scholarly journals Graphic and tabular summaries of recent changes in stream-channel cross sections for Redwood Creek and selected tributaries, Humboldt County, California

1976 ◽  
Author(s):  
K. Michael Nolan ◽  
Deborah Reid Harden ◽  
Richard J. Janda
Keyword(s):  
Cross Sections ◽  
Stream Channel ◽  
Humboldt County

Channel Morphology Below Reservoir Storage Projects

1977 ◽  
Vol 4 (4) ◽  
pp. 279-284 ◽  
Author(s):  
Paul G. Buma ◽  
J. Chadwick Day
Keyword(s):  
Cross Sections ◽  
The United States ◽  
Cross Sectional Area ◽  
Main Stream ◽  
Sectional Area ◽  
Stream Channel ◽  
Cross Sectional ◽  
Channel Changes ◽  
Reservoir Storage ◽  
Crosssectional Area

Reservoir storage projects are known to alter significantly the environmental settings in which they are established. Extensive data are required to assess quantitatively the physical effects of human interference with rivers. Methodologies must be developed to permit continual monitoring of such changes, so that environmental effects of storage projects may be considered in more integrated, comprehensive plans than hitherto for future river-development efforts.This study documents stream-channel changes over a five-years period following reservoir completion at eight cross-sections on the main stream below a dam and on one tributary. Of eight main-stream sections, four are increasing in cross-sectional area, namely numbers one, five, six, and seven. Of these, the crosssectional area of numbers one and seven is increasing laterally and that of five and six is increasing vertically. The average annual degradation of sections five and six is 0.092 m over the study period, compared with an average of 0.031 m in the United States over the first 10–15 years after dam closure. Sections three, eight, and nine, are shitfing laterally without a crosssectional area increase, while of sections 2 and 4 the cross-sectional area remained largely unchanged.Extraction of most of the sediment load by the new reservoir led to increased erosion of the stream channel below the dam. However, it is not always predictable whether the increased erosive power of released clearwater will induce the ongoing channel to erode its bed, widen its section, or cause the bed to move laterally. Nearly all of the nine Deer Creek study sections experienced one of these changes over the study period of five years.

scholarly journals An Evaluation of Data Collected by Middle School and College-Level Students in Stream Channel Geomorphic Assessment

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Martin D. Lafrenz
Keyword(s):  
Middle School ◽  
Cross Sections ◽  
Stream Velocity ◽  
College Level ◽  
Stream Channel ◽  
Channel Geometry ◽  
Student Groups ◽  
Portland State University ◽  
Bed Material ◽  
Accuracy And Repeatability

This project tested the accuracy and repeatability of geomorphic stream channel assessments conducted by two different middle school classes from the Walt Morey Middle School in Troutdale, OR and college students from Portland State University in Portland, OR. Each group surveyed the same three cross-sections in Fairview Creek, a tributary to the Lower Columbia River, in order to assess stream channel geometry, discharge, composition of the bed material, and water quality. The three student groups were all able to accurately document the stream channel geometry, including stream width and mean depth, indicating that these data can be successfully collected by volunteers of various ages. However, stream velocity obtained using the float method was consistently overestimated leading to a biased calculation of discharge, and the low precision of the measurements did not allow for a correction of the bias. The median particle size of the bed material determined by a pebble count was also overestimated by each group, but the low precision also negated the possibility of correcting the estimate. The stored fine sediment in the bed was underestimated by each group and again with low precision. The temperature, pH, and conductivity measured with a calibrated multimeter were accurate and precise for all groups.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Surface ultrastructure of danazol treated rat endometrium: A SEM study

1983 ◽  
Vol 41 ◽  
pp. 556-557
Author(s):  
R.P. Apkarian ◽  
J.S. Sanfilippo
Keyword(s):  
Cross Sections ◽  
Reproductive Tract ◽  
Preliminary Investigation ◽  
Breast Disease ◽  
Distal Segment ◽  
Uterine Horn ◽  
Female Reproductive Tract ◽  
Ultrastructural Changes ◽  
Cycle Phase ◽  
Sprague Dawley

The synthetic androgen danazol, is an isoxazol derivative of ethisterone. It is utilized in the treatment of endometriosis, fibrocystic breast disease, and has a potential use as a contraceptive. A study was designed to evaluate the ultrastructural changes associated with danazol therapy in a rat model. The preliminary investigation of the distal segment of the rat uterine horn was undertaken as part of a larger study intended to elucidate the effects of danazol on the female reproductive tract.Cross-sections (2-3 mm in length) of the distal segment of the uterine horn from sixteen Sprague-Dawley rats were prepared for SEM. Ten rats in estrus served as controls and six danazol treated rats were noted to have alterations of the estrus cycle i.e. a lag in cycle phase or noncycling patterns. Specimens were fixed in 3% glutaraldehyde in 0.05M phosphate buffer containing CaCl2 at pH 7.0-7.4 and chilled to 4°C. After a brief wash in distilled water, specimens were passed through a graded series of ethanol, critical point dryed in CO2 from absolute ethanol, and coated with 6nm Au. Observations were made with an IS1-40 SEM operated at 15kV.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

Sign in / Sign up

Export Citation Format

Share Document