Search

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Ulnar shortening osteotomy (USO) has demonstrated good outcomes for patients with ulnar impaction syndrome. To minimize complications such as non-union, precise osteotomy and firm fixation are warranted. Despite various ulnar shortening systems have been developed, current technology does not meet all needs. A considerable portion of patients could not afford those designated USO systems. To tackle this challenge, our team reported successful results in standardized free-hand predrilled USO technique. However, it is still technical demanding and requires sufficient experience and confidence to excel. Therefore, our team designed an ulnar shortening system based on our free-hand technique principle, using metal additive manufacturing technology. The goal of this study is to describe the development process and report the performance of the system. Methods: Utilizing metal additive manufacturing technology, our team developed an ulnar shortening system that requires minimal exposure, facilitates precise cutting, and allows for the easy placement of a 3.5 mm dynamic compression plate, available to patients at zero out-of-pocket cost. For performance testing, two surgeons with different levels of experience in ulnar shortening procedures were included: one fellow-trained hand and wrist surgeon and one senior resident. They performed ulnar shortening osteotomy (USO) using both the free-hand technique and the USO system-assisted technique on ulna sawbones, repeating each method three times. The recorded parameters included time-to-complete-osteotomy, total procedure time, chip diameter, shortening length, maximum residual gap, and deviation angle. Results: For the hand and wrist fellow, with the USO system, the time-to-complete osteotomy was significantly reduced. (468.7 ± 63.6 to 260.0 ± 5 s, p < 0.05). Despite the preop goal was shortening 3 mm, the average shortening length was significantly larger in the free-hand group (5 ± 0.1; 3.2 ± 0.2 mm, p < 0.05). Both maximum residual gap and deviation angle reported no statistical difference between the two techniques for the hand surgeon. As for the senior resident, the maximum residual gap was significantly reduced, using the USO system (2.9 ± 0.8; 0.4 ± 0.4 mm, p = 0.02). Between two surgeons, significant larger maximum residual gap and deviation angle were noted on the senior resident doctor, in the free-hand technique group, but not in the USO system group. Conclusion: The developed USO system may serve as a valuable tool, aiding in reliable and precise cutting as well as fixation for patients undergoing ulnar shortening osteotomy with a 3.5 mm dynamic compression plate, even for less experienced surgeons. The entire process, from concept generation and sketching to creating the CAD file and final production, serves as a translatable reference for other surgical scenarios. [ABSTRACT FROM AUTHOR]

Background: Programmable valve (PV) has been shown as a solution to the high revision rate in pediatric hydrocephalus patients, but it remains controversial among adults. This study is to compare the overall revision rate, revision cause, and revision-free survival between PV and non-programmable valve (NPV) in adult patients with different hydrocephalus etiologies. Method: We reviewed the chart of all patients with hydrocephalus receiving index ventricular cerebrospinal fluid (CSF) shunt operations conducted at a single institution from January 2017 to December 2017. Patients included in the study were followed up for at least 5 years. Statistical tests including independent t-test, chi-square test, and Fisher's exact test were used for comparative analysis, and Kaplan-Meier curve using log-rank test was performed to compare the revision-free survival between the PV and NPV groups. Results: A total of 325 patients were included in the study, of which 181 patients were receiving PVs and 144 patients receiving NPV. There were 23 patients (12.8%) with PV and 22 patients (15.3%) with NPV receiving initial revision. No significant statistical difference in the initial revision rate was observed between the two groups (p = 0.52). No survival difference was found between the PV and NPV groups. However, better revision-free survival was noted in the PV group among idiopathic normal pressure hydrocephalus (iNPH) (p = 0.0274) and post-traumatic hydrocephalus (p = 0.017). Conclusions: The combination of the different etiologies of hydrocephalus and the features of PV and NPV results in different outcomes—revision rate and revision-free survival. PV use might be superior to NPV in iNPH and post-traumatic hydrocephalus patients. Further studies are needed to clarify the indications of PV use in adult hydrocephalus patients. [ABSTRACT FROM AUTHOR]

Background: Initial tumor enlargement (or pseudoprogression) instead of true tumor progression is a common phenomenon in patients with acoustic neuromas who are treated with stereotactic radiosurgery (SRS). This phenomenon can affect clinical decision-making and patient management. This study assessed the correlation between initial tumor enlargement and magnetic resonance imaging characteristics in patients with acoustic neuromas who were treated with linear accelerator (LINAC)-based SRS. The long-term tumor control outcomes were also analyzed. Materials and methods: In total, 330 patients with sporadic acoustic neuromas who were treated with LINAC SRS between March 2006 and March 2020 were retrospectively evaluated to assess their initial tumor enlargement. The tumors were divided into homogeneously enhanced, heterogeneously enhanced, and cystic types based on the morphological characteristics noted on magnetic resonance images. Tumor control was assessed in 275 patients with a follow-up duration of more than 2 years. Results: Initial enlargement was observed in 137 of 330 (41.5%) tumors as early as 3 months after LINAC SRS. Data analysis revealed that postoperative tumors with a residual volume lower than 2.5 cm3 had a lower incidence of initial enlargement (p = 0.039). No correlation was noted between the initial enlargement and morphological characteristics of tumors. In patients with a mean follow-up duration of 82.8 ± 37.2 months, heterogeneously enhanced tumors exhibited a lower control rate than homogeneously enhanced and cystic tumors (p = 0.045). No correlation was noted between initial enlargement and tumor control. Conclusion: Initial enlargement can occur as early as 3 months after SRS. Postoperative residual tumors with a volume lower than 2.5 cm3 exhibit a lower incidence of initial enlargement. Heterogeneously enhanced tumors have a lower local control rate. [ABSTRACT FROM AUTHOR]

