Background: Numerous studies conducted over the past 30 years have pointed to the presence of Epstein-Barr virus (EBV) in gastric cancer samples. This study was aimed to provide a meta-analytic review of the prevalence of EBV in gastric cancer patients, and to clarify the relationship between EBV infection and gastric cancer. Methods: A literature search was performed electronically using online databases for English language publications until July 1, 2019. The pooled EBV prevalence and 95% confidence intervals (CIs) were estimated using a randomeffects model. To determine the association between EBV and gastric cancer, pooled odds ratio (OR) and its 95% CI were computed for case-control studies. Two separate analyses were performed on data from case-control studies with matched and non-match pairs designs to calculate the pooled estimates of ORs. Results: The pooled prevalence of EBV in 20,361 gastric cancer patients was 8.77% (95% CI: 7.73-9.92%; I 2 = 83.2%). There were 20 studies with matched pairs design, including tumor and tumor-adjacent normal tissue pairs from 4116 gastric cancer patients. The pooled ORs were 18.56 (95% CI: 15.68-21.97; I 2 = 55.4%) for studies with matched pairs design and 3.31 (95% CI: 0.95-11.54; I 2 = 55.0%) for studies with non-matched pairs design. The proportion of EBV-associated gastric cancer among male cases was significantly higher than among female cases (10.83%, vs. 5.72%) (P < 0.0001). However, the pooled OR estimate for EBV-associated gastric cancer was significantly higher among females (21.47; 95% CI: 15.55-29.63; I 2 = 0%) than in males (14.07; 95% CI: 10.46-18.93; I 2 = 49.0%) (P = 0.06). EBV was more prevalent in the cardia (12.47%) and the body (11.68%) compared to the antrum (6.29%) (P = 0.0002). Conclusions: EBV infection is associated with more than 18 times increase the risk of gastric cancer. Although the prevalence of EBV was higher in male patients than in female patients with gastric cancer, women are more likely than men to develop EBV-associated gastric cancer. Our findings showed that using tumor-adjacent normal tissues as the control group provides more robust and accurate results regarding the relationship between EBV infection and gastric cancer.

Summary In this paper, the concept of converter design, using the least number of elements and achieving high voltage gain at the low duty cycle, is proposed for the microgrids. One of the important issues in the microgrids is boosting the low voltage output of sources to the utility voltage level. Therefore, the step‐up DC‐DC converters are widely used in these systems to attain the utility voltage. The benchmarking of the converters mainly in terms of the voltage gain, efficiency, the number of active and passive components, stresses on semiconductors, and simplicity is considered. In this paper, a new extendable non‐isolated boost DC‐DC converter is presented. Comparing the conventional boost converter, the basic structure of the proposed converter has a high voltage gain and reduced stress on the switch. To increase the voltage gain, the basic structure of the proposed converter can be easily extended. The modulation technique employed is high‐frequency pulse‐width modulation (PWM). The detailed analysis of the proposed converter in continuous current mode (CCM) and discontinuous current mode (DCM) is presented. The relations between currents and voltages and the voltage gain in CCM and DCM are obtained. Experimental results are carried out to verify theoretical concepts by using the hardware prototype.

Summary In this paper, a new structure for a DC‐DC boost converter is proposed. The presented converter provides a high voltage transfer gain with lower duty cycle. Low current and low voltage stress on the switch, enlarged area of operating in continuous conduction mode (CCM), reduced size of the inductors, and the input filter are the main advantages of the proposed converter. The high voltage transfer gain with low number of elements has made it suitable to implement. Hence, using only one switch has made the control of the proposed converter easy. Besides, decreased switching losses and higher efficiency are obtained. The proposed structure is a combination of the Luo converter and a booster unit, which its analysis is studied in three modes, CCM, boundary conduction mode (BCM), and discontinuous conduction mode (DCM). Furthermore, in order to validate the analysis and feasibility of the proposed converter, the experimental results are developed on a low power prototype.

Background: Numerous studies conducted over the past 30 years have pointed to the presence of Epstein–Barr virus (EBV) in gastric cancer samples. This study was aimed to provide a meta-analytic review of the prevalence of EBV in gastric cancer patients, and to clarify the relationship between EBV infection and gastric cancer. Methods: A literature search was performed electronically using online databases for English language publications until July 1, 2019. The pooled EBV prevalence and 95% confidence intervals (CIs) were estimated using a random effects model. To determine the association between EBV and gastric cancer, pooled odds ratio (OR) and its 95% CI were computed for case-control studies with matched pairs design. Results: The pooled prevalence of EBV in 20411 gastric cancer patients was 8.78% (95% CI: 7.75-9.93%; I 2 =83.0%). The proportion of EBV-associated gastric cancer among male cases was significantly higher than among female cases (10.85%, vs 5.72%) ( P <0.01). EBV was more prevalent in the cardia (12.47%) and in the body (11.68%) compared to the antrum (6.29%) ( P <0.01). There were 20 studies with matched pairs design, including tumor and tumor-adjacent normal tissue pairs from 4116 gastric cancer patients. The pooled OR between EBV infection and gastric cancer risk was 18.56 (95% CI: 15.68–21.97; I 2 = 55.4%). Conclusion: EBV infection is associated with more than 18 times increase risk of gastric cancer. Although the prevalence of EBV was higher in male patients than in female patients with gastric cancer, women are more likely than men to develop EBV-associated gastric cancer.

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