Changes In Other Factors Research Articles

Ecosystem implications of conserving endemic versus eradicating introduced large herbivores in the Galapagos Archipelago

Restoration of damaged ecosystems through invasive species removal and native species conservation is an increasingly common practice in biodiversity conservation. Estimating the degree of ecosystem response attributable specifically to eradication of exotic herbivores versus restoration of native herbivores is often difficult and is complicated by concurrent temporal changes in other factors, especially climate. We investigated the interactive impacts of native mega-herbivores (giant tortoises) and the eradication of large alien herbivores (goats) on vegetation productivity across the Galapagos Archipelago. We examined archipelago-wide patterns of Normalized Difference Vegetation Index (NDVI) as a proxy for vegetation productivity between 2001 and 2015 and evaluated how goat and historical and current tortoise occurrence influenced productivity. We used a breakpoint analysis to detect change in trends in productivity from five targeted areas following goat eradication. We found a positive association between tortoise occurrence and vegetation productivity and a negative association with goat occurrence. We also documented an increase in plant productivity following goat removal with recovery higher in moister regions than in arid region, potentially indicating an alternate stable state has been created in the latter. Climate variation also contributed to the detected improvement in productivity following goat eradication, sometimes obscuring the effect of eradication but more usually magnifying it by up to 300%. Our work offers perspectives regarding the effectiveness and outcomes of eradicating introduced herbivores and re-introducing native herbivores, and the merits of staging them simultaneously in order to restore critical ecosystem processes such as vegetation productivity.

Malaria and large dams in sub-Saharan Africa: future impacts in a changing climate.

BackgroundSub-Saharan Africa (SSA) has embarked on a new era of dam building to improve food security and promote economic development. Nonetheless, the future impacts of dams on malaria transmission are poorly understood and seldom investigated in the context of climate and demographic change.MethodsThe distribution of malaria in the vicinity of 1268 existing dams in SSA was mapped under the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways (RCP) 2.6 and 8.5. Population projections and malaria incidence estimates were used to compute population at risk of malaria in both RCPs. Assuming no change in socio-economic interventions that may mitigate impacts, the change in malaria stability and malaria burden in the vicinity of the dams was calculated for the two RCPs through to the 2080s. Results were compared against the 2010 baseline. The annual number of malaria cases associated with dams and climate change was determined for each of the RCPs.ResultsThe number of dams located in malarious areas is projected to increase in both RCPs. Population growth will add to the risk of transmission. The population at risk of malaria around existing dams and associated reservoirs, is estimated to increase from 15 million in 2010 to 21–23 million in the 2020s, 25–26 million in the 2050s and 28–29 million in the 2080s, depending on RCP. The number of malaria cases associated with dams in malarious areas is expected to increase from 1.1 million in 2010 to 1.2–1.6 million in the 2020s, 2.1–3.0 million in the 2050s and 2.4–3.0 million in the 2080s depending on RCP. The number of cases will always be higher in RCP 8.5 than RCP 2.6.ConclusionIn the absence of changes in other factors that affect transmission (e.g., socio-economic), the impact of dams on malaria in SSA will be significantly exacerbated by climate change and increases in population. Areas without malaria transmission at present, which will transition to regions of unstable transmission, may be worst affected. Modifying conventional water management frameworks to improve malaria control, holds the potential to mitigate some of this increase and should be more actively implemented.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1498-9) contains supplementary material, which is available to authorized users.

The sensitivity of water availability to changes in the aridity index and other factors—A probabilistic analysis in the Budyko space

AbstractOne of the pending questions in the context of global change is whether climatic drivers or other factors have stronger influences on water availability. Here we present an approach that allows to estimate the probability that changes in the aridity index have a larger effect on water availability than equal relative changes in other factors. The analysis builds upon a probabilistic extension of the Budyko framework, which is subject to an analytical sensitivity assessment. The results show that changes in water availability are only dominated by changes in the aridity index in very humid climates. This implies that projected intensifications of aridity in drylands may have less influence on water availability than commonly assumed. Instead, other climatic or nonclimatic factors are dominating. The analysis does hence allow to map regions in which water availability is more sensitive to equal relative changes in either the aridity index or all other factors.

