Systemic risk contagion of green and Islamic markets with conventional markets.

Financial markets are exposed to extreme uncertain circumstances escalating their tail risk. Sustainable, religious, and conventional markets represent three different markets with various characteristics. Motivated with this, the current study measures the tail connectedness between sustainable, religious, and conventional investments by employing a neural network quantile regression approach from December 1, 2008 to May 10, 2021. The neural network recognized religious and conventional investments with maximum exposure to tail risk following the crisis periods reflecting strong diversification benefits of sustainable assets. The Systematic Network Risk Index spots Global Financial Crisis, European Debt Crisis, and COVID-19 pandemic as intensive events yielding high tail risk. The Systematic Fragility Index ranks the stock market in the pre-COVID period and Islamic stocks during the COVID sample as the most susceptible markets. Conversely, the Systematic Hazard Index nominates Islamic stocks as the chief risk contributor in the system. Given these, we portray various implications for policymakers, regulatory bodies, investors, financial market participants, and portfolio managers to diversify their risk using sustainable/green investments.

COVID-induced sentiment and the intraday volatility spillovers between energy and other ETFs.

Did Covid19 induce market turmoil impact the intraday volatility spillovers between energy and other ETFs?. To examine this, we first estimate the realized volatility of ETFs using the 5-min high-frequency data. Next, we employ time-varying parameter vector autoregressions (TVP-VAR). Finally, we utilize the wavelet coherence measure to test the time-frequency impact of COVID-induced sentiment on the spillovers by employing investors' psychological and behavioural factors. We find that oil and stock markets are net transmitters while currency, bonds, and silver markets are net receivers. The wavelet analysis embarked significant impact of media coverage and fake news index towards shaping investors' pessimism for their investments. We proposed useful implications for policymakers, governments, investors, and portfolio managers.

Cryptocurrency liquidity and volatility interrelationships during the COVID-19 pandemic.

We examine the interactions between cryptocurrency price volatility and liquidity during the outbreak of the COVID-19 pandemic. Evidence suggests that these developing digital products have played a new role as a potential safe-haven during periods of substantial financial market panic. Results suggest that cryptocurrency market liquidity increased significantly after the WHO identification of a worldwide pandemic. Significant and substantial interactions between cryptocurrency price and liquidity effects are identified. These results add further support to the argument that substantial flows of investment entered cryptocurrency markets in search of an investment safe-haven during this exceptional black-swan event.

Aye Corona! The contagion effects of being named Corona during the COVID-19 pandemic.

In the midst of the 2020 global COVID-19 pandemic and subsequent financial market collapse, corporate entities have to navigate a number of truly unforeseen contagion risks. However, one such group included those who shared their corporate identity with aspects of the rapidly evolving coronavirus. Our results indicate the existence of sharp, dynamic and new correlations between companies related to the term 'corona', outside of pre-existing interrelationships. We provide a number of observations as to why this situation occurred.

Gold and US sectoral stocks during COVID-19 pandemic.

In this study, we examine the hedging relationship between gold and US sectoral stocks during the COVID-19 pandemic. We employ a multivariate volatility framework, which accounts for salient features of the series in the computation of optimal weights and optimal hedging ratios. We find evidence of hedging effectiveness between gold and sectoral stocks, albeit with lower performance, during the pandemic. Overall, including gold in a stock portfolio could provide a valuable asset class that can improve the risk-adjusted performance of stocks during the COVID-19 pandemic. In addition, we find that the estimated portfolio weights and hedge ratios are sensitive to structural breaks, and ignoring the breaks can lead to overestimation of the hedging effectiveness of gold for US sectoral stocks. Since the analysis involves sectoral stock data, we believe that any investor in the US stock market that seeks to maximize risk-adjusted returns is likely to find the results useful when making investment decisions during the pandemic.

The contagion effects of the COVID-19 pandemic: Evidence from gold and cryptocurrencies.

At the beginning of the 2020 global COVID-2019 pandemic, Chinese financial markets acted as the epicentre of both physical and financial contagion. Our results indicate that a number of characteristics expected during a "flight to safety" were present during the period analysed. The volatility relationship between the main Chinese stock markets and Bitcoin evolved significantly during this period of enormous financial stress. We provide a number of observations as to why this situation occurred. Such dynamic correlations during periods of stress present further evidence to cautiously support the validity of the development of this new financial product within mainstream portfolio design through the diversification benefits provided.

