Upstream Step Research Articles

Src acts with WNT/FGFRL signaling to pattern the planarian anteroposterior axis.

Tissue identity determination is crucial for regeneration, and the planarian anteroposterior (AP) axis uses positional control genes expressed from body wall muscle to determine body regionalization. Canonical Wnt signaling establishes anterior versus posterior pole identities through notum and wnt1 signaling, and two Wnt/FGFRL signaling pathways control head and trunk domains, but their downstream signaling mechanisms are not fully understood. Here, we identify a planarian Src homolog that restricts head and trunk identities to anterior positions. src-1(RNAi) animals formed enlarged brains and ectopic eyes and also duplicated trunk tissue, similar to a combination of Wnt/FGFRL RNAi phenotypes. src-1 was required for establishing territories of positional control gene expression in Schmidtea mediterranea, indicating that it acts at an upstream step in patterning the AP axis. Double RNAi experiments and eye regeneration assays suggest src-1 can act in parallel to at least some Wnt and FGFRL factors. Co-inhibition of src-1 with other posterior-promoting factors led to dramatic patterning changes and a reprogramming of Wnt/FGFRLs into controlling new positional outputs. These results identify src-1 as a factor that promotes robustness of the AP positional system that instructs appropriate regeneration.

Disruption of β-Catenin-Dependent Wnt Signaling in Colon Cancer Cells Remodels the Microenvironment to Promote Tumor Invasion.

Decreased Wnt signaling in colon tumors leads to a more aggressive disease phenotype due to an upregulation of gene programs favoring cell migration in the tumor and downregulation of inflammation programs in the tumor microenvironment; these impacts must be carefully considered in developing Wnt-targeting therapies.

Shilling, Squeezing, Sniping. A further explanation for late bidding in online second-price auctions

Several studies provide empirical evidence for sniping (i.e., waiting until the last few seconds to bid) in second-price internet auctions, particularly in auctions at eBay. This evidence was regarded as puzzling and an anomaly for an extended period: How could sniping be consistent with rational behaviour in second-price auctions, where theory predicts that bids’ timing plays no role and there is no incentive to bid less than one’s private value.An essential contribution to this puzzling issue has been the insight by Bose and Daripa (2017) that late bidding is itself a response to the shilling. Their paper explains well late bidding for repeating auctions. However, late bidding also occurs in non-repeated auctions.This paper aims to show that bidders can expect shilling behaviour even in non-repeated auctions, i.e., when perishables are on the counter. For this, we introduce the notion of squeezing. It describes an upstream step to the shilling to substantially reduce the seller’s risk to become the highest bidder. We rationalize the aforementioned results for non-repeated auctions by considering the squeezing strategy.

Numerical investigation of blowing ratio, density ratio and axial position of film holes on the vane endwall film cooling effectiveness with upstream step

The aerothermal performance of interrupted slot and film holes was numerically investigated. Previous study indicates that the interrupted slot performs better compared to the conventional slot. In the meanwhile, the step formed along with the interrupted slot affects the film cooling characteristics. In this article, a row of film holes is arranged downstream of the step, and the mass flow rate for the interrupted slot is constant at 1%. Blowing ratio (BR) from 0.5 to 1.5 and density ratio from 1 to 2 were studied for the film holes. Endwall film cooling effectiveness distribution indicates that film cooling is easily affected by the secondary flow inside passage and the upstream step. Coolant traces are split into two parts due to the effects of step vortex and transverse flow. For different density ratios, increasing BR shows a different trend of film cooling effectiveness due to the variation of coolant momentum. The coolant jet is easily affected by the secondary flow when its momentum is low, but tends to liftoff when its momentum is too high. As a result, it is better to position the film holes far away from the upstream step. The total pressure loss coefficient distribution at the passage exit indicates that the coolant injection increases the total pressure loss. But density ratio has smaller effect on the loss variation. Besides, two axial positions of cooling holes were studied to improve the endwall cooling performance. Without the effect of step vortex, the film effectiveness of cooling holes is improved.

