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X-ray computed tomography (CT) scanning method is the most accurate method to construct digital core, which can reflect the microscopic pore structure of real cores; therefore, it is widely used and researched by experts and scholars all over the world. However, there are few reports about how to select the CT scan core samples at present, and the current practice is to make CT scan samples by visually observing rocks or core columns to select a region that is considered representative or interesting, which can lead to a large difference between the selected sample and the whole rock and a digital core that cannot represent the real rock as a whole. In order to construct the digital cores that can reflect the whole rock structure and reservoir properties, combining with fractal theory, a scientific and reasonable method was proposed to select representative rock samples for digital core modeling. First of all, a core column is scanned by X-ray CT at a certain resolution and CT gray scale images are obtained and stored in the order of scan. Secondly, the fractal dimension (FD) of each image is calculated by box-counting method, and the calculated porosity of each image is achieved by the existing formula. Then, according to the size of the digital core to be constructed, the CT gray scale images are grouped, and the average FD and the average porosity of each combination are calculated by the derived equations. Finally, based on the proposed criteria the best image combination is selected and the preferred sample is determined accordingly. At the same time, a facile experiment was conducted to test the effectiveness of this method. The experimental results show that there are some errors between the subjectively selected cores and the long core in terms of permeability and porosity, and the petrophysical parameters of the core selected by the proposed method are close to those of the long core; as a consequence, the validity of this method was verified and it is feasible and practical to select the representative rock samples for digital core modeling by this method. [ABSTRACT FROM AUTHOR]

Mitochondrial DNA (mtDNA) is particularly susceptible to oxidative damage and mutation due to the high rate of reactive oxygen species (ROS) production and limited DNA-repair capacity in mitochondrial. Previous studies demonstrated that the increased mtDNA copy number for compensation for damage, which was associated with cigarette smoking, has been found to be associated with lung cancer risk among heavy smokers. Given that the common and "non-pathological" mtDNA variations determine differences in oxidative phosphorylation performance and ROS production, an important determinant of lung cancer risk, we hypothesize that the mtDNA variations may play roles in lung cancer risk. To test this hypothesis, we conducted a case-control study to compare the frequencies of mtDNA haplogroups and an 822 bp mtDNA deletion between 422 lung cancer patients and 504 controls. Multivariate logistic regression analysis revealed that haplogroups D and F were related to individual lung cancer resistance (OR = 0.465, 95%CI = 0.329-0.656, p<0.001; and OR = 0.622, 95%CI = 0.425-0.909, p = 0.014, respectively), while haplogroups G and M7 might be risk factors for lung cancer (OR = 3.924, 95%CI = 1.757-6.689, p<0.001; and OR = 2.037, 95%CI = 1.253-3.312, p = 0.004, respectively). Additionally, multivariate logistic regression analysis revealed that cigarette smoking was a risk factor for the 822 bp mtDNA deletion. Furthermore, the increased frequencies of the mtDNA deletion in male cigarette smoking subjects of combined cases and controls with haplogroup D indicated that the haplogroup D might be susceptible to DNA damage from external ROS caused by heavy cigarette smoking. [ABSTRACT FROM AUTHOR]

Background: Biapenem is an injectable carbapenem antibiotic. A clinical study was designed to evaluate its efficacy and safety in the treatment of respiratory and urinary infections compared to imipenem/cilastatin. Methods: A total of 216 patients with respiratory or urinary tract infections were enrolled into this multicenter, open-label, randomized controlled clinical study. Each patient was randomly assigned to either the treatment or control group; 106 patients in each group were included in the ITT analyses. The patients were given biapenem 300 mg or imipenem/cilastatin 500 mg/500 mg two or three times daily, i.v. g.t.t. for 7–14 days according to their conditions. Results: The cure and effective rates were 67.92 and 88.68% in the biapenem group and 76.02 and 93.40% in the imipenem/cilastatin group, the bacterial eradication rates were 93.83 and 98.82%, and the adverse-event rates were 6.54 and 7.41%, respectively. There were no significant differences between the two groups (p > 0.05). Conclusion: Biapenem is as effective and well-tolerated as imipenem/cilastatin for the treatment of intermediate and severe bacterial infections. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]