L.L. Zhang

Predictions of bridge scour: Application of a feed-forward neural network with an adaptive activation function

In this study, a new procedure to determine the optimum activation function for a neural network is proposed. Unlike previous methods of optimising activation functions, the proposed approach regards selection of the most suitable activation function as a discrete optimisation problem, which involves generating various combinations of function then evaluating their performance as activation functions in a neural network, returning the function or combination of functions which yields best result as the optimum. The efficacy of the proposed optimisation method is compared with conventional approaches using the data generated from several synthetic functions. Numerical results indicate that the network produced using the proposed method achieves a better accuracy with a smaller network size, compared to other approaches. Bridge scour problem is used to further demonstrate the performance of the proposed algorithm. Based on the training and validation results, a better estimation of both equilibrium and time dependent scour depth is produced by the neural network developed using the proposed optimisation method, compared to networks with a priori chosen activation functions. Furthermore, the performance of the proposed model is compared with predictions of empirical methods, with the former making more accurate predictions.

An optimised product-unit neural network with a novel PSO-BP hybrid training algorithm: Applications to load-deformation analysis of axially loaded piles

In general, neural network training is a nonlinear multivariate optimisation problem. Unlike previous studies, in the present study, particle swarm optimisation (PSO) and back-propagation (BP) algorithms were coupled to develop a robust hybrid training algorithm with both local and global search capabilities. To demonstrate the capacity of the proposed model, we applied the model to the predictions of the load-deformation behaviour of axially loaded piles. This is a soil-structure interaction problem, involving a complex mechanism of load transfer from the pile to the supporting geologic medium. A database of full scale pile loading tests is used to train and validate the product-unit network. The results show that the proposed hybrid learning algorithm simulates the load-deformation curve of axially loaded piles more accurately than other BP, PSO, and existing PSO-BP hybrid methods. The network developed using the proposed algorithm also turns out to be more accurate than hyperbolic and t-z models.

Uncertainties of Field Pullout Resistance of Soil Nails

A large number of field pullout tests on soil nails have been carried out to provide valuable information for enhancing the understanding of pullout resistance of soil-grout interface and for reliability evaluation of soil-nailed slopes. In this paper, a data set of 167 field pullout tests performed in 23 nailed completely decomposed granite cut slopes is used for a statistical evaluation of four factors influencing the pullout resistance of soil nails, namely overburden pressure, grout length, soil suction, and soil dilatancy. For the tests in which nails were pulled out, the measured pullout resistance is essentially independent of the effective overburden pressure. A bias factor r* is defined as the ratio of the measured pullout resistance and the calculated value using a design equation. The mean value of r* is 4.30 and the coefficient of variation is 47%. When the uncertainties in grout length, soil suctions around nails, and the soil shear dilatancy are considered, the mean value of r* can finally b...

Predictive markers for early conversion of iRBD to neurodegenerative synucleinopathy diseases

Objective: To determine the predictive value of clinical assessment and dopamine transporter (DAT) uptake for the early development of neurodegenerative synucleinopathy diseases from idiopathic REM sleep behavior disorder (iRBD) over 5 years in a Chinese population. Methods: Forty-three patients with iRBD were administered clinical assessment tests, and 35 were examined by DAT-SPECT imaging during 2011. Cox proportional hazard and Kaplan-Meier analyses were used to evaluate the predictive value of the markers in a follow-up study over 5 years. Results: Eighteen patients (41.9%) developed neurodegenerative synucleinopathy diseases after a median of 4.1 years of prospective follow-up (median interval of 10.5 years from the estimated onset of iRBD symptoms). Patients with higher scores on the Nonmotor Symptom Questionnaire (hazard ratio [HR] 3.11, 95% confidence interval [CI] 1.15–8.40, p = 0.026) and Scale for Outcomes in Parkinson Disease–Autonomic questionnaire (HR 4.46, 95% CI 1.64–12.10, p = 0.003) were more likely to develop neurodegenerative synucleinopathy diseases. Furthermore, the population with decreased 99mTc-TRODAT-1 binding in the left striatum (HR 2.7, 95% CI 1.02–7.14, p = 0.046) and putamen (HR 3.23, 95% CI 1.16–8.33, p = 0.024) had a relatively higher risk of developing neurodegenerative synucleinopathy diseases. Conclusions: Our findings elucidate the predictive value of autonomic dysfunction and DAT uptake in identifying patients with iRBD at a high risk of progressing into neurodegenerative synucleinopathy diseases and could form a basis for future disease-prevention trials.

