Gradual Curvature Research Articles

Flower-shaped 2D crystals grown in curved fluid vesicle membranes

The morphologies of two-dimensional (2D) crystals, nucleated, grown, and integrated within 2D elastic fluids, for instance in giant vesicle membranes, are dictated by an interplay of mechanics, permeability, and thermal contraction. Mitigation of solid strain drives the formation of crystals with vanishing Gaussian curvature (i.e., developable domain shapes) and, correspondingly, enhanced Gaussian curvature in the surrounding 2D fluid. However, upon cooling to grow the crystals, large vesicles sustain greater inflation and tension because their small area-to-volume ratio slows water permeation. As a result, more elaborate shapes, for instance, flowers with bendable but inextensible petals, form on large vesicles despite their more gradual curvature, while small vesicles harbor compact planar crystals. This size dependence runs counter to the known cumulative growth of strain energy of 2D colloidal crystals on rigid spherical templates. This interplay of intra-membrane mechanics and processing points to the scalable production of flexible molecular crystals of controllable complex shape.

"Watching" a Molecular Twist in a Protein by Raman Optical Activity.

Light-absorbing chromophores in photoreceptors contain a π-electron system and are intrinsically planar molecules. However, within a protein environment these cofactors often become nonplanar and chiral in a manner that is widely believed to be functionally important. When the same chromophore is out-of-plane distorted in opposite directions in different members of a protein family, such conformers become a set of enantiomers. In techniques using chiral optical spectroscopy such as Raman optical activity (ROA), such proteins are expected to show opposite signs in their spectra. Here we use two microbial rhodopsins, Gloeobacter rhodopsin and sodium ion pump rhodopsin (NaR), to provide the first experimental and theoretical evidence that the twist direction of the retinal chromophore indeed determines the sign of the ROA spectrum. We disrupt the hydrogen bond responsible for the distortion of the retinal in NaR and show that the sign of the ROA signals of this nonfunctional mutant is flipped. The reported ROA spectra are monosignate, a property that has been seen for a variety of photoreceptors, which we attribute to an energetically favorable gradual curvature of the chromophore.

Forced convective heat transfer enhancement of 90° bend plate-fin heat sink with grid generated turbulence

This study numerically investigates the effects of grid-bars cross-sectional geometry and grid-fins arrangement to reshape the windward flow in promoting 90° bend plate-fin heat sink forced convection at Reynolds number 60.6 × 103. Three grid-bars cross-sections are proposed, namely: (i) reverse classic triangle (A), (ii) reverse flat-bottomed Reuleaux triangle (B), and (iii) reverse aerofoil (C), with regular grid of rectangular cross-section (G) as the control. The grid-fins configurations are structured as: (i) Inline-arranged regular grid (1), (ii) inline-arranged parallel grid (PG) (2), and (iii) staggered PG-fins (3). Results show that albeit the mild-decay in local-Nufin,L along the 90° bend, B2-grid gives the highest 57% overall system performance (a balance between Nufin and pressure coefficient) compared to the control without grid, interestingly, the G1 is −60%. Such achievement is attributed to the gradual curvature development along each bar that suppresses aerodynamic stall flow separation. The induced flow dynamic enables predominant channelling of air into fin separations. Most importantly, the vortex generation between the grid and fin strengthens the turbulence proximate to fin surface, hence enhances heat transfer. Overall, this study may shed light on the utilisation of B2-grid induced turbulence to promote an energy sustainable HVAC’s 90° bend finned-tube heat exchanger forced convection.

Effect of Nucleotide State on the Protofilament Conformation of Tubulin Octamers.

