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1.
Virus Genes ; 59(6): 868-873, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37698740

RESUMO

Clanis bilineata Walker, soybean hawkmoth, belongs to the subfamily Ambulicinae (Sphingidae, Lepidoptera) and is an edible insect that usually grows on soybean leaves. In this study, we isolated a new cypovirus from naturally diseased Clanis bilineata larvae (named CbCPV), scanned its structure, sequenced its genome, and studied its phylogenetic relationship to other cypoviruses. Microscopy showed that CbCPV polyhedral occlusion bodies were about 1.878 µm on average and contained many virions in the ultrathin sections. The complete genome sequence of CbCPV is 22,812 bp comprising 10 segmented double-stranded RNAs. Apart from segment 1 containing one open reading frame (ORF) and one sub-ORF, the other nine segments all contain one open reading frame and encoded one putative protein. The non-coding regions contained conserved sequences at 5' termini (AGUCAAA) and 3' termini (AGC), except segment 4 containing a different 5' termini (AUGUUUA). The whole sequence of the polyhedrin gene in CbCPV contained 892 nucleotides, encoding a protein of 246 amino acids. Based on amino acid sequences of polyhedrin or RNA dependent RNA polymerase (RdRp), the phylogenetic analysis indicated that CbCPV was closely related to DnCPV-23. The putative function of all segments differed from each other, but the most closely related species of segments were DnCPV-23 with 98.2-99.8% nucleotide identity. Overall, the evidence of morphology, protein analysis and nucleic acids (genomic pattern) showed that CbCPV is a new isolate in the cypovirus-23 type and can be termed Clanis bilineata cypovirus type 23 (CbCPV-23).


Assuntos
Mariposas , Reoviridae , Animais , Reoviridae/genética , Filogenia , Genoma Viral/genética , Proteínas Virais/genética , Genômica , RNA Viral/genética
2.
Virol J ; 18(1): 250, 2021 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-34906167

RESUMO

BACKGROUND: Daphnis nerii cypovirus-23 (DnCPV-23) is a new type of cypovirus and has a lethal effect on the oleander hawk moth, Daphnis nerii which feeds on leave of Oleander and Catharanthus et al. After DnCPV-23 infection, the change of Daphnis nerii responses has not been reported. METHODS: To better understand the pathogenic mechanism of DnCPV-23 infection, 3rd-instar Daphnis nerii larvae were orally infected with DnCPV-23 occlusion bodies and the transcriptional responses of the Daphnis nerii midgut were analyzed 72 h post-infection using RNA-seq. RESULTS: The results showed that 1979 differentially expressed Daphnis nerii transcripts in the infected midgut had been identified. KEGG analysis showed that protein digestion and absorption, Toll and Imd signaling pathway were down-regulated. Based on the result, we speculated that food digestion and absorption in insect midgut might be impaired after virus infection. In addition, the down-regulation of the immune response may make D. nerii more susceptible to bacterial infections. Glycerophospholipid metabolism and xenobiotics metabolism were up-regulated. These two types of pathways may affect the viral replication and xenobiotic detoxification of insect, respectively. CONCLUSION: These results may facilitate a better understanding of the changes in Daphnis nerii metabolism during cypovirus infection and serve as a basis for future research on the molecular mechanism of DnCPV-23 invasion.


Assuntos
Mariposas , Reoviridae , Animais , Perfilação da Expressão Gênica , Larva , Mariposas/genética , Reoviridae/genética , Transcriptoma
3.
J Invertebr Pathol ; 163: 43-47, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30858088

RESUMO

The oleander hawk moth, Daphnis nerii, is a serious pest of plants belonging to the family Apocynaceae. Thus far, pathogen infection has not been reported in D. nerii. In this study, a new cytoplasmic polyhedrosis virus (cypovirus; CPV) was isolated from naturally diseased D. nerii larvae and named DnCPV-23. Virions were observed in ultrathin sections of DnCPV polyhedral bodies. Electrophoretic analysis revealed that the DnCPV genome consisted of 10 segments of double-stranded RNA (dsRNA). cDNA copies of these dsRNA segments were amplified using the method of full-length amplification of cDNAs (FLAC), cloned, and sequenced. Sequencing results showed that all segments contained one open reading frame (ORF); They shared the conserved terminal sequences AGUCAAA and AGC at 5' and 3' ends respectively, except segment 4, which is different from previously reported 22 cypoviruses. Phylogenetic analysis based on amino acid sequences of polyhedrin (encoded by segment 10) indicated that this CPV was closely related to CPV type 19. Altogether, DnCPV-23 is a new type of cypovirus.


