Tremor entrainment by patterned low-frequency stimulation

High-frequency test stimulation for tremor suppression is a standard procedure for functional target localization during deep brain stimulation. This method does not work in cases where tremor vanishes intraoperatively, for example, due to general anaesthesia or due to an insertional effect. To overcome this difficulty, we developed a stimulation technique that effectively evokes tremor in a well-defined and quantifiable manner. For this, we used patterned low-frequency stimulation (PLFS), i.e. brief high-frequency pulse trains administered at pulse rates similar to neurons' preferred burst frequency. Unlike periodic single-pulse stimulation, PLFS enables one to convey effective and considerably greater integral charge densities without violation of safety requirements. In a computational investigation of an oscillatory neuronal network temporarily rendered inactive, we found that PLFS evokes synchronized activity, phase locked to the stimulus. While a stronger increase in the amount of synchrony in the neuronal population requires higher stimulus intensities, the portion of synchronously active neurons nevertheless becomes strongly phase locked to PLFS already at weak stimulus intensities. The phase entrainment effect of PLFS turned out to be robust against variations in the stimulation frequency, whereas enhancement of synchrony required precisely tuned stimulation frequencies. We applied PLFS to a patient with spinocerebellar ataxia type 2 (SCA2) with pronounced tremor that disappeared intraoperatively under general anaesthesia. In accordance with our computational results, PLFS evoked tremor, phase locked to the stimulus. In particular, weak PLFS caused low-amplitude, but strongly phase-locked tremor. PLFS test stimulations provided the only functional information about target localization. Optimal target point selection was confirmed by excellent post-operative tremor suppression.     

Nanomechanical study of polycarbonate/boehmite nanoparticles/epoxy ternary composite and their interphases

Thermoplastic modified thermosets are of great interest especially due to their improved fracture toughness. Comparable enhancements have been achieved by adding different nanofillers including inorganic particles such as nanosized boehmite. Here, we present a nanomechanical study of two composite systems, the first comprising a polycarbonate (PC) layer in contact with epoxy resin (EP) and the second consisting of a PC layer containing boehmite nanoparticles (BNP) which is also in contact with an EP layer. The interaction between PC and EP monomer is tested by in situ Fourier transformed infrared (FT-IR) analysis, from which a reaction induced phase separation of the PC phase is inferred. Both systems are explored by atomic force microscopy (AFM) force spectroscopy. AFM force-distance curves (FDC) show no alteration of the mechanical properties of EP at the interface to PC. However, when a PC phase loaded with BNP is put in contact with an epoxy system during curing, a considerable mechanical improvement exceeding the rule of mixture was detected. The trend of BNP to agglomerate preferentially around EP dominated regions and the stiffening effect of BNP on EP shown by spatial resolved measurements of Young's modulus, suggest the effective presence of BNP within the EP phase.     

Automated generation of physical surrogate vehicle models for crash optimization

International Journal of Mechanics and Materials in Design - A challenge in the design and optimization of vehicle structures is the high computational costs required for crash analysis. In this...     

All-optical switching in an asymmetric silicon Fabry-Perot étalon based on the free-carrier plasma effect

We demonstrate all-optical switching at 1.3 and 1.5 μm in the reflection mode of an asymmetric silicon Fabry-Perot étalon by a control beam at 0.85 μm. Both switch-on and switch-off operations are demonstrated at different locations of the etalon. Based on the free-carrier plasma effect, a modulation depth as large as 10% is obtained and a frequency response as high as 0.5 GHz is achieved.     

Diagnosis and investigation of headache

BACKGROUND: Headache is one of the commonest medical complaints. It is usually benign but may be the first presentation of serious disease. OBJECTIVE: This article reviews the symptoms and signs that suggest the diagnosis of the common headaches and discusses which headache presentations require investigation. DISCUSSION: An accurate clinical history is the key to diagnosing the cause of a headache. A new headache of acute onset or progressing over days to weeks or associated with abnormal neurological signs requires investigation.     

Multimodal support for social dynamics in co-located meetings

In this paper, we present a system that employs perceptual technologies (i.e. technologies that perceive the context through sensors such as cameras and microphone) to provide feedback about people’s behaviour in small group meetings. The system measures aspects of behaviour that are relevant to the social dynamics of the meeting, speaking time and gaze behaviour, and provides visual feedback about these aspects to the meeting participants through a peripheral display. We describe the system properties and the perceptual components. Also, we present a study aimed at evaluating the effect of such a system on meeting behaviour. Groups of participants, amounting to 82 participants in all, discussed topics of general interest. Analysis of the data of 58 participants showed that feedback influenced the behaviour of the participants in such a way that it made over-participators speak less and under-participators speak more. Analysis of the micro-patterns of six participants indicated that feedback on gaze behaviour had little effect on the interaction dynamics. We conclude that perceptual technologies can be used to build services that may help people to improve their meeting skills and we consider some ways in which such systems may be deployed in meetings.     

