Circuits with a mem-element: invariant manifolds control via pulse programmed sources

The paper considers the problem of controlling multistability in a general class of circuits composed of a linear time-invariant two-terminal (one port) element, containing linear R, L, C components and ideal operational amplifiers, coupled with one of the mem-elements (memory elements) introduced by Prof. L.O. Chua, i.e., memristors, memcapacitors, and meminductors. First, explicit expressions of the invariant manifolds of the circuit are directly given in terms of the state variables of the two-terminal element and the mem-element. Then, the problem of steering the circuit dynamics from an initial invariant manifold to a final one, and hence to potentially switch among different attractors of the circuit, is addressed by designing pulse shaped control inputs. The control inputs ensure that the transition between the initial and final manifolds is accomplished within a given finite time interval. Moreover, it is shown how the designed control inputs can be implemented by introducing independent voltage and current sources in the two-terminal element. Notably, it turns out that it is always possible to solve the considered control problem by using a unique independent source. Several examples are provided to illustrate how the proposed approach can be applied to different circuits with mem-elements and to highlight the influence of the features of the designed sources on the behavior of the controlled dynamics.

A Novel Floating/Grounded Meminductor Emulator

Meminductor is a nonlinear two-terminal element with storage energy and memory ability. To date, meminductor element is not available commercially as memristor and memcapacitor are. Therefore, it is of great significance to implement a meminductor emulator for breadboard experiment. In this paper, a flux-controlled floating/grounded meminductor emulator without a memristor is presented. It is built with commercially available off-the-shelf electronic devices. It consists of single operational transconductance amplifier (OTA), single multiplier, two second-generation current conveyors (CCIIs), single current-feedback operational amplifier (CFOA) and single operational amplifier. Using OTA device introduces an additional control parameter besides frequency and amplitude values of applied voltage to control the area of pinched hysteresis loop of meminductor. Mathematical model of proposed emulator circuit is given to describe the behavior of meminductor circuit. The breadboard experiment is performed using CA3080, AD844, AD633J and LM741 for OTA, CCII–CFOA, multiplier and operational amplifier, respectively. Simulation and experimental test results are given to verify the theoretical analyses. Frequency-dependent pinched hysteresis loop is maintained up to 5 kHz. The presented meminductor emulator tends to work as ordinary inductor for higher frequencies.

Current-year shoot hydraulic structure in two boreal conifers—implications of growth habit on water potential

Metabolic scaling theory allows us to link plant hydraulic structure with metabolic rates in a quantitative framework. In this theoretical framework, we considered the hydraulic structure of current-year shoots in Pinus sylvestris and Picea abies, focusing on two properties unaccounted for by metabolic scaling theories: conifer needles are attached to the entire length of shoots, and the shoot as a terminal element does not display invariant properties. We measured shoot length and diameter as well as conduit diameter and density in two locations of 14 current-year non-leader shoots of pine and spruce saplings, and calculated conductivities of shoots from measured conduit properties. We evaluated scaling exponents for the hydraulic structure of shoots at the end of the water transport pathway from the data and applied the results to simulate water potential of shoots in the crown. Shoot shape was intermediate between cylindrical and paraboloid. Contrary to previous findings, we found that conduit diameter scaled with relative, not absolute, distance from the apex and absolute under-bark shoot diameter independently of species within the first-year shoots. Shoot hydraulic conductivity scaled with shoot diameter and hydraulic diameter. Larger shoots had higher hydraulic conductance. We further demonstrate by novel model calculations that ignoring foliage distribution along the hydraulic pathway overestimates water potential loss in shoots and branches and therefore overestimates related water stress effects. Scaling of hydraulic properties with shoot size enhances apical dominance and may contribute to the decline of whole-tree conductance in large trees.

Yeast Sup35 prion structure: two types, four parts, many variants

The yeast [PSI+] prion, formed by the Sup35 (eRF3) protein, can exist as multiple structural variants exhibiting phenotypic variation in the strength of nonsense suppression and mitotic stability. Structure of [PSI+] and its variation is only partly characterized. Here, we mapped the Sup35 proteinase K-resistant amyloid cores of 26 [PSI+] prions of different origin, isolated from yeast cells. In all cases the Sup35 amino acid residues 2-32 were fully resistant and the region up to residue 72 was partially resistant. Proteinase K-resistant structures were also found within regions 73-124, 125-153 and 154-221, but their presence differed between [PSI+] isolates. The [PSI+] phenotype depended mainly, if not solely, on the structure in region 2-72. Structures in region 73-221 were in some cases mitotically unstable and heterogenous. Two distinct digestion patterns were observed for the 2-72 fragment, which correlated with the “strong” and “weak” [PSI+] nonsense-suppressor phenotypes. All [PSI+] with a weak pattern were eliminated by multicopy HSP104 gene and were not toxic when combined with multicopy SUP35. [PSI+] with a strong pattern showed opposite properties, being resistant to multicopy HSP104 and lethal in the presence of multicopy SUP35. Thus, our data suggest existence of two distinct and reliably distinguishable structural classes of [PSI+] rather than a continuum of prions with gradually altering phenotype.ImportancePrions and amyloids are relatively novel and incompletely characterized structures. To understand them better, we mapped amyloid cores of 26 isolates of the Sup35 yeast prion using proteinase K digestion and mass spectrometry. We found that these cores are composed of up to four proteinase K-resistant elements spanning almost the whole length of Sup35 region inessential for viability. However, only the N-terminal element was present in all structures. There are many variants of the Sup35 prion, and these are usually roughly combined into two groups, “strong” and “weak”, based on the strength of their nonsense-suppressor phenotype. However, it was not clear whether such groups could be distinguished by any reliable qualitative criteria. Our data indicate that these groups do exist and can be reliably distinguished based on the N-terminal element digestion pattern and the effects of the multicopy SUP35 and HSP104 genes on these prion variants.

