bluuebunny/crossref_metadata_2025 huggingface dataset:
Attractors and time averages for random maps
Authors: Araújo Vı́tor
Published: July 2002

Considering random noise in finite dimensional parameterized families of diffeomorphisms of a compact finite dimensional boundaryless manifold

M

, we show the existence of time averages for almost every orbit of each point of

M

, imposing mild conditions on the families; see Section 2.4. Moreover these averages are given by a finite number of physical absolutely continuous stationary probability measures.

We use this result to deduce that situations with infinitely many sinks and Hénon-like attractors are not stable under random perturbations, e.g., Newhouse’s and Colli’s phenomena in the generic unfolding of a quadratic homoclinic tangency by a one-parameter family of diffeomorphisms.

On considère un bruit aléatoire dans des familles paramétrées de dimension finie de difféomorphismes d’une variété compacte sans bord,

M

, de dimension finie, et on montre, sous certains conditions pas très fortes sur ces familles, l’existence de moyennes temporelles (assymptotiques) pour presque toute orbite de chaque point de

M

(
voir
Section 2.4). Ces moyennes sont données par un nombre fini de mesures de probabilité stationnaires physiques absolument continues.

On utilise ce résultat pour déduire que les situations de coexistence d’une infinité de puists et d’attracteurs de type Hénon ne sont pas stables par des perturbations aléatoires; par exemple, les phénomènes de Newhouse et de Colli dans le dédoublement générique d’une tangence homoclinique quadratique par une famille de difféomorphismes à un paramètre.
Minimization properties of Hill's orbits and applications to some N -body problems
Authors: Arioli Gianni , Gazzola Filippo , Terracini Susanna
Published: July 2002

We consider the periodic problem for a class of planar

N

-body systems in Celestial Mechanics. Our goal is to give a variational characterization of the Hill's (retrograde) orbits as minima of the action functional under some geometrical and topological constraints. The method developed here also turns out to be useful in the study of the full problem with

N

primaries each having at most two satellites.

On considère le problème périodique pour une certaine classe de systèmes de

N

-corps en Mécanique Céleste. Notre but est de donner une caractérisation variationnelle des orbites (rétrogrades) de Hill comme minima de la fonctionnelle d’action sous certaines contraintes géométriques et topologiques. La méthode ici développée est également utile pour l’étude du problème complet avec

N

corps primaires ayant chacun au plus deux satellites.
On the minimizers of the Ginzburg–Landau energy for high kappa: the axially symmetric case
Authors: Aftalion Amandine
Published: July 2002

The Ginzburg–Landau theory of superconductivity is examined in the case of a special geometry of the sample, the infinite cylinder. We restrict to axially symmetric solutions and consider models with and without vortices. First putting the Ginzburg–Landau parameter

κ

formally equal to infinity, the existence of a minimizer of this reduced Ginzburg–Landau energy is proved. Then asymptotic behaviour for large

κ

of minimizers of the full Ginzburg–Landau energy is analyzed and different convergence results are obtained. Our main result states that, when

κ

is large, the minimum of the energy is reached when there are about

κ

vortices at the center of the cylinder. Numerical computations illustrate the various behaviours.

Le modèle de Ginzburg–Landau des supraconducteurs est étudié dans le cas d’une géométrie cylindrique pour des solutions radiales, avec et sans vortex. Quand le paramètre de Ginzburg–Landau est infini, on prouve l’existence d’un minimum pour une énergie réduite. Puis on étudie le comportement asymptotique des minimiseurs pour

κ

grand et on obtient différents résultats de convergence. On montre en particulier que l’énergie est minimum pour une configuration où le nombre de vortex au centre du cylindre est de l’ordre de

κ

. Des calculs numériques illustrent les divers comportements.
Limit behaviour of thin insulating layers around multiconnected domains
Authors: Boutkrida Mohamed , Grenon Nathalie , Mossino Jacqueline , Moussa Gonoko
Published: July 2002

Let

Ω

be a bounded domain of

ℝ^{n}

, with boundary

∂Ω

. Let

Γ_0

and

Γ

be connected components of

∂Ω

. We assume that

Ω

is surrounded along

Γ_0

and

Γ

by thin insulating layers

Σ^ε_0

and

Σ^ε

of varying respective thicknesses

h^ε_0(s)

and

h^ε(s)

,

s

being the generic point of

Γ_0

and

Γ

. We denote by

Γ^ε_0

and

Γ^ε

the parts of

∂Σ^ε_0

and

∂Σ^ε

which do not meet

Ω

. We consider a class of quasilinear elliptic problems with different exponents (

p

in

Ω

,

q_0

in

Σ^ε_0

,

q

in

Σ^ε

) and with the following boundary conditions:

The restricted equations in

Σ^ε_0

and

Σ^ε

have nonconstant coefficients,

μ^ε_0

and

μ^ε

, in the form

μ^ε_0(x)=μ^ε_0(σ_0(x))

(respectively

μ^ε(x)=μ^ε(σ(x)))

,

σ_0

and

σ

being the respective projections on

Γ_0

and

Γ

. We predict the asymptotic behaviour of this problem as

h^ε_0

and

μ^ε_0

(respectively

h^ε

and

μ^ε

) tend to zero in a suitable sense, provided they are related in a convenient way.

Soit

Ω

un domaine borné de

ℝ^{n}

, de frontière

∂Ω

. Soient

Γ_0

et

Γ

des composantes connexes de

∂Ω

. Nous supposons que

Ω

est entouré le long de

Γ_0

et

Γ

par de fines couches isolantes

Σ^ε_0

et

Σ^ε

d'épaisseurs variables respectives

h^ε_0(s)

et

h^ε(s)

,

s

étant le point générique de

Γ_0

ou

Γ

. Nous désignons par

Γ^ε_0

et

Γ^ε

les parties de

∂Σ^ε_0

et

∂Σ^ε

qui ne bordent pas

Ω

. Nous considérons une classe de problèmes elliptiques quasilinéaires, avec des exposants de Sobolev différents (

p

dans

Ω

,

q_0

dans

Σ^ε_0

,

q

dans

Σ^ε

) et avec les conditions au bord suivantes :

Les équations restreintes à

Σ^ε_0

et

Σ^ε

ont des coefficients non-constants,

μ^ε_0

et

μ^ε

, de la forme

μ^ε_0(x)=μ^ε_0(σ_0(x))

(resp.

