Optical properties of tissue measured using terahertz pulsed imaging.

The first demonstrations of terahertz imaging in biomedicine were made several years ago, but few data are available on the optical properties of human tissue at terahertz frequencies. A catalogue of these properties has been established to estimate variability and determine the practicality of proposed medical applications in terms of penetration depth, image contrast and reflection at boundaries. A pulsed terahertz imaging system with a useful bandwidth 0.5-2.5 THz was used. Local ethical committee approval was obtained. Transmission measurements were made through tissue slices of thickness 0.08 to 1 mm, including tooth enamel and dentine, cortical bone, skin, adipose tissue and striated muscle. The mean and standard deviation for refractive index and linear attenuation coefficient, both broadband and as a function of frequency, were calculated. The measurements were used in simple models of the transmission, reflection and propagation of terahertz radiation in potential medical applications. Refractive indices ranged from 1.5 ± 0.5 for adipose tissue to 3.06 ± 0.09 for tooth enamel. Significant differences (P<0.05) were found between the broadband refractive indices of a number of tissues. Terahertz radiation is strongly absorbed in tissue so reflection imaging, which has lower penetration requirements than transmission, shows promise for dental or dermatological applications

Особенности воспалительных паттернов бронхов и клинико-функциональная характеристика тяжелой неконтролируемой астмы у больных с холодовой гиперреактивностью дыхательных путей

The aim of this study was to investigate airway inflammation patterns and clinical and functional features of severe uncontrolled asthma.Methods. The study involved 25 patients aged 45 to 55 years with severe uncontrolled asthma. Medical history was analyzed. Lung function tests, cytological and cytochemical investigation of induced sputum were performed in all patients. Asthma control was assessed using the Asthma Control Test questionnaire.Results. The patients were divided into groups: with eosinophilic (&gt; 2% of eosinophils; n = 11) or mixed (≥ 2% of eosinophils and ≥ 61% of neutrophils; n = 14) airway inflammation patterns according to induced sputum cytology. Oxidative function of leucocytes according to myeloper oxidase level in the cells and the degree of cytolysis were increased in the mixed inflammation group. More severe symptoms, more frequent asthma exacerbations, a tendency to worse asthma control and lower FEF50 and MEF25–75 were found in the mixed inflammation group. Coldinduced air way hyperresponsiveness was diagnosed in 12 patients of the mixed inflammation group and in 3 patients of the eosinophilic inflammation group. Severity of the disease, lung function abnormalities and coldinduced airway hyperresponsiveness in patients with severe uncontrolled asthma were related to the airway inflammation pattern.Conclusion. The mixed inflammation pattern was associated to more severe asthma course and worse control of the disease.Персистенция воспаления дыхательных путей у больных бронхиальной астмой (БА) способствует развитию тяжелого неконтролируемого течения болезни.Цель. Изучение особенностей воспалительных паттернов и клиникофункциональных параметров тяжелой неконтролируемой БА.Материалы и методы. В холодный период года (ноябрь – март) проведено обследование больных (n = 25) в возрасте от 45 до 55 лет с установленным диагнозом тяжелой неконтролируемой БА при помощи определения реактивности дыхательных путей на холодовой стимул по данным анамнестического тестирования, исследования функции внешнего дыхания по стандартной методике, цитологического и цитохимического исследования индуцированной мокроты (ИМ).Результаты. По данным анализа цитограмм ИМ больные были разделены на 2 группы: 1я (n = 11) – с эозинофильным (&gt; 2 % эозинофилов), 2я (n = 14) – со смешанным (≥ 2 % эозинофилов + ≥ 61 % нейтрофилов) паттернами воспаления. Оксидативная функция лейкоцитов, оцениваемая по уровню миелопероксидазы в клетках, степени деструкции и интенсивности цитолиза, доминировала во 2й группе. У пациентов этой группы выявлены более выраженные симптомы и большее число случаев обострения БА, тенденция к снижению уровня контроля над болезнью по вопроснику Asthma Control Test, более значимое снижение максимальной объемной скорости в момент выдоха 25, 50 и 75 % форсированной жизненной емкости легких соответственно. Холодовая гиперреактивность дыхательных путей (ХГДП) по клинически значимым признакам установлена у больных 2й (n = 12) и 1й (n = 3) групп. Показано, что проявления тяжести течения болезни, нарушения вентиляционной функции легких и частота развития ХГДП у больных тяжелой неконтролируемой БА сопряжены с паттерном воспаления бронхов.Заключение. Смешанный воспалительный паттерн связан с утяжелением течения БА и более сложной проблемой контроля над болезнью

Predictive relay space vector control of active frequency in systems in the AC electric drives

Presented is a design conception of the automatic control system (ACS) based on the predictive relay space vector algorithm and applicable to the different types of semiconductor active frequency converters in the ac electrical drives. As an example, the ACS of the active voltage and active current rectifier, direct frequency converter and induction drive with the voltage source inverter are considered. The simulation and experimental results are presented