Tip Structure Research Articles

Effect of Plastic Hinge Properties in Pushover Analysis of Reinforced Concrete Plane Frames

The four-bay, five-story Reinforced Concrete (RC) frame with two-dimensional beams and a column moment frame system that is vulnerable to Mosul, Iraq's seismic activity is examined. A plastic hinge symbolizes the member yielding failure mode in columns and beams. Utilizing SAP2000 software (V.16), the pushover study was carried out to confirm the code's fundamental goal of life safety performance under seismic events. By combining the seismic hazard with the inelastic structural analysis, one may determine the anticipated seismic performance of a structure. An essential outcome of pushover analysis for both brittle (force-controlled) and ductile (deformationcontrolled) actions of the plastic hinge behavior is the base shear vs structure's tip displacement curve. The pushover analysis, using a variety of alternatives for the plastic hinge behavior, showed that the plastic hinge formed because of its brittle nature placed it in the more severe category. All of the plastic hinges created in the beams as a result of brittle behavior are placed in the risky branch ("Collapse Prevention CP") of the plastic hinge acceptance criterion. This necessitates increasing the shear strength of the beams.

Understanding the morphology evolution of 1D BiVO4 nanoarrays from nanorods to nanocones with enhanced photocatalytic performance

The controllable synthesis of BiVO4 nanocone and nanorod arrays is reported. The morphology transformation of BiVO4 nanoarrays is accompanied with growth mechanism transformation and the tip structure results in superior photocatalytic performance.

Insight into Relationship between Thermal Dissolution of Low-Rank Coals and Their Subsequent Oxidative Depolymerization

Oxidative depolymerization of low-rank coals is promising for obtaining benzene carboxylic acids (BCAs). However, it is hindered by the low yield of BCAs along with a large number of alphatic acids. Thermal dissolution could modify the physico-chemical structural features of low-rank coals, which is expected to improve the oxidation of LRCs. In this paper, lignite and subbituminous coal were firstly subjected to thermal dissolution with cyclohexane at 250 °C for 2 h. Then, the raw coal and the corresponding thermal insoluble portion (TIP) were oxidized by NaOCl under the same conditions. The residual yields of TIPs oxidation were both lower than those of raw coals oxidation, indicating that TIPs were more easily oxidized than the raw coals. The yield of BCAs obtained by TIPs oxidation was above 19% higher than that from the oxidation of raw coals. Meanwhile, the selectivity of BCAs was improved in the resulting oxidation products from TIPs compared with that from the raw coals. The relationship between BCAs generation and thermal dissolution of low rank coals was investigated by ultimate analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results suggested that thermal dissolution could enrich aromatic portion in the remaining TIPs, resulting in an increasing of the yield and selectivity of BCAs. Simultaneously, thermal dissolution raised the specific surface area and expanded the looser space structure of TIPS, which were beneficial for the sufficient collision between aromatic structures and oxidant, facilitating the oxidative depolymerization of TIPs. This investigation would provide a novel route for promoting BCAs production by mild oxidative depolymerization of low-rank coals.

Needle Technology for Insulin Administration: A Century of Innovation.

Innovations in syringe and pen needle (PN) technology over the last 100 years have led to important advances in insulin delivery for people with diabetes, paralleling the strides made in developing recombinant DNA human insulin and insulin analogs with varying onset and duration of action. In this review, the history of advances in insulin delivery is described, focusing on progress in syringe, needle, and PN technologies. The early glass and metal syringes that required sterilization by boiling have been replaced by disposable, single-use syringes or pens with clear labeling for precise insulin dosing. The early needles ranging in length from 19 to 26 mm that required manual sharpening against a whetstone have been replaced by syringe needles of 6 mm and PNs of 4 mm in length as slender as 34 gauge. Imaging studies using ultrasound and computed tomography measured the thickness of skin and subcutaneous tissue layers to show feasibility of targeted insulin administration with shorter needles. These developments, coupled with innovations in needle/PN wall and tip structure, have led to improved injection experience for people with diabetes. It is also important to acknowledge the role of injection technique education, together with these advances in injection technology, for improving clinical outcomes and patient satisfaction. With continued projected growth of diabetes prevalence, particularly in developing countries where expensive and complex insulin delivery systems may not be practical, insulin syringes and pens will continue to serve as reliable and cost-effective means of insulin delivery for people with diabetes.

