4,966 research outputs found
Data mining: a tool for detecting cyclical disturbances in supply networks.
Disturbances in supply chains may be either exogenous or endogenous. The ability automatically to detect, diagnose, and distinguish between the causes of disturbances is of prime importance to decision makers in order to avoid uncertainty. The spectral principal component analysis (SPCA) technique has been utilized to distinguish between real and rogue disturbances in a steel supply network. The data set used was collected from four different business units in the network and consists of 43 variables; each is described by 72 data points. The present paper will utilize the same data set to test an alternative approach to SPCA in detecting the disturbances. The new approach employs statistical data pre-processing, clustering, and classification learning techniques to analyse the supply network data. In particular, the incremental k-means
clustering and the RULES-6 classification rule-learning algorithms, developed by the present authorsâ team, have been applied to identify important patterns in the data set. Results show that the proposed approach has the capability automatically to detect and characterize network-wide cyclical disturbances and generate hypotheses about their root cause
Dense stellar matter with trapped neutrinos under strong magnetic fields
We investigate the effects of strong magnetic fields on the equation of state
of dense stellar neutrino-free and neutrino-trapped matter. Relativistic
nuclear models both with constant couplings (NLW) and with density dependent
parameters (DDRH) and including hyperons are considered . It is shown that at
low densities neutrinos are suppressed in the presence of the magnetic field.
The magnetic field reduces the strangeness fraction of neutrino-free matter and
increases the strangeness fraction of neutrino-trapped matter. The mass-radius
relation of stars described by these equations of state are determined. The
magnetic field makes the overall equation of state stiffer and the stronger the
field the larger the mass of maximum mass star and the smaller the baryon
density at the center of the star. As a consequence in the presence of strong
magnetic fields the possibility that a protoneutron star evolves to a blackhole
is smaller.Comment: 18 pages, 13 figures, 5 tables, submitted to J. Phys.
Unstable states in QED of strong magnetic fields
We question the use of stable asymptotic scattering states in QED of strong
magnetic fields. To correctly describe excited Landau states and photons above
the pair creation threshold the asymptotic fields are chosen as generalized
Licht fields. In this way the off-shell behavior of unstable particles is
automatically taken into account, and the resonant divergences that occur in
scattering cross sections in the presence of a strong external magnetic field
are avoided. While in a limiting case the conventional electron propagator with
Breit-Wigner form is obtained, in this formalism it is also possible to
calculate -matrix elements with external unstable particles.Comment: Revtex, 7 pages. To appear in Phys. Rev. D53(2
Lattice Relaxation and Charge-Transfer Optical Transitions Due to Self-Trapped Holes in Non-Stoichiometric LaMnO Crystal
We use the Mott-Littleton approach to evaluate polarisation energies in
LaMnO lattice associated with holes localized on both Mn cation and
O anion. The full (electronic and ionic) lattice relaxation energy for a
hole localized at the O-site is estimated as 2.4 eV which is appreciably
greater than that of 0.8 eV for a hole localized at the Mn-site, indicating on
the strong electron-phonon interaction in the former case. Using a Born-Haber
cycle we examine thermal and optical energies of the hole formation associated
with electron ionization from Mn, O and La ions in
LaMnO lattice. For these calculations we derive a phenomenological value
for the second electron affinity of oxygen in LaMnO lattice by matching the
optical energies of La and O hole formation with maxima of binding
energies in the experimental photoemission spectra. The calculated thermal
energies predict that the electronic hole is marginally more stable in the
Mn state in LaMnO host lattice, but the energy of a hole in the
O state is only higher by a small amount, 0.75 eV, rather suggesting that
both possibilities should be treated seriously. We examine the energies of a
number of fundamental optical transitions, as well as those involving
self-trapped holes of Mn and O in LaMnO lattice. The reasonable
agreement with experiment of our predicted energies, linewidths and oscillator
strengths leads us to plausible assignments of the optical bands observed. We
deduce that the optical band near 5 eV is associated with O(2p) - Mn(3d)
transition of charge-transfer character, whereas the band near 2.3 eV is rather
associated with the presence of Mn and/or O self-trapped holes in
non-stoichiometric LaMnO compound.Comment: 18 pages, 6 figures, it was presented partially at SCES-2001
conference in Ann Arbor, Michiga
Excesses in the Cosmic Ray Spectrum and Possible Interpretations
The data collected by ATIC, PPB-BETS, FERMI-LAT and HESS all indicate that
there is an electron/positron excess in the cosmic ray energy spectrum above
100 GeV, although different instrumental teams do not agree on the
detailed spectral shape. PAMELA also reported a clear excess feature of the
positron fraction above several GeV, but no excess in anti-protons. Here we
review the observational status and theoretical models of this interesting
observational feature. We pay special attention to various physical
interpretations proposed in the literature, including modified supernova
