Waterfall Bluff is a rock shelter in eastern Pondoland, South Africa, adjacent to a narrow continental shelf that limited coastline movements across glacial/interglacial cycles. The archaeological deposits are characterized by well-preserved stratigraphy, faunal, and botanical remains alongside abundant stone artifacts and other materials. A comprehensive dating protocol consisting of 5 optically stimulated luminescence ages and 51 accelerator mass spectrometry 14C ages shows that the record of hunter-gatherer occupations at Waterfall Bluff persisted from the late Pleistocene to the Holocene, spanning the last glacial maximum and the transition from the Pleistocene to the Holocene. Here, we provide detailed descriptions about the sedimentary sequence, chronology, and characteristics of the archaeological deposits at Waterfall Bluff. Remains of marine mollusks and marine fish also show, for the first time, that coastal foraging was a component of some hunter-gatherer groups’ subsistence practices during glacial phases in the late Pleistocene. The presence of marine fish and shellfish further demonstrates that hunter-gatherers selectively targeted coastal resources from intertidal and estuarine habitats. Our results therefore underscore the idea that Pondoland's coastline remained a stable and predictable point on the landscape over the last glacial/interglacial transition being well positioned for hunter-gatherers to access resources from the nearby coastline, narrow continental shelf, and inland areas.

We derive mass changes of the Greenland ice sheet (GIS) for 2003–07 from ICESat laser altimetry and compare them with results for 1992–2002 from ERS radar and airborne laser altimetry. The GIS continued to grow inland and thin at the margins during 2003–07, but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s. The net balance changed from a small loss of 7 ± 3 Gt a−1 in the 1990s to 171 ± 4 Gt a−1 for 2003–07, contributing 0.5 mm a−1 to recent global sea-level rise. We divide the derived mass changes into two components: (1) from changes in melting and ice dynamics and (2) from changes in precipitation and accumulation rate. We use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation-driven changes to mass changes. Increased losses from melting and ice dynamics (17–206 Gt a−1) are over seven times larger than increased gains from precipitation (10–35 Gt a−1) during a warming period of ∼2 K (10 a)−1 over the GIS. Above 2000 m elevation, the rate of gain decreased from 44 to 28 Gt a−1, while below 2000 m the rate of loss increased from 51 to 198 Gt a−1. Enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers, as well as accelerating ice flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.

Energetic nitrogen implantation into austenitic stainless steel or nickel alloys leads to the formation of a very hard and wear resistant surface layer with an expanded lattice, while similar results are reported for selected martensitic steels. A comparison of the phase formation under identical process conditions at 380 °C using an austenitic (304) and a martensitic (420) steel grade (in an annealed ferrite/cementite condition) shows that the initial microstructure is retained in both of them. As the formation of dislocations and stacking faults cannot account for the dramatic hardness increase, the build-up of compressive stress is proffered as an explanation covering these two steel types. Furthermore the energetic nitrogen implantation apparently stabilizes the expanded lattice with suppressing the chemical transition to iron nitrides and, for steel 420, the metallurgical transition towards austenite at high nitrogen contents.

A detailed understanding of the physics of space-charge-dominated beams is vital in the design of heavy ion inertial fusion (HIF) drivers. In that regard, low-energy, high-intensity electron beams provide an excellent model system. The University of Maryland Electron Ring (UMER), currently being installed, has been designed to study the physics of space-charge-dominated beams with extreme intensity in a strong focusing lattice with dispersion. At 10 keV and 100 mA, the beam from the UMER injector has a generalized perveance as much as 0.0015, corresponding to that of proposed HIF drivers. Though compact (11 m in circumference), UMER will be a very complex device by the time of its completion (expected 2003). We present an update on the construction as well as recent experimental results.

Molybdenum-silicon (Mo-Si) multilayers for EUV lithography were prepared by ion beam sputter deposition at room temperature. The multilayer structure was determined by X-ray-diffraction and transmission electron microscopy. Textured molybdenum layers with preferential (110) orientation normal to the surface are observed. At the interfaces of all Mo-Si and Si-Mo pairs additional intermixing resulting in molybdenum silicide layers were noticed. These layers have a thickness of about 0.7 and 1.5 nm each, respectively. Due to this intermixing, the nominal thickness of the Mo and Si layers is reduced. The optical index contrast at the interface is also expected to decrease. This is in accordance with the obtained EUV reflectivity results of 64–65% at 13.4 nm which remains below the theoretical value of 74%. The formation of the silicide interface layers is discussed and an optimized deposition process focused on narrowing these transition layers is suggested.

Comments are made on the following question. Let m, n be positive integers and g a finite group. Suppose that for all choices of a subset of cardinality m and of a subset of cardinality n in g some member of the first commutes with some member of the second. Under what conditions on m, n is the group abelian?

A challenge by R. Padmanabhan to prove by group theory the commutativity of cancellative semigroups satisfying a particular law has led to the proof of more general semigroup laws being equivalent to quite simple ones.

A group G has all of its subgroups normal-by-finite if H / coreG(H) is finite for all subgroups H of G. These groups can be quite complicated in general, as is seen from the so-called Tarski groups. However, the locally finite groups of this type are shown to be abelian-by-finite; and they are then boundedly core-finite, that is to say, there is a bound depending on G only for the indices | H: coreG(H)|.

In this final contribution to the investigation of commutator laws in groups, we answer some of the questions left open in the previous two papers. The principal result is the independence of the Jacobi-Witt-Hall type laws from the so-called standard set of laws. The main results of the earlier papers are summarised. An interlude corrects some of the numerous printing errors in the second of our papers.

Certain central products of the binary polyhedral groups with finite cyclic groups are here shown to have presentations with two generators and two defining relations; this disproves a conjecture of the second author, stated in J. Austral. Math. Soc. Ser. A 38 (1985), 230–240.

Incoherent, inelastic neutron scattering has been used to study the vibrational spectra of tetramethylammonium montmorillonite and trimethylammonium vermiculite in the energy range 20–140 meV. For both systems peaks are observed due to the internal modes of the intercalate and to the excitations of the hydroxyl groups within the host layers. For the montmorillonite sample, it is found that the steric constraints imposed on the tetramethylammonium ion by the bounding clay layers contribute an additional 28 meV to the rotational barrier of the methyl groups. This additional barrier is shown to be strongly related to the volume that the tetramethylammonium ion occupies. For the trimethylammonium vermiculite sample normal mode analysis of the internal modes of the intercalated ion shows that the N-H bond is parallel to the c-axis of the host.

There are some well-known laws that the commutator satisfies in groups, and that go by some or all of the names Jacobi, Witt, Hall; and there are also some lesser-known laws. This is an attempt at an axiomatic study of the interdependence and independence of these laws.