The price of COVID-19-induced uncertainty in the options market.

This paper investigates the pricing of uncertainty associated with the COVID-19 responses for 28 countries/regions in 2020. We find that such uncertainty is priced in the equity options market. Specifically, there is a price premium for options that provide protection to hedge against price risk, variance risk, and tail risk caused by a variety of World Health Organization (WHO) announcements and the lockdown announcements from governments on COVID-19. Moreover, such options tend to be more expensive when the governments place stricter restrictions.

Input-to-state stability of stochastic nonlinear system with delayed impulses.

Stochastic input-to-state stability (SISS) of the stochastic nonlinear system has received extensive research. This paper aimed to investigate SISS of the stochastic nonlinear system with delayed impulses. First, when all subsystems were stable, using the average impulsive interval method and Lyapunov approach, some theoretical conditions ensuring SISS of the considered system were established. The SISS characteristic of the argumented system with both stable and unstable subsystems was also discussed, then the stochastic nonlinear system with multiple delayed impulse jumps was considered and SISS property was explored. Additionally, it should be noted that the Lyapunov rate coefficient considered in this paper is positively time-varying. Finally, several numerical examples confirmed validity of theoretical results.

Fixed-deviation stabilization and synchronization for delayed fractional-order complex-valued neural networks.

In this paper, we study fixed-deviation stabilization and synchronization for fractional-order complex-valued neural networks with delays. By applying fractional calculus and fixed-deviation stability theory, sufficient conditions are given to ensure the fixed-deviation stabilization and synchronization for fractional-order complex-valued neural networks under the linear discontinuous controller. Finally, two simulation examples are presented to show the validity of theoretical results.

Evaluation of image quality and radiation dose at prospective ECG-triggered axial 256-slice multi-detector CT in infants with congenital heart disease.

BACKGROUND: There are a limited number of reports on the technical and clinical feasibility of prospective electrocardiogram (ECG)-gated multi-detector computed tomography (MDCT) in infants with congenital heart disease (CHD). OBJECTIVE: To evaluate image quality and radiation dose at weight-based low-dose prospectively gated 256-slice MDCT angiography in infants with CHD. MATERIALS AND METHODS: From November 2009 to February 2010, 64 consecutive infants with CHD referred for pre-operative or post-operative CT were included. All were scanned on a 256-slice MDCT system utilizing a low-dose protocol (80 kVp and 60-120 mAs depending on weight: 60 mAs for ≤ 3 kg, 80 mAs for 3.1-6 kg, 100 mAs for 6.1-10 kg, 120 mAs for 10.1-15 kg). RESULTS: No serious adverse events were recorded. A total of 174 cardiac deformities, confirmed by surgery or heart catheterization, were studied. The sensitivity of MDCT for cardiac deformities was 97.1%; specificity, 99.4%; accuracy, 95.9%. The mean heart rate during scan was 136.7 ± 14.9/min (range, 91-160) with a corresponding heart rate variability of 2.8 ± 2.2/min (range, 0-8). Mean scan length was 115.3 ± 11.7 mm (range, 93.6-143.3). Mean volume CT dose index, mean dose-length product and effective dose were 2.1 ± 0.4 mGy (range, 1.5-2.8), 24.7 ± 5.9 mGy·cm (range, 14.7-35.8) and 1.6 ± 0.3 mSv (range, 1.1-2.5), respectively. Diagnostic-quality images were achieved in all cases. Satisfactory diagnostic quality for visualization of all/proximal/distal coronary artery segments was achieved in 88.4/98.8/80.0% of the scans. CONCLUSION: Low-dose prospectively gated axial 256-slice CT angiography is a valuable tool in the routine clinical evaluation of infants with CHD, providing a comprehensive three-dimensional evaluation of the cardiac anatomy, including the coronary arteries.

Diagnostic and prognostic factors for patients with primary pulmonary non-Hodgkin's lymphoma: A 16-year single-center retrospective study.

