Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates

Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask. Above that, we present the strategy for controlling both GaP NW length and diameter independently in single- or two-staged self-catalyzed growth. The proposed approach can be extended to other III-V NWs.

Evaluation of marginal adaptation of CAD/CAM vs conventional all-ceramic crowns on an implant abutment: An in vitro study

The survival of fixed prosthodontic restorations depends on the state of the marginal adaptation. Marginal gaps can create a favourable condition for biofilm deposition, thereby contributing to the development of caries and periodontal disease. The longevity of fixed prosthodontic restorations depends on the condition of the marginal adaptation to the abutment teeth. The presented work aimed to study, evaluate and compare the marginal adaptation of All-Ceramic crowns fabricated using conventional laboratory procedures with those fabricated using the CAD/CAM technology.To compare the marginal fit and adaptation of All- Ceramic crowns obtained by conventional techniques and crowns obtained by CAD/CAM technique. The presented study focused on a total of 20 samples divided into two groups viz. Group I (Conventional) and Group II (CAD/CAM) having 10 sample each. The samples were prepared with the straight abutment having a standardized collar height of 2mm, HIOSSEN that was mounted on acrylic blocks using implant analogue, HIOSSEN. A set of crowns was produced by 5-axis milling lithium disilicate using glass-ceramic blocks with laboratory fabrication methods. Another set of zirconia crowns was produced using CAD/CAM technology. Circumferential marginal gap measurements were taken at 12 measurement locations on the hexagonal die marked equidistant to each other. Both the samples were measured for marginal discrepancy at under the stereomicroscope.The results obtained showed that the mean vertical gap for the group II samples showed the least variation in the marginal discrepancy. Although the mean obtained for both the groups showed that the mean vertical marginal discrepancy was within the clinically acceptable level.It can be concluded that within the limitation of the study the data obtained showed that The Mean vertical gap was the maximum for Group I (Conventional group) i.e. 49.25 µm showing maximum variation in marginal fit. While the CAD/CAM Group had shown least vertical marginal discrepancy which depicts statistically significant better marginal fit than those fabricated using conventional laboratory procedures.

Formation of Diagonal Gaps as Stress-Relieving Sites: Rethinking the Concept of Increment Splitting in Direct Occlusal Composite Restorations

The split-increment horizontal placement technique is currently used, along with other restorative techniques, in moderate-to-large occlusal cavities for reducing the shrinkage stress generated during light polymerization. Such stress, if released uncontrolled, may cause damage within the composite, tooth or at the adhesive interface. The term “diagonal cut” was used in our original paper published in 2005 to refer to the action of dividing each composite increment into segments prior to light polymerization and was presented in two-dimensional illustration. Besides, we made no mention in the original paper of the term “diagonal gap” as an outcome of such diagonal cutting. We currently recognize the importance of introducing the “diagonal gap” term and the need for shedding some light on its role to help provide a more comprehensive view of the split-increment technique. The purpose of the current paper is to rethink our increment splitting concept used in direct occlusal composite restorations by introducing the term “diagonal gap” as a stress-relieving vertical site and demonstrating it in a three-dimensional illustration for providing a more comprehensive understanding of the split-increment technique. Conclusion: In the current paper, the term “diagonal gap” is introduced to refer to the vertical gap created by diagonal cutting of the horizontal composite increment, before light curing. This gap enables the segmented composite increment to undergo unrestrained shrinkage, where each segment being free from adhesion at the gap site can deform independently from the other segments. The relief of the polymerization shrinkage stress generated during light curing prevents formation of cracks in enamel and/or composite, and debonding of adhesive interfaces. Keywords: deformation; diagonal gap; incremental; occlusal; polymerization shrinkage; posterior composite; segment; split-increment; stress reduction; stress-relieving site

Optical Analysis of a New Solar Distiller with Cylindrical Surface Concentrator and Vertical Gap Evaporator

In this paper, a new solar distiller floating on ocean with cylindrical surface concentrator and vertical gap evaporator is proposed for solving the problem of freshwater shortage in islands. When the distiller is floating on ocean, the vertical gap will fill with seawater automatically due to the siphon effect of hydrophilic material. Then the seawater is heated to generate vapor when the incidence sunlight is concentrated to the gap by the cylindrical concentrator. Finally, the vapor reaches the arched transparent glass at the top of the device and condenses to produce fresh water. Optical simulation for the solar distiller is carried out to find the optimal radius of the cylindrical concentrator and the height of the vertical gap. The results indicate that when the radius and height is 6 cm and 5 cm respectively, 80% of the sunlight number within the incidence angle of 45° can be captured by the seawater in the vertical gap. The annual optical performance of the distiller is analyzed for the region within 17° north latitude. As the result, the device placed in east-west direction possesses superior performance. There are more than 10 working hours and 5 working hours in which the reception rate is more than 80% in summer solstice and winter solstice respectively. In autumnal equinox, there are more than 11 working hours with the reception rate exceeding 90%. Energy balance analysis for the whole system is carried out and the stable evaporation rate per unit solar collector area increases gently from 0.12 g/ (m2‧s) to 0.65 g/(m2‧s) when the solar irradiance increases from 500 W/m2 to 1000 W/m2.