Crystallographic analysis of TarI and TarJ, a cytidylyltransferase and reductase pair for CDP-ribitol synthesis in Staphylococcus aureus wall teichoic acid biogenesis

The cell wall of many pathogenic Gram-positive bacteria contains ribitol-phosphate wall teichoic acid (WTA), a polymer that is linked to virulence and regulation of essential physiological processes including cell division. CDP-ribitol, the activated precursor for ribitol-phosphate polymerization, is synthesized by a cytidylyltransferase and reductase pair known as TarI and TarJ, respectively. In this study, we present crystal structures of Staphylococcus aureus TarI and TarJ in their apo forms and in complex with substrates and products. The TarI structures illustrate the mechanism of CDP-ribitol synthesis from CTP and ribitol-phosphate and reveal structural changes required for substrate binding and catalysis. Insights into the upstream step of ribulose-phosphate reduction to ribitol-phosphate is provided by the structures of TarJ. Furthermore, we propose a general topology of the enzymes in a heterotetrameric form built using restraints from crosslinking mass spectrometry analysis. Together, our data present molecular details of CDP-ribitol production that may aid in the design of inhibitors against WTA biosynthesis.

Effects of a Novel GPR55 Antagonist on the Arachidonic Acid Cascade in LPS-Activated Primary Microglial Cells.

Neuroinflammation is a crucial process to maintain homeostasis in the central nervous system (CNS). However, chronic neuroinflammation is detrimental, and it is described in the pathogenesis of CNS disorders, including Alzheimer’s disease (AD) and depression. This process is characterized by the activation of immune cells, mainly microglia. The role of the orphan G-protein-coupled receptor 55 (GPR55) in inflammation has been reported in different models. However, its role in neuroinflammation in respect to the arachidonic acid (AA) cascade in activated microglia is still lacking of comprehension. Therefore, we synthesized a novel GPR55 antagonist (KIT 10, 0.1–25 µM) and tested its effects on the AA cascade in lipopolysaccharide (LPS, 10 ng / mL)-treated primary rat microglia using Western blot and EIAs. We show here that KIT 10 potently prevented the release of prostaglandin E2 (PGE2), reduced microsomal PGE2 synthase (mPGES-1) and cyclooxygenase-2 (COX-2) synthesis, and inhibited the phosphorylation of Ikappa B-alpha (IκB-α), a crucial upstream step of the inflammation-related nuclear factor-kappaB (NF-κB) signaling pathway. However, no effects were observed on COX-1 and -2 activities and mitogen-activated kinases (MAPK). In summary, the novel GPR55 receptor antagonist KIT 10 reduces neuroinflammatory parameters in microglia by inhibiting the COX-2/PGE2 pathway. Further experiments are necessary to better elucidate its effects and mechanisms. Nevertheless, the modulation of inflammation by GPR55 might be a new therapeutic option to treat CNS disorders with a neuroinflammatory background such as AD or depression.

Topology Automatic Identification Method for Low-Voltage Stations Based on Line Impedance Analysis

Aiming at the problems of high cost, low real-time performance of manual identification of low-voltage station topological structure, automatic identification methods such as instantaneous power failure method and voltage correlation analysis method, which affect residents’ electricity consumption, and the success rate is limited by application scenarios, this paper proposes a method based on multiple linear regression Line impedance analysis method for automatic identification of the topology of low-voltage stations. Based on the relationship between voltage, current, and impedance, multiple linear regression analysis is used to derive the upstream topology step by step from the bottom up to the top of the topology and then determine the station membership by voltage correlation. The cloud platform based on Docker technology and Hadoop technology is used for data distributed storage calculation, and an identification model in the context of big data is established to effectively improve the efficiency of the algorithm. Finally, the correctness of the algorithm verification is judged based on the results of manual field verification.

Homology Model of a Catalytically Competent Bifunctional Rel Protein.

