1,548 research outputs found
The existence of a real pole-free solution of the fourth order analogue of the Painleve I equation
We establish the existence of a real solution y(x,T) with no poles on the
real line of the following fourth order analogue of the Painleve I equation,
x=Ty-({1/6}y^3+{1/24}(y_x^2+2yy_{xx})+{1/240}y_{xxxx}). This proves the
existence part of a conjecture posed by Dubrovin. We obtain our result by
proving the solvability of an associated Riemann-Hilbert problem through the
approach of a vanishing lemma. In addition, by applying the Deift/Zhou
steepest-descent method to this Riemann-Hilbert problem, we obtain the
asymptotics for y(x,T) as x\to\pm\infty.Comment: 27 pages, 5 figure
Proactive multi-tenant cache management for virtualized ISP networks
The content delivery market has mainly been dominated by large Content Delivery Networks (CDNs) such as Akamai and Limelight. However, CDN traffic exerts a lot of pressure on Internet Service Provider (ISP) networks. Recently, ISPs have begun deploying so-called Telco CDNs, which have many advantages, such as reduced ISP network bandwidth utilization and improved Quality of Service (QoS) by bringing content closer to the end-user. Virtualization of storage and networking resources can enable the ISP to simultaneously lease its Telco CDN infrastructure to multiple third parties, opening up new business models and revenue streams. In this paper, we propose a proactive cache management system for ISP-operated multi-tenant Telco CDNs. The associated algorithm optimizes content placement and server selection across tenants and users, based on predicted content popularity and the geographical distribution of requests. Based on a Video-on-Demand (VoD) request trace of a leading European telecom operator, the presented algorithm is shown to reduce bandwidth usage by 17% compared to the traditional Least Recently Used (LRU) caching strategy, both inside the network and on the ingress links, while at the same time offering enhanced load balancing capabilities. Increasing the prediction accuracy is shown to have the potential to further improve bandwidth efficiency by up to 79%
Noninvasive Embedding of Single Co Atoms in Ge(111)2x1 Surfaces
We report on a combined scanning tunneling microscopy (STM) and density
functional theory (DFT) based investigation of Co atoms on Ge(111)2x1 surfaces.
When deposited on cold surfaces, individual Co atoms have a limited diffusivity
on the atomically flat areas and apparently reside on top of the upper
pi-bonded chain rows exclusively. Voltage-dependent STM imaging reveals a
highly anisotropic electronic perturbation of the Ge surface surrounding these
Co atoms and pronounced one-dimensional confinement along the pi-bonded chains.
DFT calculations reveal that the individual Co atoms are in fact embedded in
the Ge surface, where they occupy a quasi-stationary position within the big
7-member Ge ring in between the 3rd and 4th atomic Ge layer. The energy needed
for the Co atoms to overcome the potential barrier for penetration in the Ge
surface is provided by the kinetic energy resulting from the deposition
process. DFT calculations further demonstrate that the embedded Co atoms form
four covalent Co-Ge bonds, resulting in a Co4+ valence state and a 3d5
electronic configuration. Calculated STM images are in perfect agreement with
the experimental atomic resolution STM images for the broad range of applied
tunneling voltages.Comment: 19 pages, 15 figures, 3 table
System occupancy of a two-class batch-service queue with class-dependent variable server capacity
Due to their wide area of applications, queueing models with batch service, where the server can process several customers simultaneously, have been studied frequently. An important characteristic of such batch-service systems is the size of a batch, that is the number of customers that are processed simultaneously. In this paper, we analyse a two-class batch-service queueing model with variable server capacity, where all customers are accommodated in a common first-come-first served single-server queue. The server can only process customers that belong to the same class, so that the size of a batch is determined by the number of consecutive same-class customers. After establishing the system equations that govern the system behaviour, we deduce an expression for the steady-state probability generating function of the system occupancy at random slot boundaries. Also, some numerical examples are given that provide further insight in the impact of the different parameters on the system performance
Asymptotics for the Partition Function in Two-Cut Random Matrix Models
We obtain large N asymptotics for the Hermitian random matrix partition
function in the case where the external potential is a polynomials