Assuntos
Mariposas/virologia , Reoviridae , Animais , Genoma Viral , Vírus de Insetos/classificação , Vírus de Insetos/genética , Vírus de Insetos/isolamento & purificação , Vírus de Insetos/ultraestrutura , Filogenia , Reoviridae/classificação , Reoviridae/genética , Reoviridae/isolamento & purificação , Reoviridae/ultraestrutura , Proteínas Virais/genética
4.
Bioengineering (Basel) ; 10(9)2023 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-37760199

RESUMO

Elderly people usually have poorer surgical tolerance and a higher incidence of complications when undergoing revision surgery after posterior instrumented lumbar fusion (PILF). Full-endoscopic transforaminal surgery is a safe and effective option, but sometimes, it is difficult to revise L5-S1 foraminal stenosis (FS) after PILF. Therefore, we developed full-endoscopic lumbar decompression (FELD) at the arthrodesis level via a modified interlaminar approach under local anesthesia. This study aimed to describe the technical note and clinical efficacy of the technique. Eleven patients with unilateral lower limb radiculopathy after PILF underwent selective nerve root block and then underwent FELD. Magnetic resonance imaging (MRI) and computer tomography (CT) were performed on the second postoperative day. Their clinical outcomes were evaluated with a Visual analog scale (VAS) of low back pain and sciatica pain, Oswestry disability index (ODI), and the MacNab score. Complete decompression was achieved in every case with FELD without serious complications. Postoperative VAS of sciatica pain and ODI at each time point and VAS of low back pain and ODI after three months postoperatively were significantly improved compared with those preoperative (p < 0.05). According to the MacNab criteria, seven patients (63.6%) had excellent results at the two-year follow-up, and four patients (36.4%) had good results. No patients required further revision surgery. FELD, via a modified interlaminar approach, is effective for treating unilateral L5-S1 FS after PILF in elderly people.

5.
JBJS Case Connect ; 13(1)2023 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-36821403

RESUMO

CASE: A 20-year-old man with a Tile C1.2 pelvic fracture was treated with skeletal traction. After 3 months, the patient was unable to stand and walk, and the right lower limb was shortened by 7 cm. Radiographs showed that the sacroiliac joint dislocation was not reduced. Gradual traction reduction with the Ilizarov method was used to correct sacroiliac joint dislocation, and open internal fixation was performed. Postoperatively, the old pelvic fracture was successfully reduced without sacral plexus injury. CONCLUSION: Gradual traction reduction with the Ilizarov method can reduce the risk of sacral plexus injury and achieve satisfactory reduction of Tile C1.2 old pelvic fractures.


Assuntos
Fraturas Ósseas , Técnica de Ilizarov , Luxações Articulares , Ossos Pélvicos , Masculino , Humanos , Adulto Jovem , Adulto , Tração , Parafusos Ósseos , Fraturas Ósseas/cirurgia , Ossos Pélvicos/cirurgia , Luxações Articulares/cirurgia
6.
World Neurosurg ; 169: e235-e244, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36334710

