Matched pairs in independent Poisson processes

1979 ◽  
Vol 16 (4) ◽  
pp. 780-793
Author(s):  
David Oakes
Keyword(s):  
Observational Studies ◽  
Busy Period ◽  
Random Order ◽  
Poisson Processes ◽  
Matched Pairs ◽  
Matching Process ◽  
The Right ◽  
Matched Samples ◽  
Typical Point ◽  
Interval Distribution

Given two independent Poisson processes 𝒜 and ℬ with rates respectively α and β (α < β) we match each point of 𝒜 with the closest point of ℬ that has not already been matched. The points of 𝒜 are taken in random order. It is shown that the point process of unmatched points of ℬ is a renewal process with the same interval distribution as the busy period of an M/M/1 queue. The distribution and moments of the distance between a typical point of 𝒜 and the corresponding matched point of ℬ are obtained. Variants of the matching process in which the assigned point of ℬ must lie to the right of the point of 𝒜, and in which the matching distance must be less than a fixed tolerance are studied. The use of matched samples to control for bias in observational studies is discussed.

Matched pairs in independent Poisson processes

1979 ◽  
Vol 16 (04) ◽  
pp. 780-793
Author(s):  
David Oakes
Keyword(s):  
Observational Studies ◽  
Busy Period ◽  
Random Order ◽  
Poisson Processes ◽  
Matched Pairs ◽  
Matching Process ◽  
The Right ◽  
Matched Samples ◽  
Typical Point ◽  
Interval Distribution

Given two independent Poisson processes 𝒜 and ℬ with rates respectivelyαandβ(α&lt;β) we match each point of 𝒜 with the closest point of ℬ that has not already been matched. The points of 𝒜 are taken in random order. It is shown that the point process of unmatched points of ℬ is a renewal process with the same interval distribution as the busy period of anM/M/1 queue. The distribution and moments of the distance between a typical point of 𝒜 and the corresponding matched point of ℬ are obtained. Variants of the matching process in which the assigned point of ℬ must lie to the right of the point of 𝒜, and in which the matching distance must be less than a fixed tolerance are studied. The use of matched samples to control for bias in observational studies is discussed.

scholarly journals The effect of cannabidiol (CBD) on low-frequency activity and functional connectivity in the brain of adults with and without autism spectrum disorder (ASD)

2019 ◽  
Vol 33 (9) ◽  
pp. 1141-1148 ◽  
Author(s):  
Charlotte M Pretzsch ◽  
Bogdan Voinescu ◽  
Maria A Mendez ◽  
Robert Wichers ◽  
Laura Ajram ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Functional Connectivity ◽  
Low Frequency ◽  
Random Order ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Double Blind ◽  
Drug Challenge ◽  
The Right ◽  
Post Hoc

Background: The potential benefits of cannabis and its major non-intoxicating component cannabidiol (CBD) are attracting attention, including as a potential treatment in neurodevelopmental disorders such as autism spectrum disorder (ASD). However, the neural action of CBD, and its relevance to ASD, remains unclear. We and others have previously shown that response to drug challenge can be measured using functional magnetic resonance imaging (fMRI), but that pharmacological responsivity is atypical in ASD. Aims: We hypothesized that there would be a (different) fMRI response to CBD in ASD. Methods: To test this, task-free fMRI was acquired in 34 healthy men (half with ASD) following oral administration of 600 mg CBD or matched placebo (random order; double-blind administration). The ‘fractional amplitude of low-frequency fluctuations’ (fALFF) was measured across the whole brain, and, where CBD significantly altered fALFF, we tested if functional connectivity (FC) of those regions was also affected by CBD. Results: CBD significantly increased fALFF in the cerebellar vermis and the right fusiform gyrus. However, post-hoc within-group analyses revealed that this effect was primarily driven by the ASD group, with no significant change in controls. Within the ASD group only, CBD also significantly altered vermal FC with several of its subcortical (striatal) and cortical targets, but did not affect fusiform FC with other regions in either group. Conclusion: Our results suggest that, especially in ASD, CBD alters regional fALFF and FC in/between regions consistently implicated in ASD. Future studies should examine if this affects the complex behaviours these regions modulate.

