Spatial light modulator-controlled alignment and spinning of birefringent particles optically trapped in an array

We demonstrate the use of a phase-only liquid-crystal spatial light modulator (SLM) for polarization-controlled rotation and alignment of an array of optically trapped birefringent particles. A collimated beam incident upon a two-dimensional lenslet array yields multiple foci, scaled to produce optical gradient traps with efficient three-dimensional trapping potentials. The state of polarization of each trapping beam is encoded by the SLM, which acts as a matrix of wave plates with computer-controlled phase retardations. Control of the rotation frequency and alignment direction of the particles is achieved by the transfer of tunable photon spin angular momentum.     

Multiconjugate adaptive optics for large telescopes: analytical control of the mirror shapes

We present an analytical algorithm for deriving the shapes of the deformable mirrors to be used for multiconjugate adaptive correction on a large telescope. The algorithm is optimal in the limit where the overlap of the wave-front contributions from relevant atmospheric layers probed by the guide stars is close to the size of the pupil. The fundamental principle for correction is based on a minimization of the sum of the residual power spectra of the phase fluctuations seen by the guide stars after correction. On the basis of the expressions for the mirror shapes, so-called layer transfer functions describing the distribution of the correction of a single atmospheric layer among the deformable mirrors and the resulting correction of that layer have been derived. It is shown that for five guide stars distributed in a regular cross, two- and three-mirror correction will be possible only up to a maximum frequency defined by the largest separation of the conjugate altitudes of the mirrors and by the angular separation of the guide stars. The performance of the algorithm is investigated in the K band by using a standard seven-layer atmosphere. We present results obtained for two guide-star configurations: a continuous distribution within a given angular radius and a five-star cross pattern with a given angular arm length. The wave-front fluctuations are subjected to correction using one, two, and three deformable mirrors. The needed mirror dynamic range is derived as required root-mean-square stroke and actuator pitch. Finally the performance is estimated in terms of the Strehl ratio obtained by the correction as a function of field angle. No noise has been included in the present analysis, and the guide stars are assumed to be at infinity.     

Neurosurgical treatment of trigeminal neuralgia. A comparative study of alcohol block, neurectomy and electrocoagulation

The objective was to assess the present condition of patients previously treated with neurosurgical procedures for trigeminal neuralgia (TN). Between 1976 and 1991, 383 patients were treated for TN at the Department of Neurosurgery, Hvidovre Hospital. The latest surgical intervention performed was radiofrequency coagulation (64%), neurectomy (18%), alcohol block (16%), trigeminal tractotomy (1%), and microvascular decompression (1%). Questionnaires were sent to 316 patients treated neurosurgically for trigeminal neuralgia during the 16 year period. After radiofrequency coagulation, neurectomy and alcohol block, 83, 51 and 42% respectively experienced a pain free postoperative period. At present 49, 17 and 18% were without pain and 33, 21 and 36% had less pain compared with the preoperative state. Sequelae were described in 65, 57 and 49% of the patients. The four most common sequelae were hypaesthesia, paraesthesia, eye complaints, and dysaesthesia. If relevant pharmacotherapy has been tried without benefit, radiofrequency coagulation may still be considered as a treatment of trigeminal neuralgia.     

Monitoring Portland cement hydration: Comparison of methods

Various experimental methods of monitoring Portland cement hydration are compared. The methods are quantitative X-ray diffraction analysis (QXRD), measurement of non-evaporable water as loss on ignition and by thermogravimetry, conduction calorimetry and measurement of chemical shrinkage. Correlations between these different measures of hydration are obtained using samples of paste for three different Portland cements. The correlation between non-evaporable water and QXRD data was dependent on the chemical composition of the cement and shows that less water was chemically bound at early ages, for a given amount of cement reacted. A near-linear relationship was found between chemical shrinkage and QXRD data. The correlation between heat of hydration and QXRD data was approximately linear and not greatly affected by cement type.     

Evaluating Three Criteria for Establishing Cue-Search Hierarchies in Inferential Judgment.

