Katholieke Universiteit Leuven

About: Katholieke Universiteit Leuven is a education organization based out in Leuven, Belgium. It is known for research contribution in the topics: Population & Transplantation. The organization has 61109 authors who have published 176584 publications receiving 6210872 citations.

Alfvénic waves with sufficient energy to power the quiet solar corona and fast solar wind

Abstract: Alfven waves — travelling oscillations of ions and magnetic field — were first detected in the Sun's corona in 2007, but at amplitudes too small to explain the mystery of where the energy comes from to heat corona gases to millions of degrees and accelerate the solar wind to speeds of hundreds of kilometres per second. New observations of the transition region and corona reveal ubiquitous outward-propagating Alfvenic motions that have amplitudes of the order of 20 kilometres per second and periods of the order of 100–500 seconds throughout the quiescent atmosphere. The observations show that coronal waves fill the whole atmosphere and are sufficiently strong to play a major part in the energetics of the outer solar atmosphere. Energy is required to heat the outer solar atmosphere to millions of degrees (refs 1, 2) and to accelerate the solar wind to hundreds of kilometres per second (refs 2–6). Alfven waves (travelling oscillations of ions and magnetic field) have been invoked as a possible mechanism to transport magneto-convective energy upwards along the Sun’s magnetic field lines into the corona. Previous observations7 of Alfvenic waves in the corona revealed amplitudes far too small (0.5 km s−1) to supply the energy flux (100–200 W m−2) required to drive the fast solar wind8 or balance the radiative losses of the quiet corona9. Here we report observations of the transition region (between the chromosphere and the corona) and of the corona that reveal how Alfvenic motions permeate the dynamic and finely structured outer solar atmosphere. The ubiquitous outward-propagating Alfvenic motions observed have amplitudes of the order of 20 km s−1 and periods of the order of 100–500 s throughout the quiescent atmosphere (compatible with recent investigations7,10), and are energetic enough to accelerate the fast solar wind and heat the quiet corona.

Reductive lignocellulose fractionation into soluble lignin-derived phenolic monomers and dimers and processable carbohydrate pulps

Abstract: A catalytic lignocellulose biorefinery process is presented, valorizing both polysaccharide and lignin components into a handful of chemicals. To that end, birch sawdust is efficiently delignified through simultaneous solvolysis and catalytic hydrogenolysis in the presence of a Ru on carbon catalyst (Ru/C) in methanol under a H2 atmosphere at elevated temperature, resulting in a carbohydrate pulp and a lignin oil. The lignin oil yields above 50% of phenolic monomers (mainly 4-n-propylguaiacol and 4-n-propylsyringol) and about 20% of a set of phenolic dimers, relative to the original lignin content, next to phenolic oligomers. The structural features of the lignin monomers, dimers and oligomers were identified by a combination of GC/MS, GPC and 2D HSQC NMR techniques, showing interesting functionalities for forthcoming polymer applications. The effect of several key parameters like temperature, reaction time, wood particle size, reactor loading, catalyst reusability and the influence of solvent and gas were examined in view of the phenolic product yield, the degree of delignification and the sugar retention as a first assessment of the techno-economic feasibility of this biorefinery process. The separated carbohydrate pulp contains up to 92% of the initial polysaccharides, with a nearly quantitative retention of cellulose. Pulp valorization was demonstrated by its chemocatalytic conversion to sugar polyols, showing the multiple use of Ru/C, initially applied in the hydrogenolysis process. Various lignocellulosic substrates, including genetically modified lines of Arabidopsis thaliana, were finally processed in the hydrogenolytic biorefinery, indicating lignocellulose rich in syringyl-type lignin, as found in hardwoods, as the ideal feedstock for the production of chemicals.

Memory Aware Synapses: Learning What (not) to Forget

Abstract: Humans can learn in a continuous manner. Old rarely utilized knowledge can be overwritten by new incoming information while important, frequently used knowledge is prevented from being erased. In artificial learning systems, lifelong learning so far has focused mainly on accumulating knowledge over tasks and overcoming catastrophic forgetting. In this paper, we argue that, given the limited model capacity and the unlimited new information to be learned, knowledge has to be preserved or erased selectively. Inspired by neuroplasticity, we propose a novel approach for lifelong learning, coined Memory Aware Synapses (MAS). It computes the importance of the parameters of a neural network in an unsupervised and online manner. Given a new sample which is fed to the network, MAS accumulates an importance measure for each parameter of the network, based on how sensitive the predicted output function is to a change in this parameter. When learning a new task, changes to important parameters can then be penalized, effectively preventing important knowledge related to previous tasks from being overwritten. Further, we show an interesting connection between a local version of our method and Hebb’s rule, which is a model for the learning process in the brain. We test our method on a sequence of object recognition tasks and on the challenging problem of learning an embedding for predicting triplets. We show state-of-the-art performance and, for the first time, the ability to adapt the importance of the parameters based on unlabeled data towards what the network needs (not) to forget, which may vary depending on test conditions.

