Data-driven fractional order feedback and model-less feedforward control of a XY reluctance-actuated micropositioning stage.

This paper proposes a compound data-driven control method to solve the problems of low damping resonance, different dynamic properties, and hysteresis in the large-range compliant micropositioning stage driven by a Maxwell reluctance actuator. First, in order to verify the proposed control algorithm, a reluctance-actuated, XY compliant micropositioning stage is constructed according to the principle of operation of a reluctance actuator. Second, in order to eliminate the influence of complex dynamics on the controller design, a fractional order proportional-integral feedback controller is designed using a data iterative feedback turning algorithm. Third, the finite impulse response feedforward filter is optimized using experimental data, and the on-line inverse estimation of the system frequency response function and its iterative feedforward compensation are carried out to further eliminate the influence of light damping resonance. Finally, the proposed control method is used for tracking the experiment and compared with other methods. The experimental results show that the proposed control method can better meet the requirements of high precision, fast speed, and strong anti-interference ability for large stroke micro/nanopositioning and tracking.

AKAP2 overexpression modulates growth plate chondrocyte functions through ERK1/2 signaling.

In our previous study, the mutation c.2645A > C (p. E882A) was found in the A-Kinase Anchoring Protein 2 (AKAP2) gene, which plays an important role in regulating the development of the skeletal system; however, the specific effect of AKAP2 on chondrocyte proliferation and differentiation and the potential mechanism are still not clear. In the present study, we investigated the effect of AKAP2 in vitro. We successfully isolated human growth plate chondrocytes (GPCs) from growth plate cartilage tissues and identified GPCs by aggrecan expression and flow cytometric analysis. AKAP2 overexpression significantly promoted GPC proliferation, enhanced GPC differentiation, and promoted extracellular matrix (ECM) synthesis, whereas AKAP2 silencing exerted the opposite effects on GPCs. AKAP2 overexpression increased, while AKAP2 silencing decreased, the protein levels of p-extracellular regulated protein kinases (ERK)1/2. More importantly, the promotive effects of AKAP2 overexpression on GPC proliferation, differentiation, and ECM synthesis were significantly reversed by the ERK1/2 signaling antagonist U0126, suggesting that AKAP2 enhances GPC functions through ERK1/2 signaling. In conclusion, we demonstrate AKAP2 overexpression-induced enhancement of GPC functions through ERK1/2 signaling. Considering the critical role of GPC functions in adolescent idiopathic scoliosis (AIS) pathogenesis, the application of AKAP2 targeting in AIS treatment should be investigated in future studies.

A High-Voltage and Low-Noise Power Amplifier for Driving Piezoelectric Stack Actuators.

In this paper, based on the principles of general operational amplifiers, a high-voltage operational amplifier is developed. Considering the influences of piezoelectric stack actuators on the circuit, a novel structure using the high-voltage operational amplifier as a noninverting amplifier is proposed. Because of the simple circuit principles and the voltage feedback control structure, the proposed power amplifier has the advantages of low noise and small size, and it can be realized by discrete electric elements easily. In the application of precision positioning, a power amplifier using the proposed circuit principles for driving piezoelectric stack actuators is designed, simulated, and tested. The simulated results show that the proposed power amplifier could conform to the theory of the circuit. The experimental results show that the designed power amplifier conforms to the simulation, the bandwidth of the power amplifier is about 57 kHz, and the ripple of the power amplifier is less than 2 mV. Furthermore, the output of the proposed power amplifier maintains the same type of wave within in a large range of frequency, while the input is the sinusoidal or square wave, and the resolution of the mechanism which the power amplifier is applied in is about 4.5 nm. By selecting the critical electronic elements and using feedback control, the proposed circuit structure is able to realize a low-cost and high-performance power amplifier to drive piezoelectric stack actuators flexibly, which is the novel work of the paper.

A multi-label classification model for full slice brain computerised tomography image.

