Evaluation of pulmonary vein stenosis after pulmonary vein isolation using a novel circular mapping and ablation catheter (PVAC)

Background—Pulmonary vein stenosis (PVST) is a well-known complication of pulmonary vein isolation (PVI). Specific anatomically designed ablation catheters for antral PVI have not been evaluated with regard to the incidence of PVST. We investigated the incidence, severity, and characteristics of PVST after PVI with the Pulmonary Vein Ablation Catheter (PVAC) and phased radiofrequency technology. Methods and Results A total of 100 patients (55 men) underwent PVI for atrial fibrillation using the PVAC. PVI was guided by selective angiography of each pulmonary vein (PV) in 70 (70%) patients and by reconstructed 3D atriography (ATG) in 30 (30%) patients. Gadolinium-enhanced MRI or multidetector CT was performed in all patients before treatment and 93±78 days after PVI. PVST was classified as follows: insignificant (<25%), mild (25%–50%), moderate (50%–75%), or severe (>75%). A total of 410 PVs were analyzed. Cardiac imaging demonstrated a detectable narrowing of the PV diameter in 23 (23%) patients and in 28 (7%) PVs. In detail, insignificant PVST was observed in 12 (2.9%) PVs, mild PVST in 15 (3.7%), and moderate PVST in 1 (0.2%). No instances of severe PVST were observed. The use of 3D-ATG was associated with a lower incidence of PVST (0.8% [95% CI, 0.0%–2.2%] versus 5.4% [95% CI, 2.7%–8.1%], P=0.027). Conclusions To our knowledge, this study is the first to report the incidence of PVST using the PVAC. In this regard, the PVAC seems to be safe if used in an experienced center. In addition, the use of 3D-ATG may decrease the risk of PVST.

Stabilization of Juxta-Physeal Distal Tibial and Fibular Fractures in a Juvenile Tiger Using a Hybrid Circular-Linear External Fixator

OBJECTIVE: To report stabilization of closed, comminuted distal metaphyseal transverse fractures of the left tibia and fibula in a tiger using a hybrid circular-linear external skeletal fixator. STUDY DESIGN: Clinical report. ANIMAL: Juvenile tiger (15 months, 90 kg). METHODS: From imaging studies, the tiger had comminuted distal metaphyseal transverse fractures of the left tibia and fibula, with mild caudolateral displacement and moderate compression. Multiple fissures extended from the fractures through the distal metaphyses, extending toward, but not involving the distal tibial and fibular physes. A hybrid circular-linear external skeletal fixator was applied by closed reduction, to stabilize the fractures. RESULTS: The fractures healed and the fixator was removed 5 weeks after stabilization. Limb length and alignment were similar to the normal contralateral limb at hospital discharge, 8 weeks after surgery. Two weeks later, the tiger had fractures of the right tibia and fibula and was euthanatized. Necropsy confirmed pathologic fractures ascribed to copper deficiency. CONCLUSION: Closed application of the hybrid construct provided sufficient stability to allow this 90 kg tiger's juxta-articular fractures to heal with minimal complications and without disrupting growth from the adjacent physes.

A Faster Circular Binary Segmentation Algorithm for the Analysis of Array CGH Data

Motivation: Array CGH technologies enable the simultaneous measurement of DNA copy number for thousands of sites on a genome. We developed the circular binary segmentation (CBS) algorithm to divide the genome into regions of equal copy number (Olshen {\it et~al}, 2004). The algorithm tests for change-points using a maximal $t$-statistic with a permutation reference distribution to obtain the corresponding $p$-value. The number of computations required for the maximal test statistic is $O(N^2),$ where $N$ is the number of markers. This makes the full permutation approach computationally prohibitive for the newer arrays that contain tens of thousands markers and highlights the need for a faster. algorithm. Results: We present a hybrid approach to obtain the $p$-value of the test statistic in linear time. We also introduce a rule for stopping early when there is strong evidence for the presence of a change. We show through simulations that the hybrid approach provides a substantial gain in speed with only a negligible loss in accuracy and that the stopping rule further increases speed. We also present the analysis of array CGH data from a breast cancer cell line to show the impact of the new approaches on the analysis of real data. Availability: An R (R Development Core Team, 2006) version of the CBS algorithm has been implemented in the ``DNAcopy'' package of the Bioconductor project (Gentleman {\it et~al}, 2004). The proposed hybrid method for the $p$-value is available in version 1.2.1 or higher and the stopping rule for declaring a change early is available in version 1.5.1 or higher.

