Concave Face Research Articles

Laser performance of high repetition frequency on a 970 nm LD side-pumped Er:YSGG crystal operated at 2.79 μm

We demonstrate the laser performance of high repetition frequency on a 970 nm laser diode (LD) side-pumped Er:YSGG crystal rod with concave end faces. The laser performance under different repetition rates and pulse widths was studied with an optimal cavity length. The maximum average output power of 11.81 W operated at a repetition frequency of 500 Hz and 2.794 μm was achieved, corresponding to the slope efficiency of 10.49%. In addition, the beam quality factors M2x/M2y of 7.01/7.10 and far-field divergences Θx/Θy of 9.15/9.18 mrad were also obtained under the high repetition frequency of 500 Hz. These results show that the LD side-pumped Er:YSGG laser crystal rod with concave end faces has the potential of being operated under high repetition frequency.

Unapređenje procesa sabijanja kod četvorokrakih obradaka bazirano na kompjuterskom i fizičkom modeliranju

The method of upsetting of large ingots has been investigated in this work. The proposed method consists in upsetting of profiled workpieces with concave faces. An angle of the concave faces was 150°. A relative depth of the concave faces has been varied in range 15%…25% from workpiece's diameter. Strains effective and mean stresses in the longitudinal cross-section of the workpiece with concave faces after upsetting have been determined by FEM. A value of compressive stresses has been determined based on a parameter of the stress state. FEM allowed to find what a rational depth of the concave faces should be, which has to be 15 % from workpiece's diameter. Maximum closing of the internal defect take place for this depth of the concave faces. Results of the FEM have been tested by experimental investigations. It has been established that upsetting of the four-beam workpieces improved a quality of the massive parts.

Curvature and size effects hinder halogen bonds with extended π systems

Curvature and size effects in halogen interactions with extended aromatic species have been evaluated, employing computational methods, in dimers formed by dihalogens Cl2, Br2 and I2 with both planar (coronene and circumcoronene) and curved (corannulene, sumanene and C60) aromatic systems. The main controlling factor in these interactions is dispersion, so they become stronger as the size of the halogen grows. The nature of the interaction with the halogen changes depending on the curvature and the extension of the aromatic system. As the aromatic species becomes larger, parallel stacked structures are favoured by dispersion increases over halogen bonded ones. Parallel dimers by the concave side are also favoured as the curvature of the aromatic species increases, while the effect is the opposite by the convex side. Overall, halogen bond interactions are not favoured for large planar or curved aromatic systems; only by the convex face of the most curved structures the dispersion contribution decreases enough so as to make halogen bonded structures competitive with parallel stacked ones.

Structural Insights Into PfARO and Characterization of its Interaction With PfAIP

Apicomplexan parasites contain rhoptries, which are specialized secretory organelles that coordinate host cell invasion. During the process of invasion, rhoptries secrete their contents to facilitate interaction with, and entry into, the host cell. Here, we report the crystal structure of the rhoptry protein Armadillo Repeats-Only (ARO) from the human malaria parasite, Plasmodium falciparum (PfARO). The structure of PfARO comprises five tandem Armadillo-like (ARM) repeats, with adjacent ARM repeats stacked in a head-to-tail orientation resulting in PfARO adopting an elongated curved shape. Interestingly, the concave face of PfARO contains two distinct patches of highly conserved residues that appear to play an important role in protein-protein interaction. We functionally characterized the P. falciparum homolog of ARO interacting protein (PfAIP) and demonstrate that it localizes to the rhoptries. We show that conditional mislocalization of PfAIP leads to deficient red blood cell invasion. Guided by the structure, we identified mutations of PfARO that lead to mislocalization of PfAIP. Using proximity-based biotinylation we probe into PfAIP interacting proteins.

Focused Ultrasound Assistance to the MOS Gas Sensor System.

It is known that the ultrasound-assisted metal oxide semiconductor (MOS) gas sensor system can improve the sensitivity and lower detection limit (LDL) of a MOS gas sensor. The existing ultrasound-assisted MOS gas sensor system employs the standing-wave ultrasonic field. As the size of the sensing element is much smaller than that of the ultrasonic field, energy utilization rate of the ultrasonic subsystem has been very poor. In this work, we propose a method to raise the energy utilization rate, and the limit-sensing properties of the ultrasound-assisted MOS gas sensor system, which utilizes the focused ultrasound generated by a low-frequency ultrasonic transducer with a concave radiation face. By placing the sensing element at the focal region, the electric power input of the ultrasonic transducer can be decreased by about 50% for the same sensing response. Moreover, the maximum sensitivity can be increased by 45%, and the LDL can be decreased by 50% by the new method.

