Switch-like behaviours in biochemical networks are of fundamental significance in biological signal processing, and exist as two distinct types: ultra-sensitivity and bistability. Here we propose two new models of a reversible covalent-modification cycle with positive autoregulation (PAR), a motif structure that is thought to be capable of both ultrasensitivity and bistability in different parameter

For the Schrödinger equation − d 2 u / d x 2 + q ( x ) u = λ u on a finite x-interval, there is defined an “asymmetry function” a ( λ ; q ) , which is entire of order 1/2 and type 1 in λ. Our main result identifies the classes of square-integrable potentials q ( x ) that possess a common asymmetry function a ( λ ) . For any given a ( λ ) , there is one potential for each Dirichlet spectral sequence

In this paper we prove a perturbative result for a class of ${\mathbb Z}^2$ actions on Heisenberg nilmanifolds that have Diophantine properties. Along the way we prove cohomological rigidity and obtain a tame splitting for the cohomology with coefficients in smooth vector fields for such actions.

This paper presents the rates of uniform strong consistency of wavelet estimation for nonparametric function in sup-norm loss by introducing an empirical process approach. A compact support assumption on the explanatory variable is commonly used in nonparametric regression analysis. In the article, we consider the wavelet estimation analysis without any assumption on the compacity of the support of

Semi-Markov processes are typical tools for modeling multi state systems by allowing several distributions for sojourn times. In this work, we focus on a general class of distributions based on an arbitrary parent continuous distribution function G with Kumaraswamy as the baseline distribution and discuss some of its properties, including the advantageous property of being closed under minima. In addition

A joint and unified vision of stochastic diffusion models associated with the family of hyperbolastic curves is presented. The motivation behind this approach stems from the fact that all hyperbolastic curves verify a linear differential equation of the Malthusian type. By virtue of this, and by adding a multiplicative noise to said ordinary differential equation, a diffusion process may be associated

This article studies the variables of entrepreneurship at the regional (countries) level proposed by the Global Entrepreneurship Monitor (GEM) in its periodic global reports. This response to the suggestions and concerns of various authors is related to the need to analyze the theoretical foundation of the variables used by GEM. The validity and reliability of GEM data for the scientific study of entrepreneurship

This paper introduces a new family of distributions based on the additive model structure. Three submodels of the proposed family are studied in detail. Two simulation studies were performed to discuss the maximum likelihood estimators of the model parameters. The log location-scale regression model based on a new generalization of the Weibull distribution is introduced. Three datasets were used to

We investigate a thermoelastic Bresse system with viscoelastic damping acting on the shear force and heat conduction acting on the bending moment. We show that with weaker conditions on the relaxation function and physical parameters, the solution energy has general and optimal decay rates. Some examples are given to illustrate the findings.

One of the central issues that must be resolved for a metaheuristic optimization process to work well is the dilemma of the balance between exploration and exploitation. The metaheuristics (MH) that achieved this balance can be called balanced MH, where a Q-Learning (QL) integration framework was proposed for the selection of metaheuristic operators conducive to this balance, particularly the selection

In the field of strategic marketing, the recency, frequency and monetary (RFM) variables model has been applied for years to determine how solid a database is in terms of spending and customer activity. Retailers almost never obtain data related to their customers beyond their purchase history, and if they do, the information is often out of date. This work presents a new method, based on the fuzzy

Metaheuristics are intelligent problem-solvers that have been very efficient in solving huge optimization problems for more than two decades. However, the main drawback of these solvers is the need for problem-dependent and complex parameter setting in order to reach good results. This paper presents a new cuckoo search algorithm able to self-adapt its configuration, particularly its population and

Two collocation-based methods utilizing the novel Bessel polynomials (with positive coefficients) are developed for solving the non-linear Troesch’s problem. In the first approach, by expressing the unknown solution and its second derivative in terms of the Bessel matrix form along with some collocation points, the governing equation transforms into a non-linear algebraic matrix equation. In the second

We consider the scalar autonomous initial value problem as solved by an explicit Runge-Kutta pair of orders 6 and 5. We focus on an efficient family of such pairs, which were studied extensively in previous decades. This family comes with 5 coefficients that one is able to select arbitrarily. We set, as a fitness function, a certain measure, which is evaluated after running the pair in a couple of

The computational cost and memory demand required by computational fluid dynamics (CFD) codes simulations can become very high. Therefore, the application of convolutional neural networks (CNN) in this field has been studied owing to its capacity to learn patterns from sets of input data, which can considerably approximate the results of the CFD simulations with relative low errors. DeepCFD code has

