4 research outputs found
A Performance Comparison of Hypervisors for Cloud Computing
The virtualization of IT infrastructure enables the consolidation and pooling of IT resources so that they can be shared over diverse applications to offset the limitation of shrinking resources and growing business needs. Virtualization provides a logical abstraction of physical computing resources and creates computing environments that are not restricted by physical configuration or implementation. Virtualization is very important for cloud computing because the delivery of services is simplified by providing a platform for optimizing complex IT resources in a scalable manner, which makes cloud computing more cost effective.
Hypervisor plays an important role in the virtualization of hardware. It is a piece of software that provides a virtualized hardware environment to support running multiple operating systems concurrently using one physical server. Cloud computing has to support multiple operating environments and Hypervisor is the ideal delivery mechanism.
The intent of this thesis is to quantitatively and qualitatively compare the performance of VMware ESXi 4.1, Citrix Systems Xen Server 5.6 and Ubuntu 11.04 Server KVM Hypervisors using standard benchmark SPECvirt_sc2010v1.01 formulated by Standard Performance Evaluation Corporation (SPEC) under various workloads simulating real life situations
Abnormal circadian rhythm and cortisol excretion in autistic children: a clinical study
Aim To determine the circadian rhythm alteration of cortisol
excretion and the level of corticosteroids in children
with different grades of autism severity.
Methods The study included 45 children with different
grades of autism severity (low [LFA], medium [MFA], and
high functioning autism [HFA]), 15 in each group, and 45
age/sex-matched children with typical development. The
urinary levels of free cortisol (at three phases of 24-hour cycle),
corticosteroids, vanilylmandelic acid, and 5-hydroxyindole
acetic acid were determined.
Results Alteration in the pattern of cortisol excretion (Phases
I, II, and III) was observed in children with LFA (Phase I:
43.8 ± 4.43 vs 74.30±8.62, P = 0.000; Phase II: 21.1±2.87 vs
62±7.68, P < 0.001; Phase III: 9.9 ± 1.20 vs 40 ± 5.73, P < 0.001)
and MFA (Phase I: 43.8 ± 4.43 vs 52.6±7.90, P < 0.001; Phase
II: 21.1±2.87 vs 27.4±4.05, P < 0.001; Phase III: 9.9 ± 1.20 vs
19 ± 2.50, P < 0.001) compared to the control group. The
corticosteroids excretion levels were higher in all the
groups of children with autism than in the control group.
The level of 5-hydroxyindole acetic acid was significantly
higher in children with LFA (8.2±1.48 vs 6.8±0.85, P < 0.001)
and MFA (8.2±1.48 vs 7.4± 0.89, P = 0.001) and not significantly
higher in children with HFA than in the control
group. The changes were correlated with degrees of severity
of the disorder.
Conclusion These data suggest that altered cortisol excretion
pattern and high level of corticosteroids in urine may
probably be a consequence of altered hypothalamic-pituitary-
adrenal axis function, which may contribute to the
pathogenesis and affect the severity of autism