Tremor Amplitude Research Articles

Progression of tremor in early stages of Parkinson's disease: a clinical and neuroimaging study.

Rest tremor is one of the cardinal signs of Parkinson's disease. Kinetic and postural tremors may also occur. The coexistence of these three types of tremor at disease onset and their subsequent progression could have important clinical and therapeutic implications but remain to be fully elucidated. We aimed to: (i) evaluate prevalence and progression of these three types of tremor in early stages of the disease; and (ii) investigate longitudinally the relationship between dopaminergic and serotonergic terminal dysfunction, rest tremor severity and its response to dopaminergic therapy. The Parkinson's Progressive Markers Initiative database provided the baseline and 2-year follow-up clinical ratings and 123ioflupane-fluoropropyl-carbomethoxy-3-beta-4-iodophenyltropane (123I-FP-CIT) single photon emission computed tomography images for this study. 123I-FP-CIT measured putamen dopamine transporter and median raphe serotonin transporter availability. A raphe/putamen uptake ratio was calculated for each patient as an index of relative involvement of these structures. Clinical analysis of tremor was conducted on 378 patients: 87.8% presented with tremor at baseline; rest tremor occurred in 69.6% of patients at baseline; and 67.9% at follow-up. Postural and kinetic tremors occurred in about 50% of patients at both baseline and follow-up. Over 20% of patients presenting with tremor did not exhibit a rest component at baseline. The number of patients with isolated rest tremor was halved at follow-up. In tremor predominant patients, rest tremor severity was inversely correlated with raphe serotonin transporter availability both at baseline and follow-up (baseline: constancy P < 0.05, tremor index P < 0.05; follow-up: amplitude P < 0.05, constancy P < 0.05, tremor index P < 0.05). In the entire cohort, more severe tremor scores correlated with lower raphe/putamen uptake ratio values, indicative of more severe raphe dysfunction (baseline: constancy P < 0.01, tremor index P < 0.05; follow-up: amplitude P < 0.01, constancy P < 0.001, tremor index P < 0.001). The percentage of improvement in rest tremor amplitude after acute dopaminergic therapy was smaller in patients with lower raphe/putamen uptake ratio values (P < 0.01). Rest tremor is the most represented type of tremor in early Parkinson's disease. However, postural and kinetic tremor can affect approximately half of these patients and can occur in absence of resting tremor. As disease progresses, both raphe serotonergic dysfunction and putamen dopamine depletion could contribute to the occurrence of rest tremor. The former is linked to more severe tremor scores and poorer response to dopaminergic therapy. Non-dopaminergic treatments might be beneficial for patients whose tremor is associated with a raphe-predominant dysfunction.

Clinical and cognitive aspects of functional (psychogenic) tremor

Functional (psychogenic) tremor is the most common functional movement disorder. Characteristic clinical features, so called red flags, can help to make the clinical distinction of this type from other tremor disorders. The most common features include the variability of frequency and amplitude. Clinical examination should include different types of distraction including motor or cognitive tasks or testing the influence of suggestibility on tremor amplitude, frequency or direction. Patients often report sudden onset and remissions that may last for months or even years. In some cases, the tremor is only present in highly specific situations. Although functional tremor shares characteristics with voluntary actions, patients experience their abnormal movements as involuntary. Recent experimental approaches have revealed an impairment in sense of agency. The diagnosis can be supported by neurophysiological measurements including accelerometry, which achieved asensitivity of 89.5% and aspecificity of 95.9% in avalidated test battery, thus providing auseful additional diagnostic tool. Psychotherapeutic treatment is indicated in patients with and without evident psychological symptoms. Aspecific physiotherapeutic approach for functional tremor is re-trainment.

Tremor severity rating by Markov chains

The paper deals with mathematical modeling tools for tremor quantification, a problem arising in e.g. clinical applications and sports. Tremor is an involuntary repetitive movement of extremities, head, or trunk that occurs in disease but also in health, due to e.g. strain or fatigue. Quantification of tremor is traditionally performed by ocular observation, while numerous technologies based on wearable accelerometer data exist and have been tested in medical practice. The currently available approaches rely on spectral analysis that reduces a fundamentally nonlinear and non-stationary phenomenon to a linear combination of harmonic components. The classical nonlinear identification methods are as well of limited use because the underlying system is essentially autonomous and produces sustained oscillations without exogenous excitation. An alternative view on tremor is therefore adopted that treats the problem from a severity rating perspective aligned with clinical practices. The tremor amplitude is modelled by a Markov chain, where the states represent the predefined intervals of severity. A comparison with a previously developed event-based method of tremor quantification is provided on data collected using a smart phone in a patient diagnosed with Parkinson disease and undergoing Deep Brain Stimulation therapy. The experimental procedure is unobtrusive and can be implemented in a way that is transparent to the patient.

