Thermal fatigue and wear of compacted graphite iron brake discs with various thermomechanical properties

The increase in payload capacity of trucks has heightened the demand for cost-effective yet high performance brake discs.In this work,the thermal fatigue and wear of compacted graphite iron brake discs were investigated,aiming to provide an experimental foundation for achieving a balance between their thermal and mechanical properties.Compacted graphite iron brake discs with different tensile strengths,macrohardnesses,specific heat capacities and thermal diffusion coefficients were produced by changing the proportion and strength of ferrite.The peak temperature,pressure load and friction coefficient of compacted graphite iron brake discs were analyzed through inertia friction tests.The morphology of thermal cracks and 3D profiles of the worn surfaces were also discussed.It is found that the thermal fatigue of compacted graphite iron discs is determined by their thermal properties.A compacted graphite iron with the highest specific heat capacity and thermal diffusion coefficient exhibits optimal thermal fatigue resistance.Oxidization of the matrix at low temperatures significantly weakens the function of alloy strengthening in hindering the propagation of thermal cracks.Despite the reduced hardness,increasing the ferrite proportion can mitigate wear loss resulting from low disc temperatures and the absence of abrasive wear.

Automated evaluation of parapapillary choroidal microvasculature in crowded optic discs:a controlled,optical coherence tomography angiography study

AIM:To compare superficial and deep vascular properties of optic discs between crowded discs and controls using optical coherence tomography angiography(OCT-A).METHODS:Thirty patients with crowded discs,and 47 control subjects were enrolled in the study.One eye of each individual was included and OCT-A scans of optic discs were obtained in a 4.5×4.5 mm^(2) rectangular area.Radial peripapillary capillary(RPC)density,peripapillary retinal nerve fiber layer(pRNFL)thickness,cup volume,rim area,disc area,cup-to-disc(c/d)area ratio,and vertical c/d ratio were obtained automatically using device software.Automated parapapillary choroidal microvasculature(PPCMv)density was calculated using MATLAB software.When the vertical c/d ratio of the optic disc was absent or small cup,it was considered as a crowded disc.RESULTS:The mean signal strength index of OCT-A images was similar between the crowded discs and control eyes(P=0.740).There was no difference in pRNFL between the two groups(P=0.102).There were no differences in RPC density in whole image(P=0.826)and peripapillary region(P=0.923),but inside disc RPC density was higher in crowded optic discs(P=0.003).The PPCMv density in the inner-hemisuperior region was also lower in crowded discs(P=0.026).The pRNFL thickness was positively correlated with peripapillary RPC density(r=0.498,P<0.001).The inside disc RPC density was negatively correlated with c/d area ratio(r=-0.341,P=0.002).CONCLUSION:The higher inside disc RPC density and lower inner-hemisuperior PPCMv density are found in eyes with crowded optic discs.

Nucleus Pulposus Cells from Calcified Discs Promote the Degradation of the Extracellular Matrix through Upregulation of the GATA3 Expression

Objective Disc calcification is strongly associated with disc degeneration;however,the underlying mechanisms driving its pathogenesis are poorly understood.This study aimed to provide a gene expression profile of nucleus pulposus cells(NPCs)from calcified discs,and clarify the potential mechanism in disc degeneration.Methods Primary NPCs were isolated from calcified and control discs(CAL-NPC and CON-NPC),respectively.The proliferation and extracellular matrix(ECM)metabolism capacities of the cells were evaluated using MTT and Western blotting,respectively.RNA sequencing was used to identify differentially expressed genes(DEGs)in the CAL-NPCs.The biological functions of the DEGs were analyzed using the Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)databases.The transcription factor database and Cytoscape software were used to construct the transcription factor-DEGs regulatory network.The role of the verified transcription factor in NPC proliferation and ECM metabolism was also investigated.Results The CAL-NPCs exhibited a lower proliferation rate and higher ECM degradation capacity than the CON-NPCs.In total,375 DEGs were identified in the CAL-NPCs.The GO and KEGG analyses showed that the DEGs were primarily involved in the regulation of ribonuclease activity and NF-kappa B and p53 signaling pathways.GATA-binding protein 3(GATA3)with the highest verified levels was selected for further studies.Overexpression of GATA3 in the CON-NPCs significantly inhibited their proliferation and promoted their ECM degradation function,while the knockdown of GATA3 in the CAL-NPCs resulted in the opposite phenotypes.Conclusion This study provided a comprehensive gene expression profile of the NPCs from the calcified discs and supported that GATA3 could be a potential target for reversing calcification-associated disc degeneration.

