Pre-Silurian Stratified Rocks Southeast of the Bloody Bluff Fault

Guidebook for field trips to the Boston area and vicinity : 68th annual meeting, New England Intercollegiate Geological Conference, October 8-10, 1976: Trip A-1

The influence of management on yield and composition of tall fescue (Festuca arundinacea Schreb)

Because of its extensive use in the southeastern U.S. and previous reports of varying quality during the year, the yield, mineral and chemical composition (acid detergent fiber and cell wall constituents) and in vitro dry matter digestibility (DMD) of Kentucky 31 tall fescue (Festuca arundinacea Schreb.) grown alone and with ladino clover (Trifolium repens L.) was determined over a two-year period involving various stockpiling management practices at Knoxville and Spring Hill, Tennessee, and at Dover, Delaware. All plots received 560 kg/ha of 0-20-20 on 1 June each year; the fescue growing alone received 56 kg N/ha from 6-12-12 on 1 March and an additional 56 kg N/ha as NH4NO3 at the beginning of each stockpiling period. Stockpiling periods began in July, August, September, November, or December and lasted from one to seven months. Frequently clipped plots were used to simulate continuous grazing. Stockpiling treatments starting in July resulted in the highest yields, followed by those begun in August and September. Stockpiling treatments started after September yielded no appreciable growth during the stockpiling period, but did become green earlier and produced higher yields the following spring. Nitrogen percentages were generally greater in regrowth than in stockpiled fescue. Varying levels of N, concentration, some of which were occasionally below the crude protein requirement for a dry pregnant beef cow, indicated that animals grazing this forage may need protein supplement. Peak levels of ADF occurred in January and February at Knoxville and Dover, but those at Dover were generally less than those at Knoxville. Cell wall constituents were greatest in the cooler months. Levels of in vitro DMD were higher in the fall (October) and lowest in the summer (August). Regrowth had a higher level of DMD than stockpiled material cut on the same date. Mineral composition varied during the growing season and among locations. Fescue from similar treatments was generally lower in P, K, and Mg percentage at Dover than at Knoxville, but Ca levels were generally higher at Dover. Frequent clipping to simulate grazing did not affect mineral or chemical composition. Stockpiling fescue tended to reduce quality, but stockpiled forage can be useful in a grazing system. Season of growth appeared to have a greater effect on composition than date of start of stockpiling or duration of stockpiling

The effects of reader-generated and previously existing text marking on comprehension in readers of different skill levels

Previous research examining effects of previously existing and reader generated text marking has failed to demonstrate whether or not it is beneficial or detrimental to the reader. Furthermore, whether or not text marking has differential effects on readers of different skill has not been determined. The studies reported here attempted to clarify the questions that remain about the effects of text marking on comprehension, in readers of different skill levels, through analysis of marking in student textbooks as well as through the use of experimental methods. Study 1 demonstrated that low-skill readers claim to highlight on more occasions when studying, but do not claim to mark more of the text. However, textbook analyses failed to support this finding. Additionally, low-skill readers claim to prefer a previously marked textbook to a greater degree than high-skill readers. Study 2 found that low-skill readers claim to, and use text-marking strategies more often and mark more of the text than high-skill readers. Study 2 also confirmed that low-skill readers report higher preference for studying previously marked texts and a tendency to study only material marked by a previous reader. Finally, Study 2 demonstrated that low-skill readers are less capable of identifying the most relevant material in textbooks and that this inability is related to poorer course performance. The finding that low-skill readers report greater reliance on previously marked material, use text-marking strategies more often, and are less capable of identifying the most relevant material suggests that many low-skill readers study irrelevant material in textbooks. Study 3 examined the effects of irrelevant text marking on comprehension and found that low-skill readers are differentially affected by the presence of irrelevant marking, such that the study of text containing irrelevant marking leads to poorer comprehension. Practical implications of these findings and suggestions for future research are discussed

The influence of a fixed failure plane on the direct shear test

The analysis of the direct or box shear test for determining the shear strength of a soil makes use of the assumption that the failure plane coincides with the plane of separation between the two halves of the box. Hvorsley, Roscoe, Hansen and others have theorized and experimentally shown that this is not always the case. The stress distributions on the failure plane, however it may be oriented, are not as uniform as generally assumed. This investigation was carried out to compare direct shear tests run on granular, air dry material where the failure was allowed to take place naturally to similar tests where the failure plane was forced to follow the plane of separation. A direct shear box, constructed of steel channel, was employed. Samples of angular crushed limestone and rounded river run gravel were each tested in the two manners described above. It was observed that the failure envelopes for each size of material tested indicated a lower angle of friction when the failure plane was forced to coincide with the plane of separation of the two halves of the box --Abstract, page ii

Structure and Stratigraphy of the nantasket Locality

Guidebook to field trips in the Boston area and vicinity : 56th annual meeting October 2-4, 1964 held at Boston College, Chestnut Hill, Massachusetts: Trip