Perancangan Mekanisme Pelurusan Kawat SAE 304 (UNS S30400) Galvanized Menggunakan Prinsip Pengerolan

Wire is a complement material on the manufacturing product. Therefore, the wire processes usually bestowed to the middle-low industry. Cutting and straightening wire processes are the most basic process for wire materials. In the middle-small industry, demand of wire materials is 150 kg per day. Seeing this potential, the design of a wire straightening mechanism for middle-low industries is necessary to maximize productivity. The main purpose of wire straightening mechanism design is calculating roll diameters and placement to obtain appropriate rolling force. In designing this wire straightening mechanism, the raw materials are used 3 mm SAE 304 (UNS S30400) Galvanized. The rolling method used in this mechanism is Three-Roll Bending. The empirical method is used on this analysis. Based on the analytical results, roll used on this mechanism are 5 pieces or equal with 3 cycle of rolling process with 40 mm of diameters. The vertical gap between center of rolls is 41.5 mm with 54 mm horizontal gap. Rolling force produced by the analytical roll dimension is 1608.69 N/cycle and that’s enough to give plastic deformation on the 3 mm SAE 304 (UNS S30400) Galvanized wire.

Retrieval of Vertical Foliage Profile and Leaf Area Index Using Transmitted Energy Information Derived from ICESat GLAS Data

The vertical foliage profile (VFP) and leaf area index (LAI) are critical descriptors in terrestrial ecosystem modeling. Although light detection and ranging (lidar) observations have been proven to have potential for deriving the VFP and LAI, existing methods depend only on the received waveform information and are sensitive to additional input parameters, such as the ratio of canopy to ground reflectance. In this study, we proposed a new method for retrieving forest VFP and LAI from Ice, Cloud and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) data over two sites similar in their biophysical parameters. Our method utilized the information from not only the interaction between the laser and the forest but also the sensor configuration, which brought the benefit that our method was free from an empirical input parameter. Specifically, we first derived the transmitted energy profile (TEP) through the lidar 1-D radiative transfer model. Then, the obtained TEP was utilized to calculate the vertical gap distribution. Finally, the vertical gap distribution was taken as input to derive the VFP based on the Beer–Lambert law, and the LAI was calculated by integrating the VFP. Extensive validations of our method were carried out based on the discrete anisotropic radiative transfer (DART) simulation data, ground-based measurements, and the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI product. The validation based on the DART simulation data showed that our method could effectively characterize the VFP and LAI under various canopy architecture scenarios, including homogeneous turbid and discrete individual-tree scenes. The ground-based validation also proved the feasibility of our method: the VFP retrieved from the GLAS data showed a similar trend with the foliage distribution density in the GLAS footprints; the GLAS LAI had a high correlation with the field measurements, with a determination coefficient (R2) of 0.79, root mean square error (RMSE) of 0.49, and bias of 0.17. Once the outliers caused by low data quality and large slope were identified and removed, the accuracy was further improved, with R2 = 0.85, RMSE = 0.35, and bias = 0.10. However, the MODIS LAI product did not present a good relationship with the GLAS LAI. Relative to the GLAS LAI, the MODIS LAI showed an overestimation in the low and middle ranges of the LAI and a saturation at high values of approximately LAI = 5.5. Overall, this method has the potential to produce continental- and global-scale VFP and LAI datasets from the spaceborne lidar system.

Implications of Implant Framework Misfit: An Animal Study on an Ovine Model

Although clinicians routinely aim to provide prosthesis with accurate fit on implants, a degree of prosthesis misfit is inevitable. This exploratory animal study evaluated the effects of framework vertical misfit and the timing of implant loading on implant position and screw loosening. Four implants were placed in healed ridges of each side of mandibles of 3 sheep. On the right side, 2 immediate frameworks were placed after 2 days. One framework was fitting, and the other one had a vertical gap of 0.5 mm on the distal implant. After 8 weeks (1 st review), the left side received 2 conventional frameworks with similar fit conditions to the right side. All the animals were euthanised after 8 weeks (2 nd review). At the 1 st and 2 nd reviews, implant level impressions were taken to measure the vertical displacement of distal implants, and the retaining screws loosening torque values were measured. The loosening torque values for the immediate fitting frameworks were considerably greater than the immediate misfitting frameworks. This was noticeable at the 1 st review. At the 2 nd review, the loosening torque values were comparable for the immediate fitting and misfitting frameworks. Vertical implant displacement was observed for all the misfitting frameworks. However, much more implant displacement occurred under immediate frameworks. Therefore, implant frameworks with vertical misfit in the present study were associated with less screw stability and more implant displacement. Retightening the retaining screws during the maturation of bone seemed to maintain the torque values.

Diffusion of low-concentration surfactant from the rising drop

This paper presents an experimental study of the initial stage of extraction of surfactant from the insoluble drop, which rises slowly in quiescent fluid. The placement of the drop in a narrow vertical gap causes it to take the form of a short horizontal cylinder with a free lateral surface and flat ends. The latter feature makes it possible to use an interferometer for visualizing the structure of the resulting flows and concentration fields inside the drop and surrounding medium and to trace their evolution. The changes in the flow and concentration fields are studied for the case when the low-concentration surfactant is diffused from a quiescent drop. As a result of the performed measurements, the dependences of the characteristics of mass transfer in the droplet on the initial concentration of the diffusing reagent and time were determined.

Exploring the Effect of Train Design Features on the Boarding and Alighting Time by Laboratory Experiments

The objective of this work is to study the effect of design features such as door width, vestibule setback and vertical gap on passengers’ boarding and alighting time (BAT) at metro stations. Simulated experiments were performed at University College London’s Pedestrian Accessibility Movement Environment Laboratory (PAMELA). The mock-up included a hall or entrance to the train and a relevant portion of the platform in front of the doors. Different scenarios were tested based on existing stations. Results were compared to observations at Green Park Station of the London Underground (LU). Results from PAMELA showed that wider doors (1.80 m), larger vestibule setback (800 mm) and smaller vertical gap (50 mm) reduced the average boarding time. However, the average alighting time presented no significant differences due to other phenomenon such as congestion or formation of lines of flow at doors. The observation at LU presented a reduction of the BAT when a small vertical gap (170 mm) was presented. More experiments are needed at PAMELA to test the effect of the design features for different densities and types of passengers.