such that the random matrix eigenvalues accumulate on two disjoint intervals
(the two-cut case). We compute leading and sub-leading terms in the asymptotic
expansion for , up to terms that are small as goes to
infinity. Our approach is based on the explicit computation of the first terms
in the asymptotic expansion for a quartic symmetric potential . Afterwards,
we use deformation theory of the partition function and of the associated
equilibrium measure to generalize our results to general two-cut potentials
. The asymptotic expansion of as goes to infinity contains
terms that depend analytically on the potential and that have already
appeared in the literature. In addition our method allows to compute the
-independent terms of the asymptotic expansion of which, to
the best of our knowledge, had not appeared before in the literature. We use
rigorous orthogonal polynomial and Riemann-Hilbert techniques which had so far
been successful to compute asymptotics for the partition function only in the
one-cut case.Comment: 75 pages. To appear in Comm. Math. Physic
Intra- and intertaxon stable O and C isotope variability of fossil fish otoliths: an early Eocene test case
Knowledge of basic data variability is essential for the interpretation of any proxy-based paleotemperature record. To evaluate this for d18O stable isotope paleothermometry based on early Paleogene fish otoliths from marginal marine environments, an intra- and interspecific stable O and C isotope study was performed at a single locality in the southern North Sea Basin (Ampe Quarry, Egem, Belgium), where shallow marine sands and silts are exposed. The age of the deposits is early late Ypresian (ca. 50.9 Ma) and falls within the early Eocene climatic optimum (EECO) interval. In each of four fossiliferous levels sampled, the same three otolith species were analyzed (Platycephalus janeti, Paraconger papointi and âgenus Neobythitinorumâ subregularis). Intrataxon stable isotope spread amounts on average 2.50-3.00â° for all taxa and is present in all levels. This implies that each sample level comprises substantial variability, which can be attributed to a combination of temporal and taphonomic effects. More importantly, intertaxon offsets of 4.60â° in d13C and 2.20â° in d18O between the mean values of the three otolith species are found, with âN.â subregularis representing more positive values relative to the other species. We hypothesize that freshwater influence of coastal waters is the most likely cause for these discrepancies. Similar analyses on two coastal bivalve species (Venericardia sulcata and Callista laevigata) corroborate this hypothesis. Accordingly, d18O values measured on âN.â subregularis otoliths probably represent a more open oceanic signal, and therefore seem well-suited for d18O stable isotope paleothermometry. This study highlights the importance of investigating data variability of a biogenic carbonate paleotemperature proxy at the species level, before applying paleotemperature equations and interpreting the outcome
Ethical climate in a Belgian psychiatric inpatient setting: relation with burnout and engagement in psychiatric nurses
Research suggests a relation between the ethical climate â that is, the organisational conditions and practices that affect the way ethical issues with regard to patient care are discussed and decided - and job satisfaction of nurses. Yet no study to date has investigated the relationship between ethical climate and job satisfaction in psychiatric nurses. This study aimed to address this critical gap in our knowledge by investigating the relationships among ethical climate and features of both burnout and engagement based on the Job Demands-Resources Model (JD - R model) in a large cross-sectional study of 265 nurses working in a large psychiatric inpatient hospital in Flanders, Belgium. Correlational and multiple hierarchical regression analyses were used to investigate the relationship between ethical climate, burnout and engagement. In addition, based on the JD-R model, we also investigated whether engagement mediated the relationship between ethical climate on the one hand and job satisfaction and turnover intention on the other and whether ethical climate moderated the relationship between emotional burden and burnout. Results showed that a positive ethical climate was related to lower levels of emotional exhaustion and distancing and higher levels of engagement and job satisfaction. Furthermore, although ethical climate did not buffer against the effects of emotional burden on burnout, higher levels of engagement explained in part the relationship between ethical climate and job satisfaction
PHP251 Assessment of Consumer Likelihood to Adopt an Electronic Health Record (EHR) Mobile Application and the Impact of Perceived Risk of Privacy Leaks
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