Studies of Australian Soft Corals. XII. Further Cembranolide Diterpenes from Lobophytum crassospiculatum and a Correction of a Previous Stereochemical Assignment

1979 ◽  
Vol 32 (6) ◽  
pp. 1273 ◽  
Author(s):  
A Ahond ◽  
BF Bowden ◽  
JC Coll ◽  
J Fourneron ◽  
SJ Mitchell
Keyword(s):  
Spectroscopic Data ◽  
The Other ◽  
Chemical Degradation ◽  
Soft Corals ◽  
Stereochemical Assignment ◽  
Derivatives Of

Three new cembranolide diterpenes from Lobophytum crassospiculatum are reported. The structure of one of these was deduced from spectroscopic data and chemical degradation, then confirmed as (E,E,E)-6,10,14-trimethyl-3-methylene-trans-3a,4,7,8,11,12,15,15a- octahydrocyclotetradeca[b]furan-2(3H)-one (3), by synthesis from the previously reported (2). The other two diterpenes,(4) and (5), are shown to be the epimeric 15-acetoxyl derivatives of (2).

Energy Approximation

2017 ◽  
Author(s):  
Philip Isett
Keyword(s):  
Main Lemma ◽  
The Other ◽  
Coarse Scale ◽  
Continuous Solutions ◽  
Material Derivative ◽  
Energy Variation ◽  
Energy Approximation ◽  
The Difference ◽  
Derivatives Of

This chapter presents the equations and calculations for energy approximation. It establishes the estimates (261) and (262) of the Main Lemma (10.1) for continuous solutions; these estimates state that we are able to accurately prescribe the energy that the correction adds to the solution, as well as bound the difference between the time derivatives of these two quantities. The chapter also introduces the proposition for prescribing energy, followed by the relevant computations. Each integral contributing to the other term can be estimated. Another proposition for estimating control over the rate of energy variation is given. Finally, the coarse scale material derivative is considered.

scholarly journals Influence of artificial aging: mechanical and physicochemical properties of dental composites under static and dynamic compression

2021 ◽  
Author(s):  
D. C. Gornig ◽  
R. Maletz ◽  
P. Ottl ◽  
M. Warkentin
Keyword(s):  
Mechanical Properties ◽  
Water Sorption ◽  
Artificial Aging ◽  
Filler Content ◽  
Dynamic Compression ◽  
The Other ◽  
Chemical Degradation ◽  
Dental Composites ◽  
Compression Tests ◽  
Acid Ph

Abstract Objective The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods Specimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F =  ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C). Results Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended.

scholarly journals II. Compounds isomeric with the sulphocyanic ethers.—I. On the mustard oil of the ethyl series

1868 ◽  
Vol 16 ◽  
pp. 254-258
Keyword(s):  
Royal Society ◽  
The Other ◽  
Mustard Oil ◽  
Other Hand ◽  
Derivatives Of

The results of my researches on the chloroform-derivatives of the primary monamines, which, as I have shown, are isomeric with the nitriles, could not fail to direct my attention to allied groups of bodies, with the view of discovering similar isomerisms. In a note communicated to the Royal Society some months ago, I expressed the expectations which even then appeared to be justified in the following manner:—“In conclusion, I may be permitted to announce as everv probable the existence of a series of bodies isomeric with the sulphocyanides. Already M. Cloëz has shown that the action of chloride of cyanogen on ethylate of potassium gives rise to the formation of an ethylic cyanate possessing properties absolutely different from those belonging to the cyanate discovered by M. Wurtz. On comparing, on the other hand the properties of the methylic and ethylic sulphocyamdes with those of the sulphocyanides of allyl and phenyl, it can scarcely be doubted that we have here the representatives of two groups entirely different, and that the terms of the methyl- and ethyl-series which correspond to oil of mustard, and to the sulphocyanide of phenyl, still remain to be discovered. Experiments with which I am now engaged will show whether these bodies cannot be obtained by the action of the iodides of methyl and ethyl on sulphocyanide of silver."