BACKGROUND: Screening of the brain computerised tomography (CT) images is a primary method currently used for initial detection of patients with brain trauma or other conditions. In recent years, deep learning technique has shown remarkable advantages in the clinical practice. Researchers have attempted to use deep learning methods to detect brain diseases from CT images. Methods often used to detect diseases choose images with visible lesions from full-slice brain CT scans, which need to be labelled by doctors. This is an inaccurate method because doctors detect brain disease from a full sequence scan of CT images and one patient may have multiple concurrent conditions in practice. The method cannot take into account the dependencies between the slices and the causal relationships among various brain diseases. Moreover, labelling images slice by slice spends much time and expense. Detecting multiple diseases from full slice brain CT images is, therefore, an important research subject with practical implications. RESULTS: In this paper, we propose a model called the slice dependencies learning model (SDLM). It learns image features from a series of variable length brain CT images and slice dependencies between different slices in a set of images to predict abnormalities. The model is necessary to only label the disease reflected in the full-slice brain scan. We use the CQ500 dataset to evaluate our proposed model, which contains 1194 full sets of CT scans from a total of 491 subjects. Each set of data from one subject contains scans with one to eight different slice thicknesses and various diseases that are captured in a range of 30 to 396 slices in a set. The evaluation results present that the precision is 67.57%, the recall is 61.04%, the F1 score is 0.6412, and the areas under the receiver operating characteristic curves (AUCs) is 0.8934. CONCLUSION: The proposed model is a new architecture that uses a full-slice brain CT scan for multi-label classification, unlike the traditional methods which only classify the brain images at the slice level. It has great potential for application to multi-label detection problems, especially with regard to the brain CT images.

Full-Endoscopic Posterior Lumbar Interbody Fusion Via an Interlaminar Approach Versus Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Preliminary Retrospective Study.

OBJECTIVES: Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) has been performed as a minimally invasive surgery for lumbar degenerative disease, but previous MIS-TLIF methods have shown limitations by their own characters. In this study, we developed a newly interbody fusion technique of full-endoscopic posterior lumbar interbody fusion (FE-PLIF) via an interlaminar approach, presented its preliminary clinical results in comparison with MIS-TLIF procedure. METHODS: This study retrospectively reviewed 52 patients who underwent FE-PLIF (n = 22) or MIS-TLIF (n = 30) surgery between October 2018 and February 2019. Patient demographics, intraoperative parameters, and perioperative complications were collated. Clinical and radiologic outcomes were evaluated at each follow-up for up to 12 months. RESULTS: FE-PLIF demonstrated a longer operation time, less blood loss, and shorter hospitalization duration than MIS-TLIF. The visual analog scale (VAS) score for leg pain in both groups and for back pain in FE-PLIF group significantly improved at 1 week, while the VAS score for back pain in MIS-TLIF group significantly improved at 3 months. No significant difference in the VAS and Oswestry disability index scores was found between the groups at 3 months and 12 months. Fusion rates of definite grades were not significantly different between the groups (73.3% vs. 70.0%, P > 0.05). All patients who suffered from cage subsidence or nonunion were asymptomatic and did not require revision surgery during the follow-up. CONCLUSIONS: The FE-PLIF interlaminar approach is a safe and effective interbody fusion technique with less surgical trauma and similar outcomes compared to MIS-TLIF. However, this technique still requires technical advancements to improve efficiency and reduce technical complexity.

Celastrol regulates bone marrow mesenchymal stem cell fate and bone-fat balance in osteoporosis and skeletal aging by inducing PGC-1α signaling.

Celastrol has recently been identified as a prospective new treatment for obesity and several metabolic complications. However, the effect of Celastrol in osteoporosis (OP) remains unknown. In this study, we demonstrated that Celastrol promotes osteoblast differentiation and prevents adipocyte differentiation in bone marrow mesenchymal stem cells (BM-MSCs) in vitro. Mechanistically, Celastrol was able to control the differentiation of BM-MSCs by stimulating PGC-1α signaling. Moreover, administration of Celastrol could alleviate bone loss and bone marrow adipose tissue (MAT) accumulation in ovariectomized (OVX) mice and aged mice. Together, these results recommended that Celastrol could regulate BM-MSCs fate and bone-fat balance in OP and skeletal aging by stimulating PGC-1α, which might act as a possible therapeutic target for OP and for the prevention of skeletal aging.