Effect of solution treatment temperature on the γ′ precipitation distribution, high temperature tensile and fatigue properties of FGH96 joints prepared by inertia friction welding

Inertia friction welding (IFW) was conducted on FGH96 superalloy shaped in rings. After welding, the joints experienced solution treatment and aging-treated. There are 4 kinds of solution treatments including no solution treatment and solution treatment at 1050 °C, 1080 °C and 1120 °C, respectively. The grain size, γ′ precipitate distribution, tensile and fatigue properties at 700 °C were measured and analyzed at different solution treatments. The results shows that with the increasing of the solution treatment temperature (STT), the grain size went up slowly below 1080 °C and got a sudden growth from 1080 °C to 1120 °C. At the same time, the secondary γ′ precipitates (mainly containing Ti, Al and Ni with ordered L12 structure) became fine and the shape gradually transformed from sphere into elliptical and irregular, which was a mixture of cuboids with concave faces and octets. When the solution treatment changes from no solution to solution treatment at 1120 °C, the tensile strength gradually increases from 1243 MPa to 1337 MPa and then remains constant from 1080 °C to 1120 °C. However, the yield strength increases from 917 MPa to 990 MPa at 1080 °C and then decreases to 927 MPa at 1120 °C which is close related to the grain growth of welding nugget zone (WNZ). The change tendency of fatigue limit with STT is in agreement with that of yield strength. It reaches the maximum of 765 MPa at 1080 °C which is closely connected to the shape transition of γ′ precipitates in WNZ and the grain growth. Combining high temperature tensile properties with fatigue limit, the optimal STT is 1080 °C.

Experimental Study on the Shear Behavior of the Bonding Interface Between Sandstone and Cement Mortar Under Freeze–Thaw

Shear experiments were conducted on the cement mortar–sandstone bonding interface and the materials themselves to investigate their loss of shear strength and the deterioration mechanism caused by freezing and thawing cycles. The experimental results show that the shear strength of the bonding interface is much lower than that of the original materials themselves under the same normal stress. The shear strength of this interface decreases linearly with increasing number of freeze–thaw cycles, but it linearly increases with increasing normal stress. The cohesion and internal friction angle also decrease as the number of freeze–thaw cycles increases. In addition, obvious freeze–thaw debonding of this interface is observed and it is first caused by the difference in frost-heaving deformation between the cement mortar and the red sandstone, followed by the frost-heaving pressure in the crack formed in the interface. Finally, the shear damage of this interface has been quantified by reconstitution of the interface morphology. As a result, almost all the shear breakage occurs on the red sandstone side, and a concave rough face arises. With the absence of normal stress, the shear abscission area in the red sandstone increases quickly with increasing number of freeze–thaw cycles. However, with increasing normal stress, this shear abscission area decreases, and the layered composite specimens were prone to shear failure straightly along the bonding interface, because the shear dilatancy deformation is constrained. This study provides the shear failure characteristics of cement mortar–rock interfaces under freeze–thaw cycles and contributes to a better understanding of the freeze–thaw debonding mechanism of protective cement mortar layers on rock surfaces.

Nitrogen‐Bridged, Natural Product Like Octahydrobenzofurans and Octahydroindoles: Scope and Mechanism of Bridge‐Forming Reductive Amination via Caged Heteroadamantanes

The biological significance of sp3‐rich synthetic scaffolds with natural product like features yet distinct global frameworks is being increasingly recognized in medicinal chemistry and biochemistry. Taking inspiration from the vast array of bioactive, bridged alkaloids, we report the synthesis of unique, densely functionalized tricyclic scaffolds based on nitrogen‐bridged octahydrobenzofurans and octahydroindoles. These heterocycle‐rich frameworks were assembled by a one‐pot, two‐step bridge‐forming reductive amination process, which was shown to proceed via caged, heteroadamantane intermediates that thermodynamically drive an exo–endo epimerization, enabling intramolecular aza‐Michael addition over the concave face of the fused bicyclic precursors. In addition to evaluating the scope of this aza‐bridge‐forming reaction, further stereochemical complexity was introduced by subsequent diastereoselective ketone reductions and other manipulations. Finally, strategic diversity points (amino, carboxy) were decorated with common medicinal chemistry fragments, providing a set of exemplar derivatives with Lipinski‐compliant physicochemical properties.

