scholarly journals Quaternionic Grassmannians and Borel classes in algebraic geometry

2021 ◽  
Vol 33 (1) ◽  
pp. 97-140
Author(s):  
I. Panin ◽  
C. Walter
Keyword(s):  
Algebraic Geometry ◽  
Symplectic Form ◽  
Cell Structure ◽  
Content Type ◽  
Open Subscheme ◽  
Oriented Cohomology ◽  
Symplectic Cobordism ◽  
Sum Formula ◽  
Symplectic Vector Space ◽  
Witt Groups

The quaternionic Grassmannian H Gr ⁡ ( r , n ) \operatorname {H Gr}(r,n) is the affine open subscheme of the usual Grassmannian parametrizing those 2 r 2r -dimensional subspaces of a 2 n 2n -dimensional symplectic vector space on which the symplectic form is nondegenerate. In particular, we have HP n = H Gr ⁡ ( 1 , n + 1 ) \operatorname {HP}^n = \operatorname {H Gr}(1,n+1) . For a symplectically oriented cohomology theory A A , including oriented theories but also the Hermitian K \operatorname {K} -theory, Witt groups, and algebraic symplectic cobordism, we have A ( HP n ) = A ( pt ) [ p ] / ( p n + 1 ) A(\operatorname {HP}^n) = A(\operatorname {pt})[p]/(p^{n+1}) . Borel classes for symplectic bundles are introduced in the paper. They satisfy the splitting principle and the Cartan sum formula, and they are used to calculate the cohomology of quaternionic Grassmannians. In a symplectically oriented theory the Thom classes of rank 2 2 symplectic bundles determine Thom and Borel classes for all symplectic bundles, and the symplectic Thom classes can be recovered from the Borel classes. The cell structure of the H Gr ⁡ ( r , n ) \operatorname {H Gr}(r,n) exists in cohomology, but it is difficult to see more than part of it geometrically. An exception is HP n \operatorname {HP}^n where the cell of codimension  2 i 2i is a quasi-affine quotient of A 4 n − 2 i + 1 \mathbb {A}^{4n-2i+1} by a nonlinear action of G a \mathbb {G}_a .

Additive manufacturing of elastomeric foam with cell unit design for broadening compressive stress plateau

2018 ◽  
Vol 24 (9) ◽  
pp. 1579-1585 ◽  
Author(s):  
Xiaowei Zhu ◽  
Yanqiu Chen ◽  
Yu Liu ◽  
Yongqiang Deng ◽  
Changyu Tang ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Compressive Stress ◽  
Foam Cell ◽  
Cell Structure ◽  
Performance Testing ◽  
Elastic Buckling ◽  
Stress Plateau ◽  
Content Type ◽  
Direct Ink Writing ◽  
Unit Design

Purpose The purpose of this paper is to provide additive manufacturing-based solutions for preparation of elastomeric foam with broaden compressive stress plateau. Design/methodology/approach Mechanic models are developed for obtaining designs of foam cell units with enhanced elastic buckling. An experimental approach is taken to fabricate the foams based on direct ink writing technique. Experimental and simulation data are collected to assist understanding of our proposals and solutions. Findings A simple tetragonal structured elastomeric foam is proposed and fabricated by direct ink writing, in which its cell unit is theoretically designed by repeating every four filament layers. The foam exhibits a broader stress plateau, because of the pronounced elastic buckling under compressive loading as predicted by the authors’ mechanic modeling. A two-stage stress plateaus as observed in the foam, being attributed to the dual elastic buckling of the cell units along two lateral directions of the XY plane during compression. Research limitations/implications Future work should incorporate more microscopic parameters to tune the elastomeric foam for mechanic performance testing on linear elastic deformation and densification of polymer matrix. Practical implications Additive manufacturing offers an alternative to fabricate elastomeric foam with controlled cell unit design and therefore mechanics. Our results comment on its broad space for development such superior cushioning or damping material in the fields of vibration and energy absorption. Originality/value This work has contributed to new knowledge on preparation of high performance elastomeric foam by providing a better understanding on its cell structure, being printed using direct ink writing machines.

scholarly journals Identification and Characterization of the First Cholesterol-Dependent Cytolysins from Gram-Negative Bacteria

