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Comparisons of joint surface curvature at the base of the thumb have long been made to discern differences among living and fossil primates in functional capabilities of the hand. However, the complex shape of this joint makes it difficult to quantify differences among taxa. The purpose of this study is to determine whether significant differences in curvature exist among selected catarrhine genera and to compare these genera with hominin fossils in trapeziometacarpal curvature. Two 3D approaches are used to quantify curvatures of the trapezial and metacarpal joint surfaces: (1) stereophotogrammetry with nonuniform rational B-spline (NURBS) calculation of joint curvature to compare modern humans with captive chimpanzees and (2) laser scanning with a quadric-based calculation of curvature to compare modern humans and wild-caught Pan, Gorilla, Pongo, and Papio. Both approaches show that Homo has significantly lower curvature of the joint surfaces than does Pan. The second approach shows that Gorilla has significantly more curvature than modern humans, while Pongo overlaps with humans and African apes. The surfaces in Papio are more cylindrical and flatter than in Homo. Australopithecus afarensis resembles African apes more than modern humans in curvatures, whereas the Homo habilis trapezial metacarpal surface is flatter than in all genera except Papio. Neandertals fall at one end of the modern human range of variation, with smaller dorsovolar curvature. Modern human topography appears to be derived relative to great apes and Australopithecus and contributes to the distinctive human morphology that facilitates forceful precision and power gripping, fundamental to human manipulative activities.

The discovery of fossil hand bones from an early human ancestor at Olduvai Gorge in 1960, at the same level as primitive stone tools, generated a debate about the role of tools in the evolution of the human hand that has raged to the present day. Could the Olduvai hand have made the tools ? Did the human hand evolve as an adaptation to tool making and tool use ? The debate has been fueled by anatomical studies comparing living and fossil human and nonhuman primate hands, and by experimental observations. These have assessed the relative abilities of apes and humans to manufacture the Oldowan tools, but consensus has been hampered by disagreements about how to translate experimental data from living species into quantitative models for predicting the performance of fossil hands. Such models are now beginning to take shape as new techniques are applied to the capture, management and analysis of data on kinetic and kinematic variables ranging from hand joint structure, muscle mechanics, and the distribution and density of bone to joint movements and muscle recruitment during manipulative behaviour. The systematic comparative studies are highlighting a functional complex of features in the human hand facilitating a distinctive repertoire of grips that are apparently more effective for stone tool making than grips characterising various nonhuman primate species. The new techniques are identifying skeletal variables whose form may provide clues to the potential of fossil hominid hands for one-handed firm precision grips and fine precision manoeuvering movements, both of which are essential for habitual and effective tool making and tool use.

With an interest in exploring the limits of relative cation/anion mobilities in nonaqueous electrolyte solutions, we have measured the diffusivities of Li-and F-containing species in 0.5 M solutions of the new lithium salt, lithium bis͑perfluoropinacolato͒ borate, LiBPFPB, which contains a giant anion with 24 fluorine atoms. Using the pulsed field gradient spin echo method on the NMR resonances of 7 Li and 19 F in the temperature range 30-95°C we find, for the first time in nonaqueous salt-in-molecular solvent solutions, lithium diffusivities that are higher than those of the anion-containing species. Furthermore, solutions in propylene carbonate ͑PC͒ appear to be fully dissociated, since the conductivities calculated from the Nernst-Einstein equation exceed the measured conductivities by only 23% at ambient temperature and 41% at 95°C. These values are comparable with those observed for molten salts such as LiNO 3 , NaNO 3 , and aqueous LiCl solutions. Since such deviations are known to be due to interionic friction alone, transport numbers for Li ϩ may be calculated from the diffusivities without correction for neutral species. We obtain a value of 0.55 for PC solutions at 50°C. In the lower dielectric constant 1,2-dimethoxyethane solutions the ratio of calculated to measured conductivity is much higher. Here it would appear that ion association is still a problem and must be corrected for in calculating the transport number. For this case we obtain the value 0.53. We discuss means of increasing this value toward unity and show that this must involve abandoning simple salt solutions as electrolytes.The optimal functioning of a high-rate discharge battery demands the achievement of very specific characteristics for the electrolyte. Its performance depends not only on the ionic conductivity of the electrolyte but also on a high cationic transport number, t ϩ , since this condition minimizes the overpotentials due to the increase of concentration gradients in the vicinity of the electrodes and the depletion of electrolyte inside porous electrodes. 1 However, values of t ϩ for lithium ions commonly found in nonaqueous solutions fall below 0.5. 2,3 Furthermore, much of the transport of lithium is unfruitfully performed by neutral species according to the large deviations from the Nernst-Einstein equation that are usually found. Extensive ion-pairing has so far been the source of diffusivity-based transport numbers that fall near 0.5. 3 In an effort to obtain better electrolytes we have been attempting to design systems which combine high lithium mobilities with high lithium transport numbers and low ion-pairing.In this paper we give evidence of some progress in this direction, using a combination of self-diffusivity and conductivity studies on solutions containing a new lithium salt reported recently, 4 lithium bis͓1,2-tetrakis͑trifluoromethyl͒ ethylenediolato (2-)-O,OЈ͔ borate, LiB͓OC͑CF 3 ͒ 2 ͔ 4 , or more simply, lithium bis͑perfluoropinacolato͒ borate ͑LiBPFPB͒, which has a particularly large perfluorinated anio...

