Nearly Antiferromagnetic Fermi Liquids: A Progress Report

I describe recent theoretical and experimental progress in understanding the physical properties of the two dimensional nearly antiferromagnetic Fermi liquids (NAFL's) found in the normal state of the cuprate superconductors. In such NAFL's, the magnetic interaction between planar quasiparticles is strong and peaked at or near the commensurate wave vector, $Q \equiv (\pi,\pi)$. For the optimally doped and underdoped systems, the resulting strong antiferromagnetic correlations produce three distinct magnetic phases in the normal state: mean field above $T_{cr}$, pseudoscaling between $T_{cr}$ and $T_*$, and pseudogap below $T_*$. I present arguments which suggest that the physical origin of the pseudogap found in the quasiparticle spectrum below $T_{cr}$ is the formation of a precursor to a spin-density-wave-state, describe the calculations based on this scenario of the dynamical spin susceptibility, Fermi surface evolution, transport, and Hall effect, and summarize the experimental evidence in its support.Comment: LATEX + PS figures. To appear in the proceedings of the Euroconference on "Correlations in Unconventional Quantum Liquids," Evora, Portugal, October 199

INVESTIGATION ON THE CERVICAL SPINE MOTION

Several investigations on the problem of cervical spine motion describe the difficulties of measuring the movement exactly. Those models had to deal with the difficulties in fixation of the human head and to track the range of motion in degrees with respect to the three directions of movement; flexionlextension, lateral bending and rotation. The only objective method of measuring cervical spine movement and COlC1 or C11C2 displacements is the functional computer tomogram as described by Dvorak et al. The aim of our survey has been to identify differences between the "normaln and pathologic cervical spine (after whip leash injuries, disc diseases or spondylarthrosis in sport) as it relates to the range of movement and angular velocity. Two groups of 15 probants have been tested by a new computer-controlled setup. By using a three-dimensional motion-analysis-system special rigid-body software has been developed to calculate the cervical spine motion in all three coordinate directions. This represents the first time that it has been possible to obtain results about the movement and their time-derivations. These angles and the angular velocities were traced for 15 normal individuals and for 15 persons suffering with cervical spine problems. The setup for testing patients was no more than a small frame like sunglasses which gave exact information about the movement in space. This information gave accurate data which permitted calculation of the amount of motion concerning the patient's personal orientation in space and was additionally used to compute the coupled motions to the probants reference coordinate system. The present investigation demonstrated significant differences in the range of motion between normal individuals and patients with cervical spine problems in all defined direction. Our first conclusion so far is, that there are possibilities to measure those differences in cervical spine motion by the presented biomechanical measurement setup very easily. Furthermore, the setup is capable of providing accurate results about the range of motion, coupled motion and their time-derivations rapidly without the use of x-ray technology and x-ray exposition for the patient. These possibility and the good results are very important to judge problems after "ship leash injuries" and other cervical spine diseases in sport. The positive results raise the possibility that the technique may be employed to judge problems and other cervical spine injuries associated with sport. We conclude that the biomechanical measurement-setup presented here provides an easy method to measure differences in cervical spine motion

Redox properties and electron paramagnetic resonance spectroscopy of the transition state complex of Azotobacter vinelandii nitrogenase

AbstractNitrogenase is a two-component metalloenzyme that catalyzes a MgATP hydrolysis driven reduction of substrates. Aluminum fluoride plus MgADP inhibits nitrogenase by stabilizing an intermediate of the on-enzyme MgATP hydrolysis reaction. We report here the redox properties and electron paramagnetic resonance (EPR) signals of the aluminum fluoride-MgADP stabilized nitrogenase complex of Azotobacter vinelandii. Complex formation lowers the midpoint potential of the [4Fe-4S] cluster in the Fe protein. Also, the two-electron reaction of the unique [8Fe-7S] cluster in the MoFe protein is split in two one-electron reactions both with lower midpoint potentials. Furthermore, a change in spin-state of the two-electron oxidized [8Fe-7S] cluster is observed. The implications of these findings for the mechanism of MgATP hydrolysis driven electron transport within the nitrogenase protein complex are discussed

Revisiting Qualitative Data Reuse

Secondary analysis of qualitative data entails reusing data created from previous research projects for new purposes. Reuse provides an opportunity to study the raw materials of past research projects to gain methodological and substantive insights. In the past decade, use of the approach has grown rapidly in the United Kingdom to become sufficiently accepted that it must now be regarded as mainstream. Several factors explain this growth: the open data movement, research funders’ and publishers’ policies supporting data sharing, and researchers seeing benefits from sharing resources, including data. Another factor enabling qualitative data reuse has been improved services and infrastructure that facilitate access to thousands of data collections. The UK Data Service is an example of a well-established facility; more recent has been the proliferation of repositories being established within universities. This article will provide evidence of the growth of data reuse in the United Kingdom and in Finland by presenting both data and case studies of reuse that illustrate the breadth and diversity of this maturing research method. We use two distinct data sources that quantify the scale, types, and trends of reuse of qualitative data: (a) downloads of archived data collections held at data repositories and (b) publication citations. Although the focus of this article is on the United Kingdom, some discussion of the international environment is provided, together with data and examples of reuse at the Finnish Social Science Data Archive. The conclusion summarizes the major findings, including some conjectures regarding what makes qualitative data attractive for reuse and sharing. </jats:p

A novel S = 3/2 EPR signal associated with native Fe-proteins of nitrogenase

In addition to their g = 1.94 EPR signal, nitrogenase Fe-proteins from Azotobacter vinelandii, Azotobacter chroococcum and Klebsiella pneumoniae exhibit a weak EPR signal with g [congruent with]5. Temperature dependence of the signal was consistent with an S = 3/2 system with negative zero-field splitting, d = -5 +/- 0.7 cm-1. The ms, = +/- 3/2 ground state doublet gives rise to a transition with geff = 5.90 and the transition within the excited ms = +/- 1/2 doublet has a split geff = 4.8, 3.4. Quantitation gave 0.6 to 0.8 spin mol-1 which summed with the spin intensity of the S = 1/2 G = 1.94 line to roughly 1 spin/mol. MgATP and MgADP decreased the intensity of the s = 3/2 signal with no concomitant changes in intensity of the s = 1/2 signal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25566/1/0000108.pd

Tibial stress fracture after computer-navigated total knee arthroplasty

A correct alignment of the tibial and femoral component is one of the most important factors determining favourable long-term results of a total knee arthroplasty (TKA). The accuracy provided by the use of the computer navigation systems has been widely described in the literature so that their use has become increasingly popular in recent years; however, unpredictable complications, such as displaced or stress femoral or tibial fractures, have been reported to occur a few weeks after the operation. We present a case of a stress tibial fracture that occurred after a TKA performed with the use of a computer navigation system. The stress fracture, which eventually healed without further complications, occurred at one of the pinhole sites used for the placement of the tibial trackers

Navigated cup implantation in hip arthroplasty: A meta-analysis

Background and purpose Many studies have suggested that navigation-based implantation can improve cup positioning in total hip arthroplasty (THA). We conducted a systematic review and meta-analysis to compile the best available evidence, and to overcome potential shortcomings because of small sample sizes in individual studies