Hierarchical Quad Meshing of 3D Scanned Surfaces

AbstractIn this paper we present a novel method to reconstruct watertight quad meshes on scanned 3D geometry. There exist many different approaches to acquire 3D information from real world objects and sceneries. Resulting point clouds depict scanned surfaces as sparse sets of positional information. A common downside is the lack of normals, connectivity or topological adjacency data which makes it difficult to actually recover a meaningful surface. The concept described in this paper is designed to reconstruct a surface mesh despite all this missing information. Even when facing varying sample density, our algorithm is still guaranteed to produce watertight manifold meshes featuring quad faces only. The topology can be set‐up to follow superimposed regular structures or align naturally to the point cloud's shape. Our proposed approach is based on an initial divide and conquer subsampling procedure: Surface samples are clustered in meaningful neighborhoods as leafs of a kd‐tree. A representative sample of the surface neighborhood is determined for each leaf using a spherical surface approximation. The hierarchical structure of the binary tree is utilized to construct a basic set of loose tiles and to interconnect them. As a final step, missing parts of the now coherent tile structure are filled up with an incremental algorithm for locally optimal gap closure. Disfigured or concave faces in the resulting mesh can be removed with a constrained smoothing operator.

NMR structures in different membrane environments of three ocellatin peptides isolated from Leptodactylus labyrinthicus

The peptides ocellatin-LB1, −LB2 and −F1 have previously been isolated from anurans of the Leptodactylus genus and the sequences are identical from residue 1–22, which correspond to ocellatin-LB1 sequence (GVVDILKGAAKDIAGHLASKVM-NH2), whereas ocellatin-LB2 carries an extra N and ocellatin-F1 extra NKL residues at their C-termini. These peptides showed different spectra of activities and biophysical investigations indicated a direct correlation between membrane-disruptive properties and antimicrobial activities, i.e. ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. To better characterize their membrane interactions, we report here the detailed three-dimensional NMR structures of these peptides in TFE-d2:H2O (60:40) and in the presence of zwitterionic DPC-d38 and anionic SDS-d25 micellar solutions. Although the three peptides showed significant helical contents in the three mimetic environments, structural differences were noticed. When the structures of the three peptides in the presence of DPC-d38 micelles are compared to each other, a more pronounced curvature is observed for ocellatin-F1 and the bent helix, with the concave face composed mostly of hydrophobic residues, is consistent with the micellar curvature and the amphipathic nature of the molecule. Interestingly, an almost linear helical segment was observed for ocellatin-F1 in the presence of SDS-d25 micelles and the conformational differences in the two micellar environments are possibly related to the presence of the extra Lys residue near the peptide C-terminus, which increases the affinity of ocellatin-F1 to anionic membranes in comparison with ocellatin-LB1 and -LB2, as proved by isothermal titration calorimetry. To our knowledge, this work reports for the first time the three-dimensional structures of ocellatin peptides.

Morphology evolution of γ′ precipitates in a powder metallurgy Ni-base superalloy

Effect of the cooling rate on the morphological evolution of the γ′ precipitate in a powder metallurgy Ni-base superalloy FGH96 was studied. Results showed that as the cooling rate decreased from 600 °C/min to 2 °C/min, the precipitate morphology transformed from sphere to cuboid, octet and dendrite. As the cooling rate increased, the mean size of the γ′ precipitates decreased while the nucleation density increased. When the cooling rate was lower than 6 °C/min, the precipitate would evolve from a sphere to cuboids with concave faces, octets, dendrite to final split-off branches. The morphological transition was driven by energy balance between coherent strain induced by the γ′/γ lattice misfit and interface energy. The dendritic shape γ′ exhibited an eight-primary-branch pattern with preferred growth direction along 〈111〉, and secondary arms along 〈100〉.

Theoretical Study on Charge-transfer Excitations of Buckycatcher-Fullerene Complexes

Buckycatcher molecules (BC), bowl-shaped polycyclic hydrocarbons, have attracted attention as a new type of π conjugated compound. BC molecules with two corannulene subunits can form a complex (BC/C60) with C60 because of the π-π interaction between the convex surface of the C60 and the concave faces of corannulene subunits of the BC. We have performed DFT calculations on the structures and excitation spectra of BC and BC/C60 and found that charge transfer type excitations from BC to C60 are possible in BC/C60.

