A limited-trust capacity model for mitigating threats of internal malicious services in cloud computing

Hidden persistent malware in guest virtual machine instances are among the most common internal threats in cloud computing, affecting the security of both cloud customers and providers. With the growing sophistication of modern malware, traditional methods are becoming increasingly ineffective for tackling cloud security problems. Moreover, given the pay-per-use model of clouds, consumption of resources by these malwares and malicious services can cause huge losses to both the cloud provider and customer. Thus, it is important to develop mechanisms that can limit the scale of malicious attacks in order to minimize their resources consumption. Trust management is a fundamental technique for assessing and increasing the reliability and security of cloud services. Unfortunately, majority of existing mechanisms for trust management in clouds have limitations that prevent them from being fully effective. In this paper, we propose a novel limited-trust capacity model to mitigate the threats of internal malicious software and services in cloud computing using concepts from flow networks to reduce the scale of malicious software or services. Our limited-trust capacity model can be utilized in the following two ways: (1) to manage the trust relationship among the guest services and to evaluate the threats of unknown malicious services, and (2) to minimize risk associated with renting cloud services and limiting the resource drain caused by malicious guest services. Finally, experimental results show that our limited-trust capacity model can effectively restrict the scale of malicious services and significantly mitigate the threats of internal attacks.     

Specific inhibition of DNA polymerase beta by its 14 kDa domain: role of single- and double-stranded DNA binding and 5'-phosphate recognition.

DNA polymerase beta (beta-polymerase) has been implicated in short-patch DNA synthesis in the DNA repair pathway known as base excision repair. The native 39 kDa enzyme is organized into four structurally and functionally distinct domains. In an effort to examine this enzyme as a potential therapeutic target, we analyzed the effect of various beta-polymerase domains on the activity of the enzyme in vitro. We show that the 14 kDa N-terminal segment of beta-polymerase, which binds to both single- and double-stranded DNA, but lacks DNA polymerase activity, inhibits beta-polymerase activity in vitro. Most importantly, the 8, 27 and 31 kDa domains of beta-polymerase do not inhibit beta-polymerase activity, demonstrating that the inhibition by the 14 kDa domain is specific. The inhibition of beta-polymerase activity in vitro is abolished by increasing the concentrations of both of the substrates (template-primer and deoxynucleoside triphosphate). In contrast, an in vitro base excision repair assay is inhibited in a domain specific manner by the 14 kDa domain even in the presence of saturating substrates. The inhibition of beta-polymerase activity by the 14 kDa domain appears specific to beta-polymerase as this domain does not inhibit either mammalian DNA polymerase alpha or Escherichia coli polymerase I (Klenow fragment). These data suggest that the 14 kDa domain could be used as a potential inhibitor of intracellular beta-polymerase and that it may provide a means for sensitizing cells to therapeutically relevant DNA damaging agents.     

Guaianolides from Tricholepis glaberrima

Cynaropicrin and 11,13-dihydrodesacylcynaropicrin were isolated from Tricholepis glaberrima.     

Stability of large diffusion/perfusion mismatch in anterior circulation strokes for 4 or more hours

Background  

The stability of hypoperfused brain tissue in stroke patients with major artery occlusions is unknown. The purpose of this study was to determine the persistence of a diffusion/perfusion mismatch in patients with ICA or proximal MCA occlusions.     

Estimation of Heritability for Samples from Non-Normal Situations

Mathematical expressions, to investigate the effects of mederate departure from normality assumption on the point estimate and on the probability of getting a negative estimate of genetic heritability, in a balanced situation, have been derived. The numerical results show that the point estimate is over sensitive whereas the probability of a negative estimate is insensitive to this violation.     

Improved DNA Electrophoresis in Conditions Favoring Polyborates and Lewis Acid Complexation

Spatial compression among the longer DNA fragments occurs during DNA electrophoresis in agarose and non-agarose gels when using certain ions in the conductive buffer, impairing the range of fragment sizes resolved well in a single gel. Substitutions using various polyhydroxyl anions supported the underlying phenomenon as the complexation of Lewis acids to DNA. We saw significant improvements using conditions (lithium borate 10 mM cations, pH 6.5) favoring the formation of borate polyanions and having lower conductance and Joule heating, delayed electrolyte exhaustion, faster electrophoretic run-speed, and sharper separation of DNA bands from 100bp to 12 kb in a single run.