Background: Ulnar shortening osteotomy (USO) has demonstrated good outcomes for patients with ulnar impaction syndrome. To minimize complications such as non-union, precise osteotomy and firm fixation are warranted. Despite various ulnar shortening systems have been developed, current technology does not meet all needs. A considerable portion of patients could not afford those designated USO systems. To tackle this challenge, our team reported successful results in standardized free-hand predrilled USO technique. However, it is still technical demanding and requires sufficient experience and confidence to excel. Therefore, our team designed an ulnar shortening system based on our free-hand technique principle, using metal additive manufacturing technology. The goal of this study is to describe the development process and report the performance of the system. Methods: Utilizing metal additive manufacturing technology, our team developed an ulnar shortening system that requires minimal exposure, facilitates precise cutting, and allows for the easy placement of a 3.5 mm dynamic compression plate, available to patients at zero out-of-pocket cost. For performance testing, two surgeons with different levels of experience in ulnar shortening procedures were included: one fellow-trained hand and wrist surgeon and one senior resident. They performed ulnar shortening osteotomy (USO) using both the free-hand technique and the USO system-assisted technique on ulna sawbones, repeating each method three times. The recorded parameters included time-to-complete-osteotomy, total procedure time, chip diameter, shortening length, maximum residual gap, and deviation angle. Results: For the hand and wrist fellow, with the USO system, the time-to-complete osteotomy was significantly reduced. (468.7 ± 63.6 to 260.0 ± 5 s, p < 0.05). Despite the preop goal was shortening 3 mm, the average shortening length was significantly larger in the free-hand group (5 ± 0.1; 3.2 ± 0.2 mm, p < 0.05). Both maximum residual gap and deviation angle reported no statistical difference between the two techniques for the hand surgeon. As for the senior resident, the maximum residual gap was significantly reduced, using the USO system (2.9 ± 0.8; 0.4 ± 0.4 mm, p = 0.02). Between two surgeons, significant larger maximum residual gap and deviation angle were noted on the senior resident doctor, in the free-hand technique group, but not in the USO system group. Conclusion: The developed USO system may serve as a valuable tool, aiding in reliable and precise cutting as well as fixation for patients undergoing ulnar shortening osteotomy with a 3.5 mm dynamic compression plate, even for less experienced surgeons. The entire process, from concept generation and sketching to creating the CAD file and final production, serves as a translatable reference for other surgical scenarios. [ABSTRACT FROM AUTHOR]

Nonfused ring electron acceptors (NFREAs) have attracted much attention due to their concise synthetic routes and low cost. However, developing high-performance NFREAs with simple structure remains a great challenge. In this work, a simple building block (POBT) with noncovalently conformational locks (NoCLs) was designed and synthesized. Single-crystal X-ray study indicated the presence of S⋯O NOCLs in POBT, thus enabling it to possess a coplanar conformation comparable to that of fused-ring CPT. Two novel NFREAs based on CPT and POBT were developed, namely TT-CPT and TT-POBT, respectively. Besides, TT-POBT possessed a smaller Stokes shift and a reduced reorganization energy compared with TT-CPT, indicating the introduction of S⋯O NoCLs can enhance the molecular rigidity even if simplifying the molecular structure. As a result, the TT-POBT-based PSC device afforded an impressive power conversion efficiency of 11.15%, much higher than that of TT-CPT counterpart (7.03%), mainly resulting from the tighter π-π stacking, improved and balanced charge transport, and more favorable film morphology. This work demonstrates the potential of the simple building block POBT with NoCLs towards constructing low-cost and high-performance NFREAs. [ABSTRACT FROM AUTHOR]

Lacking large pores and insufficient bioactivity are two critical disadvantages of bacterial cellulose (BC). In this study, a new type of coating, chondroitin sulfate (CS) modified with gelatin (Gel), was selected to modify porous bacterial cellulose (PBC) for improved biocompatibility. The PBC was fabricated by adding Gel microspheres in the culture medium of BC, and the PBC-CS/Gel scaffolds were prepared by immersing PBC in the CS solutions followed by Gel modification. The morphology, chemical structure, physicochemical properties, and in vitro cell behavior of the PBC-CS/Gel scaffolds were characterized. The mechanical test shows that the tensile strength and Young's modulus of the PBC scaffold were increased with the introduction of CS/Gel coatings. The in vitro cell studies show that the CS/Gel coatings significantly promote cell proliferation, adhesion, differentiation, and ingrowth into scaffolds. The PBC-CS/Gel scaffolds are expected to be used in tissue engineering. [ABSTRACT FROM AUTHOR]

To quantitatively reveal how rock blocks falling into water affect the impulse waves, the influence of a rigid block on induced first wave and second wave is systematically investigated. The block characteristics include the initial velocity, density, volume, and incident angle, and the investigated wave behavior characteristics include the maximum kinetic energy of the water, the transformation ratio of the kinetic energy from the block to the waves, the duration of the waves, the maximum movement speed, and the maximum height and width of the waves. The coupled Eulerian-Lagrangian method (CEL) is introduced to establish the numerical models of the fluid-solid coupling, and a laboratory test of a rigid wedge sliding into water demonstrates that it can reasonably describe the dynamic behavior of a landslide-induced wave. A typical process of a block entering water and its energy variation are described and analyzed in detail. Further, the relationship between each characteristic parameter of the block and the waves is quantitatively investigated and fitted. The simulation results show that energy exchange between the block and the water is very rapid after the block collides with the water. The maximum kinetic energy, maximum velocity, duration, and side dimension of the waves mainly increase non-linearly with the above characteristic parameters of the block. The transformation ratio of the kinetic energy from the block to the water, the first wave, and the second wave are usually below 60%, 45%, and 30%, respectively. The velocity of the block first decreases and then maintains a constant speed after entering the water. The displacement of the block increases linearly with the initial velocity and density of the block and exponentially increases with the block volume at different times. With the increase in the incident angle of the block, the kinetic energy and scale of the second wave increase correspondingly. [ABSTRACT FROM AUTHOR]

This study investigates whether firms with fraudulent financial reporting time their earnings announcements strategically and finds that fraudulent firms are more likely to disclose their earnings in the after-market hours during their fraud periods to postpone fraud detection. Cross-sectional tests show that firms with lower visibility are more likely to adopt and benefit from this timing strategy. In addition, fraudulent firms are found to time their conference calls strategically and package their earning news with forecasts to flood the market with information and lower the fraud detection rate. Results also show that unethical managers may benefit from insider trading when their firms use a timing strategy to lower the detection rate. This study sheds light on a potential strategy that unethical managers may adopt to camouflage their fraudulent financial reporting. These results are robust to a variety of settings of samples and model specifications. [ABSTRACT FROM AUTHOR]