μ^ε(x)=μ^ε(σ(x)))

,

σ_0

et

σ

étant les projections respectives sur

Γ_0

et

Γ

. Nous prédisons le comportement asymptotique de ce problème, lorsque

h^ε_0

et

μ^ε_0

(resp.

h^ε

et

μ^ε

) tendent vers zéro simultanément, tout en vérifiant une relation de corrélation convenable.
Relaxation of multiple integrals below the growth exponent
Authors: Fonseca Irene , Malý Jan
Published: July 2002

The integral representation of the relaxed energies

\begin{matrix} \mathcal{F}^{q,p}\left(u,\Omega \right): =\inf_{\{u_n\}}\biggl\{\liminf_{n\to\infty}\int _{\Omega }F\left(x,u_{n},\nabla u_{n}\right)dx:u_{n} \in W^{1,q}\left(\Omega ,ℝ^{d}\right), \\ u_{n}\rightarrow u\text{ weakly in }W^{1,q}\left(\Omega ,ℝ^{d}\right) \biggr\}, \\
\mathcal{F}_{\text{loc}}^{q,p}\left(u,\Omega \right): = \inf_{\{u_n\}}\biggl\{\liminf_{n\to\infty}\int _{\Omega }F\left(x,u_{n},\nabla u_{n}\right)dx:u_{n} \in W_{\text{loc}}^{1,q}\left(\Omega ,ℝ^{d}\right), \\ u_{n}\rightarrow u\text{ weakly in }W^{1,q}\left(\Omega ,ℝ^{d}\right) \biggr\} \\
\end{matrix}

\begin{matrix} \begin{matrix} E:u\mapsto \int _{\Omega }F\left(x,u,\nabla u\right)dx, \\ \end{matrix} & u \in W^{1,q}\left(\Omega ,ℝ^{d}\right), \\ \end{matrix}

where

0 \leq F (ϰ,ζ,ξ) \leq C (1+|ζ|^r + |ξ|^q)

and

\max\left\{1,r\frac{N - 1}{N + r},q\frac{N - 1}{N}\right\} < p \leq q

, is studied. In particular,

W^{1,p}

-sequential weak lower semicontinuity of

E(\cdot)

is obtained in the case where

F = F(ξ)

is a quasiconvex function and

p > q(N − 1)/N

.

On étudie la représentation intégrale d’énergies relaxées

\begin{matrix} \mathcal{F}^{q,p}\left(u,\Omega \right): =\inf_{\{u_n\}}\biggl\{\liminf_{n\to\infty}\int _{\Omega }F\left(x,u_{n},\nabla u_{n}\right)dx:u_{n} \in W^{1,q}\left(\Omega ,ℝ^{d}\right), \\ u_{n}\rightarrow u\text{ faible dans }W^{1,q}\left(\Omega ,ℝ^{d}\right) \biggr\}, \\ \mathcal{F}_{\text{loc}}^{q,p}\left(u,\Omega \right): = \inf_{\{u_n\}}\biggl\{\liminf_{n\to\infty}\int _{\Omega }F\left(x,u_{n},\nabla u_{n}\right)dx:u_{n} \in W_{\text{loc}}^{1,q}\left(\Omega ,ℝ^{d}\right), \\ u_{n}\rightarrow u\text{ faible dans }W^{1,q}\left(\Omega ,ℝ^{d}\right) \biggr\} \\ \end{matrix}

de la fonctionnelle

\begin{matrix} E:u\mapsto \int _{\Omega }F\left(x,u,\nabla u\right)dx, & u \in W^{1,q}\left(\Omega ,ℝ^{d}\right), \\ \end{matrix}

où

0 \leq F (ϰ,ζ,ξ) \leq C (1+|ζ|^r + |ξ|^q)

et

\max\left\{1,r\frac{N - 1}{N + r},q\frac{N - 1}{N}\right\}< p \leq q

. En particulier, la

W^{1,p}

-semicontinuité inférieure séquentielle faible de

E(\cdot)

est obtenue dans le cas où

F = F(ξ)

est une fonction quasiconvexe et

p > q(N − 1)/N

.
Solitary waves of generalized Kadomtsev–Petviashvili equations
Authors: de Bouard Anne , Saut Jean-Claude
Published: July 2002

We classify the existence and non-existence cases for localized solitary waves of generalized Kadomtsev–Petviashvili equations according to the sign of the transverse dispersion coefficients and to the nonlinearity. We also prove regularity properties of the solitary waves.

Nous classifions les cas d’existence et de non-existence d’ondes solitaires localisées pour les équations de Kadomtsev–Petviashvili généralisées selon le signe des coefficients de la dispersion transverse et la puissance du terme non-linéaire. Nous montrons également des propriétés de régularité de ces ondes solitaires.
Convex symmetrization and applications
Authors: Trombetti Guido , Lions Pierre-Louis , Alvino Angelo , Ferone Vincenzo
Published: July 2002

We give a “generalized” version of the isoperimetric inequality when the perimeter is defined with respect to a convex, positively homogeneous function on

ℝ^n

. We use it to prove that, for any function

u

compactly supported in

ℝ^n

, the integral of a convex function of

Du

decreases when

u

is rearranged in the corresponding “convex” way. Similar arguments allow us, for example, to prove comparison results for solutions of the Dirichlet problem for elliptic equations when the differential operator satisfies suitable structure assumptions.