At the molecular level, the dynamic instability (random growth and shrinkage) of the microtubule (MT) is driven by the nucleotide state (GTP vs GDP) in the β subunit of the tubulin dimers at the MT cap. Here, we use large-scale molecular dynamics (MD) simulations and normal-mode analysis (NMA) to characterize the effect of a single GTP cap layer on tubulin octamers composed of two neighboring protofilaments (PFs). We utilize recently reported high-resolution structures of dynamic MTs to simulate a GDP octamer both with and without a single GTP cap layer. We perform multiple replicas of long-time atomistic MD simulations (3 replicas, 0.3 μs for each replica, 0.9 μs for each octamer system, and 1.8 μs total) of both octamers. We observe that a single GTP cap layer induces structural differences in neighboring PFs, finding that one PF possesses a gradual curvature, compared to the second PF which possesses a kinked conformation. This results in either curling or splaying between these PFs. We suggest that this is due to asymmetric strengths of longitudinal contacts between the two PFs. Furthermore, using NMA, we calculate mechanical properties of these octamer systems and find that octamer system with a single GTP cap layer possesses a lower flexural rigidity.

A Novel Incremental Sheet Bending Process of Complex Curved Steel Plate

Bending complex curved steel plates for constructing ship hull has long been a challenge in shipbuilding industry. This paper presents a novel incremental bending process to obtain complicated curved steel plates by a series of sequential and layered punches. Taking advantage of this process, the blank plate that is fixed and held by a flexible supporting system can incrementally be bent into the target shape by a press tool along a planned tool path step by step and layer by layer. Acting as a “lower die,” the flexible supporting system can provide flexible and multifunctional supports for the work piece during the forming process, whose four general motion modes are demonstrated in this paper. Meanwhile, the procedures of tool path planning and forming layering are also explained in detail. In addition, aiming at different motion modes of the flexible supporting system, two springback compensation methods are given. Furthermore, according to the forming principle presented in this paper, an original incremental prototype equipment was designed and manufactured, which is mainly composed of a three-axis computer numerical control (CNC) machine, a flexible supporting system, and a three-dimensional (3D) scanning feedback system. A series of forming experiments focusing on a gradual curvature shape were carried out using this prototype to investigate the feasibility and validity of this forming process.

Effect of stress relaxation in two different preactivation methods of beta-titanium T-loops: bends vs. continuous curvature

ObjectiveAssess the changes in the force system of T-loop springs (TLSs) preactivated by bends and curvature, when secured in place with a constant strain over time. Materials and MethodsA total of 120 TLSs with dimensions 6 x 10 mm, produced out of 0.017 × 0.025-inch TMA, were randomly divided into two groups of 60 TLSs, each according to what preactivation was going to be used, concentrated bends or gradual curvature. Subgroup 1 was tested immediately and the remaining subgroups were tested after they were secured at 5-mm activation for different periods of time in an interbracket distance of 23 mm. Subgroups 2, 3, 4, 5, and 6 were kept activated for 24, 48, and 72 hours, 1 and 2 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment, and moment-to-force (MF) ratios were recorded. ResultsBoth groups showed a decrease in force levels over time (P < 0.001 and 0.005 for bend and curvature preactivation, respectively), but with different behaviors. The group preactivated by bends showed a reduction in moments over time (P < 0.001), whereas the group preactivated by curvature did not (P = 0.410). The MF ratio has not changed over time in either group. ConclusionsThe stress-relaxation effect is more evident on group preactivated by bends.

Stability of beta-titanium T-loop springs preactivated by gradual curvature.

ABSTRACTObjective: Evaluate changes in the force system of T-Loop Springs (TLS) preactivated by curvature, due to stress relaxation. Methods: Ninety TLSs measuring 6 x 10 mm, produced out with 0.017 x 0.025-in TMA® wire and preactived by gradual curvature, were randomly distributed into nine groups according to time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief, by trial activation. The other eight groups were tested after 24, 48 and 72 hours, 1, 2, 4, 8 and 12 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment and moment-to-force ratios were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation, in an interbracket distance of 23 mm. Results: The horizontal forces decreased gradually among the groups (p< 0.001) and the moments showed a significant and slow decrease over time among the groups (p< 0.001). All groups produced similar M/F ratios (p= 0.532), with no influence of time. Conclusions: The TLSs preactivated by curvature suffered a gradual deformation over time, which affected the force system, specifically the moments, which affected the horizontal forces produced.

