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Background The authors describe the application of a new exoscope that offers 3-dimensional (3D) visualization in cranial and spinal neurosurgery in detail. Methods Five cranial and 11 spinal procedures were performed with a 3D exoscope. Instrument handling, repositioning of the exoscope, handling of the image control unit, the adjustment of magnification and focal length, the depth perception, the image quality, the illumination, and the comfort level of the posture during the procedure were assessed via a questionnaire. Results The following procedures were performed: Microvascular decompression (n = 1), craniotomy and tumor resection (n = 4), anterior cervical discectomy and fusion with cervical plating (n = 2), cervical laminectomy and lateral mass fixation (n = 1), shear cervical lateral mass osteosynthesis (n = 1), lumbar canal decompression (n = 1), transforaminal lumbar interbody fusion (n = 2), thoracic intraspinal extradural tumor resection (n = 1), and lumbar discectomy (n = 3). Instrument handling, the intraoperative repositioning and handling of the VITOM-3D, and the comfort level of the intraoperative posture was rated excellent in 100% of procedures. The image quality was rated equal to the operating microscope in 68.75% of procedures. None of the procedures had to be stopped because of technical problems. No surgical complications were noted that could be related to the use of the exoscope. Conclusions The 3D-exoscopic system is safe and effective tool to perform spinal procedures and less demanding cranial procedures. The image quality and 3D visualization were comparable with the operating microscope. The technique harbors the unique advantage of excellent comfort for the involved surgical team during the procedure.

Background Long-term clinical results after anterior cervical discectomy and fusion (ACDF) with an autologous iliac crest are rare. The purpose of this study was to assess this, with special focus on pain, functional outcome, and repeat surgery for adjacent segment disease (ASD). Methods Hospital records of 212 patients who were affected by degenerative cervical disc disease and treated by the Smith-Robinson technique were reviewed. Information about diagnosis, surgery, pre- and postoperative clinical process, and complications was analyzed. Patients were reviewed with a standardized questionnaire including the current neurologic status, Neck Disability Index, EQ-5D, Patient Satisfaction Index, Odom criteria, and limitations in quality of life. Results Ninety-five patients with a mean follow-up of 28 years were evaluated. ACDF was performed at 1 level in 67 and 2 levels in 28 patients. Ninety-two patients reported pain before surgery and 68 patients remained pain free and did not require second surgery. At follow-up, the mean Neck Disability Index was 14%, and mean EQ-5D score was 5. Postoperatively, 96.8% of patients were satisfied and 84.2% of patients reported good to excellent functional recovery. One patient had a hairline fracture at the iliac crest donor site. Fourteen patients underwent second surgery because of degenerative changes, including 11 at the symptomatic ASD. Conclusions ACDF yields significant decrease in pain, a significant increase in function, and a high degree of patient satisfaction. Overall prevalence for ASD was 12.0% after 25 years. Patients with reoperation had similar clinical outcome regarding pain, compared with patients without reoperation.

Background Anterior cervical discectomy and fusion with plate stabilization (ACDF+PS) is an accepted surgical procedure. We sought to evaluate the long-term clinical results of ACDF+PS with a special focus on pain, functional outcome, and adjacent segment disease. Methods Retrospectively, 139 patients who underwent ACDF+PS were reviewed with a standardized questionnaire including the current neurologic status, Neck Disability Index, EuroQuol-5 Dimension, Patient Satisfaction Index, Hospital Anxiety and Depression Scale, the Odom criteria, complications at the iliac crest donor side, and limitations in quality of life. Results Mean follow-up time was 22 years (range: 17–34 years). Sixty five (46.8%) patients were evaluated by completed questionnaires, and 74 (53.2%) did not participate. Forty-six patients attended a physical examination. ACDF+PS were performed at 1 level in 28 patients, at 2 levels in 29 patients, and at 3 levels in 8 patients. Fifty (83.3%) of the patients with preoperative pain remained free of pain and did not require another procedure as the result of degenerative cervical disease. The mean NDI was 14%; according to the Odom criteria 86.2% of patients reported good-to-excellent functional recovery. A total of 100% of patients were satisfied or very satisfied with their outcome and would decide to undergo ACDF+PS again. Two developed adjacent segment disease and needed a second procedure. Conclusions ACDF+PS resulted in a significant increase in function, pain relief, and to a high degree of patient satisfaction. The rate for symptomatic adjacent segment disease was 4.5% after 20 years' follow-up.

