Gap Statistics for Confined Particles with Power-Law Interactions.

We consider the N particle classical Riesz gas confined in a one-dimensional external harmonic potential with power-law interaction of the form 1/r^{k}, where r is the separation between particles. As special limits it contains several systems such as Dyson's log-gas (k→0^{+}), the Calogero-Moser model (k=2), the 1D one-component plasma (k=-1), and the hard-rod gas (k→∞). Despite its growing importance, only large-N field theory and average density profile are known for general k. In this Letter, we study the fluctuations in the system by looking at the statistics of the gap between successive particles. This quantity is analogous to the well-known level-spacing statistics which is ubiquitous in several branches of physics. We show that the variance goes as N^{-b_{k}} and we find the k dependence of b_{k} via direct Monte Carlo simulations. We provide supporting arguments based on microscopic Hessian calculation and a quadratic field theory approach. We compute the gap distribution and study its system size scaling. Except in the range -1-2 with both Gaussian and non-Gaussian scaling forms.

Titanium dioxide fiber saturable absorber for Q-switched fiber laser generation in the 1-micrometer region: publisher's note.

This publisher's note serves to correct an error in Appl. Opt. 58, 3495 (2019)APOPAI0003-693510.1364/AO.58.003495.

High-efficiency picosecond mode-locked laser using a thulium-doped nanoengineered yttrium-alumina-silica fiber as the gain medium.

We report the theoretical and experimental investigation of a self-starting mode-locked fiber laser with a nanoengineered Tm3+-doped yttrium-alumina-silica (YAS) fiber as the gain medium. The YAS fiber exhibits a higher capability of Tm3+ cluster elimination than commercial silica fibers. The Tm3+ fluorescence properties and YAS dispersion are well characterized. As a result, an efficient picosecond mode-locked fiber laser is demonstrated with a slope efficiency of 14.14% and maximum pulse energy of 1.27 nJ. To the best of our knowledge, this is the first mode-locked fiber laser based on a Tm3+-doped YAS fiber. The experimental observation is also supported by the numerical analysis.

The effect of salinity on enterocytozoon hepatopenaei infection in Penaeus vannamei under experimental conditions.

BACKGROUND: Enterocytozoon hepatopenaei (EHP) is an enteric pathogen that affects Penaeus vannamei and Penaeus monodon shrimp in many SE Asian countries. In the western hemisphere, EHP was reported for the first time in 2016 in farmed P. vannamei in Venezuela. Anecdotal evidence suggests that EHP is more prevalent in grow-out ponds where the salinity is high (> 15 parts per thousand (ppt)) compared to grow-out ponds with low salinities (< 5 ppt). Considering that P. vannamei is an euryhaline species, we were interested in knowing if EHP can propagate in P. vannamei in low salinities. RESULTS: In this study, we described an experimental infection using fecal strings as a source inoculum. Specific Pathogen Free (SPF) P. vannamei were maintained at three different salinities (2 ppt, 15 ppt, and 30 ppt) while continuously challenged using feces from known EHP-infected P. vannamei over a period of 3 weeks. The fecal strings, used as a source of EHP inocula in the challenges, was sufficient to elicit an infection in shrimp maintained at the three salinities. The infectivity of EHP in shrimp reared at 2 ppt, 15 ppt, and 30 ppt salinities was confirmed by PCR and histopathology. The prevalence and the severity of the EHP infection was higher at 30 ppt than at 2 ppt and 15 ppt. CONCLUSION: The data suggests that fecal strings are a reliable source of EHP inoculum to conduct experimental challenges via the fecal-oral route. An EHP infection can occur at a salinity as low as 2 ppt, however, the prevalence and the severity of the EHP infection is higher at a salinity of 30 ppt.

Disorderless Quasi-localization of Polar Gases in One-Dimensional Lattices.

One-dimensional polar gases in deep optical lattices present a severely constrained dynamics due to the interplay between dipolar interactions, energy conservation, and finite bandwidth. The appearance of dynamically bound nearest-neighbor dimers enhances the role of the 1/r^{3} dipolar tail, resulting in the absence of external disorder, in quasi-localization via dimer clustering for very low densities and moderate dipole strengths. Furthermore, even weak dipoles allow for the formation of self-bound superfluid lattice droplets with a finite doping of mobile, but confined, holons. Our results, which can be extrapolated to other power-law interactions, are directly relevant for current and future lattice experiments with magnetic atoms and polar molecules.

