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1.
Muscle Nerve ; 68(4): 397-403, 2023 10.
Article in English | MEDLINE | ID: mdl-37525592

ABSTRACT

INTRODUCTION/AIMS: Intravenous (IV) edaravone is a US Food and Drug Administration-approved treatment for amyotrophic lateral sclerosis (ALS), shown in clinical trials to slow physical functional decline. In this study we compared the effect of IV edaravone (edaravone-first group) versus placebo followed by IV edaravone (placebo-first group) on survival and additional milestone events. METHODS: This work is a post hoc analysis of Study 19/MCI186-19, which was a randomized, placebo-controlled, phase 3 study investigating IV edaravone versus placebo. Study 19 and its 24-week extension have been described previously (NCT01492686). Edaravone-first versus placebo-first group time to events for specific milestone(s) were analyzed post hoc. Time-to-event composite endpoints were time to death; time to death, tracheostomy, or permanent assisted ventilation (PAV); and time to death, tracheostomy, PAV, or hospitalization. RESULTS: The risk for death, tracheostomy, PAV, or hospitalization was 53% lower among patients in the edaravone-first vs placebo-first groups (hazard ratio = 0.47 [95% confidence interval 0.25 to 0.88], P = .02). The overall effect of IV edaravone on ALS progression could be seen in the significant separation of time-to-event curves for time to death, tracheostomy, PAV, or hospitalization. ALS survival composite endpoint analyses (ALS/SURV) suggested a treatment benefit (least-squares mean difference) for the edaravone-first versus the placebo-first group at week 24 (0.15 ± 0.05 [95% confidence interval 0.06 to 0.25], P < .01) and week 48 (0.11 ± 0.05 [95% confidence interval 0.02 to 0.21], P = .02). DISCUSSION: These analyses illustrate the value of timely and continued IV edaravone treatment, as earlier initiation was associated with a lower risk of death, tracheostomy, PAV, or hospitalization in patients with ALS.


Subject(s)
Amyotrophic Lateral Sclerosis , Humans , Edaravone/therapeutic use , Amyotrophic Lateral Sclerosis/drug therapy , Tracheostomy , Proportional Hazards Models , Survival Analysis
2.
Rev Sci Instrum ; 94(5)2023 May 01.
Article in English | MEDLINE | ID: mdl-37222578

ABSTRACT

In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS. Its LISA-like geometry has allowed us to make noise measurements that are more representative of those in LISA and has allowed for the characterization of the mechanisms of noise induced on a LISA GRS and their underlying physics. Noise performance results and experiments exploring the effect of temperature gradients across the sensor will also be discussed. The LISA-like sensor also includes unique UV light injection geometries for UV LED based charge management. Pulsed and DC charge management experiments have been conducted using the University of Florida charge management group's technology readiness level 4 charge management device. These experiments have allowed for the testing of charge management system hardware and techniques as well as characterizations of the dynamics of GRS test mass charging. The work presented here demonstrates the upgraded torsion pendulum's ability to act as an effective testbed for GRS technology.

3.
Muscle Nerve ; 67(2): 124-129, 2023 02.
Article in English | MEDLINE | ID: mdl-36504406

ABSTRACT

INTRODUCTION/AIMS: An intravenous (IV) formulation of edaravone has been shown to slow the rate of physical functional decline in amyotrophic lateral sclerosis (ALS). An oral suspension formulation of edaravone was recently approved by the United States Food and Drug Administration for use in patients with ALS. This study assessed the safety and tolerability of oral edaravone. METHODS: This global, open-label, phase 3 study evaluated the long-term safety and tolerability of oral edaravone in adults with ALS who had a baseline forced vital capacity ≥70% of predicted and disease duration ≤3 y. The primary safety analysis was assessed at weeks 24 and 48. Patients received a 105-mg dose of oral edaravone in treatment cycles replicating the dosing of IV edaravone. RESULTS: The study enrolled 185 patients (64.3% male; mean age, 59.9 y; mean disease duration, 1.56 y). The most common treatment-emergent adverse events (TEAEs) at week 48 were fall (22.2%), muscular weakness (21.1%) and constipation (17.8%). Serious TEAEs were reported by 25.9% of patients; the most common were worsening ALS symptoms, dysphagia, dyspnea, and respiratory failure. Twelve TEAEs leading to death were reported. Forty-six (24.9%) patients reported TEAEs that were considered related to study drug; the most common were fatigue, dizziness, headache, and constipation. Sixteen (8.6%) patients discontinued study drug due to TEAEs. No serious TEAEs were related to study drug. DISCUSSION: This study indicated that oral edaravone was well tolerated during 48 wk of treatment, with no new safety concerns identified.


