Net Loss Rates Research Articles

CrossTalk proposal: The dominant mechanism causing disuse muscle atrophy is decreased protein synthesis.

CrossTalk proposal: The dominant mechanism causing disuse muscle atrophy is decreased protein synthesis.

GABA-A receptor-dependent mechanisms prevent excessive spine elimination during postnatal maturation of the mouse cortex in vivo

Dendritic spine dynamics are implicated in the structural plasticity of cognition-related neuroconnectivity. This study utilized the transcranial in vivo imaging approach to investigate spine dynamics in intact brains of living yellow fluorescent protein-expressing mice. A developmental switch in the net spine loss rate occurred at ∼4months of age. The initially rapid rate slowed down ∼6-fold due to substantially reduced spine elimination with minor changes in formation. Furthermore, pharmacological blockade of γ-aminobutyric acid type A (GABA-A) receptors resulted in significantly increased elimination of pre-existing spines without affecting new spine formation. Spine elimination returned to normal levels following treatment cessation. Thus, GABA-A receptor-dependent mechanisms act as “brakes” – keeping spine elimination in check to prevent over-pruning, thereby preserving the integrity of cognition-related cortical circuits.

Insecticide-treated nets (ITNs) in Africa 2000-2016: coverage, system efficiency and future needs for achieving international targets

Insecticide-treated nets (ITNs), which comprise conventional (cITNs) and long-lasting insecticidal nets (LLINs), are the most widely used intervention for malaria control in Africa today. At least 700 million such nets have been financed and delivered to countries since the onset of the Roll Back Malaria (RBM) partnership at the turn of the millennium, but coverage remains inadequate. Better understanding of how and why these volumes of net deliveries translate into the levels of access and use seen in households across Africa could improve the monitoring of coverage indicators, highlight opportunities for systematic efficiency gains, and allow more accurate assessment of resources needed to meet international targets. We used a simple compartmental model to represent the system linking ITN deliveries to countries, distribution to households, and resulting coverage at the national level. We assembled coverage data from 93 national surveys representing 861,000 households between 2000 and 2013 and triangulated these against yearly ITN manufacturer delivery data and national malaria control programme ITN distribution reports for 44 sub-Saharan countries. We fitted the model to these data using Bayesian inference with minimal prior assumptions. We present contemporary estimates of LLIN coverage for all endemic African countries since the year 2000. We then explore the impact of two potential inefficiencies: uneven net distribution between households and rapid rates of net loss from households. These factors substantially reduce the levels of coverage achieved relative to the volume of LLINs financed and delivered, but are not fully captured in current approaches to calculating LLIN needs. Using these inferences, we estimate the levels of coverage achievable with differing volumes of LLIN provision by 2016 under various scenarios of current or modified future levels of distributional efficiency and retention by households. Despite dramatic gains, current levels of ITN access and use remain well below international targets. Unless inefficiencies due to uneven distribution and rapid net loss can be addressed, meeting international targets will require substantially more nets than currently assumed.

Exergoeconomic and Enviroeconomic Analysis of Photovoltaic Modules of Different Solar Cells

The exergoeconomic and enviroeconomic analysis of semitransparent and opaque photovoltaic (PV) modules based on different kinds of solar cells are presented. Annual electricity and net present values have also been computed for the composite climatic conditions of New Delhi, India. Irrespective of the solar cell type, the semitransparent PV modules have shown higher net energy loss rate (Len) and net exergy loss rate (Lex) compared to the opaque ones. Among all types of solar modules, the one based on c-Si, exhibited the minimum Len and Lex. Compared to the opaque ones, the semitransparent PV modules have shown higher CO2 reduction giving higher environmental cost reduction per annum and the highest environmental cost reduction per annum was found for a-Si PV module.

Greenhouse gas emission factors for land use and land-use change in Southeast Asian peatlands

Tropical peat swamp forests, which are predominantly located in Southeast Asia (SEA) and play a prominent role as a global carbon store, are being intensively degraded and converted to agricultural lands and tree plantations. For national inventories, updated estimates of peat emissions of greenhouse gases (GHG) from land use (LU) and land-use change in the tropics are required. In this context, we reviewed the scientific literature and calculated emission factors of peat net emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in seven representative LU categories for SEA i.e. intact peat swamp forest, degraded forest (logged, drained and affected by fire), mixed croplands and shrublands, rice fields, oil palm, Acacia crassicarpa and sago palm plantations. Peat net CO2 uptake from or emissions to the atmosphere were assessed using a mass balance approach. The balance included main peat C inputs through litterfall and root mortality and outputs via organic matter mineralization and dissolved organic carbon. Peat net CO2 loss rate from degraded forest, croplands and shrublands, rice fields, oil palm, A. crassicarpa and sago palm plantations amounted to 19.4 ± 9.4, 41.0 ± 6.7, 25.6 ± 11.5, 29.9 ± 10.6, 71.8 ± 12.7 and 5.2 ± 5.1 Mg CO2 ha−1 y−1, respectively. Total peat GHG losses amounted to 20.9 ± 9.4, 43.8 ± 6.8, 36.1 ± 12.9, 30.4 ± 10.6, 72 ± 12.8 and 8.6 ± 5.3 Mg CO2-equivalent ha−1 y−1 in the same LU categories, respectively. A single land-clearing fire would result in additional emissions of 493.6 ± 156.0 Mg CO2-equivalent ha−1.

Reduction of heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium

We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300mm×300mm collector plate with a selective absorption film on the surface. We measured the reduction rate of the convection heat loss from the collector plate and the shading effect for actual sun radiation by changing the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.

Effect of low pH exposure on Na+ regulation in two cichlid fish species of the Amazon

We evaluated the effects of acute exposure to low pH on Na+ regulation in two Amazon cichlids collected from natural ion-poor “blackwaters”, angelfish (Pterophyllum scalare) and discus (Symphysodon discus). Na+ uptake kinetic parameters, unidirectional Na+ fluxes, and net Cl− fluxes were determined at pH6.0 and 3.6. At pH6.0, both species presented low unidirectional Na+ flux rates, with kinetics showing a relatively low affinity for Na+ (angelfish Km=79, discus Km=268μmolL−1), with similar maximum transport capacities (Jmax~535nmolg−1h−1). Overall, there appeared to be high sensitivity to inhibition by low pH, yet low intrinsic branchial permeability limiting diffusive ion effluxes, resulting in relatively low net loss rates of Na+, the same strategy as seen previously in other blackwater cichlids, and very different from the strategy of blackwater characids. At low pH, Na+ uptake in angelfish was inhibited competitively (increased Km=166μmolL−1) and non-competitively (decreased Jmax=106nmolg−1h−1), whereas in discus, only a decrease in Jmax (112nmolg−1h−1) was statistically significant. An acute reduction in H+-ATPase activity, but not in Na+/K+-ATPase activity, in the gills of angelfish suggests a possible mechanism for this non-competitive inhibition at low pH. Discus fish were more tolerant to low pH than angelfish, as seen by lesser effects of exposure to pH3.6 on unidirectional Na+ uptake and efflux rates and net Na+ and Cl− loss rates. Overall, discus are better than angelfish in maintaining ionic balance under acidic, ion-poor conditions.

Carbon benefits from protected areas in the conterminous United States.

BackgroundConversion of forests to other land cover or land use releases the carbon stored in the forests and reduces carbon sequestration potential of the land. The rate of forest conversion could be reduced by establishing protected areas for biological diversity and other conservation goals. The purpose of this study is to quantify the efficiency and potential of forest land protection for mitigating GHG emissions.ResultsThe analysis of related national-level datasets shows that during the period of 1992–2001 net forest losses in protected areas were small as compared to those in unprotected areas: -0.74% and −4.07%, respectively. If forest loss rates in protected and unprotected area had been similar, then forest losses in the protected forestlands would be larger by 870 km2/yr forests, that corresponds to release of 7 Tg C/yr (1 Tg=1012 g). Conversely, and continuing to assume no leakage effects or interactions of prices and harvest levels, about 1,200 km2/yr forests could have remained forest during the period of 1992–2001 if net area loss rate in the forestland outside protected areas was reduced by 20%. Not counting carbon in harvested wood products, this is equivalent to reducing fossil-fuel based carbon emissions by 10 Tg C/yr during this period. The South and West had much higher potentials to mitigate GHG emission from reducing loss rates in unprotected forests than that of North region. Spatially, rates of forest loss were higher across the coastal states in the southeastern US than would be expected from their population change, while interior states in the northern US experienced less forest area loss than would have been expected given their demographic characteristics.ConclusionsThe estimated carbon benefit from the reduced forest loss based on current protected areas is 7 Tg C/yr, equivalent to the average carbon benefit per year for a previously proposed ten-year $110 million per year tree planting program scenario in the US. If there had been a program that could have reduced forest area loss by 20% in unprotected forestlands during 1992–2001, collectively the benefits from reduced forest loss would be equal to 9.4% of current net forest ecosystem carbon sequestration in the conterminous US.

Evolution and fluxes of 137Cs in the Black Sea/Turkish Straits System/North Aegean Sea

The vertical profiles of 137Cs were determined in the North Aegean, Marmara and Black Seas, to assess inventories and fluxes of the radionuclide in these basins. The inventory of 137Cs in the Western Black Sea integrated from the surface down to 400m water depth is 3.4±0.1kBqm−2, which is surprisingly close to the amount determined in 1988, decay corrected to 2007 (2.9±0.1kBqm−2). On the other hand, based on the comparison of profiles roughly 20years apart, it is estimated that about 1kBqm−2 has been transferred from above the halocline to depths below the halocline, emphasizing the effective redistribution of tracers within the same period.We estimate that about 12TBqy−1 of 137Cs presently leaves the Black Sea with the upper layer flow through the Bosphorus and only 2TBqy−1 is returned with the lower layer inflow of Mediterranean water from the Marmara Sea. Accounting for river fluxes, estimated on the order of 2TBqy−1 few years after the Chernobyl accident, and possibly decreased by now, we can thus estimate a net rate of loss of about 8–10TBqy−1.Investigating the effective redistribution in the upper water column, the supply by the inflowing Mediterranean water alone does not explain the increase of 137Cs concentration and inventory at intermediate depths in the Western Black Sea. The most important mechanism transferring 137Cs and dissolved contaminants from the surface water to the sub-pycnocline layer appears to be the turbulent entrainment of a larger quantity of Black Sea water into the inflowing plume of Mediterranean water through mixing processes on the southwestern shelf and continental slope following its exit from the Bosphorus. This process produces an extra export of some10TBqy−1 of 137Cs from the surface to the sub-pycnocline depths of the Black Sea, a quantity comparable in magnitude to the total export out from the basin. It is the entrainment flux resulting from the mixing, and the further advection and penetration of this water into the Black Sea deeper layer (200–600m) that seems to maintain the inventory with little change over time. Through these two processes the Black Sea surface layer (0–50m) loses every year about 4% of its total inventory of 137Cs.

Parameterized lifetime of radiation belt electrons interacting with lower‐band and upper‐band oblique chorus waves

In order to evaluate the electron lifetimes from quasi‐linear bounce‐averaged diffusion coefficients, a large amount of CPU time is required to compute scattering rates. To reduce computation time, we assume that the electron loss rates are a function of L shell and electron energy, allowing us to derive the parameterization of electron lifetime using a linear regression technique. We also present the parameterizations of lifetimes as a function of electron energy and ratios of plasma frequency to electron gyrofrequency at a fixed L shell. By considering the net loss rates due to lower‐band (0.05–0.5 |Ωce|) and upper‐band (0.5–0.7 |Ωce|) chorus waves propagating obliquely with respect to the ambient magnetic field, the parameterizations of electron lifetime for energies between 1 keV and 2 MeV are investigated in the outer radiation belt. The parameterized lifetimes indicate a strong functional dependence on electron energy, L shell, and the level of geomagnetic activity (Kp index), and are also dependent on the ratios of plasma frequency to electron gyrofrequency. During the storm time, the lifetimes for higher energy (>100 keV) electrons range from hours to days in the heart of the radiation belts. In contrast, the lifetimes for lower energy (<100 keV) electrons are mainly in the range from minutes to hours. Such parameterization efforts of radiation belt electron lifetimes are very significant for multi‐dimensional simulations of the dynamics of the radiation belt and ring current electrons.

Using 137Cs to study spatial patterns of soil erosion and soil organic carbon (SOC) in an agricultural catchment of the typical black soil region, Northeast China

Understanding the spatial pattern of soil organic carbon (SOC) is of great importance because of global environmental concerns. Soil erosion and its subsequent redistribution contribute significantly to the redistribution of SOC in agricultural ecosystems. This study investigated the relationships between 137Cs and SOC over an agricultural landscape, and SOC redistribution was conducted for an agricultural catchment of the black soil region in Northeast China. The spatial patterns of 137Cs and SOC were greatly affected by the established shelterbelts and the developed ephemeral gullies. 137Cs were significantly correlated with SOC when 137Cs were >2000 Bq m−2, while no relation was observed between them when 137Cs were <2000 Bq m−2. Factors other than soil erosion such as vegetative productivity, mineralization of SOC, landscape position and management induced their spatial difference of 137Cs and SOC. Using 137Cs technique to directly study SOC dynamics must be cautious in the black soils. The net SOC loss rate across the entire catchment during 1954–2010 was 92.8 kg ha−1 yr−1, with around 42% of the eroded SOC being redeposited within the catchment. Such information can help guide shelterbelt establishment or other land management to reduce SOC loss in the agricultural ecosystems.

Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies

We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs.

Forest Cover Change within the Russian European North after the Breakdown of Soviet Union (1990–2005)

Forest cover dynamics (defined as tree canopy cover change without regard to forest land use) within the Russian European North have been analyzed from 1990 to 2005 using a combination of results from two Landsat-based forest cover monitoring projects: 1990–2000 and 2000–2005. Results of the forest cover dynamics analysis highlighted several trends in forest cover change since the breakdown of the Soviet planned economy. While total logging area decreased from the 1990–2000 to the 2000–2005 interval, logging and other forms of anthropogenically-induced clearing increased within the Central and Western parts of the region. The most populated regions of European Russia featured the highest rates of net forest cover loss. Our results also revealed intensive gross forest cover loss due to forest felling close to the Russian-Finland border. The annual burned forest area almost doubled between the two time intervals. The 2000–2005 gross forest cover gain results suggest that tree encroachment on abandoned agriculture land is a wide-spread process over the region. The analysis demonstrates the value of regional-scale Landsat-based forest cover and change quantification. Our results supplemented official data by providing independently derived spatial information that could be used for assessing on-going trends and serve as a baseline for future forest cover monitoring.

Multiple traumatic insemination events reduce the ability of bed bug females to maintain water balance

To examine how traumatic insemination, a wounding process to females inflicted by males during copulation, reduces the longevity of females of the bedbug, Cimex lectularius, we assessed if multiple bouts of mating impact water relations of females by measuring net transpiration water loss rates. Our studies show that net transpiration rate of females correlates with frequency of mating (small increase after exposure to low numbers of males; large increase after exposure to large numbers of males), and this is reflected by reduced female survivorship for as much as 22 days at 75% RH, 25°C. Water loss occurs up to 28% more rapidly in females after being held with large groups of males. Females that were exposed to males having their paramere removed, females exposed only to other females, and females kept in isolation (unmated) exhibited no reduction in ability to retain water, indicating that traumatic insemination was responsible for the net transpiration rate increase. Mechanical piercing of the female's abdominal wall leads to increased net transpiration rates for longer periods than puncturing the ectospermalege (regular mating site), implying that inaccurate copulation by males is extremely detrimental to the water balance of females and that the ectospermalege is uniquely modified to seal off more quickly to prevent excess water loss. Mating frequency and the associated increased water loss is considerably reduced by the addition of bed bug alarm pheromone components. Thus, females experience elevated water stress due to traumatic insemination, especially at high levels and when males fail to pierce the ectospermalege, and water loss prevention, likely by more rapid sealing of the wound, is a novel function of the ectopsermalege.

Using 137Cs to quantify the sediment delivery ratio in a small watershed

Understanding the sediment delivery ratio (SDR) is important in controlling sediments for the sustainable development of natural resources and in the design of the construction such as dams and reservoirs. The purpose of this investigation is to determine the SDR by the (137)Cs tracing method in a small watershed in the Sichuan Hilly Basin of China. In the study watershed, different land plots are divided according to the land use type, and 97 sampling sites were selected from these plots. The results show that the average net soil loss rates from the forest land and sloping cultivated land are 1759 and 4468t/km(2)a, respectively. No (137)Cs was detectable on the bare rock surfaces and previous work showed that the erosion rate from the bare rock area was 14,260t/km(2)a. In the depositional zone, the sedimentation rates in the Caoto (a kind of cultivated land located at the foot of hills) and paddy field are 3113 and 3562t/km(2)a, respectively. Combining the area of each land use in the small watershed, the SDR of 0.40 is obtained in the past four decades. The (137)Cs technique was shown to provide an effective and rapid means of estimating the SDR within the small watershed.

Step toward a Deterministic Solution of the Paradoxical Hydrological Stationarity Problem

This paper presents a characterization of the paradoxical hydrological stationarity problem using long-term precipitation data of geographically sparse gauging stations in California. The metrics of this characterization for a gauging station are given by (1) the average of recorded long-term precipitation; (2) the average precision with which the precipitation can be estimated for a climatological time period; (3) an identifier of the wettest climatological period in the long-term record; (4) an identifier of the driest climatological period in the long-term record; (5) the net-gain or net-loss rate of long-term precipitation; and (6) the interclimatological period variability of precipitation. The paper then presents a step taken to find deterministic outcomes for the paradoxical hydrological stationarity problem by showing that these outcomes may hinge on the transient positions of the Earth and Moon around the sun, as observed in Saros series and cycles of historical solar eclipse trajectories (SETs). Two solar eclipse events that are one Saros cycle apart have the same Saros series; they occur at nodes that share similar geometry with the Moon at nearly the same distance from the Earth and at the same time of year. On the basis of the observation of these cyclic events, this work demonstrates that two different water years with solar eclipse event trajectories separated by one Saros cycle of about 18 years have similar hydrological conditions on Earth, as measured by the precipitation data recorded in California. This finding may significantly improve decadal to multidecadal predictions of hydrological conditions for planners and decision makers. Although these results are likely to have implications for continent and global hydrological variability, they need further validation studies using available data for other locations globally.

Kinetic magnetic dynamo in a sheath-limited high-temperature and low-density plasma

In a sheath-limited high-temperature and low-density plasma, energy and particle loss to an absorbing wall can set up a temperature anisotropy in which the normal-to-the-wall temperature is significantly lower than that of the parallel-to-the-wall directions, even for an upstream plasma source with isotropic temperature. This temperature anisotropy excites the Weibel instability and introduces a self-generated magnetic field which is parallel to the wall surface. The self-generated magnetic field modifies the sheath/presheath plasma in two ways upon saturation: (1) it suppresses the net energy loss rate to the absorbing wall, primarily through the ion channel and (2) it transfers energy between different degrees of freedom and reduces the plasma temperature anisotropy.

