Ryohei Uchida

DC micro-grid for super high quality distribution — System configuration and control of distributed generations and energy storage devices

“DC micro-grid” is the novel power system using dc distribution in order to provide super high quality power. The dc distribution system is suitable for dc output type distributed generations such as photovoltaic and fuel cells, and energy storages such as secondary batteries and electric double layer capacitors. Moreover, dc distributed power is converted to required ac or dc voltages by load side converters, and these converters do not require transformers by choosing proper dc voltage. This distributed scheme of load side converters also contributes to provide supplying high quality power. For instance, even if a short circuit occurs at one load side, it does not effect other loads. In this paper, we suppose one system configuration of DC micro-grid, and propose control methods of converters for generations and energy storages. Computer simulation results demonstrated seamless turn-on and turn-off operation of a distributed generation, a transient of connecting and disconnecting operation with a bulk power system, and the stability for sudden large load variation.

DC Voltage Control of the DC Micro-grid for Super High Quality Distribution

DC micro-grid is a novel super high quality electric power system. The power is transmitted through dc distribution line and converted to required ac or dc voltages by converters placed near loads. Those load side converters do not need transformers by choosing proper dc distribution voltage (plusmn170 V). The dc power line is composed of 3 wires: +170 V line, neutral line and -170 V line. The distribution voltages have to be balanced to keep high quality power supplying. In this paper, a voltage balancer for dc distribution are proposed and studied. Computer simulation results demonstrated that dc micro-grid was able to supply both ac and dc power to loads simultaneously and stably by 3-wire dc distribution line and load side converters. In addition, another voltage balancer (dc/dc converter type) is also proposed and studied in the last section.

Dual tunnel medial patellofemoral ligament reconstruction for patients with patellar dislocation using a semitendinosus tendon autograft.

The purpose of this study was to describe a safer and more anatomical technique of MPFL reconstruction and to report the short-term results. The subjects included 20 patients with patellar dislocation with a mean age of 23. The operation was performed using a double-looped autogenous semitendinosus tendon graft. Two small bone tunnels were made at the medial edge of the patella, mimicking the wide patellar insertion of the MPFL and a bone tunnel was made at the femoral insertion site. The free ends of the graft attached to the patella and the loop end was fixed to the femoral side. Five patients were available for follow-up interviews by telephone and the remaining 15 were directly examined by physical examination and radiographic evaluation at 2 years or longer postoperatively. The average follow-up period was 30 months. Re-dislocation or patellar fracture was not seen in any patients. The average Kujalas score was 96 with a range from 84 to 100. Six patients were classified as excellent and 14 as good, according to the Crosby and Insall grading system. Radiographically, narrowing of the patellofemoral joint space was observed in 2 cases with previous osteochondral fracture out of those who were directly examined. The dual tunnel MPFL reconstruction produces favorable results in subjective and functional assessment of outcome without complications.

Factors Affecting the Outcomes of Double-Bundle Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocations Evaluated by Multivariate Analysis

Background: Many factors are involved in causing patellar instability or recurrent patellar dislocations. However, factors affecting the outcomes of anatomic medial patellofemoral ligament (MPFL) reconstruction have not been fully documented. Purpose: To evaluate the rate of recurrent patellar instability after isolated MPFL reconstruction and to elucidate factors affecting the outcomes of isolated MPFL reconstruction using multivariable statistics. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 42 patients (44 knees) who underwent isolated, anatomic MPFL reconstruction using a semitendinosus autograft without any additional patellar stabilization procedures for treating recurrent patellar dislocations were included in this study. All patients were followed for more than 2 years; the mean follow-up period was 3.2 years (range, 2-9 years). Postoperative patellofemoral instability was diagnosed when the patient complained of recurrent patellar subluxations or dislocations or had a positive apprehension sign during follow-up. Preoperative radiographic findings were obtained using plain radiography and computed tomography. Femoral tunnel positions were assessed on postoperative radiographs. The strength of the relationship between postoperative patellofemoral instability and potential risk factors such as preoperative age, sex, body mass index, patellar type, sulcus angle, congruence angle, lateral tilt angle, patellar height, tibial tubercle–trochlear groove (TT-TG) distance, degree of trochlear dysplasia, and femoral bone tunnel position were evaluated by univariate and multivariate logistic regression analyses. Results: At follow-up, 2 knees had experienced a redislocation (4.5%). A positive apprehension sign was still evident in 8 knees (18.2%). Three factors, including the sulcus angle, the congruence angle, and trochlear dysplasia, were extracted by single linear regression analysis. Univariate logistic regression analysis showed that the sulcus angle (odds ratio [OR], 1.11; 95% CI, 1.01-1.22; P = .04) and trochlear dysplasia (OR, 3.04; 95% CI, 1.39-6.63; P = .01) were associated with postoperative patellofemoral instability. Trochlear dysplasia was independently associated with postoperative patellofemoral instability by multivariable logistic regression analysis (P < .05). An increased TT-TG distance exerted a significant effect on the outcomes of MPFL reconstruction, particularly in patients with type D trochlea. Conclusion: Severe trochlear dysplasia is the most important predictor of residual patellofemoral instability after isolated MPFL reconstruction. In addition, an increased TT-TG distance affected the outcomes in patients with type D trochlea. Additional patellar stabilization procedures should be considered for patients with severe trochlear dysplasia and an increased TT-TG distance.

