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This thesis has explored how structural techniques can be applied to the problem of formal verification for sequential circuits. Algorithms for formal verification which operate on non-canonical gate netlist representations of digital circuits have certain advantages over the traditional techniques based on canonical representations as BDDs. They allow to exploit problem-specific knowledge because they can take into account structural properties of the designs being analyzed. This allows us to break the problem down into sub-problems which are (hopefully) easier to be solved. However, in the past, the main application of such structural techniques was in the field of combinational equivalence checking. One reason for this is that the behaviour of a sequential system does not only depend on its inputs but also on its internal states, and no concepts had been developed to-date allowing structural methods to deal with large sets of states. An important goal of this research was therefore to develop structural, non-canonical forms of representing the reachable states of a finite state machine and to develop methods for reachability analysis based on such representations. In order to reach this goal, two steps were taken. Firstly, a framework for manipulating Boolean functions represented as gate netlists has been established. Secondly, using this framework, a structural method for FSM traversal was developed serving as the basis for an equivalence checking algorithm for sequential circuits. The framework for manipulating Boolean functions represented as multi-level combinational networks is based on a new concept of an implicant in a multi-level network and on an AND/ORtype enumeration technique which allows us to derive such implicants. This concept extends the classical notion of an implicant in two-level circuits to the multi-level case. Using this notion, arbitrary transformations in multi-level combinational networks can be performed. The multi-level network implicants can be determined from AND/OR reasoning graphs, which are associated with an AND/OR reasoning technique operating directly on the gate netlist description of a multi-level circuit. This reasoning technique has the important property that it is complete, i.e. the associated AND/OR trees contain all prime implicants of a Boolean function at an arbitrary node in a combinational circuit. In other words, AND/OR graphs constructed for a network function serve as a representation of this function. A great advantage over BDDs is that AND/OR graphs, besides representing the logic function, also represent some structural properties of the analyzed circuitry. This permits to develop heuristics that are specially tailored for certain applications such as logic optimization or verification. Another advantage which is especially useful for logic optimization is the fact that the proposed AND/OR enumeration scheme is not restricted to the use of a specific logic alphabet such as B3 = {0, 1, X}. By using Roth’s D-calculus based on B5 = {0, 1, D, D-Komplement} permissible implicants can be determined. Transformations based on permissible implicants exploit observability don’t-care conditions in logic synthesis by creating permissible functions at internal network nodes. In order to evaluate the new structural framework for manipulating Boolean functions represented as gate netlists, several experiments with implicant-based optimization of multi-level circuits were performed. The results show that implicant-based circuit transformations lead to significantly better optimization results than traditional synthesis techniques. Next, based on the proposed structural methods for Boolean function manipulation, techniques for representing and manipulating the set of states of a sequential circuit have been developed. The concept of a “stub circuit” was introduced which implicitly represents a set of state vectors as the range of a multi-output function given as a gate netlist. The stub circuit is the result of an existential quantification operation which is obtained by functional decomposition using implicant-based netlist transformations and a network cutting procedure. Using this existential quantification operation, a new structural FSM traversal algorithm was formulated which performs a fixed point iteration on the set of reachable states represented by the stub circuit. The proposed approach performs a reachability analysis of the states of a sequential circuit. It operates on gate netlists and naturally allows to incorporate structural properties of a design under consideration into the reasoning. Therefore, structural FSM traversal is an interesting alternative to traditional symbolic FSM traversal, especially in those applications of formal verification, where structural properties can be exploited. Structural FSM traversal was applied to the problem of sequential equivalence checking. Here, structural similarities between the designs to be compared can effectively reduce the complexity of the verification task. The FSM to be traversed is a special product machine called sequential miter. The special structural properties of this product machine have made it possible to formulate an approximate algorithm for structural FSM traversal, called record and play(). This algorithm uses an approximation on the reachable state set represented by the stub circuit which is very beneficial for performance. Instead of calculating the stub circuit using the exact algorithm, implicant-based transformations directly using structural design similarities are performed. These transformations, together with existential quantification implemented by the cutting procedure, lead to an over-approximation of the reachable state set. By this overapproximation, only such unreachable product states are added to the set of states represented by the stub circuit which are unreachable at the current point in time but which are nevertheless equivalent. Therefore, more product states are added to the set of reachable states sometimes leading to drastic acceleration of the traversal, i.e. the fixed point is reached in much fewer steps. The algorithm record and play() was applied to the problem of checking the equivalence of a circuit with its optimized and retimed version. Retiming is a form of sequential circuit optimization which can radically alter the state encoding of a circuit. Traditional FSM traversal techniques often fail because the BDDs needed to represent the reachable state set and the transition relation of the product machine become too large. Experiments were conducted to evaluate the performance of record and play() on a standard set of sequential benchmark circuits. The algorithm was capable of proving the equivalence of optimized and retimed circuits with their original versions, some of which (to our knowledge) have never before been verified using traditional techniques like symbolic FSM traversal. The experimental results are very promising. Future research will therefore explore how structural FSM traversal can be applied to model checking.
