До питання про класифікацію зворотних зв`язків у радіоелектронних колах

In the article, necessity of the analysis of conditions when it is possible to neglect direct transfer of a signal through the reversible feedback channel is shown. It allows to define a kind of a feedback correctlyПоказана необходимость анализа условий, при которых можно пренебречь прямой передачей сигнала через обратимый канал обратной передачи. Это позволяет обосновано подойти к определению вида обратной связиПоказана необхідність аналізу умов, за яких можна зневажити прямою передачею сигналу через двобічний канал зворотної передачі, причому потрібно розглядати вплив зворотного зв'язку на вхідні і всі передаточні функції. Це дозволяє обґрунтовано підійти до визначення виду зворотного зв'язк

Conversion of matrices parameters and the circuit analysis after closing and breaking the arbitrary number of branches

Доведено теорему, яка дозволяє визначати порядок величини визначника, у якого величина довільної кількості елементів нескінченно зростає. Запропоновано метод аналізу електричних схем при замиканні і розмиканні довільного числа віток, користуючись однієї з матриць параметрів вихідної схеми, коли величини окремих параметрів, опорів чи провідностей, зростають до нескінченності.The theorem allowing to define the magnitude order of determinant with infinite value growing of arbitrary quantity of elements is proved. The method of electric circuit analysis after closing and breaking of arbitrary quantity of branches is developed using only one of matrices parameters (conductivity or resistance) the initial circuit. Circuit analysis examples after closing of branch are given, using a matrix of conductivities of the initial circuit. Generally, closing arbitrary number of nodal couples theorem application also allows to find potentials of all nodes and currents of all branches, closed branches inclusively. For this purpose it is necessary to add to the appropriate elements of determinant y value with due sign and to pass to a limit applying the theorem. If the matrix of Z - parameters of the initial circuit is set it is possible to receive dual results, using the proved theorem.Доказана теорема, которая позволяет определять порядок величины определителя, у которого величина произвольного количества элементов растет бесконечно. Предложен метод анализа электрических схем при замыкании и размыкании произвольного числа ветвей, пользуясь одной из матриц параметров исходной схемы, когда величины отдельных параметров, сопротивлений или проводимостей, стремятся к бесконечности

Liver CT Perfusion Imaging as a Non-Invasive Method for Assessing Hemodynamics of the Hepatic Parenchyma in Patients with Fibrosis and Cirrhosis as a Result of Chronic Viral Hepatitis C

Objective: to determine whether liver computed tomography (CT) perfusion imaging can assess hemodynamics in patients with fibrosis and cirrhosis as a result of chronic viral hepatitis C (CVHC). Subjects and methods. The prospective study conducted at the Department of Radiation Diagnosis, M.F. Vladimirsky Moscow Regional Research and Clinical Institute, enrolled 61 patients with liver fibrosis and cirrhosis as a result of CVHC, of whom 26 patients had received antiviral therapy (AVT) and achieved a sustained virological response (SVR) at 24 weeks after the end of treatment. All the patients underwent liver CT perfusion imaging on a 256-slice Philips ICT computed tomography scanner (Netherlands). The parameters of arterial, portal, general perfusion and hepatic perfusion index were measured in each patient in his/her liver segments III, VII, and VIII, by calculating the slope of a curve. Results. The values of perfusion parameters in patients who had undergone AVT and attained SVR and who had received no specific treatment were compared with those in the fibrosis, compensated, subcompensated, and decompensated liver cirrhosis groups. In the liver fibrosis group, the patients who had achieved SVR after AVT had higher portal and total perfusion values than those who had received no specific treatment (p = 0.001 and p = 0.002; respectively). In the same group, the liver perfusion index was higher in the patients who had not undergone AVT than in the treated patients (p = 0.028). The values of total perfusion were statistically significantly higher in patients with compensated liver cirrhosis who had attained SVR after AVT than in the untreated patients (p = 0.008). In the decompensated liver cirrhosis group, portal perfusion after specific treatment was higher than in the non-AVT group (p = 0.012). The subcompensated liver cirrhosis group showed no statistically significant differences when comparing the values of liver perfusion parameters depending on the availability of treatment. Conclusion. Liver CT perfusion imaging cannot give an idea of how the hemodynamics of liver tissue changes in the presence of fibrosis and cirrhosis in patients with CVHC after AVT

