Network Topology as a Driver of Bistability in the lac Operon

The lac operon in Escherichia coli has been studied extensively and is one of the earliest gene systems found to undergo both positive and negative control. The lac operon is known to exhibit bistability, in the sense that the operon is either induced or uninduced. Many dynamical models have been proposed to capture this phenomenon. While most are based on complex mathematical formulations, it has been suggested that for other gene systems network topology is sufficient to produce the desired dynamical behavior. We present a Boolean network as a discrete model for the lac operon. We include the two main glucose control mechanisms of catabolite repression and inducer exclusion in the model and show that it exhibits bistability. Further we present a reduced model which shows that lac mRNA and lactose form the core of the lac operon, and that this reduced model also exhibits the same dynamics. This work corroborates the claim that the key to dynamical properties is the topology of the network and signs of interactions.Comment: 15 pages, 13 figures, supplemental information include

Psychosocial Environment of Science Laboratory Classrooms in Canadian Schools and Universities

The Science Laboratory Environment Inventory assesses students’ or teachers’ perceptions of five dimensions of actual or preferred classroom environment, namely, Student Cohesiveness, Open-Endedness, Integration, Rule Clarity, and Material Environment. The instrument was field-tested in Canada, Australia, the United States, England, Israel, and Nigeria, both in secondary and in post- secondary institutions. Various analyses attested to each scale’s internal consist- ency, reliability, discriminant validity, factorial validity, predictive validity, and ability to differentiate between the perceptions of students in different classes. The instrument is equally valid for use in its actual and preferred versions, for senior secondary school and university laboratory classes, for the individual or the class mean as the unit of analysis, and for each of the six countries. Le Science Laboratory Environment Inventory évalue les perceptions des étu- diants ou des enseignants ayant trait à cinq facettes de la salle de cours, à savoir la cohésion des étudiants, l’ouverture, l’intégration, la clarté du règlement et l’environnement physique. L’instrument a été utilisé au secondaire et au post- secondaire au Canada, en Australie, aux États-Unis, en Angleterre, en Israël et au Nigeria. Diverses analyses attestent la cohérence interne, la fidélité, la validité discriminante, la validité factorielle et la validité prédictive de chaque échelle comme son pouvoir de différencier les perceptions des étudiants dans diverses classes. La validité de l’instrument a également été établie dans ses versions présente et préférée, pour une utilisation dans les dernières années du secondaire et les cours de laboratoire à l’université, pour la moyenne par individu ou par classe comme unité d’analyse et pour chacun de ses six pays.

Comparison of stethoscope bell and diaphragm, and of stethoscope tube length, for clinical blood pressure measurement

OBJECTIVE: This study investigated the effect of stethoscope side and tube length on auscultatory blood pressure (BP) measurement. METHODS: Thirty-two healthy participants were studied. For each participant, four measurements with different combinations of stethoscope characteristics (bell or diaphragm side, standard or short tube length) were each recorded at two repeat sessions, and eight Korotkoff sound recordings were played twice on separate days to one experienced listener to determine the systolic and diastolic BPs (SBP and DBP). Analysis of variance was carried out to study the measurement repeatability between the two repeat sessions and between the two BP determinations on separate days, as well as the effects of stethoscope side and tube length. RESULTS: There was no significant paired difference between the repeat sessions and between the repeat determinations for both SBP and DBP (all P-values>0.10, except the repeat session for SBP using short tube and diaphragm). The key result was that there was a small but significantly higher DBP on using the bell in comparison with the diaphragm (0.66 mmHg, P=0.007), and a significantly higher SBP on using the short tube in comparison with the standard length (0.77 mmHg, P=0.008). CONCLUSION: This study shows that stethoscope characteristics have only a small, although statistically significant, influence on clinical BP measurement. Although this helps understand the measurement technique and resolves questions in the published literature, the influence is not clinically significant

A Novel Design for a Robot Grappling Hook for use in a Nuclear Cave Environment

© 2016 Within the field of robotics there exist few designs for detachable grappling hooks. This paper focusses on the novel design of a detachable grappling hook for use within a nuclear cave environment. The design seeks to exploit the complex network of pipes that is present within a nuclear cave. It is hoped that the grapple may be used to aid with mapping and characterisation of the nuclear cave, as well as increasing the movement capabilities of robots within the cave. It is shown that our prototype grapple is able to support on average 2.4kg of mass, or thirty times its own weight. In addition when dropped from a height of 7.5cm, which removes ballistic instability, the grapple is able to engage itself 87% of the time. Finally the minimum speed that the grapple must be travelling, in order to secure itself to its target, is found to be 1.08m/s

