8 research outputs found
Dynamic proofs of retrievability with low server storage
Proofs of Retrievability (PoRs) are protocols which allow a client to store
data remotely and to efficiently ensure, via audits, that the entirety of that
data is still intact. A dynamic PoR system also supports efficient retrieval
and update of any small portion of the data. We propose new, simple protocols
for dynamic PoR that are designed for practical efficiency, trading decreased
persistent storage for increased server computation, and show in fact that this
tradeoff is inherent via a lower bound proof of time-space for any PoR scheme.
Notably, ours is the first dynamic PoR which does not require any special
encoding of the data stored on the server, meaning it can be trivially composed
with any database service or with existing techniques for encryption or
redundancy. Our implementation and deployment on Google Cloud Platform
demonstrates our solution is scalable: for example, auditing a 1TB file takes
just less than 5 minutes and costs less than $0.08 USD. We also present several
further enhancements, reducing the amount of client storage, or the
communication bandwidth, or allowing public verifiability, wherein any
untrusted third party may conduct an audit
A Practical Illustration of Methods to Deal with Potential Outliers: A Multiverse Outlier Analysis of Study 3 from Brummelman, Thomaes, Orobio de Castro, Overbeek, and Bushman (2014)
Recently, Brummelman, Thomaes, Orobio de Castro, Overbeek, and Bushman (2014: Study 3) demonstrated
that inflated praise benefits challenge seeking of children with high self-esteem, but harms challenge
seeking of children with low self-esteem. In the present paper, we examined the original data set on
model-fit and prediction outliers according to various reasonable criteria and norms. Subsequently, we
carried out a multiverse outlier re-analysis on the data of Brummelman and colleagues’ Study 3, employing
the same analytical approach as the original authors did but excluding outliers. Out of the twelve
re-analyses in the multiverse, six demonstrated that removing only a small number of outliers rendered
the originally reported crucial interaction effect between self-esteem and type of praise non-significant
and produced a sizeable reduction of the effect size. The present paper illustrates the use of reporting
outlier analyses, which lies in allowing a critical evaluation of the empirical evidence and offering a more
complete picture that enhances future studies in the field
Dynamic proofs of retrievability with low server storage
International audienceProofs of Retrievability (PoRs) are protocols which allow a client to store data remotely and to efficiently ensure, via audits, that the entirety of that data is still intact. A *dynamic* PoR system also supports efficient retrieval and update of any small portion of the data. We propose new, simple protocols for dynamic PoR that are designed for practical efficiency, trading decreased persistent storage for increased server computation, and show in fact that this tradeoff is inherent via a lower bound proof of time-space for any PoR scheme. Notably, ours is the first dynamic PoR which does not require any special encoding of the data stored on the server, meaning it can be trivially composed with any database service or with existing techniques for encryption or redundancy. Our implementation and deployment on Google Cloud Platform demonstrates our solution is scalable: for example, auditing a 1TB file takes just less than 5 minutes and costs less than $0.08 USD. We also present several further enhancements, reducing the amount of client storage, or the communication bandwidth, or allowing *public verifiability*, wherein any untrusted third party may conduct an audit
Dynamic proofs of retrievability with low server storage
International audienceProofs of Retrievability (PoRs) are protocols which allow a client to store data remotely and to efficiently ensure, via audits, that the entirety of that data is still intact. A *dynamic* PoR system also supports efficient retrieval and update of any small portion of the data. We propose new, simple protocols for dynamic PoR that are designed for practical efficiency, trading decreased persistent storage for increased server computation, and show in fact that this tradeoff is inherent via a lower bound proof of time-space for any PoR scheme. Notably, ours is the first dynamic PoR which does not require any special encoding of the data stored on the server, meaning it can be trivially composed with any database service or with existing techniques for encryption or redundancy. Our implementation and deployment on Google Cloud Platform demonstrates our solution is scalable: for example, auditing a 1TB file takes just less than 5 minutes and costs less than $0.08 USD. We also present several further enhancements, reducing the amount of client storage, or the communication bandwidth, or allowing *public verifiability*, wherein any untrusted third party may conduct an audit
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Patient-centered results from a multicenter study of continuous peripheral nerve blocks and postamputation phantom and residual limb pain: secondary outcomes from a randomized, clinical trial
