On the normality of pp-ary bent functions

Depending on the parity of $n$ and the regularity of a bent function $f$ from $\mathbb F_p^n$ to $\mathbb F_p$, $f$ can be affine on a subspace of dimension at most $n/2$, $(n-1)/2$ or $n/2- 1$. We point out that many $p$-ary bent functions take on this bound, and it seems not easy to find examples for which one can show a different behaviour. This resembles the situation for Boolean bent functions of which many are (weakly) $n/2$-normal, i.e. affine on a $n/2$-dimensional subspace. However applying an algorithm by Canteaut et.al., some Boolean bent functions were shown to be not $n/2$- normal. We develop an algorithm for testing normality for functions from $\mathbb F_p^n$ to $\mathbb F_p$. Applying the algorithm, for some bent functions in small dimension we show that they do not take on the bound on normality. Applying direct sum of functions this yields bent functions with this property in infinitely many dimensions.Comment: 13 page

Secondary constructions of vectorial pp-ary weakly regular bent functions

In \cite{Bapic, Tang, Zheng} a new method for the secondary construction of vectorial/Boolean bent functions via the so-called $(P_U)$ property was introduced. In 2018, Qi et al. generalized the methods in \cite{Tang} for the construction of $p$-ary weakly regular bent functions. The objective of this paper is to further generalize these constructions, following the ideas in \cite{Bapic, Zheng}, for secondary constructions of vectorial $p$-ary weakly regular bent and plateaued functions. We also present some infinite families of such functions via the $p$-ary Maiorana-McFarland class. Additionally, we give another characterization of the $(P_U)$ property for the $p$-ary case via second-order derivatives, as it was done for the Boolean case in \cite{Zheng}

Physical Models for the Early Evolution of Cell Membranes

Cells use lipid membranes to organize and define their chemical environments. All cell membranes are based on a common structure: bilayers composed of phospholipids with two hydrocarbon chains. How did biology converge on this particular solution for cellular encapsulation? The first cell membranes are proposed to have assembled from simple, single-chain lipids, such as fatty acids and their derivatives, which would have been available in the prebiotic environment. Here we argue that the physical properties of fatty acid membranes would have made them well suited for a role as primitive cell membranes and predisposed their evolution to modern, phospholipid-based membranes. We first considered models for primitive membrane self-assembly, which faces significant concentration barriers due to the entropic cost of aggregation and the solubility of single-chain lipids. We therefore identified two physical mechanisms by which fatty acid membrane assembly can proceed from dilute solutions. Thermal diffusion columns, a proposed prebiotic concentration method, drive the formation of fatty acid vesicles by concentrating an initially isotropic solution past the critical concentration necessary for aggregation. Alternatively, mixtures of fatty acids with varying chain lengths, the expected products of abiotic lipid synthesis, intrinsically reduce the concentration barrier to aggregation through their polydispersity. These results motivated us to better understand the phase behavior of fatty acids in solutions. We found that the composition of fatty acid aggregates, whether vesicles or micelles, is also determined by concentration. Fatty acid vesicles feature significant amounts of coexisting micelles, whose abundance is enriched in low concentration solutions. We utilized this micelle-vesicle equilibrium to drive the growth of pre-existing fatty acid vesicles by changing amphiphile concentration. We next considered the evolution of phospholipid membranes, which was a critical and necessary step for the early evolution of cells. We found that the incorporation of even small amounts of phospholipids drives the growth of fatty acid vesicles by competition for monomers with neighboring vesicles lacking phospholipids. This competitive growth would have provided a strong selective advantage for primitive cells to evolve the catalytic machinery needed to synthesize phospholipids from their single-chain precursors. Growth is caused by any relative difference in phospholipid content, suggesting an evolutionary arms race among primitive cells for increasingly phospholipid membranes. What would have been the consequences for early cells of such a transition in membrane composition? We found that increasing phospholipid content inhibits the permeability of fatty acid membranes through changes in bilayer fluidity. For early heterotrophic cells, the emergence of increasingly phospholipid membranes would have therefore imposed new selective pressures for the evolution of membrane transport machinery and metabolism. Our model for early membrane evolution led us to develop prebiotic models for phospholipid chemistry. The assembly of phospholipids from single-chain substrates requires a single reaction: the acyltransfer of an activated fatty acid onto a glycerol monoester or lysophospholipid. We developed a synthetic model for this reaction that incorporates a copper-catalyzed azide-alkyne cycloaddition and showed that it drives de novo vesicle assembly