An experiment in individualized instruction as an approach introductory chemistry

A comparison was made of the achievement of two groups of students, randomly enrolled in an introductory chemistry course at the Memorial University of Newfoundland. The control group was treated by a normal lecture presentation, while the members of the experimental group progressed at an individual rate in small or large groups as each individual desired. Each member of the experimental group was given a learning guide for each chapter. -- Conclusions were drawn from the results of two criterion examinations, one taken after eight weeks and the other after twelve weeks. Analysis was by a series of regression equations, incorporating several covariates. -- The effectiveness of individualized instruction cannot be determined from the results of any one experiment, but by an accumulation of evidence from many studies. However, the results of the present study suggested that the experimental treatment produced a marginally significant greater gain in achievement. It is not clear whether this might be claimed for the experimental group as a whole or simply for those without previous chemistry. -- An attempt was also made to identify factors which might be used to predict the success of individual students differently in the individualized treatment compared to the group treatment. General ability, albeit within a restricted range, and mathematical ability did not interact with treatment. It was suggested that there were indications that students with a tendency towards neuroticism were favored by the experimental treatment, although this did not reach statistical significance. The trait extraversion-introversion was found not to interact significantly with treatment

Nectar-feeding bats

45 p. : ill. ; 26 cm.Includes bibliographica references (p. 43-45)."Dissection and histological examination of the hyoid and lingual regions of the New World nectar-feeding bats reveal marked modification of the tongue-retractor musculature (Mm. sternohyoideus, geniohyoideus, hyoglossus, styloglossus, and genioglossus) and modification of the internal and external tongue structure from the conditions found in non-nectar-feeding bats. Use of these derived characters in a cladistic analysis leads to the phylogenetic hypothesis that nectivory evolved twice independently in the family Phyllostomidae. One group of nectar-feding phyllostomids, comprising the genera Lonchophylla, Lionycteris, and Platalina (traditionally considered glossophagines) deserves separate subfamilial status based on the markedly different adaptations for nectivory observed. The other group, comprising the remaining 10 glossophagine genera (Glossophaginae, sensu stricto), plus Phyllonycteris, Erophylla, and perhaps Brachyphylla form a monophyletic group. Within the newly restricted subfamily Glossophaginae there are two major clades. One clade is composed of Glossophaga, Monophyllus, and surprisingly, Lichonycteris. The other is composed of the more derived nectar-feeding genera: Leptonycteris, Anoura, Hylonycteris, Choeroniscus, Choeronycteris, and probably, Scleronycteris and Musonycteris. Interestingly, both karyotypic evidence, and evidence from dental and basicranial studies, can be interpreted to support the phylogeny presented here"--P. [1]

Social networks : the future for health care delivery

With the rapid growth of online social networking for health, health care systems are experiencing an inescapable increase in complexity. This is not necessarily a drawback; self-organising, adaptive networks could become central to future health care delivery. This paper considers whether social networks composed of patients and their social circles can compete with, or complement, professional networks in assembling health-related information of value for improving health and health care. Using the framework of analysis of a two-sided network – patients and providers – with multiple platforms for interaction, we argue that the structure and dynamics of such a network has implications for future health care. Patients are using social networking to access and contribute health information. Among those living with chronic illness and disability and engaging with social networks, there is considerable expertise in assessing, combining and exploiting information. Social networking is providing a new landscape for patients to assemble health information, relatively free from the constraints of traditional health care. However, health information from social networks currently complements traditional sources rather than substituting for them. Networking among health care provider organisations is enabling greater exploitation of health information for health care planning. The platforms of interaction are also changing. Patient-doctor encounters are now more permeable to influence from social networks and professional networks. Diffuse and temporary platforms of interaction enable discourse between patients and professionals, and include platforms controlled by patients. We argue that social networking has the potential to change patterns of health inequalities and access to health care, alter the stability of health care provision and lead to a reformulation of the role of health professionals. Further research is needed to understand how network structure combined with its dynamics will affect the flow of information and potentially the allocation of health care resources