Patterns of excitability in human esophageal sensorimotor cortex to painful and nonpainful visceral stimulation

2002 ◽  
Vol 282 (2) ◽  
pp. G332-G337 ◽  
Author(s):  
Shaheen Hamdy ◽  
John C. Rothwell ◽  
Chris Fraser ◽  
Maxine Power ◽  
David Gow ◽  
...  
Keyword(s):  
Sensorimotor Cortex ◽  
Magnetic Stimulation ◽  
Cortical Plasticity ◽  
Visceral Pain ◽  
Random Order ◽  
Balloon Distension ◽  
Baseline Levels ◽  
The Right ◽  
The Relationship ◽  
Stimulation Of

To better understand the relationship between cortical plasticity and visceral pain, we developed a pain-induced model of altered esophageal corticobulbar excitability. In eight healthy volunteers, corticoesophageal electromyographic responses were recorded via an intraluminal catheter, following magnetic stimulation of the right sensorimotor cortex using perithreshold intensities. Corticothenar responses were used as control. Responses were assessed both before and for up to 1 h after either painful or nonpainful balloon distension of the esophagus (frequency = 1 Hz, dwell time = 200 ms, duration = 10 min), each being delivered to each subject in random order. Painful esophageal distension (mean volume = 11 ± 3 ml) induced a profound increase in esophageal responses compared with baseline levels (at 30 min: 141 ± 12 vs. 101 ± 9 μV, P < 0.01), whereas nonpainful esophageal distension (mean volume = 4 ± 2 ml) showed a decrease (at 30 min: 72 ± 8 vs. 88 ± 12 μV, P < 0.03). Thenar responses were unaffected. The results show that painful and nonpainful stimuli induce different patterns of esophageal corticobulbar excitability, suggesting a physiological link between cortical plasticity and visceral pain.

Some renewal process models for single neuron discharge

1971 ◽  
Vol 8 (4) ◽  
pp. 802-808 ◽  
Author(s):  
Howard G. Hochman ◽  
Stephen E. Fienberg
Keyword(s):  
Single Neuron ◽  
Interspike Interval ◽  
Poisson Processes ◽  
Process Models ◽  
Recurrence Time ◽  
The Laplace Transform ◽  
Mean And Variance ◽  
The Mean ◽  
Interspike Interval Distribution ◽  
Interval Distribution

Leslie (1969) obtained the Laplace transform for the recurrence time of clusters of Poisson processes, which can be thought of as yielding the interspike interval distribution for a neuron that receives Poisson excitatory inputs subject to decay. Here, several extensions of this model are derived, each including Poisson inhibitory inputs. Expressions for the mean and variance are derived for each model, and the results for the different models are compared.

scholarly journals USING OBSERVATIONAL DATA TO INFORM CANDIDATE PHENOTYPES FOR GEROSCIENCE TRIALS

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S745-S745
Author(s):  
Jason L Sanders ◽  
Alice Arnold ◽  
Robert Boudreau ◽  
Stephen Kritchevsky ◽  
Anne Newman
Keyword(s):  
Observational Data ◽  
Observational Studies ◽  
Cardiovascular Health ◽  
Health Study ◽  
Cardiovascular Health Study ◽  
Efficacy And Safety ◽  
Circulating Biomarkers ◽  
Operational Characteristics ◽  
Aging Mechanisms ◽  
The Right

Abstract Geroscience trials will manipulate aging mechanisms which may have pleiotropic effects and alter multiple biologic processes and clinical outcomes. Determining an intervention’s efficacy and safety will require measuring several aspects of aging and intermediate endpoints with less regard to specific diseases. Picking the right measurements will significantly impact a trial’s cost-effectiveness and chance of success. Observational studies are ideal resources to test candidate phenotypes before investing in trials. We present a decade’s worth of results from the Cardiovascular Health Study as examples of using observational data to inform measurement in geroscience trials. Specifically, we illustrate the underlying theory, construction, operational characteristics, and inter-relationships of candidate phenotypes spanning circulating biomarkers, tissue and organ structure, and functional status, all of which can be used in geroscience trials depending on the intervention’s target and predicted outcome.

scholarly journals Novel treatments for expressive aprosodia: A phase I investigation of cognitive linguistic and imitative interventions

