Habit formation and resource dependence in dynastic economies

This paper studies the consequences of habit formation in dynastic economies that exploit exhaustible resources. If the strength of habits is below a critical level, positive bequests generate Ramsey-Stiglitz equilibria: the altruism factor determines long-run growth and habits increase output levels by increasing capital accumulation and smoothing resource extraction during the transition. If the strength of habits is above the threshold, zero bequests induce Diamond-Mourmouras equilibria: the transitional effects become permanent and habits increase long-run growth. Results differ from those of capital-labor models because resource dependence implies that long-run growth is determined by the intergenerational distribution of wealth.     

A Cluster Reduction for Computing the Subtree Distance Between Phylogenies

Calculating the rooted subtree prune and regraft (rSPR) distance between two rooted binary phylogenetic trees is a frequently applied process in various areas of molecular evolution. However, computing this distance is an NP-hard problem and practical algorithms for computing it exactly are rare. In this paper, a divide-and-conquer approach to calculating the rSPR distance is established. This approach breaks the problem instance into a number of smaller and more tractable subproblems. Two reduction rules which were previously used to show that computing the rSPR distance is fixed-parameter tractable can easily be used to complement this new theoretical result, and so a significant positive impact on the running time of calculating this distance in practice is likely.     

Hybrid polyacrylamide chiral stationary phases for HPLC prepared by surface-initiated photopolymerization

Two hybrid polyacrylamide chiral stationary phases (CSPs) for HPLC have been synthesized by a new surface-initiated photo-induced radical polymerization approach of enantiopure N,N'-diacryloyl derivatives of (1R,2R)-diaminocyclohexane (CSP1) and (1R,2R)-diphenylethylenediamine (CSP2). This system is based on the activation of mesoporous silica microparticles by chemically bonded trichloroacetyl groups and dimanganese decacarbonyl as catalyst. UV irradiation was performed using a lab-made quartz photochemical reactor, ad hoc designed for the photo-induced polymerization process on the surface of microparticles. The two phases were evaluated and compared as chromatographic supports for the enantioselective HPLC of model chiral compounds. Their physico-chemical properties and chromatographic performances were also evaluated in comparison with those exhibited by the homologue CSPs obtained by the grafting-from thermal-induced process (CSP3 and CSP4). The new photopolymerization approach yielded higher grafting density than the thermal-induced one, especially in the case of the less reactive monomer (the diacryloyl derivative of (1R,2R)-diphenylethylenediamine), good chromatographic efficiency and a broad application field under normal phase and polar organic mode conditions.     

Expression of a Chitinase Gene from <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> in Tobacco Plants Confers Resistance against <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The chit1 gene from the entomopathogenic fungus Metarhizium anisopliae, encoding the endochitinase CHIT42, was placed under the control of the CaMV 35S promoter, and the resulting construct was transferred to tobacco. Seventeen kanamycin-resistant transgenic lines were recovered, and the presence of the transgene was confirmed by polymerase chain reactions and Southern blot hybridization. The number of chit1 copies was determined to be varying from one to four. Copy number had observable effects neither on plant growth nor development. Substantial heterogeneity concerning production of the recombinant chitinase, and both general and specific chitinolytic activities were detected in leaf extracts from primary transformants. The highest chitinase activities were found in plants harboring two copies of chit1 inserts at different loci. Progeny derived from self-pollination of the primary transgenics revealed a stable inheritance pattern, with transgene segregation following a mendelian dihybrid ratio. Two selected plants expressing high levels of CHIT42 were consistently resistant to the soilborne pathogen Rhizoctonia solani, suggesting a direct relationship between enzyme activity and reduction of foliar area affected by fungal lesions. To date, this is the first report of resistance to fungal attack in plants mediated by a recombinant chitinase from an entomopathogenic and acaricide fungus.     

