Salmonella enterica serovar Typhimurium is a major foodborne pathogen throughout the world. Until now, the specific target genes for the detection and identification of serovar Typhimurium have not been developed. To determine the specific probes for serovar Typhimurium, the genes of serovar Typhimurium LT2 that were expected to be unique were selected with the BLAST (Basic Local Alignment Search Tool) program within GenBank. The selected genes were compared with 11 genomic sequences of various Salmonella serovars by BLAST. Of these selected genes, 10 were expected to be specific to serovar Typhimurium and were not related to virulence factor genes of Salmonella pathogenicity island or to genes of the O and H antigens of Salmonella. Primers for the 10 selected genes were constructed, and PCRs were evaluated with various genomic DNAs of Salmonella and non-Salmonella strains for the specific identification of Salmonella serovar Typhimurium. Among all the primer sets for the 10 genes, STM4497 showed the highest degree of specificity to serovar Typhimurium. In this study, a specific primer set for Salmonella serovar Typhimurium was developed on the basis of the comparison of genomic sequences between Salmonella serovars and was validated with PCR. This method of comparative genomics to select target genes or sequences can be applied to the specific detection of microorganisms.

This paper reports on the thermal behavior of GaN-based laser diode (LD) package as functions of cooling systems, die attaching materials, and chip loading conditions. Thermal resistance and junction temperature was determined by electrical-thermal transient method. Significant change of thermal resistance with input current was observed under natural cooling condition due to the sensitive change of heat transfer coefficient (h) with temperature. Employment of PbSn as a die attachment was more advantageous over Ag-paste in thermal behavior of LD package. Compare the thermal resistance of LD packages epidown and epi-up structures. The partial thermal resistance from junction to submount is 4.68 K/W for epidown structure, and 9.65 K/W to epi-up structure. The results demonstrate that the total thermal resistance of LD package be controlled mainly by the packaging design rather than the chip structure itself.1 Introduction GaN-based blue laser diode (LD) is of significant importance for the applications such as optical data storage and communication system. It is well documented that the performances of LD products can be improved with higher laser power [1, 2]. However, high power operation leads to high junction temperature. High junction temperature degrades the optical performance, thus causes potential device failure and reliability problem [3,4]. Therefore, accurate and reliable characterization of thermal behavior is very important for the development of LD packages with a long-life time. The thermal resistance in the most useful indicator of thermal performance of LD package. The thermal resistance is defined as the ratio between the temperature difference between the junction and the ambient and dissipated power [5]. The thermal resistance is a direct indicator how much heat is generated under certain input power in the p-n junction, and it becomes a prime interest to package designers of high power GaN-based LD.In this paper thermal analysis was performed for different cooling system and structures of GaN LD packages. Thermal transient technique was employed for the investigation of thermal behavior. Thermal resistance was measured under forced cooling system and natural cooling system for samples with epi-up and epi-down structures. Thermal analysis was performed as a function of submount materials as well. The thermal resistance represents the contribution from each different layers of heat transfer path in LD structure. By this way, we investigated the thermal behavior as functions of input current and package structure of GaN-based LD package.