The synthesis of the isomeric N-methyl derivatives of murexine

1981 ◽  
Vol 34 (8) ◽  
pp. 1739 ◽  
Author(s):  
CC Duke ◽  
JV Eichholzer ◽  
JK Macleod
Keyword(s):  
Imidazole Ring ◽  
The Other ◽  
Pharmacological Activities ◽  
Tautomeric Forms ◽  
Methyl Derivatives ◽  
Paramagnetic Ions ◽  
Nucella Emarginata ◽  
Derivatives Of

The two isomeric N-methyl derivatives of murexine have been synthesised by independent routes and shown to be different from an 'N- methylmurexine' reportedly isolated from the mollusc Nucella emarginata. 1H n.m.r. studies have shown a marked difference in the extent of binding to paramagnetic ions of the two N-methyl derivatives of murexine in water while pharmacological results show substantially different pharmacological activities of the two isomers. Both results can be rationalized in terms of the observed activities being associated with the presence of one or the other of the tautomeric forms of the imidazole ring.

Cleavage Reactions of 5-Arylazo Derivatives of 1-Methyl-2-benzyl-2-imidazolin-4-ones

1975 ◽  
Vol 30 (7-8) ◽  
pp. 603-605 ◽  
Author(s):  
Nazmi Abdel Latif Kassab ◽  
Abdel Hamid Harhash ◽  
Sanna Osman Abd Allah
Keyword(s):  
Sodium Hydroxide Solution ◽  
Aqueous Sodium Hydroxide ◽  
The Other ◽  
Ring Cleavage ◽  
Prolonged Heating ◽  
Aqueous Sodium Hydroxide Solution ◽  
Aqueous Sodium ◽  
Triazine Derivatives ◽  
Cleavage Reactions ◽  
Derivatives Of

The 5-arylazo-1-methyl-2-benzyl-2-imidazolin-4-ones (1 a-c) undergo ring cleavage with 1% aqueous sodium hydroxide solution affording α-arylhydrazono-phenacetyl-sarcosine amide (2). Prolonged heating of 1 and 2 with the same reagent yields the cyanamide (3). On the other hand, when 1 a-c were refluxed with acetic acid the triazinones (4) were obtained. The latter adds one mole of Grignards reagent to yield the 5-hydroxy-1,2,4-triazine derivatives (5).

Application of Maple on Solving the Differential Problem of Rational Functions

2013 ◽  
Vol 479-480 ◽  
pp. 855-860
Author(s):  
Chii Huei Yu
Keyword(s):  
Problem Solving ◽  
Research Methods ◽  
Research Method ◽  
Rational Functions ◽  
The Other ◽  
Mathematical Software ◽  
Differential Problem ◽  
Binomial Theorem ◽  
Other Hand ◽  
Derivatives Of

This paper uses the mathematical software Maple as the auxiliary tool to study the differential problem of four types of rational functions. We can obtain the closed forms of any order derivatives of these rational functions by using binomial theorem. On the other hand, we propose four examples to do calculation practically. The research methods adopted in this study involved finding solutions through manual calculations and verifying these solutions by using Maple. This type of research method not only allows the discovery of calculation errors, but also helps modify the original directions of thinking from manual and Maple calculations. For this reason, Maple provides insights and guidance regarding problem-solving methods.

scholarly journals An Euler-Lagrange Equation only Depending on Derivatives of Caputo for Fractional Variational Problems with Classical Derivatives

2020 ◽  
Vol 8 (2) ◽  
pp. 590-601
Author(s):  
Melani Barrios ◽  
Gabriela Reyero
Keyword(s):  
Exact Solution ◽  
Variational Problem ◽  
Lagrange Equation ◽  
Integral Form ◽  
Variational Problems ◽  
The Other ◽  
Isoperimetric Problems ◽  
Caputo Derivatives ◽  
Fractional Variational Problems ◽  
Derivatives Of

In this paper we present advances in fractional variational problems with a Lagrangian depending on Caputofractional and classical derivatives. New formulations of the fractional Euler-Lagrange equation are shown for the basic and isoperimetric problems, one in an integral form, and the other that depends only on the Caputo derivatives. The advantage is that Caputo derivatives are more appropriate for modeling problems than the Riemann-Liouville derivatives and makes the calculations easier to solve because, in some cases, its behavior is similar to the behavior of classical derivatives. Finally, anew exact solution for a particular variational problem is obtained.