Mutual Information Analysis

Abstract: We propose a generic information-theoretic distinguisher for differential side-channel analysis. Our model of side-channel leakage is a refinement of the one given by Standaert et al.An embedded device containing a secret key is modeled as a black box with a leakage function whose output is captured by an adversary through the noisy measurement of a physical observable. Although quite general, the model and the distinguisher are practical and allow us to develop a new differential side-channel attack. More precisely, we build a distinguisher that uses the value of the Mutual Information between the observed measurements and a hypothetical leakage to rank key guesses. The attack is effective without any knowledge about the particular dependencies between measurements and leakage as well as between leakage and processed data, which makes it a universal tool. Our approach is confirmed by results of power analysis experiments. We demonstrate that the model and the attack work effectively in an attack scenario against DPA-resistant logic.

Selumetinib plus docetaxel for KRAS-mutant advanced non-small-cell lung cancer: a randomised, multicentre, placebo-controlled, phase 2 study

Abstract: Summary Background No targeted therapies are available for KRAS -mutant non-small-cell lung cancer (NSCLC). Selumetinib is an inhibitor of MEK1/MEK2, downstream of KRAS, with preclinical evidence of synergistic activity with docetaxel in KRAS -mutant cancers. We did a prospective, randomised, phase 2 trial to assess selumetinib plus docetaxel in previously treated patients with advanced KRAS -mutant NSCLC. Methods Eligible patients were older than 18 years of age; had histologically or cytologically confirmed stage IIIB–IV KRAS -mutant NSCLC; had failed first-line therapy for advanced NSCLC; had WHO performance status of 0–1; had not received previous therapy with either a MEK inhibitor or docetaxel; and had adequate bone marrow, renal, and liver function. Patients were randomly assigned (in a 1:1 ratio) to either oral selumetinib (75 mg twice daily in a 21 day cycle) or placebo; all patients received intravenous docetaxel (75 mg/m 2 on day 1 of a 21 day cycle). Randomisation was done with an interactive voice response system and investigators, patients, data analysts, and the trial sponsor were masked to treatment assignment. The primary endpoint was overall survival, analysed for all patients with confirmed KRAS mutations. This study is registered with ClinicalTrials.gov, number NCT00890825. Findings Between April 20, 2009, and June 30, 2010, we randomly assigned 44 patients to receive selumetinib and docetaxel (selumetinib group) and 43 to receive placebo and docetaxel (placebo group). Of these, one patient in the selumetinib group and three in the placebo group were excluded from efficacy analyses because their tumours were not confirmed to be KRAS -mutation positive. Median overall survival was 9·4 months (6·8–13·6) in the selumetinib group and 5·2 months (95% CI 3·8–non-calculable) in the placebo group (hazard ratio [HR] for death 0·80, 80% CI 0·56–1·14; one-sided p=0·21). Median progression-free survival was 5·3 months (4·6–6·4) in the selumetinib group and 2·1 months (95% CI 1·4–3·7) in the placebo group (HR for progression 0·58, 80% CI 0·42–0·79; one-sided p=0·014). 16 (37%) patients in the selumetinib group and none in the placebo group had an objective response (p vs 23 [55%] of 42 patients in the placebo group), febrile neutropenia (eight [18%] of 44 patients in the selumetinib group vs none in the placebo group), dyspnoea (one [2%] of 44 patients in the selumetinib group vs five [12%] of 42 in the placebo group), and asthenia (four [9%] of 44 patients in the selumetinib group vs none in the placebo group). Interpretation Selumetinib plus docetaxel has promising efficacy, albeit with a higher number of adverse events than with docetaxel alone, in previously treated advanced KRAS -mutant NSCLC. These findings warrant further clinical investigation of selumetinib plus docetaxel in KRAS -mutant NSCLC. Funding AstraZeneca.