Nanoaggregates in floating layers of azaporphyrins

2010 ◽  
Vol 14 (06) ◽  
pp. 513-522 ◽  
Author(s):  
Larissa A. Valkova ◽  
Sergei V. Zyablov ◽  
Victor V. Erokhin ◽  
Oscar I. Koifman
Keyword(s):  
Initial Conditions ◽  
Layer Structure ◽  
Quantitative Model ◽  
Initial Surface ◽  
Structure And Properties ◽  
Brewster Angle Microscopy ◽  
Stable States ◽  
Structural Units ◽  
Compression Isotherms ◽  
Floating Layer

An analysis of compression isotherms of floating layers of copper tetra-tert-butylphthalocyanine ( CuPctBu4 ) and copper tetrabenzotriazaporphyrine, obtained at varied initial conditions, is carried out. The structure of layers is determined by three methods: the traditional one (direct estimation of area per molecule from a π-A isotherm), by a quantitative analysis of compression isotherms (with the use of Volmer equation), and by Brewster angle microscopy. It is shown that in layers with edge-on arrangement of molecules (initial surface concentrations N0 > 0.15 μmol.m-2), the layer structure, determined by the quantitative method, may differ drastically from the structure obtained by the traditional one. The equation of state of the floating layer generalized to the case when structural units of 2D gas are molecular aggregates is used to describe the layer of azaporphyrines. Boundaries of existence and characteristics of structure and properties of floating layers in stable states (size of nanoaggregates formed in a layer, number of molecules in them, interaggregate spacing, compressibility) are determined. The quantitative model of floating layer of copper tetra-tert-butylphthalocyanine is proposed. Constants characterizing a stable monolayer, as well as the region where it may be formed, are determined on the base of the model created.

Aggregation behavior of unsubstituted magnesium porphyrazine in monolayers at air–water interface and in Langmuir–Schaefer films

2018 ◽  
Vol 22 (06) ◽  
pp. 509-520 ◽  
Author(s):  
Nadezhda V. Kharitonova ◽  
Larissa A. Maiorova ◽  
Oscar I. Koifman
Keyword(s):  
Surface Coverage ◽  
State Diagram ◽  
Aggregation Behavior ◽  
Initial Surface ◽  
Structure And Properties ◽  
Air Interface ◽  
Wide Range ◽  
Air Water Interface ◽  
Compression Isotherms ◽  
First Time

The aggregation behavior of unsubstituted magnesium porphyrazine (MgPz) was studied in layers at the water–air interface and in Langmuir–Schaefer films. Regions of existence and characteristics of the structure and properties of stable nanostructured monolayers of MgPz were determined with the method of quantitative analysis of compression isotherms of floating layers in a wide range of initial surface coverage degrees (ISCD). MgPz on the water surface forms monolayers of three types: a face-on type and two edge-on types that differ in the structure. The specific feature of the monolayers of the second type is the independence of the structure of two-dimensional MgPz nanoparticles formed on water on the ISCD. A mathematical model and a state diagram of the monolayer were constructed and a passport of MgPz monolayers was compiled. For the first time, the state diagram contains boundary isotherms based on data obtained from the model. Langmuir–Schaefer films of MgPz formed from layers of various types were prepared and studied by UV-vis absorption spectroscopy.

scholarly journals Synthesis, Crystal Structure, and Properties of a Zn(II) Coordination Polymer Based on a Difunctional Ligand Containing Triazolyl and Carboxyl Groups

Crystals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 424 ◽  
Author(s):  
Jia-Le Li ◽  
Wei-Dong Li ◽  
Zi-Wei He ◽  
Shuai-Shuai Han ◽  
Shui-Sheng Chen
Keyword(s):  
Coordination Polymer ◽  
Weak Interactions ◽  
Layer Structure ◽  
Three Dimensional ◽  
Stacking Interactions ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Visible Spectroscopy ◽  
X Ray ◽  
Uv Visible