A steady-state, variable-density, 2-layer, ocean model (VLOM) is used to investigate basic dynamics of the Atlantic meridional overturning circulation and Southern Ocean. The domain consists of idealized (rectangular) representations of the Atlantic, Southern, and Pacific Oceans. The model equations represent the depth-averaged, layer-1 response (except for one solution in which they represent the depth-integrated flow over both layers). To allow for overturning, water can cross the bottom of layer 1 at the velocity w e = w d + w m + w n , the three parts representing: interior diffusion w d that increases the layer-1 thickness h throughout the basin, mixed-layer entrainment w m that ensures h is never less than a minimum value h m , and diapycnal (cooling) processes external to the basin w n that adjust h to h n . For most solutions, horizontal mixing has the form of Rayleigh damping with coefficient ν , which we interpret to result from baroclinic instability through the closure, V ∗ = - ( ν / f 2 ) ∇ P , where ∇ P = ∇ 1 2 g ′ h 2 is the depth-integrated pressure gradient, g ′ is the reduced-gravity coefficient, and ν is a mixing coefficient; with this interpretation, the layer-1 flow corresponds to the sum of the Eulerian-mean and eddy-mean ( V ∗ ) transport/widths, that is, the “residual” circulation. Finally, layer-1 temperature cools polewards in response to a surface heat flux Q, and the cooling can be strong enough in the Southern Ocean for g ′ = 0 south of a latitude y 0 , in which case layer 1 vanishes and the model reduces to a single layer 2. Solutions are obtained both numerically and analytically. The analytic approach splits fields into interior and boundary-layer parts, from which a coupled set of integral constraints can be derived. The set allows properties of the circulation (upwelling-driven transport out of the Southern Ocean M , downwelling transport in the North Atlantic, transport of the Antarctic Circumpolar Current) and stratification (Atlantic thermocline depth, and the latitudes, y ′ and y 0 , where h thins to h m or layer 1 vanishes in the Southern Ocean) to be evaluated in terms of model forcings (Southern-Ocean wind strength τ a , Q , entrainment due to w d ), processes ( ν , V ∗ in the Southern Ocean, northern sinking, upwelling within the Atlantic Subpolar Gyre), and to the presence of the Pacific Ocean. A hierarchy of solutions is reported in which forcings and processes are individually introduced. The complete solution set includes a wide variety of solution types: with M > 0 and M ⩽ 0 ; with and without wind forcing; with, without, and for two parameterizations of northern-boundary sinking that represent cooling external to and within the North Atlantic; for a wide range of ν and τ a ; and for different closures. Novel aspects of the model and solutions include the following: use of VLOM, which allows Q forcing to be introduced realistically; the aforementioned closure, which allows V ∗ to be determined when layer 1 represents both the surface mixed layer ( h = h m ) and the depth of subsurface isopycnals ( h > h m ); latitude y ′ , where layer 1 outcrops in the Southern Ocean, being internally determined rather than externally specified; and a boundary layer, based on Gill’s (1968) solution, that smoothly connects the Southern- and Atlantic-Ocean responses across the latitude of the southern tip of South America. Finally, some solutions in the set are comparable to solutions to idealized, ocean general circulation models (OGCMs); in these cases, our solutions provide insight into the underlying dynamics of the OGCM solutions, for example, pointing toward processes that may be involved in eddy saturation and compensation.

Objective 3D exoscopic visualization in neurosurgical procedures is of interest for several reasons. The VITOM-3D exoscopic system is cheaper compared to the operating microscope (OM) and offers each person involved in the procedure the same image of the operative field. Little is known of limitations of this visualization technique. Patients and methods : Prospectively, a consecutive series 34 procedures were assessed with focus on the following aspects: intraoperative limitation and the cause for a switch to the OM or endoscopy. A standardized questionnaire was answered by each individual involved in the procedure to assess the image quality, illumination, and magnification of the operative field. Intraoperative video recording and pre- and postoperative MRI and CT-scan were analyzed to assess the dimensions of the surgical approach. Results Sixteen cranial and 18 spinal procedures (10 intra-axial, 6 extra-axial, 6 cervical, and 12 lumbar) were performed by seven neurosurgical attendings, twelve residents and twelve scrub nurses who all completed a standardized questionnaire after each procedure. Handling and identification of anatomical structures was rated equal or superior to the OM in 62 % and over 80 % of cases, respectively. The illumination and magnification of the operative field on the surface was rate in equal od superior in all cases and on the depth it was rated inferior to the OM over 60 % of cases. In one spinal and five cranial procedures a switch to the OM or endoscope were performed for the following reasons: poor illumination (4 cases), tissue identification (1 case), need for fluorescence imaging (1 case). Conclusion 3D exoscopic visualization using the VITOM-3D is best suited for spinal procedures and for extra-axial cranial procedures. In case of small approach dimensions, the illumination and magnification of the depth of the operative field is rated inferior to the OM which resulted in difficulty of tissue identification and a switch to the OM.

