2,178 research outputs found

    Towards a unification of HRT and SCOZA. Analysis of exactly solvable mean-spherical and generalized mean-spherical models

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    The hierarchical reference theory (HRT) and the self-consistent Ornstein-Zernike approximation (SCOZA) are two liquid state theories that both furnish a largely satisfactory description of the critical region as well as the phase coexistence and equation of state in general. Furthermore, there are a number of similarities that suggest the possibility of a unification of both theories. Earlier in this respect we have studied consistency between the internal energy and free energy routes. As a next step toward this goal we here consider consistency with the compressibility route too, but we restrict explicit evaluations to a model whose exact solution is known showing that a unification works in that case. The model in question is the mean spherical model (MSM) which we here extend to a generalized MSM (GMSM). For this case, we show that the correct solutions can be recovered from suitable boundary conditions through either of SCOZA or HRT alone as well as by the combined theory. Furthermore, the relation between the HRT-SCOZA equations and those of SCOZA and HRT becomes transparent.Comment: Minimal correction of some typos found during proof reading. Accepted for publication in Phys. Rev.

    The relationship between foreign direct investment and GDP in Cameroon (2000–2020)

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    Relevance. In the last 20 years Cameroon has faced a series of crises. The 2035 governmental programme of recovery aims to transform the country into an emerging economy nation. The effects of the COVID-19 pandemic have slowed down economic growth in Cameroon and the country is hoping to attract foreign direct investment (FDI) and thus benefit from the new business opportunities to revitalize its economy. This context makes the research on the relationship between FDI and GDP particularly relevant.Research objective. This paper is designed to assess the relationship between GDP and FDI in Cameroon in 2000-2020. In addition, we aim to assess the scope of internationalization through FDI as a possible catalyst for economic recovery.Data and methods. The paper uses correlation and regression analysis to show the relationship between FDI and GDP.Results. The results show that FDI can increase Cameroon’s GDP and may be used as an empirical basis for policy- and strategy-making in Cameroon.Conclusions. We found a strong correlation between FDI and GDP in Cameroon for a 21-year period. This result is supported by the double effect of FDI on the national economy: FDI directly affects the investment component of GDP, but it also influences economic growth indirectly. The activities of foreign firms in Cameroon can support trade and even balance of payment, which indirectly influences the export and import component of GDP. Foreign subsidiaries both solely owned or joint ventures pay indirect taxes to the government and thus influence government spending

    Quantifying the role of fire in the Earth system – Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

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    Fire is the primary form of terrestrial ecosystem disturbance on a global scale. It affects the net carbon balance of terrestrial ecosystems by emitting carbon directly and immediately into the atmosphere from biomass burning (the fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (the fire indirect effect). Here, we provide the first quantitative assessment of the impact of fire on the net carbon balance of global terrestrial ecosystems during the 20th century, and investigate the roles of fire's direct and indirect effects. This is done by quantifying the difference between the 20th century fire-on and fire-off simulations with the NCAR Community Land Model CLM4.5 (prescribed vegetation cover and uncoupled from the atmospheric model) as a model platform. Results show that fire decreases the net carbon gain of global terrestrial ecosystems by 1.0 Pg C yr<sup>−1</sup> averaged across the 20th century, as a result of the fire direct effect (1.9 Pg C yr<sup>&minus;1</sup>) partly offset by the indirect effect (−0.9 Pg C yr<sup>&minus;1</sup>). Post-fire regions generally experience decreased carbon gains, which is significant over tropical savannas and some North American and East Asian forests. This decrease is due to the direct effect usually exceeding the indirect effect, while they have similar spatial patterns and opposite sign. The effect of fire on the net carbon balance significantly declines until &sim;1970 with a trend of 8 Tg C yr<sup>−1</sup> due to an increasing indirect effect, and increases subsequently with a trend of 18 Tg C yr<sup>−1</sup> due to an increasing direct effect. These results help constrain the global-scale dynamics of fire and the terrestrial carbon cycle

    Induction of Parturition in Beef Cattle With Dexamethasone

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    In recent years many reports have shown that synthetic glucocorticoids such as dexamethasone (DXMS) and flumethasone will induce parturition in cattle when injected intramuscularly during various stages of gestation. A study was conducted at South Dakota State University to determine, under field conditions, the effectiveness of DXMS coupled with estradiol on the precision of parturition induction, the incidence of retained placentas and subsequent reproductive performance of beef cows

    Picosecond ionization dynamics in femtosecond filaments at high pressures

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    We investigate the plasma dynamics inside a femtosecond-pulse-induced filament generated in an argon gas for a wide range of pressures up to 60 bar. At higher pressures, we observe ionization immediately following a pulse, with up to a threefold increase in the electron density within 30 ps after the filamentary propagation of a femtosecond pulse. Our study suggests that this picosecond evolution can be attributed to collisional ionization including Penning and associative ionizations and electron-impact ionization of excited atoms generated during the pulse. The dominance of excited atoms over ionized atoms at the end of the pulse also indicates an intrapulse inhibition of avalanche ionization. This delayed ionization dynamics provides evidence for diagnosing atomic and molecular excitation and ionization in intense laser interaction with high-pressure gases

    Dynamics and hysteresis in square lattice artificial spin-ice

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    Dynamical effects under geometrical frustration are considered in a model for artificial spin ice on a square lattice in two dimensions. Each island of the spin ice has a three-component Heisenberg-like dipole moment subject to shape anisotropies that influence its direction. The model has real dynamics, including rotation of the magnetic degrees of freedom, going beyond the Ising-type models of spin ice. The dynamics is studied using a Langevin equation solved via a second order Heun algorithm. Thermodynamic properties such as the specific heat are presented for different couplings. A peak in specific heat is related to a type of melting-like phase transition present in the model. Hysteresis in an applied magnetic field is calculated for model parameters where the system is able to reach thermodynamic equilibrium.Comment: Revised versio

    Kajian Faktor Sosial Ekonomi terhadap Respon Petani dalam Menerapkan Inovasi Double Track untuk Meningkatkan Ketahanan Pangan Petani pada Masa Pandemi Covid-19

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    Penelitian ini telah dilaksanakan pada akhir tahun 2022,&nbsp; bertujuan mengetahui&nbsp; factor social ekonomi berkorelasi dengan&nbsp; respon petani dalam penerapan&nbsp; inovasi Double Track pada tanaman jagung. Sebanyak 83 petani dipilih secara acak. Pengumpulan data menggunakan metode survei.&nbsp; Data dianalisis dengan menggunakan korelasi Rank Spearman dengan sistem komputasi SPPS 26. Hasilnya adalah faktor berkorelasi nyata dengan respon petani adalah pendidikan formal, pendidikan nonformal, dan luas lahan.. Dibutuhkan perhatian pemerintah untuk peningkatan kegiatan&nbsp; penyuluhan dan pendampingan dengan metode gabungan yang terdiri dari ceramah, diskusi, pelatihan partisipatif, SLP dan konsultasi pribadi tentang sistem ‘double track’.Sebaliknya, faktor umur, pengalaman berusahatani dan jumlah tanggungan keluarga tidak memiliki korelasi dengan respon petani
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