Selection of optimal window length using STFT for quantitative SNR analysis of LFM signal

An adaptive approach to select analysis window param- eters for linear frequency modulated （LFM） signals is proposed to obtain the optimal 3 dB signal-to-noise ratio （SNR） in the short- time Fourier transform （STFT） domain. After analyzing the instan- taneous frequency and instantaneous bandwidth to deduce the relation between the window length and deviation of the Gaus- sian window, high-order statistics is used to select the appropriate window length for STFT and get the optimal SNR with the right time-frequency resolution according to the signal characteristic under a fixed sampling rate. Computer simulations have verified the effectiveness of the new method.

Mutant Selection Windows of Azalomycin F5a in Combination with Vitamin K3 against Methicillin-Resistant Staphylococcus aureus

Azalomycin F5a, a 36-membered macrocyclic lactone isolated from several streptomyces strains, presented remarkable anti-methicillin-resistant Staphylococcus aureus (MRSA) activities. To improve its anti-MRSA potential and to evaluate the probability of MRSA resistant to it before development, the anti-MRSA activities of azalomycin F5a in combination with vitamin K3 were first evaluated using checkerboard assay. Then the minimal concentration inhibiting colony formation by 99% (MIC99) and mutant prevention concentration (MPC) of azalomycin F5a alone and in combination with vitamin K3 against MRSA were determined using agar plates with linear antimicrobial concentration decrease. The fractional inhibitory concentration indexes (FICIs) of 0.25 - 0.50 showed the synergistic activity of azalomycin F5a in combination with vitamin K3. The mutant selection windows (MSWs, MIC99-MPC) of azalomycin F5a alone against MRSA tested were 2.07 - 6.40 μg/mL, and the MPCs of azalomycin F5a in combination with vitamin K3 against MRSA tested were 1.60 - 3.20 μg/mL. These indicated that the MPCs of azalomycin F5a in combination could drop down to below its MIC99 alone. According to the hypothesis of MSW, the narrower MSWs of azalomycin F5a alone, even closed MSWs in combination with vitamin K3, together with their synergistic anti-MRSA activities, indicated that azalomycin F5a had a good potential to develop as a new antimicrobial agent.

Geographical classification of Nanfeng mandarin by near infrared spectroscopy coupled with chemometrics methods

Near infrared spectroscopy(NIRS),coupled with principal component analysis and wavelength selection techniques,has been sed to develop a robust and reliable reduced-spectrum classifi-cation model for determining the geographical origins of Nanfeng mandarins.The application of the changeable size moving window principal component analysis(CSMWPCA)provided a notably improved lassification model,with correct classification rates of 92.00%,100.00%,90.00%,100.00%,100.00%,100.00%and 100.00%for Fujian,Guangxi,Hunan,Baishe,Baofeng,Qiawan,Sanxi samples,respectively,as well as,a total dassification rate of 97.52%in the wavelength range from 1007 to 1296 nm.To test and apply the proposed method,the procedure was applied to the analysis of 59 samples in an independent test set.Good identification results(correct rate of 96.61%)were also received.The improvement achieved by the application of CSMWPCA method was particularly remarkable when taking the low complexities of the final model(290 variables)into account.The results of the study showed the great potential of NIRS as a fast,nondestructive and environmentally acceptable method for the rapid and reliable determination for geographical classifcation of Nanfeng mandarins.