Primary pulmonary non-Hodgkin's lymphoma (PP-NHL) is a rare entity with non-specific symptoms and radiographic findings, as well as a difficult preoperative diagnosis. A limited number of studies have described PP-NHL in Chinese patients. The goal of the present study was to improve early diagnosis by examining prognostic factors in patients with PP-NHL. Therefore, a total of 29 patients with PP-NHL were included in the study between January 2001 and June 2017, including 14 with aggressive-type and 15 with indolent-type lymphomas (10 male, 19 female; median age, 50.3 years; range, 19-87 years). Pulmonary nodules and masses (55.2%) were the most common radiographic features. The diagnostic yield was 80% (12/15) by endobronchial biopsy or transbronchial lung biopsy and 100% by computed tomography (CT)-guided percutaneous needle lung biopsy (11/11) or surgery (8/8). Elevated lactate dehydrogenase levels and systemic symptoms were observed considerably more often in patients with aggressive disease than in those with indolent disease. The 1-, 3- and 5-year overall survival (OS) rates were 42, 32, and 21%, respectively, for all patients, 72, 57 and 43%, respectively, for patients with indolent lymphomas, and 13, 6 and 0%, respectively, for patients with aggressive lymphomas. The median OS rate for all patients was 12.0 months; however, the OS rate for patients with aggressive lymphomas was significantly shorter compared with those with indolent lymphomas (7.1 months vs. 16.6 months; P=0.002). Aggressive vs. indolent lymphoma status was indicated to be an independent prognostic factor for poor 5-year OS rate (hazard ratio, 5.98; P=0.014). In conclusion, bronchoscopic and CT-guided percutaneous needle lung biopsies were the most useful and least invasive procedures for diagnosing PP-NHL. Furthermore, aggressive PP-NHL was highly associated with poor 5-year OS rate and a poor prognosis.

Critical ratio between the amplitudes of two overtaking solitary water waves.

In this paper, we study the critical ratio between the amplitudes of two overtaking solitary waves on a layer of water with uniform depth. At the center of encounter, the wave profile is fore-and-aft symmetric, but it could have a single peak or double peaks. The critical ratio separates these two regimes. At the critical point, the wave peak is flat with zero slope and curvature. We solve the full water wave problem numerically by using a fully nonlinear and highly dispersive Boussinesq model. The model is numerically justified to be a good approximation of the Euler equations for solitary waves with very large amplitude. For small amplitude water waves, our calculated critical ratio reduces to the well-known result of 3 predicted by the Korteweg-de Vries equation, a weakly nonlinear and weakly dispersive model. For large amplitude water waves, the nonlinear effect is significant; we find that the critical ratio deviates significantly from 3. For water waves with very high amplitude, e.g., 0.6 relative wave height, the critical ratio could be as large as 4. Our result suggests that higher-order nonlinear and dispersive effects are important when modeling the strong interaction between large amplitude water waves.

Grading of rabbit skeletal muscle trauma by diffusion tensor imaging and tractography on magnetic resonance imaging.

OBJECTIVE: To distinguish the edema, injury, or rupture in the traumatic skeletal muscle fiber in vivo using diffusion tensor imaging (DTI) and tractography on magnetic resonance imaging (MRI). METHODS: The skeletal muscle trauma models were made in 4 rabbits (eight hindlimbs) by iron discus (weight 1.0 kg, diameter 6 cm) falling down vertically from 45 cm height to rabbits' thighs. Conventional sequences and two-dimensional (2D) diffusion-weighted (DW) spin-echo (SE) echo planar imaging (EPI) sequence with fat suppression (b = 600 s/mm2) were performed on 1. 5T MRI scanner. The grading of edema, injury, and fiber rupture in the damaged muscle were made according to their histopathological views, which was consistent with the images. The mean apparent diffusion coefficient (ADC) values and fractional anisotropy (FA) values were measured from the region of interests (ROIs) of all groups on 2D DW images used for tractography. Analysis of variance test was performed to analyze all data. RESULTS: ADC values of the areas in normal muscle, edema muscle, injury muscle, and ruptured muscle were (6.12 +/- 1.34) x 10(-3), (6.38 +/- 1.30) x 10(-3), (8.06 +/- 0.97) x 10(-3), and (9.57 +/- 0.93) x 10(-3) mm2/s, respectively. There was significant difference among groups (P < 0.001), but no difference between edema muscle and normal muscle group (P > 0.05). The FA values of normal muscle, edema muscle, injury muscle, and ruptured muscle were 0.42 +/- 0.12, 0.36 +/- 0.12, 0.26 +/- 0.09, 0.12 +/- 0.08, respectively, with a significant difference among groups (P < 0.001). In the edema muscle, the tracking cross-fiber could be seen but it decreased slightly. In the injury muscle, the tracking fiber decreased markedly. In the ruptured muscle, the transverse-orientation tracking fiber vanished, yet some interrupted longitudinal-orientation tracking fiber could be found. CONCLUSION: The edema, injury, and rupture of muscle fiber in rabbit damaged skeletal muscle can be verified according to the ADC and the FA on DTI and tractography.

