The Ordos Basin is a large‐scale sedimentary basin in northwestern China. The hydrostratigraphic units from bottom to top are pre‐Cambrian metamorphic rocks, Lower Paleozoic carbonate rocks, Upper ...Paleozoic to Mesozoic clastic rocks and Cenozoic deposits. The total thickness is up to 6000 m. Three groundwater systems are present in the Ordos Basin, based on the geological settings, i.e. the karst groundwater system, the Cretaceous clastic groundwater system and the Quaternary groundwater system. This paper describes systematically the groundwater flow patterns of each system and overall assessment of groundwater resources.
Purpose:
In this study, the authors investigated the feasibility of a dual resolution volume-of-interest (VOI) cone beam breast CT technique and compared two implementation approaches in terms of ...dose saving and scatter reduction.
Methods:
With this technique, a lead VOI mask with an opening is inserted between the x-ray source and the breast to deliver x-ray exposure to the VOI while blocking x rays outside the VOI. A CCD detector is used to collect the high resolution projection data of the VOI. Low resolution cone beam CT (CBCT) images of the entire breast, acquired with a flat panel (FP) detector, were used to calculate the projection data outside the VOI with the ray-tracing reprojection method. The Feldkamp–Davis–Kress filtered backprojection algorithm was used to reconstruct the dual resolution 3D images. Breast phantoms with
180
μ
m
and smaller microcalcifications (MCs) were imaged with both FP and FP-CCD dual resolution CBCT systems, respectively. Two approaches of implementing the dual resolution technique, breast-centered approach and VOI-centered approach, were investigated and evaluated for dose saving and scatter reduction with Monte Carlo simulation using a GEANT4 package.
Results:
The results showed that the breast-centered approach saved more breast absorbed dose than did VOI-centered approach with similar scatter reduction. The MCs in fatty breast phantom, which were invisible with FP CBCT scan, became visible with the FP-CCD dual resolution CBCT scan.
Conclusions:
These results indicate potential improvement of the image quality inside the VOI with reduced breast dose both inside and outside the VOI.
Purpose: To investigate the environmental, immune, and inflammatory factors associated with chronic obstructive pulmonary disease (COPD) in middle-aged and older Chinese individuals. Patients and ...Methods: A community-based case--control study was conducted among 471 patients with COPD and 485 controls. The information on COPD of the participants was collected through face-to-face interviews, and serum samples were measured at the laboratory. The main risk factors for COPD were analyzed using principal component analysis (PCA) and logistic regression. Results: Nine hundred and fifty-six respondents were included in the analysis. The results of the PCA-logistic regression analysis showed significant differences in the environmental factors, medical history, and serum C-reactive protein (CRP) levels between patients and controls. COPD was markedly more usual in those with smoking index >200 (OR, 1.42; 95% CI, 1.28-1.57); exposure to outdoor straw burning (OR, 1.64; 95% CI, 1.47-1.83); use of coal, wood, and straw indoors (OR, 2.31; 95% CI, 1.92-2.78); history of respiratory disease and coronary heart disease (OR, 3.58; 95% CI, 3.12-4.10), congestive heart failure (OR, 1.23; 95% CI, 1.09-1.38), and cerebrovascular disease (OR, 1.15; 95% CI,1.02-1.31); and higher serum level of CRP (OR, 1.20; 95% CI, 1.11-1.30). Compared to the logistic regression analysis, PCA logistic regression analysis identified more important risk factors for COPD. Conclusion: PCA-logistic regression analysis was first utilized to explore the influencing factors among rural residents in Northeast China Environmental aged 40 years and above, it was found that environmental factors, medical history, and serum CRP levels mainly affected the prevalence of COPD. Keywords: chronic obstructive pulmonary disease, collinearity, principal component, logistic regression
β- Ga2O3 films were grown by radio-frequency magnetron sputtering method. The influence of Ga2O3 buffer layers and annealing treatment on the structural, optical, morphological and electrical ...properties of Ga2O3 films was studied. The results revealed an improvement of crystalline quality and transmittance of annealed β- Ga2O3 films prepared with homo-buffer layers. Ga2O3 film UV photodetectors were fabricated with a new B and Ga co-doped ZnO films (BGZO)/Au interdigitated electrode. A good ohmic contact was formed between the film and the electrode. For the detector based on Ga2O3 films with buffer layers, a higher value of photo response and faster response times was obtained.
•Bending stress exerted on the plasma membrane by sickle hemoglobin polymerization enhances sulfatide-mediated adhesion of mature erythrocytes in SCD.•Inflammatory sphingomyelinase activity could ...result in abnormal adhesion and membrane damage in sickle mature erythrocytes.
