Theoretical Perspectives on Deep Learning Methods in Inverse Problems

In recent years, there have been significant advances in the use of deep learning methods in inverse problems such as denoising, compressive sensing, inpainting, and super-resolution. While this line of works has predominantly been driven by practical algorithms and experiments, it has also given rise to a variety of intriguing theoretical problems. In this paper, we survey some of the prominent theoretical developments in this line of works, focusing in particular on generative priors, untrained neural network priors, and unfolding algorithms. In addition to summarizing existing results in these topics, we highlight several ongoing challenges and open problems

Development and validation of a new tool to measure the facilitators, barriers and preferences to exercise in people with osteoporosis

Abstract Background Despite the widely known benefits of exercise and physical activity, adherence rates to these activities are poor. Understanding exercise facilitators, barriers, and preferences may provide an opportunity to personalize exercise prescription and improve adherence. The purpose of this study was to develop the Personalized Exercise Questionnaire (PEQ) to identify these facilitators, barriers, and preferences to exercise in people with osteoporosis. Methods This study comprises two phases, instrument design and judgmental evidence. A panel of 42 experts was used to validate the instrument through quantitative (content validity) and qualitative (cognitive interviewing) methods. Content Validity Index (CVI) is the most commonly used method to calculate content validity quantitatively. There are two kinds of CVI: Item-CVI (I-CVI) and Scale-level CVI (S-CVI). Results Preliminary versions of this tool showed high content validity of individual items (I-CVI range: 0.50 to 1.00) and moderate to high overall content validity of the PEQ (S-CVI/UA = 0.63; S-CVI/Ave = 0.91). Through qualitative methods, items were improved until saturation was achieved. The tool consists of 6 domains and 38 questions. The 6 domains are: 1) support network; 2) access; 3) goals; 4) preferences; 5) feedback and tracking; and 6) barriers. There are 35 categorical questions and 3 open-ended items. Conclusions Using an iterative approach, the development and evaluation of the PEQ demonstrated high item-content validity for assessing the facilitators, barriers, and preferences to exercise in people with osteoporosis. Upon further validation it is expected that this measure might be used to develop more client-centered exercise programs, and potentially improve adherence

Determining known-group validity and test-retest reliability in the PEQ (personalized exercise questionnaire)

© 2019 The Author(s). Background: To determine the known-group validity, a type of construct validity, and the test-retest reliability of a newly developed tool, the Personalized Exercise Questionnaire (PEQ), that assesses the barriers, facilitators, and preferences to exercise in individuals with low bone mass and osteoporosis. Methods: A comparative design was used to assess known-group validity and a test-retest design to examine the reproducibility. Ninety-five participants with low bone mass and osteoporosis were recruited from an outpatient clinic in Hamilton, Ontario. The questionnaire was administered to 95 participants at baseline and a subset of 42 participants completed the survey again one week later. The known-group validity of the PEQ was determined using four hypotheses that compared two known groups based on employment level, age, socioeconomic status, and physical activity level. The reproducibility of individual responses was analyzed using the Kappa Coefficient (κ). Results: There was known-group validity for three of the four hypotheses. Test-retest reliability scores ranged from no agreement to almost perfect agreement; seven items had almost perfect agreement (κ: 0.81-1.00), 12 substantial agreement (κ: 0.68-0.74), six moderate agreement (κ: 0.56-0.60), two fair agreement (κ: 0.36-0.40), one slight agreement (κ = 0.23) and one no agreement (κ = - 0.03). Conclusion: Preliminary support for the usefulness of the PEQ is indicated since the majority of the items had at least substantial agreement and known-group validity was moderately supported for some items. Trial registration: This study was retrospectively registered with ClinicalTrials.gov, NCT03125590, on April 24, 2017

Enabling digital grid for industrial revolution: self-healing cyber resilient platform