Subject(s)
Amyotrophic Lateral Sclerosis , Edaravone , Female , Humans , Male , Middle Aged , Administration, Oral , Amyotrophic Lateral Sclerosis/drug therapy , Constipation , Edaravone/administration & dosage , Edaravone/adverse effects
4.
Clin Pharmacol Drug Dev ; 12(1): 57-64, 2023 01.
Article in English | MEDLINE | ID: mdl-36168148

ABSTRACT

Dysphagia is highly prevalent in patients with amyotrophic lateral sclerosis (ALS). Riluzole is a US Food and Drug Administration-approved treatment for ALS. Riluzole oral film (ROF; Exservan™) contains riluzole in a polymer-based film matrix. The ROF is administered by placing on the tongue, where it dissolves and the drug is ingested with the saliva. Two clinical trials assessed the safety and tolerability of the ROF. Bioavailability and pharmacokinetics (PK) were evaluated in an open-label, randomized, single-dose, replicate crossover study of 50 mg of ROF and riluzole 50-mg tablets in 32 healthy volunteers. The second study was a videofluoroscopic swallowing examination conducted with nine patients with ALS before and after receiving a single dose of 50 mg of ROF. The primary outcome was change on penetration-aspiration scale (PAS) scores from pre- to post-dose. Overall, the PK parameters for ROF and riluzole tablets were comparable between treatments and administrations when administered under fasting conditions. Administration of ROF with food resulted in a 15% reduction in area under the curve and a 45% reduction in maximum serum concentration. A total of 44 treatment-emergent adverse events (AEs) were reported in the study; all were mild in severity. No serious AEs were observed and no subjects discontinued due to AEs. In the swallowing study, very little numerical or categorical change was observed following the dose of ROF. No evidence of deterioration of swallowing function was observed post-dose. The ROF was bioequivalent to riluzole tablets, was well tolerated, and had no detrimental effect on swallowing.


Subject(s)
Amyotrophic Lateral Sclerosis , Riluzole , United States , Humans , Riluzole/adverse effects , Amyotrophic Lateral Sclerosis/drug therapy , Amyotrophic Lateral Sclerosis/chemically induced , Biological Availability , Deglutition , Cross-Over Studies
5.
PLoS One ; 17(6): e0258614, 2022.
Article in English | MEDLINE | ID: mdl-35700157

ABSTRACT

BACKGROUND: Edaravone slowed the rate of functional decline in subjects with amyotrophic lateral sclerosis (ALS) in phase 3 study MCI186-19 (Study 19). One of the Study 19 inclusion criteria was forced vital capacity (FVC) ≥80% of predicted (≥80%p). Therefore, the study provided no information on edaravone efficacy in subjects with FVC <80%p. In Study 19, 24-week, double-blind treatment was followed by open-label treatment where all subjects received edaravone. At 24 weeks, some subjects had FVC <80%p (FVC24 <80%p). This allowed for post-hoc assessment of the effects of edaravone in subgroups of subjects with FVC24 ≥80%p vs <80%p. OBJECTIVE: To address the question of the efficacy of edaravone in ALS patients with FVC <80%p. METHODS: Post-hoc analysis of Study 19 comparing edaravone efficacy at week 48 in subjects with FVC24 ≥80%p vs <80%p. RESULTS: With edaravone treatment, subjects in both the FVC24 ≥80%p and the FVC24 <80%p subgroups experienced a reduction in ALS Functional Rating Scale-Revised (ALSFRS-R) score loss vs placebo subjects through week 48. For the FVC24 ≥80%p subgroup, the changes in ALSFRS-R scores from baseline to week 48 were -7.63 for edaravone-edaravone vs -9.69 for placebo-edaravone, a difference of 2.05 (P = .034; 95% CI: 0.16, 3.94). For the FVC24 <80%p subgroup, the changes in ALSFRS-R scores from baseline to week 48 were -10.26 for edaravone-edaravone vs -15.20 for placebo-edaravone, a difference of 4.94 (P = .0038; 95% CI: 1.64, 8.25). Linear regression analysis indicated that, in the FVC24 <80%p subgroup, there was a notable change in the slope of the ALSFRS-R score-vs-time graph after the start of edaravone treatment. CONCLUSION: ALS subjects in the Study 19 placebo arm had a slowing in disease progression, even when edaravone was added with an FVC of <80%p prior to starting edaravone. A randomized, placebo-controlled study is needed to validate these post-hoc findings.