A new compound, namely, [Zn(L)2]n (1) was obtained by the reaction of 2-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) with ZnSO4·7H2O, and the compound was characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis. The linear HL ligands were deprotonated to be L− anions and act as two-connectors to link Zn2+ to form a two-dimensional (2D) lay structure with (4, 4) topology. The large vacancy of 2D framework allows another layer structure to interpenetrate, resulting in the formation of 2D + 2D → 2D parallel interpenetration in 1. The weak interactions, such as hydrogen bonding and π–π stacking interactions, connect the adjacent 2D layers into a three-dimensional (3D) coordination polymer. The solid-state UV-visible spectroscopy and luminescent property have also been studied.

MULTIPLE OSCILLATORY STATES IN MODELS OF COLLECTIVE NEURONAL DYNAMICS

2014 ◽  
Vol 24 (06) ◽  
pp. 1450020 ◽  
Author(s):  
STILIYAN KALITZIN ◽  
MARCUS KOPPERT ◽  
GEORGE PETKOV ◽  
FERNANDO LOPES DA SILVA
Keyword(s):  
Analytical Model ◽  
Large Scale ◽  
Computational Models ◽  
Phase Synchronization ◽  
Initial Conditions ◽  
State Transitions ◽  
Model Parameters ◽  
Reactive Control ◽  
Stable States ◽  
Optimal Method

In our previous studies, we showed that the both realistic and analytical computational models of neural dynamics can display multiple sustained states (attractors) for the same values of model parameters. Some of these states can represent normal activity while other, of oscillatory nature, may represent epileptic types of activity. We also showed that a simplified, analytical model can mimic this type of behavior and can be used instead of the realistic model for large scale simulations. The primary objective of the present work is to further explore the phenomenon of multiple stable states, co-existing in the same operational model, or phase space, in systems consisting of large number of interconnected basic units. As a second goal, we aim to specify the optimal method for state control of the system based on inducing state transitions using appropriate external stimulus. We use here interconnected model units that represent the behavior of neuronal populations as an effective dynamic system. The model unit is an analytical model (S. Kalitzin et al., Epilepsy Behav. 22 (2011) S102–S109) and does not correspond directly to realistic neuronal processes (excitatory–inhibitory synaptic interactions, action potential generation). For certain parameter choices however it displays bistable dynamics imitating the behavior of realistic neural mass models. To analyze the collective behavior of the system we applied phase synchronization analysis (PSA), principal component analysis (PCA) and stability analysis using Lyapunov exponent (LE) estimation. We obtained a large variety of stable states with different dynamic characteristics, oscillatory modes and phase relations between the units. These states can be initiated by appropriate initial conditions; transitions between them can be induced stochastically by fluctuating variables (noise) or by specific inputs. We propose a method for optimal reactive control, allowing forced transitions from one state (attractor) into another.

Laser-melted amorphous anodized Al2O3 layer: Structure and properties

1991 ◽  
Vol 196 (2) ◽  
pp. 243-252 ◽  
Author(s):  
G. Shafirstien ◽  
M. Bamberger ◽  
G. Revesz
Keyword(s):  
Layer Structure ◽  
Structure And Properties ◽  
Al2o3 Layer

scholarly journals Model analysis for plant disease dynamics co-mediated by herbivory and herbivore-borne phytopathogens

2012 ◽  
Vol 8 (4) ◽  
pp. 685-688 ◽  
Author(s):  
Takefumi Nakazawa ◽  
Takehiko Yamanaka ◽  
Satoru Urano
Keyword(s):  
Plant Disease ◽  
Initial Conditions ◽  
Alternative Stable States ◽  
Model Analysis ◽  
Plant Diseases ◽  
Disease Dynamics ◽  
Stable States ◽  
Tripartite Interactions ◽  
Model Combining ◽  
Nutritive Quality

