The diverse output pulsewidths, linewidths and polarization states of fibre lasers provide both high efficiency and high output power in a small, low-maintenance format that is ideal for applications ...throughout research, defence and industry. New directions are constantly being pursued to exploit the capabilities of this technology. One such direction involves extending the emission wavelength further into the infrared, which will benefit numerous existing and future applications. Many exciting advances have been demonstrated and many challenges remain, the most significant of which are summarized in this Review.
The mid-infrared (MIR) represents a large portion of the electromagnetic spectrum that is progressively being exploited for an enormous number of applications. Thermal imaging cameras, dental and ...skin resurfacing lasers, and narcotics detectors at airports are all mainstream examples involving the MIR, but potential applications of MIR technologies are much larger. Accessing the unique opportunities afforded by the MIR is critically dependent on the specific characteristics of MIR emitting sources that become available. In this review, we survey an important enabling technology to the opening up of MIR science and applications, namely that driven by fiber-based sources of coherent MIR radiation . In this review paper, we describe many of the key advances in the innovation and development of such sources over the past few decades and discuss many of the underlying science and technology issues that have resulted in specific recent source achievements, especially in light of new applications enabled by these new source capabilities. We also discuss a few specific anticipated future needs and some potentially disruptive approaches to future MIR fiber source development.
With growing interest in the mid‐infrared spectral region, dysprosium has recently been revisited for efficient high‐performance infrared source development. Despite historically receiving less ...attention than other rare earth ions, in recent years lasers utilizing the dysprosium ion as the laser material have set record mid‐infrared performance, including tunability from 2.8 to 3:4 µm (in addition to 4:3 µm lasing), continuous wave powers exceeding 10 W, greater than 73% slope efficiencies, and even ultrafast pulsed operation. Herein, the unique energy level structure and spectroscopy of the dysprosium ion are examined and the major developments that have led to this resurgence of interest and subsequent record mid‐infrared laser performance are surveyed. Also mid‐infrared applications of emerging dysprosium lasers are highlighted, in addition to surveying the many opportunities that lie ahead.
Although it has been several decades since the first demonstration of a dysprosium laser, it is relatively recently that a growing research interest is seen. Herein, the unique energy level structure and spectroscopy of the dysprosium ion are examined and the major developments that have led to this resurgence are surveyed, in addition to assessing the opportunities that lie ahead.
The evolution of parasitism is a recurrent event in the history of life and a core problem in evolutionary biology. Trypanosomatids are important parasites and include the human pathogens Trypanosoma ...brucei, Trypanosoma cruzi, and Leishmania spp., which in humans cause African trypanosomiasis, Chagas disease, and leishmaniasis, respectively. Genome comparison between trypanosomatids reveals that these parasites have evolved specialized cell-surface protein families, overlaid on a well-conserved cell template. Understanding how these features evolved and which ones are specifically associated with parasitism requires comparison with related non-parasites. We have produced genome sequences for Bodo saltans, the closest known non-parasitic relative of trypanosomatids, and a second bodonid, Trypanoplasma borreli. Here we show how genomic reduction and innovation contributed to the character of trypanosomatid genomes. We show that gene loss has “streamlined” trypanosomatid genomes, particularly with respect to macromolecular degradation and ion transport, but consistent with a widespread loss of functional redundancy, while adaptive radiations of gene families involved in membrane function provide the principal innovations in trypanosomatid evolution. Gene gain and loss continued during trypanosomatid diversification, resulting in the asymmetric assortment of ancestral characters such as peptidases between Trypanosoma and Leishmania, genomic differences that were subsequently amplified by lineage-specific innovations after divergence. Finally, we show how species-specific, cell-surface gene families (DGF-1 and PSA) with no apparent structural similarity are independent derivations of a common ancestral form, which we call “bodonin.” This new evidence defines the parasitic innovations of trypanosomatid genomes, revealing how a free-living phagotroph became adapted to exploiting hostile host environments.
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•The Bodo saltans genome reveals evolutionary changes at the origin of parasitism•Parasite genomes are streamlined, consistent with a loss of functional redundancy•Expanded parasite transporter genes reflect a reorientation of membrane function•Non-homologous, parasite cell-surface proteins evolved from a common ancestor
An enduring question in biology is how parasites evolved from free-living organisms. To understand how trypanosomatids became parasitic, Jackson et al. sequenced the genome of a free-living relative (Bodo saltans), showing how trypanosomatid genomes became adapted for parasitism through both reduction and elaboration of their free-living legacy.
Patients with dilated cardiomyopathy whose symptoms and cardiac function have recovered often ask whether their medications can be stopped. The safety of withdrawing treatment in this situation is ...unknown.
We did an open-label, pilot, randomised trial to examine the effect of phased withdrawal of heart failure medications in patients with previous dilated cardiomyopathy who were now asymptomatic, whose left ventricular ejection fraction (LVEF) had improved from less than 40% to 50% or greater, whose left ventricular end-diastolic volume (LVEDV) had normalised, and who had an N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) concentration less than 250 ng/L. Patients were recruited from a network of hospitals in the UK, assessed at one centre (Royal Brompton and Harefield NHS Foundation Trust, London, UK), and randomly assigned (1:1) to phased withdrawal or continuation of treatment. After 6 months, patients in the continued treatment group had treatment withdrawn by the same method. The primary endpoint was a relapse of dilated cardiomyopathy within 6 months, defined by a reduction in LVEF of more than 10% and to less than 50%, an increase in LVEDV by more than 10% and to higher than the normal range, a two-fold rise in NT-pro-BNP concentration and to more than 400 ng/L, or clinical evidence of heart failure, at which point treatments were re-established. The primary analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT02859311.
Between April 21, 2016, and Aug 22, 2017, 51 patients were enrolled. 25 were randomly assigned to the treatment withdrawal group and 26 to continue treatment. Over the first 6 months, 11 (44%) patients randomly assigned to treatment withdrawal met the primary endpoint of relapse compared with none of those assigned to continue treatment (Kaplan-Meier estimate of event rate 45·7% 95% CI 28·5–67·2; p=0·0001). After 6 months, 25 (96%) of 26 patients assigned initially to continue treatment attempted its withdrawal. During the following 6 months, nine patients met the primary endpoint of relapse (Kaplan-Meier estimate of event rate 36·0% 95% CI 20·6–57·8). No deaths were reported in either group and three serious adverse events were reported in the treatment withdrawal group: hospital admissions for non-cardiac chest pain, sepsis, and an elective procedure.
Many patients deemed to have recovered from dilated cardiomyopathy will relapse following treatment withdrawal. Until robust predictors of relapse are defined, treatment should continue indefinitely.
British Heart Foundation, Alexander Jansons Foundation, Royal Brompton Hospital and Imperial College London, Imperial College Biomedical Research Centre, Wellcome Trust, and Rosetrees Trust.
We report on a Dy 3+ -doped fluoroindate glass fiber laser operating in the yellow (∼576 nm) wavelength region that is pumped by a blue GaN diode laser (∼450 nm). Using single-clad Dy 3+ -doped ...fluoroindate glass fiber with 0.5 mol% concentration and a ∼0.48 m length, a slope efficiency of ∼26.6% and maximum output power of ∼467 mW was produced. This result demonstrates that fluoroindate glass fiber has a sufficiently low background loss at visible wavelengths to support efficient visible light generation. We compared all our measurements with a Dy 3+ -doped fluorozirconate glass fiber and found that most of the laser performance and spectroscopic parameters are similar to ZBLAN. We therefore conclude that fluoroindate glass fiber can be further developed for visible light emission.
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