719 research outputs found
Inclusive Flavour Tagging Algorithm
Identifying the flavour of neutral mesons production is one of the most
important components needed in the study of time-dependent violation. The
harsh environment of the Large Hadron Collider makes it particularly hard to
succeed in this task. We present an inclusive flavour-tagging algorithm as an
upgrade of the algorithms currently used by the LHCb experiment. Specifically,
a probabilistic model which efficiently combines information from reconstructed
vertices and tracks using machine learning is proposed. The algorithm does not
use information about underlying physics process. It reduces the dependence on
the performance of lower level identification capacities and thus increases the
overall performance. The proposed inclusive flavour-tagging algorithm is
applicable to tag the flavour of mesons in any proton-proton experiment.Comment: 5 pages, 5 figures, 17th International workshop on Advanced Computing
and Analysis Techniques in physics research (ACAT-2016
Designing a Scaffold-Free Bio-Orthogonal Click Chemistry Method of Cell Assembly for Application in Tissue Engineering
Tissue engineering is a growing field of science that relies on the use of material chemistry, engineering, genetics, and cell biology to produce functional tissues for use in transplantation, drug testing and disease modelling. Presently, there is an urgent need for a technology which would enable assembly of cells into 3-dimensional multilayered tissues. Current cell-assembly technologies rely on biodegradable polymer scaffolds to assemble cells into 3D structures and to support the cell mass of the growing tissue. The presence of these materials in tissues, however, lowers the cell density and the process of scaffold biodegradation results in accumulation of monomer byproducts within the tissue. To overcome these issues we developed a scaffold free method of cell-assembly based on bio-orthogonal ligation reactions between oxyamine and ketone groups to form a stable oxime bond. The reaction is quick, specific and occurs under physiological conditions without a catalyst. To deliver the bio-orthogonal functionalities onto cell surfaces, ketone- and oxyamine- functionalized lipids were incorporated into liposomes which were subsequently fused with cell membranes. The surface engineered cells were assembled into three-dimensional tissues. Using this approach, we were able to produce functional cardiac and liver tissues with variable thicknesses and cell orientations for drug testing as well as the complex 3D co-cultures of stem cells to study stem cell differentiation. The rapid bio-orthogonal cell ligation process also enables assembly of cells into co-culture spheroids in flow, inside a microchannel. The introduction of a bi-functional oxyamine crosslinker molecule allowed for the rapid crosslinking of ketone-functionalized cells into 3D tissues. This bio-orthogonal click chemistry technology can be used with different cell types to produce customized tissues for applications in drug development and regenerative medicine
Reproducible Experiment Platform
Data analysis in fundamental sciences nowadays is an essential process that
pushes frontiers of our knowledge and leads to new discoveries. At the same
time we can see that complexity of those analyses increases fast due to
a)~enormous volumes of datasets being analyzed, b)~variety of techniques and
algorithms one have to check inside a single analysis, c)~distributed nature of
research teams that requires special communication media for knowledge and
information exchange between individual researchers. There is a lot of
resemblance between techniques and problems arising in the areas of industrial
information retrieval and particle physics. To address those problems we
propose Reproducible Experiment Platform (REP), a software infrastructure to
support collaborative ecosystem for computational science. It is a Python based
solution for research teams that allows running computational experiments on
shared datasets, obtaining repeatable results, and consistent comparisons of
the obtained results. We present some key features of REP based on case studies
which include trigger optimization and physics analysis studies at the LHCb
experiment.Comment: 21st International Conference on Computing in High Energy Physics
(CHEP2015), 6 page
LHCb Topological Trigger Reoptimization
The main b-physics trigger algorithm used by the LHCb experiment is the
so-called topological trigger. The topological trigger selects vertices which
are a) detached from the primary proton-proton collision and b) compatible with
coming from the decay of a b-hadron. In the LHC Run 1, this trigger, which
utilized a custom boosted decision tree algorithm, selected a nearly 100% pure
sample of b-hadrons with a typical efficiency of 60-70%; its output was used in
about 60% of LHCb papers. This talk presents studies carried out to optimize
the topological trigger for LHC Run 2. In particular, we have carried out a
detailed comparison of various machine learning classifier algorithms, e.g.,
AdaBoost, MatrixNet and neural networks. The topological trigger algorithm is
designed to select all "interesting" decays of b-hadrons, but cannot be trained