Plants are subject to diseases caused by pathogens, many of which are transmitted by herbivorous arthropod vectors. To understand plant disease dynamics, we studied a minimum hybrid model combining consumer–resource (herbivore–plant) and susceptible–infected models, in which the disease is transmitted bi-directionally between the consumer and the resource from the infected to susceptible classes. Model analysis showed that: (i) the disease is more likely to persist when the herbivore feeds on the susceptible plants rather than the infected plants, and (ii) alternative stable states can exist in which the system converges to either a disease-free or an endemic state, depending on the initial conditions. The second finding is particularly important because it suggests that the disease may persist once established, even though the initial prevalence is low (i.e. the R 0 rule does not always hold). This situation is likely to occur when the infection improves the plant nutritive quality, and the herbivore preferentially feeds on the infected resource (i.e. indirect vector–pathogen mutualism). Our results highlight the importance of the eco-epidemiological perspective that integration of tripartite interactions among host plant, plant pathogen and herbivore vector is crucial for the successful control of plant diseases.

A novel low on-resistance Schottky-barrier diode with p-buried floating layer structure

2004 ◽  
Vol 51 (5) ◽  
pp. 797-802 ◽  
Author(s):  
W. Saito ◽  
I. Omura ◽  
K. Tokano ◽  
T. Ogura ◽  
H. Ohashi
Keyword(s):  
Schottky Barrier ◽  
Layer Structure ◽  
Schottky Barrier Diode ◽  
Floating Layer

Sensitivity of 24-h Forecast Dryline Position and Structure to Boundary Layer Parameterizations in Convection-Allowing WRF Model Simulations

2015 ◽  
Vol 30 (3) ◽  
pp. 613-638 ◽  
Author(s):  
Adam J. Clark ◽  
Michael C. Coniglio ◽  
Brice E. Coffer ◽  
Greg Thompson ◽  
Ming Xue ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Initial Conditions ◽  
Layer Structure ◽  
Vertical Mixing ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
The North ◽  
Boundary Layer Processes ◽  
Moisture Profiles ◽  
Dry Bias

Abstract Recent NOAA Hazardous Weather Testbed Spring Forecasting Experiments have emphasized the sensitivity of forecast sensible weather fields to how boundary layer processes are represented in the Weather Research and Forecasting (WRF) Model. Thus, since 2010, the Center for Analysis and Prediction of Storms has configured at least three members of their WRF-based Storm-Scale Ensemble Forecast (SSEF) system specifically for examination of sensitivities to parameterizations of turbulent mixing, including the Mellor–Yamada–Janjić (MYJ); quasi-normal scale elimination (QNSE); Asymmetrical Convective Model, version 2 (ACM2); Yonsei University (YSU); and Mellor–Yamada–Nakanishi–Niino (MYNN) schemes (hereafter PBL members). In postexperiment analyses, significant differences in forecast boundary layer structure and evolution have been observed, and for preconvective environments MYNN was found to have a superior depiction of temperature and moisture profiles. This study evaluates the 24-h forecast dryline positions in the SSEF system PBL members during the period April–June 2010–12 and documents sensitivities of the vertical distribution of thermodynamic and kinematic variables in near-dryline environments. Main results include the following. Despite having superior temperature and moisture profiles, as indicated by a previous study, MYNN was one of the worst-performing PBL members, exhibiting large eastward errors in forecast dryline position. During April–June 2010–11, a dry bias in the North American Mesoscale Forecast System (NAM) initial conditions largely contributed to eastward dryline errors in all PBL members. An upgrade to the NAM and assimilation system in October 2011 apparently fixed the dry bias, reducing eastward errors. Large sensitivities of CAPE and low-level shear to the PBL schemes were found, which were largest between 1.0° and 3.0° to the east of drylines. Finally, modifications to YSU to decrease vertical mixing and mitigate its warm and dry bias greatly reduced eastward dryline errors.