2012 ◽  
Vol 81 (1) ◽  
pp. 216-225 ◽  
Author(s):  
Eileen M. Hotze ◽  
Huynh M. Le ◽  
Jessica R. Sieber ◽  
Christina Bruxvoort ◽  
Michael J. McInerney ◽  
...  
Keyword(s):  
Cell Structure ◽  
Bacterial Species ◽  
Cytolytic Activity ◽  
Opportunistic Pathogens ◽  
Gram Positive ◽  
Gram Negative ◽  
Content Type ◽  
Positive Type ◽  
Secretion Signal ◽  
Anaerobic Soils

The cholesterol-dependent cytolysins (CDCs) are pore-forming toxins that have been exclusively associated with a wide variety of bacterial pathogens and opportunistic pathogens from theFirmicutesandActinobacteria, which exhibit a Gram-positive type of cell structure. We have characterized the first CDCs from Gram-negative bacterial species, which includeDesulfobulbus propionicustype species Widdel 1981 (DSM 2032) (desulfolysin [DLY]) andEnterobacter lignolyticus(formerlyEnterobacter cloacae) SCF1 (enterolysin [ELY]). The DLY and ELY primary structures show that they maintain the signature motifs of the CDCs but lack an obvious secretion signal. Recombinant, purified DLY (rDLY) and ELY (rELY) exhibited cholesterol-dependent binding and cytolytic activity and formed the typical large CDC membrane oligomeric pore complex. Unlike the CDCs from Gram-positive species, which are human- and animal-opportunistic pathogens, neitherD. propionicusnorE. lignolyticusis known to be a pathogen or commensal of humans or animals: the habitats of both organisms appear to be restricted to anaerobic soils and/or sediments. These studies reveal for the first time that the genes for functional CDCs are present in bacterial species that exhibit a Gram-negative cell structure. These are also the first bacterial species containing a CDC gene that are not known to inhabit or cause disease in humans or animals, which suggests a role of these CDCs in the defense against eukaryote bacterial predators.

scholarly journals Equivariant Giambelli formula for the symplectic Grassmannians — Pfaffian Sum Formula

2015 ◽  
Vol DMTCS Proceedings, 27th... (Proceedings) ◽  
Author(s):  
Takeshi Ikeda ◽  
Tomoo Matsumura
Keyword(s):  
Vector Space ◽  
Closed Formula ◽  
International Audience ◽  
Sum Formula ◽  
Isotropic Subspaces ◽  
Espace Vectoriel ◽  
Symplectic Vector Space ◽  
Symplectic Grassmannians ◽  
Schubert Class

International audience We prove an explicit closed formula, written as a sum of Pfaffians, which describes each equivariant Schubert class for the Grassmannian of isotropic subspaces in a symplectic vector space On démontre une formule close explicite, écrite comme une somme de Pfaffiens, qui décrit toute classe de Schubert équivariante pour la Grassmannienne des sous-espaces isotropes dans un espace vectoriel symplectique.

Desulfosporosinus metallidurans sp. nov., an acidophilic, metal-resistant sulfate-reducing bacterium from acid mine drainage

2021 ◽  
Vol 71 (7) ◽  
Author(s):  
Inna A. Panova ◽  
Olga Ikkert ◽  
Marat R. Avakyan ◽  
Dmitry S. Kopitsyn ◽  
Andrey V. Mardanov ◽  
...  
Keyword(s):  
Mine Drainage ◽  
Sequence Similarity ◽  
Cell Structure ◽  
Draft Genome ◽  
Electron Acceptors ◽  
Rrna Gene ◽  
Protein Coding ◽  
Content Type ◽  
Sulfate Reducing ◽  
Link Type

A novel, spore-forming, acidophilic and metal-resistant sulfate-reducing bacterium, strain OLT, was isolated from a microbial mat in a tailing dam at a gold ore mining site. Cells were slightly curved immotile rods, 0.5 µm in diameter and 2.0–3.0 µm long. Cells were stained Gram-negative, despite the Gram-positive cell structure revealed by electron microscopy of ultrathin layers. OLT grew at pH 4.0–7.0 with an optimum at 5.5. OLT utilised H2, lactate, pyruvate, malate, formate, propionate, ethanol, glycerol, glucose, fructose, sucrose, peptone and tryptone as electron donors for sulfate reduction. Sulfate, sulfite, thiosulfate, nitrate and fumarate were used as electron acceptors in the presence of lactate. Elemental sulfur, iron (III), and arsenate did not serve as electron acceptors. The major cellular fatty acids were C16:1ω7c (39.0 %) and C16 : 0 (12.1 %). The draft genome of OLT was 5.29 Mb in size and contained 4909 protein-coding genes. The 16S rRNA gene sequence placed OLT within the phylum Firmicutes , class Clostridia , family Peptococcaceae , genus Desulfosporosinus. Desulfosporosinus nitroreducens 59.4BT was the closest relative with 97.6 % sequence similarity. On the basis of phenotypic and phylogenetic characteristics, strain OLT represents a novel species within the genus Desulfosporosinus , for which we propose the name Desulfosporosinus metallidurans sp. nov. with the type strain OLT (=DSM 104464T=VKM В−3021T).