Nickel species analysis of human colonic tissue using liquid chromatography,gel electrophoresis and mass spectrometry

Studies to specify metal-binding species, such as metalloproteins that are present in trace amounts in colonic cell cytosol, using chromatographic separation methods in combination with inductively coupled plasma mass spectrometry (ICP-MS) as element-specific detection require an optimised sample preparation regarding the solubilisation of the proteins. Focus should be taken to avoid metal contamination, enzymatic digestion by different proteases and oxidation. In this article different sample preparation methods are studied to find a suitable method for the isolation and characterisation of Ni species previously found in cytosols from normal and malignant tissues of the human colon. The total Ni concentrations of the cytosols were determined as well as the total protein content. Thus, a Ni-containing protein could be isolated from cytosols of malignant human colonic tissues using size-exclusion chromatography with ICP-MS for element-specific detection. Ni-containing species in the molecular mass range from 10,000 to 20,000 Da were found and pre-concentrated. The determination of the molecular mass of the species was performed through online coupling of reversed-phase chromatography with electrospray ionisation quadrupole time-of-flight MS. Using identical chromatographic conditions and ICP-MS the detected protein was shown to contain Ni.     

Temperature dependence of thermal diffusion for aqueous solutions of monosaccharides, oligosaccharides, and polysaccharides

We studied the thermal diffusion behavior for binary aqueous solutions of glucose, maltotriose, maltohexaose, pullulan, and dextran by means of thermal diffusion forced Rayleigh scattering (TDFRS). The investigated saccharides with molar masses between 0.180 and 440 kg mol(-1) were studied in the temperature range between 15 and 55 °C. The thermal diffusion coefficient D(T) and the Soret coefficient S(T) of all solutions increase with increasing temperature. For maltohexaose and the polymers the thermal diffusion coefficient changes sign from negative to positive with increasing temperature, whereas glucose and maltotriose show only positive values in the entire investigated temperature range. While we were able to find a master curve to describe the temperature dependence of D(T), we were not able to find a similar expression for S(T). This comprehensive study allows for the first time the determination of the interaction parameters for the polymer and the solvent within the theoretical framework suggested by Würger [Phys. Rev. Lett., 2009, 102, 078302].     

Competing magnetoresistance contributions in sputtered FePt thin films

Fe-Pt thin films were deposited by rf sputtering on an MgO substrate heated at different temperatures to induce the formation of the perpendicular Fe-Pt L1₀ phase with a different grain morphology on the nanometer scale. All films are characterized by a mazelike pattern of FePt nanograins with interconnected bases. MFM images and magnetization curves indicate that all samples have a strong perpendicular magnetic anisotropy arising from (0 0 1) growth. The temperature behaviour of the electrical resistance indicates that a percolating path exists for conduction electrons in the mazelike pattern. The magnetoresistance was measured as a function of magnetic field (applied longitudinally) and temperature in the ranges −70 kOe<H<+70 kOe and 4 K<T<150 K, respectively. All samples display a complex behaviour of the electrical resistance as a function of applied field. The role of the different magnetoresistance effects (both intrinsic and extrinsic) measured in these FePt thin films is elucidated.     

On an iterated construction of irreducible polynomials over finite fields of even characteristic by Kyuregyan

We deal with the construction of sequences of irreducible polynomials with coefficients in finite fields of even characteristic. We rely upon a transformation used by Kyuregyan in 2002, which generalizes the Q-transform employed previously by Varshamov and Garakov (1969) as well as by Meyn (1990) for the synthesis of irreducible polynomials. While in the iterative procedure described by Kyuregyan the coefficients of the initial polynomial of the sequence have to satisfy certain hypotheses, in the present paper these conditions are removed. We construct infinite sequences of irreducible polynomials of nondecreasing degree starting from any irreducible polynomial.     

On a Class of Weakly Coupled Systems of Elliptic Operators with Unbounded Coefficients

We consider a class of weakly coupled systems of elliptic operators \({\mathcal{A}}\) with unbounded coefficients defined in \({\mathbb{R}^N}\). We prove that a semigroup (T(t))t ≥ 0 of bounded linear operators can be associated with \({\mathcal{A}}\), in a natural way, in the space of all bounded and continuous functions. We prove a compactness property of the semigroup as well as some uniform estimates on the derivatives of the function T(t)f, when f belongs to some spaces of Hölder continuous functions, which are the key tools to prove some optimal Schauder estimates for the solution to some nonhomogeneous elliptic equations and Cauchy problems associated with the operator \({\mathcal{A}}\). Under suitable additional conditions, we then prove that the restriction of the semigroup to the subspace of smooth and compactly supported functions extends by a strongly continuous semigroup to L ^p -spaces over \({\mathbb{R}^N}\), related to the Lebesgue measure, when \({p \in [1,\infty)}\). We also provide sufficient conditions for this semigroup to be analytic when \({p \in [1,\infty)}\). Finally, we prove some L ^p ?L ^q -estimates.