A role for accelerometry in the differential diagnosis of tremor syndromes.

Accelerometry is a reliable tool for gauging the occurrence, amplitude and frequency of tremor. However, there is no consensus on criteria for accelerometric diagnosis of tremor syndromes. We enrolled 20 patients with essential tremor (ET), 20 with dystonic tremor (DT), and 20 with classic parkinsonian tremor (PD-T), all meeting accepted clinical criteria. All the patients underwent dopamine transporter imaging (by means of single-photon emission computed tomography) and triaxial accelerometric tremor analysis. The latter revealed groupwise differences in tremor frequency, peak dispersion, spectral coherence, unilaterality and resting vs action tremor amplitude. From the above, five diagnostic criteria were extrapolated for each condition. Receiver operating characteristic curves, depicting criteriabased scoring of each tremor type, showed negligible declines in specificity for scores ≥4 in patients with ET or DT and scores ≥3 in patients with PD-T, thus providing a simple scoring method (accelerometrically derived) for differential diagnosis of the principal tremor syndromes.

The influence of the fault zone width on land surface vibrations after the high-energy tremor in the “Rydułtowy-Anna” hard coal mine

In the article, a numerical analysis of the impact of the width of the fault zone on land surface tremors on the area of the “Rydułtowy – Anna” hard coal mine was performed. The analysis covered the dynamic impact of the actual seismic wave after the high-energy tremor of 7 June 2013. Vibrations on the land surface are a measure of the mining damage risk. It is particularly the horizontal components of land vibrations that are dangerous to buildings which is reflected in the Mining Scales of Intensity (GSI) of vibrations. The run of a seismic wave in the rock mass from the hypocenter to the area’s surface depends on the lithology of the area and the presence of fault zones. The rock mass network cut by faults of various widths influences the amplitude of tremor reaching the area’s surface. The analysis of the impact of the width of the fault zone was done for three alternatives.

Analyzing the continuous volcanic tremors detected during the 2015 phreatic eruption of the Hakone volcano

In the present study, we analyze the seismic signals from a continuous volcanic tremor that occurred during a small phreatic eruption of the Hakone volcano, in the Owakudani geothermal region of central Japan, on June 29, 2015. The signals were detected for 2 days, from June 29 to July 1, at stations near the vents. The frequency component of the volcanic tremors showed a broad peak within 1–6 Hz. The characteristics of the frequency component did not vary with time and were independent of the amplitude of the tremor. The largest amplitude was observed at the end of the tremor activity, 2 days after the onset of the eruption. We estimated the location of the source using a cross-correlation analysis of waveform envelopes. The locations of volcanic tremors are determined near the vents of eruption and the surface, with the area of the upper extent of an open crack estimated using changes in the tilt. The duration-amplitude distribution of the volcanic tremor was consistent with the exponential scaling law rather than the power law, suggesting a scale-bound source process. This result suggests that the volcanic tremor originated from a similar physical process occurring practically in the same place. The increment of the tremor amplitude was coincident with the occurrence of impulsive infrasonic waves and vent formations. High-amplitude seismic phases were observed prior to the infrasonic onsets. The time difference between the seismic and infrasonic onsets can be explained assuming a common source located at the vent. This result suggests that both seismic and infrasonic waves are generated when a gas slug bursts at that location. The frequency components of the seismic phases observed just before the infrasonic onset were generally consistent with those of the tremor signals without infrasonic waves. The burst of a gas slug at the surface vent may be a reasonable model for the generation mechanism of the volcanic tremor and the occurrence of impulsive infrasonic signals.

Comparison of the Fahn-Tolosa-Marin Clinical Rating Scale and the Essential Tremor Rating Assessment Scale.

The Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (FTM) has been used in large trials for essential tremor (ET), but its anchors for ratings from 0 to 4 of upper limb tremor are probably too low for patients with severe tremor (tremor amplitude >4 cm; grade 4). The Essential Tremor Rating Assessment Scale (TETRAS) is a validated clinical scale designed specifically for the assessment of ET severity. TETRAS has anchors that span a larger range of tremor amplitudes (>20 cm = grade 4), making it more suitable for assessing patients with severe ET. However, there is no direct comparison of these scales in any clinical trial. Upper limb postural and kinetic tremor items from both scales were compared using blinded, video-recorded examinations of patients with moderate-to-severe ET who participated in a trial of focused ultrasound thalamotomy. FTM ratings of postural and kinetic tremor correlated strongly with those of TETRAS. However, FTM exhibited a ceiling effect for severe tremor. Rest tremor, exclusive to FTM, correlated poorly with postural and kinetic tremor and had very poor test-retest reliability. In contrast, wing-beating postural tremor, exclusive to TETRAS, exhibited excellent test-retest reliability and a strong correlation with kinetic and limbs-extended-forward postural tremor. Test-retest reliabilities of the other TETRAS and FTM ratings were excellent, and both scales had good sensitivity to treatment effect. TETRAS has 2 main advantages over FTM in the assessment of tremor severity: (1) the absence of a ceiling effect in patients with severe ET, and (2) the inclusion of wing-beating tremor.

Physiological tremor increases when skeletal muscle is shortened: implications for fusimotor control.

In tonic, isometric, plantarflexion contractions, physiological tremor increases as the ankle joint becomes plantarflexed. Modulation of physiological tremor as a function of muscle stretch differs from that of the stretch reflex amplitude. Amplitude of physiological tremor may be altered as a function of reflex pathway gains. Healthy humans likely increase their γ-static fusimotor drive when muscles shorten. Quantification of physiological tremor by manipulation of joint angle may be a useful experimental probe of afferent gains and/or the integrity of automatic fusimotor control. The involuntary force fluctuations associated with physiological (as distinct from pathological) tremor are an unavoidable component of human motor control. While the origins of physiological tremor are known to depend on muscle afferentation, it is possible that the mechanical properties of muscle-tendon systems also affect its generation, amplification and maintenance. In this paper, we investigated the dependence of physiological tremor on muscle length in healthy individuals. We measured physiological tremor during tonic, isometric plantarflexion torque at 30% of maximum at three ankle angles. The amplitude of physiological tremor increased as calf muscles shortened in contrast to the stretch reflex whose amplitude decreases as muscle shortens. We used a published closed-loop simulation model of afferented muscle to explore the mechanisms responsible for this behaviour. We demonstrate that changing muscle lengths does not suffice to explain our experimental findings. Rather, the model consistently required the modulation of γ-static fusimotor drive to produce increases in physiological tremor with muscle shortening - while successfully replicating the concomitant reduction in stretch reflex amplitude. This need to control γ-static fusimotor drive explicitly as a function of muscle length has important implications. First, it permits the amplitudes of physiological tremor and stretch reflex to be decoupled. Second, it postulates neuromechanical interactions that require length-dependent γ drive modulation to be independent from α drive to the parent muscle. Lastly, it suggests that physiological tremor can be used as a simple, non-invasive measure of the afferent mechanisms underlying healthy motor function, and their disruption in neurological conditions.

42. Functional Tremor: When neurophysiology makes the difference

Functional tremor (FT) still remains a challenge for clinicians; here, we propose a simple and fast test battery for an early diagnosis of FT. We enrolled ten patients with probable FT and compared them with patients with essential tremor (ET) or tremor-dominant Parkinson’s Disease (PD). Surface polymyography was bilaterally performed with arms relaxed, with arms outstretched at shoulder level without or with a 500-g mass attached to the wrist (“mass loading”), during voluntary contralateral motor activation and while performing ballistic movements. We also asked to the patient to use the index finger of the left hand to tap in time with a metronome at rates of 1, 3 and 5 Hz. At the end of the test, we recorded Blink Reflex Habituation. Polymyography revealed (a) a paradoxical increase of tremor amplitude with mass loading, (b) jerks’ synchronization between antagonistic muscles performing voluntary contralateral motor activation and (c) tremor inhibition during a ballistic movement. Co-activation sign was present. Finally, all the patients showed a Blink-Reflex habituation preserved. Our results prompt further studies to integrate clinical and electrodiagnostic criteria in the whole field of hyperkinetic movement disorders, exploring the floating border between organic and functional disease.

