Numerical investigation of GHz repetition rate fundamentally mode-locked all-fiber lasers

GHz repetition rate fundamentally mode-locked lasers have attracted great interest for a variety of scientific and practical applications. A passively mode-locked laser in all-fiber format has the advantages of high stability, maintenance-free operation, super compactness, and reliability. In this paper, we present numerical investigation on passive mode-locking of all-fiber lasers operating at repetition rates of 1-20 GHz. Our calculations show that the reflectivity of the output coupler, the small signal gain of the doped fiber, the total net cavity dispersion, and the modulation depth of the saturable absorber are the key parameters for producing stable fundamentally mode-locked pulses at GHz repetition rates in very short all-fiber linear cavities. The instabilities of GHz repetition rate fundamentally mode-locked all-fiber lasers with different parameters were calculated and analyzed. Compared to a regular MHz repetition rate mode-locked all-fiber laser, the pump power range for the mode-locking of a GHz repetition rate all-fiber laser is much larger due to the several orders of magnitude lower accumulated nonlinearity in the fiber cavity The presented numerical study provides valuable guidance for the design and development of highly stable mode-locked all-fiber lasers operating at GHz repetition rates.National Science Foundation Engineering Research Center for Integrated Access Networks [EEC-0812072]; Technology Research Initiative Fund (TRIF) Photonics Initiative of the University of Arizona; National Natural Science Foundation of China (NSFC) [61575075]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Quantitative proteomics assay reveals G protein-coupled receptor kinase 4-induced HepG2 cell growth inhibition

Background and aim: To investigate the biological effects and putative biological mechanism of G protein-coupled receptor kinase 4 (GRK4) on HepG2 cells. Materials and methods: Cell proliferation, cycle, and apoptosis were evaluated by Cell Counting Kit-8 and flow cytometry (FCM) in HepG2 cells infected with either the GRK4-overexpressing lentivirus vector (OE) or the negative control lentivirus vector (NC). The protein profiles and differentially expressed proteins (DEPs) of the OE and NC cells were analyzed and compared using the quantitative proteomics technique, and their function, expression, and probable mechanism were investigated using bioinformatic assays and parallel reaction monitoring (PRM). Results: HepG2 cells that received the OE grew more slowly than those that received the NC. FCM revealed that, when compared to the NC cells, the OE cells had undergone S-phase cycle arrest, and neither the OE nor NC cells underwent apoptosis. Among the 7006 proteins that were identified by quantitative proteomics, 403 DEPs were examined based on the filtering parameters, with the expressions of 135 being downregulated and 268 being upregulated. In addition to being involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, the DEPs were implicated in the biological processes of cell proliferation, cycle, and metabolism. PRM verified the expressions of DEPs that were connected to the PPAR pathway. Conclusions: This study shows that GRK4 prevents HepG2 cells from proliferating and causes cell cycle arrest in the S-phase, while the PPAR pathway is involved in the regulation of HepG2 cells via GRK4

Mechanical Properties and Microstructure Characteristics of the Loess Modified by the Consolid System

The soil stabilizer of the Consolid system (content: 0%–2.46%) was used for the modification of collapsible loess. The consolidation test, compression test, collapsibility test, and strength test of modified loess were conducted. In addition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury injection tests were carried out to study the loess before and after modification. The results indicated that with an increase in the content of the stabilizers, the optimal water content of the modified loess increased, whereas the dry density decreased. Furthermore, as the content of the stabilizers increased, the compressibility and collapsibility of the modified loess decreased. When the stabilizer content was 0.86%, the modified loess exhibited almost no collapsibility. The unconfined compressive strength of the modified loess demonstrated an exponential relationship with the content of the stabilizers. The shear strength increased with the increase in the content of the stabilizers. When the stabilizer content reached 1.66%, the friction angle started to decrease. The microstructure analysis indicated that the cumulative pore volume of the modified loess decreased with the increase in the content of the stabilizers, which could facilitate the formation of a more stable soil structure and improve the impermeability and strength

