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Electrochemical N2 fixation using renewable electricity in water provides a renewable route for artificial NH3 synthesis, whereas developing active and selective catalysts is highly necessary for an efficient N2 reduction reaction (NRR) process. In this work, we report ultrasmall iridium nanoparticles on reduced graphene oxide (Ir/RGO) as an effective NRR electrocatalyst, achieving an NH3 yield of 55.6 μg h−1 mg−1 with a faradaic efficiency of 15.3% at −0.3 V (RHE), outperforming most previously reported catalysts. Density functional theory calculations reveal that Ir is active for the NRR, while the RGO can further boost the NRR activity of supported Ir by imparting the enriched electrons on Ir that induce the upshift of the d-band center, resulting in enhanced N2 adsorption and a decreased energy barrier for the potential-determining step. [ABSTRACT FROM AUTHOR]

Using group rings and characters as in the theory of abelian difference sets, some nonexistence results for strong difference families are provided. Existences of strong difference families with base block size 3≤k≤9 are discussed. Via strong difference families, eight 2‐(v,k,λ) designs whose existences were unknown are constructed for (v,k,λ)∈{(3417,8,1),(3753,8,1),(2665,9,1),(3817,9,1),(4393,9,1),(7353,9,1),(12537,9,1),(345,9,3)}. [ABSTRACT FROM AUTHOR]

In this paper we introduce the 3-way intersection problem for G-designs, and we consider this problem for kite systems. Let bv=v(v-1)/8 and I3(v)={0,1,…,bv}\{bv-1}. Let J3(v)={s: there exist three kite systems of order v intersecting in s blocks}. We show that for any positive integer v≡0,1(mod8) and v≥8, J3(v)=I3(v). [ABSTRACT FROM AUTHOR]

We consider the existence problem for a semi-cyclic holey group divisible design of type [ABSTRACT FROM AUTHOR]

A cyclic balanced sampling plans excluding contiguous units, CBSEC (v , k , λ) , is equivalent to a cyclic K k -decomposition of λ (K v ∖ C v). Direct and recursive constructions are established for CBSEC with block size four. As a corollary, we show that a CBSEC (v , 4 , λ) (or a cyclic K 4 -decomposition of λ (K v ∖ C v)) exists for any v ≥ 12 and some integer λ ∈ { 1 , 2 , 3 , 4 , 6 } , with the possible exception of v ≡ 0 (mod 16). [ABSTRACT FROM AUTHOR]

Hedayat et al. first introduced balanced sampling plans for the exclusion of contiguous units. Wright detailed the results of a preliminary investigation of two-dimensional balanced sampling plans avoiding adjacent units (2-BSAs), and pointed out explicitly three types of 2-BSAs, which have different adjacency scheme, namely “Row and Column”, “Sharing a Border” and “Island”. This paper will provide more details for the three types of 2-BSAs from the point of view of design theory. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel luminescence enhanced sensor for β-hydroxybutyrate (β-HB) is developed based on a Tb3+ complex (TbL2 ). [•] A 1:1 binding model between TbL2 and β-HB is proposed. [•] The binding constant of TbL2 -β-HB is 9.3×105 M−1. [ABSTRACT FROM AUTHOR]

This study investigated the effects of priming time (5, 30 or 60 s), 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer’s concentrations (0.5, 1, 5, 10 and 20% (w/w)) and two neutral primers (5% (w/w) of 10-MDP-Na or EDTA-2Na) on bovine enamel microtensile bond strength (μTBS) using a novel prime-and-rinse approach. After priming, the enamel surfaces were thoroughly water-sprayed and dried before resin composite was placed. There was a significant influence of primer’s concentrations and priming time on bovine enamel μTBS when 10-MDP-containing primers were used (p < 0.001), revealing the optimal priming time (30 s) and the best combination (priming with 20% of 10-MDP for 30 s). The prime-and-rinse approach might be an innovative supplement to contemporary dental adhesive procedures. The neutral primer (5% of 10-MDP-Na) produced moderate enamel μTBS on highly polished enamel surfaces, while another neutral primer (5% of EDTA-2Na) failed, suggesting that chemical bonding of 10-MDP to enamel hydroxyapatite crystallites could yield detectable bond strengths on smooth enamel surfaces. [ABSTRACT FROM PUBLISHER]

