Approximate High Dimensional Graph Mining With Matrix Polar Factorization: A Twitter Application

At the dawn of the Internet era graph analytics play an important role in high- and low-level network policymaking across a wide array of fields so diverse as transportation network design, supply chain engineering and logistics, social media analysis, and computer communication networks, to name just a few. This can be attributed not only to the size of the original graph but also to the nature of the problem parameters. For instance, algorithmic solutions depend heavily on the approximation criterion selection. Moreover, iterative or heuristic solutions are often sought as it is a high dimensional problem given the high number of vertices and edges involved as well as their complex interaction. Replacing under constraints a directed graph with an undirected one having the same vertex set is often sought in applications such as data visualization, community structure discovery, and connection-based vertex centrality metrics. Polar decomposition is a key matrix factorization which represents a matrix as a product of a symmetric positive (semi)definite factor and an orthogonal one. The former can be an undirected approximation of the original adjacency matrix. The proposed graph approximation has been tested with three Twitter graphs with encouraging results with respect to density, Fiedler number, and certain vertex centrality metrics based on matrix power series. The dataset was hosted in an online MongoDB instance

Simulating Blockchain Consensus Protocols in Julia: Proof of Work vs Proof of Stake

Consensus protocols constitute an important part in virtually any blockchain stack as they safeguard transaction validity and uniqueness. This task is achieved in a distributed manner by delegating it to certain nodes which, depending on the protocol, may further utilize the computational resources of other nodes. As a tangible incentive for nodes to verify transactions many protocols contain special reward mechanisms. They are typically inducement prizes aiming at increasing node engagement towards blockchain stability. This work presents the fundamentals of a probabilistic blockchain simulation tool for studying large transaction volumes over time. Two consensus protocols, the proof of work and the delegate proof of stake, are compared on the basis of the reward distribution and the probability bound of the reward exceeding its expected value. Also, the reward probability as a function of the network distance from the node initiating the transaction is studied

TbSAP is a novel chromatin protein repressing metacyclic variant surface glycoprotein expression sites in bloodstream form Trypanosoma brucei

The African trypanosome Trypanosoma brucei is a unicellular eukaryote, which relies on a protective variant surface glycoprotein (VSG) coat for survival in the mammalian host. A single trypanosome has >2000 VSG genes and pseudogenes of which only one is expressed from one of ∼15 telomeric bloodstream form expression sites (BESs). Infectious metacyclic trypanosomes present within the tsetse fly vector also express VSG from a separate set of telomeric metacyclic ESs (MESs). All MESs are silenced in bloodstream form T. brucei. As very little is known about how this is mediated, we performed a whole genome RNAi library screen to identify MES repressors. This allowed us to identify a novel SAP domain containing DNA binding protein which we called TbSAP. TbSAP is enriched at the nuclear periphery and binds both MESs and BESs. Knockdown of TbSAP in bloodstream form trypanosomes did not result in cells becoming more 'metacyclic-like'. Instead, there was extensive global upregulation of transcripts including MES VSGs, VSGs within the silent VSG arrays as well as genes immediately downstream of BES promoters. TbSAP therefore appears to be a novel chromatin protein playing an important role in silencing the extensive VSG repertoire of bloodstream form T. brucei

A sacral filum terminale arteriovenous fistula fed by a left T9 artery of Adamkiewicz

This is a case of 62-year-old patient presenting with tingling and numbness extending from the buttocks area towards the lower extremities and gait instability. Contrast Magnetic Resonance Imaging (MRI) and time-resolved imaging of contrast kinetics Magnetic Resonance Imaging (TRICKS MRI) raised suspicion for a possible dural arteriovenous fistula. Diagnostic Digital Subtraction Angiography (DSA) showed a filum terminale arterio venous fistula (AVF) fed by the left T9 from the anterior spinal artery of Adamkiewicz all the way down to the fistulous point at L5-S1. The patient underwent successful laminectomy of L5-S1 and clipping of the filum terminale arteriovenous fistula

Sphenopalatine Artery Pseudoaneurysm Formation Following Facial Trauma: A case Report and Literature Review

Facial fractures, specifically orbitozygomatic and zygomaticomaxillary complex fractures, are well-documented and common injuries. Pseudoaneurysm formation following cerebrovascular blunt trauma is a rarely experienced complication with an incidence rate of less than 1% with only a few cases reported in the literature. Traumatic pseudoaneurysm formation of the sphenopalatine artery (SPA), the deepest branch of the maxillary artery, is extremely rare due to the deep location of the SPA and its protection from bony landmarks. In craniofacial trauma, pseudoaneurysm formation is not apparent on physical examination due to its deep location and usually presents as persistent nasal bleeding. SPA pseudoaneurysms can present as complications of surgical osteotomies, endoscopic sinus surgeries, facial trauma, or even as a progression of nasopharyngeal cancer. Endovascular embolization provides, safe, quick, and effective treatment while minimizing the morbidity of extensive surgical exposure. In this case report we describe a sphenopalatine artery pseudoaneurysm formation post trauma to provide insight to these rare entities and highlight the importance of early detection and treatment

