The influence of habitat quality and population density on occupancy dynamics may surpass that of traditional metrics of area and isolation, but often this is not considered explicitly in studies of spatially structured populations. In landscapes that are not easily characterized as binary habitat/non-habitat (e.g. variegated landscapes), this influence may be even more important and occur at both local and landscape levels. It follows that occupancy dynamics may be driven by disparate processes depending on how extinction or colonization relate to habitat quality and population density. We examined the relative influence of area, structural isolation, habitat quality, local population density, and neighborhood population density (i.e. population density in the landscape around a site) on the probability of extinction and colonization of snowshoe hare Lepus americanus across an expansive forest mosaic landscape (encompassing the northern third of Idaho). Habitat quality and population density ...
A population is the number of living things that live together in the same place.[1] A citys population is the number of people living in that city. These people are called inhabitants or residents. The population includes all individuals that live in that certain area.The world population was estimated to have reached 7.5 billion in April 2017. Asia is the most populous continent, with its 4.3 billion inhabitants being 60% of the world population. Population density is the average number of people in a place. Urban areas such as big cities have a high population density. People there live close to each other. In areas with a low population density, people usually live far away from each other, such as in rural areas out in the countryside. Usually population refers to the number of humans in a certain area. The maximum population that can be supported in an area is called the carrying capacity. ...
The difficulty to locate mates and overcome predation can hamper species establishment and population maintenance. The effects of sparseness between individuals or the effect of predators on the probability of population growth can be difficult to measure experimentally. For testing hypotheses about population density and predation, we contend that habitat complexity can be simulated using insect mazes of varying mathematical difficulty. To demonstrate the concept, we investigated whether the use of 3D printed mazes of varying complexity could be used to increase spatial separation between sexes of Drosophila simulans, and whether the presence of a generalist predator hampered mate-finding. We then examined how increasing D. simulans population density might overcome the artificially created effects of increasing the distance between mates and having a predator present. As expected, there was an increase in time taken to find a mate and a lower incidence of mating as habitat complexity increased.
Bangladesh is a developing country with a very high population density. The country has 160 million populations with a small area of only 147, 570 km . Currently, the population density is around 1200 persons per km 2 which is 50 times higher than the global average density of population, 3 times that of our neighbor India, 7 times that of China and 35 times that of the United States of America. The density in urban areas, particularly within Dhaka Megacity remains very high. The average density within the 1500 km 2 DMC region was over 10,000 persons per km 2 2 . in 2011 Census. However, within the urban built up area the density mostly varied from 20,000 to 75,000 persons per km . In some parts of the city, mostly at the older part, the density was found as high as over 200,000 inhabitants per km 2 2 . This thesis mainly deals with the population dynamics of Dhaka Megacity (DMC), more particularly the distribution and variation of population density and growth within the DMC region in recent ...
This paper addresses the complex relationship between geography and macroeconomic growth. We investigate the ways in which geography may matter directly for growth, controlling for economic policies and institutions, as well as the effects of geography on policy choices and institutions. We find that location and climate have large effects on income levels and income growth, through their effects on transport costs, disease burdens, and agricultural productivity, among other channels. Furthermore, geography seems to be a factor in the choice of economic policy itself. When we identify geographical regions that are not conducive to modern economic growth, we find that many of these regions have high population density and rapid population increase. This is especially true of populations that are located far from the coast, and thus face large transport costs for international trade, as well as populations in tropical regions of high disease burden. Furthermore, much of the population increase in the next
Many common bacterial pathogens use chemical signals to coordinate group behaviors. In the canonical quorum sensing (QS) system of V. fischeri, a synthase, LuxI, produces an N-acyl homoserine lactone (AHL) that is recognized by a receptor, LuxR, at high signal density. LuxR is a transcription factor that regulates bioluminescence and other group behaviors at high population density in an AHL dependent manner. SdiA is a LuxR homolog found in Escherichia coli and Salmonella enterica serovar typhimurium. SdiA does not have a corresponding synthase, however, and these species do not produce AHL signals. SdiA does not respond to population density, but rather has been shown to respond to AHLs produced by other bacterial species in its environment. SdiA regulates many aspects of pathogenesis including directing the location of the infection, survival in the mammalian digestive system, and the production of virulence factors. Accordingly, modulation of SdiA activity might be a useful anti-virulence ...
