In 2023, Washington, D.C. had the highest population density in the United States, with 11,130.69 people per square mile. As a whole, there were about 94.83 residents per square mile in the U.S., and Alaska was the state with the lowest population density, with 1.29 residents per square mile. The problem of population density Simply put, population density is the population of a country divided by the area of the country. While this can be an interesting measure of how many people live in a country and how large the country is, it does not account for the degree of urbanization, or the share of people who live in urban centers. For example, Russia is the largest country in the world and has a comparatively low population, so its population density is very low. However, much of the country is uninhabited, so cities in Russia are much more densely populated than the rest of the country. Urbanization in the United States While the United States is not very densely populated compared to other countries, its population density has increased significantly over the past few decades. The degree of urbanization has also increased, and well over half of the population lives in urban centers.

We have calculated the dielectronic recombination rate coefficients from Li-like Ne (Ne^{7+}) ions to Be-like Ne (Ne^{6+}) ions for selected excited states of Ne^{6+} ions. A collisional-radiative model (CRM) for Ne^{6+} ions is constructed to calculate the population density of each excited state in non-equilibrium ionization plasmas, including recombining processes. NeVII spectral line intensities and the radiative power loss are calculated with the CRM. A density effect caused by collisional excitation from the metastable state 2s2p ^3P is found at an electron density of 10^5 - 10^{17} cm^{-3}. The collisional excitations between excited states become important at high electron temperature T_e >~ 100eV. / Keywords: NeVII, dielectronic recombination rate coefficient, non-equilibrium ionization plasma, population densities, spectral line intensities, intensity ratios, plasma diagnostics, radiative power loss【リソース】Fulltext

White-tailed deer harvest records were compiled from state agencies for all available years between 2007 and 2023. Records were compiled at the town level for all states except Massachusetts, for which town-level records were not available and records by wildlife management zone were used instead. We calculated mean annual total harvest of both males and females ("Total"), the land area of each town ("Area", in square kilometers) and the mean annual density of deer harvested ("Density", in deer per square kilometer per year). This layer was used as an indicator of white-tailed deer population density and therefore browsing pressure for a study of tree regeneration.This work was supported by the Northeastern States Research Cooperative through funding made available by the USDA Forest Service. For further details, see:Harris, L. B., Pastore, M. A., & D’Amato, A. W. (2025). Effects of browsing by white-tailed deer on tree regeneration vary by ontogeny and palatability in forests of the northeastern USA. Forest Ecology and Management, 593, 122906. https://doi.org/10.1016/j.foreco.2025.122906

Global Population of the World (GPW) translates census population data to a latitude-longitude grid so that population data may be used in cross-disciplinary studies. There are three data files with this data set for the reference years 1990 and 1995. Over 127,000 administrative units and population counts were collected and integrated from various sources to create the gridded data. In brief, GPW was created using the following steps:

* Population data were estimated for the product reference years, 1990 and 1995, either by the data source or by interpolating or extrapolating the given estimates for other years.
* Additional population estimates were created by adjusting the source population data to match UN national population estimates for the reference years.
* Borders and coastlines of the spatial data were matched to the Digital Chart of the World where appropriate and lakes from the Digital Chart of the World were added.
* The resulting data were then transformed into grids of UN-adjusted and unadjusted population counts for the reference years.
* Grids containing the area of administrative boundary data in each cell (net of lakes) were created and used with the count grids to produce population densities.

As with any global data set based on multiple data sources, the spatial and attribute precision of GPW is variable. The level of detail and accuracy, both in time and space, vary among the countries for which data were obtained.

Centaurea stoebe (Asteraceae; spotted knapweed) is an emerging invader in northeast US, and is a major invasive plant in the northern Midwest and western USA. Although it has been present in New York State (NYS) for over 100 years, its apparent recent population increases and spread provide a rare opportunity to study a plant in the early stages of invasion. Therefore, a study was carried out understand how distinct environmental factors influence the distribution, density and change in density C. stoebe at different spatial scales within its novel range in the northeastern USA. First, we collected field data on the occurrence, density and change in density of this species in North Eastern United States, from 2013 to 2014. Then, using species distribution models, we assessed the potential influence of environmental factors on the invasion of spotted knapweed in northeast US. Within different parts of C. stoebe‘s range, different factors explained its occurrence, density and change in density over 2 years. Across northeast US, climate and soil factors were the most influential predictors explaining C. stoebe‘s distribution, while within Long Island in southeastern NYS and the Adirondack Mountains in northern NYS, precipitation and disturbance respectively were the most important. These results are published in the paper titled The influence of environmental factors on the distribution and density of invasive Centaurea stoebe across Northeastern USA (Akin-Fajiye and Gurevitch, 2018).

1. Interactions between hosts and pathogens are dynamic at both ecological and evolutionary levels. In the resultant “eco-evolutionary dynamics” ecological and evolutionary processes affect each other. For example, the house finch (Haemorhous mexicanus) and its recently-emerged pathogen, the bacterium Mycoplasma gallisepticum, form a system in which evidence suggests that changes in bacterial virulence through time enhance levels of host immunity in ways that drive the evolution of virulence in an arms race.

2. We use data from two associated citizen science projects in order to determine whether this arms race has had any detectable effect at the population level in the northeastern United States.

3. We used data from two citizen science projects, based on observations of birds at bird feeders, which provide information on the long-term changes in sizes of aggregations of house finches (host population density), and the probabilities that these house finches have observable disease (disease prevalence).

4. The initial emergence of M. gallisepticum caused a rapid halving of house finch densities; this was then followed by house finch populations remaining stable or slowly declining. Disease prevalence also decreased sharply after the initial emergence and has remained low, although with fluctuations through time. Surprisingly, while initially higher local disease prevalence was found at sites with higher local densities of finches, this relationship has reversed over time.

5. The ability of a vertebrate host species, with a generation time of at least one year, to maintain stable populations in the face of evolved higher virulence of a bacterium, with generation times measurable in minutes, suggests that genetic changes in the host are insufficient to explain the observed population-level patterns. We suggest that acquired immunity plays an important role in the observed interaction between house finches and M. gallisepticum.

Methods Three of the four data files are collected by volunteer observers taking part in projects coordinated by the Cornell Lab of Ornithology; the fourth data file contains a set of latitude-longitude locations laid on in a grid across the study area. The data describing the relative abundances of the bird species, the House Finch (Haemorhous mexicanus) were collected in Project FeederWatch. The process of data collection, and examples of use of these data can be found in the following papers:

Bonter, D.N. & Cooper, C.B. (2012) Data validation in citizen science: a case study from Project FeederWatch. Frontiers in Ecology and the Environment, 10, 305-307.

Greig, E.I., Wood, E.M. & Bonter, D.N. (2017) Winter range expansion of a hummingbird is associated with urbanization and supplementary feeding. Proceedings of the Royal Society B: Biological Sciences, 284, 20170256.

States, S.L., Hochachka, W.M. & Dhondt, A.A. (2009) Spatial variation in an avian host community: implications for disease dynamics. Ecohealth, 6, 540-545.

Zuckerberg, B., Bonter, D.N., Hochachka, W.M., Koenig, W.D., DeGaetano, A.T. & Dickinson, J.L. (2011) Climatic constraints on wintering bird distributions are modified by urbanization and weather. Journal of Animal Ecology, 80, 403-413.

The data describing prevalence of disease caused by the bacterium Mycoplasma gallisepticum were collected and processed as described in the paper with which this data archive is associated, and is papers including:

Dhondt, A.A., Badyaev, A.V., Dobson, A.P., Hawley, D.M., Driscoll, M.J.L., Hochachka, W.M. & Ley, D.H. (2006) Dynamics of mycoplasmal conjunctivitis in the native and introduced range of the host. Ecohealth, 3, 95-102.

Dhondt, A.A., Tessaglia, D.L. & Slothower, R.L. (1998) Epidemic mycoplasmal conjunctivitis in House Finches from eastern North America. Journal of Wildlife Diseases, 34, 265-280.

Hartup, B.K., Dhondt, A.A., Sydenstricker, K.V., Hochachka, W.M. & Kollias, G.V. (2001) Host range and dynamics of mycoplasmal conjunctivitis among birds in North America. Journal of Wildlife Diseases, 37, 72-81.

States, S.L., Hochachka, W.M. & Dhondt, A.A. (2009) Spatial variation in an avian host community: implications for disease dynamics. Ecohealth, 6, 540-545.

Household and CATI characteristics by state, Northeast Nigeria, September 15 to December 25, 2021.

The threat of isolation to red deer (Cervus elaphus) has been described in numerous European studies. The consequences range from reduced genetic diversity and increased inbreeding to inbreeding depression. It has been shown that the underlying factors cannot be generalised, but vary greatly in their effects depending on local conditions. The aim of this study was to analyse in detail the genetics of red deer in a large German federal state with a population density of 532 inhabitants per km2 and 23.8% settlement and traffic area, in order to generate data for future management of the region. 1199 individual samples of red deer were collected in all 20 Administrative Management Units (AMUs) and compared with existing results from the neighbouring state of Hesse (19 AMUs). All 2490 individuals from both states were clustered using Bayesian methods and connectivity between neighbouring AMUs was quantified. Overall, 30% of the AMUs were found to be highly isolated, mostly with effective population sizes (Ne) < 100. In contrast, 47.5% of the AMUs still had clear connectivity, allowing them to be merged into 4 larger red deer regions. For the small isolated areas, low genetic diversity was found in units with high homozygosity and low Ne. With high sampling density and identical methodology, detailed information on AMUs can be obtained and the degree of vulnerability of individual AMUs as part of the overall population can specifically be validated. Such data can help improve future wildlife management.

Cholera Cluster Characteristics by State, Northeast Nigeria, Sept 15 to Dec 25, 2021.

Mean values of population genetic parameters by federal state and region.

A. The effective population sizes of AMUs in NRW, as well as the regions and states according to NeEstimator, Wang et al. [57] and Caballero [58]. B. Effective population sizes of AMUs in Hesse, regions and states according to NeEstimator, Wang et al. [57] and Caballero [58].

A. Population genetic parameters of the red deer administrative management units (AMUs) in North Rhine-Westphalia (NRW). B. Population genetic parameters of the red deer administrative management units (AMUs) in Hesse.