Cellular automaton for bacterial towers

A simulation approach to the stochastic growth of bacterial towers is presented, in which a non-uniform and finite nutrient supply essentially determines the emerging structure through elementary chemotaxis. The method is based on cellular automata and we use simple, microscopic, local rules for bacterial division in nutrient-rich surroundings. Stochastic nutrient diffusion, while not crucial to the dynamics of the total population, is influential in determining the porosity of the bacterial tower and the roughness of its surface. As the bacteria run out of food, we observe an exponentially rapid saturation to a carrying capacity distribution, similar in many respects to that found in a recently proposed phenomenological hierarchical population model, which uses heuristic parameters and macroscopic rules. Complementary to that phenomenological model, the simulation aims at giving more microscopic insight into the possible mechanisms for one of the recently much studied bacterial morphotypes, known as "towering biofilm", observed experimentally using confocal laser microscopy. A simulation suggesting a mechanism for biofilm resistance to antibiotics is also shown

Change – social and personal: Thomas and Znaniecki’s The Polish Peasant for the study of present-day change in global higher education

The present work represents an extrapolation of W.I. Thomas and Florian Znaniecki’s study, The Polish Peasant in Europe and America, on behalf of the development of sociological theory. The article focuses on careers and institutions in higher education. The curriculum vitae serves as the novel human document by which to investigate both social and personal change. Academic careers are studied by virtue of their objective and subjective dimensions. Objectively, the institution of education is revealed through the shifting expectations that govern work in academia in specific historical times (indicated by the cohort in which academics earned their Ph.D.s) and in specific socially bound places (indicated by the type of university in which academics work). Major social change in education is likely to spell personal change for the way in which people subjectively experience the contemporary academic career. The data come from U.S.-based academics; parallel transformational changes are observable globally. The global change discussed in the work centres on the diffusion and institutionalization of the research role. The sources and consequences of this change are problematic. Akin to Thomas and Znaniecki’s larger analytic aims, patterns of change are used inductively to formulate theory: the paper culminates by postulating a theory of increasing tendencies in the way knowledge is produced in higher education institutions throughout the world

Hierarchical population model with a carrying capacity distribution

A time- and space-discrete model for the growth of a rapidly saturating local biological population $N(x,t)$ is derived from a hierarchical random deposition process previously studied in statistical physics. Two biologically relevant parameters, the probabilities of birth, $B$, and of death, $D$, determine the carrying capacity $K$. Due to the randomness the population depends strongly on position, $x$, and there is a distribution of carrying capacities, $\Pi (K)$. This distribution has self-similar character owing to the imposed hierarchy. The most probable carrying capacity and its probability are studied as a function of $B$ and $D$. The effective growth rate decreases with time, roughly as in a Verhulst process. The model is possibly applicable, for example, to bacteria forming a "towering pillar" biofilm. The bacteria divide on randomly distributed nutrient-rich regions and are exposed to random local bactericidal agent (antibiotic spray). A gradual overall temperature change away from optimal growth conditions, for instance, reduces bacterial reproduction, while biofilm development degrades antimicrobial susceptibility, causing stagnation into a stationary state.Comment: 25 pages, 11 (9+2) figure

A WISE method for designing IIR filters

The problem of designing optimal digital IIR filters with frequency responses approximating arbitrarily chosen complex functions is considered. The real-valued coefficients of the filter's transfer function are obtained by numerical minimization of carefully formulated cost, which is referred here to as the weighted integral of the squared error (WISE) criterion. The WISE criterion linearly combines the WLS criterion that is used in the weighted least squares approach toward filter design and some time-domain components. The WLS part of WISE enforces quality of the frequency response of the designed filter, while the time-domain part of the WISE criterion restricts the positions of the filter's poles to the interior of an origin-centred circle with arbitrary radius. This allows one not only to achieve stability of the filter but also to maintain some safety margins. A great advantage of the proposed approach is that it does not impose any constraints on the optimization problem and the optimal filter can be sought using off-the-shelf optimization procedures. The power of the proposed approach is illustrated with filter design examples that compare favorably with results published in research literature

Practical tips for communicating research findings in a gender-responsive way

This two-page publication highlights 12 key aspects that scientists working on research for development projects in agriculture and natural resource management should bear in mind to share their research findings in a gender-responsive way. A gender-responsive communications strategy must be adequately planned and budgeted for at the earliest stages of the research process, and comprises four facets: understanding your audience; showcasing relevant gender findings; sharing these findings with differentiated stakeholders through gender sensitive channels and monitoring and evaluating all these efforts for continuous improvement. This requires a good understanding of the topics that capture the interest of these stakeholders, their preferred ways of accessing your findings, capacity to interpret the information you produce, and the intended use of this information. Knowledge is power. Ensuring that research and action partners, but also the local women, men and marginalized groups who are the target beneficiaries of our research are able to equitably access our findings can support their empowerment and is an essential part of the research-for-development process

Simultaneous removal of phosphorus and nitrogen from sewage using a novel combo system of fluidized bed reactor-membrane bioreactor (FBR-MBR)

A FBR-MBR combo system was designed as a novel approach for simultaneous phosphorus and nitrogen removal from sewage. The combo system was evaluated more than 7months under variable pH (7.5-9.5), hydraulic retention times (HRT=2-10h), intermittent aeration cycles (IAC) (on/off=60/60-15/45min) and sludge retention times (SRT=10-60d). Prior recovery of phosphorus as struvite in the FBR enhanced nitrogen and COD removal efficiency in MBR. Under optimum operating conditions (pH=9, HRT=6h and IAC=45/15min), PO43--P, NH4+-N and COD removal efficiencies were 92.6±4.2, 98.7±1.2 and 99.3±0.5%, respectively. Stable mixed liquor suspended solid concentration (3.0-5.0g/L); enhanced nitrification-denitrification activity (78-92%) and reduced transmembrane pressure were also achieved. Compared to soluble microbial products, extracellular polymeric substances (EPS) showed strong correlation with fast membrane fouling. Among EPS components, carbohydrate rather than protein was associated with membrane fouling. Except HRT, all parameters considered (pH, IAC, SRT) showed a significant effect on removal efficiency. © 2013 Elsevier Ltd

