scholarly journals Influence of meso-linker attachment on the formation of core···π interactions in urea-functionalized porphyrins

2020 ◽  
Vol 75 (8) ◽  
pp. 755-764
Author(s):  
Keith J. Flanagan ◽  
Aoife A. Ryan ◽  
Brendan Twamley ◽  
Mathias O. Senge
Keyword(s):  
Anion Binding ◽  
Attractive Feature ◽  
Π Interactions ◽  
The Core ◽  
Porphyrin Macrocycle ◽  
Linker Group ◽  
The Face ◽  
Urea Group ◽  
Direct Linkage ◽  
Porphyrin Core

AbstractThe ability to cover the face of a porphyrin macrocycle selectively is an attractive feature for concepts such as catalysis and anion binding that is reliant on porphyrin core interactions. Herein, we have synthesized a family of mono-urea functionalized porphyrin complexes with intent to investigate their potential to form core···π interactions selectively to one face of the porphyrin macrocycle. By altering the distance between the urea moiety and the porphyrin through direct linkage or introducing a linker group we can control the formation of the core interactions. This is clearly seen in the crystal structure of 1-phenyl-3-(2-([10,15,20-triphenylporphyrinato]zinc(II)-5-yl)phenyl)urea where a unique face capping effect is demonstrated. In the crystal of this complex, there is a hydrogen-bonding network between the urea group and the axial methanol ligand forming head-to-tail aggregates with the Zn–O axis all molecules pointing in one direction.

Cambiarenes: Single-Step Synthesis and Anion Binding of a Clip- Shaped Macrocycle with a Redox-Active Core

2019 ◽  
Author(s):  
Riley J. Petersen ◽  
Brett J. Rozeboom ◽  
Shalisa Oburn ◽  
Nolan Blythe ◽  
Tanner Rathje ◽  
...  
Keyword(s):  
Electron Density ◽  
Single Step ◽  
Anion Binding ◽  
Host Molecule ◽  
Selective Binding ◽  
The Core ◽  
Redox Active ◽  
Active Core ◽  
Guest Binding

<div>We report the synthesis of a novel macrocyclic host molecule that forms in a single step from commercially available starting materials. The core of the macrocycle backbone possesses two quinone rings and, thus, is redox-active. Host-guest binding involving the clip-shaped cavity indicates selective binding of pyridine <i>N</i>-oxides based of the electron density of and steric bulk of the anionic oxygen.</div>

Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process

2017 ◽  
Vol 742 ◽  
pp. 317-324
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Manufacturing Process ◽  
Sandwich Structures ◽  
Bending Stiffness ◽  
Effective Density ◽  
Sandwich Composites ◽  
Open Cell ◽  
The Core ◽  
Bending Modulus ◽  
The Face ◽  
Spraying Process

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.

Comparison of P- and As-core-modified porphyrins with the parental porphyrin: a computational study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Aleksey E. Kuznetsov
Keyword(s):  
Computational Study ◽  
Electron Delocalization ◽  
Energy Structure ◽  
Frontier Molecular Orbitals ◽  
The Core ◽  
Potential Applications ◽  
Noticeable Reduction ◽  
Internal Electron ◽  
Porphyrin Core ◽  
Homo Lumo

Abstract The first comparative DFT (B3LYP/6-31G*) study of the Zn-porphyrin and its two derivatives, ZnP(P)4 and ZnP(As)4, is reported. For all three species studied, ZnP, ZnP(P)4 and ZnP(As)4, the singlet was calculated to be the lowest-energy structure and singlet-triplet gap was found to decrease from ca. 41—42 kcal/mol for N to ca. 17—18 kcal/mol for P and to ca. 10 kcal/mol for As. Both ZnP(P)4 and ZnP(As)4 were calculated to attain very pronounced bowl-like shapes. The frontier molecular orbitals (MOs) of the core-modified porphyrins are quite similar to the ZnP frontier MOs. For the HOMO-2 of the core-modified porphyrins due to the ZnP(P)4/ZnP(As)4 bowl-like shapes we might suppose the existence of “internal” electron delocalization inside the ZnP(P)4/ZnP(As)4 “bowls”. Noticeable reduction of the HOMO/LUMO gaps was calculated for ZnP(P)4 and ZnP(As)4, by ca. 1.10 and 1.47 eV, respectively, compared to ZnP. The core-modification of porphyrins by P and especially by As was found to result in significant decrease of the charge on Zn-centers, by ca. 0.61—0.67e for P and by ca. 0.69—0.76e for As. Charges on P- and As-centers were computed to have large positive values, ca. 0.41—0.45e and ca. 0.43—0.47e, for P and As, respectively, compared to significant negative values, ca. −0.65 to −0.66e for N. The porphyrin core-modification by heavier N congeners, P and As, can noticeably modify the structures, electronic, and optical properties of porphyrins, thus affecting their reactivity and potential applications.

