Study on the Release of Muscle Passive Force by Ultrasonic Mechanical Effect and its Related Mechanism

Background: Excessive muscle force impedes physical movement and relaxing passive muscle force substantially improves movement impairment. Ultrasound is an energy carrier with the characteristics of repetitive mechanical stimulation, which may be a feasible method to relieve muscle tension.Methods: We performed stress relaxation experiments on soleus muscle and combine the obtained results with the standard linear solid model to extract information of viscoelastic effect of ultrasound on muscle, and calculated muscle fibril content by histological analysis.Results: Ultrasound can accelerate muscle stress relaxation; the viscosity and elasticity coefficient of the ultrasound group was higher than that of the control group, and there was no significant difference between the three ultrasound intensities; H&E staining showed that muscle fibrillar content decreased and the matrix substance increased.Conclusion: We considered that ultrasound can change the microstructure of muscle, and the matrix substance plays a significant role in the relaxation process. In this paper, the relationship between muscle viscoelasticity and passive muscle force is obtained. The results provide an important theoretical basis and a feasible method for monitoring muscle functional characteristics by measuring muscle viscoelasticity.

Влияние критических параметров технологии на свойства композитов на основе портландитовой матрицы

Представлены результаты экспериментальных исследований критических параметров технологии на свойства контактно-конденсационных бесклинкерных систем твердения на основе портландитовой матрицы и алюмосиликатного наполнителя. В исследованиях в качестве алюмосиликатного наполнителя использовался трепел. Выявлены основные факторы, влияющие на свойства изделий, полученных по технологии контактно-конденсационного твердения. К ним относятся прежде всего характеристики наполнителя (минералогический состав, тонкость помола) и параметры технологии (соотношение матрицы и наполнителя, величина прессового давления). С помощью рентгенофазового анализа установлено, что минералогический состав выбранного алюмосиликатного компонента (трепела) позволяет получать композиты по контактно-конденсационной технологии. Получены количественные данные о влиянии соотношения матрицы и наполнителя и величины прессового давления на прочность композита разных сроков твердения. Структура этого композита состоит из кристаллических сростков в основном матричной субстанции с присутствием низкоосновных гидросиликатов и гидроалюминатов кальция. Установлено, что оптимальный расход наполнителя составляет 15–30% от массы матрицы, давление прессования – 80 МПа. Ключевые слова: портландитовая матрица, алюмосиликатный компонент, контактно-конденсационная технология, бесклинкерная система твердения, диаграмма Исикавы, прессовое давление. The results of experimental studies of critical parameters of the technology on the properties of contact-condensation linker-free hardening systems based on portlandite matrix and aluminosilicate filler are presented. The flutter was used as an alumosilicate filler in studies. The main factors affecting on properties of the products obtained with the contact-condensation hardening technology have been revealed. These include, first of all, the characteristics of the filler (mineralogical composition, fineness of grinding) and the technology parameters (matrix to filler ratio, press pressure). Using X-ray phase analysis, it was found that the mineralogical composition of the selected aluminosilicate component (trepel) allows to obtain the composites using contact-condensation technology. The quantitative data on effect of matrix-filler ratio and press pressure value on strength of obtained composite in different hardening periods are obtained. The structure of this composite consists of crystalline splices in the main matrix substance the portlandite with the presence of lowbase hydrosilicates and calcium hydroaluminates. It has been established that the optimal flow rate of the filler is 15–30% of the mass of the matrix, the pressing pressure is 80 MPa. Keywords: portlandite matrix, aluminosilicate component, contact-condensation technology, linkless hardening system, Ishikawa diagram, press pressure

Embedding resins: An historical perspective

There are several factors that were requisites for the biological applications of electron microscopy. One of these was, clearly, the development of a matrix substance that could infiltrate biological material and encapsulate tissue components so that they could be thin sectioned and examined under an electron beam. Without such matrix substances, examination of tissue as we know it today, would not be possible.Perhaps the start of practical electron microscopy in the context stated above was the application of methacrylate resins for tissue embedment. Methacrylates have a very low viscosity and maintain this viscosity until polymerization is initiated (for days or weeks if one should wish). The two most commonly used methacrylates were n-butyl (soft) and n-methyl (hard) which could be mixed in various proportions to yield almost any block hardness. Methacrylates can be cross-linked with divinyl benzene to improve stability but this was not commonly done. Methacrylates are very easy to section which was an important aspect at the time since sectioning had to be done with glass knives.