Harmonically Confined Particles with Long-Range Repulsive Interactions.

We study an interacting system of N classical particles on a line at thermal equilibrium. The particles are confined by a harmonic trap and repel each other via pairwise interaction potential that behaves as a power law ∝∑[under i≠j][over N]|x_{i}-x_{j}|^{-k} (with k>-2) of their mutual distance. This is a generalization of the well-known cases of the one-component plasma (k=-1), Dyson's log gas (k→0^{+}), and the Calogero-Moser model (k=2). Because of the competition between harmonic confinement and pairwise repulsion, the particles spread over a finite region of space for all k>-2. We compute exactly the average density profile for large N for all k>-2 and show that while it is independent of temperature for sufficiently low temperature, it has a rich and nontrivial dependence on k with distinct behavior for -21 and k=1.

Global distribution of white spot syndrome virus genotypes determined using a novel genotyping assay.

White spot disease, caused by infection with white spot syndrome virus (WSSV), is a serious panzootic affecting prawn aquaculture. The disease has spread rapidly around the prawn-culturing regions of the world through a number of previously identified mechanisms. The ability to distinguish and trace strains of WSSV is of great benefit to identify, and then limit, the translocation routes of the disease. Here, we describe a novel genotyping method using 34 short tandem repeat regions of the viral genome concurrently. This technique is highly sensitive to strain differences when compared to previous methods. The efficacy of the described method is demonstrated by testing WSSV isolates from around the globe, showing regional genotypic differences. The differences in the genotypes were used to create a global minimum spanning network, and in most cases the observed relationships were substantiated with verification of transboundary movement. This novel panel of STR markers will provide a valuable epidemiological tool for white spot disease. We have applied this to an outbreak of the disease in Queensland, Australia, that occurred in 2016. While the results indicate that the source of this outbreak currently remains cryptic, the analyses have provided valuable insights with which to further study the origins of the strains involved.

Titanium dioxide fiber saturable absorber for Q-switched fiber laser generation in the 1-micrometer region.

A passively Q-switched ytterbium-doped fiber laser (YDFL) operating at 1062 nm was demonstrated by using a segment of 20 cm titanium dioxide-doped fiber saturable absorber (TiO2DF SA). The Q-switched YDFL emerged stably with tunable repetition rates ranging from 32 kHz to 53 kHz as the pump power rose from 109 mW to 233 mW. Within this range of pump power, a maximum output power of 10.1 mW, maximum peak power of 75 mW, and maximum pulse energy of 191 nJ were obtained. The narrowest pulse width of 2.55 µs was attained at the maximum pump power of 233 mW, while the signal-to-noise ratio of the fundamental frequency was 47 dB. This demonstration reveals that the proposed TiO2DF SA is feasible for constructing a flexible and reliably stable Q-switched pulsed fiber laser in the 1-micrometer region.

The Royal Free Hospital 'hub-and-spoke network model' delivers effective care and increased access to liver transplantation.

OBJECTIVES: 'Hub-and-spoke' networks may be one solution to reduce the geographical inequality in access to liver transplantation (LT) and the growing demands on, and saturation of, LT centres. It is not clear if such networks improve equity of access, deliver comparable patient outcomes or effect patient satisfaction. STUDY DESIGN: Retrospective evaluation of outcomes and patient satisfaction within the Royal Free liver transplant 'hub-and-spoke' network. METHODS: Patient outcomes in those assessed for LT between September 2011 and 2014 at spoke centres (n = 4) were compared retrospectively with those assessed at the LT hub centre. Patient satisfaction questionnaires were completed and changes in LT referral patterns were explored with data obtained directly from NHS Blood and Transplant (NHSBT). RESULTS: A total of 655 patients (180 spoke; 475 hub) were assessed for LT. Patients referred from spoke centres were more likely to have viral hepatitis as an underlying aetiology (72/180 vs 110/475; P < 0.001), or hepatocellular carcinoma (48/180 vs 60/475; P < 0.001) as an indication for LT and were more likely to be listed for LT when compared with hub patients (139/180 vs 312/475, P = 0.005). Mortality on the waiting list (9/123 vs 25/269, P = 0.57), waiting time to LT (64-days vs 78-days, P = 0.91) and Model for End-Stage liver disease (MELD)/United Kingdom End-Stage Liver Disease (UKELD) score (P = 0.24/0.26) in listed patients were equivalent as were 1- and 3-year patient and graft survival rates. Patient satisfaction rates were high at both types of centre, with significantly more patients preferring 'locally delivered care' at spoke vs hub (11/50 vs 70/73, P≤0.0001). Since the development of formal hub-and-spoke networks data from NHSBT based on postcode confirmed a significant increase in patients undergoing LT (153%) from spoke centres, whereas numbers assessed and transplanted from the hub centre have remained static. CONCLUSION: Hub-and-spoke LT networks are effective in offering equivalent clinical outcomes, high patient satisfaction and alleviate clinical pressure on the hub centre. They have to potential to help eliminate the geographical disparity in mortality rates from chronic liver disease.

