Cooling a low noise amplifier with a micromachined cryogenic cooler

The sensitivity of antenna systems increases with increasing active area, but decreases at higher noise figure of the low-noise amplifier (LNA). Cooling the LNA locally results in significant improvement in the gain and in lowering the noise figure of the LNA. Micromachined Joule-Thomson (JT) coolers can provide a cryogenic environment to the LNA. They are attractive because they have no cold moving parts and can be scaled down to match the size and the power consumption of LNAs. The performance of a LNA mounted on a JT microcooler with dimensions of 60.0 × 9.5 × 0.72 mm3 is reported in this paper. The microcooler is operated with nitrogen gas and the cold-end temperature is controlled at 115 K. The measured net cooling power of the microcooler is about 43 mW when the LNA is not operating. The power dissipation of the LNA is 26 mW, with a supply voltage of 2 V. At room temperature the noise figure of the LNA is 0.83 dB and the gain lies between 17.9 and 13.1 dB, in the frequency range of 0.65 and 1.05 GHz. Upon cooling to 115 K, the noise figure drops to 0.50 dB and the increase in gain varies in the range of 0.6–1.5 d

Severe COVID-19 and chronic kidney disease: bidirectional mendelian randomization study

Abstract Traditional observational research has revealed an association between severe COVID-19 and chronic kidney disease (CKD). It is unclear whether there is a causative connection between them. Our goal was to determine whether genetically predicted CKD is associated with the risk of critical COVID-19. We aimed to investigate potential underlying genetic mechanisms that could explain this relationship, paving the way for personalized risk assessment and targeted interventions to mitigate the effects of COVID-19 on individuals with CKD. Using combined data from a GWAS on European ancestry and CKD (n = 117,165) and critical COVID-19 (n = 1,059,456), bidirectional Mendelian randomization analysis was performed. Four single nucleotide polymorphisms (SNPs) were chosen from the genome as CKD instrumental variables (IVs). In addition to MR‒Egger regression, weighted mode approaches, and weighted medians, we employed the inverse-variance weighted estimate as our primary analytical method. A significant association of CKD with critical COVID-19 (OR = 1.28, 95% confidence interval [CI]: 1.04–1.58, p = 0.01811) was found. However, using 6 genome-wide significant SNPs as IVs for critical COVID‐19, we could not discover a meaningful correlation between severe COVID‐19 and CKD (OR = 1.03, 95% CI: 0.96–1.10, p = 0.3947). We found evidence to support a causal relationship between CKD and severe COVID-19 in European population. This underscores the need for comprehensive monitoring and specialized care strategies for individuals with CKD to mitigate the heightened risk and severity of COVID-19 complications

Optimization design of microchannel heat sink geometry for high power laser mirror

Microchannel heat sink for high power laser mirror with water cooling was analyzed as a function of microchannel geometry and operation parameters. A comparative analysis of the thermal deformation on the mirror surface without cooling and that with cooling revealed that the maximal thermal deformation on the mirror surface could decrease from about 0.115 mu m to around 0.040 mu m under the laser power of 200 W/cm(2) by using microchannel heat sink designed. In order to enhance the performance of microchannel heat sink, the effects of channel width, channel depth, fin width, mirror thickness and cooling region were investigated. The results indicated that the heat transfer performance of the microchannel heat sink could be further improved by narrow and deep channel, narrow fin, thin mirror and large cooling region. (C) 2010 Elsevier Ltd. All rights reserved

Predictive biomarkers for immune-related adverse events in cancer patients treated with immune-checkpoint inhibitors

