Over the past two decades, cluster policies have become a standard instrument of public authorities and economic development practitioners in many parts of the world. This paper takes a critical stance on this phenomenon and provides theoretical arguments that challenge the widespread application of cluster initiatives to promote long-term regional development. We distinguish between and compare two main bodies of thought: the neoclassical view and the agglomeration view. We show that there are no rationales for cluster policy from the perspective of neoclassical theory. The agglomeration view, in contrast, provides a convincing conceptual basis for justifying economic policies implemented in form of cluster initiatives. At the same time, however, it points to major problems related with the cluster policy approach. We identify and elaborate on three essential difficulties, i.e. the proper (1) targeting, (2) dosing, and (3) timing of cluster policy actions. We highlight that the problems related with these fundamental issues of each public initiative constitute powerful pitfalls and booby traps of cluster policies. (author's abstract) / Series: SRE - Discussion Papers

Résumé : Les transferts d’électrons photo-induits et d’énergie jouent un rôle primordial dans un grand nombre de processus photochimiques et photobiologiques, comme la respiration ou la photosynthèse. Une très grande quantité de systèmes à liaisons covalentes ont été conçus pour copier ces processus de transferts. Cependant, les progrès sont, en grande partie, limités par les difficultés rencontrées dans la synthèse de nouveaux couples de types donneurs-accepteurs. Récemment, des espèces utilisant des liaisons non-covalentes, comme les liaisons hydrogènes, les interactions [pi]-[pi], les liaisons de coordination métal-ligands ou encore les interactions électrostatiques sont le centre d’un nouvel intérêt du fait qu’ils soient plus faciles à synthétiser et à gérer pour obtenir des comportements de transferts d’électrons ou d’énergie plus flexibles et sélectifs. C’est dans cette optique que le travail de cette thèse a été mené, i.e. de concevoir des composés auto-assemblés avec des porphyrines et un cluster de palladium pour l’étude des transferts d’électrons photo-induits et d’énergie. Cette thèse se divise en quatre parties principales. Dans la première section, le chapitre 3, deux colorants porphyriniques, soit le 5-(4-carboxylphényl)-10, 15, 20-tristolyl(porphyrinato)zinc(II) (MCP, avec Na+ comme contre-ion) et 5, 15-bis(4-carboxylphényl)-15, 20-bistolyl(porphyrinato)zinc(II) (DCP, avec Na+ comme contre-ion) ont été utilisés comme donneurs d’électrons, et le [Pd3(dppm)3(CO)]2+ ([Pd32+], dppm = (Ph2P)2CH2, PF6‾ est le contre-ion) a été choisi comme accepteur d’électrons. La structure de l’assemblage [Pd32+]•••porphyrine a été élucidée par l’optimisation des géométries à l’aide de calculs DFT. La spectroscopie d’absorption transitoire (TAS) montre la vitesse de transferts d’électrons la plus rapide (< 85 fs, temps inférieurs à la limite de détection) jamais enregistrée pour ce type de système (porphyrine-accepteur auto-assemblés). Généralement, ces processus sont de l’ordre de l’échelle de la ps-ns. Cette vitesse est comparable aux plus rapides transferts d’électrons rapportés dans le cas de systèmes covalents de type porphyrine-accepteur rapide (< 85 fs, temps inférieurs à la limite de détection). Ce transfert d’électrons ultra-rapide (ket > 1.2 × 1013 s-1) se produit à l’état énergétique S1 des colorants dans une structure liée directement par des interactions ioniques, ce qui indique qu’il n’est pas nécessaire d’avoir de forts liens ou une géométrie courbée entre le donneur et l’accepteur. Dans une deuxième section, au chapitre 4, nous avons étudié en profondeur l’effet de l’utilisation de porphyrines à systèmes π-étendus sur le comportement des transferts d’électrons. Le colorant 9, 18, 27, 36-tétrakis-meso-(4-carboxyphényl)tétrabenzoporphyrinatozinc(II) (TCPBP, avec Na+ comme contre-ion) a été sélectionné comme candidat, et le 5, 10, 15, 20-tétrakis-meso-(4-carboxyphényl)porphyrineatozinc(II) (TCPP, avec Na+ comme contre-ion) a aussi été utilisé à des fins de comparaisons. TCPBP et TCPP ont, tous deux, été utilisés comme donneurs d’électrons pour fabriquer des assemblages supramoléculaires avec le cluster [Pd32+] comme accepteur d’électrons. Les calculs DFT ont été réalisés pour expliquer les structures de ces assemblages. Dans les conditions expérimentales, ces assemblages sont composés principalement d’une porphyrine avec 4 équivalents de clusters. Ces systèmes