase shifter and types of beam forming phased array circuits; to create a mathematical apparatus for calculating the minimum step of beam movement for the sum and difference radiation patterns.Materials and methods. Analytical relations were determined for calculating the step depending on the geometric dimensions and location of the radiators. A software application was developed for calculating radiation patterns. A software and hardware complex was designed for beam control of an experimental C-band ESA.Results. A method was developed for calculating the minimum step of ESA scanning. Mathematical relations for calculating the minimum step and accuracy of the ESA beam setting were obtained. A comparison of the experimental and theoretical data on the minimum step of movement of the sum and difference beams of a C-band ESA with the ratio D/λ=10 in the X coordinate and D/λ=5 in the Y coordinate showed good agreement.Conclusion. The created mathematical apparatus makes it possible to calculate the minimum step of electron beam scanning with sufficient accuracy. The experimentally measured steps of the beam movement for an array of 144 elements confirmed the obtained analytical relationships. In an ESA with a small number of elements (N < 10), the minimum step of movement can be variable. The theoretically achievable minimum step of beam movement is determined by the phase shift of the least significant bit of the phase shifter and the electrical length of the antenna aperture.Введение. Антеннам с электронным сканированием уже скоро 100 лет. Методы их проектирования и производства достаточно изучены, однако есть параметры, которые в научно-технической литературе не раскрыты. Одним из таких параметров является минимальный шаг движения и связанный с этим параметр – точность установки луча в заданном направлении. Из электродинамической задачи излучения очевидно, что шаг связан с количеством излучателей и точностью установки фазы в аналоговых фазовращателях (ФВ) либо с шагом квантования в случае использования фазовращателей с дискретным шагом.Цель исследования. Нахождение связи между конструктивными параметрами фазированной антенной решетки (ФАР) и шагом движения луча. Исследование зависимости шага от параметров фазовращателя и типов диаграммообразующих схем ФАР. Создание математического аппарата для вычисления минимального шага движения луча для суммарной и разностной диаграмм направленности.Материалы и методы. Аналитические соотношения для расчета шага в зависимости от геометрических размеров ФАР и расположения излучателей. Создание программ для расчета диаграмм направленности и программно-аппаратного комплекса для управления лучом экспериментальной ФАР С-диапазона.Результаты. Найдена методика вычисления минимального шага сканирования ФАР. Математические соотношения для расчета минимального шага и точности установки луча ФАР. Сравнение экспериментальных и теоретических данных минимального шага движения суммарного и разностного лучей ФАР С-диапазона c соотношением D/λ=10 по координате Х и D/λ=5  по координате Y показало хорошее совпадение.Заключение. Созданный математический аппарат позволяет точно рассчитать минимальный шаг электронного сканирования луча. Экспериментально измеренные шаги движения луча для решетки из 144 элементов подтверждают полученные аналитические соотношения. В ФАР с небольшим количеством элементов (N < 10) минимальный шаг перемещения может быть переменным. Теоретически достижимый минимальный шаг движения луча определяется фазовым сдвигом младшего разряда ФВ и электрической длиной апертуры антенны

Inflammation in benign prostate tissue and prostate cancer in the finasteride arm of the Prostate Cancer Prevention Trial

BACKGROUND: A previous analysis of the placebo arm of the Prostate Cancer Prevention Trial (PCPT) reported 82% overall prevalence of intraprostatic inflammation and identified a link between inflammation and higher-grade prostate cancer and serum PSA. Here we studied these associations in the PCPT finasteride arm. METHODS: Prostate cancer cases (N=197) detected either on a clinically indicated biopsy or on protocol-directed end-of-study biopsy, and frequency-matched controls (N=248) with no cancer on an end-of-study biopsy were sampled from the finasteride arm. Inflammation in benign prostate tissue was visually assessed using digital images of H&E stained sections. Logistic regression was used for statistical analysis. RESULTS: In the finasteride arm, 91.6% of prostate cancer cases and 92.4% of controls had at least one biopsy core with inflammation in benign areas; p < 0.001 for difference compared to placebo arm. Overall, the odds of prostate cancer did not differ by prevalence (OR=0.90, 95% CI 0.44-1.84) or extent (P-trend=0.68) of inflammation. Inflammation was not associated with higher-grade disease (prevalence: OR=1.07, 95% CI 0.43-2.69). Furthermore, mean PSA concentration did not differ by the prevalence or extent of inflammationin either cases or controls. CONCLUSION: The prevalence of intraprostatic inflammation was higher in the finasteride than placebo arm of the PCPT, with no association with higher-grade prostate cancer. IMPACT: Finasteride may attenuate the association between inflammation and higher-grade prostate cancer. Moreover, the missing link between intraprostatic inflammation and PSA suggests that finasteride may reduce inflammation-associated PSA elevation

A mathematical model for top-shelf vertigo: the role of sedimenting otoconia in BPPV

