1,696 research outputs found
Snapshot Provisioning of Cloud Application Stacks to Face Traffic Surges
Traffic surges, like the Slashdot effect, occur when a web application is overloaded by a huge number of requests, potentially leading to unavailability. Unfortunately, such traffic variations are generally totally unplanned, of great amplitude, within a very short period, and a variable delay to return to a normal regime. In this report, we introduce PeakForecast as an elastic middleware solution to detect and absorb a traffic surge. In particular, PeakForecast can, from a trace of queries received in the last seconds, minutes or hours, to detect if the underlying system is facing a traffic surge or not, and then estimate the future traffic using a forecast model with an acceptable precision, thereby calculating the number of resources required to absorb the remaining traffic to come. We validate our solution by experimental results demonstrating that it can provide instantaneous elasticity of resources for traffic surges observed on the Japanese version of Wikipedia during the Fukushima Daiichi nuclear disaster in March 2011.Les pics de trafic, tels que l'effet Slashdot, apparaissent lorsqu'une application web doit faire face un nombre important de requêtes qui peut potentiellement entraîner une mise hors service de l'application. Malheureusement, de telles variations de traffic sont en général totalement imprévues et d'une grande amplitude, arrivent pendant une très courte période de temps et le retour à un régime normal prend un délai variable. Dans ce rapport, nous présentons PeakForecast qui est une solution intergicielle élastique pour détecter et absorber les pics de trafic. En particulier, PeakForecast peut, à partir des traces de requêtes reçues dans les dernières secondes, minutes ou heures, détecter si le système sous-jacent fait face ou non à un pic de trafic, estimer le trafic futur en utilisant un modèle de prédiction suffisamment précis, et calculer le nombre de ressources nécessaires à l'absorption du trafic restant à venir. Nous validons notre solution avec des résultats expérimentaux qui démontrent qu'elle fournit une élasticité instantanée des ressources pour des pics de trafic qui ont été observés sur la version japonaise de Wikipedia lors de l'accident nucléaire de Fukushima Daiichi en mars 2011
Nitrogen and sulphur management: challenges for organic sources in temperate agricultural systems
A current global trend towards intensification or specialization of agricultural enterprises has been accompanied by increasing public awareness of associated environmental consequences. Air and water pollution from losses of nutrients, such as nitrogen (N) and sulphur (S), are a major concern. Governments have initiated extensive regulatory frameworks, including various land use policies, in an attempt to control or reduce the losses. This paper presents an overview of critical input and loss processes affecting N and S for temperate climates, and provides some background to the discussion in subsequent papers evaluating specific farming systems. Management effects on potential gaseous and leaching losses, the lack of synchrony between supply of nutrients and plant demand, and options for optimizing the efficiency of N and S use are reviewed. Integration of inorganic and organic fertilizer inputs and the equitable re-distribution of nutrients from manure are discussed. The paper concludes by highlighting a need for innovative research that is also targeted to practical approaches for reducing N and S losses, and improving the overall synchrony between supply and demand
Gaseous Galaxy Halos
Galactic halo gas traces inflowing star formation fuel and feedback from a
galaxy's disk and is therefore crucial to our understanding of galaxy
evolution. In this review, we summarize the multi-wavelength observational
properties and origin models of Galactic and low redshift spiral galaxy halo
gas. Galactic halos contain multiphase gas flows that are dominated in mass by
the ionized component and extend to large radii. The densest, coldest halo gas
observed in neutral hydrogen (HI) is generally closest to the disk (< 20 kpc),
and absorption line results indicate warm and warm-hot diffuse halo gas is
present throughout a galaxy's halo. The hot halo gas detected is not a
significant fraction of a galaxy's baryons. The disk-halo interface is where
the multiphase flows are integrated into the star forming disk, and there is
evidence for both feedback and fueling at this interface from the temperature
and kinematic gradient of the gas and HI structures. The origin and fate of
halo gas is considered in the context of cosmological and idealized local
simulations. Accretion along cosmic filaments occurs in both a hot (> 10^5.5 K)
and cold mode in simulations, with the compressed material close to the disk
the coldest and densest, in agreement with observations. There is evidence in
halo gas observations for radiative and mechanical feedback mechanisms,
including escaping photons from the disk, supernova-driven winds, and a
galactic fountain. Satellite accretion also leaves behind abundant halo gas.
This satellite gas interacts with the existing halo medium, and much of this
gas will become part of the diffuse halo before it can reach the disk. The
accretion rate from cold and warm halo gas is generally below a galaxy disk's
star formation rate, but gas at the disk-halo interface and stellar feedback
may be important additional fuel sources.Comment: 50 pages, 9 figures (1 in 3D, view with a current version of Adobe),
to appear in ARA&A, 50, 49
Elevated expression of c-kit in small venous malformations of blue rubber bleb nevus syndrome
The blue rubber bleb nevus syndrome (BRBNS, syn. bean syndrome) is a rare disease
characterized by multiple cutaneous and gastrointestinal venous malformations
associated with severe bleeding. However, the underlying molecular mechanisms
are unknown and no targeted therapeutic approach exists to date. Here we report
the case of a 19-year-old male patient with severe BRBNS in whom we analyzed the
expression of tyrosine kinases frequently involved in tumor development by
immunohistochemistry (vascular endothelial growth factor receptor-2, stem cell
growth factor receptor (c-kit), platelet-derived growth factor
receptor-β, and stem cell tyrosine kinase-1). A prominent expression of
c-kit was detectable in smaller blood vessels, which also showed a moderate
expression of the proliferation marker MIB1. Surprisingly, other growth factor
receptors stained negatively. We therefore conclude that pharmacological
inhibition of the c-kit signaling pathway in cavernous hemangiomas by selective
kinase inhibitors may offer options in the treatment of BRBNS patients
Coupled-Channel Effects in Collisions between Heavy Ions near the Coulomb Barrier
With the recent availability of state-of-the-art heavy-ion stable and
radioactive beams, there has been a renew interest in the investigation of
nuclear reactions with heavy ions. I first present the role of inelastic and
transfer channel couplings in fusion reactions induced by stable heavy ions.