RESUMO

OBJECTIVE: To evaluate and describe the clinical efficacy and safety of a modified unilateral biportal endoscopic lumbar discectomy. METHODS: From February 2019 to February 2020, patients who met the inclusion criteria were treated using a modified unilateral biportal endoscopic lumbar discectomy. During the operation, the herniated disc was removed and the ligamentum flavum was preserved. Clinical efficacy was assessed via postoperative imaging and follow-up. RESULTS: A total of 70 patients were followed up for more than 2 years, including 51 males and 19 females, aged 49.4 ± 16.0 years. All operations were completed and no complications were noted. Postoperative lumbar magnetic resonance imaging showed that the decompression of the nerve root was sufficient and the ligamentum flavum was preserved in all patients. Postoperative lumbar CT showed that the caudal lamina and inferior articular process of the cephalad vertebral were partially removed. Lower back and leg pain were significantly relieved after surgery, and the Oswestry Disability Index was significantly improved compared to presurgery measurements (P < 0.01). After 2 years of follow-up, the sensory and muscle strength of nerve roots were significantly recovered (P < 0.01). According to the MacNab score of the patients, 40 cases were defined as "excellent," 26 cases were "good," 2 cases were "fair," and 2 cases were "poor." CONCLUSIONS: Modified unilateral biportal endoscopic lumbar discectomy can completely remove a lumbar herniated disc; relieve lower back and leg pain; improve lumbar function; reduce the risk of dural tearing, cerebrospinal fluid leakage, and epidural hematoma; and reduce the epidural adhesion and arachnoiditis caused by ligamentum flavum resection.


Assuntos
Discotomia Percutânea , Deslocamento do Disco Intervertebral , Masculino , Feminino , Humanos , Deslocamento do Disco Intervertebral/diagnóstico por imagem , Deslocamento do Disco Intervertebral/cirurgia , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/cirurgia , Endoscopia/métodos , Discotomia/métodos , Resultado do Tratamento , Dor/cirurgia , Região Lombossacral/cirurgia , Estudos Retrospectivos , Discotomia Percutânea/métodos
7.
Guang Pu Xue Yu Guang Pu Fen Xi ; 32(8): 2089-94, 2012 Aug.
Artigo em Zh | MEDLINE | ID: mdl-23156758

RESUMO

By using the Rosemount gas analyzer and the test platform of fixed bed built by carbon furnace, the harmful gaseous compositions and the release rules of asphalt and mortar under high temperature rate were analyzed quantitatively based on infrared spectral analysis technology. The results indicated that the combustion process of the asphalt and mortar can be approximately divided into two stages stage of primary volatile combustion, and stage of secondary volatile release combined with fixed carbon combustion in isothermal condition with high heating rate. The major gaseous products are CO2, CO, NO, NO2 and SO2. the volatile content is one of the key factors affecting the release rules of gaseous combustion products in asphalt, and reducing the volatile content in asphalt materials can effectively reduce the generation of gaseous combustion products, especially CO.

8.
World Neurosurg ; 165: e457-e468, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35752422

RESUMO

OBJECTIVE: The objective of this study was to compare the safety and clinical efficacy of full-endoscopic lumbar interbody fusion (FE-LIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). METHODS: A total of 70 patients with single-level lumbar degenerative diseases underwent FE-LIF or MIS-TLIF with a tubular retractor system from August 2018 to August 2020. Postoperatively, the efficacy and safety were compared using several clinical and radiological indices. RESULTS: A total of 32 patients underwent FE-LIF and 38 received MIS-TLIF with a tubular retractor system, and all patients had no apparent complications. The FE-LIF group had higher radiation exposure, longer operation time, and less bleeding than the MIS-TLIF group (P < 0.05). Postoperative lumbar magnetic resonance imaging showed that the nerve decompression was sufficient. The pain in the lower back and legs was significantly relieved, and the Oswestry Disability Index (ODI) score was greatly improved after surgery (P < 0.01) in both the groups. The sensory and motor functions of nerve roots were remarkably recovered in both the groups at the 1-year follow-up (P < 0.05), and there was no significant difference in MacNab scores between the 2 groups. As per Mannion's fusion classification, the interbody fusion rate was significantly better in the FE-LIF group than in the MIS-TLIF group. CONCLUSIONS: FE-LIF, which is safe, effective, and minimally invasive, exhibits the same clinical efficacy as MIS-TLIF but with longer operation time and increased radiation exposure.


