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This study uses the data provided by the Leiden Ranking 2020 to support the claim that percentile-based indicators are linked by a power law function. A constant calculated from this function, ep, and the total number of papers fully characterize the percentile distribution of publications. According to this distribution, the probability that a publication from a country or institution is in the global xth percentile can be calculated from a simple equation: P = ep(2−lgx). By taking the Leiden Ranking PPtop 10%/100 as an approximation of the ep constant, our results demonstrate that other PPtop x% indicators can be calculated applying this equation. Consequently, given a PPtop x% indicator, all the others are redundant. Even accepting that the total number of papers and a single PPtop x% indicator are sufficient to fully characterize the percentile distribution of papers, the results of comparisons between universities and research institutions differ depending on the percentile selected for the comparison. We discuss which Ptop x% and PPtop x% indicators are the most convenient for these comparisons to obtain reliable information that can be used in research policy.

Objectives: Research is the foundation of technological progress; the aim of this study is to investigate research success in the USA, the EU and other countries in basic medical, biochemical and biotechnological topics. Methods: Research assessments were performed using the number of publications, the e(p) index and the probability that a publication reaches the top 0.01% by citation. The index reveals an important characteristic of citation distribution. The distribution of the publications from a country in global percentiles follows a power law and the e(p) index is a mathematical derivative of the exponent of this power law. In addition to its intrinsic value as performance indicator, this index allows calculating a country's probability of publishing highly cited papers and, consequently, of achieving important discoveries or scientific breakthroughs. Findings: Our results show that the USA is scientifically ahead of all countries and that its research is likely to produce approximately 80% of the important global breakthroughs in the research topics investigated in this study. EU research has maintained a constant weak position with reference to USA research over the last 30 years. Countries different from the USA and the EU are increasing enormously their number of publications. Currently, the probability that these publications report an important breakthrough is slightly lower than that of the EU.

In research policy, effective measures that lead to improvements in the generation of knowledge must be based on reliable methods of research assessment, but for many countries and institutions this is not the case. Publication and citation analyses can be used to estimate the part played by countries and institutions in the global progress of knowledge, but a concrete method of estimation is far from evident. The challenge arises because publications that report real progress of knowledge form an extremely low proportion of all publications; in most countries and institutions such contributions appear less than once per year. One way to overcome this difficulty is to calculate probabilities instead of counting the rare events on which scientific progress is based. This study reviews and summarizes several recent publications, and adds new results that demonstrate that the citation distribution of normal publications allows the probability of the infrequent events that support the progress of knowledge to be calculated.

The use of bibliometric indicators would simplify research assessments. The 2014 Research Excellence Framework (REF) is a peer review assessment of UK universities, whose results can be taken as benchmarks for bibliometric indicators. In this study we use the REF results to investigate whether the ep index and a top percentile of most cited papers could substitute for peer review. The probability that a random university's paper reaches a certain top percentile in the global distribution of papers is a power of the ep index, which can be calculated from the citation-based distribution of university's papers in global top percentiles. Making use of the ep index in each university and research area, we calculated the ratios between the percentage of 4-star-rated outputs in REF and the percentages of papers in global top percentiles. Then, we fixed the assessment percentile so that the mean ratio between these two indicators across universities is 1.0. This method was applied to four units of assessment in REF: Chemistry, Economics & Econometrics joined to Business & Management Studies, and Physics. Some relevant deviations from the 1.0 ratio could be explained by the evaluation procedure in REF or by the characteristics of the research field; other deviations need specific studies by experts in the research area. The present results indicate that in many research areas the substitution of a top percentile indicator for peer review is possible. However, this substitution cannot be made straightforwardly; more research is needed to establish the conditions of the bibliometric assessment., 38 pages, 7 tables and 2 figures in one single PDF file

SUMMARY Improving crop plants to be productive in saline soils or under irrigation with saline water would be an important technological advance in overcoming the food and freshwater crises that threaten the world population. However, even if the transformation of a glycophyte into a plant that thrives under seawater irrigation were biologically feasible, current knowledge about Na+ effects would be insufficient to support this technical advance. Intriguingly, crucial details about Na+ uptake and its function in the plant have not yet been well established. We here propose that under saline conditions two nitrate-dependent transport systems in series that take up and load Na+ into the xylem constitute the major pathway for the accumulation of Na+ in Arabidopsis shoots; this pathway can also function with chloride at high concentrations. In nrt1.1 nitrate transport mutants, plant Na+ accumulation was partially defective, which suggests that NRT1.1 either partially mediates or modulates the nitrate-dependent Na+ transport. Arabidopsis plants exposed to an osmotic potential of -1.0 MPa (400 mOsm) for 24 h showed high water loss and wilting in sorbitol or Na/MES, where Na+ could not be accumulated. In contrast, in NaCl the plants accumulated Na+, lost a low amount of water, and only suffered transitory wilting. We discuss that in Arabidopsis plants exposed to high NaCl concentrations, root Na+ uptake and tissue accumulation fulfill the primary function of osmotic adjustment, even if these processes lead to long-term toxicity. This article is protected by copyright. All rights reserved.

