Conventional Head Research Articles

Bioink homogeneity control during 3D bioprinting of multicomponent micro/nanocomposite hydrogel for even tissue regeneration using novel twin screw extrusion system

The 3D bioprinting of an advanced multicomponent bioink requires the homogeneous distribution of bioink components to control the biological and structural properties of the printed tissue engineering construct. To ensure the homogeneous mixing of micro/nanomaterials in a bioink and then bioprinting, currently, multiple preparation steps must be followed before feeding the bioink to the conventional bioprinting extruder head. To overcome these limitations, a real-time one-step process was obtained by developing a semi-automated twin-screw extruder (TSE) head to synchronously perform systematic mixing and 3D bioprinting. In this study, as a proof of concept, the parameter optimizations for semi-automated mixing of bioink components and 3D bioprinting with the TSE head were demonstrated with an ionic gel (alginate), alpha-tricalcium phosphate (α-TCP) micro/nanoparticles, and osteoblast cells. The TSE-processed bioink samples showed better bioprintability, with better mechanical and biological properties than the conventional ones. The micro/nanoparticles were uniformly dispersed in the bioink within 60 s of screw mixing them inside the barrel (with the barrel outlet closed). The live cell distribution in the printed constructs was significantly superior to conventional mixing even with continuous feeding and extrusion-based bioink printing. This novel extrusion head ensured the control of uniform micro/nanomaterials and cell distribution throughout the directly mixed printable bioink with minimal cell damage. Further, they delivered increased batch consistency in real time mixing and bioink printing owing to its highly efficient variable screw pitch design. Higher repeatability than the conventional method of bioink component mixing and its subsequent 3D bioprinting was obtained through increased automation, as well as reduced processing time, demonstrating strong potential in tissue engineering applications through the controlled mixing of bioink components and its 3D bioprinting without damaging the cells.

Test validated 0D/1D engine model of a swinging valve internal combustion engine

In the quest for reaching ever higher power density of IC engines a much simpler solution has been investigated that allows vehicles to reach a comparable power level with cars equipped with turbo charged engines. The new Swinging Valve (SwV) arrangement enables the unhindered gas exchange process through an engine. In this experiment a flow bench was used to examine a normal poppet valve cylinder head and a cylinder head constructed for the same engine but with Swinging Valves. The flow parameters of the original cylinder head were obtained then the SwV head was investigated in the same way. To examine the practical use of a SwV system a 0D/1D engine simulation had been created, first using the engine with conventional cylinder head. That model had been validated with dynamometer tests. After this stage the results of the Swinging Valve flow measurements were fed in the same 0D/1D engine simulation then the results were compared and examined.

Diffusion Kurtosis Imaging Reflects GFAP, TopoIIα, and MGMT Expression in Astrocytomas.

Preliminary study of magnetic resonance (MR) diffusion kurtosis imaging (DKI) assessing the pathological glial fibrillary acidic protein (GFAP), TopoIIα, and O 6-methylguanine-DNA methyltransferase (MGMT) expression in astrocytomas. This study was approved by the local ethics committee, and informed consent was obtained from all participants. Sixty-six cases with pathologically proven astrocytomas were enrolled in this study; of which, 34 were high grade and remaining 32 were low grade. They patients underwent conventional MRI head scan, DKI scan, and enhanced scan under the same conditions. Fractional anisotropy (FA) and mean kurtosis (MK) calculated from DKI, as well as GFAP, TopoIIα, and MGMT expression level were compared prospectively between high and low-grade astrocytomas. Spearman rank correlation analysis was used for comparing values of DKI and GFAP, TopoIIα, and MGMT expression level in the two groups. The MK values were significantly higher in high-grade astrocytomas than those in low-grade astrocytomas (P < 0.05); FA values demonstrated no significant difference between the two groups (P = 0.331). GFAP expression level was significantly lower in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). Topo-IIα expression level were significantly higher in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). There was no significant difference in MGMT expression level between the two groups (P = 0.679). MK values were negatively correlated with the expression of GFAP (r = -0.836; P = 0.03), however, they were positively correlated with the expression of Topo-IIα (r = 0.896; P = 0.01). FA values were not correlated with the expression of GFAP (r = 0.366; P = 0.05), Topo-IIα (r = -0.562; P = 0.05), and MGMT (r = -0.153; P = 0.10). MK, the DKI parameter values of astrocytomas, was significantly correlated to the expression of GFAP and TopoIIα. To a certain extent, applying DKI may provide the biological behavior of tumor cell differentiation, proliferation activity, invasion and metastasis, and can guide individual treatment.