scholarly journals Bromobenzoylation of Methyl α-D-Mannopyranoside: Synthesis and Spectral Characterization

2021 ◽  
pp. 171-183
Author(s):  
Farhana Yasmin ◽  
Md. R. Amin ◽  
Anowar Hosen ◽  
M.A. Kawsar Sarkar
Keyword(s):  
Spectroscopic Data ◽  
Direct Method ◽  
Good Method ◽  
Substitution Product ◽  
X Ray ◽  
Chemical Structures ◽  
Therapeutic Drugs ◽  
Health And Disease ◽  
Derivatives Of ◽  
Acyl Derivatives

The widening importance of carbohydrate derivatives as unrivaled potential antimicrobial and therapeutic drugs has attracted attentionto the synthesis of mannopyranoside derivatives. In the present study, regioselective 3-bromobenzoylation of methyl α-D-mannopyranoside (1) was carried out using the direct method and gave the corresponding 6-O-(3-bromobenzoyl) derivative (2) in excellent yield. A number of 2,3,4-tri-O-acyl derivatives (3–10) of this 6-substitution product using a wide variety of acylating agents were also prepared in order to obtain newer derivatives of synthetic and biological importance. The chemical structures of the newly synthesized compounds were ascertained by analyzing their physicochemical, elemental, and spectroscopic data. Additionally, the X-ray powder diffraction (XRD) of these acylated products was studiedfor quantitatively identifying crystalline compounds.Therefore, due to the importance of carbohydrates, it might be useful to develop a good method for the synthesis of carbohydrate-based drugs of the current global situation for health and disease

scholarly journals Photometric Study of two Southern Algol Type Binaries

1989 ◽  
Vol 107 ◽  
pp. 376-376
Author(s):  
K. D. Abhyankar ◽  
M. L. Vyas
Keyword(s):  
Spectroscopic Data ◽  
Main Sequence ◽  
Light Curves ◽  
The Other ◽  
Main Sequence Star ◽  
Photometric Study ◽  
The Absolute ◽  
Better Than ◽  
Absolute Dimensions

Complete UBV light-curves of RR-Lep and RX-Hya have been obtained during 1983-87 seasons. Preliminary elements were computed using modified Wellmann’s method. With these parameters as inputs Wilson-Devinney program was executed for Blue and Yellow passbands simultaneously in detached and semi-detached modes for both the systems. The semidetached mode fitted better than the other solution for both the systems. For RR-Lep, the absolute dimensions were computed by assuming the primary to be a slightly evolved main sequence star. For RX-Hya, the absolute dimensions were computed using Struve’s spectroscopic data. The following table gives all the elements for both the systems. The secondaries of both the systems are overluminous for their masses suggesting that they have lost considerable mass.

Reactions of organotin compounds. X. Reactions of tin hydrides with CF2=CFRe(CO)5, CF3CF=CFRe(CO)5, and some fluorinated alkenes

1969 ◽  
Vol 47 (20) ◽  
pp. 3753-3758 ◽  
Author(s):  
M. Akhtar ◽  
H. C. Clark
Keyword(s):  
Ultraviolet Irradiation ◽  
Spectroscopic Data ◽  
Organotin Compounds ◽  
Vinyl Fluoride ◽  
New Compounds ◽  
Derivatives Of

Trimethyltin hydride reacts with CF2=CFRe(CO)5 under ultraviolet irradiation to give new fluorovinyl derivatives of —Re(CO)5. Similar products were obtained using dimethyltin dihydride, but no reaction occurred between trimethyltin hydride and CF3CF=CFRe(CO)5. The reactions of trifluoroethylene, 1,1-difluoroethylene, and vinyl fluoride with trimethyltin hydride have been studied, thus completing the sequence of such reactions with fluorinated ethylenes. While both possible addition products were obtained with trifluoroethylene, and also from the corresponding reaction with perfluoropropene, 1,1-difluoroethylene gave only (CH3)3SnCH2CF2H, and with vinyl fluoride only trimethyltin fluoride and ethylene were isolated. Possible explanations are proposed and spectroscopic data for the new compounds are presented.

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