Background: The reported prevalence of sleep disorders in children with chronic kidney disease (CKD) varies greatly. A quantitative meta-analysis to estimate the prevalence of sleep disorders among pediatric CKD patients may provide further information. Objectives: The objective of this study is to estimate the prevalence of sleep disorders in children with CKD. The study protocol was registered on PROSPERO (registration number CRD42021268378). Data sources: Two authors independently searched the PubMed, MEDLINE, EMBASE, and Cochrane review databases up to June 2021. Study eligibility criteria: Eligible studies include data of prevalence of sleep disorders in children with CKD. Study appraisal and synthesis methods: The prevalence of restless legs syndrome, sleep-disordered breathing, pediatric obstructive sleep apnea (i.e., apnea–hypopnea index > 1 event/h in polysomnography), excessive daytime sleepiness, and insomnia/insufficient sleep was estimated using a random-effects model. Subgroup analyses were conducted to compare the prevalence of sleep disorders between children on dialysis and not on dialysis. This meta-analysis included 12 studies with 595 children (mean age: 12.9 years; gender ratio: 55.6% boys; mean sample size: 49.6 patients). Results: The prevalence of restless legs syndrome in children with CKD was 21% (95% confidence interval [CI], 14–30%). The prevalence of sleep-disordered breathing, pediatric obstructive sleep apnea, excessive daytime sleepiness, and insomnia/insufficient sleep was 22% (95% CI, 12–36%), 34% (95% CI, 19–53%), 27% (95% CI, 17–41%), and 14% (95% CI, 7–27%), respectively. Subgroup analysis revealed the pooled prevalence of excessive daytime sleepiness was significantly higher in children on dialysis than in children not on dialysis (43.3% vs. 11.2%; P = 0.018). Children on dialysis also had a high prevalence of other sleeping disorders, although the differences did not reach statistical significance. Children with CKD exhibited a 3.9-fold (95% CI, 1.37 to 10.93) increased risk of restless legs syndrome and a 9.6-fold (95% CI, 3.57 to 25.76) increased risk of excessive daytime sleepiness compared with controls. Limitations: The selected papers are of small sample size, lack of a control group, and exhibit substantial heterogeneity. Conclusions: Sleep disorders are common in children with CKD. Our results indicate that while the prevalence rates of various sleep disorders were higher in children on dialysis than in children not on dialysis, the prevalence of excessive daytime sleepiness was statistically significant in children on dialysis. A higher resolution version of the Graphical abstract is available as Supplementary information. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of minor Ru on the electrochemical behaviour and structural characteristics of passive films on the surface of Ti-6Al-4V alloys under various oil and gas exploration conditions, electrochemical techniques, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and corrosion simulation tests were carried out. The results revealed that the oil and gas exploration conditions had a serious impact on the electrochemical behaviour and corrosion resistance of the tested alloys. The passivation film resistance and corrosion potential of the tested titanium alloys were significantly reduced with increasing acidity and temperature. With the addition of minor ruthenium, the potential of the passive film on the Ti-6Al-4V-0.11Ru alloy surface increased because of the high surface potential of the ruthenium element. The contents of metallic ruthenium and tetravalent titanium oxide TiO2 in the surface film of the Ti-6Al-4V-0.11Ru alloy both increased with increasing temperature, which led to increase the thickness, stability, corrosion resistance and repairability of the passive film on the surface of the Ti-6Al-4V-0.11Ru alloy being better than those qualities of Ti-6Al-4V. These results were also confirmed by corrosion simulation tests. [ABSTRACT FROM AUTHOR]

Mechanical ventilation may cause ventilator-induced lung injury (VILI) in patients requiring ventilator support. Inhibition of autophagy is an important approach to ameliorate VILI as it always enhances lung injury after exposure to various stress agents. This study aimed to further reveal the potential mechanisms underlying the effects of geranylgeranyl diphosphate synthase large subunit 1 (GGPPS1) knockout and autophagy in VILI using C57BL/6 mice with lung-specific GGPPS1 knockout that were subjected to mechanical ventilation. The results demonstrate that GGPPS1 knockout mice exhibit significantly attenuated VILI based on the histologic score, the lung wet-to-dry ratio, total protein levels, neutrophils in bronchoalveolar lavage fluid, and reduced levels of inflammatory cytokines. Importantly, the expression levels of autophagy markers were obviously decreased in GGPPS1 knockout mice compared with wild-type mice. The inhibitory effects of GGPPS1 knockout on autophagy were further confirmed by measuring the ultrastructural change of lung tissues under transmission electron microscopy. In addition, knockdown of GGPPS1 in RAW264.7 cells reduced cyclic stretch-induced inflammation and autophagy. The benefits of GGPPS1 knockout for VILI can be partially eliminated through treatment with rapamycin. Further analysis revealed that Rab37 was significantly downregulated in GGPPS1 knockout mice after mechanical ventilation, while it was highly expressed in the control group. Simultaneously, Rab37 overexpression significantly enhances autophagy in cells that are treated with cyclin stretch, including GGPPS1 knockout cells. Collectively, our results indicate that GGPPS1 knockout results in reduced expression of Rab37 proteins, further restraining autophagy and VILI. [ABSTRACT FROM AUTHOR]

The original online version of this article was revised. [ABSTRACT FROM AUTHOR]

The polycystic ovary syndrome (PCOS), a common endocrine disorder, is mainly related to infertility. Moreover, it is characterized by promoted androgen, suppressed ovulation and insulin resistance. Long non-coding RNA X inactive specific transcript (lncRNA XIST), known as an oncogene or a cancer inhabited factor, is involved in several disease. However, the diagnostic mechanisms of lncRNA XIST in PCOS have not been clarified. Our study aimed to explain whether lncRNA XIST regulates KGN cells proliferation and apoptosis via microRNA (miR)-212-3p/RASA1 axis in PCOS. Levels of lncRNA XIST, miR-212-3p and RASA1 in KGN cells were detected through reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay. Fluorescence in situ Hybridization (FISH) was performed to confirm the expression of lncRNA XIST and miR-212-3p in KGN cells. StarBase and dual-luciferase reporter assay were applied for exploring the interaction between miR-212-3p and RASA1. Cell viability, apoptosis, protein expression of Bcl-2 and Bax were assessed by MTT, flow cytometry analysis, RT-qPCR and western blot, respectively. We found that lncRNA XIST was low-expressed, miR-212-3p was over-expressed, and RASA1 was dramatically down-regulated in KGN cells. LncRNA XIST negatively regulated miR-212-3p expression in KGN cells. MiR-212-3p interacted with RASA1 and negatively regulated RASA1 levels in KGN cells. Up-regulation of lncRNA XIST signally decreased cells viability, stimulated more apoptotic cells, enhanced Bax expression, and depressed Bcl-2 level in KGN cells. However, these observations were abolished after miR-212-3p mimic treatment. Furthermore, miR-212-3p inhibitor significantly inhibited cell proliferation, enhanced more apoptotic cells, increased Bax expression, and decreased Bcl-2 level in KGN cells, and these effects were eliminated by RASA1-siRNA transfection. Our observations revealed that lncRNA XIST protects against PCOS through regulating miR-212-3p/RASA1 axis, suggesting that lncRNA XIST may be a promising therapeutic target for PCOS therapy. [ABSTRACT FROM AUTHOR]