The European Union (EU) seems to presume that the mass production of European research papers indicates that Europe is a leading scientific power, and the so-called European paradox of strong science but weak technology is due to inefficiencies in the utilization of this top level European science by European industry. We fundamentally disagree, and will show that Europe lags far behind the USA in the production of important, highly cited research. We will show that there is a consistent weakening of European science as one ascends the citation scale, with the EU almost twice as effective in the production of minimal impact papers, while the USA is at least twice as effective in the production of very highly cited scientific papers, and garnering Nobel prizes. Only in the highly multinational, collaborative fields of Physics and Clinical Medicine does the EU seem to approach the USA in top scale impact.

The journal impact factor (JIF) is the average of the number of citations of the papers published in a journal, calculated according to a specific formula; it is extensively used for the evaluation of research and researchers. The method assumes that all papers in a journal have the same scientific merit, which is measured by the JIF of the publishing journal. This implies that the number of citations measures scientific merits but the JIF does not evaluate each individual paper by its own number of citations. Therefore, in the comparative evaluation of two papers, the use of the JIF implies a risk of failure, which occurs when a paper in the journal with the lower JIF is compared to another with fewer citations in the journal with the higher JIF. To quantify this risk of failure, this study calculates the failure probabilities, taking advantage of the lognormal distribution of citations. In two journals whose JIFs are ten-fold different, the failure probability is low. However, in most cases when two papers are compared, the JIFs of the journals are not so different. Then, the failure probability can be close to 0.5, which is equivalent to evaluating by coin flipping., 24 pages, 1 figure and 4 tables in the main text, plus 1 table as supplementary material. One single pdf file

Scientific progress is driven by important, infrequent discoveries that cannot be readily identified and quantified, which makes research assessment very difficult. Bibliometric indicators of important discoveries have been formulated using an empirical approach, based on the mathematical properties of the high-citation tail of the citation distribution. To investigate the theoretical basis of such formulations this study compares the US/European research performance ratios expressed in terms of highly cited papers and Nobel Prize-winning discoveries. The research performance ratio in terms of papers was studied from the citation distributions in the fields of chemistry, physics, and biochemistry and molecular biology. It varied as a function of the citation level. Selecting an appropriate high citation level, the ratios in terms of highly cited papers were compared with the corresponding ratios for Nobel Prize-winning discoveries in Chemistry, Physics, and Physiology or Medicine. Research performance ratios expressed in terms of highly cited papers and Nobel Prize-winning discoveries are reasonably similar, and suggest that the research success of the United States is almost 3 times that of Europe. A similar conclusion was obtained using articles published in Nature and Science.

The function of HAK transporters in high-affinity K+ uptake in plants is well established; this study aims to demonstrate that some transporters of the same family play important roles in endomembranes. The PpHAK2-PpHAK4 genes of Physcomitrella patens encode three transporters of high sequence similarity. Quantitative PCR showed that PpHAK2 and PpHAK3 transcripts are expressed at approximately the same level as the PpACT5 gene, while the expression of PpHAK4 seems to be restricted to specific conditions that have not been determined. KHA1 is an endomembrane K+/H+ antiporter of Saccharomyces cerevisiae, and the expression of the PpHAK2 cDNA, but not that of PpHAK3, suppressed the defect of a kha1 mutant. Transient expression of the PpHAK2-green fluorescent protein (GFP) and PpHAK3-GFP fusion proteins in P. patens protoplasts localized to the endoplasmic reticulum and Golgi complex, respectively. To determine the function of PpHAK2 and PpHAK3 in planta, we constructed ΔPphak2 and ΔPphak2 ΔPphak3 plants. ΔPphak2 plants were normal under all of the conditions tested except under K+ starvation or at acidic pH in the presence of acetic acid, whereupon they die. The defect observed under K+ starvation was suppressed by the presence of Na+. We propose that PpHAK2 may encode either a K(+)-H(+) symporter or a K+/H+ antiporter that mediates the transfer of H+ from the endoplasmic reticulum lumen to the cytosol. PpHAK2 may be a model of the second function of HAK transporters in plant cells. The disruption of the PpHAK3 gene in ΔPphak2 plants showed no effect.