Subject(s)
Amyotrophic Lateral Sclerosis , Amyotrophic Lateral Sclerosis/drug therapy , Antipyrine/pharmacology , Antipyrine/therapeutic use , Double-Blind Method , Edaravone/therapeutic use , Free Radical Scavengers/pharmacology , Humans , Vital Capacity
6.
Drugs R D ; 22(3): 205-211, 2022 Sep.
Article in English | MEDLINE | ID: mdl-35723868

ABSTRACT

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease with no curative therapies. Edaravone (Radicava®) (Mitsubishi Tanabe Pharma Corporation, Tokyo, Japan), approved in the United States (US) for ALS in adults in 2017, was shown in a clinical trial to slow the rate of physical functional decline in ALS and is administered intravenously. The aim of this paper is to summarize the observed safety profile from real-world patient use during the first 3 years of edaravone availability in the US. METHODS: Edaravone usage data were collected, and adverse events (AEs) were identified from a postmarketing safety database from August 8, 2017 through August 7, 2020 (cutoff date). RESULTS: As of October 3, 2020, 5207 ALS patients had been treated with edaravone. As of August 7, 2020, the most commonly reported AEs included death (not specified), drug ineffective, disease progression, therapeutic response unexpected, fall, asthenia, fatigue, muscular weakness, gait disturbance, and dyspnea. The most commonly reported serious AEs (SAEs) included death (not specified), pneumonia, disease progression, ALS, fall, dyspnea, respiratory failure, device-related infection, hospitalization, and injection-site infection. There were 687 deaths, with 494 reported as death without specifying the cause. Deaths were most commonly attributed to ALS, disease progression, respiratory failure, or pneumonia. Review for administration-site reactions revealed 95 AEs, including 34 site infections, with 22 SAEs (all non-fatal). Five non-fatal SAEs of anaphylaxis were reported. CONCLUSION: In the postmarketing reporting to date, no new safety signals were identified beyond those already known from the edaravone clinical trial program.


Subject(s)
Amyotrophic Lateral Sclerosis , Edaravone , Adult , Amyotrophic Lateral Sclerosis/drug therapy , Disease Progression , Dyspnea/chemically induced , Edaravone/adverse effects , Humans , Respiratory Insufficiency/chemically induced , United States
7.
Article in English | MEDLINE | ID: mdl-34251911

ABSTRACT

Introduction: The edaravone development program for amyotrophic lateral sclerosis (ALS) included trials MCI186-16 (Study 16) and MCI186-19 (Study 19). A cohort enrichment strategy was based on a Study 16 post hoc analysis and applied to Study 19 to elucidate a treatment effect in that study. To determine whether the Study 19 results could be generalized to a broader ALS population, we used a machine learning (ML) model to create a novel risk-based subgroup analysis tool. Methods: A validated ML model was used to rank order all Study 16 participants by predicted time to 50% expected vital capacity. Subjects were stratified into nearest-neighbor risk-based subgroups that were systematically expanded to include the entire Study 16 population. For each subgroup, a statistical analysis generated heat maps that revealed statistically significant effect sizes. Results: A broad region of the Study 16 heat map with significant effect sizes was identified, including up to 70% of the trial population. Incorporating participants identified in the cohort enrichment strategy yielded a broad group comprising 76% of the original participants with a statistically significant treatment effect. This broad group spanned the full range of the functional score progression observed in Study 16. Conclusions: This analysis, applying predictions derived using an ML model to a novel methodology for subgroup identification, ascertained a statistically significant edaravone treatment effect in a cohort of participants with broader disease characteristics than the Study 19 inclusion criteria. This novel methodology may assist clinical interpretation of study results and potentially inform efficient future clinical trial design strategies.