Fabrication of three dimensional open porous regular structure of PA-2200 for enhanced strength of scaffold using selective laser sintering

2016 ◽  
Vol 22 (4) ◽  
pp. 752-765 ◽  
Author(s):  
Jatender Pal Singh ◽  
Pulak M. Pandey ◽  
Anita Kamra Verma
Keyword(s):  
Porous Structure ◽  
Pore Size ◽  
Process Parameters ◽  
Cell Structure ◽  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Open Cell ◽  
Content Type ◽  
Open Porous Structure

Purpose Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more prone to compressive loading. Open porous structure lacks in strength in comparison to solid. Selective laser sintering (SLS) process is prominently used for fabrication of polymer/composite scaffolds. So, this paper aims to study for fabrication of three-dimensional open porous scaffolds with enhanced strength, process parameters of SLS of a biocompatible material are required to be optimized. Design/methodology/approach Regular open porous structures with suitable pore size as per computer-aided design models were fabricated using SLS. Polyamide (PA-2200) was used to fabricate the specimen/scaffold. To optimize the strength of the designed structure, response surface methodology was used to design the experiments. Specimens as per ASTM D695 were fabricated using SLS and compressive testing was carried out. Analysis of variance was done for estimating contribution of individual process parameters. Optimized process parameters were obtained using a trust region algorithm and correlated with experimental results. Accuracy of the fabricated specimen/scaffold was also assessed in terms of IT grades. In vitro cell culture on the fabricated structures confirmed the biocompatibility of polyamide (PA-2200). Findings Optimized process parameters for open cell process structures were obtained and confirmed experimentally. Laser power, hatch spacing and layer thickness have contributed more in the porous part’s strength than scan speed. The accuracy of the order of IT16 has been found for all functional dimensions. Cell growth and proliferation confirmed biocompatibility of polyamide (PA-2200) for scaffold applications. Originality/value This paper demonstrates the biocompatibility of PA-2200 for scaffold applications. The optimized process parameters of SLS process for open cell structure having pore size 1.2 × 1.2 mm2 with strut diameter of 1 mm have been obtained. The accuracy of the order of IT16 was obtained at the optimized process factors.

Design and characterization of tunable three-dimensional acoustic composite metamaterials

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guochang Lin ◽  
Chaonan Hu ◽  
Lin Cong ◽  
Yongtao Yao
Keyword(s):  
Elastic Modulus ◽  
Structural Material ◽  
Cell Structure ◽  
Three Dimensional ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Content Type ◽  
Acoustic Metamaterial ◽  
Material Parameters ◽  
Initial Frequency

Purpose The purpose of this paper is to developing a kind of acoustic metamaterial with wide frequency band especially in low frequency region. At the same time, its the tunability of sound insulation frequency is achieved. Design/methodology/approach A three-dimensional (3D) acoustic metamaterial consisting of rigid frame, spherical attachment and thin film is proposed. The material parameters and the effect of the attachment hole on the forbidden band are investigated by finite element simulation. The sound insulation effect of the structure is validated by the combination of simulation and experiment. Findings The results show that the elastic modulus of the structural material determines the initial frequency of the forbidden band of the proposed 3D acoustic metamaterials. The lower the elastic modulus of the structural material, the lower the initial frequency of the forbidden band. The material parameters of the frame mainly affect the initial frequency of the first forbidden band, and the material parameters of the attachment will affect both the initial and termination frequency of the first forbidden band. Holes in the attachments reduce the band gap width. The characteristic curve moves down with the increase of subtracted mass. Research limitations/implications The findings may greatly benefit the application of the acoustic metamaterials in the fields of sound insulation and noise reduction. Originality/value This acoustic metamaterial structure has excellent sound insulation performance. At the same time, the single cell structure can be assembled into any shape. The structure can achieve sound selective filtering and combination control.

