Abstract
Soil phosphorus (P) loss from agricultural systems will limit food and feed production in the future. Here, we combine spatially distributed global soil erosion estimates (only considering ...sheet and rill erosion by water) with spatially distributed global P content for cropland soils to assess global soil P loss. The world’s soils are currently being depleted in P in spite of high chemical fertilizer input. Africa (not being able to afford the high costs of chemical fertilizer) as well as South America (due to non-efficient organic P management) and Eastern Europe (for a combination of the two previous reasons) have the highest P depletion rates. In a future world, with an assumed absolute shortage of mineral P fertilizer, agricultural soils worldwide will be depleted by between 4–19 kg ha
−1
yr
−1
, with average losses of P due to erosion by water contributing over 50% of total P losses.
Examining a series of processes (Islamization, Arabization, Africanization) and case studies from North, West and East Africa, this book gives snapshots of Muslim societies in Africa over the last ...millennium. In contrast to traditions which suggest that Islam did not take root in Africa, author David Robinson shows the complex struggles of Muslims in the Muslim state of Morocco and in the Hausaland region of Nigeria. He portrays the ways in which Islam was practiced in the 'pagan' societies of Ashanti (Ghana) and Buganda (Uganda) and in the ostensibly Christian state of Ethiopia - beginning with the first emigration of Muslims from Mecca in 615 CE, well before the foundational hijra to Medina in 622. He concludes with chapters on the Mahdi and Khalifa of the Sudan and the Murid Sufi movement that originated in Senegal, and reflections in the wake of the events of September 11, 2001.
Soil erosion is a major global soil degradation threat to land, freshwater, and oceans. Wind and water are the major drivers, with water erosion over land being the focus of this work; excluding ...gullying and river bank erosion. Improving knowledge of the probable future rates of soil erosion, accelerated by human activity, is important both for policy makers engaged in land use decision-making and for earth-system modelers seeking to reduce uncertainty on global predictions. Here we predict future rates of erosion by modeling change in potential global soil erosion by water using three alternative (2.6, 4.5, and 8.5) Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios. Global predictions rely on a high spatial resolution Revised Universal Soil Loss Equation (RUSLE)-based semiempirical modeling approach (GloSEM). The baseline model (2015) predicts global potential soil erosion rates of
43
−
7
+
9.2
Pg yr−1, with current conservation agriculture (CA) practices estimated to reduce this by ∼5%. Our future scenarios suggest that socioeconomic developments impacting land use will either decrease (SSP1-RCP2.6–10%) or increase (SSP2-RCP4.5 +2%, SSP5-RCP8.5 +10%) water erosion by 2070. Climate projections, for all global dynamics scenarios, indicate a trend, moving toward a more vigorous hydrological cycle, which could increase global water erosion (+30 to +66%). Accepting some degrees of uncertainty, our findings provide insights into how possible future socioeconomic development will affect soil erosion by water using a globally consistent approach. This preliminary evidence seeks to inform efforts such as those of the United Nations to assess global soil erosion and inform decision makers developing national strategies for soil conservation.
The Capital Structure Decisions of New Firms Robb, Alicia M.; Robinson, David T.
Review of financial studies/The Review of financial studies,
01/2014, Letnik:
27, Številka:
1
Journal Article
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We study capital structure choices that entrepreneurs make in their firms' initial year of operation, using restricted-access data from the Kauffman Firm Survey. Firms in our data rely heavily on ...external debt sources, such as bank financing, and less extensively on friends-and-family-based funding sources. Many startups receive debt financed through the personal balance sheets of the entrepreneur, effectively resulting in the entrepreneur holding levered equity claims in their startups. This fact is robust to numerous controls, including credit quality. The reliance on external debt underscores the importance of credit markets for the success of nascent business activity.
We debate the motivation for and effectiveness of public policies to encourage individuals to become entrepreneurs. Reviewing established evidence we find that most Western world policies do not ...greatly reduce or solve any market failures but instead waste taxpayers' money, encourage those already intent on becoming entrepreneurs, and mostly generate one-employee businesses with low-growth intentions and a lack of interest in innovating. Most policy initiatives that would have the effect of promoting valuable entrepreneurship would not be recognizable as such, because they would primarily address other market failures: A central-payer health care would remove healthcare-related distortions affecting employment choices; greater STEM education would produce more engineers of which some start valuable new firms; and labor market reform to encourage hiring immigrants in jobs they have been educated for would reduce inefficient allocation of talent to entrepreneurship.
