Knowledge Update

​New York, June 9 (IANS) Researchers have prepared the first spatially explicit data set of the location and size of urban settlements globally over the past 6,000 years -- offering fresh clarity as to how the growth of cities transforms humans into an "urban species".

The researchers from the Yale School of Forestry and Environmental Studies created maps through digitising, transcribing, and geocoding a deep trove of historical, archaeological, and census-based urban population data previously available only in tabular form. 

The study, published recently in the journal Scientific Data, has made it possible to access information on urban centres from 3700 B.C. to A.D. 2000.

"To better understand urbanisation today it is helpful to know what urbanisation looked like through history," said lead author Meredith Reba.

"By understanding how cities have grown and changed over time, throughout history, it might tell us something useful about how they are changing today," she added.

The findings have broad applications. The dataset offers an important first step toward understanding the geographic distribution of urban populations throughout history and across the world.

Currently the only spatially explicit data available at a global scale is the United Nations World Urbanisation Prospects, which provides population values, latitudes, and longitudes for places with populations of 300,000 or more. However, it goes back only to 1950.

The new study allows researchers to map and visualise city level population changes through time. For example, Istanbul in Turkey underwent a major period of population decline between AD 1057 and AD 1453. During this time the population dropped from approximately 300,000 to 45,000 due to a series of events including a city sacking by the Crusaders and a bout with the plague.

According to the researchers, the ability to pinpoint the size and location of human populations over time will help researchers understand the evolving characteristics of the human species -- particularly human interactions with the environment.​

​Toronto, June 9 (IANS) Lignin, a natural material in plants and a major waste product of the paper industry, can be added to sunscreen creams to protect you from getting sunburn, says a new study.

Most sunscreen products currently in the market contain synthetic compounds that help prevent ultraviolet rays from damaging skin. But consumers are searching for better product performance that comes from natural sources. This has led scientists to experiment with compounds from a variety of sources. 

According to the study published recently in the journal Sustainable Chemistry and Engineering, Shiping Zhu from Canada's McMaster University and Qiu Xueqing of South China University of Technology found that out of five types of lignin tested, organosolv lignin improved the sun protection factor (SPF) of sunblock the most. 

Sunscreen containing just one percent of this compound doubled the lotion's original SPF -- it went from 15 to 30. 

A lotion with 10 percent organosolv lignin increased SPF even further, from 15 to almost 92, but excessive amounts of hydrophilic lignin such as lignosulfonate caused the product to start separating. 

The researchers said that although more work is needed to be done, the results represent a promising first step toward the development of lignin-containing sunscreen.

​London, June 10 (IANS) Deficiency of zinc can adversely impact the essential metabolic functions of most living organisms, finds a new study suggesting that even moderate levels of deficiency of the trace element can be bad for digestion.

The findings showed that zinc deficiency in an animal's diet impedes pancreatic digestive activity and results in significant digestive impairment, even at an early stage. 

In humans, it has been known to increase the levels of inflammation markers and reduce immunocompetence -- the ability of the body to produce a normal immune response following exposure to an antigen.

As zinc only exists in small amounts in an organism, it has to be consumed by way of nutrition, the researchers said. 

The beginning of zinc depletion usually goes unnoticed and without any visible symptoms, but minute changes can be identified in the liver and in the blood. 

Pancreas, known as the control centre for food digestion and energy homeostasis in the body, pumps zinc into the gastrointestinal tract in order to maintain a consistent zinc level. 

Conversely, if an organism is depleted of zinc, it reduces its pancreatic zinc excretion to a minimum. 

"The accumulation of undigested food inside the gastrointestinal tract due to zinc deficiency results in feeling less hungry," said lead author Daniel Brugger of the Chair of Animal Nutrition at Technical University of Munich (TUM) in Germany.

"We proved that there is a direct correlation between the amount of digestive enzymes inside the pancreas and zinc levels in the organism as a whole," Brugger added in the paper published in the British Journal of Nutrition.

For the purpose of this study, the team fed piglets that had just been weaned on a diet containing different amounts of zinc to develop early-stage zinc deficiency. 

On the one hand, it was observed that the body tried to absorb zinc more efficiently, while on the other it reduced pancreatic zinc excretion. 

"Even short intervals of zinc deficiency in the diet should be avoided," Brugger said, adding that particularly older adults need to monitor their zinc intake with foods that are high in zinc like seafood, spinach, pumpkin nuts, cocoa, chocolate and mushrooms.​

​Wellington, June 10 (IANS) Air pollution, including environmental and household air pollution, has emerged as the leading risk factor for stroke globally, finds a new study.

The findings showed that about a third (29.2 per cent) of global disability associated with stroke such as loss of vision and/or speech, paralysis and confusion, is linked to air pollution (including environmental air pollution and household air pollution). 

This is especially high in developing countries -- 33.7 per cent vs 10.2 per cent in developed countries, the researchers said.

From 1990 to 2013, stroke associated with environmental air pollution showed an increase by over 33 per cent worldwide. However, second-hand smoke saw a decrease by 31 per cent between the same period. 