Hysteresis Modelling and Feedforward Control of Piezoelectric Actuator Based on Simplified Interval Type-2 Fuzzy System.

The piezoelectric actuator is indispensable for driving the micro-manipulator. In this paper, a simplified interval type-2 (IT2) fuzzy system is proposed for hysteresis modelling and feedforward control of a piezoelectric actuator. The partial derivative of the output of IT2 fuzzy system with respect to the modelling parameters can be analytically computed with the antecedent part of IT2 fuzzy rule specifically designed. In the experiments, gradient based optimization was used to identify the IT2 fuzzy hysteresis model. Results showed that the maximum error of model identification is 0.42% with only 3 developed IT2 fuzzy rules. Moreover, the model validation was conducted to demonstrate the generalization performance of the identified model. Based on the analytic inverse of the developed model, feedforward control experiment for tracking sinusoidal trajectory of 20 Hz was carried out. As a result, the hysteresis effect of the piezoelectric actuator was reduced with the maximum tracking error being 4.6%. Experimental results indicated an improved performance of the proposed IT2 fuzzy system for hysteresis modelling and feedforward control of the piezoelectric actuator.

The LncRNA H19/miR-1-3p/CCL2 axis modulates lipopolysaccharide (LPS) stimulation-induced normal human astrocyte proliferation and activation.

Reactive astrocyte proliferation post SCI (spinal cord injury) leads to the formation of glial scars, thus hindering axon regeneration and SCI repair, during which the activation of astrocytes plays a central role. This study attempted to identify the lncRNA-miRNA-mRNA network which exerts a critical effect on normal human astrocyte (NHA) activation and proliferation during SCI inflammation. Herein, lncRNA H19 expression was increased by LPS in NHAs, and H19 was positively correlated with CCL2. H19 silencing in NHAs significantly attenuated the promoting effects of LPS stimulation on NHA proliferation and activation as manifested by inhibited cell viability and DNA synthesis capacity, reduced NHA activation markers, and reduced inflammatory factor concentrations (CCL2, IL-6, and TNF-α). miR-1-3p directly bound to H19 and the CCL2 3'UTR. miR-1-3p overexpression also attenuated the promoting effects of LPS stimulation on NHA proliferation and activation. H19 relieved miR-1-3p-induced inhibition of CCL2 expression by acting as a ceRNA. The inhibition of miR-1-3p could significantly reverse the effects of H19 silencing on NHA proliferation and activation, suggesting that the H19/miR-1-3p axis regulates the proliferation and activation of NHAs via CCL2. In conclusion, lncRNA H19, miR-1-3p, and CCL2 form a lncRNA-miRNA-mRNA axis that modulates NHA proliferation and activation in vitro.

High-precision compliant mechanism for lens XY micro-adjustment.

The high resolution of lithography lenses has led to a requirement for high-precision lens-adjusting compensators. This paper presents the design, analysis, and testing of a high-precision two-degrees-of-freedom compliant mechanism to be used for lens XY micro-adjustment. The monolithic mechanism, which is based on a 1RR-2RRR configuration, uses flexure hinges to connect the movable inner ring with the fixed outer ring. The apparatus is driven using two piezoelectric actuators, and the lens terminal displacement is fed back in real time using two capacitive sensors. This paper describes the principle of the mechanism. Simulations and experiments are then performed to evaluate the system. The results show that the strokes along both the x-axis and the y-axis exceed ±25 µm. The accuracy of the proposed mechanism is better than ±7 nm. The root-mean-square induced figure error is better than 0.051 nm. The coupling z and tip/tilt rigid motions are less than 50 nm and 220 mas, respectively. The first natural frequency of the mechanism is 212 Hz. These results indicate that the mechanism has advantages that include high accuracy, low coupling errors, high rigidity, and compactness and that it will act as an efficient compensator for lithography lenses.

Full-Endoscopic Decompression for Lumbar Lateral Recess Stenosis via an Interlaminar Approach versus a Transforaminal Approach.