Surgical Evacuation for Chronic Subdural Hematoma: Predictors of Reoperation and Functional Outcomes

Background Although chronic subdural hematoma (CSDH) incidence has increased, there is limited evidence to guide patient management after surgical evacuation. Objective To identify predictors of reoperation and functional outcome after CSDH surgical evacuation. Methods We identified all patients with CSDH between 2010 and 2018. Clinical and radiographic variables were collected from the medical records. Outcomes included reoperation within 90 days and poor (3–6) modified Rankin Scale score at 3 months. Results We identified 461 surgically treated CSDH cases (396 patients). The mean age was 70.1 years, 29.7 % were females, 298 (64.6 %) underwent burr hole evacuation, 152 (33.0 %) craniotomy, and 11 (2.4 %) craniectomy. Reoperation rate within 90 days was 12.6 %, whereas 24.2 % of cases had a poor functional status at 3 months. Only female sex was associated with reoperation within 90 days (OR = 2.09, 95 % CI: 1.17–3.75, P = 0.013). AMS on admission (OR = 5.19, 95 % CI: 2.15–12.52, P \u3c 0.001) and female sex (OR = 3.90, 95 % CI: 1.57–9.70, P = 0.003) were independent predictors of poor functional outcome at 3 months. Conclusion Careful management of patients with the above predictive factors may reduce CSDH reoperation and improve long-term functional outcomes. However, larger randomized studies are necessary to assess long-term prognosis after surgical evacuation

The evolution of minimally invasive surgery in liver transplantation for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a malignant neoplasm associated with significant mortality worldwide. The most commonly applied curative options include liver resection and liver transplantation (LT). Advances in technology have led to the broader implementation of minimally invasive approaches for liver surgery, including laparoscopic, hybrid, hand-assisted, and robotic techniques. Laparoscopic liver resection for HCC or living donor hepatectomy in LT for HCC are considered to be feasible and safe. Furthermore, the combination of laparoscopy and LT is a recent impressive and promising achievement that requires further investigation. This review aims to describe the role of minimally invasive surgery techniques utilized in LT for HCC

Frailty and Liver resection: where do we stand?

As the world population is continuously aging, the number of older patients requiring liver surgery is also on the rise. Data have shown that age should not be a limiting factor for liver resection, as it cannot accurately predict postoperative outcomes. Instead, frailty can serve as a more reliable measure of the patient’s overall health and functional reserves. Several frailty assessment tools have been implemented for preoperative risk stratification before liver surgery, and higher scores have commonly been associated with postoperative morbidity, mortality, and length of hospital stay. However, no consensus has been reached on the most useful screening tool. Future studies should focus on comparing the currently available assessment tools, constructing a liver resection-specific tool, and assessing the role of frailty assessment tools in preoperative patient optimization

Risk factors for pediatric glioma

Brain tumours are a heterogenic group, a subtype of which is arising from glial cells. Pediatric low-grade gliomas are the most common primary CNS tumour group in childhood, representing 25% to over 30% of pediatric CNS tumours. Pediatric high-grade gliomas are relatively rare and have a poor prognosis. Epidemiological studies have reported various potential risk factors, such as demographics, ionizing and nonionizing radiation, allergic conditions, and infections, immunologic, parental, genetic, and developmental risk factors. These risk factors are relatively unclear and understudied; thus, this narrative review aims to summarize all studies connecting risk factors and pediatric gliomas

“Security dilemma”: active immunotherapy before versus after radiation therapy alone or chemo-radiotherapy for newly diagnosed glioblastoma

Management of glioblastoma should be aggressive and personalised to increase the quality of life. Many new therapies, such as active immunotherapy, increase the overall survival, yet they result in complications which render the search for the optimal treatment stra-tegy challenging. In order to answer whether the available treatment options should be administered in a specific row, we performed a literature search and meta-analysis. The results show that overall survival among the different treatment groups was equal, while the rates of complications were unequal. After surgery, when active immunotherapy was administered before radiation, radiation and chemotherapy, complication rates were lower. For newly diagnosed glioblastoma in adults, applying active immunotherapy after total resection but before the other complementary treatment options is associated with lower complication rates