Transient Turbulence in Taylor-Couette Flow

Recent studies have brought into question the view that at sufficiently high Reynolds number turbulence is an asymptotic state. We present the first direct observation of the decay of turbulent states in Taylor-Couette flow with lifetimes spanning five orders of magnitude. We also show that there is a regime where Taylor-Couette flow shares many of the decay characteristics observed in other shear flows, including Poisson statistics and the coexistence of laminar and turbulent patches. Our data suggest that characteristic decay times increase super-exponentially with increasing Reynolds number but remain bounded in agreement with the most recent data from pipe flow and with a recent theoretical model. This suggests that, contrary to the prevailing view, turbulence in linearly stable shear flows may be generically transient.Comment: 4 pages, 4 figures v2: Addressed referee comments for PRE. Made some cosmetic changes. Added inset to Fig.

Towards a Comprehensive Evidence-Based Approach For Information Security Value Assessment

This thesis is motivated by the goals of understanding in depth which information security value aspects are relevant in real-world business environments and contributing a value-prioritised information security investment decision model suitable for practitioners in the field. Pursuing this goal, we apply a mixed method research approach that combines the analysis of the relevant literature, expert interviews, practitioner survey data and structural equation modelling and multicriteria decision analysis. In the first step, we address the identified terminology gap to clarify the meaning of ‘cyber security’ by analysing authoritative definition sources in the literature and presenting an improved definition distinct from that of ‘information security’. We then investigate the influence of repeated information security breaches on an organisation’s stock market value to benchmark the wider economic impact of such events. We find abnormal returns following a breach event as well as weak statistical significance on abnormal returns for later breach events, confirming that data breaches have a negative impact on organisations. To understand how security practitioners view this topic, we conduct and analyse semi-structured interviews following a grounded theory approach. Our research identifies 15 principles aligned with a conceptual information security investment framework. The key components of this framework such as the business environment, drivers (threat landscape, legal and regulatory) and challenges (cost of security, uncertainty) are found to be a crucial part of value-prioritised information security investment decisions. We verify these findings through a structural model consisting of five latent variables representing key areas in value-focused information security investment decisions. The model shows that security capabilities have the largest direct effect on the value organisations gain from information security investment. In addition, the value outcome is strongly influenced by organisation-specific constructs such as the threat landscape and regulatory requirements, which must therefore be considered when creating security capabilities. By addressing one of the key uncertainty issues, we use a probabilistic topic modelling approach to identify latent security threat prediction topics from a large pool of security predictions publicised in the media. We further verify the prediction outcomes through a survey instrument. The results confirm the feasibility of forecasting notable threat developments in this context, implying that practitioners can use this approach to reduce uncertainty and improve security investment decisions. In the last part of the thesis, we present a multicriteria decision model that combines our results on value-prioritised information security investments in an organisational context. Based on predefined criteria and preferences and by utilising stochastic multicriteria acceptability analysis as the adopted methodology, our model can deal with substantial uncertainty while offering ease of use for practitioners

Towards a More Representative Definition of Cyber Security

In recent years, ‘Cyber Security’ has emerged as a widely-used term with increased adoption by practitioners and politicians alike. However, as with many fashionable jargon, there seems to be very little understanding of what the term really entails. Although this is may not be an issue when the term is used in an informal context, it can potentially cause considerable problems in context of organizational strategy, business objectives, or international agreements. In this work, we study the existing literature to identify the main definitions provided for the term ‘Cyber Security’ by authoritative sources. We then conduct various lexical and semantic analysis techniques in an attempt to better understand the scope and context of these definitions, along with their relevance. Finally, based on the analysis conducted, we propose a new improved definition that we then demonstrate to be a more representative definition using the same lexical and semantic analysis techniques

The Impact Of Repeated Data Breach Events On Organisations’ Market Value

Purpose – In this study, we examined the influence of one or more information security breaches on an organization’s stock market value as a way to benchmark the wider economic impact of such events. Design/Methodology/approach – We used an event studies based approach where a measure of the event’s economic impact can be constructed using security prices observed over a relatively short period of time. Findings – Based on the results, we argue that although no strong conclusions could be made given the current data constraints, there was enough evidence to show that such correlation exists, especially for recurring security breaches. Research limitations/implications – One of the main limitations of this study was the quantity and quality of published data on security breaches, as organisations tend not to share this information. Practical implications – One of the challenges in information security management is assessing the wider economic impact of security breaches. Subsequently, this helps drive investment decisions on security programmes that are usually seen as cost rather than moneymaking initiatives. Originality/value – We envisage that as more breach event data become more widely available due to compliance and regulatory changes, this approach has the potential to emerge as an important tool for information security managers to help support investment decisions. Keywords - Information Security, Event Based Analysis, Information Security Breaches Paper type - Research pape