Effect of an Ectomycorrhizal Fungus on the Growth of Castanea henryi Seedlings and the Seasonal Variation of Root Tips’ Structure and Physiology

Castanea henryi is a ubiquitous hardwood chestnut species in southern China and is important both ecologically and economically. It is mainly cultivated for nut production, just like other chestnut species. However, the establishment of C. henryi seedlings in a new orchard has proven to be difficult because few seedlings survive transplanting due to the incompatibility of their coarse root architecture with nutrient-depleted red acid soils in southern China. Root architecture can be profoundly modified and nutrient can be stress alleviated due to the association of roots with ectomycorrhizal (ECM) fungi. Boletus edulis is an ECM fungus with edible and medicinal fruiting bodies. However, its impact on plant growth varies with the plant species it is associated with. In order to elucidate the role of B. edulis in C. henryi afforestation, we evaluated growth parameters and soil enzymatic activities, as well as seasonal variations in physiology and structure of ECM root tips. Growth responses and soil enzymatic activities were measured 6 months after inoculation. The physiological characteristics of root tips were also compared at various seasons throughout the year. B. edulis colonization of C. henryi roots was successful at a 60% colonization rate. Height, base diameter, and biomass (especially the underground part) of inoculated seedlings (JG) were higher than those of uninoculated seedlings (CK). JG had higher root total length, root surface area, root volume, root average diameter, and number of root tips than CK. Additionally, JG exhibited higher total nitrogen and phosphorus content. Abnormal mantle and Harting net were observed in winter. No matter the season, ECM tips had higher antioxidant enzyme activities, root activities, soluble protein content, and lower malondialdehyde compared to non-ECM tips (nE) and those without ECM tips (woE), and there were no differences between nE and woE. It is important to understand the growth of the host plant in response to ECM and that the seasonal variation of ECM root tips is important when growing high-quality C. henryi seedlings, due to the crucial role of B. edulis in improving seedling initial survival rate.

Study on Influencing Factors of the Tip Softness of Epidural Anesthesia Catheter

This article aims to study the factors affecting the flexibility of the tip of an epidural anesthesia catheter. The flexibility of the tip of the epidural anesthesia catheter was tested with a softness tester from four aspects:raw materials, tip structure, tip processing technology, and the outer diameter of the catheter. Highly flexible and malleable polymer material with a smooth tip, the tip softening process and the proper outer diameter can effectively improve the tip flexibility of the epidural anesthesia catheter.

Two New Species of Philometrid Nematodes (Philometridae), Barracudia Notabilis n. sp. and Philometra Consimilis n. sp., from the Ovary of the Hound Needlefish Tylosurus Crocodilus (Belonidae) Off Florida, USA.

SummaryTwo new species of philometrid nematodes (Philometridae), Barracudia notabilis n. sp. and Philometra consimilis n. sp., are described from males found in the ovary of the hound needlefish Tylosurus crocodilus (Péron et Lesueur) (Belonidae) from off the Atlantic coast of Florida, USA. Both species are described and illustrated based on light and scanning electron microscopical examinations. Barracudia notabilis n. sp., the first representative of this genus from fishes in the Atlantic Ocean, can be differentiated from other congeners by the body length of the male (2.69 mm), the length of the gubernaculum (57 μm) and spicules (81 μm), and by the shape of the gubernaculum. Philometra consimilis n. sp. differs from all congeners mainly in the unique structure of the distal tip of the gubernaculum (bearing two smooth dorsal barbs) and the species is also characterized by the length of spicules (111 μm) and the length of the gubernaculum (84 μm). Further studies are needed to discover and describe so far unknown gravid females of Barracudia spp.

Frustrated peptide chains at the fibril tip control the kinetics of growth of amyloid-β fibrils

Amyloid fibrillization is an exceedingly complex process in which incoming peptide chains bind to the fibril while concertedly folding. The coupling between folding and binding is not fully understood. We explore the molecular pathways of association of Aβ40 monomers to fibril tips by combining time-resolved in situ scanning probe microscopy with molecular modeling. The comparison between experimental and simulation results shows that a complex supported by nonnative contacts is present in the equilibrium structure of the fibril tip and impedes fibril growth in a supersaturated solution. The unraveling of this frustrated state determines the rate of fibril growth. The kinetics of growth of freshly cut fibrils, in which the bulk fibril structure persists at the tip, complemented by molecular simulations, indicate that this frustrated complex comprises three or four monomers in nonnative conformations and likely is contained on the top of a single stack of peptide chains in the fibril structure. This pathway of fibril growth strongly deviates from the common view that the conformational transformation of each captured peptide chain is templated by the previously arrived peptide. The insights into the ensemble structure of the frustrated complex may guide the search for suppressors of Aβ fibrillization. The uncovered dynamics of coupled structuring and assembly during fibril growth are more complex than during the folding of most globular proteins, as they involve the collective motions of several peptide chains that are not guided by a funneled energy landscape.

