A mechanized proof of loop freedom of the (untimed) AODV routing protocol

The Ad hoc On-demand Distance Vector (AODV) routing protocol allows the nodes in a Mobile Ad hoc Network (MANET) or a Wireless Mesh Network (WMN) to know where to forward data packets. Such a protocol is 'loop free' if it never leads to routing decisions that forward packets in circles. This paper describes the mechanization of an existing pen-and-paper proof of loop freedom of AODV in the interactive theorem prover Isabelle/HOL. The mechanization relies on a novel compositional approach for lifting invariants to networks of nodes. We exploit the mechanization to analyse several improvements of AODV and show that Isabelle/HOL can re-establish most proof obligations automatically and identify exactly the steps that are no longer valid.Comment: The Isabelle/HOL source files, and a full proof document, are available in the Archive of Formal Proofs, at http://afp.sourceforge.net/entries/AODV.shtm

Mechanizing a Process Algebra for Network Protocols

This paper presents the mechanization of a process algebra for Mobile Ad hoc Networks and Wireless Mesh Networks, and the development of a compositional framework for proving invariant properties. Mechanizing the core process algebra in Isabelle/HOL is relatively standard, but its layered structure necessitates special treatment. The control states of reactive processes, such as nodes in a network, are modelled by terms of the process algebra. We propose a technique based on these terms to streamline proofs of inductive invariance. This is not sufficient, however, to state and prove invariants that relate states across multiple processes (entire networks). To this end, we propose a novel compositional technique for lifting global invariants stated at the level of individual nodes to networks of nodes.Comment: This paper is an extended version of arXiv:1407.3519. The Isabelle/HOL source files, and a full proof document, are available in the Archive of Formal Proofs, at http://afp.sourceforge.net/entries/AWN.shtm

Genetic mapping in polyploids

Many of our most important crop species are polyploid – an unusual phenomenon whereby each chromosome is present in multiple copies (more than the usual two copies). The most common such arrangement is tetraploidy, where each chromosome is present four times. Plant species can tolerate this condition quite well (the same cannot be said of animals or humans). In fact, polyploidy can confer certain advantages such as larger fruits and flowers, seedless fruits (useful for fruit growers) or improved tolerance to environmental stresses. However, carrying multiple copies of each chromosome complicates things, particularly when crop breeders would like to use DNA information to help inform selection decisions. This PhD project looked at how DNA information of polyploids should be best analysed, developing methods and new software tools to achieve this. We analysed DNA information from polyploid crops such as potato, rose and chrysanthemum, yielding many novel insights and important results.</p

Established liked versus disliked brands: brain activity, implicit associations and explicit

Consumers' attitudes towards established brands were tested using implicit and explicit measures. In particular, late positive potential (LPP) effects were assessed as an implicit physiological measure of motivational significance. The implicit Association Test (IAT) was used as an implicit behavioural measure of valence-related aspects (affective content) of brand attitude. We constructed individualised stimulus lists of liked and disliked brand types from participants' subjective pre-assessment. Participants then re-rated these visually presented brands whilst brain potential changes were recorded via electroencephalography (EEG). First, self-report measures during the test confirmed pre-assessed attitudes underlining consistent explicit rating performance. Second, liked brands elicited significantly more positive going waveforms (LPPs) than disliked brands over right parietal cortical areas starting at about 800 ms post stimulus onset (reaching statistical significance at around 1000 ms) and lasting until the end of the recording epoch (2000 ms). In accordance to the literature this finding is interpreted as reflecting positive affect-related motivational aspects of liked brands. Finally, the IAT revealed that both liked and disliked brands indeed are associated with affect-related valence. The increased levels of motivation associated with liked brands is interpreted as potentially reflecting increased purchasing intention, but this is of course only speculation at this stage. (authors' abstract