Digitalis intoxication: specifity and significance of cardiac and extracardiac symptoms. part II. Patients with extracardiac symptoms of digitalis intoxications (author's transl)

In 1148 cases the serum digoxin concentration (SDC) was correlated with the extracardiac signs of digitalis intoxication. There is a considerably overlap of SDC levels of patients with and without extracardiac signs of toxicity even though the mean SDC's of these two groups differ significantly. An increasing percentage of clinical intoxicated patients with increasing SDC levels was found at digoxin concentrations of 2.0 ng/ml and higher. At lower SDC levels patients with and without extracardiac signs of digitalis intoxication did not differ significantly in their mean SDC but in mean age and in mean creatinine concentration indicating that at least part of the symptoms in these patients might be due to a more severe illness. We could show that many of the extracardiac signs of digitalis intoxication are also seen in patients with impaired kidney function at low SDC levels and may lead to a wrong diagnosis. The most common complaint in patients with SDC's of 2.0 ng/ml and more is nausea (39.4%), followed by tiredness (30.4%), dizzyness (23.7%), vomiting (23.1%), headache (16.0%), visual disturbances (13,5%), colour (yellow) seeing (6;7%), diarrhea (4.2%) and severe neuro-psychiatric disturbances (3.8%). In patients with digitalis-induced arrhythmias the sequence of symptoms is the same only with a somewhat higher percentage rate. Only about one half of the patients with digitalis-induced arrhythmias and SDC values up to 2.5 ng/ml showed also extracardiac signs of intoxication. Therefore these signs are not to be taken as early symptoms of digitalis intoxication. Divided into subgroups (patients with/without digitalis-induced arrhythmias, patients with SDC values of more/less than 2.0 ng/ml) the patients with and without extracardiac signs of digitalis toxicity are compared with each other in regard to: mean body height and weight, concentration of digoxin, potassium and creatinine, digoxin dosage and mean age. The greatest differences were found between patients with combined cardiac and extracardiac signs of intoxication and patients with neither cardiac nor extracardiac signs of intoxication: These intoxicated patients are of significantly higher mean age and lower body weight, their mean concentration of digoxin and creatinine and the digoxin dosage administered are significantly greater, but there is no significant difference in potassium concentration. An important group of patients, namely the elderly with impaired kidney function, are especially prone to develop digitalis intoxication. In this group, however, the extracardial symptoms are of little benefit in the diagnosis of digitalis intoxication. In these patients rhythm disturbances and intoxication-like symptoms are frequently caused by other reasons. In most cases the SDC value can clarify the diagnosis without withdrawal of the drug.     

Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean

Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from 相似文献   

Design principles of microwave applicators for small-scale process equipment

In this work, we bridge fundamental electromagnetics and chemical process engineering with the aim to develop tailor-made (microwave or high frequency radiowave) applicators for heating of micro- and small-structured process equipment. In this context, two simple configurations with well-defined single mode field patterns, namely a cylindrical and a rectangular cavity both containing a homogeneous cylindrical load were analyzed either analytically or numerically. We present design charts that illustrate how important operating, geometric and materials parameters relate with each other. It was found that load size, heating uniformity and desired frequency mutually constrain one another. The required cavity volume increases with increasing heating uniformity or with increasing load permittivity for a given heating uniformity requirement. At the popular frequency of 2.45 GHz the load is restricted to a small size, compared to the cavity size, in order to achieve high heating uniformity. Opting for lower resonance frequencies allows for bigger load volumes to be heated uniformly. Furthermore, we show that the relations found for the operating, structural and material properties on the basis of these simple configurations can provide design guidelines and first approximations for more realistic process equipment geometries.     

Thermoelectric properties of hot-pressed Ruddlesden-Popper phases CaO(CaMnO3)m

We investigated the Ruddlesden-Popper series CaO(CaMnO₃)_m with m = 1, 2, 3, ∞, to study the impact of the varying amounts of CaO layers on their thermoelectric properties. Previous studies showed that highly dense samples are difficult to obtain due to the refractory nature of these materials. In this study, we managed to obtain dense pellets during a classical hot-pressing step, if and only if the samples were subjected to extended ball-milling prior to pressing, resulting in crystallite sizes of 30–35 nm after hot-pressing. The sample with the largest amount of CaO layers (m = 1) had the lowest electrical and thermal conductivity, and the highest Seebeck coefficient, as predicted. Ultimately the perovskite CaMnO₃ (m = ∞, no CaO layers) exhibited the best thermoelectric properties.