ont aussi été investigués par des mesures de quenching (perte de luminescence), par électrochimie et par d’autres techniques. Les transferts d’électrons (< 85 fs; temps inférieurs à la limite de détection) étaient aussi observés, de façon similaire aux assemblages MCP•••[Pd32+] et [Pd32+]•••DCP•••[Pd32+]. Les résultats nous indiquent que la modification de la structure de la porphyrine vers la tétrabenzoporphyrine ne semble pas influencer le comportement des cinétiques de transferts d’électrons (aller ou retour). Dans la troisième section, le chapitre 5, nous avons synthétisé la porphyrine hautement [pi]-conjuguée: 9, 18, 27, 36-tétra-(4-carboxyphényléthynyl)tétrabenzoporphyrinatozinc(II) (TCPEBP, avec Na+ comme contre-ion) par des fonctionnalisations en positions meso- et β, β-, qui présente un déplacement vers le rouge de la bande de Soret et des bandes Q. TCPEBP était utilisé comme donneur d’électrons pour fabriquer des motifs supramoléculaires avec le [Pd32+] comme accepteur d’électrons. Des expériences en parallèle ont été menées en utilisant la 5, 10, 15, 20-tétra-(4-carboxyphényl)éthynylporphyrinatozinc(II) (TCPEP, avec Na+ comme contre-ion). Des calculs DFT et TDDFT ont été réalisés pour de nouveau déterminer de façon théorique les structures de ces systèmes. Les constantes d’association pour les assemblages TCPEBP•••[Pd32+]x sont les plus élevées parmi tous les assemblages entre des porphyrines et le cluster de palladium rencontrés dans la littérature. La TAS a montré, encore une fois, des processus de transferts d’électrons dans des échelles de l’ordre de 75-110 fs. Cependant, les transferts de retour d’électrons sont aussi très rapides (< 1 ps), ce qui est un obstacle potentiel pour des applications en cellules solaires à pigment photosensible (DSSCs). Dans la quatrième section, le chapitre 6, les transferts d’énergie triplets (TET) ont été étudiés pour les assemblages MCP•••[Pd32+] et [Pd32+]•••DCP•••[Pd32+]. Les analyses spectrales des états transitoires dans l’échelle de temps de la ns-[mu]s démontrent de façon évidente les TETs; ceux-ci présentent des transferts d’énergie lents et/ou des vitesses moyennes pour des transferts d’énergie T1-T1 (3dye*•••[Pd32+] → dye•••3[Pd32+]*) opérant à travers exclusivement le mécanisme de Förster avec des valeurs de kET autour de ~ 1 × 105 s-1 selon les mesures d’absorption transitoires à 298 K. Des forces motrices non-favorables rendent ces types de processus non-opérants ou très lents dans les états T1. L’état T1 de [Pd32+] (~8190 cm-1) a été qualitativement déterminé par DFT et par la mise en évidence de l’émission S0 ← Tn retardée à 680-700 nm provenant de l’annihilation T1-T1, ce qui fait que ce cluster peut potentiellement agir comme un donneur à partir de ses états Tn, et accepteur à partir de T1 à l’intérieur de ces assemblages. Des pertes d’intensités de types statiques pour la phosphorescence dans le proche-IR sont observées à 785 nm. Ce travail démontre une efficacité modérée des colorants à base de porphyrines pour être impliquée dans des TETs avec des fragments organométalliques, et ce, même attachées grâce à des interactions ioniques. En conclusion, les assemblages ioniques à base de porphyrines et de clusters de palladium présentent des propriétés de transferts d’électrons S1 ultra-rapides, et des transferts d’énergie T1 de vitesses modérées, ce qui est utile pour de possibles applications comme outils optoélectroniques. D’autres études, plus en profondeur, sont présentement en progrès. / Abstract : Photoinduced electron and energy transfers play the pivotal role in various photochemical and photobiological redox processes including photosynthesis and respiration. Abundant covalently bonded systems have been designed to mimic the natural electron and energy transfer processes. However, the progress is often interfered by the difficulties to synthesize novel and versatile covalent donor-acceptor pairs. Recently, entities utilizing non-covalent interactions including hydrogen-bonding, [pi]-[pi] stacking, metal-ligand coordination and electrostatic interactions are becoming a hot topic since they are easy to be fabricated and tuned for selective and flexible electron and energy transfer behaviors. In this respect, the work presented in this thesis designed self-assemblies with porphyrins and a palladium cluster for photoinduced electron and energy transfers. It includes four main sections. In the first section, Chapter 3, two porphyrinic dyes, 5-(4-carboxylphenyl)-10, 15, 20-tristolyl(porphyrinato)zinc(II) (MCP, as sodium salt) and 5, 15-bis(4-carboxylphenyl)-15, 