Measuring effusion rates of obsidian lava flows by means of satellite thermal data

Space-based thermal data are increasingly used for monitoring effusive eruptions, especially for calculating lava discharge rates and forecasting hazards related to basaltic lava flows. The application of this methodology to silicic, more viscous lava bodies (such as obsidian lava flows) is much less frequent, with only few examples documented in the last decades. The 2011–2012 eruption of Cordón Caulle volcano (Chile) produced a voluminous obsidian lava flow (~0.6km3) and offers an exceptional opportunity to analyze the relationship between heat and volumetric flux for such type of viscous lava bodies. Based on a retrospective analysis of MODIS infrared data (MIROVA system), we found that the energy radiated by the active lava flow is robustly correlated with the erupted lava volume, measured independently. We found that after a transient time of about 15days, the coefficient of proportionality between radiant and volumetric flux becomes almost steady, and stabilizes around a value of ~5×106Jm−3. This coefficient (i.e. radiant density) is much lower than those found for basalts (~1×108Jm−3) and likely reflects the appropriate spreading and cooling properties of the highly-insulated, viscous flows. The effusion rates trend inferred from MODIS data correlates well with the tremor amplitude and with the plume elevation recorded throughout the eruption, thus suggesting a link between the effusive and the coeval explosive activity. Modelling of the eruptive trend indicates that the Cordón Caulle eruption occurred in two stages, either incompletely draining a single magma reservoir or more probably tapping multiple interconnected magmatic compartments.

Upper Limb Intention Tremor in Multiple Sclerosis: An Evidence-Based Review of Assessment and Treatment.

To present the current knowledge on the characteristics, assessment, and treatment of upper limb intention tremor to inform and improve future intervention studies in patients with multiple sclerosis (MS), we conducted a literature review for articles on upper limb intention tremor in patients with MS. Two reviewers conducted searches in PubMed, Web of Science, and MEDLINE (Ovid). Relevant articles, sorted on inclusion criteria, were examined for descriptions and assessments of upper limb intention tremor, and intervention studies were evaluated based on treatment type. Eight descriptive studies were found reporting on the incidence and severity of tremor, impairments, and lesion load. Ten studies focused on measurement of tremor using various assessments. Intervention studies included eight articles using a diverse set of noninvasive techniques mainly showing transient reduction in tremor amplitude and temporary increase in function. Eighteen studies on pharmacologic interventions were found, with most displaying positive outcomes and mediation of tremor; others showed little to no benefit. Surgical interventions included 17 studies on thalamotomy and 20 on deep brain stimulation. Most studies showed tremor improvement after surgery; however, most sample sizes were small, and interventions were highly invasive, with potential adverse effects resulting from surgery. The literature on upper limb intention tremor in MS is relatively sparse. More studies are required to determine mechanism of action and to provide more suitable and sustainable interventions to decrease upper limb intention tremor and improve quality of life of individuals with MS.

The differentiated networks related to essential tremor onset and its amplitude modulation after alcohol intake

The dysregulation of endogenous rhythms within brain networks have been implicated in a broad range of motor and non-motor pathologies. Essential tremor (ET), classically the purview of a single aberrant pacemaker, has recently become associated with network-level dysfunction across multiple brain regions. Specifically, it has been suggested that motor cortex constitutes an important node in a tremor-generating network involving the cerebellum. Yet the mechanisms by which these regions relate to tremor remain a matter of considerable debate. We sought to discriminate the contributions of cerebral and cerebellar dysregulation by combining high-density electroencephalography with subject-specific structural MRI. For that, we contrasted ET with voluntary (mimicked) tremor before and after ingestion of alcohol to regulate the tremorgenic networks. Our results demonstrate distinct loci of cortical tremor coherence, most pronounced over the sensorimotor cortices in healthy controls, but more frontal motor areas in ET-patients consistent with a heightened involvement of the supplementary motor area. We further demonstrate that the reduction in tremor amplitude associated with alcohol intake is reflected in altered cerebellar – but not cerebral – coupling with movement. Taken together, these findings implicate tremor emergence as principally associated with increases in activity within frontal motor regions, whereas modulation of the amplitude of established tremor relates to changes in cerebellar activity. These findings progress a mechanistic understanding of ET and implicate network-level vulnerabilities in the rhythmic nature of communication throughout the brain.

