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Photodynamic therapy (PDT) is a promising new treatment technique which can potentially destroy unwanted and malignant tissues, such as those of cancer. The photodynamic mechanisms of three tetrapyrrole compounds: Mg-purpurin-18, tetra(meso-chlorophenyl)porphyrin (m-TCPP) and 2,7,12,18-tetramethyl-3,8-di[(1-isobutoxyl)ethyl]-13,17-bis[3-di(2-chloroethyl)aminopropyl]porphyrin (TDBP) in acetonitrile were investigated by 355 nm laser flash photolysis. It was found that after laser flash photolysis (LFP), the excited states of TDBP and Mg-purpurin-18 could react with O 2 and 1 O 2 was produced, which proved that TDBP and Mg-purpurin-18 took effects through type II mechanism in PDT. This suggested that TDBP and Mg-purpurin-18 should be suitable for target tissues containing enough O 2 . Mg-purpurin-18 has two extra absorptions at 550 and 700 nm, which means it has broad choices of laser wavelength in PDT. It was also found that m-TCPP could be photoionized when excited with 355 nm laser under N 2 -saturated condition. It could also react with O 2 to produce reactive oxygen species such as superoxide and the peroxide anions, but not 1 O 2 . These were known as the Type I mechanism. So m-TCPP could be used even at low oxygen concentration or more polar environments with good behavior in PDT. From the above studies on the three different tetrapyrrole compounds it could be concluded that the structure of porphin ring takes a main role in PDT. And there was important impact on the photodynamic mechanism for the functional group directly connecting with porphin ring, while little influence for the functional group indirectly connecting with porphin ring. These will be of great value in the discovery of new PDT drugs.

Detecting the discrete gross error and regional gross error in shipborne gravity is a key step for improving the measurement quality. The traditional wavelet threshold shrinkage (WTS) method misidentifies discrete gross errors and cannot detect regional gross errors. Here we propose a shifted double wavelet iteration (SDWI) method. This method decomposes the measurement sequence by shifted double wavelet to obtain wavelet coefficients, and then apply threshold processing to the obtained coefficients to accurately detect gross errors. After that, we reconstruct the identified gross errors, and perform iterative processing to the regional gross errors. Finally, the difference of the gravity before and after gross error detection is used for gross error positioning. In the simulation experiment, we use the proposed SDWI method to detect the discrete gross error, the regional gross error and discrete-region gross error in the shipborne gravity, separately. The results show that the detection success rate is 100% and failure rate is 0 for all three kinds of gross errors, better than that of the traditional WTS method. The real data experiment also confirms that the proposed method is effective in detecting gross errors.