Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Experimental Results

Local heat transfer and pressure drop measurements were made during condensation of a nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double-tube condensers. The inner tube was a 19.1mm o.d. corrugated copper tube with soldered wire fins on the outer surface. The outer tubes were smooth tubes with inside diameter D_i of 29.9 and 25.0mm. The pressure drop and the heat transfer coefficient based on the bulk vapor-to-wall temperature difference were considerably smaller for R114/R113 than for R113. The vapor phase mass transfer coefficient β_n was higher for larger test fluid mass velocity G and D_i. At constant values of G and D_i, β_n was higher for larger condensation mass flux. The radial distribution of the vapor temperature was affected by the vapor velocity, becoming flatter at the outer part of the annulus and steeper near the liquid-vapor interface as the vapor velocity increased.蒸気圧縮式ヒートポンプ、冷凍機などの成績係数を向上させるための一方策としてローレンツサイクルが提案され、このサイクルに近づけることのできる非共沸2成分混合冷媒が実用されつつある。しかし、この冷媒が凝縮する際には低沸点蒸気が不凝縮ガスと類似の挙動を示すため、凝縮伝熱性能が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器の性能向上を図るためには、凝縮液膜の熱抵抗と混合気の拡散抵抗の両者を減少させる必要がある。著者らは前提で純冷媒用の伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管環状部における非共沸混合冷媒R114/R113の凝縮実験を行い、圧力降下の摩擦成分は純冷媒に対する実験式で整理できること、凝縮側の熱抵抗にしめる気相の熱抵抗の割合は冷媒流量の増大につれて減少することを示した。そして、混合気相の物質伝達係数を円管上の強制対流凝縮理論から導かれた無次元パラメータを用いて整理した。しかし、より一般性のある整理式を得るためにはフィン形状、内外管径比などの影響を明らかにする必要がある。なお、フロン系非共沸2成分混合冷媒の管内、シェル側あるいは環状部における凝縮については最近多くの実験的研究が報告されているが、混合気相の物質伝達について検討したものは少なく、実験データの蓄積が望まれる。本報では、前報の内管とフィン配列が多少異なる管を内管とし、内径の異なる2種類の平滑管を外管とする水平二重管環状部におけるR114/R113の凝縮実験を行い、前報の結果と比較する。また、混合気相の温度分布測定結果についても述べる

Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Correlation of Frictional Pressure Drop and Vapor Phase Mass Transfer

Frictional pressure gradient and vapor phase mass transfer correlations were developed for condensation of nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double tubes with an enhanced inner tube. The frictional pressure gradient data were correlated fairly well by a previously developed empirical equation for condensation of pure refrigerants. The vapor phase mass transfer correlation was based on the previous results for turbulent flow in smooth and rough tubes with and without surface suction. For given conditions of vapor and tube wall, the heat transfer coefficient can be calculated by using the correlations for the vapor phase mass transfer coefficient and the heat transfer coefficient for the condensate film. The calculated values agree with the measured data to a mean absolute deviation of 14.3%.蒸気圧縮式ヒートポンプ、冷凍機の成績係数向上させることのできる作動媒体として、非共沸2成分混合冷媒が有望視されており、最近その凝縮熱伝達に関する研究が開発に行われている。非共沸2成分混合冷媒が凝縮する際には、低沸点蒸気が不凝縮ガスと類似な挙動を示すため、熱伝達係数が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器については液膜の伝熱促進とともに混合気の物質伝達促進をはかる必要がある。著者らは伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管の環状部における冷媒R11およびR113ならびに非共沸混合冷媒R114/R113の凝縮な関する一連の実験を行い、圧力降下と熱伝達の特性を明らかにした。R114/R113に関する第1報では液膜の伝熱特性がR113の場合と同一であると仮定して、混合気相の物質伝達係数を求め、円管上の強制対流凝縮理論から導かれた無次元パラメータを用いてデータ整理を行った。また、圧力降下の摩擦成分は純冷媒に対する実験式によって良好に整理できることを示した。第2報では、第1報の内管とフィン配列が多少異なる内管を使用し、外管内径を2種類に変化させて混合気相の物質伝達特性をより詳細に調べた。その結果、第1報で得られた物質伝達の式は凝縮質量流束の影響をよく表現するが、質量速度の影響および予測精度に関しては十分でないことが明らかになった。本報では、管内の乱流熱・物質伝達に関する従来の実験および理論解析の結果をもとにして、より一般性のある物質伝達の整理式を導く。また、圧力降下の摩擦成分の整理法についても検討する。なお、記号表中には本報で用いる主な記号のみ列挙する。その他の記号は第2報と同一である

Spinal Metaplastic Meningioma with Osseous Differentiation in the Ventral Thoracic Spinal Canal

Ossified meningioma is classified histologically as a phenotype of metaplastic meningioma, and it is extremely rare. There are only 12 cases involving ossified spinal meningiomas in the literature. We present the case of a 61-year-old female with a primary tumor within the ventral spinal canal at T12. Although we performed a total tumor excision using an ultrasonic bone aspirator, a temporary deterioration of motor evoked potentials (MEPs) was observed during curettage with a Kerrison rongeur. The neurologic findings worsened immediately after surgery. Histologically, the tumor was diagnosed as a metaplastic meningioma with osseous differentiation. In order to avoid spinal cord injury, great care must be taken when removing an ossified meningioma located on the ventral spinal cord

A Sillén Oxyhalide SrBi₃O₄Cl₃ as a Promising Photocatalyst for Water Splitting: Impact of the Asymmetric Structure on Light Absorption and Charge Carrier Dynamics