Assessment of the EU 10% interconnection target in the context of CO2 mitigation

The European Commission has proposed the target of achieving an interconnection capacity of at least 10% of the installed electricity production capacity for each Member State by 2020 in the context of the envisaged Energy Union. The underlying objectives are to increase the security of supply at affordable prices via market integration and to contribute to decarbonization by accommodating an increasing level of renewable generation. In this article we have assessed whether this target could effectively fulfil these two objectives. Our main focus is on the assessment of the impacts of compliance with the 10% interconnection target on the carbon emission of the European electricity system. Our main research question concerns the impact of interconnection capacity increases on EU carbon emission due to the better market integration, disregarding the RES-E integration aspects. In order to arrive at workable scenarios for the future cross-border capacity extension, the security of supply and market integration impacts are also assessed.We concluded on the basis of our European dispatch model that full compliance would slightly increase carbon emission in the EU, ceteris paribus. This impact is due to increased coal- and lignite-based electricity production, mainly in Germany, Poland and the Czech Republic. By increasing the interconnections of these countries with their neighbours at the present low carbon price under the EU emissions trading scheme, these carbon-intensive electricity systems run on higher utilization rates and consequently increase carbon emission. It has to be emphasized that the increase is found for the current situation, and changes in other factors, such as increases in carbon prices or renewable generation, could modify this result.Policy relevanceOur results demonstrate that EU network development and climate policies are highly interconnected. Changing patterns in the interconnections of the EU electricity systems connect diverse generation portfolios and in a low carbon price environment could increase carbon emission at the community level. Policy makers should be aware of the interactions between these areas and design policy tools that also consider negative synergies.

Photoperiod and Nitrogen Supply Limit the Scope of Northward Migration and Seed Transfer of Black Spruce in a Future Climate Associated with Doubled Atmospheric CO2 Concentration

The predicated changes in precipitation and temperature associated with the continued elevation of atmospheric CO2 concentration will trigger the northward shift of the Climate Envelopes for 130 North America tree species by as much as 10 degrees. However, climate envelope models do not take into account changes in other factors that may also influence the survival and growth of plants at the predicted new locations, such as photoperiod and nutrient regimes. This study investigated how photoperiod and nitrogen supply would affect the ecophysiological traits of black spruce (Picea mariana (Mill) B. S. P.) that are critical for survival and growth at new locations predicted by climate envelope models. We exposed black spruce seedlings to the photoperiod regime at the seed origin (PS) and that 10° north of the seed origin (PNM) as predicted by climate envelope models under the current and doubled atmospheric CO2 concentration and different levels of N supply (30 vs. 300 μmol·mol-1 N). We found that the PNM and the 30 μmol·mol-1 N supply both had negative impact on the development of seedling cold hardiness in the fall, and led to earlier burst of the terminal bud and greater rate of mortality in the following growing season. While the PNM stimulated seedling growth in the first growing season, the effect was not sustained in the second growing season. Our results suggest that the photoperiod regimes and poor nutrient conditions at higher latitudes will likely constrain the scope of the northward migration or seed transfer of black spruce.

Roller compaction of hydrophilic extended release tablets-combined effects of processing variables and drug/matrix former particle size.

The present study shows that roller compaction (RC) can successfully be used as a granulation method to prepare hydroxypropyl methylcellulose (HPMC)-based extended release matrix tablets containing a high drug load, both for materials deforming mainly by fragmentation (paracetamol) as for those having mainly plastic deformation (ibuprofen). The combined effect of RC process variables and composition on the manufacturability of HPMC tablets was investigated. Standard wet granulation grade HPMC was compared with a larger particle size direct compressible HPMC grade. Higher roll pressure was found to result in larger paracetamol granules and narrower granule particle size distributions, especially for formulations containing smaller size HPMC. However, for ibuprofen, no clear effect of roll pressure was observed. High roll pressure also resulted in denser ribbon and less bypass fines during RC. Loss of compactibility was observed for granules compared to powder blends, which was found to be related to differences in granule porosity and morphology. Using the large-sized HPMC grade did in some cases result in lower tensile strength tablets but had the advantage to improve the powder flow into the roller compactor. This work also indicates that when the HPMC level lies near the percolation threshold, significant changes can occur in the drug release rate due to changes in other factors (raw material characteristics and processing).

Levels of adiponectin and leptin at onset of type 1 diabetes have changed over time in children and adolescents.