Assuntos
Fusão Vertebral , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/cirurgia , Região Lombossacral/cirurgia , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Estudos Retrospectivos , Fusão Vertebral/métodos , Resultado do Tratamento
9.
World Neurosurg ; 158: e618-e626, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34775095

RESUMO

OBJECTIVE: We sought to introduce technical notes of full endoscopic lumbar interbody fusion (FE-LIF) with an anterior expandable cylindrical fusion cage. METHODS: This study retrospectively reviewed patients who underwent FE-LIF with an anterior expandable cylindrical fusion cage through transforaminal or interlaminar approaches from August 2018 to April 2019. Patient demographics and operation-related complications were recorded. Clinical and radiologic outcomes were evaluated at 1 year after surgery. RESULTS: A total of 32 patients (34 segments) were included in this study. Among them, 14 received full endoscopic transforaminal lumbar interbody fusion and 18 received full endoscopic interlaminar lumbar interbody fusion. There were significant differences in interbody fusion indications between the 2 groups (P < 0.05). All operations were successfully completed without complications. Postoperative lumbar magnetic resonance imaging showed that nerve decompression was sufficient in all patients, and the visual analog scale scores of low back pain and leg pain, the Oswestry Disability Index scores, and sensory and muscle strength were significantly improved after surgery (P < 0.01). The MacNab score included 9 excellent ratings, 4 good ratings, and 1 fair rating in the full endoscopic transforaminal lumbar interbody fusion group and included 10 excellent ratings and 8 good ratings in the full endoscopic interlaminar lumbar interbody fusion group; the scores were not significantly different between the 2 groups at 1 year after surgery (P > 0.05). Complete interbody fusion was achieved in both groups according to computed tomography at 1 year after surgery. CONCLUSIONS: FE-LIF is a safe and effective minimally invasive lumbar surgery with an anterior expandable cylindrical fusion cage.


Assuntos
Vértebras Lombares , Fusão Vertebral , Seguimentos , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/cirurgia , Região Lombossacral/cirurgia , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Estudos Retrospectivos , Fusão Vertebral/métodos , Resultado do Tratamento
10.
Materials (Basel) ; 14(11)2021 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-34199776

RESUMO

This study has investigated the impact of graphene oxide (GO) in enhancing the performance properties of an asphalt binder. The control asphalt binder (60/70 PEN) was blended with GO in contents of 0%, 0.5%, 1%, 1.5%, 2%, and 2.5%. The permanent deformation behavior of the modified asphalt binders was evaluated based on the zero shear viscosity (ZSV) parameter through a steady shear test approach. Superpave fatigue test and the linear amplitude sweep (LAS) method were used to evaluate the fatigue behavior of the binders. A bending beam rheometer (BBR) test was conducted to evaluate the low-temperature cracking behavior. Furthermore, the storage stability of the binders was investigated using a separation test. The results of the ZSV test showed that GO considerably enhanced the steady shear viscosity and ZSV value, showing a significant contribution of the GO to the deformation resistance; moreover, GO modification changed the asphalt binder's behavior from Newtonian to shear-thinning flow. A notable improvement in fatigue life was observed with the addition of GO to the binder based on the LAS test results and Superpave fatigue parameter. The BBR test results revealed that compared to the control asphalt, the GO-modified binders showed lower creep stiffness (S) and higher creep rate (m-value), indicating increased cracking resistance at low temperatures. Finally, the GO-modified asphalt binders exhibited good storage stability under high temperatures.