Nous donnons une version « généralisée å de l’inégalité isopérimétrique lorsque la définition du périmètre dépend d’une fonction convexe et positivement homogène sur

ℝ^n

. Cette inégalité est employée pour démontrer que, pour toutes les fonctions

u

avec support compact dans

ℝ^n

, l’intégrale d’une fonction convexe de

Du

décroît quand

u

est rearrangée à une façon « convexe å. Avec des arguments du même type nous démontrons, par exemple, les résultats de comparaison pour les solutions du problème de Dirichlet pour des équations elliptiques quand l’opérateur différentiel satisfait des hypothèses de structure convenables.
Classification générique de synthèses temps minimales avec cible de codimension un et applications
Authors: Bonnard B. , Launay G. , Pelletier M.
Published: July 2002

In this article we consider the problem of constructing the optimal closed loop control in the time minimal control problem, with terminal constraints belonging to a manifold of codimension one, for systems of the form

\.{\upsilon} = X + uY

,

c\in ℝ^2

,

ℝ^3

,

|u| ≤ 1

under generic assumptions. The analysis is localized near the terminal manifold and is motivated by the problem of controlling a class of chemical systems.

Soit un système de la forme

\.{\upsilon}(t) = X(\upsilon(t)) + u(t)Y(\upsilon (t)), \qquad \upsilon \in ℝ^{n}

X, Y

sont des champs de vecteurs analytiques,

u

une application mesurable bornée à valeurs dans

[−1, + 1]

et soit

N^*

une sous-variété analytique de

ℝ^n

, de codimension 1. Dans cet article, on étudie le problème suivant : construire la loi optimale

u^*

pour le problème de contrôle en temps minimal où la variété terminale est

N

, ceci au voisinage de

N

. On se restreint à étudier toutes les situations génériques lorsque

v\in ℝ^2

ou

ℝ^3

. Cette étude est motivée par un problème de contrôle de systèmes chimiques et sera appliquée au cas

A ↦ B ↦ C

.
A kinetic formulation for multi-branch entropy solutions of scalar conservation laws
Authors: Brenier Y. , Corrias L.
Published: July 2002

Multivalued solutions with a limited number of branches of the inviscid Burgers equation can be obtained by solving closed systems of moment equations. For this purpose, a suitable concept of
entropy
multivalued solutions with

K

branches is introduced.

On reconstruit les solutions multivoques de l’équation de Burgers sans viscosité, quand leur nombre de branches est connu
a priori
, en résolvant un système fermé d’équations de moments. A cet effet, on introduit un concept de solutions multivoques entropiques à

K

branches.
Blow-up results for vector-valued nonlinear heat equations with no gradient structure
Authors: Zaag Hatem
Published: July 2002

We construct a blow-up solution for the following nonlinear complex equation:

u_{t} = \Delta u + \left(1 + i\delta \right)\left|u\right|^{p - 1}u,u \in ℂ.

We also find the asymptotic profile near the singularity, and generalize the result to other vector-valued equations.

On construit une solution explosive de l’équation non linéaire complexe suivante:

u_{t} = \Delta u + \left(1 + i\delta \right)\left|u\right|^{p - 1}u,u \in ℂ.

On donne aussi son profil asymptotique au voisinage de la singularité, et on généralise le résultat à d’autres équations à valeurs vectorielles.
Équation de Burgers avec conditions initiales à accroissements indépendants et homogènes
Authors: Carraro Laurent , Duchon Jean
Published: July 2002

We study here solutions of inviscid Burgers equation with a stochastic initial value with homogeneous and independent increments without positive jumps. We define the notion of intrinsic statistical solution of this evolution equation and show that a family

(X (t); t ≥ 0)

of homogeneous Lévy processes is an intrinsic statistical solution of Burgers equation if and only if the exponent functions

ψ (t, w)

satisfy the differential equation:

∂_tψ = i ψ ∂_wψ

. The existence of such solutions follows then from the examination of that last equation. The case of a brownian initial condition is made explicit.

On s’intéresse ici aux solutions de l’équation de Burgers non visqueuse avec condition initiale à accroissements indépendants et homogènes, à sauts négatifs. On dégage la notion de solution statistique intrinsèque de cette équation d’évolution et on montre qu’une famille

(X (t); t ≥ 0)

de processus de Lévy homogènes est solution statistique intrinsèque de l’équation de Burgers si et seulement si les fonctions exposants

ψ (t, w)

satisfont l’équation:

∂_tψ = i ψ ∂_wψ

. L’étude de cette équation permet d’établir l’existence d’une telle solution. Le cas d’une condition initiale brownienne est explicité.
Comparison theorems for some quasilinear degenerate elliptic operators and applications to symmetry and monotonicity results
Authors: Damascelli Lucio
Published: July 2002

We prove some weak and strong comparison theorems for solutions of differential inequalities involving a class of elliptic operators that includes the

p

-laplacian operator. We then use these theorems together with the method of moving planes and the sliding method to get symmetry and monotonicity properties of solutions to quasilinear elliptic equations in bounded domains.

Nous prouvons quelques théorèmes de comparaison faible et fort pour solutions de certaines inéqualités différentielles liées à une classe d’opérateurs elliptiques qui comprend le

p

-laplacien. Ces théorèmes sont utilisés avec la méthode de « déplacement d’hyperplanes å et la méthode de « translation å pour obtenir des propriétés de symétrie et de monotonie des solutions d’équations elliptiques quasilinéaires dans des domaines bornés.
Local boundedness of minimizers of anisotropic functionals
Authors: Cianchi Andrea
Published: July 2002

The local boundedness of minimizers of functionals is proved under growth conditions depending on the full gradient.
On the structure of quasiconvex hulls
Authors: Zhang Kewei
Published: July 2002

We define the set

K_{q,e} ⊂ K

of quasiconvex extreme points for compact sets

K ⊂ M^{N×n}

and study its properties. We show that

K_{q,e}

is the smallest generator of

Q(K)

