The basic building blocks of matter – quarks and electrons – floated freely in an incredibly hot, dense soup. As the Universe grew and cooled, the quarks bound together into the protons and neutrons that abound today.

This is what physicists think happened at the beginning of the Universe. To prove it, teams at particle accelerators all over the world have been racing to recreate that primordial soup – called quark-gluon plasma.

Physicists at CERN, near Geneva, claimed to have seen signs of such a plasma after smashing lead ions into each other (żěèśĚĘÓĆľ print edition, 12 February 2000). But not everyone was convinced and the experiment closed before the researchers could follow up their results. Now teams at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, New York, are claiming the prize.

Jet quenching

Their heavyweight equipment fires gold ions at one another, creating 10 times the energy thought to be needed to make the quark-gluon plasma. During the last run in 2001, all four of RHIC’s detectors – STAR, PHENIX, BRAHMS and PHOBOS – saw a peculiar effect called jet quenching.

But theorists wondered if the missing jets could be to do with the high energy of the gold nuclei, rather than any new kind of matter. To prove their case, the teams ran the experiment again, this time colliding gold ions with smaller deuterium ions. Although the energy of the gold ions was the same as before, the overall energy was not high enough to make quark-gluon plasma.

New physics

The results are still being analysed, but to those involved the answer is clear. “We do not see jet suppression in the deuterium-gold collisions,” says Barbara Jacek from PHENIX, a result confirmed by researchers at the other detectors.

That suggests the jet quenching must have been due to quark-gluon plasma, not the gold ions themselves. So the teams are confident that their gold-gold collisions did create quark-gluon plasma for the first time.

“It is inconceivable that what we see in the gold-gold collisions is just an extremely hot gas of ordinary matter,” says Thomas Ulrich from STAR. “This is new physics.”

The researchers plan more experiments to be absolutely certain of their result. They also plan to carry out collisions at lower energies in the hope of seeing the transition from ordinary matter into quark-gluon plasma.

A NEW era is dawning for the design of catalysts, researchers in Denmark say.
Using only basic rules of physics, they have tailor-made a metal catalyst that
may one day bring cheaper fuel.

Until now, scientists looking for new catalysts experimented intensively with
different materials. Flemming Besenbacher of the University of Aarhus, Jens
Nørskov at the Technical University of Denmark in Copenhagen and their
colleagues wanted to design a catalyst the direct way—by using theory to
figure out the properties it should have, then finding the ideal recipe to make
it.

As an example, they took the catalyst for a process called steam reforming,
where hydrocarbons from natural gas are converted to molecular hydrogen and
carbon monoxide. These can be used to produce ammonia, methanol and fuels, for
instance. The active ingredient in the catalyst used is nickel. But if pure
nickel is used, carbon atoms tend to stick to it, eventually stopping the
catalyst working.

Nørskov’s team thought the key lay in changing the catalyst’s reactivity
slightly. They calculated the optimum value to minimise carbon formation yet
keep it reactive enough to carry out its role. They hoped to fine-tune the
catalyst’s reactivity by adding gold. Nickel and gold don’t mix in bulk, but can
form a stable surface alloy.

Using quantum mechanical calculations, Nørskov’s team predicted how different
amounts of gold would affect the nickel’s reactivity (Science, vol 279,
p 1913) and worked out the ideal nickel-to-gold ratio for steam reforming. They
then joined forces with Haldor Topsøe Research Laboratories in Lyngby, where
chemists made the catalyst. They showed it is highly efficient at catalysing the
steam reforming of butane, and that no carbon forms on it.

“The research is a major breakthrough,” says Jens Rostrup Nielsen of Topsøe.
“Now we are able to tailor-make catalysts on a much more rational basis than
before.” He adds that better catalysts for steam reforming may reduce the cost
of producing fuels.

“This is the first time that atomic surface theory has led directly to
significant technological advances in catalysis,” comments David King, an atomic
surface chemist at the University of Cambridge. “These results are a new
˛őłŮ˛š°ůłŮ.”

For the animal experiments, Savio Woo of the Center for Gene Therapy
at Baylor College of Medicine in Houston and his colleagues first isolated
liver cells from transgenic mice that produce the human protein a1-antitrypsin
in their livers, from where it is secreted into the blood. ‘The liver cells
were then transplanted into mice which do not express the human protein,
but otherwise are genetically identical to the donors,’ says Woo. This was
done by injecting the cells into the portal vein, which carries blood to
the liver, or into the spleen, from where they migrate to the liver.

A few days later the human protein appeared in the mouse blood, showing
that the transplant had been successful. The protein’s level remained stable
in the animal for the rest of its natural life – 400 days. Similar experiments
with dogs and baboons were also successful.

Woo’s technique may one day be used to treat the metabolic disorder
phenylketonuria (PKU), in which the gene for the hepatic enzyme known as
phenylalanine hydroxylase (PAH) is defective. PAH normally converts the
amino acid phenylanaline into tyrosine, but in children where the enzyme
is missing phenylanaline accumulates in the body and causes severe mental
brain damage. Such children are normal at birth and can be treated with
a special diet that is low in phenylalanine but treatment has to start when
they are a few days old.

Another of Woo’s experiments involved a PAH-deficient mouse strain developed
by William Dove and colleagues at the University of Wisconsin in Madison.
Woo inserted the gene for mouse PAH into liver cells isolated from these
mice and found that this fully restored enzymic activity to the cells. Woo
intends to transplant these cells into the PAH-deficient mice to see whether
they can treat PKU in the animals.

Now Fred Ledley and his colleagues from the department of paediatrics
at Baylor College of Medicine are planning to test both methods in children
whose life is threatened due to acute liver failure caused by infectious
disease or metabolic disorders. Ledley will transplant normal liver cells
into a sick child with the aim of keeping the child alive until it is possible
to find a donor for a conventional liver transplant, or to give the child’s
own liver function time to recover.

‘A marker gene will be inserted into these liver cells,’ says Ledley.
‘The presence of the marker gene in the child’s liver will show whether
the transplantation is successful or not. In this way we hope to lay a clinical
groundwork for two new techniques: liver cell transplantation and liver
gene therapy.’

Woo and Ledley predict that clinical trials using gene therapy for metabolic
disorders such as PKU could start within eight years. Woo thinks the ultimate
applications could be far-reaching.