Harvesting local cylinder autograft from adjacent vertebral body for anterior lumbar interbody fusion: surgical technique, operative feasibility and preliminary clinical results

Autogenous iliac crest has long served as the gold standard for anterior lumbar arthrodesis although added morbidity results from the bone graft harvest. Therefore, femoral ring allograft, or cages, have been used to decrease the morbidity of iliac crest bone harvesting. More recently, an experimental study in the animal showed that harvesting local bone from the anterior vertebral body and replacing the void by a radio-opaque beta-tricalcium phosphate plug was a valid concept. However, such a concept precludes theoretically the use of posterior pedicle screw fixation. At one institution a consecutive series of 21 patients underwent single- or multiple-level circumferential lumbar fusion with anterior cages and posterior pedicle screws. All cages were filled with cancellous bone harvested from the adjacent vertebral body, and the vertebral body defect was filled with a beta-tricalcium phosphate plug. The indications for surgery were failed conservative treatment of a lumbar degenerative disc disease or spondylolisthesis. The purpose of this study, therefore, was to report on the surgical technique, operative feasibility, safety, benefits, and drawbacks of this technique with our primary clinical experience. An independent researcher reviewed all data that had been collected prospectively from the onset of the study. The average age of the patients was 39.9 (26-57) years. Bone grafts were successfully harvested from 28 vertebral bodies in all but one patient whose anterior procedure was aborted due to difficulty in freeing the left common iliac vein. This case was converted to a transforaminal interbody fusion (TLIF). There was no major vascular injury. Blood loss of the anterior procedure averaged 250 ml (50-350 ml). One tricalcium phosphate bone plug was broken during its insertion, and one endplate was broken because of wrong surgical technique, which did not affect the final outcome. One patient had a right lumbar plexopathy that was not related to this special technique. There was no retrograde ejaculation, infection or pseudoarthrosis. One patient experienced a deep venous thrombosis. At the last follow up (mean 28 months) all patients had a solid lumbar spine fusion. At the 6-month follow up, the pain as assessed on the visual analog scale (VAS) decreased from 6.9 to 4.5 (33% decrease), and the Oswestry disability index (ODI) reduced from 48.0 to 31.7 with a 34% reduction. However, at 2 years follow up there was a trend for increase in the ODI (35) and VAS (5). The data in this study suggest that harvesting a cylinder of autograft from the adjacent vertebral body is safe and efficient. Filling of the void defect with a beta-tricalcium phosphate plug does not preclude the use of posterior pedicle screw stabilization.

Osseointegration of hollow cylinder based spinal implants in normal and osteoporotic vertebrae: a sheep study

