Parametric fluorescence in periodically poled silica fibres

We report the observation of quasiphase matched parametric fluorescence from a periodically poled silica fiber. A pair-photon production rate of more than 100 MHz around 1532 nm was achieved in second-order nonlinear gratings for 300 mW of pump power at 766 nm. These results are very promising for the realization of reliable all-fiber single-photon sources for quantum cryptography systems and metrology applications

Mitochondria matter: Systemic aspects of nonalcoholic fatty liver disease (nafld) and diagnostic assessment of liver function by stable isotope dynamic breath tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β‐oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. “Dynamic” liver function tests include the breath test (BT) based on the use of substrates marked with the non‐radioactive, naturally occurring stable isotope13C. Hepatocellular metabolization of the substrate will generate13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13 CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria.13 C‐BTs explore distinct chronic liver diseases including simple liver steatosis, non‐alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD,13C‐BT use substrates such as α‐ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease.13C‐BTs represent an indirect, cost‐effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of13C‐BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD

Effects of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 in IBS patients

Background: Irritable bowel syndrome (IBS) is a common gastrointestinal disorder, which still lacks effective therapy. We aimed to investigate the effects of a novel formulation of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 with vitamin B6 (LBB) on symptoms, intestinal permeability, cultivable bacteria and metabolome in IBS subjects. Materials and methods: Twenty-five IBS patients (Rome IV criteria) (M:F = 8:17; age 48 years ± 11 SD) were randomized to treatment (LBB) or placebo (one month each) in a crossover randomized double-blind controlled trial. Symptoms, intestinal habits, disease severity, intestinal permeability and intestinal microbiota were analysed at 0, 30, 45 and 60 days. Results: Percentage decrease from baseline of abdominal pain (−48.8% vs −3.5%), bloating (−36.35% vs +7.35%) and severity of disease (−30.1% vs −0.4%) was significantly (P <.0001) greater with LBB than placebo, respectively. In IBS-D patients, the improvement from baseline of Bristol score was more consistent with LBB (from 6 ± 0.4 to 4.3 ± 1.1, P <.00001) than placebo (from 6.2 ± 0.7 to 5.3 ± 1.1, P =.04). In IBS-C patients, Bristol score tended to improve from baseline after LBB (2.6 ± 1.1 vs 3.2 ± 0.5, P =.06). LBB significantly improved the percentage of sucralose recovery (colonic permeability) (1.86 ± 0.1 vs 1.1 ± 0.2, P =.01). During treatment, presumptive lactic acid bacteria and bifidobacteria, relative abundance of propanoic, butanoic, pentanoic acids and hydrocarbons increased, while phenol decreased. Conclusions: The novel formulation of B. longum BB536 and L. rhamnosus HN001 with B6 vitamin improves symptoms and severity of disease, restores intestinal permeability and gut microbiota in IBS patients

A Stimuli-Responsive Nanocomposite for 3D Anisotropic Cell-Guidance and Magnetic Soft Robotics

Stimuli-responsive materials have the potential to enable the generation of new bioinspired devices with unique physicochemical properties and cell-instructive ability. Enhancing biocompatibility while simplifying the production methodologies, as well as enabling the creation of complex constructs, i.e., via 3D (bio)printing technologies, remains key challenge in the field. Here, a novel method is presented to biofabricate cellularized anisotropic hybrid hydrogel through a mild and biocompatible process driven by multiple external stimuli: magnetic field, temperature, and light. A low-intensity magnetic field is used to align mosaic iron oxide nanoparticles (IOPs) into filaments with tunable size within a gelatin methacryloyl matrix. Cells seeded on top or embedded within the hydrogel align to the same axes of the IOPs filaments. Furthermore, in 3D, C2C12 skeletal myoblasts differentiate toward myotubes even in the absence of differentiation media. 3D printing of the nanocomposite hydrogel is achieved and creation of complex heterogeneous structures that respond to magnetic field is demonstrated. By combining the advanced, stimuli-responsive hydrogel with the architectural control provided by bioprinting technologies, 3D constructs can also be created that, although inspired by nature, express functionalities beyond those of native tissue, which have important application in soft robotics, bioactuators, and bionic devices

Counter-propagating entangled photons from a waveguide with periodic nonlinearity

The conditions required for spontaneous parametric down-conversion in a waveguide with periodic nonlinearity in the presence of an unguided pump field are established. Control of the periodic nonlinearity and the physical properties of the waveguide permits the quasi-phase matching equations that describe counter-propagating guided signal and idler beams to be satisfied. We compare the tuning curves and spectral properties of such counter-propagating beams to those for co-propagating beams under typical experimental conditions. We find that the counter-propagating beams exhibit narrow bandwidth permitting the generation of quantum states that possess discrete-frequency entanglement. Such states may be useful for experiments in quantum optics and technologies that benefit from frequency entanglement.Comment: submitted to Phys. Rev.

