Thesis (MA) -- Stellenbosch University, 1971. / No abstract available

The aim of this thesis is to analyze the process of securitization of immigration and multiculturalism within the framework of migration, immigration and integration policies focusing on the case of Germany. Using the migration-security nexus as a primary theoretical foundation, I argue that within the policies and legislations related to immigration, German governments ultimately perceive immigration as a threat at the level of state security as well as Germany's national identity. The first government I have selected for my analysis is the cabinet led by Gerhard Schröder (1998 - 2005) who challenged the romanticized perception of the German nation as a "nation of descent" by saying that "Germany is a country of immigration." Secondly, I focus on the chancellorship of Angela Merkel whose approach toward the Syrian asylum seekers in the context of the current migration crisis (9/2015 - 11/2016) has been called "Wilkommenskutlur" (or "Welcome culture"). Nonetheless, by studying the policies related to immigration as well as governments' discourses, I argue that in both cases, immigration and multiculturalism are indeed linked to security issues. Hence, immigrants are perceived as a threat to Germany's national security and its identity.

<p>Ako je<em> L </em>relacijski jezik, kondenzacioni pretporedak na skupu<em> Int</em>_L <em>(X)</em> svih <em>L-</em>interpretacija nad domenom <em>X,</em> dat je sa: &rho;≼_c <em>&sigma;</em> ako postoji bijektivni homomorfizam (kondenzacija)<em> f:〈X,&rho;</em>〉&rarr;<em>〈X,&sigma;〉.</em> Odgovarajući antisimetrični količnik <em>〈Int_L</em> (X)/~_c,&le;_c〉 ~naziva se kondenzacioni poredak. Za proizvoljnu<em> L-</em>interpretaciju &rho;, klasa [&rho;]~_c&nbsp; je konveksno zatvorenje klase [&rho;]_&cong; u Booleovoj mreži 〈<em>IntL (X</em>),&sube;〉. Za <em>L</em>-interpretaciju &rho; reći ćemo da je jako reverzibilna (redom, reverzibilna, slabo reverzibilna) akko je klasa [&rho;]_&cong;&nbsp; (ili, ekvivalentno, klasa [&rho;]~_c)) singlton (redom, antilanac, konveksan skup) u Booleovoj mreži 〈<em>IntL (X)</em>,&sube;〉. U cilju ispitivanja poseta 〈<em>Int(_Lb</em>) (X)/~c,&le;c〉, za &rho;&isin;<em>Irrefl_X</em> uveden je skup D_&rho;:={[&rho;&cup;&Delta;_A ](~_c ):<em>A&sube;X</em>} i pokazano je kako je poduređenje 〈D_&rho;,&le;_c 〉 izomorfno određenom količniku partitivnog skupa<em> P(X)</em>. Fenomen reverzibilnosti relacijskih struktura igra istaknutu ulogu u istraživanju tog poduređenja.</p><p>U slučaju prebrojivog jezika <span id="cke_bm_1038S" style="display: none;">&nbsp;</span><em>L</em><span id="cke_bm_1038E" style="display: none;">&nbsp;</span> i prebrojivog domena <em>X</em>, pokazano je da su ~_c i [&rho;]~_canalitički skupovi u poljskim prostorima, redom, <em>Int_L(&omega;)&times;Int_L(&omega;) i Int_L (&omega;)</em>, i pomoću toga, pokazano ja da su, u slučaju prebrojivog jezika i domena, klase [&rho;]&cong;&nbsp; i [&rho;]~_c iste veličine, i da je to neki kardinal iz {1,&omega;,c}. Dalje je istražena hijerarhija između kondenzacione ekvivalencije, elementarne ekvivalencije, ekvimorfizma (bi-utopivosti) i drugih sličnosti <em>L-</em>struktura određenih nekim sličnostima njihovih monoida samoutapanja.</p><p>Naposletku, temeljno je istražen fenomen reverzibilnosti <em>L</em>-struktura. Data je karakterizacija jako reverzibilnih<em> L</em>-intepretacija kao onih čije su komponentne relacije definabilne formulama praznog jezika<em> L</em>_&empty;, bez kvantifikatora i parametara. Pokazano je kako su slabo reverzibilne interpretacije upravo one koje imaju svojstvo Cantor-Schrӧder-Bernstein (kraće, svojstvo CSB) za kondenzacije.</p><p>Poseban naglasak stavljen je na detektovanje relevantnih klasa reverzibilnih struktura. Pri tome, prvo su proučene strukture koje su ekstremni elementi L_{&infin;&omega;}-definabilnih klasa interpretacija, pri određenim sintaktičkim ograničenjima, a zatim su istražene nepovezane<em> L</em>_b-strukture, gde je dato nekoliko karakterizacija njihove reverzibilnosti.</p> / <p>If <em>L</em> is a relational language, the condensational preorder on the set <em>Int_L (X)</em> of all <em>L-</em>interpretations over the domain<em> X</em>, is given with: &rho;≼_c &sigma; iff there exists a bijective homomorphism (condensation) <em>f:〈X,&rho;〉&rarr;〈X,&sigma;〉. </em>The corresponding antisymmetric quotient 〈<em>Int_L (X)/</em>~_<em>c</em>,&le;__c〉 will be called the condensational order. For any <em>L</em>-interpretation &rho;, the class<em> [&rho;]~_c )</em> is the convex closure of the class [<em>&rho;</em>]&cong; in the Boolean lattice 〈<em>IntL (X</em>),&sube;〉. An <em>L</em>-interpretation &rho; is said to be strongly reversible&nbsp; (respectively, reversible, weakly reversible) iff the class <em>[&rho;]</em>&cong;&nbsp; (or, equivalently, the class<em> [&rho;]~c )</em>) is a singleton (respectively, an antichain, a convex set) in the poset 〈 <em>IntL</em> <em>(X)</em>,&sube;〉. In order to investigate the poset 〈<em>Int_(Lb ) (X)/~c,&le;_c</em>〉, for &rho;&isin;<em> IrreflX</em> the following set is defined <em>D_&rho;</em>:={[&rho;&cup;&Delta;_A ]_~c :A&sube;X}. It is shown that the suborder 〈<em>D_&rho;,</em>&le;_c 〉 is isomorphic to a certain quotient of the power set <em>P(X)</em>. The phenomenon of reversibility plays prominent role in the investigation of that suborder.<br />In the case of a countable language<em> L</em> and a countable domain&nbsp; <em>X</em>, it is shown that ~c&nbsp; and [<em>&rho;]__~c&nbsp;</em>are analytic sets in the Polish spaces, respectively,<em> IntL (&omega;)&times; IntL (&omega;)</em> and <em>Int_L (&omega;)</em>, and, using those results, in the case of a countable language and domain it is shown that the classes <em>[&rho;]_</em>&cong;&nbsp; and <em>[&rho;]~_c&nbsp;</em>are of the same size, and that it is a cardinals from _{{1,&omega;,c}. N}ext, the hierarchy between condensational equivalence, elementary equivalence, equimorphism (bi- embedability) and other similarities of <em>L</em>-structures, determined by some similarities of their self-embedding monoids, is investigated.<br />In the last part, the phenomenon of reversibility of<em> L</em>-structures is investigated. Strongly reversible <em>L</em>-intepretations are characterized as those whose component relations are definable by the formulae of the empty language<em> L_&empty;, </em>without quantifiers and parameters. It is shown that weakly reversible interpretations are exactly those having the property Cantor-Schrӧder-Bernstein (shorter, the property CSB) for condensations.<br />Particular emphasis is put on detecting relevant classes of reversible structures. First, the structures that are extreme elements of<em> L</em>_{&infin;&omega;}-definable classes of interpretations, under certain syntactical restrictions, are investigated. Following that, disconnected Lb-structures are investigated, where several equivalents of their reversibility are proven.</p>