Analytical model for the perceived retinal image formation of 3D display systems.

The optical design process of conventional stereoscope-type head mounted displays for virtual and augmented reality applications typically neglects the inherent aberrations of the eye optics or refractive errors of a viewer, which misses the opportunity of producing personal devices for optimal visual experiences. Although a few research efforts have been made to simulate the retinal image formation process for some of the emerging 3D display systems such as light field displays that require modeling the eye optics to complete the image formation process, the existing works generally are specific for one type of display methods, unable to provide a generalized framework for different display methods for the benefit of comparison, and often require the use of at least two different software platforms for implementation which is challenging in handling massive data and implementing compensation of wavefront aberrations induced by display engine or eye refractive errors. To overcome those limits, we present a generalized analytical model for accurately simulating the visual responses such as retinal PSF, MTF, and image formation of different types of 2D and 3D display systems. This analytical model can accurately simulate the retinal responses when viewing a given display system, accounting for the residual eye aberrations of schematic eye models that match with the statistical clinical measurements, eye accommodative change as required, the effects of different eye refractive errors specific to viewers, and the effects of various wavefront aberrations inherited from a display engine. We further describe the numerical implementation of this analytical model for simulating the perceived retinal image with different types of HMD systems in a single computational platform. Finally, with a test setup, we numerically demonstrated the application of this analytical model in the simulation of the perceived retinal image, accommodative response and in the investigation of the eye refractive error impacts on the perceived retinal image based on the multifocal plane display, integral imaging based light field display, computational multilayer light field display, as well as the stereoscope and natural viewing for comparison.

Introduction and discussion about three types of fine grain products and their harvesters

Fine grain products are harvested in two manual and mechanized forms. Nowadays, common combine harvesters are used, but fine grain products such as Rapeseed, Sesame and Sorghum cannot be harvested with conventional heads of combine harvesters due to the excessive grain loss in the head of the combine. Therefore, the necessity of design and fabricating machines and heads of combine harvesters became the center of attention to researchers because of the nutritional and medicinal benefits of fine-grain products. This research, encompasses an overview of the special headers and machines for harvesting three type of fine grain products with high loss and an evaluation of each of these harvesters.

Application of Adaptive Image Receive Coil Technology for Whole-Brain Imaging.

OBJECTIVE. The Adaptive Image Receive (AIR) radiofrequency coil is an emergent technology that is lightweight and flexible and exhibits electrical characteristics that overcome many of the limitations of traditional rigid coil designs. The purpose of this study was to apply the AIR coil for whole-brain imaging and compare the performance of a prototype AIR coil array with the performance of conventional head coils. SUBJECTS AND METHODS. A phantom and 15 healthy adult participants were imaged. A prototype 16-channel head AIR coil was compared with conventional 8-and 32-channel head coils using clinically available MRI sequences. During consensus review, two board-certified neuroradiologists graded the AIR coil compared with an 8-channel coil and a 32-channel coil on a 5-point ordinal scale in multiple categories. One- and two-sided Wilcoxon signed rank tests were performed. Noise covariance matrices and geometry factor (g-factor) maps were calculated. RESULTS. The signal-to-noise ratio, structural sharpness, and overall image quality scores of the prototype 16-channel AIR coil were better than those of the 8-channel coil but were not as good as those of the 32-channel coil. Noise covariance matrices showed stable performance of the AIR coil across participants. The median g-factors for the 16-channel AIR coil were, overall, less than those of the 8-channel coil but were greater than those of the 32-channel coil. CONCLUSION. On average, the prototype 16-channel head AIR coil outperformed a conventional 8-channel head coil but did not perform as well as a conventional 32-channel head coil. This study shows the feasibility of the novel AIR coil technology for imaging the brain and provides insight for future coil design improvements.