Photocrosslinkable nonlinear optical polymers and directly-patternable polyimide dielectrics

textThe development of high-efficiency nonlinear optical (NLO) polymers has opened up many opportunities in the field of electro-optics. However, current NLO polymers do not meet stability requirements for semiconductor integration. In an effort to improve this, we examined the effects of crosslinking following electric field poling. A series of photocrosslinkable polymers bearing side chain chromophores was synthesized, poled and evaluated on the basis of the thermal stability of Second Harmonic Generation. Photoinitiation allowed for control of the onset of curing. Crosslinking was monitored by FTIR and optimal conversion was achieved by applying a slow temperature ramp during exposure. The ultimate stability of the poled polymers was directly related to the number of crosslinking substituents attached to the chromophore pendant group. With two reactive groups per chromophore significant SHG was retained at temperatures beyond the polymer Tg. In integrated circuit packaging there is a need for directly-patternable polymers of low dielectric constant. Bridging the gap between the high-value silicon chip and circuit board is a substrate comprising alternating layers of metal conductor and polymer dielectric. PMDA-ODA, an aromatic polyimide, meets many of the requirements for integration and can be patterned using a photobase generator (PBG). Due to absorbance by the PMDA-ODA precursor, this PBG must have activity at visible wavelengths. Several oxime urethanes were synthesized and evaluated as candidate long wavelength PBG. These compounds exhibit clean photochemistry and high visible light sensitivity. Unfortunately, carbamate thermal stability is insufficient for patterning PMDA-ODA. For improved material properties, PMDA-TFMB, a fluorinated polyimide, was also evaluated. Importantly, the polymer precursor is sufficiently transparent to employ thermally-stable near-UV photobases. With photobase, 2.5 micron features were resolved in PMDA-TFMB. An ancillary benefit of this methodology is reduced cure temperature (~200 °C), a traditional drawback of polyimides. This material demonstrates a dielectric constant near 3 and a thermal expansion coefficient (CTE) of approximately 6 ppm/°C in-plane. Through-plane thermal expansion is somewhat problematic, with a CTE of approximately 160 ppm/°C, and will likely require a nanoparticle composite strategy. However, this combination of material and lithographic properties make PMDA-TFMB a promising candidate for this application.Chemistr

Comparison of Two Ground Modification Techniques to Reduce Settlement

At the La Rosita Power Plant site in Mexicali, Mexico, a 3-m thick layer of loose very fine sandy silt was encountered at about 7.5 m depth. Settlement calculations performed for the heavier (150 to 200 kPa) settlement sensitive structures indicated values of up to 65 mm, compared to an allowable settlement of 50 mm. During the design of the base plant, various options for limiting settlement were reviewed. Based on a cost and schedule review, jet grouting of the loose silt layer was chosen. The predicted post-grouting foundation settlement was approximately 35 to 40 mm. During construction of the base plant, the owner elected to add an additional unit on an adjacent site that had very similar subsurface conditions. The same ground modification options were again considered for this expansion unit. However, this time removal of a portion of the upper clayey soils and replacement with compacted structural fill materials was chosen as the best option. Computations indicated that removal to a depth of 3 m would reduce the predicted settlement to less than 50mm. Measured settlements on both sites (base plant with jet grouting and expansion plant with soil replacement) were well within predicted limits. A comparison of the settlements showed that the soil replacement was slightly more effective than the jet grouting in these circumstances. One meter of structural fill was required under all structures to prevent shrink-swell of the upper clayey soils. During the jet grouting operation at the base plant, the jet grout spoil materials were used in lieu of structural fill under the cooling tower foundation. At the expansion site, the cooling towers were supported on 1 m of structural fill since no jet grout spoils were available. The measured settlements of these two structures were almost identical, confirming that the jet grouting spoils produced an excellent fill material when properly handled

A comparison of theoretical line intensity ratios for Ni XII with extreme ultraviolet observations from the JET tokamak

Recent R-matrix calculations of electron impact excitation rates in Ni XII are used to derive the emission line ratios R1 = I (154.17 Å)/I (152.15 Å), R2 = I (152.95 Å)/I (152.15 Å) and R3 = I (160.55 Å)/I (152.15 Å). This is the first time (to our knowledge) that theoretical emission line ratios have been calculated for this ion. The ratios are found to be insensitive to changes in the adopted electron density (Ne) when Ne >= 5 × 10^11 cm−3, typical of laboratory plasmas. However, they do vary with electron temperature (Te), with for example R1 and R3 changing by factors of 1.3 and 1.8, respectively, between Te = 10^5 and 10^6 K. A comparison of the theoretical line ratios with measurements from the Joint European Torus (JET) tokamak reveals very good agreement between theory and observation for R1, with an average discrepancy of only 7%. Agreement between the calculated and experimental ratios for R2 and R3 is less satisfactory, with average differences of 30 and 33%, respectively. These probably arise from errors in the JET instrument calibration curve. However, the discrepancies are smaller than the uncertainties in the R2 and R3 measurements. Our results, in particular for R1, provide experimental support for the accuracy of the Ni XII line ratio calculations, and hence for the atomic data adopted in their derivation