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Abstract The challenges posed by energy and environmental issues have forced mankind to explore and utilize unconventional energy sources. It is imperative to convert the abundant coalbed gas (CBG) into high value-added products, i.e., selective and efficient conversion of methane from CBG. Methane activation, known as the “holy grail”, poses a challenge to the design and development of catalysts. The structural complexity of the active metal on the carrier is of particular concern. In this work, we have studied the nucleation growth of small Co clusters (up to Co6) on the surface of CeO2(110) using density functional theory, from which a stable loaded Co/CeO2(110) structure was selected to investigate the methane activation mechanism. Despite the relatively small size of the selected Co clusters, the obtained Co x /CeO2(110) exhibits interesting properties. The optimized Co5/CeO2(110) structure was selected as the optimal structure to study the activation mechanism of methane due to its competitive electronic structure, adsorption energy and binding energy. The energy barriers for the stepwise dissociation of methane to form CH3*, CH2*, CH*, and C* radical fragments are 0.44, 0.55, 0.31, and 1.20 eV, respectively, indicating that CH* dissociative dehydrogenation is the rate-determining step for the system under investigation here. This fundamental study of metal-support interactions based on Co growth on the CeO2(110) surface contributes to the understanding of the essence of Co/CeO2 catalysts with promising catalytic behavior. It provides theoretical guidance for better designing the optimal Co/CeO2 catalyst for tailored catalytic reactions.

Clathrin-mediated endocytosis is one of the major pathways by which cells internalise cargo molecules. Recently it has been shown that clathrin triskelia can first assemble as flat lattices before the membrane starts to bend. However, for fully assembled clathrin lattices high energetic and topological barriers exist for the flat-to-curved transition. Here we explore the possibility that flat clathrin lattices grow with vacancies that are not visible in traditional imaging techniques but would lower these barriers. We identify the Eden model for cluster growth as the most appropriate modeling framework and systematically derive the four possible variants that result from the specific architecture of the clathrin triskelion. Our computer simulations show that the different models lead to clear differences in the statistical distributions of cluster shapes and densities. Experimental results from electron microscopy and correlative light microscopy provide first indications for the model variants with a moderate level of lattice vacancies.

The challenges posed by energy and environmental issues have forced mankind to explore and utilize unconventional energy sources. It is imperative to convert the abundant coalbed gas (CBG) into high value-added products, i.e., selective and efficient conversion of methane from CBG. Methane activation, known as the “holy grail”, poses a challenge to the design and development of catalysts. The structural complexity of the active metal on the carrier is of particular concern. In this work, we have studied the nucleation growth of small Co clusters (up to Co 6 ) on the surface of CeO 2 (110) using density functional theory, from which a stable loaded Co/CeO 2 (110) structure was selected to investigate the methane activation mechanism. Despite the relatively small size of the selected Co clusters, the obtained Co x /CeO 2 (110) exhibits interesting properties. The optimized Co 5 /CeO 2 (110) structure was selected as the optimal structure to study the activation mechanism of methane due to its competitive electronic structure, adsorption energy and binding energy. The energy barriers for the stepwise dissociation of methane to form CH 3 *, CH 2 *, CH*, and C* radical fragments are 0.44, 0.55, 0.31, and 1.20 eV, respectively, indicating that CH* dissociative dehydrogenation is the rate-determining step for the system under investigation here. This fundamental study of metal-support interactions based on Co growth on the CeO 2 (110) surface contributes to the understanding of the essence of Co/CeO 2 catalysts with promising catalytic behavior. It provides theoretical guidance for better designing the optimal Co/CeO 2 catalyst for tailored catalytic reactions.

Australia’s response to the human immunodeficiency virus type 1 (HIV-1) pandemic led to effective control of HIV transmission and one of the world’s lowest HIV incidence rates—0.14%. Although there has been a recent decline in new HIV diagnoses in New South Wales (NSW), the most populous state in Australia, there has been a concomitant increase with non-B subtype infections, particularly for the HIV-1 circulating recombinant form CRF01_(A)E. This aforementioned CRF01_(A)E sampled in NSW, were combined with those sampled globally to identify NSW-specific viral clades. The population growth of these clades was assessed in two-year period intervals from 2009 to 2017. Overall, 109 NSW-specific clades were identified, most comprising pairs of sequences; however, five large clades comprising ≥10 sequences were also found. Forty-four clades grew over time with one or two sequences added to each in different two-year periods. Importantly, while 10 of these clades have seemingly discontinued, the remaining 34 were still active in 2016/2017. Seven such clades each comprised ≥10 sequences, and are representative of individual sub-epidemics in NSW. Thus, although the majority of new CRF01_(A)E infections were associated with small clades that rarely establish ongoing chains of local transmission, individual sub-epidemics are present and should be closely monitored.

The cruise industry has been for the last couple decades one of the fastest growing sectors of the maritime economy. The level of development varies from geographical area, the Mediterranean being one of the most advanced. Current research focuses on the industry’s supply chain mainly from a business organization perspective and less in terms of spatial/regional impacts. This paper aims at investigating the spatial organization of the suppliers involved in the cruise supply chain. Alongside uncovering broad scientific insights, the paper’s ultimate aim is to offer policy recommendations to enhance the competitive advantage – via job creation and the expansion of the local maritime cluster – brought about by a cruise terminal.