Adiponectin and leptin are proteins secreted by the adipose tissue and have an influence on insulin sensitivity and on inflammatory markers. Altered levels could play a part in the pathogenesis of type 1 diabetes mellitus. We determined adiponectin and leptin levels over a nine-year period in children with type 1 diabetes mellitus (T1D) in relation to the increasing incidence of T1D, and studied the impact of patient status, age, gender and body mass index (BMI). Data were derived from a population-based registry of diabetic children (DanDiabKids) from 1997 to 2005. Children with newly diagnosed T1D (n = 482) were included, and healthy siblings (n = 479) were chosen as a control group. Leptin levels were significantly higher in recent years (in both patients and siblings), whereas for adiponectin, the levels were lower in recent years in the patient group. Leptin levels were lower in children with T1D (RR 0.74, p = 0.003) and in males (RR 0.52, p < 0.001) and increasing with age in both groups. For adiponectin, there was a negative association between level and age in patients. Both adipokines showed a significant correlation with BMI and lower levels in children with blood samples taken within the first 2 days after initiation of insulin treatment. There has been a change in leptin and adiponectin levels in children with or without T1D from 1997 to 2005. This is not explained by changes in BMI and may reflect changes in other factors like diet or physical activity.

A new understanding of the relationship between sugars, dental caries and fluoride use: implications for limits on sugars consumption.

To examine the quantitative relationship between sugar intake and the progressive development of dental caries. A critical in-depth review of international studies was conducted. Methods included reassessing relevant studies from the most recent systematic review on the relationship between levels of sugars and dental caries. Reanalysis of dose-response relationships between dietary sugars and caries incidence in teeth with different levels of caries susceptibility in children was done using data from Japanese studies conducted by Takeuchi and co-workers. Global, with emphasis on marked differences in both national sugar intake and fluoride use and preferably where one factor such as sugar intake changed progressively without changes in other factors over a decade or more. Children aged 6 years or more and adults. Caries occurred in both resistant and susceptible teeth of children when sugar intakes were only 2-3 % of energy intake, provided that the teeth had been exposed to sugars for >3 years. Despite increased enamel resistance after tooth eruption, there was a progressive linear increase in caries throughout life, explaining the higher rates of caries in adults than in children. Fluoride affects progression of caries development but there still is a pandemic prevalence of caries in populations worldwide. Previous analyses based on children have misled public health analyses on sugars. The recommendation that sugar intakes should be ≤10 % of energy intake is no longer acceptable. The much greater adult burden of dental caries highlights the need for very low sugar intakes throughout life, e.g. 2-3 % of energy intake, whether or not fluoride intake is optimum.

Global Regulation of Transcription by a Small RNA: A Quantitative View

Small RNAs are integral regulators of bacterial gene expression, the majority of which act posttranscriptionally by basepairing with target mRNAs, altering translation or mRNA stability. 6S RNA, however, is a small RNA that is a transcriptional regulator, acting by binding directly to σ70-RNA polymerase (σ70-RNAP) and preventing its binding to gene promoters. At the transition from exponential to stationary phase, 6S RNA accumulates and globally downregulates the transcription of hundreds of genes. At the transition from stationary to exponential phase (outgrowth), 6S RNA is released from σ70-RNAP, resulting in a fast increase in free σ70-RNAP and transcription of many genes. The transition from stationary to exponential phase is sharp, and is thus accessible for experimental study. However, the transition from exponential to stationary phase is gradual and complicated by changes in other factors, making it more difficult to isolate 6S RNA effects experimentally at this transition. Here, we use mathematical modeling and simulation to study the dynamics of 6S RNA-dependent regulation, focusing on transitions in growth mediated by altered nutrient availability. We first show that our model reproduces the sharp increase in σ70-RNAP at outgrowth, as well as the behavior of two experimentally tested mutants, thus justifying its use for characterizing the less accessible dynamics of the transition from exponential to stationary phase. We characterize the dynamics of the two transitions for Escherichia coli wild-type, as well as for mutants with various 6S RNA-RNAP affinities, demonstrating that the 6S RNA regulation mechanism is generally robust to a wide range of such mutations, although the level of regulation at single promoters and their resulting expression fold change will be altered with changes in affinity. Our results provide insight into the potential advantage of transcription regulation by 6S RNA, as it enables storage and efficient release of σ70-RNAP during transitions in nutrient availability, which is likely to give a competitive advantage to cells encountering diverse environmental conditions.