Devolution processes and the theory of historical development by S. Sanderson

2021 ◽  
pp. 72-77
Author(s):  
A.V. Verkhoturov ◽  
◽  
A.A. Obukhov
Keyword(s):  
Historical Development ◽  
World System ◽  
Human Society ◽  
Evolutionary Trend ◽  
The Core ◽  
The World ◽  
The Face ◽  
American Historian ◽  
Immanuel Wallerstein ◽  
Main Ideas

Analyzed is one of the most comprehensive modern approaches to the problem of the existence of evolution of human society as such and of specific human communities, i.e. “General Theory of Historical Development” by American historian and sociologist Stephen Sanderson. While agreeing, in general, with its main ideas, we believe that it is important to note that the issue of existence of individual communities demonstrating devolution (regression to an earlier historical state), stagnation or degeneration at certain historical stages is practically ignored in the framework of the theory under consideration. This creates its vulnerability in the face of specific empirical data, indicating a deviation from the evolutionary trend. We believe that overcoming this theoretical difficulty is possible in the process of comprehending the theory of S. Sanderson in the context of ideas of the world-system approach of Immanuel Wallerstein. We want to show that examples of devolution, stagnation and degeneration of societies do not deny general progressive evolutionary tendencies, characteristic for the world-system as a whole, but only indicate the transition of a particular society to a lower level within the world-system (from the core to the semi-periphery, or from the semi-periphery to the periphery).

scholarly journals Cryo-EM Structures of Prestin and the Molecular Basis of Outer Hair Cell Electromotility

2021 ◽  
Author(s):  
Navid Bavi ◽  
Michael D Clark ◽  
Gustavo F Contreras ◽  
Rong Shen ◽  
Bharat Reddy ◽  
...  
Keyword(s):  
Outer Hair Cell ◽  
Binding Pocket ◽  
Structural Features ◽  
Outer Hair Cells ◽  
Anion Binding ◽  
Structural Basis ◽  
Inhibition Mechanism ◽  
Core Domain ◽  
The Core ◽  
Voltage Dependent

The voltage-dependent motor protein, Prestin (SLC26A5) is responsible for the electromotive behavior of outer hair cells (OHCs). Here, we determined the structure of dolphin Prestin in complex with Cl- and the inhibitor Salicylate using single particle cryo-electron microscopy. These structures establish the specific structural features of mammalian Prestin and reveal small but significant differences with the transporter members of the SLC26 family of membrane proteins. Comparison with SLC26A9 point to conformational differences in the special relationship between the core and gate domains. Importantly, we highlight substantial alterations to the hydrophobic footprint of Prestin as it relates to the membrane, which point to a potential influence of Prestin on its surrounding lipid. The structure of Prestin bound to the inhibitor Salicylate confirms the nature of the anion binding pocket, formed by TM3 and TM10 in the Core domain and a set of anion coordinating residues which include Q97, F101, F137, S398 and R399. The presence of a well-defined density for Salycilate points to an inhibition mechanism based on competition for the anion-binding pocket of Prestin. These observations illuminate the structural basis of Prestin electromotility, a key component in the mammalian cochlear amplifier.

scholarly journals Public Space as a Venue for Peacebuilding in Lebanon? The Role of Civic Movements in Reclaiming Public Space in Beirut and Tripoli

2021 ◽  
pp. 25-46
Author(s):  
Aseel Naamani ◽  
Ruth Simpson
Keyword(s):  
Public Space ◽  
Public Life ◽  
Public Spaces ◽  
Urban Spaces ◽  
Building Relationships ◽  
The Core ◽  
The Face ◽  
History Of ◽  
Post War