scholarly journals Form and Function of Clostridium thermocellum Biofilms

2012 ◽  
Vol 79 (1) ◽  
pp. 231-239 ◽  
Author(s):  
Alexandru Dumitrache ◽  
Gideon Wolfaardt ◽  
Grant Allen ◽  
Steven N. Liss ◽  
Lee R. Lynd
Keyword(s):  
Acetic Acid ◽  
Clostridium Thermocellum ◽  
Cell Attachment ◽  
Cell Structure ◽  
Hydrolysis Rate ◽  
Cellulolytic Bacterium ◽  
Biofilm Growth ◽  
Content Type ◽  
Lignocellulose Conversion ◽  
Continuous Flow Reactors

ABSTRACTThe importance of bacterial adherence has been acknowledged in microbial lignocellulose conversion studies; however, few reports have described the function and structure of biofilms supported by cellulosic substrates. We investigated the organization, dynamic formation, and carbon flow associated with biofilms of the obligately anaerobic cellulolytic bacteriumClostridium thermocellum27405. Using noninvasive,in situfluorescence imaging, we showed biofilms capable of near complete substrate conversion with a characteristic monolayered cell structure without an extracellular polymeric matrix typically seen in biofilms. Cell division at the interface and terminal endospores appeared throughout all stages of biofilm growth. Using continuous-flow reactors with a rate of dilution (2 h−1) 12-fold higher than the bacterium's maximum growth rate, we compared biofilm activity under low (44 g/liter) and high (202 g/liter) initial cellulose loading. The average hydrolysis rate was over 3-fold higher in the latter case, while the proportions of oligomeric cellulose hydrolysis products lost from the biofilm were 13.7% and 29.1% of the total substrate carbon hydrolyzed, respectively. Fermentative catabolism was comparable between the two cellulose loadings, with ca. 4% of metabolized sugar carbon being utilized for cell production, while 75.4% and 66.7% of the two cellulose loadings, respectively, were converted to primary carbon metabolites (ethanol, acetic acid, lactic acid, carbon dioxide). However, there was a notable difference in the ethanol-to-acetic acid ratio (g/g), measured to be 0.91 for the low cellulose loading and 0.41 for the high cellulose loading. The results suggest that substrate availability for cell attachment rather than biofilm colonization rates govern the efficiency of cellulose conversion.

scholarly journals Antimicrobial Mechanism of Monocaprylate

2012 ◽  
Vol 78 (8) ◽  
pp. 2957-2965 ◽  
Author(s):  
Morten Hyldgaard ◽  
Duncan S. Sutherland ◽  
Maria Sundh ◽  
Tina Mygind ◽  
Rikke Louise Meyer
Keyword(s):  
Lipid Bilayers ◽  
Cell Structure ◽  
Membrane Integrity ◽  
Membrane Vesicles ◽  
Antimicrobial Effect ◽  
Threshold Concentration ◽  
Content Type ◽  
Force Microscopy ◽  
Calcein Leakage ◽  
A Site

ABSTRACTMonoglyceride esters of fatty acids occur naturally and encompass a broad spectrum of antimicrobial activity. Monocaprylate is generally regarded as safe (GRAS) and can function both as an emulsifier and as a preservative in food. However, knowledge about its mode of action is lacking. The aim of this study was therefore to elucidate the mechanism behind monocaprylate's antimicrobial effect. The cause of cell death inEscherichia coli,Staphylococcus xylosus, andZygosaccharomyces bailiiwas investigated by examining monocaprylate's effect on cell structure, membrane integrity, and its interaction with model membranes. Changes in cell structure were visible by atomic force microscopy (AFM), and propidium iodide staining showed membrane disruption, indicating the membrane as a site of action. This indication was confirmed by measuring calcein leakage from membrane vesicles exposed to monocaprylate. AFM imaging of supported lipid bilayers visualized the integration of monocaprylate into the liquid disordered, and not the solid ordered, phase of the membrane. The integration of monocaprylate was confirmed by quartz crystal microbalance measurements, showing an abrupt increase in mass and hydration of the membrane after exposure to monocaprylate above a threshold concentration. We hypothesize that monocaprylate destabilizes membranes by increasing membrane fluidity and the number of phase boundary defects. The sensitivity of cells to monocaprylate will therefore depend on the lipid composition, fluidity, and curvature of the membrane.