Bacteria have developed different bet hedging strategies to survive hostile environments and stressful conditions with persistency being maybe the most elegant yet still poorly understood one. Persisters’ temporary tolerance to antibiotic treatment hints at their role not only in chronic and recurrent infections but also in the insurgence of resistant strains. Therefore, hampering persisters formation might represent an innovative strategy in the quest for new effective antimicrobial compounds. Among the molecular mechanisms postulated for the persister phenotypic switch, we decided to focus our attention on the stringent response and, in particular, on the upstream triggering step that is the accumulation of guanosine tetra- and pentaphosphate, collectivity called (p)ppGpp. Intracellular levels of (p)ppGpp are regulated by a superfamily of enzymes called RSH (RelA/SpoT homologue) that are able to promote its synthesis via pyrophosphate transfer from an ATP molecule to the 3’ position of either GDP or GTP. These enzymes are classified based on the structural domain(s) present (only synthetase, only hydrolase, or both). Here we present our work on RelSeq (from S. equisimilis), still the only bifunctional Rel protein for which a GDP-bound “synthetase-ON” structure is available. Analysis of the synthetase site, occupied only by GDP, revealed a partially active state, where the supposed ATP binding region is not conformationally apt to accommodate it. In order to achieve a protein model that gets closer to a fully active state, we generated a chimera structure of RelSeq by homology modeling, starting from the crystal structure of the catalytically competent state of RelP, a smaller, single-domain, Rel protein from S. aureus. Molecular dynamics simulations allowed verifying the stability of the generated chimera model. Virtual screening and ligand design studies are underway.

Lactobacillus bile salt hydrolase substrate specificity governs bacterial fitness and host colonization

Primary bile acids (BAs) are a collection of host-synthesized metabolites that shape physiology and metabolism. BAs transit the gastrointestinal tract and are subjected to a variety of chemical transformations encoded by indigenous bacteria. The resulting microbiota-derived BA pool is a mediator of host-microbiota interactions. Bacterial bile salt hydrolases (BSHs) cleave the conjugated glycine or taurine from BAs, an essential upstream step for the production of deconjugated and secondary BAs. Probiotic lactobacilli harbor a considerable number and diversity of BSHs; however, their contribution to Lactobacillus fitness and colonization remains poorly understood. Here, we define and compare the functions of multiple BSHs encoded by Lactobacillus acidophilus and Lactobacillus gasseri Our genetic and biochemical characterization of lactobacilli BSHs lend to a model of Lactobacillus adaptation to the gut. These findings deviate from previous notions that BSHs generally promote colonization and detoxify bile. Rather, we show that BSH enzymatic preferences and the intrinsic chemical features of various BAs determine the toxicity of these molecules during Lactobacillus growth. BSHs were able to alter the Lactobacillus transcriptome in a BA-dependent manner. Finally, BSHs were able to dictate differences in bacterial competition in vitro and in vivo, defining their impact on BSH-encoding bacteria within the greater gastrointestinal tract ecosystem. This work emphasizes the importance of considering the enzymatic preferences of BSHs alongside the conjugated/deconjugated BA-bacterial interaction. These results deepen our understanding of the BA-microbiome axis and provide a framework to engineer lactobacilli with improved bile resistance and use probiotics as BA-altering therapeutics.

Coal direct chemical looping process: 250 kW pilot-scale testing for power generation and carbon capture

Chemical looping combustion (CLC) is an energy conversion technology that can produce concentrated CO2 stream without the need for a gas separation step, and thus, has the potential to drastically reduce the energy consumption and cost associated with CO2 capture in power generation. The coal-direct chemical looping (CDCL) process is a CLC technology that uses a moving bed reducer configuration that can directly consume coal as a feedstock without requiring an upstream gasification step. An integrated 250 kWth CDCL pilot unit using iron-based oxygen carriers was constructed and demonstrated for over 1000 h of testing. The principles for the CDCL pilot unit design and operation are summarized in this article. During the 288-hour continuous operation testing, the CDCL pilot unit achieved >96% coal conversion with a CO2 purity of >97%. Low carbon carryover into the combustor, i.e. <2%, was also confirmed during the test, which shows the capability of the moving bed reactor to retain and convert coal using the oxygen available on the iron-based oxygen carrier. The results from the pilot unit testing confirms the CDCL concept as a promising coal combustion technology for heat and power generation with CO2 capture.