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Abnormal erythrocyte adhesion owing to polymerization of sickle hemoglobin is central to the pathophysiology of sickle cell disease (SCD). Mature erythrocytes constitute >80% of all erythrocytes in SCD; however, the relative contributions of erythrocytes to acute and chronic vasculopathy in SCD are not well understood. Here, we showed that bending stress exerted on the erythrocyte plasma membrane by polymerization of sickle hemoglobin under hypoxia, enhances sulfatide-mediated abnormal mature erythrocyte adhesion. We hypothesized that sphingomyelinase (SMase) activity, which is upregulated by accumulated bending energy, leads to elevated membrane sulfatide availability, and thus, hypoxic mature erythrocyte adhesion. We found that mature erythrocyte adhesion to laminin in controlled microfluidic experiments is significantly greater under hypoxia than under normoxia (1856 ± 481 vs 78 ± 23, mean ± SEM), whereas sickle reticulocyte (early erythrocyte) adhesion, high to begin with, does not change (1281 ± 299 vs 1258 ± 328, mean ± SEM). We showed that greater mean accumulated bending energy of adhered mature erythrocytes was associated with higher acid SMase activity and increased mature erythrocyte adhesion (P = .022, for acid SMase activity and P = .002 for the increase in mature erythrocyte adhesion with hypoxia, N = 5). In addition, hypoxia results in sulfatide exposure of the erythrocyte membrane, and an increase in SMase, whereas anti-sulfatide inhibits enhanced adhesion of erythrocytes. These results suggest that the lipid components of the plasma membrane contribute to SCD complications. Therefore, sulfatide and the components of its upregulation pathway, particularly SMase, should be further explored as potential therapeutic targets for inhibiting sickle erythrocyte adhesion.
In this paper, the mesoporous silica MCM-41 supporting nano zero valent iron (MSNZVI) composite was synthesized in a facile way and characterized by XRD, FT-IR, TEM and N
2
adsorption–desorption. The ...catalytic activity of the as-prepared MSNZVI composite as a catalyst was evaluated on the
p
-nitrophenol reduction in the presence of excess NaBH
4
. And the rate constant is 4.89 × 10
−3
s
−1
when the mole ratio of NaBH
4
to
p
-nitrophenol is 500. MSNZVI composite can be reused for at least five cycles with stable catalytic activity. Moreover, a possible catalytic mechanism of MSNZVI was proposed to explain the reduction of
p
-nitrophenol by NaBH
4
.
Purpose:
Cone beam breast computed tomography (breast CT) with true three‐dimensional, nearly isotropic spatial resolution has been developed and investigated over the past decade to overcome the ...problem of lesions overlapping with breast anatomical structures on two‐dimensional mammographic images. However, the ability of breast CT to detect small objects, such as tissue structure edges and small calcifications, is limited. To resolve this problem, the authors proposed and developed a volume‐of‐interest (VOI) breast CT technique to image a small VOI using a higher radiation dose to improve that region's visibility. In this study, the authors performed Monte Carlo simulations to estimate average breast dose and average glandular dose (AGD) for the VOI breast CT technique.
Methods:
Electron–Gamma‐Shower system code‐based Monte Carlo codes were used to simulate breast CT. The Monte Carlo codes estimated were validated using physical measurements of air kerma ratios and point doses in phantoms with an ion chamber and optically stimulated luminescence dosimeters. The validated full cone x‐ray source was then collimated to simulate half cone beam x‐rays to image digital pendant‐geometry, hemi‐ellipsoidal, homogeneous breast phantoms and to estimate breast doses with full field scans. 13‐cm in diameter, 10‐cm long hemi‐ellipsoidal homogeneous phantoms were used to simulate median breasts. Breast compositions of 25% and 50% volumetric glandular fractions (VGFs) were used to investigate the influence on breast dose. The simulated half cone beam x‐rays were then collimated to a narrow x‐ray beam with an area of 2.5 × 2.5 cm2 field of view at the isocenter plane and to perform VOI field scans. The Monte Carlo results for the full field scans and the VOI field scans were then used to estimate the AGD for the VOI breast CT technique.
Results:
The ratios of air kerma ratios and dose measurement results from the Monte Carlo simulation to those from the physical measurements were 0.97 ± 0.03 and 1.10 ± 0.13, respectively, indicating that the accuracy of the Monte Carlo simulation was adequate. The normalized AGD with VOI field scans was substantially reduced by a factor of about 2 over the VOI region and by a factor of 18 over the entire breast for both 25% and 50% VGF simulated breasts compared with the normalized AGD with full field scans. The normalized AGD for the VOI breast CT technique can be kept the same as or lower than that for a full field scan with the exposure level for the VOI field scan increased by a factor of as much as 12.
Conclusions:
The authors’ Monte Carlo estimates of normalized AGDs for the VOI breast CT technique show that this technique can be used to markedly increase the dose to the breast and thus the visibility of the VOI region without increasing the dose to the breast. The results of this investigation should be helpful for those interested in using VOI breast CT technique to image small calcifications with dose concern.
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