"A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries," said lead author Valery L Feigin, Professor at Auckland University of Technology in New Zealand. 

Also, over 90 per cent of the global burden of stroke was caused by modifiable risk factors and 74 per cent of them are behavioural risk factors such as smoking, poor diet and low physical activity. 

"Controlling these risk factors could prevent about three-quarters of strokes worldwide," Feigin added.

Further, air pollution, environmental risks, tobacco smoke, high blood pressure and dietary risks were the other risk factors found for stroke in developing countries compared to developed countries.

Household air pollution was found to be an important risk factor for stroke in central, eastern and western sub-Saharan Africa as well as south Asia.

Every year, approximately 15 million people worldwide suffer a stroke. High blood pressure, diet low in fruit, high body mass index (BMI), diet high in sodium, smoking, diet low in vegetables, environmental air pollution, household pollution from solid fuels, diet low in whole grains and high blood sugar were found as the ten major risk factors for stroke. 

"Our findings are important for helping national governments and international agencies to develop and prioritise public health programmes and policies," Feigin noted.

For the study, published in The Lancet Neurology journal, the team used data from the Global Burden of Disease Study to estimate the disease burden of stroke associated with 17 risk factors in 188 countries between 1990-2013. 

"Air pollution is not just a problem in big cities, but is also a global problem. It is one aspect of the fossil fuel and global warming problem, which is itself partly a result of westernisation and urbanisation, especially in India and China," the researchers concluded.​

​Wellington, June 10 (IANS) Air pollution, including environmental and household air pollution, has emerged as the leading risk factor for stroke globally, finds a new study.

The findings showed that about a third (29.2 per cent) of global disability associated with stroke such as loss of vision and/or speech, paralysis and confusion, is linked to air pollution (including environmental air pollution and household air pollution). 

This is especially high in developing countries -- 33.7 per cent vs 10.2 per cent in developed countries, the researchers said.

From 1990 to 2013, stroke associated with environmental air pollution showed an increase by over 33 per cent worldwide. However, second-hand smoke saw a decrease by 31 per cent between the same period. 

"A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries," said lead author Valery L Feigin, Professor at Auckland University of Technology in New Zealand. 

Also, over 90 per cent of the global burden of stroke was caused by modifiable risk factors and 74 per cent of them are behavioural risk factors such as smoking, poor diet and low physical activity. 

"Controlling these risk factors could prevent about three-quarters of strokes worldwide," Feigin added.

Further, air pollution, environmental risks, tobacco smoke, high blood pressure and dietary risks were the other risk factors found for stroke in developing countries compared to developed countries.

Household air pollution was found to be an important risk factor for stroke in central, eastern and western sub-Saharan Africa as well as south Asia.

Every year, approximately 15 million people worldwide suffer a stroke. High blood pressure, diet low in fruit, high body mass index (BMI), diet high in sodium, smoking, diet low in vegetables, environmental air pollution, household pollution from solid fuels, diet low in whole grains and high blood sugar were found as the ten major risk factors for stroke. 

"Our findings are important for helping national governments and international agencies to develop and prioritise public health programmes and policies," Feigin noted.

For the study, published in The Lancet Neurology journal, the team used data from the Global Burden of Disease Study to estimate the disease burden of stroke associated with 17 risk factors in 188 countries between 1990-2013. 

"Air pollution is not just a problem in big cities, but is also a global problem. It is one aspect of the fossil fuel and global warming problem, which is itself partly a result of westernisation and urbanisation, especially in India and China," the researchers concluded.​

​New York, June 10 (IANS) Large animals hunted for their parts -- such as elephant ivory and shark fins -- are in double jeopardy of extinction due to their large body size and high value, says a study.

The study reveals underappreciated risk to marine species similar to that of iconic terrestrial species.

"We typically assume that if a species is reduced to low numbers, individuals will be hard to find, hunters will stop hunting, and populations will be given a chance to recover," said one of the researchers Loren McClenachan of Colby College in Waterville, Maine, US. 

"But the extreme values of these species mean that without significant conservation intervention, they will be hunted to extinction," McClenachan noted.

In the new study, the researchers identified a taxonomically diverse group of more than 100 large marine and terrestrial species that are targeted for international luxury markets. 

They estimated the value of these species across three points of sale and explored the relationships among extinction risk, value, and body size. 

The analysis showed a threshold above which economic value is the key driver of extinction risk. 

Although lower-value species are influenced primarily by their biology, the most valuable species are at high risk of extinction no matter their size. 

Once mean product values are greater than $12,557 per kilogram, body size no longer drives risk, the report showed.

The researchers also uncovered important differences between marine and terrestrial species that point to elevated risk in the sea.

Although marine products are generally less valuable on a per kilogram basis, individual animals are still just as valuable as the most valuable terrestrial species. 

An individual whale shark, for example, is about as valuable as the most valuable terrestrial species: rhinoceroses and tigers.

The risk to marine species is not reduced for species with larger ranges as it is on land, either, the researchers said.