Deep Brain Stimulation of the Dentato-Rubro-Thalamic Tract: Outcomes of Direct Targeting for Tremor

Targeting the dentato-rubro-thalamic tract (DRTt) has been suggested to be efficacious in deep brain stimulation (DBS) for tremor suppression, both in case reports and post-hoc analyses. This prospective observational study sought to analyze outcomes after directly targeting the DRTt in tremor patients. 20 consecutively enrolled intention tremor patients obtained pre-operative MRI with diffusion tensor (dTi) sequences. Mean baseline tremor amplitude based on The Essential Tremor Rating Assessment Scale was recorded. The DRTt was drawn for each individual on StealthViz software (Medtronic) using the dentate nucleus as the seed region and the ipsilateral pre-central gyrus as the end region and then directly targeted during surgery. Intraoperative testing confirmed successful tremor control. Post-operative analysis of electrode position relative to the DRTt was performed, as was post-operative assessment of tremor improvement. The mean age of patients was 66.8 years; mean duration of tremor was 16 years. Mean voltage for the L electrode = 3.4 V; R = 2.6 V. Mean distance from the center of the active electrode contact to the DRTt was 0.9 mm on the L, and 0.8 mm on the R. Improvement in arm tremor amplitude from baseline after DBS was significant (P < 0.001). Direct targeting of the DRTt in DBS is an effective strategy for tremor suppression. Accounting for hardware, software, and model limitations, depiction of the DRTt allows for placement of electrode contacts directly within the fiber tract for modulation despite any anatomical variation, which reproducibly resulted in good tremor control.

Task-dependent variability of Essential Tremor

IntroductionIn Essential Tremor (ET), tremor characteristics and the impairment caused by tremor may vary from task to task. A variability of tremor frequency between postural and kinetic tasks has been proposed in ET, suggesting either multiple central oscillating networks, or peripheral or proprioceptive feedback-mechanisms. This electrophysiological study aimed to assess tremor frequencies and amplitudes in tasks involving postural and kinetic tremor, and compare findings within and across tasks, to delineate physiological differences underlying individually affected manual tasks in ET. Methods40 ET patients were included in the study. Tremor was characterized clinically, as well as electrophysiologically using accelerometry and digitizing tablet tasks. Tremor amplitude measures and frequencies were extracted for tasks involving kinetic (digital spiral drawing, handwriting), as well as postural tremor. Tremor was compared between and within tasks. ResultsDigital spiral tremor frequencies were significantly higher compared to postural tremor frequencies, as measured by accelerometry, with a mean difference of >2 Hz (p < 0.001). Within-task variability of repeated digital spirals revealed a significant amplitude reduction over time in both hands (p < 0.001), with an up to 32% reduction compared to the first spiral. ConclusionET exhibited a frequency variability, which was dependent on activation condition, suggesting neurophysiologically distinct pathways between postural and kinetic tremor. The reduction of tremor amplitudes observed in repeated digital spiral drawing may be explained by a learning effect or adaptation, and should be considered as non-random factor of variability when using spirals in ET to assess effects of interventions.

Decrease selected graphomotor skills in early stages of Alzheimer's dementia

IntroductionIn the early stages of Alzheimer's disease (AD) motor and cognitive dysfunctions has been observed.ObjectivesIn previous studies we have shown that AD patients present abnormalities of selected graphomotor skills, but results were vary and not conclusive. In this study, we conducted more extensive tests on a larger study group.AimsThe aim of the study is to identify which graphomotor functions are impaired in the early stages of AD.MethodsSeventy-one patients with mild and moderate AD (F.00.0, F.00.1, F.00.2) (MMSE 20.3 ± 3.8; age 79.1 ± 5.21) were examined. Forty-four healthy ones (C) without symptoms of dementia, matched for demographic characteristics (MMSE 29 ± 1.1; age 78.3 ± 4.7) were examined. Graphomotor skills were assessed by the original drawing test (the eight figures and the signature) performed in a magnetic field (resolution 2540 dpi and 1024 pressure levels). These test were implemented on a graphic tablet (Wacom Intuos) with the specialized software. The length and time of drawing, the average and maximum speed of drawing, the average and maximum momentary speed, the amplitude and frequency (with FFT spectrum analysis) of hand tremors were measured.ResultsStatistical analysis of the graphomotor signal revealed differences between the AD group and the C group with respect to various parameters. The largest differences have been observed in partially automated skills such as signature, and not drawing shapes (lines, spiral, etc.). The average speed of signature and maximum momentary speed of signature is lower in the AD group.ConclusionsThis method allows for quantitative and objective measurement of the biophysical signal and assessment of the graphomotor skills.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Effect of D-Ala2GIP, a stable GIP receptor agonist on MPTP-induced neuronal impairments in mice

