Several theoretical studies have predicted that refrigerant mixtures with glides of more than 20 K can yield COP improvements in heat pumps for operating conditions where the temperature difference ...between the heat source and heat sink is large, but experimental validations and quantifications are scarce. The application of high-glide mixtures (>20 K) in industrial heat pumps in the field is, therefore, still hampered by concerns about the behavior and handling of the mixtures. This study experimentally investigates hydrocarbon (HC) mixtures R-290/600 (propane/butane) and R-290/601 (propane/pentane) and compares them to previously tested mixtures of synthetic refrigerants. Comprehensive evaluations are presented regarding COP, compressor performance, pressure drop, heat transfer, and the possibility of inline composition determination. The mixtures were tested over a range of compositions at a source inlet temperature of 60 °C and a sink outlet temperature of 100 °C, with the heat sink and heat source temperature differences controlled to 35 K. R-290/601 at a mass composition of 70%/30% was found as the best mixture with a COP improvement of 19% over R-600 as the best pure fluid. The overall isentropic compressor efficiency was similar for HC and synthetic refrigerants, given equal suction and discharge pressures. Pressure drops in heat exchangers and connecting lines were equal for synthetic and HC mixtures at equal mass flow rates. This allows higher heating capacities of HC mixtures at a given pressure drop (mass flow rate) due to their wider vapor dome. A previously developed evaporator heat transfer correlation for synthetic refrigerant mixtures was applicable to the HC mixtures. A condenser heat transfer correlation previously fitted for synthetic refrigerants performed significantly worse for HC mixtures. Composition determination during operation and without sampling was possible with a deviation of at most 0.05 mass fraction using simple temperature and pressure measurements and REFPROP for thermodynamic property calculations. Overall, high-glide HC mixtures, just like mixtures of synthetic refrigerants, showed significant COP improvements for specific operating conditions despite a decreased heat transfer coefficient. Potential problems like composition shift or poor compressor performance were not encountered. As a next step, testing high-glide mixtures in pilot-plant installations is recommended.
By utilising an asymmetric metallisation scheme to fabricate an AlGaN-based solar-blind metal–semiconductor–metal photodetector, a zero-bias external quantum efficiency (EQE) of 24% for illumination ...at 240 nm wavelength from the substrate side was obtained. Moreover, an asymmetric bias-dependence of dark current and EQE is observed. The EQE saturates at about 38% in reverse direction, whereas in forward direction the presence of an internal gain mechanism is indicated.
Purpose
Expression of the translocator protein (TSPO) is upregulated in activated macrophages/microglia and is considered to be a marker of neuroinflammation. We investigated the novel TSPO ligand
...18
FGE-180 in patients with relapsing–remitting multiple sclerosis (RRMS) to determine the feasibility of
18
FGE-180 PET imaging in RRMS patients and to assess its ability to detect active inflammatory lesions in comparison with the current gold standard, contrast-enhanced magnetic resonance imaging (MRI).
Methods
Nineteen RRMS patients were prospectively included in this study. All patients underwent TSPO genotyping and were classified as high-affinity, medium-affinity or low-affinity binders (HAB/MAB/LAB). PET scans were performed after administration of 189 ± 12 MBq
18
FGE-180, and 60–90 min summation images were used for visual analysis and assessment of standardized uptake values (SUV). The frontal nonaffected cortex served as a pseudoreference region (PRR) for evaluation of SUV ratios (SUVR). PET data were correlated with MRI signal abnormalities, i.e. T2 hyperintensity or contrast enhancement (CE). When available, previous MRI data were used to follow the temporal evolution of individual lesions.
Results
Focal lesions were identified as hot spots by visual inspection. Such lesions were detected in 17 of the 19 patients and overall 89
18
FGE-180-positive lesions were found. TSPO genotyping revealed 11 patients with HAB status, 5 with MAB status and 3 with LAB status. There were no associations between underlying binding status (HAB, MAB and LAB) and the signal intensity in either lesions (SUVR 1.87 ± 0.43, 1.95 ± 0.48 and 1.86 ± 0.80, respectively;
p
= 0.280) or the PRR (SUV 0.36 ± 0.03, 0.40 ± 0.06 and 0.37 ± 0.03, respectively;
p
= 0.990). Of the 89
18
FGE-180-positive lesions, 70 showed CE on MRI, while the remainder presented as T2 lesions without CE. SUVR were significantly higher in lesions with CE than in those without (2.00 ± 0.53 vs. 1.60 ± 0.15;
p
= 0.001). Notably, of 19
18
FGE-180-positive lesions without CE, 8 previously showed CE, indicating that
18
FGE-180 imaging may be able to detect lesional activity that is sustained beyond the blood–brain barrier breakdown.
Conclusion
18
FGE-180 PET can detect areas of focal macrophage/microglia activation in patients with RRMS in lesions with and without CE on MRI. Therefore,
18
FGE-180 PET imaging is a sensitive and quantitative approach to the detection of active MS lesions. It may provide information beyond contrast-enhanced MRI and is readily applicable to all patients.
