In the two-step analysis of Pebble-Bed type High-Temperature Gas-Cooled Reactor (PB-HTGR), the lattice physics calculation for the generation of homogenized cross-sections is based on the fuel ...pebble. However, the randomly-dispersed fuel particles in the fuel pebble introduce double heterogeneity and randomness. Compared to the deterministic method, the Monte Carlo method which is flexible in geometry modeling provides a high-fidelity treatment. Therefore, the Monte Carlo code NECP-MCX is extended in this study to perform the lattice physics calculation of the PB-HTGR. Firstly, the capability for the simulation of randomly-dispersed media, using the explicit modeling approach, is developed in NECP-MCX. Secondly, the capability for the generation of the homogenized cross-section is also developed in NECP-MCX. Finally, simplified PB-HTGR problems are calculated by a two-step neutronics analysis tool based on Monte Carlo homogenization. For the pebble beds mixed by fuel pebble and graphite pebble, the bias is less than 100 pcm when compared to the high-fidelity model, and the bias is increased to 269 pcm for pebble bed mixed by depleted fuel pebble. Numerical results show that the Monte Carlo lattice physics calculation for the two-step analysis of PB-HTGR is feasible.
To investigate the possible impact of urban development on lightning activity, an eight-year (2010–2017) cloud-to-ground (CG) lightning dataset provided by the National-Wide Lightning Detection ...Network in China was analyzed to characterize the CG lightning activity in the metropolitan area of Beijing. There is a high CG flash density area over the downtown of Beijing, but different from previous studies, the downwind area of Beijing is not significantly enhanced. Compared with the upwind area, the CG flash density in the downtown area was enhanced by about 50%. Negative CG flashes mainly occurred in the downtown and industrial area, while positive CG flashes were distributed evenly. The percentage of positive CG flashes with Ipeak ≥ 75 kA is more than six times that of the corresponding negative CG flashes in the Beijing area. The enhancement of lightning activity varies with season and time. About 98% of CG flashes occurred from May to September, and the peak of CG diurnal variation is from 1900 to 2100 local time. Based on the analysis of thunderstorm types in Beijing, it is considered that the abnormal lightning activity is mainly responsible for an enhancement of the discharge number in frontal systems rather than the increase of the number of local thunderstorms. In addition, there is a non-linear relationship between pollutant concentrations and CG flash number, which indicates that there are other critical factors affecting the production of lightning.
The canonical Wnt/ß-catenin signaling pathway has implications in early facial development; yet, its function and signaling mechanism remain poorly understood. We report here that the frontonasal and ...upper jaw primordia cannot be formed after conditional ablation of ß-catenin with Foxg1-Cre mice in the facial ectoderm and the adjacent telencephalic neuroepithelium. Gene expression of several cell-survival and patterning factors, including Fgf8, Fgf3, and Fgf17, is dramatically diminished in the anterior neural ridge (ANR, a rostral signaling center) and/or the adjacent frontonasal ectoderm of the ß-catenin conditional mutant mice. In addition, Shh expression is diminished in the ventral telencephalon of the mutants, while Tcfap2a expression is less affected in the facial primordia. Apoptosis occurs robustly in the rostral head tissues following inactivation of Fgf signaling in the conditional mutants. Consequently, the upper jaw, nasal, ocular and telencephalic structures are absent, but the tongue and mandible are relatively developed in the conditional mutants at birth. Using molecular biological approaches, we demonstrate that the Fgf8 gene is transcriptionally targeted by Wnt/ß-catenin signaling during early facial and forebrain development. Furthermore, we show that conditional gain-of-function of ß-catenin signaling causes drastic upregulation of Fgf8 mRNA in the ANR and the entire facial ectoderm, which also arrests facial and forebrain development. Taken together, our results suggest that canonical Wnt/ß-catenin signaling is required for early development of the mammalian face and related head structures, which mainly or partly acts through the initiation and modulation of balanced Fgf signaling activity.
► The dorsal face is absent after conditional deletion of ß-catenin with Foxg1-Cre. ► Massive apoptosis follows diminished Fgf8 expression in the rostral head primordia. ► Fgf8 is a positive target of Wnt/ß-catenin signaling in the ANR and facial ectoderm. ► Fgf8 is ectopically expressed in the facial ectoderm by gain-of-function of ß-catenin. ► Shh expression is diminished in the telencephalon by loss-of-function of ß-catenin.
To assess the visual prognosis of optic neuritis (ON) in dependence of the glial autoimmune antibody status and associated factors.
Longitudinal observational cohort study.
Patients with ON and ...measurements of serum concentrations of glial autoantibodies were consecutively and longitudinally examined with a minimal follow-up of 3 months. Patients with multiple sclerosis and double seronegative results were excluded.
