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Background Polycyclic triterpenoids (PTs) are common in plants, and have attracted considerable interest due to their remarkable biological activities. Currently, engineering the ergosterol synthesis pathway in Saccharomyces cerevisiae is a safe and cost-competitive way to produce triterpenoids. However, the strict regulation of ERG1 involved in the epoxidation of squalene limits the triterpenoid production. Results In this study, we found that the decrease in ERG7 protein level could dramatically boost the epoxidation of squalene by improving the protein stability of ERG1. We next explored the potential factors that affected the degradation process of ERG1 and confirmed that ERG7 was involved in the degradation process of ERG1. Subsequently, expression of four different triterpene cyclases utilizing either 2,3-oxidosqualene or 2,3:22,23-dioxidosqualene as the substrate in ERG7-degraded strains showed that the degradation of ERG7 to prompt the epoxidation of squalene could significantly increase triterpenoid production. To better display the potential of the strategy, we increased the supply of 2,3-oxidosqualene, optimized flux distribution between ergosterol synthesis pathway and β-amyrin synthesis pathway, and modified the GAL-regulation system to separate the growth stage from the production stage. The best-performing strain ultimately produced 4216.6 ± 68.4 mg/L of β-amyrin in a two-stage fed-fermentation (a 47-fold improvement over the initial strain). Conclusions This study showed that deregulation of the native restriction in ergosterol pathway was an effective strategy to increase triterpenoid production in yeast, which provided a new insight into triterpenoids biosynthesis.

Grinding is the main processing method for the particle-reinforced composites, where removal mechanism is of great significance to surface usability performance. In this study, Hopkinson pressure bar tests of SiCp/Al composite were carried out, and the constitutive model of SiCp/Al composite was obtained. Based on the finite element model of Hopkinson pressure bar tests, the interfacial constitute model of SiCp/Al composite was obtained. Single abrasive grain grinding experiments were designed and conducted to obtain the grinding force. Based on the interfacial constitute model, a new integrated grinding simulation model for the high volume fraction SiCp/Al composite was established and verified by the results of the single abrasive grain experiments, then the single abrasive grain grinding force prediction model was established and verified. Several grinding mechanism models for SiCp/Al composites were proposed, and the debonding between the interface of silicon carbides and aluminum alloy was observed. Finally, the multi-abrasive grain grinding forces were measured under different grinding process parameters and the influence of the grinding process parameters on the grinding force was discussed. This research about the micro-grinding mechanism of SiCp/Al composites provides a theoretical support for the study of surface quality.

Surface wear of drilling bit in the drilling process is complex, and the traditional wear index is not suitable to reflect the wear condition of drilling bit well; it is necessary to investigate on the appropriate wear testing and evaluation method. In this paper, a visual measurement system is set up to obtain the drilling bit wear characteristics based on machine vision. The wear area image is grayscale processed, and the gray image is thresholding segmentation processed, then the boundary feature is extracted based on the chain code method. A comprehensive evaluation system is established, in which the wear perimeter, the equivalent wear diameter, and maximum wear width of different areas are proposed as the wear indicators. The wear fusion feature based on the principal component analysis is proposed to characterize the drilling bit wear degree, the wear indicators of different regions are characterized and fused as the wear degree of different regions, then the prediction model of the drilling bit wear degree is established based on support vector machine. The results show that the predicted results are mainly consistent with the experimental results. The research of the drilling bit wear characteristics based on principal component analysis can provide guidance for the study of drilling bit wear mechanism.

Grinding is the main processing technique for particle-reinforced composites, in which grinding force and temperature are significant for investigating the removal mechanism and surface properties. In this study, a grinding force prediction model is established based on the response surface methodology. The energy density of surface heat source in the grinding area is calculated by combining the contact area between the grinding wheel and workpiece. Based on the integration algorithm in time and space, a theoretical ideal grinding temperature prediction model is deduced. The grinding heat energy transfer coefficient is defined as the percentage of heat energy, which is transferred from the grinding heat energy to the workpiece. According to the experimental and ideal theoretical highest grinding temperatures, a prediction model of the heat energy transfer coefficient is established, and the modified theoretical highest grinding temperature prediction model is obtained. Furthermore, a finite element model of SiCp/Al composite in grinding is established. The highest grinding temperature in the finite element model is consistent with the modified theoretical highest grinding temperature, and the grinding temperature field is analysed. The highest grinding temperature increases as the wheel speed and grinding depth increase, while it decreases as table speed increases, which differs from that of some common materials. Thus, the grinding temperature prediction model provides an important reference for the study of removal mechanism and surface properties of SiCp/Al composite.

Grinding is the main processing method for particle-reinforced composites, and grinding force prediction models are very important for research on removal mechanisms. In this study, single-abrasive-grain grinding experiments on SiCp/Al composites were conducted to determine the grinding forces at different grinding process parameters. In addition, a prediction model for the single-abrasive-grain grinding force was established to study the influence of the grinding process parameters and grinding grain angle on the grinding force of SiCp/Al composite. Moreover, multi-abrasive-grain grinding experiments were conducted at different grinding process parameters, which resulted in different grinding forces. The support vector machine (SVM) prediction method based on particle swarm optimisation (PSO) was used to establish a prediction model for the multi-abrasive-grain grinding force; the single-abrasive-grain grinding forces at different grinding grain angles were the input, and the average experimental grain grinding force was the output. The results show that the error between the predicted and experimental grinding forces is below 12%. Furthermore, the grinding force decreases with increasing wheel speed and increases with increasing feed velocity and grinding depth. The PSO–SVM algorithm–based grinding force prediction model can accurately predict the grinding force of SiCp/Al composite and provides theoretical support for improved surface quality.