Subject(s)
Amyotrophic Lateral Sclerosis , Amyotrophic Lateral Sclerosis/drug therapy , Double-Blind Method , Edaravone/therapeutic use , Humans , Machine Learning , Vital Capacity
8.
Muscle Nerve ; 65(2): 180-186, 2022 02.
Article in English | MEDLINE | ID: mdl-34816454

ABSTRACT

INTRODUCTION: Phase 3 study MCI186-19 demonstrated less loss of physical function with edaravone versus placebo, as measured by the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) total score. A 1-point drop in an individual ALSFRS-R item may be clinically meaningful. We assessed ALSFRS-R item score changes to identify clinical features protected by edaravone treatment. METHODS: Time-to-event analysis was used to assess the cumulative probabilities of reductions in ALSFRS-R item scores and Amyotrophic Lateral Sclerosis Assessment Questionnaire (ALSAQ-40) subdomain scores. RESULTS: Edaravone use was accompanied by: (1) delayed drop of ≥1 point in ALSFRS-R item score for four items: salivation, walking, climbing stairs, orthopnea (unadjusted), or for two items: walking, climbing stairs (after Bonferroni correction for multiple comparisons); (2) delayed score transition from 4 or 3 at baseline to ≤2 for five items: swallowing, eating motion, walking, climbing stairs, orthopnea (unadjusted), or for one item: climbing stairs (after Bonferroni correction for multiple comparisons); and (3) delayed worsening of ALSAQ-40 domain scores representing daily living/independence, eating and drinking (unadjusted). DISCUSSION: These post-hoc analyses identified the ALSFRS-R item scores and ALSAQ-40 domain scores that were associated with preserved gross motor function and health-related quality of life, respectively, after edaravone treatment. Limitations of post-hoc analyses should be considered when interpreting these results. We recommend that clinical trials employing the ALSFRS-R include this type of analysis as a pre-specified secondary outcome measure.


Subject(s)
Amyotrophic Lateral Sclerosis , Amyotrophic Lateral Sclerosis/drug therapy , Double-Blind Method , Edaravone/therapeutic use , Humans , Quality of Life , Surveys and Questionnaires
9.
Neurol Clin Pract ; 11(4): e472-e479, 2021 Aug.
Article in English | MEDLINE | ID: mdl-34476128

ABSTRACT

OBJECTIVES: To identify putative biomarkers that may serve as quantifiable, biological, nonclinical measures of the pharmacodynamic effect of edaravone in amyotrophic lateral sclerosis (ALS) and to report real-world treatment outcomes. METHODS: This is a prospective, observational, longitudinal, multicenter (up to 40 sites) US study (Clinicaltrials.gov; NCT04259255) with at least 200 patients with ALS who will receive edaravone for 24 weeks (6 cycles; Food and Drug Administration-approved regimen). All participants must either be treatment naive for edaravone or be more than 1 month without receiving any edaravone dose before screening. Biomarker quantification and other assessments will be performed at baseline (before cycle 1) and during cycles 1, 3, and 6. Selected biomarkers of oxidative stress, inflammation, neuronal injury and death, and muscle injury, as well as biomarker discovery panels (EpiSwitch and SOMAscan), will be evaluated and, when feasible, compared with biobanked samples. Clinical efficacy assessments will include the ALS Functional Rating Scale-Revised, King's clinical staging, ALS Assessment Questionnaire-40, Appel ALS Score (Rating Scale), slow vital capacity, hand-held dynamometry and grip strength, and time to specified states of disease progression or death. DNA samples will also be collected for potential genomic evaluation. The predicted rates of progression and survival, and their potential correlations with biomarkers, will be evaluated. Adverse events related to the study will be reported. RESULTS: The study is estimated to be completed in 2022 with an interim analysis planned. CONCLUSIONS: Findings may help to further the understanding of the pharmacodynamic effect of edaravone, including changes in biomarkers, in response to treatment.