Complexity in financial asset returns: Evidence from the compass rose.

The compass rose pattern in financial data may indicate the presence of a nonlinear, possibly chaotic, data generating mechanism. The analysis of three key financial asset and denoised returns, gold, the Great British Pound/US dollar spot exchange rate, and the Standard & Poor's 500 stock index, reveals that over four equivalent subperiods, from 1996 to 2015, the compass rose pattern changes. This finding provides an opportunity to establish how noise affects financial time series. We conclude that the compass rose pattern is unlikely the product of an underlying nonlinear structure, since there is evidence of nonlinearity in all time periods, even those where the compass rose pattern is not evident. Therefore, the compass rose patterns, seen in the denoised data, suggest that the presence of noise masks the underlying dynamics of the asset returns.

Stylized facts of intraday precious metals.

This paper examines the stylized facts, correlation and interaction between volatility and returns at the 5-minute frequency for gold, silver, platinum and palladium from May 2000 to April 2015. We study the full sample period, as well as three subsamples to determine how high-frequency data of precious metals have developed over time. We find that over the full sample, the number of trades has increased substantially over time for each precious metal, while the bid-ask spread has narrowed over time, indicating an increase in liquidity and price efficiency. We also find strong evidence of periodicity in returns, volatility, volume and bid-ask spread. Returns and volume both experience strong intraday periodicity linked to the opening and closing of major markets around the world while the bid-ask spread is at its lowest when European markets are open. We also show a bilateral Granger causality between returns and volatility of each precious metal, which holds for the vast majority subsamples.

Diverticular disease is associated with benign intra-abdominal cystic disease.

BACKGROUND: Diverticular disease (DD) and hepatic and renal cysts have been linked with defects in collagen and dysfunctional matrix metalloproteinases. METHODS: Consecutive abdominal computed tomography scans between January-July 2015 were prospectively studied to determine a correlation between visceral cysts and DD. Patients with a sigmoid colectomy for pathology other than DD and scans in which DD and/or solid organs were not fully visualized were excluded. A subgroup analysis was performed on youthful DD patients (<55 years of age, n = 32) vs. older controls (>55, n = 213). RESULTS: 238 DD patients (50.8% male) and 369 controls (40.5% male, p = .02) were included. Incidence of visceral cystic disease in DD patients vs. controls was 71.4% vs. 22.5% (p < 0.00001). Renal cysts, present in 53.4% of the DD patients and 18.7% of the controls (p < .00001), were more common than hepatic cysts in both groups. Hepatic cyst prevalence was 8.8 vs. 2.4% (p = .0008). In the subgroup analysis, cystic disease was present in 56.2% of youthful DD patients vs. 29.1% of older controls (p = .004). CONCLUSIONS: A significant association between cystic disease and DD was demonstrated overall and in subgroup analysis inclusive of youthful DD patients and older controls. These findings suggest a global defect in connective tissue integrity in DD patients.

Influence of body habitus and use of oral contrast on reader confidence in patients with suspected acute appendicitis using 64 MDCT.

The purpose of this study is to evaluate how body habitus affects reader confidence in diagnosing acute appendicitis and appendiceal visualization using 64 MDCT technology with and without oral contrast. We conducted a HIPAA compliant, IRB approved study of adult patients presenting to the Emergency Department with nontraumatic abdominal pain. Subjects were randomized to two groups: 64 MDCT scans performed with oral and intravenous contrast or scans performed solely with intravenous contrast. Three radiologists established their confidence about the presence of appendicitis as well as recording whether the appendix was visualized. Reader confidence in diagnosing acute appendicitis was compared between the two groups for the three readers. The impact of patient BMI and estimated intra-abdominal fat on reader confidence in diagnosing appendicitis was determined. Finally, a comparison of the effect of BMI and intra-abdominal fat on appendiceal visualization between the two groups was carried out. Three hundred three patients were enrolled in this study. There was a statistically significant difference in confidence based on BMI for reader 2, group 1 in diagnosing appendicitis. No further statistically significant differences in reader confidence for diagnosing appendicitis based on BMI or intra-abdominal fat were identified. There was no influence of BMI or intra-abdominal fat on appendiceal visualization. Increasing BMI was seen to improve reader confidence for one of three readers in patients that received both oral and intravenous contrast. No further effects of BMI or intra-abdominal fat on confidence in diagnosing or excluding appendicitis were seen. Neither BMI nor intra-abdominal fat were seen to influence appendiceal visualization.

