Orthogonal protection of peptides and peptoids for cyclization by the thiol-ene reaction and conjugation

Cyclic peptides and peptoids were prepared using the thiolene Michael-type reaction. The linear precursors were provided with additional functional groups allowing for subsequent conjugation: an orthogonally protected thiol, a protected maleimide, or an alkyne. The functional group for conjugation was placed either within the cycle or in an external position. The click reactions employed for conjugation with suitably derivatized nucleoside or oligonucleotides were either cycloadditions (Diels-Alder, Cu(I)-catalyzed azide-alkyne) or the same Michael-type reaction as for cyclization.

Spontaneous Emergence of Chirality in the Limited Enantioselectivity Model: Autocatalytic Cycle Driven by an External Reagent

The emergence of chirality in enantioselective autocatalysis for compounds unable to transform according to the Frank-like reaction network is discussed with respect to the controversial limited enantioselectivity (LES) model composed of coupled enantioselective and non-enantioselective autocatalyses. The LES model cannot lead to spontaneous mirror symmetry breaking (SMSB) either in closed systems with a homogeneous temperature distribution or in closed systems with a stationary non-uniform temperature distribution. However, simulations of chemical kinetics in a two-compartment model demonstrate that SMSB may occur if both autocatalytic reactions are spatially separated at different temperatures in different compartments but coupled under the action of a continuous internal flow. In such conditions, the system can evolve, for certain reaction and system parameters, toward a chiral stationary state; that is, the system is able to reach a bifurcation point leading to SMSB. Numerical simulations in which reasonable chemical parameters have been used suggest that an adequate scenario for such a SMSB would be that of abyssal hydrothermal vents, by virtue of the typical temperature gradients found there and the role of inorganic solids mediating chemical reactions in an enzyme-like role.

Business Cycle Regimes in CEECs Production: A Threshold SURE Approach

We use a threshold seemingly unrelated regressions specification to assess whether the Central and East European countries (CEECs) are synchronized in their business cycles to the Euro-area. This specification is useful in two ways: First, it takes into account the common institutional factors and the similarities across CEECs in their process of economic transition. Second, it captures business cycle asymmetries by allowing for the presence of two distinct regimes for the CEECs. As the CEECs are strongly affected by the Euro-area these regimes may be associated with Euro-area expansions and contractions. We discuss representation, estimation by maximum likelihood and inference. The methodology is illustrated by using monthly industrial production in 8 CEECs. The results show that apart from Lithuania the rest of the CEECs experience ���normal��� growth when the Euro-area contracts and ���high��� growth when the Euro-area expands. Given that the CEECs are ���catching up��� with the Euro-area this result shows that most CEECs seem synchronized to the Euro-area cycle. Keywords: Threshold SURE; asymmetry; business cycles; CEECs. JEL classification: C33; C50; E32.

Estudi de la reductibilitat de catalitzadors basats en cobalt i el seu comportament en la reacci�� de despla��ament de gas d'aigua de CO

Projecte de recerca elaborat a partir d���una estada a la universitat d'Udine, It��lia, entre setembre i desembre del 2006.S'han caracteritzat mitjan��ant la reducci�� a temperatura programada i tests catal��tics catalitzadors en pols basats en cobalt i supostats en ��xid de zinc i mon��lits cer��mics funcionaliltzats tamb�� amb cobalt i ��xid de zinc. L'addici�� de promotors (mangan��s, crom i ferro ) als catalitzadors en pols, preparats per impregnaci�� i precipitaci��, no afecta significativament ni la temperatura a la qual t�� lloc la reducci�� ni al percentatge global de reducci��. En els cicles de reducci��-oxidaci�� s�� que s'observen difer��ncies entre el primer perfil de reducci�� i els seg��ents, especialment en el cas de la mostra que t�� ferro com a promotor, on les difer��ncies s'accentuen en cicles successius (fins al quart). S'ha evaluat l'activitat d'aquests catalitzadors en la reacci�� de despla��ament de gas d'aigua, obtenint uns resultats satisfactoris. Finalment s'han realitzat reduccions a temperatura programada i tests catal��tics en la reacci�� de despla��ament de gas d'aigua amb mon��lits funcionalitzats amb cobalt i ��xid de zinc (en cap d'ells s'ha introdu��t promotors). El nivell de conversi�� assolit ��s menor que en el cas de catalitzadors en pols, fet que s'associa a la geometria d'aquests sistemes catal��tics, per�� la relaci�� CH4/CO2 ��s m��s favorable que en els catalitzadors en pols, el que els converteix en sistemes molt selectius.