We have found that cell-cell signaling is used to regulate horizontal transfer of the integrative and conjugative element ICEBs1, a conjugative transposon found in the B. subtilis genome. These types of elements are widespread in the microbial world and contribute to horizontal gene transfer, evolution, virulence, and the spread of antibiotic resistance. ICEBs1 is regulated by population density and cell-cell signaling in two ways. 1) At high population density, in the presence of potential mating partners, the element is stimulated to excise from the chromosome and can then transfer to potential recipients. 2) However, if the potential recipients already contain a copy of the element, then excision of the element is inhibited and there is little or no transfer to the potential recipients that already contain the element. We found that the secreted pentapeptide, a product of phrI, that regulates this "recognition of self" is encoded in the element. In the absence of this peptide, as cells grow ...
Background Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating...
If a river or lake is in good condition, we usually find that there is much more nitrogen than phosphorus, and if the growth of algae and aquatic plants is limited it is usually due to a lack of phosphorous," explains Peñuelas. However, the constant dumping of detergents, pesticides, fertilizers, and urban and industrial wastewater in many river basins throughout the world adds huge quantities of phosphorous, which is accumulating much more quickly than nitrogen or other elements such as potassium. With this, the special role of phosphorus has changed from a desirable nutrient to a contaminant in urban areas with high population density and areas with intensive agriculture.. Under natural conditions, algae tissues contain seven times more nitrogen than phosphorous, and in terrestrial plants this proportion can be as high as 15 times greater. "Most soils and rocks contain low amounts of phosphorous, an element which has very low solubility in water. For this reason, freshwater species have ...
Ammonia emissions have been increasing as a result of agricultural activities in Canada. Since 1981, emissions from fertilizer have more than doubled (from 63,000 kilotonnes of nitrogen in 1981, up to 130,000 kilotonnes of nitrogen in 2011). Conversely, livestock-related emissions have been decreasing, particularly since 2006. These trends reflect Canadas national trend towards more land under annual crops, and less area given to livestock and associated forage production.. Use the interactive map below to zoom in and explore different regions. Note that some of the highest emissions per hectare (relating to both livestock and fertilizer emissions) occur in the Mixedwood Plains region of southern Ontario and Quebec. The high population density in these regions increases the potential for human health implications. Other areas of relatively high emissions include the Aspen Parkland, Moist Mixed Grassland and Lake Manitoba Plain regions of the Prairies. The Lower Fraser Valley region of British ...
One of the most important threats to global public health, especially in developing countries is parasitic infections. These infections are very common in children and young people especially those who kept in kindergarten and primary schools. Because of the high population density and sometimes by the lack of adequate hygiene, these places are prone to parasitic infections. Infestation causes by ectoparasites like pediculosis, water-borne protozoan infections like giardiasis and the last but not less important, helminth infection like as Oxyuris are a permanent threat for children in this places.
It was a hazy and hot day as I sat in my grade school New York City classroom. Suddenly, everyones attention was drawn to my classmates wheezing and labored breathing. Àngel was one of the biggest kids in our class, but he was clearly in distress and the memory of his pain is vivid. I now understand that my friend was having an asthma attack. Thankfully, our teacher knew precisely what to do and she had his inhaler inside her desk and ready.. Our Manhattan public school was located adjacent to a major highway known as the FDR Drive, which snakes up Manhattans eastside near the Williamsburg Bridge. The combination of high population density, cars, trucks and industrial activity was a recipe for dismal air quality.. Àngel and many of my inner-city cohort shared a Puerto Rican ancestry. To this day, I remain puzzled by the disproportionately high asthma rate among Latinos. Latinos are 30 percent more likely to go to the hospital for asthma, as compared to non-Hispanic Whites. For reasons that ...