2004 ◽  
Vol 10 (5) ◽  
pp. 786-793 ◽  
Author(s):  
JOHN C. ROSENBEK ◽  
GREGORY P. CRUCIAN ◽  
SUSAN A. LEON ◽  
BETHANY HIEBER ◽  
AMY D. RODRIGUEZ ◽  
...  
Keyword(s):  
Phase I ◽  
Treatment Effect ◽  
Right Hemisphere ◽  
Random Order ◽  
Single Subject ◽  
Emotional Communication ◽  
Emotional Prosody ◽  
Novel Treatments ◽  
Cognitive Linguistic ◽  
The Right

This study investigated two mechanism-based treatments for expressive aprosodia, a disturbance in emotional prosody thought to be governed by the right hemisphere. The 3 participants all suffered right CVA's resulting in expressive aprosodia. Presence of expressive aprosodia was determined by performance on two batteries of emotional communication. A single subject ABAC design was employed in which two treatments, one imitative and one cognitive linguistic, were assigned in random order. All participants in this study were randomly assigned to begin with the cognitive linguistic treatment. Probes of treated and untreated emotions were completed during baseline and therapy phases. Probe items were judged by a reliable, trained rater blind to time of testing. Visual and statistical analyses were completed. These analyses confirmed that both treatments were active. For example, effect size calculations confirmed modest to substantial treatment effects for both treatments in all 3 patients. Replication to increase confidence about treatment effect and enhance understanding of the neuromechanisms underlying aprosodia is underway. (JINS, 2004, 10, 786–793.)

scholarly journals Is This the Prime Time for Transradial Access Left Ventricular Endomyocardial Biopsy?

2021 ◽  
Vol 16 ◽  
Author(s):  
Zaccharie Tyler ◽  
Oliver P Guttmann ◽  
Konstantinos Savvatis ◽  
Daniel Jones ◽  
Constantinos O’Mahony
Keyword(s):  
Pericardial Effusion ◽  
Endomyocardial Biopsy ◽  
Observational Studies ◽  
Left Ventricular ◽  
Prime Time ◽  
Common Complication ◽  
Transradial Access ◽  
Guide Catheter ◽  
Feasible Alternative ◽  
The Right

Left ventricular endomyocardial biopsy (EMB) is an essential tool in the management of myocarditis and is conventionally performed via transfemoral access (TFA). Transradial access EMB (TRA-EMB) is a novel alternative and the authors sought to determine its safety and feasibility by conducting a systematic review of the literature. Medline was searched in 2020, and cohort demographics, procedural details and complications were extracted from selected studies. Four observational studies with a combined total of 496 procedures were included. TRA-EMB was most frequently performed with a sheathless MP1 guide catheter via the right radial artery. The most common complication was pericardial effusion (up to 11% in one study), but pericardial drainage for tamponade was rare (one reported case). Death and mitral valve damage have not been reported. TRA-EMB was successful in obtaining samples in 99% of reported procedures. The authors concluded that TRA-EMB is a safe and feasible alternative to TFA-EMB and the most common complication is uncomplicated pericardial effusion.

scholarly journals Influence of Lenslet Configuration on Short-Term Visual Performance in Myopia Control Spectacle Lenses

2021 ◽  
Vol 15 ◽  
Author(s):  
Xue Li ◽  
Chenglu Ding ◽  
Yuhao Li ◽  
Ee Woon Lim ◽  
Yi Gao ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Random Order ◽  
Optical Quality ◽  
Visual Performance ◽  
Modulation Transfer ◽  
Short Term ◽  
Spatial Frequencies ◽  
Full Correction ◽  
The Right ◽  
Myopia Control