Common Malocclusion Problems and their Management: A Hospital based study

Aims: Orthodontics is the branch of dentistry concerned with the prevention, interception and correction of malocclusion. The present study aimed at the common malocclusion problems and their management in Bangladeshi population. It was also aimed to align for aesthetics reason, functional efficiency and structural balance. Methods: A cross-sectional study was carried out among 120 respondents having malocclusions. Students, especially young women and urban residents were selected as the main respondents of our series which reflected its aesthetic value against malocclusion Results: Mean age of the respondents was 22.22±9.07 years with a male and female ratio of 1:3.1. Among the respondents, 37.5% were within the 11 to 20 years age group with a past (21.0%) and present (7.5%) history of finger sucking habit and abnormal over jet (71.7%) and over bite (55.8%). Mean over jet and overbite were 4.4 ±3.47 (range, -2 to 12) mm and 3.47±1.98 (range, 0 to 7) mm, respectively. Angle’s classification revealed type 1, type 2 (division 1), type 2 (division 2) and type 3 were 55.0%, 28.3%, 3.3% and 13.3%, respectively, and based on skeletal relationships, type 1, type 2 and type 3 were 64.2%, 25.0% and 10.8%, respectively. Of all patients, 66.7% had convex, 22.5% straight and 10.8% had concave face profiles. They also had 44.2% competent, 36.7% incompetent and 19.2% habitual competent anterior lip seals. Conclusions: Smile is a global language though many of our patients are deprived of both socially and economically, especially young women from this language. With growing importance imposed on preventive orthodontic treatment and proper oral health education, incidence of malocclusion can be reduced. DOI: http://dx.doi.org/10.3329/cdcj.v10i1.13827 City Dent. Coll. J Volume-10, Number-1, January-2013

Curving effects of concave dodecahedral nanocarbons enable enhanced Li-ion storage

Concave dodecahedral nanocarbons with highly curving concave faces and protuberant vertexes exhibit high specific capacity and superior cycle stability.

Canopy architecture and PAR absorption of Euphorbia cooperi in the Matobo Hills, Zimbabwe

Tree euphorbias share many traits with arborescent cacti in having tall and multi-branched forms of growth which have selective value for maximizing photosynthetic surface area and water storage. The candelabra growth form of Euphorbia cooperi, and likely other Euphorbia species with similar canopy architecture in southern Africa, allows these plants to add photosynthetic surface area as they grow and increase in size while at the same time minimizing problems of transpirational water loss. This increase in branch surface area occurs with age and increase in size and numbers of branches at the same time that the amount of potential storage volume to support water loss from this expanded surface area is also increasing. Key to this ability is the morphological trait of a heavily suberized trunk that increases with age, providing added capacity for water storage without adding to surface area subject to transpirational water loss. This trait and the associated canopy architecture allows the development of increasing surface area with minimal self-shading as new branches develop so long as older branches are shed. Beyond the canopy architecture, the cross-sectional morphology of branches in E. cooperi with concave faces has selective value in balancing increased surface area with maintenance of adequate storage volume. Simulated patterns of branch morphology with a square cross-sectional morphology show a “safe” result in producing little change in S:V ratio as plants mature, but at the expense of limiting photosynthetic surface area. At the other extreme, a simulated cross-sectional morphology with deep concave flutes, as seen in young plants, would significantly increase photosynthetic surface area, but at a potential cost of increased sensitivity to drought stress.

Crystal structure of an anti-idiotype variable lymphocyte receptor.

Variable lymphocyte receptors (VLRs), the leucine-rich repeat (LRR)-based antigen receptors of jawless fish, have great utility in a wide variety of biochemical and biological applications, similar to classical Ig-based antibodies. VLR-based reagents may be particularly useful when traditional antibodies are not available. An anti-idiotype lamprey VLR, VLR39, has previously been identified that recognizes the heavy-chain CDR3 of the B-cell receptor (BCR) of a leukemic clone from a patient with chronic lymphocytic leukemia (CLL). VLR39 was used successfully to track the re-emergence of this clone in the patient following chemotherapy. Here, the crystal structure of VLR39 is presented at 1.5 Å resolution and compared with those of other protein-specific VLRs. VLR39 adopts a curved solenoid fold and exhibits substantial structural similarity to other protein-binding VLRs. VLR39 has a short LRRCT loop that protrudes outwards away from the concave face and is similar to those of its protein-specific VLR counterparts. Analysis of the VLR39-BCR interaction by size-exclusion chromatography and biolayer interferometry using the scFv version of the BCR confirms that VLR39 recognizes the BCR Fv region. Such VLR-based reagents may be useful for identifying and monitoring leukemia in CLL patients and in other clinical diagnostic assays.

