Friction surface development and its structure on carbon fibre reinforced silicon carbide disc

Carbon fibre reinforced ceramic composites (Cf/C-SiC) have been explored as lightweight and durable disc in a friction brake. This composite was manufactured through infiltration of liquid silicon into a Cf/C perform. It has heterogeneous microstructure, composed of three key phases, silicon carbide, Cf/C, and un-reacted residual silicon. The development of the transfer layer on the friction surface of Cf/C-SiC was studied through microstructural image registration of the surface after a range of braking stops on a laboratory-scale dynamometer test rig. When an organic pad was used as the counter face brake pad, it was found that a steady transfer layer was developed in silicon regions right after initial stops; in carbon-fibre/carbon (Cf/C) regions and most of the silicon carbide region, the friction surfaces were unsteady and any possible friction transfer layers were hardly built up. Large voids and cracks/crevices likely became pools to quickly and efficiently collect the transferred materials generated by the friction, but the compacts formed inside the pools were susceptible to be stripped off by further braking operation. Three types of friction surfaces were generalized: type I, the friction transfer layer had a steady relationship with the matrix and respectable longevity; type II, the transfer layer had an unstable relationship with the matrix and poor durability; type III, the friction transfer layer had a steady relationship with the matrix but short lifetime. After testing against organic pads under the laboratory scale dynamometer testing condition, the friction surface of each key phase in Cf/C-SiC composites disc was studied by transmission electron microscopy (TEM). It was found that the transfer layer developed on Si consists of fine particles of metal silicides, silicates and minerals. The substrate damage of Si was not observed, while the precipitates having high oxygen content were found in the substrate. Formation of an interfacial bonding between transfer layer and silicon substrate is believed to be the key factor for the formation of a stable transfer layer on Si. However, the interfacial bonding between transferred materials and SiC was not detected. Kinks are common features developed on the friction surface of SiC. The interface between carbon fibre and carbon matrix was experienced mechanical damage, in form of microcracks, and the transferred material was developed in the interface. Instead of transfer layer, a thin amorphous film, produced by friction induced amorphisation of carbon fibre, was developed on top of carbon fibre

Retention Studies In HPLC

The effect of increasing temperature on retention time, efficiency and peak symmetry on a PS-DVB column was investigated using two sets of homologous compounds, phenylalkanols (benzyl alcohol to 5-phenylpentanol) and alkyl aryl ketones (benzaldehyde to heptanophenone) as standard compounds. It was found that efficiency and peak symmetry can be improved by an increase of temperature in both RP-HPLC and NP-HPLC In NP-HPLC, the use of a low level of polar organic modifier can reduce retention times and give improved peak shapes and column efficiencies. A different elution order was obtained in RP-HPLC compared with NP-HPLC The study was extended to retention prediction in RP-HPLC Retention indices can be calculated from the molecular structure of a compound as the sum of the parent index, substituent indices, and interaction indices. In this study the substituent contributions have been determined for 7 aromatic functional groups and 8 aliphatic functional groups over a range of methanol, acetonitrile and THF buffer eluents based on the alkyl aryl ketone retention index scale. The effect of intramolecular hydrogen-bonding in THF has been studied. A general prediction model was used for the retention prediction of disubstituted compounds. It was found -that the use of the Hammett constant (0") had its limitations and was not suitable if THF was the eluent

九州におけるソバ遺伝資源の諸特性の品種間差異および機能性の選抜法に関する研究

博士（農学）神戸大

Microstructure of friction surface developed on carbon fibre reinforced carbon-silicon carbide (Cf /C-SiC)

We have used TEM to study the microstructure of friction surface of carbon fibre/carbon-silicon carbide composites brake discs after multi braking stop by using organic pads. A friction surface layer was developed consistently on the top of Si regions of the composites, but inconsistently on that of SiC and C. Inside the layer, amorphous silicon/silicon oxides appeared extensively with various non-metallic and metallic crystallites dispersed inside with sizes ranging from a few nanometers to several microns. A coherent interface between the friction layer and the composite surface was established under the braking conditions, whilst its sustainability varied notably in SiC and C regions. Microcracking near the friction surface appeared in SiC and C /C regions largely due to the extensive ductile deformation of SiC and weak interfaces between C and C . Material joining mechanisms were discussed to enlighten the friction transfer layer development on the surface of the composite discs

Microstructure of friction surface developed on carbon fibre reinforced carbon-silicon carbide (Cf /C-SiC)

We have used TEM to study the microstructure of friction surface of carbon fibre/carbon-silicon carbide composites brake discs after multi braking stop by using organic pads. A friction surface layer was developed consistently on the top of Si regions of the composites, but inconsistently on that of SiC and C. Inside the layer, amorphous silicon/silicon oxides appeared extensively with various non-metallic and metallic crystallites dispersed inside with sizes ranging from a few nanometers to several microns. A coherent interface between the friction layer and the composite surface was established under the braking conditions, whilst its sustainability varied notably in SiC and C regions. Microcracking near the friction surface appeared in SiC and C /C regions largely due to the extensive ductile deformation of SiC and weak interfaces between C and C . Material joining mechanisms were discussed to enlighten the friction transfer layer development on the surface of the composite discs

Data_Sheet_2_Association between maternal lipid levels during pregnancy and delivery of small for gestational age: A systematic review and meta-analysis.DOCX