Defining an Upstream VEGF (Vascular Endothelial Growth Factor) Priming Signature for Downstream Factor-Induced Endothelial Cell-Pericyte Tube Network Coassembly.

In this work, we have sought to define growth factor requirements and the signaling basis for different stages of human vascular morphogenesis and maturation. Approach and Results: Using a serum-free model of endothelial cell (EC) tube morphogenesis in 3-dimensional collagen matrices that depends on a 5 growth factor combination, SCF (stem cell factor), IL (interleukin)-3, SDF (stromal-derived factor)-1α, FGF (fibroblast growth factor)-2, and insulin (factors), we demonstrate that VEGF (vascular endothelial growth factor) pretreatment of ECs for 8 hours (ie, VEGF priming) leads to marked increases in the EC response to the factors which includes; EC tip cells, EC tubulogenesis, pericyte recruitment and proliferation, and basement membrane deposition. VEGF priming requires VEGFR2, and the effect of VEGFR2 is selective to the priming response and does not affect factor-dependent tubulogenesis in the absence of priming. Key molecule and signaling requirements for VEGF priming include RhoA, Rock1 (Rho-kinase), PKCα (protein kinase C α), and PKD2 (protein kinase D2). siRNA suppression or pharmacological blockade of these molecules and signaling pathways interfere with the ability of VEGF to act as an upstream primer of downstream factor-dependent EC tube formation as well as pericyte recruitment. VEGF priming was also associated with the formation of actin stress fibers, activation of focal adhesion components, upregulation of the EC factor receptors, c-Kit, IL-3Rα, and CXCR4 (C-X-C chemokine receptor type 4), and upregulation of EC-derived PDGF (platelet-derived growth factor)-BB, PDGF-DD, and HB-EGF (heparin-binding epidermal growth factor) which collectively affect pericyte recruitment and proliferation. Overall, this study defines a signaling signature for a separable upstream VEGF priming step, which can activate ECs to respond to downstream factors that are necessary to form branching tube networks with associated mural cells.

The Effect of Step Misalignment on Purge Flow Cooling of Nozzle Guide Vane at Transonic Conditions

Abstract This study describes a detailed investigation on the effects that upstream step misalignment and upstream purge film cooling have on the endwall heat transfer for first stage nozzle guide vanes (NGVs) in a gas turbine at transonic conditions. Endwall Nusselt number and adiabatic film-cooling effectiveness distributions were experimentally measured and compared with flow visualization. Tests were conducted in a transonic linear cascade blowdown facility at an inlet freestream turbulence intensity of 16%, an exit Mach number of 0.85, and an exit Re = 1.5 × 106 based on axial chord. Varied upstream purge blowing ratios (BRs) and a no-blowing case were tested for three different upstream step geometries, the baseline (no misalignment), a span-wise upstream step of +4.86% span, and a step of −4.86% span. Experimentation shows that compared with no-blowing case, the addition of upstream purge film cooling increases the Nusselt number at injection upward of 50% but lowers it in the passage throat by approximately 20%. The backward facing step induces more turbulent mixing between the coolant and mainstream flows, thus reducing film effectiveness coverage and increasing Nusselt number by nearly 40% in the passage throat. In contrast, the presence of a forward step creates a more stable boundary layer for the coolant flow aiding to help keep the film attached to the endwall. Increasing the blowing ratio increases film-cooling effectiveness and endwall coverage up to a certain point, beyond which, the high momentum of the coolant results in poor cooling performance due to jet liftoff.

Crosslinking of PCR primers reduces unspecific amplification products in multiplex PCR

The polymerase chain reaction is not only essential for many DNA-based diagnostic methods but is also exploited in other molecular methods that require an upstream amplification step. Multiplex PCRs are especially attractive as they reduce the number of individual reactions. However, the multiplexing efficiency is impaired by primer interactions such as the formation of primer dimers. In this study, covalent crosslinking of primers via their 5′-ends was used to avoid those undesired effects. The specificity of the primers as well as the efficiency of the PCR could be increased upon primer crosslinking in reactions containing up to 34 primer pairs targeting the most important antibiotic resistance genes in a single multiplex reaction.

