Robert F. Marzke

Evolution of the human hand: approaches to acquiring, analysing and interpreting the anatomical evidence

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.

Structures of Orthoborate Anions and Physical Properties of Their Lithium Salt Nonaqueous Solutions

We compare the physical properties and solution conductivities of three new lithium orthoborate salts with those of the well-known salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The three new lithium salts are lithium bis(perfluoropinacolato)borate (LiBPFPB), lithium bis(oxalato)borate, 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 0.5-1 M, which is advantageous for their applications. Self-diffusivity measurements for 7 Li. 19 F, and 1 H are presented and are consistent with the very high ionic dissociation levels proposed for these salts based on other evidence. The lithium-ion transport number at room temperature for LiBPFPB in nonaqueous solutions exceeds 0.5 and for LiBMB is about 0.4.

High Li + Self-Diffusivity and Transport Number in Novel Electrolyte Solutions

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 bis(perfluoropinacolato) 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 arc higher than those of the anion-containing species. Furthermore, solutions in propylene carbonate (PC) 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 LiCI solutions. Since such deviations are known to be due to interionic friction alone, transport numbers for Li + may be calculated from the diffusivities without correction for neutral species We obtain n 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 he 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.

Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins

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.

Chimpanzee thumb muscle cross sections, moment arms and potential torques, and comparisons with humans

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 muscles 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.

LiMOB, an Unsymmetrical Nonaromatic Orthoborate Salt for Nonaqueous Solution Electrochemical Applications

Synthesis, characterization, ionic conductivity, electrochemical stability, and lithium-ion transport number of an asymmetric version of the successful orthoborate lithium salt lithium bis(oxalato)borate (LiBOB), are described. The salt, lithium (malonato oxalato) borate (LiMOB), is thermally stable up to 273°C. It is poorly soluble in common organic solvents such as 1,2-dimethoxyethane, tetrahydrofuran, acetonitrile, dimethyl carbonate, and propylene carbonate, but has moderate solubility in γ-butyrolactone (GBL) and N,N-dimethylformamide (DMF), and high solubility in dimethyl sulfoxide (DMSO). The 0.5 M solutions of LiMOB in GBL, DMSO, and DMF show high conductivities (5.0 X 10 -3 S cm -1 , 5.1 × 10 -3 S cm -1 , and 11.8 X 10 -3 S cm -1 at 25°C, respectively) relative to most 0.5 M nonaqueous solutions. Even the room temperature conductivity of the 0.08 M LiMOB-PC solution is close to 10 -3 S cm -1 . The conductivities of LiMOB solutions are close to those of LiBOB solutions, which has been demonstrated in recent studies to be a successful substitute for LiPF 6 in lithium-ion batteries. The cyclic voltammograms show that LiMOB solutions in PC and GBL have electrochemical stability as high as 4.3 V vs. Li + /Li. The lithium-ion transport number at room temperature for 0.5 M LiMOB in DMSO-d 6 was 0.36, obtained from self-diffusivity measurement by the pulsed field gradient spin echo nuclear magnetic resonance technique. The highest occupied molecular orbital energy, which is usually correlated with electrochemical stability has been calculated, and electrostatic potential maps for the new anion and its fluorinated derivatives are presented. They suggest that the fluorinated analogue of LiMOB should be more stable and more soluble, and may have unique properties.

Aerosol synthesized mesoporous silica containing high loading of alumina and zirconia

Mesoporous silica particles with high loadings of Al (Si/Al molar ratio 20 to 2) and Zr (Si/Zr molar ratio 37 to 5) were synthesized by evaporation induced self assembly (EISA) using an aerosol route. The aerosol synthesis process allows us to produce mesoporous silica particles with a high loading of heteroelements (Al or Zr) while retaining uniformity of composition and an ordered pore structure. 27Al NMR TRAPDOR experiments indicate that Al is in close proximity to Si, within the mesoporous silica structure. The submicron particles are spherical and consist of interconnected, hexagonally ordered domains of pores. The hydrothermal stability of these composite mesoporous silica particles was tested in 10 mol% water vapor at various temperatures (500 °C to 750 °C) and also in boiling water. Pure mesoporous silica particles were not stable under hydrothermal treatment and their surface area dropped from 1300 m2 g−1 to 300 m2 g−1 after treatment at 750 °C in steam. In contrast, the aluminium and zirconium containing powders retained a surface area of 800 m2 g−1 after similar treatment. The improvement in hydrothermal stability was found to be dependent on Al and Zr content. The three-dimensional interconnected network of pores, higher loading of heteroelement and their hydrothermal stability, make these spherical particles attractive as adsorbents and as supports for heterogeneous catalysts.

Three-Dimensional Quantitative Comparative Analysis of Trapezial-Metacarpal Joint Surface Curvatures in Human Populations

PURPOSE Trapezial-metacarpal (TM) joint surfaces appear to be shallower in Asian than in white postmortem specimens, and the frequency of TM osteoarthritis seems to be substantially lower in Asian TM joints. This study tested the hypothesis that there are significant differences among human populations in TM joint surface curvature and that populations of Asian descent have less curvature than those of recent European descent. METHODS The sample included trapeziums and first metacarpals from skeletons of 80 individuals of recent European and Asian descent and from skeletons of 34 African and 9 Australian aboriginal individuals. We scanned the surfaces using a laser digitizer to generate 3-dimensional models of each articular surface. We calculated dorsovolar, radioulnar, and root mean square curvatures by fitting modeled quadric surfaces to the TM joint surfaces. We tested pairwise comparisons of mean curvatures between populations for statistical significance using a standard resampling method (ie, bootstrapping). We also made pairwise comparisons of mean curvatures between males and females for a combined African and European sample. RESULTS Mean dorsovolar metacarpal curvature was significantly higher in the European sample than in the Asian, African, and Australian samples. Mean root mean square curvature of the trapezial surface was significantly higher in the European sample than in the Asian sample. The European sample had the highest root mean square and dorsovolar trapezial curvatures of all the populations. We found no significant differences between male and female specimens. CONCLUSIONS A tendency toward higher mean dorsovolar curvature of both the metacarpal and trapezial surface in the European sample may help to explain the higher frequency of TM osteoarthritis reported in Europeans. CLINICAL RELEVANCE The greater TM curvatures affect basal thumb joint mechanics in thumb opposition and therefore may be a factor in the development of osteoarthritis at this joint in Europeans.

Interaction of muonium with oxygen on silica powder surfaces

Results of the first μSR studies using Merck FO Optipur silica powder, which contains paramagnetic impurities at the ppb level and has a surface area of 610±20 m2/g. are reported. Above 20 K, the transverse field muonium relaxation rate is roughly constant at 0.5 μs−1. Upon the addition of oxygen at ppm levels, the relaxation rate increases linearly with O2 concentration in the temperature range from 40–100 K yielding two-dimensional depolarization rate constants on the order of 10−4 cm2 molecule−1 s−1. As the temperature is increased further, both oxygen and muonium desorb from the surface yielding a three-dimensional rate constants at 300 K of 3.1(3)×10–10−10 cm3 molecule−1 s−1, in agreement with the gas phase value. Longitudinal field measurements suggest that MuO2 is formed and is able to spin exchange with other oxygen molecules.

μSR Investigation of ethyl radicals adsorbed on silica

AbstractμSR spectra of the ethyl radical adsorbed on porous silica were observed in transverse and in longitudinal magnetic fields in the temperature range 190–298 K. The line widths reflect the dynamic partial averaging of the hyperfine anisotropy due to reorientation and surface diffusion.