Comparación de métodos manuales para el estudio del jitter neurofisiológico

La diferencia temporal con la que se activan las fibras musculares de una motoneurona puede variar en sucesivas contracciones. Esta variabilidad se conoce como jitter neuromuscular y resulta aumentada en diversas patologías neurógenas y de la unidad motora. En la actualidad los equipos comerciales que se utilizan para evaluar el jitter (Keypoint y Synergy) implementan dos métodos distintos para realizar la medida: el método de los picos y el método de los flancos. Sin embargo, no existen evidencias de que las medidas obtenidas con ambos métodos ofrezcan resultados comparables. Para realizar este estudio se ha utilizado un banco de señales con 184 registros. Todos los registros han sido alineados por alguno de los picos utilizando el método de los picos y posteriormente el de los flancos. Una vez alineado, sobre los demás picos presentes en el registro, se han tomado medidas de jitter utilizando ambos métodos (picos y flancos), de manera que por cada par de picos válidos presentes se han obtenido cuatro medidas de jitter distintas. Para comparar si existían diferencias estadísticamente significativas entre las medidas registradas para cada una de las cuatro configuraciones posibles se ha utilizado el test de Wilcoxon. El resultado que se obtiene es que únicamente no existen diferencias significativas para las medias obtenidas con la configuración pico-flanco y flanco-pico. Para el resto de configuraciones existen diferencias estadísticamente significativas, lo cual demanda nuevos estudios para determinar qué métodos son los más precisos desde el punto de vista clínico

Motor unit potential morphology differences in individuals with non-specific arm pain and lateral epicondylitis

<p>Abstract</p> <p>Background</p> <p>The pathophysiology of non-specific arm pain (NSAP) is unclear and the diagnosis is made by excluding other specific upper limb pathologies, such as lateral epicondylitis or cervical radiculopathy. The purpose of this study was to determine: (i) if the quantitative parameters related to motor unit potential morphology and/or motor unit firing patterns derived from electromyographic (EMG) signals detected from an affected muscle of patients with NSAP are different from those detected in the same muscle of individuals with lateral epicondylitis (LE) and/or control subjects and (ii) if the quantitative EMG parameters suggest that the underlying pathophysiology in NSAP is either myopathic or neuropathic in nature.</p> <p>Methods</p> <p>Sixteen subjects with NSAP, 11 subjects with LE, eight subjects deemed to be at-risk for developing a repetitive strain injury, and 37 control subjects participated. A quantitative electromyography evaluation was completed using decomposition-based quantitative electromyography (DQEMG). Needle- and surface-detected EMG signals were collected during low-level isometric contractions of the extensor carpi radialis brevis (ECRB) muscle. DQEMG was used to extract needle-detected motor unit potential trains (MUPTs), and needle-detected motor unit potential (MUP) and surface detected motor unit potential (SMUP) morphology and motor unit (MU) firing rates were compared among the four groups using one-way analysis of variance (ANOVA). Post hoc analyses were performed using Tukey's pairwise comparisons.</p> <p>Results</p> <p>Significant group differences were found for all MUP variables and for MU firing rate (<it>p</it> < 0.006). The post-hoc analyses revealed that patients with NSAP had smaller MUP amplitude and SMUP amplitude and area compared to the control and LE groups (<it>p </it>< 0.006). MUP duration and AAR values were significantly larger in the NSAP, LE and at-risk groups compared to the control group (<it>p </it>< 0.006); while MUP amplitude, duration and AAR values were smaller in the NSAP compared to the LE group. SMUP duration was significantly shorter in the NSAP group compared to the control group (<it>p </it>< 0.006). NSAP, LE and at-risk subjects had lower mean MU firing rates than the control subjects (<it>p </it>< 0.006).</p> <p>Conclusion</p> <p>The size-related parameters suggest that the NSAP group had significantly smaller MUPs and SMUPs than the control and LE subjects. Smaller MUPs and SMUPs may be indicative of muscle fiber atrophy and/or loss. A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.</p

Роль КТ-перфузии печени в выявлении предикторов тромбоза воротной вены у пациентов с компенсированным и субкомпенсированным циррозом печени

