Thin Strings Research Articles

Vacuum Interaction of Topological Strings at Short Distances

The paper provides an extended overview of recent results obtained by the authors in the process of studying the vacuum interaction of topological cosmic strings at short distances, taking into account their transverse size a and the mass m of the quantized field. We consider the case of a massive real-valued scalar field with minimal coupling. It is shown that at the interstring distances significantly larger than the Compton length, lc=1/m, the Casimir effect is damped exponentially. On the other hand, at distances smaller than lc but much larger than the typical string width, the field-mass influence becomes insignificant. In this case, the partial contribution of a massive field to the Casimir energy is of the same order as the contribution of a massless one. At these distances, the string’s transverse size is insignificant also. However, at the interstring distances of the same order as a string radius, the energy of the vacuum interaction of thick strings may significantly surpass the one for two infinitely thin strings with the same mass per unit length.

Use of AI-based second harmonic generation digital pathology for predicting patient survival for triple negative breast cancer patients.

e12526 Background: Extracellular matrix (ECM) in the stromal region has been known to be associated with tumorigenesis and metastasis in breast cancers. About 10-20% of all breast cancers are triple-negative breast cancers (TNBC), considered to be more aggressive with poorer prognosis than other types of breast cancer. AI-based Second Harmonic Generation (SHG) digital pathology, which is a fully quantitative fibrosis assessment, has been widely used innon-alcoholic steatohepatitis (NASH) and is FDA approved primary endpoint in NASH phase 2 clinical trials. In oncology, AI-based SHG digital pathology has demonstrated its relevance in survival prognosis for hepatocellular carcinoma and renal cell carcinoma after surgical treatment, based on analysis of tumor and non-tumor tissue collagen parameters. In this study, we study its potential applications for survival prognosis of TNBC patients. Methods: 68 patients with TNBC were treated by breast-cancer excision surgery. Tumor and non-tumor tissue from excised mass was imaged by SHG microscope (Genesis200, HistoIndex Pte. Ltd., Singapore). Regular follow-up was performed for patients post-operatively. A total of 33 collagen morphology features for collagen strings were quantified, such as length/width of strings, number of long/short/thick/thin strings, from tumour and non-tumour tissues. We used these collagen parameters to build two survival prediction models (RFS-index and OS-index) to predict patient’s recurrence-free survival (RFS) and overall survival (OS) years. The models were validated using the leave-one-out method. Results: Both RFS-index and OS-index were created using 10 specific collagen parameters chosen by sequential selection methods from overall 33 collagen parameters evaluated. 9 out of 10 parameters were selected from non-tumour tissue. The RFS-index can differentiate patients with RFS≥3 years (n = 36) and RFS < 3 years (p < 0.001) with cut-off value of RFS-index = 0.50. The OS-index can differentiate patients with OS≥5 years (n = 42) and OS < 5 years (p < 0.001) with cut-off value of RFS-index = 0.55. The log-rank test showed RFS-index (p = 0.026) and OS-index (p < 0.001) can be used for prediction of disease-free and overall survival based on collagen parameters. Conclusions: SHG based AI-aided quantitative assessment of ECM collagen has been shown to correlate with survival rates of TNBC patients. This is a proof of concept study applying AI based digital pathology in helping predict survival rates for TNBC patients based on tumor and non-tumor tissue ECM collagen parameters. This could help identify patients with a higher risk of recurrence of disease and lower overall survival rates. Such patients can be followed-up more carefully, and be considered for earlier treatment interventions to improve their survival outcomes.

Directionality‐Aware Design of Embroidery Patterns

AbstractEmbroidery is a long‐standing and high‐quality approach to making logos and images on textiles. Nowadays, it can also be performed via automated machines that weave threads with high spatial accuracy. A characteristic feature of the appearance of the threads is a high degree of anisotropy. The anisotropic behavior is caused by depositing thin but long strings of thread. As a result, the stitched patterns convey both color and direction. Artists leverage this anisotropic behavior to enhance pure color images with textures, illusions of motion, or depth cues. However, designing colorful embroidery patterns with prescribed directionality is a challenging task, one usually requiring an expert designer. In this work, we propose an interactive algorithm that generates machine‐fabricable embroidery patterns from multi‐chromatic images equipped with user‐specified directionality fields. We cast the problem of finding a stitching pattern into vector theory. To find a suitable stitching pattern, we extract sources and sinks from the divergence field of the vector field extracted from the input and use them to trace streamlines. We further optimize the streamlines to guarantee a smooth and connected stitching pattern. The generated patterns approximate the color distribution constrained by the directionality field. To allow for further artistic control, the trade‐off between color match and directionality match can be interactively explored via an intuitive slider. We showcase our approach by fabricating several embroidery paths.