Variations of the tooth morphology of the Woolly Mammoth Mammuthus primigenius (Blumenbach, 1799) (Mammalia: Elephanthidae)

Cases of variations in the morphology of isolated upper teeth M3 of Mammuthus primigenius (Blumenbach, 1799) from the south-east of West Siberia and Yakutiya are described. The anomaly of M. primigenius tooth from Yakutiya is expressed in changing of the tooth crown shape and position of dental plates in M3. Development of the anomaly was probably associated with a delay of loosing the tooth of the previous generation (M2) and disorder of the formation of M3 at the stage of its mineralization. Two M3 teeth from Novosibirsk Province are characterized by changing of the wearing surface and root shape. One of them shows two wearing surfaces in parallel to initial masticatory surface, shifted lingually. The upper part of the root is bent buccally, that is connected with the falling out of the tooth from the alveolus. The appearance of such a change, presumably, is connected with a mechanical injury of the cheek region of skull. The reconstruction of the formation of this tooth anomaly in M. primigenius was carried out. The second of these teeth also has a wrong position of the masticatory surface, which has a gradual curvature from nearly perpendicular (to enamel plates) in the anterior part of the tooth to about 45° in the posterior plates.

곡률궤적을 이용한 실시간 이동하는 음원을 추종하는 모바일 로봇

It is suggested that the curvature trajectory be used to estimate the real-time moving sound sources and efficiently the robot estimating the sound sources. Since the target points of the real-time moving sound sources change, the mobile robot continuously estimates the changed target points. In such a case, the robot experiences a slip phenomenon due to the abnormal velocity and the changes of the navigating state. By selecting an appropriate curvature and navigating the robot gradually by using it, it is possible to enable the robot to reach the target points without having much trouble. In order to recognize the sound sources in real time, three microphones need to be organized in a straight form. Also, by applying the cross-correlation algorithm to the TDOA base, the signals can be analyzed. By using the analyzed data, the locations of the sound sources can be recognized. Based on such findings, the sound sources can be estimated. Even if the mobile robot is navigated by selecting the gradual curvature based on the changed target points, there could be errors caused by the inertia and the centrifugal force related to the velocity. As a result, it is possible to control the velocity of both wheels of the robot through the velocity PID controller in order to compensate for the slip phenomenon and minimize the estimated errors. In order to examine whether the suggested curvature trajectory is appropriate for estimating the sound sources, two mobile robots are arranged to carry out an actual experiment. The first robot is moved by discharging the sound sources, while the second robot recognizes and estimates the locations of the discharged sound sources in real time.

Meander dynamics: A reduced‐order nonlinear model without curvature restrictions for flow and bed morphology

AbstractReduced‐order models remain essential tools for meander modeling, especially for processes at large length scales and long time scales, probabilistic simulations, rapid assessments, or when input data are scarce or uncertain. Present reduced‐order meander models consider their dependent variables either as small‐amplitude variations compared to a basic state (linearity) or as varying gradually in a spatial sense (gradual variation). In a prequel, Blanckaert and de Vriend () derived a nonlinear reduced‐order hydrodynamic model without curvature restrictions and showed that linearity or gradual curvature variations assumptions do not hold in strongly curved channels. Moreover, in strongly curved channels, a nonlinear feedback mechanism causes the secondary flow strength to be smaller than its linear mild‐curvature equivalent. In the limit of mild‐amplitude variations and mild curvature, their nonlinear meander flow model simplifies to a well‐known linear formulation. The present paper extends this nonlinear modeling to the bed morphology in strongly curved bends, making use of Exner's sediment conservation principle. Furthermore, the model quantifying the relative influence of the downslope gravitational force is refined by considering nonlinear effects. The coupled nonlinear flow and bed morphology model yields satisfactory results for the bed topography, whereas the corresponding linear model strongly overpredicts the magnitude of the transverse bed slope. Analysis of the forcing mechanisms indicate that this erroneous behavior is caused by an overestimation of the upslope drag force due to the secondary flow.