The study included 529 patients (aquaporin-4 immunoglobulin AQP4-IgG seropositive, n = 291; myelin oligodendrocyte glycoprotein immunoglobulin MOG-IgG seropositive, n = 112; double-seronegative, n = 126) with 1022 ON episodes (AQP4-IgG seropositive, n = 550; MOG-IgG seropositive, n=254; double-seronegative, n = 218). Prevalence of severe vision loss (best-corrected visual acuity BCVA ≤20/200 at the end of follow-up) was higher (P < .001) in the AQP4-IgG group (236/550; 42.9%) than in the seronegative group (68/218; 31.2%) and in the MOG-IgG group (15/254; 5.9%). Prevalence of good vision recovery (BCVA≥20/40) was higher (P < .001) in the MOG-IgG group (229/254; 90.2%) than in the seronegative group (111/218; 50.9%) and in the AQP4-IgG group (236/550; 42.9%). In multivariable logistic analysis, higher prevalence of severe vision loss was associated with AQP4-IgG seropositivity (odds ratio OR 1.66; 95% CI 1.14, 2.43; P = .008), male sex (OR 1.97, 95% CI 1.33, 2.93; P < .001), age at ON onset >45 years (OR 1.93, 95% CI 1.35, 2.77; P < .001), nadir vision ≤20/200 (OR 14.11, 95% CI 6.54, 36.93; P < .001), and higher number of recurrences (OR 1.35, 95% CI 1.14, 1.61; P = .001). Higher prevalence of good vision outcome was associated with MOG-IgG seropositivity (OR 8.13, 95% CI 4.82, 14.2; P < .001), age at ON onset <18 years (OR 1.78, 95% CI 1.18, 2.71; P = .006), nadir visual acuity ≥20/40 (OR 4.03; 95% CI 1.45, 14.37; P = .015), and lower number of recurrences (OR 0.60; 95% CI 0.50, 0.72; P < .001).
Severe vision loss (prevalence in the AQP4-IgG group, MOG-IgG group, and seronegative group: 42.9%, 5.9%, and 31.2%, respectively) was associated with AQP4-IgG seropositivity, male gender, older age at onset, worse nadir vision, and higher number of recurrences.
High‐speed video observations of two sprites with halo features were analyzed with concurrent measurements of broadband magnetic sferics. Both events were produced by positive cloud‐to‐ground (CG) ...strokes. Moreover, the halo features appeared less than 0.5 ms after the return stroke, and the first sprite elements followed within 1 and 3 ms, respectively, for the two cases. The persistent charge transfer in the causative stroke from long continuing current can maintain the continuous glowing of existing sprite elements, and also may aid the vertical development and enhanced luminescence of later sprite elements. The observations with electric field (E‐field) simulations by the transmission line model provide evidence that the induction component of the lightning‐induced E‐field contributes significantly to halo formation. Our results suggest additional measurements and analysis are needed to identify the specific role of induction E‐field in addition to the well‐known quasi‐electrostatic (QE) field in the lightning‐induced impact on the mesosphere.
Plain Language Summary
We analyze two cases of sprite observations demonstrating the halo feature that were both produced by positive cloud‐to‐ground (CG) strokes over a mesoscale convective system in the central United States. The first event was the brightest sprites observed on that night, while the second event was a dancing sprite event containing three sprite elements all following a single +CG. The broadband (<1 Hz–400 kHz) lightning sferic signals recorded at various ranges are analyzed in comparison with the high‐speed and low‐light‐level video to reveal the detailed development and evolution of sprite events. The first case contains an elves, halo, and sprite elements; the second case includes a halo as well as three sprite elements. In both case, the halo features appeared less than 0.5 ms after the return stroke. From this observation with relatively high time resolution and the simulation of lightning‐induced electrical field (E‐field) change at the height of halo formation, we attribute the occurrence of halo to the induction E‐field from the initial portion (within 1 ms) of charge transfer in the causative stroke mainly. The continuous illumination of the existing sprite element and the time delay and vertical structure of following sprites are associated with the subsequent continuing current of causative strokes.
Key Points
Two sprite events featured with halo were captured on the high‐speed video camera with coordinated broadband sferic data
In both cases, the halo initiated within 0.5 ms after the causative return stroke
The induction component of lightning‐induced transient E‐field appears to make a considerable contribution to the halo formation
Neither the mechanisms that govern lip morphogenesis nor the cause of cleft lip are well understood. We report that genetic inactivation of Lrp6, a co-receptor of the Wnt/beta-catenin signaling ...pathway, leads to cleft lip with cleft palate. The activity of a Wnt signaling reporter is blocked in the orofacial primordia by Lrp6 deletion in mice. The morphological dynamic that is required for normal lip formation and fusion is disrupted in these mutants. The expression of the homeobox genes Msx1 and Msx2 is dramatically reduced in the mutants, which prevents the outgrowth of orofacial primordia, especially in the fusion site. We further demonstrate that Msx1 and Msx2 (but not their potential regulator Bmp4) are the downstream targets of the Wnt/beta-catenin signaling pathway during lip formation and fusion. By contrast, a ;fusion-resistant' gene, Raldh3 (also known as Aldh1a3), that encodes a retinoic acid-synthesizing enzyme is ectopically expressed in the upper lip primordia of Lrp6-deficient embryos, indicating a region-specific role of the Wnt/beta-catenin signaling pathway in repressing retinoic acid signaling. Thus, the Lrp6-mediated Wnt signaling pathway is required for lip development by orchestrating two distinctively different morphogenetic movements.