Urban public transport systems must be economically efficient and additionally environmentally sustainable. Available decision support systems, including multiple criteria decision models, allow identifying which urban public transport vehicles are acceptable and those that should no longer be used in efficient and environmentally friendly cities. Previous research has ranked urban public transport

A long-standing conjecture of Erdős and Simonovits asserts that for every rational number $r\in (1,2)$ there exists a bipartite graph H such that $\mathrm{ex}(n,H)=\Theta(n^r)$ . So far this conjecture is known to be true only for rationals of form $1+1/k$ and $2-1/k$ , for integers $k\geq 2$ . In this paper, we add a new form of rationals for which the conjecture is true: $2-2/(2k+1)$ , for $k\geq

We present a novel class of integrators for differential equations that are suitable for parallel in time computation, whose structure can be considered as a generalization of the extrapolation methods. Starting with a low order integrator (preferably a symmetric second order one) we can build a set of second order schemes by few compositions of this basic scheme that can be computed in parallel. Then

This paper will investigate the linear quadratic (LQ) control problem for a stochastic system with different intermittent observations. Different from traditional LQ control problems, two controllers with different information structures are considered to minimize a quadratic performance index. Specifically, the information sets available to two controllers are different and mutually exclusive (i.e

In industrial control systems, industrial infrastructure is often attacked by hackers. Due to the serious sample imbalance in industrial control data, the traditional machine learning method has poor performance in anomaly detection. In this paper, TrAdaboost algorithm is applied to industrial control anomaly detection. The samples that are easy to classify are taken as the source domain data, and

The latest science news, in brief.

Hear the biggest stories from the world of science | 28 July 2021

Jupiter’s upper atmosphere is considerably hotter than expected from the amount of sunlight that it receives1,2,3. Processes that couple the magnetosphere to the atmosphere give rise to intense auroral emissions and enormous deposition of energy in the magnetic polar regions, so it has been presumed that redistribution of this energy could heat the rest of the planet4,5,6. Instead, most thermospheric

Macroscale analogues1,2,3 of microscopic spin systems offer direct insights into fundamental physical principles, thereby advancing our understanding of synchronization phenomena4 and informing the design of novel classes of chiral metamaterials5,6,7. Here we introduce hydrodynamic spin lattices (HSLs) of ‘walking’ droplets as a class of active spin systems with particle–wave coupling. HSLs reveal

Reproductive longevity is essential for fertility and influences healthy ageing in women1,2, but insights into its underlying biological mechanisms and treatments to preserve it are limited. Here we identify 290 genetic determinants of ovarian ageing, assessed using normal variation in age at natural menopause (ANM) in about 200,000 women of European ancestry. These common alleles were associated with

During the splicing of introns from precursor messenger RNAs (pre-mRNAs), the U2 small nuclear ribonucleoprotein (snRNP) must undergo stable integration into the spliceosomal A complex—a poorly understood, multistep process that is facilitated by the DEAD-box helicase Prp5 (refs. 1,2,3,4). During this process, the U2 small nuclear RNA (snRNA) forms an RNA duplex with the pre-mRNA branch site (the U2–BS

Key to our understanding of how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber. Even in phases of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still has a band structure. Theoretical models for the band structure of liquid metals were formulated more than five decades

One in four women suffers from uterine leiomyomas (ULs)—benign tumours of the uterine wall, also known as uterine fibroids—at some point in premenopausal life. ULs can cause excessive bleeding, pain and infertility1, and are a common cause of hysterectomy2. They emerge through at least three distinct genetic drivers: mutations in MED12 or FH, or genomic rearrangement of HMGA23. Here we created genome-wide

Flooding affects more people than any other environmental hazard and hinders sustainable development1,2. Investing in flood adaptation strategies may reduce the loss of life and livelihood caused by floods3. Where and how floods occur and who is exposed are changing as a result of rapid urbanization4, flood mitigation infrastructure5 and increasing settlements in floodplains6. Previous estimates of

MFSD2A is a sodium-dependent lysophosphatidylcholine symporter that is responsible for the uptake of docosahexaenoic acid into the brain1,2, which is crucial for the development and performance of the brain3. Mutations that affect MFSD2A cause microcephaly syndromes4,5. The ability of MFSD2A to transport lipid is also a key mechanism that underlies its function as an inhibitor of transcytosis to regulate

Global concern over widely documented declines in pollinators1,2,3 has led to the identification of anthropogenic stressors that, individually, are detrimental to bee populations4,5,6,7. Synergistic interactions between these stressors could substantially amplify the environmental effect of these stressors and could therefore have important implications for policy decisions that aim to improve the

