Topologies of Organization: Space in Continuous Deformation

2019 ◽  
Vol 41 (11) ◽  
pp. 1513-1530 ◽  
Author(s):  
Helene Ratner
Keyword(s):  
Spatial Organization ◽  
Transient Condition ◽  
Material Production ◽  
Continuous Deformation ◽  
Danish School ◽  
The Stability ◽  
Constant Deformation ◽  
Empirical Material

This paper offers to extend existing discussions about the socio-material production of organizational space through the concept of topology. It does so by: (1) connecting the concept of topology to existing approaches to spatial organization that emphasize its socio-material and open-ended emergence; (2) theorizing organizational space as being in constant deformation across different topological shapes; and (3) exploring this in an empirical example that juxtaposes a management meeting with its interruption. The empirical material is collected through the method of shadowing managers at a Danish school. Theoretically, the paper argues that the shaping of space is contingent upon dis/continuities between (non)human agencies. The topological deformation of space testifies to the continuous but under-acknowledged work provided by (non)human agencies to both achieve and challenge the stability of organizational space. It further situates the boundary between inside and outside as a transient condition. This renders spatial matters such as scale and size situational achievements. Topology thus implies that we cannot in advance scale organization into micro and macro spatialities, and further, foregrounds the inherent dis/organization of space.

scholarly journals TNRC6 proteins modulate hepatitis C virus replication by spatially regulating the binding of miR-122/Ago2 complexes to viral RNA

2019 ◽  
Vol 47 (12) ◽  
pp. 6411-6424 ◽  
Author(s):  
You Li ◽  
Li Wang ◽  
Efraín E Rivera-Serrano ◽  
Xian Chen ◽  
Stanley M Lemon
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Spatial Organization ◽  
Host Factor ◽  
Viral Rna ◽  
Fine Tuning ◽  
Hcv Rna ◽  
Human Hepatoma Cells ◽  
Translational Activity ◽  
The Stability

AbstractThe liver-specific microRNA, miR-122, is an essential host factor for replication of the hepatitis C virus (HCV). miR-122 stabilizes the positive-strand HCV RNA genome and promotes its synthesis by binding two sites (S1 and S2) near its 5′ end in association with Ago2. Ago2 is essential for both host factor activities, but whether other host proteins are involved is unknown. Using an unbiased quantitative proteomics screen, we identified the TNRC6 protein paralogs, TNRC6B and TNRC6C, as functionally important but redundant components of the miR-122/Ago2 host factor complex. Doubly depleting TNRC6B and TNRC6C proteins reduced HCV replication in human hepatoma cells, dampening miR-122 stimulation of viral RNA synthesis without reducing the stability or translational activity of the viral RNA. TNRC6B/C were required for optimal miR-122 host factor activity only when S1 was able to bind miR-122, and restricted replication when S1 was mutated and only S2 bound by miR-122. TNRC6B/C preferentially associated with S1, and TNRC6B/C depletion enhanced Ago2 association at S2. Collectively, these data suggest a model in which TNRC6B/C regulate the assembly of miR-122/Ago complexes on HCV RNA, preferentially directing miR-122/Ago2 to S1 while restricting its association with S2, thereby fine-tuning the spatial organization of miR-122/Ago2 complexes on the viral genome.

scholarly journals Remodeling of the postsynaptic plasma membrane during neural development

2016 ◽  
Vol 27 (22) ◽  
pp. 3480-3489 ◽  
Author(s):  
Karolina Tulodziecka ◽  
Barbara B. Diaz-Rohrer ◽  
Madeline M. Farley ◽  
Robin B. Chan ◽  
Gilbert Di Paolo ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Neural Development ◽  
Lipid Composition ◽  
Spatial Organization ◽  
Postsynaptic Membrane ◽  
Membrane Microdomains ◽  
Synaptic Membranes ◽  
Synaptic Remodeling ◽  
Neuronal Synapses ◽  
The Stability