Portal vein thrombosis is one of the most common complications of liver cirrhosis, the risk factors for which are still not fully understood.Purpose: to develop a prognostic model to determine the likelihood of portal vein thrombosis based on anamnestic, etiological factors, the presence of hepatocellular carcinoma, as well as parameters of CT perfusion of liver tissue.Material and methods. 43 patients with compensated liver cirrhosis (58.1% of men) and 38 patients with subcompensated liver cirrhosis (50% of men) were included in the prospective study. The age of patients in the first group was 52.56 ± 9.62 years, in the second group - 50.95 ± 9.94 years. The number of patients with 1 etiological factor of liver cirrhosis in the study groups was 62.8% and 81.5%, respectively. Type 2 diabetes mellitus was exhibited in 23.3% of patients with compensated liver cirrhosis and in 15.8% of patients with subcompensated liver cirrhosis. The diagnosis of hepatocellular carcinoma was established in 27.9% of patients with compensated liver cirrhosis and in 18.4% of patients with subcompensated liver cirrhosis. All patients, after the native study, underwent CT perfusion of the liver using a 256-slice Philips ICT apparatus. As a result of postprocessing, the values of arterial, portal, total perfusion and perfusion index of liver tissue were determined. Statistical analysis of the data was carried out using the binary logistic regression method and the construction of ROC curves.Results. A logistic stepwise multivariate analysis showed that an increase in arterial perfusion (p = 0.002) and a decrease in portal perfusion (p = 0.004) were independently associated with portal vein thrombosis in patients with compensated liver cirrhosis, and a history of primary liver cancer (p &lt; 0.001) was a dependent factor in this model. In patients with subcompensated liver cirrhosis, a history of hepatocellular carcinoma (p &lt; 0.001) and a decrease in portal perfusion (p = 0.001) became independent predictors of portal vein thrombosis, male gender (p = 0.029) was a dependent factor in the developed model.Conclusion. CT-perfusion of the liver makes it possible to determine predictors that can be used together with such factors as the presence of hepatocellular carcinoma and gender in the construction of prognostic models to determine the likelihood of portal vein thrombosis in patients with compensated and subcompensated liver cirrhosis. Age, etiological factor and the presence of type 2 diabetes mellitus in the developed models were not statistically significant.Тромбоз воротной вены является одним из наиболее частых осложнений цирроза печени, факторы риска возникновения которого остаются все еще не до конца изученными.Цель исследования: разработать прогностическую модель для определения вероятности тромбоза воротной вены исходя из анамнестических, этиологических факторов, наличия гепатоцеллюлярной карциномы, а также параметров КТ-перфузии ткани печени.Материал и методы. В проспективное исследование было включено 43 пациента с компенсированным циррозом печени (58,1% мужчин) и 38 пациентов с субкомпенсированным циррозом печени (50% мужчин). Возраст пациентов в первой группе составил 52,56 ± 9,62 года, во второй группе – 50,95 ± 9,94 года. Количество пациентов с одним этиологическим фактором цирроза печени в исследуемых группах составило соответственно 62,8 и 81,5%. Сахарный диабет 2 типа был выставлен у 23,3% пациентов с компенсированным циррозом печени и у 15,8% пациентов с субкомпенсированным циррозом печени. Диагноз гепатоцеллюлярной карциномы был установлен у 27,9% пациентов с компенсированным циррозом печени и у 18,4% пациентов с субкомпенсированным циррозом печени. Всем пациентам после нативного исследования проводилась КТ-перфузия печени на 256-срезовом аппарате Philips ICT. В результате постпроцессинга определялись значения артериальной, портальной, общей перфузии и индекса перфузии ткани печени. Статистический анализ данных проводился с использованием метода бинарной логистической регрессии и построения ROC-кривых.Результаты. Логистический пошаговый многофакторный анализ показал, что повышение артериальной перфузии (р = 0,002) и снижение портальной перфузии (p = 0,004) были независимо связаны с тромбозом воротной вены у пациентов с компенсированным циррозом печени, а наличие первичного рака печени в анамнезе (р &lt; 0,001) явилось зависимым фактором в данной модели. У пациентов с субкомпенсированным циррозом печени гепатоцеллюлярная карцинома в анамнезе (р &lt; 0,001) и снижение портальной перфузии (p = 0,001) стали независимыми предикторами развития тромбоза воротной вены, мужской пол (p = 0,029) оказался зависимым фактором в разработанной модели.Заключение. КТ-перфузия печени позволяет определить предикторы, которые могут использоваться вместе с такими факторами, как наличие гепатоцеллюлярной карциномы и пол обследуемых, при построении прогностических моделей для определения вероятности тромбоза воротной вены у пациентов с компенсированным и субкомпенсированным циррозом печени. Возраст, этиологический фактор и наличие сахарного диабета 2 типа в разработанных моделях не были статистически значимыми

Behaviour of motor unit action potential rate, estimated from surface EMG, as a measure of muscle activation level

