N.R. Diao’s research while affiliated with Fudan University and other places

Although MTBDRplus is validated for the detection of multidrug-resistant tuberculosis (MDR-TB), its role in the assessment of treatment outcome is less clear. We evaluated the association of MTBDRplus results with treatment outcome in new and previously treated patients in an endemic setting in China and determined factors associated with poor treatment outcomes. We prospectively enrolled 298 smear-positive pulmonary TB patients who received the World Health Organization recommended initial treatment regimen or retreatment regimen. MTBDRplus was compared with conventional drug susceptibility testing and DNA sequencing for the detection of MDR-TB. Treatment responses were monitored using sputum smear, culture and chest radiography. MTBDRplus successfully identified all MDR-TB and had good concordance with sequencing. MDR-TB rates were low among new patients (4/187, 2.1%), but high in previously treated patients (12/28, 42.9%); 65.2% (15/23) of previously treated cases and 17.1% (27/158) of new cases were unsuccessfully treated (P < 0.001). Seven of eight (87.5%) previously treated MDR-TB patients failed the retreatment regimen. In addition to drug resistance, sputum smear positivity at week 8 and cavitation are associated with treatment failure. Not only did MTBDRplus correctly identify all MDR-TB cases, MTBDRplus results are also associated with treatment outcomes in previously treated patients. The retreatment regimen should no longer be used; treatment should be guided by molecular testing.

To assess the new GenoType® MTBDRplus assay for the rapid detection of multidrug-resistant tuberculosis (MDR-TB) in comparison with DNA sequencing to identify drug resistance mutation profiles in China. Using MTBDRplus, drug susceptibility testing (DST) and DNA sequencing, 237 Mycobacterium tuberculosis strains were tested. The sensitivity of MTBDRplus was 75.0% (126/168) for isoniazid (INH) resistant strains, and 93.5% (157/168) for rifampicin (RMP) resistant strains. It correlated well with sequencing, with 94.9% and 99.6% agreement for each strain category and 100% specificity for all categories. The two most common rpoB mutations were S531L (53.6%, 90/168) and D516G (17.3%, 29/168) in RMP-resistant strains. INH resistance was dominated by the katG 315 locus (S to T, N, R, I) mutation (73.7%, 124/168), and a rare katG mutation, S315N (6.5%, 11/168), not covered by MTBDRplus was identified. The mutation combination inhA-15/inhA-8 and katG315 (34 strains) was characteristically displayed in MDR-TB strains (23.5%), but not in INH-monoresistant strains. Although Genotype MTBDRplus is a rapid and reliable molecular test for detecting MDR-TB, a significant proportion of strains in China contain a rare katG S315N mutation that would be missed by the assay. Further improvements may be achieved by incorporating this mutation into the assay to increase sensitivity in detecting INH resistance in China.

The standing column well for ground source heat pump systems is a promising technology with high efficiency and environmental benefit, where groundwater is drawn from the bottom of a well and then re-injected to its top after transferring heat with heat pumps. Heat transfer analysis of great significance and aquifer involves complex problems. Determining the groundwater seepage flow is a precondition to solve the energy equation describing the heat transfer of the system. Only when piezometric head is obtained, the seepage velocity can be determined according to Darcy's law. In this article the groundwater seepage flow in an axial symmetrical geometry was studied under the assumption that gross groundwater flow is neglected. An analytical solution of the groundwater seepage flow for a confined aquifer was acquired by using the integral transform method, which may provide a foundation for heat transfer analysis of the standing column well system.

The heat transfer model of vertical ground heat exchangers for ground-source heat pump systems is discussed. An explicit solution of a finite line-source model has been derived to better describe temperature response of boreholes for long time steps, which can be easily incorporated into computer programs for thermal analysis of ground heat exchangers. A quasi-three-dimensional model is also presented for heat transfer inside the borehole, accounting for thermal interference between the U-tube legs. On this basis a concise expression is obtained for the thermal resistance inside the borehole. These models have a more solid theoretical basis, would help to improve design procedures recommended by available literature, and are yet suitable for engineering applications.

This paper summarizes the authors' study on heat transfer analyses of the ground heat exchangers (GHE). First, taking the fluid axial convective heat transfer and thermal 'short-circuiting' among U-tube legs into account, a quasi-3-D model for boreholes in GHEs is established, and analytical solutions of the fluid temperature profiles along the borehole depth have been obtained. Secondly, an explicit solution of the transient 2-D temperature response in a semi-infinite medium with a line-source of finite length has been derived to take the place of the Kelvin's 1-D line-source model. Finally, an explicit solution is also obtained for a line heat source in an infinite porous medium with water advection. These models are helpful to improve GHE design procedures, and are yet suitable for engineering applications.