IntroductionWe previously reported that a 6-day continuous peripheral nerve block reduces established postamputation phantom pain. To provide patients and providers with the information to best inform treatment decisions, here we reanalyze the data and present the results in a more patient-centered format. We also provide information on patient-defined clinically relevant benefits to facilitate evaluation of available studies and guide future trial design.MethodsThe original trial enrolled participants with a limb amputation and phantom pain who were randomized to receive a 6-day continuous peripheral nerve block(s) of either ropivacaine (n=71) or saline (n=73) in a double-masked fashion. Here we calculate the percentage of each treatment group that experienced a clinically relevant improvement as defined by previous studies as well as present what the participants of our study defined as small, medium, and large analgesic improvements using the 7-point ordinal Patient Global Impression of Change scale.ResultsAmong patients who were given a 6-day ropivacaine infusion, 57% experienced at least a 2-point improvement on the 11-point numeric rating scale in their average and worst phantom pain 4 weeks postbaseline as compared with 26% (p<0.001) for average and 25% (p<0.001) for worst pain in patients given a placebo infusion. At 4 weeks, the percentage of participants rating their pain as improved was 53% for the active vs 30% for the placebo groups (95% CI 1.7 (1.1, 2.7), p=0.008). For all patients combined, the median (IQR) phantom pain Numeric Rating Scale improvements at 4 weeks considered small, medium, and large were 2 (0-2), 3 (2-5), and 5 (3-7), respectively. The median improvements in the Brief Pain Inventory interference subscale (0-70) associated with small, medium, and large analgesic changes were 8 (1-18), 22 (14-31), and 39 (26-47).ConclusionsAmong patients with postamputation phantom pain, a continuous peripheral nerve block more than doubles the chance of a clinically relevant improvement in pain intensity. Amputees with phantom and/or residual limb pain rate analgesic improvements as clinically relevant similarly to other chronic pain etiologies, although their smallest relevant improvement in the Brief Pain Inventory was significantly larger than previously published values.Trial registration numberNCT01824082
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Ambulatory continuous peripheral nerve blocks to treat postamputation phantom limb pain: a multicenter, randomized, quadruple-masked, placebo-controlled clinical trial
Phantom limb pain is thought to be sustained by reentrant neural pathways, which provoke dysfunctional reorganization in the somatosensory cortex. We hypothesized that disrupting reentrant pathways with a 6-day-long continuous peripheral nerve block reduces phantom pain 4 weeks after treatment. We enrolled patients who had an upper- or lower-limb amputation and established phantom pain. Each was randomized to receive a 6-day perineural infusion of either ropivacaine or normal saline. The primary outcome was the average phantom pain severity as measured with a Numeric Rating Scale (0-10) at 4 weeks, after which an optional crossover treatment was offered within the following 0 to 12 weeks. Pretreatment pain scores were similar in both groups, with a median (interquartile range) of 5.0 (4.0, 7.0) for each. After 4 weeks, average phantom limb pain intensity was a mean (SD) of 3.0 (2.9) in patients given local anesthetic vs 4.5 (2.6) in those given placebo (difference [95% confidence interval] 1.3 [0.4, 2.2], P = 0.003). Patients given local anesthetic had improved global impression of change and less pain-induced physical and emotional dysfunction, but did not differ on depression scores. For subjects who received only the first infusion (no self-selected crossover), the median decrease in phantom limb pain at 6 months for treated subjects was 3.0 (0, 5.0) vs 1.5 (0, 5.0) for the placebo group; there seemed to be little residual benefit at 12 months. We conclude that a 6-day continuous peripheral nerve block reduces phantom limb pain as well as physical and emotional dysfunction for at least 1 month
Symptoms of PTSD associated with painful and nonpainful vicarious reactivity following amputation
Although the experience of vicarious sensations when observing another in pain have been described postamputation, the underlying mechanisms are unknown. We investigated whether vicarious sensations are related to posttraumatic stress disorder (PTSD) symptoms and chronic pain. In Study 1, 236 amputees completed questionnaires about phantom limb phenomena and vicarious sensations to both innocuous and painful sensory experiences of others. There was a 10.2% incidence of vicarious sensations, which was significantly more prevalent in amputees reporting PTSD-like experiences, particularly increased arousal and reexperiencing the event that led to amputation (φ = .16). In Study 2, 63 amputees completed the Empathy for Pain Scale and PTSD Checklist-Civilian Version. Cluster analyses revealed 3 groups: 1 group did not experience vicarious pain or PTSD symptoms, and 2 groups were vicarious pain responders, but only 1 had increased PTSD symptoms. Only the latter group showed increased chronic pain severity compared with the nonresponder group (p = .025) with a moderate effect size (r = .35). The findings from both studies implicated an overlap, but also divergence, between PTSD symptoms and vicarious pain reactivity postamputation. Maladaptive mechanisms implicated in severe chronic pain and physical reactivity posttrauma may increase the incidence of vicarious reactivity to the pain of others