Эффект Лейденфроста на струнах

New manifestations of the Leidenfrost effect (levitation of limited volumes of liquid over an overheated surface) on smooth and morphologically complex thin metal strings are described for the first time. Various dynamic modes of Leidenfrost levitation are presented, including a new one - a combined thermohydrodynamic mechanism of levitation as a sum of the effects of a viscous vapor flow under a drop and a convective flow around a drop with a mixture of vapor + air due to natural convection. Keywords: Leidenfrost effect, thin strings, surface morphology, levitation mechanism, vapor layer.

A didactic proposal for the construction of the ellipse

The purpose of the present is to propose the construction of the ellipse in a didactic way in which the work deals with the exposure of a specific methodology for the 3rd year of high school when dealing with ellipse content. Followed by the results of the realization of a workshop aimed at the construction of the ellipse in a didactic way, constructed with low cost material, thereby proposing the teaching of mathematics in a more pleasant and effective way, where the ellipse equations were defined with the theoretical concept and afterwards, the gardener's method was used to construct this curve in a terrain, using ropes and civil construction fasteners, so that the student could concretize and apply this content in practice. After that, it was used for construction in the classroom using thread threads or thin strings to make the tracing and to finish it used the Geogebra software to finish the work showing the perfection of the curve explained in the classroom. The didactic process carried out showed a real interest of the students mainly with the use of the field practice. In conclusion, teaching mathematics in a didactic and interactive way provides a favorable environment for learning, stimulating students with a critical sense and an investigative spirit.

Tying up the Loose Ends: A Mathematically Knotted Protein.

Knots have attracted scientists in mathematics, physics, biology, and engineering. Long flexible thin strings easily knot and tangle as experienced in our daily life. Similarly, long polymer chains inevitably tend to get trapped into knots. Little is known about their formation or function in proteins despite >1,000 knotted proteins identified in nature. However, these protein knots are not mathematical knots with their backbone polypeptide chains because of their open termini, and the presence of a “knot” depends on the algorithm used to create path closure. Furthermore, it is generally not possible to control the topology of the unfolded states of proteins, therefore making it challenging to characterize functional and physicochemical properties of knotting in any polymer. Covalently linking the amino and carboxyl termini of the deeply trefoil-knotted YibK from Pseudomonas aeruginosa allowed us to create the truly backbone knotted protein by enzymatic peptide ligation. Moreover, we produced and investigated backbone cyclized YibK without any knotted structure. Thus, we could directly probe the effect of the backbone knot and the decrease in conformational entropy on protein folding. The backbone cyclization did not perturb the native structure and its cofactor binding affinity, but it substantially increased the thermal stability and reduced the aggregation propensity. The enhanced stability of a backbone knotted YibK could be mainly originated from an increased ruggedness of its free energy landscape and the destabilization of the denatured state by backbone cyclization with little contribution from a knot structure. Despite the heterogeneity in the side-chain compositions, the chemically unfolded cyclized YibK exhibited several macroscopic physico-chemical attributes that agree with theoretical predictions derived from polymer physics.

Automation Concepts for Industrial-Scale Production of Seaweed

In order to industrialize macroalgal cultivation in Norway, new automated methods and solutions for seeding, deployment and harvesting need to be developed. Today's solutions are time and resource demanding, still yielding volumes nationally in the range of 100–200 tons per year in total (not including wild harvest), while the potential is in the megaton range. Standardization of equipment and automation can be one way to upscale production. Here we present results from a design study of a module-based solution for industrial cultivation, with specific solutions for spinning of thin seedling strings onto longlines, and a robotic module for interaction with the submerged farm at deployment and harvest. A reduced-scale physical prototype of the farm concept with the robot has been built for testing of deployment and harvesting techniques. The concept has been named SPOKe: Standardized Production of Kelp.