-the quasiconvex hull of

K

, in the sense that

Q(K_{q,e}) = Q(K)

, and that for every compact subset

W ⊂ Q(K)

with

Q(W) = Q(K)

,

K_{q,e} ⊂ W

. The set of quasiconvex extreme points relies on

K

only in the sense that

Q\left(K\right)_{q,e} \subset K_{q,e} \subset \overline{[Q\left(K\right)_{q,e}]}

. We also establish that

K_e ⊂ K_{q,e}

, where

K_e

is the set of extreme points of

C(K)

-the convex hull of

K

. We give various examples to show that

K_{q,e}

is not necessarily closed even when

Q(K)

is not convex; and that for some nonconvex

Q(K)

,

K_{q,e} = K_e

. We apply the results to the two well and three well problems studied in martensitic phase transitions.
On the non-locality of quasiconvexity
Authors: Kristensen Jan
Published: July 2002

It is shown that in the class of smooth real-valued functions on

n × m

matrices (

n ≥ 3

,

m ≥ 2

) there can be no “local condition” which is equivalent to quasiconvexity.

On démontre qu’il n’existe pas de condition locale qui dans l’espace des fonctions regulières est equivalente à celle de quasiconvexité.
Elastic knots in Euclidean 3-space
Authors: Von Der Mosel Heiko
Published: July 2002

This paper deals with the problem of minimizing the curvature functional

\int κ^2ds

on isotopy classes of closed knotted curves in

ℝ^3

. We show existence of minimizers under a given topological knot type and develop a regularity theory by analyzing different touching situations.

Dans cet article nous minimisons la fonctionnelle de courbure

\int κ^2ds

dans des classes d’isotopie des courbes fermées et nouées. L’existence des courbes minimales étant donné un type de nœud topologique est démontrée et une théorie sur la régularité est développée par l’analyse de situations de touchage différentes.
Poincaré's inequality and global solutions of a nonlinear parabolic equation
Authors: Souplet Philippe , Weissler Fred B.
Published: July 2002

We study the equation

u_t − Δu = u^p − μ|∇u|^q

,

t ≥ 0

in a general (possibly unbounded) domain

Ω ⊂ ℝ^N

. When

q ≥ p

, we show a close connection between the Poincaré inequality and the boundedness of the solutions. To be more precise, if

q > p

(or

q = p

and

μ

large enough), we prove global existence of all solutions for any domain

Ω

where the Poincaré inequality is valid. When

μ

is large enough, all solutions are bounded and decay exponentially to zero. Conversely, if

Ω

contains arbitrarily large balls (if

N < 2

and

Ω

is finitely connected, this means precisely that the Poincaré inequality does not hold), then there always exist unbounded solutions. Moreover, if

Ω = ℝ^N

, there exist global solutions which blow-up at every point in infinite time. Various qualitative properties of the solutions are also obtained.

Nous étudions l'équation

u_t − Δu = u^p − μ|∇u|^q

,

t ≥ 0

dans un domaine

Ω ⊂ ℝ^N

général, éventuellement non borné. Lorsque

q ≥ p

, nous montrons l'existence d'un lien étroit entre l'inégalité de Poincaré et le caractère borné des solutions. Plus précisément, si

q > p

(ou si

q = p

et

μ

est assez grand), nous prouvons l'existence globale de toutes les solutions, dans tout domaine

Ω

ou l'inégalité de Poincaré est vérifiée. Lorsque

μ

est suffisamment grand, toutes les solutions sont bornées et tendent exponentiellement vers zéro. Inversement, si

Ω

contient des boules de rayon arbitrairement grand (lorsque

N < 2

et

Ω

est finiment connexe, cela signifie exactement que l'inégalité de Poincaré n'a pas lieu), alors il existe toujours des solutions non bornées. De plus, si

Ω = ℝ^N

, il existe des solutions globales qui explosent en tout point en temps infini. Diverses propriétés qualitatives des solutions globales sont également obtenues.
Cyclic tensile stretch inhibition of nitric oxide release from osteoblast‐like cells is both G protein and actin‐dependent
Authors: Hara Fumihiko , Fukuda Kanji , Asada Shigeki , Matsukawa Masataka , Hamanishi Chiaki
Published: July 2002

Recent reports indicate the alteration of nitric oxide (NO) synthesis with mechanical stress loaded on the osteoblast and NO is considered to have a significant role in mechanotransduction. We found the involvement of guanine‐nucleotide‐binding regulatory proteins (G proteins), especially Gi, in stress‐inhibited NO release of osteoblast‐like cells (JOR:17;593–597, 1999). To determine further the mechanism involved in this process, we measured c‐Jun N‐terminal kinase/stress‐activated protein kinase (JNK/SAPK) activity under cyclic tensile stretch loaded on osteoblast‐like cells. Cyclic stretch significantly enhanced JNK/SAPK activity and pertussis toxin clearly reversed stress‐enhanced JNK/SAPK activity. Cytochalasin D, actin microfilament disrupting reagent, also abolished the stress activation of JNK/SAPK. We propose a model for signaling events induced by cyclic tensile stretch, namely a transmembrane mechanosensor which couples Gi‐protein, actin cytoskeleton and finally activates JNK/SAPK activity of osteoblasts. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
Genetic factors in anorexia nervosa
Authors: Kipman A. , Gorwood P. , Mouren-Siméoni M.C. , Adès J.
Published: July 2002

Anorexia nervosa is a severe and complex disorder with incompletely known vulnerability factors. It is generally recognized that anorexia nervosa is a familial disorder, but the majority of twin studies have shown that the concordance rate for monozygotic twins is higher (on average 44%) than for dizygotic twins (on average 12.5%). This difference in concordance rates shows that genetic factors, more than common familial environment, may explain why the `anorexia nervosa' phenotype runs in families. In order to estimate the heritability in the broad sense of anorexia nervosa according to published familial and twin studies, we first assessed the intrapair correlation between monozygotic and dizygotic twins, and secondly calculated the deviation threshold of relatives of affected probands from the relative mean. In this review, we obtained an estimation of the heritability at 0.72 according to all published controlled familial studies (six references quoted in MEDLINE®), and 0.71 for all published twin studies (59 references quoted in MEDLINE®). This estimation is close to the ones previously proposed, between 0.5 and 0.8.

