Search

Finding out the reason of the fracture fault of tail rotor on a helicopter is of practical significance for using and maintaining the helicopter and is of significant reference for improving safety of new type helicopter. The fracture fault of tail rotor blade on a helicopter is analyzed by fault tree analysis method, and the bottom event analysis results are obtained. Then, the macro and micro fractographic analysis of the tail rotor blade is carried out. Finally,the simulation analysis of the fractographic damage evolution of flexible beam is performed. The results show that the fracture property of the blade is low-stress and high-cycle bidirectional bending fatigue fracture. When the strength value of the fiber compression direction of the flexible beam is less than 700 MPa, the fractographic type is similar to that of the faulty tail rotor flexible beam. The tail rotor will produce large vibration under large fatigue load condition, and the increase of vibration can intensify the load of the tail rotor, which leads to the increase of load at the root of the flexible beam and exceeds the designed bearing capacity of the flexible beam, then fatigue fracture will occur at the root of the flexible beam of the blade.

Objective To compare the differences between the gray matter structures of amyotrophic lateral sclerosis (ALS) patients with limb-onset and bulbar-onset. Methods A total of 35 ALS patients with normal cognitive function were enrolled in Peking Union Medical College Hospital ALS Registry Platform from September 2013 to March 2018, and 20 healthy controls with matched age and education were included in the study. ALS patients were divided into limb-onset group (ALS-L group, n = 20) and bulbar-onset group (ALS-B group, n = 15) according to their clinical onset sites. Three-dimensional T1-fast spoiled gradient-recalled (3D-T1-FSPGR) of all subjects was collected. Gray matter volume of each group were compared using voxel-based morphometry (VBM). Within the compound region of interest (ROI) consisting of bilateral primary motor cortex, premotor cortex and supplementary motor area, the atrophy patterns of the motor cortex were compared between ALS-L group and ALS-B group. Results Compared with the control group, the ALS-L group had decreased gray matter volume in the left superior temporal gyrus-temporal pole (t = 3.932, uncorrected P < 0.001), left middle temporal gyrus (t = 3.836, uncorrected P < 0.001), right insula (t = 3.992, uncorrected P < 0.001). Compared with the ALS-B group, the ALS-L group had decreased gray matter volume in the right superior frontal gyrus (t = -3.158, uncorrected P < 0.001), left cingulate gyrus (t = -3.002, uncorrected P < 0.001). In the analysis of the motor cortex as ROI, the gray matter volume of the segments representing hand (t = 2.237, uncorrected P < 0.001) and lower limb (t = 2.728, uncorrected P < 0.001) of the left motor cortex in the ALS-L group was reduced significantly than that of ALS-B group. Conclusions ALS-L has more significant gray matter atrophy than ALS-B, and the local atrophy pattern of motor cortex in ALS patients corresponds to its functional disability.

Objective To evaluate the clinical and paraclinical features of Chinese patients with anti- LGI1 encephalitis. Methods Patients with memory deficits, psychiatric symptoms, seizures or altered level of consciousness, suspicious of encephalitis, at presentation to Peking Union Medical College Hospital were recruited between July 2013 and January 2018, and tested for anti-LGI1 antibodies in their serum and/or cerebrospinal fluid(CSF) samples. Patients with anti-LGI1 antibodies were enrolled. The demographic characteristics, clinical manifestations, laboratory examination results, neuroimaging features, immunotherapy, follow-up practices and outcomes for included patients were registered and analyzed. Results The study enrolled 120 patients, of whom 66.7% were male. The median age was 61 years (interquartile range [IQR]: 49-66 years). Seizures(65.0%) were the most common initial symptoms. Most patients developed seizures (95.0%), including faciobrachial dystonic seizures (54.2%), memory deficits (92.5%), and psychiatric symptoms (69.1%). Brain MRI and 18F-FDG PET / CT showed that the lesions were mainly located in unilateral or bilateral medial temporal lobes, and (or) basal ganglia. Of the patients, 95.0% received intravenous immunoglobulin (IVIg) or corticosteroids, 47.5% received mycophenolate mofetil as long-term immunotherapy, and no one received second-line immunotherapy. The median follow-up was 34.2 months(IQR: 22.0-45.6 months). 91.2% had a good outcome (modified Rankin Scale score≤2 points). Residual mild memory deficits were present in 47.8% of the patients. Nine deaths were documented. Relapses occurred in 24.8% of the patients in the first year. In total, 24 (20%)cases were young patients(onset age ≤45 years).There were fewer males among the younger patients(37.5% vs. 74.0%, P < 0.01). Besides, there were fewer younger patients with psychiatric symptoms(50.0% vs. 74.0%, P=0.02), hyponatremia(33.3% vs. 68.8%, P < 0.01), and abnormalities on brain 18F-FDG PET/CT(20.8% vs. 47.9%, P=0.02). The relapse-free survival rate was significantly higher in the young patients. Conclusions Elderly males were predominant in patients with anti-LGI1 encephalitis. Most patients developed symptoms of limbic encephalitis and/or FDBS during the disease course. Several patients were young adults and lacked typical symptoms. Neuroimaging features were consistent with the involvement of limbic system or basal ganglia. Patients with anti-LGI1 encephalitis respond well to immunotherapy, irrespective of the age.