The topological protection of wave transport, originally observed in the context of the quantum Hall effect in two-dimensional electron gases1, has been shown to apply broadly to a range of physical platforms, including photonics2,3,4,5, ultracold atoms in optical lattices6,7,8 and others9,10,11,12. That said, the behaviour of such systems can be very different from the electronic case, particularly

Olfactory systems must detect and discriminate amongst an enormous variety of odorants1. To contend with this challenge, diverse species have converged on a common strategy in which odorant identity is encoded through the combinatorial activation of large families of olfactory receptors1,2,3, thus allowing a finite number of receptors to detect a vast chemical world. Here we offer structural and mechanistic

The genomes of virtually all organisms contain repetitive sequences that are generated by the activity of transposable elements (transposons). Transposons are mobile genetic elements that can move from one genomic location to another; in this process, they amplify and increase their presence in genomes, sometimes to very high copy numbers. In this Review we discuss new evidence and ideas that the activity

An animal’s nervous system changes as its body grows from birth to adulthood and its behaviours mature1,2,3,4,5,6,7,8. The form and extent of circuit remodelling across the connectome is unknown3,9,10,11,12,13,14,15. Here we used serial-section electron microscopy to reconstruct the full brain of eight isogenic Caenorhabditis elegans individuals across postnatal stages to investigate how it changes

Regulated cell death is an integral part of life, and has broad effects on organism development and homeostasis1. Malfunctions within the regulated cell death process, including the clearance of dying cells, can manifest in diverse pathologies throughout various tissues including the gastrointestinal tract2. A long appreciated, yet elusively defined relationship exists between cell death and gastrointestinal

Globally, there has been a recent surge in ‘citizens’ assemblies’1, which are a form of civic participation in which a panel of randomly selected constituents contributes to questions of policy. The random process for selecting this panel should satisfy two properties. First, it must produce a panel that is representative of the population. Second, in the spirit of democratic equality, individuals

Analysis reveals combinations of stressors that threaten pollinators.

A step closer to predicting and treating early menopause.

International coalition aims to identify how universities use impact factors and related metrics.

Let K be a set of positive integers and let G be an additive group. A (G,K,1) difference packing is a set of subsets of G with sizes from K whose list of differences covers every element of G at most once. It is balanced if the number of blocks of size k∈K does not depend on k. In this paper, we determine a balanced (Z4u×Z8v,{4,5},1) difference packing of the largest possible size whenever uv is odd

Let m be a positive integer, and γ be a non-zero element of F2m. The Lee distance of all cyclic codes and (1+uγ)-constacyclic codes of length 2s over F2m+uF2m is completely determined. In particular, it is shown that the Lee distance of such codes is independent of the choice of a trace orthogonal basis of F2m.

Upon reading the famous book on integral transforms volume II by Erdeyli et al., we encounter a formula which we use to derive a Mellin transform given by , where the parameters , and are general complex numbers. This Mellin transform will be derived in terms of the Lerch function and is not listed in current literature to the best of our knowledge. We will use this transform to create a table of definite

As the two largest economies in the world, the investor sentiment and stock return of China and the United States are the focus of global attention. In this paper, we study the dynamic spillover effects of investor sentiment and return between China and the United States. First, we use the relative price differences of 9 dual-listed companies in China and the United States simultaneously to verify

In April 2017, the Chinese government announced a plan to establish a national new district: the Xiong’an New Area (hereinafter referred to as Xiong’an). Xiong’an plays a major role in optimizing the layout of Beijing-Tianjin-Hebei city cluster, promoting the rapid development of regional cities and cultivating new drivers of innovative economy. As a result, Xiong’an is recognized in China as a millennium

With the prosperity of venture capital, all kinds of government venture capital guiding funds have sprung up, and the scale is explosive growth. However, the current investment of government guiding funds in enterprises has not fundamentally solved the financial difficulties in the early development of enterprises. This study examines the determinants of investment timing of government guiding funds

The spillovers of β-coronaviruses in humans and the emergence of SARS-CoV-2 variants highlight the need for broad coronavirus countermeasures. We describe five monoclonal antibodies (mAbs) cross-reacting with the stem helix of multiple β-coronavirus spike glycoproteins isolated from COVID-19 convalescent individuals. Using structural and functional studies we show that the mAb with the greatest breadth