20-bistolyl(porphyrinato)zinc(II) (DCP, as sodium salt), were used as electron donors, and [Pd3(dppm)3(CO)]2+ ([Pd32+], dppm = (Ph2P)2CH2, as PF6‾ salt) cluster was adopted as the electron acceptor. The structure of [Pd32+]•••porphyrin assemblies was elucidated by geometry optimization using Density Functional Theory (DFT) calculations. Transient absorption spectroscopy (TAS) indicated a record fast electron transfer rate (< 85 fs, the time resolution limit) among the porphyrin-acceptor self-assemblies. Typically, these occur in ps-ns time scale. This rate is also comparable to the fastest electron transfer rate reported for the covalently linked porphyrin-acceptor systems (~ 50 fs, the time resolution limit). The ultrafast photo-induced electron transfers (ket > 1.2 × 1013 s-1) occurring at the S1 levels of the dyes in the structurally well-defined “straight up” ionic assemblies indicate that it is not necessary to have a strong bond and bent geometry between the donor and acceptor. In the second section, Chapter 4, we further studied the effect of using π-extended porphyrins on the electron transfer behavior of these assemblies. 9, 18, 27, 36-Tetrakis-meso-(4-carboxyphenyl)tetrabenzoporphyrinatozinc(II) (TCPBP, as a sodium salt) was selected as the candidate, and the 5, 10, 15, 20-tetrakis-meso-(4-carboxyphenyl)porphyrinatozinc(II) (TCPP, as a sodium salt) dye was also studied for comparison purposes. TCPBP and TCPP were both utilized as electron donors to fabricate supramolecular assemblies with the [Pd32+] cluster as the electron acceptor. DFT calculations were used to explain the structure of these assemblies. Under the experimental conditions used, these assemblies mainly exist in the form of one porphyrin with four equivalent clusters. These systems were also investigated by quenching measurements, electrochemistry, and other techniques. Ultrafast electron transfers (< 85 fs; time resolution limit) were also observed, which is similar as those for MCP•••[Pd32+] and [Pd32+]•••DCP•••[Pd32+] assemblies. The results indicate the structural modification from porphyrin to tetrabenzoporphyrin does not seemingly influence the kinetic behavior of the forward and back electron transfers. In the third section, Chapter 5, we synthesized a highly [pi]-conjugated porphyrin, 9, 18, 27, 36-tetra-(4-carboxyphenylethynyl)tetrabenzoporphyrinatozinc(II) (TCPEBP, as a sodium salt) by meso- and β, β-bifunctionalization, which exhibits large red shift of the Soret and Q-bands. TCPEBP was utilized as electron donors to fabricate supramolecular motifs with [Pd32+] cluster as the electron acceptor. Parallel experiments were conducted using 5, 10, 15, 20-tetra-(4-carboxyphenyl)ethynylporphyrinatozinc(II) (TCPEP, as a sodium salt). DFT and TDDFT calculations were applied to elucidate the structure of these assemblies. Binding constants for TCPEBP•••[Pd32+]x is the largest one among all the assemblies with porphyrin and palladium cluster. TAS showed again the ultrafast electron transfer process within the 75-110 fs time frame. However, the back electron transfers are also very fast (< 1 ps), which may be a potential obstacle for future applications in dye-sensitized solar cells (DSSCs). In the fourth section, Chapter 6, triplet energy transfers (TET) of the assemblies MCP•••[Pd32+] and [Pd32+]•••DCP•••[Pd32+] were studied. The transient spectral analysis in the ns-[mu]s time scale clearly demonstrates evidence for TET, which shows a slow to medium T1-T1 energy transfer (3dye*•••[Pd32+] → dye•••3[Pd32+]*) operating through a Förster mechanism exclusively with kET values of ~ 1 × 105 s-1 based on transient absorption measurements at 298 K. Unfavourable reductive and oxidative driving forces make this type of process inoperative or very slow in the T1 states. The T1 state of [Pd32+] (~8190 cm-1) has been quantitatively determined by DFT computations and by evidence for a delayed S0 ← Tn emission at 680-700 nm arising from T1-T1 annihilation, which makes this cluster potentially acting as the energy donor from its Tn state, and T1 acceptor within the assemblies. The static quenching of their near-IR phosphorescence at 785 nm was observed. This work demonstrated a moderate efficiency of the porphyrin dye to be involved in TET with an organometallic fragment, even when attached through ionic interactions. Conclusively, ionic assemblies with porphyrins and palladium clusters exhibit ultrafast S1 electron transfer and moderate T1 energy transfer properties, which is useful for possible application as optoelectronic devices. Further research in more depth is in progress.

