Search

Secondary nucleation is an emerging approach for synthesizing higher-order supramolecular polymers with exciting topologies. However, a detailed understanding of growth processes and the synthesis of homochiral superstructures is yet to be demonstrated. Here, we report the non-covalent synthesis of dendritic homochiral superstructures using NIR triimide dyes as building blocks via a secondary nucleation elongation process. Detailed analysis of kinetics and temporal evolution of morphology indicates that the formation of dendritic homochiral superstructures proceeds via growth on the surface and growth from the surface of the seeds. The combination of these two processes leads to the formation of elegant homochiral superstructures with a size of ~0.4 mm 2 , having a superhelix at the center and helical fibres as branches. Moreover, these dendritic homochiral superstructures exhibit significantly high chiro-optical photoresponse with the magnitude of g factor reaching a value as high as 0.55 - 0.6. Thus, our results provide insights into the growth process of homochiral superstructures with dendritic topology, which can be critically important for the design and optimization of chiral-selective optoelectronic devices leveraging controlled self-assembly., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

We study the Bak-Sneppen evolution model on a regular hypercubic lattice in high dimensions. Recent work [Phys. Rev. E 108, 044109 (2023)2470-004510.1103/PhysRevE.108.044109] showed the emergence of the 1/f^{α} noise for the fitness observable with α≈1.2 in one-dimension (1D) and α≈2 for the random neighbor (mean-field) version of the model. We examine the temporal correlation of fitness in 2, 3, 4, and 5 dimensions. As obtained by finite-size scaling, the spectral exponent tends to take the mean-field value at the upper critical dimension D_{u}=4, which is consistent with previous studies. Our approach provides an alternative way to understand the upper critical dimension of the model. We also show the local activity power spectra, which offer insight into the return time statistics and the avalanche dimension.

We consider discrete models of kinetic rough interfaces that exhibit space-time scale invariance in height-height correlation. We use the generic scaling theory of Ramasco et al. [Phys. Rev. Lett. 84, 2199 (2000)0031-900710.1103/PhysRevLett.84.2199] to confirm that the dynamical structure factor of the height profile can uniquely characterize the underlying dynamics. We apply both finite-size and finite-time scaling methods that systematically allow an estimation of the critical exponents and the scaling functions, eventually establishing the universality class accurately. The finite-size scaling analysis offers an alternative way to characterize the anomalous rough interfaces. As an illustration, we investigate a class of self-organized interface models in random media with extremal dynamics. The isotropic version shows a faceted pattern and belongs to the same universality class (as shown numerically) as the Sneppen model (version A). We also examine an anisotropic version of the Sneppen model and suggest that the model belongs to the universality class of the tensionless Kardar-Parisi-Zhang (tKPZ) equation in one dimension.

The synthesis of supramolecular polymers with controlled architecture is a grand challenge in supramolecular chemistry. Although living supramolecular polymerization via primary nucleation has been extensively studied for controlling the supramolecular polymerization of small molecules, the resulting supramolecular polymers have typically exhibited one-dimensional morphology. In this report, we present the synthesis of intriguing supramolecular polymer architectures through a secondary nucleation event, a mechanism well-established in protein aggregation and the crystallization of small molecules. To achieve this, we choose perylene diimide with 2-ethylhexyl chains at the imide position as they are capable of forming dormant monomers in solution. Activating these dormant monomers via mechanical stimuli and hetero-seeding using propoxyethyl perylene diimide seeds, secondary nucleation event takes over, leading to the formation of three-dimensional spherical spherulites and scarf-like supramolecular polymer heterostructures, respectively. Therefore, the results presented in this study propose a simple molecular design for synthesizing well-defined supramolecular polymer architectures via secondary nucleation., (© 2024. The Author(s).)