Final detailed design of an all-in-one attachment-based PHC pile head cutting robot and its structural stability analysis

ABSTRACT Conventional pretensioned spun, high-strength concrete (PHC), pile head cutting process is associated with safety, quality uniformity, and labor productivity problems. However, trend analysis has revealed that no technology has been developed to address these problems as these pertain to specific Korean construction site situations. This study aims to derive the final detailed design for an all-in-one attachment-based PHC pile head cutting robot, and analyzes its structural stability. To this end, the key functions of an all-in-one attachment-based PHC pile head cutting robot have been defined, and the related core element technologies have been analyzed. This has led to the presentation of two detailed design alternatives. Both of these were then subjected to an analytical hierarchal process (AHP) and trade-off analysis that led to the final selection of the diamond wheel saw-based detailed design. In a structural stability analysis of the final detailed design, all tested parts did not surpass the threshold yield strengths of 230 MPa (SS400) and 255 MPa (AL6061 T6). If a prototype is developed based on the final detailed design derived in this study, it is expected to have improved work safety, quality uniformity, and work efficiency characteristics compared with the conventional PHC pile head cutting process.

Computed tomography of the head and the risk of brain tumours during childhood and adolescence: results from a case–control study in Japan

To clarify whether medical radiation exposure, especially from head computed tomography (CT), increases the risk of brain tumours in young patients in Japan, which ranks the second highest in the world in the number of paediatric CT examinations following the US. From 2011 to 2015, we performed a case–control study of 120 brain tumour patients and 360 appendicitis patients as controls. Reasons, the number of brain and head CT scans date were available from interviews. A cumulative radiation dose to the brain was calculated as a sum of doses received from head CT scans and from conventional x-rays and estimated using a reference table derived from a literature review of published studies. We performed conditional logistic regression to assess the risk of brain tumours from brain and head CT, and from conventional head x-ray procedures. The case group received on average 1.8 CTs to the brain area and 2.2 CTs to the whole head, with a mean estimated brain dose of 32 ± 13 mGy. The odds ratio for developing a brain tumour from having a brain CT was 0.93 (95% confidence interval: 0.38–1.82). This was hardly altered when adjusting for parental educational history and for other diseases (history of neurological disease and attention-deficit disorder/attention-deficit hyperactivity disorder). Neither whole head CT nor cumulative brain dose to the brain increased the risk of glioma or of all brain tumours. Although this study conducted in Japan, where ranks second in the number of CT scans conducted in the world, did not show an increased risk of brain tumours related to CT scans, it should be taken with caution due to a case–control study with limited sample size.

Evaluation of Six-Dimensional Cranial Target Positioning Accuracy in Two Different Immobilization Methods Using Exactrac System

Introduction: The aim of this study was to determine the accuracy of two different immobilization methods in patient positioning in cranial radiotherapy. The six-dimensional (6D) target localization accuracy of using a dedicated stereotactic mask was compared with that of a conventional head mask by the ExacTrac system. Material and Methods: A total of 56 patients with cranial lesions were included in this study (26 patients with a dedicated stereotactic mask and 30 subjects with a conventional head mask). The ExacTrac image-guided positioning system was utilized to obtain daily translational and rotational patient positioning displacement from the intended position. The 6D setup data was analyzed to obtain population mean, systematic and random errors, and three-dimensional (3D) vector shifts in all the patients. Results: The population mean values of setup errors were comparable with both immobilization systems; however, the spread as indicated by population systematic and population random errors was more in the use of a conventional head mask. The mean values of the 3D vector shifts were 2.09±1.00 and 4.51±3.38 mm with the use of a dedicated stereotactic mask and conventional head mask, respectively. The frequency distribution of maximum rotational deviation and statistical analysis demonstrated a significant difference in immobilization accuracy between stereotactic immobilization and 3-clamp immobilization (p <0.05). Conclusion: The results revealed that there was a significant reduction in target positioning errors with a dedicated stereotactic mask, compared to that with a conventional cranial mask. Furthermore, a dedicated stereotactic mask is required to keep rotational deviations within system correctable limits.