Exploring the interactive effects of safety investments, safety culture and project hazard on safety performance: An empirical analysis

This study aims to explore the interactive effects of safety investments, safety culture and project hazard on construction safety performance. Data were collected using multiple techniques from 47 completed building projects in Singapore. Data were analyzed using correlation analysis, regression analysis, moderation analysis and mediation analysis. The results show that: (1) safety performance improves when there is a higher level of safety investments, a higher level of safety culture or a lower level of project hazard; (2) the effect of any individual factor on safety performance varies with the changes in other factors; (3) the effect of voluntary safety investments on safety performance is mediated by safety culture; and (4) the relationship between accident frequency rate and accident severity rate is moderated by project hazard level. The study suggests that safety performance of building projects is determined by the synergy effect of safety investments, safety culture and project hazard.

The effect of cholecalciferol for lowering albuminuria in chronic kidney disease: a prospective controlled study

Growing evidence indicates that vitamin D receptor activation may have antiproteinuric effects. We aimed to evaluate whether vitamin D supplementation with daily cholecalciferol could reduce albuminuria in proteinuric chronic kidney disease (CKD) patients. This 6-month prospective, controlled, intervention study enrolled 101 non-dialysis CKD patients with albuminuria. Patients with low 25(OH) vitamin D [25(OH)D] and high parathyroid hormone (PTH) levels (n = 50; 49%) received oral cholecalciferol (666 IU/day), whereas those without hyperparathyroidism (n = 51; 51%), independent of their vitamin D status, did not receive any cholecalciferol, and were considered as the control group. Cholecalciferol administration led to a rise in mean 25(OH)D levels by 53.0 ± 41.6% (P < 0.001). Urinary albumin-to-creatinine ratio (uACR) decreased from (geometric mean with 95% confidence interval) 284 (189-425) to 167 mg/g (105-266) at 6 months (P < 0.001) in the cholecalciferol group, and there was no change in the control group. Reduction in a uACR was observed in the absence of significant changes in other factors, which could affect proteinuria, like weight, blood pressure (BP) levels or antihypertensive treatment. Six-month changes in 25(OH)D levels were significantly and inversely associated with that in the uACR (Pearson's R = -0.519; P = 0.036), after adjustment by age, sex, body mass index, BP, glomerular filtration rate and antiproteinuric treatment. The mean PTH decreased by -13.8 ± 20.3% (P = 0.039) only in treated patients, with a mild rise in phosphate and calcium-phosphate product [7.0 ± 14.7% (P = 0.002) and 7.2 ± 15.2% (P = 0.003), respectively]. In addition to improving hyperparathyroidism, vitamin D supplementation with daily cholecalciferol had a beneficial effect in decreasing albuminuria with potential effects on delaying the progression of CKD.

The coupling relationship among bottleneck shifting factors in job shop

Aiming at the phenomenon of bottleneck shifting in job shop, this article presents the findings on the coupling relationship among the bottleneck shifting factors. We first defined the chain probability to show the relation that the change of one bottleneck shifting factor causes the changes of other factors in job shop. Then, we used three variables (time-capability, time-load, and quality-assurance) and the transaction probability to describe the changes of the factors. Considering the interaction among the bottleneck shifting factors, we established the independent contributions and comprehensive contributions, showing how the changes of various shifting factors may impact the bottleneck shifting phenomenon interactively. Finally, an instance of analysis of the coupling relation of several bottleneck shifting factors in some job shop is given to test the validity and rationality of the method established in this research.

Fine-tuning of Voltage Sensitivity of the Kv1.2 Potassium Channel by Interhelix Loop Dynamics

Many proteins function by changing conformation in response to ligand binding or changes in other factors in their environment. Any change in the sequence of a protein, for example during evolution, which alters the relative free energies of the different functional conformations changes the conditions under which the protein will function. Voltage-gated ion channels are membrane proteins that open and close an ion-selective pore in response to changes in transmembrane voltage. The charged S4 transmembrane helix transduces changes in transmembrane voltage into a change in protein internal energy by interacting with the rest of the channel protein through a combination of non-covalent interactions between adjacent helices and covalent interactions along the peptide backbone. However, the structural basis for the wide variation in the V50 value between different voltage-gated potassium channels is not well defined. To test the role of the loop linking the S3 helix and the S4 helix in voltage sensitivity, we have constructed a set of mutants of the rat Kv1.2 channel that vary solely in the length and composition of the extracellular loop that connects S4 to S3. We evaluated the effect of these different loop substitutions on the voltage sensitivity of the channel and compared these experimental results with molecular dynamics simulations of the loop structures. Here, we show that this loop has a significant role in setting the precise V50 of activation in Kv1 family channels.