Towards a More Representative Definition of Cyber Security

In recent years, ‘Cyber Security’ has emerged as a widely-used term with increased adoption by practitioners and politicians alike. However, as with many fashionable jargon, there seems to be very little understanding of what the term really entails. Although this is may not be an issue when the term is used in an informal context, it can potentially cause considerable problems in context of organizational strategy, business objectives, or international agreements. In this work, we study the existing literature to identify the main definitions provided for the term ‘Cyber Security’ by authoritative sources. We then conduct various lexical and semantic analysis techniques in an attempt to better understand the scope and context of these definitions, along with their relevance. Finally, based on the analysis conducted, we propose a new improved definition that we then demonstrate to be a more representative definition using the same lexical and semantic analysis techniques

Callous-Unemotional Traits Among Adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD): Associations with Parenting

This study examined the extent to which positive and negative parenting relates to conduct problems (CP) and callous-unemotional (CU) traits among 172 adolescents (72 % males; Mage = 16.91 years, SD = .67) with attention-deficit/hyperactivity disorder and whether CU traits moderate the link between parenting and CP. Mothers reported on their adolescents’ CP, CU traits, and their own parenting practices. Maternal behaviors were observed during a problem-solving communication task. Parents who engaged in more positive parenting (self-reported and observed) reported their adolescents as having lower levels of CU traits. No effect was found for negative parenting. Moderation analyses indicated that lower levels of positive maternal behavior was only associated with higher CP in the presence of higher levels of CU traits. Negative parenting was positively related to CP regardless of CU traits. Positive parenting, irrespective of measurement approach, uniquely relates to adolescents’ CU traits while both positive and negative parenting relate to CP

Novel suspension retroviral packaging cells generated by transposition using transposase encoding mRNA advance vector yields and enable production in bioreactors

To date, the establishment of high-titer stable viral packaging cells (VPCs) at large scale for gene therapeutic applications is very time- and cost-intensive. Here we report the establishment of three human suspension 293-F-derived ecotropic MLV-based VPCs. The classic stable transfection of an EGFP-expressing transfer vector resulted in a polyclonal VPC pool that facilitated cultivation in shake flasks of 100 mL volumes and yielded high functional titers of more than 1 × 106 transducing units/mL (TU/mL). When the transfer vector was flanked by transposon terminal inverted repeats (TIRs) and upon co-transfection of a plasmid encoding for the transposase, productivities could be slightly elevated to more than 3 × 106 TU/mL. In contrast and using mRNA encoding for the transposase, as a proof of concept, productivities were drastically improved by more than ten-fold exceeding 5 × 107 TU/mL. In addition, these VPC pools were generated within only 3 weeks. The production volume was successfully scaled up to 500 mL employing a stirred-tank bioreactor (STR). We anticipate that the stable transposition of transfer vectors employing transposase transcripts will be of utility for the future establishment of high-yield VPCs producing pseudotype vector particles with a broader host tropism on a large scale

Dissociative electron attachment to the H2O molecule. II. Nuclear dynamics on coupled electronic surfaces within the local complex potential model

We report the results of a first-principles study of dissociative electron attachment to H2O. The cross sections are obtained from nuclear dynamics calculations carried out in full dimensionality within the local complex potential model by using the multi-configuration time-dependent Hartree method. The calculations employ our previously obtained global, complex-valued, potential-energy surfaces for the three (doublet B1, doublet A1, and doublet B2) electronic Feshbach resonances involved in this process. These three metastable states of H2O- undergo several degeneracies, and we incorporate both the Renner-Teller coupling between the B1 and A1 states as well as the conical intersection between the A1 and B2 states into our treatment. The nuclear dynamics are inherently multidimensional and involve branching between different final product arrangements as well as extensive excitation of the diatomic fragment. Our results successfully mirror the qualitative features of the major fragment channels observed, but are less successful in reproducing the available results for some of the minor channels. We comment on the applicability of the local complex potential model to such a complicated resonant system.Comment: Corrected version of Phys Rev A 75, 012711 (2007