We have investigated OsHKT2;1 natural variation in a collection of 49 cultivars with different levels of salt tolerance and geographical origins. The effect of identified polymorphism on OsHKT2;1 activity was analysed through heterologous expression of variants in Xenopus oocytes. OsHKT2;1 appeared to be a highly conserved protein with only five possible amino acid substitutions that have no substantial effect on functional properties. Our study, however, also identified a new HKT isoform, No-OsHKT2;2/1 in Nona Bokra, a highly salt-tolerant cultivar. No-OsHKT2;2/1 probably originated from a deletion in chromosome 6, producing a chimeric gene. Its 5' region corresponds to that of OsHKT2;2, whose full-length sequence is not present in Nipponbare but has been identified in Pokkali, a salt-tolerant rice cultivar. Its 3' region corresponds to that of OsHKT2;1. No-OsHKT2;2/1 is essentially expressed in roots and displays a significant level of expression at high Na⁺ concentrations, in contrast to OsHKT2;1. Expressed in Xenopus oocytes or in Saccharomyces cerevisiae, No-OsHKT2;2/1 exhibited a strong permeability to Na⁺ and K⁺, even at high external Na⁺ concentrations, like OsHKT2;2, and in contrast to OsHKT2;1. Our results suggest that No-OsHKT2;2/1 can contribute to Nona Bokra salt tolerance by enabling root K⁺ uptake under saline conditions.

The widespread presence of Na(+)-specific uptake systems across plants and fungi is a controversial topic. In this study, we identify two HAK genes, one in the moss Physcomitrella patens and the other in the yeast Yarrowia lipolytica, that encode Na(+)-specific transporters. Because HAK genes are numerous in plants and are duplicated in many fungi, our findings suggest that some HAK genes encode Na(+) transporters and that Na(+) might play physiological roles in plants and fungi more extensively than is currently thought.

In this study, we report an inventory of the K(+) uptake systems in 62 fungal species for which the complete genome sequences are available. This inventory reveals that three types of K(+) uptake systems, TRK and HAK transporters and ACU ATPases, are widely present in several combinations across fungal species. PAT ATPases are less frequently present and are exceptional in Ascomycota. The genome of Magnaporthe oryzae contains four TRK, one HAK, and two ACU genes. The study of the expression of these genes at high K(+), K(+) starvation, and in infected rice leaves revealed that the expression of four genes, ACU1, ACU2, HAK1, and TRK1 is much lower than that of TRK2, TRK3, and TRK4, except under K(+) starvation. The two ACU ATPases were cloned and functionally identified as high-affinity K(+) or Na(+) uptake systems. These two ATPases endow Saccharomyces cerevisiae with the capacity to grow for several generations in low Na(+) concentrations when K(+) was absent, which produces a dramatic increase of cellular Na(+)/K(+) ratio.

PurposeSeveral bibliometric indicators that are extensively used to estimate research performance have not been validated against an external criterion of excellence. This paper aims to investigate whether this validation is possible using the number of Nobel Prize awards.Design/methodology/approachThis study uses several analytical treatments of the data to investigate: whether Nobel Prize awards are sporadic events or they depend on the scientific activity of countries or institutions and can be used in research evaluation; and the association between the number of Nobel Prize achievements and conventional bibliometric indicators across countries and institutions.FindingsThis study finds that conventional bibliometric indicators, numbers of publications, citations, and top 1 per cent most cited publications, correlate with the number of Nobel Prize achievements in several advanced countries with similar research abilities. Contrarily, in countries and institutions with more variable research characteristics, there is no association between conventional bibliometric indicators and the number of Nobel Prize achievements, and their use as indicators of research excellence is not valid. In contrast, the number of national articles in Nature and Science correlates with the number of Nobel Prize achievements across countries and institutions.Practical implicationsScience administrators implementing research evaluations and research incentives based on conventional bibliometric indicators should consider that increasing the scores of these indicators does not imply an improvement in research excellence.Originality/valueThe study demonstrates that Nobel Prize achievements are not singular events that occur by chance. Therefore, the number of Nobel Prize achievements can be used to validate bibliometric indicators.