Discs大同源物关联蛋白5在肝细胞肝癌中的表达及临床预后意义

目的探讨肝细胞肝癌患者肝癌组织中Discs大同源物关联蛋白5(DLGAP5)表达及其与预后的关系,并研究DLGAP5对于肝癌细胞生长迁移的影响。方法 134例接受根治性肝癌切除术肝细胞肝癌患者术中肝癌样本及其癌旁组织,通过免疫组织化学染色比较癌与癌旁组织DLGAP5的表达,同时取其中30例癌与癌旁组织利用Western Blot和RT-PCR研究DLGAP5在两者之间转录和翻译水平的差异。分析其表达与肝细胞肝癌患者临床病理特征、预后之间的关系。在体外构建SMMC-7721干扰DLGAP5稳定转染的细胞系,观察DLGAP5对细胞生物学行为影响。结果 134例肝细胞肝癌组织中101例(75.6%)DLGAP5的表达显著高于癌旁组织(P<0.05)。DLGAP5的表达与患者的年龄(P=0.0028)、甲胎蛋白水平(P=0.011)、乙肝病史(P=0.011)、肿瘤的大小(P=0.004)、肿瘤是否有包膜(P=0.027)、肿瘤BCLC分期(P=0.034)均有显著的相关性,而与门静脉(P=0.138)和显微镜下血管癌栓(P=0.202)无显著的相关性。高表达DLGAP5的患者总体生存率(OS,对数秩检验,P=0.0002)和无瘤生存率(DFS,对数秩检验,P<0.0001)较低表达患者显著降低。体外实验也证实干扰SMMC-7721 DLGAP5后,细胞的生长和迁移要显著低于对照细胞。结论 DLGAP5对肝细胞肝癌的进展具有促进作用,其表达水平可以作为判断预后的标志。

Pullout of soil nail with circular discs: A three-dimensional finite element analysis

An internal failure mode for a soil-nailed system consists of failure at nail heads,slope facing,nail strength,along groutesoil interface and pullout failure.A better understanding of pullout of soil nail thus becomes important to assess the stability of a soil-nailed system.In the present study,an investigation into the pullout behaviour of soil nail with circular discs along the shaft has been carried out by a threedimensional finite element analysis using Abaqus/Explicit routine.A total of 67 simulations have been performed to accurately predict the pullout behaviour of soil nail.The soil nail under study has circular discs along its shaft varying in numbers from 1 to 4.The pullout of this soil nail in a pullout test box has been simulated with a constant overburden pressure of 20 kPa acting on the nail.The pullout load edisplacement characteristics,stresses around soil nail and failure mechanism during pullout are studied.Variations of dimensionless factors such as normalised pullout load factor and bearing capacity factor have been obtained with different combinations of parameters in terms of relative disc spacing ratio,anchorage length ratio,embedment ratio,diameter ratio and displacement ratio.From the results of analyses,it is found that nail with more circular discs requires higher pullout load.There are critical relative disc spacing ratio and diameter ratio which significantly affect the pullout behaviour of nail.

Ediacaran Discs from the Jodhpur Sandstone, Marwar Supergroup, India: A Biological Diversification or Taphonomic Interplay?