OBJECTIVE: To compare the results of full-endoscopic decompression (FED) in lumbar lateral recess stenosis via an interlaminar or transforaminal approach. METHODS: A total of 102 patients with lumbar lateral recess stenosis who underwent FED from February 2015 to June 2016 in our hospital were enrolled. A total of 58 patients underwent interlaminar FED (IL-FED) and 44 patients underwent transforaminal FED (TF-FED). The intraoperative radiation and operation time, length of hospital stay, time to return to work, and complications were compared between both groups. The surgical effectiveness was assessed according to the visual analog scale, Oswestry Disability Index, and modified MacNab criteria. RESULTS: In the IL-FED group, the mean operation time was 59.4 ± 8.5 minutes, and the intraoperative radiation time was 0.50 ± 0.16 seconds. In the TF-FED group, the mean operation time was 64.1 ± 10.2 minutes, and the intraoperative radiation time was 7.50 ± 1.25 seconds. There were significant differences in the operation and radiation time between the 2 groups (P < 0.01). There was no significant difference in the visual analog scale and Oswestry Disability Index scoring between both groups either in the pre- or postoperation (P > 0.05). Based on the modified MacNab scores at the final follow-up, the satisfactory rate in the IL-FED group was 91.4% and that in the TF-FED group was 88.6%, no significant difference was observed between the 2 groups (P > 0.05). CONCLUSIONS: FED could provide satisfactory clinical outcomes for lumbar lateral recess stenosis. However, the IL-FED procedure demonstrated shorter operation time and lesser radiation exposure, but higher risk for anesthetic when compared with the TF-FED procedure.

Active lens for thermal aberration compensation in lithography lens.

High laser absorption and strong resolution enhancement technology make thermal aberration control of lithography lenses more challenging. We present an active lens that uses four bellows actuators to generate astigmatism (Z5) on the lens surface. The apparatus utilizes optical path difference to compensate the system wavefront. In order to assess the specifications of the compensator, the finite element method and experimental analyses are carried out to obtain and validate the general properties of the apparatus. The results show that the Z5 deformation quantity of lens's upper surface exceeds 600 nm; further, Z5 coefficient accuracy is better than ±1 nm. The apparatus can be an efficient compensator for thermal aberration compensation, especially aberration caused by the dipole illumination.

[Concentration, Solubility, and Dry Deposition Flux of Trace Elements in Fine and Coarse Particles in Qingdao During Summer].

PM2.5 and total suspended particulate (TSP) samples were synchronously collected in Qingdao from June to July 2016. The total and water-soluble concentrations of 12 trace elements in these samples were analyzed to investigate their distribution characteristics in fine and coarse particles as well as their dry deposition fluxes. The results showed that the total mass concentrations of Al, Fe, Sr, Mn, and Ba, which are expected to mainly originate from crustal sources, were generally distributed in the coarse particles, and the part mass in the coarse mode accounted for 55%-60% of their total concentrations. Cr, Ni, V, Zn, Pb, As, and Cd, which mainly originate from anthropogenic contributors, generally existed in fine particles where the part mass accounted for 65%-85% of their total concentrations. The soluble mass concentrations of trace elements, whether from crustal or anthropogenic sources, were mainly distributed in the fine particles. The proportions of Al, Fe, Mn, and Ba in soluble mass concentration existing in the fine particles were 50%-80% and 70%-90% for Cr, Ni, V, Zn, Pb, As, and Cd. The solubility of trace elements was higher in fine particles than in coarse particles. The soluble concentrations of trace elements exhibited a positive correlation with acid compounds, and the solubility exhibited a negative correlation with pH in the fine particles, implying that acidification processes play a key role in determining the solubility of trace elements in fine particles. The soluble fractions in the total dry deposition flux of Al and Fe were only 1%-2%; that of Sr, Ba, Cr, and Pb were about 30%-40%; and that of Mn, Ni, V, Zn, As, and Cd were about 50%-60%. The atmospheric deposition of soluble Fe supported phytoplankton carbon production of (194±150) mg·(m2·d)-1, contributing about 10% of the primary productivity in the Yellow Sea.