A Scooping-Binding Robotic Gripper for Handling Various Food Products.

Food products are usually difficult to handle for robots because of their large variations in shape, size, softness, and surface conditions. It is ideal to use one robotic gripper to handle as many food products as possible. In this study, a scooping-binding robotic gripper is proposed to achieve this goal. The gripper was constructed using a pneumatic parallel actuator and two identical scooping-binding mechanisms. The mechanism consists of a thin scooping plate and multiple rubber strings for binding. When grasping an object, the mechanisms actively makes contact with the environment for scooping, and the object weight is mainly supported by the scooping plate. The binding strings are responsible for stabilizing the grasping by wrapping around the object. Therefore, the gripper can perform high-speed pick-and-place operations. Contact analysis was conducted using a simple beam model and a finite element model that were experimentally validated. Tension property of the binding string was characterized and an analytical model was established to predict binding force based on object geometry and binding displacement. Finally, handling tests on 20 food items, including products with thin profiles and slippery surfaces, were performed. The scooping-binding gripper succeeded in handling all items with a takt time of approximately 4 s. The gripper showed potential for actual applications in the food industry.

Elastic Rayleigh-Plateau instability: dynamical selection of nonlinear states.

A slender thread of elastic hydrogel is susceptible to a surface instability that is reminiscent of the classical Rayleigh-Plateau instability of liquid jets. The final, highly nonlinear states that are observed in experiments arise from a competition between capillarity and large elastic deformations. Combining a slender analysis and fully three-dimensional numerical simulations, we present the phase map of all possible morphologies for an unstable neo-Hookean cylinder subjected to capillary forces. Interestingly, for softer cylinders we find the coexistence of two distinct configurations, namely, cylinders-on-a-string and beads-on-a-string. It is shown that for a given set of parameters, the final pattern is selected via a dynamical evolution. To capture this, we compute the dispersion relation and determine the characteristic wavelength of the dynamically selected profiles. The validity of the "slender" results is confirmed via simulations and these results are consistent with experiments on elastic and viscoelastic threads.

Vibration-heating in ADR Kevlar suspension systems

The cryogenics group at NASA’s Goddard Space Flight Center has a long-standing development and test program for laboratory and space-flight adiabatic demagnetization refrigerators (ADRs). These devices are used to cool components to temperatures as low as 0.05 K. At such low temperatures the ADR systems can provide a few micro-Watts of cooling power, so it is important to minimize the conduction of heat to these cold stages from the surroundings. The cold ADR elements are held in place by thin tensioned strings made of Kevlar, chosen for its high strength and stiffness and low thermal conductivity. During laboratory testing, we have observed that occasional significant additional heat loads on the coldest ADR stages correlate with unusually high vibration levels in the cryostat due to a noisy mechanical cryocooler. We theorized that this heat results from plastic deformation of the Kevlar fibers and frictional interactions among them, driven by the cryostat vibrations. We describe tests and calculations performed in attempt to confirm this source of the heating.

Wavelength variation of a standing wave along a vertical spring

Hand-driven resonance can be observed readily in a number of mechanical systems including thin boards, rods, strings, and springs. In order to show such behavior in the vertical spring pictured in Fig. 1, a section of spring is grasped at a location about one meter from its free end and driven by small, circular motions of the hand. At driving frequencies of a few hertz, a dramatic standing wave is generated. One of the fascinating features of this particular standing wave is that its wavelength varies along the length of the spring.

