Isogeny graphs of ordinary abelian varieties

Fix a prime number $\ell$. Graphs of isogenies of degree a power of $\ell$ are well-understood for elliptic curves, but not for higher-dimensional abelian varieties. We study the case of absolutely simple ordinary abelian varieties over a finite field. We analyse graphs of so-called $\mathfrak l$-isogenies, resolving that they are (almost) volcanoes in any dimension. Specializing to the case of principally polarizable abelian surfaces, we then exploit this structure to describe graphs of a particular class of isogenies known as $(\ell, \ell)$-isogenies: those whose kernels are maximal isotropic subgroups of the $\ell$-torsion for the Weil pairing. We use these two results to write an algorithm giving a path of computable isogenies from an arbitrary absolutely simple ordinary abelian surface towards one with maximal endomorphism ring, which has immediate consequences for the CM-method in genus 2, for computing explicit isogenies, and for the random self-reducibility of the discrete logarithm problem in genus 2 cryptography.Comment: 36 pages, 4 figure

Expression of ADP-ribosylation enzymes in mouse embryos and muscle cell cultures

Skeletal muscle myogenesis is a highly regulated process involving distinct changes in activation of transcription factors and gene expression driven by these transcription factors. Various regulatory signals from the local cellular environment play an important role in the commitment of cells to the myogenic pathway that eventually leads to terminal differentiation into multinucleated myotubes to form skeletal muscle. ADP-ribosylation activity has been detected in many avian and mammalian adult cardiac and skeletal muscle samples, but it is currently not known which enzymes are responsible for this activity, or if these same enzymes are expressed in the developing somites during embryogenesis. ADP-ribosylation has also been shown to be required for terminal differentiation in skeletal muscle cell cultures; however its mechanism of action has not been determined. This investigation examined the expression of the key ADP-ribosylation enzymes during embryo development in the mouse and during terminal differentiation in mouse C2C12 skeletal myoblast cell cultures. We also examined the effect of meta-Iodobenzylguanidine (MIBG), a known specific inhibitor of ADP-ribosyltransferase enzyme activity, on gene expression of select myogenic regulatory factors known to control terminal differentiation. The results demonstrated that Artl, Art3, Art5 and Adprh are expressed in the developing mouse embryos and that Art5 expression displayed the most restricted localization, mainly in the dorsal-medial lip of the dermamyotome, of the ADP-ribosylation enzymes. The localization of Art5 correlates with the known localization of integrin [alpha]7, a known substrate for ADP-ribosylation. Our investigations using C2C12 cell cultures as a model for terminal differentiation confirmed that MIBG inhibits differentiation of these cells. Inhibition with MIBG correlated with the failure to express Myodl, P21, and myogenin at distinct time points during the terminal differentiation process as compared to control treated cells. The expression of Artl, Art5 and Adprh were also shown to possess temporal patterns that were significantly affected by treatment with MIBG. Our results demonstrate the expression of key ADP-ribosylation enzymes during both somite development in the embryo and during terminal differentiation of C2C12 cell cultures. These data show that ADP-ribosylation may play an important role in determination and differentiation of skeletal muscle cells and that specific myogenic factors are regulated during differentiation by ADP-ribosylation

Security risk assessment: Group approach to a consensual outcome

AS/NZS4360:2004 suggests that the risk assessment process should not be conducted or information gathered in isolation. This insular method of data collection may lead to inaccurate risk assessment, as stakeholders with vested interests may emphasise their own risks or game the risk assessment process. The study demonstrated how a consensual risk assessment approach may result in a more acceptable risk assessment outcome when compared to individual assessments. The participants were senior managers at a West Australian motel located on the West Coast Highway, Scarborough. The motel consists of four three storey blocks of units, resulting in a total of 75 units. The three main areas of the business are Reception and Management, Housekeeping and Maintenance. The participants were interviewed individually and then as a group. Two activities took place in the study, an individual identification and analysis of risks affecting the facility, followed by a consensual group analysis of the same risks. The individual risk assessment results were collated and compared to the results of the consensus group. This demonstrated that individuals over or under emphasise some risks, dependant on personal affect. The study illustrated that a consensual style of risk information collection and assessment was more acceptable to the group then assessments conducted in isolation

Kinematic Evolution of Simulated Star-Forming Galaxies

Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ~8 billion years since z=1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking as the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (sigma_g) and increase in ordered rotation (Vrot) with time. The slopes of the relations between both sigma_g and Vrot with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations, and they both have similarly large scatter. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.Comment: ApJ accepted; 6 pages; A pdf with full resolution figures can be found at https://db.tt/8y4Vzaff (2.8M

Consensual security risk assessment: Overcoming bias, conflicting interests and parochialism

In a risk assessment process, insular methods of data collection and analysis may lead to an inaccurate risk assessment as stakeholders hold individual biases, conflicting interests and parochial approaches to certain risks. The article considered these issues and tested a consensual risk assessment approach that can overcome many of these issues. A staged risk assessment process was applied within an entertainment complex in the Security, and Food and Beverage Departments. Eight supervisors from the two departments participated in the study, with each participants individually interviewed on their view of predefined risks followed by the same risks discussed within a facilitated group. The study first identified a list of the twenty most important risks according to the two departmental managers. From this initial identification of risks, four supervisors from each department ranked, from highest to lowest, all twenty risks as individuals. Following this stage, the consensus activities involved four supervisors from one department who ranked all twenty risks as a group and with the aim that all participants had to agree. Finally, the consensus activity was repeated with all eight participants present. Such a staged approach allowed the various approaches and resulting outcomes from the various risk assessment methods to be compared. Such a comparison found that there was a need to gain common understanding or clear definition of risks within the group, that an individual’s assessment of a risk was driven by their own perceptions and that less important risks held a more common view, whereas higher risk had a greater diversity of views

A Comparison of Laboratory and Vulnerability Evaluation Methods for the Testing Security Equipment

A facility wide security system cannot be tested without causing disruption or creating vulnerabilities within the system. To overcome this issue, individual components or equipment may be evaluated to a priori performance standard. The two common approaches to security equipment evaluations are vulnerability attacks and laboratory testing. Laboratory testing of security equipment can reduce the costs and time associated with evaluations, as well as limiting the subjectivity of the tests. Vulnerability attacks will produce more realistic evaluation results of the whole security system; nevertheless, the data obtained is dependent on the physical attributes and skill of the attackers. This study ascertained what methodology, namely laboratory testing or vulnerability testing, was the most effective. To achieve this, both testing methodologies were applied to security padlocks with expert validation. The study confirmed that if security equipment has been laboratory tested to a designed priori performance level, the degree of security vulnerability can be effectively identified. As the security padlocks demonstrated, the high level achieved in the laboratory tests correlated with a high delay factor in vulnerability testing. Such an approach to security equipment testing resulted in a reliable and valid quantitative data set that could be applied at a later stage to other similar equipment. Nevertheless, it is suggested that when considering a facility wide security system, some degree of both laboratory and vulnerability testing has to be applied as they are complimentary