Microstructure and Corrosion Behavior of Advanced Alloys

In many industrial applications, metallic materials are exposed to harsh operating conditions. Due to a combination of chemical and thermal stresses, the constructional and functional materials are degraded, and their utility properties are lost. These undesirable events are of a physicochemical nature and are commonly known as ‘corrosion’. In this Special Issue Book, 3 reviews and 18 original research papers focused on the complex relationships between the microstructure, phase constitution, and corrosion behavior of metallic materials are collected. Both high temperature and low temperature corrosion studies are included as they investigate the physicochemical processes at the material interfaces. Furthermore, possibilities for increasing the corrosion resistance of metallic materials are studied by means of surface modification and application of protective layers. This Special Issue Book, Microstructure and Corrosion Behavior of Advanced Alloys, displays the diversity and complexity of modern corrosion research. It is hoped that it will become a valuable source of reference for corrosion scientists

빙하 후퇴에 따른 극지역 토양 미생물의 군집 구조와 잠재적 기능의 천이 변화

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 생명과학부, 2022. 8. 이은주.Glacier forelands have long fascinated ecologists and soil scientists by providing ideal places to study the patterns and processes of ecological succession. Previous studies on ecological succession in glacier forelands have focused mainly on the vegetation development or pedogenesis, but relatively less attention has been paid to microbial succession, especially in polar regions such as the High Arctic and Antarctica. In addition, former studies on microbial succession have typically focused on a single taxonomic group and often lack the examination on chemical turnover of organic substrates corresponding to biological turnover, resulting in a limited understanding of microbial succession in glacier forelands. In order to get a comprehensive understanding of microbial succession in glacier forelands of polar regions, this thesis aimed to investigate the successional changes of microbial communities in both the biological aspects (e.g., taxonomic compositions, functional profiles, and interactions between microbial groups) and the chemical aspects (e.g., diversity and compositional changes of dissolved organic matters). To acquire the knowledge on microbial community succession at the very early successional stages prior to plant colonization, the successional dynamics and assembly processes of bacterial and fungal communities were compared along a soil age gradient of 10 years on the Fourcade glacier foreland. Bacterial and fungal communities in recently deglaciated soils are largely decoupled from each other during succession and exert very divergent trajectories of succession and assembly under different selective forces. In addition to the study on successional patterns of microbial communities in unvegetated glacier forelands, the compositional changes of four different microbial communities (bacteria, fungi, protists, and archaea) and their interactions were investigated to gain a holistic view of microbial succession on a glacier foreland of the High Arctic along the 100 years of