This paper argues that short (clause-internal) scrambling to a pre-subject position has A properties in Japanese but A'-properties in German, while long scrambling (scrambling across sentence boundaries) from finite clauses, which is possible in Japanese but not in German, has A'-properties throughout. It is shown that these differences between German and Japanese can be traced back to parametric variation of phrase structure and the parameterized properties of functional heads. Due to the properties of Agreement, sentences in Japanese may contain multiple (Agro- and Agrs-) specifiers whereas German does not allow for this. In Japanese, a scrambled element may be located in a Spec AgrP, i.e. an A- or L-related position, whereas scrambled NPs in German can only appear in an AgrP-adjoined (broadly-L-related) position, which only has A'-properties. Given our assumption that successive cyclic adjunction is generally impossible, elements in German may not be long scrambled because a scrambled element that is moved to an adjunction site inside an embedded clause may not move further. In Japanese, long distance scrambling out of finite CPs is possible since scrambling may proceed in a successive cyclic manner via embedded Spec- (AgrP) positions. Our analysis of the differences between German and Japanese scrambling provides us with an account of further contrasts between the two languages such as the existence of surprising asymmetries between German and Japanese remnant-movement phenomena, and the fact that unlike German, Japanese freely allows wh-scrambling. Investigation of the properties of Japanese wh-movement also leads us to the formulation of the "Wh-cluster Hypothesis", which implies that Japanese is an LF multiple wh-fronting language.
Left dislocation in Zulu
(2004)
This paper examines left dislocation constructions in Zulu, a Southern Bantu language belonging to the Nguni group (Zone S 40). In Zulu left dislocation configurations, a topic phrase in the beginning of the sentence is linked to a resumptive element within the associated clause. Typically, the resumptive element is an incorporated pronoun (cf. Bresnan & Mchombo 1987), as illustrated by the examples in (1) and (2). In these examples, the object pronoun (in italics) is part of the verbal morphology and agrees with the noun class (gender) of the dislocate. This situation is schematically illustrated in (3), where co-indexation represents agreement: ...
In this paper I discuss the properties of particle verbs in light of a proposal about syntactic projection. In section 2 I suggest that projection involves functional structure in two important ways: (i) only functional phrases can be complements, and (ii) lexical heads that take complements and project must be inflected. In section 3, I show that the structure of particle verbs is not uniform with respect to (i) and (ii). On the one hand, a particle always combines with an inflected verb; in this respect, particle verbs look like verb-complement constructions. On the other hand, the particle is not a functional phrase and therefore is not a proper complement, which makes the combination of the particle and the verb look more like a morphologically complex verb. I argue that syntactic rules can in fact interpret the node dominating the particle and the verb as a projection and as a complex head. In section 4, I show that many of the characteristic properties of particle verbs in the Germanic languages follow from the fact that they are structural hybrids.
In this article, I discuss some important properties of wh-questions and wh-scrambling in Japanese. The questions I will address are (i) which instances of (wh-) scrambling involve reconstruction and (ii) how the undoing effects of scrambling can be derived. First I will discuss the claim that (wh-) scrambling is semantically vacuous and is therefore undone at LF (Saito 1989, 1992). Then I consider the data that led Takahashi (1993) to the conclusion that at least some instances of wh-scrambling have to be analyzed as instances of "full wh-movement" i.e., overt movement of the wh-phrase in its scopal position. It will be argued that these examples are not instances of full wh-movement in Japanese, but that they also represent semantically vacuous scrambling. Those instances of scrambling that apprently cannot be undone are best explained with recourse to parsing effects. I conclude that wh-scrambling in Japanese is always triggered by a ([-wh]-) scrambling feature. In addition, long distance scrambling (scrambling out of finite CPs) is analyzed as adjunction movement, whereas short distance scrambling is movement to a specifier position of IP. Turning to the mechanisms of undoing, I will argue that only long distance scrambling is undone. This is shown to follow from Chomsky's (1995) bare phrase structure analysis, according to which multi-segmental categories derived by adjunction movement are not licensed at LF. The article is organized as follows. In section 2, the wh-scrambling phenomenon is described. In section 3, I discuss the reconstruction properties of scrambling. In addition, this section provides some basic assumptions about my analysis of Japanese scrambling in general. In section 4, I turn to the analysis of wh-scrambling as an instance of full wh-movement in Japanese. Section 5 provides discussion of multiple wh-questions in Japanese, and section 6 gives the conclusion.
