390 research outputs found

    Possible canted antiferromagnetism in UCu9_9Sn4_4

    Full text link
    We report on the new compound UCu9{}_9Sn4{}_4 which crystallizes in the tetragonal structure \emph{I}4/\emph{mcm} with lattice parameters a=8.600AËša = 8.600{\rm\AA} and c=12.359AËšc = 12.359{\rm\AA}. This compound is isotyp to the ferromagnetic systems RECu9{}_9Sn4{}_4 (RE = Ce, Pr, Nd) with Curie temperatures TCT{}\rm_C = 5.5 K, 10.5 K and 15 K, respectively. UCu9{}_9Sn4{}_4 exhibits an uncommon magnetic behavior resulting in three different electronic phase transitions. Below 105 K the sample undergoes a valence transition accompanied by an entropy change of 0.5 Rln2. At 32 K a small hump in the specific heat and a flattening out in the susceptibility curve probably indicate the onset of helical spin order. To lower temperatures a second transition to antiferromagnetic ordering occurs which develops a small ferromagnetic contribution on lowering the temperature further. These results are strongly hinting for canted antiferromagnetism in UCu9{}_9Sn4{}_4.Comment: 2 pages, 3 figures, SCES0

    Unusual Single-Ion Non-Fermi Liquid Behavior in Ce_(1-x)La_xNi_9Ge_4

    Full text link
    We report on specific heat, magnetic susceptibility and resistivity measurements on the compound Ce_(1-x)La_xNi_9Ge_4 for various concentrations ranging from the stoichiometric system with x=0 to the dilute limit x=0.95. Our data reveal single-ion scaling with the Ce-concentration and the largest ever recorded value of the electronic specific heat c/T approximately 5.5 J K^(-2)mol^(-1) at T=0.08K for the stoichiometric compound x=0 without any trace of magnetic order. While in the doped samples c/T increases logarithmically below 3K down to 50mK, their magnetic susceptibility behaves Fermi liquid like below 1K. These properties make the compound Ce_(1-x)La_xNi_9Ge_4 a unique system on the borderline between Fermi liquid and non-Fermi liquid physics.Comment: 4 pages, 5 figures; v2 contains additional resisitivity measurements; final version to appear in Phys. Rev. Let

    Ultra-distal access of the M1 segment with the 5 Fr Navien distal access catheter in acute (anterior circulation) stroke: is it safe and efficient?

    Get PDF
    Background and aim The importance of mechanical thrombectomy in acute stroke treatment has grown over recent years. Mechanical thrombectomy comprises many different techniques. Technical improvements in the catheter material have led to the development of large-bore distal access catheters which can enter tortuous intracranial vessels. This has promising applications for endovascular stroke treatment. This study evaluated the safety and success rate of ultra-distal access of the middle cerebral artery (MCA) M1 segment with the 5 Fr Navien 58 distal access catheter in the treatment of acute stroke in combination with stent retrievers. Methods We retrospectively analyzed 81 patients with an acute stroke of the anterior circulation in whom ultra-distal access to the M1 segment was carried out using the Navien 58 catheter with an anchoring technique with a stent retriever for mechanical thrombectomy. Technical complications, success rates of catheter placement, success rates of thrombectomy using the modified Thrombolysis In Cerebral Infarction (mTICI) score, and the procedure times were evaluated. Results Ultra-distal access with the Navien 58 was successful in 75% (61/81) of cases. Recanalization success with a mTICI score of 2b and better was achieved in 83% overall (67/81), in 90% (55/61) of cases with successful ultra-distal access and in 60% (12/20) of cases without ultra-distal access. No severe adverse effects such as dissections or perforations occurred as a result of the ultra-distal catheter placement in the M1 segment. In 4% (3/81) of the cases a reversible MCA vasospasm occurred. Conclusions Ultra-distal placement of the Navien 58 distal access catheter into the M1 segment in acute anterior circulation stroke can be achieved consistently, is safe in practice, and results in good recanalization success rates

    CESAR: conventional ventilatory support vs extracorporeal membrane oxygenation for severe adult respiratory failure.