The findings appeared in the journal Current Biology. ​

Beijing, June 8 (IANS) Chinese children are much taller and stronger than they were four decades ago, with the height gap standing at 8 cm, a government survey showed on Wednesday.

The National Health and Family Planning Commission (NHFPC) surveyed 161,774 healthy children under seven-years-old from nine cities and their suburbs in 2015. 

Health authorities have conducted the survey once every 10 years since 1975, Xinhua news agency reported.

Taking children aged five to five-and-half years old for example, the boys on average measure 113.6 cm, 8 cm taller than boys in 1975 and 1.7 cm taller than boys in 2005, while girls have an average height of 112.5 cm, 8.2 cm more than four decades ago and 1.8 cm more than ten years ago, according to the 2015 survey results.

They also weigh 3.7 to 3.28 kg more than children four decades ago, the survey showed.

The physical development of the children surveyed surpassed the World Health Organisation's child growth standards, according to the NHFPC.

The weight and height gaps between urban children and rural children have also narrowed, according to the survey.

In 1975, urban boys aged four to five were on average 4 cm taller than their rural peers, but the gap was only 0.6 cm in 2015, while for girls of the same age the difference dropped from 4.3 cm to 0.4 cm.

​New York, June 8 (IANS) Scientists have concocted an artificial seawater medium that can be used to successfully cultivate abundant marine micro-organisms, a study says.

"We developed an artificial media which means you can make it in the lab; and anyone can order these chemicals and make this media anywhere in the world," said one of the researchers Cameron Thrash, assistant professor at Louisiana State University in the US.

The artificial seawater media consists of about 60 ingredients that include chemical elements such as calcium, sodium, magnesium plus organic and inorganic nitrogen, carbon, trace metals and B vitamins.

Prior to this discovery, many of the most abundant micro-organisms in the ocean that have been successfully cultured were done so with the aid of natural seawater media. 

Seawater is naturally low in nutrients, and many marine microbes are adapted to those conditions. 

The painstaking culturing process that includes filtering and sterilising the seawater can pose many challenges. 

First, it requires access to large volumes of seawater, which can be logistically challenging for research labs that are not located near the coast. 

Secondly, the composition of natural seawater is not clearly defined or understood. Therefore, it is difficult to characterise it physiologically. Thirdly, the composition of seawater at various times and places chemically changes.

To solve some of these challenges, the researchers created a complex yet defined artificial seawater media that is portable and reproducible. 

The findings were published in the open access journal mSphere.

Although there are other artificial seawater media available, this is the first time an artificial medium has led to the isolation of highly abundant marine microbes such as SAR11, a group of organisms that has been difficult to cultivate. 

This new tool may benefit genomics researchers, marine chemists and the microbial research community.​

New York, June 9 (IANS) Scientists have discovered that hair-like filaments on the surface of Geobacter bacteria exhibit electrical conductivity comparable to that of copper -- paving the way for the employment of biological materials in nanoscale electron devices.

Scientists from the University of Massachusetts at Amherst used X-ray diffraction to analyse the structure of the filaments called the pili. 

They found that the electronic arrangement and small molecular separation distances of less than 0.3 nanometres give the pili an excellent conductivity.

Although proteins are usually electrically insulating, the researchers said the study supports the concept that the pili of G. sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport.

The research findings, published recently in the journal mBio, can provide useful feedback for studies targeting the enhancement of pili's electrical conductivity through genetic engineering.

It could subsequently be used to construct low-cost, non-toxic, nanoscale, biological sources of electricity for light-weight electronics and for bioremediation.​

​London, June 6 (IANS) Researchers have successfully identified the four keys that unlock the genetic code of skin cells and reprogramme them to start producing red blood cells instead.

The findings could lead to personalised red blood cells for those in need of blood transfusion, for instance, people suffering from chronic anemia -- a condition in which the patient has an insufficient amount of red blood cells.

"This is the first time anyone has ever succeeded in transforming skin cells into red blood cells, which is incredibly exciting," said lead author of the study Sandra Capellera from Lund University in Sweden.

"We have performed this experiment on mice, and the preliminary results indicate that it is also possible to reprogramme skin cells from humans into red blood cells,” Johan Flygare, who is also from Lund University, noted.

The study was published in the journal Cell Reports.

Every individual has a unique genetic code, which is a complete instruction manual describing exactly how all the cells in the body are formed. 

This instruction manual is stored in the form of a specific DNA sequence in the cell nucleus. All human cells -- brain, muscle, fat, bone and skin cells -- have the exact same code. 

The thing that distinguishes the cells is which chapter of the manual the cells are able to read. 

The research team wanted to find out how the cells open the chapter that contains instructions on how to produce red blood cells. 

Here is how the researchers got the skin cells to open the chapter describing red blood cells.

With the help of a retrovirus, they introduced different combinations of over 60 genes into the skin cells' genome, until one day they had successfully converted the skin cells into red blood cells. 

The study showed that out of 20,000 genes, only four are necessary to reprogramme skin cells to start producing red blood cells. Also, all four are necessary in order for it to work.​