The aim of the present study was to evaluate the ability of D-Ala2GIP, a gastric inhibitory polypeptide (GIP) receptor agonist, to attenuate the behavioral phenotype of Parkinson's disease caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in mice. In the behavioral studies, MPTP administration led to spontaneous locomotor activity deficits, impaired rotarod performance, akinesia, muscular rigidity and increased tremor amplitude, which was attenuated by pretreatment with D-Ala2GIP (50–100 nmol/kg, i.p.). This acute neuroprotective response by D-Ala2GIP was found to be blocked by a selective GIP receptor antagonist, (Pro3)GIP (50 nmol/kg, i.p.), indicating that the observed effects are mediated through GIP receptor mediated signaling pathway. Biochemical studies revealed that D-Ala2GIP reduced the brain malondialdehyde levels and enhanced the brain glutathione levels, thereby mitigating the MPTP-induced oxidative stress. MPTP administration resulted in reduction of the striatal concentration of dopamine and its metabolites, homovanillic acid (HVA) and 3, 4-Dihydroxyphenylacetic acid (DOPAC). Pretreatment with D-Ala2GIP attenuated the loss of striatal dopamine levels without affecting the normal dopamine catabolism. Thus, the observed effects in the MPTP-induced Parkinsonism model could be in part attributable to the antioxidant properties of D-Ala2GIP and enhanced turnover of dopamine in the nigrostriatal pathways in mouse brain. These findings together suggest that GIP receptor could be a therapeutic target in the management of symptoms of Parkinson's disease.

Chlorine isotope composition of volcanic rocks and gases at Stromboli volcano (Aeolian Islands, Italy): Inferences on magmatic degassing prior to 2014 eruption

Among the magmatic volatiles, chlorine (Cl) is degassed at shallow depths offering the opportunity to investigate the behavior of magmatic degassing close to the surface, and the possible occurrence of chemical and isotopic fractionation related to gas/melt partitioning. However, it is still unclear if the isotopic composition of Cl (δ37Cl) can be used as a proxy of magmatic degassing. In this work, we investigate the concentrations of chlorine and sulfur, and the Cl isotope composition of rocks and plume gases collected at Stromboli volcano, Aeolian Islands, Italy. This volcano was chosen because it is characterized by persistent eruptive activity (i.e., Strombolian explosions) and by the presence of magma at very shallow levels in the conduits. Rocks belonging to the different magmatic series erupted throughout the formation of the volcano have δ37Cl values ranging between −1.0 and +0.7‰. The isotopic composition seems independent of the Cl concentration of the rocks, but shows a negative correlation with SiO2 content. Plume gases have a greater isotopic compositional variability than the rocks (−2.2‰≤δ37Cl≤+1.5‰) and the composition seems related to the level of volcanic activity at Stromboli. Gases collected in 2011–2013 during days of ordinary eruptive activity are characterized by δ37Cl values ranging from +0.3 to +1.5‰ and S/Cl molar ratios between 1.4 and 2.2, similar to previous S/Cl measurements performed at Stromboli with other techniques. Plume gases collected in July 2014, in days of high-level eruptive activity preceding the onset of the 2014 effusive eruption, have negative δ37Cl values (−2.2‰≤δ37Cl≤−0.1‰) and S/Cl between 0.9 and 1.2, which are among the lowest S/Cl values measured at this volcano. The amplitude of the volcanic tremor and the variation in the inclination of very long period (VLP) seismic signal polarization clearly indicate that in July 2014 the intensity and frequency of Strombolian explosions, as well as the level of magma in the conduits, were higher than normal. This suggests that when magmatic degassing occurs at very shallow depths (magma residing at few tens of meters below the craters), isotopic fractionation between gaseous and dissolved chlorine (lnαgas-melt>0) can occur, resulting in a depletion of 37Cl in the melt. Finally, we argue that the range of δ37Cl values measured in rocks and gases at Stromboli overlaps most of the known mantle reservoirs (i.e., DMM, HIMU and EM-EM1), indicating that the transfer of chlorine from the mantle to the surface occurs without significant isotopic fractionation. This work opens new perspectives for better constraining the isotope signature of chlorine of different magmatic systems and mantle reservoirs on the Earth.