Rigorous derivation of a nonlinear diffusion equation as fast-reaction limit of a continuous coagulation-fragmentation model with diffusion

Weak solutions of the spatially inhomogeneous (diffusive) Aizenmann-Bak model of coagulation-breakup within a bounded domain with homogeneous Neumann boundary conditions are shown to converge, in the fast reaction limit, towards local equilibria determined by their mass. Moreover, this mass is the solution of a nonlinear diffusion equation whose nonlinearity depends on the (size-dependent) diffusion coefficient. Initial data are assumed to have integrable zero order moment and square integrable first order moment in size, and finite entropy. In contrast to our previous result [CDF2], we are able to show the convergence without assuming uniform bounds from above and below on the number density of clusters.

Stabilized Petrov-Galerkin methods for the convection-diffusion-reaction and the Helmholtz equations

We present two new stabilized high-resolution numerical methods for the convection���diffusion���reaction (CDR) and the Helmholtz equations respectively. The work embarks upon a priori analysis of some consistency recovery procedures for some stabilization methods belonging to the Petrov���Galerkin framework. It was found that the use of some standard practices (e.g. M-Matrices theory) for the design of essentially non-oscillatory numerical methods is not feasible when consistency recovery methods are employed. Hence, with respect to convective stabilization, such recovery methods are not preferred. Next, we present the design of a high-resolution Petrov���Galerkin (HRPG) method for the 1D CDR problem. The problem is studied from a fresh point of view, including practical implications on the formulation of the maximum principle, M-Matrices theory, monotonicity and total variation diminishing (TVD) finite volume schemes. The current method is next in line to earlier methods that may be viewed as an upwinding plus a discontinuity-capturing operator. Finally, some remarks are made on the extension of the HRPG method to multidimensions. Next, we present a new numerical scheme for the Helmholtz equation resulting in quasi-exact solutions. The focus is on the approximation of the solution to the Helmholtz equation in the interior of the domain using compact stencils. Piecewise linear/bilinear polynomial interpolation are considered on a structured mesh/grid. The only a priori requirement is to provide a mesh/grid resolution of at least eight elements per wavelength. No stabilization parameters are involved in the definition of the scheme. The scheme consists of taking the average of the equation stencils obtained by the standard Galerkin finite element method and the classical finite difference method. Dispersion analysis in 1D and 2D illustrate the quasi-exact properties of this scheme. Finally, some remarks are made on the extension of the scheme to unstructured meshes by designing a method within the Petrov���Galerkin framework.

Macroeconomic shocks and the business cycle: evidence from a structural factor model

We use a dynamic factor model to provide a semi-structural representation for 101 quarterly US macroeconomic series. We find that (i) the US economy is well described by a number of structural shocks between two and six. Focusing on the four-shock specification, we identify, using sign restrictions, two non-policy shocks, demand and supply, and two policy shocks, monetary and fiscal. We obtain the following results. (ii) Both supply and demand shocks are important sources of fluctuations; supply prevails for GDP, while demand prevails for employment and inflation. (ii) Policy matters, Both monetary and fiscal policy shocks have sizeable effects on output and prices, with little evidence of crowding out; both monetary and fiscal authorities implement important systematic countercyclical policies reacting to demand shocks. (iii) Negative demand shocks have a large long-run positive effect on productivity, consistently with the Schumpeterian "cleansing" view of recessions.

Uranium reserve, nuclear fuel cycle delusion, CO2 emission from the sea, and electricity supply: reflections after the fuel meltdown of Fukushima nuclear power units

The Great Tohoku-Kanto earthquake and resulting tsunami has brought considerable attention to the issue of the construction of new power plants. We argue in this paper, nuclear power is not a sustainable solution to energy problems. First, we explore the stock of uranium-235 and the different schemes developed by the nuclear power industry to exploit this resource. Second, we show that these methods, fast breeder and MOX fuel reactors, are not feasible. Third, we show that the argument that nuclear energy can be used to reduce CO2 emissions is false: the emissions from the increased water evaporation from nuclear power generation must be accounted for. In the case of Japan, water from nuclear power plants is drained into the surrounding sea, raising the water temperature which has an adverse affect on the immediate ecosystem, as well as increasing CO2 emissions from increased water evaporation from the sea. Next, a short exercise is used to show that nuclear power is not even needed to meet consumer demand in Japan. Such an exercise should be performed for any country considering the construction of additional nuclear power plants. Lastly, the paper is concluded with a discussion of the implications of our findings.