Familial and twin studies may also help to define the boundaries of the phenotype, shedding light on the complex relationship between anorexia nervosa on the one hand, and bulimia nervosa, mood disorders, and alcoholism on the other. Demonstrating the importance of genetic factors in anorexia nervosa, and more specifically for anorexia of the restrictive type, requires not only prospective and adoption studies (which are still lacking), but also genetic polymorphisms analyses, which began very recently.
Women And Smoking (1)
Authors: Krulewitch Cara J.
Published: July 2002

Every ten seconds, somewhere in the world tobacco kills another victim. If current smoking trends continue, this toll will increase up to one tobacco‐caused death every three seconds over the next thirty to forty years ().
Physical and relational aggression as predictors of children's friendship experiences: Examining the moderating role of preference norms
Authors: Correia Stephanie , Brendgen Mara , Turgeon Lyse , Vitaro Frank
Published: April 2021

Aggressive behavior is generally detrimental to children's friendships, both in terms of having friends and in terms of keeping friends. Despite this general tendency, many aggressive children have friends and some of these friendships are stable. We examined the moderating role of preference norms in the classroom and child's sex in the association between children's physical and relational aggression and their friendship experiences. A total of 1135 children (M = 10.24 years, SD = 1.01) in Grades 4 to 6 completed a peer nomination inventory in the Fall (T1) and Spring (T2) of the same school year. Norms were operationalized as the class‐ and sex‐specific correlation between physical or relational aggression and social preference. Norms moderated associations between each form of aggression and number of friends. At T1, physical and relational aggression were concurrently associated with having more friends when norms favored this behavior and with fewer friends when norms were unfavorable. The latter effect was especially pronounced in girls. Over time, youth lost friends when norms favored physical aggression and gained friends when norms favored relational aggression. T1 friends' physical and relational aggression were strong predictors of new friends' aggressive behavior, suggesting that friends provide a type of norm more significant to new friend selection than norms of the peer group and individual aggressive behavior. Overall, our results suggest that physical and relational aggression are not necessarily detrimental to children's friendship experiences and may even be beneficial in specific social contexts.
Insulating Paper Cellulose with High Mechanical Performance and Low Polarizability: The Effect of Doping Concentration on Polyhedral Oligomeric Silsesquioxanes‐Modified Cellulose
Authors: Yang Lu , Gao Jin , Qiu Qinpan , Qin Jinshan , Peng Xiao , Tang Chao
Published: April 2021

To study the effect of doping concentration on polyhedral oligomeric silsesquioxane (POSS)‐modified cellulose and its internal mechanism, molecular dynamics is used to establish a pure cellulose model and 1, 2, 3, 4, and 5 wt% POSS‐modified cellulose models, and the cohesive energy density and solubility parameter, mechanical properties, free volume, mean square displacement, and polarizability are calculated at 343 K. The simulation results show that the addition of POSS effectively improves the compatibility and mechanical performance of cellulose and at the same time enhances its thermal stability. Among the five modified cellulose models, the modification effect of the 3 wt% POSS‐modified cellulose model is the best. It is also found that the addition of POSS effectively reduces the polarizability of cellulose and even the electric field distribution in the oil paper insulation system, so as to enhance the insulation of the transformer. With the increase in concentration, the polarizability decreases.
Agronomic approach to understanding climate change and food security
Authors: O'Brien Peter , Kral‐O'Brien Katherine , Hatfield Jerry L.
Published: April 2021

Climate impacts agricultural productivity and the distribution of crops grown around the world. Because the United States is a leader in food exports, climate change impacts in the United States have the potential to disproportionately affect the global food supply. Given the change in temperature, precipitation, and carbon dioxide occurring now and expected into the future, the potential for agroecosystems to produce sufficient quantities of food to meet world demand is in question. To address this question, the concept of yield gaps, as the difference between potential yield (PY) and farm or actual yield (FY), provides a framework for the evaluation of progress in production. Across all crops, there have been increases in both PY (breeding, technological advances) and FY (implementation of improved genetic resources and management practices); however, climate change threatens to diminish those advances due to temperature stresses and more uncertain precipitation patterns. Climate change will not only directly increase the yield gap in the future but also further indirectly widen the yield gap by the degradation of the soil resource due to interactions of climate and management. Modern agricultural systems must adapt to become more resilient to climate change, and the tools to this adaptation involve genetics, environmental monitoring, and evolving management practices. However, progress can only begin once agricultural systems are managed from a more holistic view of providing both quantity and quality of a more diverse mixture of agricultural crops that will provide sustainability, equity, nutrition, and a secure food future.
Enantio‐ and Diastereoselective Synthesis of Chiral Syn‐Aryl β‐Hydroxy α‐Amino Esters via Biocatalytic Dynamic Reductive Kinetic Resolution
Authors: Zhang Qing‐Chun , Lu Zuo‐Lin , Hu Chen , Zhu Kejie , Jiang Meifen , Huang Zedu , Chen Fener
Published: April 2021