Titanium alloy has become a promising candidate material for oil country tubular goods (OCTGs) in harsh service environments owing to its high specific strength, low density, low elastic modulus, excellent toughness, excellent anti-fatigue and corrosion resistance. However, because the high-quality natural gas resources in China are mainly concentrated deep underground, titanium alloy tubing and casing will bear great external pressure loads underground, so the collapse strength of titanium alloy tubing and casing is very important for the safety of the string in the well. In this paper, a new collapse strength calculation model, the strength collapse criterion model (SCM), was proposed for titanium alloy tubing and casing. 35 different specifications of titanium alloy tubing and casing were selected for the full-scale collapse tests to verify the reliability of the established SCM model. Furthermore, the effect of different key parameters (such as strength, ovality, eccentricity and residual stress) on collapse strength of titanium alloy pipes were investigated systematically and compared with the same specifications of steel pipes. The strength collapse criterion model and analysis results can provide a technical reference for the design and use of titanium alloy OCTGs in the petroleum and natural gas industries. [ABSTRACT FROM AUTHOR]

The load rejection imposes a danger in the pumped storage hydropower plants (PSPs), especially when two or more pump turbines reject their loads simultaneously. In this paper, the simultaneous load rejection scenarios in the PSPs are simulated and analyzed by using a 1-D, 3-D coupling method. The PSP pipe system is modeled by using the 1-D method of characteristics (MOC) and one pump turbine is modeled by using the 3-D computational fluid dynamics (CFD). The simulated flow and head are transmitted between the 1-D, 3-D regions through the interfaces between these two regions. By assuming that the installed pump turbines are of the same type and the corresponding branch pipes have the same properties, the variations of the transient pressures and the flowrates in different pump turbines will be identical. Therefore, only one pump turbine is modeled by the CFD in this study. A new branching junction boundary is proposed to assign the simulated dynamic pressures and flowrates obtained by the 3-D model to other pump turbines. The 1-D-3-D coupling method is validated by experiments with only one pump turbine rejecting its load. The simultaneous load rejection of two pump turbines is then simulated and validated by comparing the results with those of the 1-D simulation. By building only one pump turbine 3-D model, a large amount of computational resources can be saved. The simultaneous load rejection scenario is then analyzed and compared with the single load rejection scenario. Higher water hammer pressures and a larger rotational speed occur in the simultaneous load rejection scenario, which leads to larger pressure pulsations in the pump turbine. The larger pressure pulsations can be further explained by the flow patterns in the runner channels, in which heavier flow separations and vortexes can be observed in the simultaneous load rejection scenario. [ABSTRACT FROM AUTHOR]

The main goal of this study is to examine future changes in meteorological, hydrological drought under the impact of climate change in Dong Nai River Basin, using Standardized Precipitation Index (SPI) and Stream flow Drought Index (SDI). The Soil and Water Assessment Tool (SWAT) is used as a simulated tool to estimate the streamflow in baseline (1980–2005) and climate change (RCP 4.5, 2016–2035) scenarios for meteorological, hydrological calculation. The results show that both types of drought tend to occur in the dry season. The area affected by meteorological and hydrological drought expand in both baseline and RCP 4.5 scenarios. In addition, meteorological drought duration is also significantly increased, especially severely drought months. Although it was detected slightly decreasing in the duration of hydrological drought, the number of months which is occurred moderately drought in sub-basins still goes up in the climate change scenario. These findings could be useful for water shortage assessment and allocation planning in this area in the climate change context in the Dong Nai River Basin. [ABSTRACT FROM AUTHOR]

This study examines whether customer firms' unethical behavior distorts suppliers' investment decisions. Using litigation and restatement to measure unethical behavior, we find that suppliers with customers engaged in frauds tend to invest more during the cheating period, compared to unaffected suppliers. In cross-sectional analyses, we examine the moderating effect of suppliers' reliance on customer information and peer information. Results show that more industry peers' voluntary disclosures and analyst coverage, lower sales volatility, and lower relationship-specific investments mitigate the distortion effect on suppliers. Suppliers' overinvestments caused by customers' misreporting also lead to the suppliers' inferior future performance and subsequent negative market reaction, and the severity of customers' misreporting influences the magnitude of suppliers' investment distortions. These results are robust in a dynamic difference-in-difference specification, an SEC enforcement sample, and a sample that excludes observations for suppliers and customers in the same industry. This paper contributes to the ethics literature by emphasizing the importance of creditable supply-chain information transfer to investment decisions and clarifying the nontrivial influence of principal customers in the supply-chain network. [ABSTRACT FROM AUTHOR]

The aim of pre-stack seismic data’s AVA (Amplitude-versus-angle) inversion is to obtain the underground rocks’ elastic parameters. It is an effective technique of reservoir prediction, reservoir characterization, fluid identification, and other applications. To preserve edges of underground layers and protect small weak reflectors, we propose a new AVA inversion method in this paper which uses adaptive edge-preserving smoothing (Ad-EPS) operator to precondition the elastic parameters model. Ad-EPS preconditioning operator incorporates a priori blocky features to make the geological edges and formation interfaces more precise in the inversion results. The results of numerical examples indicate that, in comparison to AVA inversion with conventional edge-preserving smoothing (EPS) operator preconditioning and AVA inversion with sparse constraint, AVA inversion with Ad-EPS preconditioning operator can preserve small geologic features and protect weak reflectors, such as thin-bedded layers, edges of small lenticular-bodies. Real seismic data application tests indicate that the inverted elastic parameters can well-match with the real well-log curves. The interfaces or edges of geological bodies in the inverted elastic parameters are very clear. [ABSTRACT FROM AUTHOR]

