Studies of Some Strained-Ring Systems: Tricyclo-Octanes

10.26686/wgtn.16934971 ◽

2021 ◽

Author(s):

◽

Martin Gerhardt Banwell

Keyword(s):

Fold Increase ◽

Ring Systems ◽

Styrene Conversion

<p>The present study has been directed towards the synthesis and base promoted rearrangements of some saturated and unsaturated halogenotricyclo-octanes. The preparation of a number of previously unknown 4,4,8- and 4,4,8,8-tetra-halogeno-anti-tricyclo[5,1,0,03,5]- octanes and the corresponding 3,3,8-tri- and 3,3,8,8-tetra-halogeno-anti-tricyclo[5,1,0,02,4] octanes has been accomplished and the stereo-chemistries of their ring systems established. The former tricyclo-octanes are base sensitive and on treatment with potassium t-butoxide give rise to mixtures of (E) - and (Z) -Beta-t-butoxystyrenes. However, the anti-tricyclo[5,1,0,02,4] octanes give no characterisable products on treatment with base. The mechanistic implications of the tricycle-octane - styrene conversion have been studied in some detail and halogenocyclo-octatetraenes and phenylacetylenes have been eliminated as intermediates. The behaviour of several methoxy-substituted 4,4,8,8-tetrahalogeno-anti-tricyclo[5,1,0,03,5] octanes with the same base has been studied, and it has been found that homotropilidenes are formed regiospecifically by 1,4-elimination. These conversions constitute the first known examples of such elimination experienced by ring-fused halogenocyclopropanes. From these studies, evidence is presented which implicates homotropilidenes and bicyclo[4,2,0]octa-2,4-dienes as intermediates in the production of styrenes, and a mechanism for the tricyclo-octane - styrene rearrangement has been proposed. A new and potentially versatile synthesis of 3,3-dihalogeno-anti tricyclo[5,1,0,02,4] oct-5-enes (anti-bishomobenzenes) has been developed. The new route employs readily available starting materials, involves sequential introduction of the cyclopropyl, gem-dihalogenocyclopropyl, and olefinic moieties and proceeds in an overall yield of about 14%. This represents a five-fold increase over the previously reported yields.</p>

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Comments on collision mechanics in ring systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100101472 ◽

1984 ◽

Vol 75 ◽

pp. 407-422

Author(s):

William K. Hartmann

Keyword(s):

Asteroid Belt ◽

Surface Erosion ◽

Surface Layers ◽

Ring Systems ◽

Eclipse Observations ◽

Saturn’S Rings ◽

Saturn's Rings

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.

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Stochasting modeling of planetary ring systems

International Astronomical Union Colloquium ◽

10.1017/s025292110010154x ◽

1984 ◽

Vol 75 ◽

pp. 461-469 ◽

Cited By ~ 1

Author(s):

Robert W. Hart

Keyword(s):

Maximum Entropy ◽

Ring System ◽

The Sun ◽

Ultimate State ◽

Interparticle Interactions ◽

Ring Systems ◽

First Order ◽

Planetary Ring ◽

Insight Into

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.

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Detection of viruses by electron microscopy: Increased sensitivity by direct micro-ultracentrifugation of samples

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128821 ◽

1987 ◽

Vol 45 ◽

pp. 908-909

Author(s):

Alain R. Trudel ◽

M. Trudel

Keyword(s):

Electron Microscopy ◽

Fold Increase ◽

Observation Time ◽

Clinical Samples ◽

Maximum Speed ◽

Viral Particles ◽

Structural Details ◽

Latex Spheres ◽

Increased Sensitivity ◽

Size Of Particles

AirfugeR (Beckman) direct ultracentrifugation of viral samples on electron microscopy grids offers a rapid way to concentrate viral particles or subunits and facilitate their detection and study. Using the A-100 fixed angle rotor (30°) with a K factor of 19 at maximum speed (95 000 rpm), samples up to 240 μl can be prepared for electron microscopy observation in a few minutes: observation time is decreased and structural details are highlighted. Using latex spheres to calculate the increase in sensitivity compared to the inverted drop procedure, we obtained a 10 to 40 fold increase in sensitivity depending on the size of particles. This technique also permits quantification of viral particles in samples if an aliquot is mixed with latex spheres of known concentration.Direct ultracentrifugation for electron microscopy can be performed on laboratory samples such as gradient or column fractions, infected cell supernatant, or on clinical samples such as urine, tears, cephalo-rachidian liquid, etc..