BACKGROUND: Surface electromyography (EMG) parameters such as root-mean-square value (RMS) are commonly used to assess the muscle activation level that is imposed by the central nervous system (CNS). However, RMS is influenced not only by motor control aspects, but also by peripheral properties of the muscle and recording setup. To assess motor control separately, the number of motor unit action potentials (MUAPs) per second, or MUAP Rate (MR) is a potentially useful measure. MR is the sum of the firing rates of the contributing MUs and as such reflects the two parameters that the CNS uses for motor control: number of MUs and firing rate. MR can be estimated from multi-channel surface EMG recordings. The objective of this study was to explore the behaviour of estimated MR (eMR) in relation to number of active MUs and firing rate. Furthermore, the influence of parameters related to peripheral muscle properties and recording setup (number of fibers per MU, fiber diameter, thickness of the subcutaneous layer, signal-to-noise-ratio) on eMR was compared with their influence on RMS. METHODS: Physiological parameters were varied in a simulation model that generated multi-channel EMG signals. The behaviour of eMR in simulated conditions was compared with its behaviour in experimental conditions. Experimental data was obtained from the upper trapezius muscle during a shoulder elevation task (20–100 N). RESULTS: The simulations showed strong, monotonously increasing relations between eMR and number of active MUs and firing rate (r(2 )> 0.95). Because of unrecognized superimpositions of MUAPs, eMR was substantially lower than the actual MUAP Rate (aMR). The percentage of detected MUAPs decreased with aMR, but the relation between eMR and aMR was rather stable in all simulated conditions. In contrast to RMS, eMR was not affected by number of fibers per MU, fiber diameter and thickness of the subcutaneous layer. Experimental data showed a strong relation between eMR and force (individual second order polynomial regression: 0.96 < r(2 )< 0.99). CONCLUSION: Although the actual number of MUAPs in the signal cannot be accurately extracted with the present method, the stability of the relation between eMR and aMR and its independence of muscle properties make eMR a suitable parameter to assess the input from the CNS to the muscle at low contraction levels non-invasively

Techniques of EMG signal analysis: detection, processing, classification and applications

Electromyography (EMG) signals can be used for clinical/biomedical applications, Evolvable Hardware Chip (EHW) development, and modern human computer interaction. EMG signals acquired from muscles require advanced methods for detection, decomposition, processing, and classification. The purpose of this paper is to illustrate the various methodologies and algorithms for EMG signal analysis to provide efficient and effective ways of understanding the signal and its nature. We further point up some of the hardware implementations using EMG focusing on applications related to prosthetic hand control, grasp recognition, and human computer interaction. A comparison study is also given to show performance of various EMG signal analysis methods. This paper provides researchers a good understanding of EMG signal and its analysis procedures. This knowledge will help them develop more powerful, flexible, and efficient applications

Умови існування і класифікація зворотних зв'язків в електронних колах

The article analyzes the state of matter on existence and classification of feedback in electronic circuits. It is shown that the presence of dependent sources is necessary but it is not sufficient condition for the feedback implementation. As a criterion for the existence of feedback in electronic circuit it is proposed to consider the possibility of instability changing the circuit parameters and changing the direction of dependent sources, as well as the feedbacks affect on the circuit functions. To determine the type of feedback in electronic circuits it's necessary to analyze its influence on all functions of the circuit - the input and transmission characteristicsdescribing the input and output mode by both voltage and current.В статье проанализировано состояние вопроса о существовании и классификации обратных связей в электронных цепях. Показана необходимость, но недостаточность присутствия зависимых источников для реализации обратных связей. Предложено критериями существования обратных связей (ОС) в электронной цепи рассматривать возможность получения режима самовозбуждения в схеме замещения при варьировании параметров схемы и изменении направления зависимых источников, а также характер влияния ОС на схемные функции. При определении вида ОС в электронных цепях нужно анализировать их влияние на все функции цепи, входные и передаточные, характеризуя режим на входе и выходе как напряжениями, так и токами.У статті проаналізовано стан питання про існування і класифікацію зворотних зв'язків в електронних колах. Показано необхідність, але недостатність присутності залежних джерел для реалізації зворотних зв'язків. Запропоновано умовами існування зворотних зв'язків в електронних колах розглядати можливість отримання режиму самозбудження в схемі заміщення при варіюванні параметрів схеми і зміні напрямку залежних джерел, а також характер впливу зворотних зв'язків на схемні функції. При визначенні видузворотних зв'язків в електронних колах потрібно аналізувати їх вплив на всі функції кола, вхідні і передавальні, характеризуючи режим на вході і виході як напругами, так і струмами