Solution of Physics-based Bayesian Inverse Problems with Deep Generative Priors

Inverse problems are notoriously difficult to solve because they can have no solutions, multiple solutions, or have solutions that vary significantly in response to small perturbations in measurements. Bayesian inference, which poses an inverse problem as a stochastic inference problem, addresses these difficulties and provides quantitative estimates of the inferred field and the associated uncertainty. However, it is difficult to employ when inferring vectors of large dimensions, and/or when prior information is available through previously acquired samples. In this paper, we describe how deep generative adversarial networks can be used to represent the prior distribution in Bayesian inference and overcome these challenges. We apply these ideas to inverse problems that are diverse in terms of the governing physical principles, sources of prior knowledge, type of measurement, and the extent of available information about measurement noise. In each case we apply the proposed approach to infer the most likely solution and quantitative estimates of uncertainty.Comment: Paper: 18 pages, 5 figures. Supplementary: 9 pages, 6 Figures, 2 Table

Investigating an ‘Agile-Rigid’ Approach in Globally Distributed Requirements Analysis

The global software development environment brings with itself abundant business opportunities as well as challenges in terms of coordination, communication and control. Recent years have also witnessed the growth of the agile movement. To address the global software development challenges there is a need to combine the flexibility offered by the growing agile development approaches with the rigidity offered by the traditional plan-based approaches. This paper reports an exploratory quasi-experimental study, which investigates the performance of requirements analysis projects in an ‘agile-rigid’ distributed environment. The study yields several interesting conclusions that can assist organizations in managing their global software projects more effectively. Our experiment indicates that project monitoring and control, project communication, and process facilitation between peer teams significantly influence the success of such projects. Creation of an agile-rigid environment can help organizations mitigate various risks inherent in globally distributed software development

Use of dorsalis pedis artery flap in coverage of distal lower leg defects

Soft tissue defect in the distal one third of leg have always posed a challenge for reconstructive surgeons. Such wounds are difficult to manage due the tenuous blood supply, limited subcutaneous cover over the tendons and bones. The aim of our study is to investigate the outcome of Dorsalis pedis artery flap for the coverage of such defects. In the present study, we share our clinical experience with the use of dorsalis pedis artery flap for the coverage of defect in the distal one third leg. This is a series of 4 cases where dorsalis pedis artery flap was used to cover lower one third defect. One case had focal squamous cell carcinoma due to long standing post burns contracture in distal one third of leg anteriorly. Other 3 cases had chronic non healing ulcer in the malleolar region. Patient outcome was assessed according to patients’ age distribution, duration of surgery, hospital stay, and post-operative complications. All 4 patients had excellent outcome with no major donor site complications, infection, and graft loss. Donor site was closed with split thickness skin graft. One patient developed a minor raw area over the dorsum of foot which healed secondarily. Although a potential risk in applying this flap is insufficient venous drainage, no problems with blood inflow or outflow were encountered in the present case series. The flaps survived, and the patient had good postoperative outcome. Hence dorsalis pedis flap can be used for the coverage of the distal foot as a good option

Medial plantar artery flap: a versatile workhorse flap for foot reconstruction, our experience

Soft tissue defect in the foot is commonly seen as it is more prone to trophic ulcers since it is the main weight bearing area of the body. Reconstruction of the weight bearing area of the foot requires the provision of a stable, supple, durable and preferably sensate skin coverage. Following Sir Gilli’s principle of replacing like with like, medial plantar artery flap provides an anatomically similar, glabrous skin for coverage on the plantar surface. In the present study, we share our clinical experience with the use of medial plantar artery flap for coverage of soft tissue defect over sole of foot. At our institution, a total of 10 patients presented with soft tissue defect of the sole, underwent medial plantar artery flap coverage. All the 10 patients were diagnosed cases of type 2 DM. patient outcome was assessed according to patients’ age distribution, duration of surgery, hospital stay, and post operative complications. Out of all the 10 patients, 5 were male and 5 were female. All the flaps healed uneventfully without major complications like partial flap necrosis. Donor site was covered with split thickness skin graft. There was suture site dehience in 2 cases which healed with secondary healing. Medial plantar artery flap has been described as an optimal reconstructive option for this type of soft tissue defect.

