Primordial power spectrum from a matter-Ekpyrotic bounce scenario in loop quantum cosmology

A union of matter bounce and Ekpyrotic scenarios is often studied in an attempt to combine the most promising features of these two models. Since non-perturbative quantum geometric effects in loop quantum cosmology (LQC) result in natural bouncing scenarios without any violation of energy conditions or fine tuning, an investigation of matter-Ekpyrotic bounce scenario is interesting to explore in this quantum gravitational setting. In this work, we explore this unified phenomenological model for a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe in LQC filled with dust and a scalar field in an Ekpyrotic scenario like negative potential. Background dynamics and the power spectrum of the comoving curvature perturbations are numerically analyzed with various initial conditions and a suitable choice of the initial states. By varying the initial conditions we consider different cases of dust and Ekpyrotic field domination in the contracting phase. We use the dressed metric approach to numerically compute the primordial power spectrum of the comoving curvature perturbations which turns out to be almost scale invariant for the modes which exit the horizon in the matter-dominated phase. But, in contrast with a constant magnitude power spectrum obtained under approximation of a constant Ekpyrotic equation of state using deformed algebra approach in an earlier work, we find that the magnitude of power spectrum changes during evolution. Our analysis shows that the bouncing regime only leaves imprints on the modes outside the scale-invariant regime. However, an analysis of the spectral index shows inconsistency with the observational data, thus making further improvements in such a model necessary.Comment: 20 pages, 8 figures, 1 tabl

Investigating the distance limit of a metal nanoparticle based spectroscopic ruler

Conventional Förster resonance energy transfer (FRET) processes involving a pair of fluorophore and organic quencher are restricted to an upper distance limit of ~10 nm. The application of a metal nanoparticle as a quencher can overcome the distance barrier of the traditional FRET technique. However, no standard distance dependence of this resonance energy transfer (RET) process has been firmly established. We have investigated the nonradiative energy transfer process between an organic donor (fluorescein) and gold nanoparticle quencher connected by double stranded (ds) DNA. The quenching efficiency of the gold nanoparticle as a function of distance between the donor and acceptor was determined by time-resolved lifetime analyses of the donor. Our results showed a 1/d4 distance dependence for the RET process for longer distances (>10 nm) and 1/d6 distance dependence for shorter distances (<10 nm). Our results clearly indicate the applicability of metal nanoparticle based quenchers for studying systems that exceed the 10 nm FRET barrier

Weak Effects of Biochar and Nitrogen Fertilization on Switchgrass Photosynthesis, Biomass, and Soil Respiration

Application of nitrogen (N) fertilizer plus biochar may increase crop yield, but how biochar will interact with N fertilization to affect bioenergy crop switchgrass physiology, biomass, and soil CO2 emission (i.e., soil respiration) from switchgrass fields remains unclear. Here, we assessed this issue by conducting a field experiment near Nashville TN with two levels of biochar treatment (a control without biochar addition and biochar addition of 9 Mg ha−1), and four N fertilization levels (0 kg N ha−1, 17 kg N ha−1, 34 kg N ha−1, and 67 kg N ha−1, labeled as ON, LN, MN, and HN, respectively). Results showed that both biochar addition and N fertilization did not influence switchgrass leaf photosynthesis and biomass, but biochar addition enhanced leaf transpiration, and reduced water use efficiency. Soil respiration was reduced by biochar addition, but significantly enhanced by N fertilization. Biochar and N fertilization interactively influenced soil respiration and seasonal variation of soil respiration was mostly controlled by soil temperature. Our results indicated that switchgrass can maintain high productivity without much N input, at least for several years. The findings from this study are useful to optimize N fertilization and biochar addition in the switchgrass fields for maintaining relatively high productive switchgrass biomass while reducing soil CO2 emission

Cosmological scalar fields that mimic the ΛCDM\Lambda CDM cosmological model

We look for cosmologies with a scalar field (dark energy without cosmological constant), which mimic the standard $\Lambda CDM$ cosmological model yielding exactly the same large-scale geometry described by the evolution of the Hubble parameter (i.e. photometric distance and angular diameter distance as functions on $z$). Asymptotic behavior of the field solutions is studied in the case of spatially flat Universe with pressureless matter and separable scalar field Lagrangians (power-law kinetic term + power-law potential). Exact analytic solutions are found in some special cases. A number of models have the field solutions with infinite behavior in the past or even singular behavior at finite redshifts. We point out that introduction of the cosmological scalar field involves some degeneracy leading to lower precision in determination of $\Omega_m$. To remove this degeneracy additional information is needed beyond the data on large-scale geometry.Comment: VIII International Conference "Relativistic Astrophysics, Gravitation and Cosmology": May 21-23, 2008, Kyiv, Ukrain

