Zinc oxide nanoparticles mediate bacterial toxicity in Mueller-Hinton Broth via Zn2.

As antibiotic resistance increases and antibiotic development dwindles, new antimicrobial agents are needed. Recent advances in nanoscale engineering have increased interest in metal oxide nanoparticles, particularly zinc oxide nanoparticles, as antimicrobial agents. Zinc oxide nanoparticles are promising due to their broad-spectrum antibacterial activity and low production cost. Despite many studies demonstrating the effectiveness of zinc oxide nanoparticles, the antibacterial mechanism is still unknown. Previous work has implicated the role of reactive oxygen species such as hydrogen peroxide, physical damage of the cell envelope, and/or release of toxic Zn2+ ions as possible mechanisms of action. To evaluate the role of these proposed methods, we assessed the susceptibility of S. aureus mutant strains, ΔkatA and ΔmprF, to zinc oxide nanoparticles of approximately 50 nm in size. These assays demonstrated that hydrogen peroxide and electrostatic interactions are not crucial for mediating zinc oxide nanoparticle toxicity. Instead, we found that Zn2+ accumulates in Mueller-Hinton Broth over time and that removal of Zn2+ through chelation reverses this toxicity. Furthermore, we found that the physical separation of zinc oxide nanoparticles and bacterial cells using a semi-permeable membrane still allows for growth inhibition. We concluded that soluble Zn2+ is the primary mechanism by which zinc oxide nanoparticles mediate toxicity in Mueller-Hinton Broth. Future work investigating how factors such as particle morphology (e.g., size, polarity, surface defects) and media contribute to Zn2+ dissolution could allow for the synthesis of zinc oxide nanoparticles that possess chemical and morphological properties best suited for antibacterial efficacy.

Estimating a social cost of carbon for global energy consumption.

Estimates of global economic damage caused by carbon dioxide (CO2) emissions can inform climate policy1-3. The social cost of carbon (SCC) quantifies these damages by characterizing how additional CO2 emissions today impact future economic outcomes through altering the climate4-6. Previous estimates have suggested that large, warming-driven increases in energy expenditures could dominate the SCC7,8, but they rely on models9-11 that are spatially coarse and not tightly linked to data2,3,6,7,12,13. Here we show that the release of one ton of CO2 today is projected to reduce total future energy expenditures, with most estimates valued between -US$3 and -US$1, depending on discount rates. Our results are based on an architecture that integrates global data, econometrics and climate science to estimate local damages worldwide. Notably, we project that emerging economies in the tropics will dramatically increase electricity consumption owing to warming, which requires critical infrastructure planning. However, heating reductions in colder countries offset this increase globally. We estimate that 2099 annual global electricity consumption increases by about 4.5 exajoules (7 per cent of current global consumption) per one-degree-Celsius increase in global mean surface temperature (GMST), whereas direct consumption of other fuels declines by about 11.3 exajoules (7 per cent of current global consumption) per one-degree-Celsius increase in GMST. Our finding of net savings contradicts previous research7,8, because global data indicate that many populations will remain too poor for most of the twenty-first century to substantially increase energy consumption in response to warming. Importantly, damage estimates would differ if poorer populations were given greater weight14.

Traditional attributes moo-ve over for some consumer segments: Relative ranking of fluid milk attributes.

Due to the decrease in fluid milk consumption as a beverage in the United States, the importance for dairy industry stakeholders to understand attribute preferences for consumer segments has increased. This paper uses a representative sample of U.S. residents to determine shopping behavior and a Best-Worst experimental design to examine consumer preferences for select milk attributes. The Random Parameters Logit model revealed the largest preference shares were for price (19.1%), fat content (17.6%), and humane handling (16.1%). Segmentation of the respondents was analyzed using a Latent Class Model, and the demographics of segments were analyzed by probabilistic assignment. This contribution, which may be applied to other products, allows for a detailed understanding of consumer preferences for fluid milk. Demographics such as gender and age were not statistically different across the five classes for this topic, unlike shopping behavior. Class 2 was named "The Balancing Act" due to respondents' balance between animal welfare aspects and the physical characteristics of milk. Class 5 was dubbed "Value and Volume" due to large preference shares for price and container size. A lower percentage of respondents in "The Balancing Act" (12.2%) reported purchasing fat-free skim milk when compared to the percentage of respondents in "Value and Volume" (18.6%). Due to the large preference shares for traditional milk attributes, Class 3 was named "Traditional Milk Shoppers." A higher percentage of respondents in "Value and Volume" also reported always reading the information on meat, egg, or milk products when compared to "Traditional Milk Shoppers" (12.2%). Although price is still important to many consumers, certain segments have preferences or demand for other attributes that may be satisfied by producers to increase market share or price premiums.

Downscaling of national crop area statistics using drivers of cropland productivity measured at fine resolutions.

Despite substantial research and policy interest in pixel level cropland allocation data, few sources are available that span a large geographic area. The data used for much of this research are derived from complex modeling techniques that may include model simulation and other data processing. We develop a transparent econometric framework that uses pixel level biophysical measurements and aggregate cropland statistics to develop pixel level cropland allocation predictions. Such pixel level land use data can be used to investigate the impact of human activities on the environment. Validation exercises show that our approach is effective at downscaling cropland allocation to multiple levels of resolution.