Geometry of torn boudin–An indicator of relative viscosity

The present study determines the role of viscosity on the development of rectangular torn boudin and its various types, defined by the curvature of their exterior and face margins. Numerical modeling was performed with the help of Finite Element Method considering Maxwell visco-elastic materials in commercial code ANSYS. Seven different viscosities were used and interchanged among the boudin, inter-boudin and matrix materials to understand the effect of viscosity ratios, specifically of relative viscosity of inter-boudin material. Results show that the viscosity of inter-boudin material has significant control on the shape of torn boudins apart from the viscosity ratio of boudin to matrix material. Bone-shaped boudin develops only when the inter-boudin is more competent than boudin and it becomes more prominent when matrix is also competent than boudin, but incompetent than inter-boudin. When boudins are stiffer than inter-boudin, barrel-shaped and fish-head boudins with concave faces develop. Exterior or face margins remain almost straight when boudin is relatively rigid compared to its surrounding matrix materials, or when there is no or very little viscosity contrast between boudin and inter-boudin material even in case of large boudin-matrix viscosity contrast. Therefore, the relative viscosity among the boudin, inter-boudin and matrix materials can be estimated qualitatively by studying the shape of boudin in the field.

Evaluation of the hydrogen adsorption onto Li and Li+ decorated circumtrindene (C36H12): A theoretical study

Circumtrindene as a π-bowl shaped carbon structure decorated by Li and Li+ and examined for H2 adsorption using M06-2X/6-311++G(d,p)//B3LYP/GEN level of theory. All polygons, bonds and various carbon types, in concave and convex sides, were examined to find the best location for Li and Li+. ZPE and BSSE-corrected interaction energy values were calculated for connection of Li or Li+ to circumtrindene and for connection of H2 to LiC36H12 or Li+-C36H12. Better understanding of the adsorption properties were achieved by DOS, PDOS, OPDOS diagrams and NBO analysis. Results showed that in LiC36H12 and Li+-C36H12 complexes, the concave side has more binding energy than the convex ones and Li+-C36H12 has more binding energy than LiC36H12. Also, for LiC36H12, when Li was in center polygon and concave side and for Li+-C36H12, when Li+ was in 6-2 polygon and convex side, the highest interaction energy were obtained. For H2 adsorption, the complexes contain Li and Li+ in center polygon and concave face have the highest binding energy, equal to 15.72 and 16.29 kcal mol−1, respectively. Binding energy values indicated that adsorption of Li or Li+ onto C36H12 and adsorption of H2 onto LiC36H12 or Li+-C36H12 in all positions are chemisorptions, but the connections are not so strong for H2 molecules.

The Inheritance Angle: A Determinant for the Number of Members in the Substituted Cucurbit[n]uril Family.

Two new glycoluril diethers have been prepared, bearing strained cyclobutene and cyclobutane rings at the fused junction of the two imidazolidinone rings. The wide angle of the concave face of the cyclobutano derivative enabled the synthesis of cyclobutanocucurbit[5-8]uril, the largest member being the most significant achievement. A limited binding affinity study compared the new substituted family to classical cucurbit[5-8]uril. Surprisingly lower affinities were found, except for cyclobutanocucurbit[6]uril, which was 3.3-fold higher.

Histology and Surface Ultra-Structure of the Gill of A Minor Carp, <i>Labeo bata</i> (Hamilton)

The histology and surface ultra-structures of the gill epithelium of Labeo bata has been examined through light and electron microscopy. Gill arches bear double rows of primary lamellae and each primary lamella is provided with two rows of delicate rectangular secondary lamellae on its upper and lower surfaces. Gill arches and filaments are lined by thick stratified epithelium while the epithelium of secondary lamella is made up of thin single layered pavement cells. The thin epithelium is supported and kept apart from each other by the pillar cells. The pavement cells are polygonal with well-defined cell boundary and microridges on its apical surface. The epithelial cells are interspersed by large chloride cells located at the base of secondary lamellae and PAS positive mucous cells. Mucous cells are found abundant at the base and tip of the primary lamellae. Taste buds are found on the concave anterior faces of gill arches. The short and soft gill rakers are covered with stratified epithelium. This finding demonstrated that the fish has well developed respiratory system matching to its active life.