The authors identify and provide an integration of 3 criteria for establishing cue-search hierarchies in inferential judgment. Cues can be ranked by information value according to expected information gain (Bayesian criterion), cue-outcome correlation (correlational criterion), or ecological validity (accuracy criterion). All criteria significantly predicted information acquisition behavior; however, in 3 experiments, the most successful predictor was the correlational criterion (followed by the Bayesian). Although participants showed sensitivity to task constraints, searching for less information when it was more expensive (Experiment 1) and when under time constraints (Experiment 2), concomitant changes in the relative frequency of acquisition of cues with different information values were not observed. A rational analysis illustrates why such changes in the frequency of acquisition would be beneficial, and reasons for the failure to observe such behavior are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size constancy in schizophrenia: A reanalysis.

Perceptual differences between normals and schizophrenics revealed by traditional size-constancy experiments are questionable because of S variability, procedural difficulties, and problems inherent in traditional psychophysical methods. A review of the literature reveals few consistent results. The present study compared normals, paranoid schizophrenics, and nonparanoid schizophrenics on a size-constancy task which allowed derivation of additional dependent variables from signal-detection and uncertainty analysis. No group differences were revealed using the size-constancy procedure, but signal-detection analysis indicated nonparanoid schizophrenics were significantly lower in perceptual sensitivity. Uncertainty analysis revealed additional response dispositions characteristic of the schizophrenic groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality, anxiety, and muscle tension as determinants of response stereotypy.

"The stereotypy and bias with which Ss used the number series 1-11 in a pseudo-ESP experiment was determined under three experimental conditions: (a) experimentally induced anxiety, (b) experimentally induced muscular tension, and (c) a control condition." Ss scoring in the highest and lowest quartile of the MMPI psychasthenia scale were used. "Under the control condition, the high group was found to be more stereotyped and predictable in their use of the number responses, but under the anxiety and muscle tension conditions this relationship was reversed." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some characteristics of posthypnotic amnesia.

This experiment investigated (a) the differences in post-hypnotic amnesic characteristics of Ss with high and low hypnotic susceptibility and (b) the extent of the amnesia. The experimental Ss were presented 6 words under hypnosis with instructions for amnesia. The simulation Ss pretended they were hypnotized and received the words with instructions for posthypnotic amnesia. The control Ss were given the words with instructions only to remember them. Recognition, recall, and associative tests, administered immediately after, assessed the amnesia. Posthypnotic amnesia impaired recall and recognition among the experimental Ss, but did not reduce the availability of the words as associative responses. The simulating Ss overplayed their amnesic role and also showed impaired performance on the associative tests. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction of chloride ingress and binding in cement paste

This paper summarizes recent work on an analytical model for predicting the ingress rate of chlorides in cement-based materials. An integral part of this is a thermodynamic model for predicting the phase equilibria in hydrated Portland cement. The model’s ability to predict chloride binding in Portland cement pastes at any content of chloride, alkalis, sulfates and carbonate was verified experimentally and found to be equally valid when applied to other data in the literature. The thermodynamic model for predicting the phase equilibria in hydrated Portland cement was introduced into an existing Finite Difference Model for the ingress of chlorides into concrete which takes into account its multi-component nature. The “composite theory” was then used to predict the diffusivity of each ion based on the phase assemblage present in the hydrated Portland cement paste. Agreement was found between profiles for the Cl/Ca ratio predicted by the model and those determined experimentally on 0.45 water/powder ratio Portland cement pastes exposed to 650 mM NaCl for 70 days. This confirms the assumption of essentially instantaneous binding where quasi-equilibrium is established locally. This does not imply steady state diffusion however. It simply implies that incremental increases in the concentration of diffusing ions in the pore solution will rapidly re-equilibrate with the hydrates present locally, where, the greater the ratio of bound to free ions, the greater the buffering effect which slows down the rate of ingress. In the case of chlorides, this buffering effect is greatest at high contents of AFm (AFm is aluminium ferrite compounds with a single (mono) formula unit CaX.) phase and low alkali metal contents.