Thermal Profile Of A Reciprocating Compressor Using Low GWP Refrigerants

To contribute to the global effort to phase down highly polluting HFC refrigerants, refrigeration industry is dedicating significant resources in evaluation process of alternative refrigerants. In the light commercial refrigeration segment the most difficulties were found to replace R404A refrigerant. Embraco, being one of major compressors manufacturers, took part in AHRI AREP program with performances evaluation on several refrigerant alternatives with GWP below 150, limit that is widely used as a threshold in regional and local legislations in the years to come. Except natural refrigerants like hydrocarbons and CO2, new chemical blends, classified in A2L safety class, were developed with GWP \u3c 150 to meet criteria of regional regulation in different parts of the world. This paper shows summary of evaluation of a hermetic reciprocating compressor based on its thermal profile when using an A2L blend. It is then compared with R404A and R290 profiles in order to understand limitations when using an A2L chemical blend in the product which originally have been designed for R404A operation

Strength training in elderly people improves static balance

Aim of this study was to investigate the effects of two different types of strength training programs on static balance in elderly subjects. Subjects older than 65 years of age were enrolled and assigned to control group (CG, n =19), electrical stimulation group (ES, n = 27) or leg press group (LP, n = 28). Subjects in both the training groups were exposed to training (2-3x/week) for a period of 9 weeks. In the ES group the subjects received neuromuscular electrical stimulation of the anterior thigh muscles. In the LP group the subjects performed strength training on a computer-controlled leg press machine. Before and after the training period, static balance of the subject was tested using a quiet stance task. Average velocity, amplitude and frequency of the center-of-pressure (CoP) were calculated from the acquired force plate signal. The data was statistically tested with analysis of (co)variance and t-tests. The three groups of subjects showed statistically significant differences (p < 0.05) regarding the pre-training vs. post-training changes in CoP velocity, amplitude and frequency. The differences were more pronounced for CoP velocity and amplitude, while they were less evident in case of mean frequency. The mean improvements were higher in the LP group than in the ES group. Our results provide supportive evidence to the existence of the strength-balance relationship. Additionally, results indicate the role of recruiting central processes and activation of functional kinetic chains for the better end effec

Energy Potential of Biomass Sources in Slovakia

Renewable energy has provided many potential benefits, including a reduction in greenhouse gas (GHG) emissions, the diversification of energy supplies, and a reduced dependency on fossil fuel markets (oil and gas in particular). The growth of renewable energy sources (RES) may also have the potential to stimulate employment in the European Union (EU), through the creation of jobs in new green technologies. In this chapter, first, we introduce the information on renewable energy sources, their statistics, and legislation background in Slovakia. In more detail, we further introduce the information on forest and agricultural biomass as a renewable energy source. In the experimental part, we introduce two case studies—the assessment of the potential stock of woody biomass and the determination of energetic properties of woody biomass, i.e., selected fast-growing tree species based on the implementation of laboratory fire tests and calorimetric analyses

Reliability of novel postural sway task test

The purpose of this study was to examine the reliability of parameters obtained from a novel postural sway task test based on body movements controlled by visual feedback. Fifty-nine volunteers were divided into two groups. The first group consisted of young (n = 32, 16 females and 16 males, age: 25.2 3.4 years) and the second group of elderly individuals (n = 27, 17 females and 10 males, age: 75.7 6.9 years). Participants stood in parallel on a computer based stabilographic platform with the feet approximately a shoulder width apart, the toes slightly pointing outwards, the hands placed on the hips. The computer screen was placed approximately 1.5 meter from the platform at a height of subjects eyes. An instantaneous visual feedback of participants centre of pressure (COP) was given in a form of a blue cross visible on the screen. Participants were instructed to keep the blue cross driven by movements of their hips as close as possible to a predefined curve flowing on the screen. Out of the 6 parameters studied, only the average distance of COP from the curve line and the sum of the COP crossings through the curve line showed high reliability. Correlation between these two highly reliable parameters was -0.89. There was also a statistical difference (p<0.001) between young and elderly in both the average distance of COP from the curve line and the sum of the COP crossings through the curve. To conclude, the novel postural sway task provides a simple tool with relatively low time burden needed for testing. The suggested output parameters measured are highly reliable and easy to interpre

Electrical stimulation counteracts muscle atrophy associated with aging in humans

Functional and structural muscle decline is a major problem during aging. Our goal was to improve in old subjects quadriceps m. force and mobility functional performances (stair test, chair rise test, timed up and go test) with neuromuscular electrical stimulation (9 weeks, 2-3times/week, 20-30 minutes per session). Furthermore we performed histological and biological molecular analyses of vastus lateralis m. biopsies. Our findings demonstrate that electrical stimulation significantly improved mobility functional performancies and muscle histological characteristics and molecular markers

Long-term high-level exercise promotes muscle reinnervation with age.

The histologic features of aging muscle suggest that denervation contributes to atrophy, that immobility accelerates the process, and that routine exercise may protect against loss of motor units and muscle tissue. Here, we compared muscle biopsies from sedentary and physically active seniors and found that seniors with a long history of high-level recreational activity up to the time of muscle biopsy had 1) lower loss of muscle strength versus young men (32% loss in physically active vs 51% loss in sedentary seniors); 2) fewer small angulated (denervated) myofibers; 3) a higher percentage of fiber-type groups (reinnervated muscle fibers) that were almost exclusive of the slow type; and 4) sparse normal-size muscle fibers coexpressing fast and slow myosin heavy chains, which is not compatible with exercise-driven muscle-type transformation. The biopsies from the old physically active seniors varied from sparse fiber-type groupings to almost fully transformed muscle, suggesting that coexpressing fibers appear to fill gaps. Altogether, the data show that long-term physical activity promotes reinnervation of muscle fibers and suggest that decades of high-level exercise allow the body to adapt to age-related denervation by saving otherwise lost muscle fibers through selective recruitment to slow motor units. These effects on size and structure of myofibers may delay functional decline in late aging