Photoperiod-gonadotropin mismatches induced by treatment with acyline or FSH in Siberian hamsters: impacts on ovarian structure and function

Many seasonal breeders time their reproductive efforts to specific times of the year to ensure adequate resources for the production and care of young. For long-day (LD) breeders, females born before the summer solstice (LDs) reach sexual maturity quickly and often breed that same year, whereas females born after the summer solstice (short days (SDs)) may delay reproductive development to the following spring when environmental conditions are favorable for reproduction. In Siberian hamsters, development in SD is associated with structural and functional differences in the ovary compared with females held in LD, including a greater number of primordial follicles and an abundance of hypertrophied granulosa cells (HGCs), which are immunoreactive for anti-Müllerian hormone. The goal of this study was to determine whether SD-induced gonadotropin suppression is responsible for these phenotypic differences. Gonadotropin levels were suppressed in LD hamsters using the GNRH antagonist acyline. Conversely, to determine whether the SD ovarian phenotype is completely reversed by gonadotropin stimulation, recombinant human FSH (rhFSH) was administered. Our treatments were successful in mimicking FSH concentrations of the opposite photoperiod, but they did not produce a comparable change in the ovarian phenotype. Most notable was the lack of HGCs in the ovaries of acyline-treated LD females. Similarly, HGCs were maintained in the ovaries of SD females treated with rhFSH. Our data suggest that gonadotropins alone do not account for the SD ovarian phenotype. Future studies will determine whether SD-induced changes in other factors underlie these phenotypic changes.

The RANKL Distal Control Region Is Required for the Increase in RANKL Expression, But Not the Bone Loss, Associated with Hyperparathyroidism or Lactation in Adult Mice

Osteoclast-mediated bone resorption plays an essential role in calcium homeostasis and lactation. The cytokine receptor activator of nuclear factor κB ligand (RANKL) is one of a number of factors that controls the production, survival, and activity of osteoclasts. Calciotropic hormones, such as PTH, control RANKL transcription in part via an enhancer known as the distal control region (DCR), and mice lacking this enhancer have fewer osteoclasts under normal physiological conditions. Here, we have addressed the role of the DCR in situations in which activation of the PTH receptor is thought to stimulate bone resorption via elevation of RANKL expression. Dietary calcium deficiency stimulated RANKL expression in the bone of young (1 month old) wild-type, but not DCR knockout (KO), mice. Consistent with this, the cancellous bone loss and the increase in osteoclasts caused by dietary calcium deficiency were blunted in young KO mice. DCR deletion also prevented the increase in RANKL expression caused by dietary calcium deficiency in 6-month-old mice. However, the diet-induced bone loss was similar in wild-type and KO mice at this age. The increase in RANKL expression caused by lactation was also blunted in DCR KO mice, but lactation-induced bone loss was similar in both genotypes. These results demonstrate that, even though the DCR is required for the increase in RANKL expression associated with hyperparathyroidism or lactation, this increase is not required for the bone loss caused by these conditions in adult mice, suggesting that changes in other factors, such as osteoprotegerin or estrogen levels, play a dominant role.

Declining impacts of hot spells on mortality in the Czech Republic, 1986–2009: adaptation to climate change?

The study examines temporal changes in mortality associated with spells of large positive temperature anomalies (hot spells) in extended summer season in the population of the Czech Republic (Central Europe) during 1986–2009. Declining trends in the mortality impacts are found in spite of rising temperature trends. The finding remains unchanged if possible confounding effects of within-season acclimatization to heat and the mortality displacement effect are taken into account. Recent positive socioeconomic development, following the collapse of communism in Central and Eastern Europe in 1989, and better public awareness of heat-related risks are likely the primary causes of the declining vulnerability. The results suggest that climate change may have relatively little influence on heat-related deaths, since changes in other factors that affect vulnerability of the population are dominant instead of temperature trends. It is essential to better understand the observed nonstationarity of the temperature-mortality relationship and the role of adaptation and its limits, both physiological and technological, and to address associated uncertainties in studies dealing with climate change projections of temperature-related mortality.