The noncarbonaceous Ediacaran discs of variable morphologies from the Jodhpur Sandstone Formation of the Marwar Supergroup, western Rajasthan, suggest different biologic affinities of plant and animal kingdom. These discs are commonly preserved on the bedding surfaces of siliciclastic sandstone and shale in strong positive relief and appear to possess a flexible to rigid body. Discs assignable to Aspidella, Cyclomedusa, Nimbia and Heimalora;all possibly inclining towards cnidarian affinity are being reported from the sandstone beds in Sursagar area. Variable morphologies among discs preserved in siliciclastic shale beds from the Artiya Kalan area support scyphozoan affinity (earlier named Marsonia from the same locality) and cnidarian affinity for small discs comparable with Funisia (considered being the first animals having sexual reproduction). Disc’s morphologies also suggest ephyra stage of Aurilia (a cnidarian form) or budding stages of some fungi, like Germinosphaera (multicellular benthic fungal fossils) and noncarbonaceous discs with well preserved wrinkles and folds like in Chuaria. Discs from the Jodhpur Sandstone, may at times display taphonomic interplay, but consistency and repetition in morphology support variable biological affinities representing diverse assemblage and advance ecosystem prevailing during Ediacaran period. A degree of genetic variability can be expected within any taxa, and this may be compounded by preservation factors affecting the Jodhpur Ediacaran discs. Sudden increase in size or gigantism is a common feature of Ediacaran life, which is evident in case of Jodhpur discs also. On the basis of fossil assemblage, the Jodhpur Group (the Marwar Supergroup) is regionally correlated with the Bhander Group of the Vindhyan Supergroup and Krol Group of Lesser Himalaya. Globally, the assemblage is comparable with the Long Mynd Group, Shropshire, UK, Fermuse Formation Newfoundland, South Australia, Russia and Norway.

抑郁强度量表环(DISCs):用于脑损伤后抑郁最初评估的简单工具

Objective: To assess the validity, responsiveness, and test-retest reliability of DISCs (Depression Intensity Scale Circles) as a simple screening tool for depression in patients with cognitive or communicative deficits following acquired brain injury. Design: Cohort analysis of consecutive patients entered into an integrated care pathway for screening and management of depression in the context of rehabilitation. Setting: Regional neurological rehabilitation service in the UK. Participants: 114 patients with complex disabilities caused by acquired brain injury (mean (SD) age, 42.8 (14.5) years). Main outcome measures: DISCs (a graphic rating scale depicting six circles with increasing proportion of dark shading), Numbered Graphic Rating Scale (NGRS), Yale single question (“Do you often feel sad or depressed”), Beck Depression Inventory-II (BDI-II), DSM-IV criteria for depression. Results: At initial assessment the DISCs correlated with total BDI-II scores (Spearman ρ= 0.66, P < 0.001), NGRS (ρ= 0.87, P < 0.001), and DSM-IV (ρ= 0.59, P < 0.001).A DISCs score≥2 identified depression (major or minor) according to DSM-IV criteria with 60%sensitivity, 87%specificity, 75%positive predictive value, and 77%negative predictive value. Test-retest reliability after 24 hours (n = 66) showed“excellent”.level of agreement (weighted κ= 0.84). In 45 patients who received intervention for depression, the DISCs showed a significant change in response to treatment (Wilcoxon; P < 0.001). Conclusions: DISCs had acceptable convergent validity, reliability, and responsiveness as a simple graded tool for screening and assessment of depression in patients with complex disabilities following acquired brain injury. It warrants further investigation in patients with more profound language and cognitive deficits for which it is primarily intended.

Axisymmetric Waves in Isothermal Accretion Discs with Vertical Self-Gravity

We extend the research of axisymmetric waves in accretion discs with three-dimensional structure to the case that vertical self-gravity of the discs is included. We derive and analyze the dispersion relation and solve the eigenfunctions numerically. The following results have been reached: vertical self-gravity expands the forbidden region of the wave propagation. As the influence of the vertical self-gravity increases, the group velocities of the waves get smaller and the vertical nodes of the wave shrink to the middle plane of the disc.