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Advantages of Complementary Stereo Images as Viewed with the Low-Temperature Field-Emission SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131206 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1314-1315

Author(s):

William P. Wergin ◽

Eric F. Erbe

Keyword(s):

Fold Increase ◽

Horizontal Displacement ◽

Three Dimensions ◽

Stereo Image ◽

Stereo Pair ◽

Sem Micrograph ◽

Left And Right ◽

The Common ◽

The Brain ◽

Pair Analysis

The eye-brain complex allows those of us with normal vision to perceive and evaluate our surroundings in three-dimensions (3-D). The principle factor that makes this possible is parallax - the horizontal displacement of objects that results from the independent views that the left and right eyes detect and simultaneously transmit to the brain for superimposition. The common SEM micrograph is a 2-D representation of a 3-D specimen. Depriving the brain of the 3-D view can lead to erroneous conclusions about the relative sizes, positions and convergence of structures within a specimen. In addition, Walter has suggested that the stereo image contains information equivalent to a two-fold increase in magnification over that found in a 2-D image. Because of these factors, stereo pair analysis should be routinely employed when studying specimens.Imaging complementary faces of a fractured specimen is a second method by which the topography of a specimen can be more accurately evaluated.

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Prevalence of Self-Reported Depression Symptoms and Perceived Anxiety Among Community-Dwelling U.S. Adults Reporting Tinnitus

Perspectives of the ASHA Special Interest Groups ◽

10.1044/2020_persp-19-00178 ◽

2020 ◽

Vol 5 (4) ◽

pp. 959-970

Author(s):

Kelly M. Reavis ◽

James A. Henry ◽

Lynn M. Marshall ◽

Kathleen F. Carlson

Keyword(s):

Mental Health ◽

Fold Increase ◽

Community Dwelling ◽

Self Report ◽

Depression Symptoms ◽

Community Based Interventions ◽

Data Set ◽

Health Distress ◽

Validated Questionnaire ◽

Mental Health Distress

Purpose The aim of this study was to examine the relationship between tinnitus and self-reported mental health distress, namely, depression symptoms and perceived anxiety, in adults who participated in the National Health and Nutrition Examinations Survey between 2009 and 2012. A secondary aim was to determine if a history of serving in the military modified the associations between tinnitus and mental health distress. Method This was a cross-sectional study design of a national data set that included 5,550 U.S. community-dwelling adults ages 20 years and older, 12.7% of whom were military Veterans. Bivariable and multivariable logistic regression was used to estimate the association between tinnitus and mental health distress. All measures were based on self-report. Tinnitus and perceived anxiety were each assessed using a single question. Depression symptoms were assessed using the Patient Health Questionnaire, a validated questionnaire. Multivariable regression models were adjusted for key demographic and health factors, including self-reported hearing ability. Results Prevalence of tinnitus was 15%. Compared to adults without tinnitus, adults with tinnitus had a 1.8-fold increase in depression symptoms and a 1.5-fold increase in perceived anxiety after adjusting for potential confounders. Military Veteran status did not modify these observed associations. Conclusions Findings revealed an association between tinnitus and both depression symptoms and perceived anxiety, independent of potential confounders, among both Veterans and non-Veterans. These results suggest, on a population level, that individuals with tinnitus have a greater burden of perceived mental health distress and may benefit from interdisciplinary health care, self-help, and community-based interventions. Supplemental Material https://doi.org/10.23641/asha.12568475

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