Lumbar disc herniation (LDH) is a common degenerative disease, and up to 10% of LDH migrates into the so-called "hidden zone." The traditional interlaminar approach carries the risk of subsequent instability due to osseous destruction by reaching the hidden zone and exposing the nerve root. In the 1990s, the first reports were published on the open microsurgical "translaminar approach" (TLA) for the resection of migrated LDH with the intention to minimize osseous destruction. However, the open technique still had the disadvantage of soft-tissue and muscle dissection. Endoscopic tubular procedures were developed to reduce approach-related muscle trauma. Endoscopic tubular surgery combines the bimanual microsurgical technique with continuous endoscopic visualization of the surgical field. The high-definition endoscopic visualization allows for excellent illumination and identification of tissue and anatomical structures. The rate of clinical success for the treatment of migrated LDH via endoscopic TLA has been reported to be up to 95%. However, endoscopic TLA has not been analyzed extensively, and reports with a detailed description are rare. The purpose of the present video is to demonstrate endoscopic tubular TLA and resection of a migrated LDH. This is the case of a 62-year-old man with right-sided leg pain and quadriceps paresis due to LDH that migrated behind the L3 vertebral body. Special focus is given to the planning of the skin incision and the trajectory toward the disc herniation. Furthermore, the dissection and extraction of large disc herniation are explained in detail.

Consider a particle which is randomly accelerated by Gaussian white noise on the half line x>0, with an absorbing boundary at x=0. The nonequilibrium statistics of this system was analyzed exactly by McKean in 1963. Recent results for two other boundary conditions of physical interest will be reviewed. In the case of a partially absorbing boundary, the randomly accelerated particle is absorbed, on arriving at x = 0 , with probability 1−p and reflected elastically with probability p. In the case of an inelastic boundary, the velocities of the particle just after and before striking the boundary satisfy vf=−rvi, where r is the coefficient of restitution. The absorption of a particle moving between two boundaries and some related results for confined semi-flexible polymers, which have similar statistical properties, will also be discussed.

Fluorine- and tungsten-doped vanadium dioxide (VO2) is a promising coating material for applications as energy-conserving windows. We prepared VO2 films simultaneously co-doped with fluorine and tungsten and report on the results of optical measurements and photoelectron spectrometry. A comparison is given to single-element doping. Clear evidence for an interaction of fluorine and tungsten in VO2 is found in the switching behaviour at the semiconductor-to-metal phase transition. An explanation is given based on two different effects of fluorine incorporation observed in the ultraviolet photoelectron spectrometry results. Concerning other film properties, the two elements act independently of each other.

Thin CuInSe2 films on glass substrate and solar cells were processed using the ultrasound treatment technique (UST). The SIMS measurements on the films showed a strong reduction of the Na-signal after the UST, which is most likely caused by ultrasonically induced chemical reaction of the mobile sodium ions. The change of the solar cell efficiency due to the UST depends on the initial efficiency. For the cells with efficiencies below 10% relative improvements of up to 50% are observed. On the contrary, the cells with higher efficiencies remain stable after the UST. In addition, parameters of CuInSe2 cells affected by the UST show the relaxation.

Thermochromic tungsten- and fluorine-doped vanadium dioxide films, which are in discussion as intelligent window coatings, were deposited by reactive sputtering. Results of optical measurements and photoelectron spectrometry (XPS, UPS) at low doping levels (≤2.6%) are presented, and together with structural properties they can be well correlated. By applying antireflective coatings the transmittance of films in the visible spectral range may be enhanced to more than 60% with fairly good switching characteristics at room temperature in the case of tungsten doping.

Hilhorst and van Leeuwen showed how to calculate boundary properties of the Ising model on the triangular lattice by iterating a mapping based on the star–triangle transformation. We apply this approach to the Ising model with homogeneous initial couplings in both the semi-infinite and strip geometries. Several exact results for the boundary correlation length and the magnetization are reproduced. The correlation-dimensionality transition for enhanced edge couplings (dual of Abraham’s interface-unbinding transition) is also considered.

The two-dimensional critical O( N ) model with ordinary, extraordinary, and special boundary conditions is analyzed with conformal-invariance methods. Contrary to an earlier conjecture, the energy density does not vanish at an edge with special boundary conditions. Exact expressions for the energy-energy correlation function in the half-space are given for all three boundary conditions. For several sets of mixed boundary conditions the Casimir contribution to the free energy in the strip geometry and the profile of the energy density are calculated.

We consider the two-dimensional critical Ising model with a defect line of strength μ. The non-universal correlation functions 〈 ϵ 1 … ϵ n 〉 μ and 〈 Tϵ 1 … ϵ n 〉 μ are calculated for arbitrary μ and n . Here ϵ is the energy density, and T is the stress-energy tensor. The results are consistent with degeneracy of the energy density at level 2 in conformal-invariance theory.