Water monomer and dimer encapsulations into D-2(22)-C-84 fullerene are evaluated. The encapsulation energy is computed at the M06-2X/6-31++G** level, and it is found that the monomer and dimer storage in C-84 yields an energy gain of 10.7 and 17.4kcalmol(-1), respectively. Encapsulation equilibrium constants are computed by using partition functions based on the M06-2X/6-31G** and M06-2X/6-31++G** molecular data. Under high-temperature/high-pressure conditions, similar to that for the encapsulation of rare gases in fullerenes, the computed (H2O)(2)@C-84-to-H2O@C-84 ratio is close to 1:2.

There is compelling observational evidence for the existence of dark matter in the Universe, including our own Galaxy, which could possibly consist of weakly interacting massive particles (WIMPs) not contained in the standard model (SM) of particle physics. WIMPs may get gravitationally trapped inside heavy celestial bodies of ordinary matter. The Sun is a nearby candidate for such a capture process which is driven by the scattering of WIMPs on its nuclei. Forming an over-density at the Sun's core the WIMPs would self-annihilate yielding energetic neutrinos, which leave the Sun and can be detected in experiments on Earth. The cubic-kilometer sized IceCube neutrino observatory, constructed in the clear glacial ice at the Amundsen-Scott South Pole Station in Antarctica offers an excellent opportunity to search for this striking signal. This thesis is dedicated to the search for these solar dark matter signatures in muon neutrinos from the direction of the Sun. Newly developed techniques based on hit clustering and hit-based vetos allow more accurate reconstruction and identification of events in the detector and thereby a stronger rejection of background. These techniques are also applicable to other IceCube analyses and event filters. In addition, new approaches to the analysis without seasonal cuts lead to improvements in sensitivity especially in the low-energy regime (&lt;=100 GeV), the target of the more densely instrumented DeepCore sub-array. This first analysis of 369 days of data recorded with the completed detector array of 86 strings revealed no significant excess above the expected background of atmospheric neutrinos. This allows us to set strong limits on the annihilation rate of WIMPs in the Sun for the models probed in this analysis. The IceCube limits for the spin-independent WIMP-proton scattering cross-section are the most stringent ones for WIMP masses above 100 GeV. / IceCube

In this paper we present a fuzzy voting scheme for cluster algorithms. This fuzzy voting method allows us to combine several runs of cluster algorithms resulting in a common fuzzy partition. This helps us to overcome instabilities of the cluster algorithms and results in a better clustering. / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

Clusters constitute an intermediate state of matter between molecules and solids whose properties are size dependent and can be tailored. In recent years, cluster science has become one of the most exciting areas of research since their study can not only bridge our understanding between atoms and their bulk but also between various disciplines. In addition, clusters can serve as a source of new materials with uncommon properties. This dissertation deals with an in-depth study of clusters as a bridge across physics, chemistry, and materials science and provides a fundamental understanding of the structure-property relationships by focusing on three different topics. The first topic deals with superatoms which are clusters that mimic the chemistry of atoms. I show that superhalogens and superalkalis can be designed to mimic the chemistry of halogen and alkali atoms, respectively. An entirely new class of salts can then be synthesized by using these superatoms as the building blocks. I have also explored the possibility of designing highly electronegative species called hyperhalogens by using superhalogens as ligands or superalkalis as core and a combination of both. Another aspect of my work on superatom is to examine if traditional catalysts (namely Pd) can be replaced by clusters composed of earthabundant elements (namely Zr and O). This is accomplished by comparing the electronic structure and reactivity of Pd clusters with isoelectronic ZrO clusters. The second topic deals with a study of the electronic structure of coinage metal (Cu and Ag) clusters and see if they remain unchanged when a metal atom is replaced by an isoelectronic hydrogen atom as is the case with Au-H clusters. The third topic deals with clusters as model of polymeric materials to understand their gas storage and sequestration properties. This is accomplished by studying the trapping of H2, CO2, CH4 and SO2 molecules in borazine-linked polymers (BLPs) and benzimidazole-linked polymers (BILPs). The first two topics provide a bridge between physics and chemistry, while the third topic provides a bridge to materials science.

