Inductive Effects on Molecular Ionization Potentials. III. Primary,Secondary and Tertiary Aliphatic Amines

It is demonstrated that the ionization potentials of primary, secondary, and tertiary aliphatic amines correlate very well with the inductive and polar substituent constants, the only seriously deviating value being that for ammonia, itself. The correlation equation is found to be E_I = 9.62 + 13.8 Σσ_I.     

Carrier Tracking Loop Performance in the Presence of Strong CW Interference

In a coherent data link, narrow-band radio frequency interference (RFI) near the carrier frequency can degrade the link performance by impacting the carrier tracking loop behavior and producing a partial or complete loss of coherence. If the RFI is strong enough, this effect can occur even though the frequency of the interference lies well beyond the carrier tracking loop bandwidth. In 1973, Bruno and Bianchard independently performed similar analyses of the response of a phase-locked loop (PLL) to a continuous wave (CW) interferor, and derived conditions under which the loop drops carrier lock and tracks the interference instead. This paper compares the contributions of these two analysts, and extends Bruno's closed form approximation for the loop phase error to the entire lock region.     

Chemical stimulation of the brain: Relationship between neural activity and water ingestion in the rat.

Implanted cannulae in the lateral septal nucleus, lateral hypothalamic area, or lateral caudate nucleus of 76 male Long-Evans rats. Ss then received injections of carbachol, atropine sulfate, or isotonic saline. Injecting carbachol into cholinergic drinking sites in the limbic system (septal nucleus or lateral hypothalamus) produced an immediate increase in neural firing at the stimulated site and at a contralateral nonstimulated site. The time course of the change in neural firing was similar to the time course of water ingestion. Increased neural firing was not produced by cholinergic stimulation of nondrinking caudate nucleus sites or by atropine or isotonic saline injection into the limbic system or caudate nucleus. Results suggest that drinking results from increased neural firing in a diffuse cholinergically coded circuit whose activity facilitates water ingestion. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formalization and Automation of Time-Space Conflict Analysis

With increasing pressure for shorter delivery schedules, space is a critical resource at construction sites. Current industry practice lacks a formalized approach or tool to help project managers analyze spatial conflicts between activities prior to construction. Consequently, time-space conflicts occur frequently and significantly impact construction processes. Time-space conflicts have three characteristics that impede the detection and analysis of time-space conflicts prior to construction: (1) They have a temporal aspect; (2) they have different forms creating different problems; and (3) multiple types of spatial conflicts can exist between a pair of conflicting activities. This research formalizes time-space conflict analysis as a classification task and addresses these challenges by automatically (1) detecting conflicts in four dimensions; (2) categorizing the conflicts according to a taxonomy of time-space conflicts that is developed; and (3) prioritizing the multiple types of conflicts between the same pair of conflicting activities. This research extends previous research on construction space management by developing a taxonomy of time-space conflicts and by defining an approach for the analysis of time-space conflicts prior to construction.     

Techniques for the Measurement of Small Anisotropies in Magic Angle Spinning NMR Spectra

Two novel methods for enhancing the effect of small anisotropies on magic angle spinning (MAS) NMR spectra are described. The first method is a simple two-dimensional (2D) spin echo experiment, which generates rotational sidebands at a fraction of the spinning frequency in the ω₁ dimension, while maintaining the effective spinning speed in ω₂. It is shown that the rotational sidebands in the 2D spectrum are much larger than in a normal one-dimensional MAS spectrum obtained at the same spinning speed, and the relative intensities of the two-dimensional sideband array can be analyzed to yield the anisotropy and asymmetry parameter of the coupling tensor. The second method is designed to measure homonuclear dipolar couplings. We show that the effect of a dipolar coupling between members of an isolated spin pair can be enhanced by adjusting the spinning speed such that nω_r = ω_Δ^iso, where n is an integer, ω_r is the spinning speed, and ω_Δ^iso is the difference between isotropic shifts. When this condition, termed rotational resonance, is satisfied, a broadening or a splitting of the normally sharp resonance lines is observed. In addition, rapid exchange of Zeeman order between the dipolar coupled spins is seen. This method holds promise for the measurement of through space dipolar couplings and thus internuclear distances in polycrystalline solids.     

A prospective evaluation of the safety and efficacy of methohexital in the emergency department

OBJECTIVE: Knowledge of a possible correlation between distal polyps found at screening sigmoidoscopy and proximal colonic lesions is important for deciding whether to perform total colonoscopy or not. PATIENTS: A prospective analysis of 2439 consecutive patients with colorectal polyps. Of these, 304 were asymptomatic subjects who underwent complete colonoscopy for screening and were found to have adenomatous or hyperplastic polyps in the distal colorectum. RESULTS: Ten (15%) out of 65 patients with distal hyperplastic polyps only and 86 (36%) out of 239 with distal adenomatous polyps were found to have adenomatous polyps in the proximal colon as well (P < 0.001). The frequency of synchronous proximal adenomas in patients with small (< or = 5 mm) or large distal adenomas (> 5 mm) was comparable (37% and 35%, respectively). However, patients with small distal adenomas had significantly smaller proximal adenomas (P = 0.004) containing less villous component (P = 0.017) than those with large distal adenomas. Neither the patient's age nor the presence of multiple distal adenomas increased the prevalence of proximal adenomas. CONCLUSION: Hyperplastic polyps found on rectosigmoidoscopy do not indicate a need for a complete colorectal examination, as 15% of patients with distal hyperplastic polyps will have proximal adenomatous polyps, a figure that is comparable with that of asymptomatic patients having no distal polyps, either hyperplastic or adenomatous. When only small distal adenomas are found at screening sigmoidoscopy in asymptomatic persons the decision to do a total colonoscopy should be based on individual considerations, as in such cases only small polyps are to be expected in the proximal colon.