Computational study of the multi hydrogen jets in presence of the upstream step in a Ma=4 supersonic flow

The injection of the hydrogen is the main noteworthy stage for the advance of the supersonic engine. In our computational study, the incidence of the step condition in the upstream of the hydrogen multi-jet is investigated for the augmentation of the fuel distribution in downside of the fuel jets at Mach = 4. To perform our research, a 3-dimensional computational domain is taken to unveil the primary flow organization of the hydrogen jets and its interactions with the freestream for the advance of fuel mixing. This work comprehensively examined the impression of the jet pressure on the mixing value and flow structure. Besides, the three-dimensional outcome of the step on the pattern of the four multi-jets is compared with the single equivalent jet. According to our results, the existence of step improves the fuel mixing efficiency up to 30% close to of early jets. Our findings reveal that increasing the step height from 0.5 to 2 mm enhances the fuel mixing more than 15%.

Mixing enhancement of the multi hydrogen fuel jets by the backward step

For the improvement of the present high-speed vehicles, fuel mixing is the significant process in the combustor. Current article employed numerical tools to scrutinize the role of the upstream step condition on the mixing efficiency of the multi hydrogen jets within the scramjet. This work tries to disclose the impact of the free-stream Mach and multi-jet arrangements on the feature of the fuel jets. Besides, the fuel mixing efficiency of the step condition is studied in the downstream of the jets. To do this, a three-dimensional model is considered to ensure that the real physics of the problem associated with hydrogen jets and freestream is considered. To solve the problem, RANS equations are chosen, and the SST approach is selected for the calculation of the viscosity in high-speed flow. The fuel jet has been injected within four multi sonic injectors and the free stream Mach number (Ma) is within 3–4. The computational simulations show that the impact of the step condition declines as the free-stream Ma is increased. Besides, the impact of the step on the fuel mixing enhances when the pressure ratio of the jets declines. Our findings show that fuel mixing in region of the fuel injection declines as the jet space increases from 4 Dj to 10 Dj while the downstream mixing efficiency enhances up to 28%.

Eco-efficiency analysis of desalination by precipitation integrated with reverse osmosis for zero liquid discharge in oil refineries

In a process for industrial water reuse with zero liquid discharge (ZLD), a membrane separation step followed by an evaporative process is usually required. It is proposed here to maximize water conversion in the reverse osmosis (RO) membranes, in order to reduce the associated environmental impacts and economic costs from evaporative process. Considering a typical oil refinery wastewater with high inorganic scaling tendency, three ZLD virtual scenarios were proposed. A RO water recovery of 59% (default scenario SI) was increased to 89.2% with an upstream BaSO4 desupersaturation step (scenario SII). A 96.3% RO water recovery (SIII) was obtained adopting also a RO intermediate softening with CaO addition and calcite seeding, as well as MgSO4 dosing for additional silica removal. In all cases, the water not separated in the membrane was completely recovered in downstream evaporation and evaporative crystallization steps. A life cycle assessment (LCA) analysis suggests that the proposed scenarios enabled expressive reduction in the environmental impacts related to global warming, freshwater ecotoxicity and water consumption. Besides, it has been shown that the proposed scenarios were economically favorable. By means of an eco-efficiency analysis, economic, energetic and environmental implications appointed to benefits on developing of chemical precipitation techniques for a high RO desalting recovery in ZLD operations for aqueous effluents of petroleum refineries. It has also been found that some degree of intervention may lead to an improvement of all eco-efficiency indicators, but at some extent of intervention, at least some of the eco-efficiency indicators may become less favorable.

Numerical Investigation of the Combustion in an Improved Microcombustion Chamber with Rib

This study proposes an improved microcombustor with a rectangular rib to improve the temperature level of the combustor wall. Moreover, the OH mass fraction, temperature distribution, and outer wall temperature of the original and improved combustors of premixed hydrogen/air flames are numerically investigated under various inlet velocities and equivalence ratios. Results show that the improved microcombustor enhances heat transfer between the mixture and wall because its recirculation zone is larger than that of the original, thereby resulting in high wall temperature. Conversely, thermal resistance in the horizontal direction increases with upstream and downstream step lengths. Consequently, the outer wall temperature decreases with step length in the improved combustor. A high equivalence ratio (e.g., 0.6) may result in the destruction of the combustor because the wall temperature has exceeded the acceptable temperature of wall material quartz. Therefore, the improved microcombustor is recommended for micro-thermo-photovoltaic systems.