on every such decay. Studies have therefore been performed to determine how to
optimize the performance of the classification algorithm on decays not used in
the training. Methods studied include cascading, ensembling and blending
techniques. Furthermore, novel boosting techniques have been implemented that
will help reduce systematic uncertainties in Run 2 measurements. We demonstrate
that the reoptimized topological trigger is expected to significantly improve
on the Run 1 performance for a wide range of b-hadron decays.Comment: 21st International Conference on Computing in High Energy Physics
(CHEP2015
A deterministic approximation algorithm for computing the permanent of a 0, 1 matrix
We consider the problem of computing the permanent of a n by n matrix. For a class of matrices corresponding to constant degree expanders we construct a deterministic polynomial time approximation algorithm to within a multiplicative factor ( 1 + ∈)[superscript η] for arbitrary∈ > 0. This is an improvement over the best known approximation factor e[superscript η] obtained in Linial, Samorodnitsky and Wigderson (2000), though the latter result was established for arbitrary non-negative matrices. Our results use a recently developed deterministic approximation algorithm for counting partial matchings of a graph (Bayati, Gamarnik, Katz, Nair and Tetali (2007)) and Jerrum–Vazirani method (Jerrum and Vazirani (1996)) of approximating permanent by near perfect matchings
Non-contractible loops in the dense O(n) loop model on the cylinder
A lattice model of critical dense polymers is considered for the
finite cylinder geometry. Due to the presence of non-contractible loops with a
fixed fugacity , the model is a generalization of the critical dense
polymers solved by Pearce, Rasmussen and Villani. We found the free energy for
any height and circumference of the cylinder. The density of
non-contractible loops is found for and large . The
results are compared with those obtained for the anisotropic quantum chain with
twisted boundary conditions. Using the latter method we obtained for any
model and an arbitrary fugacity.Comment: arXiv admin note: text overlap with arXiv:0810.223
Research of Polymetallic Sulfide Industrial Waste Nitric Acid Treatment
Thermodynamic and kinetic features studies of polymetallic sulfide industrial waste nitric acid leaching were carried out. Elemental and phase composition of investigated raw material were studied with X-ray diffraction and electron microscopy methods. Calculations of the Gibbs energy change for the likely reactions of sulfide minerals with nitric acid were performed. In order to determine the most probable conditions of the sulfide industrial waste leaching in nitric acid, as well as the mutual influence of the produced pulp components on the performance of the process, the kinetics evaluation of multicomponent sulfide industrial waste in a nitric medium was studied using mathematical methods.
Keywords: nitric acid leaching, polymetallic sulfide industrial waste, Gibbs energy change, kinetic feature
Colloid-chemical properties of surfactant–nitric acid–water systems
The behavior of the surfactants Tween 80, SaS and alkyl betaine in aqueous and nitric acid environments as promising additives for nitrate leaching of hard-to-process ore concentrates of non-ferrous metals was studied. The influence of surfactant concentration (0.04–1.28 g/dm3), nitric acid concentration (0.1–10 g/dm3) and temperature (295–343 K) on the surface tension, critical micelle concentration (CMC), pH and optical density of aqueous surfactant solutions and surfactant–HNO3–H2O systems was found. The critical micelle concentration of the surfactants used was estimated. A positive effect of nitric acid on the surface activity of surfactants was discovered, which manifests itself in a decrease in both the CMC and the surface tension at the liquid–gas interface. The values of surface activity and Gibbs energy of surfactant micelle formation in aqueous and nitric acid media were calculated. Associative processes in the solutions and compositions were confirmed by measuring the optical density of the systems under study
Alkali Fusion-Leaching Method For Comprehensive Processing Of Fly Ash
Fly ash, composed of mullite, hematite, amorphous silica and quartz, is a promising source for the recovery of alumina and silica. Desilication with help of NaOH and alkali fusion-leaching method and utilization of alumina and silica in the fly ash for preparation of sodalite and silica white were explored in this research. The samples were characterized by using wet chemical analysis and X-ray diffraction. The optimal extraction of SiO2 from Reftinskaya power plant fly ash was 46.2% with leaching at 95 oC for 3 h. Sodalite was synthesized at 200 °C for 1 h followed water leaching at 95 °C for 1 h. Silica white with specific surface area 180-220 m2/g was prepared by carbonation of the Na2SiO3 solution at 40 oC for 90-120 min. The as-prepared silica has a purity of 98,8%. The proposed method is suitable for the comprehensive utilization of the fly ash.
Keywords: fly ash, alkali fusion, desilication, sodalite, silica white, carbonization, comprehensive utilizatio
- …