Factors affecting the relative stability of a series of iminium cation stereoisomers

2007 ◽  
Vol 806 (1-3) ◽  
pp. 223-230 ◽  
Author(s):  
Powen Hsueh ◽  
Mark Lukowski ◽  
Harriet A. Lindsay ◽  
M.C. Milletti
Keyword(s):  
Relative Stability ◽  
Factors Affecting

FULLY FLUORINATED ALKOXIDES: PART I. TRIFLUOROMETHOXIDES OF ALKALI METALS

1965 ◽  
Vol 43 (7) ◽  
pp. 1893-1898 ◽  
Author(s):  
M. E. Redwood ◽  
C. J. Willis
Keyword(s):  
Relative Stability ◽  
Alkali Metals ◽  
Reversible Reaction ◽  
Metal Fluoride ◽  
Factors Affecting ◽  
Ionic Solids ◽  
Fluorinated Alkoxides ◽  
Carbonyl Fluoride

The preparation is described of the trifluoromethoxides of the heavier alkali metals, i.e. MOCF3 where M = K, Rb, or Cs. These are stable, crystalline, ionic solids made by the reversible reaction of carbonyl fluoride with the appropriate metal fluoride. No trifluoromethoxides could be prepared from lithium, sodium, barium, or thallium(I) fluorides. Factors affecting the relative stability of such compounds are discussed.

Quantum-chemical calculation as an aid in synthesis of prostaglandins, attempt of prediction of relative stability of four stereoisomeric methyl 7-hydroxy-2-oxa-3-oxobicyclo[3.3.0]octane-6-carboxylates

1980 ◽  
Vol 45 (8) ◽  
pp. 2179-2186 ◽  
Author(s):  
Josef Kuthan ◽  
Stanislav Böhm ◽  
Jiří Mostecký
Keyword(s):  
Quantum Chemical Calculation ◽  
Relative Stability ◽  
Quantum Chemical ◽  
Energy Characteristic ◽  
Chemical Calculation ◽  
Factors Affecting ◽  
Chemical Models ◽  
Calculated Energy ◽  
Electron Distributions ◽  
Quantum Chemical Models

Partial optimization of conformation structure of quantum-chemical models of the stereoisomeric lactones I to IV has been carried out by the CNDO/2 method. The calculated energy characteristic and electron distributions have been used for discussion of some factors affecting retention of 5,6-trans-configuration in the key intermediate of prostaglandin syntheses (formulaI) with regard to conditions of the preparative experiments.

scholarly journals Factors Affecting the Clinical Measurement of Visuo-Spatial Neglect

1992 ◽  
Vol 5 (4) ◽  
pp. 233-240 ◽  
Author(s):  
L. Pizzamiglio ◽  
C. Bergego ◽  
P. Halligan ◽  
V. Homberg ◽  
I. Robertson ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Relative Stability ◽  
Single Case ◽  
Case Analysis ◽  
Spatial Neglect ◽  
Clinical Measurement ◽  
Factors Affecting ◽  
Unilateral Spatial Neglect ◽  
Extrapersonal Space ◽  
Spatial Exploration

The present study examined a battery of tests to evaluate unilateral spatial neglect; the tests included different tasks involving several modalities of spatial exploration mapping perceptual, motor, attentional and personal or extrapersonal space dimensions. The subjects, 121 right-brain-damaged patients with unilateral neglect, were studied in seven laboratories in four European countries. Relationships among the various tests were examined by correlations, a cluster analysis and by an analysis of individual cases. Different sensitivity was found among various tests for detecting neglect performances. Both the cluster analysis and the single case analysis clearly showed a segregation between personal and extrapersonal neglect. Analysis of the large cluster, including a variety of tests of extra personal neglect, together with the study of single cases, suggests the possibility of differentiating the various manifestations of spatial neglect which can be interpreted on the basis of the descriptions of other individual cases previously reported in the literature. Finally, the present study indicated the relative stability of neglect following the acute phase and its independence from age.

Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

1977 ◽  
Vol 35 ◽  
pp. 214-217
Author(s):  
F. A. Heckman ◽  
E. Redman ◽  
J.E. Connolly
Keyword(s):  
Image Analysis ◽  
Image Quality ◽  
Exposure Time ◽  
Image Contrast ◽  
Automated Image Analysis ◽  
Practical Application ◽  
Factors Affecting ◽  
High Image Quality ◽  
Qualitative Evidence ◽  
Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

Factors affecting microstructural scale in liquid crystalline polymers

1990 ◽  
Vol 48 (4) ◽  
pp. 220-221
Author(s):  
Christine M. Dannels ◽  
Christopher Viney
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Factors Affecting ◽  
Crystalline Polymers ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Lower Viscosity ◽  
Fine Microstructure ◽  
Planar Orientation ◽  
Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

Factors affecting dentist participation in a state Medicaid program

1990 ◽  
Vol 54 (11) ◽  
pp. 638-643 ◽  
Author(s):  
PC Damiano ◽  
ER Brown ◽  
JD Johnson ◽  
JP Scheetz
Keyword(s):  
Medicaid Program ◽  
Factors Affecting

Speech Therapy Services in a Large School System: A Six-Year Overview

1976 ◽  
Vol 7 (4) ◽  
pp. 207-219 ◽  
Author(s):  
Constance P. DesRoches
Keyword(s):  
School System ◽  
Speech Therapy ◽  
Factors Affecting ◽  
Case Load ◽  
Number Of Children ◽  
School Population ◽  
System A ◽  
Therapy Services ◽  
And Shifts ◽  
Selection Factors

A statistical review provides analysis of four years of speech therapy services of a suburban school system which can be used for comparison with other school system programs. Included are data on the percentages of the school population enrolled in therapy, the categories of disabilities and the number of children in each category, the sex and grade-level distribution of those in therapy, and shifts in case-load selection. Factors affecting changes in case-load profiles are identified and discussed.

Assessing the Link Between Perception and Production in Cantonese Tone Acquisition

2019 ◽  
Vol 62 (5) ◽  
pp. 1243-1257 ◽  
Author(s):  
Peggy Pik Ki Mok ◽  
Holly Sze Ho Fung ◽  
Vivian Guo Li
Keyword(s):  
Language Acquisition ◽  
General Principle ◽  
Choice Task ◽  
Factors Affecting ◽  
Tone Pair ◽  
Tone Production ◽  
Monosyllabic Words ◽  
Early Production ◽  
Forced Choice Task ◽  
Production Accuracy

Purpose Previous studies showed early production precedes late perception in Cantonese tone acquisition, contrary to the general principle that perception precedes production in child language. How tone production and perception are linked in 1st language acquisition remains largely unknown. Our study revisited the acquisition of tone in Cantonese-speaking children, exploring the possible link between production and perception in 1st language acquisition. Method One hundred eleven Cantonese-speaking children aged between 2;0 and 6;0 (years;months) and 10 adolescent reference speakers participated in tone production and perception experiments. Production materials with 30 monosyllabic words were transcribed in filtered and unfiltered conditions by 2 native judges. Perception accuracy was based on a 2-alternative forced-choice task with pictures covering all possible tone pair contrasts. Results Children's accuracy of production and perception of all the 6 Cantonese tones was still not adultlike by age 6;0. Both production and perception accuracies matured with age. A weak positive link was found between the 2 accuracies. Mother's native language contributed to children's production accuracy. Conclusions Our findings show that production and perception abilities are associated in tone acquisition. Further study is needed to explore factors affecting production accuracy in children. Supplemental Material https://doi.org/10.23641/asha.7960826

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