Bismuth-based oxyhalides with layered Sillén(–Aurivillius) structures have attracted significant attention as photocatalysts. Recent studies have unveiled a part of the structure–property relationship of the materials; however, it has not been fully understood. In the present study, we investigated a Sillén-type oxyhalide SrBi₃O₄Cl₃ with single and double halogen layers. Interestingly, SrBi₃O₄Cl₃ showed a visible light response up to ∼460 nm, whereas SrBiO₂Cl and BiOCl with single and double halogen layers, respectively, did not. Rietveld refinement and STEM-EDX mapping determined the asymmetric Bi occupation in the fluorite [Sr₀.₅Bi₁.₅O₂] layer of SrBi₃O₄Cl₃, which was derived from the coexistence of the halogen layers. DFT calculations and Madelung potential calculations showed that the asymmetric Bi occupation affords both the Bi–Bi interaction across the single halogen layer and the electrostatic destabilization of Cl in the double halogen layer, probably leading to the narrow bandgap of SrBi₃O₄Cl₃. Another merit of possessing the two different halogen layers was revealed by time-resolved microwave conductivity measurements as well as DFT calculations; the spatial separation of the conduction band minimum and valence band maximum based on the coexistence of the halogen layers would promote charge carrier separation. Visible-light-driven Z-scheme water splitting was accomplished using a RuO₂-loaded SrBi₃O₄Cl₃ sample as an O₂-evolving photocatalyst. This study provides another option for engineering band structures and promoting the charge carrier separation of layered oxyhalides for efficient water splitting under visible light

Brain Metastasis from Gastrointestinal Stromal Tumor: A Case Report and Review of the Literature

Metastasis of gastrointestinal stromal tumor (GIST) into the central nervous system is extremely rare. We report a patient with synchronous GIST and brain metastasis. At disease onset, there was left hemiplegia and ptosis of the right eyelids. Resection cytology of the brain tumor was reported as metastasis of GIST. After positron emission tomography examination, another tumor in the small bowel was discovered, which suggested a small bowel GIST associated with intracranial metastasis. Immunohistochemical analysis of the intestinal tumor specimen obtained by double balloon endoscopy showed a pattern similar to the brain tumor, with the tumors subsequently identified as intracranial metastases of jejunal GIST. After surgical resection of one brain tumor, the patient underwent whole brain radiation therapy followed by treatment with imatinib mesylate (Gleevec; Novartis Pharma, Basel, Switzerland). Mutational analysis of the original intestinal tumor revealed there were no gene alterations in KIT or PDGFRα. Since the results indicated the treatment had no apparent effect on either of the tumors, and because ileus developed due to an intestinal primary tumor, the patient underwent surgical resection of the intestinal lesion. However, the patient's condition gradually worsen and she subsequently died 4 months after the initial treatment

Reduced risk of recurrent myocardial infarction in homozygous carriers of the chromosome 9p21 rs1333049 c risk allele in the contemporary percutaneous coronary intervention era: A prospective observational study

Hara M, Sakata Y, Nakatani D on behalf of the OACIS Investigators, et al. Reduced risk of recurrent myocardial infarction in homozygous carriers of the chromosome 9p21 rs1333049 C risk allele in the contemporary percutaneous coronary intervention era: a prospective observational study. BMJ Open 2014;4:e005438. doi: 10.1136/bmjopen-2014-00543

Risk prediction models for dementia constructed by supervised principal component analysis using miRNA expression data

Alzheimer’s disease (AD) is the most common subtype of dementia, followed by Vascular Dementia (VaD), and Dementia with Lewy Bodies (DLB). Recently, microRNAs (miRNAs) have received a lot of attention as the novel biomarkers for dementia. Here, using serum miRNA expression of 1,601 Japanese individuals, we investigated potential miRNA biomarkers and constructed risk prediction models, based on a supervised principal component analysis (PCA) logistic regression method, according to the subtype of dementia. The final risk prediction model achieved a high accuracy of 0.873 on a validation cohort in AD, when using 78 miRNAs: Accuracy = 0.836 with 86 miRNAs in VaD; Accuracy = 0.825 with 110 miRNAs in DLB. To our knowledge, this is the first report applying miRNA-based risk prediction models to a dementia prospective cohort. Our study demonstrates our models to be effective in prospective disease risk prediction, and with further improvement may contribute to practical clinical use in dementia

Cross-ancestry genome-wide analysis of atrial fibrillation unveils disease biology and enables cardioembolic risk prediction

心房細動の遺伝的基盤を解明 --大規模ゲノムデータによる病態解明と遺伝的リスクスコア構築--. 京都大学プレスリリース. 2023-01-20.Atrial fibrillation (AF) is a common cardiac arrhythmia resulting in increased risk of stroke. Despite highly heritable etiology, our understanding of the genetic architecture of AF remains incomplete. Here we performed a genome-wide association study in the Japanese population comprising 9, 826 cases among 150, 272 individuals and identified East Asian-specific rare variants associated with AF. A cross-ancestry meta-analysis of >1 million individuals, including 77, 690 cases, identified 35 new susceptibility loci. Transcriptome-wide association analysis identified IL6R as a putative causal gene, suggesting the involvement of immune responses. Integrative analysis with ChIP-seq data and functional assessment using human induced pluripotent stem cell-derived cardiomyocytes demonstrated ERRg as having a key role in the transcriptional regulation of AF-associated genes. A polygenic risk score derived from the cross-ancestry meta-analysis predicted increased risks of cardiovascular and stroke mortalities and segregated individuals with cardioembolic stroke in undiagnosed AF patients. Our results provide new biological and clinical insights into AF genetics and suggest their potential for clinical applications