Investigation of Application of Suction Line Heat Exchanger in R290 Air Conditioner with Small Diameter Copper Tube

R290 is a potential refrigerant replacing R22 because of its zero Ozone Depletion Potential (ODP) and virtually zero Global Warming Potential (GWP). However, R290 is flammable and requires excellent containment to avoid leakage and reduce the risk of fire. The use of small diameter copper tube (5 mm or even smaller) is an effective way to reduce refrigerant charge and thus reduce the risk of fire in the event of a refrigerant leak. However, employing small diameter copper tube will increase pressure drop and consequently reduce system performance. A suction line heat exchanger which employs the low temperature refrigerant in suction line to cool down the refrigerant before expansion value is a potential solution to improve system performance because R290 has low discharge temperature compared with HFC refrigerants (e.g. R22, R410A). This paper presents an investigation of application of a suction line heat exchanger in an R290 air conditioner with small diameter copper tube. A theoretical analysis is proposed at first to investigate the effect of the suction line heat exchanger on capacity and system energy efficiency under variable evaporating and cooling temperatures. A prototype R290 air conditioner with and without a suction line heat exchanger is tested in order to explore the effect of a suction line heat exchanger on system performance and refrigerant charge in real working conditions. Finally, a refrigerant circuit solution for heat pump air conditioners is proposed. The results of theoretical analysis indicate that the capacity and system energy efficiency increase linearly with the heat exchange of the suctionline heat exchanger, and the suction line heat exchanger can improves capacity by up to 12% and system energy efficiency by up to 4% under both cooling and heating modes. This is because the suction line heat exchanger increases the sub-cooling but has less impact on compressor power due to good thermal properties of R290. Further, the evaporating and condensation temperature have insignificant impact on the performance of suction line heat exchanger. The experimental results show that the suction line heat exchanger improves the cooling capacity and system efficiency by 5.3% and 4.5%, respectively. These results agree well with that of the system analysis. The sub-cooling temperature increases 10.2o C and the discharge temperature increases 25.4o C. Further, the suction line heat exchanger reduces the refrigerant charge by as much as 6%. This is because suction line heat exchanger increases the discharge temperature, and thus the superheat region of the condenser increases resulting in less refrigerant in the condenser. Overall, the use of a suction line heat exchanger in a system with small diameter copper tube improves the performance of R290 and more importantly reduces the refrigerant charge

A comparison of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion: a literature review and meta-analysis

BACKGROUND: We compared the perioperative results and complications associated with PLIF and TLIF, and collected evidence for choosing the better fusion method. METHODS: A literature survey of the MEDLINE and EMBASE databases identified 7 comparative observational studies that met our inclusion criteria. Checklists by Cowley were used to evaluate the risk of bias of the included studies. A database including patient demographic information, perioperative results, and complications was established. The summary odds ratio and weighed mean difference with 95% confidence interval were calculated with a random-effects model. RESULTS: We found that PLIF had a higher complication rate (P <0.00001), and TLIF reduced the rate of durotomy (P = 0.01). No statistical difference was found between the two groups with regard to clinical satisfaction (P = 0.54), blood loss (P = 0.14), vertebral root injury (P = 0.08), graft malposition (P = 0.06), infection (P = 0.36), or rate of radiographic fusion (P = 0.27). The evidence indicated that PLIF required longer operative time (P = 0.03). CONCLUSIONS: The evidence indicated that TLIF could reduce the complication rate and durotomy. Neither TLIP nor PLIF was found superior in terms of clinical satisfaction or radiographic fusion rate. PLIF might result in longer time in surgery. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2474-15-367) contains supplementary material, which is available to authorized users

SecureBoost Hyperparameter Tuning via Multi-Objective Federated Learning

SecureBoost is a tree-boosting algorithm leveraging homomorphic encryption to protect data privacy in vertical federated learning setting. It is widely used in fields such as finance and healthcare due to its interpretability, effectiveness, and privacy-preserving capability. However, SecureBoost suffers from high computational complexity and risk of label leakage. To harness the full potential of SecureBoost, hyperparameters of SecureBoost should be carefully chosen to strike an optimal balance between utility, efficiency, and privacy. Existing methods either set hyperparameters empirically or heuristically, which are far from optimal. To fill this gap, we propose a Constrained Multi-Objective SecureBoost (CMOSB) algorithm to find Pareto optimal solutions that each solution is a set of hyperparameters achieving optimal tradeoff between utility loss, training cost, and privacy leakage. We design measurements of the three objectives. In particular, the privacy leakage is measured using our proposed instance clustering attack. Experimental results demonstrate that the CMOSB yields not only hyperparameters superior to the baseline but also optimal sets of hyperparameters that can support the flexible requirements of FL participants.Comment: FL-ICAI'2

A Guanosine-Quadruplex Hydrogel as Cascade Reaction Container Consuming Endogenous Glucose for Infected Wound Treatment-A Study in Diabetic Mice

