Exchange Based Noise Spectroscopy of a Single Precessing Spin with STM

ESR-STM is an emerging technique which is capable of detecting the precession of a single spin. We discuss the mechanism of ESR-STM based on a direct exchange coupling between the tunneling electrons and the local precessing spin S. We claim that since the number of tunneling electrons in a single precessing period is small (~20) one may expect a net temporary polarization within this period that will couple via exchange interaction to the localized spin. This coupling will randomly modulate the tunneling barrier and create a dispersion in the tunneling current which is a product of a Larmor frequency component due to the precession of the single spin and the dispersion of the spin of the tunneling electrons. This noise component is spread over the whole frequency range for random white noise spin polarization of electrons. In opposite case the power spectrum of the spins of the tunneling electrons has a peak at zero frequency an elevated noise in the current at omega_L will appear. We discuss the possible source of this spin polarization. We find that for relevant values of parameters signal to noise ratio in the spectral characteristic is 2-4 and is comparable to the reported signal to noise ratio. The magnitude of the current fluctuation is a relatively weak increaing function of the DC current and the magnetic field. The linewidth produced by the back action effect of tunneling electrons on the precessing spin is also discussed.Comment: Added discussion on spin polarization of tunneling electrons and the role of paramagnetic centers on the tip. To be published; 5 pages latex file, 1 ps figure fil

Design approaches in technology enhanced learning

Design is a critical to the successful development of any interactive learning environment (ILE). Moreover, in technology enhanced learning (TEL), the design process requires input from many diverse areas of expertise. As such, anyone undertaking tool development is required to directly address the design challenge from multiple perspectives. We provide a motivation and rationale for design approaches for learning technologies that draws upon Simon's seminal proposition of Design Science (Simon, 1969). We then review the application of Design Experiments (Brown, 1992) and Design Patterns (Alexander et al., 1977) and argue that a patterns approach has the potential to address many of the critical challenges faced by learning technologists

New Modularity of DAP-Kinases: Alternative Splicing of the DRP-1 Gene Produces a ZIPk-Like Isoform

DRP-1 and ZIPk are two members of the Death Associated Protein Ser/Thr Kinase (DAP-kinase) family, which function in different settings of cell death including autophagy. DAP kinases are very similar in their catalytic domains but differ substantially in their extra-catalytic domains. This difference is crucial for the significantly different modes of regulation and function among DAP kinases. Here we report the identification of a novel alternatively spliced kinase isoform of the DRP-1 gene, termed DRP-1β. The alternative splicing event replaces the whole extra catalytic domain of DRP-1 with a single coding exon that is closely related to the sequence of the extra catalytic domain of ZIPk. As a consequence, DRP-1β lacks the calmodulin regulatory domain of DRP-1, and instead contains a leucine zipper-like motif similar to the protein binding region of ZIPk. Several functional assays proved that this new isoform retained the biochemical and cellular properties that are common to DRP-1 and ZIPk, including myosin light chain phosphorylation, and activation of membrane blebbing and autophagy. In addition, DRP-1β also acquired binding to the ATF4 transcription factor, a feature characteristic of ZIPk but not DRP-1. Thus, a splicing event of the DRP-1 produces a ZIPk like isoform. DRP-1β is highly conserved in evolution, present in all known vertebrate DRP-1 loci. We detected the corresponding mRNA and protein in embryonic mouse brains and in human embryonic stem cells thus confirming the in vivo utilization of this isoform. The discovery of module conservation within the DAPk family members illustrates a parsimonious way to increase the functional complexity within protein families. It also provides crucial data for modeling the expansion and evolution of DAP kinase proteins within vertebrates, suggesting that DRP-1 and ZIPk most likely evolved from their ancient ancestor gene DAPk by two gene duplication events that occurred close to the emergence of vertebrates

Dysexecutive symptoms and carer strain following acquired brain injury: changes measured before and after holistic neuropsychological rehabilitation