Benign Paroxysmal Positional Vertigo (BPPV) is a mechanical disorder of the vestibular system in which calcite particles called otoconia interfere with the mechanical functioning of the fluid-filled semicircular canals normally used to sense rotation. Using hydrodynamic models, we examine the two mechanisms proposed by the medical community for BPPV: cupulolithiasis, in which otoconia attach directly to the cupula (a sensory membrane), and canalithiasis, in which otoconia settle through the canals and exert a fluid pressure across the cupula. We utilize known hydrodynamic calculations and make reasonable geometric and physical approximations to derive an expression for the transcupular pressure $\Delta P_c$ exerted by a settling solid particle in canalithiasis. By tracking settling otoconia in a two-dimensional model geometry, the cupular volume displacement and associated eye response (nystagmus) can be calculated quantitatively. Several important features emerge: 1) A pressure amplification occurs as otoconia enter a narrowing duct; 2) An average-sized otoconium requires approximately five seconds to settle through the wide ampulla, where $\Delta P_c$ is not amplified, which suggests a mechanism for the observed latency of BPPV; and 3) An average-sized otoconium beginning below the center of the cupula can cause a volumetric cupular displacement on the order of 30 pL, with nystagmus of order $2^\circ$/s, which is approximately the threshold for sensation. Larger cupular volume displacement and nystagmus could result from larger and/or multiple otoconia.Comment: 15 pages, 5 Figures updated, to be published in J. Biomechanic

The future of enterprise groupware applications

This paper provides a review of groupware technology and products. The purpose of this review is to investigate the appropriateness of current groupware technology as the basis for future enterprise systems and evaluate its role in realising, the currently emerging, Virtual Enterprise model for business organisation. It also identifies in which way current technological phenomena will transform groupware technology and will drive the development of the enterprise systems of the future

Tissue Effects in a Randomized Controlled Trial of Short-term Finasteride in Early Prostate Cancer.

BackgroundIn the Prostate Cancer Prevention Trial, finasteride selectively suppressed low-grade prostate cancer and significantly reduced the incidence of prostate cancer in men treated with finasteride compared with placebo. However, an apparent increase in high-grade disease was also observed among men randomized to finasteride. We aimed to determine why and hypothesized that there is a grade-dependent response to finasteride.MethodsFrom 2007 to 2012, we randomized dynamically by intranet-accessible software 183 men with localized prostate cancer to receive 5mg finasteride or placebo daily in a double-blind study during the 4-6weeks preceding prostatectomy. As the primary end point, the expression of a predefined molecular signature (ERβ, UBE2C, SRD5A2, and VEGF) differentiating high- and low-grade tumors in Gleason grade (GG) 3 areas of finasteride-exposed tumors from those in GG3 areas of placebo-exposed tumors, adjusted for Gleason score (GS) at prostatectomy, was compared. We also determined androgen receptor (AR) levels, Ki-67, and cleaved caspase 3 to evaluate the effects of finasteride on the expression of its downstream target, cell proliferation, and apoptosis, respectively. The expression of these markers was also compared across grades between and within treatment groups. Logistic regression was used to assess the expression of markers.FindingsWe found that the predetermined molecular signature did not distinguish GG3 from GG4 areas in the placebo group. However, AR expression was significantly lower in the GG4 areas of the finasteride group than in those of the placebo group. Within the finasteride group, AR expression was also lower in GG4 than in GG3 areas, but not significantly. Expression of cleaved caspase 3 was significantly increased in both GG3 and GG4 areas in the finasteride group compared to the placebo group, although it was lower in GG4 than in GG3 areas in both groups.InterpretationWe showed that finasteride's effect on apoptosis and AR expression is tumor grade dependent after short-term intervention. This may explain finasteride's selective suppression of low-grade tumors observed in the PCPT

Neuronal guidance molecule netrin-1 attenuates inflammatory cell trafficking during acute experimental colitis

Background: Inflammatory bowel diseases, encompassing Crohn’s disease and ulcerative colitis, are characterised by persistent leucocyte tissue infiltration leading to perpetuation of an inappropriate inflammatory cascade. The neuronal guidance molecule netrin-1 has recently been implicated in the orchestration of leucocyte trafficking during acute inflammation. We therefore hypothesised that netrin-1 could modulate leucocyte infiltration and disease activity in a model of inflammatory bowel disease. Design: DSS-colitis was performed in mice with partial genetic netrin-1 deficiency (Ntn-1+/- mice) or wild-type mice treated with exogenous netrin-1 via osmotic pump to examine the role of endogenous and therapeutically administered netrin-1. These studies were supported by in vitro models of transepithelial migration and intestinal epithelial barrier function. Results: Consistent with our hypothesis, we observed induction of netrin-1 during intestinal inflammation in vitro or in mice exposed to experimental colitis. Moreover, mice with partial netrin-1 deficiency demonstrated an exacerbated course of DSS-colitis compared to littermate controls, with enhanced weight loss and colonic shortening. Conversely, mice treated with exogenous mouse netrin-1 experienced attenuated disease severity. Importantly, permeability studies and quantitative assessment of apoptosis reveal that netrin-1 signalling events do not alter mucosal permeability or intestinal epithelial cell apoptosis. In vivo studies of leucocyte transmigration demonstrate suppression of neutrophil trafficking as a key function mediated by endogenous or exogenously administered netrin-1. Finally, genetic studies implicate the A2B adenosine receptor in netrin-1-mediated protection during DSS-colitis. Conclusions: The present study identifies a previously unrecognised role for netrin-1 in attenuating experimental colitis through limitation of neutrophil trafficking

Prevention and early detection of prostate cancer

This Review was sponsored and funded by the International Society of Cancer Prevention (ISCaP), the European Association of Urology (EAU), the National Cancer Institute, USA (NCI) (grant number 1R13CA171707-01), Prostate Cancer UK, Cancer Research UK (CRUK) (grant number C569/A16477), and the Association for International Cancer Research (AICR