Top PDF Dynamics of Seasonally-Varying Tropical Convergence Zones

Dynamics of Seasonally-Varying Tropical Convergence Zones

Dynamics of Seasonally-Varying Tropical Convergence Zones

Most of the Earth’s precipitation falls in the tropics, the latitudinal band within 30 degrees north and south of the equator. Mechanisms controlling the spatial and temporal distribution of large-scale tropical rain bands, including the oceanic intertropical convergence zone (ITCZ) and its excursions into summer tropical con- tinents in association with monsoons, remain an open question and a major challenge for the climate sciences. Tropical and subtropical regions, with increasing popu- lations and rapidly growing economies, heavily rely on rainfall and are extremely susceptible to rainfall changes under global warming. Yet, predictions remain highly uncertain on all timescales, emphasizing the need for improved understanding. In the past decade, significant advances have been made in our theoretical un- derstanding of controls on tropical precipitation. An emerging framework has emphasized the atmospheric energy balance as possibly more fundamental than the traditional surface energetic perspective to understand how the zonally-averaged ITCZ responds to radiative and surface flux perturbations. In particular, this frame- work allows for the explanation of shifts in the ITCZ position in response to higher latitude thermal forcing as part of the anomalous meridional energy flux needed to restore energy balance, without the need to invoke changes in tropical SSTs. More specifically, for an hemispherically asymmetric energetic perturbation in the extrat- ropics (for instance arising from changes in surface albedo, clouds and aerosols), the atmospheric general circulation will restore energy balance by transporting energy from the hemisphere with net energy input to the hemisphere with net energy deficit, resulting in a non-zero cross-equatorial energy transport (e.g., Frierson and Hwang, 2012; Hwang et al., 2013; Kang et al., 2009, 2008). Given that in the tropics most of the energy transport is effected by the Hadley circulation, the required anomalous cross-equatorial energy transport will be accomplished through shifts in the Hadley cell’s ascending branch and ITCZ in the relatively warmed hemisphere, under the assumption that the effective energy stratification remains positive.
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Dynamics of the Intertropical Convergence Zone

Dynamics of the Intertropical Convergence Zone

The intertropical convergence zone (ITCZ) migrates north–south on seasonal and longer time scales. Previous studies have shown that the zonal-mean ITCZ dis- placement off the equator is negatively correlated with the energy flux across the equator: When the ITCZ lies in the northern hemisphere, energy flows southward across the equator, and vice versa. The hemisphere that exports energy across the equator is the hemisphere with more net energy input, and it is usually the warmer hemisphere. But states with a double ITCZ straddling the equator also occur, for ex- ample, seasonally over the eastern Pacific, and frequently in climate models. Here it is shown how the ITCZ position is connected to the energy balance near the equator in a broad range of circumstances, including states with single and double ITCZs. Taylor expansion of the variation of the meridional energy flux around the equator leads to the conclusion that for large positive net energy input into the equatorial atmosphere, the ITCZ position depends linearly on the cross-equatorial energy flux. For small positive equatorial net energy input, the dependence of the ITCZ position on the cross-equatorial energy flux weakens to the third root. When the equatorial net energy input or its curvature becomes negative, a bifurcation to double-ITCZ states occurs. Simulations with an idealized aquaplanet general circulation model (GCM) confirm the quantitative adequacy of these relations. The results provide a framework for assessing and understanding causes of common climate model biases and for interpreting tropical precipitation changes, such as those evident in records of climates of the past.
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The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Vertical diffusion of momentum strongly impacts the strength of the Hadley circulation. Vertical diffusion weakens the circulation by mixing meridional momentum between its upper and lower branches. Consequently, neglecting verti- cal diffusion of momentum leads to a two to three times stronger circulation, with the associated changes in the cir- culation leaving a direct imprint on the tropical hydrologi- cal cycle. An important implication of this result is that the- ories for Snowball Earth Hadley circulations, and realistic dry Hadley circulations in general, ought to take into account vertical diffusion of momentum, although this might be dif- ficult because of the small-scale nature of vertical diffusion. Moreover, the results suggest that the scaling laws for dry Hadley circulations derived in dry theories and idealized at- mosphere models that neglect vertical diffusion of momen- tum (e.g. Held and Hou, 1980; Walker and Schneider, 2006; Caballero et al., 2008) might not hold in Snowball Earth at- mospheres. This should not be necessarily interpreted as a failure of these theories and idealized models, as they were often developed to capture the dynamics of present-day Earth Hadley circulations, for which surface sensible heat and dry buoyancy fluxes are comparably small and vertical diffusion does not play a dominant role. Nevertheless, the fact that these dry theories and idealized models do not take into ac- count vertical diffusion limits their applicability to the Snow- ball Earth atmosphere, as well as to realistic dry atmospheres in general.
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Time-Varying and Regional Dynamics in Swiss Housing Markets

Time-Varying and Regional Dynamics in Swiss Housing Markets

guiding legislation and to coordinate the canton’s spatial planning activities. The development and implementation of spatial planning acts are established on a cantonal basis, while the cantons can delegate tasks to municipalities. This set-up leads to very different spatial planning rules across Switzerland. For instance, the cantons of Geneva and Basel are very restrictive in handing on responsibilities to the communal level, while other cantons delegate extensive tasks (Müller- Jentsch and Rühli, 2010). Furthermore, cantons with larger urban areas such as Geneva, Zurich or Basel are more active and efficient in its urban planning activities while other cantons (particularly small cantons) follow a laissez-faire style. This results in varying availability of building areas which could than feed- back to land and house prices (see i. e. building area statistic Switzerland), which adds to the per se heterogeneous structure of Swiss cantons (language, topologi- cal differences).
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Fine-suspended sediment and water budgets for a large, seasonally dry tropical catchment: Burdekin River catchment, Queensland, Australia

Fine-suspended sediment and water budgets for a large, seasonally dry tropical catchment: Burdekin River catchment, Queensland, Australia

) has an annual average discharge of 9.18 million ML (range: 0.25–54.03 million ML) over a 91 year gauge record to 2012 (1921–2012) [Department of Environment and Resource Management, 2012]. The Burdekin contributes the highest suspended sediment load to the GBR (30% of total) of all the coastal catchments, exporting an average of 3.93 million tonnes of suspended sediment annually, corresponding to an average area yield of 30 t km 22 yr 21 (1986–2010) [Kuhnert et al., 2012]. Historical records from inshore coral cores influenced by Burdekin River discharge and recent catchment modeling efforts suggest that annual sediment export is five to eight times higher than pre- European loads [McCulloch et al., 2003; Kroon et al., 2012]. Although low compared to tropical rivers globally (see discussion), this marked increase in export since European settlement (1850) threatens the sensitive ecosystems of the GBR, making efforts to reduce sediment runoff from the Burdekin catchment a manage- ment priority [Bartley et al., 2014]. To inform targeted and effective management of sediment erosion within the Burdekin, catchment-wide sediment source and transport annual budgets were constructed using empiri- cal field data collected at key river network locations between 2005 and 2010. The contributions of clay (<4 mm), fine silt (4–16 mm), and coarse (>16 mm) sediment fractions were quantified to isolate sediment sources at a relatively coarse ‘‘sub-catchment’’ scale before ‘‘hot-spot’’ tributaries were identified and specific environ- mental drivers for erosion were investigated. This study builds on sediment trapping estimates of a large res- ervoir within the catchment reported in Lewis et al. [2013], and quantifies the significant influence this impoundment has on downstream sediment transport and end-of-river export. This study reveals that the highest loads of the finer sediment fraction (i.e., clay and fine silt), which are of most interest from a manage- ment perspective are not necessarily derived from areas yielding the highest total suspended sediment load, and highlights how climate variability influences sediment loads; for example, elevated loads are typically transported by run-off events following prolonged drought. This study demonstrates that sediment budgets incorporating sediment particle-size fractions are far more useful to managers seeking to reduce fine sedi- ment export and inshore turbidity than the traditional ‘‘yield-only’’ approach.
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Weak breeding seasonality of a songbird in a seasonally arid tropical environment arises from individual flexibility and strongly seasonal moult

Weak breeding seasonality of a songbird in a seasonally arid tropical environment arises from individual flexibility and strongly seasonal moult

Timing of breeding is a crucial component of the annual cycle of relatively short-lived organisms but may be less important for long-lived species where fitness may depend more on survival than on annual reproduction. Early ornithological observations out- side temperate systems suggested that both the degree of seasonal limitation to the occurrence of breeding and the relative contribution of annual reproduction to overall fi tness are low in tropical birds and this was largely attributed to milder food seasonality and high nest predation (Lack 1950a,b, Moreau 1950, Skutch 1950, Thomson 1950, Voous 1950, Ashmole 1963a, Cody 1966). More recent studies (Dittami & Gwinner 1985, Tye 1992, Oscha- dleus & Underhill 2006, Greeney 2010, Reynolds et al. 2014), however, have revealed that breeding strategies are diverse and closely related to species niche, albeit with exceptions such as Ndithia et al. (2017) who found no relationship between timing of breeding, invertebrate abundance and weather vari- ables in equatorial larks. Birds in equatorial regions with small variation in day length have sometimes been shown to respond to this minimal environmen- tal variability (Wikelski et al. 2000, Quispe et al. 2017, Shaw 2017), so year-round breeding at the population level may not necessarily equate to an absence of breeding seasonality due to weak environ- mental seasonality.
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Dynamics of stochastic Boissonade system on the time varying domain

Dynamics of stochastic Boissonade system on the time varying domain

The well-posedness and dynamics of the partial differential equations defined on the time- varying domains are interesting questions to study, and they have attracted a lot of atten- tions recently. There are many papers on this topic, we refer the reader to [–] and the references therein. The stochastic dynamical systems defined on time-varying domains are more attractive. Crauel, Kloeden, and Real established the framework for determinis- tic PDE on time-varying domains, and later, they also developed a new approach to de- fined noise on time-varying domain, and established the existence and uniqueness of the solutions for stochastic partial different equations with additive noise on time-varying domains in []. Recently, Crauel, Kloeden, and Yang developed the theory of ‘partial- random’ dynamical systems to obtain the existence of random attractors for stochastic reaction-diffusion equations on time-varying domains in [].
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The dynamics of liquid drops and their interaction with solids of varying wettabilites

The dynamics of liquid drops and their interaction with solids of varying wettabilites

The impact and spreading of liquid drops on solid substrates is the key element of a range of technological processes. Examples include spray cooling of surfaces, crop spraying, spray coating, solder jetting and DNA synthesis (Grissom and Wierum, 1981; Bergeron and Qu´ er´ e, 2001; Attinger et al., 2000; Maier et al., 2000). Thus far, research activity has been overwhelmingly devoted to the behaviour of millimetre-sized drops (Lesser and Field, 1983; Rein, 1993; Yarin, 2006) where the spatio-temporal scales of interest allow experiments to be performed routinely (Rioboo et al., 2002). However, increasingly, there is an interest in the dynamics of microdrops, whose behaviour is critical to the functioning of a number of microfluidic devices (Squires and Quake, 2005). The ink-jet printer is one such device which, as well as being utilized in the graphic arts, is beginning to become a viable alternative to traditional fabrication methods (Gao and Sonin, 1994; Hong and Wagner, 1999; Calvert, 2001; Burns et al., 2003), such as in the cost effective printing of P-OLED displays (Singh et al., 2010) or the building of complex 3D structures through additive manufacturing (Derby, 2010). In such processes, the interaction of the microdrops with the solid substrate on which it impacts is directly related to the quality of the product, so that it is important to be able to predict and understand the behaviour of microdrops in such situations.
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The Dynamics of AdaBoost: Cyclic Behavior and Convergence of Margins

The Dynamics of AdaBoost: Cyclic Behavior and Convergence of Margins

AdaBoost, as shown repeatedly (Breiman, 1997; Friedman et al., 2000; R¨atsch et al., 2001; Duffy and Helmbold, 1999; Mason et al., 2000), is actually a coordinate descent algorithm on a particular exponential loss function. However, minimizing this function in other ways does not necessarily achieve large margins; the process of coordinate descent must be somehow responsible. Hence, we look to AdaBoost’s dynamics to understand the process by which the margin is generated. In this work, we took an unusual approach to this problem. We simplified AdaBoost to reveal a nonlinear iterated map for AdaBoost’s weight vector. This iterated map gives a direct relation between the weights at time t and the weights at time t +1, including renormalization, and thus pro- vides a much more concise mapping than the original algorithm. We then analyzed this dynamical system in specific cases. Using a small toolbox of techniques for analyzing dynamical systems, we were able to avoid the problem that progress (with respect to the margin) does not occur at every iteration. Instead, we measure progress another way; namely, via the convergence towards limit cycles.
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“Tree mulberry- Sustainable and economically viable Sericultural farming for southern tropical zones”

“Tree mulberry- Sustainable and economically viable Sericultural farming for southern tropical zones”

Traditional paired row system of mulberry plantation raised in [(3’x2’)X5’] spacing accommodating 13,888 plants/hectare as low bush plantation resulted in practical problems viz. difficult to cultivate in limited water resource, prevents mechanization, inconvenient for cultural and intercultural operations, susceptible for drought stricken conditions, involves manpower drudgery and prevents silkworm rearing during summer period due to low and poor quality leaf production. Therefore, tree mulberry farming accommodating limited number of plants grown in wider spacing supplementing limited water, manure and fertilizer inputs with reduced manpower drudgery is gaining popularity among the Southern Tropical Zones. Keeping the above thrust area of research, efforts were made to develop suitable and sustainable tree mulberry farming technology for enhanced quality leaf production was attempted. It was noticed that tree mulberry raised in wider spacing (8’x3’) accommodating 4547 plants/ha yielded higher leaf (67,072kg/ha/yr) over the traditional paired row spacing [(3’x2’)x5’] with 13,888 plants/ha (60,144kg/ha/yr) followed by (8’x5’) spacing with 2728 plants/ha (51,174kg/ha/yr). However, 10’x10’ spacing with 1093 plants resulted in 70% reduction of leaf yield (21,084kg/ha/yr) indicating that economically not viable for the welfare and benefit of sericulturist. Other plant growth and leaf quality parameters also indicated the similar trend.
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Adaptation to a seasonally varying environment : a strong latitudinal cline in reproductive diapause combined with high gene flow in Drosophila montana

Adaptation to a seasonally varying environment : a strong latitudinal cline in reproductive diapause combined with high gene flow in Drosophila montana

Diapause can be triggered by a variety of environmen- tal cues, such as photoperiod, temperature, and/or humidity (Tauber and Tauber 1986). For a majority of organisms liv- ing in temperate zones, photoperiod is the most reliable cue evoking diapause as it changes gradually around the year re- gardless of other environmental cues. As the photoperiodic changes are tightly linked to latitude, they help the individuals to keep track of changing seasons and prepare for forthcom- ing cold periods in advance. In some species, individuals can perceive the photoperiodic cues evoking diapause a long time before the actual diapause response takes place and store this information over several developmental stages or even gen- erations (Tauber and Tauber 1986).
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Plate tectonics drive tropical reef biodiversity dynamics

Plate tectonics drive tropical reef biodiversity dynamics

habitats promoting both modes of speciation (Supplementary Fig. 5), but the biodiversity peak in the Western Tethys is most consistent with parapatric speciation fuelled by waves of disconnection and reconnection of isolated reef regions (Supplementary Fig. 6). The highly dynamic and complex tectonics of the Western Tethys 13 provided fertile ground for parapatric speciation. Modelled diversification, computed as speciation minus extinction rates, peaked at 85 Ma (Supple- mentary Figs 7 and 8) when fragmentation was highest, underpinning the biodiversity hotspot in Western Tethys (Supplementary Fig. 5). During the mid/late Eocene–Oligocene times, the closure of the Tethys was associated with a narrowing coastal corridor 14 , that allowed Tethyan biodiversity to move eastward (Fig. 2), supporting the hypothesis of faunal migration into the IAA 2,15 . Since high faunal turnover is expected at the transition across the Cretaceous–Paleogene (K/Pg) 16,17 , which is not considered in our habitat reconstructions, a sensitivity analyses demonstrated the robustness of this dynamic to a high degree of forced extinction at 66 Ma (80%, Supplementary Fig. 9). In addition, our results showed robustness in regards to the choice of plate kinematic model used to reconstruct plate positions (Supplementary Fig. 10). Together, these results indicate that the Tethys was a major diversification and emigration hotspot explaining the Tethyan origin of most tropical shallow reef lineages, here shown for corals, but with parallels in fishes 18 and foraminifera 2 .
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Functional perspectives on tropical tree demography and forest dynamics

Functional perspectives on tropical tree demography and forest dynamics

Foundational to nearly all trait-based studies in community ecology is the expectation that the traits measured are related to individual-level demographic performance. Thus, correlations between a single trait of interest and some environmental variable or demo- graphic rate have been performed to explore co-occurrence and try to explain the vast diversity of trees seen in the tropics. However, in many instances, the relationships found between functional traits and these variables are often weak (Baraloto et al. 2012; Paine et al. 2015; Yang et al. 2018) and unable to explain the great diversity of form and function seen (Marks and Lechowicz 2006). For example, Paine et al. (2015) mod- eled the effects of functional traits (SLA, wood density, and seed mass) and potential evapotranspiration (PET) on size-standardized relative height growth rates (SGR) of 278 species globally and found that functional traits only explained 3.1% of the variation. Poorter et al. (2008) reported Pearson correlation coefficients between functional traits and relative diameter growth rate and mortality rate for five neotropical forests and found be- tween 2 and 74% of the variation explained depending on the trait and location. The range in the amount of variation explained draws attention to the complexity that each forest brings to trait-rate relationships (Fig. 1a). A low percentage of variation explained (r²) is a com- mon theme in functional trait tropical plant community ecology (Fig. 1b). This is alarming as it may indicate that the foundation of functional trait-based tropical tree
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SURVEILLANCE ON THE SHORT AND LONG TERM VARIATIONS OF pH IN THE LOWER AND UPPER ZONES OF A TROPICAL ESTUARY

SURVEILLANCE ON THE SHORT AND LONG TERM VARIATIONS OF pH IN THE LOWER AND UPPER ZONES OF A TROPICAL ESTUARY

Declining water quality is an acute problem around the world, particularly in developing countries where there are notable increase in agricultural and industrial production coupled with a lack of adequate waste water treatment. Main sources of pollution include oil spillage from fishing boats of Neendakara, industrial wastes, coconut husk retting, untreated sewage, and human excreta etc. In addition the habitat of various marine organisms faces serious degradation due to activities such as reclamation of the estuary. The seepage of polluted water from the estuary in to the wells in the estuarine shores is a major health hazard for many who live around estuary and depend on wells for drinking safe water. Monitoring the fluctuations in water pH is needed to understand the dynamics of this aquatic ecosystem. The scientific knowledge provide by this work will remind the need for its restoration.
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ECONOMIC GROWTH CONVERGENCE: TRANSITIONAL DYNAMICS AND MULTIPLE EQUILIBRIA

ECONOMIC GROWTH CONVERGENCE: TRANSITIONAL DYNAMICS AND MULTIPLE EQUILIBRIA

The first part introduces the model and derives the optimal conditions for characterizing family and business behavior. The second part proves that when the externality of capital is high enough, there is a continuous equilibrium trajectory. This shows that all these trajectories form as many possible transitional dynamics converging towards the balanced growth path.

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Market Integration Dynamics and Asymptotic Price Convergence in Distribution

Market Integration Dynamics and Asymptotic Price Convergence in Distribution

The empirical analysis in this section considers the historical annual series of wheat prices in seven cities in the USA, namely New York (NY), Philadelphia (P), Alexandria (A), Cincinnati (CI), Chicago (CH), Indianapolis (I), and San Francisco (SF). All of these cover a common period in the second part of the 19th Century. 4 The sources of data are given in Jacks (2005, 2006). Nominal prices are annual averages, and are expressed in US dollars. The selection of the markets is based on data availability and geographical representativeness. Markets in the coastal zones and inland territories in the 19th Century USA are represented. The series of nominal prices are shown in Figure 1, and their relative prices are given in Figure 2.
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New proof on exponential convergence for cellular neural networks with time-varying delays

New proof on exponential convergence for cellular neural networks with time-varying delays

In this paper, we deal with a class of cellular neural networks with time-varying delays. Applying differential inequality strategies without assuming the boundedness conditions on the activation functions, we obtain a new sufficient condition that ensures that all solutions of the considered neural networks converge exponentially to the zero equilibrium point. We give an example to illustrate the effectiveness of the theoretical results. The results obtained in this paper are completely new and

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Reputation dynamics and convergence: A basis for evaluating reputation systems

Reputation dynamics and convergence: A basis for evaluating reputation systems

The biggest weakness of our desiderata list is the computational complexity required to model reputation aggregation across a large number of agents and against strategic agents with high discount factors. Because we simply exhaust all possible actions, a number of states exponential in the number of actions must be computed. Solving a specific reputation system behavior against a strategic agent may be feasible with a simple reputation system and lead to an efficient solution, but large and complex reputation systems, particularly those without closed form solutions and highly domain-specific features (i.e., those having complex relationships between the reputation system and the interaction model), exacerbate the matter. Graphing Ω can offer insight into the dynamics of a reputation system, but visualing Ω may be nontrivial for systems that employ reputations of high dimensions that do not collapse easily to a scalar value. Determining measurable desiderata that work well in complex scenarios is an interesting and useful avenue for future work.
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Convergence of Learning Dynamics in Information Retrieval Games

Convergence of Learning Dynamics in Information Retrieval Games

Consider the exposure target utility, and assume that D is strictly decreasing, the number of authors equals the number of topics, and that the matrix Q is generic, i.e., has n × m distinct values. The induced game exhibits a unique equi- librium: topic 1 is assigned to the author with the highest quality w.r.t. topic 1. Topic 2 is assigned to the author with the highest quality on that topic, from the set of authors who were not assigned before. Clearly, the PNE is computed by following this process until every author/topic is assigned. Consequently, any best-response dynamics where the au- thors play in a round-robin fashion will converge after at most a quadratic number of improvement steps in the num- ber of authors. A similar observation applies to action tar- geted utility under a slightly different notion of generality of Q. The general question of convergence rate is nevertheless left open.
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African Financial Development Dynamics: Big Time Convergence

African Financial Development Dynamics: Big Time Convergence

In the first critical assessment of convergence in financial development dynamics in Africa, we find overwhelming support for integration. The empirical evidence is premised on 11 homogenous panels based on regions(Sub-Saharan and North Africa), income-levels(low, middle, lower-middle and upper-middle), legal-origins(English common-law and French civil- law) and religious dominations(Christianity and Islam). We examine convergence in financial intermediary dynamics of depth, efficiency, activity and size. Findings suggest that countries with small-sized financial intermediary depth, efficiency, activity and size are catching-up with countries with large-sized financial intermediary depth, efficiency, activity and size respectively. We also provide the speeds of convergence and time necessary to achieve a full(100%) convergence. As a policy implication African governments should not relent in structural and institutional reforms.
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