Continuous-wave Raman laser pumped within a semiconductor disk laser cavity

A KGd(WO4)(2) Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5: 6W of absorbed diode pump power, and output power up to 0.8W at 1143nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157nm

Chemical Validation of Methionyl tRNA Synthetase (MetRS) as a Druggable Target in <i>Leishmania donovani</i>

Methionyl-tRNA synthetase (MetRS) has been chemically validated as a drug target in the kinetoplastid parasite Trypanosoma brucei. In the present study we investigate the validity of this target in the related trypanosomatid Leishmania donovani. Following development of a robust highthroughput compatible biochemical assay, a compound screen identified DDD806905 as a highly potent inhibitor of LdMetRS (Ki 18 nM). Crystallography revealed this compound binds to the methionine pocket of MetRS with enzymatic studies confirming DDD806905 displays competitive inhibition with respect to methionine and mixed inhibition with respect to ATP binding. DDD806905 showed activity, albeit with different levels of potency, in various Leishmania cell-based viability assays, with on-target activity observed in both Leishmania promastigote cell assays and a Leishmania tarentolae in vitro translation assay. Unfortunately this compound failed to show efficacy in an animal model of leishmaniasis. We investigated the potential causes for the discrepancies in activity observed in different Leishmania cell assays and the lack of efficacy in the animal model and found that high protein binding as well as sequestration of this dibasic compound into acidic compartments may play a role. Despite medicinal chemistry efforts to address the dibasic nature of DDD806905 and analogues, no progress could be achieved with the current chemical series. Although DDD806905 is not a developable anti-leishmanial compound, MetRS remains an attractive anti-leishmanial drug target

Cyclin-dependent kinase 12 is a drug target for visceral leishmaniasis

Visceral leishmaniasis causes considerable mortality and morbidity in many parts of the world. There is an urgent need for the development of new, effective treatments for this disease. Here we describe the development of an anti-leishmanial drug-like chemical series based on a pyrazolopyrimidine scaffold. The leading compound from this series (7, DDD853651/GSK3186899) is efficacious in a mouse model of visceral leishmaniasis, has suitable physicochemical, pharmacokinetic and toxicological properties for further development, and has been declared a preclinical candidate. Detailed mode-of-action studies indicate that compounds from this series act principally by inhibiting the parasite cdc-2-related kinase 12 (CRK12), thus defining a druggable target for visceral leishmaniasis

Preclinical candidate for the treatment of visceral leishmaniasis that acts through proteasome inhibition

Visceral leishmaniasis (VL), caused by the protozoan parasites Leishmania donovani and Leishmania infantum, is one of the major parasitic diseases worldwide. There is an urgent need for new drugs to treat VL, because current therapies are unfit for purpose in a resource-poor setting. Here, we describe the development of a preclinical drug candidate, GSK3494245/DDD01305143/compound 8, with potential to treat this neglected tropical disease. The compound series was discovered by repurposing hits from a screen against the related parasite Trypanosoma cruzi. Subsequent optimization of the chemical series resulted in the development of a potent cidal compound with activity against a range of clinically relevant L. donovani and L. infantum isolates. Compound 8 demonstrates promising pharmacokinetic properties and impressive in vivo efficacy in our mouse model of infection comparable with those of the current oral antileishmanial miltefosine. Detailed mode of action studies confirm that this compound acts principally by inhibition of the chymotrypsin-like activity catalyzed by the β5 subunit of the L. donovani proteasome. High-resolution cryo-EM structures of apo and compound 8-bound Leishmania tarentolae 20S proteasome reveal a previously undiscovered inhibitor site that lies between the β4 and β5 proteasome subunits. This induced pocket exploits β4 residues that are divergent between humans and kinetoplastid parasites and is consistent with all of our experimental and mutagenesis data. As a result of these comprehensive studies and due to a favorable developability and safety profile, compound 8 is being advanced toward human clinical trials.</p

Validation of Trypanosoma cruzi inactivation techniques for laboratory use

Trypanosoma cruzi (T. cruzi) is the causative agent of Chagas’ disease, a parasitic infection responsible for significant morbidity and mortality in Latin America. The current treatments have many serious drawbacks and new drugs are urgently required. In the UK, T. cruzi is classified by the Advisory Committee on Dangerous Pathogens (ACDP) as a Hazard Group 3 organism and strict safety practices must be adhered to when handling this pathogen in the laboratory. Validated inactivation techniques are required for safe T. cruzi waste disposal and removal from Containment Level 3 (CL3) facilities for storage, transportation and experimental analysis. Here we assess three T. cruzi. inactivation methods. These include three freeze-thaw cycles, chemical inactivation with Virkon disinfectant, and air drying on Whatman FTA cards (A, B, C, Elute) and on a Mitra microsampling device. After each treatment parasite growth was monitored for 4–6 weeks by microscopic examination. Three freeze-thaw cycles were sufficient to inactivate all T. cruzi CLBrener Luc life cycle stages and Silvio x10/7 A1 large epimastigote cell pellets up to two grams wet weight. Virkon treatment for one hour inactivated T. cruzi Silvio x10/7 subclone A1 and CLBrener Luc both in whole blood and cell culture medium when incubated at a final concentration of 2.5% Virkon, or at ≥1% Virkon when in tenfold excess of sample volume. Air drying also inactivated T. cruzi CLBrener Luc spiked blood when dried on FTA A, B or Elute cards for ≥30 minutes and on a Mitra Microsampler for two hours. However, T. cruzi CLBrener Luc were not inactivated on FTA C cards when dried for up to two hours. These experimentally confirmed conditions provide three validated T. cruzi inactivation methods which can be applied to other related ACDP Hazard Group 2–3 kinetoplastid parasites.</p