The stage of steel crystallization is one of the most critical in the metallurgical production process as far as arise of the future product imperfections is concerned. This paper investigates some promising directions for the development of metallurgy concerning the casting and solidification of steel ingots to be used in the production of critically important items (i.e. items with enhanced reability) for power and heavy engineering industry. The authors consider, from the standpoint of cluster growth theory, the possibility of managing the crystallization process by supplying additional external energy. In particular, the authors pointed out that electroslag heating of the hot top of the ingot which is used to increase the metal utilization factor, can be applied not only as a way to minimize the effects of shrinkage phenomena (formation of physical heterogeneity), but also as a means of managing the crystallization process and thus managing the formation of other types of heterogeneity (chemical, structural) through external electromagnetic field. The factors affecting the chemical heterogeneity of the ingot and the susceptibility of steel to segregation are described. The importance of developing an ingot technological summary that provides detailed description of the physical, chemical and structural heterogeneities throughout the ingot’s cross-section, and its application in actual production is emphasized. The authors outline ways of using such a technological summary as a source of additional information about the ingot for the subsequent processing stages (i.e. forging, heat treatment) which would help to achieve the required quality of the finished product while minimizing its cost. The considered development directions are directly related to the issue of increasing the production capabilities and reducing the costs of produced metallurgical outputs.

Australia’s response to the human immunodeficiency virus type 1 (HIV-1) pandemic led to effective control of HIV transmission and one of the world’s lowest HIV incidence rates—0.14%. Although there has been a recent decline in new HIV diagnoses in New South Wales (NSW), the most populous state in Australia, there has been a concomitant increase with non-B subtype infections, particularly for the HIV-1 circulating recombinant form CRF01_AE. This aforementioned CRF01_AE sampled in NSW, were combined with those sampled globally to identify NSW-specific viral clades. The population growth of these clades was assessed in two-year period intervals from 2009 to 2017. Overall, 109 NSW-specific clades were identified, most comprising pairs of sequences; however, five large clades comprising ≥10 sequences were also found. Forty-four clades grew over time with one or two sequences added to each in different two-year periods. Importantly, while 10 of these clades have seemingly discontinued, the remaining 34 were still active in 2016/2017. Seven such clades each comprised ≥10 sequences, and are representative of individual sub-epidemics in NSW. Thus, although the majority of new CRF01_AE infections were associated with small clades that rarely establish ongoing chains of local transmission, individual sub-epidemics are present and should be closely monitored.

We consider a cluster growth model on ℤ d , called internal diffusion limited aggregation (internal DLA). In this model, random walks start at the origin, one at a time, and stop moving when reaching a site not occupied by previous walks. It is known that the asymptotic shape of the cluster is spherical. When dimension is 2 or more, we prove that fluctuations with respect to a sphere are at most a power of the logarithm of its radius in dimension d ≥ 2. In so doing, we introduce a closely related cluster growth model, that we call the flashing process, whose fluctuations are controlled easily and accurately. This process is coupled to internal DLA to yield the desired bound. Part of our proof adapts the approach of Lawler, Bramson and Griffeath, on another space scale, and uses a sharp estimate (written by Blachère in our Appendix) on the expected time spent by a random walk inside an annulus.

We consider internal diffusion limited aggregation in dimension larger than or equal to two. This is a random cluster growth model, where random walks start at the origin of the d-dimensional lattice, one at a time, and stop moving when reaching a site that is not occupied by previous walks. It is known that the asymptotic shape of the cluster is a sphere. When the dimension is two or more, we have shown in a previous paper that the inner (resp., outer) fluctuations of its radius is at most of order log(radius) [resp., log 2 (radius)]. Using the same approach, we improve the upper bound on the inner fluctuation to √log(radius) when d is larger than or equal to three. The inner fluctuation is then used to obtain a similar upper bound on the outer fluctuation.

Synthesis of magnetic nanoparticles is relevant to many applications in the fields of catalysis, energy storage, and biomedicine. Understanding the growth mechanisms and morphology of nanoparticles during inert gas condensation is crucial to rationally improve the performance of the final nanoparticles. In this work, molecular dynamics simulations are carried out to study the structural and thermodynamic behavior of Ni–Fe nanoparticles from homogenous vapor phase in Ar atmosphere. It is revealed that the final morphology of the resulting nanoparticles presents a spherical shape by cluster coalescence at high temperatures where the small clusters are liquid droplets prior to their collisions. However, probabilistic nucleation and cluster growth indicate that the occurrence of spherical shape is more controlled by the probability limits for different Fe concentrations. Meanwhile, a larger inert gas density induces a more efficient cooling effect leading to a larger probability control of the cluster formation with non-spherical shape by agglomeration. Furthermore, the solidification of the as-formed Ni–Fe clusters is examined by evaluating the evolution of crystalline and amorphous structure. The linear scaling-down dependence of the solidification temperature on the reciprocal of the nanoparticle size clearly signifies a linear size-depression effect for the liquid-to-solid phase change of Ni–Fe nanoparticles. Our findings thus extend the current understanding of inert gas condensation behavior and mechanisms of Ni–Fe nanoparticles from an atomic/molecular perspective. Graphical abstract