Matching the Low and High Energy Determinations of αs(Mz)\alpha_s(M_z) in the MSSM

Recent calculations of supersymmetric corrections to the conflicting ratios $R_b$ and $R_c$ have shown that an alleged discrepancy between the SM predictions of these observables and the corresponding experimental values can be cured in the MSSM within a certain region of the parameter space. Here we show that, in this very same region, also a well-known discrepancy between the low and high energy determinations of $\alpha_s(M_Z)$ can be disposed of. Specifically, we find that the lineshape determination of the strong coupling constant, which in the SM points towards the large central value $\alpha_s(M_Z) \stackrel{\scriptstyle >}{{ }_{\sim}} 0.125$, can be matched up with the value suggested by the wealth of low-energy data, namely $\alpha_s(M_Z) \simeq 0.11$, which is smaller and more in line with the traditional QCD expectations at low energy. Our approach differs from previous analyses in that we argue that the desired matching could originate to a large extent from a purely electroweak supersymmetric quantum effect.Comment: 16 pages, LaTeX. Figures included and a few comments added. Full postscript version with figures embedded also available at ftp://ftp.ifae.es/preprint/ft/uabft365.p

Induction and suppression of gene silencing in plants by nonviral microbes

Gene silencing is a conserved mechanism in eukaryotes that dynamically regulates gene expression. In plants, gene silencing is critical for development and for maintenance of genome integrity. Additionally, it is a critical component of antiviral defence in plants, nematodes, insects, and fungi. To overcome gene silencing, viruses encode effectors that suppress gene silencing. A growing body of evidence shows that gene silencing and suppression of silencing are also used by plants during their interaction with nonviral pathogens such as fungi, oomycetes, and bacteria. Plant–pathogen interactions involve trans-kingdom movement of small RNAs into the pathogens to alter the function of genes required for their development and virulence. In turn, plant-associated pathogenic and nonpathogenic microbes also produce small RNAs that move trans-kingdom into host plants to disrupt pathogen defence through silencing of plant genes. The mechanisms by which these small RNAs move from the microbe to the plant remain poorly understood. In this review, we examine the roles of trans-kingdom small RNAs and silencing suppressors produced by nonviral microbes in inducing and suppressing gene silencing in plants. The emerging model is that gene silencing and suppression of silencing play critical roles in the interactions between plants and their associated nonviral microbes

Induction and suppression of gene silencing in plants by nonviral microbes

Gene silencing is a conserved mechanism in eukaryotes that dynamically regulates gene expression. In plants, gene silencing is critical for development and for maintenance of genome integrity. Additionally, it is a critical component of antiviral defence in plants, nematodes, insects, and fungi. To overcome gene silencing, viruses encode effectors that suppress gene silencing. A growing body of evidence shows that gene silencing and suppression of silencing are also used by plants during their interaction with nonviral pathogens such as fungi, oomycetes, and bacteria. Plant–pathogen interactions involve trans-kingdom movement of small RNAs into the pathogens to alter the function of genes required for their development and virulence. In turn, plant-associated pathogenic and nonpathogenic microbes also produce small RNAs that move trans-kingdom into host plants to disrupt pathogen defence through silencing of plant genes. The mechanisms by which these small RNAs move from the microbe to the plant remain poorly understood. In this review, we examine the roles of trans-kingdom small RNAs and silencing suppressors produced by nonviral microbes in inducing and suppressing gene silencing in plants. The emerging model is that gene silencing and suppression of silencing play critical roles in the interactions between plants and their associated nonviral microbes

Analysing Scientific Mobility and Collaboration in the Middle East and North Africa

This study investigates the scientific mobility and international collaboration networks in the Middle East and North Africa (MENA) region between 2008 and 2017. By using affiliation metadata available in scientific publications, we analyse international scientific mobility flows and collaboration linkages. Three complementary approaches allow us to obtain a detailed characterization of scientific mobility. First, we uncover the main destinations and origins of mobile scholars for each country. Results reveal geographical, cultural and historical proximities. Cooperation programs also contribute to explain some of the observed flows. Second, we use the academic age. The average academic age of migrant scholars in MENA was about 12.4 years. The academic age group 6-to-10 years is the most common for both emigrant and immigrant scholars. Immigrants are relatively younger than emigrants, except for Iran, Palestine, Lebanon, and Turkey. Scholars who migrated to Gulf Cooperation Council countries, Jordan and Morocco were in average younger than emigrants by 1.5 year from the same countries. Third, we analyse gender differences. We observe a clear gender gap: Male scholars represent the largest group of migrants in MENA. We conclude discussing the policy relevance of the scientific mobility and collaboration aspects.Comment: 37 pages, 9 figures, 5 table

Dehydration accelerates reductions in cerebral blood flow during prolonged exercise in the heat without compromising brain metabolism

Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, while the cerebral metabolic rate for oxygen (CMRO2) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled to fatigue. Two studies were undertaken. In study 1, ten male cyclists cycled in the heat for ~2 h with (control) and without fluid replacement (dehydration) while internal (ICA) and external (ECA) carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples were assessed with dehydration to evaluate the CMRO2. In study 2 (8 males), middle cerebral artery blood velocity (MCA Vmean) was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, ICA flow declined to baseline with progressive dehydration (P < 0.05). However, cerebral metabolism remained stable through enhanced oxygen and glucose extraction (P < 0.05). ECA flow increased for one hour but declined prior to exhaustion. Fluid ingestion maintained cerebral and extra-cranial perfusion throughout non-fatiguing exercise. During exhaustive exercise, however, euhydration delayed but did not prevent the decline in cerebral perfusion. In conclusion, during prolonged exercise in the heat dehydration accelerates the decline in CBF without affecting CMRO2 and also restricts extra-cranial perfusion. Thus fatigue is related to reduction in CBF and extra-cranial perfusion rather than in CMRO2.The study was supported by a grant from the Gatorade Sports Science Institute, PepsiCo Inc, USA

Changes in Subcellular Localization of Host Proteins Induced by Plant Viruses

Viruses are dependent on host factors at all parts of the infection cycle, such as translation, genome replication, encapsidation, and cell-to-cell and systemic movement. RNA viruses replicate their genome in compartments associated with the endoplasmic reticulum, chloroplasts, and mitochondria or peroxisome membranes. In contrast, DNA viruses replicate in the nucleus. Viral infection causes changes in plant gene expression and in the subcellular localization of some host proteins. These changes may support or inhibit virus accumulation and spread. Here, we review host proteins that change their subcellular localization in the presence of a plant virus. The most frequent change is the movement of host cytoplasmic proteins into the sites of virus replication through interactions with viral proteins, and the protein contributes to essential viral processes. In contrast, only a small number of studies document changes in the subcellular localization of proteins with antiviral activity. Understanding the changes in the subcellular localization of host proteins during plant virus infection provides novel insights into the mechanisms of plant–virus interactions and may help the identification of targets for designing genetic resistance to plant viruses

N-dimensional electron in a spherical potential: the large-N limit

We show that the energy levels predicted by a 1/N-expansion method for an N-dimensional Hydrogen atom in a spherical potential are always lower than the exact energy levels but monotonically converge towards their exact eigenstates for higher ordered corrections. The technique allows a systematic approach for quantum many body problems in a confined potential and explains the remarkable agreement of such approximate theories when compared to the exact numerical spectrum.Comment: 8 pages, 1 figur