11.
Int J Spine Surg ; 15(3): 504-513, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33963038

RESUMO

BACKGROUND: Oblique lateral lumbar interbody fusion (OLLIF) is a minimally invasive lumbar interbody fusion procedure using a bullet-shaped polyetheretherketone (PEEK) nonexpandable fusion cage modified to diminish risk to the exiting nerve root during posterolateral implantation through the Kambin safe zone under fluoroscopic guidance. The objective of this study was to present feasibility of this procedure and 1-year clinical outcome data. METHODS: The authors present a prospective cohort study of 20 patients who underwent fluoroscopy-guided and full-endoscopic OLLIF in 22 segments allowing protection of the exiting nerve root from January 2018 to March 2019. The foraminoplasty, discectomy, endplate preparation, placement of bone graft and insertion of the fusion cage was done under continuous full-endoscopic visualization. The OLLIF fusion was backed up with bilateral percutaneous posterior supplemental pedicle screw fixation. Primary clinical outcome measures were the visual analog scale (VAS) of low back and leg pain, and Oswestry disability index (ODI) at 1 week, 3 months, 6 months, and 1 year after the operation. At final follow-up, the Macnab score was also evaluated. Secondary outcome measures were computed tomography (CT) assessment fusion using the Mannion classification of spinal fusion and adverse events related to the device as well as magnetic resonance imaging (MRI) assessment of nerve root decompression. RESULTS: All patients had significant relief of low back pain and leg pain, by VAS and ODI scores that improved significantly (P < .01). There were no complications. Postoperative lumbar MRI of all patients showed sufficient direct nerve decompression. At 1-year follow-up, excellent Macnab outcomes were obtained 13 patients, good in six, and fair in one. Impaired sensation and muscle strength of the involved nerve root significantly recovered in all but 2 patients (P < .05). According to the Mannion CT-based classification of spinal fusion, CT showed complete interbody fusion achieved in all 22 segments. CONCLUSIONS: Full-endoscopic OLLIF is a safe, effective, minimally invasive, economical, practical, and widely applicable minimally invasive interbody fusion technique in the lumbar spine. LEVEL OF EVIDENCE: 3.

12.
Materials (Basel) ; 13(4)2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32093003

RESUMO

The recovery property of asphalt binders plays an important role in the performance and service life of asphalt pavements. Since the internal stress is the driving force for the recovery of asphalt binders, the accurate measurement of the internal stress is full of significance. Based on this rationale, this paper aims to measure the internal stress of asphalt binders using a creep and step-loading recovery (CSR) test and characterizing the recovery behaviors by the internal stress. One base asphalt binder and one styrene-butadiene-styrene (SBS)-modified binder are selected in this study. The key elements of the CSR test are carefully designed and its accuracy is verified in three aspects, including the loading conditions, the effect of disturbance by step-loads, and accuracy of measured internal stress. Then, a kinetics-based recovery model is proposed to evaluate and predict the recovery properties of asphalt binders from its causal relationship. The constant-rate recovery activation energy indicates a major difference with nondestructive and destructive loading conditions, while the fast-rate recovery activation energy keeps almost constant regardless of the loading conditions. After that, the healing activation energy is calculated by using the kinetics-based recovery model and the results indicate that SBS modified asphalt binder shows better healing abilities than a base binder.

13.
J Orthop Surg Res ; 15(1): 163, 2020 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-32354340

RESUMO

Following publication of the original article [1], we have been notified that there was a spelling mistake in the author affiliations. In this Correction, correct and incorrect versions are shown.

14.
World J Clin Cases ; 8(18): 4017-4021, 2020 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-33024758

RESUMO

BACKGROUND: Variations in the methylene tetrahydrofolate reductase (MTHFR) gene have been reported as risk factors for numerous conditions, including cardiovascular disease, thrombophilia, stroke, hypertension and pregnancy-related complications. Moreover, it was reported there is an association between breast cancer and mutations in MTHFR-C677T. However, whether there is an association between MTHFR gene polymorphism and granulomatous lobular mastitis or not has been rarely investigated. AIM: To analyze the association between MTHFR gene polymorphism and granulomatous lobular mastitis. METHODS: Fifty-one patients with granulomatous lobular mastitis admitted to The First Hospital of Kunming were selected as study samples. Their hospitalization time ranged from February 2018 to February 2019. The 51 patients were included in the experimental group, and another 51 women who underwent physical examination at The First Hospital of Kunming in the same period were included in the control group. Deoxyribonucleic acid and MTFR genetic polymorphism testing were performed in each group. The association between MTHFR gene polymorphism and granulomatous lobular mastitis was observed. RESULTS: There were significant differences in genotype frequency and allele frequency of C/C and C/T between the experimental group and the control group (all P < 0.05). However, there was no significant difference in frequency of T/T genotype between the two groups (P > 0.05). In addition, there was no significant difference in genotype frequency and allele frequency of A/A, A/C and C/C between the two groups (P > 0.05). CONCLUSION: MTHFR gene C677T locus polymorphism is closely related to granulomatous lobular mastitis.