Our study aimed to investigate whether changes in brain function measured with functional magnetic resonance imaging (fMRI) can be detected among individuals with depressive disorders and suicidal ideation. The association between depression severity and brain images is also discussed. Our study recruited 111 participants in three groups: 35 depressive patients with suicidal ideation (SI), 32 depressive patients without suicidal ideation (NS), and 44 healthy controls (HCs). All participants were scanned using 3T MRI to obtain resting-state functional images, and functional connectivity (FC), amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and graph theoretical analysis (GTA) were performed. We found functional activity differences, such as the hippocampus and thalamus, in the SI group compared with the NS group. We also concluded lower activity in the thalamus and cuneus regions were related to suicidal ideation. We also found several functional connectivity of the brain areas, such as hippocampus, cuneus, and frontal regions, in the SI group correlated with Hamilton Depression Rating Scale (HAM-D) and Hospital Anxiety and Depression Scale (HADS). A graph theoretical analysis (GTA) and network-based statistical (NBS) analysis revealed different topological organization and slightly better local segregation of the brain network in healthy participants compared with those in depressive patients with suicidal ideation. We suggest that brain functional connectivity may be affected in depressive patients with suicidal ideation. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) deteriorates suddenly primarily due to excessive inflammatory injury, and insulin-like growth factor-1 (IGF-1) is implicated in endocrine control of the immune system. However, the effect of IGF-1 levels on COVID-19 prognosis remains unknown. Using UK Biobank resource, we investigated the association between circulating IGF-1 concentrations and mortality risk (available death data updated on 07 Sep 2020) among COVID-19 patients who had pre-diagnostic serum IGF-1 measurements at baseline (2006–2010). Unconditional logistic regression was performed to estimate the odds ratio (OR) and 95% confidence intervals (CIs) of mortality. Among 1670 COVID-19 patients, 415 deaths occurred due to COVID-19. Compared to the lowest quartile of IGF-1 concentrations, the highest quartile was associated with a 41% lower risk of mortality (OR = 0.59, 95% CI 0.41–0.86, P-trend = 0.01). In the continuous model, per 1-standard deviation increment in log-transformed IGF-1 was associated with a 15% reduction in the risk (intraclass correlation coefficients corrected OR = 0.85, 95% CI 0.73–0.99). The association was largely consistent in the various stratified and sensitivity analyses. In conclusion, our data suggest that higher IGF-1 concentrations are associated with a lower risk of COVID-19 mortality. Further studies are required to determine whether and how targeting IGF-1 pathway might improve COVID-19 prognosis. [ABSTRACT FROM AUTHOR]

Fibroblast-like synoviocytes (FLS) play a pathogenic role in rheumatoid arthritis (RA). STAT3 signaling is activated in FLS of RA patients (RA-FLS), which in turn causes RA-FLS hyperproliferation. RL is a traditional remedy for treating inflammatory diseases in China. It comprises Rosae Multiflorae Fructus and Lonicerae Japonicae Flos. A standardized ethanolic extract of RL (RLE) has been shown to exert anti-arthritic effects in collagen-induced arthritis (CIA) rats. Some constituents of RLE were reported to inhibit JAK2/STAT3 signaling in rat FLS. Here, we determined whether RLE inhibits FLS hyperproliferation, and explored the involvement of STAT3 signaling in this inhibition. In joints of CIA rats, RLE increased apoptotic FLS. In IL-6/sIL-6R-stimulated RA-FLS, RLE reduced cell viability and evoked cell apoptosis. In synovial tissues of CIA rats, RLE lowered the protein level of phospho-STAT3. In IL-6/sIL-6R-stimulated RA-FLS, RLE inhibited activation/phosphorylation of STAT3 and JAK2, decreased the nuclear localization of STAT3, and downregulated protein levels of Bcl-2 and Mcl-1. Over-activation of STAT3 diminished RLE's anti-proliferative effects in IL-6/sIL-6R-stimulated RA-FLS. In summary, RLE inhibits hyperproliferation of FLS in rat and cell models, and suppression of STAT3 signaling contributes to the underlying mechanisms. This study provides further pharmacological groundwork for developing RLE as a modern anti-arthritic drug. [ABSTRACT FROM AUTHOR]

Amplitude versus offset (AVO) attribute inversion can help to constrain lithologies and interpret oil and gas accumulations. In this paper, we simulate four different gas hydrate and free gas configurations through AVO forward modeling. When there is no free gas under gas hydrate, the AVO attribute characteristics of gas hydrate are only related to the saturation of gas hydrate. When there is free gas under gas hydrate, if the gas hydrate saturation is high, the AVO attribute characteristics [such as the product of intercept (P) and gradient (G)] are not sensitive to identify gas hydrate. Otherwise, the AVO attribute characteristics are sensitive for identifying gas hydrate, but greatly affected by free gas. The results of this paper constrain the distribution of gas hydrate in the Shenhu area and provide a basis for future gas hydrate exploration. [ABSTRACT FROM AUTHOR]

Among many seismic inversion methods, the sparse spike inversion for post-stack seismic data uses the migrated and stacked seismic data which is regarded as zero offset reflection seismic data in the case of normal incidence to extract reflectivity and impedance of underground rocks. The seismic reflectivity and impedance can reflect underground rocks' lithology, petrophysical property, oil–gas possibility, and so forth. However, the common used post-stack seismic inversion adopts single trace in the process of inversion and completes the whole data cube's inversion through trace by trace. It cannot use lateral regularization. Hence, the lateral continuity of single trace inversion result is poor. It is difficult to represent the lateral variation features of underground rocks. Based on the conventional sparse spike inversion, the nuclear norm of matrix in the matrix completion theory is introduced in the process of post-stack seismic inversion. At the same time, the strategy of multi-trace seismic data simultaneous inversion is used to carry out lateral regularization constraint. Numerical tests on 2D model indicate that the inversion results obtained from the proposed method can clearly represent not only the vertical variation features but also the lateral variation features of underground rocks. At last, the inversion results of real seismic data further show the feasibility and superiority of the proposed method in practical application. [ABSTRACT FROM AUTHOR]