Einstein-Gauss-Bonnet black strings at large D

We study the black string solutions in the Einstein-Gauss-Bonnet(EGB) theory at large D. By using the 1/D expansion in the near horizon region we derive the effective equations that describe the dynamics of the EGB black strings. The uniform and non-uniform black strings are obtained as the static solutions of the effective equations. From the perturbation analysis of the effective equations, we find that thin EGB black strings suffer from the Gregory-Laflamme instablity and the GB term weakens the instability when the GB coefficient is small, however, when the GB coefficient is large the GB term enhances the instability. Furthermore, we numerically solve the effective equations to study the non-linear instability. It turns out that the thin black strings are unstable to developing inhomogeneities along their length, and at late times they asymptote to the stable non-uniform black strings. The behavior is qualitatively similar to the case in the Einstein gravity. Compared with the black string instability in the Einstein gravity at large D, when the GB coefficient is small the time needed to reach to final state increases, but when the GB coefficient is large the time to reach to final state decreases. Starting from the point of view in which the effective equations can be interpreted as the equations for the dynamical fluid, we evaluate the transport coefficients and find that the ratio of the shear viscosity and the entropy density agrees with that obtained previously in the membrane paradigm after taking the large D limit.

Polarimetric analysis of stress anisotropy in nanomechanical silicon nitride resonators

We realise a circular gray-field polariscope to image stress-induced birefringence in thin (sub-micron thick) silicon nitride membranes and strings. This enables quantitative mapping of the orientation of principal stresses and stress anisotropy, complementary to, and in agreement with, finite element modeling. Furthermore, using a sample with a well-known stress anisotropy, we extract a value for the photoelastic (Brewster) coefficient of silicon nitride, C ≈ (3.4 ± 0.1) × 10−6 MPa−1. We explore possible applications of the method to analyse and quality-control stressed membranes with phononic crystal patterns.

Abiotic streamers in a microfluidic system.

In this work, we report the phenomenon of formation of particle aggregates in the form of thin slender strings when a polyacrylamide (PAM) solution, laden with polystyrene (PS) beads is introduced into a microfluidic device containing an array of micropillars. PAM and a dilute solution of PS beads are introduced into the microfluidic channel through two separate inlets and localized particle aggregation is found to occur under certain flow regimes. The particle aggregates initially have a string-like morphology and are tethered at their ends to the micropillar walls, while the structure remains suspended in the fluid medium. Such a morphology inspired us to name these structures streamers. The flow regimes under which streamer formation is observed are quantified through state diagrams. We discuss the streamer formation time-scales and also show that streamer formation is likely the result of the flocculation of PS beads. Streamer formation has implications in investigating particle-laden complex flows through porous media.

Physicochemical modeling of the main stages of formation of a chirally pure prebiotic world

The formation of a chirally pure prebiotic environment was modeled using solutions of chiral trifluoroacetylated amino alcohols (TFAAA). We have previously shown that, homochiral TFAAA solutions, molecularly thin strings are formed. In TFAAA-1 and TFAAA-5 solutions in heptane, the physicochemical annihilation of antipodes occurs, whereby isometric granules or a viscous liquid are formed from a racemic solution. In a heterochiral solution, the chiral polarization grows spontaneously, so that its chiral purity becomes high enough to produce TFAAA homochiral strings. A racemic solution of TFAAA-6 in CCl4 forms TFAAA homochiral strings of two opposite chiralities; i.e., the separation of the isomers takes place. It demonstrated two possible scenarios for the formation of a chirally pure system.

A note on $3$d-$1$d dimension reduction with differential constraints

Starting from three-dimensional variational models with energies subject to a general type of PDE constraint, we use Γ-convergence methods to derive reduced limit models for thin strings by letting the diameter of the cross section tend to zero. A combination of dimension reduction with homogenization techniques allows for addressing the case of thin strings with fine heterogeneities in the form of periodically oscillating structures. Finally, applications of the results in the classical gradient case, corresponding to nonlinear elasticity with Cosserat vectors, as well as in micromagnetics are discussed.

Six Degree-of-Freedom Haptic Simulation of a Stringed Musical Instrument for Triggering Sounds.