Determination of nine organophosphorus pesticides in cereals and kidney beans by capillary gas chromatography with flame photometric detection.

A method is developed for the determination of nine organophosphorus pesticide residues in cereals and kidney beans by capillary gas chromatography with flame-photometric detection. In this method, dichloromethane is used for clean-up after liquid-liquid extraction. It is shown that good separations are obtained using a fused-silica capillary column (DB-1701) by the optimized temperature program. In the spiked levels of 0.012-0.43 mg/kg, the recoveries are from 83.7% to 107%, with the relative standard deviation between 3.2% and 13% and limits of detection from 8.2 to 15 microg/kg. The method is rapid, sensitive, and practical.

Bidirectional solitons on water.

A theory of bidirectional solitons on water is developed by using an integrable Boussinesq surface-variable equation. We present an explicit transformation between the system and a member of the Ablowitz-Kaup-Newell-Segur system, and derive an exact multisoliton solution by using a Darboux transformation. The phase shifts and the maximum wave heights during the interaction are studied for two-soliton overtaking and head-on collisions. They agree with the Korteweg-de Vries solution for overtaking collision and the perturbation solution for head-on collision.

Clinical and imaging findings in patients with severe acute respiratory syndrome.

OBJECTIVE: To investigate the clinical and imaging characteristics of severe acute respiratory syndrome (SARS), and to study their relationship. METHODS: Forty-six SARS confirmed patients were admitted to our hospital from February to April, 2003. X-ray examination documents were available in all cases and chest CT scanning was acquired in 6 cases, which were analyzed retrospectively, accompanied by their clinical features. RESULTS: Fever was found in 97.8% of the patients. Clinical symptoms were mild, but X-ray and CT findings were distinct. CT scanning demonstrated ground glass like lesions and large patchy exudation and consolidation at the early stage in 6 cases. Different findings on radiography and CT were related to the different phases of the disease. After treatment, most lesions were absorbed completely, but slowly in patients with multi-lobe consolidation and/or extensive interstitial infiltration. CONCLUSION: Special clinical and imaging findings could be found in SARS cases. The prognosis of SARS patients is related to the degree of lesions detected by radiography and CT.

Feasibility of histological scoring and colony count for evaluating infective severity in mouse vaginal candidiasis.

Qualitative measurement of the infective level is relatively difficult in experimental vaginal candidiasis. Female BALB/c mice aged 8 to 10 weeks were randomly divided into E1, E2 and E0 groups, which received subcutaneous injection of 0.05 mg, 0.1 mg of estradiol benzoate or 0.1 ml soybean oil 3 days before vaginal inoculation, respectively, and hormone treatment continued every other day thereafter. Each group was further divided into infected and noninfected subgroups. The infected mice were inoculated intravaginally with 10 µl (5 × 10(4) conidia) of Candida albicans suspension, while the noninfected mice were inoculated with 10 µl phosphate-buffered saline. Direct microscopic examination, colony count and vaginal histopathology including infection degree and inflammation extent were performed at 3, 7 and 14 days post inoculation. Estrogen treatment increased the vaginal fungal burden and extent of infection and inflammation compared with the control group, and 0.3 mg/week estrogen generally induced more severe infection and inflammation than 0.15 mg/week estrogen did. Colony count peaked on day 3 and decreased remarkably after 7 days. Infection score increased gradually during the first 7 days and decreased on day 14, while inflammation extent exacerbated progressively over the course of 14 days. This study demonstrates that the modified histological scoring system might be more feasible than colony count for evaluation of infectivity and dynamic change in experimental vaginal candidiasis.

[Influence of novel porous calcium phosphate cement on biological behavior of bone marrow mesenchymal stem cells].