BACKGROUND: Following acquired brain injury (ABI), deficits in executive functioning (EF) are common. As a result many brain-injured patients encounter problems in every-day functioning, and their families experience significant strain. Previous research has documented the benefits of cognitive rehabilitation for executive dysfunction, and rehabilitation programmes designed to ameliorate functional problems associated with ABI. OBJECTIVES: This study primarily aims to evaluate whether a neuropsychological rehabilitation programme reduces reported symptoms of everyday dysexecutive behaviour and carer strain. METHODS: In this study 66 ABI outpatients attended comprehensive holistic neuropsychological rehabilitation programme. A repeated-measures design was employed to determine the effect of rehabilitation on EF and carer strain, as part of a service evaluation. Outcome measures comprised the dysexecutive questionnaire (DEX/DEX-I) and carer strain index (CSI), applied pre- and post-rehabilitation. RESULTS: Results indicate rehabilitation benefited clients and carers in 5 of 6 DEX/DEX-I subscales, and 2 of 3 CSI subscales, (p<.05). An effect of aetiology on rehabilitation was found on the metacognitive scale of the DEX-I. CONCLUSIONS: Therefore, this study supports a comprehensive holistic neuropsychological rehabilitation programme as effective in reducing reported symptoms of dysexecutive behaviour and carer strain following ABI

Cognitive rehabilitation treatment for mental slowness in conversion disorder : A case report

Cognitive rehabilitation treatment (CRT) has been described in patients with brain injury, but it has not been attempted in cases of cognitive dysfunction without organic cause. This case report describes CRT of neurocognitive impairment in a 54-year-old female patient with conversion disorder (CD). She experienced difficulties with regard to speaking, motor function, and pain symptoms, which developed after stressful life circumstances. Baseline neuropsychological assessment (NPA) showed mental slowness and impaired (working) memory. Time Pressure Management (TPM) was used as CRT to teach the patient a compensatory strategy to overcome mental slowness in 12 sessions. During treatment, physical symptoms were monitored with the Physical Symptom Questionnaire (LKV), and mental slowness with the Mental Slowness Questionnaire (MSQ). After treatment, the LKV score dropped from 85 to 47, indicating 54% treatment response. Mental slowness showed improvement based on the MSQ and was confirmed by an NPA after treatment. Other neurocognitive functions improved as well and the motoric CD symptoms subsided. This case report suggests that improvement of mental slowness, as well as motor CD symptoms, can be achieved by TPM in non-organic neurocognitive impairment in CD. This finding has not been described in the literature. Further research is warranted to explore the efficacy of TPM in CD.Keywords: conversion disorder, neurocognitive impairment, cognitive rehabilitation treatment, time pressure management, pai

The role of the peripheral and central nervous systems in rotator cuff disease

Rotator cuff (RC) disease is an extremely common condition associated with shoulder pain, reduced functional capacities and impaired quality of life. It primarily involves alterations in tendon health and mechanical properties that can ultimately lead to tendon failure. RC tendon tears induce progressive muscular changes that negatively impact surgical reparability of the RC tendons and clinical outcomes. At the same time, a significant base of clinical data suggests a relatively weak relationship between RC integrity and clinical presentation, emphasizing the multifactorial aspects of RC disease. This review aims to summarize the potential contribution of peripheral, spinal and supraspinal neural factors that may: (i) exacerbate structural and functional muscle changes induced by tendon tear, (ii) compromise the reversal of these changes during surgery and rehabilitation, (iii) contribute to pain generation and persistence of pain, iv) impair shoulder function through reduced proprioception, kinematics and muscle recruitment, and iv) help to explain interindividual differences and response to treatment. Given the current clinical and scientific interest in peripheral nerve injury in the context of RC disease and surgery, we carefully reviewed this body of literature with a particular emphasis for suprascapular neuropathy that has generated a large number of studies in the past decade. Within this process, we highlight the gaps in current knowledge and suggest research avenues for scientists and clinicians