Coherent beam combining of a narrow-linewidth long-pulse Er3+-doped multicore fiber amplifier

Active phase locking of a multicore erbium-doped fiber amplifier is demonstrated for 180 ns narrow-linewidth pulses at 1545 nm. A spatial light modulator is used at the input of the amplifier to control the optical phase of 7 beams injected in the hexagonally-arranged cores, ensuring efficient combining through a SPGD algorithm. At the output, combining is performed using a diffractive optical element. This experiment establishes multicore amplifiers as a promising way to scale the energy of Brillouin-limited pulsed amplifiers for LIDAR applications. We also present a simple lensless technique to measure phase shifts between pairs of adjacent channels that could be implemented in future active coherent combining systems.

High-energy few-cycle Yb-doped fiber amplifier source based on a single nonlinear compression stage

A simple, compact, and efficient few-cycle laser source at a central wavelength of 1 µm is presented. The system is based on a high-energy femtosecond ytterbium-doped fiber amplifier delivering 130 fs, 250 µJ pulses at 200 kHz, corresponding to 1.5 GW of peak power and an average power of 50 W. The unprecedented short pulse duration at the output of this system is obtained by use of spectral intensity and phase shaping, allowing for both gain narrowing mitigation and the compensation of the nonlinear accumulated spectral phase. This laser source is followed by a single-stage of nonlinear compression in a xenon-filled capillary, allowing for the generation of 14 fs, 120 µJ pulses at 200 kHz resulting in 24 W of average power. High-harmonic generation driven by this type of source will trigger numerous new applications in the XUV range and attosecond science.

Extracorporeal shockwave therapy in the treatment of chronic diabetic foot ulcers: a prospective randomised trial

OBJECTIVE

To investigate the efficacy of extracorporeal shockwave therapy (ESWT) on healing chronic diabetic foot ulcers (DFU).

METHOD

Patients with chronic DFUs were randomised (1:1) to receive a series of six ESWT treatments over 3 weeks in combination with standard care or standard care alone. ESWT was performed on DFUs using 250 shocks/cm² and 500 shocks on arterial beds supplying the ulcer location.

RESULTS

We recruited 23 patients, 11 in the intervention group and 12 in the control. Transcutaneous oxygen tension was significantly increased in patients treated with ESWT compared with those receiving standard care alone at 3 weeks (p=0.044). Ulcer area reduction was 34.5% in the intervention group versus 5.6% in the control group at 7 weeks (p=0.387). Within-group analysis revealed a significant reduction of ulcer area in the intervention group (p<0.01), while healing was not demonstrated in the control group (p>0.05) (data tested for trend).

CONCLUSION

This randomised study indicates a potential beneficial effect of ESWT on ulcer healing as well as tissue oxygenation. Owing to weaknesses of the study and the fact that ulcer healing was not significantly improved in the intervention group compared with the control group, a larger randomised trial with blinded design is suggested.

Management of mixed type congenital mesoblastic nephroma: Case series and review of the literature

Congenital mesoblastic nephroma (CMN) is the most common renal tumor of infancy; however, it occurs infrequently with an incidence of 1 : 125,000. The cellular and classical variants are the most common subtypes of tumors, with a mixed variant occurring infrequently. We describe two cases of mixed variant CMN, which presented within days of each other differing in their clinical behavior. The first case followed a typical course, previously described in the literature, while the other deviated significantly. Traditionally, CMN presents as large abdominal mass in the neonatal period associated with a paraneoplastic syndrome, which can result in hypertension or hypercalcemia. Surgical resection is curative in most cases and long-term prognosis is excellent. Hypertension rarely persists after removal of the tumor, but remained in one of our two patients.

Coherent combining efficiency in strongly saturated divided-pulse amplification systems

Numerical simulations are performed to analyze effects that limit the combining efficiency in divided-pulse amplification setups. The model allows us to evaluate the impact of self- and cross-phase modulation between pulse replicas, Kramers-Krönig-related phase shifts, and inter- and intra-replica saturation effects. In particular, we show that when the energy per replica approaches the saturation energy, pulse reshaping induced by the gain saturation coupled with self-phase modulation imparts a temporal differential phase that decreases the combining efficiency. This effect limits the energy that can be extracted by a single replica, thereby providing design rules to scale the performances of short pulse laser sources using this technique.

Rear-side resonator architecture for the passive coherent combining of high-brightness laser diodes

We describe a new coherent beam combining architecture based on passive phase locking of emitters in an extended cavity on the rear facet and their coherent combination on the front facet. This rear-side technique provides strong optical feedback for phase locking while maintaining a high electrical-to-optical efficiency. Two high-brightness high-power tapered laser diodes are coherently combined using a Michelson-based cavity. The combining efficiency is above 82% and results in an output power of 6.7 W in a nearly diffraction-limited beam with an M(4σ)(2)≤1.2. A semi-active automatic adjustment of the current enhances the long-term stability of the combination, while the short-term stability is passively ensured by the extended cavity. This new laser configuration exhibits the simplicity of passive self-organizing architectures while providing a power conversion efficiency of 27% that is comparable to master oscillator power amplifier architectures.