Development of an efficient, stereoselective, sustainable synthesis of chiral aryl β‐hydroxy α‐amino acids and their derivatives is of paramount importance, owing to the broad utility of these molecules in pharmaceutical application and asymmetric synthesis. We report a systematic study on ketoreductase (KRED)‐catalyzed dynamic reductive kinetic resolution (DYRKR) of aryl α‐amino β‐keto esters 6, furnishing 20 structurally diverse chiral syn‐aryl β‐hydroxy α‐amino esters (syn‐(2S,3R)‐7) in moderate‐to‐excellent isolated yield (up to 93%), along with moderate‐to‐excellent diastereoselectivity (up to >99 : 1 dr) and excellent enantioselectivity (mostly >99% ee). The practical synthesis potential of our developed method was showcased by the asymmetric, chemo‐enzymatic total synthesis of thiamphenicol (1).
Hybrid Amyloid‐Based Redox Hydrogel for Bioelectrocatalytic H2 Oxidation
Authors: Duraffourg Nicolas , Leprince Maxime , Crouzy Serge , Hamelin Olivier , Usson Yves , Signor Luca , Cavazza Christine , Forge Vincent , Albertin Luca
Published: April 2021

An artificial amyloid‐based redox hydrogel was designed for mediating electron transfer between a [NiFeSe] hydrogenase and an electrode. Starting from a mutated prion‐forming domain of fungal protein HET‐s, a hybrid redox protein containing a single benzyl methyl viologen moiety was synthesized. This protein was able to self‐assemble into structurally homogenous nanofibrils. Molecular modeling confirmed that the redox groups are aligned along the fibril axis and are tethered to its core by a long, flexible polypeptide chain that allows close encounters between the fibril‐bound oxidized or reduced redox groups. Redox hydrogel films capable of immobilizing the hydrogenase under mild conditions at the surface of carbon electrodes were obtained by a simple pH jump. In this way, bioelectrodes for the electrocatalytic oxidation of H2 were fabricated that afforded catalytic current densities of up to 270 μA cm−2, with an overpotential of 0.33 V, under quiescent conditions at 45 °C.
Three‐Component Aminoarylation of Electron‐Rich Alkenes by Merging Photoredox with Nickel Catalysis
Authors: Jiang Heng , Yu Xiaoye , Daniliuc Constantin G. , Studer Armido
Published: April 2021

A three‐component 1,2‐aminoarylation of vinyl ethers, enamides, ene‐carbamates and vinyl thioethers by synergistic photoredox and nickel catalysis is reported. 2,2,2‐Trifluoroethoxy carbonyl protected α‐amino‐oxy acids are used as amidyl radical precursors. anti‐Markovnikov addition of the amidyl radical to the alkene and Ni‐mediated radical/transition metal cross over lead to the corresponding 1,2‐aminoarylation product. The radical cascade, which can be conducted under practical and mild conditions, features high functional group tolerance and broad substrate scope. Stereoselective 1,2‐aminoarylation is achieved using a L‐(+)‐lactic acid derived vinyl ether as the substrate, offering a novel route for the preparation of protected enantiopure α‐arylated β‐amino alcohols. In addition, 1,2‐aminoacylation of vinyl ethers is achieved by using an acyl succinimide as the electrophile for the Ni‐mediated radical coupling.
Strain‐Engineered Nano‐Ferroelectrics for High‐Efficiency Piezocatalytic Overall Water Splitting
Authors: Su Ran , Wang Zhipeng , Zhu Lina , Pan Ying , Zhang Dawei , Wen Hui , Luo Zheng‐Dong , Li Linglong , Li Fa‐tang , Wu Ming , He Liqiang , Sharma Pankaj , Seidel Jan
Published: April 2021

Developing nano‐ferroelectric materials with excellent piezoelectric performance for piezocatalysts used in water splitting is highly desired but also challenging, especially with respect to reaching large piezo‐potentials that fully align with required redox levels. Herein, heteroepitaxial strain in BaTiO3 nanoparticles with a designed porous structure is successfully induced by engineering their surface reconstruction to dramatically enhance their piezoelectricity. The strain coherence can be maintained throughout the nanoparticle bulk, resulting in a significant increase of the BaTiO3 tetragonality and thus its piezoelectricity. Benefiting from high piezoelectricity, the as‐synthesized blue‐colored BaTiO3 nanoparticles possess a superb overall water‐splitting activity, with H2 production rates of 159 μmol g−1 h−1, which is almost 130 times higher than that of the pristine BaTiO3 nanoparticles. Thus, this work provides a generic approach for designing highly efficient piezoelectric nanomaterials by strain engineering that can be further extended to various other perovskite oxides, including SrTiO3, thereby enhancing their potential for piezoelectric catalysis.
Cooperative Bond Activation and Facile Intramolecular Aryl Transfer of Nickel–Aluminum Pincer‐type Complexes
Authors: Graziano Brendan J. , Vollmer Matthew V. , Lu Connie C.
Published: April 2021

Pincer‐type nickel–aluminum complexes were synthesized using two equivalents of the phosphinoamide, [PhNCH2PiPr2]−. The Ni0–AlIII complexes, {(MesPAlP)Ni}2(μ‐N2) and {(MesPAlP)Ni}2(μ‐COD), where MesPAlP is (Mes)Al(NPhCH2PiPr2)2, were structurally characterized. The (PAlP)Ni system exhibited cooperative bond cleavage mediated by the two‐site Ni–Al unit, including oxidative addition of aryl halides, H2 activation, and ortho‐directed C−H bond activation of pyridine N‐oxide. One intriguing reaction is the reversible intramolecular transfer of the mesityl ring from the Al to the Ni site, which is evocative of the transmetalation step during cross‐coupling catalysis. The aryl‐transfer product,(THF)Al(NPhCH2PiPr2)2Ni(Mes), is the first example of a first‐row transition metal–aluminyl pincer complex. The addition of a judicious donor enables the Al metalloligand to convert reversibly between the alane and aluminyl forms via aryl group transfer to and from Ni, respectively. Theoretical calculations support a zwitterionic Niδ−–Alδ+ electronic structure in the nickel–aluminyl complex.
Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence
Authors: Pei Xiao‐Li , Guan Zong‐Jie , Nan Zi‐Ang , Wang Quan‐Ming
Published: April 2021

