Numerical and Experimental Studies of a Two-Stage Pulse Tube Cryocooler Working Around 20K

The absence of cold moving parts in pulse tube cryocoolers has allowed it to has advantages of low vibration, high reliability, and low cost, which can meet requirements of many high-temperature superconducting applications. However, Stirling type pulse tube cryocoolers working around 20 K are still not commerally aviable due to low efficiency and low power density. With Comprehensive consideration of higher specific power of whole system and performance in relative lower working temperature of 20K, this paper proposes a thermally coupled two stage co-axial pulse tube cryocooler to pursue several watts cooling power around 20K.At the first stage, an ultrahigh frequency operation of 100 Hz is utilized to precoo the second stage for seeking a higher power density. At the second stage, a relative lower frequency of around 30Hz is used for improving system efficiency. Firstly, a quasi-one-dimensional numeric model based on the thermoacoustic theory is used to optimize the operating and structure parameters and some simulation results are briefly introduced. The influences of different phase shifters such as doule-inlet and room temperature displacers are also also investigated numerically. Then, in the experiments, typically a lowest no-load temperature of 13 K has been obtained and the cooling power at 20K was 2 W with an input electric power of 500 W, which mean an efficiency of 5.6% of Carnot. The influences of different operating and structure parameters such as frequency, mean pressure and precooling temperature were also investigated numerically and experimentally

Development of a High Efficiency Pulse Tube Cryocooler Using Room Temperature Displacers for HTS Applications

The compact and high efficiency coolers working in the liquid nitrogen temperature region play an important role in HTS Applications. Stirling type pulse tube cooler servers as a promising candidate for cooling HTS devices for its advantages such as low vibration, high reliability and low cost due to absence of the moving parts in the cold head compared with traditional coolers. However, phase shift mechanisms used in a conventional pulse tube cryocooler need to dissipate expansion power at the ambient end of the pulse tube, which leads to a lower thermodynamic efficiency than that of a Stirling cryocooler. In order to improve the efficiency and obtain a reliable cryocooler system, this article presents a pulse tube cryocooler which uses room temperature displacers as the phase shifter, which aims at providing more than 10 W cooling power at 77 K. The cryocooler with a model number of TC4189 consists of linear compressor, coaxial pulse tube and two dual-opposed ambient displacers. High pressure ratio and high frequency operation are used to increase the power density. The whole system has a total mass of 4.3 kg. At an optimum working point, a lowest no-load temperature of 44 K has been obtained and the cooling power at 80K reaches 15 W with an input electric power of 240 W, which means an efficiency of 17.1% of Carnot. The influence of displacers operating and structural parameters were investigated through simulations and experiments

Alterations in intra- and inter-network connectivity associated with cognition impairment in insulinoma patients

ObjectiveCognitive dysfunction is common in insulinoma patients, but the underlying neural mechanisms are less well understood. This study aimed to explore the alterations of intra- and inter-network connectivity patterns associated with patients with insulinoma.MethodsResting-state fMRI were acquired from 13 insulinoma patients and 13 matched healthy controls (HCs). Group Independent component analysis (ICA) was employed to capture the resting-state networks (RSNs), then the intra- and inter-network connectivity patterns, were calculated and compared. Montreal Cognitive Assessment (MoCA) was used to assess the cognitive function. The relationship between connectivity patterns and MoCA scores was also examined.ResultsInsulinoma patients performed significantly worse on MoCA compared to HCs. The intra-network connectivity analysis revealed that patients with insulinoma showed decreased connectivity in the left medial superior frontal gyrus within anterior default mode network (aDMN), and decreased connectivity in right lingual gyrus within the visual network (VN). The intra-network connectivity analysis showed that patients with insulinoma had an increased connectivity between the inferior-posterior default mode network (ipDMN) and right frontoparietal network (rFPN) and decreased connectivity between the ipDMN and auditory network (AUN). There was a significant negative correlation between the ipDMN-rFPN connectivity and MoCA score.ConclusionThis study demonstrated significant abnormalities in the intra- and inter-network connectivity in patients with insulinoma, which may represent the neural mechanisms underlying the cognitive impairment in insulinoma patients

Tauroursodeoxycholic acid: a bile acid that may be used for the prevention and treatment of Alzheimer’s disease

Alzheimer’s disease (AD) is a prevalent neurodegenerative disease that has become one of the main factors affecting human health. It has serious impacts on individuals, families, and society. With the development of population aging, the incidence of AD will further increase worldwide. Emerging evidence suggests that many physiological metabolic processes, such as lipid metabolism, are implicated in the pathogenesis of AD. Bile acids, as the main undertakers of lipid metabolism, play an important role in the occurrence and development of Alzheimer’s disease. Tauroursodeoxycholic acid, an endogenous bile acid, has been proven to possess therapeutic effects in different neurodegenerative diseases, including Alzheimer’s disease. This review tries to find the relationship between bile acid metabolism and AD, as well as explore the therapeutic potential of bile acid taurocursodeoxycholic acid for this disease. The potential mechanisms of taurocursodeoxycholic acid may include reducing the deposition of Amyloid-β protein, regulating apoptotic pathways, preventing tau hyperphosphorylation and aggregation, protecting neuronal synapses, exhibiting anti-inflammatory properties, and improving metabolic disorders. The objective of this study is to shed light on the use of tauroursodeoxycholic acid preparations in the prevention and treatment of AD, with the aim of identifying effective treatment targets and clarifying various treatment mechanisms involved in this disease

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat