A Novel Strategy to Tune Magnetic Properties of Nickel(II)-Schiff Base Coordination Bridged Polysilsesquioxane

2019 ◽  
Vol 11 (12) ◽  
pp. 1705-1711
Author(s):  
Yijun Feng ◽  
Jincheng Zhang ◽  
Yongbing Pei ◽  
Qiu Chen ◽  
Yue Yan ◽  
...  
Keyword(s):  
Molecular Level ◽  
Magnetic Measurement ◽  
Sol Gel ◽  
Electronic Transitions ◽  
Coordination Interaction ◽  
Weiss Temperature ◽  
Measurement Results ◽  
Bridged Polysilsesquioxane ◽  
Novel Strategy ◽  
Very High

In this paper, liquid state solvent-free organosilica-based nickel-bithiazole complexes (PBSIBTHM-Ni2+, PBSIBTMeM-Ni2+) were synthesized through sol–gel processes respectively, and these two metal complexes and their precursors were characterized. The precursors with bithiazole were successfully prepared, their inorganic and organic parts were connected on molecular level. The DSC results indicated they would all exist in liquid phase at temperature ranging from 180 K to 280 K. The UV-VIS showed that a red shift of the main electronic transitions from 254 to 268 nm of PBSIBTHM to PBSIBTHM-Ni2+, Δν = 14 (from 249 to 266 nm of PBSIBTMeM to PBSIBTMeM-Ni2+, Δν = 17). This verified the formation of a more extensive π→π* conjugating system due to coordination interaction between Ni2+ and PBSIBTHM or PBSIBTMeM. The magnetic measurement results of PBSIBTHM-Ni2+ and PBSIBTMeM-Ni2+ reflected they both exhibited ferromagnetic properties at low temperature. For PBSIBTMeM-Ni2+, it had a transition temperature (Ttran) at 160 K, and became an anti-ferromagnet above Ttran. For PBSIBTHM-Ni2+, it had a very high Curie-Weiss temperature (Tc = 253 K). This strategy was expected to find potential application in fabricating the complexes with desired physicochemical properties.

Molecular Architecture and its role in Silica Sol-Gel Polymerization

1990 ◽  
Vol 180 ◽  
Author(s):  
P. C. Cagle ◽  
W. G. Klemperer ◽  
C. A. Simmons
Keyword(s):  
Molecular Level ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Sol ◽  
Molecular Architecture ◽  
Model Studies ◽  
Large Size ◽  
Neutral Conditions ◽  
Very High

ABSTRACTSol-gel polymerization of [Si8O12](OCH3)8 in CH3CN under neutral conditions yields very high surface area (SBET > 900 m2/g) xerogels. This property is seen to result from the structure of the gel on the molecular level. According to N2 adsorption studies, model studies, and TEM studies, the large size and rigidity of the cubic [Si8O12] core structure leads to polymers whose rigidity inhibits extensive crosslinking of the type observed in orthosilicate derived xerogels.

scholarly journals Parameter Modeling Analysis and Experimental Verification on Magnetic Shielding Cylinder of All-Optical Atomic Spin Magnetometer

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Hong Zhang ◽  
Sheng Zou ◽  
Xi-Yuan Chen ◽  
Wei Quan
Keyword(s):  
Magnetic Measurement ◽  
Magnetic Shielding ◽  
Key Factors ◽  
Actual Measurement ◽  
Atomic Spin ◽  
Modeling Analysis ◽  
Measurement Results ◽  
All Optical ◽  
Ultrahigh Sensitivity ◽  
Shielding Effects

The ultrahigh sensitivity atomic spin magnetometer as the magnetic measurement sensor has received much concern. The performance of the magnetic shielding cylinder is one of the key factors constraining the atomic spin magnetometer’s sensitivity. In order to effectively improve the performances of the magnetic shielding, the parameter optimization models of the magnetic shielding cylinder were established in this paper. Under the condition of changing only one parameter while the others keeping constant, the effects of various parameters influencing the axial shielding coefficient were comprehensively analyzed, and the results showed that the smaller the innermost length, the innermost radius, and the radial spacing were, and the greater the axial spacing was, the better the shielding performance could be obtained. According to these results and the actual needs, the magnetic shielding cylinder was optimally designed, and then the shielding effects were simulated via the software Ansoft. The simulation results showed that the optimized magnetic shielding cylinder had the advantages of small size, high shielding performance, and lager uniformity than that of the nonoptimized one. The actual measurement results showed that the residual magnetism in the optimized magnetic shielding cylinder was below 0.1 nT, which was 2~4 times lower than the nonoptimized one.

scholarly journals Treynor Ratio to Measure Islamic Stock Performance in Indonesia

2019 ◽  
Vol 8 (1) ◽  
pp. 1-13
Author(s):  
Mohammad Farhan Qudratullah
Keyword(s):  
Interest Rates ◽  
Stock Returns ◽  
Capital Market ◽  
The Other ◽  
Islamic Finance ◽  
Ratio Model ◽  
Stock Performance ◽  
Measurement Results ◽  
Domestic Products ◽  
Very High

Treynor Ratio merupakan model pioner inovatif ukuran kinerja saham yang dikemukakan Jack Treynor pada tahun 1965 yang terdiri atas 3 (tiga) komponen, yaitu return saham, return bebas risiko, dan beta saham. Banyak penelitian mendekati return bebas risiko dengan suku bunga termasuk saat mengukur kinerja saham syariah, sedangkan suku bunga dilarang dalam konsep keuangan islam. Tulisan ini membahas variabel alternatif untuk mendekati return bebas risiko selain dengan suku bunga (BI-Rate), yaitu dengan 4 (empat) pendekatan, yaitu: menghilangkan suku bunga, mengganti dengan zakat rate, mengganti dengan inflasi, dan mengganti dengan gross domestic produc (GDP) pada model Treynor Ratio yang diimplementasikan pada pasar modal syariah di Indonesia periode Januari 2011-Juli 2018. Hasil yang diperoleh adalah terdapat kesesuaian yang sangat tinggi hasil pengukuran model Treynor Ratio dengan suku bunga dengan keempat model lainnya. Namun, model-model tersebut tidak menjamin bahwa saham yang memilki kinerja terbaik pada saat ini akan memilki kinerja terbaik dimasa yang akan datang atau sebaliknya. Dilihat dari kedekatan hasil pengukuran kinerjanya, kelima model Treynor Ratio tersebut dapat dikelompokan jadi 2 (dua), yaitu model dengan suku bunga, model dengan inflasi, dan model dengan GDP sebagai kelompok pertama, sedangkan model tanpa suku bunga dan model dengan zakat-rate sebagai kelompok kedua. [Treynor Ratio is an innovative pioneer model the size of stock performance proposed by Jack Treynor in 1965 which consists of 3 (three) components, namely stock returns, risk free returns, and stock beta. Many studies approach risk-free returns with interest rates, including when measuring the performance of Islamic stocks, while interest rates are prohibited in the concept of Islamic finance. This paper discusses alternative variables to approach risk-free returns other than interest rates (BI-Rate), namely with 4 (four) approaches, namely: eliminating interest rates, changing zakat rates, changing inflation, and substituting gross domestic products (GDP) in the Treynor Ratio model that is implemented in the Islamic capital market in Indonesia for the period January 2011 - July 2018. The results obtained are very high conformity in the measurement results of the Treynor Ratio model with interest rates with the other four models. However, these models do not guarantee that stocks that have the best performance at this time will have the best performance in the future or vice versa. Judging from the closeness of the results of performance measurement, the five Treynor Ratio models can be grouped into 2 (two), namely models with interest rates, models with inflation, and models with GDP as the first group, while models without interest rates and models with zakat-rate as second group.]

scholarly journals Mutation rate variability as a driving force in adaptive evolution

2018 ◽  
Author(s):  
Dalit Engelhardt ◽  
Eugene I. Shakhnovich
Keyword(s):  
Mutation Rate ◽  
Bacterial Population ◽  
Molecular Level ◽  
Fitness Function ◽  
System Level ◽  
Resistance Evolution ◽  
High Fitness ◽  
Evolutionary Advantage ◽  
Stress Result ◽  
Very High

Mutation rate is a key determinant of the pace as well as outcome of evolution, and variability in this rate has been shown in different scenarios to play a key role in evolutionary adaptation and resistance evolution under stress. Here we investigate the dynamics of resistance fixation in a bacterial population with variable mutation rates and show that evolutionary outcomes are most sensitive to mutation rate variations when the population is subject to environmental and demographic conditions that suppress the evolutionary advantage of high-fitness subpopulations. By directly mapping a molecular-level biophysical fitness function to the system-level dynamics of the population we show that both low and very high, but not intermediate, levels of stress result in a disproportionate effect of hypermutation on resistance fixation and that traditional definitions of the selection coefficient are insufficient to account for this effect. We demonstrate how this behavior is directly tied to the extent of genetic hitchhiking in the system, the propagation of high-mutation rate cells through association with high-fitness mutations. Our results indicate a substantial role for mutation rate flexibility in the evolution of antibiotic resistance under conditions that present a weak advantage over wildtype to resistant cells.

scholarly journals High Performance Mixed Potential Type NO2 Gas Sensor Based on Porous YSZ Layer Formed with Graphite Doping

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3337 ◽  
Author(s):  
Hao Hong ◽  
Jianwen Sun ◽  
Cinan Wu ◽  
Zewen Liu
Keyword(s):  
High Performance ◽  
Sol Gel ◽  
Yttria Stabilized Zirconia ◽  
Mixed Potential ◽  
Stabilized Zirconia ◽  
No2 Gas Sensor ◽  
Potential Type ◽  
Measurement Results ◽  
Good Repeatability ◽  
Sensor Measurement

High performance mixed potential type NO2 sensors using porous yttria-stabilized zirconia (YSZ) layers doped with different concentration graphite as solid electrolyte and LaFeO3 as sensing electrode were fabricated and characterized. LaFeO3 was prepared by a typical citrate sol–gel method and characterized using XRD. The surface morphology and porosity of porous YSZ layers were characterized by field emission scanning electron microscope (FESEM). The sensor doped with 3 wt% graphite shows the highest response (−76.4 mV to 80 ppm NO2) and the response is linearly dependent on the logarithm of NO2 concentration in the range of 10–200 ppm. The sensor measurement results also present good repeatability and cross-sensitivity.

Study of Magnetoresistance Effect and Magnetic Properties of La0.67Sr0.33Mn1-xNixO3 (x = 0 and 0.2) Material Prepared by Sol-Gel Method

2019 ◽  
Vol 966 ◽  
pp. 363-369
Author(s):  
Utami Widyaiswari ◽  
Budhy Kurniawan ◽  
Agung Imaduddin ◽  
Isao Watanabe
Keyword(s):  
Magnetic Properties ◽  
Magnetic Measurement ◽  
Sol Gel ◽  
Mixed Valence ◽  
Magnetoresistance Effect ◽  
Metallic Behavior ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Mr Effect

Mixed valence manganite materials have been studied due to their interesting physical properties such as their magnetoresistance (MR) effect. The change of Mn3+/Mn4+ ratio affects the possible bonds between anion and cation and their spin structure that may occur in the samples. The aim of this research is to study the change of magnetoresistance effect and magnetic properties of La0.67Sr0.33MnO3 (LSMO) by doping the Mn site with Ni ion. La0.67Sr0.33Mn1-xNixO3 samples were synthesized by using sol-gel method and characterized by using X-ray diffractometer (XRD) and Energy Dispersive X-ray spectroscopy (EDX) to confirm whether Ni has been doped successfully to the parental compound or not. XRD results showed that the samples have a single phase and Ni peak has been detected in the EDX result of Ni-doped LSMO. Resistivity and magnetic measurement showed that LSMO material has ferromagnetic metallic behavior, while x = 0.20 Ni-doped LSMO sample showed paramagnetic insulator behavior. The absolute value of the MR for un-doped sample is higher than the doped sample when the low field is applied, while under the influence of the high magnetic field, it become smaller than the doped sample.

scholarly journals Cross-Condensation Reactions in an Organically Modified Silica Sol-Gel

1994 ◽  
Vol 346 ◽  
Author(s):  
S. Prabakar ◽  
R. A. Assink ◽  
N. K. Raman ◽  
C. J. Brinker
Keyword(s):  
Experimental Error ◽  
Molecular Level ◽  
Sol Gel ◽  
Resonance Assignments ◽  
Silica Sol ◽  
Modified Silica ◽  
Organically Modified ◽  
Organically Modified Silica ◽  
Acid Catalyzed ◽  
Hydrolysis Of

ABSTRACTHigh resolution 29Si NMR has been used to study the extent of cross condensation taking place in a hybrid organic/inorganic sol-gel system. Tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) sol-gels were chosen for this purpose. The sols were prepared by acid catalyzed hydrolysis of TEOS and MTEOS with a H2O/Si ratio of 0.3. 29Si NMR shows signals due to both self-condensation and cross-condensation between TEOS and MTEOS. Resonance assignments were made by comparing the positions and intensities of peaks in the spectra of single and multicomponent systems. It was found that, within experimental error, the self- and cross-condensation rates are equal and that extensive molecular level mixing takes place during the early stages of the reaction.

Controlled Hierarchical Pore Structures in Ethylene-Bridged Polysilsesquioxane Gels

2003 ◽  
Vol 788 ◽  
Author(s):  
Yuki Kobayashi ◽  
Kazuki Nakanishi ◽  
Kazuyuki Hirao
Keyword(s):  
Phase Separation ◽  
Ethylene Glycol ◽  
Triblock Copolymers ◽  
Sol Gel ◽  
Poly Ethylene Glycol ◽  
Bridged Polysilsesquioxane ◽  
Sol Gel Transition ◽  
Poly Ethylene ◽  
Hierarchical Pore ◽  
Gel Transition

ABSTRACTFormation of hierarchical macropores and mesopores in ethylene-bridged polysilsesquioxane sol-gel systems via concurrent sol-gel transition and phase separation induced by the incorporation of supramolecular templats has been investigated. A series of poly(ethylene-glycol)-poly(propyleneglycol)- poly(ethyleneglycol) triblock copolymers, EOPOEOs, have been employed as supramolecular templates, while 1,2-bis(trimethoxysilyl)ethane was used as a polysilsesquioxane source. Successful combination of templated mesopores and well-defined macropores due to phase-separation has been found in the system with EOPOEOs having 70 PO units and respective 20 EO units. Although similar macroporous morphology has been obtained for all the EOPOEOs with EO chain longer or shorter than 20 units, the optimum composition for the co-continuous macropores and that for templated mesopores deviated from each other, resulting in the failure of producing hierarchical macropores and mesopores.

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