Chondral fragment of the lateral femoral trochlea of the knee in adolescents.

Most injuries to the osteochondral region in adolescents have generally been believed to occur as osteochondral fractures. However, we report three cases of pure chondral fragments of the knee in adolescents. The patients were injured during sports activities and as a result had acute limitation of ROM of the knee joint. Only one case out of three could be diagnosed by MRI, and arthroscopic examinations were needed to make a final diagnosis in the remaining two cases. Re-fixation of the fragments was performed using bio-absorbable pins. All the patients were eventually able to return to their previous level of sports activity. Two years after the operation they experienced no symptoms and MRI showed that the re-fixed fragments were continuous to the bed without any abnormal intervening signal area, suggesting successful healing. Moreover, the arthroscopic integration between the re-fixed fragment and the surrounding articular cartilage was acceptable. Chondral fragment of the lateral femoral trochlea in active adolescents should be recognized as a clear entity that can be successfully treated by re-fixation.

Cell Sheet Stiffness Sensing without taking out from culture liquid

Stiffness could be an important index for evaluating the vitality of cell sheet. This paper challenges the measurement of stiffness of transparent cell sheet in culture liquid without taking it out from petri dish. The system is composed of a micro air nozzle for supplying an air jet and a regular reflective type laser sensor for measuring the the deformation of transparent cell sheet. This system is called as Cell Sheet Stiffness Sensing system (CS3 system). When an air jet is given to a cell sheet in culture liquid, it pushes away the liquid toward the outer direction at initial phase and reaches the surface of cell sheet. Without any switching motion, the air jet continuously imparts a force to the surface of cell sheet so that the sensor can measure the stiffness of the cell sheet.

3D Computed Tomography Evaluation of Morphological Changes in the Femoral Tunnel After Medial Patellofemoral Ligament Reconstruction With Hamstring Tendon Graft for Recurrent Patellar Dislocation

Background: Reconstruction of the medial patellofemoral ligament (MPFL) for recurrent lateral patellar dislocation is gaining popularity. However, the morphological changes in the femoral tunnel after MPFL reconstruction are still not fully documented. Purpose: This study used 3-dimensional (3D) computed tomography to evaluate morphological changes in the femoral tunnel after MPFL reconstruction with hamstring tendon graft to investigate factors affecting the phenomenon and to elucidate whether it is associated with clinical outcomes. Study Design: Case series; Level of evidence, 4. Methods: Twenty-three patients with recurrent patellar dislocation were prospectively enrolled in this study. The patients included 6 males and 17 females with a mean age of 24 years (range, 14-53). The MPFL was reconstructed by creating 2 patellar bone sockets and 1 femoral bone socket anatomically under X-ray control, and the semitendinosus autograft was fixed with cortical suspension devices. Computed tomography scans obtained 3 weeks and 1 year after surgery were reconstructed into 3D constructs with a volume analyzer. Cross-sectional areas (CSAs) of the aperture and inside the femoral tunnel were compared between the 2 time points. Likewise, the location of tunnel walls and center of the femoral tunnel footprint were evaluated. Relationships were assessed between femoral tunnel morphological changes and potential risk factors—such as age, body mass index, sex, femoral tunnel positioning, patellar height, sulcus angle, congruence angle, lateral tilt angle, degree of trochlear dysplasia, lateral deviation of the tibial tubercle, and Kujala score. Results: No patient reported recurrence of patellar dislocation during the follow-up period. The CSA of the femoral tunnel aperture enlarged by 41.1% ± 34.7% (P < .01). The center, anterior border, and proximal border of the femoral tunnel significantly shifted in the anterior direction (P < .01). The distal border significantly shifted in both anterior and distal directions (P < .01). Patella alta was associated with distal migration of the tunnel center (P < .05). Morphological changes were not associated with other risk factors or Kujala score. Conclusion: The CSA of the femoral tunnel aperture enlarged, and the tunnel aperture migrated anteriorly with time after MPFL reconstruction. Risk factors for patellar dislocation other than patella alta did not influence morphological changes of the femoral tunnel.