The languages of the world differ with respect to argument extraction possibilities. In languages such as English, wh-movement is possible from Spec IP and from the complement position, whereas in languages such as Malagasy only extraction from Spec IP is possible. This difference correlates with the fact that these language types obey different island constraints and behave differently with respect to wh-in situ and superiority effects. The goal of this paper is to outline an analysis for these differences. The basic idea is that in contrast to languages such as English, in Malagasy-type languages every argument can be merged in the complement position of the selecting head.
Expletives as features
(2000)
Expletives have always been a central topic of theoretical debate and subject to different analyses within the different stages of the Principles and Parameter theory (see Chomsky 1981, 1986, 1995; Lasnik 1992, 1995; Frampton and Gutman 1997; among others). However, most analyses center on the question how to explain the behavior of expletives in A-chains (such as there in English or Þad in Icelandic). No account relates wh-expletives (as one finds them in so-called partial wh-movement constructions in languages such as Hungarian, Romani, and German) to expletives in Achains. In this paper, I argue that the framework of the Minimalist Program opens up the possibility of accounting for expletive-associate relations in A-/A'-chains in a unified manner. The main idea of the unitary analysis is that an expletive is an overtly realized feature bundle that is (sub)extracted from its associate DP. There in an expletive-associate chain is a moved D-feature which orginates inside the associate DP. Similarily, in A'-chains, the whexpletive originates as a focus-/wh-feature in the wh-phrase with which it is associated. This analysis provides evidence for the feature-checking theory in Chomsky (1995). The paper is organized as follows. Section 2 contains the discussion of expletive there. In section 3 I suggest an analysis for whexpletives, and I also explore whether this analysis can be extended to relations between X°-categories such as auxiliary and participle complexes.
In this paper I show that Clitic Climbing (CC) in Spanish and Long Scrambling (LS) in German (and Polish) are (im-)possible out of the same environments. For an explanation of this fact I propose a feature-oriented analysis of incorporation phenomena. The idea is that restructuring is a phenomenon of syntactic incorporation. In German and Polish, Agro incorporates covertly into the matrix clause and licenses LS out of the infinitival into the matrix clause. Similarily the clitic in Spanish, which is analysed as an Agro-head, incorporates into the matrix clause. I argue that this movement is necessary for reasons of feature-checking, i. e. for checking of an [+R]- or Restructuring-feature. In section 2 I discuss several differences between CC and LS. For example, the proposed analysis correctly predicts that clitics in contrast to scrambled phrases are subject to several serialization restrictions. Throughout the paper I use the term restructuring only in a descriptive sense, in order to describe the phenomenon in question.
The assumption that mankind is able to have an in uence on global or regional climate, respectively, due to the emission of greenhouse gases, is often discussed. This assumption is both very important and very obscure. In consequence, it is necessary to clarify definitively which meteorological elements (climate parameters) are in uencend by the anthropogenic climate impact, and to which extent in which regions of the world. In addition, to be able to interprete such an information properly, it is also necessary to know the magnitude of the different climate signals due to natural variability (for example due to volcanic or solar activity) and the magnitide of stochastic climate noise. The usual tool of climatologists, general circulation models (GCM) suffer from the problem that they are at least quantitatively uncertain with regard to the regional patterns of the behaviour of climate elements and from the lack of accurate information about long-term (decadal and centennial) forcing. In contrast to that, statistical methods as used in this study have the advantage to test hypotheses directly based on observational data. So, we focus to the very reality of climate variability as it has occurred in the past. We apply two strategies of time series analyis with regard to the observed climate variables under consideration. First, each time series is splitted into its variation components. This procedure is called 'structure-oriented time series separation'. The second strategy called 'cause-oriented time series separation' matches various time series representing various forcing mechanisms with those representing the climate behaviour (climate elements). In this way it can be assessed which part of observed climate variability can be explained by this (combined) forcing and which part remains unexplained.