10.
Neuroepidemiology ; 55(4): 275-285, 2021.
Article in English | MEDLINE | ID: mdl-34153964

ABSTRACT

BACKGROUND: Various methodologies have been reported to assess the real-world epidemiology of amyotrophic lateral sclerosis (ALS) in the United States. The aim of this study was to estimate the prevalence, incidence, and geographical distribution of ALS using administrative claims data and to model future trends in ALS epidemiology. METHODS: We performed a retrospective analysis of deidentified administrative claims data for >100 million patients, using 2 separate databases (IBM MarketScan Research Databases and Symphony Health Integrated DataVerse [IDV]), to identify patients with ALS. We evaluated disease prevalence, annual incidence, age- and population-controlled geographical distribution, and expected future trends. RESULTS: From 2013 to 2017, we identified 7,316 and 35,208 ALS patients from the MarketScan databases and IDV, respectively. Average annual incidence estimates were 1.48 and 1.37 per 100,000 and point prevalence estimates were 6.85 and 5.16 per 100,000 and in the United States for the MarketScan databases and IDV, respectively. Predictive modeling estimates are reported out to the year 2060 and demonstrate an increasing trend in both incident and prevalent cases. CONCLUSIONS: This study provides incidence and prevalence estimates as well as geographical distribution for what the authors believe to be the largest ALS population studied to date. By using 2 separate administrative claims data sets, confidence in our estimates is increased. Future projections based on either database demonstrate an increase in ALS cases, which has also been seen in other large-scale ALS studies. These results can be used to help improve the allocation of healthcare resources in the future.


Subject(s)
Amyotrophic Lateral Sclerosis , Amyotrophic Lateral Sclerosis/epidemiology , Databases, Factual , Humans , Incidence , Prevalence , Retrospective Studies , United States/epidemiology
11.
Article in English | MEDLINE | ID: mdl-32838576

ABSTRACT

In the planning and design of the Radicava/Edaravone Findings in Biomarkers From Amyotrophic Lateral Sclerosis (REFINE-ALS) study, we sought to elicit feedback from patients with ALS and their caregivers to ensure that patient-centric issues would be addressed. Ten ALS Clinical Research Learning Institute (ALS-CRLI) Research Ambassadors participated in 2 meetings. They provided perspectives on patients' interest in the study, the schedule of study visits, and data sharing. The findings were used to help revise the study design, as appropriate. Key concerns identified were (1) the frequency of sample collections, (2) participant travel burden, (3) enrollment criteria, and (4) data reporting and sharing with participants. Several of the identified issues were promptly addressed. The number of visits was reduced, travel optimized, entry criteria clarified, and plans for sharing participants' data with them were codified. The feedback from the Ambassadors was substantive and resulted in constructive patient-centric changes to the study protocol.


Subject(s)
Amyotrophic Lateral Sclerosis , Caregivers , Amyotrophic Lateral Sclerosis/diagnosis , Amyotrophic Lateral Sclerosis/epidemiology , Biomarkers , Edaravone , Humans
12.
J Neurol Neurosurg Psychiatry ; 92(2): 165-171, 2021 02.
Article in English | MEDLINE | ID: mdl-33109706

ABSTRACT

OBJECTIVE: This was a post hoc analysis of the Edaravone Phase III Study MCI186-19 ('Study 19') to examine the utility of clinical staging systems as end points in clinical trials in amyotrophic lateral sclerosis (ALS). METHODS: Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised item scores from Study 19 were retrospectively mapped to King's stage and Milano-Torino staging (MiToS) stage. We assessed the percentage of patients who experienced progression in King's and MiToS stages during Study 19. We also assessed disease progression in subgroups of patients according to baseline King's stage. RESULTS: During double-blind treatment, the percentage of patients who experienced a progression in King's stage was lower for edaravone (42.0%, 95% CI 30.4% to 53.6%) than placebo (55.9%, 95% CI 44.1% to 67.6%). The most pronounced effect was noted among patients who were in stage 1 and was maintained throughout open-label treatment. An analysis of a ≥2-stage progression in MiToS stage showed no difference between treatment arms during double-blind treatment, but during the open-label period, more rapid progression was noted among patients in the placebo-edaravone arm than among those in the edaravone-edaravone arm (log-rank test, p<0.001). CONCLUSIONS: The King's and MiToS staging systems provided utility in assessing clinical progression in Edaravone Study 19. These findings may support the use of staging systems as end points in ALS clinical trials and to understand the timing of benefit as measured by these scales.