The key market objectives driving digital grid development are to provide sustainable, reliable and secure network systems that can support variety of applications against any potential cyber attacks. Therefore, there is an urgent demand to accelerate the development of intelligent Software-Defined Networking (SDN) platform that can address the tremendous challenges of data protection for digital resiliency. Modern grid technology tends to adopt distributed SDN controllers for further slicing power grid domain and protect the boundaries of electric data at network edges. To accommodate these issues, this article proposes an intelligent secure SDN controller for supporting digital grid resiliency, considering management coordination capability, to enable self-healing features and recovery of network traffic forwarding during service interruptions. A set of advanced features are employed in grid controllers to configure the network elements in response to possible disasters or link failures. In addition, various SDN topology scenarios are introduced for efficient coordination and configurations of network domains. Finally, to justify the potential advantages of intelligent secure SDN system, a case study is presented to evaluate the requirements of secure digital modern grid networks and pave the path towards the next phase of industry revolution

Nerve Agent Hydrolysis Activity Designed into a Human Drug Metabolism Enzyme

Organophosphorus (OP) nerve agents are potent suicide inhibitors of the essential neurotransmitter-regulating enzyme acetylcholinesterase. Due to their acute toxicity, there is significant interest in developing effective countermeasures to OP poisoning. Here we impart nerve agent hydrolysis activity into the human drug metabolism enzyme carboxylesterase 1. Using crystal structures of the target enzyme in complex with nerve agent as a guide, a pair of histidine and glutamic acid residues were designed proximal to the enzyme's native catalytic triad. The resultant variant protein demonstrated significantly increased rates of reactivation following exposure to sarin, soman, and cyclosarin. Importantly, the addition of these residues did not alter the high affinity binding of nerve agents to this protein. Thus, using two amino acid substitutions, a novel enzyme was created that efficiently converted a group of hemisubstrates, compounds that can start but not complete a reaction cycle, into bona fide substrates. Such approaches may lead to novel countermeasures for nerve agent poisoning

Cerebrovascular Variants and the Role of the Selfish Brain in Young-Onset Hypertension

Background: Variants in the posterior anatomy of the cerebral circulation are associated with hypertension and lower cerebral blood flow in midlife (age ≈55 years); however, whether these variants are a result of aging or long-term exposure to high blood pressure is unclear. Additionally, the role these variants play in early onset of hypertension (<40 years) and poor cerebral perfusion in this population is unknown. Methods: We retrospectively examined whether specific cerebrovascular variants (vertebral artery hypoplasia and absent/hypoplastic posterior communicating arteries (an incomplete posterior circle of Willis) measured via magnetic resonance angiography) were associated with a diagnosis of hypertension in 220 young adults (<40 years; n=164 primary hypertensive [mean age±SD, 32±6 years] and n=56 [30±6 years] normotensive adults). Whether cerebrovascular variants were associated with lower cerebral blood flow (phase-contrast angiography) was measured in the hypertensive group only (n=146). Results: Binary logistic regression (adjusted for age, sex, and body mass index) showed that vertebral artery hypoplasia with an incomplete posterior circle of Willis was associated with hypertension diagnosis (P<0.001, odds ratio; 11.79 [95% CI, 3.34–41.58]). Vertebral artery hypoplasia plus an incomplete circle of Willis was associated with lower cerebral blood flow in young adults with hypertension (P=0.0172). Conclusions: Vertebral artery hypoplasia plus an incomplete posterior circle of Willis independently predicts hypertension in young adults suggesting that this variant is not acquired with aging into midlife. Importantly this variant combination was associated with lower cerebral perfusion, which may have long-term consequences on cerebrovascular health in young adults with hypertension

Surgical site infection following surgery for hand trauma: a systematic review and meta-analysis

Surgical site infection is the most common healthcare-associated infection. Surgical site infection after surgery for hand trauma is associated with increased antibiotic prescribing, re-operation, hospital readmission and delayed rehabilitation, and in severe cases may lead to amputation. As the risk of surgical site infection after surgery for hand trauma remains unclear, we performed a systematic review and meta-analysis of all primary studies of hand trauma surgery, including randomized controlled trials, cohort studies, case-control studies and case series. A total of 8836 abstracts were screened, and 201 full studies with 315,618 patients included. The meta-analysis showed a 10% risk of surgical site infection in randomized control trials, with an overall risk of 5% when all studies were included. These summary statistics can be used clinically for informed consent and shared decision making, and for power calculations for future clinical trials of antimicrobial interventions in hand trauma