Diabetic foot ulcers infected with antibiotic‐resistant bacteria form a severe complication of diabetes. Antimicrobial‐loaded hydrogels are used as a dressing for infected wounds, but the ongoing rise in the number of antimicrobial‐resistant infections necessitates new, nonantibiotic based designs. Here, a guanosine‐quadruplex (G(4))‐hydrogel composed of guanosine, 2‐formylphenylboronic acid, and putrescine is designed and used as a cascade‐reaction container. The G(4)‐hydrogel is loaded with glucose‐oxidase and hemin. The first cascade‐reaction, initiated by glucose‐oxidase, transforms glucose and O(2) into gluconic acid and H(2)O(2). In vitro, this reaction is most influential on killing Staphylococcus aureus or Pseudomonas aeruginosa in suspension, but showed limited killing of bacteria in biofilm‐modes of growth. The second cascade‐reaction, however, transforming H(2)O(2) into reactive‐oxygen‐species (ROS), also enhances killing of biofilm bacteria due to hemin penetration into biofilms and interaction with eDNA G‐quadruplexes in the biofilm matrix. Therewith, the second cascade‐reaction generates ROS close to the target bacteria, facilitating killing despite the short life‐time of ROS. Healing of infected wounds in diabetic mice proceeds faster upon coverage by these G(4)‐hydrogels than by clinically common ciprofloxacin irrigation. Moreover, local glucose concentrations around infected wounds decrease. Concluding, a G(4)‐hydrogel loaded with glucose‐oxidase and hemin is a good candidate for infected wound dressings, particularly in diabetic patients

Salt Freeze-Thaw Damage Characteristics of Concrete based on Computed Tomography

Freeze–thaw damage and salt erosion are important factors that influence the durability of concrete. In this study, degradation laws of concrete in salt freeze–thaw environment were discussed from the microscopic perspective based on the 3D reconstruction of computed tomography images. A damage model based on concrete aggregate volume and porosity was constructed. Furthermore, the main causes of concrete degradation in the salt freeze–thaw environment were analyzed. Results reveal that, with the increase in salt freeze–thaw cycles, the damage of concrete intensifies gradually, and the uniaxial compressive strength declines steadily. Concrete damages have two causes, namely, changes in concrete porosity and variations in concrete aggregate volume. Damages caused by aggregate volume changes are divided into frost heaving and peeling. In accordance with the constructed damage model, the porosity of concrete materials changes slightly, whereas concrete aggregate volume varies significantly. Aggregate volume changes are the main causes of intensified concrete damages and decreased compressive strength. Research conclusions provide theoretical references to disclosing microscopic damage mechanism of concrete in the salt freeze–thaw environment

Expression and clinical significance of geranylgeranyl diphosphate synthase1 (GGPS1) in lung squamous cell carcinoma

Objective·To investigate the expression and clinical significance of geranylgeranyl diphosphate synthase1 (GGPS1) in lung squamous cell carcinoma (LUSC) by bioinformatics and immunohistochemistry.Methods·Firstly, the transcriptome data of LUSC tissues and paired normal tissues were downloaded from UCSC Xena platform. The data were standardized and differentially expressed by R language, and verified by UALCAN database. UALCAN and LinkedOmics databases were used to analyze the relationship between GGPS1 expression and clinicopathological features in LUSC patients. The Kaplan-Meier Plotter database was used to explore the effect of GGPS1 expression on prognosis in LUSC patients. The least absolute shrinkage and selection operator (LASSO) regression analyses were applied to screen gene correlation coefficients and risk scores. The diagnostic value of GGPS1 for LUSC was evaluated by nomogram and calibration curve. The protein-protein interaction (PPI) network of GGPS1 was constructed by using STRING and GeneMANIA databases. R language was used to select the differential genes related to GGPS1, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed. The expression of GGPS1 in LUSC patients was detected by immunohistochemistry, and its correlation with clinicopathological features and prognosis was analyzed.Results·Through the TIMER2.0 database, it was found that GGPS1 expression was increased in most tumors and was highly expressed in LUSC. The expression of GGPS1 in LUSC was higher than that in adjacent tissues in UCSC Xena and UALCAN databases (both P<0.05). It was found that the expression level of GGPS1 was higher in patients with late stage in UALCAN and LinkedOmics databases, and the overall survival (OS) of LUSC patients with high expression of GGPS1 was shorter (P<0.05) in the Kaplan-Meier Plotter database. Assessment of LUSC patients based on LASSO regression had good risk prediction efficacy. Constructing an individualised prediction model for LUSC patients has the best prediction accuracy. The results of GO and KEGG showed that GGPS1-related genes were mainly related to protein metabolism, regulation of lipid and cholesterol metabolism, nicotine addiction, phosphatidylinositol3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), peroxisome proliferator-activated receptors (PPAR) signaling pathway and so on. The metabolic function of GGPS1 may promote tumorigenesis. The results of immunohistochemistry showed that GGPS1 was mainly located in the cytoplasm, and the expression of GGPS1 in LUSC tissues was higher than that in adjacent tissues (P<0.05). The high expression of GGPS1 was related to tumor size, lymph node metastasis and TNM stage of LUSC patients (all P<0.05), and the OS of patients with high expression of GGPS1 was significantly shorter than that of patients with low expression (P=0.000). Multivariate Cox regression analysis suggested that GGPS 1 could be used as an independent prognostic factor for LUSC.Conclusion·Compared with normal lung tissue, the expression of GGPS1 in LUSC is significantly increased, especially in patients with large tumor volume, positive lymph node metastasis and advanced stage. GGPS1 overexpression is an independent predictor of poor prognosis in LUSC patients. GGPS1 is expected to become a new molecular target for the diagnosis, treatment and prevention of LUSC