Six degree-of-freedom (DoF) haptic rendering of multi-region contacts between a moving hand avatar and varied-shaped components of a music instrument is fundamental to realizing interactive simulation of music playing. There are two aspects of computational challenges: first, some components have significantly small sizes in some dimensions, such as the strings on a seven-string plucked instrument (e.g., Guqin), which makes it challenging to avoid pop-through during multi-region contact scenarios. Second, deformable strings may produce high-frequency vibration, which requires simulating diversified and subtle force sensations when a hand interacts with strings in different ways. In this paper, we propose a constraint-based approach to haptic interaction and simulation between a moving hand avatar and various parts of a string instrument, using a cylinder model for the string that has a large length-radius ratio and a sphere-tree model for the other parts that have complex shapes. Collision response algorithms based on configuration-based optimization is adapted to solve for the contact configuration of the hand avatar interacting with thin strings without penetration. To simulate the deformation and vibration of a string, a cylindrical volume with variable diameters is defined with response to the interaction force applied by the operator. Experimental results have validated the stability and efficiency of the proposed approach. Subtle force feelings can be simulated to reflect varied interaction patterns, to differentiate collisions between the hand avatar with a static or vibrating string and the effects of various colliding forces and touch locations on the strings.

Evolution and End Point of the Black String Instability: Large D Solution.

We derive a simple set of nonlinear, (1+1)-dimensional partial differential equations that describe the dynamical evolution of black strings and branes to leading order in the expansion in the inverse of the number of dimensions D. These equations are easily solved numerically. Their solution shows that thin enough black strings are unstable to developing inhomogeneities along their length, and at late times they asymptote to stable nonuniform black strings. This proves an earlier conjecture about the end point of the instability of black strings in a large enough number of dimensions. If the initial black string is very thin, the final configuration is highly nonuniform and resembles a periodic array of localized black holes joined by short necks. We also present the equations that describe the nonlinear dynamics of anti-de Sitter black branes at large D.

Texture, microstructure and consumer preference of mango bars jellified with gellan gum

Studies for the development of a novel convenient fruit product based on mango puree and gellan gum were carried out. Two gellan types (low acyl-L and high acyl-H) used in specific L/H ratios (75/25, 50/50, 25/75) for an overall concentration of 1 g of gellan/100 g of puree were tested, in order to design different mango bars. The influence of the L/H gellan ratio on their texture properties (TPA and SR tests), microstructure (Cryo-Scanning Electron Microscopy) and texture sensory acceptance (Preference-Ranking test) was studied. The results obtained enabled to separate the bars in two groups: the ones showing greater hardness and brittleness (only L gellan, and L/H at the ratios of 75/25 and 50/50); and those presenting a softer structure with higher cohesiveness and springiness values (L/H of 25/75 and only H gellan). The microstructure of mango bars was consistent with the texture results. Those presenting higher hardness have shown a microstructure composed of a denser biopolymer network with lower pore size; while for softer bars with higher springiness, larger pores and thin strings were observed. From the Preference-Ranking test, the most appreciated mango bar in terms of texture was the one prepared with a L/H ratio of 25/75.

Investigation of the microscopic displacement mechanisms and macroscopic behavior of alkaline flooding at different wettability conditions in shaly glass micromodels

Among various chemical methods, alkaline flooding has a great potential for enhancing heavy oil recovery, especially for reservoirs which contain acidic crude oil. However, fundamental understanding about microscopic displacement mechanisms and macroscopic behavior during alkaline floods at different wettabilities is not well understood, especially in five-spot shaly models. In this work several alkaline floods are performed on a glass micromodel containing randomly distributed shale streaks at different wettability conditions. Various mechanisms responsible for enhancing heavy oil recovery during alkaline flooding are investigated at different wettability conditions. These mechanisms include IFT reduction, deformation of residual oil, pore wall transportation, inter-pore and intra-pore bridging of oil and alkaline solution, the flow of long thin oil strings, production of W/O emulsion at the front, formation of high non-uniform pressure gradient, production of O/W emulsion in the swept regions that leads to emulsification and entrainment and emulsification and entrapment, and wettability reversal (from oil-wet to water-wet and water-wet to oil-wet). The macroscopic investigation of the experiments shows that alkaline injection improves sweep efficiency via formation of W/O emulsion at the front. It also modifies the fingering pattern so that the displacing fluid penetrates and sweeps the oil from around and between the shales. It lingers the breakthrough and reduces the amount of bypassed oil so that a considerable increase in oil recovery factor is observed.