Co-crystals of 9,9′-bianthracene-10,10′-dicarboxylic acid with linear bidentate basic ligand molecules: synthesis, crystal structure, and properties based on the layer structure exfoliated by water

CrystEngComm ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 497-505
Author(s):  
Misaki Okayasu ◽  
Shoko Kikkawa ◽  
Hidemasa Hikawa ◽  
Isao Azumaya
Keyword(s):  
Crystal Structure ◽  
Dicarboxylic Acid ◽  
Title Compound ◽  
Layer Structure ◽  
Structure And Properties ◽  
Layer Structures

Co-crystals of the title compound with bases formed 1D and layer structures and the layer structure was separated by water.

Synthesis, structure, and properties of nickel(II) and copper(II) coordination polymers with the 5-ethyl-pyridine-2,3-dicarboxylate ligand

2019 ◽  
Vol 74 (6) ◽  
pp. 491-496
Author(s):  
Long Tang ◽  
YingLu Wang ◽  
SiYu Yin ◽  
DeQian Shi ◽  
JiJiang Wang ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Exchange Interactions ◽  
Hydrothermal Condition ◽  
Octahedral Geometry ◽  
Stacking Interactions ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Structural Units ◽  
X Ray ◽  
Two Sides

AbstractThe reactions of Ni(NO3)2 · 6H2O/Cu(OAc)2 · H2O, 5-ethyl-pyridine-2,3-dicarboxylic acid (H2epda), and 2,2′-bipyridine (2,2′-bipy) under hydrothermal condition produced two new coordination polymers [Ni(Hepda)2(H2O)2] (1) and [Cu(epda)(2,2′-bipy)] (2), which were characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. In 1, each NiII center is six-coordinated in a distorted NiO4N2 octahedral geometry. Adjacent structural units are joined by strong intermolecular O–H · · · O hydrogen bonding to generate a layered structure. In 2, the CuII centers are bridged by epda dianions to form chains, where the 2,2′-bipy ligands bristle out on two sides, establishing π-π stacking interactions, Adjacent chains are thus aggregated in layers. The magnetic properties of 1 and 2 were investigated, and the exchange interactions were found to be −1.62 and −2.24 cm−1, respectively.

Critical Structures of Metal Destruction Under the Process of Wear

1999 ◽  
Vol 122 (1) ◽  
pp. 361-366 ◽  
Author(s):  
I. I. Garbar
Keyword(s):  
Initial Conditions ◽  
Layer Structure ◽  
Low Carbon Steel ◽  
Maximum Level ◽  
Metal Structure ◽  
Wear Intensity ◽  
Relaxation Processes ◽  
Low Carbon ◽  
Surface Layers ◽  
Critical Structure

Resistance to wear is determined by the ability of the metal structure to change in such a way that it can withstand friction stresses. The structure of surface layers which have undergone wear can be identified as a “critical” structure. This is where destruction takes place. To study the surface structure specimens of low-carbon steel, aluminum and copper were subjected to wear tests and then investigated by X-ray. Under certain test conditions it was found that the changes in the surface layer structure, evidenced by the structural broadening of diffraction lines, reach a maximum level. The tests showed that as one progresses from mild wear to harsher friction conditions and correspondingly higher wear intensity, the structural broadening of the diffraction lines is first increased but than reduced. The results show that under low and moderate wear conditions, the structure of the surface layers is changed by the friction process, the surface layers being hardened by fragmentation. The level of metal hardening corresponds to the friction stresses that occur in the surface layers, and reaches a maximum when the fragment dimensions are minimal. As the friction conditions become more severe, the critical structure of the metal approaches the initial conditions, and therefore its strength is less than that of the hardened structure formed under moderate wear conditions. Such results can be explained by the difference in the rates of the plastic deformation and of plastic relaxation processes. Therefore, the critical structure under the process of wear depends on the friction conditions. To put the mechanical properties of the material to best use, one should choose optimal friction and wear conditions so that the metal will be hardened as much as possible. [S0742-4787(00)04801-3]

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