Combinatorial objects can be represented by strings, such as 21534 for the permutation (1 2) (3 5 4), or 110100 for the binary tree corresponding to the balanced parentheses (()()). Given a string s = s1 s2 sn, the right-shift operation shift(s, i, j) replaces the substring si si+1..sj by si+1..sj si. In other words, si is right-shifted into position j by applying the permutation (j j−1 .. i) to the indices of s. Right-shifts include prefix-shifts (i = 1) and adjacent-transpositions (j = i+1). A fixed-content language is a set of strings that contain the same multiset of symbols. Given a fixed-content language, a shift Gray code is a list of its strings where consecutive strings differ by a shift. This thesis asks if shift Gray codes exist for a variety of combinatorial objects. This abstract question leads to a number of practical answers. The first prefix-shift Gray code for multiset permutations is discovered, and it provides the first algorithm for generating multiset permutations in O(1)-time while using O(1) additional variables. Applications of these results include more efficient exhaustive solutions to stacker-crane problems, which are natural NP-complete traveling salesman variants. This thesis also produces the fastest algorithm for generating balanced parentheses in an array, and the first minimal-change order for fixed-content necklaces and Lyndon words. These results are consequences of the following theorem: Every bubble language has a right-shift Gray code. Bubble languages are fixed-content languages that are closed under certain adjacent-transpositions. These languages generalize classic combinatorial objects: k-ary trees, ordered trees with fixed branching sequences, unit interval graphs, restricted Schr oder and Motzkin paths, linear-extensions of B-posets, and their unions, intersections, and quotients. Each Gray code is circular and is obtained from a new variation of lexicographic order known as cool-lex order. Gray codes using only shift(s, 1, n) and shift(s, 1, n−1) are also found for multiset permutations. A universal cycle that omits the last (redundant) symbol from each permutation is obtained by recording the first symbol of each permutation in this Gray code. As a special case, these shorthand universal cycles provide a new fixed-density analogue to de Bruijn cycles, and the first universal cycle for the "middle levels" (binary strings of length 2k + 1 with sum k or k + 1).