[Concentrations and Solubility of Trace Elements in Atmospheric Precipitation in Qingdao].

Thirty-five atmospheric precipitation samples were collected at an urban site in Qingdao from June 2016 to May 2017. The total and soluble concentrations of eight trace elements in the samples were determined, and the variable characteristics of the concentrations and solubility of trace elements, as well as the factors affecting the solubility of trace elements in atmospheric precipitation, have been discussed. Based on the overall data, the total concentrations of the trace elements were found to be in the order Al > Fe > Zn > Mn > Ba > Pb > Sr > V, but the soluble concentrations of the trace elements were in the order Zn > Al > Mn > Fe > Ba > Sr > Pb > V. Solubility was about 5% for the crustal elements Al and Fe, and the solubility of the elements affected by anthropogenic sources was relatively higher, 10%-40% for Pb and Ba, 20%-60% for Mn and Sr, and nearly 55% for Zn and V. The total and soluble concentrations of the trace elements were higher in winter and spring than in summer and autumn, but element solubility in spring was the highest. During continuous rainfall, the total concentrations of trace elements in precipitation decreased appreciably, but the variation trend of the solubility of trace elements was not consistent during the different rainfall processes. The variation in pH was the main factor controlling the solubility of trace elements in precipitation.

High expression of Sam68 in sacral chordomas is associated with worse clinical outcomes.

Src-associated in mitosis of 68 kDa (Sam68), also known as KHDRBS1 (KH domain-containing, RNA-binding, signal transduction-associated 1), is a member of the signal transduction and activation of RNA family. Previous studies have demonstrated that the aberrant expression of Sam68 is associated with the progression and prognosis of a variety of cancers, but little is known about its expression and role in chordomas, which are rare and aggressive bone neoplasms. In this study, we analyzed 40 tumor tissues and 20 distant normal tissues obtained from 40 patients with sacral chordoma using immunohistochemistry, and observed the expression of Sam68 was significantly upregulated in sacral chordomas compared with normal tissues (P=0.001). A positive correlation between the expression of Sam68 and the cell proliferation index Ki-67 was determined using Spearman's rank correlation test (γ =0.599, P<0.001). In addition, high expression of Sam68 was significantly associated with surrounding muscle invasion (P<0.001). Moreover, Kaplan-Meier curves showed that patients with overexpressed Sam68 had shorter local recurrence-free survival time (P<0.001). Lastly, multivariate analysis indicated that Sam68 is an independent prognostic factor for the local recurrence-free survival of sacral chordomas (hazard ratio =5.929, 95% CI: 1.092-32.188, P=0.039). Our findings suggest the use of Sam68 as a predictor for the recurrence of sacral chordomas.

Diagnostic accuracy of Xpert MTB/RIF assay for musculoskeletal tuberculosis: a meta-analysis.

OBJECTIVES: Xpert MTB/RIF assay, a rapid and automated real-time nucleic acid amplification test, has been reported for the diagnosis of musculoskeletal tuberculosis (TB) in current years. This meta-analysis aims to determine the diagnostic accuracy of Xpert for the detection of musculoskeletal TB and rifampicin (RIF) resistance. METHODS: We searched PubMed, Embase, China National Knowledge Infrastructure, and Wanfang for original articles published up to 1st June 2017 to identify studies in which the Xpert assay was applied to diagnose musculoskeletal TB. Pooled estimates were calculated using a random-effects model or a fixed-effects model according to heterogeneity. Summary receiver operating characteristic curves and the area under the curve (AUC) were used to summarize overall diagnostic performance. Deeks' test was performed to evaluate potential publication bias. RESULTS: Twelve studies were identified with a pooled sensitivity and specificity of respectively 0.81 (95% confidence interval [CI] 0.78-0.83) and 0.83 (95% CI 0.80-0.86) of Xpert for the diagnosis of musculoskeletal TB. Xpert was highly sensitive (0.89, 95% CI 0.79-0.95) and highly specific (0.96, 95% CI 0.92-0.98) in detecting RIF resistance. AUC (over 0.9) suggested a relatively high level of overall diagnostic accuracy of Xpert for detecting musculoskeletal TB and RIF resistance. Prevalence and reference standard were indicated to be sources of heterogeneity between studies. No publication bias was found. CONCLUSION: This study provides available evidence of the rapid and effective role of Xpert in diagnosing musculoskeletal TB and detecting RIF resistance.