Works of Friction? Originator-Sponsor Affiliation and Losses on Mortgage-Backed Securities

This paper examines how originator risk retention is related to the structure, pricing, and performance of securitized pools of residential mortgages created during the 2003-2007 period. We argue that originator risk retention is likely to vary positively with originator-sponsor and originator-servicer affiliation. We refer to the lack of affiliation as measures of distance-from-loss. Overall, we find that, after controlling for borrower and deal characteristics, cumulative net loss and foreclosure rates are significantly higher for mortgage-backed securities (MBS) in which originators are not affiliated with the sponsor or servicer (i.e., the loss distance is greater). We also find that the losses and foreclosures occur earlier in MBS with greater distance-from-loss. Consistent with screening being more important for loans with limited or no documentation (low-doc) than full documentation loans, we find that affiliation is related to loan performance only in the case of low-doc loans. Moreover, we find that the distance was also related to losses before the peak of the housing market. Consistent with investors recognizing the potential loss exposure from greater distance-from-loss, we find that the average yield spreads are higher on MBS with greater distance. Consistent with the performance results, we find a positive relation between yields and distance from loss only for deals that consist primarily of low-doc loans. We also find that the percentage of AAA-rated securities issued against the mortgage pool is decreasing in the distance. Finally, deals with greater distance are significantly more likely to employ overcollateralization accounts (that require the sponsor to have greater skin in the game). These results suggest that, while ex post investors might have misestimated their exposure to losses arising from incentive conflicts with the originator, ex ante frictions were reflected (at least in part) in the pricing and the structure of MBS.

Soil redistribution rate and its relationship with soil organic carbon and total nitrogen using 137Cs technique in a cultivated complex hillslope in western Iran

The spatial pattern of soil redistribution rate was investigated using cesium-137 ( 137Cs) within a cultivated complex hillslope in western Iran. The relationship between soil redistribution rate and soil organic carbon and total nitrogen pattern were studied using co-regionalization analysis. Ninety-one soil cores were sampled for 137Cs, total nitrogen, and soil organic carbon measurements. The simplified mass balance model estimated a gross erosion rate of 29.8 t ha −1 yr −1 and a net soil deposition rate of 21.8 t ha −1 yr −1; hence, a net soil loss rate of 8 t ha −1 yr −1. This magnitude of soil erosion rate is higher than the acceptable rate in semiarid regions. Co-regionalization analysis and co-dispersive coefficients among the selected variables showed that only a small fraction of the variability in total nitrogen and soil organic carbon could be explained by soil redistribution and that the remaining might be the result of different management practices by local farmers.

Budget Analysis of Escherichia coli at a Southern Lake Michigan Beach

Escherichia coli (EC) concentrations at two beaches impacted by river plume dynamics in southern Lake Michigan were analyzed using three-dimensional hydrodynamic and transport models. The relative importance of various physical and biological processes influencing the fate and transport of EC were examined via budget analysis and a first-order sensitivity analysis of model parameters. The along-shore advective flux of EC (CFU/m(2).s) was found to be higher compared to its cross-shore counterpart; however, the sum of diffusive and advective components was of a comparable magnitude in both directions showing the importance of cross-shore exchange in EC transport. Examination of individual terms in the EC mass balance equation showed that vertical turbulent mixing in the water column dominated the overall EC transport for the summer conditions simulated. Dilution due to advection and diffusion accounted for a large portion of the total EC budget in the nearshore, and the net EC loss rate within the water column (CFU/m(3).s) was an order of magnitude smaller compared to the horizontal and vertical transport rates. This result has important implications for modeling EC at recreational beaches; however, the assessment of the magnitude of EC loss rate is complicated due to the strong coupling between vertical exchange and depth-dependent EC loss processes such as sunlight inactivation and settling. Sensitivity analysis indicated that solar inactivation has the greatest impact on EC loss rates. Although these results are site-specific, they clearly bring out the relative importance of various processes involved.