L���impacte de les institucions internacionals sobre la Uni�� Europea: presa de decisions, integraci�� i europe��tzaci��

Projecte de recerca elaborat a partir d���una estada a la Center for European Integration de la Freie Universit��t Berlin, Alemania, entre 2007 i 2009. El tema central del projecte consisteix en la descripci�� matem��tica de processos espai-temporals mitjan��ant la teoria dels Continuous-Time Random Walks. L'aportaci�� m��s significativa del nostre treball en aquest camp consisteix en considerar per primera vegada la interacci�� entre diversos processos actuant de manera acoblada, ja que fins ara els models existents es limitaven a l'estudi de processos individuals o independents. Aquesta idea fa possible, per exemple, plantejar un sistema de transport en l'espai i a la vegada un proc��s de reacci�� (una reacci�� qu��mica, per exemple), i estudiar estad��sticament com cada un pot alterar el comportament de l'altre. Aix�� suposa un salt qualitatiu important en la descripci�� de processos de reacci��-dispersi��, ja que els nostres models permeten incorporar patrons de dispersi�� i comportaments temporals (cicles de vida) for��a realistes en comparaci�� amb els models convencionals. Per tal de completar aquest treball te��ric ha estat necessari tamb�� desenvolupar algunes eines num��riques (models de xarxa) per facilitar la implementaci�� dels models. En la vessant pr��ctica, hem aplicat aquestes idees al cas de la din��mica entre virus i el sistema immunol��gic que t�� lloc quan es produeix una infecci�� a l'organisme. Diferents estudis experimentals portats a terme els ��ltims anys mostren com la resposta immunol��gica dels organismes superiors presenta una din��mica temporal for��a complexa (per exemple, en el cas de la resposta programada). Per aquest motiu, les nostres t��cniques matem��tiques s��n d'especial utilitat per a l'an��lisi d'aquests sistemes. Finalment, altres possibles aplicacions dels models, com ara l'estudi d'invasions biol��giques, tamb�� han estat considerades.

Eliminaci�� autotr��fica de nitrogen en una pila biol��gica (microbial fuel cells )

L���aigua i l���energia formen un binomi indissociable. En relaci�� al cicle de l���aigua, des de fa varies d��cades s���han desenvolupat diferents formes per recuperar part de l���energia relacionada amb l���aigua, per exemple a partir de centrals hidroel��ctriques. No obstant, l�����s d���aquesta aigua tamb�� porta associat un gran consum energ��tic, relacionat sobretot amb el transport, la distribuci��, la depuraci��, etc... La depuraci�� d���aig��es residuals porta associada una elevada demanda energ��tica (Obis et al.,2009). En termes energ��tics, tot i que la despesa el��ctrica d���una EDAR varia en funci�� de diferents par��metres com la configuraci�� i la capacitat de la planta, la c��rrega a tractar, etc... es podria considerar que el rati mig seria d��� aproximadament 0.5 KWh���m-3.Els principals costos d���explotaci�� estan relacionats tant amb la gesti�� de fangs (28%) com amb el consum el��ctric (25%) (50% tractament biol��gic). Tot i que moltes investigacions relacionades amb el tractament d���aigua residual estan encaminades en disminuir els costos d���operaci��, des de fa poques d��cades s���est�� investigant la viabilitat de que l���aigua residual fins i tot sigui una font d���energia, canviant la perspectiva, i comen��ant a veure l���aigua residual no com a una problem��tica sin�� com a un recurs. Concretament s���estima que l���aigua dom��stica cont�� 9.3 vegades m��s energia que la necess��ria per el seu tractament mitjan��ant processos aerobis (Shizas et al., 2004). Un dels processos m��s desenvolupats relacionats amb el tractament d���aig��es residuals i la producci�� energ��tica ��s la digesti�� anaer��bia. No obstant, aquesta tecnologia permet el tractament d���altes c��rregues de mat��ria org��nica generant un efluent ric en nitrogen que s���haur�� de tractar amb altres tecnologies. Per altre banda, recentment s���est�� investigant una nova tecnologia relacionada amb el tractament d���aig��es residuals i la producci�� energ��tica: les piles biol��giques (microbial fuel cells, MFC). Aquesta tecnologia permet obtenir directament energia el��ctrica a partir de la degradaci�� de substrats biodegradables (Rabaey et al., 2005). Les piles biol��giques, m��s conegudes com a Microbial Fuel Cells (acr��nim en angl��s, MFC), s��n una emergent tecnologia que est�� centrant moltes mirades en el camp de l��� investigaci��, i que es basa en la producci�� d���energia el��ctrica a partir de substrats biodegradables presents en l���aigua residual (Logan., 2008). Els fonaments de les piles biol��giques ��s molt semblant al funcionament d���una pila Daniell, en la qual es separa en dos compartiments la reacci�� d���oxidaci�� (compartiment an��dic) i la de reducci�� (compartiment cat��dic) amb l���objectiu de generar un determinat corrent el��ctric. En aquest estudi, b��sicament es mostra la posada en marxa d'una pila biol��gica per a l'eliminaci�� de mat��ria org��nica i nitrogen de les aig��es residuals.