Radioresistance of chordoma cells is associated with the ATM/ATR pathway, in which RAD51 serves as an important downstream effector.

Surgery followed by radiotherapy is the standard treatment for chordomas, which are a rare but low-grade type of bone cancer arising from remnants of the embryonic notochord. However, disease recurrence following radiotherapy is common, most likely due to endogenous DNA repair mechanisms that promote cell survival upon radiation strikes. The ataxia telangiectasia mutated/ataxia telangiectasia mutated and Rad3 related (ATM/ATR)-mediated pathway has a critical role in DNA repair mechanisms; however, it has rarely been investigated in chordomas. In the present study, the expression of signal molecules related to the ATM/ATR pathway in chordoma tissues and adjacent normal tissues were initially examined using immunohistochemistry and western blot analysis. Chordoma U-CH1 and U-CH2 cells were subsequently used to investigate cell responses to ionizing radiation and the potential protective actions mediated by the ATM/ATR pathway. Phosphorylated (p)-ATM, p-ATR, γ-H2A histone family, member X (H2AX) and RAD51 were significantly upregulated in chordoma tissues relative to adjacent normal tissues (P<0.05). No significant reductions were observed in the viability of U-CH1 and U-CH2 cells following exposure to low-dose (1 and 2 Gy) radiation. Radiation (1 and 2 Gy) triggered a significant upregulation in p-ATM, γ-H2AX and RAD51 expression in U-CH1 cells (P<0.05), as well as a significant upregulation in p-ATM, p-ATR and RAD51 levels in U-CH2 cells (P<0.05). RAD51 knockdown increased the responses of both U-CH1 and U-CH2 cells to 1 Gy radiation, as evidenced by the significantly decreased cell viability and increased apoptosis rate (P<0.05). Collectively, the results of the present study indicated that radioresistance of chordoma cells is associated with the ATM/ATR pathway, in which RAD51 serves as an important downstream effector. Thus, RAD51 presents a promising therapeutic target for improving the outcome of radiotherapy treatment in chordomas.

Expression of far upstream element-binding protein 1 correlates with c-Myc expression in sacral chordomas and is associated with tumor progression and poor prognosis.

The far upstream element (FUSE)-binding protein 1 (FUBP1), a well-known transcriptional regulator of the proto-oncogene c-Myc, has been demonstrated by previous work to be aberrantly expressed in a variety of tumors and plays a critical role in tumor progression; however, its expression and function in relatively rare and aggressive chordomas remains unclear. In this retrospective study, we reviewed clinicopathologic characteristics of 40 patients diagnosed with sacral chordoma, and analyzed 40 tumor and 20 distant normal tissues obtained from patients during the primary surgical tumor excision. Using immunohistochemistry, we observed an up-regulation in the expression of FUBP1 and c-Myc in sacral chordomas compared with the normal tissues (P = 0.001 for both). Additionally, positive correlations of FUBP1 expression with c-Myc (γ = 0.651, P < 0.001) and the cell proliferation index Ki-67 expression (γ = 0.447, P = 0.004) were indicated using Spearman's rank correlation coefficient. Increased expression of FUBP1 was significantly associated with tumor invasion into the surrounding muscles (P = 0.002). Kaplan-Meier curves demonstrated the association between FUBP1 levels and the patients' local recurrence-free survival (LRFS) (P < 0.001) but not with the overall survival (OS) (P = 0.070). The independent prognostic significance of FUBP1 levels for the LRFS was indicated by multivariate analysis (HR = 4.272; 95% CI, 1.133-16.112; P = 0.032). Our findings demonstrate an association between FUBP1 levels and chordoma progression and prognosis, suggesting that FUBP1 can be used as a biomarker and a potential therapeutic target.