Acetelyenediide (C22−) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)6Ag7(C≡C)3](BF4)7 (2) and [(AuL)6AgCu6(C≡C)3](BF4)7 (3), L=phenylbis(2‐pyridyl)phosphine (PPhpy2). Single‐crystal X‐ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu‐C≡C‐AuL)M2Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu‐doping significantly increases the energy level of (C2‐Cu)‐involved occupied orbital, thus inducing interesting transition coupling of dual‐emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi‐congeneric metal components.
A Cooperatively Activatable, DNA‐based Fluorescent Reporter for Imaging of Correlated Enzymatic Activities
Authors: Fan Zetan , Zhao Jian , Chai Xin , Li Lele
Published: April 2021

The dynamic variation of the expression profile and spatial landscape of multiple enzymes are crucial factors influencing tumor progression and drug treatment. However, the comprehensive analysis of these events has been hampered by the limitations of existing imaging technologies. Here we report a cooperatively activatable, DNA‐based fluorescent reporter programmed to detect the correlated activity of dual enzymes, telomerase (TE) and apurinic/apyrimidinic endonuclease 1 (APE1), both in vitro and in vivo. The conformational change of the DNA probe can be orthogonally triggered through TE‐induced DNA elongation and APE1‐mediated specific cleavage, producing a fluorescent signal for imaging the activity of the two enzymes in an AND‐gated manner. Furthermore, we demonstrate the capability of the system for specific tumor imaging through “dual lock‐and‐key” strategy, and visualizing the correlated enzymatic activities during drug treatment of cancer.
Antioxidant packaging development and optimization using agroindustrial wastes
Authors: Santos Fabiana Helen , Siqueira Luana Elisa , Cardoso Giselle Pereira , Molina Gustavo , Pelissari Franciele Maria
Published: April 2021

The increasing use of non‐biodegradable materials and the difficulty in recycling most of the available packaging have been pushing the development of biodegradable packaging. In this study, the potential uses of agroindustrial wastes to produce biodegradable films with antioxidant capacity were investigated. Starch films were produced by casting method using bran from jaboticaba peel, mango peel, and broccoli stalk. The influence of the concentration or type of bran in the properties of the films was evaluated through a central composite design. The results were analyzed by response surface and desirability function. Except for elongation and water solubility, the fitted equations were predictive in all studied properties. The films prepared from a higher concentration of mango peel exhibited better antioxidant capacity, while the broccoli stalk had no significant effect on antioxidant properties. The optimal formulation of the film (2.8% of jaboticaba peel and 20.0% of mango peel) and their predicted response variables (0.8 MPa for tensile strength, 40.0 MPa for Young's modulus, 4.5 mg/ml for IC50, and 41.6% for inhibition percentage) were defined according to the results. The optimization was satisfactory and the film presented high antioxidant capacity and moderate mechanical properties, proving to be an alternative to replace plastic packaging.
The aminosilane functionalization of cellulose nanocrystal aerogel via vapor‐phase reaction and its CO2 adsorption characteristics
Authors: Xu Jing , Jia Peipei , Wang Xingjuan , Xie Zhongyuan , Chen Zhangyun , Jiang Hua
Published: April 2021

The cellulose nanocrystal (CNC) aerogel was functionalized using aminosilane via vapor‐phase reaction and then the modified CNC aerogel was characterized by several techniques such as Fourier transform infrared spectroscopy, FE‐SEM, and elemental analysis. Finally, the CO2 adsorption on the aminosilane‐grafted CNC aerogel was featured using a dual‐site Langmuir adsorption model. The result showed triethylamine significantly enhanced the amine loading, being 7.06 mmol g−1 at 120°C. The primary amine groups in the aminosilane survived the vapor‐phase reaction. The amine groups were homogeneously distributed inside the aerogel due to its porous structure. The dual‐site Langmuir model could well describe its CO2 sorption characteristics. The adsorption capacity was up to 2.57 mmolCO2 g−1 at 25°C and 101.33 kPa, of which the chemisorption entirely dominated, and it decreased only 3%–4% after six runs. Therefore, these features positively suggested the vapor‐phase reaction provided a new and feasible method to functionalize CNC aerogel for the capture of CO2.
Seasonal use of a macrotidal estuary by the endangered dwarf sawfish, Pristis clavata
Authors: Morgan David L. , Lear Karissa O. , Dobinson Emma , Gleiss Adrian C. , Fazeldean Travis , Pillans Richard D. , Beatty Stephen J. , Whitty Jeff M.
Published: April 2021

Sawfishes (Family: Pristidae) are one of the most imperilled fish families worldwide. There is an increasingly urgent need to better understand the biology, ecology, and population status of the five sawfish species to develop more effective conservation measures. The dwarf sawfish, Pristis clavata, is one of the least researched members of the pristids, with literature limited to analysing disparate datasets or collations of rare encounters in northern Australia.

This study examined the spatial ecology of dwarf sawfish using targeted surveys and acoustic telemetry to determine its habitat use in a macrotidal estuary in northern Australia. Seventeen dwarf sawfish were tagged with acoustic transmitters and monitored in the Fitzroy River estuary and adjacent King Sound (Kimberley, Western Australia) between August 2015 and November 2017.

Dwarf sawfish observed within the Fitzroy River estuary and King Sound were juveniles, ranging between 740 and 2,540 mm in total length. Catch per unit effort of dwarf sawfish in the late dry season was relatively high in the estuary, with the catch rate in 2015 being one of the highest reported for any sawfish species.

Acoustic detections revealed a distinct seasonal pattern in the use of different parts of the estuary and King Sound, which was found to be driven by salinity. Dwarf sawfish predominately occupied a single large pool near the terminus of the tidal limit in the late dry season (August–November), before transitioning to regions in closer proximity to the river mouth or in King Sound in the wet and early dry seasons (December–July).