    Get PDF
    BACKGROUND: An estimated 350 adults develop severe, but potentially reversible respiratory failure in the UK annually. Current management uses intermittent positive pressure ventilation, but barotrauma, volutrauma and oxygen toxicity can prevent lung recovery. An alternative treatment, extracorporeal membrane oxygenation, uses cardio-pulmonary bypass technology to temporarily provide gas exchange, allowing ventilator settings to be reduced. While extracorporeal membrane oxygenation is proven to result in improved outcome when compared to conventional ventilation in neonates with severe respiratory failure, there is currently no good evidence from randomised controlled trials to compare these managements for important clinical outcomes in adults, although evidence from case series is promising. METHODS/DESIGN: The aim of the randomised controlled trial of Conventional ventilatory support vs extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR) is to assess whether, for patients with severe, but potentially reversible, respiratory failure, extracorporeal membrane oxygenation will increase the rate of survival without severe disability ('confined to bed' and 'unable to wash or dress') by six months post-randomisation, and be cost effective from the viewpoints of the NHS and society, compared to conventional ventilatory support. Following assent from a relative, adults (18-65 years) with severe, but potentially reversible, respiratory failure (Murray score >/= 3.0 or hypercapnea with pH < 7.2) will be randomised for consideration of extracorporeal membrane oxygenation at Glenfield Hospital, Leicester or continuing conventional care in a centre providing a high standard of conventional treatment. The central randomisation service will minimise by type of conventional treatment centre, age, duration of high pressure ventilation, hypoxia/hypercapnea, diagnosis and number of organs failed, to ensure balance in key prognostic variables. Extracorporeal membrane oxygenation will not be available for patients meeting entry criteria outside the trial. 180 patients will be recruited to have 80% power to be able to detect a one third reduction in the primary outcome from 65% at 5% level of statistical significance (2-sided test). Secondary outcomes include patient morbidity and health status at 6 months. DISCUSSION: Analysis will be based on intention to treat. A concurrent economic evaluation will also be performed to compare the costs and outcomes of both treatments

    On the Employment of Machine Learning in the Blockchain Selection Process

    Full text link
    Given the growing increase in the number of blockchain (BC) platforms, cryptocurrencies, and tokens, non-technical individuals face a complex question when selecting a BC that meets their requirements (e.g., performance or security). In addition, current approaches that aid such a selection process present drawbacks (e.g., require specific BC knowledge or are not automated and scalable), which hinders the decision process even further. Fortunately, techniques such as Machine Learning (ML) allow the creation of selection models without human interaction by identifying the BC features that match the requirements provided by the user in an automated and flexible manner. Thus, this work presents the design and implementation of an ML-based BC selection approach that employs five ML models to select the most suitable BC given user requirements (e.g., BC popularity, fast block inclusion, or Smart Contract - SC support). The approach follows an ML-specific data flow and defines a novel equation to quantify the popularity of a BC. Furthermore, it details the models’ accuracy and functionality in two distinct use cases, which shows their good accuracy (>85%). Finally, discussions on (a) the ML usefulness, (b) advantages over rule-based systems, and (c) the most relevant features for the BC selection are presented

    Maximizing Seaweed Growth on Autonomous Farms: A Dynamic Programming Approach for Underactuated Systems Navigating on Uncertain Ocean Currents

    Full text link
    Seaweed biomass offers significant potential for climate mitigation, but large-scale, autonomous open-ocean farms are required to fully exploit it. Such farms typically have low propulsion and are heavily influenced by ocean currents. We want to design a controller that maximizes seaweed growth over months by taking advantage of the non-linear time-varying ocean currents for reaching high-growth regions. The complex dynamics and underactuation make this challenging even when the currents are known. This is even harder when only short-term imperfect forecasts with increasing uncertainty are available. We propose a dynamic programming-based method to efficiently solve for the optimal growth value function when true currents are known. We additionally present three extensions when as in reality only forecasts are known: (1) our methods resulting value function can be used as feedback policy to obtain the growth-optimal control for all states and times, allowing closed-loop control equivalent to re-planning at every time step hence mitigating forecast errors, (2) a feedback policy for long-term optimal growth beyond forecast horizons using seasonal average current data as terminal reward, and (3) a discounted finite-time Dynamic Programming (DP) formulation to account for increasing ocean current estimate uncertainty. We evaluate our approach through 30-day simulations of floating seaweed farms in realistic Pacific Ocean current scenarios. Our method demonstrates an achievement of 95.8% of the best possible growth using only 5-day forecasts. This confirms the feasibility of using low-power propulsion and optimal control for enhanced seaweed growth on floating farms under real-world conditions.Comment: 8 pages, submitted to 2023 IEEE 62th Annual Conference on Decision and Control (CDC) Matthias Killer and Marius Wiggert contributed equally to this wor

    The optic nerve: a new window into cerebrospinal fluid composition?