INTRODUCTION: Osteoporosis is not only responsible for an increased number of metaphyseal and spinal fractures but it also complicates their treatment. To prevent the initial loosening, we developed a new implant with an enlarged implant/bone interface based on the concept of perforated, hollow cylinders. We evaluated whether osseointegration of a hollow cylinder based implant takes place in normal or osteoporotic bone of sheep under functional loading conditions during anterior stabilization of the lumbar spine. MATERIALS AND METHODS: Osseointegration of the cylinders and status of the fused segments (ventral corpectomy, replacement with iliac strut, and fixation with testing implant) were investigated in six osteoporotic (age 6.9 +/- 0.8 years, mean body weight 61.1 +/- 5.2 kg) and seven control sheep (age 6.1 +/- 0.2 years, mean body weight 64.9 +/- 5.7 kg). Osteoporosis was introduced using a combination protocol of ovariectomy, high-dose prednisone, calcium and phosphor reduced diet and movement restriction. Osseointegration was quantified using fluorescence and conventional histology; fusion status was determined using biomechanical testing of the stabilized segment in a six-degree-of-freedom loading device as well as with radiological and histological staging. RESULTS: Intact bone trabeculae were found in 70% of all perforations without differences between the two groups (P = 0.26). Inside the cylinders, bone volume/total volume was significantly higher than in the control vertebra (50 +/- 16 vs. 28 +/- 13%) of the same animal (P<0.01), but significantly less (P<0.01) than in the near surrounding (60 +/- 21%). After biomechanical testing as described in Sect. "Materials and methods", seven spines (three healthy and four osteoporotic) were classified as completely fused and six (four healthy and two osteoporotic) as not fused after a 4-month observation time. All endplates were bridged with intact trabeculae in the histological slices. CONCLUSIONS: The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.

Bislug flow in circular and noncircular channels and the role of interface stretching on energy dissipation

The area of microfluidics has increased in popularity with such fields as MEMS, microreactors, microscaleheat exchangers, etc. A comprehensive understanding of dissipation mechanisms for fluid flow in microchannels is required to accurately predict the behavior in these small systems. Tests were performed using a constant pressure potential created by two immiscible fluids juxtaposed in a microchannel. This study focused on the flow and dissipation mechanisms in round and square microchannels. There are four major dissipation mechanisms in slug flow; wall shear, dissipation at the contact line, menisci interaction and the stretching of the interface. A force balance between the internal driving potential, viscous drag and interface stretching was used to develop a model for the prediction of the velocity of a bislug in a microchannel. Interface stretching is a dissipation mechanism that has been included due to the unique system properties and becomes increasingly more important as the bislug decreases in length.

Cylinder wall waste heat recovery from liquid-cooled internal combustion engines utilizing thermoelectric generators

This report is a dissertation proposal that focuses on the energy balance within an internal combustion engine with a unique coolant-based waste heat recovery system. It has been predicted by the U.S. Energy Information Administration that the transportation sector in the United States will consume approximately 15 million barrels per day in liquid fuels by the year 2025. The proposed coolant-based waste heat recovery technique has the potential to reduce the yearly usage of those liquid fuels by nearly 50 million barrels by only recovering even a modest 1% of the wasted energy within the coolant system. The proposed waste heat recovery technique implements thermoelectric generators on the outside cylinder walls of an internal combustion engine. For this research, one outside cylinder wall of a twin cylinder 26 horsepower water-cooled gasoline engine will be implemented with a thermoelectric generator surrogate material. The vertical location of these TEG surrogates along the water jacket will be varied along with the TEG surrogate thermal conductivity. The aim of this proposed dissertation is to attain empirical evidence of the impact, including energy distribution and cylinder wall temperatures, of installing TEGs in the water jacket area. The results can be used for future research on larger engines and will also assist with proper TEG selection to maximize energy recovery efficiencies.

Implementation of a Variable Compression Ratio Mechanism in a Four Cylinder Engine

Ever since the invention of the internal combustion engine, generating more power and achieving better efficiency has been a major goal for the designers. Variable compression ratio technology is way to achieve those goals. This paper will discuss the method of varying the compression ratio of an inline 4-cylinder engine through the use of a 4-bar linkage and gear mechanism. This mechanism was proven to easily vary the compression ratio of the engine and shows promise of becoming a technology used for future engine designer.