Analysis of experimental fusion cross sections by using standard
coupled-channel calculations is discussed. The role of multi-neutron transfer
is investigated in the fusion process below the Coulomb barrier by analyzing
S+Zr as benchmark reactions. The enhancement of fusion cross
sections for S+Zr is well reproduced at sub-barrier energies by
NTFus code calculations including the coupling of the neutron-transfer channels
following the Zagrebaev semi-classical model. Similar effects for
Ca+Zr and Ca+Zr fusion excitation functions are
found. The breakup coupling in both the elastic scattering and in the fusion
process induced by weakly bound stable projectiles is also shown to be crucial.
In this lecture, full coupled-channel calculations of the fusion excitation
functions are performed by using the breakup coupling for the more neutron-rich
reaction and for the more weakly bound projectiles. I clearly demonstrate that
Continuum-Discretized Coupled-Channel calculations are capable to reproduce the
fusion enhancement from the breakup coupling in Li+Co.Comment: 14 pages. 6 figure
Correlates of Obsessive–Compulsive Disorder in a Sample of HIV-Positive, Methamphetamine-using Men Who have Sex with Men
Substance use has been identified as a risk factor for elevated levels of obsessive–compulsive disorder (OCD). This study examined methamphetamine use and sexual risk behaviors as correlates of OCD in a sample of 245 HIV-positive men having sex with men (MSM) in San Diego, CA. In a logistic regression analysis, OCD was associated with greater frequency of methamphetamine use, more depressive symptoms, seeking out risky venues and risky sexual partners when “high” on methamphetamine, and reporting fewer sex acts in the past 2 months. These data suggest the need for increased awareness and understanding of the role that OCD may play in the drug use behaviors and risky sexual practices of methamphetamine users
Neuron-glia cross talk in rat striatum after transient forebrain ischemia
Striatum is highly vulnerable to transient forebrain ischemia induced by the 4 vessel occlusion (4V0) method (Brierley 1976. Pulsinelli et al. 1982, Zini et al. 1990a). Massive degeneration and loss of Nissl-stained neurons occur within 24 hr from an ischemia of long duration (30 min) (Pulsinelli et al. 1982). Neuronal loss is mainly restricted to the lateral part of caudate-putamen (Pulsinelli et al. 1982, Zini et al. 1990a). Cellular alterations include loss of medium-size spiny projection neurons (Pulsinelli et al. 1982, Francis and Pulsinelli 1982), largely corresponding to dopaminoceptive neurons (Benfenati et al. 1989, Zoli et al. 1989), and increase in reactive astrocytes (Pulsinelli et al. 1982, Grimaldi et al. 1990) and microglia (Gehrmann et al. 1982). On the other hand, large cholinergie (Francis and Pulsinelli 1982) and medium-size aspiny somatostatin (SS)/neuropeptide Y (NPY)-containing interneurons are resistant to the ischemic insult (Pulsinelli et al. 1982, Grimaldi et al. 1990). In a few instances, such as in the case of SS and NPY immunoreactivity (IR), the initial loss is followed by full recovery within 7 (SS) or 40 (NPY) days post-ischemia (Grimaldi et al. 1990). However, it is not known whether some kind of recovery is present for the bulk of medium-size spiny projections neurons after the first days post-ischemia
Exploratory Case‐Control Analysis of Psychosocial Factors and Adult Periodontitis
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141163/1/jper1060.pd
State–Space Forecasting of Schistosoma haematobium Time-Series in Niono, Mali
Adequate forecasting and early warning systems are based upon observations of human behavior, population, disease time-series, climate, environment, and/or a combination thereof, whichever option best compromises among realism, feasibility, robustness, and parsimony. Fully automatic and user-friendly state–space forecasting frameworks, incorporating myriad options (e.g., expert opinion, univariate, multivariate, and spatial-temporal), could considerably enhance disease control and hazard mitigation efforts in regions where vulnerability to neglected tropical diseases is pervasive and statistical expertise is scarce. The operational simplicity, generality, and flexibility of state–space frameworks, encapsulating multiple methods, could conveniently allow for 1) unsupervised model selection without disease-specific methodological tailoring, 2) on-line adaptation to disease time-series fluctuations, and 3) automatic switches between distinct forecasting methods as new time-series perturbations dictate. In this investigation, a univariate state–space framework with the aforementioned properties was successfully applied to the Schistosoma haematobium time-series for the district of Niono, Mali, to automatically generate contemporaneous on-line forecasts and hence, providing a basis for local re-organization and strengthening public health programs in this and potentially other Sahelian districts
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