A new tardigrade Doryphoribius maasaimarensis sp. nov. (Eutardigrada: Hypsibiidae) from Kenya.

A new tardigrade, Doryphoribius maasaimarensis sp. nov., is described from a moss sample collected in Masai Mara Game Reserve, Kenya. The new species is characterized by having a reticulate dorsal cuticle with small tubercles; nine transverse rows of dorsal gibbosities (configuration IX:4-6-4-6-4-6-4-4-2); pharyngeal bulb with two macroplacoids and no microplacoid; claws with short and thin accessory points; small, smooth lunules under the claws. The new species is most similar to Doryphoribius zyxiglobus (Horning, Schuster & Grigarick, 1978). Both exhibit two macroplacoids, similar cuticular pattern and the same configuration of gibbosities. However, in Doryphoribius maasaimarensis sp. nov. the cuticular tubercles are less close, buccal tube slightly longer with respect to the body length, more gradual curvature of the buccal tube, different claws shape and thinner accessory points.

Functional shape of the earthquake frequency‐magnitude distribution and completeness magnitude

We investigated the functional shape of the earthquake frequency‐magnitude distribution (FMD) to identify its dependence on the completeness magnitude Mc. The FMD takes the form N(m) ∝ exp(−βm)q(m) where N(m) is the event number, m the magnitude, exp(−βm) the Gutenberg‐Richter law and q(m) a detection function. q(m) is commonly defined as the cumulative Normal distribution to describe the gradual curvature of bulk FMDs. Recent results however suggest that this gradual curvature is due to Mc heterogeneities, meaning that the functional shape of the elemental FMD has yet to be described. We propose a detection function of the form q(m) = exp(κ(m − Mc)) for m &lt; Mc and q(m) = 1 for m ≥ Mc, which leads to an FMD of angular shape. The two FMD models are compared in earthquake catalogs from Southern California and Nevada and in synthetic catalogs. We show that the angular FMD model better describes the elemental FMD and that the sum of elemental angular FMDs leads to the gradually curved bulk FMD. We propose an FMD shape ontology consisting of 5 categories depending on the Mc spatial distribution, from Mc constant to Mc highly heterogeneous: (I) Angular FMD, (II) Intermediary FMD, (III) Intermediary FMD with multiple maxima, (IV) Gradually curved FMD and (V) Gradually curved FMD with multiple maxima. We also demonstrate that the gradually curved FMD model overestimates Mc. This study provides new insights into earthquake detectability properties by using seismicity as a proxy and the means to accurately estimate Mc in any given volume.

A COMPACT ULTRAWIDEBAND MONOPOLE ANTENNA WITH 5.5 GHZ NOTCHED BAND

This paper proposes a compact ultrawideband monopole antenna fed by CPW with a 5.5GHz notched band of WLAN/WiMAX systems. The antenna input section is designed by using a gradual curvature central line and ground planes for ultrawideband achievement. In order to reject the unwanted frequency of the existing WLAN/WiMAX band, the C-shaped slit with perimeter length of a half wavelength at center frequency of 5.5GHz has been embedded into the monopole patch. The designed antenna is completely implemented and measured for impedance bandwidth covering UWB range and stably performs omnidirectional pattern in xz plane from 3.1 to 10GHz. The proposed antenna could potentially minimize frequency interference in the WLAN/WiMAX bands.

Nanoscale deformation of MEMS materials

ABSTRACTUsing a novel in-situ TEM triboprobe holder, nanoscale structures formed from polysilicon MEMS materials have been loaded to characterise the failure mechanisms of reduced scale components. Nanobridges with cross-section dimensions much less than 1μm have been deformed using both single, high displacement indentation and low displacement cyclic fatigue. In both deformation modes, significant residual plastic deformation is measured, occurring and accumulating in the polysilicon. This can be seen as a gradual curvature along the entire crossbeam upon unloading. Where the radius of curvature is very high, fracture of the beams at the centre point was generally also seen. When loading at much lower displacement but under fatigue conditions, localised heating around the moving contact point initiates carbon migration, forming a very strong bond. A high tensile force was needed to severe the contact during unload. Such in-situ techniques demonstrate a range of time dependant failure modes which can be overlooked using post-mortem analysis. In particular, the combined effect of localised frictional heating and contamination on the reliability of components that repeatedly comes into contact with one another.