ATCA and Spitzer Observations of the Binary Protostellar Systems CG30 and BHR71

We present interferometric observations with resolution of ~3 arcsecs of the isolated, low-mass protostellar double cores CG30 and BHR71 in the N2$H+(1-0) line and at 3mm dust continuum, using the Australian Telescope Compact Array (ATCA). The results are complemented by infrared data from the Spitzer Space Telescope. In CG30, the 3mm dust continuum images resolve two compact sources with a separation of ~21.7 arcsecs (~8700 AU). In BHR71, strong dust continuum emission is detected at the position of the mid-infrared source IRS1, while only weak emission is detected from the secondary mid-infrared source IRS2. Assuming optically thin 3mm dust continuum emission, we derive hydrogen gas masses of 0.05--2.1$M_\odot$for the four sub-cores. N2H+(1-0) line emission is detected in both CG30 and BHR71, and is spatially associated with the thermal dust continuum emission. We derive the velocity fields and find symmetric velocity gradients in both sources. Assuming that these gradients are due to core rotation, we estimate the specific angular momenta and ratios of rotational energy to gravitational energy for all cores. We also find that the N2H+ emission is strongly affected by the outflows, both in terms of entrainment and molecule destruction.$Spitzer$images show the mid-infrared emission from all four sub-cores. All four sources appear to drive their own outflows. Based on the ATCA and$Spitzer$ observations, we construct spectral energy distributions (SEDs) and derive temperatures and luminosities for all cores. Based on the morphology and velocity structure, we suggest that the sub-cores in CG30 were formed by initial fragmentation of a filamentary prestellar core, while those in BHR71 could originate from rotational fragmentation of a single collapsing protostellar core.Comment: 31 pages, 10 figures, to be published by ApJ in Sep. 200

Helminth coinfection and COVID-19: an alternate hypothesis

[Extract] In their recently published commentary, Bradbury and colleagues [1] drew attention to the possible negative interactions between helminth infection and COVID-19 severity in helminth-endemic regions. Helminth infections are known to be powerful modulators of the human immune response, and numerous studies now highlight the effects this may have on human infectious, inflammatory, and metabolic diseases. We believe, however, that any interaction between pre-existing helminth infection and the subsequent severity of COVID-19 need not necessarily be a negative one, and theoretical and empirical evidence suggests that helminths may indeed have a mitigating effect

The acute oncologist's role in managing patients with cancer and other co-morbidities

Background: An Acute Oncology Service (AOS) is paramount to providing timely and improved pathways of care for patients who are admitted to hospital with cancer-related problems or suspected cancer. Objective: To establish an AOS pilot study to decide how best to implement such a service locally. Methods: The AOS, which included collaboration between the oncology and palliative care teams at the Northern General Hospital in Sheffi eld, UK, ensured that the majority of oncology patients in the region received timely assessment by an oncologist if they became acutely unwell as a result of their cancer or its treatment. The AOS consisted of a thrice-weekly ward round, and daily telephone advice service. Results: We report on patient data during the fi rst 12 months of the pilot study. Delivery of the AOS enhanced communication between the services and provided inter-professional education and support, resulting in earlier oncological team involvement in the management of patients with cancer admitted under other teams, as well as provision of advice to patients and their caregivers and families. Provision of the AOS shortened the mean length of hospital stay by 6 days. Two case studies are presented to illustrate the typical challenges faced when managing these patients. Conclusions: Establishment of the AOS enabled effective collaboration between the oncology and other clinical teams to provide a rapid and streamlined referral pathway of patients to the AOS. Locally, this process has been supported by the development of acute oncology protocols, which are now in use across the local cancer network

Researching teacher educators’ preparedness to teach to and about diversity : Investigating epistemic reflexivity as a new conceptual framework

There is growing international concern about the extent to which teachers are prepared to work with an increasingly diverse student (and community) population. To date, research into the relationship between teacher preparation and preparedness to teach diverse learners has not focused on teacher educators’ understandings about teaching to/about diversity. Such understandings can be informed by epistemic aspects of professional work. Epistemic cognitions (cognitions about knowledge and knowing) allow professionals to generate perspectives necessary to tackle new and old challenges. The social lab reported in this paper investigated 12 Australian teacher educators’ perspectives about teaching to/about diversity using the 3R-Epistemic Cognition (EC) framework. The findings showed that the 3R-EC framework could be useful for capturing epistemic reflexive dialogues about teaching to/about diversity, although some aspects of the framework were identified by the teacher educators as challenging. On the basis of these identified challenges, refinements concerning communication and use of the 3R-EC framework were identified. The feedback also led to some refinements of the social lab methodology for use in the larger national study