The results presented here strongly indicate that ubiquitination of the recombinant human alpha1 GlyR at the plasma membrane of Xenopus oocytes is involved in receptor internalisation and degradation. Ubiquitination of the human alpha1 GlyR has been demonstrated by radio-iodination of plasma membrane-boundalpha1 GlyRs, whose subunits differed in molecular weight by additional 7, 14 or 21 kDa, corresponding to the molecular weights of one, two and three conjugated ubiquitin molecules, respectively, and by co-isolation of the non-tagged human alpha1 GlyR through hexahistidyl-tagged ubiquitin. Ubiquitin conjugated GlyRs where prominent at the plasma membrane, but could be hardly detected in total cell homogenates, indicating that ubiquitination takes place exclusively at the plasma membrane. Ubiquitination of the alpha1 GlyR at the plasma membrane was no longer detectable when the ten lysine residues of the cytoplasmic loop between transmembrane segments M3 and M4 were replaced by arginines. Despite this proteolytic cleavage continued to take place at the same extent as with the wild type alpha1 GlyR, suggesting that removal of GlyRs from the plasma membrane and routing to lysosomes for degradation were not dependent on ubiquitination. Also replacing a tyrosine in position 339, which was speculated to be part of an additional endocytosis motif, did not lead to a significant reduction of cleavage of the GlyR alpha1 subunits. However, a mutant lacking both, ubiquitination sites and 339Y, was significantly less processed. These results may suggest that the GlyR alpha1 subunit harbors at least two endocytosis motifs, which may act independently to regulate the density of alpha1 GlyR. Apparently, each of the two signals may be capable of compensating entirely the loss of the other. Part two of this Dissertation demonstrates that the correct topology of the glycine receptor alpha1 subunit depends critically on six positively charged residues within a basic cluster, RFRRKRR, located in the large cytoplasmic loop following the C-terminal end of M3. Neutralization of one or more charges of this cluster, but not of other charged residues in the M3-M4 loop, led to an aberrant translocation into the endoplasmic reticulum lumen of the M3-M4 loop. However, when two of the three basic charges located in the ectodomain linking M2 and M3 were neutralized, in addition to two charges of the basic cluster, endoplasmic reticulum disposition of the M3-M4 loop was prevented. We conclude that a high density of basic residues C-terminal to M3 is required to compensate for the presence of positively charged residues in the M2-M3 ectodomain, which otherwise impair correct membrane integration of the M3 segment. Part three of this Dissertation describes my contribution (blue native PAGE analysis of metabolically labeled alpha7 and 5HT3A receptors and the examination of the glycosylation state of metabolically labeled alpha7 subunits) to a work on the limited assembly capacity of Xenopus oocytes for nicotinic alpha7 subunits. While 5HT3A subunits combined efficiently to pentamers, alpha7 subunits existed in various assembly states including trimers, tetramers, pentamers, and aggregates. Only alpha7 subunits that completed the assembly process to homopentamers acquired complex-type carbohydrates and appeared at the cell surface. We conclude that Xenopus oocytes have a limited capacity to guide the assembly of alpha7 subunits, but not 5HT3A subunits to homopentamers. Accordingly, ER retention of imperfectly assembled alpha7 subunits rather than inefficient routing of fully assembled alpha7 receptors to the cell surface limits surface expression levels of alpha7 nicotinic acetylcholine receptors. Part four of this Dissertation describes my contribution (the biochemical analysis of the human P2X2 and P2X6 subtypes) to studies on the quaternary structure of P2X receptors. Armaz Aschrafi, the main author of the paper showed that subsequent to isolation under non-denaturing conditions from Xenopus oocytes the His-rP2X2 protein migrated on blue native PAGE predominantly in an aggregated form. The only discrete protein band detectable could be assigned to homotrimers of the His-rP2X2 subunit. Because of the exceptional assembly-behaviour of the rP2X2 protein compared to the rP2X1, rP2X3, rP2X4 and rP2X5 proteins, its human orthologue was investigated in the same manner. In contrast to rP2X2 subunits, hP2X2 subunits migrated under virtually identical conditions in a single defined assembly state, which could be clearly assigned to a trimer. P2X6 subunits represent the sole P2X subtype that is unable to form functional homomeric receptors in Xenopus oocytes. The blue native PAGE analysis of metabolically labeled hP2X6 receptors and the examination of the glycosylation state revealed that hP2X6 subunits form tetramers and aggregates that are not exported to the plasma membrane of Xenopus oocytes.