Objective: The effect of frozen temperature on the storage characteristics of ready-to-eat snakehead sausages were investigated. Methods: In this study, The freezing temperature dehydration technique was used to control the moisture content of snakehead sausage at about 50%, and then the temperature was lowered to-5.6 ℃. Subsequently, the sausage was stored at -4 ℃, and those stored at 4 ℃ were set as the control. The changes in the quality and microstructure of the snakehead sausages were analyzed, by measuring the physicochemical indexes such as total bacterial colony, color, water holding capacity, textural properties, biogenic amines and scanning electron microscopy during storage. Results: The logarithmic values of TVC were （5.37±0.06）; TVB-N were （17±0.03） mg/100 g; the total amine mass fraction were （324.93±1.89） mg/kg at 42 d. The results of colony count and TVB-N analysis showed that, compared to those stored at 4 ℃, frozen storage could extend the shelf life of snakehead sausage by 1-fold. The low-field NMR results showed that the moisture distribution of snakehead sausage during frozen storage was better than that of the control. Scanning electron microscopy showed that the gel network of the frozen-storage group had a higher degree of binding to fat particles. The frozen storage of snakehead sausage was superior to the refrigerated storage. Conclusion: The preservation effect of snakehead sausage stored at freezing temperature is better than that of refrigerated storage.

Capsaicin is an active ingredient that characterizes the pungency of pepper, and is the key to the 'door of spicy sensation', that is, the source of spicy sensation. Through the interaction with the oral cavity, capsaicin substances make TRPV1 activated by capsaicin, increase intracellular calcium ions, trigger nerve endings, release neuropeptides, and finally cause the formation of pain sensation in the cerebral cortex, thus generating a spicy sensation. It has been found that capsaicin has certain damage to taste. Capsaicin may directly or indirectly inhibit the transmission of taste nerve by reducing the number of taste buds and changing the excitability of taste transduction or taste receptor cells, thus causing damage to relevant taste cells and nerves. This paper summarizes the regulation and damage mechanism of capsaicin to taste and the research status of the new capsaicin taste interaction technology, discusses the shortcomings of its potential influence mechanism, and looks forward to the future research direction, in order to provide reference for the application of capsaicin in food and the prevention of damage caused by capsaicin. [ABSTRACT FROM AUTHOR]

In order to quantitatively characterize the ability of PVD(physical vapor deposition) film sensors to detect cracks in metallic structures, the process parameters applied to LY12-CZ aluminium alloys were first optimized using orthogonal tests, and coin shape, 1mm concentric dual ring shape, 0.5mm concentric tricyclic shape PVD film sensors were prepared on three groups of specimen with central hole using these parameters. Subsequently, the on-line monitoring experiment of fatigue cracks was carried out under laboratory conditions, the potential output signals of the PVD film sensors and microscope observations were compared and analysed. Finally, the probability of detection curves of all kinds of PVD thin-film sensors and PVD film sensor in different shapes were plotted separately using the improved crack size separation method and binomial distribution detection model. PVD thin-film sensors have 93.56% detection probability for cracks with length greater than 0.99mm at 95% confidence level. Compared to coin-shaped thin-film sensors, concentric ring shape film sensors are more sensitive to cracks smaller than 0.5mm, and the sensors with finer channel width have the higher probability of detection on small size cracks.