A (1,0)-super solution is a satisfying assignment such that if the value of any one variable is flipped to the opposite value, the new assignment is still a satisfying assignment. Namely, every ...clause must contain at least two satisfied literals. Because of its robustness, super solutions are concerned in combinatorial optimization problems and decision problems. In this paper, we investigate the existence conditions of the (1,0)-super solution of ( k , s ) -CNF formula, and give a reduction method that transform from k-SAT to (1,0)- ( k + 1 , s ) -SAT if there is a ( k + 1 , s )-CNF formula without a (1,0)-super solution. Here, ( k , s ) -CNF is a subclass of CNF in which each clause has exactly k distinct literals, and each variable occurs at most s times. (1,0)- ( k , s ) -SAT is a problem to decide whether a ( k , s ) -CNF formula has a (1,0)-super solution. We prove that for k > 3 , if there exists a ( k , s ) -CNF formula without a (1,0)-super solution, (1,0)- ( k , s ) -SAT is NP-complete. We show that for k > 3 , there is a critical function φ ( k ) such that every ( k , s ) -CNF formula has a (1,0)-super solution for s ≤ φ ( k ) and (1,0)- ( k , s ) -SAT is NP-complete for s > φ ( k ) . We further show some properties of the critical function φ ( k ) .
With the increasing emphasis on the ecology and environment of rivers, the construction of ecological waterway projects has become a development trend in China. In recent years, more and more ...attention has been paid to the qualitative and quantitative evaluation of the ecological effects of ecological waterway construction. Based on pressure-state-response (PSR) and driver-pressure-state-impact-response (DPSIR) logical frameworks, this paper established a state-pressure-impact-response (SPIR) conceptual model. The model took the river ecology and environment state as the main line, and described the disturbance pressure of the engineering construction on the river state, the impacts of the project on the river comprehensive function, and the positive responses taken in the full lifetime cycle of the project. The analytic hierarchy process (AHP) and fuzzy evaluation model were used to study the changes of the river ecosystem status after suffering from the construction pressure and taking positive responses. Taking the 12.5 m deep water waterway project in the Taicang-Nantong section of the lower reaches of the Yangtze River as an example, the disturbance on the ecology and environment at different stages of the project construction and the effort of relieving the negative impacts of the project on the ecology and environment were evaluated by the health level of the ecosystem. The paper can provide a scientific method for the evaluation of ecological projects in river ecosystems.
This paper shows the verification work of SARAX code system in the reactor core transient calculation based on the simplified EBR-II Benchmark. The SARAX code system is an analysis package developed ...by Xi'an Jiaotong University and aims at the advanced reactor R&D. In this work, a neutron-photon coupled power calculation model and a spatial-dependent reactivity feedback model were introduced. To verify the models used in SARAX, the EBR-II SHRT-45R test was simplified to an ULOF transient with an input flowrate change curve by fitting from reference. With the neutron-photon coupled power calculation model, SARAX gave close results in both power fraction and peak power prediction to the reference results. The location of the hottest assembly from SARAX and reference are the same and the relative power deviation of the hottest assembly is 2.6%. As for transient analysis, compared with experimental results and other calculated results, SARAX presents coincident results both in trend and absolute value. The minimum value of core net reactivity during the transient agreed well with the reported results, which ranged from −0.3$ to −0.35$. The results verify the models in SARAX, which are correct and able to simulate the in-core transient with reliable accuracy.
Pharmacological targeting of breast cancer stem cells (CSCs) is highly promising for the treatment of breast cancer, as the small population of CSCs is responsible for tumor initiation, progression, ...recurrence and chemo-resistance. Celecoxib is one of the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs), which have chemo-preventive activity against cancers, including breast cancer and colorectal cancer. However, the mechanisms by which NSAIDs exert its cancer prevention effects have yet been completely understood. In the present study, we investigated for the first time the effect of celecoxib on breast CSCs inhibition and its potential molecular mechanisms. Our results demonstrated that celecoxib suppresses CSC self-renewal, sensitizes chemo-resistance, inhibits epithelial to mesenchymal transition (EMT), and attenuates metastasis and tumorigenesis. Further exploring the underlying mechanism revealed that celecoxib targets breast CSCs by inhibiting the synthesis of prostaglandin E2 and down-regulating the Wnt pathway activity. Our findings suggest that celecoxib, by targeting CSCs, may be used as an adjuvant chemotherapy drug to improve breast cancer treatment outcomes.
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