The issue of public spaces is increasingly at the core of civic movements and discourse of reform in Lebanon, coming to the fore most recently in the mass protests of October 2019. Yet, these most recent movements build on years of activism and contestation, seeking to reclaim rights to access and engage with public spaces in the face of encroachments, mainly by the private sector. Urban spaces, including the country’s two biggest cities – Beirut and Tripoli – have been largely privatised and the preserve of an elite few, and post-war development has been marred with criticism of corruption and exclusivity. This article explores the history of public spaces in Beirut and Tripoli and the successive civic movements, which have sought to realise rights to public space. The article argues that reclaiming public space is central to reform and re-building relationships across divides after years of conflict. First, the article describes the evolution of Lebanon’s two main urban centres. Second, it moves to discuss the role of the consociational system in the partition and regulation of public space. Then it describes the various civic movements related to public space and examines the opportunities created by the October 2019 movement. Penultimately it interrogates the limits imposed by COVID-19 and recent crises. Lastly, it explores how placemaking and public space can contribute to peacebuilding and concludes that public spaces are essential to citizen relationships and inclusive participation in public life and affairs.

Effect of Core Plasticity on the Post-Buckling Behavior of Debonded Sandwich Beams

2000 ◽  
Author(s):  
Bhavani V. Sankar ◽  
Manickam Narayanan ◽  
Abhinav Sharma
Keyword(s):  
Plastic Material ◽  
Maximum Load ◽  
Face Sheet ◽  
Compression Tests ◽  
Element Analysis ◽  
The Core ◽  
Perfectly Plastic ◽  
The Face ◽  
Post Buckling ◽  
Elastic Perfectly Plastic

Abstract Nonlinear finite element analysis was used to simulate compression tests on sandwich composites containing debonded face sheets. The core was modeled as an elastic-perfectly-plastic material, and the face-sheet as elastic isotropic. The effects of core plasticity, face-sheet and core thickness, and debond length on the maximum load the beam can carry were studied. The results indicate that the core plasticity is an important factor that determines the maximum load.

Buckling and Postbuckling of Sandwich Beams With Delaminated Faces Based on Higher Order Core Theory

1999 ◽  
Author(s):  
R. F. Li ◽  
Y. Frostig ◽  
G. A. Kardomateas
Keyword(s):  
Nonlinear Distortion ◽  
Variational Principles ◽  
Vertical Direction ◽  
Initial Imperfection ◽  
Order Theory ◽  
Sandwich Beams ◽  
Postbuckling Behavior ◽  
The Core ◽  
Core Theory ◽  
The Face

Abstract Delaminations within the face sheets are often observed when a sandwich structure is exposed to impact loads. The buckling and postbuckling behavior of sandwich beams with delaminated faces is investigated in this work. The governing nonlinear equations, boundary conditions, and continuity conditions are formulated through variational principles. The beam construction consists of upper and lower, metallic or composite laminated symmetric skins, and a soft core of a foam or low strength honeycomb type. A high order theory is used for the core that accounts for the nonlinear distortion of the plane of section of the core and the compressibility in the vertical direction. The delamination considered is an interface crack, in which the substrate includes the transversely flexible core. The case of a debond at one of the skin-core interfaces is also included. The effects of the delamination length and location on the overall and local behavior are examined with an arbitrary initial imperfection.

The New Method for Machining Bigger Holes of Carbon Fiber Reinforced Plastics (CFRP)

2011 ◽  
Vol 186 ◽  
pp. 161-164 ◽  
Author(s):  
Jiang Min Ding ◽  
Yan Jie Sun ◽  
Chong Su
Keyword(s):  
Carbon Fiber ◽  
New Method ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
The Core ◽  
Whole Process ◽  
The Face ◽  
Fiber Reinforced Plastics ◽  
Carbon Fiber Reinforced

The new method is put forward for machining bigger holes of carbon fiber reinforced plastics (CFRP) in the face of the existent problems. The core drill is applied to machine CFRP from two end-faces according to regular order. The thrust is less than felted intensity between adjacent layers of CFRP in their whole process. Through special experiment, the method is not only economical but also convenient. The finishing workpieces have not defects such as burrs, avulsion and delamination. In addition, its precision and efficiency are very satisfactory to manufacturer.

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