Optical orthogonal codes are commonly used as signature codes for optical code-division multiple access systems. So far, research on 2-D optical orthogonal codes has mainly concentrated on the same autocorrelation and cross-correlation constraints. In this paper, we are concerned about optimal 2-D optical orthogonal codes with the autocorrelation \lambdaa and the cross-correlation 1. Some combinatorial constructions for 2-D (n\times m,k,\lambdaa,1)-optical orthogonal codes are presented. When k=3 and \lambdaa=2, the exact number of codewords of an optimal 2-D (n\times m,3,2,1)-optical orthogonal code is determined for any positive integers n\equiv 0,1,3,6,9,10\;(mod\;12) and m\equiv 2\;(mod\;4). [ABSTRACT FROM AUTHOR]

Abstract: Let denote the maximum possible size among all -OOCs. A -OOC is said to be optimal if its size is equal to . In this paper, the constructions and the sizes of optimal -OOCs are investigated. An upper bound for is improved. The exact value of with is given with the aid of computer search. An optimal -OOC with and , where prime is constructed recursively. The existence of -regular -OOCs for , and a prime satisfying a suitable congruence is established by direct constructions. Furthermore, the sizes of several new infinite classes of optimal -OOCs are obtained. In particular, for positive integer . [Copyright &y& Elsevier]

Abstract: In this paper, the necessary and sufficient conditions for the existence of a cyclic -GDD of type with exactly short block orbits are determined for all possible parameters and . [Copyright &y& Elsevier]

Abstract: In this paper, it is shown that an ASP exists for and . The existence of a -PDF is investigated by taking advantage of the relationship between ASPs and perfect difference families (PDFs). It is proved that a -PDF exists for and . Several recursive constructions for ASPs and PDFs are also presented. As a consequence, the existence results of an optimal -OOC is updated. [Copyright &y& Elsevier]

Strong difference families will be used to get: seven 2-designs whose parameter sets were previously in doubt; a strong indication about the existence of 2- ( p q , p , 1 ) designs with p ∈ { 13 , 17 } and q a prime power; a better asymptotic bound on prime powers q for which there exists an ( F p × F q , F p × { 0 } , k , λ ) relative difference family with p a prime power and k ∈ { p , p + 1 } . [ABSTRACT FROM AUTHOR]

We report that Zn nanosheets can serve as a cost-effective and efficient metallic catalyst towards the electrochemical reduction of NO to NH3 (NORR), delivering the maximum NO-to-NH3 faradaic efficiency of 88.2% and NH3 yield rate of 149.7 μmol h−1 cm−2. Theoretical calculations reveal that Zn active centers enable the effective activation and protonation of NO through a NOH pathway, while concurrently restraining H adsorption for HER inhibition, facilitating both NORR activity and selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: MDP (10-methacryloyloxydecyl dihydrogenphosphate) has been proven to possess chemical bonding ability to tooth hard tissues, but its contribution to the enamel bond strength has not been recognized. The aim of this study was to investigate the contribution of chemical bonding to the short- and long-term bovine enamel micro-tensile bond strengths (μTBS). Methods: The acid-etched enamel surfaces were treated without any primer (control) or with one of three MDP-containing primers (containing different ratio of MDP/HEMA/Bis-GMA, Kuraray Co.) for 5s, water-sprayed and air-dried. Subsequently, the pretreated enamel surfaces were applied with an etch-and-rinse adhesive Durafill Bond (Heraeus Kulzer) and placed with composite resin Durafill VS (Heraeus Kulzer). The specimens were prepared for μTBS tests after 24-h or 1-yr water storage. The etched enamel surfaces treated with or without MDP-containing primers were analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results: The acid-etched enamel treated with the MDP-primers for a very short time could produce the greater enamel μTBS than the control did (p <0.05), and change enamel micromorphology. No significant different μTBS were found between 24-h and 1-yr water storage (p >0.05). The chemical bonding of MDP on the enamel surfaces was re-confirmed by XPS. Significance: The additional chemical bonding of MDP around the enamel crystallites of the etched enamel substrate could significantly increase the short- and long-term enamel μTBS, and their μTBS surpass those of the etch-and-rinse adhesive alone. [Copyright &y& Elsevier]

The study of optical orthogonal codes has been motivated by an application in an optical code-division multiple access system. From a practical point of view, compared to one-dimensional optical orthogonal codes, two-dimensional optical orthogonal codes tend to require smaller code length. On the other hand, in some circumstances only with good cross-correlation one can deal with both synchronization and user identification. These motivate the study of two-dimensional optical orthogonal codes with better cross-correlation than auto-correlation. This paper focuses on optimal two-dimensional optical orthogonal codes with the auto-correlation [ABSTRACT FROM AUTHOR]

By giving previously unknown a pair of orthogonal orthomorphisms of cyclic groups of order 18 t + 9 for any positive integer t , we complete the existence spectrum of a pair of orthogonal orthomorphisms of cyclic groups. As a corollary, we complete the existence spectrum of a difference matrix with four rows over any finite abelian group. [ABSTRACT FROM AUTHOR]