US census maps - demographics ECPM Département de langues Map United States Population Density , Direct Maps File:US population map.png Wikimedia Commons Map United States Population Density , Direct Maps What is a map? Map skills and higher order thinking The Functional Art: An Introduction to Information Graphics and Map of NFL teams overlaying a US population density map : nfl US census maps - demographics ECPM Département de langues US Population Density Map in 3D , ...
Knowledge of the effective size of populations, Ne, and the ratio of effective population size to the size of the mature population Ne/N, provide important information of the genetic diversity and fitness of populations. However, the theoretical parameter Ne was originally defined for populations with discrete generations, and most models that aim to estimate Ne for populations with overlapping generations relies on a set of simplifying, often unrealistic assumptions. Whenever these assumptions are violated, the predicted size of Ne may be highly biased and this may potentially lead to erroneous decisions in conservation and management. Hence, there is a need for more knowledge about how different processes occurring in natural populations affect the effective size of populations, and the Ne/N ratio. The main goal of this thesis was to relax one of the most unrealistic assumptions underlying many models: constant population size, or at the very best that fluctuations are only caused by density ...
An increase in offspring-number variation leads to more variable population dynamics, which on one hand lets successful populations escape even faster from the range of small population sizes than under the Poisson model. On the other hand, a large variation also prevents successful Allee-effect populations from spending much time near or above the critical population size because those that do still have a high risk of going extinct even at such high population sizes. Therefore, an increase in variability reinforces the speed-up effect but mitigates the slow-down effect and thus increases the range of founder population sizes for which the genetic consequences of the Allee effect are positive (see Figure 2 and Figure 4). In that sense, variation in family sizes plays a similar role as variation in founder population size and in the number of introduction events (see Figure 4), two factors that were examined in Wittmann et al. (2014) and, in the case of founder population size, also by Kramer ...
The temporal method for estimating effective population size (Ne) from the standardized variance in allele frequency change (F) is presented in a generalized form. Whereas previous treatments of this method have adopted rather limiting assumptions, the present analysis shows that the temporal method is generally applicable to a wide variety of organisms. Use of a revised model of gene sampling permits a more generalized interpretation of Ne than that used by some other authors studying this method. It is shown that two sampling plans (individuals for genetic analysis taken before or after reproduction) whose differences have been stressed by previous authors can be treated in a uniform way. Computer simulations using a wide variety of initial conditions show that different formulas for computing F have much less effect on Ne than do sample size (S), number of generations between samples (t), or the number of loci studied (L). Simulation results also indicate that (1) bias of F is small unless ...
NeEstimator v2 is a completely revised and updated implementation of software that produces estimates of contemporary effective population size, using several different methods and a single input file. NeEstimator v2 includes three single-sample estimators (updated versions of the linkage disequilibrium and heterozygote-excess methods, and a new method based on molecular coancestry), as well as the two-sample (moment-based temporal) method. New features include the following: (i) an improved method for accounting for missing data; (ii) options for screening out rare alleles; (iii) confidence intervals for all methods; (iv) the ability to analyse data sets with large numbers of genetic markers (10000 or more); (v) options for batch processing large numbers of different data sets, which will facilitate cross-method comparisons using simulated data; and (vi) correction for temporal estimates when individuals sampled are not removed from the population (Plan I sampling). The user is given ...
From a microbes "point of view" the human body is a vast array of surfaces some internal, others external that are continuously colonized by endemic and exotic microbes beginning from the time of our birth and continuing throughout life up until and even beyond the point of death. The surfaces on which these organisms grow and are constantly being sloughed off as new tissues form beneath existing ones resulting in the loss of established biofilms but providing new and uncolonized, or at least less colonized, cell surfaces on which new biofilm communities can be come established. These interconnected ecosystems vary from highly abraded, exceptionally dry habitats on the surface of the skin (e.g. the elbow) to constantly moist, highly nutritious membranous surfaces (the conjunctiva of the eye), from niches of low population density and a pH of 3 (stomach) to habitats with a hydrogen ion concentration a million fold lower and a population density of 1011 cells /gram (gut). Then, within the same ...