Luminescence and advanced mass spectroscopic characterization of sodium zinc orthophosphate phosphor for low-cost light-emitting diodes.

A new rare-earth-free NaZnPO4:Mn(2+) (NZP:Mn) phosphor powder has been developed by our group and investigated meticulously for the first time using secondary ion mass spectroscopy and chemical imaging techniques. The studies confirmed the effective incorporation of Mn(2+) into the host lattice, resulting in an enhancement of photoluminescence intensity. Phase purity has been verified and structure parameters have been determined successfully by Rietveld refinement studies. The NZP:Mn phosphor powder exhibits strong absorption bands in the ultraviolet and visible (300-470 nm) regions with a significant broad yellow-green (~543 nm) emission due to the characteristic spin forbidden d-d transition ((4)T1→(6)A1) of Mn(2+) ions, indicating weak crystal field strength at the zinc-replaced manganese site. The decay constants are a few milliseconds, which is a pre-requisite for applications in many display devices. The results obtained suggest that this new phosphor powder will find many interesting applications in semiconductor physics, as cost-effective light-emitting diodes (LEDs), as solar cells and in photo-physics.

Three mode Er3+ ring-doped fiber amplifier for mode-division multiplexed transmission.

We successfully fabricate three-mode erbium doped fiber with a confined Er(3+) doped ring structure and experimentally characterize the amplifier performance with a view to mode-division multiplexed (MDM) transmission. The differential modal gain was effectively mitigated by controlling the relative thickness of the ring-doped layer in the active fiber and pump launch conditions. A detailed study of the modal gain properties, amplifier performance in a MDM transmission system and inter-modal cross-gain modulation and associated transient effects is presented.

Erbium-doped multi-element fiber amplifiers for space-division multiplexing operations.

Erbium-doped multi-element fiber (MEF) amplifiers have been fabricated to simultaneously amplify multiple transmission channels. MEF devices comprise of multiple single-core fibers (elements) combined in a common coating, with each element working as a single fiber in isolation. MEFs containing 3-elements and 7-elements have been fabricated and characterized. Each element of the fabricated MEFs provides nearly 32 dB of gain with a noise figure of <5 dB for an input signal level of -23 dBm at 1530 nm. Different permutations of element pairs within the MEFs were checked for crosstalk and none was detected, confirming the simultaneous multi-channel amplification capabilities of MEFs.

73.7 Tb/s (96 x 3 x 256-Gb/s) mode-division-multiplexed DP-16QAM transmission with inline MM-EDFA.

Transmission of a 73.7 Tb/s (96 x 3 x 256-Gb/s) DP-16QAM mode-division-multiplexed signal over 119 km of few-mode fiber transmission line incorporating an inline multi mode EDFA and a phase plate based mode (de-)multiplexer is demonstrated. Data-aided 6 x 6 MIMO digital signal processing was used to demodulate the signal. The total demonstrated net capacity, taking into account 20% of FEC-overhead and 7.5% additional overhead (Ethernet and training sequences), is 57.6 Tb/s, corresponding to a spectral efficiency of 12 bits/s/Hz.

Optical and bio-sensing characteristics of ZnO nanotubes grown by hydrothermal method.

