On sign-changeable interaction in FLRW cosmology

We investigate an interacting two-fluid model in a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe, when the energy transfer between these two dark components is produced by a factorisable nonlinear sign-changeable interaction depending linearly on the energy density and quadratically on the deceleration parameter. We solve the source equation and obtain the effective energy densities of the dark sector and their components. We show that the effective equation of state of the dark sector includes some of the several kind of Chaplygin gas equations of state as well as a generalization of the polytropic equation of state. We use bayesian statistics methods to constrain free parameters in the models during its most recent evolution considering supernovae type Ia and measurements of the Hubble expansion rate. The resulting constraints provide new information on sign-changeable interactions, its equivalences and compatibility with previous models and novel late time universe dynamics.Comment: 8 figure

Improved diffusion Monte Carlo for bosonic systems using time-step extrapolation "on the fly"

A diffusion Monte Carlo algorithm employing "on the fly" extrapolation with respect to the time step is implemented and demonstrated simulating realistic systems. Significant advantages are obtained when using on the fly extrapolation, leading to reduced systematic and statistical errors. The sound theoretical basis of extrapolation on the fly is discussed and compared to justifications for the a posteriori extrapolation

Peningkatan hasil belajar Matematika melalui Modil pembelajaran Kooperatif tipe Think Pairs Share(TPS) bagi siswa Kelas IV Sekolah Dasar Negeri 3 Kalongan Kecamatan Purwodadi Kabupaten Grobogan Tahun Pelajaran 2011/2012

Penelitian ini bertujuan untuk meningkatkan hasil belajar siswa dalam pembelajaran matematika melalui model pembelajaran kooperatif tipe think pairs share (TPS). Dalam penelitian ini merupakan penelitian tindakan kelas (PTK) terdiri dari dua siklus, tiap siklus terdiri dari lima tahapan yaitu perencanaan, pelaksanaan, observasi, refleksi dan evaluasi. Lokasi penelitian ini di SD Negeri 3 Kalongan Kecamatan Purwodadi Kabupaten Grobogan. Sebagai subjek penerima tindakan adalah siswa kelas IV yang berjumlah 13 siswa, terdiri dari 9 siswa lakilaki dan 4 siswa perempuan, dan subjek pelaksanaan tindakan adalah peneliti dan guru matematika kelas IV. Metode pengumpulan data yang digunakan dalam penelitian ini adalah wawancara, observasi, tes, dan dokumentasi. Untuk menjamin validitas data digunakan teknik triangulasi sumber dan trianggulasi tehnik. Trianggulasi sumber yaitu mencocokkan data hasil belajar siswa dengan hasil pengamatan langsung terhadap aktivitas belajar siswa. Trianggulasi tehnik yaitu metode pengumpulan data yang berasal dari hasil observasi, wawancara, dan tes. Tehnik analisis data yang digunakan adalah analisis interaktif yang terdiri dari reduksi data, penyajian data dan penarikan kesimpulan. Hasil penelitian ini adalah adanya peningkatan hasil belajar siswa melalui model pembelajaran kooperatif tipe Think Pairs Share (TPS). Hal ini dapat dilihat pada pra siklus rata-rata kelas 59,23, siswa yang mencapai KKM 4 (30,76%); pada siklus I meningkat nilai rata-rata kelas menjadi 61,35 siswa yang mencapai KKM 5 (38,46%); pada siklus II meningkat nilai rata-rata kelas menjadi 67,69, siswa yang mencapai KKM 10 (76,92%). Kesimpulan penelitian ini adalah dengan menerapakan model pembelajaran kooperatif tipe Think Pairs Share (TPS) dapat meningkatkan hasil belajar siswa kelas IV SD Negeri 3 Kalongan kecamatan Purwodadi Kabupaten Grobogan Tahun Ajaran 2011/2012

Collateral, Renegotiation and the Value of Diffusely Held Debt

Debt with many creditors is analyzed in a continuous-time pricing model of the levered firm. We specifically allow for debtor opportunism vis-a-vis a non-coordinated group of creditors, in form of repeated strategic renegotiation offers and default threats. We show that the creditors' initial entitlement to non-collateralized assets will be expropriated through exchange offers. Exchange offers successively increase the level of collateral until all assets are fully collateralized. The ex ante optimal debt contract is neither fully collateralized nor without any collateral. Diffusely held debt allows for a larger debt capacity and bears lower credit risk premia than privately held debt. We derive simple closed-form solutions for the value of equity and defaultable bonds. Numerical estimates show that the bond valuation is very sensitive to the correct specification of the debt renegotiation model.

