Tijuana, with an estimated population of 1.4 million, is the largest city on the U.S./Mexican border. In addition to being a major transportation route for migrants headed to the United States, Tijuana is also situated on a major drug trafficking route. It is home to Mexico's largest number of drug users per capita and to a thriving zona roja (red light zone), work district of the city's estimated 5,000 female sex workers.

These factors have contributed to Tijuana's growing epidemic of HIV and other sexually transmitted infections. The study compared HIV infection among male and female injection drug users (IDUs) in Tijuana, assessing a range of potential risk factors – individual, social and environmental – that might contribute to higher risk of HIV and could lead to new avenues for intervention.

Male injection drug users deported from the United States to Tijuana have four-fold higher odds of HIV infection compared to those living in Tijuana who were not deported there, according to a study to be presented at the International AIDS Conference on August 5, 2008 in Mexico City.

A new study of DNA from ancient and modern chickens has shed light on the controversy about the extent of pre-historic Polynesian contact with the Americas.

The study questions recent claims that chickens were first introduced into South America by Polynesians, before the arrival of Spanish chickens in the 15th century following Christopher Columbus.

University of Adelaide’s Australian Centre for Ancient DNA (ACAD) Director Professor Alan Cooper says there has been considerable debate about the existence and degree of contact between Polynesians and South Americans, with the presence of the sweet potato throughout the Pacific often used as evidence of early trading contacts.

A frequent sign of the maturity of a spiral galaxy is the formation of a ribbon of stars and gas that slices across the nucleus, like the slash across a "no smoking" sign.

In a landmark study of more than 2,000 spiral galaxies from the largest galaxy census conducted by NASA's Hubble Space Telescope, astronomers found that so-called barred spiral galaxies were far less plentiful 7 billion years ago than they are today, in the local universe.

The study's results confirm the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. The observations are part of the Cosmic Evolution Survey (COSMOS).

The age of your housing plan may influence your risk of obesity, according to a new study from the University of Utah. Neighborhoods built before 1950 tend to offer greater overall walkability as they more often were designed with the pedestrian in mind, while newer neighborhoods often were designed to facilitate car travel.

The study in the September issue of the American Journal of Preventive Medicine, linked the body mass index (BMI) of nearly a half million Salt Lake County residents to 2000 Census data. The study found that residents were at less risk of being obese or overweight if they lived in walkable neighborhoods; more densely populated, more friendly to pedestrians and have a range of destinations for pedestrians.

Accurate measurement of thermal performance is crucial if legislation aimed at producing dramatic reductions in CO2 emissions is to be successful. The UK's National Physical Laboratory (NPL) is offering construction companies a way of meeting this mandate.

Two factors are making the need for accurate measurement of the thermal performance of building products ever more important. Firstly, the Code for Sustainable Homes published by the Department for Communities and Local Government in 2006 set a target of producing zero carbon homes by 2016. The second is the draft Climate Change Bill with its declared intention of setting a legal framework for ensuring a specific reduction in CO2 emissions by 2020 and a 60% reduction of 1990 levels by 2050. This will result in a constant stream of legislation and regulations aimed at minimising energy use in new buildings.

By the age of 18 years, two in every five South African schoolboys report being forced to have sex, mostly by female perpetrators. A new study, reported in International Journal for Equity in Health, reveals the shocking truth about endemic sexual abuse of male children that has been suspected but until now only poorly documented.

Some 28% of victims said a non-family member or teacher was the perpetrator. Another 28% had been forced by a fellow student, while 20% had been abused by a teacher and 18% by an adult family member.

Until 2007, forced sex with males in South Africa did not count as rape but as ‘indecent assault’, a much less serious offense.