Given the high abundance and residency of dwarf sawfish in the Fitzroy River estuary, this area is an important nursery for the species during the late dry season and should be formally recognized as a habitat protection area for the species.
Needs assessment in unmet healthcare and family support services: A survey of caregivers of children and youth with autism spectrum disorder in Delaware
Authors: Srinivasan Sudha , Ekbladh Annalisa , Freedman Brian , Bhat Anjana
Published: April 2021

The study aimed to collect data from families of children and youth with Autism Spectrum Disorder (ASD) in the state of Delaware, USA to understand their ongoing needs and challenges in accessing child healthcare and family support services. We analyzed responses from 263 caregivers of children and youth with ASD from 3 to 24 years using a statewide needs assessment survey. Over 50% caregivers indicated having unmet needs relative to both child/youth healthcare services and family support services. Between 24 and 38% caregivers expressed unmet needs for healthcare services such as social skills training, speech‐language therapy, behavioral intervention, and occupational therapy for their child and 20–24% expressed needs for family support services such as respite care, parent/sibling support groups, counseling, and babysitting support. Additionally, number of prior early interventions received, limitations in accessing healthcare services, and unmet needs for family support services significantly predicted child/youth unmet healthcare needs. Greater ASD severity and difficulties accessing child/youth healthcare services predicted participant's functional dependence on caregivers for activities of daily living. Together, these findings call for designing holistic, family‐centered interventions that address needs of both children and youth with ASD and their families.

Lay summary

A statewide needs assessment survey of caregivers of children and youth with ASD revealed that 50% responders had unmet needs relative to both child/youth healthcare services and family support services. Number of prior services received, limitations in accessing healthcare, and unmet needs for family support are linked to child/youth unmet healthcare needs. Severity of autism and difficulties accessing child/youth healthcare are associated with participant's functional dependence. Together, these findings call for placing the family at the heart of the service system in ASD.
Implications of Co‐Feeding Water on the Growth Mechanisms of Retained Species on a SAPO‐18 Catalyst during the Methanol‐to‐Olefins Reaction
Authors: Valecillos José , Hita Idoia , Sastre Enrique , Aguayo Andrés T. , Castaño Pedro
Published: April 2021

The dynamics of retained and deactivating species in a SAPO‐18 catalyst during the methanol‐to‐olefins reaction have been followed using a combination of ex‐situ and in‐situ techniques in differential and integral reactors.The retained species were analyzed using extraction, in‐situ FTIR and in‐situ UV‐vis spectroscopies combined with online product analysis (gas chromatography and mass spectrometry). The composition of the extracted soluble species was determined using gas chromatography‐mass spectrometry and that of the insoluble species using high‐resolution mass spectrometry. We observe a decrease in the formation and degradation rates of retained species when co‐feeding water, whereas the extent of the decreases is the same across the entire spectrum of retained molecules. This indicates that co‐feeding water unselectively quenches the formation of active and deactivating species. At the same time, the catalyst has an extended lifetime when co‐feeding water due to the diffusion of species (particularly olefins) out of the SAPO‐18 crystals, and subsequent growth of heavy polycyclic aromatic structures that imply less deactivation. These conclusions can be extrapolated to other MTO catalysts with relatively similar pore topology such as SAPO‐34 or SSZ‐13 structures.
Li[(FSO2)(n‐C4F9SO2)N]: A Difunctional Salt for Ethylene‐Carbonate‐ and Additive‐Free Electrolyte for Li‐Ion Cells
Authors: Ma Qiang , Song Ziyu , Liu Juanjuan , Zheng Liping , Zhang Heng , Huang Xuejie , Armand Michel , Feng Wenfang , Nie Jin , Zhou Zhibin
Published: April 2021

An ethylene carbonate (EC) free and additive‐free base electrolyte, simply comprising a solid‐electrolyte‐interphase (SEI)‐forming salt (i. e., lithium (fluorosulfonyl)(n‐nonafluorobutanesulfonyl)imide (Li[(FSO2)(n‐C4F9SO2)N], LiFNFSI)) and dimethyl carbonate (DMC), for stable cycling graphite||LiNi0.6Mn0.2Co0.2O2 (NMC622) full cells at different temperatures (i. e., 25 °C and 60 °C) is reported. The utilization of the LiFNFSI‐based, EC‐free electrolyte endows the graphite||NMC622 cell with superior cycling performances, especially at an elevated temperature of 60 °C, outperforming the lithium hexafluorophosphate (LiPF6)‐based ones with and without EC. X‐ray photoelectron spectroscopy and electrochemical impedance spectra analyses demonstrate that a thin, compact, and robust Li‐ion conductive SEI film is formed on the overall surface of the graphite anode in LiFNFSI‐DMC, while that formed in LiPF6‐DMC is discrete. These results suggest the potential application of LiFNFSI as a main conducting salt for building high‐performance LIBs with EC‐free electrolytes.
Nucleophilic Reactions of Osmanaphthalynes with PMe3 and H2O
Authors: Zhang Ming‐Xing , Lin Lu , Yang Xiaofei , Yin Jun , Zhu Jun , Liu Sheng Hua
Published: April 2021

Members of a new class of complexes, 2(CF3), 2(H), 2(Br), 2(I), and 2(OCH3), have been synthesized in a one‐pot method involving the treatment of osmanaphthalynes bearing corresponding substituents (1(CF3), 1(H), 1(Br), 1(I), and 1(OCH3)) with trimethylphosphine (PMe3) and water. The main reaction process involves two steps, namely a ligand‐exchange with trimethylphosphine and nucleophilic addition of water to the Os≡C bond of the osmanaphthalyne. The substituents have a significant influence on the rate of the reaction, as befits a nucleophilic addition. Fortunately, the key intermediate [1(OCH3)]′ could be successfully captured, and the detailed reaction mechanism has been explored with the aid of density functional theory (DFT) calculations, which were in excellent agreement with the experimental findings. All of the target complexes have been fully characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy, high‐resolution mass spectrometry, and elemental analysis.