流れと風圧の同時測定による立方体屋根面上流れの時空間構造と風圧特性の評価

In order to clarify characteristics of temporal-spatial flow structures above and wind pressures on the roof of a cubic structure, a wind tunnel experiment was carried out in two types of turbulent boundary layers. The flow was measured by Particle Image Velocimetry (PIV) system and simultaneous multi-pressure measurements on the surface were also performed. The time-averaged separation bubble on the roof had flat shape with a gradual curvature. When the intensity of turbulence of the approaching flow was large, and strong local negative pressure was generated in the windward edge corner, a flat conical vortex was formed, and the spatial structure of the flow was different from the time-averaged flow.

Supercritical channel flow in the coastal atmospheric boundary layer: Idealized numerical simulations

Numerical simulations of supercritical coastal flows were performed with a three‐dimensional, nonlinear, hydrostatic meso‐γ‐scale model with a higher‐order turbulence closure. The purpose was to resolve questions from previous studies related to terrain forcing. Idealized terrain, representing northern California, was used; this facilitated testing of hypotheses in a simple fashion. It was found that the angle by which the coast turns away from the flow regulates the acceleration in the expansion fan and determines how far downstream the maximum in the wind speed is located. Simulations with curved coastlines confirmed that the gradual curvature of the coastal mountains north of Cape Mendocino is sufficient to excite an expansion fan. A decreasing height of the terrain along the coast lead to an increased acceleration of the flow, largest when the slope of the terrain was confined to the change in coastline orientation. A cape perpendicular to the main coastal mountains significantly blocked the flow, even when as low as half the upstream marine atmospheric boundary layer (MBL) depth. Moreover, a realistic cape caused gravity‐wave breaking. These simulations confirmed that the local terrain at Cape Mendocino is responsible for the collapse of the MBL in Shelter Cove. One striking feature in this study was that the flow started to accelerate far upstream of the change in coastline orientation, even in supercritical conditions. This phenomenon was most pronounced in the cases with the highest wind speeds. Using normalized wind speed and the Bernoulli function from calculated back‐ trajectories, it was concluded that this feature is not due to deviations from linearity or from the shallow‐water concept.

A-tract bending: insights into experimental structures by computational models

While solution structures of adenine tract (A-tract) oligomers have indicated a unique bend direction equivalent to negative global roll (commonly termed “minor-groove bending”), crystallographic data have not unambiguously characterized the bend direction; nevertheless, many features are shared by all A-tract crystal and solution structures (e.g. propeller twisting, narrow minor grooves, and localized water spines). To examine the origin of bending and to relate findings to the crystallographic and solution data, we analyze molecular dynamics trajectories of two solvated A-tract dodecamers: 1D89, d(CGCGA6CG), and 1D98, d(CGCA6GCG), using a new general global bending framework for analyzing bent DNA and DNA/protein complexes. It is significant that the crystallographically-based initial structures are converted from dissimilar to similar bend directions equivalent to negative global roll, with the average helical-axis bend ranging from 10.5 ° to 14.1 °. The largest bend occurs as positive roll of 12 ° on the 5′ side of the A-tracts (supporting a junction model) and is reinforced by gradual curvature at each A-tract base-pair (bp) step (supporting a wedge model). The precise magnitude of the bend is subtly sequence dependent (consistent with a curved general sequence model). The conversion to negative global roll only requires small local changes at each bp, accumulated over flexible moieties both outside and inside the A-tract. In contrast, the control sequence 1BNA, d(CGCGA2TTCGCG), bends marginally (only 6.9 °) with no preferred direction. The molecular features that stabilize the bend direction in the A-tract dodecamers include propeller twisting of AT base-pairs, puckering differences between A and T deoxyriboses, a narrow minor groove, and a stable water spine (that extends slightly beyond the A-tract, with lifetimes approaching 0.2 ns). The sugar conformations, in particular, are proposed as important factors that support bent DNA. It is significant that all these curvature-stabilizing features are also observed in the crystallographic structures, but yield overall different bending paths, largely due to the effects of sequences outside the A-tract. These results merge structural details reported for A-tract structures by experiment and theory and lead to structural and dynamic insights into sequence-dependent DNA flexibility, as highlighted by the effect of an A-tract variant of a TATA-box element on bending and flexibility required for TBP binding.