Tremor analysis separates Parkinson's disease and dopamine receptor blockers induced parkinsonism.

Parkinson's disease, the most common cause of parkinsonism is often difficult to distinguish from its second most common etiology due to exposure to dopamine receptor blocking agents such as antiemetics and neuroleptics. Dual axis accelerometry was used to quantify tremor in 158 patients with parkinsonism; 62 had Parkinson's disease and 96 were clinically diagnosed with dopamine receptor blocking agent-induced parkinsonism. Tremor was measured while subjects rested arms (resting tremor), outstretched arms in front (postural tremor), and reached a target (kinetic tremor). Cycle-by-cycle analysis was performed to measure cycle duration, oscillation amplitude, and inter-cycle variations in the frequency. Patients with dopamine receptor blocker induced parkinsonism had lower resting and postural tremor amplitude. There was a substantial increase of kinetic tremor amplitude in both disorders. Postural and resting tremor in subjects with dopamine receptor blocking agent-induced parkinsonism was prominent in the abduction-adduction plane. In contrast, the Parkinson's disease tremor had equal amplitude in all three planes of motion. Tremor frequency was comparable in both groups. Remarkable variability in the width of the oscillatory cycles suggested irregularity in the oscillatory waveforms in both subtypes of parkinsonism. Quantitative tremor analysis can distinguish Parkinson's disease from dopamine receptor blocking agent-induced parkinsonism.

Structural control and biomechanical tremor suppression: Comparison between different types of passive absorber

Active and semi-active control devices can be used as advanced and accurate controllers to reduce the undesired vibration of a structure. However, some of these controllers may have a complex design, especially for systems excited with multi-degree-of-freedom frequencies, which demand the use of high anti-fatigue material properties, and others that may require a large power source. So, improvements in the design of passive controllers are of high interest for researchers. These controllers have a very simple design and aim to counteract vibration with no power requirements. In this paper, six different passive controllers were designed to analyze and compare their performance. The performance is considered in terms of the percentage of reduction in the primary system’s displacement amplitude and the bandwidth of each designed passive controller. The system of interest is taken as the three-degree-of-freedom dynamic hand system reflecting the behavior of Parkinsonian patients. Four joint muscles operating at two resonance harmonic excitation frequencies are considered to produce movements. Each controller was attached to the forearm of the hand set in the horizontal plane to analyze their capability in reducing the rest tremor (3–7 Hz) at the proximal joint. The dual series elastic–viscous absorber is shown to be a very effective controller. It is formed from a series connection between an elastic absorber (mass–spring) and a viscous absorber (mass–dashpot). It causes about 80% reduction in tremor amplitude with 4 Hz wide frequency band at the shoulder, elbow and wrist joints. This range of operational frequency is close to that of healthy cases, 4.5 Hz.

Intermittent tremor migrations beneath Guerrero, Mexico, and implications for fault healing within the slow slip zone

AbstractSlow slip events exhibit significant complexity in slip evolution and variations in recurrence intervals. Behavior that varies systematically with recurrence interval is likely to reflect different extents of fault healing between these events. Here we use high‐resolution tremor catalogs beneath Guerrero, Mexico, to investigate the mechanics of slow slip. We observe complex tremor propagation styles, including rapid tremor migrations propagating either along the main tremor front or backward, reminiscent of those in northern Cascadia. We also find many migrations that originate well behind the front and repeatedly occupy the same source region during a tremor episode, similar to those previously reported from Shikoku, Japan. These migrations could be driven by slow slip in the surrounding regions, with recurrence intervals possibly modulated by tides. The propagation speed of these migrations decreases systematically with time since the previous migration over the same source area. Tremor amplitudes seem consistent with changes in the propagation speeds being controlled primarily by changes in the slip speeds. One interpretation is that the high propagation speeds and inferred high slip speeds during the migrations with short recurrence intervals are caused by incomplete healing within the host rock adjacent to the shear zone, which could lead to high permeability and reduced dilatant strengthening of the fault gouge. Similar processes may operate in other slow slip source regions such as Cascadia.