Salivary DJ-1 could be an indicator of Parkinson's disease progression.

Objective: The goal of the current investigation was to explore whether salivary DJ-1 could be a potential biomarker for monitoring disease progression in Parkinsons disease (PD) by evaluating the association between salivary DJ-1 concentrations and nigrostriatal dopaminergic function. Methods: First, in 74 patients with PD and 12 age-matched normal controls, single photon emission computed tomography (SPECT) imaging with labeled dopamine transporters (DAT) (99mTc-TRODAT-1), which has been used for measuring DAT density in PD was prformed. Then, the DJ-1 level in their saliva was analyzed by quantitative and sensitive Luminex assay and compared to caudate or putamen DAT density. Finally, based on the above, our cross-section study was carried out in 376 research volunteers (285 patients with PD and 91 healthy controls) to measure salivary DJ-1 level. Results: From our analysis, we found a correlation between salivary concentration of DJ-1 and putamen nucleus uptake of 99mTc-TRODAT-1 in the PD group. Although salivary DJ-1 levels were not affected by UPDRS scores, gender, age, and pharmacotherapy, DJ-1 levels in H&Y 4 stage of PD were higher than those in H&Y 1-3 stage as well as those in healthy controls. Salivary DJ-1 also decreased significantly in mixed type PD patients compared to the tremor-dominant type (TDT) and akinetic-rigid dominant type (ARDT) PD patients. Conclusions: According to the investigation in a large cohort, we reported for the first time the prognostic potential of the salivary DJ-1 as a biomarker for evaluating nigrostriatal dopaminergic function in PD.

Transcranial sonography of the substantia nigra and its correlation with DAT-SPECT in the diagnosis of Parkinson's disease

INTRODUCTIONS Transcranial sonography (TCS) of the substantia nigra is a new and promising method to diagnose Parkinsons disease (PD) but its effectiveness is controversial. METHODS All 55 PD patients involved in the study underwent single photon emission computed tomography (SPECT) imaging using the labeled dopamine transporter radiotracer (99m)Tc-TRODAT-1 to assess nigrostriatal dopaminergic function. The echogenicity of the substantia nigra was measured by TCS in all patients who received DAT-SPECT scanning. Finally, statistical analysis was carried out to determine the diagnostic accuracy of TCS as well as its correlation with (99m)Tc-TRODAT-1 SPECT, its positive predictive value (PPV), and negative predictive value (NPV). RESULTS Contralateral striatal (99m)Tc-TRODAT-1 uptake was significantly reduced compared to ipsilateral striatal uptake, and had a negative correlation with UPDRS-Ⅲ(r = -0.334, p = 0.013), disease duration (r = -0.393, p = 0.003) and H-Y stage (r = -0.330, p = 0.014). After TCS measurement, the contralateral SN echogenic area was similar to the ipsilateral SN echogenic area (27.77 ± 13.19 vs 25.98 ± 11.94 mm(2), p = 0.402, n = 24). No correlation was identified between TCS and UPDRS-Ⅲ (r = 0.383, p = 0.065), disease duration (r = 0.371, p = 0.075) or H-Y stage (r = 0.259, p = 0.222). The sensitivity and specificity of SN TCS for the diagnosis of PD were calculated as 64.70% and 60% according to DAT-SPECT, respectively, while the positive predictive value and negative predictive value was calculated as 91.67% and 20%, respectively. CONCLUSIONS Compared to DAT-SPECT, TCS is a non-radioactive and convenient procedure to perform. In our investigation, TCS had no correlation with DAT-SPECT. However, the high positive predictive value of TCS highlights its possible utility as a routine diagnostic test.

Navigation-guided en bloc resection and defect reconstruction of craniomaxillary bony tumours.