On the analysis of travelling waves to a nonlinear flux limited reaction-diffusion equation

In this paper we study the existence and qualitative properties of travelling waves associated to a nonlinear flux limited partial differential equation coupled to a Fisher-Kolmogorov-Petrovskii-Piskunov type reaction term. We prove the existence and uniqueness of finite speed moving fronts of C2 classical regularity, but also the existence of discontinuous entropy travelling wave solutions.

Determinants of Spanish firms' life cycle and job

This paper examines the role of human capital, individual entrepreneurial traits and the business environment on firms' life cycle and on job creation in Spain. For this purpose, we have constructed a pseudo-panel, by using the Global Entrepreneurship Monitor survey over the period 2001-2008. We have found that the creation, maturity and survival of firms were aided by the availability of bank credit and the large immigration inflows that Spain received over this period. However, of these two factors, only bank credit had a positive effect on the creation of jobs and on improving expectations of job expansion. The relatively high levels of youth unemployment experienced even before the crises of 2008 hurt the firm's chances of maturity and survival. The results also suggested that the gender gap in entrepreneurial activities had narrowed. In relative terms, women with higher levels of education were more likely to create mature firms than men. Based on the empirical findings and those of related literature, the paper offers policy recommendations to foster a sustainable entrepreneurial sector capable of contributing to the recovery of the Spanish economy.

Consumption heterogenity over the business cycle

We study consumption heterogeneity over the business cycle. Using household panel data from 1984 to 2010 in the US we find that the welfare cost of the business cycle is non-negligible, once agents heterogeneity is taken into account, and sums to about 1% of yearly consumption. This is due to the structure of comovements between the different parts of the consumption distribution, in particular the tails are highly volatile and negatively related to each other. We also find that business cycle fluctuations originating from exogenous financial shocks only hit the top end of the consumption distribution and therefore reduce consumption inequality.

Ab initio absorption spectrum of NiO combining molecular dynamics with the embedded cluster approach in a discrete reaction field

We developed a procedure that combines three complementary computational methodologies to improve the theoretical description of the electronic structure of nickel oxide. The starting point is a Car-Parrinello molecular dynamics simulation to incorporate vibrorotational degrees of freedom into the material model. By means ofcomplete active space self-consistent field second-order perturbation theory (CASPT2) calculations on embedded clusters extracted from the resulting trajectory, we describe localized spectroscopic phenomena on NiO with an efficient treatment of electron correlation. The inclusion of thermal motion into the theoretical description allowsus to study electronic transitions that, otherwise, would be dipole forbidden in the ideal structure and results in a natural reproduction of the band broadening. Moreover, we improved the embedded cluster model by incorporating self-consistently at the complete active space self-consistent field (CASSCF) level a discrete (or direct) reaction field (DRF) in the cluster surroundings. The DRF approach offers an efficient treatment ofelectric response effects of the crystalline embedding to the electronic transitions localized in the cluster. We offer accurate theoretical estimates of the absorption spectrum and the density of states around the Fermi level of NiO, and a comprehensive explanation of the source of the broadening and the relaxation of the charge transferstates due to the adaptation of the environment

Continuous-time formulation of reaction-diffusion processes on heterogeneous metapopulations

We present the derivation of the continuous-time equations governing the limit dynamics of discrete-time reaction-diffusion processes defined on heterogeneous metapopulations. We show that, when a rigorous time limit is performed, the lack of an epidemic threshold in the spread of infections is not limited to metapopulations with a scale-free architecture, as it has been predicted from dynamical equations in which reaction and diffusion occur sequentially in time