2,778 research outputs found
Tremor in motor neuron disease may be central rather than peripheral in origin
BACKGROUND AND PURPOSE:
Motor neuron disease (MND) refers to a spectrum of degenerative diseases affecting motor neurons. Recent clinical and post-mortem observations have revealed considerable variability in the phenotype. Rhythmic involuntary oscillations of the hands during action, resembling tremor, can occur in MND, but their pathophysiology has not yet been investigated.
METHODS:
A total of 120 consecutive patients with MND were screened for tremor. Twelve patients with action tremor and no other movement disorders were found. Ten took part in the study. Tremor was recorded bilaterally using surface electromyography (EMG) and triaxial accelerometer, with and without a variable weight load. Power spectra of rectified EMG and accelerometric signal were calculated. To investigate a possible cerebellar involvement, eyeblink classic conditioning was performed in five patients.
RESULTS:
Action tremor was present in about 10% of our population. All patients showed distal postural tremor of low amplitude and constant frequency, bilateral with a small degree of asymmetry. Two also showed simple kinetic tremor. A peak at the EMG and accelerometric recordings ranging from 4 to 12 Hz was found in all patients. Loading did not change peak frequency in either the electromyographic or accelerometric power spectra. Compared with healthy volunteers, patients had a smaller number of conditioned responses during eyeblink classic conditioning.
CONCLUSIONS:
Our data suggest that patients with MND can present with action tremor of a central origin, possibly due to a cerebellar dysfunction. This evidence supports the novel idea of MND as a multisystem neurodegenerative disease and that action tremor can be part of this condition
A simple all-microwave entangling gate for fixed-frequency superconducting qubits
We demonstrate an all-microwave two-qubit gate on superconducting qubits
which are fixed in frequency at optimal bias points. The gate requires no
additional subcircuitry and is tunable via the amplitude of microwave
irradiation on one qubit at the transition frequency of the other. We use the
gate to generate entangled states with a maximal extracted concurrence of 0.88
and quantum process tomography reveals a gate fidelity of 81%
Searching for "monogenic diabetes" in dogs using a candidate gene approach
BACKGROUND: Canine diabetes is a common endocrine disorder with an estimated breed-related prevalence ranging from 0.005% to 1.5% in pet dogs. Increased prevalence in some breeds suggests that diabetes in dogs is influenced by genetic factors and similarities between canine and human diabetes phenotypes suggest that the same genes might be associated with disease susceptibility in both species. Between 1-5% of human diabetes cases result from mutations in a single gene, including maturity onset diabetes of the adult (MODY) and neonatal diabetes mellitus (NDM). It is not clear whether monogenic forms of diabetes exist within some dog breeds. Identification of forms of canine monogenic diabetes could help to resolve the heterogeneity of the condition and lead to development of breed-specific genetic tests for diabetes susceptibility. RESULTS: Seventeen dog breeds were screened for single nucleotide polymorphisms (SNPs) in eighteen genes that have been associated with human MODY/NDM. Six SNP associations were found from five genes, with one gene (ZFP57) being associated in two different breeds. CONCLUSIONS: Some of the genes that have been associated with susceptibility to MODY and NDM in humans appear to also be associated with canine diabetes, although the limited number of associations identified in this study indicates canine diabetes is a heterogeneous condition and is most likely to be a polygenic trait in most dog breeds. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/2052-6687-1-8) contains supplementary material, which is available to authorized users
High coherence hybrid superconducting qubit
We measure the coherence of a new superconducting qubit, the {\em
low-impedance flux qubit}, finding s. It is a
three-junction flux qubit, but the ratio of junction critical currents is
chosen to make the qubit's potential have a single well form. The low impedance
of its large shunting capacitance protects it from decoherence. This qubit has
a moderate anharmonicity, whose sign is reversed compared with all other
popular qubit designs. The qubit is capacitively coupled to a high-Q resonator
in a configuration, which permits the qubit's state to be read out
dispersively
TMS excitability study in essential tremor: Absence of gabaergic changes assessed by silent period recordings
BACKGROUND: Essential tremor (ET) is thought to emerge from activity in a distributed cerebello-thalamo-cortical network. It has been proposed that the network goes into oscillation because of abnormal GABAergic inhibitory transmission. OBJECTIVE: To test this idea by investigating GABAergic circuitry in motor cortex using transcranial magnetic stimulation (TMS). METHODS: Motor cortex excitability was examined using TMS in 21 patients with essential tremor and in 20 control subjects. Resting and active motor threshold (RMT, AMT) and input-output curves examined corticospinal excitability. Contralateral silent period (cSP) at a different range of stimulation intensities, and the ipsilateral silent period (iSP) using a stimulus intensity of 150% RMT were used as measures of GABAergic function. RESULTS: RMT and AMT were significantly lower in patients than controls and patients had a steeper I/O curve. However, there were no significant differences in either cSP at different intensities or in iSP. CONCLUSION: We found no evidence in favour of the GABA hypothesis in ET
Efficient measurement of quantum gate error by interleaved randomized benchmarking
We describe a scalable experimental protocol for obtaining estimates of the
error rate of individual quantum computational gates. This protocol, in which
random Clifford gates are interleaved between a gate of interest, provides a
bounded estimate of the average error of the gate under test so long as the
average variation of the noise affecting the full set of Clifford gates is
small. This technique takes into account both state preparation and measurement
errors and is scalable in the number of qubits. We apply this protocol to a
superconducting qubit system and find gate errors that compare favorably with
the gate errors extracted via quantum process tomography.Comment: 5 pages, 2 figures, published versio
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