Largest Ediacaran discs from the Jodhpur Sandstone, Marwar Supergroup, India: Their palaeobiological significance

Ediacaran discs from the Jodhpur Sandstone of the Marwar Supergroup, Rajasthan, exhibit a wide size ranging from a few millimetres to 75 cm in diameter. Exceptionally large size of the discs in these rocks represent the largest reported so far from any Ediacaran assemblage. Although, larger medu-soid discs have been reported from USA, they are from the middle Cambrian and even younger rocks. Presence of microbial mats and weed-like structures with well preserved hold fasts and horizontal rhizome-like structures in association with some of these large-sized discs support their animal affinity, which probably feed on this weed-like vegetations. This association also supports their benthic habitat. Unlike the general trend of sudden increase in size of organisms in Ediacaran period and further decrease in size during Cambrian, these discs continued increasing in size in Cambrian also.

Stability of Accretion Discs around Magnetized Stars

We study the stability of accretion disc around magnetised stars. Starting from the equations of magnetohydrodynamics we derive equations for linearized perturbation of geometrically thin, optically thick axisymmetric accretion disc with an internal dynamo around magnetized stars. The structure and evolution of such discs are governed by an evolution equation for matter surface density ∑(R,T). Using the time-dependent equations for an accretion disc we do a linear stability analysis of our steady disc solutions in the presence of the magnetic field generated due to an internal dynamo.

The Case against Dark Matter and Modified Gravity: Flat Rotation Curves Are a Rigorous Requirement in Rotating Self-Gravitating Newtonian Gaseous Discs

By solving analytically the various types of Lane-Emden equations with rotation, we have discovered two new coupled fundamental properties of rotating, self-gravitating, gaseous discs in equilibrium: isothermal discs must, on average, exhibit strict power-law density profiles in radius x on their equatorial planes of the form , where A and k-1 are the integration constants;and “flat” rotation curves precisely such as those observed in spiral galaxy discs. Polytropic discs must, on average, exhibit strict density profiles of the form , where n is the polytropic index;and “flat” rotation curves described by square roots of upper incomplete gamma functions. By “on average”, we mean that, irrespective of the chosen boundary conditions, the actual profiles must oscillate around and remain close to the strict mean profiles of the analytic singular equilibrium solutions. We call such singular solutions the “intrinsic” solutions of the differential equations because they are demanded by the second-order equations themselves with no regard to the Cauchy problem. The results are directly applicable to gaseous galaxy discs that have long been known to be isothermal and to protoplanetary discs during the extended isothermal and adiabatic phases of their evolution. In galactic gas dynamics, they have the potential to resolve the dark matter—modified gravity controversy in a sweeping manner, as they render both of these hypotheses unnecessary. In protoplanetary disc research, they provide observers with a powerful new probing tool, as they predict a clear and simple connection between the radial density profiles and the rotation curves of self-gravitating discs in their very early (pre-Class 0) phases of evolution.

Apparent diffusion coefficient in normal and abnormal pattern of intervertebral lumbar discs: initial experience

The aim of the present study was to compare the relationship of morphologically defined non-bulging/herni-ated, bulging and herniated intervertebral lumbar discs with quantitative apparent diffusion coefficient （ADC）. Thirty-two healthy volunteers and 28 patients with back pain or sciatica were examined by MRI. All intervertebral lumbar discs from L1 to S1 were classified according to morphological abnormality and degenerated grades. The ADC values of nucleus pulposus （NP） were measured and recorded. The significant differences about mean ADC values of NP were found between non-bulging/herniated discs and bulging discs as well as herniated discs （P 0.05）, whereas there were no significant differences in ADC values between bulging and herniated discs （P 0.05）. Moreover, statistically significant relationship was found in the mean ADC values of NP between ＂non-bulging/herniated and non-degenerated discs＂ and ＂non-bulging/herniated degenerated discs＂ as well as herniated discs （P 0.05）. Linear regression analysis between ADC value and disc level revealed an inverse correlation （r = -0.18）. The ADC map of the NP is a potentially useful tool for the quantitative assessment of componential and molecular alterations accompanied with lumbar disc abnormalities.