Abdominal 64-MDCT for suspected appendicitis: the use of oral and IV contrast material versus IV contrast material only.

OBJECTIVE: The objective of our study was to compare the diagnostic accuracy of IV contrast-enhanced 64-MDCT with and without the use of oral contrast material in diagnosing appendicitis in patients with abdominal pain. MATERIALS AND METHODS: We conducted a randomized trial of a convenience sample of adult patients presenting to an urban academic emergency department with acute nontraumatic abdominal pain and clinical suspicion of appendicitis, diverticulitis, or small-bowel obstruction. Patients were enrolled between 8 am and 11 pm when research assistants were present. Consenting subjects were randomized into one of two groups: Group 1 subjects underwent 64-MDCT performed with oral and IV contrast media and group 2 subjects underwent 64-MDCT performed solely with IV contrast material. Three expert radiologists independently reviewed the CT examinations, evaluating for the presence of appendicitis. Each radiologist interpreted 202 examinations, ensuring that each examination was interpreted by two radiologists. Individual reader performance and a combined interpretation performance of the two readers assigned to each case were calculated. In cases of disagreement, the third reader was asked to deliver a tiebreaker interpretation to be used to calculate the combined reader performance. Final outcome was based on operative, clinical, and follow-up data. We compared radiologic diagnoses with clinical outcomes to calculate the diagnostic accuracy of CT in both groups. RESULTS: Of the 303 patients enrolled, 151 patients (50%) were randomized to group 1 and the remaining 152 (50%) were randomized to group 2. The combined reader performance for the diagnosis of appendicitis in group 1 was a sensitivity of 100% (95% CI, 76.8-100%) and specificity of 97.1% (95% CI, 92.7-99.2%). The performance in group 2 was a sensitivity of 100% (73.5-100%) and specificity of 97.1% (92.9-99.2%). CONCLUSION: Patients presenting with nontraumatic abdominal pain imaged using 64-MDCT with isotropic reformations had similar characteristics for the diagnosis of appendicitis when IV contrast material alone was used and when oral and IV contrast media were used.

Reticuloendothelium malignancy: current role of imaging.

Imaging has an important role in the diagnosis and staging of patients with lymphoma, with a major influence on both patient management and outcome. CT is probably the most widely used modality in patients with lymphoma bur MRI is probably as useful as CT in the initial work-up of the patient. Finally, PET/CT can detect residual disease in patients post-treatment better than both CT and MRI and is playing an increasing role in the imaging of patients with lymphoma.

Development of renal scars on CT after abdominal trauma: does grade of injury matter?

OBJECTIVE: The objective of our study was to determine whether there is an association between the grade of a traumatic renal injury and the subsequent development of renal parenchymal scars on CT. MATERIALS AND METHODS: We performed a retrospective study encompassing all acute trauma patients admitted to our institution over a 42-month period found to have renal parenchyma injuries on initial MDCT and also to have undergone a follow-up CT performed at least 1 month after trauma. We identified 54 patients who sustained blunt (n = 44) or penetrating (n = 10) abdominal trauma. The renal injuries were graded by two radiologists according to the Organ Injury Scaling Committee of the American Association for the Surgery of Trauma (AAST), grades I through V. Follow-up CT was reviewed for the presence of parenchymal distortion, scarring, or perfusion defects. RESULTS: Of the 54 patients, 12 had grade I injury, eight had grade II injury, 22 had grade III injury, 10 had grade IV injury, and two had grade V injury. Grades I and II traumatic renal injuries were undetectable on follow-up CT. Grade III injuries resulted in the development of renal scars in 14 of 22 (64%) patients. Scarring resulted in all patients with grades IV and V injuries. CONCLUSION: Grades I and II renal injuries heal completely, whereas higher grades of renal trauma result in permanent parenchymal scarring. Hence, incidentally discovered renal scars in patients with a history of minor renal trauma should be attributed tentatively to other causes that may or may not require additional investigation.

Blunt trauma: feasibility and clinical utility of pelvic CT angiography performed with 64-detector row CT.