Clusters of microRNAs emerge by new hairpins in existing transcripts

Genetic linkage may result in the expression of multiple products from a polycistronic transcript, under the control of a single promoter. In animals, protein-coding polycistronic transcripts are rare. However, microRNAs are frequently clustered in the genomes of animals, and these clusters are often transcribed as a single unit. The evolution of microRNA clusters has been the subject of much speculation, and a selective advantage of clusters of functionally related microRNAs is often proposed. However, the origin of microRNA clusters has not been so far explored. Here, we study the evolution of microRNA clusters in Drosophila melanogaster. We observed that the majority of microRNA clusters arose by the de novo formation of new microRNA-like hairpins in existing microRNA transcripts. Some clusters also emerged by tandem duplication of a single microRNA. Comparative genomics show that these clusters are unlikely to split or undergo rearrangements. We did not find any instances of clusters appearing by rearrangement of pre-existing microRNA genes. We propose a model for microRNA cluster evolution in which selection over one of the microRNAs in the cluster interferes with the evolution of the other linked microRNAs. Our analysis suggests that the study of microRNAs and small RNAs must consider linkage associations

International evidence on the link between foreign direct investment and economic freedom

Foreign direct investment (FDI) is viewed as one of the key component in the development strategy for many countries,especially for developing ones. However, the distribution of FDI across countries is not uniform as only few countries are able to attract the bulk of FDI. In an effort to further understand the evolution in MNCs locational decision and understand their changing need, this paper examines whether economic freedom has any important role in attracting FDI inflows. To test the hypothesis, this study utilises data from 75 countries over the 1981-2005 period. The resultsof system generalised method-of-moment panel estimator uncover that the importance of economic freedom in attracting FDI inflows is undisputable. This is consistent with the view that improvements in freedom of economic activity provide a better environment for business activity

Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array

Purpose: To investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 Gafchromic TM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector. Methods: These three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter. The measurements were performed at 10 cm depth and 90 cm SSD. Results: The SRS cone beam profiles measured with DUO, EBT3 film, and IBA SFD agreed well, results being in agreement within ±0.5 mm in the FWHM, and ±0.7 mm in the penumbra region. The output factor measured by DUO with 0.5 mm air gap above agrees within ±1% with EBT3. The OF measured by IBA SFD (corrected for the over-response) agreed with both EBT3 and DUO within ±2%. All three detectors agree within ±2% for PDD measurements for all SRS cones. Conclusions: The characteristics of the ELEKTA SRS cone collimator have been evaluated by using a monolithic silicon high spatial resolution detector DUO, EBT3, and IBA SFD diode. The DUO detector is suitable for fast real-time quality assurance dosimetry in small radiation fields typical for SRS/SRT. This has been demonstrated by its good agreement of measured doses with EBT 3 films

International evidence on the link between foreign direct investment and institutional quality

