Switching and Extension of a [c2]Daisy-Chain Dimer Polymer

We report the synthesis of a [c2]daisy-chain dimer via ruthenium-catalyzed ring-closing olefin metathesis. Confirmation of the interlocked nature of the structure was achieved through single-crystal X-ray diffraction analysis. The dimer could be readily switched from the bound to the unbound conformation by treatment with 3.0 equiv of KOH and subsequently reprotonated by treatment with 3.0 equiv of HPF_6. Azide functionalization of the dimer enabled incorporation in linear step-growth polymer chains using the alkyne-azide “click” reaction. Gel permeation chromatography coupled with multiangle laser light scattering analysis showed the polymers contained 22 dimers and had a radius of gyration of 14.8 nm. Acylation of the amines of the dimers sterically forced elongation of the interlocked units, and MALLS analysis of the polymer showed a 48% increase in the R_g (21.4 nm)

The Influence of pH Variation on CooA Activity

CooA, a CO-sensing heme protein, acts as a transcriptional activator of CO-metabolizing proteins in bacteria such as Rhodospirillum rubrum and Carboxydothermus hydrogenoformans through sequence-specific DNA binding. Previous research indicated a reduced iron center and CO gas were necessary for CooA to achieve its active conformation and bind DNA. To determine if other reaction conditions facilitate CooA activation, the role of pH on CooA function was tested. Specifically, a fluorescence anisotropy assay was employed to measure possible Fe(III) CooA DNA binding from pH 3 - 12. Interestingly, CooA was observed to bind DNA without CO at acidic conditions, with optimal binding observed at pH ~3. These results are discussed in light of the normal CO-dependent activation mechanism of CooA proteins

Analysis of fluid/mechanical systems using EASY5

This paper illustrates how the use of a general analysis package can simplify modeling and analyzing fluid/mechanical systems. One such package is EASY5, a Boeing Computer Services product. The basic transmission line equations for modeling piped fluid systems are presented, as well as methods of incorporating these equations into the EASY5 environment. The paper describes how this analysis tool has been used to model several fluid subsystems of the Space Shuttle Orbiter

Acoustic modes in fluid networks

Pressure and flow rate eigenvalue problems for one-dimensional flow of a fluid in a network of pipes are derived from the familiar transmission line equations. These equations are linearized by assuming small velocity and pressure oscillations about mean flow conditions. It is shown that the flow rate eigenvalues are the same as the pressure eigenvalues and the relationship between line pressure modes and flow rate modes is established. A volume at the end of each branch is employed which allows any combination of boundary conditions, from open to closed, to be used. The Jacobi iterative method is used to compute undamped natural frequencies and associated pressure/flow modes. Several numerical examples are presented which include acoustic modes for the Helium Supply System of the Space Shuttle Orbiter Main Propulsion System. It should be noted that the method presented herein can be applied to any one-dimensional acoustic system involving an arbitrary number of branches

Sprinklers, Crop Water Use, and Irrigation Time: Cache County

Sprinkler irrigation has been an important part of Utahs agricultural production since the early 1950s. About 40 % of Utahs 1.3 million irrigated acres are watered with sprinklers, including hand move, wheel move, center pivot and other types. Sprinkler irrigation is even more important in Iron County, accounting for 80 percent of all irrigated acreage. Sprinklers can be a good investment when properly designed, installed, maintained and managed. For every acre-foot of water supplied to an efficient sprinkler system a farmer can expect to harvest about 1 3/4 tons of alfalfa and 46 bushels of wheat. In contrast, the expected harvest with a typical surface irrigation system (flood or furrow) is less than 1 1/4 tons of alfalfa or about 30 bushels of wheat for each acre-foot of water applied. Sprinklers apply water more efficiently and uniformly than typical surface irrigation systems, thus they produce more yield for each acre-foot of water. Not all water applied by an irrigation system is used by the crop. Some water is lost to deep percolation, evaporation, or runoff. Application efficiency (Ea) is a term that tells how much of the water applied by the system is actually stored in the root zone for crop use. In Utah a typical sprinkler system has an Ea of 70 % which means that 70 % of the water applied by the sprinkler heads is actually stored in the soil for crop use. The actual Ea depends upon how evenl

Assessing the Impact of Course-Related Electronic Communications on Student Performance in an Introductory Programming Course

This paper describes a system which utilizes a campus computer network to facilitate class-related faculty-student communication. The system uses electronic mail, system utilities and application programs to provide students and faculty with menu-driven access to an electronic gradebook, a class bulletin board, and to the electronic exchange of assignments. We report on an experiment in which one section of the introductory programming course used this system while another did not. Surveys and usage data from this experiment indicate a favorable perception of the system by student users, but analysis of student achievement shows no significant correlation between student performance and system usage