Sub-Milliarcsecond Imaging of Quasars and Active Galactic Nuclei

We have used the Very Long Baseline Array at 15 GHz to image the structure of 132 strong compact active galactic nuclei (AGNs) and quasars with a resolution better than 1 mas and a dynamic range typically exceeding 1000:1. These observations were made as part of a program to investigate the subparsec structure of quasars and AGNs and to study the changes in their structure with time. Many of the sources included in our study, particularly those located south of declination +35?, have not been previously imaged with milliarcsecond resolution. Each of the sources has been observed at multiple epochs. In this paper, we show images of each of the 132 sources that we have observed. For each source we present data at the epoch that had the best quality data. In a future paper we will discuss the kinematics derived from the observations at all epochs. Most of the sources we have observed show the canonical core-jet morphology with structure somewhat characteristic of the jets seen on arcsecond scales with the Very Large Array and Westerbork telescopes. The milliarcsecond jets generally appear one-sided, but two-sided structure is often found in lower luminosity radio galaxies and in high-luminosity quasars with gigahertz-peaked spectra. In many cases there is significant curvature, sometimes up to 90? or more, particularly close to the core. In other cases the jets have a more gradual curvature. In some sources there are multiple bends or twists along the jet, suggestive of a three-dimensional curved structure. Many of the jets may be described by a small number of apparently discrete components, but in other cases there appears to be a monotonically decreasing distribution of radio emission. Usually the structure is unresolved along the direction perpendicular to the jet, but a few sources have broad plumes. Much of the visible parsec-scale structure in compact radio sources can probably be explained as the projection of a relativistic beamed, twisted jet, which appears bright at those positions where it approaches the viewer. In some low-luminosity radio galaxies, the structure appears more symmetric at 2 cm than at longer wavelengths. The apparent long-wavelength asymmetry in these sources is probably due to absorption by intervening ionized material. A few sources contain only a single component, with any secondary feature at least 1000 times weaker. Peak rest-frame brightness temperatures are typically of the order of 1011?1012 K, with no evidence for any excess over the limit of 1012 K expected from inverse Compton cooling. We find no obvious correlation of radio morphology and the detection of gamma-ray emission by EGRET.

Measurement of mixed-mode crack profiles by holographic interferometry

Holographic interferometry was used to study the mixed-mode fracture characteristics of mortar. The nature of crack propagation in such quasibrittle materials and the theoretical model used to interpret the experimental results indicated that a highly sensitive measurement technique was required. The gradual curvature of the propagating crack at different sections of the specimen necessitated full-field observation capability. The nature of the problem made holographic interferometry the ideal technique for this application. To measure the in-plane components of the opening and sliding of the crack surfaces during propagation, a single holographic plate was placed very close to the specimen. This allowed four independent observations of any point on the specimen from the four corners of the plate without any need for additional optics of exposures. Double-exposure holograms were made at different crack-propagation stages. The developed plate was illuminated by an unexpanded reference beam to form a real image of the object and observe displacement fringes. Fringe data were interpreted by using computer software written for this research.

Space closure in adult patients using the segmented arch technique.

Periodontally compromised adult patients may benefit from modified appliance designs for space closure. TMA T-loops of .016" x .022" and .017" x .025" cross sections, with angulations incorporated via concentrated bends and gradual curvature bends are presented. The force systems these appliances produce are measured, and their clinical performances discussed. Templates for these T-loops are presented. By producing lower forces and higher moment to force ratios, this type of T-loop may benefit patients with bony loss.