FROM LINGUISTIC REPRESENTATION TO FUZZY MATHEMATICS IN GROWN UP PEOPLE

The aim of this note is to give some critical examples where even the use of the same clustering rules lead to fuzziness. It starts from poor numerical systems and compares them with the expanded Sergeyev model, where the grossone is used, as an infinite terminal element. It can be compared with terminal elements of the ancient languages, such as the Greek myriad and the Chinese wan. On them some propositions that hold in the arithmetic of the grossone are similar, while they are not meaningful for the countable system of infinity. The note shows that both the upward and downward trend are actually present in human language and in conceptual arrangements. The note then goes on to sketch the model of evolution of Bak-Sneppen, showing two significant applications: the case of the evolution and study of foreign languages and, according to the model of Lloyd, the territorial analysis. In both cases it is highlighted how the Bak-Sneppen model becomes more stable when the universe is segmented, as already proven by the authors in previous works. The third part examines some cases of false probabilistic intuition due to incomplete perception of the phenomena, what could therefore be defined as hidden conditional probability. Interesting is the classic application of the theory of games to lotteries and ternary games, such as Chinese morra.

An N-Terminal Retention Module Anchors the Giant Adhesin LapA ofPseudomonas fluorescensat the Cell Surface: a Novel Subfamily of Type I Secretion Systems

ABSTRACTLapA ofPseudomonas fluorescensPf0-1 belongs to a diverse family of cell surface-associated bacterial adhesins that are secreted via the type I secretion system (T1SS). We previously reported that the periplasmic protease LapG cleaves the N terminus of LapA at a canonical dialanine motif to release the adhesin from the cell surface under conditions unfavorable to biofilm formation, thus decreasing biofilm formation. Here, we characterize LapA as the first type I secreted substrate that does not follow the “one-step” rule of T1SS. Rather, a novel N-terminal element, called the retention module (RM), localizes LapA at the cell surface as a secretion intermediate. Our genetic, biochemical, and molecular modeling analyses support a model wherein LapA is tethered to the cell surface through its T1SS outer membrane TolC-like pore, LapE, until LapG cleaves LapA in the periplasm. We further demonstrate that this unusual retention strategy is likely conserved among LapA-like proteins, and it reveals a new subclass of T1SS ABC transporters involved in transporting this group of surface-associated LapA-like adhesins. These studies demonstrate a novel cell surface retention strategy used throughout theProteobacteriaand highlight a previously unappreciated flexibility of function for T1SS.IMPORTANCEBacteria have evolved multiple secretion strategies to interact with their environment. For many bacteria, the secretion of cell surface-associated adhesins is key for initiating contact with a preferred substratum to facilitate biofilm formation. Our work demonstrates thatP. fluorescensuses a previously unrecognized secretion strategy to retain the giant adhesin LapA at its cell surface. Further, we identify likely LapA-like adhesins in various pathogenic and commensal proteobacteria and provide phylogenetic evidence that these adhesins are secreted by a new subclass of T1SS ABC transporters.

“Cell surface associated LapA ofPseudomonas fluorescensis anchored inside its Type-1 Secretion TolC-like Pore”

The type-1 secretion system (T1SS) of gram-negative bacteria enables a one-step translocation strategy known to move functionally diverse proteins from the cytoplasm into the extracellular environment without a periplasmic intermediate. LapA ofPseudomonas fluorescensPf0-1 is a giant type-1 secreted (T1S) adhesin that facilitates biofilm formation only when displayed at the cell surface. A LapA-targeting periplasmic protease, LapG, connects intracellular cyclic diguanylate (c-di-GMP) levels with cell surface-associated LapA by cleaving and absolving LapA from the cell surface under conditions unsuitable for biofilm formation. Here, we demonstrate that LapA contains a novel N-terminal element, called the retention module (RM), which prohibits classical one-step T1S of LapA. We provide evidence that the RM of LapA tethers LapA at the cell surface through its outer membrane TolC-like pore, LapE, where LapA is accessible to the periplasmic protease LapG. We also demonstrate that this unusual retention strategy is likely conserved among LapA-like proteins and represents a new subclass of T1SS ABC transporters exclusively involved in transporting LapA-like adhesins.Significance StatementBacteria have evolved multiple secretion strategies to interact with their environment. For many bacteria, the secretion of cell surface associated adhesins is often key for initiating contact with a preferred substrate to facilitate biofilm formation. Our work demonstrates thatP. fluorescensuses a previously unrecognized secretion strategy to retain the giant adhesin LapA at its cell surface. Further, we identify likely LapA-like adhesins in various pathogenic and commensal Proteobacteria and provide phylogenetic evidence these adhesins are secreted by a new subclass of T1SS ABC transporters.