15.
J Orthop Surg Res ; 14(1): 459, 2019 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-31864378

RESUMO

BACKGROUND: The management of old bony mallet fingers is complicated. The aim of the study is to present a new method of open reduction and compression with double Kirschner wires (K-wires) in treating old bony mallet fingers. METHODS: This was a retrospective analysis of patients with old closed bony mallet fingers treated between June 2013 and December 2016. Complications were observed. The range of motion (ROM) of the DIP joints was measured using a protractor. At the last follow-up, anteroposterior and lateral X-ray of the affected finger was performed, the flatness of the articular surface was scored, and the results were graded using Crawford's criteria. RESULTS: Seventeen patients were followed up for 8 (6-19) months. The width of the avulsion fracture block accounted for 25-62% of the articular surface of the distal phalanx. Twelve (70.6%) patients had anterior dislocation of the interphalangeal joint. All patients reported healing at the fracture sites. Healing time was 7.6 ± 2.1(5-13) weeks. All patients had incision healing of I/Class A. Lateral X-ray showed 13 and four patients had excellent and good articular surface flatness, respectively. At the last follow-up, no traumatic arthritis was present. Only one patient developed mild pain after surgery (VAS score of 3). Postoperative ROM was 76.5 ± 10.6° (P = 0.0625 vs. healthy side). At the last follow-up, the angle of loss of dorsiflexion was 0-10° (P < 0.0001 vs. baseline). The flexion angle was 50-90° (P = 0.0625 vs. healthy side). CONCLUSIONS: Open reduction and compression with double K-wires is feasible in treating old bony mallet finger.


Assuntos
Fios Ortopédicos , Falanges dos Dedos da Mão/lesões , Falanges dos Dedos da Mão/cirurgia , Fixação de Fratura/métodos , Fraturas Ósseas/cirurgia , Adolescente , Adulto , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Redução Aberta , Estudos Retrospectivos , Fatores de Tempo , Adulto Jovem
16.
Materials (Basel) ; 12(12)2019 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-31238527

RESUMO

A method was developed for solving the relaxation modulus of high viscosity asphalt sand (HVAS) based on the three-point bending creep test, and was verified by comparison with experimental results. In this method, firstly, a transcendental equation was obtained by the convolution, and then equations were obtained by Taylor's formula, which were solved by Mathmatica to obtain the relaxation modulus by Newton's method. Subsequently, the laboratory investigations of the viscoelastic parameters of the Burgers model for the HVAS by three-point bending creep tests were carried out. In addition, the method was verified by comparing the relaxation moduli with the indoor relaxation experiments. Results showed that the numerical calculation and the test data were in good agreement, and the relaxation characteristics of the HVAS were reflected more accurately. The method can be used to study the relaxation characteristics of the asphalt mixtures effectively. In addition, this study provides a research basis for road crack prevention.

17.
Materials (Basel) ; 12(6)2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30909416

RESUMO

To study the dynamic response of saturated asphalt pavement under moving load and temperature load, 3-D finite element models for asphalt pavements with hydro-mechanical coupling and thermal-hydro-mechanical coupling were built based on the porous media theory and Biot theory. First, the asphalt pavement structure was considered as an ideal saturated fluid⁻solid biphasic porous medium. Following this, the spatial distribution and the change law of the pore-water pressure with time, the transverse stress, and the vertical displacement response of the asphalt pavement under different speeds, loading times, and temperatures were investigated. The simulation results show that both the curves of the effective stress and the pore-water pressure versus the external loads have similar patterns. The damage of the asphalt membrane is mainly caused by the cyclic effect of positive and negative pore-water pressure. Moreover, the peak value of pore-water pressure is affected by the loading rate and the loading time, and both have positive exponential effects on the pore-water pressure. In addition, the transverse stress of the upper layer pavement is deeply affected by the temperature load, which is more likely to cause as transverse crack in the pavement, resulting in the formation of temperature cracks on the road surface. The vertical stress at the middle point in the upper layer of the saturated asphalt pavement, under the action of the temperature load and the driving load, shows a single peak.