Effect of axial vertical vibration on degeneration of lumbar intervertebral discs in modified bipedal rats: An in-vivo study

Objective: To assess the effects of axial vibrations on gene expression and lumbar intervertebral disc degeneration in vivo. Methods: A modified bipedal rat model was established using a brachial plexus rhizotomy approach to imitate human upright posture. The experimental animals were randomly divided into three groups: control, vertical vibration, and whole-body vibration. Gene expression in degeneration of the intervertebral discs was assessed by reverse transcription-quantitative polymerase chain reaction. Results: The expression of aggrecan, Col1α1, Col2α1, and decorin were shown to be up-regulated in 14-week-old rats in the vertical vibration and whole-body vibration groups, whereas biglycan and versican expression was down-regulated in 14-week-old rats of the two experimental groups. Furthermore, biglycan and versican expression levels were shown to be lower in the whole-body vibration group than in the vertical vibration group(P<0.05). Conclusions: This in-vivo study demonstrated that vibrations can influence the expression of anabolic genes. Furthermore, whole-body vibrations seem to have a greater effect in this regard than vertical vibrations. A new method is expected to relieve the low back pain of the patients through our research.

Biocompatibility of KLD-12 Peptide Hydrogel as a Scaffold in Tissue Engineering of Intervertebral Discs in Rabbits

KLD-12 peptide with a sequence of AcN-KLDLKLDLKLDL-CNH2 was synthesized and its biocompatibility was assessed in animals. Rabbit MSCs were cultured in the hydrogel for 2 weeks. Live cells were counted by using Calcein-AM/P1 fluorescence staining. MTT was employed to assess the viability of MSCs cultured in KLD-12 peptide solution of 0.01%, 0.03%, and 0.05%. Hemolysis test, skin irritation test and implantation test were conducted to evaluate its biocompatibility with host tissues. Our results demonstrated that the MSCs in hydrogel grew well and maintained round shape. Cell survival rate was 92.15% （mean： 92.15%±1.17%） at the 7th day and there was no difference in survival rate between day 7 and day 14. Cell proliferation test showed that the A value of the KLD-12 solutions was not significantly different from that of control groups （complete culture media） （P〉0.05） at the 24th and 48th h. The hemolysis rate of KLD-12 solution was 0.112%. Skin irritation test showed that the skin injected with KLD-12 solution remained normal and the score of skin irritation was 0. The histological examination with HE staining exhibited that the skin layers were clear and there was no infiltration with neutrophilic granulocytes and lymphocytes. It is concluded that KLD-12 peptide hydrogel bad a good biocompatibility with host rabbit and MSCs, and KLD-12 pep- tide hydrogel can provide an appropriate microenvironment for MSCs.

Correlation between Osteoporosis and Degeneration of Intervertebral Discs in Aging Rats

This study examined the correlation between osteoporosis and the degeneration of intervertebral discs. Sprague-Dawley rats were maintained up to 22 or 28 months. The femoral bone, tibial bone and lumbar vertebra were histologically studied and the expression of collagen type Ⅱ and Ⅹ in intervertebral discs was immunohistochemiscally determined. Several indices for the degeneration of intervertebral discs and osteoporosis and the correlation among them were then analyzed. Close correlations were found among the indices for the degeneration of intervertebral discs, including the relative area of the vascular bud, the ratio of the uncalcified and the calcified layers, the expression of collagen type Ⅱ and Ⅹ. The correlation with collagen type Ⅹ was negative. There existed positive correlations among the indices for osteoporosis, including the thickness ratio of cortical bone, the relative area of bone trabecula, the density of femoral and vertebral body bones, and the maximum stress and strain on bone. Analysis on the relationship of osteoporosis and the disease on disc showed that the indices of osteoporosis were negatively correlated with the indices of the degeneration of intervertebral discs but the expression of collagen type Ⅹ was positively correlated, with the density of vertebral body bones having the strongest dependence on collagen type Ⅹ. The maximum stress and strain bore no correlation with the degeneration of intervertebral discs. These results suggest that osteoporosis was negatively correlated with the degeneration of intervertebral discs.