Neuronal synapses are the fundamental units of neural signal transduction and must maintain exquisite signal fidelity while also accommodating the plasticity that underlies learning and development. To achieve these goals, the molecular composition and spatial organization of synaptic terminals must be tightly regulated; however, little is known about the regulation of lipid composition and organization in synaptic membranes. Here we quantify the comprehensive lipidome of rat synaptic membranes during postnatal development and observe dramatic developmental lipidomic remodeling during the first 60 postnatal days, including progressive accumulation of cholesterol, plasmalogens, and sphingolipids. Further analysis of membranes associated with isolated postsynaptic densities (PSDs) suggests the PSD-associated postsynaptic plasma membrane (PSD-PM) as one specific location of synaptic remodeling. We analyze the biophysical consequences of developmental remodeling in reconstituted synaptic membranes and observe remarkably stable microdomains, with the stability of domains increasing with developmental age. We rationalize the developmental accumulation of microdomain-forming lipids in synapses by proposing a mechanism by which palmitoylation of the immobilized scaffold protein PSD-95 nucleates domains at the postsynaptic plasma membrane. These results reveal developmental changes in lipid composition and palmitoylation that facilitate the formation of postsynaptic membrane microdomains, which may serve key roles in the function of the neuronal synapse.

scholarly journals Metabolic enzyme clustering by coiled coils improves the biosynthesis of resveratrol and mevalonate

2020 ◽  
Author(s):  
Tina Fink ◽  
Bojana Stevović ◽  
René Verwaal ◽  
Johannes A. Roubos ◽  
Rok Gaber ◽  
...  
Keyword(s):  
Spatial Organization ◽  
Noncovalent Interactions ◽  
Coiled Coil ◽  
Product Yield ◽  
Coiled Coils ◽  
Metabolic Enzyme ◽  
Biosynthetic Enzymes ◽  
Reaction Products ◽  
Interaction Domains ◽  
The Stability

Abstract The clustering of biosynthetic enzymes is used in nature to channel reaction products and increase the yield of compounds produced by multiple reaction steps. The coupling of multiple enzymes has been shown to increase the biosynthetic product yield. Different clustering strategies have particular advantages as the spatial organization of multiple enzymes creates biocatalytic cascades with a higher efficiency of biochemical reaction. However, there are also some drawbacks, such as misfolding and the variable stability of interaction domains, which may differ between particular biosynthetic reactions and the host organism. Here, we compared different protein-based clustering strategies, including direct fusion, fusion mediated by intein, and noncovalent interactions mediated through small coiled-coil dimer-forming domains. The clustering of enzymes through orthogonally designed coiled-coil interaction domains increased the production of resveratrol in Escherichia coli more than the intein-mediated fusion of biosynthetic enzymes. The improvement of resveratrol production correlated with the stability of the coiled-coil dimers. The coiled-coil fusion-based approach also increased mevalonate production in Saccharomyces cerevisiae , thus demonstrating the wider applicability of this strategy.

Polarity of the ascidian egg cortex before fertilization

Development ◽  
1992 ◽  
Vol 115 (1) ◽  
pp. 221-237 ◽  
Author(s):  
C. Sardet ◽  
J. Speksnijder ◽  
M. Terasaki ◽  
P. Chang
Keyword(s):  
Spatial Organization ◽  
Cytochalasin B ◽  
Centrifugal Forces ◽  
Calcium Dependent ◽  
Isolated Cortex ◽  
Coated Surface ◽  
The Stability ◽  
Polar Organization ◽  
Polar Distribution ◽  
Egg Cortex

The unfertilized ascidian egg displays a visible polar organization along its animal-vegetal axis. In particular, the myoplasm, a mitochondria-rich subcortical domain inherited by the blastomeres that differentiate into muscle cells, is mainly situated in the vegetal hemisphere. We show that, in the unfertilized egg, this vegetal domain is enriched in actin and microfilaments and excludes microtubules. This polar distribution of microfilaments and microtubules persists in isolated cortices prepared by shearing eggs attached to a polylysine-coated surface. The isolated cortex is further characterized by an elaborate network of tubules and sheets of endoplasmic reticulum (ER). This cortical ER network is tethered to the plasma membrane at discrete sites, is covered with ribosomes and contains a calsequestrin-like protein. Interestingly, this ER network is distributed in a polar fashion along the animal-vegetal axis of the egg: regions with a dense network consisting mainly of sheets or tightly knit tubes are present in the vegetal hemisphere only, whereas areas characterized by a sparse tubular ER network are uniquely found in the animal hemisphere region. The stability of the polar organization of the cortex was studied by perturbing the distribution of organelles in the egg and depolymerizing microfilaments and microtubules. The polar organization of the cortical ER network persists after treatment of eggs with nocodazole, but is disrupted by treatment with cytochalasin B. In addition, we show that centrifugal forces that displace the cytoplasmic organelles do not alter the appearance and polar organization of the isolated egg cortex. These findings taken together with our previous work suggest that the intrinsic polar distribution of cortical membranous and cytoskeletal components along the animal-vegetal axis of the egg are important for the spatial organization of calcium-dependent events and their developmental consequences.