Characterization of a novel 10T SRAM cell with improved data stability and delay performance for 20-nm tri-gated FinFET technology

Circuit World ◽  
2018 ◽  
Vol 44 (4) ◽  
pp. 187-194 ◽  
Author(s):  
Mitesh Jethabhai Limachia ◽  
Rajesh A. Thakker ◽  
Nikhil J. Kothari
Keyword(s):  
Power Dissipation ◽  
Cell Structure ◽  
Silicon On Insulator ◽  
Performance Characteristics ◽  
Cell Performance ◽  
Main Body ◽  
Content Type ◽  
Sram Cell ◽  
Static Power ◽  
Tcad Simulations

PurposeThis paper aims to propose a new ten-transistor (10T) SRAM bit-cell with differential read and write operations. The cell structure has read buffer on each side of the cell to improve read performance and comprises six main body transistors’ connections similar to the commercial 6T SRAM cell to improve write performance. The proposed bit-cell is designed with tri-gated FinFET technology and implemented on a silicon-on-insulator (SOI) substrate. 3D TCAD simulations are performed to characterize the efficacy of the proposed bit-cell. Performance characteristics of the proposed bit-cell are compared with the recently reported 8T bit-cell as well as the commercial 6T cell. The proposed bit-cell achieves 26.50 per cent and 35.10 per cent higher read static noise margin (RSNM) as compared with that of 8T and 6T bit-cells, respectively, at a VDD of 0.9 V. The proposed bit-cell also offers 54.78 per cent and 21.18 per cent smaller read delay compared with 8T SRAM-NEW and 6T bit-cells, respectively. The static power dissipation of the proposed bit-cell is comparable with that of the 6T bit-cell and 24.5 per cent lesser compared with that of the 8T bit- cell. The overall electrical quality of the SRAM circuit with the proposed bit-cell is enhanced up to 1.673 times and 1.22 times as compared with the 8T SRAM-NEW and 6T bit-cells, respectively. Design/methodology/approachA new 10T SRAM bit-cell with differential read and write operations is proposed. The proposed bit-cell is designed with tri-gated FinFET technology and implemented on an SOI substrate. 3D TCAD simulations are performed to characterize the efficacy of the proposed bit-cell. Performance characteristics of the proposed bit-cell are compared with the recently reported 8T bit-cell as well as the commercial 6T cell. FindingsThe proposed bit-cell achieves 26.50 per cent and 35.10 per cent higher RSNM as compared with that of the 8T and 6T bit-cells, respectively, at a VDD of 0.9V. The proposed bit-cell also offers 54.78 per cent and 21.18 per cent smaller read delay compared with the 8T SRAM-NEW and 6T bit-cells, respectively. The static power dissipation of the proposed bit-cell is comparable with that of the 6T bit-cell and 24.5 per cent lesser compared with that of the 8T bit-cell. Originality/valueThe proposed bit-cell is novel compared with existing bit-cells.

Stack of solid oxide fuel cells

2014 ◽  
Vol 31 (3) ◽  
pp. 207-211 ◽  
Author(s):  
Barbara Dziurdzia ◽  
Zbigniew Magonski ◽  
Henryk Jankowski
Keyword(s):  
Fuel Cell ◽  
Cell Structure ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Content Type ◽  
Fuel Distribution ◽  
Temperature Changes ◽  
Rapid Temperature ◽  
Ceramic Fuel ◽  
Full Power

Purpose – The paper aims to present the innovative design of a planar multilayered high temperature solid oxide fuel cell (SOFC), which is easy to manufacture, and features high resistance to rapid temperature changes. Temperature resistance was accomplished thanks to easy to heat, thin flat ceramic structure of the cell and elimination of metallic interconnections. Design/methodology/approach – The ceramic fuel cell consists of the anode core made of six to eight layers of nickel/yttria-stabilized zirconia tapes (Ni/YSZ) isostatically pressed into a laminate. Two networks of fuel distribution microchannels are engraved on both sides of the anode laminate. The microchannels are subsequently covered with a thin layer of the functional anode tape made of Ni/YSZ and a solid electrolyte tape made of YSZ. Findings – The single planar double-sided ceramic SOFC of dimensions 19 × 60 × 1.2 mm3 provides 3.2 Watts of electric power. The prototype of the battery which consists of four SOFCs provides an output power of > 12 W. Tests show that the stack is resistant to the rapid temperature change. If inserted into a chamber preheated to 800°C, the stack provides the full power within 5 minutes. Multiple cycling does not destroy the stack. Originality/value – This anode-supported fuel cell structure is provided with thin anode functional layers suspended on a large number of fine beams. The whole anode structure is made with the same ceramic material, so the mechanical stress is minimized during the cell operation.

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