One-Step Synthesis of Silver Nanowires with Ultra-Long Length and Thin Diameter to Make Flexible Transparent Conductive Films

High aspect ratio silver nanowires (AgNWs) with ultra-long length and thin diameter were synthesized through bromine ion (Br−)-assisted one-step synthesis method. The bromine ions were used as pivotal passivating agent. When the molar ratio of Br−/Cl− was 1:4, the average diameter of AgNWs was as low as ~40 nm, the average length was as high as ~120 μm, and the aspect ratio reached 2500. Networks of AgNWs were fabricated using as-prepared high-quality AgNWs as conducting material and hydroxyethyl cellulose (HEC) as the adhesive polymer. As a result, a low sheet resistance down to ~3.5 Ω sq−1 was achieved with a concomitant transmittance of 88.20% and a haze of 4.12%. The ultra-low sheet resistance of conductive film was attributed to the long and thin AgNWs being able to form a more effective network. The adhesion of the AgNWs to the substrate was 0/5B (ISO/ASTM). The insights given in this paper provide the key guidelines for bromine ion-assisted synthesis of long and thin AgNWs, and further designing low-resistance AgNW-based conductive film for optoelectronic devices

Study on Quantitative Phase Imaging by Dual-Wavelength Digital Holography Microscopy

A dual-wavelength digital holographic microscopy with premagnification is proposed to obtain the object surface measurements over the large gradient. The quantitative phase images of specimens are captured in high precision by the processing of filtering and phase compensation. The phase images are acquired without phase unwrapping, which is necessary in traditional digital holographic microscopy; thereby the proposed system can greatly increase the speed of reconstruction. The results of numerical simulation and optical experiments demonstrated that the reconstructed speed increased by 37.9 times, and the relative error of measurement is 4% compared with the traditional holographic microscopy system. It means that the proposed system can directly acquire the higher quality quantitative phase distribution for specimens

Multiple pulmonary cavities in an immunocompetent patient: a case report and literature review

Legionella pneumonia (LP) is a relatively uncommon yet well-known type of atypical community-acquired pneumonia (CAP). It is characterized by a rapid progression to severe pneumonia and can be easily misdiagnosed. In most patients, chest computed tomography (CT) showed patchy infiltration, which may progress to lobar infiltration or even lobar consolidation. While pulmonary cavities are commonly observed in immunocompromised patients with LP, they are considered rare in immunocompetent individuals. Herein, we present a case of LP in an immunocompetent patient with multiple cavities in both lungs. Pathogen detection was performed using metagenomic next-generation sequencing (mNGS). This case highlights the unusual radiographic presentation of LP in an immunocompetent patient and emphasizes the importance of considering LP as a possible diagnosis in patients with pulmonary cavities, regardless of their immune status. Furthermore, the timely utilization of mNGS is crucial for early pathogen identification, as it provides multiple benefits in enhancing the diagnosis and prognosis of LP patients

Wavelength Tunable Ho3+-Doped ZBLAN Fiber Lasers in the 1.2-mu m Wavelength Region

Wavelength tunability of continuous-wave holmium doped ZrF4-BaF2-LaT3-AlF3-NaF fiber lasers operating in the 1.2-arm wavelength region was investigated with a Littrow configuration. A wavelength tuning range of 1184-1198 nm was obtained from the fiber output port of the laser. The spectral width was measured to be around 0.02 nm over the entire tunable range and a maximum output power of 81.6 mW at 1192 nm was obtained at a pump power of 1.97 W. The wavelength tunable range was found to be limited by the transmission of the fiber-optic wavelength division multiplexer and coupler. A broader wavelength tuning range of 1177-1201 nm was obtained with a simpler fiber laser construction from the zero-order diffraction output of the bulk grating.NSF CIAN [EEC-0812072]; Photonics Initiative of University of Arizona; China Scholarship CouncilThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]