The K+ and Na+ concentrations in living cells are strictly regulated at almost constant concentrations, high for K+ and low for Na+. Because these concentrations correspond to influx–efflux steady states, K+ and Na+ effluxes and the transporters involved play a central role in the physiology of cells, especially in environments with high Na+ concentrations where a high Na+ influx may be the rule. In eukaryotic cells two P-type ATPases are crucial in these homeostatic processes, the Na,K-ATPase of animal cells and the H+-ATPase of fungi and plants. In fungi, a third P-type ATPase, the ENA ATPase, was discovered nineteen years ago. Although for many years it was considered to be exclusively a fungal enzyme, it is now known to be present in bryophytes and protozoa. Structurally, the ENA (from exitus natru: exit of sodium) ATPase is very similar to the sarco/endoplasmic reticulum Ca2+ (SERCA) ATPase, and it probably exchanges Na+ (or K+) for H+. The same exchange is mediated by Na+ (or K+)/H+ antiporters. However, in eukaryotic cells these antiporters are electroneutral and their function depends on a ΔpH across the plasma membrane. Therefore, the current notion is that the ENA ATPase is necessary at high external pH values, where the antiporters cannot mediate uphill Na+ efflux. This occurs in some fungal environments and at some points of protozoa parasitic cycles, which makes the ENA ATPase a possible target for controlling fungal and protozoan parasites. Another technological application of the ENA ATPase is the improvement of salt tolerance in flowering plants.

Potassium or Na(+) efflux ATPases, ENA ATPases, are present in all fungi and play a central role in Na(+) efflux and Na(+) tolerance. Flowering plants lack ENA ATPases but two ENA ATPases have been identified in the moss Physcomitrella patens, PpENA1 and PpENA2. PpENA1 mediates Na(+) efflux in Saccharomyces cerevisiae. To propose a general function of ENA ATPases in bryophytes it was necessary to demonstrate that these ATPases mediate Na(+) efflux in planta and that they exist in more bryophytes than P. patens. For these demonstrations (1) we cloned a third ATPase from P. patens, PpENA3, and studied the expression pattern of the three PpENA genes; (2) we constructed and studied the single and double Deltappena1 and Deltappena2 mutants; and (3) we cloned two ENA ATPases from the liverwort Marchantia polymorpha, MpENA1 and MpENA2, and expressed them in S. cerevisiae. The results from the first two approaches revealed that the expression of ENA ATPases was greatly enhanced at high pH and that Na(+) efflux at high pH depended on PpENA1. The ENA1 ATPase of M. polymorpha suppressed the defective growth of a S. cerevisiae mutant at high K(+) or Na(+) concentrations, especially at high K(+).

Potassium uptake is one of the most basic processes of plant physiology. However, a comprehensive description is lacking. At a cellular level fungi have provided a helpful but imperfect plant model, which we aim to improve using Physcomitrella patens. Blast searches in expressed sequence tag databases demonstrated that Physcomitrella expresses the same families of K(+) and Na(+) transport systems as flowering plants. We cloned two inward rectifier channels, PpAKT1-2, and four HAK-type transporters (PpHAK1-4). In both types of transport system, phylogenetic analyses revealed that despite their high sequence conservation they could not be included in Arabidopsis or rice (Oryza sativa) clusters. Both inward rectifier channels and one HAK transporter (PpHAK1) were expressed in yeast. PpAKT1 and activated mutants of PpAKT2 and PpHAK1 showed clear functions that were similar to those of homologous systems of flowering plants. A pphak1 null mutant line of Physcomitrella failed to deplete K(+) below 10 mum. Moreover, in a non-K(+)-limiting medium in which wild-type plants grew only as protonema, pphak1-1 plants produced leafy gametophores and contained 60% more K(+). We found that Physcomitrella takes up K(+) through several systems. PpHAK1 is the dominant system in plants that underwent K(+) starvation for long periods but an as-yet unidentified system, which is non-selective for K(+), Rb(+), and Cs(+), dominates in many other conditions. Finally, we discuss that, similar to PpHAK1, one of the functions of AtHAK5 may be to control cellular K(+) content and that a non-selective as-yet unidentified system also exists in Arabidopsis.

The applicability of Hirsch’s h index (Hirsch, 2005) for evaluating scientific research in Spain has been investigated. A series of derivative indexes that take into account: i) the overall low scientific production in Spain before the’ 80s; ii) differences among areas due to size (overall number of citations for publications in a given area); and iii) the number of authors, are suggested. Their applicability has been tested for two different areas in the Biological Sciences. The proposed set of indexes accurately summarizes both the success and evolution of scientists’ careers in Spain, and it may be useful in the evaluation of other not well established national scientific research systems.