Homing in with GPS
(2000)
In the present work, the Heidelberg electron beam ion trap (EBIT) at the Max-Planck-Institute für Kernphysik (MPIK) has been used to produce, trap highly charged argon ions and study their magnetic dipole (M1) forbidden transitions. These transitions are of relativistic origin and, hence, provide unique possibilities to perform precise studies of relativistic effects in many electron systems. In this way, the transitions energies of the 1s22s22p for the 2P3/2 - 2P1/2 transition in Ar13+ and the 1s22s2p for the 3P1 - 3P2 transition in Ar14+, for 36Ar and 40Ar isotopes were compared. The observed isotopic effect has confirmed the relativistic nuclear recoil effect corrections due to the finite nuclear mass in a recent calculation made by Tupitsyn [TSC03], in which major inconsistencies of earlier theoretical methods have been corrected for the first time. The finite mass, or recoil effect, composed of the normal mass shift (NMS), and the specific mass shift (SMS) were corrected for relativistic contributions, RNMS and RSMS. The present experimental results have shown that the recoil effects on the Breit level are indeed very important, as well as the effects of the correlated relativistic dynamics in a many electron ion.
This a review of the present status of heavy-ion collisions at intermediate energies. The main goal of heavy-ion physics in this energy regime is to shed some light on the nuclear equation of state (EOS), hence we present the basic concept of the EOS in nuclear matter as well as of nuclear shock waves which provide the key mechanism for the compression of nuclear matter. The main part of this article is devoted to the models currently used for describing heavy-ion reactions theoretically and to the observables useful for extracting information about the EOS from experiments. A detailed discussion of the flow effects with a broad comparison with the avaible data is presented. The many-body aspects of such reactions are investigated via the multifragmentation break up of excited nuclear systems and a comparison of model calculations with the most recent multifragmentation experiments is presented.
In the framework of the relativistic quantum dynamics approach we investigate antiproton observables in Au-Au collisions at 10.7A GeV. The rapidity dependence of the in-plane directed transverse momentum p(y) of p's shows the opposite sigh of the nucleon flow, which has indeed recently been discovered at 10.7A GeV by the E877 group. The "antiflow" of p's is also predicted at 2A GeV and at 160 A GeV and appears at all energies also for pi's and K's. These predicted p anticorrelations are a direct proof of strong p annihilation in massive heavy ion reactions.
The quantum statistical model (QSM) is used to calculate nuclear fragment distributions in chemical equilibrium. Several observable isotopic effects are predicted for intermediate energy heavy ion collisions. It is demonstrated that particle ratios for different systemsdo not depend on the breakup density-the only free parameter in our model.The importance of entropy measurements is discussed. Specific particle ratios for the system Au-Au are predicted, which can be used to determine the chemical potentials of the hot midrapidity fragment source in nearly central heavy ion collisions. Pacs-Nr. 25.70 Pq
The Monte Carlo parton string model for multiparticle production in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions at high energies is described. An adequate choice of the parameters in the model gives the possibility of recovering the main results of the dual parton model, with the advantage of treating both hadron and nuclear interactions on the same footing, reducing them to interactions between partons. Also the possibility of considering both soft and hard parton interactions is introduced.
The properties of pions from the hot and dense reaction stage of relativistic heavy ion collisions are investigated with the quantum molecular dynamics model. Pions originating from this reaction stage stem from resonance decay with enhanced mass. They carry high transverse momenta. The calculation shows a direct correlation between high pt pions, early freeze-out times and high freeze-out densities.
Dilepton spectra for p+p and p+d reactions at 4.9GeV are calculated. We consider electromagnetic bremsstrahlung also in inelastic reactions. N* and Delta* decay present the major contributions to the pho and omega meson yields.Pion annihilation yields only 1.5% of all pho's in p+d. The pho mass spectrum is strongly distorted due to phase space effects, populating dominantly dilepton masses below 770MeV.