Splitting culture medium by air-jet and rewetting for the assessment of the wettability of cultured epithelial cell surfaces

This study found that the phenomenon of rewetting after squeezing culture medium varied in different culture conditions for rat oral mucosal epithelial cells. When culture medium covering over cultured cells was squeezed by an air-jet application, the motion of squeezed culture medium was able to be observed by using a commercially available movie camera. Squeezed width on cells cultured in keratinocyte culture medium (KCM), which contained with fetal bovine serum, was one-sixth of that in FBS-free KCM. This result corresponded to the mucous layer staining statuses of cultured cells in both cases; positive in KCM and negative in FBS-free medium. Furthermore, the gene expression of mucous glycoprotein MUC4 in KCM was 100 times higher than that in FBS-free medium, and the expression of MUC4 protein only showed on the apical surface of cells cultured in KCM. The relative gene expression levels of MUC1, 13, 15, and 16 in both the normal and FBS-free medium were found to be no more than one-thirtieth of that of MUC4 in KCM. The main factor of the wettability difference between KCM and FBS-free medium was speculated to be the difference of MUC4 expression between both media. This method can be a simple technique for testing not only the surface wettability but also the mucous formation of cultured cells.

Point-type non-contact stiffness sensing of soft tissue with coupling effect

This paper discusses the point-type non-contact active sensing for evaluating the stiffness of a soft tissue with coupling effect. Tfhe sensing system imparts a point force to a tissue and measures the displacement at the point of application of force. The benefit is that such point based information enables us to estimate two stiffness parameters constructing the 3D spring network tissue model. Through the experiment for a human skin, we show that the deformation shapes between human skin surface and the model with the estimated parameters are nicely coincident.

Vibration acceleration promotes bone formation in rodent models

All living tissues and cells on Earth are subject to gravitational acceleration, but no reports have verified whether acceleration mode influences bone formation and healing. Therefore, this study was to compare the effects of two acceleration modes, vibration and constant (centrifugal) accelerations, on bone formation and healing in the trunk using BMP 2-induced ectopic bone formation (EBF) mouse model and a rib fracture healing (RFH) rat model. Additionally, we tried to verify the difference in mechanism of effect on bone formation by accelerations between these two models. Three groups (low- and high-magnitude vibration and control-VA groups) were evaluated in the vibration acceleration study, and two groups (centrifuge acceleration and control-CA groups) were used in the constant acceleration study. In each model, the intervention was applied for ten minutes per day from three days after surgery for eleven days (EBF model) or nine days (RFH model). All animals were sacrificed the day after the intervention ended. In the EBF model, ectopic bone was evaluated by macroscopic and histological observations, wet weight, radiography and microfocus computed tomography (micro-CT). In the RFH model, whole fracture-repaired ribs were excised with removal of soft tissue, and evaluated radiologically and histologically. Ectopic bones in the low-magnitude group (EBF model) had significantly greater wet weight and were significantly larger (macroscopically and radiographically) than those in the other two groups, whereas the size and wet weight of ectopic bones in the centrifuge acceleration group showed no significant difference compared those in control-CA group. All ectopic bones showed calcified trabeculae and maturated bone marrow. Micro-CT showed that bone volume (BV) in the low-magnitude group of EBF model was significantly higher than those in the other two groups (3.1±1.2mm3 v.s. 1.8±1.2mm3 in high-magnitude group and 1.3±0.9mm3 in control-VA group), but BV in the centrifuge acceleration group had no significant difference compared those in control-CA group. Union rate and BV in the low-magnitude group of RFH model were also significantly higher than those in the other groups (Union rate: 60% v.s. 0% in the high-magnitude group and 10% in the control-VA group, BV: 0.69±0.30mm3 v.s. 0.15±0.09mm3 in high-magnitude group and 0.22±0.17mm3 in control-VA group). BV/TV in the low-magnitude group of RFH model was significantly higher than that in control-VA group (59.4±14.9% v.s. 35.8±13.5%). On the other hand, radiographic union rate (10% in centrifuge acceleration group v.s. 20% in control-CA group) and micro-CT parameters in RFH model were not significantly different between two groups in the constant acceleration studies. Radiographic images of non-union rib fractures showed cartilage at the fracture site and poor new bone formation, whereas union samples showed only new bone. In conclusion, low-magnitude vibration acceleration promoted bone formation at the trunk in both BMP-induced ectopic bone formation and rib fracture healing models. However, the micro-CT parameters were not similar between two models, which suggested that there might be difference in the mechanism of effect by vibration between two models.