Over the past few decades, Cluster Randomized Trials (CRT) have become a design of choice in many research areas. One of the most critical issues in planning a CRT is to ensure that the study design is sensitive enough to capture the intervention effect. The assessment of power and sample size in such studies is often faced with many challenges due to several methodological difficulties. While studies on power and sample size for cluster designs with one and two levels are abundant, the evaluation of required sample size for three-level designs has been generally overlooked. First, the nesting effect introduces more than one intracluster correlation into the model. Second, the variance structure of the estimated treatment difference is more complicated. Third, sample size results required for several levels are needed. In this work, we developed sample size and power formulas for the three-level data structures based on the generalized linear mixed model approach. We derived explicit and general power and sample size equations for detecting a hypothesized effect on continuous Gaussian outcomes and binary outcomes. To confirm the accuracy of the formulas, we conducted several simulation studies and compared the results. To establish a connection between the theoretical formulas and their applications, we developed a SAS user-interface macro that allowed the researchers to estimate sample size for a three-level design for different scenarios. These scenarios depend on which randomization level is assigned and whether or not there is an interaction effect.

The purpose of the present study was to determine whether distinct patterns of adolescent adjustment existed when four domains of functioning were considered. The study included a sample of 299 high-risk urban adolescents, predominantly African American, ages 9-16 and their maternal caregivers. Cluster analysis was used to identify patterns of adjustment. Logistic regression analyses were used to explore whether variations in levels of five theoretically and empirically supported protective factors predicted cluster membership. A four-cluster model was determined to best fit the data. Higher rates of goal directedness and anger regulation coping predicted membership within the highest functioning cluster over a cluster demonstrating high externalizing problem behaviors, and neighborhood cohesion predicted highest functioning cluster membership over a cluster demonstrating high internalizing symptoms. Findings suggest that within a high-risk population of adolescents, significant variability in functioning will exist. The presence or absence of specific protective factors predicts developmental outcomes.

In this work we have studied the relationship between the kinematics and shapes of Early Type Galaxies (ETGs) in rich clusters. In particular we were interested to extend the kinematic morphology density relation to the richest clusters. We obtained data from FLAMES/GIRAFFE to probe the stellar kinematics of a sample of 30 ETGs in the massive cluster Abell 1689 at z = 0.183, to classify them as Slow Rotators (SRs) or Fast Rotators (Frs). To date, this is the highest redshift cluster studied in this way. We simulated FLAMES/GIRAFFE observations of the local SAURON galaxies to account for the bias introduced compared to the ATLAS3D sample, which we used as a local comparison. We find that the luminosity function of SRs in Abell 1689 is the same as that in ATLAS^3D, down to the faintest objects probed (M_K ≈ -23). The number fraction of SRs over the ETG population in Abell 1689 is f_SR = 0.15 +/- 0.03, consistent with the value found in the Virgo Cluster. However, within the cluster, f_SR rises sharply with the projected number density of galaxies, rising from f_SR = 0.01 in the least dense bin to f_SR = 0.58 in the densest bin. We conclude that the fraction of SRs is not determined by the local number density of galaxies, but rather by the physical location within the cluster. This might be due to dynamical processes which cause SRs (on average more massive) to sink in the gravitational potential of the cluster. Next we explore the distribution of projected ellipticity &epsilon; in galaxies belonging to a sample of clusters from SDSS (z </~ 0.1) and the CLASH survey (z ≈ 0.2). We were interested to establish whether the fraction of galaxies flatter than &epsilon; = 0.4 (a proxy for FRs) varies from cluster to cluster. We find some significant variations. We go on to probe the projected shape as a function of projected cluster-centric radius. In both samples we find that on average galaxies have progressively rounder projected shapes at lower cluster-centric projected distance. In the SDSS sample we show that this trend exists above and beyond the trend for brighter galaxies to be more common near the centre of clusters (bright galaxies are on average rounder). In order to disentangle the trend for SRs (which are rounder) to be more common near the centre of clusters, we isolate a subsample of FRs only, by considering only galaxies with &epsilon; > 0.4. We find that even the intrinsically flat FRs are on average rounder at lower projected cluster-centric distance. We conclude that the observed trend is due either to the dynamic heating of the stellar discs being strongest near the centre of clusters, or due to an anti-correlation of the bulge fractions with the cluster-centric distance.

No description available.