BackgroundStudies investigating the relationship between gestational dyslipidemia and small for gestational age (SGA) have reported differing results. This review was performed to determine whether maternal lipid levels during pregnancy were associated with SGA.MethodsLiterature searches for relevant studies were conducted systematically from establishment until February 2022 with PubMed, Embase, Cochrane Library and Web of Science. Risk of bias was assessed with the Newcastle-Ottawa Scale and 11-item checklist. According to the classification of GHD parameters, meta-analyses reporting cases regarding total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C) were performed respectively. If I2 ≥ 50%, considered to demonstrate substantial heterogeneity, the random effect model was employed. Otherwise, a fixed effect model was employed.ResultsEight studies (14,213 pregnancies) were included. Decreased levels of TC (MD −0.13; 95% CI −0.24 to −0.02), TG (MD −0.09; 95% CI −0.14 to −0.03) and LDL-C (MD −0.12; 95% CI −0.23 to −0.00) were risk factors for SGA infant birth. No evident association was observed between HDL-C and delivery of SGA (MD −0.08; 95% CI −0.19 to 0.02).ConclusionGestations complicated with dyslipidemia, especially lower concentrations of TC, TG and LDL-C, were at significantly higher risk of delivery of SGA.Systematic review registration[www.crd.york.ac.uk/prospero], identifier [CRD42022304648].</p

Data_Sheet_1_Association between maternal lipid levels during pregnancy and delivery of small for gestational age: A systematic review and meta-analysis.docx

BackgroundStudies investigating the relationship between gestational dyslipidemia and small for gestational age (SGA) have reported differing results. This review was performed to determine whether maternal lipid levels during pregnancy were associated with SGA.MethodsLiterature searches for relevant studies were conducted systematically from establishment until February 2022 with PubMed, Embase, Cochrane Library and Web of Science. Risk of bias was assessed with the Newcastle-Ottawa Scale and 11-item checklist. According to the classification of GHD parameters, meta-analyses reporting cases regarding total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C) were performed respectively. If I2 ≥ 50%, considered to demonstrate substantial heterogeneity, the random effect model was employed. Otherwise, a fixed effect model was employed.ResultsEight studies (14,213 pregnancies) were included. Decreased levels of TC (MD −0.13; 95% CI −0.24 to −0.02), TG (MD −0.09; 95% CI −0.14 to −0.03) and LDL-C (MD −0.12; 95% CI −0.23 to −0.00) were risk factors for SGA infant birth. No evident association was observed between HDL-C and delivery of SGA (MD −0.08; 95% CI −0.19 to 0.02).ConclusionGestations complicated with dyslipidemia, especially lower concentrations of TC, TG and LDL-C, were at significantly higher risk of delivery of SGA.Systematic review registration[www.crd.york.ac.uk/prospero], identifier [CRD42022304648].</p

Regioselective Direct C‑4 Functionalization of Indole: Total Syntheses of (−)-Agroclavine and (−)-Elymoclavine

An efficient rhodium-catalyzed method for direct C–H functionalization at the C4 position of unprotected indoles has been developed. The utility of this method is demonstrated by the concise total syntheses of agroclavine and elymoclavine in a divergent manner. These syntheses feature a Pd-catalyzed asymmetric allylic alkylation reaction to assemble the triyclic indole moiety, and a ring-closing metathesis reaction to form the D ring

Scalable Fabrication Framework of Implantable Ultrathin and Flexible Probes with Biodegradable Sacrificial Layers

For long-term biocompatibility and performance, implanted probes need to further reduce their size and mechanical stiffness to match that of the surrounding cells, which, however, makes accurate and minimally invasive insertion operations difficult due to lack of rigidity and brings additional complications in assembling and surgery. Here, we report a scalable fabrication framework of implantable probes utilizing biodegradable sacrificial layers to address this challenge. Briefly, the integrated biodegradable sacrificial layer can dissolve in physiological fluids shortly after implantation, which allows the in situ formation of functional ultrathin film structures off of the initial small and rigid supporting backbone. We show that the dissolution of this layer does not affect the viability and excitability of neuron cells in vitro. We have demonstrated two types of probes that can be used out of the box, including (1) a compact probe that spontaneously forms three-dimensional bend-up devices only after implantation and (2) an ultraflexible probe as thin as 2 μm attached to a small silicon shaft that can be accurately delivered into the tissue and then get fully released in situ without altering its shape and position because the support is fully retracted. We have obtained a >93% yield of the bend-up structure, and its geometry and stiffness can be systematically tuned. The robustness of the ultraflexible probe has been tested in tissue-mimicking agarose gels with <1% fluctuation in the test resistance. Our work provides a general strategy to prepare ultrasmall and flexible implantable probes that allow high insertion accuracy and minimal surgical damages with the best biocompatibility

Small-Angle Neutron Scattering Study of Cyclic Poly(ethylene glycol) Adsorption on Colloidal Particles

The adsorptions of cyclic PEG and linear PEG on colloidal silica particles were compared. Their adsorption volume fraction profiles were generated through model fitting of small-angle neutron scattering data from the adsorbed polymer layers. The two important parameters to describe adsorbed polymer layers were discussed in detail. It was found that the adsorption amounts of cyclic PEGs increased with molecular weight but were generally higher than their linear counterparts. However, the root-mean-square layer thickness, δ_rms, of adsorbed cyclic PEGs was found to decrease with molecular weight, opposing adsorbed linear PEGs and the theoretic prediction based on SF model. This disagreement was ascribed to the topological restriction of cyclic polymer at low molecular weight. An illustrated structural evolution with molecular weight for adsorbed polymer at interface was tentatively proposed based on the observations of this study