Conformal-invariance methods are applied to semi-infinite two-dimensional critical systems defined on the upper half-plane with different boundary conditions a and b on the positive and negative x-axis. (The half-space with ab boundary conditions is equivalent, under a conformal mapping, to a strip with boundary conditions a and b on opposite edges.) The conformal Ward identity is derived. The n-point correlation function in the system with mixed boundary conditions follows from the same differential equations as a particular bulk (2n + 2)-point correlation function. We calculate all density profiles 〈φ(r)〉ab determined by the condition of degeneracy at levels 2 and 3. The profiles and pair correlation functions of the magnetization and the energy density in the Ising model with + − and +f (fixed-free) boundary conditions are obtained. Corresponding results for profiles in the Q-state Potts model are given. We also derive some useful general expressions for bulk four-point correlation functions involving operators degenerate at levels 2 and 3.

The utility of photochemical methods for the directed synthesis of mixed-metal metal clusters has been explored. The 366 nm photolysis of a solution containing [PPN] [Co(CO)4] (PPN = (Ph3P)2N+) and Os3(CO)12 gives the new cluster [PPN][CoOs3(CO)13] in 33% yield. Irradiation of a mixture of Fe(CO)5 and H2Os3(CO)10 yields H2FeOs3(CO)13 in 95% yield, and photolysis of Ru3(CO)12 in the presence of H2Os3(CO)10 gives the new cluster H2RuOs3(CO)13. Details of these syntheses, their probable mechanisms, and the characterization of the new compounds are discussed.

With conformal-invariance methods we calculate the energy-energy correlation function of the semi-infinite two-dimensional O(N) model with −2 ⩽ N ⩽ 2. Boundary conditions corresponding to ordinary, extraordinary, and special surface critical behaviour are considered. The crossover exponent φ of the special transition has the value φ = 1 2 . Particular attention is given to the limit N → 0, corresponding to the self-avoiding walk or polymer.

A kinetic equation describing the growth of a crystal is formulated in the spirit of the time-dependent Ginzburg-Landau theory. The equation, which is applicable to two and three-dimensional problems, takes into account the anisotropy of the edge free energy γ and of a transport coefficient D as well as spatial and temporal variations in the chemical-potential difference. Anisotropic expressions for γ and D are obtained from a microscopic model. Numerical solutions of the generalized kinetic equation are presented which show the influence of the anisotropy on the two-dimensional growth spiral of a screw dislocation.

The profiles of the order parameter and of other local densities in confined systems at the bulk critical temperature are considered. For a great variety of two-dimensional confined geometries and for spherical boundaries in general dimension d, conformal invariance completely determines the functional form of the profile when a uniform scale-invariant boundary condition is imposed. The analytic expression for the profile in a two-dimensional strip of semi-infinite length and finite width implies the surface scaling dimension xs = 2. The exact magnetization profile in an Ising strip at the bulk critical temperature with spins on opposite edges fixed in opposing directions is derived with conformal-invariance methods.

Although scattering phase shifts reveal that the interaction of two free 3He atoms with the momenta and spins of quasi-particles in liquid 3He is attractive, the experimental spin-averaged effective quasi-particle interaction (Fs) defined in Landau's Fermi-liquid theory is repulsive in liquid 3He. To understand the role of many-body effects in the repulsive interaction, we have calculated the bulk properties of liquid 3He using the Bethe-Goldstone method and using Goldstone perturbation theory. The compressibility yields a value for F0s, the angular average of Fs. The potential used in our calculations is a hard-core square-well potential adjusted to approximate the phase shifts of the de Boer 6–12 potential. The properties we computed with the Bethe-Goldstone method give good agreement with experiment for effective masses m B ∗ between 1.0 and 1.4 times the true mass. We were unable to determine m B ∗ self-consistently. In liquid 3He three-body correlations are expected to be important. Using techniques developed for nuclear matter by Bethe and his co-workers, we estimated all two and three-body Goldstone diagrams. The properties we computed are in very good agreement with experiment. Since the net three-body energy is obtained in our calculation by adding repulsive and attractive contributions much larger in absolute value than their sum, these numbers should not be taken too seriously. Three-body diagrams contribute most of the binding energy in our calculation. The three-body repulsive energy is about 60% of the two-body repulsive energy. We describe qualitatively how the Pauli principle helps suppress the contributions of higher clusters. As particles are added to a self-bound many-body system or a system under pressure, the binding energy per particle decreases. Those particles originally present are rearranged into an “excited” state. In both the Bethe-Goldstone and Goldstone-perturbation-theory calculations, the rearrangement contributions are large enough to make the calculated effective quasi-particle interaction repulsive.

Formulae relating the binding energy of a Λ particle in nuclear matter to single-particle Green functions of the Λ particle are derived and discussed.