The fatigue life scatter factor is an important reliability index of the assessment of aircraft fatigue life. At present,the safe-life of a fleet is gotten by using the total test hours and the fatigue scatter factor. Usually,the environment scatter factor caused by the different service environments is not considered,and the fatigue scatter factor mainly includes two parts,one is the load scatter factor caused by the load spectrum difference of fleets; the other is the structure scatter factor caused by the difference of material and manufacturing quality. The expressions of scatter factor of fatigue life obeying the log-normal distribution and Weibull distribution are introduced and analyzed. To the situation that the structure fatigue life of the same aircraft model under different load spectrums obeys the log-normal distribution,the condition that the fatigue scatter factor is the product of the load scatter factor and the structure scatter factor is deduced. To the situation that the structure fatigue life obeys the different distributions,the service flying hours can be converted into the equivalent flying hours under the same test load spectrum based on the equal damage principle,the structure scatter factor under this spectrum can be calculated and can be taken as the fatigue life scatter factor,the safe-life calculated by this scatter factor can be seen as the reference value for the management of individual aircraft life.

Magnesia-calcia refractories are widely used in the iron and steel smelting industry because of their advantages of steel liquid purification, high refractoriness, good thermal shock resistance and high corrosion resistance in basic slag. However, MgO and CaO usually hydrate in the process of manufacturing, storage and use of magnesia-calcia refractories, which seriously restricts the application and the development of magnesia-calcia refractories. In this work, the characteristics and hydration mechanism of magnesia-calcia refractories were reviewed, and the current research status and existing problems of the anti-hydration of magnesia-calcia refractories were summarized from three aspects: sintering densification, surface treatment and sealed packaging. In addition, the development trends and the research emphases of anti-hydration technology of magnesia-calcia refractories in the future were also prospected. [ABSTRACT FROM AUTHOR]

According to the real-time crack monitoring demand of metallic structures during their service, a film sensor is presented to monitor the metal structure crack based on the electric potential method. Firstly, the corresponding finite element model(FEM) of the film sensor is established, and the output characteristics of the sensor are analyzed by FEM. The results indicate that the extension direction and the length of crack can be obtained through analyzing the electric potential differences between monitoring points. And then the film sensor is prepared on the surface of the 2A12 aluminum alloy specimen by ion plating technology, which can integrate with metal surface firmly. Finally, crack monitoring experiments are carried out with the film sensor. Experimental results show that the structural crack propagation stage can be learned through analyzing the change extent of the adjacent monitoring data of the film sensor. [ABSTRACT FROM AUTHOR]

The similarities and differences between trigger points of myalgia and acupoints were explored. Nodules could be detected by B-ultrasound at trigger points of myalgia, but not acupoints. In clinical symptoms, the referred pain pathway of trigger points of myalgia is similar with the pathway of acupuncture meridian. Therefore, the location of trigger points of myalgia should take referred pain as pathway, which is similar with locating acupoints as meridian. Acupuncture at trigger points of myalgia takes jumping feeling as criterion, while acupuncture at acupoints are mainly based on acid swelling and numbness. From clinical observation to basic experimental research, a lot of pathophysiological evidence is provided for trigger point of myalgia. It is believed that the trigger point of myalgia might be the precise acupoint in modern scientific research, and the meridian is the synthesis of the mechanics of nerve, blood vessel and fascia. Although acupuncture and dry needling are different in theory, but the scientific foundation of TCM and western medicine is coherent.

Objective To evaluate the correlation of the positron emission tomography/magnetic resonance imaging (PET/MR) parameters with the pathological differentiation of head and neck squamous cell carcinoma(HNSCC) and the diagnostic efficiencies of PET/MR parameters. Methods Patients with clinical suspicion of HNSCC were included and underwent PET/MR scan. HNSCC was pathologically confirmed in all these patients. The PET/MR examination included PET and MR sequences of diffusion-weighted imaging (DWI) and T2-and T1-weighted imaging. The multiple parameters of PET/MR included the mean values of apparent diffusion coefficient(ADC mean ) and the maximum and mean values of standardized uptake value (SUV max and SUV mean ) were measured and estimated. The correlations of all the parameters and distribution between the different tumor differentiation groups were analyzed. Logistic regression was utilized to build the model as the PET/MR combined parameter for predicting the differentiation by multiple parameters of PET/MR. The receiver operating characteristic curve was calculated for each parameter and the combination. Results Totally 23 patients were included in this study:9 patients (9 males and 0 female) had well-differentiated tumor,with an average age of (61.0±6.8)years;14 cases had moderately-differentiated (n=10) or poorly-differentiated tumors (n=4),with an average age of (62.0±9.1) years. All the patients were males. There was statistical correlation between SUV mean and SUV max (P<0.001);however,ADC mean showed no statistical correlation with SUV max and with SUV mean (P=0.42,P=0.13). ADC mean and SUV mean showed significant difference between well-differentiated group and moderately-poorly-differentiated group (P=0.005,P=0.007). Compared with the individual parameters,the combination of PET/MR parameters with SUV mean and ADC mean had higher efficacy in predicting tumor differentiation,with an area under curve of 0.84. Conclusions The distributions of ADC mean ,SUV max and SUV mean differ among HNSCC with different pathological differentiation. Compared with the individual parameters,the combination of the PET/MR parameters has higher efficiency in predicting tumor differentiation.