Importance: Metastases to the submandibular gland (SMG) from oral cavity primaries are very rare. Hence, a gland-preserving level IB dissection technique is a feasible option without compromising the lymph node yield (LNY)., Objective: To assess the feasibility and noninferiority of the SMG-preserving dissection technique to the conventional en bloc removal of level IB in terms of LNY in patients with cN0 oral squamous cell carcinoma (OSCC) undergoing elective neck dissection., Design: Parallel-design, single-center, open-label, randomized controlled trial., Setting: Tertiary care health care center-Department of Otorhinolaryngology-Head & Neck Surgery, AIIMS Rishikesh., Participants: Thirty-eight (n = 38) participants with 46 (n = 46) neck dissection specimens of OSCC were randomly allocated (1:1) into gland-preserving (n 1  = 23) and en bloc (n 2  = 23) dissection groups., Intervention: Elective neck dissection comparing SMG-sparing level IB dissection technique versus en bloc level IB dissection., Main Outcome Measures: LNY, lymph node density, and level IB operative time in both groups were compared between groups (α < .05)., Results: Median LNY ( P  = .543) and lymph node density ( P  = 1.000) in level IB did not show significant differences between the groups. LNY in level IB by gland-preserving technique is also not inferior to the conventional en bloc dissection technique (mean difference = 0.217; 95% CI: [-0.597, 1.032]; P  = .593). The mean level IB operative time is significantly longer in the gland-preserving group ( P  < .001)., Conclusions and Relevance: None of the examined SMGs were involved by the tumor. SMG-preserving technique is noninferior to the traditional technique of level IB clearance and can be used in elective neck dissections without compromising the LNY. Functional neck dissection has greatly evolved to decrease patient morbidity, and this method can be adopted in case-specific situations., Trial Registration: The trial was registered in the Clinical Trials Registry-India (CTRI/2022/05/042344) on May 2, 2023, https://ctri.nic.in/., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

We study the one-dimensional Bak-Sneppen model for the evolution of species in an ecosystem. Of particular interest are the temporal fluctuations in fitness variables. We numerically compute the power spectral density and apply the finite-size scaling method to get data collapse. A clear signature of 1/f^{α} noise with α≈1.2 (long-time correlations) emerges for both local and global (or average) fitness noises. The limiting value of the spectral exponent, 0 or 2, corresponds to no interaction or a random neighbor version of the model, respectively. The local power spectra are spatially uncorrelated and also show an additional scaling, ∼1/L, in the frequency regime L^{-λ}≪f≪1/2, where L is the linear extent of the system.

Double post-synthetic modification is used for the π-extension of perylene based conjugated porous polymers (CPPs) using sequential annulative π-extension (APEX) reactions. This approach enabled us to synthesize new CPPs rendered with donor-acceptor rigid π-systems such as benzoperylene anhydride (BPA-CPP) and benzoperylene benzimidazole (BPBI-CPP) with distinct optical properties. Despite its low surface area, BPBI-CPP shows good CO 2 uptake and pH responsive behaviour owing to the presence of benzimidazole rings.

Air pollution has become one of the biggest challenges for human and environmental health. Major pollutants such as Nitrogen Dioxide (NO 2 ), Sulphur Dioxide (SO 2 ), Ozone (O 3 ), Carbon Monoxide (CO), and Particulate matter (PM 10 and PM 2.5 ) are being ejected in a large quantity every day. Initially, authorities did not implement the strictest mitigation policies due to pressures of balancing the economic needs of people and public safety. Still, after realizing the effect of the COVID-19 pandemic, countries around the world imposed a complete lockdown to contain the outbreak, which had the unexpected benefit of causing a drastic improvement in air quality. The present study investigates the air pollution scenarios over the Dublin city through satellites (Sentinel-5P and Moderate Resolution Imaging Spectroradiometer) and ground-based observations. An average of 28% reduction in average NO 2 level and a 27.7% improvement in AQI (Air Quality Index) was experienced in 2020 compared to 2019 during the lockdown period (27 March-05 June). We found that PM 10 and PM 2.5 are the most dominating factor in the AQI over Dublin., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Elsevier B.V. All rights reserved.)