Let G be a finite group and let K = x G be the conjugacy class of an element x of G. In this paper, it is proved that if N is a normal subgroup of G such that the coset x N is the union of K and K − 1 (the conjugacy class of the inverse of x), then N and the subgroup ⟨ K ⟩ are solvable. As an application, we prove that if there exists a natural number n ≥ 2 such that K n = K ∪ K − 1 , then ⟨ K ⟩ is solvable

We study invariance for eigenvalues of selfadjoint Sturm–Liouville operators with local point interactions. Such linear transformations are formally defined by H ω : = − d 2 d x 2 + V ( x ) + ∑ n ∈ I ω ( n ) δ ( x − x n ) or similar expressions with δ ′ instead of δ. In a probabilistic setting, we show that a point is either an eigenvalue for all ω or only for a set of ω's of measure zero. Using classical

In this note, we obtain new classification results for static and V-static manifolds under pinching conditions of two different kinds. Firstly, we prove a classification result in higher dimensions assuming a condition of nonnegative Ricci curvature. This extends some recently obtained gap results on the traceless Ricci tensor. Furthermore, we employ the construction of an Einstein manifold associated

Chan studied the cubic partition function a(n), the number of partitions of a positive integer n where the even parts appear in two colors. Also, he obtained an infinite family of congruences modulo large powers of 3 for a(n), which are analogues to the Ramanujan-type congruences. Let \(\overline{a}_\ell (n)\) denote the number of \(\ell \)-regular cubic partitions of n where the first occurrence of

In this short note, we study the prescribed Q-curvature equation with a singularity at the origin in \({\mathbb {R}}^4\), namely, $$\begin{aligned} \Delta ^2u=(1-|x|^p)e^{4u}-c\delta _0\quad \text {in}\quad {\mathbb {R}}^4 \end{aligned}$$ under a finite volume condition, where \(p>0\) and \(c\in {\mathbb {R}}\). We prove the nonexistence of normal solutions to the above equation. This partly generalizes

A longstanding conjecture asserts that every finite nonabelian p-group admits a noninner automorphism of order p. In this paper, we give a lower bound for the coclass of finite nonabelian p-groups G having no noninner automorphism of order p leaving the Frattini subgoup \(\Phi (G)\) elementwise fixed. As a consequence, the verification of the conjecture is reduced to the case of finite nonabelian p-groups

In this paper, we give characterizations of the category of finitely generated projective modules having a right rejective chain. By focusing on the characterizations, we give sufficient conditions for right rejective chains to be total right rejective chains. Moreover, we prove that Nakayama algebras with heredity ideals, locally hereditary algebras and algebras of global dimension at most two satisfy

A sequence $\left \{g_k\right \}_{k=1}^{\infty }$ in a Hilbert space ${\cal H}$ has the expansion property if each $f\in \overline {\text {span}} \left \{g_k\right \}_{k=1}^{\infty }$ has a representation $f=\sum _{k=1}^{\infty } c_k g_k$ for some scalar coefficients $c_k.$ In this paper, we analyze the question whether there exist small norm-perturbations of $\left \{g_k\right \}_{k=1}^{\infty }$

The norm of a partition is defined as the product of its parts. This paper aims to conduct a thorough study of norms of prime partitions which are partitions with all prime parts. The analysis begins by defining rp(i,n), called the primal norm counting function, which refers to number of times i appears as a norm to the prime partitions of n. The generating function for this function is deduced, using

We give an asymptotic formula with a power saving error term for traces of CM values of a generic class of weak Maass forms. We apply this result to study the asymptotic distribution of several arithmetic functions, including the partition function, the Andrews smallest parts function, and the coefficients of Ramanujan's mock theta function f ( q ) .

APPLIED BIOLOGICAL SCIENCES Trichonephila clavata weaving an orb web. Mechanical properties of spider silk A synthetic material akin to spider silk—a highly elastic structural protein with more tensile strength than steel—could be exploited across a range of industrial applications. Researchers have engineered genetically optimized organisms that artificially spin recombinant proteins...

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) associated with the destruction of oligodendrocyte-produced myelin, which results in neuron and oligodendrocyte loss (1, 2). The dysregulated activity of cells of the adaptive immune system, specifically T cells and B cells, plays an important role in MS pathology, particularly during the relapsing–remitting phase

Recently, the interest in charged polymers has been rapidly growing due to their uses in energy storage and transfer devices. Yet, polymer electrolyte-based devices are not on the immediate horizon because of the low ionic conductivity. In the present study, we developed a methodology to enhance the ionic conductivity of charged block copolymers comprising ionic liquids through the electrostatic control