Objective: To evaluate the clinical and musculoskeletal characteristics of localized scleroderma with lower extremities affected., Methods: All the localized scleroderma patients,who received magnetic resonance (MR ) examinations of affected lower extremities at Peking Union Medical College Hospital from April 2013 to June 2014,were retrospectively reviewed. Their clinical data and laboratory results of antinuclear antibody,anti-double stranded-DNA antibody, and anti-extractable nuclear antigen antibody were collected and analyzed. All the MR examinations were non-contrast imaging using Siemens Skyra 3.0T MR scanner., Results: There were 16 localized scleroderma patients with lower extremities affected, 11 of whom were linear scleroderma, 4 generalized morphea, and 1 deep morphea. Female to male ratio was 1:2.2. The mean age was 22.5 years. The mean time span was 7.4 years. Four of the 14 patients (28.6%) who received antinuclear antibody test were positive. All the 10 patients who received anti-double stranded-DNA antibody test and the 7 patients who received anti-extractable nuclear antigen antibody test were negative. The most common musculoskeletal MR features were subcutaneous septal thickening (16/16) and fascial thickening (11/16). The thickened speta and fascia could either be hypointenstiy or hyperintensity on turbo inversion recovery magnitude/proton density weighted imaging. Other MR manifestations were intramuscular speta thickening (3/16), muscular abnormal signals (1/16), and bone marrow abnormal signals (2/16)., Conclusion: Musculoskeletal manifestations of the lower extremities with localized scleroderma can be well revealed using MR imaging.

Objective: To use the technique of magnetic resonance imaging (MRI) T2* mapping to diagnose and follow-up of patients with iron overload., Methods: 107 patients who were suspected to have iron overload between 2011.7-2014.3 in Peking Union Medical Colleague Hospital were analyzed retrospectively. Patients had the document of MRI T2* value of liver, heart and pancreas, serum ferritin (SF), transferrin saturation (TS), transfusion amount and other related laboratory tests. T2* values were compared with SF and transfusion amount. T2* values in different organs and their relationship with SF were also evaluated. 10 patients who had been adequately chelated for more than half a year were followed up for their SF and T2* values., Results: There were 65 males and 42 females with the median age of 51(8-77)-year-old. They were 50 myelodysplastic syndromes (MDS), 36 aplastic anemia, 10 myelofibrosis, 7 hemachromatosis and 4 thalassemia carriers. Liver T2* value was significantly related to SF (r=0.120, P=0.001), but not related to transfusion amount (r=0.019, P=0.175), whereas cardiac MRI T2* was not related either to SF or to transfusion amount. No correlation of the T2* value was found between liver and heart (r=0.015, P=0.235). 70 patients was detected for liver, heart and pancreas T2* simultaneously. Pancreas T2* was compatible to SF (r=0.061，P=0.039) and cardiac T2* (r=0.110, P=0.005), but not correlated to heptic T2* (r=0.047, P= 0.071) or transfusion amount (r=0.000, P=0.960). For the 10 well-chelated patients, during the half year follow-up period, SF changed significantly from (2 566.5±1 152.2) μg/L before chelation to (1 473.4±803.0) μg/L after chelation(P=0.001), while liver T2* remained the same [(6.0±5.1) ms, (6.3±6.0) ms respectively, P=0.629]., Conclusion: MRI, although related to SF to some extent, was a valuable additional methods for quantifying iron overload. Iron deposition in different organs might be not related to each other and needed to be evaluated separately. Well-chelation therapy could change SF in half-year follow-up, but T2* change needed longer time to follow-up.