deglaciation. Overall, microbial community structures changed in a directional manner and environmental properties played a key role in the compositional changes following deglaciation. A higher proportion of the interactions between microbial groups in late than early soil-age gradients suggested that bacterial, fungal, and protistan communities less independently respond to glacier retreat along the soil-age gradient. Microbial succession involves not only changes in other biological communities but also at the same time changes in the diversity and composition of organic molecules mediated by biological processes. The successional dynamics of soil dissolved organic matter (DOM) and its relationship with microbial communities were examined following deglaciation in the High Arctic. The succession of DOM followed a distinct pattern from the patterns of microbial communities but is strongly associated with biological soil crusts (BSCs). Also, the abundance and richness of DOM molecule showed closer relationships with potential metabolic capability and in situ activity than the taxonomic structure of microbial communities. This thesis advanced the understanding of microbial succession in newly exposed glacier forelands of polar regions by providing the knowledge on not only successional dynamics of various microbial communities but also multitrophic interactions following soil-age gradient since deglaciation. Additionally, this study provides novel insights into interactions between organic compounds and microbial communities during succession. Consequently, these results can advance our understanding of belowground microbial succession in deglaciated terrains of polar regions.빙하 후퇴 지역 (glacier forelands)은 시간에 따른 생태학적 천이 과정 및 패턴을 연구하는데 이상적인 장소를 제공함으로써 지난 오랜 시간 동안 많은 생태학자와 토양학자들을 매료시켜왔다. 빙하 후퇴 지역에서 이루어진 생태적 천이 (ecological succession)에 대한 이전 연구들은 주로 식생 천이나 토양 발달에 초점을 맞추었으며 특히 고위도 북극이나 남극에서의 미생물 천이 (microbial succession)에 대한 연구는 많이 이루어지지 않았다. 또한 미생물 천이에 대한 이전 연구들은 주로 단일 분류군에 대해서만 초점을 맞추고 있으며 생물학적 변화에 상응하는 유기물의 화학적 변화에 대한 연구가 부족하여 이는 빙하 후퇴 지역에서의 미생물 천이에 대한 이해가 부족해지는 결과를 낳았다. 극지역 빙하 후퇴 지역에서의 미생물 천이에 대한 포괄적인 이해를 얻고자 본 연구는 미생물 천이의 생물학적 측면 (예를 들어, 군집의 구성, 기능적 프로파일, 미생물 그룹간의 상호작용)과 화학적 측면 (예를 들어, 용존 유기물의 다양성 및 구성의 변화)에서 연구하였다. 식물이 발달하기 이전의 극 초기 빙하 후퇴 지역에서의 미생물 천이에 대한 지식을 얻고자 세균 및 곰팡이 군집의 천이적 변화를 빙하가 후퇴한 지 약 10년여 지난 포케이드(Fourcade) 빙하 후퇴 지역에서 연구하였다. 그 결과, 극 초기 빙하 후퇴 지역에서 세균과 곰팡이 군집의 천이는 서로 분리되어 진행되며 서로 다른 선택적 요인의 영향으로 상반된 천이 패턴을 나타내었다. 극 초기 지역에서의 미생물 천이에 대한 연구에 이어, 미생물 천이를 전체적인 관점에서 이해하고자 고위도 북극에 위치한 약 100여년간 빙하가 후퇴한 지역에서 4개의 서로 다른 미생물 군집들 (세균, 진균, 원생생물 그리고 고세균)의 천이 패턴과 그들의 상관관계를 연구하였다. 종합적으로, 여러 미생물 군집의 구조는 빙하 후퇴 이후 시간에 따라 방향적으로 변화하였으며 이에 환경 요인들이 큰 영향을 주었다. 그리고 미생물 그룹들 간의 상관관계는 초기보다 후기에서 그 비중이 높았는데 이는 세균, 진균, 원생생물의 군집이 점차 덜 독립적으로 (보다 상호작용하며) 빙하 후퇴에 반응한다는 것을 시사한다. 미생물 천이는 다른 생물학적 군집의 천이 뿐만 아니라 동시에 생물학적 과정과 관련된 유기물의 다양성 및 구성적 변화를 함께 동반하기에, 토양의 용존 유기물의 천이 변화 및 미생물 군집간의 관계에 대해 연구를 고위도 북극의 빙하 후퇴 지역에서 진행하였다. 토양의 용존 유기물의 변화 패턴은 미생물의 천이와 다른 패턴을 나타내었으나 biological soil crusts (BSCs)의 발달과 강한 상관관계가 있었다. 그리고 용존 유기물의 양과 다양성은 미생물 군집의 분류학적 구조보다 미생물의 잠재적 대사능 (potential metabolic capability) 및 실제 물질 대사 능력 (in situ activity)과 보다 밀접한 관계를 나타내었다. 본 연구는 빙하 후퇴에 따른 다양한 미생물 군집들의 천이 패턴 및 이들의 상관관계 변화에 대한 지식을 제공함으로써 빙하 후퇴 지역의 미생물 천이에 대한 이해를 증진시켰다. 또한, 천이가 진행되는 동안 토양 유기물과 미생물 군집 간의 상호작용에 대한 새로운 관점을 제공하였다. 