We present a polarization-manipulated multispectral perfect absorber based on a 2D metal/insulator/metal nanocavity array, in which a periodic structure of stacked Au–Al2O3 elliptical nanodisk is deposited on a bulk flat Au substrate. Theoretical analysis of the electromagnetic property showed that both the dipolar plasmon resonance and the plasmon cavity mode are the physical origins of the near-perfect absorption. Owing to the azimuthally symmetry breaking, the reflectivity difference can reach up to 90% through an orthogonal rotation of the incident light polarization. In addition, the central wavelength of these absorption bands is highly sensitive to variation of the surrounding liquid sample's refractive index. This proposed sub-wavelength plasmonic platform with both features of the polarized manipulation and the sensitive sensing may provide promising applications in multi-wavelength filtering and bio-sensing. [ABSTRACT FROM AUTHOR]

Bioreactor-cultured adventitious roots (ARs) of the endangered medicinal plant Oplopanax elatus Nakai is a novel alternative plant material. To utilize ARs in the product production, the present study investigated the anti-inflammatory effect of O. elatus ARs. In the in vivo experiment, lipopolysaccharide (LPS)-induced acute lung injury disease model was established and several inflammatory indexes were determined. For the LPS-stimulated mice, after pretreatment of AR crude extract (200 mg/kg), cell infiltration in lungs was decreased, the production of proinflammatory mediators, including nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin (IL)-6, and 1β in the bronchoalveolar lavage fluid was evidently reduced, which indicated that O. elatus ARs had an anti-inflammatory effect. In the in vitro experiment, ethyl acetate (EtOAc) fractions (12.5, 25, and 50 μg/mL) were used to treat LPS-induced peritoneal macrophages (PMs) of mice. The production of NO, prostaglandin E2, TNF-α, IL-6, and IL-1β in LPS-stimulated PMs was obviously inhibited (p < 0.05) after pretreatment with EtOAc fractions, and the expression of the inducible nitric oxide synthase and cyclooxygenase were also suppressed. To clarify the anti-inflammatory mechanism, effects of EtOAc fraction on changes of proteins related to the pathways of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB) were investigated. The phosphorylation of extracellular regulated protein kinases, c-jun n-terminal kinase, and p38 MAPK in LPS-induced PMs was inhibited after pretreatment of EtOAc fractions. In addition, EtOAc fractions enhanced inhibitor of nuclear factor-kappa B-α expression and decreased nuclear translocation of p65 NF-κB. Thus, EtOAc from O. elatus ARs is involved in regulating MAKP and NF-κB signaling pathways to inhibit LPS-induced inflammation. [ABSTRACT FROM AUTHOR]

We investigate the negative refraction effect at a planar interface of a highly absorptive material, where the direct experimental verification is difficult because of the loss-induced skin depth effect. An apparent contradiction occurs when we try to determine the group velocity direction by the method of equifrequency contours (EFCs) in detail. This contradiction forbids any physical solution to be found for negative refraction. We conclude that this paradox is mainly caused by the definition of complex wavevector ~k which is conventionally adopted in the case of complex permittivity. The complex wavevector may result in ambiguously defined optical path, which limits the application of the classical Snell's law. We propose a bold suggestion that the complex wavevector ~k should be replaced by a complex frequency ~ω. Therefore, the optical path can always be defined as real. The proposed hypothesis is capable of resolving the contradiction about the loss-induced negative refraction, and the obtained theoretical prediction fits well with the reported experimental results. [ABSTRACT FROM AUTHOR]

PARK14 patients with homozygous (D331Y) PLA2G6 mutation display motor deficits of pure early-onset Parkinson's disease (PD). The aim of this study is to investigate the pathogenic mechanism of mutant (D331Y) PLA2G6-induced PD. We generated knockin (KI) mouse model of PARK14 harboring homozygous (D331Y) PLA2G6 mutation. Then, we investigated neuropathological and neurological phenotypes of PLA2G6D331Y/D331Y KI mice and molecular pathogenic mechanisms of (D331Y) PLA2G6-induced degeneration of substantia nigra (SN) dopaminergic neurons. Six-or nine-month-old PLA2G6D331Y/D331Y KI mice displayed early-onset cell death of SNpc dopaminergic neurons. Lewy body pathology was found in the SN of PLA2G6D331Y/D331Y mice. Six-or nine-month-old PLA2G6D331Y/D331Y KI mice exhibited early-onset parkinsonism phenotypes. Disrupted cristae of mitochondria were found in SNpc dopaminergic neurons of PLA2G6D331Y/D331Y mice. PLA2G6D331Y/D331Y mice displayed mitochondrial dysfunction and upregulated ROS production, which may lead to activation of apoptotic cascade. Upregulated protein levels of Grp78, IRE1, PERK, and CHOP, which are involved in activation of ER stress, were found in the SN of PLA2G6D331Y/D331Y mice. Protein expression of mitophagic proteins, including parkin and BNIP3, was downregulated in the SN of PLA2G6D331Y/D331Y mice, suggesting that (D331Y) PLA2G6 mutation causes mitophagy dysfunction. In the SN of PLA2G6D331Y/D331Y mice, mRNA levels of eight genes that are involved in neuroprotection/neurogenesis were decreased, while mRNA levels of two genes that promote apoptotic death were increased. Our results suggest that PARK14 (D331Y) PLA2G6 mutation causes degeneration of SNpc dopaminergic neurons by causing mitochondrial dysfunction, elevated ER stress, mitophagy impairment, and transcriptional abnormality. [ABSTRACT FROM AUTHOR]

In this paper, the secrecy performance of cooperative heterogeneous networks with unreliable backhaul over Nakagami-m fading channels is investigated. To secure the proposed system, a friendly jammer is considered to confuse eavesdroppers. To transmit the signals from the source to the destination, a two-phase transmitter/relay selection scheme is proposed. The best transmitter is selected when the signal-to-noise ratio at the relays is maximized. In the second phase, the best relay is chosen when the jamming signal-to-interference-plus-noise ratio of the eavesdroppers is minimized. To investigate the system performance, closed -form expressions are derived for the secrecy outage probability, ergodic capacity and non-zero achievable secrecy rate. In order to gain an insight into the system, asymptotic analysis is also provided. The results show that the degree of cooperative transmission and backhaul reliability are key parameters in the system and these parameters determine the secrecy performance. [ABSTRACT FROM AUTHOR]