Reactivated shear zones: A case study in a tectonic superposition zone between the Southern Brasília and Ribeira orogens, southeastern Brazil

New data are presented related to the evolution of major shear zones in the Neoproterozoic Southern Brasília and Ribeira orogens, considering their attitude, kinematics and metamorphic conditions. The integration and analysis of geological maps, aerogeophysical and new geochronological U-Pb data, allowed to unravel the kinematics and reactivation of these shear zones. The first major event related to the collision of the São Francisco and Paranapanema paleocontinents is represented by the Alterosa Suture Zone (ASZ), interpreted as the suture of the Southern Brasília Orogen, which is a low to medium angle shear zone with mylonitic fabric indicative of granulite facies conditions. Geochronological analyzes in zircon from this zone provided three age peaks of 630 Ma, 610 Ma and 600 Ma associated with the collision of this orogen. A second regional event related to the Ribeira Orogen was responsible for the formation of steep NE-SW shear zones of low to high metamorphic grade and the local reactivation of the ASZ. Metamorphic zircon from one of these shear zones yielded an age of 574 ± 2 Ma, with minor rim growth and/or lead loss at 553 ± 2 Ma and 524 ± 4 Ma. The age of 574 ± 2 Ma fits well in the peak activity period of the Ribeira Orogen (600-560 Ma). The ages of 553 ± 2 Ma and 524 ± 4 Ma probably reflect reactivation. Several of these shear zones show evidence of original sinistral and later dextral kinematics. The paper also presents a new structure resulting from this dextral reactivation of former sinistral shear zones, which is named here “arrow tip structure”.

Influence of main cutting edge structure on hole defects in CFRP/titanium alloy stacks drilling

Tool structure plays an important role in CFRP/titanium alloy (Ti) stacks drilling. The purpose of this paper is to study the performance of drills with different main cutting edge structures in CFRP/Ti stacks drilling. The effects of the main cutting edge structure on thrust force, chip morphology, interface damage and burr are analyzed. The results show that the interface damage is the least after candle stick drill drilling, because the outer corner tip structure can remove part of heat that left on the machined surface in the cutting stage of the main cutting edge. Compared with the other two kinds of drill bits, the height of burr produced by candle stick drill at titanium alloy layer is the smallest. The reason is that outer corner tip structure of the candle stick drill can counteract part of the radial cutting force which produced by the main cutting edge, and push the material inside to facilitate material removal. The outer corner structure of the drill bit has an important influence on the thrust force, the interface damage and the exit burr, so the special drill design for CFRP/Ti stacks must focus on the outer corner structure.

Influence of rounding corners on the wake of a finite-length cylinder: An experimental study

This study aims to investigate experimentally the influence of rounding corners (r) as well as aspect ratio (AR) on the flow structures of a surface-mounted finite cylinder. The cylinders with sharp (r* = r/D = 0) and rounded corners (r*=0.167, 0.25 and 0.5) and aspect ratio or height-to-width/diameter ratio (AR = H/D) between 2 and 7 are utilized. The experiments are based on the five-hole probe and hot-wire measurements as well as the oil flow visualization. Wake measurements are made in an open return wind tunnel at the Reynolds number, Re = 1.6 × 104, where Re is defined based on the side width/diameter (D) of the cylinder cross-section and the freestream velocity. It is found that r* and AR have significant effects on the flow structure from the perspective of wake topology, strength of streamwise vortices, and vortex shedding frequency. For all r* considered, the wake is characterized by a quadrupole type (both the tip and base vortices are present) at AR = 7, while a dipole type occurs for AR = 2 and 4 (the base vortices are absent). The strength (circulation) of the streamwise vortex structures is affected by r*. For all AR examined in the present study, the strengths of tip and base vortex structures decrease with increasing r*. The oil flow visualization demonstrates that the features of the horseshoe vortex are sensitive to r* and AR. With increasing r*, the location of the separation line moves downstream and the distance between horseshoe vortex legs decreases. Velocity measurements reveal that the downwash flow enhances with increasing r*. It is also found that the Strouhal number increases progressively by 60% as r* increases from 0 to 0.5, regardless of AR.

