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Jim Al-Khalili describes the new experiments and theories exploring whether quantum tunnelling of hydrogen causes mutations in our DNA.

There are more than a billion Muslims in the world today – over a fifth of the world's total population – spread over many more than the 57 member states of the Organisation of the Islamic Conference (OIC) in which Islam is the official religion. These include some of the world's wealthiest nations, such as Saudi Arabia and Kuwait, as well as some of the poorest, like Somalia and Sudan. The economies of some of these countries – such as the Gulf States, Iran, Turkey, Egypt, Morocco, Malaysia and Pakistan – have been growing steadily for a number of years, and yet, in comparison with the West, the Islamic world still appears somewhat disengaged from modern science.

A quark-model framework for studying nuclear medium effects on nucleon resonances is described and applied here to pion photoproduction on the deuteron, which is the simplest composite nucleon system and serves as a first test case. Pion photoproduction on nuclei is discussed within a chiral constituent quark model in which the quark degrees of freedom are explicitly introduced through an effective chiral Lagrangian for the quark-pseudoscalar-meson coupling. The advantage of this model is that a complete set of nucleon resonances can be systematically included with a limited number of parameters. Also, the systematic description of the nucleon and its resonances at quark level allows us to self-consistently relate the nuclear medium's influence on the baryon properties to the intrinsic dynamic aspects of the baryons. As the simplest composite nucleus, the deuteron represents the first application of this effective theory for meson photoproduction on light nuclei. The influence of the medium on the transition operators for a free nucleon is investigated in the Delta resonance region. No evidence is found for a change of the Delta properties in the pion photoproduction reaction on the deuteron since the nuclear medium here involves just one other nucleon and the low binding energy implies low nuclear density. However, we show that the reaction mechanism is in principle sensitive to changes of Delta properties that would be produced by the denser nuclear medium of heavier nuclei through the modification of the quark model parameters., Revtex, 8 pages, 4 figures

While many physicists regard the subject of time travel as having no place in serious scientific discussion and teaching, I will show that, on the contrary, this is just the topic to fire the imagination, and it provides an ideal opportunity to introduce some of the ideas behind our most beautiful and fundamental theories about the nature of space and time. The mathematics, if and when required, can be made simple to follow, and the logical steps in the explanations are, while counter-intuitive, perfectly straightforward.

At school we are taught that an atom consists of electrons orbiting around a nucleus of tightly packed protons and neutrons. At university I learned that these nucleons are confined to the nucleus with an average binding energy of 8 MeV. For my PhD I studied the simplest composite nucleus, the deuteron, in which a proton and a neutron are loosely bound by an energy of just 2 MeV. This weak binding explains why the deuteron is much larger than the α-particle, which has four nucleons but is much more strongly bound. so, contrary to our school-day physics, nucleons do not have to be closely packed to be bound.

A semi-phenomenological model is constructed for the 6Li(p eta )7Be reaction using cluster decomposition models for the 6Li and 7Be nuclei. Wavefunctions derived from potential model descriptions of these two nuclei give rise to form factors which are too small to fit the new experimental data. On the other hand, form factors deduced from experimental data on the analogous 6Li(p, pi +)7Li and 6Li(d,p)7Li single-nucleon transfer reactions at high momentum transfers give a plausible description.

Arabic science has long made valuable contributions to mathematics and astronomy, Jim Al-Khalili calls for reforms to foster another "golden age".

A loose interpretation of the second law of thermodynamics is that "there is no such thing as a free lunch". And so it is with energy production. If you burn things, you get greenhouse gases and asthma-triggering particulates. If you build dams, you destroy the ecology of entire valleys. Nuclear power generation is no exception. If you carry out controlled fission, you get long-lived radioactivity – and lots of it.

Atomic nuclei are classified according to the number of protons and neutrons they contain. Most of the 7000 or so nuclides that are possible are highly unstable, and many are only now being studied for the first time. On the other hand, it has been known for many years that nuclides containing "magic" numbers (2, 8, 20, 28, 50, 82 and 126) of protons or neutrons are unusually stable. However, three international teams of nuclear physicists have recently found new exceptions to this rule. They have shown that the old magic numbers disappear, and new ones appear, in certain exotic nuclei.

In his "Lateral thoughts" article, Jonathan Dowling sees himself as impartial and not aligned to any particular interpretation of quantum mechanics–be it the Copenhagen, the many-worlds or the Bohmian interpretation (November 2001 p64). He explains his argument with the amusing metaphor of a ball trapped under the wall-to-wall carpet of his apartment. The ball, which represents the "weirdness" of quantum mechanics, can be pushed into different rooms (each corresponding to a different interpretation) but never removed.

The role of the spin dependence associated with Pauli-principle-induced break-up is studied quantitatively in the case of intermediate-energy deuteron elastic scattering from a 58Ni target. The magnitude of the momentum-dependent Tp tensor interaction, calculated using realistic theoretical models of the nucleon-nucleon interaction, is shown to pass through a local maximum in the region of 400 MeV incident deuteron energy. Comparison of numerical calculations with the available experimental data at this energy shows that the Pauli mechanism is not responsible for the outstanding discrepancies between theory and experiment.