Brain-localized CD4 and CD8 T cells perform correlated random walks and not Levy walks [version 2; peer review: 1 approved, 2 approved with reservations]

Background. For survival of the organism, T cells must efficiently control pathogens invading different peripheral tissues. Whether or not such control is achieved by utilizing different movement strategies in different tissues remains poorly understood. Liver-localized CD8 T cells perform correlated random walks  --- a type of a Brownian walk -- in liver sinusoids but in some condition these T cells may also perform Levy flights -- rapid and large displacements by floating with the blood flow. CD8 T cells in lymph nodes or skin also undergo Brownian walks. A recent study suggested that brain-localized CD8 T cells, specific to Toxoplasma gondii, perform generalized Levy walks -- a walk type in which T cells alternate pausing and displacing long distances --- which may indicate that brain is a unique organ where T cells exhibit movement strategies different from other tissues. Methods.  We quantified movement patterns of brain-localized Plasmodium berghei-specific CD4 and CD8 T cells by using well-established statistical and computational methods. Results.  We found that T cells change their movement pattern with time since infection and that CD4 T cells move faster and turn less than CD8 T cells. Importantly, both CD4 and CD8 T cells move in the brain by correlated random walks without long displacements challenging previous observations. We have also re-analyzed the movement data of brain-localized CD8 T cells in T. gondii-infected mice and found no evidence of Levy walks. We hypothesize that the previous conclusion of Levy walks of T. gondii-specific CD8 T cells in the brain was reached due to missing time-frames in the data that create an impression of large movement lengths between assumed-to-be-sequential movements.  Conclusion. Our results suggests that movement strategies of CD8 T cells are largely similar between LNs, liver, and the brain and consistent with correlated random walks and not Levy walks

Clinical and endoscopic features of pill-induced esophagitis

Background: Medication can cause an injury in the esophagus by local and systemic effect, leading to esophagitis. Many such medications have been identified as a cause of pill-induced esophagitis. This study was performed to evaluate the clinical and endoscopic findings of pill-induced esophagitis.Methods: This was retrospective observational study, conducted among patients diagnosed endoscopically with pill-induced esophagitis at Ansh gastroenterology clinic, Ahmedabad, India, from April 2017 to March 2021. The data of these patients were recorded in pre-designed case record form by evaluating their past medical records.Results: Total 90 patients were diagnosed with pill-induced esophagitis. Retrosternal chest pain (68.9%), odynophagia (41.1%), dysphagia (25.6%), and epigastric pain (14.4%) were common clinical findings. The major culprit medications were antibiotics, and NSAIDs (non-steroidal anti-inflammatory drugs). Common esophageal endoscopic findings were ulcer (84.4%), erosion (17.8%), and active ulcer bleeding (12.2%). Kissing ulcers were observed in the majority (46.7%) of cases. The majority of ulcer and erosion were located in middle third of the esophagus. All the patients were recovered within 6 to 10 days after treatment with PPIs (proton pump inhibitors) and/or antacids, and withdrawal of the causative medication.Conclusions: Pill-induced esophagitis commonly manifests as retrosternal chest pain, odynophagia and dysphagia, and endoscopy reveals kissing ulcer and erosion in the majority of cases. The condition can be treated with PPIs and/or antacids, and withdrawal of the offending medication.

Implementing a Fast Unbounded Quantum Fanout Gate Using Power-Law Interactions

The standard circuit model for quantum computation presumes the ability to directly perform gates between arbitrary pairs of qubits, which is unlikely to be practical for large-scale experiments. Power-law interactions with strength decaying as $1/r^\alpha$ in the distance $r$ provide an experimentally realizable resource for information processing, whilst still retaining long-range connectivity. We leverage the power of these interactions to implement a fast quantum fanout gate with an arbitrary number of targets. Our implementation allows the quantum Fourier transform (QFT) and Shor's algorithm to be performed on a $D$-dimensional lattice in time logarithmic in the number of qubits for interactions with $\alpha \le D$. As a corollary, we show that power-law systems with $\alpha \le D$ are difficult to simulate classically even for short times, under a standard assumption that factoring is classically intractable. Complementarily, we develop a new technique to give a general lower bound, linear in the size of the system, on the time required to implement the QFT and the fanout gate in systems that are constrained by a linear light cone. This allows us to prove an asymptotically tighter lower bound for long-range systems than is possible with previously available techniques.Comment: 6 pages, 1 figur