Regulation of microtubule dynamics, mechanics and function through the growing tip.

Microtubule dynamics and their control are essential for the normal function and division of all eukaryotic cells. This plethora of functions is, in large part, supported by dynamic microtubule tips, which can bind to various intracellular targets, generate mechanical forces and couple with actin microfilaments. Here, we review progress in the understanding of microtubule assembly and dynamics, focusing on new information about the structure of microtubule tips. First, we discuss evidence for the widely accepted GTP cap model of microtubule dynamics. Next, we address microtubule dynamic instability in the context of structural information about assembly intermediates at microtubule tips. Three currently discussed models of microtubule assembly and dynamics are reviewed. These are considered in the context of established facts and recent data, which suggest that some long-held views must be re-evaluated. Finally, we review structural observations about the tips of microtubules in cells and describe their implications for understanding the mechanisms of microtubule regulation by associated proteins, by mechanical forces and by microtubule-targeting drugs, prominently including cancer chemotherapeutics.

Field emission behavior of titanium alloy nanosheets

In this study, the field emission behavior of titanium alloy nanosheets is observed for the first time. The titanium alloy nanosheets on titanium alloy substrate display low turn-on and threshold field, whose values are 3.02 V/μm and 4.51 V/μm, respectively. In addition, the titanium alloy nanosheets exhibit excellent emission stability over a period time of 1200 min. Such good field emission properties can be attributed to the relatively low work function and abundant tip structures for electrons emitting. These results show the potential of titanium alloy nanosheets as a cathode material in field-emission devices.

Achieving enhanced adhesion through optimal stress distributions

Dry adhesives that rely on surface force mediated adhesion, such as van der Waals forces, are important in applications ranging from robotics to manufacturing. The maximum theoretical adhesion strength of a contact is achieved when the stress is uniformly distributed over the entire contact area as the full potential of all the bonds at the interface is realized in this scenario. Most dry adhesive structures are composed of a tip layer that forms contact and a support structure that transfers load from the far field to this tip structure. Here, we determine the displacement distribution that must be applied on the tip layer to generate an optimum interfacial stress distribution. We realize this through a linear, closed-form optimization framework that uses data obtained from finite element analysis for a few basis cases. It was found that adhesion can be maximized by applying an optimum displacement on the tip layer that consists of uniform tension in the center, a peak tension between the center and the edge, and compression near the edge. The displacement applied on the tip layer of a mushroom-shaped, composite, and novel segmented composite structures are then analyzed and compared with the optimal case to guide the design of dry adhesives.

Directly anchoring non-noble metal single atoms on 1T-TMDs with tip structure for efficient hydrogen evolution

Owing to tip effect can introduce localized enhanced electric field and reduce interfacial energy barrier, design of atomic tip structure in single-atom catalysts (SACs) may be a fascinating strategy to further improve its electrocatalytic activity. However, conventional synthesis methods, such as defect-trapping or substitution, only lead to the formation of planar geometry of SACs without tip atoms. Good conductive 1T-TMDs with electrocatalytically active basal plane can provide platform to directly stabilize single atoms (SAs) on the top sites of its surface to form atomic tip structure. Herein, a universal Laser-molecular beam epitaxy (L-MBE) method for precisely controlling non-noble metal SAs directly immobilizing on the Cr top site of 1T-CrS2 metallic basal plane is developed. In case of Mo, the Mo SAs@1T-CrS2 with single-atom tip structure can exhibit enhanced electric field surrounding Mo atoms and an almost zero hydrogen adsorption free energy, resulting in superior HER performance together with high stability. This work provides a general way to design varieties of SACs in widely catalytic application.

Nanoscale Vacuum Diode Based on Thermionic Emission for High Temperature Operation.

Vacuum diodes, based on field emission mechanisms, demonstrate a superior performance in high-temperature operations compared to solid-state devices. However, when considering low operating voltage and continuous miniaturization, the cathode is usually made into a tip structure and the gap between cathode and anode is reduced to a nanoscale. This greatly increases the difficulty of preparation and makes it difficult to ensure fabrication consistency. Here, a metal-insulator-semiconductor (MIS) structural nanoscale vacuum diode, based on thermionic emission, was numerically studied. The results indicate that this device can operate at a stable level in a wide range of temperatures, at around 600 degrees Kelvin above 260 K at 0.2 V voltage bias. Moreover, unlike the conventional vacuum diodes working in field emission regime where the emission current is extremely sensitive to the gap-width between the cathode and the anode, the emission current of the proposed diode shows a weak correlation to the gap-width. These features make this diode a promising alternative to vacuum electronics for large-scale production and harsh environmental applications.