18
FGE-180 PET imaging is therefore a promising new tool for the assessment of focal inflammatory activity in MS.
The degradation of AlGaN-based metal-semiconductor-metal photodetectors under UV illumination has been studied. Oxidation triggered by the presence of moisture and mobile carriers at the ...semiconductor surface was found to be the degradation mechanism. UVC devices with Al0.5Ga0.5N absorbers show stable performance for more than 1000 h at intensities around 10 mW cm−2 and low dark current when passivated after metallization by SiNx. UVB devices with Al0.25Ga0.75N absorber layers were found to be more sensitive and here additional protection by a thin SiN layer grown in situ in the MOVPE growth chamber against any contamination yielded stable devices. As a result now stable UVB and UVC detectors with high external quantum efficiency, low dark current and no indications for persistent photocurrent are available.
Purpose
Progressive supranuclear palsy (PSP) is primary 4-repeat tauopathy. Evidence spanning from imaging studies indicate aberrant connectivity in PSPs. Our goal was to assess functional ...connectivity network alterations in PSP patients and the potential link between regional tau-burden and network-level functional connectivity using the next-generation tau PET tracer
18
FPI-2620 and resting-state functional MRI (fMRI).
Material and methods
Twenty-four probable PSP patients (70.9 ± 6.9 years, 13 female), including 14 Richardson syndrome (RS) and 10 non-RS phenotypes, underwent
18
FPI-2620 PET/MRI imaging. Distribution volume ratios (DVRs) were estimated using non-invasive pharmacokinetic modeling. Resting-state fMRI was also acquired in these patients as well as in thirteen older non-AD MCI reference group (64 ± 9 years, 4 female). The functional network was constructed using 141 by 141 region-to-region functional connectivity metrics (RRC) and network-based statistic was carried out (connection threshold
p
< 0.001, cluster threshold pFDR < 0.05).
Results
In total, 9870 functional connections were analyzed. PSPs compared to aged non-AD MCI reference group expressed aberrant connectivity evidenced by the significant NBS network consisting of 89 ROIs and 118 connections among them (NBS mass 4226, pFDR < 0.05). Tau load in the right globus pallidus externus (GPe) and left dentate nucleus (DN) showed significant effects on functional network connectivity. The network linked with increased tau load in the right GPe was associated with hyperconnectivity of low-range intra-opercular connections (NBS mass 356, pFDR < 0.05), while the network linked with increased tau load in the left cerebellar DN was associated with cerebellar hyperconnectivity and cortico-cerebellar hypoconnectivity (NBS mass 517, pFDR < 0.05).
Conclusions
PSP patients show altered functional connectivity. Network incorporating deep gray matter structures demonstrate hypoconnectivity, cerebellum hyperconnectivity, while cortico-cortical connections show variable changes. Tau load in the right GPe and left DN is associated with functional networks which strengthen low-scale intra-opercular and intra-cerebellar connections and weaken opercular-cerebellar connections. These findings support the concept of tau load-dependent functional network changes in PSP, by that providing evidence for downstream effects of neuropathology on brain functionality in this primary tauopathy.
Islet transplantation as a biological β-cell replacement therapy has emerged as a promising option for achieving restoration of metabolic control in type 1 diabetes patients. However, partial or ...complete loss of islet graft function occurs in relatively short time (months to few years) after implantation. The high rate of early transplant dysfunction has been attributed to poorly viable and/or functional islets and is mediated by innate inflammatory response at the intravascular (hepatic) transplant site and critical lack of initial nutrient/oxygen supply prior to islet engraftment. In addition, the diabetogenic effect of mandatory immunosuppressive agents, limited control of alloimmunity, and the recurrence of autoimmunity limit the long-term success of islet transplantation. In order to abrogate instant blood-mediated inflammatory reaction and to provide oxygen supply for the islet graft, we have developed an extravascular (subcutaneous) transplant macrochamber (the 'βAir' device). This device contains islets immobilized in alginate, protected from the immune system by a thin hydrophilized teflon membrane impregnated with alginate and supplied with oxygen by daily refueling with oxygen-CO (2) mixture. We have demonstrated successful utilization of the oxygen-refueling macrochamber for sustained islet viability and function as well as immunoprotection after allogeneic subcutaneous transplantation in healthy minipigs. Considering the current limitations of intraportal islet engraftment and the restricted indication for islet transplantation mainly due to necessary immunosuppressive therapy, this work could very likely lead to remarkable improvements in the procedure and moreover opens up further strategies for porcine islet cell xenotransplantation.
Purpose
According to the World Health Organization classification for tumors of the central nervous system, mutation status of the isocitrate dehydrogenase (
IDH
) genes has become a major diagnostic ...discriminator for gliomas. Therefore, imaging-based prediction of
IDH
mutation status is of high interest for individual patient management. We compared and evaluated the diagnostic value of radiomics derived from dual positron emission tomography (PET) and magnetic resonance imaging (MRI) data to predict the
IDH
mutation status non-invasively.
