Establishment of a hypoxia ischemia reperfusion brain damage model in neonatal rats

Objective: Rice-Vannucci model has been widely used as HIE（Hypoxic ischemic encephalopathy ） animal model in the past forty years, but it does not mimic reperfusion injury that occurs during HIE. The aim of the present study was to establish a new neonatal rat model by simulating hypoxia ischemia reperfusion brain damage (HIRBD) through "common carotid artery (CCA) muscle bridge". Methods: Sixty 7-day-old male Sprague-Dawley rats were randomly assigned to group A (HIRBD groups, n=36), group B (Rice-Vannucci group, n=12), and group C (sham-operated group, n=12). Rats in group A were assigned to 3 subgroups (A1-A3, 12 animals/subgroup). Dynamic changes in cerebral blood flow (CBF) were evaluated by the laser speckle imaging system. The status of the CCA was observed under a stereomicroscope. Changes in body weight, gross morphology as well as pathological sections of brain tissue were examined to evaluate the feasibility of the model. Results: The results indicated that CCA muscle bridge successfully blocked the CBF. CBF was restored after removal of the CCA muscle bridge in HIRBD groups. The CCA was in good condition after removing the muscle bridge, and blood supply was not affected. Changes in body weight, gross morphology and pathological sections of brain tissue indicated that ischemia reperfusion induced by the CCA muscle bridge method caused varying degrees of brain damage. Conclusion: CCA muscle bridge method is effective for establishing a reliable, stable, and reproducible neonatal rat model for study of HIRBD.

Bridge method for studying the spectra of current fluctuations in tungsten filaments at the frequency range 1.5∙10–5–5∙10–1 Hz

The problem of the absence of methods for measuring low-frequency fluctuation processes at high temperatures is considered. An original bridge method is proposed for measuring the spectra of low-frequency current fluctuations in tungsten filaments of electric lamps in a controlled temperature range of 300–2700 K. Application of the bridge measurement scheme allows us to reduce the influence of degradation processes in the filament and the power source's own noise on the measurement results by several orders of magnitude. Spectral analysis of low frequency current fluctuations is performed at the frequency range 1.5∙10–5–5∙10–1 Hz using an automated setup based on a personal computer under the control of specially developed software.

Influence of Soil’s Vertical Stiffness on Estimation of Fatigue Life for Steel Catenary Risers (SCRs)

Fatigue damage estimation is a key part in a Steel Catenary Riser (SCR) system design. The riser-soil interaction has a significant influence on the fatigue assessment for a SCR system at the Touch-Down Zone (TDZ) because the soil’s vertical stiffness is a critical parameter. The conventional methods developed to calculate the soil’s vertical stiffness, for example, DNV method [10], Bridge method [4] and Audibert method [3], were based on the assumption that at the TDZ area the soil mass being interacted by the pipe is always under intact condition. Recently, Chen et al. published a newly developed method [5, 6], which was based on the laboratory test results carried out by Texas A&M University in the late 1980s and was further verified by recent laboratory displacement-controlled tests by Texas A&M University [2], resulting in softer soil’s vertical stiffness. In order to understand the difference between Chen method and the conventional methods as well as the influence of Chen method on the SCR design, a study was carried out for a given soil condition and three typical sizes of riser pipes and is documented in this paper. In this paper, firstly, various methods used to calculate soil’s vertical stiffness, i.e., DNV method, Bridge method, Audibert method, and Chen method, were briefly introduced. Secondly, a discussion was performed on the model of the conventional methods and the model of Chen method. Thirdly, as an example for a given soil condition, the soil’s vertical stiffness was estimated using these methods respectively for 6″-dia., 12″-dia., and 18″-dia. riser pipes. Finally, the fatigue damages for various riser pipes were computed using the estimated soil’s vertical stiffness and a comparison on the estimated fatigue damages was performed. The study results showed that the soil’s vertical stiffness estimated by Chen method was about one order magnitude weaker than these estimated by the conventional methods. In other words, the soil’s vertical stiffness estimated by the conventional methods was about 5 to 11 times that estimated by Chen method. The pipe’s fatigue life estimated using the soil’s vertical stiffness of Chen method was about 1.5 times (i.e., 50% longer than) that estimated using the soil’s vertical stiffness of the conventional methods. These study results could improve a SCRs designer’s understanding on: 1) the difference between the model of the conventional methods and the model of Chen method, 2) the impact of Chen method on the estimated fatigue life, and 3) that as the model of the conventional methods is a closer representative of the prototype and their results are more conservative, it is recommended to use the conventional methods for SCRs design. Eventually, these will help the designers to select an appropriate method for calculating the soil’s vertical stiffness in the SCRs design.

The Implication of Multi-System and Fluency Bridge Method in Learning English to the Learning Result of Students in Hary English Course for Elementary Level

The low level of English mastery of learners in Indonesia, which is categorized far from the target, can be seen from the inappropriate application and implementation of English learning systems and methods that are applied in most formal educational institutions that are different from English course institutions. This research is aimed to determine the implication of the multi-system and the fluency bridge method for the enhancement of English mastery of HEC students. The object of the research is 3 students of elementary level of Hary English Course branch Manggisan Indah residential area, Wonosobo. The research has been conducted for approximately 4 months, started from April to July and October to November in 2019 with a private class system. Each class has a different elementary level namely level 1 and 5 elementary accompanied by different learning materials and methods. The result of the research stated that the application of multi-system and fluency bridge method was proven effectively to improve the understanding and the English abilities of HEC elementary students in Wonosobo. This statement is proven through the observation of HEC students before joining and after taking the course, showing a drastic difference in their ability to speak English. This is also showed in their level of interest in learning English, the speed level of understanding the given materials and the results of the post-test which states they graduated from the level that just learned.