Reorganization Law and Dilution Threats in Different Financial Systems

In a market-based financial system, credit is held by dispersed creditors, and out-of-court renegotiation of debt is more likely to fail because of hold-out problems; in a bank-based system, out-of-court renegotiation stands good chances to succeed. Since out-of-court renegotiation is a substitute for court-supervised reorganization, the design of a reorganization law cannot abstract from the financial system. Chapter 11-style renegotiation is shown to benefit public debt firms and to be harmful for private debt firms; the overall effect depends on the financial system, but is likely to be positive only in a market-based system. The case for a reorganization law is weakened if dilution threats like exit consents are taken into account: such a law is then in most cases undesirable. Legislation, however, which jointly introduces a reorganization law while facilitating the use of dilution threats will improve welfare in a market-based system, but reduce welfare in a bank-based system. Thus, the paper indentifies a new determinant in the debate over optimal bankruptcy codes, which is how easily dilution threats can be deployed.Workouts;reorganization law;Chapter 11;financial systems;dilution threats;exit consents;hold-in effect

Collateral, Renegotiation and the Value of Diffusely Held Debt

Debt with many creditors is analyzed in a continuous-time pricing model of the levered firm. We specifically allow for debtor opportunism vis-a-vis a non-coordinated group of creditors, in form of repeated strategic renegotiation offers and default threats. We show that the creditors' initial entitlement to non-collateralized assets will be expropriated through exchange offers. Exchange offers successively increase the level of collateral until all assets are fully collateralized. The ex ante optimal debt contract is neither fully collateralized nor without any collateral. Diffusely held debt allows for a larger debt capacity and bears lower credit risk premia than privately held debt. We derive simple closed-form solutions for the value of equity and defaultable bonds. Numerical estimates show that the bond valuation is very sensitive to the correct specification of the debt renegotiation model.Debt reorganization;multiple creditors

Mycoplasma isolation in milk samples from dairy herds in Chile

Mycoplasma bovine mastitis is a highly contagious disease, usually associated with clinical cases refractory to antibiotic treatment. The aim of this study was the isolation of Mycoplasma species in cattle milk samples from dairy herds in Chile. Bulk tank milk samples selected by convenience from 91 Holstein Friesian dairy herds located in Los Rios (66) and Los Lagos (25), the two most important dairy Regions in the country, were collected. Additionally, 100 individual milk samples from cows with a high incidence of clinical mastitis, refractory to antibiotic therapy, and negative bacteriological results for traditional mastitis pathogens, all from the Biobío Region and received in our diagnostic laboratory, were included. All samples were cultured for 10 days on PPLO medium. The differentiation of suspect colonies between genus Mycoplasma and Acholeplasma was performed by the digitonin test and a specific PCR. The species identification was performed by a M. bovis specific PCR and 16S rRNA sequencing. Mycoplasma was isolated from 3 (3.3%) bulk tank milk samples and 2 (2%) individual cow milk samples. All colonies were identified as Mycoplasma by the digitonin test and by a specific PCR. At species level, one strain isolated from a bulk tank milk sample was identified as M. bovis. The remaining two strains isolated from bulk tank milk samples were identified as M. bovigenitalium, while the two strains isolated from milk of individual cows were identified as M. alkalescens. These results show that not only M. bovis is present in Chilean dairy herds, but also other pathogenic species not previously described in Chile such as M. bovigenitalium and M. alkalescens, which pose a potential risk for dairy herds in southern Chile

Decomposition of homogeneous polynomials with low rank

Let $F$ be a homogeneous polynomial of degree $d$ in $m+1$ variables defined over an algebraically closed field of characteristic zero and suppose that $F$ belongs to the $s$-th secant varieties of the standard Veronese variety $X_{m,d}\subset \mathbb{P}^{{m+d\choose d}-1}$ but that its minimal decomposition as a sum of $d$-th powers of linear forms $M_1, ..., M_r$ is $F=M_1^d+... + M_r^d$ with $r>s$. We show that if $s+r\leq 2d+1$ then such a decomposition of $F$ can be split in two parts: one of them is made by linear forms that can be written using only two variables, the other part is uniquely determined once one has fixed the first part. We also obtain a uniqueness theorem for the minimal decomposition of $F$ if the rank is at most $d$ and a mild condition is satisfied.Comment: final version. Math. Z. (to appear