Effects of Sample Disturbance and Consolidation Procedures on Cyclic Strengths of Intermediate Soils

Sampling and testing of soils to measure engineering properties, such as monotonic and cyclic undrained shear strengths, requires an understanding of the potential effects of sampling disturbance and the selection of appropriate laboratory testing procedures. For clays, past research has provided insights on how sampling methods and laboratory testing procedures can be used in practice to assess and minimize sample disturbance effects. For sands, past research has shown that conventional tube sampling techniques cause excessive disturbance to the soil fabric, such that subsequent measurement of monotonic or cyclic strengths can be greatly in error and misleading. For intermediate soils, the effects of disturbance and consolidation procedures on monotonic and cyclic strengths are not well understood. In the present study, a test protocol was developed to assess the effects that disturbance during sample extrusion, trimming, and mounting have on subsequent measurements of compressibility, monotonic undrained strength, and cyclic undrained strength. Detailed laboratory tests were performed on tube samples from deposits of low-plasticity silty clay, for which conventional sampling and testing were expected to work reasonably well, and low-plasticity clayey sand, for which the effects of sample disturbance were of primary concern. Test results using this protocol for these two soils are presented and discussed

The Evolutionary Dynamics of Digital and Nucleotide Codes: A Mutation Protection Perspective

Both digital codes in computers and nucleotide codes in cells are protected against mutations. Here we explore how mutation protection affects the random change and selection of digital and nucleotide codes. We illustrate our findings with a computer simulation of the evolution of a population of self replicating digital amoebae. We show that evolutionary programming of digital codes is a valid model for the evolution of nucleotide codes by random change within the boundaries of mutation protection, not for evolution by unbounded random change. Our mutation protection perspective enhances the understanding of the evolutionary dynamics of digital and nucleotide codes and its limitations, and reveals a paradox between the necessity of dysfunctioning mutation protection for evolution and its disadvantage for survival. Our mutation protection perspective suggests new directions for research into mutational robustness

Vocational perspectives after spinal cord injury

Objective: To give insight into the vocational situation several years after a traumatic spinal cord injury (SCI) and describe the personal experiences and unmet needs; to give an overview of health and functional status per type of SCI and their relationship with employment status. Design: Descriptive analysis of data from a questionnaire. Setting: Dutch rehabilitation centre with special department for patients with spinal cord injuries. Subjects: Fifty-seven patients with a traumatic SCI, aged 18-60 years, admitted to the rehabilitation centre from 1990 to 1998. Main measures: Questionnaire with items related to vocational outcome, job experiences, health and functional status. Results: Of 49 patients who were working at the moment of SCI 60% currently had a paid job. Vocational outcome was related to a higher educational level. A significant relation between the SCI-specific health and functional status and employment was not found. The respondents who changed to a new employer needed more time to resume work, but seemed more satisfied with the job and lost fewer working hours than those who resumed work with the same employer. In spite of reasonable to good satisfaction with the current work situation, several negative experiences and unmet needs were reported. Conclusions: Despite a high participation in paid work following SCI, the effort of the disabled worker to have and keep a job should not be underestimated

Energy-resolved electron-spin dynamics at surfaces of p-doped GaAs

Electron-spin relaxation at different surfaces of p-doped GaAs is investigated by means of spin, time and energy resolved 2-photon photoemission. These results are contrasted with bulk results obtained by time-resolved Faraday rotation measurements as well as calculations of the Bir-Aronov-Pikus spin-flip mechanism. Due to the reduced hole density in the band bending region at the (100) surface the spin-relaxation time increases over two orders of magnitude towards lower energies. At the flat-band (011) surface a constant spin relaxation time in agreement with our measurements and calculations for bulk GaAs is obtained.Comment: 6 pages, 4 figure

Material and Seismic Assessment of the Great House at Casa Grande Ruins National Monument, Arizona

The authors characterized earthen wall materials and plasters in a mid-fourteenth-century Hohokam great house at Casa Grande Ruins National Monument (Arizona) and assessed the seismic susceptibility of its puddled earth walls. Characterization included determining the microstructure, microcomposition, porosity, aggregate mineralogy, and identification of phases in the binding matrix for each of 36 samples and reconstructing plaster technologies, including material selection, preparation, and application sequences. Findings support the ideas that earthen materials were manipulated to optimize their performance to suit the unique site conditions and needs of the ancient people using the structure and included finishes that were unusual in southwestern sites from this time period. By using a new set of tools that integrate the complicated geometry of individual wall segments as captured in light detection and ranging (LiDAR) scans (models were generated in Rhino version 5) with the dynamic analysis of rocking mechanisms (tools for this analysis were developed in Rhino), seismic collapse assessment was used to identify the most vulnerable parts of the building to earthquake loading and provided an initial evaluation of the seismic overturning capacity of these wall segments

BAGGER: An EBL System that Extends and Generalizes Explanations

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / NSF IST 85-1154

A Model of Attention Focussing During Problem Solving

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / NSF IST 85-1154

An Explanation-Based Approach to Generalizing Number

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / NSF IST 85-1154