Abstract Purpose The objective of this study was to identify potential predictors of immune-related adverse events (irAEs) in cancer patients receiving immune checkpoint inhibitor therapy among serum indexes, case data, and liquid biopsy results. Methods We retrospectively analyzed 418 patients treated with anti-programmed cell death 1(PD-1)/PD-1 ligand (PD-L1) inhibitors from January 2018 to May 2022 in our cancer center. We identified factors that correlated with the occurrence of irAEs and evaluated associations between irAEs and anti-PD-1/PD-L1 inhibitor responses. Results The incidence of irAEs was 42.1%, and pneumonitis (9.1%), thyroid toxicity (9.1%), cardiotoxicity (8.1%), and dermatologic toxicity (6.9%) were the four most common irAEs. Multivariate logistic analysis identified female sex, antibiotic use, higher post-treatment neutrophil-to-lymphocyte ratio (NLR), and higher baseline circulating tumor cell (CTC) level, as predictive biomarkers for the occurrence of irAEs. A lower baseline prognostic nutritional index (PNI), body mass index (BMI) ≥ 25 kg/m2, and higher post-treatment lactate dehydrogenase (LDH) level were predictive factors for more severe irAEs (higher severity grade). Patients without irAEs had better overall survival than those with irAEs. Specifically, pneumonitis and cardiotoxicity were found to be significant predictors of poor prognosis in the irAE subgroup with different organ-related irAEs. Low-dose steroid (dexamethasone 10 mg) treatment had no significant effect on outcomes. Conclusions Gender, antibiotic use, post-treatment NLR, and baseline CTC level are potential predictive biomarkers of irAEs, while baseline PNI, BMI, and post-treatment LDH may predict the severity of irAEs. The predictive effect of irAE occurrence on survival benefit may depend on the type of irAE

Research on Quantitative Demand of Underground Space Development for Urban Rail Transit Station Areas: A Case Study of Metro Line 1 in Xuzhou, China

Abstract Under the background of the rapid development of urban rail transit in China, the development demand of urban underground space has also greatly increased especially in the rail transit station areas. In this paper, taking the high-speed railway station area of Xuzhou Metro Line 1 as an example, the underground space development demand evaluation is conducted by considering the principle of urban underground space stock planning, the local underground space development conditions, as well as the special planning of the local urban constructions. Using the Analytic Hierarchy Process (AHP), a specific weight indicator scale is employed after the rationality of different weight indicator scales being compared. And then the weight indicator of different function types, i.e., commercial, parking, road, etc., are calculated and laterly utilized to forecast the recent development demand of underground space in the station area. Moreover, the steps to forecast the underground space development demand in rail transit station area are proposed, which can provide a reference for the forecasting of underground space development demand in the urban rail transit station areas

Performance comparison of sorption compressors for methane using metal-organic frameworks and activated carbon as adsorbents

Many optical devices can benefit from cryogenic cooling; however, the resolution of these devices suffers from microvibration from mechanical cryocoolers. Unlike mechanical cryocoolers, sorption cryocoolers do not have any active moving parts and are essentially vibration-free. Sorption cryocoolers are thermally driven and their performance is highly determined by the properties of the adsorbents employed in the compressors. In this study, the thermodynamic and dynamic modelling of sorption compressors adopting Saran activated carbon, MOF-5 and HKUST-1 metal–organic frameworks as adsorbents are conducted to find suitable adsorbents to realize efficient compression. It is found that a sorption compressor with MOF-5 as the adsorbent has the worst performance. Saran carbon has the highest mass-flow rate. And whether HKUST-1 or Saran carbon has higher efficiency depends on the operating conditions. The effects of heat sink temperature and heater power on the performance of sorption compressors are also investigated. The analysis method can be employed to choose suitable sorbent materials and operating conditions when designing sorption compressors

Characterization of a thermoelectric/Joule–Thomson hybrid microcooler

Micromachined Joule–Thomson (JT) coolers are attractive for cooling small electronic devices. However, microcoolers operated with pure gases, such as nitrogen gas require high pressures of about 9 MPa to achieve reasonable cooling powers. Such high pressures severely add complexity to the development of compressors. To overcome this disadvantage, we combined a JT microcooler with a thermoelectric (TE) pre-cooler to deliver an equivalent cooling power with a lower pressure or, alternatively, a higher cooling power when operating with the same pressure. This hybrid microcooler was operated with nitrogen gas as the working fluid at a low pressure of 0.6 MPa. The cooling power of the microcooler at 101 K operating with a fixed high pressure of 8.8 MPa increased from 21 to 60 mW when the precooling temperature was reduced by the thermoelectric cooler from 295 to 250 K. These tests were simulated using a dynamic numerical model and the accuracy of the model was verified through the comparison between experimental and simulation results. Based on the model, we found the high pressure of the microcooler can be reduced from 8.8 to 5.5 MPa by lowering the precooling temperature from 295 to 250 K. Moreover, the effect of TE cooler position on the performance of the hybrid microcooler was evaluated through simulation analysis