We examine probability distribution for avalanche sizes observed in self-organized critical systems. While a power-law distribution with a cutoff because of finite system size is typical behavior, a systematic investigation reveals that it may also decrease with increasing the system size at a fixed avalanche size. We implement the scaling method and identify scaling functions. The data collapse ensures a correct estimation of the critical exponents and distinguishes two exponents related to avalanche size and system size. Our simple analysis provides striking implications. While the exact value for avalanches size exponent remains elusive for the prototype sandpile on a square lattice, we suggest the exponent should be 1. The simulation results represent that the distribution shows a logarithmic system size dependence, consistent with the normalization condition. We also argue that for the train or Oslo sandpile model with bulk drive, the avalanche size exponent is slightly less than 1, which differs significantly from the previous estimate of 1.11.

The hypothesis of self-organized criticality explains the existence of long-range "space-time" correlations, observed inseparably in many natural dynamical systems. A simple link between these correlations is yet unclear, particularly in fluctuations at an "external drive" timescale. As an example, we consider a class of sandpile models displaying nontrivial correlations. We apply the scaling method and determine spatial cross-correlation by establishing a relationship between local and global temporal correlations. We find that the spatial cross-correlation decays in a power-law manner with an exponent γ=1-δ, where δ characterizes a scaling of the total power of the global temporal process with the system size.

We propose a variant model of the Pólya urn process, where the dynamics consist of two competing elements: suppression of growth and enhancement of dormant character. Here the level of such features is controlled by an internal parameter in a random manner, so that the system self-organizes and characteristic observables exhibit scale invariance, suggesting the existence of criticality. Varying the internal control parameter, one can explain interesting universality classes for avalanche-type events. We also discuss different versions of the model. It is pointed out that such an underlying mechanism has earlier been noted to operate in a neural network.

We study survival time statistics in a noisy sample-space-reducing (SSR) process. Our simulations suggest that both the mean and standard deviation scale as ∼N/N^{λ}, where N is the system size and λ is a tunable parameter that characterizes the process. The survival time distribution has the form P&#95;{N}(τ)∼N^{-θ}J(τ/N^{θ}), where J is a universal scaling function and θ=1-λ. Analytical insight is provided by a conjecture for the equivalence between the survival time statistics in the noisy SSR process and the record statistics in a correlated time series modeled as a drifted random walk with Cauchy distributed jumps.

We consider the response of a memoryless nonlinear device that acts instantaneously, converting an input signal ξ(t) into an output η(t) at the same time t. For input Gaussian noise with power-spectrum 1/f^{α}, the nonlinearity can modify the spectral index of the output to give a spectrum that varies as 1/f^{α^{'}} with α^{'}≠α. We show that the value of α^{'} depends on the nonlinear transformation and can be tuned continuously. This provides a general mechanism for the ubiquitous 1/f noise found in nature.

Stochastic processes wherein the size of the state space is changing as a function of time offer models for the emergence of scale-invariant features observed in complex systems. I consider such a sample-space reducing (SSR) stochastic process that results in a random sequence of strictly decreasing integers {x(t)},0≤t≤τ, with boundary conditions x(0)=N and x(τ) = 1. This model is shown to be exactly solvable: P&#95;{N}(τ), the probability that the process survives for time τ is analytically evaluated. In the limit of large N, the asymptotic form of this probability distribution is Gaussian, with mean and variance both varying logarithmically with system size: 〈τ〉∼lnN and σ&#95;{τ}^{2}∼lnN. Correspondence can be made between survival-time statistics in the SSR process and record statistics of independent and identically distributed random variables.

We study a neural network model of interacting stochastic discrete two-state cellular automata on a regular lattice. The system is externally tuned to a critical point which varies with the degree of stochasticity (or the effective temperature). There are avalanches of neuronal activity, namely, spatially and temporally contiguous sites of activity; a detailed numerical study of these activity avalanches is presented, and single, joint, and marginal probability distributions are computed. At the critical point, we find that the scaling exponents for the variables are in good agreement with a mean-field theory.

We consider a directed Abelian sandpile on a strip of size 2×n, driven by adding a grain randomly at the left boundary after every T timesteps. We establish the exact equivalence of the problem of mass fluctuations in the steady state and the number of zeros in the ternary-base representation of the position of a random walker on a ring of size 3^{n}. We find that while the fluctuations of mass have a power spectrum that varies as 1/f for frequencies in the range 3^{-2n}≪f≪1/T, the activity fluctuations in the same frequency range have a power spectrum that is linear in f.