Generalizing a result by Buratti et al.[M. Buratti, F. Rania, and F. Zuanni, Some constructions for cyclic perfect cycle systems, Discrete Math 299 (2005), 33-48], we present a construction for i-perfect k-cycle decompositions of the complete m-partite graph with parts of size k. These decompositions are sharply vertex-transitive under the additive group of [ABSTRACT FROM AUTHOR]

Given a subgroup H of a group (G , +) , a (G , H , k , 1) difference family (DF) is a set F of k -subsets of G such that { f − f ′ : f , f ′ ∈ F , f ≠ f ′ , F ∈ F } = G ∖ H. Let g Z g h be the subgroup of order h in Z g h generated by g. A (Z g h , g Z g h , k , 1) -DF is called cyclic and written as a (g h , h , k , 1) -CDF. This paper shows that for h ∈ { 2 , 3 , 6 } , there exists a (g h , h , 4 , 1) -CDF if and only if g h ≡ h (mod 12) , g ⩾ 4 and (g , h) ∉ { (9 , 3) , (5 , 6) }. As a corollary, it is shown that a 1-rotational Steiner system S (2 , 4 , v) exists if and only if v ≡ 4 (mod 12) and v ≠ 28. This solves the long-standing open problem on the existence of a 1-rotational S (2 , 4 , v). As another corollary, we establish the existence of an optimal (v , 4 , 1) -optical orthogonal code with ⌊ (v − 1) / 12 ⌋ codewords for any positive integer v ≡ 1 , 2 , 3 , 4 , 6 (mod 12) and v ≠ 25. We also give applications of our results to cyclic group divisible designs with block size four and optimal cyclic 3-ary constant-weight codes with weight four and minimum distance six. [ABSTRACT FROM AUTHOR]

Let G be a finite group and let k⩾2 be an integer. A (G,k,1)‐difference matrix (DM) is a k×∣G∣ matrix D=(dij) with entries from G, such that for all distinct rows x and y, the multiset of differences dxjdyj−1:1⩽j⩽∣G∣ contains each element of G exactly once. Let H be a finite abelian group and let D2H=〈H,b∣b2=1,bhb=h−1,h∈H〉 be the generalized dihedral group of H. It is proved that a (D2H,4,1)‐DM exists if and only if H is of even order and H is not isomorphic to Z4. Also for the nine non‐abelian groups G of order 16, we obtain (G,6,1)‐DMs over five of them, (G,5,1)‐DMs over three of them and a (G,4,1)‐DM over one of them. No (G,5,1)‐DM exists for this last group, where G=Q16. [ABSTRACT FROM AUTHOR]

Novák conjectured in 1974 that for any cyclic Steiner triple systems of order v with v ≡ 1 (mod 6) , it is always possible to choose one block from each block orbit so that the chosen blocks are pairwise disjoint. We consider the generalization of this conjecture to cyclic (v , k , λ) -designs with 1 ⩽ λ ⩽ k − 1. Superimposing multiple copies of a cyclic symmetric design shows that the generalization cannot hold for all v , but we conjecture that it holds whenever v is sufficiently large compared to k. We confirm that the generalization of the conjecture holds when v is prime and λ = 1 and also when λ ⩽ (k − 1) / 2 and v is sufficiently large compared to k. As a corollary, we show that for any k ⩾ 3 , with the possible exception of finitely many composite orders v , every cyclic (v , k , 1) -design without short orbits is generated by a (v , k , 1) -disjoint difference family. [ABSTRACT FROM AUTHOR]

This paper introduces almost partitionable sets (APSs) to generalize the known concept of partitionable sets. These notions provide a unified frame to construct Z‐cyclic patterned starter whist tournaments and cyclic balanced sampling plans excluding contiguous units. The existences of partitionable sets and APSs are investigated. As an application, a large number of optical orthogonal codes achieving the Johnson bound or the Johnson bound minus one are constructed. [ABSTRACT FROM AUTHOR]

We determine a necessary and sufficient condition for the existence of semicyclic holey group divisible designs with block size three and group type (n,mt). New recursive constructions on semicyclic incomplete holey group divisible designs are introduced to settle this problem completely. [ABSTRACT FROM AUTHOR]

Strong difference families of special types are introduced to produce new relative difference families from the point of view of both asymptotic existences and concrete examples. As applications, group divisible designs of type 3 0 u with block size 6 are discussed, r -rotational balanced incomplete block designs with block size 6 are derived for r ∈ { 6 , 10 } , and several classes of optimal optical orthogonal codes with weight 5, 6, 7, or 8 are obtained. [ABSTRACT FROM AUTHOR]