Magnify is a universal molecular anchoring strategy for expansion microscopy

Expansion microscopy enables nanoimaging with conventional microscopes by physically and isotropically magnifying preserved biological specimens embedded in a crosslinked water-swellable hydrogel. Current expansion microscopy protocols require prior treatment with reactive anchoring chemicals to link specific labels and biomolecule classes to the gel. We describe a strategy called Magnify, which uses a mechanically sturdy gel that retains nucleic acids, proteins and lipids without the need for a separate anchoring step. Magnify expands biological specimens up to 11 times and facilitates imaging of cells and tissues with effectively around 25-nm resolution using a diffraction-limited objective lens of about 280 nm on conventional optical microscopes or with around 15 nm effective resolution if combined with super-resolution optical fluctuation imaging. We demonstrate Magnify on a broad range of biological specimens, providing insight into nanoscopic subcellular structures, including synaptic proteins from mouse brain, podocyte foot processes in formalin-fixed paraffin-embedded human kidney and defects in cilia and basal bodies in drug-treated human lung organoids

Metabolomic profiles of bovine mammary epithelial cells stimulated by lipopolysaccharide

Bovine mammary epithelial cells (bMECs) are the main cells of the dairy cow mammary gland. In addition to their role in milk production, they are effector cells of mammary immunity. However, there is little information about changes in metabolites of bMECs when stimulated by lipopolysaccharide (LPS). This study describes a metabolomics analysis of the LPS-stimulated bMECs to provide a basis for the identification of potential diagnostic screening biomarkers and possible treatments for bovine mammary gland inflammation. In the present study, bMECs were challenged with 500 ng/mL LPS and samples were taken at 0 h, 12 h and 24 h post stimulation. Metabolic changes were investigated using high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF MS) with univariate and multivariate statistical analyses. Clustering and metabolic pathway changes were established by MetaboAnalyst. Sixty-three differential metabolites were identified, including glycerophosphocholine, glycerol-3-phosphate, L-carnitine, L-aspartate, glutathione, prostaglandin G2, α-linolenic acid and linoleic acid. They were mainly involved in eight pathways, including D-glutamine and D-glutamic acid metabolism; linoleic acid metabolism; α-linolenic metabolism; and phospholipid metabolism. The results suggest that bMECs are able to regulate pro-inflammatory, anti-inflammatory, antioxidation and energy-producing related metabolites through lipid, antioxidation and energy metabolism in response to inflammatory stimuli

Endogenous PTH Deficiency Impairs Fracture Healing and Impedes the Fracture-Healing Efficacy of Exogenous PTH(1-34)

Although the capacity of exogenous PTH1-34 to enhance the rate of bone repair is well established in animal models, our understanding of the mechanism(s) whereby PTH induces an anabolic response during skeletal repair remains limited. Furthermore it is unknown whether endogenous PTH is required for fracture healing and how the absence of endogenous PTH would influence the fracture-healing capacity of exogenous PTH.Closed mid-diaphyseal femur fractures were created and stabilized with an intramedullary pin in 8-week-old wild-type and Pth null (Pth(-/-)) mice. Mice received daily injections of vehicle or of PTH1-34 (80 µg/kg) for 1-4 weeks post-fracture, and callus tissue properties were analyzed at 1, 2 and 4 weeks post-fracture. Cartilaginous callus areas were reduced at 1 week post-fracture, but were increased at 2 weeks post-fracture in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice respectively. The mineralized callus areas, bony callus areas, osteoblast number and activity, osteoclast number and surface in callus tissues were all reduced in vehicle-treated and PTH-treated Pth(-/-) mice compared to vehicle-treated and PTH-treated wild-type mice, but were increased in PTH-treated wild-type and Pth(-/-) mice compared to vehicle-treated wild-type and Pth(-/-) mice.Absence of endogenous PTH1-84 impedes bone fracture healing. Exogenous PTH1-34 can act in the absence of endogenous PTH but callus formation, including accelerated endochondral bone formation and callus remodeling as well as mechanical strength of the bone are greater when endogenous PTH is present. Results of this study suggest a complementary role for endogenous PTH1-84 and exogenous PTH1-34 in accelerating fracture healing