We compare the physical properties and solution conductivities of three new lithium orthoborate salts with those of the well known slat lithium bis(trifluoromethanesulfony)imide LiTFSI. The three n ew lithium salts are lithium bis(perfluoropinacolato)borate (LiBPFPB), lithium bis(oxalato)borate (LiBOB) and lithium bis(malonato)borate (LiBMB). Computational models of the three orthoborate anions show that the borate oxygens in BPFPB − anion are the least exposed. The oxygens are electronically identical in BPFPB − , but not in the other anions. The three new lithium salts show conductivities that closely approach those of LiTFSI but show surprising and solvent-dependent orderings. The conductivity is nearly independent of the salt content in the salt concentration range of 0.5 ~ 1M, which is advantageous for their applications.

The development, mechanics, and pathology of the third carpometacarpal joint have been investigated in order to explain the unique presence in humans of a styloid process on the third metacarpal. Structure and functions of the joint are compared in a large series of Old World anthropoid hand skeletons, cadavers, and X-rays, and shown to differ in the three groups. Developmental anomalies reveal the source of the human styloid in a group of cells which fuse with the capitate in other Old World Anthropoidea. The absence of the process in Australopithecus afarensis and its presence in Neandertals suggest that an explanation for the evolution of the process may be sought in stresses on the hand in stone tool-use. Film analysis of stone tool-use shows that hammering and digging with hand-held stones direct forces on the palmar aspect of the metacarpal head. From a biomechanical analysis of these forces it may be seen that the styloid process prevents subluxation of the base. The effectiveness of the process in this function is reflected by the rarity of injury and arthritis in the region. Individuals lacking the process tend to undergo degeneration of bone at the joint. Since repetitive impulsive forces on joints are known to cause osteoarthritis, it is suggested that there may be a link between the increasing reliance of early hominids on manipulative behavior that stressed this region of the hand and the evolution of a structural pattern that protects the joint from these stresses.

This study investigates the morphological basis of differences between humans and chimpanzees in the kinematical and dynamical parameters of the musculature of the thumb. It is partly intended to test an hypothesis that human thumb muscles can exert significantly greater torques, due to larger muscle cross-sectional areas or to longer tendon moment arms or to both. We focus on the estimation of the potentials of thumb muscles to exert torques about joint axes in a sample of eight chimpanzee cadaver hands. The potential torque of a muscle is estimated by taking the product of a muscle's physiological cross-sectional area (an estimator of force) with its dynamical moment arm (derived from the slope of tendon excursion versus joint angular displacement, obtained during passive movements of cadaver thumb joints). Comparison of our results with similar data obtained for humans at the same Mayo Clinic laboratory shows significant differences between humans and chimpanzees in potential torque of most thumb muscles, those of humans generally exhibiting larger values. The primary reason for the larger torques in humans is that their average moment arms are significantly longer, permitting greater torque for a given muscle size. An additional finding is that chimpanzees and humans differ in the direction of secondary thumb metacarpal movements elicited by contraction of some muscles, as shown by differences in moment arm signs for a given movement in the same muscle. The differences appear to be related to differences in the musculo-skeletal structures of the trapeziometacarpal joint.