SUSTAINABLE URBAN DEVELOPMENT AND DEVELOPING COUNTRIES

Cities are the biggest challenge for judging the validity and applicability of concepts of and policies for sustainable development. The importance of cities is based not solely on demographic grounds, but on economic, political and social grounds as well. Cities around the world are growing at a never experienced rate. Over the past thirty years, the number of people living in cities in the developing countries has grown with more than 200%. Explosive urban migration, high birth rates, high unemployment rates, increasing crime, limited or ineffective health and education services, crumbling or missing infrastructure, and unfavourable business climates have created inhospitable cities. The cities suffer from widespread air and water pollution and soil contamination. Health conditions in many cities are often far below decent standards. Even in more flourishing countries, many health disorders are related to the negative effects of the urban environment. Nevertheless, cities will largely influence the social, cultural, economic, and environmental sustainability of our societies and the earth in the future. If cities are not only to survive but also to prosper in the 21st century, they must undergo a major transformation, which in developing countries cannot be carried out without global plans and commitments. In my paper I will (i) summarize the current situation of and future challenges for cities in developing countries, (ii) assess the impact of them on global welfare and sustainable development, (iii) review the role of developed countries (with focus on the EU) in promoting development; and (iv) delineate some possible directions for the future.sustainable development, city, demographic grounds, urban migration

New bounds on even cycle creating Hamiltonian paths using expander graphs

We say that two graphs on the same vertex set are $G$-creating if their union (the union of their edges) contains $G$ as a subgraph. Let $H_n(G)$ be the maximum number of pairwise $G$-creating Hamiltonian paths of $K_n$. Cohen, Fachini and K\"orner proved $$n^{\frac{1}{2}n-o(n)}\leq H_n(C_4) \leq n^{\frac{3}{4}n+o(n)}.$$ In this paper we close the superexponential gap between their lower and upper bounds by proving $$n^{\frac{1}{2}n-\frac{1}{2}\frac{n}{\log{n}}-O(1)}\leq H_n(C_4) \leq n^{\frac{1}{2}n+o\left(\frac{n}{\log{n}} \right)}.$$ We also improve the previously established upper bounds on $H_n(C_{2k})$ for $k>3$, and we present a small improvement on the lower bound of F\"uredi, Kantor, Monti and Sinaimeri on the maximum number of so-called pairwise reversing permutations. One of our main tools is a theorem of Krivelevich, which roughly states that (certain kinds of) good expanders contain many Hamiltonian paths.Comment: 14 pages, LaTeX2e; v2: updated Footnote 1 on Page 5; v3: revised version incorporating suggestions by the referees (the changes are mainly in Section 5); v4: final version to appear in Combinatoric

New bounds on even cycle creating Hamiltonian paths using expander graphs

We say that two graphs on the same vertex set are $G$-creating if their union (the union of their edges) contains $G$ as a subgraph. Let $H_n(G)$ be the maximum number of pairwise $G$-creating Hamiltonian paths of $K_n$. Cohen, Fachini and K\"orner proved $$n^{\frac{1}{2}n-o(n)}\leq H_n(C_4) \leq n^{\frac{3}{4}n+o(n)}.$$ In this paper we close the superexponential gap between their lower and upper bounds by proving $$n^{\frac{1}{2}n-\frac{1}{2}\frac{n}{\log{n}}-O(1)}\leq H_n(C_4) \leq n^{\frac{1}{2}n+o\left(\frac{n}{\log{n}} \right)}.$$ We also improve the previously established upper bounds on $H_n(C_{2k})$ for $k>3$, and we present a small improvement on the lower bound of F\"uredi, Kantor, Monti and Sinaimeri on the maximum number of so-called pairwise reversing permutations. One of our main tools is a theorem of Krivelevich, which roughly states that (certain kinds of) good expanders contain many Hamiltonian paths.Comment: 14 pages, LaTeX2e; v2: updated Footnote 1 on Page 5; v3: revised version incorporating suggestions by the referees (the changes are mainly in Section 5); v4: final version to appear in Combinatoric

Questions on the Structure of Perfect Matchings inspired by Quantum Physics

We state a number of related questions on the structure of perfect matchings. Those questions are inspired by and directly connected to Quantum Physics. In particular, they concern the constructability of general quantum states using modern photonic technology. For that we introduce a new concept, denoted as inherited vertex coloring. It is a vertex coloring for every perfect matching. The colors are inherited from the color of the incident edge for each perfect matching. First, we formulate the concepts and questions in pure graph-theoretical language, and finally we explain the physical context of every mathematical object that we use. Importantly, every progress towards answering these questions can directly be translated into new understanding in quantum physics.Comment: 10 pages, 4 figures, 6 questions (added suggestions from peer-review

Properties of minimally tt-tough graphs

A graph $G$ is minimally $t$-tough if the toughness of $G$ is $t$ and the deletion of any edge from $G$ decreases the toughness. Kriesell conjectured that for every minimally $1$-tough graph the minimum degree $\delta(G)=2$. We show that in every minimally $1$-tough graph $\delta(G)\le\frac{n+2}{3}$. We also prove that every minimally $1$-tough claw-free graph is a cycle. On the other hand, we show that for every $t \in \mathbb{Q}$ any graph can be embedded as an induced subgraph into a minimally $t$-tough graph

„Ami nem is jó, azt is, most is értem”. Kulturális és szociálpszichológiai kérdések a mai magyar cserkészetben

A következőkben valóban elméleti munkát várjon tőlem az olvasó, tehát nem gazdasági, politikai és egyéb kérdésfölvetéseket, hanem a világcserkészet és a magyar cserkészet elméletét érintő implikációkat. Bár lassan négy éve gyakorlatilag szabadúszóként járom e testvérvilágot, mégis – és talán éppen ezen autonómia révén – élesebben látom azokat az anomáliákat, amelyeket a szorosabb kisközösségi létben élő vezetőtársaim aktuál-problémái elfödnek. Az a kötelességérzés – Márai Sándor kifejezésével: „Pflichtgefühl” – vezetett e munka létrehozására, mely fogadalmunkkal elévülhetetlen karakterként pecsételődik lelkünkbe, sőt, egyes gyermekeknek már jóval korábban is

Investigation of the effect of flooring on the living performance of sows using survival analysis

Pig-farming has a long tradition in Hungary, most significantly within the Alföld region. In my analysis I studied the lifespan of sows in two nucleus pig herds on the Great Plain, also examining the probability of the occurrence of different reasons for culling. During my research I collected data (from 2001 to 2010) relating to more than 10,000 sows from the farms conducting a breeding programme and I searched for the answer to the question of whether can I find a significant difference in the lifespan of sows with the same feeding and the same genotype if the floor type of farms is different (Herd A has a solid floor with straw and Herd B has a slatted floor). Regarding the reasons for culling ANOVA was used to investigate mean differences in logarithms of the lifespan of sows in each herd. Between the herds the seven most common culling reasons were estimated with the Kaplan-Meier method and the significant difference was demonstrated with the logrank test. The results of the log-rank test showed that there was a significant difference in leg problems as a cause of culling and deaths (p < 0.05) between the two farms, which is the consequence of different floor types