Downloadable (with restrictions)! This paper investigates nonparametric estimation of density on [0, 1]. The kernel estimator of density on [0, 1] has been found to be sensitive to both bandwidth and kernel. This paper proposes a unified Bayesian framework for choosing both the bandwidth and kernel function. In a simulation study, the Bayesian bandwidth estimator performed better than others, and kernel estimators were sensitive to the choice of the kernel and the shapes of the population densities on [0, 1]. The simulation and empirical results demonstrate that the methods proposed in this paper can improve the way the probability densities on [0, 1] are presently estimated.
Learning Goals: Use a quadrat to sample an area of the school lawn and calculate the population density of 4 common weeds.. Key Concepts: density, carrying capacity, biodiversity, quadrat sampling. Download a copy of the Population Density lab Indoor Quadrat Alternate Assignment:. http://www.patriotspointsciencespotlight.com/images-and-data-submission.html. Lab - Introduction to Quadrats. Quadrats - the Point-Intercept Method. ...
As predicted, invasion-front toads were more likely to approach conspecifics and spent more time with them than did toads from long-colonized populations. We also found a sex effect; males were more likely to approach conspecifics and spent more time with them than did females. Because our stimulus toads were female, that sex bias might reflect sexual rather than social attraction. However, the greater sociality of male than female toads was seen in both long-colonized and range-edge populations, suggesting that the effect of invasion history on social attraction was not due to differences in sexual selection among populations. Below, we consider possible explanations for the divergence in social attraction between long-colonized and invasion-front populations.. First, the costs and benefits of social attraction may differ at high versus low population densities, which in turn differ predictably across the invasion range. For example, low densities at the invasion front may reduce ecological ...
The conditions for enterprise differ in some respects between companies in urban and rural areas. The geographical situation in rural areas entails large distances to customer and suppliers. A limited labour market and other functions of significance mean that travel and transports are more expensive and take more time. The possibility of recruiting personnel with the right expertise is affected by a limited local labour market. Long distances make work commutes difficult. Properties and facilities in rural areas often have low second-hand value which makes it difficult for companies to provide collateral for bank loans. Low population density and climate need not necessarily always be competitive disadvantages. For enterprises where the business has a special need for space, natural resources, climate, etc. these characteristics are often an advantage and in some cases a prerequisite. Agriculture, forestry, mineral extraction, some kinds of tourism, testing activities, etc. are examples of ...
Establish transportation services for areas with low population densities using publicly funded buses and vans on a set schedule, dial-a-ride transit, volunteer ridesharing, etc. ...
Figure 1 of Nielsen et al., paper shows multiple (up to 21) synonymous and non-synonymous substitutions in thousands of chimp proteins compared to the related human proteins. In the second paper Behe & Snoke conclude that in order to generate a new function that requires mutations of two amino acids, like forming a disulfide bridge, 108 generations are needed with a population size of at least 109. In the third paper, Lynch countered that much smaller populations could reach this goal in less time. Now, if we take the human population size from the above two studies (Ne about 104) for the population size in Figure 3 of the Lynch article, we can see that it would take 108 generations for the arrival of a new function, even if the two changed amino acid were any 2 of 50 (with a high s = 0.01). For humans, 108 generations mean 2 Billion years: an impossibly long period. Needless to say, a new function requiring 3, 4 … up to 21 amino acid changes would take much longer than 108 generations. And ...
Figure 1 of Nielsen et al., paper shows multiple (up to 21) synonymous and non-synonymous substitutions in thousands of chimp proteins compared to the related human proteins. In the second paper Behe & Snoke conclude that in order to generate a new function that requires mutations of two amino acids, like forming a disulfide bridge, 108 generations are needed with a population size of at least 109. In the third paper, Lynch countered that much smaller populations could reach this goal in less time. Now, if we take the human population size from the above two studies (Ne about 104) for the population size in Figure 3 of the Lynch article, we can see that it would take 108 generations for the arrival of a new function, even if the two changed amino acid were any 2 of 50 (with a high s = 0.01). For humans, 108 generations mean 2 Billion years: an impossibly long period. Needless to say, a new function requiring 3, 4 … up to 21 amino acid changes would take much longer than 108 generations. And ...