Evaluation of emission indices and air quality implications of liquefied petroleum gas burners

Major cities in Nigeria has adopted the use of liquefied petroleum gas (LPG) as their main source for domestic cooking, however, this adoption led to different designs of LPG burners in Nigeria market. The emission indices of these burners and their air quality implications are yet to be ascertain. To solve these problems and fill the data gap, laboratory analysis were carried out on 16 conventional LPG burner heads identified in Nigeria market. The emission factors for Carbon monoxide (CO), Oxide of Nitrogen (NOx), Carbon dioxide (CO2), Hydrocarbons (HC) and sulphur dioxide (SO2) on the basis of useful energy delivered were 0.123–21.784 g/MJd, 1.973–32.943 g/MJd, 73.819–147.639 g/MJd, 4.069–171.643 g/MJd and 0–0.1644 g/MJd while the emission rates were 0.000238–0.1125 g/s, 0.0071–0.2 g/s, 0.1083–0.7 g/s, 0.0117–1.2583 g/s and 0–0.000194 g/s respectively. It was observed that results from the study were within the International Organization for Standardization, International Workshop Agreement 11 and World Health Organization indoor air quality guidelines for human protection.

Transfer of functional structures from multiple bovine teeth to a multilevel grinding head via a biomimetic approach

It is highly desirable to improve the crushing performance in powder processing. This study presents a bionic multilevel grinding head for a grinder inspired by the natural friction pairs of bovine teeth. The mechanism of adaptive mastication for various teeth in bovine dentition was revealed, and the main functional structures of the incisor and molars were extracted to construct the biomimetic multilevel surface. To optimize bionic structure parameters, a discrete element method was introduced to simulate the crushing process, and surrogate models that respond to the breakage rate and heat production were constructed and solved. Compared with the conventional multilevel grinding head, highly efficient crushing effects were achieved for the bionic type. Furthermore, its efficient crushing mechanism was discussed.

Behaviour of a new type of shear connector for steel-concrete composite construction

Abstract The objective of this study was to investigate the structural behaviour of a new type of shear connector developed known as the Embossed Steel Plate connector (ESP). The need for the development for a new type of shear connector was due to the advancement of composite structures which subsequently enhances the composite behaviour as the shear connectors plays an important role in predominating the bearing capacity of the composite structure as a whole. Therefore, this study attempted to explore the structural behaviour of the newly developed shear connector by conducting push out test in accordance with Eurocode 4. The test results were correlated with the conventional head stud shear connectors and the structural behaviour of ESP connector was evaluated from the load slip curves.

Energy model of pumped hydro storage station

In order to meet the design and operation requirements of uncertain renewable energy accommodation in power grid, this paper establishes the energy model of pumped hydro storage station, including energy water head, energy storage and the relationship of conversion between power and energy. The energy water head which directly describes the potential energy of water storage of upper reservoir is different from the conventional water head; the change of supply water storage has obvious influence on the energy water head, and the conservation of the energy water head increment describes the influence of the change of supply water storage on energy water head; energy storage is determined by the water storage of upper reservoir and the energy water head; energy storage capacity is determined by the power generation storage capacity and the rated energy water head; the sensitivity analysis shows that the change of the water storage of upper reservoir is the main cause of the energy storage change. The concept and construction method of the storage function are put forward to calculate the energy storage situation quickly.