Methods
Eighty-seven glioma patients at initial diagnosis who underwent PET targeting the translocator protein (TSPO) using
18
FGE-180, dynamic amino acid PET using
18
FFET, and T1-/T2-weighted MRI scans were examined. In addition to calculating tumor-to-background ratio (TBR) images for all modalities, parametric images quantifying dynamic
18
FFET PET information were generated. Radiomic features were extracted from TBR and parametric images. The area under the receiver operating characteristic curve (AUC) was employed to assess the performance of logistic regression (LR) classifiers. To report robust estimates, nested cross-validation with five folds and 50 repeats was applied.
Results
TBR
GE-180
features extracted from TSPO-positive volumes had the highest predictive power among TBR images (AUC 0.88, with age as co-factor 0.94). Dynamic
18
FFET PET reached a similarly high performance (0.94, with age 0.96). The highest LR coefficients in multimodal analyses included TBR
GE-180
features, parameters from kinetic and early static
18
FFET PET images, age, and the features from TBR
T2
images such as the kurtosis (0.97).
Conclusion
The findings suggest that incorporating TBR
GE-180
features along with kinetic information from dynamic
18
FFET PET, kurtosis from TBR
T2
, and age can yield very high predictability of
IDH
mutation status, thus potentially improving early patient management.
Flavonoids are polyphenolic compounds that occur ubiquitously in plants. They are discussed to represent cancer preventive food components in a human diet that is rich in fruits and vegetables. To ...understand the molecular basis of the putative anticancer activity of flavonoids, we investigated whether and how the core structure of the flavones, 2-phenyl-4H-1-benzopyran-4-one (flavone) affects proliferation, differentiation, and apoptosis in HT-29 human colon cancer cells. Moreover, the effects of flavone in transformed epithelial cells were compared with those obtained in nontransformed primary mouse colonocytes. Proliferation, differentiation, and apoptosis in transformed as well as nontransformed colon cells were measured by fluorescence-based techniques. Apoptosis was also determined by changes in membrane permeability, FACScan analysis, and detection of DNA fragmentation. Semiquantitative reverse transcription PCR was performed to assess the effects of flavone on transcript levels. Flavone was found to reduce cell proliferation in HT-29 cells with an EC(50) value of 54.8 +/- 1.3 microM and to potently induce differentiation as well as apoptosis. The flavonoid proved to be a stronger apoptosis inducer than the clinically established antitumor agent camptothecin. The effects of flavone in HT-29 cells were associated with changed mRNA levels of cell-cycle- and apoptosis-related genes including cyclooxygenase-2 (COX-2), nuclear transcription factor kappaB (NF-kappaB), and bcl-X(L). Moreover, flavone, but not camptothecin, displayed a high selectivity for the induction of apoptosis and of growth inhibition only in the transformed colonocytes. In conclusion, the plant polyphenol flavone induces effectively programmed cell death, differentiation, and growth inhibition in transformed colonocytes by acting at the mRNA levels of genes involved in these processes. Because these genes play a crucial role in colon carcinogenesis, flavone may prove to be a potent new cytostatic compound with improved selectivity toward transformed cells.
Objectives: To systematically compare two modified Look-Locker inversion recovery (MOLLI) T1 mapping sequences and their impact on (1) myocardial T1 values native, (2) post-contrast and (3) ...extracellular volume (ECV). Methods: 200 patients were prospectively included for 1.5 T CMR for work-up of ischemic or non-ischemic cardiomyopathies. To determine native and post-contrast T1 for ECV calculation, two different T1 mapping MOLLI acquisition schemes, 5(3)3 (designed for native scans with long T1) and 4(1)3(1)2 (designed for post-contrast scans with short T1), were acquired in identical mid-ventricular short-axis slices. Both schemes were acquired in native and post-contrast scans. Results: Datasets from 163 patients were evaluated (age 55 ± 17 years; 38% female). Myocardial T1 native for 5(3)3 was 1017 ± 42 ms vs. 956 ± 40 ms for 4(1)3(1)2, with mean intraindividual difference −61 ms (p < 0.0001). Post-contrast myocardial T1 in patients was similar for both acquisition schemes, with 494 ± 48 ms for 5(3)3 and 490 ± 45 ms for 4(1)3(1)2 and mean intraindividual difference −4 ms. Myocardial ECV for 5(3)3 was 27.6 ± 4% vs. 27 ± 4% for 4(1)3(1)2, with mean difference −0.6 percentage points (p < 0.0001). Conclusions: The T1 MOLLI 5(3)3 acquisition scheme provides a reliable estimation of myocardial T1 for the clinically relevant range of long and short T1 values native and post-contrast. In contrast, the T1 MOLLI 4(1)3(1)2 acquisition scheme may only be used for post-contrast scans according to its designed purpose.
![TSPO PET with [18F]GE-180 s...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1619-7070/small "TSPO PET with [18F]GE-180 sensitively detects focal neuroinflammation in patients with relapsing–remitting multiple sclerosis")
PDF
