Laser frequency stabilization by combining modulation transfer and frequency modulation spectroscopy.

We present a hybrid laser frequency stabilization method combining modulation transfer spectroscopy (MTS) and frequency modulation spectroscopy (FMS) for the cesium D2 transition. In a typical pump-probe setup, the error signal is a combination of the DC-coupled MTS error signal and the AC-coupled FMS error signal. This combines the long-term stability of the former with the high signal-to-noise ratio of the latter. In addition, we enhance the long-term frequency stability with laser intensity stabilization. By measuring the frequency difference between two independent hybrid spectroscopies, we investigate the short-and long-term stability. We find a long-term stability of 7.8 kHz characterized by a standard deviation of the beating frequency drift over the course of 10 h and a short-term stability of 1.9 kHz characterized by an Allan deviation of that at 2 s of integration time.

Molecular characteristic of mcr-1 gene in Escherichia coli from aquatic products in Guangdong, China.

OBJECTIVES: Aquatic ecosystems serve as a dissemination pathway and a reservoir of both antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). This study aimed to determine the prevalence of colistin-resistant mcr-like genes in Enterobacteriales in aquatic products, which may be contribute to the transfer of ARGs in water environments. METHODS: The mcr-1-positive Escherichia coli were recovered from 123 freshwater fish and 34 cultured crocodile cecum samples from 10 farmers' markets in Guangdong, China. Minimum inhibitory concentration (MIC) was determined using the agar dilution method. Genotyping was performed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Conjugation assay was carried out to investigate the transferability of mcr-1. Genomic information was obtained by whole genome sequencing (WGS) and bioinformatic analysis. RESULTS: Forty-four mcr-1 positive isolates showed co-resistance to tetracycline, trimethoprim/sulfamethoxazole, and gentamicin, while they were all sensitive to tigecycline, meropenem, and amikacin. They were typed into sixteen PFGE clusters. ST10 and ST117 were the most popular sequence types, followed by ST1114. S1-PFGE verified the presence of the mcr-1 gene on plasmids in sizes of ∼60 kb (n = 1) and ∼240 kb (n = 3). Whole genome sequencing-based analysis identified mcr-1 integrated in IncHI2 plasmid (n = 3), IncI2 plasmid (n = 2), and bacterial chromosome in two copies (n = 1). In addition to mcr-1, they carried several other antibiotic resistance genes, such as blaCTX-M-14, fosA3, and aac(6')-Ib-cr. CONCLUSION: These data suggest that aquatic products are an important antibiotic resistance reservoir and highlight possible risks regarding food safety.

The hepatoprotective effect of aspirin on carbon tetrachloride­induced hepatic fibrosis via inhibition of TGFß­1 pathway and pro­inflammatory cytokines IL­1ß and COX­2 in rats.

Aspirin decreases liver fibrosis index and inflammation levels. However, the exact mechanism underlying the effects of aspirin are yet to be elucidated. The aim of the study was to investigate the potential protective effects of aspirin on carbon tetrachloride (CCl4)-induced hepatic fibrosis in Sprague-Dawley rats. Rats were divided into four groups, including healthy and CCl4 control and low-(aspirin 10 mg/kg + CCl4) and high-dose aspirin group (aspirin 300 mg/kg + CCl4). After 8 weeks treatment, the histopathological examinations of hepatocyte fibrosis in liver and serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), IL-1ß, transforming growth factor-ß1 (TGF-ß1), hyaluronic acid (HA), laminin (LN) and type IV collagen (IV.C) were determined. Histopathological examination suggested that aspirin decreased CCl4-induced hepatic fibrosis and liver inflammation. The high-dose aspirin group significantly decreased the serum levels of ALT, AST, HA and LN compared with the CCl4 control group. High-dose aspirin group significantly decreased the levels of pro-inflammatory cytokines IL-1ß compared with CCl4 group. The high-dose aspirin group significantly inhibited the expression of TGFß-1 protein compared with CCl4 group. Overall, the present study indicated that aspirin exhibited potent protective effects against CCl4-induced hepatic fibrosis via inhibition of the TGFß-1 pathway and pro-inflammatory cytokine IL-1ß.

Measurement of the fine-structure constant as a test of the Standard Model.

Measurements of the fine-structure constant α require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: α = 1/137.035999046(27) at 2.0 × 10-10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Bordé interferometer and control systematic effects at a level of 0.12 part per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly ge - 2 via the Standard Model of particle physics is now limited by the uncertainty in ge - 2; a 2.5σ tension rejects dark photons as the reason for the unexplained part of the muon's magnetic moment at a 99% confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation.