4,442 research outputs found
Rubber smallholders' flexibility No windfall, no crisis
A few decades ago rubber was one of the first tree crops to be characterized by a spectacular breakthrough, the production of new, highly productive clonal material. With regard to rubber, the adoption of clonal planting materials led to a spectacular improvement in labour-productivity and revenues. It requires also different cropping patterns during immature period. An increase in return to labour costs is usually the first priority of smallholders. As this adoption of clones by smallholders only started in the 1970s in Indonesia, this is an extremely important strategy which must be stressed before we begin to analyze the impact of the krismon (a contraction of âKrisis Monetarâ in Indonesian or âmonetary crisisâ). With regard to rubber, there is clearly a dualism of seedlings and clonal material. This dualism is more important than with other tree crops. Rubber seedlings are often grown under a complex agroforestry system and nicknamed locally âjungle rubber'. Clonal rubber is generally grown in monoculture sometimes with intercrops during the first three years.âEven when computing the cost of the investment and the credit that has to be repaid, the net income per hectare and per labour day from a clonal plantation is at least 50% higher (sometimes 100%) than the income from a jungle rubber plantationâ (Gouyon 1999, 31). What was the situation before krismon? Due to capital and information constraints, only 15% of the smallholders already had access to highly productive clonal material rubber in 1996. This percentage was achieved, first and foremost, through official projects. Then in the late 1990s, the âcopying effectâ started playing its role, however rather limited. More and more farmers were able to observe the advantages of clonal material. This led to a booming network of private nurseries that helped to accelerate the adoption of this material. This means that a relatively strong dynamism was observed before krismon. It also means that most clonal plantations are still young, which is important in terms of potential response to price changes (Chapter 1). However, when krismon arrived, around 85% of traditionnal rubber farmers still relied on ageing jungle rubber with limited productivity. How may krismon influence these âjungle rubber' and âclonal' farming systems? Is it going to accelerate or reduce the investment in rubber plantings? Is it going to help to accelerate the adoption of clones? In 1998, rubber farmers did not benefit from the spectacular windfall, which affected cocoa and coffee (Chapters 5-7). Can this be explained by the different performances of farming systems or by variations of the International market? Is there a direct relationship between the decline of global prices and the interference of the Asian crisis in Indonesian rubber supply and exports (Chapter 2)? Page 2 How did the monetary crisis affect the other dramatic changes faced by Indonesian rubber smallholders? In addition to the economic crisis, as in other regions of the country, the ecological crisis also struck Sumatra and Kalimantan in 1997-98. Huge fires destroyed millions of hectares of forests, fallows and crops, including rubber. Will both crisis reduce investment in clonal plantings? Eventually, regions such as West-Kalimantan were the theatre for grave social troubles related to conflicts between autochtons and some immigrants, especially spontaneous immigrants1. A lack of confidence in the country's regime was evident well before the crisis. Last but not least, oil palm development looms in traditional rubber regions. Might it hamper the development of clonal rubber technology in Indonesia? Does the crisis encourage the adoption of oil palm at the expense of rubber? Does the crisis deepen the social imbalance between smallholders who already have access to clones and those who do not? To try to answer these questions , the paper is structured in 4 sections: 1 A brief overview of the rubber sector : the situation before krismon 2 Krismon and its impact on rubber smallholdings 3 The rubber crisis on the international market 4 A conclusion including the future for the rubber smallholder sector
Rubber smallholders' flexibility No windfall, no crisis
A few decades ago rubber was one of the first tree crops to be characterized by a spectacular breakthrough, the production of new, highly productive clonal material. With regard to rubber, the adoption of clonal planting materials led to a spectacular improvement in labour-productivity and revenues. It requires also different cropping patterns during immature period. An increase in return to labour costs is usually the first priority of smallholders. As this adoption of clones by smallholders only started in the 1970s in Indonesia, this is an extremely important strategy which must be stressed before we begin to analyze the impact of the krismon (a contraction of âKrisis Monetarâ in Indonesian or âmonetary crisisâ). With regard to rubber, there is clearly a dualism of seedlings and clonal material. This dualism is more important than with other tree crops. Rubber seedlings are often grown under a complex agroforestry system and nicknamed locally âjungle rubber'. Clonal rubber is generally grown in monoculture sometimes with intercrops during the first three years.âEven when computing the cost of the investment and the credit that has to be repaid, the net income per hectare and per labour day from a clonal plantation is at least 50% higher (sometimes 100%) than the income from a jungle rubber plantationâ (Gouyon 1999, 31). What was the situation before krismon? Due to capital and information constraints, only 15% of the smallholders already had access to highly productive clonal material rubber in 1996. This percentage was achieved, first and foremost, through official projects. Then in the late 1990s, the âcopying effectâ started playing its role, however rather limited. More and more farmers were able to observe the advantages of clonal material. This led to a booming network of private nurseries that helped to accelerate the adoption of this material. This means that a relatively strong dynamism was observed before krismon. It also means that most clonal plantations are still young, which is important in terms of potential response to price changes (Chapter 1). However, when krismon arrived, around 85% of traditionnal rubber farmers still relied on ageing jungle rubber with limited productivity. How may krismon influence these âjungle rubber' and âclonal' farming systems? Is it going to accelerate or reduce the investment in rubber plantings? Is it going to help to accelerate the adoption of clones? In 1998, rubber farmers did not benefit from the spectacular windfall, which affected cocoa and coffee (Chapters 5-7). Can this be explained by the different performances of farming systems or by variations of the International market? Is there a direct relationship between the decline of global prices and the interference of the Asian crisis in Indonesian rubber supply and exports (Chapter 2)? Page 2 How did the monetary crisis affect the other dramatic changes faced by Indonesian rubber smallholders? In addition to the economic crisis, as in other regions of the country, the ecological crisis also struck Sumatra and Kalimantan in 1997-98. Huge fires destroyed millions of hectares of forests, fallows and crops, including rubber. Will both crisis reduce investment in clonal plantings? Eventually, regions such as West-Kalimantan were the theatre for grave social troubles related to conflicts between autochtons and some immigrants, especially spontaneous immigrants1. A lack of confidence in the country's regime was evident well before the crisis. Last but not least, oil palm development looms in traditional rubber regions. Might it hamper the development of clonal rubber technology in Indonesia? Does the crisis encourage the adoption of oil palm at the expense of rubber? Does the crisis deepen the social imbalance between smallholders who already have access to clones and those who do not? To try to answer these questions , the paper is structured in 4 sections: 1 A brief overview of the rubber sector : the situation before krismon 2 Krismon and its impact on rubber smallholdings 3 The rubber crisis on the international market 4 A conclusion including the future for the rubber smallholder secto
Experimental infection of the pig with Mycobacterium ulcerans : a novel model for studying the pathogenesis of Buruli ulcer disease
Buruli ulcer (BU) is a slowly progressing, necrotising disease of the skin caused by infection with Mycobacterium ulcerans. Non-ulcerative manifestations are nodules, plaques and oedema, which may progress to ulceration of large parts of the skin. Histopathologically, BU is characterized by coagulative necrosis, fat cell ghosts, epidermal hyperplasia, clusters of extracellular acid fast bacilli (AFB) in the subcutaneous tissue and lack of major inflammatory infiltration. The mode of transmission of BU is not clear and there is only limited information on the early pathogenesis of the disease available.; For evaluating the potential of the pig as experimental infection model for BU, we infected pigs subcutaneously with different doses of M. ulcerans. The infected skin sites were excised 2.5 or 6.5 weeks after infection and processed for histopathological analysis. With doses of 2Ă107 and 2Ă106 colony forming units (CFU) we observed the development of nodular lesions that subsequently progressed to ulcerative or plaque-like lesions. At lower inoculation doses signs of infection found after 2.5 weeks had spontaneously resolved at 6.5 weeks. The observed macroscopic and histopathological changes closely resembled those found in M. ulcerans disease in humans.; Our results demonstrate that the pig can be infected with M. ulcerans. Productive infection leads to the development of lesions that closely resemble human BU lesions. The pig infection model therefore has great potential for studying the early pathogenesis of BU and for the development of new therapeutic and prophylactic interventions
Volatility and arbitrage
The capitalization-weighted cumulative variation d i=1 0 ”i(t)d(log ”i)(t) in an equity market consisting of a fixed number d of assets with capitalization weights ”i(·) ; is an observable and a nondecreasing function of time. If this observable of the market is not just nondecreasing but actually grows at a rate bounded away from zero, then strong arbitrage can be constructed relative to the market over sufficiently long time horizons. It has been an open issue for more than ten years, whether such strong outperformance of the market is possible also over arbitrary time horizons under the stated condition. We show that this is not possible in general, thus settling this long-open question. We also show that, under appropriate additional conditions, outperformance over any time horizon indeed becomes possible, and exhibit investment strategies that effect it
Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling
Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling
Quantifying electronic correlation strength in a complex oxide: a combined DMFT and ARPES study of LaNiO
The electronic correlation strength is a basic quantity that characterizes
the physical properties of materials such as transition metal oxides.
Determining correlation strengths requires both precise definitions and a
careful comparison between experiment and theory. In this paper we define the
correlation strength via the magnitude of the electron self-energy near the
Fermi level. For the case of LaNiO, we obtain both the experimental and
theoretical mass enhancements by considering high resolution
angle-resolved photoemission spectroscopy (ARPES) measurements and density
functional + dynamical mean field theory (DFT + DMFT) calculations. We use
valence-band photoemission data to constrain the free parameters in the theory,
and demonstrate a quantitative agreement between the experiment and theory when
both the realistic crystal structure and strong electronic correlations are
taken into account. These results provide a benchmark for the accuracy of the
DFT+DMFT theoretical approach, and can serve as a test case when considering
other complex materials. By establishing the level of accuracy of the theory,
this work also will enable better quantitative predictions when engineering new
emergent properties in nickelate heterostructures.Comment: 10 pages, 5 figure
Time-Frequency Analysis of Rocket Nozzle Wall Pressures During Start-up Transients
Surveys of the fluctuating wall pressure were conducted on a sub-scale, thrust- optimized parabolic nozzle in order to develop a physical intuition for its Fourier-azimuthal mode behavior during fixed and transient start-up conditions. These unsteady signatures are driven by shock wave turbulent boundary layer interactions which depend on the nozzle pressure ratio and nozzle geometry. The focus however, is on the degree of similarity between the spectral footprints of these modes obtained from transient start-ups as opposed to a sequence of fixed nozzle pressure ratio conditions. For the latter, statistically converged spectra are computed using conventional Fourier analyses techniques, whereas the former are investigated by way of time-frequency analysis. The findings suggest that at low nozzle pressure ratios -- where the flow resides in a Free Shock Separation state -- strong spectral similarities occur between fixed and transient conditions. Conversely, at higher nozzle pressure ratios -- where the flow resides in Restricted Shock Separation -- stark differences are observed between the fixed and transient conditions and depends greatly on the ramping rate of the transient period. And so, it appears that an understanding of the dynamics during transient start-up conditions cannot be furnished by a way of fixed flow analysis
Effect of Stagger on the Vibroacoustic Loads from Clustered Rockets
The effect of stagger startup on the vibro-acoustic loads that form during the end- effects-regime of clustered rockets is studied using both full-scale (hot-gas) and laboratory scale (cold gas) data. Both configurations comprise three nozzles with thrust optimized parabolic contours that undergo free shock separated flow and restricted shock separated flow as well as an end-effects regime prior to flowing full. Acoustic pressure waveforms recorded at the base of the nozzle clusters are analyzed using various statistical metrics as well as time-frequency analysis. The findings reveal a significant reduction in end- effects-regime loads when engine ignition is staggered. However, regardless of stagger, both the skewness and kurtosis of the acoustic pressure time derivative elevate to the same levels during the end-effects-regime event thereby demonstrating the intermittence and impulsiveness of the acoustic waveforms that form during engine startup
- âŠ