종합적으로, 본 연구를 통해 극지역 빙하 후퇴 지역 토양 밑의 미생물 천이에 대한 이해를 향상시킬 수 있었다.Chapter 1. General Introduction 1 1.1. Ecological succession in glacier forelands 1 1.2. Microbial succession in glacier forelands 3 1.3. Objectives of this study 6 Chapter 2. Early-stage successional dynamics of bacterial and fungal communities in a recently deglaciated terrain of the maritime Antarctica 10 2.1. Introduction 11 2.2. Materials and Methods 14 2.2.1. Site description and sampling strategy 14 2.2.2. Soil physicochemical analysis and meteorological data 16 2.2.3. Abundances of bacteria and fungi 17 2.2.4. DNA extraction, amplicon sequencing, and community analysis 20 2.2.5. Bioinformatics analysis 21 2.2.6. Statistical analyses 22 2.2.7. Null model analysis 26 2.2.8. Co-occurrence network analysis 27 2.3. Results 27 2.3.1. Soil geochemistry and microbial abundance 27 2.3.2. Microbial taxa 32 2.3.3. Microbial alpha- and beta-diversity 37 2.3.4. Key drivers of microbial beta-diversity 46 2.3.5. Biotic interactions within- and between-taxonomic groups 47 2.4. Discussion 52 Chapter 3. Successional dynamics of microbial communities along a 100-year deglaciation gradient in the High Arctic 60 3.1. Introduction 61 3.2. Materials and Methods 63 3.2.1. Site description and sampling strategy 63 3.2.2. Soil physicochemical analysis 66 3.2.3. Phospholipid fatty acid (PLFA) analysis 67 3.2.4. RNA/DNA isolation, cDNA synthesis, amplicon sequencing, and community analysis 68 3.2.5. Shotgun metagenomic sequencing 69 3.2.6. Annotation of microbial functional groups 70 3.2.7. Statistical analyses 71 3.2.8. Network analysis 72 3.3. Results 73 3.3.1. Soil physicochemical properties and microbial biomass 73 3.3.2. Taxonomic composition of RNA-based and DNA -based microbial communities 77 3.3.3. Changing trends of microbial taxa in RNA- and DNA-based microbial communities 80 3.3.4. Changes in putative functional profiles and functional potential along the chronosequence 86 3.3.5. Microbial alpha- and beta-diversity 91 3.3.6. Key drivers of microbial beta-diversity 97 3.3.7. Biotic interactions within- and between-taxonomic groups 101 3.4. Discussion 105 Chapter 4. Chemical succession of dissolved organic matter (DOM) molecules and its relation to microbial communities in a deglaciated foreland of the High Arctic 108 4.1. Introduction 109 4.2. Materials and Methods 116 4.2.1. Study site, soil sampling, soil physicochemical properties, and NDVI 116 4.2.2. Preparation of soil organic matter 116 4.2.3. FT-ICR MS analysis 117 4.2.4. Data processing and elemental composition assignments 117 4.2.5. Dissolved organic matter (DOM) chemodiversity and multivariate analysis 118 4.2.6. Chlorophyll a extraction 119 4.2.7. Long-read amplicon sequencing using LoopSeq 119 4.2.8. Statistical analyses 121 4.2.9. Network analysis 122 4.2.10. Community-level physiological profiles 123 4.3. Results 124 4.3.1. General characteristics of DOM compounds in the foreland of Midtre Lovénbreen 121 4.3.2. Changes in DOM characteristics along the gradient of time since deglaciation 121 4.3.3. Underlying mechanisms and primary drivers of DOM compositional changes 134 4.3.4. Network associations between N-containing DOM compounds and microbial OTUs 141 4.4. Discussion 151 Chapter 5. Conclusion 158 References 161 Appendix 179 Abstract in Korean(국문초록) 229박