Physical barriers are often due to the nature of the environment.

The presence of a physical barrier also acted as a legal one.

When factors change, especially physical barriers, often, species will branch off.

Physical barriers to gene flow are usually, but not always, natural.

These may be physical barriers, such as living far from your doctor or pharmacy.

These include physical barriers, which make the effort of stealing the vehicle more difficult.

Hasn't technology made the physical barrier obsolete to border security?

In both cases, treatment provides a physical barrier to flame spread.

Without physical barriers it is very hard to police.

Few have physical barriers, something that is not true of most bodegas.

Current silicon technology will hit fundamental physical barriers in the next decade or two.

The book she was reading had once been the physical barrier between her and her mother.

The room shall be fully separated with physical barriers from other areas of the building.

Indeed, the absence of physical barriers reinforced the need for emotional ones.

The thought checked her as if it had erected a physical barrier.

It acts like a true physical barrier to the best wa sense.

"I don't mean to sound discouraged by these physical barriers, because I'm not.

The use of two locking devices and a physical barrier for the equipment.

And they also are reminded by the physical barriers that prohibit their access to many public places.

"The doorway was a psychological and physical barrier that they were not going to cross," he said.

It was the physical barrier that balked him, not the spiritual one.

First, the physical barrier is provided by the fine sediments on the top of the ocean floor.

He took the stairs slowly, and regarded the purely physical barrier.

One way they mate guard is by creating a physical barrier to turn away any other males.

That being the case, how could he circumvent the physical barrier, without breaking it?