Population Density Defined as total population size per unit of area. Population densities depend on: Interactions within the environment Quality of habitat
Background Increasing evidence shows that the cancer microenvironment affects both tumorigenesis and the response of cancer to drug treatment. Therefore in vitro models that selectively reflect characteristics of the in vivo environment are greatly needed. Current methods allow us to screen the effect of extrinsic parameters such as matrix composition and to model the complex and three-dimensional (3D) cancer environment. However, 3D models that reflect characteristics of the in vivo environment are typically too complex and do not allow the separation of discrete extrinsic parameters. Methodology/Principal Findings In this study we used a poly(ethylene glycol) (PEG) hydrogel-based microwell array to model breast cancer cell behavior in multilayer cell clusters that allows a rigorous control of the environment. The innovative array fabrication enables different matrix proteins to be integrated into the bottom surface of microwells. Thereby, extrinsic parameters including dimensionality, type of matrix
In summary, the spectrum of protein-coding variation is considerably different today compared to what existed as recently as 200 to 400 generations ago. Of the putatively deleterious protein-coding SNVs, 86.4% arose in the last 5,000 to 10,000 years, and they are enriched for mutations of large effect as selection has not had sufficient time to purge them from the population. Thus, it seems likely that rare variants have an important role in heritable phenotypic variation, disease susceptibility and adverse drug responses. In principle, our results provide a framework for developing new methods to prioritize potential disease-causing variants in gene-mapping studies. More generally, the recent dramatic increase in human population size, resulting in a deluge of rare functionally important variation, has important implications for understanding and predicting current and future patterns of human disease and evolution. For example, the increased mutational capacity of recent human populations has ...
Using a relatively simple density-dependent population model and assuming constant young of year survival with no immigration/emigration, reductions in cumulative fecundity have been predicted to yield declines in population size over time (Miller and Ankley 2004). Under real-world environmental conditions, outcomes may vary depending on how well conditions conform with model assumptions. Nonetheless, cumulative fecundity can be considered one vital rate that contributes to overall population trajectories (Kramer et al. 2011).. ...
Access Frankston Heights population density figures plus suburb map, boundaries, population distribution, demographics, in an accurate, easy to use website.
Access Reynella population density figures plus suburb map, boundaries, population distribution, demographics, in an accurate, easy to use website.
A brilliant new dataset produced by the European Commission JRC and CIESIN Columbia University was recently released- the Global Human Settlement Layer (GHSL). This is the first time that detailed and comprehensive population density and built-up area for the world has been available as open data. As usual, my first thought was to make an…
The second map in the post provides a 3d visualization on the same population data, with each grids population density shown as a 3d tower or block on the map. The usual problem with such an approach is that the towers or blocks in the foreground obscure the view of the towers in the background. Bjørns 3d interactive map largely overcomes this problem by allowing you to rotate and zoom in and out on the map ...
We can also look at factors that determine carrying capacity in terms of their density-dependence. Density-dependent limiting factors make the per capita growth rate decrease as the population increases. Density-dependent limiting factors tend to be biotic, including factors such as food and disease. For example, in a population of panthers, there is access to a fixed amount of food. When the population remains small there will be plenty of food for all panthers. When the panther population gets large enough the food may become insufficient, leading to competition among panthers, from this competition, panthers may starve, or die, and stop reproducing. As such, the per capita growth rate of the panther population may shrink or level off. Food in this case is an example of a density-dependent limiting factor.. ...
A nonlinear mathematical model for innovation diffusion is proposed. The system of ordinary differential equations incorporates variable external influences (the cumulative density of marketing efforts), variable internal influences (the cumulative density of word of mouth) and a logistically growing human population (the variable potential consumers). The change in population density is due to various demographic processes such as intrinsic growth rate, emigration, death rate etc. Thus the problem involves two dynamic variables viz. a non-adopter population density and an adopter population density. The model is analysed qualitatively using the stability theory of differential equations, with the help of the corresponding characteristic equation of the system. The interior equilibrium point can be stable for all time delays to a critical value, beyond which the system becomes unstable and a Hopf bifurcation occurs at a second critical value. Employing normal form theory and a centre manifold ...
Lecture 9 BIOL 3500 Chapter 11: Intraspecific Population Regulation Learning Objectives Contrast: Density dependance vs. independence Scramble vs. contest competition Home range vs. territory Define:
Land cover-based: Through detailed mapping of settlements, and linkage of these settlement extents with gazetteer population numbers, the substantial majority of resident population can be mapped within settlements with good precision. Mapping of the remaining minority rural populations follows the approaches outlined in detail elsewhere. The settlement maps are used to refine land cover data, while local high resolution census data is exploited to identify typical regional per-land cover class population densities, which are then applied to redistribute census counts to map human population distributions. This population mapping approach forms the basis of some older WorldPop datasets, but is now being replaced by an alternative Random Forest mapping approach described below.. Random Forest: Stevens et al (2015) provides full details on the novel random forest regression tree-based mapping approach. In brief, a new semi-automated dasymetric modeling approach has been built that incorporates ...
When publishing monthly population number, only registered population change is taken into account (both natural increase and net migration). In the 2nd quarter of the following year, the population number at the beginning of the year and in previous month is specified considering non-registered migration as well as fertility and mortality data in line with the actual month of the event.. Number of live births. The data on registered number of live births occurred during the corresponding month in the database short-term statistical data section are published in the last reference year. It means that statistics on the number of births includes part of the births occurred during the previous month, but not all births occurred during the respective month are included in the statistics, as in line with the Law On Registration of Civil Status Documents a child shall be registered within a month after the birth thereof. In June of the following year, the data on all live births occurred during the ...
Figure 4 represents an initial cell concentration of one. The population still spikes up, but the leveling off occurs at a lower population than in figure 1 (note change in y-axis scale here). In figure 5 the inflow rate (and therefore the amount of nutrients in the system) was increased, allowing the cell population to increase past the 110 count in figure 4. However, there is still the knee where the initial higher concentration of nutrients is depleted and the increase in cells proceeds at a slower rate ...
A general method for the analysis of ecological count data with extra zeros is presented using a Markov birth process representation of discrete distributions. The method uses a non parametric...
(29-10-2013 06:16 PM)ridethespiral Wrote: ..but if you put the right chemicals (found in abundance on old earth) in a flask and apply enough energy you get the kinds of organic molecules with the pote
Over the decades engineers and manufacturing were desperate to find more uses for PM primarily due to the net shape capability they provided. However, PM has two major stumbling blocks that they continue to try and overcome: First, the part had to be capable of being removed from a hydraulic press, therefore any component had to be fairly simple in configuration - cylindrical or some similar shape with straight sides. Second, although extreme pressure is used to compress parts, 100 percent void free is impossible to achieve. Why? First, a binder is blended with the powder because without a binder/lube the compact has no strength when its removed from the press and some strength is required for the parts to hold their shape through the handling required to transport parts between processes. Since the maximum practical sintered density can vary depending on the alloy grade and application about 85 to 92 to 98 percent the binder/lube serves two purposes. It allows the part to retain its shape and ...