Purpose: This study aimed to evaluate short-term visual performance and optical quality of three different lenslet configurations on myopia control spectacle lenses.Materials and Methods: This study utilized a cross-over design. Distance visual acuity (VA) was measured in 50 myopic children; contrast sensitivity (CS) was measured in 36 myopic children. For each test, four spectacle lenses were evaluated in a random order: single-vision lens (SVL), lens with concentric rings of highly aspherical lenslets (HAL), lens with concentric rings of slightly aspherical lenslets (SAL), and lens with honeycomb configuration of spherical lenslets (HC). The modulation transfer function (MTF) and MTF area (MTFa) were used to determine optical quality. All tests were performed monocularly on the right eye with full correction.Results: HAL and SAL had larger MTFa than HC. VA in lenses with lenslets was significantly reduced compared to SVL (all p &lt; 0.01). The reduction in VA was worse with HC than with SAL (p = 0.02) and HAL (p = 0.03); no effect of lenslet asphericity was found (p &gt; 0.05). VA changes induced by lenslets showed no correlation with spherical equivalent refraction (all p &gt; 0.05) and were weakly positively associated with age for SAL (r = 0.36, p = 0.01) and HC (r = 0.31, p = 0.03), but not for HAL (p = 0.30). The area under the log contrast sensitivity function (AULCSF) decreased with HAL and HC (all p &lt; 0.001) in all illumination levels, and AULCSF with HAL was higher than that with HC in a photopic condition (1.17 ± 0.10 vs. 1.10 ± 0.13, p = 0.0004). The presence of lenslets did not affect CS at 3 cycles per degree (cpd) (p = 0.80). At 6 to 18 cpd, CS was significantly reduced by HAL and HC (all p &lt; 0.05), but not SAL (p &gt; 0.05) compared to SVL. At high spatial frequencies (&gt;12 cpd) both SAL and HAL reduced CS significantly less than HC (all p &lt; 0.01).Conclusion: Short-term visual performance was minimally impaired by looking through the lenslet structure of myopia control spectacle lenses. Concentric rings with aspherical lenslets had a significantly lower impact on both VA and CS than honeycomb configuration with spherical lenslets.

scholarly journals Investigating the potential for the development of a just-in-time knowledge management model

2010 ◽  
Vol 41 (2) ◽  
pp. 1-12 ◽  
Author(s):  
P. D. Steyn ◽  
A. S.A. Du Toit
Keyword(s):  
Knowledge Management ◽  
Real Time ◽  
Just In Time ◽  
Development Effort ◽  
Demand And Supply ◽  
Production Logistics ◽  
Matching Process ◽  
Knowledge Requirements ◽  
The Right ◽  
Insight Into

There have been numerous approaches to knowledge management over the past number of years. The term Just-in-Time (JIT) can be defined as a production or inventory scheduling technique found within the more complex production logistics disciplines. JIT is more appropriately thought of as a philosophy, as it is more than a mere set of management and production principles. JIT knowledge management is an endeavour to provide the right knowledge at the right time to the right person. This requires insight into the knowledge demand and supply process as well as the time horizon applicable to the knowledge required. Over the longer term business forecasts, environmental scans and strategic planning can be applied to close the gap between these variables. However, it is in the short term and in the satisfaction of immediate requirements that the present systems fail and management concerns are emphasised. JIT knowledge management seeks an optimisation of the matching process between demand and supply of knowledge within enterprises, i.e. it endeavours to translate the logistic concept of JIT to the knowledge management field. In addition to JIT knowledge management the concept of real-time knowledge management is introduced as an alternative, since present research indicates that the implementation of JIT knowledge management presents major challenges in terms of cost and development effort, restricting its use to mission critical applications. A more generic application of JIT knowledge management needs to be developed and it is contended that real-time knowledge management fits the requirements of enabling the enterprise to be agile in respect of its ability to respond to knowledge demands and to be sensitive to future knowledge requirements.

Trial designs, including observational to interventional

2020 ◽  
pp. 57-64
Author(s):  
Edo Richard
Keyword(s):  
Study Design ◽  
Treatment Effect ◽  
Clinical Relevance ◽  
Observational Studies ◽  
Research Question ◽  
Sample Size Calculation ◽  
Target Population ◽  
Ethical Considerations ◽  
Neuropsychiatric Diseases ◽  
The Right

Observational studies have taught us a lot about the origin of neurological and neuropsychiatric diseases. This chapter describes how we can translate this knowledge into action. Before engaging in a large RCT, several steps have to be taken. First, the potential for a treatment effect has to be compelling. The target population in the RCT has to resemble the population in which observational studies described an association. Second, the outcome of an RCT has to be chosen, and has to have clinical relevance or at least have the potential of clinical relevance in the future. Third, the right study design has to be decided on. Each research question will require a specific study design with accompanying sample size calculation. Lastly, specific ethical considerations have to be taken into account when designing and executing an intervention study. This chapter presents an overview of these issues.

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