PURPOSE: To retrospectively evaluate the integration of pelvic computed tomographic (CT) angiography into the thoracoabdominal CT examination of blunt trauma by using 64-detector row CT to differentiate active arterial from active venous hemorrhage. MATERIALS AND METHODS: This study was institutional review board approved and HIPAA compliant; the requirement for informed patient consent was waived. Fifty-three patients (30 male, 23 female; mean age, 42 years) with multiple blunt trauma underwent pelvic CT angiography with 64-detector row CT at admission. Arterial phase and portal venous phase pelvic CT angiograms were evaluated for evidence of vascular injury. In patients with active extravasation, the size of the hemorrhaging area was measured on arterial, portal venous, and delayed phase images. The Fisher exact test was used to correlate presence of vascular injury with subsequent clinical management. The Wilcoxon rank sum test was used to test the association between size of active hemorrhage during the vascular enhancement phases and subsequent clinical outcome. Finally, the Fisher exact test was used to correlate presence of vascular injury with severity of osseous injury. RESULTS: At pelvic CT angiography, 21 of the 53 patients had evidence of vascular injury: 10 isolated active arterial extravasations, three isolated arterial occlusions, three cases of both arterial extravasation and occlusion, two cases of arterial and venous extravasations, and three isolated venous extravasations. Eleven of the 21 patients also underwent conventional angiography, with subsequent embolization performed in seven of these 11 patients. The remaining 10 patients were successfully treated conservatively. When the foci of active arterial extravasation were compared on arterial, portal venous, and delayed phase images, the mean areas of hemorrhage across all three phases were larger in patients who required conventional angiography than in those successfully treated with conservative management. CONCLUSION: With use of 64-detector row scanning, pelvic CT angiography was successfully integrated into the authors' CT protocols and enabled differentiation between active arterial and active venous hemorrhage, which may influence clinical management.

64-detector row computed tomography: an improved tool for evaluating the biliary and pancreatic ducts?

The imaging evaluation of patients with suspected pancreaticobiliary abnormality includes noninvasive imaging modalities such as sonography and MRI. The use of computed tomography (CT) has typically been limited to the evaluation and staging of malignancy affecting the pancreas and biliary tree. With the increasing use of CT in abdominal imaging for patients with a wide variety of indications, biliary and pancreatic abnormalities are being initially identified with increasing frequency on CT. The evolution of CT technology to multi-detector channel row (MDCT) scanners, currently culminating in use of 64-detector-row MDCT scanners, has provided unprecedented image quality. We have recently installed three 64-MDCT scanners in our institution and, in this article, we describe our experience in their application to imaging of the pancreatic and biliary ducts. Our current protocols for imaging the biliary tree and pancreatic duct using this technology are discussed. Additionally, the advantages of novel interpretation techniques including multi-planar and minimum intensity projection reformations are detailed. Various diseases affecting the pancreaticobiliary tree are briefly discussed along with their typical imaging evaluation. The application of 64-MDCT technology to these abnormalities is described along with expected imaging findings on CT. The imaging findings of various pancreaticobiliary abnormalities using 64-MDCT scanner technology encountered at our institution are illustrated. In summary, 64-MDCT technology offers several technical advances which may increase utilization of CT in the evaluation and diagnosis of pancreaticobiliary abnormalities.

64 MDCT in multiple trauma patients: imaging manifestations and clinical implications of active extravasation.

The finding of active hemorrhage on computed tomography (CT) in trauma patients has been shown to have significant clinical implications and has been incorporated into numerous CT grading schema. As CT technology has advanced, the sensitivity for detection of active hemorrhage in the trauma population has significantly improved. Currently, with the improved spatial and temporal resolution afforded by 64 multidetector computed tomography (64 MDCT) technology, the clinical implications of the CT findings of active extravasation may need to be reconsidered. This article illustrates the various imaging manifestations of active extravasation throughout the body using 64 MDCT. Additionally, protocol issues specific to the findings of active hemorrhage using 64 MDCT are detailed, including novel interpretation techniques, which offer aid in detecting and characterizing hemorrhage. Finally, the clinical implication of active extravasation using this new technology is discussed. Although more sensitive to the detection of small hemorrhagic foci and with clinical implications highly dependent upon location, active bleeding remains as a salient finding that affects subsequent clinical management of trauma patients.

