17 research outputs found
Too good to be true: when overwhelming evidence fails to convince
Is it possible for a large sequence of measurements or observations, which
support a hypothesis, to counterintuitively decrease our confidence? Can
unanimous support be too good to be true? The assumption of independence is
often made in good faith, however rarely is consideration given to whether a
systemic failure has occurred.
Taking this into account can cause certainty in a hypothesis to decrease as
the evidence for it becomes apparently stronger. We perform a probabilistic
Bayesian analysis of this effect with examples based on (i) archaeological
evidence, (ii) weighing of legal evidence, and (iii) cryptographic primality
testing.
We find that even with surprisingly low systemic failure rates high
confidence is very difficult to achieve and in particular we find that certain
analyses of cryptographically-important numerical tests are highly optimistic,
underestimating their false-negative rate by as much as a factor of
Convergence of marine megafauna movement patterns in coastal and open oceans
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 115 (2018): 3072-3077, doi:10.1073/pnas.1716137115.The extent of increasing anthropogenic impacts on large marine
vertebrates partly depends on the animals’ movement patterns.
Effective conservation requires identification of the key drivers of
movement including intrinsic properties and extrinsic constraints
associated with the dynamic nature of the environments the animals
inhabit. However, the relative importance of intrinsic versus
extrinsic factors remains elusive. We analyse a global dataset of
2.8 million locations from > 2,600 tracked individuals across 50
marine vertebrates evolutionarily separated by millions of years
and using different locomotion modes (fly, swim, walk/paddle).
Strikingly, movement patterns show a remarkable convergence,
being strongly conserved across species and independent of body
length and mass, despite these traits ranging over 10 orders of
magnitude among the species studied. This represents a fundamental
difference between marine and terrestrial vertebrates not
previously identified, likely linked to the reduced costs of locomotion
in water. Movement patterns were primarily explained by the
interaction between species-specific traits and the habitat(s) they
move through, resulting in complex movement patterns when
moving close to coasts compared to more predictable patterns
when moving in open oceans. This distinct difference may be
associated with greater complexity within coastal micro-habitats,
highlighting a critical role of preferred habitat in shaping marine
vertebrate global movements. Efforts to develop understanding
of the characteristics of vertebrate movement should consider the
habitat(s) through which they move to identify how movement
patterns will alter with forecasted severe ocean changes, such as
reduced Arctic sea ice cover, sea level rise and declining oxygen
content.Workshops funding granted by the UWA Oceans Institute, AIMS, and
KAUST. AMMS was supported by an ARC Grant DE170100841 and an IOMRC
(UWA, AIMS, CSIRO) fellowship; JPR by MEDC (FPU program, Spain); DWS by
UK NERC and Save Our Seas Foundation; NQ by FCT (Portugal); MMCM by
a CAPES fellowship (Ministry of Education)
Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries
Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely
Linear measurements from nonlinear sensors: identifying distortion with incidental noise
Nonlinearity in many systems is heavily dependent on component variation and environmental factors such as temperature. This is often overcome by keeping signals close enough to the device’s operating point that it appears approximately linear. But as the signal being measured becomes larger, the deviation from linearity increases, and the device’s nonlinearity specification will be exceeded. This limits the range over which the device will produce directly useful measurements, often to far less than the device’s safe range of operation. Although these nonlinear measurements may exceed the device’s nonlinearity specification, they nevertheless contain useful information. We have shown that the input noise of a system can provide the necessary information to determine the function relating the input signal to the output signal, allowing us to invert it numerically and recover the original signal, even if the device has been driven quite heavily into nonlinearity. In this article, we will provide an overview the technique and results from [1]–[3] and show how it can be used to provide real-time compensation of distortion, providing a significant advantage over the state-of-the-art techniques standardized in [4] when dealing with grossly-distorting systems. We begin by showing how noise can be used to measure the nonlinearity of a system; then we discuss different models of nonlinearity that are suitable for use in real-time compensation tools and show how this can be applied in practice.Peer reviewe
Circumventing Cryptographic Deniability with Remote Attestation
Deniable messaging protocols allow two parties to have ‘off-the-record’ conversations without leaving any record that can convince external verifiers about what either of them said during the conversation. Recent events like the Podesta email dump underscore the importance of deniable messaging to politicians, whistleblowers, dissidents and many others. Consequently, messaging protocols like Signal and OTR are designed with cryptographic mechanisms to ensure deniable communication, irrespective of whether the communications partner is trusted
BliMe: Verifiably Secure Outsourced Computation with Hardware-Enforced Taint Tracking
We present Blinded Memory (BliMe), a way to realize efficient and secure
outsourced computation. BliMe consists of a novel and minimal set of ISA
extensions that uses taint tracking to ensure the confidentiality of sensitive
(client) data even in the presence of server malware, run-time attacks, and
side-channel attacks.
To secure outsourced computation, the BliMe extensions can be used together
with an attestable, fixed-function hardware security module (HSM) and an
encryption engine that provides atomic decrypt-and-taint and
encrypt-and-untaint operations. The HSM engages in an attestation and key
agreement protocol with the client. It provides the resulting client-specific
keys to the encryption engine. Clients rely on remote attestation to ensure
that their data will always be protected by BliMe's taint tracking policy after
decryption.
We provide a machine-checked security proof and FPGA implementations
(BliMe-Ibex) of BliMe's taint tracking policy. We show that BliMe-Ibex does not
reduce performance relative to the unmodified core, and incurs only minor
increases in resource consumption in terms of power (), LUTs
(), and registers ()