The aim of this study was to evaluate the validity of navigation-guided en bloc tumour resection and defect reconstruction in the treatment of craniomaxillary bony tumours. Three patients with ossifying fibroma and two patients with fibrous dysplasia were enrolled in this study. After preoperative planning and three-dimensional simulation, the osteotomy lines for resection were delineated and the normal anatomic structures for defect reconstruction were ascertained. With the guidance of an Accu-Navi navigation system, an en bloc tumour resection and simultaneous defect rehabilitation were performed. The system provided continuously updated information on the position and movement of surgical instruments in the operating field in relation to the preoperative imaging data set. The system error measured by the computer did not exceed 1mm. The osteotomy lines and reconstruction contour were checked by postoperative computed tomography, and good matching with the preoperative planning was achieved. Patients showed no signs of tumour recurrence or prosthesis infection during follow-up (range 12-35 months). Image-guided navigation makes radical bone tumour resection more reliable by implementing preoperative planning, showing the determined safety margins, preserving vital structures and guiding reconstruction.

Similarity of soil variability in centrifuge models

The soil specimen in a centrifuge model is subject to spatial variability depending on the method of sample preparation and the stress field induced by the centrifugal acceleration, even though it is intended to be uniformly pre- pared. In contrast to extensive measurements for studying the variability of in situ soil properties, soil variability in centri- fuge models, especially that which is based on data at very close sampling distances, is less understood. In this paper, the variability of soil density in two centrifuge models is presented. Random field theory is adopted to characterize the spatial soil variability in the two centrifuge models. The importance of taking spatial variability parameters as a model similarity requirement in centrifuge model design is illustrated and discussed. It is demonstrated that, although centrifuge models of different sizes can be designed to simulate the same prototype, the prototypes these models actually represent are not iden- tical in terms of soil spatial variability. To achieve similarity in spatial variability between a centrifuge model and its pro- totype, one may need to control either the point coefficient of variation or the scale of fluctuation of the model soil so that the coefficients of variation of the spatially averaged soil property in the model and the prototype are the same.

Endoscope-assisted conservative condylectomy in the treatment of condylar osteochondroma through an intraoral approach

Mandibular condylar osteochondroma (OC) can result in morphological and functional disturbances, including facial asymmetry and temporomandibular joint (TMJ) dysfunction. The aim of this study was to explore the feasibility of endoscope-assisted tumour resection and conservative condylectomy via an intraoral approach. Seven patients with condylar OC were enrolled in this study. Endoscope-assisted tumour resection and conservative condylectomy were achieved intraorally, and no conventional extraoral incision was needed. Direct vision of the magnified and illuminated operative field was realized with the assistance of an endoscope. No facial nerve injury or salivary fistula occurred in any patient. Stable occlusion was realized through postoperative orthodontic treatment. The patients showed no signs of tumour recurrence or TMJ ankylosis during follow-up (range 18-43 months). Endoscope-assisted condylar OC resection and conservative condylectomy via intraoral approach offers great advantages with no significant complications compared with conventional extraoral incisions. The endoscope provides us with a valuable treatment option for this potentially complicated procedure.

Association of rapid eye movement sleep behavior disorder with sleep-disordered breathing in Parkinson's disease

OBJECTIVE Rapid eye movement (REM) sleep behavior disorder (RBD) and sleep-disordered breathing (SDB) are two major sleep disturbances observed in patients with Parkinsons disease (PD). However, prior studies exploring the clinical correlations between RBD and SDB in PD have been limited. We aimed to investigate the relationship between RBD and SDB in PD using a case-control study. METHODS A total of 46 PD patients with Hoehn-Yahr stages ranging from 1 to 3 participated in the present study. Participants underwent polysomnography to diagnose the presence of RBD and SDB, and were classified into groups, accordingly. SDB was defined as an apnea-hypopnea index greater than 5. Comparison of clinical and sleep-respiratory parameters was performed among them. RESULTS SDB was more frequent in the RBD group than in the non-RBD group (51.4% vs 9.1%, p = 0.016). PD patients with RBD had significantly reduced mean SaO2 and more severe sleep apnea-related parameters during total sleep and non-REM sleep in comparison with non-RBD PD patients. However, there were no differences on the REM-related apnea/hypopnea variables between participants with and without RBD (p > 0.05). Both the frequency of RBD and RBD screening questionnaire (RBDSQ) scores were higher in the participants with SDB than in the participants without SDB (p <0.05). Furthermore, a significant negative correlation was found between RBDSQ and mean SaO2 in all participants. CONCLUSIONS In PD patients, SDB is more frequent and more severe in patients with RBD than in patients without, and RBD increases the risk of hypoxemia during sleep.