Multinational corporations (MNCs) are known for their huge investments in research and development activity. They are also known for superior patents, trade secrets, brand names, management techniques and marketing strategies. The provision of incentives (i.e., tax incentives and/or subsidies) and the adoption of FDI-stimulating policies stem from the expectationsthat FDI bringsenormous benefits such as the transfer of new technology.Numerous empirical studies have demonstrated FDI has a positive impact on economic growth of the host countries.However, it should be noted that the distribution of FDI across countries is not uniformwith some countries receive more FDI than the others. This observation raises the question of whether it is possible to identify a set of policies that might enhance the attractiveness of host countries as destinations for MNCs. In the investigation of factors that influence FDI flows, existing studies have mainly focussed on the traditional factors such as market size, trade openness, infrastructure and human capital. The role of other factors such as the quality of institution in the host country was largely ignored.Institution can be defined as the humanly devised constraints or rules of the game that structure political, economic, and social interaction. Institutions provide the incentive structure of an economy. Specifically, it affects security of property rights, prevalence of corruption, distorted or extractive policies, and thereby affects the incentive to invest in human and physical capital, and hence economic growth.The role of institutional quality in the development process has been extensively examined and economists have reached a consensus on the importance of good domestic institutions in explaining cross-country differences in both growth rates and income per capita. Following recent literature that emphasize on the importance of institution, this paper examines whether domestic institutional quality has any important role in attracting FDI. Instead of investigating the direct effect of institution on growth, this paper focuses on the indirect effect that institution may bring via FDI inflows. Arguably, countries with better institutional quality should be able to attract more investment because it improves productivity prospect, reduces the cost of doing business and uncertainty. In order to test the hypothesis, data from 77 countries over the 1981-2005 period is utilised. Methodologically, this paper uses a system generalised method-of-moment panel estimator to address some of the weaknesses encountered in the previous literature on FDI-institution link. Specifically, this estimator is able to formally address biases induced by the inclusion of lagged dependent variable, country-specific effects and endogeneity problem. There are several important conclusions emerge from this analysis. First, institution appears to be important determinant of FDI inflows. This finding is line with the view that improvements in the quality of domestic institution will reduce the cost of doing business, reduce uncertainty, and improve productivity prospect. This will eventually lead to more investments. Second, FDI is also seeking human capital and trade openness. The availability of quality workforce in the host countries is an important pre-condition for the successful operations of MNCs as they need people who are able to understand and work with new technology.Trade openness is important because most FDI is export oriented in nature such that MNC will invest in countries that pursue trade-promotion policies. In addition, MNCs investment decision also depends on the amount of existing FDI invested in the countries. This is consistent with the view that the success of MNCs in the host countries is an important signal for further investments by MNCs.Finally,FDI is not influenced by market size and infrastructurequality. This is not surprising and in fact consistent with recent literature. Importantly, the finding on the important role played by domestic institution in attracting FDI is robust and is not driven by outlier observations, or problems caused by weak instruments and simultaneity bias

International evidence on the link between foreign direct investment and institutional quality

Multinational corporations (MNCs) are known for their huge investments in research and development activity. They are also known for superior patents, trade secrets, brand names, management techniques and marketing strategies. The provision of incentives (i.e., tax incentives and/or subsidies) and the adoption of FDI-stimulating policies stem from the expectationsthat FDI bringsenormous benefits such as the transfer of new technology.Numerous empirical studies have demonstrated FDI has a positive impact on economic growth of the host countries.However, it should be noted that the distribution of FDI across countries is not uniformwith some countries receive more FDI than the others. This observation raises the question of whether it is possible to identify a set of policies that might enhance the attractiveness of host countries as destinations for MNCs. In the investigation of factors that influence FDI flows, existing studies have mainly focussed on the traditional factors such as market size, trade openness, infrastructure and human capital. The role of other factors such as the quality of institution in the host country was largely ignored.Institution can be defined as the humanly devised constraints or rules of the game that structure political, economic, and social interaction. Institutions provide the incentive structure of an economy. Specifically, it affects security of property rights, prevalence of corruption, distorted or extractive policies, and thereby affects the incentive to invest in human and physical capital, and hence economic growth.The role of institutional quality in the development process has been extensively examined and economists have reached a consensus on the importance of good domestic institutions in explaining cross-country differences in both growth rates and income per capita. Following recent literature that emphasize on the importance of institution, this paper examines whether domestic institutional quality has any important role in attracting FDI. Instead of investigating the direct effect of institution on growth, this paper focuses on the indirect effect that institution may bring via FDI inflows. Arguably, countries with better institutional quality should be able to attract more investment because it improves productivity prospect, reduces the cost of doing business and uncertainty. In order to test the hypothesis, data from 77 countries over the 1981-2005 period is utilised. Methodologically, this paper uses a system generalised method-of-moment panel estimator to address some of the weaknesses encountered in the previous literature on FDI-institution link. Specifically, this estimator is able to formally address biases induced by the inclusion of lagged dependent variable, country-specific effects and endogeneity problem. There are several important conclusions emerge from this analysis. First, institution appears to be important determinant of FDI inflows. This finding is line with the view that improvements in the quality of domestic institution will reduce the cost of doing business, reduce uncertainty, and improve productivity prospect. This will eventually lead to more investments. Second, FDI is also seeking human capital and trade openness. The availability of quality workforce in the host countries is an important pre-condition for the successful operations of MNCs as they need people who are able to understand and work with new technology.Trade openness is important because most FDI is export oriented in nature such that MNC will invest in countries that pursue trade-promotion policies. In addition, MNCs investment decision also depends on the amount of existing FDI invested in the countries. This is consistent with the view that the success of MNCs in the host countries is an important signal for further investments by MNCs.Finally,FDI is not influenced by market size and infrastructurequality. This is not surprising and in fact consistent with recent literature. Importantly, the finding on the important role played by domestic institution in attracting FDI is robust and is not driven by outlier observations, or problems caused by weak instruments and simultaneity bias