Copper-Triggered Aggregation of Ubiquitin

Neurodegenerative disorders share common features comprising aggregation of misfolded proteins, failure of the ubiquitin-proteasome system, and increased levels of metal ions in the brain. Protein aggregates within affected cells often contain ubiquitin, however no report has focused on the aggregation propensity of this protein. Recently it was shown that copper, differently from zinc, nickel, aluminum, or cadmium, compromises ubiquitin stability and binds to the N-terminus with 0.1 micromolar affinity. This paper addresses the role of copper upon ubiquitin aggregation. In water, incubation with Cu(II) leads to formation of spherical particles that can progress from dimers to larger conglomerates. These spherical oligomers are SDS-resistant and are destroyed upon Cu(II) chelation or reduction to Cu(I). In water/trifluoroethanol (80∶20, v/v), a mimic of the local decrease in dielectric constant experienced in proximity to a membrane surface, ubiquitin incubation with Cu(II) causes time-dependent changes in circular dichroism and Fourier-transform infrared spectra, indicative of increasing β-sheet content. Analysis by atomic force and transmission electron microscopy reveals, in the given order, formation of spherical particles consistent with the size of early oligomers detected by gel electrophoresis, clustering of these particles in straight and curved chains, formation of ring structures, growth of trigonal branches from the rings, coalescence of the trigonal branched structures in a network. Notably, none of these ubiquitin aggregates was positive to tests for amyloid and Cu(II) chelation or reduction produced aggregate disassembly. The early formed Cu(II)-stabilized spherical oligomers, when reconstituted in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes and in POPC planar bilayers, form annular and pore-like structures, respectively, which are common to several neurodegenerative disorders including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis, and prion diseases, and have been proposed to be the primary toxic species. Susceptibility to aggregation of ubiquitin, as it emerges from the present study, may represent a potential risk factor for disease onset or progression while cells attempt to tag and process toxic substrates

Optical parametric processes in periodically poled silica fibres

Glass, an amorphous centrosymmetric material, does not possess any macroscopic second-order optical nonlinearity, thus preventing processes such as linear electro-optic modulation and parametric frequency conversion. This thesis describes work carried out at Southampton using poling techniques in order to induce a significant second-order nonlinearity in optical glass fibres, so as to achieve efficient quasi-phase-matched optical parametric processes. An all-fibre frequency converter presents several interesting advantages over traditional nonlinear crystals, in particular with respect to ruggedness, damage threshold and integrability with existing optical circuits. Also, parametric fluorescence is a source of twin-photon pairs, presenting peculiar correlation properties that can be exploited both for the realisation of quantum key distribution systems (Quantum Cryptography) and for the investigation of fundamental phenomena in quantum optics. Studying and better understanding of the poling processes and optimisation of the quasi-phase-matching technique in poled optical fibres led to the fabrication of novel nonlinear fibre devices. The achievement of more than 20% second-harmonic generation efficiency, the first demonstration of parametric fluorescence from an optical fibre and of periodic UV erasure of the nonlinearity in a germano-silicate fibre represent the key results described in this thesis

Periodic UV erasure of the nonlinearity for quasi-phase-matching in optical fibres

A periodic second-order nonlinearity is obtained exposing uniformly poled samples to a periodic UV pattern. Second-harmonic conversion efficiencies around 6% were achieved for 29 mW of fundamental average power from a high power pulsed EDFA system

Periodically poled glass fibres for optical frequency conversion

D-shaped glass fibres have been periodically poled using standard planar lithography to define the patterned electrode and applying high voltage at elevated temperature. The resulting nonlinear gratings, uniform over 75 mm have been used for efficient second-order nonlinear frequency conversion. Efficiencies of ~1% have been achieved with demonstrated potential of several 10s

Single-frequency MOPA Er³⁺ DBR fiber laser for WDM digital telecommunication systems

The realization, the characteristics and the bit-error-rate (BER) performance of a single frequency, linear polarization Er3+-doped distributed Bragg reflector fiber laser are reported. The device, pumped at 980 nm, gives a maximum output power of 13 mW with an overall slope efficiency η =24%, a continuous wave intensity ripple around 1% and a linewidth of 2.2 kHz. The BER test, performed without any polarization control system in a complete 475-km-long 2.5-Gb/s wavelength-division-multiplexed transmission line, shows only a 0.5-dB penalty is introduced