OBJECTIVE: To investigate the effect of novel porous calcium phosphate cement (CPC) scaffoldings on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs). METHODS: BMSCs of Beagle dogs were implanted and cultured with CPC scaffoldings in vitro, tricalcium phosphate (TCP) and poly (lactide-coglycolide) (PLGA) scaffoldings as controls. The attachment, proliferation and differentiation of BMSCs were detected through morphological characters, growth curve and the semi-quantitative detection of alkaline phosphatase (ALP) and osteocalcin (OC) activity. RESULTS: Cell morphology and growth curve illustrated that BMSCs attached to and grown better on the surface of novel porous CPC scaffoldings than that of PLGA group (P < 0.05). Semi-quantitative analysis of ALP showed that ALP expression level in BMSCs on the CPC and TCP group were significantly higher than that of the PLGA group (P < 0.05), the CPC group was slightly higher than the TCP group, but no significant difference was found between the two groups (P > 0.05). The staining and semi-quantitative analysis results of OC demonstrated that calcium deposition of the PLGA group was significantly less than the CPC and TCP group on both observation point (P < 0.05), but no significant difference between the CPC and TCP group (P > 0.05). CONCLUSION: The novel porous CPC material used in this study has good biocompatibility similar to TCP but much better than PLGA which is favorable of BMSCs adhesion, proliferation and osteogenic differentiation. The novel porous CPC material is a suitable scaffolding for BMSCs to fabricate tissue-engineered bone in vitro.

[Distributions and seasonal variations of total dissolved inorganic arsenic in the estuaries and coastal area of eastern Hainan].

The concentrations of total dissolved inorganic arsenic (TDIAs) were measured by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS). Two cruises were carried out in the river, estuary, coastal area and groundwater of eastern Hainan in December 2006 and August 2007. The concentrations of TDIAs in the Wanquan and Wenchang/Wenjiao rivers and their estuaries, coastal area in December 2006 were 4.0-9.4, 1.3-13.3, 13.3-17.3 nmol x L(-1), respectively. The concentrations of TDIAs in the Wanquan and Wenchang/Wenjiao rivers and their estuaries, coastal area in August 2007 were 1.6-15.5, 2.4-15.9, 10.8-17.6 nmol x L(-1), respectively. There was no significantly seasonal variation of TDIAs in the rivers and estuaries during the dry and wet seasons. Compared with other areas in the world, the concentration of TDIAs in the Eastern Hainan remained at pristine levels. TDIAs showed conservatively mixing in the both estuaries. The concentration of TDIAs of groundwater was below detection limit (BDL)-41.7 nmol x L(-1). The submarine groundwater discharge (SGD) to the coastal area was estimated in the drainage basin of Wenchang/Wenjiao river based on the average concentration of TDIAs in the groundwater and SGD water discharge, with the value of 1 153 mol x a(-1). Budget estimation indicated that the SGD discharge is one of the important sources of arsenic in the coastal area.

Individualized radiation dose control in 256-slice CT coronary angiography (CTCA) in retrospective ECG-triggered helical scans: using a measure of body size to adjust tube current selection.

PURPOSE: To reduce radiation dose for retrospective ECG-triggered helical 256-slice CTCA by determining an optimal body size index to prospectively adjust tube current. METHODS: 102 consecutive patients with suspected CAD underwent retrospective ECG-triggered CTCA using 256-slice CT scanner. Six body size indexes including BMI, nipple level (NL) bust, thoracic anteroposterior diameter at NL, chest circumference (CC) at NL, left main and right coronary artery (RCA) origin level were measured and their correlation with noise was evaluated using linear regression. An equation was developed to use this index to adjust tube current. Additional 102 consecutive patients were scanned with the index-based mAs adjustment. A t-test for independent samples was used to compare radiation dose levels with and without the index-based mAs selection method. RESULTS: Linear regression indicated that CC RCA had the best correlation with noise (R2=0.603). Effective radiation dose was reduced from 16.6±0.9 to 9.8±2.7 mSv (p<0.01), i.e. 40.9% lower dose with the CC RCA-adapted tube current method. The image quality scores indicated no significant difference with and without the size-based mAs selection method. CONCLUSION: An accessible measure of body size, such as CC RCA, can be used to adapt tube current for individualized radiation dose control.