scholarly journals ANALISA WAKTU PEMUTUSAN KRITIS SUATU SISTEM KELISTRIKAN

2013 ◽  
Vol 12 (2) ◽  
pp. 153
Author(s):  
Nathaniel L Bijang
Keyword(s):  
Transient Stability ◽  
Electrical Power ◽  
Circuit Breaker ◽  
Transient Condition ◽  
Electrical Power System ◽  
Circuit Breakers ◽  
Voltage Level ◽  
Transfer Capability ◽  
Clearing Time ◽  
The Stability

ANALISA  WAKTU PEMUTUSAN KRITIS SUATU SISTEM KELISTRIKAN  ABSTRAK Kestabilan adalah kemampuan mesin sinkron dari sistem tenaga listrik untuk mencapai kondisi stabil pada kondisi operasi baru yang sama atau identik dengan kondisi sebelum terjadi gangguan. Umumnya analisa kestabilan terbagi dalam dua kategori yaitu kestabilan steady  state yaitu analisa sistem untuk kembali ke kondisi stabil setelah mengalami gangguan kecil dan kestabilan transient yaitu analisa sistem untuk kembali ke kondisi normal/stabil setelah mengalami gangguan besar. Studi/analisa stabilitas sangat diperlukan saat perencanaan pembangkit  dan transmisi.   Analisa/studi stabilitas  sistem tenaga listrik membantu untuk menentukan setting waktu on/off relai proteksi , waktu pemutusan kritis circuit breaker, level tegangan dan kapasitas transfer diantara sistem-sistem. Kata kunci: Mesin sinkron, stabilitas, waktu pemutusan kritis  CRITICAL CLEARING TIME ANALYSIS ELECTRICAL POWER SYSTEM ABSTRACT The stability problem is concerned with the behavior of the synchronous machines after  a disturbance. Transient stability studies are needed to ensure the system can withstand the transient condition following a major disturbance. Frequently,such studies are conducted when new generating and transmitting facilities are planned. The studies are helpful  in determining such things as the nature of the relaying system needed, critical clearing time of circuit breakers, voltage level of, and transfer capability between systems. Keywords: Synchronous machine, stability, critical clearing time

scholarly journals The dam slope stability under the transient condition during an extreme flood

2021 ◽  
Vol 280 ◽  
pp. 10010
Author(s):  
Svitlana Velychko ◽  
Olena Dupliak
Keyword(s):  
Slope Stability ◽  
Water Level ◽  
Flood Control ◽  
Transient Condition ◽  
Mountainous Area ◽  
The Core ◽  
Upstream Slope ◽  
Flood Level ◽  
Extreme Flood ◽  
The Stability

Mountain Flood Control Reservoir (MFC Reservoir) is used to reduce the flood level in the mountainous area and protect settlements downstream. The special feature of this MFC Reservoir is the fast filling during 1-2 days, short storage time at the maximum level and speed falling of the water level. Simulation of the MFC Reservoir operation was carried out on the software Midas GTS NX. Two rockfill dam models were developed: with the core and with the screen. The fluctuation of the water level in the MFC Reservoir was taken as the transformed flood from 1% to 10% probability. The fast water level change in the MCF Reservoir creates the transient seepage condition during the flood. During the water level rising in the MFC Reservoir, the upstream slope stability gradually increases because of hydrostatic pressure. After the water level begins to fall with rate of 0.7 m/hour, the slope stability decreases. The core or screen location significantly affects the stability of the upstream dam slope. The simulation showed that the upstream slope of the dam with the core was more stable. Due to the high hydraulic conductivity, the upstream dam prism with the berm significantly dampens the pore pressure in the dam and increases the stability of the upstream slope.

Cell interactions in nerve and muscle cell cultures

1980 ◽  
Vol 89 (1) ◽  
pp. 85-101
Author(s):  
C. N. Christian ◽  
G. K. Bergey ◽  
M. P. Daniels ◽  
P. G. Nelson
Keyword(s):  
Nervous System ◽  
Action Potentials ◽  
Cell Biology ◽  
Spatial Organization ◽  
Surface Membrane ◽  
Synaptic Activity ◽  
Number Of Factors ◽  
Cell Culture Systems ◽  
Presynaptic Release ◽  
The Stability