    Get PDF
    Cerebrospinal fluid (CSF) pressure and composition are generally thought to be homogeneous within small limits throughout all CSF compartments. CSF sampled during lumbar puncture therefore should be representative for all CSF compartments. On the basis of clinical findings, histology and biochemical markers, we present for the first time strong evidence that the subarachnoid spaces (SAS) of the optic nerve (ON) can become separated from other CSF compartments in certain ON disorders, thus leading to an ON sheath compartment syndrome. This may result in an abnormal concentration gradient of CSF molecular markers determined in locally sampled CSF compared with CSF taken during lumbar punctur

    Cerebrospinal fluid dynamics between the intracranial and the subarachnoid space of the optic nerve. Is it always bidirectional?

    Get PDF
    CSF is thought to flow continuously from the site of production in the ventricles into interconnected spaces; i.e. cisterns and subarachnoid spaces (SASs). Since the SAS of the optic nerve is defined by a cul-de-sac anatomy, it is not evident how local CSF might recycle from that region to the general SAS. The concept of free communication of CSF has recently been challenged by the description of a concentration gradient of beta-trace protein, a lipocalin-like prostaglandin d-synthase (L-PGDS), between the spinal CSF and that in the SAS of the optic nerve, indicating diminished local clearance or local overproduction of L-PGDS here. In fact, computed cisternography with a contrast agent in three patients with idiopathic intracranial hypertension and asymmetric papilloedema demonstrate a lack of contrast-loaded CSF in the SAS of the optic nerve despite it being present in the intracranial SAS, thus suggesting compartmentation of the SAS of the optic nerve. The concept of an optic nerve compartment syndrome is further supported by a concentration gradient of brain-derived L-PGDS between the spinal CSF and the CSF from the optic nerve SAS in the same patient

    Bifidobacterium canis sp. Nov., a novel member of the bifidobacterium pseudolongum phylogenetic group isolated from faeces of a dog (canis lupus f. familiaris)

    Get PDF
    A fructose-6-phosphate phosphoketolase-positive strain (GSD1FST) was isolated from a faecal sample of a 3 weeks old German Shepherd dog. The closest related taxa to isolate GSD1FST based on results from the EZBioCloud database were Bifidobacte-rium animalis subsp. animalis ATCC 25527T, Bifidobacterium animalis subsp. lactis DSM 10140T and Bifidobacterium anseris LMG 30189T, belonging to the Bifidobacterium pseudolongum phylogenetic group. The resulting 16S rRNA gene identities (compared length of 1454 nucleotides) towards these taxa were 97.30, 97.23 and 97.09 %, respectively. The pairwise similarities of strain GSD1FST using argS, atpA, fusA, hsp60, pyrG, rpsC, thrS and xfp gene fragments to all valid representatives of the B. pseudo-longum phylogenetic group were in the concatenated range of 83.08–88.34 %. Phylogenomic analysis based on whole-genome methods such as average nucleotide identity revealed that bifidobacterial strain GSD1FST exhibits close phylogenetic relatedness (88.17 %) to Bifidobacetrium cuniculi LMG 10738T. Genotypic characteristics and phylogenetic analyses based on nine molecular markers, as well as genomic and comparative phenotypic analyses, clearly proved that the evaluated strain should be considered as representing a novel species within the B. pseudolongum phylogenetic group named as Bifidobacterium canis sp. nov. (GSD1FST=DSM 105923T=LMG 30345T=CCM 8806T)

    Cerebral Localized Marginal Zone Lymphoma Presenting as Hypothalamic-Pituitary Region Disorder

    Get PDF
    Introduction: Marginal zone B-cell lymphoma is a rare disease which can be considerably difficult to recognize and diagnose when signs of systemic involvement are absent. Case Presentation: We report the case of a 57-year-old woman with initial olfactory disturbance, followed by psychosis, diabetes insipidus and hypothalamic eating disorder as an uncommon clinical presentation of marginal zone B-cell lymphoma. Conclusion: Marginal zone B-cell lymphoma should be considered as a potential differential diagnosis in patients with hypothalamic disturbances
    • …
    corecore