ZnO nanostructures were fabricated on copper substrates by hydrothermal method at an optimized growth temperature of -95 degrees C. Structural properties were investigated by field emission scanning electron and transmission electron microscopy. Distinct morphologies were found to be formed at different growth times. The formation of nanotubes mainly involved the initial nucleation followed by the growth of nanorods at 95 degrees C, and then with the increase of dissolution time at room temperature, the preferential chemical dissolution of the metastable Zn-rich [0001] polar surfaces resulted in removing the atoms from the surfaces, thus leading to the thinning of the wall of the nanostructures. Completely hollow ZnO nanotubes could be obtained at a high dissolution time. The room temperature photoluminescence and optical absorption properties of ZnO nanotubes have been studied as a function of dissolution time. The efficacy of ZnO nanotubes for glucose sensing applications has been studied.

Retinoic acid syndrome--cardiac complication.

Retinoic acid syndrome is a novel complication of therapy with all-trans retinoic acid (ATRA) in patients with acute promyelocytic leukemia (APML). Primarily the syndrome consists of fever and respiratory distress. Additional features include weight gain, oedema over lower extremities, pleural or pericardial effusion and hypotension. We report electrophysiological changes in a 16 year old patient with acute promyelocytic leukemia following treatment with ATRA. Such an unusual complication is a rarity and to the best of our knowledge has not been previously reported.

Protein stability and folding kinetics in the nucleus and endoplasmic reticulum of eucaryotic cells.

We measure the stability and folding relaxation rate of phosphoglycerate kinase (PGK) Förster resonance energy transfer (FRET) constructs localized in the nucleus or in the endoplasmic reticulum (ER) of eukaryotic cells. PGK has a more compact native state in the cellular compartments than in aqueous solution. Its native FRET signature is similar to that previously observed in a carbohydrate-crowding matrix, consistent with crowding being responsible for the compact native state of PGK in the cell. PGK folds through multiple states in vitro, but its folding kinetics is more two-state-like in the ER, so the folding mechanism can be modified by intracellular compartments. The nucleus increases PGK stability and folding rate over the cytoplasm and ER, even though the density of crowders in the nucleus is no greater than in the ER or cytoplasm. Nuclear folding kinetics (and to a lesser extent, thermodynamics) vary less from cell to cell than in the cytoplasm or ER, indicating a more homogeneous crowding and chemical environment in the nucleus.

First demonstration and detailed characterization of a multimode amplifier for Space Division Multiplexed transmission systems.

We present the first demonstration of a multimode (two mode-group) erbium-doped fiber amplifier for Space Division Multiplexed (SDM) applications and demonstrate various design and performance features of such devices. In particular we experimentally demonstrate that differential modal gains can be controlled and reduced both by fiber design and control of the pump field distribution. Using a suitably designed fiber we demonstrate simultaneous modal gains of ~20 dB for different pair-wise combinations of spatial and polarization modes in an EDFA supporting amplification of 6 distinct modes.

Silicon dioxide embedded germanium nanocrystals grown using molecular beam epitaxy for floating gate memory devices.

SiO2/Ge nanocrystals/SiO2 trilayer memory structure has been fabricated by oxidizing and subsequent annealing of self assembled SiGe nanoislands grown by molecular beam epitaxy. The optical and charge storage characteristics of trilayer structures have been studied through Raman spectroscopy and capacitance-voltage measurements, respectively. An anti-clockwise hysteresis in the C-V characteristics indicated the net electron trapping in the floating gate containing Ge nanocrystals. Frequency dependent measurements of device characteristics indicate that neither interface defects nor deep traps are dominant for the charging or discharging processes of nanocrystal floating gates.

Shape and size distribution of molecular beam epitaxy grown self-assembled Ge islands on Si (001) substrates.

We have performed a series of annealing experiments with Ge islands on Si (001) grown by molecular beam epitaxy, in order to clarify issues related to island stability and coarsening. The shape and size distribution of nanoislands as a function of annealing time at a temperature of 650 degrees C have been studied. Optical phonons from Raman spectra have been used as efficient probes to study the evolution of Si(1-x)Ge(x) islands. Both the alloy composition and residual strain in the islands have been determined from the phonon frequencies and Raman intensities. The experimental results are in good agreement with the strain relaxation estimated using X-ray rocking curves. The results indicate that the shape and size distribution of Ge islands are controlled via structural and compositional changes through strain relaxation by the periodic creation and extinction of tiny nanocrystals.