The study of migration of bone mesenchymal stem cells transplanted in intervertebral discs of rabbits and expression of exogenous gene

Objective： To explore the survival and migration of bone mesenchymal stem cells transplantated in intervertebral disc of rabbits and expression of the exogenic genes. Methods. Thirty-two rabbits were used, A randomized block design was used and discs in the same rabbit were one block,the lumbar discs from L2-3 to L5-6 were randomly divided into blank group, saline group, cell transplantation group Ⅰand cell transplantation group Ⅱ. The fluorescence microscopy was used to determine the fluorescence of the maker protein GFP and DNA-PCR was used to analyze the copies of DNA of neomycin-resistant gene at 1, 3, 6, months after transplantation. Results： There was fluorescence in cell transplantation group Ⅰ and Ⅱ and none in blank group, saline group at 1, 3, 6 months after transplantation. In cell transplantation groups,the fluorescent distribution was more scatter with time, but no significant difference between cell groups Ⅰ and Ⅱ. The test of neomycin resistant gene expressed in cell transplantation group Ⅰ and Ⅱ and quantitative analysis showed that there was no significant difference between the cell groups Ⅰ and Ⅱ （P〉0.05）. Conclusion： The transplanted bone mesenchymal stem cells can survive, migrate and the transfer genes can express efficiently, it suggests that the BMSC therapy may be effective to prevent and treat intervertebral disc degeneration.

Stability Loss of Rotating Elastoplastic Discs of the Specific Form

A method of calculating a possible stability loss by a rotating circular annular disc of variable thickness is suggested within the theory of perfect plasticity with the help of small parameter method. A characteristic equation for a critical radius of a plastic zone is obtained as a first approximation. The formula for the critical angular velocity, determining the stability loss of the disc according to the self-balanced form, is derived. The method using which we can take into account the disc’s geometry and loading parameters is also specified. The efficiency of the proposed method is shown in Section 5 while considering an illustrative example. The values of critical angular velocity of rotating are found numerically for different parameters of the disc.

Wet and Dry Tribological Behaviors of Circular Islandic Protrusion Patterns on M2 Steel Discs under Spinning Condition

Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.

Analysis of Degenerative Discs in Lumbar Spondylolisthesis Using MRI T2 Mapping

Background: Spinal instability, including lumbar degenerative spondylolisthesis (DS), mainly results from degeneration of intervertebral discs (IVD) and the facet joints (FJ). Characterization of the relationship between IVD degeneration in cases of lumbar degenerative spondylolisthesis (DS), and T2 values may be useful for accurate noninvasive evaluation and subsequent treatment. Thus, the goal of this study was to measure T2 values of IVDs in cases with (DS) and without (NS) spondylolisthesis, and to characterize changes of IVDs in DS. Methods: A total of 40 subjects who presented with L4 spondylolisthesis comprised the DS group. Another 40 subjects who did not have lumbar spondylolisthesis, constituted the NS group. T2 values of IVDs were measured and compared in these groups. Results: T2 values for IVDs tended to be lower in the DS group than in the NS group, and these values were significantly different (p < 0.01) within the anterior annulus fibrosus (AF). No significant differences in T2 values between Meyerding grades I and II were observed in any areas of IVDs. Conclusions: It is speculated that in the early stages, the degeneration of the anterior AF develops and is related to the onset of lumbar spondylolisthesis, while in later stages, degeneration of facet joints influences the progression of spondylolisthesis.