The induction of -helical structure in partially unfolded HypF-N does not affect its aggregation propensity

The conversion of proteins into structured fibrillar aggregates is a central problem in protein chemistry, biotechnology, biology and medicine. It is generally accepted that aggregation takes place from partially structured states of proteins. However, the role of the residual structure present in such conformational states is not yet understood. In particular, it is not yet clear as to whether the α-helical structure represents a productive or counteracting structural element for protein aggregation. We have addressed this issue by studying the aggregation of pH-unfolded HypF-N. It has previously been shown that the two native α-helices of HypF-N retain a partial α-helical structure in the pH-unfolded state and that these regions are also involved in the formation of the cross-β structure of the aggregates. We have introduced mutations in such stretches of the sequence, with the aim of increasing the α-helical structure in the key regions of the pH-unfolded state, while minimizing the changes of other factors known to influence protein aggregation, such as hydrophobicity, β-Sheet propensity, etc. The resulting HypF-N mutants have higher contents of α-helical structure at the site(s) of mutation in their pH-unfolded states, but such an increase does not correlate with a change of aggregation rate. The results suggest that stabilisation of α-helical structure in amyloidogenic regions of the sequence of highly dynamic states does not have remarkable effects on the rate of protein aggregation from such conformational states. Comparison with other protein systems indicate that the effect of increasing α-helical propensity can vary if the stabilised helices are in non-amyloidogenic stretches of initially unstructured peptides (accelerating effect), in amyloidogenic stretches of initially unstructured peptides (no effect) or in amyloidogenic stretches of initially stable helices (decelerating effect).

In silico studies on the sensitivity of myocardial PCr/ATP to changes in mitochondrial enzyme activity and oxygen concentration

The ratio of myocardial phosphocreatine (PCr)/ATP reflects the balance of energy consumption and energy supply in the heart. It is reduced in a range of important physiological conditions including during and after acute hypoxia, after a prolonged visit to high-altitude, and in those suffering from both type 2 diabetes mellitus and various forms of heart failure. Yet despite its significance, the factors underlying the reduced PCr/ATP ratio seen in heart failure remain poorly understood. Given that oxidative phosphorylation is the only viable steady-state provider of ATP in the heart, the argument has been put forward that the observed reduction in myocardial PCr/ATP in all these conditions can be accounted for by some form of mitochondrial insufficiency. Thus we used a computer model of oxidative phosphorylation, coupled with creatine kinase, to study the effects of hypoxia and mitochondrial dysfunction on myocardial PCr/ATP. In physiological normoxia, all oxidative phosphorylation complexes, NADH supply and proton leak exerted comparable (of the same order of magnitude) control over PCr/ATP, as defined within Metabolic Control Analysis (MCA). Under hypoxia, the control increased considerably for all components of the system, especially for cytochrome oxidase and mitochondrial proton leak. Hypoxia alone, without any changes in other factors, exerted a pronounced effect on PCr/ATP. Our simulations support three important ideas: First, that mitochondrial abnormalities can contribute considerably to a blunted PCr/ATP; second, that hypoxia and mitochondrial dysfunction can interact in important ways to determine the energy status of the failing heart; and third, that hypoxia alone can account for significant decreases in cardiac PCr/ATP.

Entry Costs &amp; Increasing Trade

Using confidential microdata from the US Census, we find that the fraction of manufacturing plants that export rose from 21% in 1987 to 39% in 2006. It has been suggested that similar trends in other countries may have been caused by declining costs of entering foreign markets. Our study tests this hypothesis for the first time. Both reduced form and structural estimation approaches find little evidence that the entry costs declined significantly in the US over this period. We instead argue that changes in other factors that determine export status are sufficient to explain these trends.

WHAT DETERMINES FAMILY STRUCTURE?

We use data from the 1979 cohort of the National Longitudinal Survey of Youth to estimate the effects of policy and labor market variables on the demographic behaviors that determine children's family structure experiences: union formation and dissolution, and fertility. Male and female wages have substantial effects on family structure for children of black and Hispanic mothers. The tax treatment of children also affects family structure. Welfare reform, welfare benefits, and unilateral divorce had much smaller effects on family structure for the children of this cohort of women. Trends in wages and tax rates explain only a small share of the observed changes in family structure in recent decades. (JEL J12)