Objective: To evaluate the significance of magnetic resonance imaging (MRI) T2(*) value analysis in patients with iron overload and compare it with other clinical parameters., Methods: A total of 53 patients with suspected iron overload were recruited from four Beijing hospitals from December 2010 to December 2012. Their liver and heart T2(*) values were calculated and their serum ferritin (SF), transferrin saturation, blood transfusion volume and other clinical parameters were recorded and analyzed., Results: There were 37 males and 16 females with a medium age of 50 years(15-72 years). Their etiologies included myelodysplastic syndromes (MDS, n = 25), aplastic anemia (AA, n = 16), myelofibrosis (n = 5), hemochromatosis (n = 2) and β thalassaemia (n = 2), and 3 patients with high SF values were found on regular health examinations. Among them, there were transfusion history (n = 45), SF>1000 µg/L (n = 49), sign of iron overload (n = 10), abnormal liver function (n = 38) and hyperglycemia (n = 32). T2(*) value analysis showed that 10 patients had no evidence of iron overload, 43 patients had liver iron overload (14 mild, 22 moderate and 7 severe) and 2 patients had heart iron overload (1 MDS with heavy transfusion history and 1 AA with heart failure). No relations existed between T2(*) value and SF (P = 0.050) , T2(*) value and transfusion volume (P = 0.820) , and liver T2(*) value and heart T2(*) value (P = 0.129) ., Conclusions: MRI T2(*) value is an accurate way of quantitative detection of iron overload. It provides a comprehensive understanding of patients with iron overload in conjunctions with MRI T2(*) value and other clinical parameters.

Objective: To construct luxS mutant aften luxS gene of Streptococcus mutans (S. mutans) was knocked out, and examine their ability of biofilm formation., Methods: A recombinant plasmid containing the flanking fragment of luxS of S. mutans was transformed into S. mutans UA159, and selected by brain heart infusion (BHI) agar medium with kanamicin. The luxS mutant further confirmed via polymerase chain reaction (PCR) and the autoinducer-2 (AI-2) bioluminescence assay of Vibrio harveyi (V. harveyi), and ability of luxS mutant and S. mutans UA159 biofilm formation was examined in different phases, in BHI medium with 1% sucrose and 1% glycose by scanning electron microscopy (SEM)., Results: LuxS-deficient S. mutans strains were successfully constructed. Compared with S. mutans UA159, the luxS mutant maintained in BHI medium containing 1% sucrose displayed an apparent defect in biofilm formation, while they showed no significant deviation in BHI medium containing 1% glycose., Conclusion: luxS gene in S.mutans can play a role in dental plaque biofilm formation, and the luxS gene is possible to regulate sucrose-dependent biofilm formation.

Objective: To establish a high-throughput chemiluminescence assay of serotype 5 specific neutralizing antibody and understand the epidemiology of this antibody in the healthy adults and children in Guangzhou., Methods: Using rAd5 carrying the reporter gene of secreted alkaline phosphatases (SEAP), serum samples from 116 healthy adults and 94 healthy children were examined with chemiluminescence assay to detect the presence of Ad5 neutralizing antibody. The reliability of this assay was tested against conventional cytopathic effect observation., Results: The chemiluminescence assay using secreted alkaline phosphatases (SEAP) as the reporter allowed rapid, sensitive, specific and reproducible detection of serotype 5 specific neutralizing antibody for epidemiological study of Ad5, which was positive in 26.72% of the adults and 17.02% of the children in this study., Conclusion: Ad5 neutralizing antibody is prevalent in the population of Guangzhou, suggesting the necessity of developing other serotype adenovectors for better vaccination and therapeutic effects.

Objective: To evaluate the expression of p27 protein in oral precancerous lesions and oral squamous cell carcinoma (OSCC)., Methods: Immunohistochemistry was used to detect p27, p53, murine double minute (MDM2) and p21 protein expression in a series of 13 specimens with simple hyperplasia, 44 with dysplasia and 48 with OSCC. An attempt was made to correlate the protein levels with clinicopathologic parameters and Ki-67 protein levels., Results: Positive p27 staining was present in 79.55% of the dysplasia samples, as well as in 81.25% of the OSCC samples. p27 protein overexpression in OSCC group was significantly higher than that in leukoplakia group (P < 0.001). The extent of p27 expression was positively associated with Ki-67 expression (P < 0.001). Cases with p27 overexpression displayed concurrent expression of p53 and/or MDM2 (P = 0.034) in OSCC group., Conclusions: p27, p53, MDM2 and p21 may all play important roles in the genesis of OSCC. The alterations of one or more cell cycle regulators are prevalent in oral premalignant lesions and OSCC and the regulators can regulate each other.