Numerical simulation of flow distribution in the header of plate-fin heat exchanger

Plate-fin heat exchangers are widely used in industry at present due to their compact structure and high efficiency. However, there is a problem of flow maldistribution, resulting in poor performance of heat exchangers. The influence of the header configuration on fluid flow distribution is studied by using CFD software FLUENT. The numerical results show that the fluid flow inside the header is seriously uneven. The reliability of the numerical simulation is validated against the published results. They are found to be basically consistent within considerable error. The optimal number of the punch baffle is investigated. Various header configuration with different opening ratios have been studied under the same boundary conditions. The gross flow maldistribution parameter (S) is used to evaluate flow nonuniformity, and the flow maldistribution parameters of different schemes under different Reynolds numbers are listed and compared. The optimal header with minimum flow maldistribution parameter is obtained through the performance analysis of headers. It is found that the flow maldistribution of the improved header is significantly smaller compared with the conventional header. Hence, the efficiency of the heat exchanger is effectively enhanced. The conclusion provides a reference for the optimization design of plate-fin heat exchanger.

The Ecological Status of Livestock and Poultry in the Border Regions of Russia and South-East Finland

Intensifi cation of agricultural production increases the burden on the environment. Modern management and planning of agricultural activity requires a comprehensive assessment of the environmental status of the industry. (Research purpose) To develop recommendations for improving the environmental safety of agricultural production based on the implementation of the best available technologies, methods for monitoring and controlling technological processes for the disposal of organic animal waste. (Materials and methods) The authors studied agricultural enterprises, their specialization and production capacities, technologies for manure and litter utilization. The studies included an assessment of enterprises according to the criteria approved in the recommendations of Helsinki Commission for the Baltic Sea. The authors used standard methods for processing statistical, fi eld and personal data. (Results and discussion) The authors conducted a state analysis of the agro-industrial complex of Leningrad Region in terms of the organic waste formation from animal husbandry and poultry farming, and evaluated the potential for their use. They studied 142 large complexes, which produce more than 90 percent of livestock and poultry products. The average livestock density in Leningrad Region is 2.2 conventional heads per hectare of cultivated agricultural land. They showed that there are 22,200 households in southern Finland, 79 percent of which are plant growing enterprises that are engaged in small-scale production. They took into account the specifi c features of the studied territories in terms of nutrient load and proposed a system of environmental impact regulation. (Conclusions) The authors developed 4 main recommendation sections to reduce the risks of biogenic environmental pollution: the development of an industrial environmental control system based on technological regulations; mastering the system of regional monitoring and coordination of work with organic fertilizers; adoption and implementation of a program of livestock enterprises technological and technical modernization in terms of the organic waste disposal; creation of demonstration platforms for environmental specialists advanced training in the implementation of modern technological solutions.

Characterization and improvement of flow distribution in a vertical dual-compartment header of a microchannel heat exchanger

Abstract Poor distribution of two-phase flow in a microchannel heat exchanger header requires a solution to maximize its potential advantage of compactness while offering a high heat-transfer rate. While previous works have attempted to improve two-phase flow distribution, most have focused on horizontal headers, which commonly appear in indoor units. However, there are a few studies on vertical headers that function as an evaporator in heat pump mode that are typical in outdoor units. This study describes the development of a modified vertical header with a dual-compartment structure aimed at improving the flow distribution. Experiments and visualizations were conducted using R410A in a test section that represented the size and capacity of an actual heat exchanger. The inlet mass flux was 309–1235 kg·m−2s−1 (50–200 kg·h−1), vapor quality was 0.1–0.2, and the evaporating temperature was maintained at 15 °C. The results were compared to the conventional header previously evaluated by our research group. Results showed that the dual-compartment header was able to enhance the liquid flow distribution at low inlet mass flux from approximately 30% to 80% based on relative standard deviation (RSD), with a generally higher liquid Reynolds number when compared to the conventional header.

On-scalp MEG sensor localization using magnetic dipole-like coils: A method for highly accurate co-registration

Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor array and the anatomical structure of the measured individual’s head. In conventional MEG, the positions and orientations of the sensors relative to each other are fixed and known beforehand, requiring only localization of the head relative to the sensor array. Since the sensors in on-scalp MEG are positioned on the scalp, locations of the individual sensors depend on the subject’s head shape and size. The positions and orientations of on-scalp sensors must therefore be measured at every recording. This can be achieved by inverting conventional head localization, localizing the sensors relative to the head - rather than the other way around.In this study we present a practical method for localizing sensors using magnetic dipole-like coils attached to the subject’s head. We implement and evaluate the method in a set of on-scalp MEG recordings using a 7-channel on-scalp MEG system based on high critical temperature superconducting quantum interference devices (high-Tc SQUIDs). The method allows individually localizing the sensor positions, orientations, and responsivities with high accuracy using only a short averaging time (≤ 2 ​mm, < 3° and < 3%, respectively, with 1-s averaging), enabling continuous sensor localization. Calibrating and jointly localizing the sensor array can further improve the accuracy of position and orientation (< 1 ​mm and < 1°, respectively, with 1-s coil recordings).We demonstrate source localization of on-scalp recorded somatosensory evoked activity based on co-registration with our method. Equivalent current dipole fits of the evoked responses corresponded well (within 4.2 ​mm) with those based on a commercial, whole-head MEG system.

Experimental and numerical study on the performance of a minichannel heat sink with different header geometries using nanofluids

Inefficient distributor and collector header design in a minichannel heat sink causes flow maldistribution which can severely degrade the thermal and hydraulic performance of the heat sink. This paper presents an experimental and numerical investigation on the thermohydraulic performance of minichannel heat sinks with two different header geometries using nanofluids. A series of tests are conducted on a minichannel heat sink with optimized and conventional header geometries by using (Al2O3-H2O) nanofluids and distilled water as coolants. The effects of header geometry, nanoparticle concentration, and coolant flow rate on the overall heat transfer coefficient, heat transfer enhancement, thermal resistance, and base temperature are investigated. The experimental and numerical results exhibited good agreement, indicating that the thermohydraulic performance of the heat sink with the optimized header geometry is superior to that with the conventional header geometry. The minichannel heat sink with the optimized header geometry exhibited 17% higher overall heat transfer coefficient and 43% reduction in pressure drop while achieving lower values for base temperature and thermal resistance for each employed flow rate and volumetric concentration of nanoparticles. Furthermore, the performance evaluation criteria (PEC) indicated a 41% improvement in hydraulic performance while using minichannel heat sink with optimized header geometry compared to that with the conventional header geometry.

Previous Announcement Method Using 3D CG Face Interface for Mobile Robot

When a robot works among people in a public space, its behavior can make some people feel uncomfortable. One of the reasons for this is that it is difficult for people to understand the robot’s intended behavior based on its appearance. This paper presents a new intention expression method using a three dimensional computer graphics (3D CG) face model. The 3D CG face model is displayed on a flat panel screen and has two eyes and a head that can be rotated freely. When the mobile robot is about to change its traveling direction, the robot rotates its head and eyes in the direction it intends to go, so that an oncoming person can know the robot’s intention from this previous announcement. Three main types of experiment were conducted, to confirm the validity and effectiveness of our proposed previous announcement method using the face interface. First, an appropriate timing for the previous announcement was determined from impression evaluations as a preliminary experiment. Secondly, differences between two experiments, in which a pedestrian and the robot passed each other in a corridor both with and without the previous announcement, were evaluated as main experiments of this study. Finally, differences between our proposed face interface and the conventional robot head were analyzed as a reference experiments. The experimental results confirmed the validity and effectiveness of the proposed method.

A novel omnidirectional tin-alloyed ring retractor for craniotomy in neurosurgery: technical note.

In neurosurgical operations, proper craniotomy using retractors is necessary. Various surgical instruments are used for this purpose, including standard retractors and multipurpose head frame retractor systems. However, the conventional multipurpose head frame system is often not optimal for use in some craniotomies and postures because of its size and complexity of setting. We have invented a new omnidirectional tin-alloyed (ODT) ring retractor for craniotomy with malleability and shape memory characteristics to resolve these issues. It is principally elliptical in shape, approximately 30 × 20cm in diameter, and sufficiently firm. Accordingly, this ODT ring can retract the surgical field in all directions. Here, we report our experiences of 281 neurosurgical craniotomies using this ODT ring retractor system in various craniotomy sites and postures. Our novel ODT ring retractor is useful because of its low profile, multidirectional retractability, and less obstructiveness with its malleability. It could be used with pediatric patients where strong traction is not desirable.