Author Correction: Demonstration of sub-luminal propagation of single-cycle terahertz pulses for particle acceleration.

The original version of this Article contained an error in the abstract, referring to "multi-megawatt-per-metre" instead of "multi-megavolt-per-metre". This has now been corrected in both the PDF and HTML versions of the Article.

Demonstration of sub-luminal propagation of single-cycle terahertz pulses for particle acceleration.

The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of sub-luminal phase-velocity in laser-driven particle acceleration schemes imposes a limit on the total acceleration achievable in free space, and necessitates the use of dispersive structures or waveguides for extending the field-particle interaction. We demonstrate a travelling source approach that overcomes the sub-luminal propagation limits. The approach exploits ultrafast optical sources with slow group velocity propagation, and a group-to-phase front conversion through nonlinear optical interaction. The concept is demonstrated with two terahertz generation processes, nonlinear optical rectification and current-surge rectification. We report measurements of longitudinally polarised single-cycle electric fields with phase and group velocity between 0.77c and 1.75c. The ability to scale to multi-megavolt-per-metre field strengths is demonstrated. Our approach paves the way towards the realisation of cheap and compact particle accelerators with femtosecond scale control of particles.Controlled generation of terahertz radiation with subluminal phase velocities is a key issue in laser-driven particle acceleration. Here, the authors demonstrate a travelling-source approach utilizing the group-to-phase front conversion to overcome the sub-luminal propagation limit.

Glass formation via structural fragmentation of a 2D coordination network.

The structure of a glass obtained by the melt quenching of a two-dimensional (2D) coordination network was examined. X-ray analyses disclosed a 2D-to-0D structural transformation before and after glass formation. The mechanism is unique to coordination compounds, as it is characterized by labile and flexible coordination bonds.

Role of misalignment-induced angular chirp in the electro-optic detection of THz waves.

A general description of electro-optic detection including non-collinear phase matching and finite transverse beam profiles is presented. It is shown theoretically and experimentally that non-collinear phase matching in ZnTe (and similar materials) produces an angular chirp in the χ(2)-generated optical signal. Due to this, in non-collinear THz and probe arrangements such as single-shot THz measurements or through accidental misalignment, measurement of an undistorted THz signal is critically dependent on having sufficient angular acceptance in the optical probe path. The associated spatial walk-off can also preclude the phase retardation approximation used in THz-TDS. The rate of misalignment-induced chirping in commonly used ZnTe and GaP schemes is tabulated, allowing ready analysis of a detection system.

The use of symptom validity testing in the diagnosis of functional sensory and memory deficits: a review.

This paper reviews the use of a modern psychophysical technique known as symptom validity testing. The technique employs a forced choice procedure providing an objective method for distinguishing between functional and organic aetiology in cases with sensory or memory deficit. The determination of functionality is by the objective demonstration that behaviour is controlled by stimuli in the sense modality in which the deficit is claimed. The data can be evaluated using conventional statistical techniques. The method is an advance on classical psychophysical methods as it does not depend upon the patient reporting whether he can or cannot perceive a single stimulus.

Symptom-validity testing of feigned sensory or memory deficits: a further elaboration for subjects who understand the rationale.

Symptom-validity testing has been used to detect feigning in patients claiming sensory and memory deficits. Such patients typically give significantly fewer correct responses on forced-choice testing than would be expected by chance. Some subjects have been able to understand the rationale and respond at the chance level. Some have evaded detection by elaborations of the technique which seek evidence of non-randomness in the sequence of correct and incorrect responses. This paper reports the stratagem used by one such subject and a further elaboration of the technique by which it was detected.

Behaviour modification by successive approximation: Saxon age examples from Bede.

This paper describes the treatment of a case of mutism in Saxon England. The shaping procedure employed was similar to that reported in modern behaviour modification studies. The paper quotes from a seventh century papal letter showing an understanding of the principle of shaping as applied to populations.

Paradoxical psychotherapy in a case of transvestism.

Paradoxical psychotherapy succeeded in removing the compulsive element and reducing the guilt attached to transvestism in a male transvestite patient. Cross-dressing at home became acceptable to him and the temptation to cross-dress in public ended. Data suggested three independent motivational systems in this patient.

Psychiatric morbidity in acromegaly.

Previous reports on psychiatric morbidity in acromegaly have been unsystematic. This study examined 51 acromegalic patients for psychiatric morbidity using the General Health Questionnaire and a standard psychiatric interview, the Present State Examination. Although psychiatric morbidity was higher in the female than the male acromegalics, the study showed no increase in psychiatric morbidity in general, nor an increased incidence of depression, in comparison with general population and patient samples. No relationship was found between growth hormone levels and psychiatric morbidity. The results raise the question whether acromegalic patients show lower psychiatric morbidity than expected from patients with such an illness. The data suggest that previous reports of depression in acromegalic patients examplify the simple coincidence of a likely and an unlikely condition.

A monozygotic twin pair discordant for anorexia nervosa.

This case study describes a female monozygotic twinship in which one of the twins presented with anorexia nervosa. The case supports the suggestion from the few such discordant pairs previously reported that the affected twin tends to have been relatively disadvantaged from an early age and to be the less dominant of the pair. A review of previously reported cases suggests a concordance rate for anorexia nervosa of about 50% in female MZ twin pairs. Some methodological problems associated with the derivation of such estimates are noted.

On an empirical calculus of reinforcement magnitude.

Current available measures of sexual orientation are briefly reviewed. A novel sexual orientation measure is proposed, based on experiments in operant psychology. Previous relevant studies are reviewed, and it is suggested that a deficiency is their reliance on a single response as the dependent variable. The matching law is introduced, and it is argued that this provides a potentially powerful framework within which the relative reinforcement magnitudes of sexual stimuli may be computed, using as the dependent variable the relative rates of two responses. The proposed assessment method provides a means of answering the question "What is the reinforcement magnitude of various classes of erotic stimuli for a given individual?"