Subject(s)
Amyotrophic Lateral Sclerosis/diagnosis , Amyotrophic Lateral Sclerosis/drug therapy , Amyotrophic Lateral Sclerosis/pathology , Disease Progression , Double-Blind Method , Edaravone/therapeutic use , Female , Humans , Kaplan-Meier Estimate , Male , Middle Aged , Neuroprotective Agents/therapeutic use , Time Factors
13.
Muscle Nerve ; 61(2): 218-221, 2020 02.
Article in English | MEDLINE | ID: mdl-31621933

ABSTRACT

BACKGROUND: In a Phase 3 study, amyotrophic lateral sclerosis (ALS) patients experienced significantly less physical functional decline with 24-week edaravone vs placebo, followed by open-label treatment for an additional 24 weeks. METHODS: Outcome (the change in ALS Functional Rating Scale-Revised, ALSFRS-R, from baseline) was projected for placebo patients through 48 weeks and compared with 48-week edaravone or 24-week edaravone after switching from placebo. RESULTS: A total of 123 patients received open-label treatment (65 edaravone-edaravone; 58 placebo-edaravone). The projected ALSFRS-R decline for placebo from baseline through week 48 was greater than for 48-week edaravone (P < .0001). For patients switching from placebo to edaravone, ALSFRS-R slope approached that of continued edaravone for 48 weeks. ALSFRS-R decline did not differ between actual and projected edaravone through week 48. CONCLUSIONS: Compared with placebo, these analyses suggest that edaravone is beneficial in ALS patients even after 6 mo of receiving placebo, and efficacy is maintained for up to 1 year.


Subject(s)
Amyotrophic Lateral Sclerosis/drug therapy , Edaravone/therapeutic use , Neuroprotective Agents/therapeutic use , Aged , Disease Progression , Double-Blind Method , Female , Humans , Male , Middle Aged , Treatment Outcome
14.
Article in English | MEDLINE | ID: mdl-30982356

ABSTRACT

Objectives: The edaravone development program established a study design in which a treatment effect slowing functional loss in amyotrophic lateral sclerosis (ALS) could be documented within a 24-week time frame. This report elucidates the strategic enrichment design utilized to create efficiency and precision in the development program. Methods: Post-hoc analyses describe learning, sequential iteration, and evolution in study design. Results: The first Phase 3 study of edaravone in ALS (Study MCI186-16) included a large proportion (35%) of placebo patients who were minimal progressors. These patients demonstrated high heterogeneity in change in ALSFRS-R score (-4 median with interquartile range [IQR] 7.5) and a modal distribution score of 0, suggesting evidence of minimal change in ALSFRS-R during the study. This level of variability and rate of progression may have made it difficult to detect a prospective treatment effect in the study. A strategic enrichment strategy provided the second Phase 3 study (Study MCI186-19) with the ability to detect a treatment effect. In Study MCI186-19, only 13% of the placebo patients were minimal progressors. Further, these placebo patients demonstrated less heterogeneity and greater functional progression of ALS, thereby providing greater likelihood of detecting a treatment effect. The enrichment strategy may have excluded some rapidly progressing patients, potentially supporting the detection of a treatment effect. As previously published, Study MCI186-19 prospectively documented a 33% reduction in rate of progression of ALS (p = 0.0013). Conclusions: Strategic choices in the design of Study MCI186-19 reduced the proportion of minimally progressing patients and supported detection of a treatment effect.


Subject(s)
Amyotrophic Lateral Sclerosis/diagnosis , Amyotrophic Lateral Sclerosis/drug therapy , Clinical Trials, Phase II as Topic/methods , Clinical Trials, Phase III as Topic/methods , Edaravone/therapeutic use , Neuroprotective Agents/therapeutic use , Randomized Controlled Trials as Topic/methods , Disease Progression , Double-Blind Method , Humans , Treatment Outcome
15.
Rev Sci Instrum ; 88(6): 064502, 2017 Jun.
Article in English | MEDLINE | ID: mdl-28667997

ABSTRACT

We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 µm-diameter tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end. This structure converts the rotation of the torsion pendulum into translation of the test masses. Two test masses are enclosed in capacitive sensors which provide readout and actuation. These test masses are electrically insulated from the rest of the crossbar and their electrical charge is controlled by photoemission using fiber-coupled ultraviolet light emitting diodes. The capacitive readout measures the test mass displacement with a broadband sensitivity of 30 nm∕Hz and is complemented by a laser interferometer with a sensitivity of about 0.5 nm∕Hz. The performance of the pendulum, as determined by the measured residual torque noise and expressed in terms of equivalent force acting on a single test mass, is roughly 200 fN∕Hz around 2 mHz, which is about a factor of 20 above the thermal noise limit of the fiber.

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