Does anyone know the best Signifinace Test for a dataset following a hypergeometric distribution with sample size over 30? If you have 100 recipe
[1] WORLD POPULATION June 3, 2011 Density Population density is a measure of total population to land size. There are two types of population...
|h2|Content Objective(s):|/h2| |p|Students will be able to:|/p| |ul| |li|Apply recognized scouting methods to sample insect populations.|/li| |li|Compare population densities with action thresholds.|/li| |li|Analyze and re-evaluate existing management pro
Objective. To assess whether higher mortality rates among individuals in motor vehicle crashes in areas with low population density depend on injury type and severity or are related to the performance of emergency medical services (EMS).. Methods Prehospital and hospital deaths were studied in a population-based cohort of 41 243 motor vehicle crashes that occurred in Sweden between 1998 and 2004. The final multivariable analysis was restricted to 6884 individuals in motor vehicle crashes, to minimise the effects of confounding factors.. Results Crude mortality rates following motor vehicle crashes were inversely related to regional population density. In regions with low population density, the unadjusted rate ratio for prehospital death was 2.2 (95% CI 1.9 to 2.5) and for hospital death 1.5 (95% CI 1.1 to 1.9), compared with a high-density population. However, after controlling for regional differences in age, gender and the type/severity of injuries among 6884 individuals in motor vehicle ...
Data & statistics on Population Poverty Rates by Sex of Household Head and Residence: Poverty Indices according to Region of Residence, Gender, Sector of Employment, Education Level, and Mode of Living of Head of Household (1990, 1996), Disaggregates rural poverty rates across Malawis three regions. Poverty rates in the rural south have historically been highest, while those in the north are lowest. The relative disadvantage of southerners relates in part to land constraints in the face of high population density: the 2008 Population Census puts the population density in the south at 184 persons per square kilometer compared to only ..., Descriptive statistics of variables Variable District-level Access to services Distance from Accra Distance from regional capital Agro-ecological zone Forest Coastal Ethnic fractionalization Share of rural population Population density (log) Literacy rate Headcount ratio Poverty gap Per capita total expenditures (log) Per capita capital expenditures (log) Internal
A cohort effect is a phenomenon where cohorts of a population differ from each other in some key attribute(s), such body mass. Birth mass, birth dates, rate of growth of juveniles, survival over the first winter, age of first reproduction, and adult survival rates are often related to the influence of the time of birth, which itself is a product of the environmental conditions cohorts face at birth as well as the nutritional condition of their mothers (itself a reflection of environmental conditions faced at or prior to birth). Environmental conditions that can influence birth and early growth attributes include droughts, abnormally high rainfall, late snowfall, and high population density. These and other factors influence birth attributes and early development of juveniles, and these early effects may persist and affect phenotypic quality throughout the lifetime of the cohort. Because many of these cohort effects - body size, body mass, etc. - are tied to survival and reproductive fitness, ...
We analysed the data from the control group in a typhoid vaccine trial in Karachi to assess the differences in individual-, household- and cluster-level characteristics for developing typhoid fever. The annual incidence of typhoid in children aged 2-16 years in the control arm of the vaccine trial was 151/100 000 population. After adjustment, the risk of typhoid was lower with increasing age [risk ratio (RR) 0·89, 95% confidence interval (CI) 0·83-0·95], was higher with an increase in population density (RR 1·13, 95% CI 1·05-1·21) and was lower in the households using a safe drinking-water source (RR 0·63, 95% CI 0·41-0·99). Typhoid fever affects younger children living in areas of high population density and lack of access to safe water in Pakistan. A combination of environmental and biological interventions is required to prevent the continued epidemiological and economic impact of typhoid fever in high-risk areas of Pakistan.
The staggering 65 per cent of Japans- a high population density country- terrestrial area under forest cover owes it largely to the forced land reforms in the post world war two period, although the original intention of the occupying Americans was to wither the feudal support base of the king. Nicaraguas land reforms initiated by President Daniel Ortega in the 80s -shelved later with the change in government- were followed by a reduction in forest encroachments. Cubas small holdings were central to shaping its success in expanding agrobiodiversity and reducing the use of agrochemicals in the post Soviet period. On the other hand, apartheids appropriation of farmlands created the twin crises of accelerating rural poverty and biodiversity degradation in southern Africa. The land reform move initiated by the Soviet sponsored government in Afghanistan was at the core of the feudal resistance which was strategically utilized by the US to generate self perpetuating violence of formidable ...