Estimating economic damage from climate change in the United States.

Estimates of climate change damage are central to the design of climate policies. Here, we develop a flexible architecture for computing damages that integrates climate science, econometric analyses, and process models. We use this approach to construct spatially explicit, probabilistic, and empirically derived estimates of economic damage in the United States from climate change. The combined value of market and nonmarket damage across analyzed sectors-agriculture, crime, coastal storms, energy, human mortality, and labor-increases quadratically in global mean temperature, costing roughly 1.2% of gross domestic product per +1°C on average. Importantly, risk is distributed unequally across locations, generating a large transfer of value northward and westward that increases economic inequality. By the late 21st century, the poorest third of counties are projected to experience damages between 2 and 20% of county income (90% chance) under business-as-usual emissions (Representative Concentration Pathway 8.5).

Trends and disparities in the prevalence of physicians' counseling on exercise among the U.S. adult population, 2000-2010.

Recognizing the undisputed health benefits of exercise, physicians' counseling has been included in the Healthy People Objectives since 2000. To address the paucity of data on such counseling at the national level, we examined changing trends and disparities in receiving physicians' counseling on exercise among the physically-able, non-institutionalized U.S. adult population. Data from the 2000, 2005, and 2010 National Health Interview Surveys (NHIS) were examined using logistic regression that included race/ethnicity, age, gender, education, insurance status, number of physician visits in the past year, and body mass index. In 2000, only 22.9% of NIHS respondents had received counseling on exercise, increasing to 33.6% in 2010. Compared with non-Hispanic Whites, non-Hispanic Blacks were 27% less likely to receive exercise advice in 2000 (adjusted odds ratio [AOR] 0.73, 95% confidence interval [CI] 0.61-0.87). In later years, they were equally likely to receive advice. Although decreased over the years, male respondents were significantly (34% to 23%) less likely to report receipt of exercise counseling than female patients (in 2010: AOR 0.77, CI 0.72-0.83). Uninsured respondents were 35% less likely to report receiving exercise advice from their provider in all study years (2010: AOR 0.64, CI 0.59-0.72). Patients with increasing levels of education were increasingly more likely to report receipt of counseling in each successive survey year. The overall prevalence of physicians' counseling on exercise increased moderately between 2000 and 2010. Some disparities narrowed and even reversed but significant disparities continue to exist across gender, insurance status, and education level.

Trends and disparities in the prevalence of physicians' counseling on diet and nutrition among the U.S. adult population, 2000-2011.

BACKGROUND: Although healthy eating plays a crucial role in addressing the obesity and chronic disease epidemics, a few Americans have diets that meet dietary guidelines. Because physicians-delivered counseling is a strong predictor for behavioral modification among patients, the Healthy People Objectives have emphasized diet counseling since 2000. However, research on impact of physicians' counseling over time on a national level has been limited. METHODS: We used data from the 2000 and 2011 National Health Interview Surveys to apply a logistic regression model to identify predictors of physicians' counseling and examine any changes in disparities over a decade. RESULTS: In 2000, only 23.7% of our national sample had received dietary counseling, it increased to 32.6% in 2011. Hispanics were less likely than Whites to receive advice on diet in 2000 (adjusted odds ratio [AOR]=0.74, 95% confidence interval [CI]=0.62-0.88). By 2011, Hispanics 18% (AOR=1.18, CI=1.09-1.28) and Blacks were 42% (AOR=1.42, CI=1.32-1.54) more likely to receive advice from their physicians on diet than Whites. In both years, men were significantly less likely than women to receive counseling. The uninsured patients were increasingly less likely than insured patients in receiving diet counseling, being 60% less likely in 2011 (AOR=0.40, CI=0.37-0.40). Obese patients were substantially (88% in 2000 to 290% in 2011) more likely to receive counseling than normal-weight patients. CONCLUSIONS: The overall prevalence of physicians' counseling on diet increased moderately between 2000 and 2011. However, substantial disparities in dietary counseling related to access to care and gender continue to exist.

Dynamic adjustment in agricultural practices to economic incentives aiming to decrease fertilizer application.

Input- and output-based economic policies designed to reduce water pollution from fertilizer runoff by adjusting management practices are theoretically justified and well-understood. Yet, in practice, adjustment in fertilizer application or land allocation may be sluggish. We provide practical guidance for policymakers regarding the relative magnitude and speed of adjustment of input- and output-based policies. Through a dynamic dual model of corn production that takes fertilizer as one of several production inputs, we measure the short- and long-term effects of policies that affect the relative prices of inputs and outputs through the short- and long-term price elasticities of fertilizer application, and also the total time required for different policies to affect fertilizer application through the adjustment rates of capital and land. These estimates allow us to compare input- and output-based policies based on their relative cost-effectiveness. Using data from Indiana and Illinois, we find that input-based policies are more cost-effective than their output-based counterparts in achieving a target reduction in fertilizer application. We show that input- and output-based policies yield adjustment in fertilizer application at the same speed, and that most of the adjustment takes place in the short-term.