Analysis of in-cylinder pressure transducer data quality utilizing a SIDI turbocharged engine

In-cylinder pressure transducers have been used for decades to record combustion pressure inside a running engine. However, due to the extreme operating environment, transducer design and installation must be considered in order to minimize measurement error. One such error is caused by thermal shock, where the pressure transducer experiences a high heat flux that can distort the pressure transducer diaphragm and also change the crystal sensitivity. This research focused on investigating the effects of thermal shock on in-cylinder pressure transducer data quality using a 2.0L, four-cylinder, spark-ignited, direct-injected, turbo-charged GM engine. Cylinder four was modified with five ports to accommodate pressure transducers of different manufacturers. They included an AVL GH14D, an AVL GH15D, a Kistler 6125C, and a Kistler 6054AR. The GH14D, GH15D, and 6054AR were M5 size transducers. The 6125C was a larger, 6.2mm transducer. Note that both of the AVL pressure transducers utilized a PH03 flame arrestor. Sweeps of ignition timing (spark sweep), engine speed, and engine load were performed to study the effects of thermal shock on each pressure transducer. The project consisted of two distinct phases which included experimental engine testing as well as simulation using a commercially available software package. A comparison was performed to characterize the quality of the data between the actual cylinder pressure and the simulated results. This comparison was valuable because the simulation results did not include thermal shock effects. All three sets of tests showed the peak cylinder pressure was basically unaffected by thermal shock. Comparison of the experimental data with the simulated results showed very good correlation. The spark sweep was performed at 1300 RPM and 3.3 bar NMEP and showed that the differences between the simulated results (no thermal shock) and the experimental data for the indicated mean effective pressure (IMEP) and the pumping mean effective pressure (PMEP) were significantly less than the published accuracies. All transducers had an IMEP percent difference less than 0.038% and less than 0.32% for PMEP. Kistler and AVL publish that the accuracy of their pressure transducers are within plus or minus 1% for the IMEP (AVL 2011; Kistler 2011). In addition, the difference in average exhaust absolute pressure between the simulated results and experimental data was the greatest for the two Kistler pressure transducers. The location and lack of flame arrestor are believed to be the cause of the increased error. For the engine speed sweep, the torque output was held constant at 203 Nm (150 ft-lbf) from 1500 to 4000 RPM. The difference in IMEP was less than 0.01% and the PMEP was less than 1%, except for the AVL GH14D which was 5% and the AVL GH15DK which was 2.25%. A noticeable error in PMEP appeared as the load increased during the engine speed sweeps, as expected. The load sweep was conducted at 2000 RPM over a range of NMEP from 1.1 to 14 bar. The difference in IMEP values were less 0.08% while the PMEP values were below 1% except for the AVL GH14D which was 1.8% and the AVL GH15DK which was at 1.25%. In-cylinder pressure transducer data quality was effectively analyzed using a combination of experimental data and simulation results. Several criteria can be used to investigate the impact of thermal shock on data quality as well as determine the best location and thermal protection for various transducers.

A STUDY ON REGIONAL CIRCULAR ECONOMY SYSTEM AND ITS CONSTRUCTION, OPERATION AND SUGGESTION FOR SHANGHAI

The characteristics of the traditional linear economic model are high consumption, high emission and low efficiency. Economic development is still largely at the expense of the environment and requires a natural resource investment. This can realize rapid economic development but resource depletion and environmental pollution become increasingly serious. In the 1990's a new economic model, circular economics, began to enter our vision. The circular economy maximizes production and minimizes the impact of economic activities on the ecological environment through organizing the activities through the closed-loop feedback cycle of "resources - production - renewable resource". Circular economy is a better way to solve the contradictions between the economic development and resource shortages. Developing circular economy has become the major strategic initiatives to achieving sustainable development in countries all over the world. The evaluation of the development of circular economics is a necessary step for regional circular economy development. Having a quantitative evaluation of circular economy can better monitor and reveal the contradictions and problems in the process of the development of recycling economy. This thesis will: 1) Create an evaluation model framework and new types of industries and 2) Make an evaluation of the Shanghai circular economy currently to analyze the situation of Shanghai in the development of circular economy. I will then propose suggestions about the structure and development of Shanghai circular economy.