Proof planning Non-standard Analysis

This paper presents work carried out in the Clam proof-planner (Richardson et al. 00) on automating mathematical proofs using induction and non-standard analysis. The central idea is to show that the proofs we present are well-suited to proof-planning, due to their shared common structure. The theorems presented in this paper belong to standard analysis, and have been proved using induction and techniques from non-standard analysis. We rst give an overview of the proof-planning paradigm, giving a brief exposition of rippling as a heuristic for guiding rewriting. We then present the basic notions of non-standard analysis and explain our axiomatisation. We then go on to explain the theorems we intend to prove and sketch their proofs. Finally we show the parts of the proofs which have been planned automatically in Clam and draw some conclusions from the work completed so fa

Automating Event-B invariant proofs by rippling and proof patching

This work is supported by EPSRC grants EP/H024204/1, EP/E005713/1, EP/M018407/1 and EP/J001058/1.The use of formal method techniques can contribute to the production of more reliable and dependable systems. However, a common bottleneck for industrial adoption of such techniques is the needs for interactive proofs. We use a popular formal method, called Event-B, as our working domain, and set invariant preservation (INV) proofs as targets, because INV proofs can account for a significant proportion of the proofs requiring human interactions. We apply an inductive theorem proving technique, called rippling, for Event-B INV proofs. Rippling automates proofs using meta-level guidance. The guidance is in particular useful to develop proof patches to recover failed proof attempts. We are interested in the case when a missing lemma is required. We combine a scheme-based theory-exploration system, called IsaScheme [MRMDB10], with rippling to develop a proof patch via lemma discovery. We also develop two new proof patches to unfold operator definitions and to suggest case-splits, respectively. The combined use of rippling with these three proof patches as a proof method significantly improves the proof automation for our evaluation set.Publisher PDFPeer reviewe

Real-time In-Situ Passive Acoustic Array Beamforming from the AutoNaut Wave-Propelled Uncrewed Surface Vessel

This article presents the first demonstration of beamforming, detection, and bearing estimation of an underwater acoustic source from an eight-element thin line hydrophone array towed behind the AutoNaut wave-propelled uncrewed surface vessel. This has been achieved in situ and in real time during an experimental sea trial off the coast of Plymouth, U.K. A controlled acoustic source was towed from a support vessel while emitting seven tonals with frequencies between 480&amp;#x2013;1630&amp;#x00A0;Hz and source levels between 93&amp;#x2013;126&amp;#x00A0;dB. This allowed the detection performance of the array to be assessed and demonstrated for an acoustic source with known bearing and range. In postprocessing, the shape of the array was estimated using a cubic spline model, exploiting measurements from pressure and three-axis compass sensors integrated at each end of the array. The beamforming was repeated using the estimated array shape to infer the hydrophone positions, which resulted in a median improvement of 0.38&amp;#x00A0;dB and maximum of 5.8&amp;#x00A0;dB in the MUSIC beamforming output, and a potential reduction in the left/right bearing estimation ambiguities. The outcomes of this work demonstrate that the AutoNaut is an effective platform for towed array passive acoustic monitoring.</p

IceBird Summer 2024 Campaign Report

Scientific focus in summer 2024: In addition to continuing long-term objectives of IceBird, a scientific focus of the IceBird Summer campaing in 2024 is to validate and improve novel satellite-based sea ice freeboard and thickness estimates from altimetry missions like CryoSat-2 during the melting phase. It was planned to conduct satellite underflights of CryoSat-2 and ICESat-2; however, poor weather conditions meant a lack of opportunities, and this goal was not achieved. Other goals of the 2024 campaign, to coordinate with scheduled field work (e.g. RV Kronprins Haakon servicing an oceanographic mooring in the Amundsen basin) and a separate airborne campaign, the NASA ARCSIX https://espo.nasa.gov/arcsix project, were achieved successfully. We also overflew an array of ice mass balance (CRREL) and weather buoys (UiT) www.cryosphereinnovation.com/data deployed by twin otter landings in April 2024