Familial lumbar Scheuermann disease with idiopathic scoliosis in China: First case report.

RATIONALE: Given that Scheuermann disease rarely occurs in the lumbar region and that the co-occurrence of Scheuermann disease and idiopathic scoliosis (IS) has not been reported-the etiology of Scheuermann disease and IS is not clear. In this case report, we present familaiar lumbar Scheuermann disease with IS, in a Chinese proband, who was successfully treated with surgery. PATIENT CONCERNS: A 16-year-old boy presented at the Second XiangYa Hospital of Central South University with a chief complaint of kyphotic deformity in the lower back for 4 years and obvious lower back pain. In addition, he complained of limited lumbar activity. And The proband's family history was obtained by routine inquiring. In this Chinese family with 17 members over 3 generations. The 3 patients (proband, proband's sister and father) shared the characteristics of vertebral wedging from L1 to L3 and a kyphosis Cobb angle of 37°, 70°, or 73°, respectively. The main deformity of the proband's mother was at T7-L1 with a Cobb angle of 102° in the coronal plane at T7-L1, thoracic kyphosis of 73°, and lumbar lordosis of 62°. DIAGNOSES: Scheuermann's disease. INTERVENTIONS: Clinical history, physical examination, laboratory tests, and radiographs of those in the pedigree were recorded, and the related literature was reviewed. The proband accepted osteotomy and orthopedic surgery for treatment. OUTCOMES: After 3 months of treatment, postoperative lateral radiographs showed a significantly improved sagittal vertical axis (SVA). The other patients were continued to be seen in follow-up visits. LESSONS: This series of lumbar Scheuermann patients with IS in a pedigree support the genetic contribution to Scheuermann disease. Therefore, this study provides some insight into the genetic etiology of Scheuermann disease with IS.

Piezoelectric Actuated Phase Shifter Based on External Laser Interferometer: Design, Control and Experimental Validation.

To improve the phase-shifting accuracy, this paper presents a novel integrated framework for design, control and experimental validation of the piezoelectric actuated phase shifter with a trade-off between accuracy and cost. The piezoelectric actuators with built-in sensors are adopted to drive the double parallel four-bar linkage flexure hinge-based mechanisms. Three mechanisms form the tripod structure of the assembled phase shifter. Then, a semi-closed loop controller with inner feedback and outer feedforward loops via the external laser interferometer is developed for accurate positioning of the phase shifter. Finally, experiments related with travel range, step response, linearity and repeatability are carried out. The linearity error is 0.21% and the repeatability error of 10 µ m displacement is 3 nm. The results clearly demonstrate the good performance of the developed phase shifter and the feasibility of the proposed integrated framework.

Ultra-precise tracking control of piezoelectric actuators via a fuzzy hysteresis model.

In this paper, a novel Takagi-Sugeno (T-S) fuzzy system based model is proposed for hysteresis in piezoelectric actuators. The antecedent and consequent structures of the fuzzy hysteresis model (FHM) can be, respectively, identified on-line through uniform partition approach and recursive least squares (RLS) algorithm. With respect to controller design, the inverse of FHM is used to develop a feedforward controller to cancel out the hysteresis effect. Then a hybrid controller is designed for high-performance tracking. It combines the feedforward controller with a proportional integral differential (PID) controller favourable for stabilization and disturbance compensation. To achieve nanometer-scale tracking precision, the enhanced adaptive hybrid controller is further developed. It uses real-time input and output data to update FHM, thus changing the feedforward controller to suit the on-site hysteresis character of the piezoelectric actuator. Finally, as to 3 cases of 50 Hz sinusoidal, multiple frequency sinusoidal and 50 Hz triangular trajectories tracking, experimental results demonstrate the efficiency of the proposed controllers. Especially, being only 0.35% of the maximum desired displacement, the maximum error of 50 Hz sinusoidal tracking is greatly reduced to 5.8 nm, which clearly shows the ultra-precise nanometer-scale tracking performance of the developed adaptive hybrid controller.