Serum bilirubin concentration is modified by UGT1A1 haplotypes and influences risk of type-2 diabetes in the Norfolk Island genetic isolate

Background

Located in the Pacific Ocean between Australia and New Zealand, the unique population isolate of Norfolk Island has been shown to exhibit increased prevalence of metabolic disorders (type-2 diabetes, cardiovascular disease) compared to mainland Australia. We investigated this well-established genetic isolate, utilising its unique genomic structure to increase the ability to detect related genetic markers. A pedigree-based genome-wide association study of 16 routinely collected blood-based clinical traits in 382 Norfolk Island individuals was performed.

Results

A striking association peak was located at chromosome 2q37.1 for both total bilirubin and direct bilirubin, with 29 SNPs reaching statistical significance (P < 1.84 × 10⁻⁷). Strong linkage disequilibrium was observed across a 200 kb region spanning the UDP-glucuronosyltransferase family, including UGT1A1, an enzyme known to metabolise bilirubin. Given the epidemiological literature suggesting negative association between CVD-risk and serum bilirubin we further explored potential associations using stepwise multivariate regression, revealing significant association between direct bilirubin concentration and type-2 diabetes risk. In the Norfolk Island cohort increased direct bilirubin was associated with a 28 % reduction in type-2 diabetes risk (OR: 0.72, 95 % CI: 0.57-0.91, P = 0.005). When adjusted for genotypic effects the overall model was validated, with the adjusted model predicting a 30 % reduction in type-2 diabetes risk with increasing direct bilirubin concentrations (OR: 0.70, 95 % CI: 0.53-0.89, P = 0.0001).

Conclusions

In summary, a pedigree-based GWAS of blood-based clinical traits in the Norfolk Island population has identified variants within the UDPGT family directly associated with serum bilirubin levels, which is in turn implicated with reduced risk of developing type-2 diabetes within this population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0291-z) contains supplementary material, which is available to authorized users.

Nutritional outcomes with implementation of probiotics in preterm infants

OBJECTIVE

To assess nutritional outcomes in preterm infants after the implementation of probiotics.

STUDY DESIGN

Retrospective chart review of infants with birth weight⩽1250 grams and/or⩽28 weeks of gestational age admitted to the KCH-Neonatal Intensive Care Unit was done. Data were collected over two periods, period 1 (before probiotics) and period 2 (after probiotics) and included demographic data, daily weight gain, feeding strategies (type, amount, caloric content and frequency of feeds) and comorbidities affecting feedings (Patent ductus arteriosus, Sepsis). Primary outcomes-extra uterine growth restriction (EUGR) status and incidence of necrotizing enterocolitis (NEC) as well as secondary outcomes-time to reach full feeds, feeding intolerance episodes and weight gain were compared between the two groups.

RESULTS

A total of 113 infants (period 1) were compared with 108 infants (period 2). The odds of EUGR was significantly lower with probiotics (odds ratio: 0.3, 95% confidence interval 0.138 to 0.611). Time to reach full feeds was significantly reduced and weight gain was significantly better in period 2. Significant reduction was also noted in number of total parental nutrition days, central line days, nil per os days and number of feeding intolerance episodes in period 2. There was no significant difference in the incidence of NEC.

CONCLUSION

Probiotics improve feeding tolerance leading to better overall growth and decreases the incidence of EUGR in preterm infants.

D-dimer and risk of thromboembolic and bleeding events in patients with atrial fibrillation--observations from the ARISTOTLE trial

BACKGROUND

D-dimer is related to adverse outcomes in arterial and venous thromboembolic diseases.

OBJECTIVES

To evaluate the predictive value of D-dimer level for stroke, other cardiovascular events, and bleeds, in patients with atrial fibrillation (AF) treated with oral anticoagulation with apixaban or warfarin; and to evaluate the relationship between the D-dimer levels at baseline and the treatment effect of apixaban vs. warfarin.

METHODS

In the ARISTOTLE trial, 18 201 patients with AF were randomized to apixaban or warfarin. D-dimer was analyzed in 14 878 patients at randomization. The cohort was separated into two groups; not receiving vitamin K antagonist (VKA) treatment and receiving VKA treatment at randomization.

RESULTS

Higher D-dimer levels were associated with increased frequencies of stroke or systemic embolism (hazard ratio [HR] [Q4 vs. Q1] 1.72, 95% confidence interval [CI] 1.14-2.59, P = 0.003), death (HR [Q4 vs. Q1] 4.04, 95% CI 3.06-5.33) and major bleeding (HR [Q4 vs. Q1] 2.47, 95% CI 1.77-3.45, P < 0.0001) in the no-VKA group. Similar results were obtained in the on-VKA group. Adding D-dimer level to the CHADS2 score improved the C-index from 0.646 to 0.655 for stroke or systemic embolism, and from 0.598 to 0.662 for death, in the no-VKA group. D-dimer level improved the HAS-BLED score for prediction of major bleeds, with an increase in the C-index from 0.610 to 0.641. There were no significant interactions between efficacy and safety of study treatment and D-dimer level.

CONCLUSION

In anticoagulated patients with AF, the level of D-dimer is related to the risk of stroke, death, and bleeding, and adds to the predictive value of clinical risk scores. The benefits of apixaban were consistent, regardless of the baseline D-dimer level.