Increased prevalence of val(66)met BDNF genotype among subjects with cervical dystonia

Abnormalities of cortical representational maps and their plasticity have been described in dystonia. A common polymorphism for BDNF has been associated with abnormal cortical plasticity, and thus might contribute to pathogenesis of dystonia in some subjects. As a first step towards this suggestion, the current study examined the prevalence of this polymorphism. BDNF genotype was examined in 34 subjects with cervical dystonia, 54 age-matched healthy controls, and 53 subjects with a different movement disorder, Parkinson\u27s disease. ApoE genotype, known to influence neurological outcome in some conditions, was also examined as a control. In subjects with cervical dystonia, the val(66)met polymorphism was approximately twice as prevalent when compared to either control group. This was not true of ApoE genotype, which was similarly distributed across subject groups. The current findings suggest that the BDNF val(66)met polymorphism might play a role in the pathogenesis of cervical dystonia in some subjects

Circulating proteasome activity following mild head injury in children

PURPOSE: The aim of the study is to characterize changes in circulating proteasome (c-proteasome) activity following mild traumatic brain injury in children. METHODS: Fifty children managed at the Department of Pediatric Surgery because of concussion—mild head injury was randomly included into the study. The children were aged 11 months to 17 years (median = 10.07 + −1.91 years). Plasma proteasome activity was assessed using Suc-Leu-Leu-Val-Tyr-AMC peptide substrate, 2–6 h, 12–16 h, and 2 days after injury. Twenty healthy children admitted for planned inguinal hernia repair served as controls. RESULTS: Statistically significant elevation of plasma c-proteasome activity was noted in children with mild head injury 2–6 h, 12–16 h, and 2 days after the injury. CONCLUSIONS: Authors observed a statistically significant upward trend in the c-proteasome activity between 2–6 and 12–16 h after the mild head injury, consistent with the onset of the symptoms of cerebral concussion and a downward trend in the c-proteasome activity in the plasma of children with mild head injury between 12–16 h and on the second day after the injury, consistent with the resolving of the symptoms of cerebral concussion. Further studies are needed to demonstrate that the proteasome activity could be a prognostic factor, which can help in further diagnostic and therapeutic decisions in patients with head injury

6,4–PP Photolyase Encoded by AtUVR3 is Localized in Nuclei, Chloroplasts and Mitochondria and its Expression is Down-Regulated by Light in a Photosynthesis-Dependent Manner

search input Abstract Pyrimidine dimers are the most important DNA lesions induced by UVB irradiation. They can be repaired directly by photoreactivation or indirectly by the excision repair pathways. Photoreactivation is carried out by photolyases, enzymes which bind to the dimers and use the energy of blue light or UVA to split bonds between adjacent pyrimidines. Arabidopsis thaliana has three known photolyases: AtPHR1, AtCRY3 and AtUVR3. Little is known about the cellular localization and regulation of AtUVR3 expression. We have found that its transcript level is down-regulated by light (red, blue or white) in a photosynthesis-dependent manner. The down-regulatory effect of red light is absent in mature leaves of the phyB mutant, but present in leaves of phyAphyB. UVB irradiation does not increase AtUVR3 expression in leaves. Transiently expressed AtUVR3–green fluorescent protein (GFP) is found in the nuclei, chloroplasts and mitochondria of Nicotiana benthamiana epidermal cells. In the nucleoplasm, AtUVR3–GFP is distributed uniformly, while in the nucleolus it forms speckles. Truncated AtUVR3 and muteins were used to identify the sequences responsible for its subcellular localization. Mitochondrial and chloroplast localization of AtUVR3 is independent of its N-terminal sequence. Amino acids located at the C-terminal loop of the protein are involved in its transport into chloroplasts and its retention inside the nucleolus

Fine tuning chloroplast movements through physical interactions between phototropins

Phototropins are plant photoreceptors which regulate numerous responses to blue light, including chloroplast relocation. Weak blue light induces chloroplast accumulation, whereas strong light leads to an avoidance response. Two Arabidopsis phototropins are characterized by different light sensitivities. Under continuous light, both can elicit chloroplast accumulation, but the avoidance response is controlled solely by phot2. As well as continuous light, brief light pulses also induce chloroplast displacements. Pulses of 0.1s and 0.2s of fluence rate saturating the avoidance response lead to transient chloroplast accumulation. Longer pulses (up to 20s) trigger a biphasic response, namely transient avoidance followed by transient accumulation. This work presents a detailed study of transient chloroplast responses in Arabidopsis. Phototropin mutants display altered chloroplast movements as compared with the wild type: phot1 is characterized by weaker responses, while phot2 exhibits enhanced chloroplast accumulation, especially after 0.1s and 0.2s pulses. To determine the cause of these differences, the abundance and phosphorylation levels of both phototropins, as well as the interactions between phototropin molecules are examined. The formation of phototropin homo- and heterocomplexes is the most plausible explanation of the observed phenomena. The physiological consequences of this interplay are discussed, suggesting the universal character of this mechanism that fine-tunes plant reactions to blue light. Additionally, responses in mutants of different protein phosphatase 2A subunits are examined to assess the role of protein phosphorylation in signaling of chloroplast movements