THz wave generation by repeated and continuous frequency conversions from pump wave to high-order Stokes waves

We propose a novel scheme for THz wave generation by repeated and continuous frequency conversions from pump wave to high-order Stokes waves(HSWs).The repeated frequency conversions are accomplished by oscillations of Stoke waves in resonant cavity(RC)where low-order Stokes waves(LSWs)are converted to high-order Stokes waves again and again.The continuous frequency conversions are accomplished by optimized cascaded difference frequency generation(OCDFG)where the poling periods of the optical crystal are aperiodic leading to the frequency conversions from low-order Stokes waves to high-order Stokes waves uninterruptedly and unidirectionally.Combined with the repeated and continuous frequency conversions,the optical-to-THz energy conversion efficiency(OTECE)exceeds 26%at 300 K and 43%at 100 K with pump intensities of 300 MW/cm^(2).

High-efficiency terahertz wave generation with multiple frequencies by optimized cascaded difference frequency generation

High-efficiency terahertz(THz) wave generation with multiple frequencies by optimized cascaded difference frequency generation(OCDFG) is investigated at 100 K using a nonlinear crystal consisting of a periodically poled lithium niobate(PPLN) part and an aperiodically poled lithium niobate(APPLN) part.Two infrared pump waves with a frequency difference ω_(T1) generate THz waves and a series of cascaded optical waves in the PPLN part by cascaded difference frequency generation(CDFG).The generated cascaded optical waves with frequency interval ω_(T1) then further interact in the APPLN part by OCDFG,yielding the following two advantages.First,OCDFG in the APPLN part is efficiently stimulated by inputting multi-order cascaded optical waves rather than the only two intense infrared pump waves,yielding unprecedented energy conversion efficiencies in excess of 37% at 1 THz at 100 K.Second,THz waves with M timesω_(T1) are generated by mixing the mth-order and the(m+M)th-order cascaded optical waves by designing poling period distributions of the APPLN part.

China antimicrobial resistance surveillance network for pets(CARPet),2018 to 2021

China Antimicrobial Resistance Surveillance Network for Pets(CARPet)was established in 2021 to monitor the resist-ance profiles of clinical bacterial pathogens from companion animals.From 2018 to 2021,we recovered and tested 4,541 isolates from dogs and cats across 25 Chinese provinces,with Escherichia coli(18.5%)and Staphylococcus pseudintermedius(17.8%)being the most predominant bacterial species.The Enterobacterales were highly susceptible to tigecycline,meropenem,colistin,and amikacin(70.3%-100.0%),but showed moderate resistance to ampicillin,ceftriaxone,doxycycline,florfenicol,levofloxacin,enrofloxacin,and trimethoprim-sulfamethoxazole(29.3%-56.7%).About 66.3%of Acinetobacter spp.were resistant to florfenicol,with relatively low resistance to another 11 antibiot-ics(1.2%-23.3%).The Pseudomonas spp.showed high susceptibility to colistin(91.7%)and meropenem(88.3%).The coagulase-positive Staphylococcus spp.showed higher resistance rates to most antimicrobial agents than coagulase-negative Staphylococcus isolates.However,over 90.0%of Staphylococcus spp.were susceptible to linezolid,dapto-mycin and rifampin,and no vancomycin-resistant isolates were detected.E.faecium isolates demonstrated higher resistance rates to most antimicrobial agents than E.faecalis isolates.Streptococcus spp.isolates showed low resistance to most antimicrobial agents except for doxycycline(78.2%)and azithromycin(68.8%).Overall,the tested clinical isolates showed high rates of resistance to commonly used antimicrobial agents in companion animals.Therefore,it is crucial to strengthen the monitoring of bacterial resistance in pets.By timely and effectively collecting,analyzing,and reporting antimicrobial resistance dynamics in pets,the CARPet network will become a powerful platform to provide scientific guidance for both pet medical care and public health.

The Least Eigenvalue of Unicyclic Graphs with Application to Spectral Spread

Let U^(g)_(n)be the set of connected unicyclic graphs of order n and girth g.Let C(T_(1),T_(2),…,T_(g))∈U^(g)_(n)be obtained from a cycle v_(1)v_(2)…v_(g)v_(1)(in an anticlockwise direction)by identifying v_(i)with the root of a rooted tree T_(i)of order n_(i)for each i=1,2,…,g,where n_(i)≥1 and∑^(g)_(i=1)n_(i)=n.In this note,the graph with the minimal least eigenvalue(and the graph with maximal spread)in C(T_(1),T_(2),…,T_(g))is determined.