Thyroid hormone is a kind of important hormone which regulates metamorphosis. Its role is well described in amphibian metamorphosis. Thyroid hormones (T3 and T4) have also been demonstrated to play a role in metamorphosis of marine invertebrates. However, the mechanism of thyroid hormone in metamorphosis of marine invertebrates remains unknown. A homolog of vertebrate thyroid hormone receptor (TR) was cloned and identified in abalone Haliotis diversicolor and was named HdTR. The mRNA expressions of HdTR, thyroid peroxidase (TPO), thyroid peroxidase 1 (TPO1), idothyronine deiodinase III (IDIII) and integrin alpha-V (ITGAV) had significant difference in metamorphosis of H. diversicolor. Metamorphosis rate and mortality rate were significantly different in HdTR RNAi experiment and T3 inducing experiment. In RNAi experiment, ITGAV and CCND1 (cyclin D1) expression of dsRNA HdTR exposing group were significantly lower than those of blank control and negative control. But CTNNB (catenin beta) expression of dsRNA HdTR exposing group was higher than that those of blank control and negative control. ERK (extracellular signal regulated kinases) and PI3K (phosphoinositide-3-kinase) had no significant difference in RNAi experiment. Moreover, ITGAV of 1 μmol/L T3 group was significantly lower than that of 0 μmol/L T3 group, PI3K expression of 10 μmol/L T3 group was higher than that of 0 μmol/L T3 group, and the other genes expression had no significant difference in T3 inducing experiment. The data of genes expression suggested that CCND1 might be an effector gene of TR genomic action, while CTNNB might be regulated by unliganded TR. CCND1 and CTNNB may be involved in cell proliferation of metamorphosis. T3 might regulate the expression level of PI3K via nongenomic way. These results shed light on the mechanism of thyroid hormone in abalone metamorphosis. [ABSTRACT FROM AUTHOR]

Objective: The aim of this retrospective observational study was to analyze the clinical and pathological characteristics of small-cell neuroendocrine carcinoma of the gynecologic tract (SCNCGT).Methods: Twenty patients with SCNCGT were enrolled and their clinic-pathological features were analyzed. All patients were treated at the Beijing Obstetrics and Gynecology Hospital, Capital Medical University, China, and were followed up until December 31, 2017.Results: (1) Patient characteristics: The incidence of SCNCGT was 0.3% (20/6578) of gynecologic cancer in our hospital from January 1, 2007, to December 31, 2017. The average age of the patients was 42.0 ± 11.8 (23-63 years). Out of 20 patients enrolled, seven (35.0%) had lymph node metastasis. Out of 17 patients treated with complete surgery, 14 (82.4%) had lymph-vascular space invasion. (2) Treatment: Eleven out of the 14 patients with small-cell neuroendocrine carcinoma of the cervix (SCNCC) were treated with radical surgery; all the 11 patients received chemotherapy and radiotherapy postoperatively. The remaining three patients received comprehensive chemotherapy and/or radiotherapy instead of radical surgery. The six patients who had one or the other type of SCNCGT (involving the ovary, endometrium, or vagina) were all treated with comprehensive surgery. (3) Prognosis: The follow-up time for the study ranged from 8 to 87 months. Three (15.0%) of the 20 patients were diagnosed with distant metastasis at the beginning of the study. Eight (40.0%) patients died as of December 31, 2017, while the other 12 patients were in follow-up. The average survival time was 43.6 months (16-77 months).Conclusion: SCNCGT is a highly malignant tumor characterized by rare morbidity, a propensity for metastasis, and poor prognosis. Comprehensive treatment may be a good approach to prolong survival in some patients. [ABSTRACT FROM AUTHOR]

An improved cascade control scheme is proposed based on modified Smith predictor for controlling a class of unstable processes with time delay. The proposed control structure consist three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed according to Internal Model Control (IMC) principles. The primary loop set point tracking controller and disturbance rejection controller are designed using the same procedure based on modified Smith predictor control structure. An analytical method on the basis of the Internal Model Control design principle is adopted for the two controllers which reduces complexity in design. The two controllers in primary loop are designed as proportional, integral and derivative (PID) controller cascaded with a lead-lag filter. Moreover, suitable values are recommended for the three controllers based on extensive simulations. Simulations studies are carried out to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, an energy harvesting relay network over Nakagami-m fading is investigated. In the considered system, the power beacon can provide wireless energy for the source and relays which deploy time-switching-based radio frequency energy harvesting technique. Two relay selection schemes, namely partial relay selection and optimal relay selection, are proposed in order to enhance the system performance. In the former, the source only has the channel state information of the first hop, while in the latter it has the full knowledge of the channel state information. The eavesdropper is able to wiretap to the signal transmitted from the source and the relays. The exact closed-form expressions of secrecy outage probability are derived. The results show that optimal relay selection performs better than partial relay selection. With increasing number of relays, the considered system shows better performance. In addition, the energy harvesting duration has a significant effect on the secrecy outage probability. [ABSTRACT FROM AUTHOR]

High-quality insulator region proposals play important roles in the process of transmission line inspection images. A generation method of insulator region proposals based on edge boxes is proposed in this paper, and edge boxes are applied to the localization of insulators in inspection images creatively. We take a series of operations to generate insulator region proposals: K-means cluster is used on curvature scale space (CSS) points extracted from edge images, the most appropriate cluster number is chosen, and the circle is drawn on the insulator subclass. We consider the characteristics of insulators' edge images, and combine these characteristics with edge boxes. As a result, more insulator region proposals are displayed. The experimental results show that our method can effectively reduce the interference area, meanwhile, has high quality of region proposals with fast calculation speed. [ABSTRACT FROM AUTHOR]