18.
Materials (Basel) ; 11(9)2018 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-30213088

RESUMO

The three-point bending fatigue tests were carried out in order to accurately predict the fatigue life of an asphalt mixture based on the plateau value (PV) of the dissipated strain energy ratio (DSER). The relations of the dissipated strain energy (DSE) to the stress-strength ratio, temperature and loading rate were studied, and the constructions of the mathematical models of DSE and DSER were completed based on the change laws of the DSE. The relation of the fatigue life to the PV was determined based on the analysis of damage evolution, based on which the fatigue equation was established and used to predict the fatigue life. The results show that the change laws of DSE and DSER can be well described by the proposed mathematical models. The PV is defined as the average value of the DSER in the second stage and the fatigue life decreases in power function with the increase of PV, based on which the fatigue equation of Nf = A(PV)B was established, and the established fatigue equation is very close to that is used in the MEPDG. The fatigue equation can well predict the fatigue life asphalt mixture.

19.
Materials (Basel) ; 11(5)2018 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-29751515

RESUMO

Laboratory predictions for the fatigue life of an asphalt mixture under cyclic loading based on the plateau value (PV) of the permanent deformation ratio (PDR) were carried out by three-point bending fatigue tests. The influence of test conditions on the recovery ratio of elastic deformation (RRED), the permanent deformation (PD) and PDR, and the trends of RRED, PD, and PDR were studied. The damage variable was defined by using PDR, and the relation of the fatigue life to PDR was determined by analyzing the damage evolution process. The fatigue equation was established based on the PV of PDR and the fatigue life was predicted by analyzing the relation of the fatigue life to the PV. The results show that the RRED decreases with the increase of the number of loading cycles, and the elastic recovery ability of the asphalt mixture gradually decreases. The two mathematical models proposed are based on the change laws of the RRED, and the PD can well describe the change laws. The RRED or the PD cannot well predict the fatigue life because they do not change monotonously with the fatigue life, and one part of the deformation causes the damage and the other part causes the viscoelastic deformation. The fatigue life decreases with the increase of the PDR. The average PDR in the second stage is taken as the PV, and the fatigue life decreases in a power law with the increase of the PV. The average relative error of the fatigue life predicted by the fatigue equation to the test fatigue life is 5.77%. The fatigue equation based on PV can well predict the fatigue life.

20.
Materials (Basel) ; 11(12)2018 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-30544569

RESUMO

In order to represent the mechanical response laws of high-modulus asphalt pavement (HMAP) faithfully and objectively, the viscoelasticity of high-modulus asphalt mixture (HMAM) was considered, and the viscoelastic mechanical responses were calculated systematically based on moving load by numerical simulations. The performances of the HMAP in resistance to the deformation and the cracking at the bottom layer were compared with the ordinary asphalt pavement. Firstly, Lubao and Honeywell 7686 (H7686) were selected as the high modulus modifiers. The laboratory investigations of Asphalt mix-70 penetration, Asphalt mix-SBS (styrene-butadiene-styrene), HMAM-Lubao and HMAM-H7686 were carried out by dynamic modulus tests and wheel tracking tests. The conventional performances related to the purpose of using the HMAM were indicated. The master curves of the storage moduli were obtained and the viscoelastic parameters were fitted based on viscoelastic theories. Secondly, 3D pavement models based on moving loads for the viscoelastic structures were built using the non-linear finite element software ABAQUS. The wheel path was discretized in time and space to apply the Haversine wave load, and then the mechanical responses of four kinds of asphalt pavement were calculated. Finally, the sensitivity analysis was carried out. The results showed that the addition of the high modulus modifiers can improve the resistance to high-temperature rutting of the pavements. Except for the tensile strain and stress at the bottom of the underlayer, other responses decreased with the increases of the dynamic moduli and the change laws of the tensile strain and stress were affected by the range of the dynamic modulus. The tensile stress at the bottom of the asphalt layer would be too large if the modulus of the layer were too large, and a larger tensile strain would result. Therefore, the range of the modulus must be restricted to avoid the cracking due to excessive tension when using the HMAM. The resistance of the HMAP to deformation was better and the HMAP was less sensitive to load changes and could better withstand the adverse effects inflicted by heavy loads.

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