CT-guided intervention with low radiation dose: feasibility and experience.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of performing CT-guided interventional procedures with a very low radiation dose. MATERIALS AND METHODS: We performed 291 CT-guided interventional procedures using a low dose of radiation. The subjects were 165 men and 126 women 22-89 years old with a mean age of 65 years. CT fluoroscopy was not used. The procedures were 201 percutaneous biopsies and 90 percutaneous aspiration or drainage procedures. Before the procedure, images were obtained with standard mAs of 175-250 mAs. All subsequent CT was performed at a reduced mAs. Technical success of catheter placement and biopsy was calculated, and the results were compared with those of procedures performed over the previous 12 months with standard radiation doses. Patient weight, lesion size, and number of CT acquisitions needed to complete the procedure were recorded. RESULTS: All but three aspiration or drainage procedures performed at 30 mAs were successful, for a success rate of 96.7%. The technical success rate of biopsy performed at 30 mAs was 93.5%. In the cases of 13 patients undergoing biopsy, the masses were not identified with low-dose technique, and these procedures were completed at a higher dose. Results were independent of patient weight and lesion size. The technical success rate was 98% for percutaneous drainage performed at a standard radiation dose in the 12 months before introduction of the low-dose technique. The technical success rate was 87.5% for biopsy performed at a standard radiation dose in the 12 months before introduction of the low-dose technique. The complication rate of the low-dose technique was comparable to that of the standard-dose technique. CONCLUSION: Low-dose radiation technique using 30 mAs results in technical success for both catheter placement and percutaneous biopsy comparable to standard radiation dose.

Spontaneous hemoperitoneum: a bloody mess.

Spontaneous hemoperitoneum may be a life-threatening occurrence. It most frequently presents with acute abdominal pain. Computed tomography (CT) is the most commonly used modality in the initial work up of these patients, but sonography and magnetic resonance imaging (MRI) play a role in the diagnosis. The etiology is varied, yet may be broadly classified into gynecologic, hepatic, splenic, vascular, and coagulopathic causes. This review will describe the common imaging findings of spontaneous hemoperitoneum, as it presents through the emergency room, and will detail the underlying causes and significance of spontaneous hemoperitoneum.

Blunt splenic trauma: delayed-phase CT for differentiation of active hemorrhage from contained vascular injury in patients.

PURPOSE: To retrospectively evaluate delayed-phase computed tomography (CT) in the differentiation of active splenic hemorrhage requiring emergent treatment from contained vascular injuries (pseudoaneurysms or arteriovenous fistulas) that can be treated electively or managed conservatively. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant retrospective study; the informed consent requirement was waived. Forty-seven patients with blunt splenic injury diagnosed at CT after blunt abdominal trauma were evaluated. Abdominal and pelvic dual-phase CT was performed; images were obtained 60-70 seconds and 5 minutes after contrast material injection. Scans were reviewed in consensus by two radiologists. Splenic injuries were graded with the American Association for the Surgery of Trauma Splenic Injury Scale. Patients with intrasplenic hyperattenuating foci on portal venous phase images were classified as having active splenic hemorrhage (group 1) or a contained vascular injury (group 2) on the basis of delayed-phase imaging findings. Findings suggestive of active hemorrhage included areas that remained hyperattenuating or increased in size on delayed-phase images. The clinical outcome of these patients was determined by reviewing their medical records. Relationships between several factors were tested with the Fisher exact test, including (a) the presence or absence of hyperattenuating foci and management and (b) the presence of contained vascular injury or active extravasation and management. RESULTS: Portal venous phase CT revealed a focal high-attenuation parenchymal contrast material collection in 19 patients: nine patients were classified as group 1 and 10 were classified as group 2. All patients in group 1 underwent emergent splenectomy, and all patients in group 2 were initially treated without surgery. Significant differences in management were noted on the basis of whether hyperattenuating foci were seen on portal venous phase images (P < .001) and whether hyperattenuating foci seen at portal venous phase imaging were further characterized as active splenic hemorrhage or a contained vascular injury at delayed-phase CT (P < .001). CONCLUSION: In blunt splenic injury, delayed-phase CT helps differentiate patients with active splenic hemorrhage from those with contained vascular injuries.