remnant models for the background, new astrophysical sources, and new
physics (the dark matter models). We suggest that although most models can make
a case to interpret the data, with the current observational constraints the
dark matter interpretations, especially those invoking annihilation, require
much more exotic assumptions than some astrophysical interpretations. Future
observations may present some ``smoking-gun'' observational tests to
differentiate among different models and to identify the correct interpretation
to the phenomenon.Comment: 48 pages, including 10 figures and 1 tabel. Invited review to be
published in IJMP
Laboratory evidence of disseminated intravascular coagulation is associated with a fatal outcome in children with cerebral malaria despite an absence of clinically evident thrombosis or bleeding
Background A procoagulant state is implicated in cerebral malaria (CM ) pathogenesis, but whether disseminated intravascular coagulation (DIC ) is present or associated with a fatal outcome is unclear. Objectives To determine the frequency of overt DIC , according to ISTH criteria, in children with fatal and nonâfatal CM . Methods/patients Malawian children were recruited into a prospective cohort study in the following diagnostic groups: retinopathyâpositive CM (n = 140), retinopathyânegative CM (n = 36), nonâmalarial coma (n = 14), uncomplicated malaria (UM ), (n = 91), mild nonâmalarial febrile illness (n = 85), and healthy controls (n = 36). Assays in the ISTH DIC criteria were performed, and three fibrinârelated markers, i.e. protein C, antithrombin, and soluble thrombomodulin, were measured. Results and conclusions Data enabling assignment of the presence or absence of âovert DIC â were available for 98 of 140 children with retinopathyâpositive CM . Overt DIC was present in 19 (19%), and was associated with a fatal outcome (odds ratio [OR] 3.068; 95% confidence interval [CI] 1.085â8.609; P = 0.035]. The levels of the three fibrinârelated markers and soluble thrombomodulin were higher in CM patients than in UM patients (all P < 0.001). The mean fibrin degradation product level was higher in fatal CM patients (71.3 ÎŒg mLâ1 [95% CI 49.0â93.6]) than in nonâfatal CM patients (48.0 ÎŒg mLâ1 [95% CI 37.7â58.2]; P = 0.032), but, in multivariate logistic regression, thrombomodulin was the only coagulationârelated marker that was independently associated with a fatal outcome (OR 1.084 for each ng mLâ1 increase [95% CI 1.017â1.156]; P = 0.014). Despite these laboratory derangements, no child in the study had clinically evident bleeding or thrombosis. An overt DIC score and high thrombomodulin levels are associated with a fatal outcome in CM , but infrequently indicate a consumptive coagulopathy
Furthering alternative cultures of valuation in higher education research
The value of higher education is often implicit or assumed in educational research. The underlying and antecedent premises that shape and influence debates about value remain unchallenged which perpetuates the dominant, but limiting, terms of the debate and fosters reductionism. I proceed on the premise that analyses of value are not selfâsupporting or self-referential but are embedded within prevailing cultures of valuation. I contend that challenging, and providing alternatives to, dominant narratives of higher education requires an appreciation of those cultures. I therefore highlight some of the existing cultures of valuation and their influence. I then propose Sayerâs concept of lay normativity as a culture of valuation and discuss how it translates into the practices of research into higher education, specifically the practice of analysis. I animate the discussion by detecting the presence of lay normativity in the evaluative space of the capability approach
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Multi-catheter cryotherapy for the treatment of resistant accessory pathways.
OBJECTIVE: To investigate the utility of simultaneous multi-catheter cryotherapy for the treatment of APs that were previously resistant to standard radiofrequency (RF) catheter ablation. BACKGROUND: Catheter ablation is established in the treatment of accessory pathways (AP), with high rates of permanent procedural success with a single attempt. However, there are still instances of acute procedural failure and AP recurrences with standard RF and cryotherapy methods. METHODS: Seven consecutive cases of pre-excitation syndromes with prior failed RF catheter ablation had the novel treatment. Cryotherapy was delivered using two 8Â mm tip focal cryoablation catheters (FreezorÂź Max, Medtronic, Minneapolis, Minnesota, USA). RESULTS: Accessory pathway localisation was septal in 5 cases, left posterolateral in 1, right lateral in 1. In all cases, ablation of the AP was acutely successful with no procedural complications. Median procedure and fluoroscopy durations were 199 and 35Â min, sequentially. Median Procedure duration fell significantly in the second half of series (174Â min) compared to the first half (233Â min, PÂ =Â 0.05). One patient had evidence of a recurring AP conduction with pre-excitation at 5-week follow up. After a median follow up of 66.8+-6.5 months, 6 out of 7 patients remained asymptomatic and free of pre-excitation. CONCLUSION: Simultaneous multi-catheter cryotherapy is feasible, safe and can provide definitive cure of accessory pathways that were previously resistant to standard radiofrequency ablation. Further study is required in the assessment of this novel form of advanced cryotherapy to treat complex and resistant arrhythmias
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