Synthesis, Antimicrobial Activity, and Molecular Docking Studies of Aminoguanidine Derivatives Containing an Acylhydrazone Moiety.

A series of aminoguanidine derivatives containing an acylhydrazone moiety was designed based on combination principles to find new antibacterial agents with wide spectra and high activities. The synthesized compounds were characterized by spectral methods and screened for their antibacterial activity. The results showed that several compounds provided great antimicrobial activities against Gram-positive bacteria (including the multidrug-resistant clinical isolates). Especially, this series of compounds presented high potency against Staphylococcus aureus, among which the derivative 3f was the most promising one with a MIC value of 4 µg/mL. Compound 3d, with a tertiary butyl group, was found to have the broad spectrum inhibitory capacity, which is effective to eight strains and showed the most potent inhibitory activity against B. subtilis CMCC 63501 with a MIC value of 4 µg/mL. What's more, compound 3d also presented high activities against four multidrug-resistant strains, which were comparable or potent to oxacillin and penicillin. Molecular docking studies revealed that H-bond interaction with amino acid residue THR81 and alkyl hydrophobic interaction with residue ALA246 of FabH were crucial for their binding force and in-vitro antimicrobial activities.

Synthesis of ring-opened derivatives of triazole-containing quinolinones and their antidepressant and anticonvulsant activities.

Based on the potent antidepressant and anticonvulsant activities of the triazole-containing quinolinones reported in our previous work, a series of ring-opened derivatives of them were designed, synthesized in this work. Their antidepressant and anticonvulsant activities were screened using the forced swimming test (FST) and the maximal electroshock seizure test (MES), respectively. The results showed that compounds 4a, 5a, 6c-6e, 6g-6i, and 7 led to significant reductions in the accumulated immobility time in the FST at a dose of 50 mg/kg. Especially compound 7 exhibited higher levels of efficacy than the reference standard fluoxetine in the FST and the tail suspension test. The results of an open field test excluded the possibility of central nervous stimulation of 7, which further confirmed its antidepressant effect. Meanwhile, compounds 6a-6i and 7 showed different degrees of anticonvulsant activity in mice at the doses range from 300 to 30 mg/kg in the MES. Among them, compounds 6e and 7 displayed the ED50 of 38.5 and 32.7 mg/kg in the MES, and TD50 of 254.6 and 245.5 mg/kg, respectively. No one showed neurotoxicity at the dose of 100 mg/kg. The preliminary investigation forward to their mechanism indicated that regulation of GABAergic system might contribute to their anticonvulsive and anti-depressive action.

Optical amplification and pulse interleaving for low-noise photonic microwave generation.

We investigate the impact of pulse interleaving and optical amplification on the spectral purity of microwave signals generated by photodetecting the pulsed output of an Er:fiber-based optical frequency comb. It is shown that the microwave phase noise floor can be extremely sensitive to delay length errors in the interleaver, and the contribution of the quantum noise from optical amplification to the phase noise can be reduced ∼10 dB for short pulse detection. We exploit optical amplification, in conjunction with high power handling modified unitraveling carrier photodetectors, to generate a phase noise floor on a 10 GHz carrier of -175 dBc/Hz, the lowest ever demonstrated in the photodetection of a mode-locked fiber laser. At all offset frequencies, the photodetected 10 GHz phase noise performance is comparable to or better than the lowest phase noise results yet demonstrated with stabilized Ti:sapphire frequency combs.

InP-based waveguide photodiodes heterogeneously integrated on silicon-on-insulator for photonic microwave generation.

High-linearity modified uni-traveling carrier photodiodes on silicon-on-insulator with low AM-to-PM conversion factor are demonstrated. The devices deliver more than 2.5 dBm RF output power up to 40 GHz and have an output third order intercept point of 30 dBm at 20 GHz. Photodiode arrays exceed a saturation current-bandwidth-product of 630 mA · GHz and reach unsaturated RF output power levels of 10 dBm at 20 GHz.

Improved sinusoidal gating with balanced InGaAs/InP Single Photon Avalanche Diodes.

We report balanced InGaAs/InP single photon avalanche diodes (SPADs) operated in sinusoidal gating mode with a tunable phase shifter to reduce common mode noise. This technique enables detection of small avalanche pulses, which results in reduced afterpulsing. For laser repletion rate of 20 MHz at 240 K, the dark count rate for photon detection efficiency of 10% is 8.9 kHz.

High-power flip-chip mounted photodiode array.

Four-element modified uni-traveling-carrier (MUTC) photodiode arrays (PDA) flip-chip bonded onto transmission lines on AlN substrates are demonstrated. High RF output powers of 26.2 dBm and 21.0 dBm are achieved at 35 GHz and 48 GHz, respectively, using a PDA with 28-µm diameter photodiodes. A systematic comparison between a PDA with four 20 µm-diameter elements and a discrete detector with the same active area (40-µm diameter) is presented. The PDA achieved higher output power and thermal dissipation compared to its discrete counterpart.

Nanosphere natural lithography surface texturing as anti-reflective layer on SiC photodiodes.

Natural lithography with 100-nm-diameter SiO(2) spheres followed by inductively coupled plasma etching was used to texture the surface of 4H-SiC for a wide-spectrum large-acceptance-angle anti-reflective layer. The surface showed low normal-incidence reflectance of < 5% over a wide spectrum from 250 nm to 550 nm. Photodiodes fabricated from the surface-textured SiC showed broader spectral and angular responsivity than SiC photodiodes with SiO(2) antireflective coating. The textured SiC photodiodes showed peak responsivity of 116 mA/W, large angle of acceptance angle (< 2% decrease in responsivity at 50° incident angle) and low dark current at 10V.

High quantum efficiency GaP avalanche photodiodes.

Gallium Phosphide (GaP) reach-through avalanche photodiodes (APDs) are reported. The APDs exhibited dark current less than a pico-ampere at unity gain. A quantum efficiency of 70% was achieved with a recessed window structure; this is almost two times higher than previous work.

Laser-textured silicon photodiode with broadband spectral response.

A femtosecond-laser-textured Si photodetector is reported. Broadband spectral optical response is detected from UV to NIR. A quantum efficiency of greater than 80% from 490 nm to 780 nm has been achieved. The quantum efficiency at 245 nm is 62%, which is comparable to UV-enhanced Si photodiodes. The bandwidth of a 250-µm-diameter device is 60 MHz.

SiC avalanche photodiode array with microlenses.

A simple technique to incorporate microlenes with small photodiode arrays is demonstrated and analyzed. Using this method, the fill factor was increased from 2.6% to 22.4% for a two by two array. Simulation results are also shown. The photocurrent with microlens was approximately 8.6 times larger than without the microlens, which is consistent with simulation results.

Vector iterative algorithm for the design of diffractive optical elements applied to uniform illumination.

A vector angular-spectrum iterative algorithm for the design of diffractive optical elements to produce uniform illumination is described. In the algorithm, the variation of beam polarization is related to a unit wave vector and a random mixture of intensity is used for super-Gaussian beam shaping [corrected]. The simulated results show that approximately 95.3% of the incident energy has converged into the desired region. The greatest profile error and the mean-square error of intensity fitted to the corresponding parameters of the 100th-power super-Gaussian function are approximately 8 x 10(-4) and 3.5 x 10(-3), respectively.