This review focuses on the diagnosis, evaluation, and management of valve bladder syndrome (VBS) following initial treatment of posterior urethral valves (PUV). Based on current literature, we discuss the effect of PUV management in VBS and investigate the role of medications, catherization, surgery, and novel interventions. The current initial management of PUV involves valve ablation. Cutaneous urinary diversions are secondary options based on patient characteristics, PUV severity, and response to catheter drainage. VBS can independently occur as a consequence of PUV due to reduced nephron endowment leading to renal tubular dysfunction and polyuria, high bladder filling pressures secondary to a non-compliant bladder, and poor bladder emptying due to bladder neck hypertrophy. Options to mitigate the risk of upper tract deterioration include behavioral modifications and medical therapy (anticholinergics or alpha-blockers), bladder neck incision, clean intermittent catheterization and overnight catheter drainage, or more invasive approaches such as botulinum toxin injections and creation of a Mitrofanoff channel. Several experimental therapies to attenuate bladder fibrosis are currently under investigation. The management of VBS starts with initial management of PUV and is subsequently dependent on the evolving bladder filling dynamics and bladder neck hypertrophy affecting bladder filling and emptying. This requires a pre-emptive management protocol to identify VBS in boys with PUV to prevent renal damage using various therapeutic interventions. The lack of prospective studies to investigate effectiveness of available therapeutic options to treat VBS limits the development of an evidence-based approach for severity-based management of PUV-associated VBS.

Background Galloway-Mowat syndrome (GAMOS) (OMIM #251300) is a severe autosomal recessive disease characterized by the combination of early-onset steroid-resistant nephrotic syndrome (SRNS) and microcephaly with brain anomalies caused by WDR73 as well as OSGEP, TP53RK, TPRKB, or LAGE3 mutations. Objective We report on the hitherto undescribed urological and nephrological complications of the homozygous c.974G>A (p.Arg325Gln) OSGEP mutations in a 7-year-old Caucasian girl. Case Diagnosis The patient came to the attention of pediatric nephrology at the age of 3 years and 11 months, when she presented with status epilepticus due to profound hypomagnesemia (0.31 mmol/L, normal 0.65-1.05). A 24-h urine demonstrated a magnesium loss of 0.6 mmol/kg/day with associated proteinuria suggesting renal tubulopathy. Subsequently, she developed recurrent urinary tract infections (UTIs) and was diagnosed with neurogenic bladder dysfunction. The patient continued to have UTIs associated with seizures and sequential cultures growing multi-drug-resistant organisms despite of antibiotic prophylaxis. In addition, the proteinuria (median microalbumin/creatinine ratio 647 mg/mmol) increased, and she developed partial Fanconi syndrome. At age 7, she developed a large bladder calculus (3.3 × 3.2 cm) and three left non-obstructing renal calculi associated with elevated urinary cystine, hypercalciuria, and ongoing hypomagnesemia and required surgical intervention. Glomerular filtration rate (GFR) remained normal and she never developed frank nephrotic syndrome (average albumin 31 g/L). Conclusions It is unclear if patients with OSGEP mutations with tubular symptoms rather than nephrotic syndrome should be considered a different entity. Nephrological and urological complications of OSGEP mutations can be challenging and require a multidisciplinary approach.

Ag-doped Bi2Se3 with the formula AgxBi2Se3 and Bi2−xAgxSe3 were prepared and their electrical and magnetic transport properties have been investigated to study the influence of silver doping on transport properties of Bi2Se3 with different Ag-doped method. All samples exhibited metallic resistivity and the resistivity increased with increasing Ag concentration. The lattice parameter c of Ag-substituted and Ag-intercalated samples displays a contrary change as the Ag concentration increased. For the Ag-intercalated samples, both the resistance upturn were observed in the curves of temperature dependent of resistivity and temperature dependent of magnetoresistance, respectively, indicating that the enhanced surface effect was obtained in those samples. Monotonously, field-induced MR peaks around 200 K were also observed in those samples. Similar behaviors were not observed in the Ag-substituted samples.

Based on our experiment of borehole breakouts with a group of sandstone samples described in this paper, a multi-step failure model of borehole breakouts are proposed to quantitatively explain the relationship between the section shape of borehole breakouts and the state of crustal stress. In this model the borehole spalling is not only related to the state of stress at a single point but also the state of stress on its neighboring area. The comparison between the experimental results of borehole breakouts and the calculation results shows a good agreement.

China is facing the three major agroenvironment problems, which include: chemical pollution, abnormal ecological balance and natural resource deterioration. These environment problems have depleted part of the comprehensive agricultural productivity and hence become a resistance to the further development of agriculture. A number of measures have been taken for controlling over pollution and ecosystem declining. But for the sustainable development the more efforts are suggested to make, including the more stern measures in the population control, adopting the new techniques of saving natural resources and high efficiency, encouraging a frugal life style as well as paying more attentions to the research on the agricultural environment protection.

In the present paper we establish a sharp asymptotic formula for\(\sum\limits_{x\bmod q} {\smallint _0^T } |L(\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} + it,x)|^2 dt\) with an error term\(O(T^{\frac{1}{3} - \delta + e} )\) (σ is a suitable positive constant) uniformly inq andT, which improves the best result hitherto given.

The well-known Goldback-Vinogradov theorem states that every large odd integer is a sum of three primes. In the present paper it is further proved that every large odd integerN can be represented as $$N = p_1 + p_2 + p_3 , with p_i = N/3 + O(N^{{5 \mathord{\left/ {\vphantom {5 6}} \right. \kern-\nulldelimiterspace} 6}} (\log N)^c )$$ wherc>0 is an absolute constant, andp i (1≦i≦3) are primes. The result is obtained by means of Hardy-Littlewood circle method, Heath-Brown's identity and power moments of DirichletL-functions over short intervals.