Recently, the seismic illumination analysis has progressed considerably in methodology which has been developed not only from one-way wave equation-based illumination to full-wave equation-based illumination but also from conventional illumination analysis to directional illumination analysis with local plane-wave decomposition. Because of the inherent defects of the one-way wave equation, the full-wave equation-based seismic illumination methods have increasingly attracted more attention. However, full-wave equation-based wavefield includes both downgoing and upgoing waves, such as transmissive, turning, and reflected waves. This hybrid wavefield can mislead us in seismic illumination analysis. For the sake of a preferable seismic illumination analysis method, we separated upgoing and downgoing wavefields in the time domain using Poynting vector and defined the incident and reflected illumination analysis functions based on the separated wavefields. Furthermore, we applied these two new illumination functions in seismic illumination analysis with the Sigsbee2a model. Multiple-shot illumination results show that the full-wave illumination and incident illumination maps are consistent with the seismic migration image. Because of no interference caused by the interactions between upgoing and downgoing waves, the incident illumination is superior for illumination analysis. Successful application of the full-wave equation-based incident and reflected illumination functions in the actual acquisition direction design of marine seismic geometry verifies their applicability and reveals their excellent prospects. [ABSTRACT FROM AUTHOR]

Ticks are blood-sucking ectoparasites of great medical and veterinary significance that can transmit bacteria, protozoa, fungi and viruses, causing a variety of human and animal diseases worldwide. In the present study, the intestinal bacterial flora associated with Haemaphysalis flava ticks in different developmental stages were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). Eleven distinct DGGE bands were found using PCR-DGGE method. Sequences analyses indicated that they belonged to Bacillus cereus, Candidatus rickettsia, Erwinia sp., Klebsiella pneumoniae, Pectobacterium carotovorum, Pseudomonas aeruginosa, Rickettsia peacockii, Rickettsia helvetica, Rickettsia slovaca, Staphylococcus simulans and Uncultured bacterium clone. Our find that the K. pneumoniae and P. aeruginosa isolates were presented in all H. flava ticks in different developmental stages. The present results indicated that zoonotic pathogens are present in H. flava ticks in Henan province, China. To our knowledge, this is the first report on intestinal bacterial flora associated with H. flava ticks in China. [ABSTRACT FROM AUTHOR]

This paper investigates the outage performance of cognitive spectrum-sharing multi-relay networks in which the relays operate in a full-duplex (FD) mode and employ the decode-and-forward (DF) protocol. Two relay selection schemes, i.e., partial relay selection (PRS) and optimal relay selection (ORS), are considered to enhance the system performance. New exact expressions for the outage probability (OP) in both schemes are derived based on which an asymptotic analysis is carried out. The results show that the ORS strategy outperforms PRS in terms of OP, and increasing the number of FD relays can significantly improve the system performance. Moreover, novel analytical results provide additional insights for system design. In particular, from the viewpoint of FD concept, the primary network parameters (i.e., peak interference at the primary receivers, number of primary receivers, and their locations) should be carefully considered since they significantly affect the secondary network performance. [ABSTRACT FROM AUTHOR]

Pore structure and mineral matrix elastic moduli are indispensable in rock physics models. We propose an estimation method of pore structure and mineral moduli based on Kuster-Toksöz model and Biot's coefficient. In this technique, pore aspect ratios of five different scales from 100 to 10−4 are considered, Biot's coefficient is used to determine bounds of mineral moduli, and an estimation procedure combined with simulated annealing (SA) algorithm to handle real logs or laboratory measurements is developed. The proposed method is applied to parameter estimations on 28 sandstone samples, the properties of which have been measured in lab. The water saturated data are used for estimating pore structure and mineral moduli, and the oil saturated data are used for testing these estimated parameters through fluid substitution in Kuster-Toksöz model. We then compare fluid substitution results with lab measurements and find that relative errors of P-wave and S-wave velocities are all less than 5%, which indicates that the estimation results are accurate. [ABSTRACT FROM AUTHOR]

Glycosyltransferase-1 from Bacillus cereus ( BcGT1) catalyzes a reaction that transfers a glucosyl moiety to flavonoids, such as quercetin, kaempferol, and myricetin. The enzymatic glucosidation shows a broad substrate specificity when the reaction is catalyzed by wild-type BcGT1. Preliminary assays demonstrated that the F240A mutant significantly improves the regioselectivity of enzymatic glucosidation toward quercetin. To unveil and further to control the catalytic function of BcGT1, mutation of F240 to other amino acids, such as C, E, G, R, Y, W, and K, was performed. Among these mutants, F240A, F240G, F240R, and F240K greatly altered the regioselectivity. The quercetin-3- O-glucoside, instead of quercetin-7- O-glucoside as for the wild-type enzyme, was obtained as the major product. Among these mutants, F240R showed nearly 100 % product specificity but only retained 25 % catalytic efficiency of wild-type enzyme. From an inspection of the protein structure, we found two other amino acids, F132 and F138, together with F240, are likely to form a hydrophobic binding region, which is sufficiently spacious to accommodate substrates with varied aromatic moieties. Through the replacement of a phenylalanine by a tyrosine residue in the substrate-binding region, the mutants may be able to fix the orientation of flavonoids, presumably through the formation of a hydrogen bond between substrates and mutants. Multiple mutants-F240R_F132Y, F240R_F138Y, and F240R_F132Y_F138Y-were thus constructed for further investigation. The multiple points of mutants not only maintained the high product specificity but also significantly improved the catalytic efficiency, relative to F240R. The same product specificity was obtained when kaempferol and myricetin were used as a substrate. [ABSTRACT FROM AUTHOR]

The dynamics of the bubble collapse near a rigid boundary is a fundamental issue for the bubble collapse application and prevention. In this paper, the bubble collapse is modeled by adopting the lattice Boltzmann method (LBM) and is verified, and then the dynamic characteristics of the collapsing bubble with the second collapse is investigated. The widely used Shan-Chen model in the LBM multiphase community is modified by coupling with the Carnahan-Starling equation of state (C-S EOS) and the exact difference method (EDM) for the forcing term treatment. The simulation results of the bubble profile evolution by the LBM are in excellent agreements with the theoretical and experimental results. From the two-dimensional pressure field evolution, the dynamic characteristics of the different parts during the bubble collapse stage are studied. The role of the second collapse in the rigid boundary damage is discussed, and the impeding effect between two collapses is demonstrated. [ABSTRACT FROM AUTHOR]