We measure financial literacy among LinkedIn members, complementing standard questions with additional questions that allow us to gauge self-perceptions of financial literacy. Average financial ...literacy is surprisingly low given the demographics of our sample: fewer than two-thirds of chief financial officers, chief executive officers, and chief operating officers complete the test correctly. Financial literacy, precautionary savings and retirement planning are positively correlated, but this is mostly driven by perceived, not actual, literacy: controlling for self-perceptions, actual literacy has low predictive power. Perceptions drive decision-making among low-literacy respondents and are associated with mistaken beliefs about financial products and less willingness to accept financial advice.
Plant Golgi ultrastructure ROBINSON, DAVID G.
Journal of microscopy (Oxford),
November 2020, Letnik:
280, Številka:
2
Journal Article
Recenzirano
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Summary
The plant Golgi apparatus (sensu lato: Golgi stack + Trans Golgi Network, TGN) is a highly polar and mobile key organelle lying at the junction of the secretory and endocytic pathways. Unlike ...its counterpart in animal cells it does not disassemble during mitosis. It modifies glycoproteins sent to it from the endoplasmic reticulum (ER), it recycles ER resident proteins, it sorts proteins destined for the vacuole from secretory proteins, it receives proteins internalised from the plasma membrane and either recycles them to the plasma membrane or retargets them to the vacuole for degradation. In functional terms the Golgi apparatus can be likened to a car factory, with incoming (COPII traffic) and returning (COPI traffic) railway lines at the entry gate, and a distribution centre (the TGN) at the exit gate of the assembly hall. In the assembly hall we have a conveyor belt system where the incoming car parts are initially assembled (in the cis‐area) then gradually modified into different models (processing of secretory cargo) as the cars pass along the production line (cisternal maturation). After being released the trans‐area, the cars (secretory cargos) are moved out of the assembly hall and passed on to the distribution centre (TGN), where the various models are placed onto different trains (cargo sorting into carrier vesicles) for transport to the car dealers. Cars with motor problems are returned to the factory for repairs (endocytosis to the TGN). This simple analogy also incorporates features of quality control at the COPII entry gate with defective parts being returned to the manufacturing center (the ER) via the COPI trains (vesicles).
In recent years, numerous studies have contributed to our knowledge on Golgi function and structure in both animals, yeast and plants. This review, rather than giving a balanced account of the structure as well as of the function of the Golgi apparatus has purposely a marked slant towards plant Golgi ultrastructure integrating findings from the mammalian/animal field.
The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. Global advocacy organizations claim ...routine deworming has substantive health and societal effects beyond the removal of worms. In this update of the 2015 edition we included six new trials, additional data from included trials, and addressed comments and criticisms.
To summarize the effects of public health programmes to regularly treat all children with deworming drugs on child growth, haemoglobin, cognition, school attendance, school performance, physical fitness, and mortality.
We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; Embase; LILACS; the metaRegister of Controlled Trials (mRCT); reference lists; and registers of ongoing and completed trials up to 19 September 2018.
We included randomized controlled trials (RCTs) and quasi-RCTs that compared deworming drugs for soil-transmitted helminths (STHs) with placebo or no treatment in children aged 16 years or less, reporting on weight, height, haemoglobin, and formal tests of cognition. We also sought data on other measures of growth, school attendance, school performance, physical fitness, and mortality.
At least two review authors independently assessed the trials for inclusion, risk of bias, and extracted data. We analysed continuous data using the mean difference (MD) with 95% confidence intervals (CIs). Where data were missing, we contacted trial authors. We stratified the analysis based on the background burden of STH infection. We used outcomes at time of longest follow-up. We assessed the certainty of the evidence using the GRADE approach.