A comprehensive index for evaluating and enhancing effective wastewater treatment in two industrial parks in China

Industrial parks have been important to China's rapid economic development. The wastewater generated by these industrial parks tends toward large volumes, varied compositions, high pollutant concentrations, and it generally is toxic and difficult to biodegrade. The abilities of treatment plants to effectively treat industrial wastewater are greatly influenced by the upstream treatment step that occurs at the source in the industrial park. Based on the notion of the water footprint, a wastewater treatment assessment index was developed and tested to evaluate and enhance the centralized wastewater treatment plants of two industrial parks. The treatment performance of a plant in a comprehensive industrial park was compared to that of a chemical industrial park. The former scored significantly higher than the latter. Because of its low scores in the evaluation, the treatment problems of the chemical industrial park were diagnosed and enhancement measures were implemented. After the enhancements were in place, the plant was re-evaluated. Its post-enhancement scores on the index's primary indicator for process advancement and its dependent performance regarding the downstream environment greatly increased, indicating that the wastewater treatment performance had significantly improved. Therefore, the index developed by this study successfully evaluated and determined effective enhancements for wastewater treatment in China's industrial parks, which contributes to industrial wastewater pollution control.

N-terminal methionine excision of proteins creates tertiary destabilizing N-degrons of the Arg/N-end rule pathway

All organisms begin protein synthesis with methionine (Met). The resulting initiator Met of nascent proteins is irreversibly processed by Met aminopeptidases (MetAPs). N-terminal (Nt) Met excision (NME) is an evolutionarily conserved and essential process operating on up to two-thirds of proteins. However, the universal function of NME remains largely unknown. MetAPs have a well-known processing preference for Nt-Met with Ala, Ser, Gly, Thr, Cys, Pro, or Val at position 2, but using CHX-chase assays to assess protein degradation in yeast cells, as well as protein-binding and RT-qPCR assays, we demonstrate here that NME also occurs on nascent proteins bearing Met-Asn or Met-Gln at their N termini. We found that the NME at these termini exposes the tertiary destabilizing Nt residues (Asn or Gln) of the Arg/N-end rule pathway, which degrades proteins according to the composition of their Nt residues. We also identified a yeast DNA repair protein, MQ-Rad16, bearing a Met-Gln N terminus, as well as a human tropomyosin-receptor kinase-fused gene (TFG) protein, MN-TFG, bearing a Met-Asn N terminus as physiological, MetAP-processed Arg/N-end rule substrates. Furthermore, we show that the loss of the components of the Arg/N-end rule pathway substantially suppresses the growth defects of naa20Δ yeast cells lacking the catalytic subunit of NatB Nt acetylase at 37 °C. Collectively, the results of our study reveal that NME is a key upstream step for the creation of the Arg/N-end rule substrates bearing tertiary destabilizing residues in vivo.

Step Clearance Seals: An Analysis to Demonstrate Their Unique Performance

Hydraulic turbines and centrifugal pumps at times show low frequency vibrations when installed with upstream step (band) clearance seals with a narrow clearance facing the incoming external flow. When implementing a downstream step clearance seal, one with the narrow clearance located at the seal exit, the same machine does not show the same problem. This paper presents both theoretical and experimental analysis on the leakage and dynamic force coefficients of both upstream and downstream step clearance seals. The predicted and measured results show that an upstream step clearance seal produces a significant negative direct stiffness (K &lt; 0) that could cause a static instability. On the other hand, a downstream step clearance seal generates a positive direct stiffness (K &gt; 0) that is beneficial to a rotor system. Both the upstream and downstream step clearance seals show positive direct damping and virtual mass coefficients.