Records of two gonad-infecting species of Philometra (Nematoda: Philometridae) from marine fishes off Iraq, including the description of Philometra parabrevicollis n. sp. from the bigeye snapper Lutjanus lutjanus Bloch (Pisces, Lutjanidae).

Recent examinations of some marine fishes from off the southern coast of Iraq revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. parabrevicollis n. sp. (males and subgravid and nongravid females) from the ovary of the bigeye snapper Lutjanus lutjanus Bloch (Perciformes, Lutjanidae) and Philometra sp. (subgravid females) from the ovary of the bartail flathead Platycephalus indicus (Linnaeus) (Perciformes, Platycephalidae). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra parabrevicollis n. sp. is mainly characterised by the length of spicules (267–285 µm) and gubernaculum (159–168 µm), the gubernaculum/spicule length ratio (1:1.64–1.76), the structure of the gubernaculum distal tip and of the male caudal end, and the body length of males (4.03–4.90 mm). The description of this new species again confirms a high degree of host specificity of gonad-infecting species of Philometra in congeneric lutjanid hosts. Although Philometra sp. parasitising P. indicus in Iraqi waters was previously recorded, its subgravid females are described for the first time. A key to gonad-infecting species of Philometra parasitic in fishes of the family Lutjanidae is provided.

Bioinspired Omniphobic Microchamber Structure

AbstractIn this study, a novel cylindrical, mushroom‐shaped architecture array is proposed to achieve containable microchamber structures with stable omniphobic properties. By implementing a simple yet robust lithography method, a unique geometry of a double‐tip shape with high structural fidelity is fabricated. Such cylindrical re‐entrant structures are found to have omniphobic properties without surface chemical treatments. A microchamber morphology based on the formation of a Norland optical adhesive polymer roof on the surfaces of the donut‐shaped tip structures with micro‐dewetting phenomena is also demonstrated. Finally, SiO2 nanoparticles with an average size of 1.5 µm are successfully stored in the microchamber and protected with the polymer roof. This is expected to provide innovative inspiration for various application areas.

Mixing enhancement in T-junction microchannel with acoustic streaming induced by triangular structure.

The T-shaped microchannel system is used to mix similar or different fluids, and the laminar flow nature makes the mixing at the entrance junction region a challenging task. Acoustic streaming is a steady vortical flow phenomenon that can be produced in the microchannel by oscillating acoustic transducer around the sharp edge tip structure. In this study, the acoustic streaming is produced using a triangular structure with tip angles of 22.62°, 33.4°, and 61.91°, which is placed at the entrance junction region and mixes the inlets flow from two directions. The acoustic streaming flow patterns were investigated using micro-particle image velocimetry (μPIV) in various tip edge angles, flow rate, oscillation frequency, and amplitude. The velocity and vorticity profiles show that a pair of counter-rotating streaming vortices were created around the sharp triangle structure and raised the Z vorticity up to 10 times more than the case without acoustic streaming. The mixing experiments were performed by using fluorescent green dye solution and de-ionized water and evaluated its performance with the degree of mixing (M) at different amplitudes, flow rates, frequencies, and tip edge angles using the grayscale value of pixel intensity. The degree of mixing characterized was found significantly improved to 0.769 with acoustic streaming from 0.4017 without acoustic streaming, in the case of 0.008 μl/min flow rate and 38 V oscillation amplitude at y = 2.15 mm. The results suggested that the creation of acoustic streaming around the entrance junction region promotes the mixing of two fluids inside the microchannel, which is restricted by the laminar flow conditions.

Fiber tip Michelson interferometer for temperature sensing based on polymer-filled suspended core fiber

A low-cost fiber tip temperature sensor is proposed and experimentally demonstrated. It is based on the Michelson interferometer (MI) structure which is partially filled with polymer-UV glue in the suspended core fiber (SCF). Due to the greater thermal properties of UV glue compared with the silica optical fiber, the length of the inner cavity in the MI structure is susceptible to temperature modulation, resulting in the interference wavelength drift. Experimental results show that the sensor achieves a sensitivity of −164 pm/°C in the temperature range of 25–60 °C, and the sensor offers good wavelength and power stability at room temperature. In addition, the sensor has advantages such as robust, small size, and low cost, especially the reflective tip structure is more suitable for remote sensing in practical applications.