The neurotransmitter synthesized by a given class of neurones is subject to modification and, indeed, a qualitative switchover in transmitter biochemistry recently has been demonstrated (Furshpan, POtter & Landis, 1980; Walicke, Campenot & Patterson, 1977). In conjunction with the specification of transmitter biosynthesis that becomes established in a given neurone, a complementary specification of appropriate receptor production is required in any cell functionally post-synaptic to that neurone. An additional requirement of peculiar force in the nervous system has to do with the spatial organization of the receptors in the surface membrane of the post-synaptic cell once the receptors are synthesized. Inappropriately distributed receptors are useless receptors. The perfect registration of a variety of types of presynaptic release sites with high post-synaptic concentrations of appropriate receptors constitutes one of the outstanding features of nervous-system organization that must be accounted for. We report some experiments directed toward understanding the cell biology of regulation of receptor distribution over the surface membrane of muscle cells. Functional synaptic connexions are formed quite early in development and the stability and maturation of synaptic networks is contingent on a number of factors. One interesting contingency is that related to the functional activity of developing networks. Do only those networks survive and mature which are activated by stimuli impinging from the environment? (Wiesel & Hubel, 1963). Put more simple, are action potentials and synaptic activity essential for neuronal maturation? We address this question in cell culture systems from the mammalian central nervous system.

A theorem in thermoelasticity and its application to linear stability

1989 ◽  
Vol 424 (1866) ◽  
pp. 143-153 ◽  
Keyword(s):  
Small Amplitude ◽  
Wave Speed ◽  
Final Section ◽  
Stability Result ◽  
Positive Definite ◽  
Fourier Synthesis ◽  
Acoustic Tensor ◽  
Thermoelastic Body ◽  
The Stability ◽  
Constant Deformation

Equations are written down governing the propagation of plane sinusoidal waves of small amplitude through a homogeneously prestrained equilibrium state of a materially homogeneous thermoelastic body of arbitrary elastic and thermal symmetry. The symmetric isothermal and isentropic acoustic tensors are defined in the usual way and it is assumed that the former is positive definite, so that it has three real and positive eigenvalues. It is shown, under the usual assumption that the specific heat at constant deformation is positive, that the three real and positive eigenvalues of the isentropic acoustic tensor are interlaced with those of the isothermal acoustic tensor, the smallest eigenvalue belonging to the isothermal and the largest to the isentropic acoustic tensor. Under the additional assumption that the symmetrized thermal conductivity tensor is positive definite, it is further shown that this result on the interlacing of the eigenvalues is sufficient to guarantee, for all positive values of the frequency of the sinusoidal waves, that the material is linearly stable in the sense that sinusoidal waves may not increase without bound in the direction of propagation. In the final section, the wide diversity in behaviour of the complex squared wave speed as a function of frequency is illustrated graphically. The stability result is extended to negative frequencies as these would be required in any Fourier synthesis of the sinusoidal wave solutions. A connection with Whitham’s wave hierarchy approach is mentioned.

scholarly journals Metabolic enzyme clustering by coiled coils improves the biosynthesis of resveratrol and mevalonate

2020 ◽  
Author(s):  
Tina Fink ◽  
Bojana Stevović ◽  
René Verwaal ◽  
Johannes A. Roubos ◽  
Rok Gaber ◽  
...  
Keyword(s):  
Spatial Organization ◽  
Noncovalent Interactions ◽  
Coiled Coil ◽  
Product Yield ◽  
Coiled Coils ◽  
Metabolic Enzyme ◽  
Biosynthetic Enzymes ◽  
Reaction Products ◽  
Interaction Domains ◽  
The Stability

Abstract The clustering of biosynthetic enzymes is used in nature to channel reaction products and increase the yield of compounds produced by multiple reaction steps. The coupling of multiple enzymes has been shown to increase the biosynthetic product yield. Different clustering strategies have particular advantages as the spatial organization of multiple enzymes creates biocatalytic cascades with a higher efficiency of biochemical reaction. However, there are also some drawbacks, such as misfolding and the variable stability of interaction domains, which may differ between particular biosynthetic reactions and the host organism. Here, we compared different protein-based clustering strategies, including direct fusion, fusion mediated by intein, and noncovalent interactions mediated through small coiled-coil dimer-forming domains. The clustering of enzymes through orthogonally designed coiled-coil interaction domains increased the production of resveratrol in Escherichia coli more than the intein-mediated fusion of biosynthetic enzymes. The improvement of resveratrol production correlated with the stability of the coiled-coil dimers. The coiled-coil fusion-based approach also increased mevalonate production in Saccharomyces cerevisiae , thus demonstrating the wider applicability of this strategy.

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