We identified 51 trials, including 10 cluster-RCTs, that met the inclusion criteria. One trial evaluating mortality included over one million children, and the remaining 50 trials included a total of 84,336 participants. Twenty-four trials were in populations categorized as high burden, including nine trials in children selected because they were helminth-stool positive; 18 with intermediate burden; and nine as low burden.First or single dose of deworming drugsFourteen trials reported on weight after a single dose of deworming drugs (4970 participants, 14 RCTs). The effects were variable. There was little or no effect in studies conducted in low and intermediate worm burden groups. In the high-burden group, there was little or no effect in most studies, except for a large effect detected from one study area in Kenya reported in two trials carried out over 30 years ago. These trials result in qualitative heterogeneity and uncertainty in the meta-analysis across all studies (I
statistic = 90%), with GRADE assessment assessed as very low-certainty, which means we do not know if a first dose or single dose of deworming impacts on weight.For height, most studies showed little or no effect after a single dose, with one of the two trials in Kenya from 30 years ago showing a large average difference (2621 participants, 10 trials, low-certainty evidence). Single dose probably had no effect on average haemoglobin (MD 0.10 g/dL, 95% CI 0.03 lower to 0.22 higher; 1252 participants, five trials, moderate-certainty evidence), or on average cognition (1596 participants, five trials, low-certainty evidence). The data are insufficient to know if there is an effect on school attendance and performance (304 participants, one trial, low-certainty evidence), or on physical fitness (280 participants, three trials, very low-certainty evidence). No trials reported on mortality.Multiple doses of deworming drugsThe effect of regularly treating children with deworming drugs given every three to six months on weight was reported in 18 trials, with follow-up times of between six months and three years; there was little or no effect on average weight in all but two trials, irrespective of worm prevalence-intensity. The two trials with large average weight gain included one in the high burden area in Kenya carried out over 30 years ago, and one study from India in a low prevalence area where subsequent studies in the same area did not show an effect. This heterogeneity causes uncertainty in any meta-analysis (I
= 78%). Post-hoc analysis excluding trials published prior to 2000 gave an estimate of average difference in weight gain of 0.02 kg (95%CI from 0.04 kg loss to 0.08 gain, I
= 0%). Thus we conclude that we do not know if repeated doses of deworming drugs impact on average weight, with a fewer older studies showing large gains, and studies since 2000 showing little or no average gain.Regular treatment probably had little or no effect on the following parameters: average height (MD 0.02 cm higher, 95% CI 0.09 lower to 0.13 cm higher; 13,700 participants, 13 trials, moderate-certainty evidence); average haemoglobin (MD 0.01 g/dL lower; 95% CI 0.05 g/dL lower to 0.07 g/dL higher; 5498 participants, nine trials, moderate-certainty evidence); formal tests of cognition (35,394 participants, 8 trials, moderate-certainty evidence); school performance (34,967 participants, four trials, moderate-certainty evidence). The evidence assessing an effect on school attendance is inconsistent, and at risk of bias (mean attendance 2% higher, 95% CI 5% lower to 8% higher; 20,650 participants, three trials, very low-certainty evidence). No trials reported on physical fitness. No effect was shown on mortality (1,005,135 participants, three trials, low-certainty evidence).
Public health programmes to regularly treat all children with deworming drugs do not appear to improve height, haemoglobin, cognition, school performance, or mortality. We do not know if there is an effect on school attendance, since the evidence is inconsistent and at risk of bias, and there is insufficient data on physical fitness. Studies conducted in two settings over 20 years ago showed large effects on weight gain, but this is not a finding in more recent, larger studies. We would caution against selecting only the evidence from these older studies as a rationale for contemporary mass treatment programmes as this ignores the recent studies that have not shown benefit.The conclusions of the 2015 edition have not changed in this update.
We study the liquidity properties of private equity cash flows using data from 837 buyout and venture capital funds from 1984 to 2010. Most cash flow variation at a point in time is diversifiable — ...either idiosyncratic to a given fund or explained by the fund’s age. Both capital calls and distributions also have a procyclical systematic component. Distributions are more sensitive than calls, implying procyclical aggregate net cash flows. A consequence is that the well-known finding that funds raised in hot markets underperform in absolute terms is sharply attenuated when comparing to public equities. Consistent with a liquidity premium for calling capital in bad times, we find that funds with a relatively high propensity to do so perform better in both absolute and relative terms. Venture capital cash flows and performance are considerably more cyclical than buyout, and the links between cyclical cash flows and performance are likewise stronger.
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