Measuring 3D pyroelectric distributions with high resolution in thin films by a laser scanning microscope.

A laser scanning microscope for measuring 3D pyroelectric distributions inside thin vinylidene fluoride-trifluoroethylene copolymer films using the Laser Intensity Modulation Method was developed. The setup consists of a laser unit, a laser driver, an xyz-stepper motor unit, a transimpedance amplifier, and a lock-in amplifier. The focus lens at the laser unit is fixed by magnetic levitation and can correct a defocusing of the system or a tilt of the sample surface. It has been demonstrated in different samples that the system has a lateral resolution of 1 µm for measuring the topological surface structure or the pyroelectric distributions. The self-developed laser driver and transimpedance amplifier combined with a fast lock-in amplifier are able to measure small pyroelectric currents and their variation inside a pyroelectric sample in the range of some 1 pA. The maximum measure frequency of 4 MHz and the fast lock-in make it possible to measure the 3D pyroelectric distributions with high resolution. A 3D scan of 30 different layers with depths of 100 nm-5 µm inside the sample and 100 × 100 points in the xy-direction per layer is performed in 3 days.

Structure variations within RSi2 and R2TSi3 silicides. Part I. Structure overview.

Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group-subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.

Structure variations within RSi2 and R2Si3 silicides. Part II. Structure driving factors.

To gain an overview of the various structure reports on RSi2 and R2TSi3 compounds (R is a member of the Sc group, an alkaline earth, lanthanide or actinide metal, T is a transition metal), compositions, lattice parameters a and c, ratios c/a, formula units per unit cell, and structure types are summarized in extensive tables and the variations of these properties when varying the R or T elements are analyzed. Following the structural systematization given in Part I, Part II focuses on revealing the driving factors for certain structure types, in particular, the electronic structure. Here, concepts of different complexity are presented, including molecular orbital theory, the principle of hard and soft acids and bases, and a Bader analysis based on Density Functional Theory calculations for representatives of the reported structure types. The potential Si/T ordering in different structures is discussed. Additionally, the influences from intrinsic and extrinsic properties (e.g. elemental size and electronics as well as lattice parameters and structure type) are investigated on each other using correlation plots. Thermal treatment is identified as an important factor for the ordering of Si/T atoms.

Resolution of multiply recurrent and multifocal diverticulitis after fecal microbiota transplantation.

BACKGROUND: The exact pathophysiology of diverticulitis is not well understood and may be multifactorial. Recent studies highlight dysbiosis as a plausible mechanism. FMT is a safe strategy to restore commensal colon microbiota and has proven to be an effective treatment for gastrointestinal dysbiosis such as Clostridium difficile infection (CDI). There have been no studies reporting the treatment of diverticulitis with FMT. Our aim was to describe the novel application of fecal microbiota transplantation (FMT) for the treatment of recurrent diverticulitis. CASE: We report a case of a 63-year-old woman who had a 13-year history of multiply recurrent and multifocal diverticulitis previously treated with numerous short courses of intravenous and oral antibiotics for acute flares, two segmental colon resections, and suppressive antibiotic therapy for recurrent disease. Secondary to multiple courses of antibiotics , the patient developed CDI. She was treated with a single round of FMT and subsequently stopped all antibiotics at the time of FMT. RESULTS: In 20 months of follow-up, the patient has had no further recurrence of diverticulitis or CDI. CONCLUSIONS: FMT could prove to be a novel therapy for refractory diverticulitis but requires further investigation.

The lever arm ratio of the rotator cuff to deltoid muscle explains and predicts pseudoparalysis of the shoulder: the Shoulder Abduction Moment index.

AIMS: In patients with a rotator cuff tear, tear pattern and tendon involvement are known risk factors for the development of pseudoparalysis of the shoulder. It remains unclear, however, why similar tears often have very different functional consequences. The present study hypothesizes that individual shoulder anatomy, specifically the moment arms (MAs) of the rotator cuff (RC) and the deltoid muscle, as well as their relative recruitment during shoulder abduction, plays a central role in pseudoparalysis. MATERIALS AND METHODS: Biomechanical and clinical analyses of the pseudoparalytic shoulder were conducted based on the ratio of the RC/deltoid MAs, which were used to define a novel anatomical descriptor called the Shoulder Abduction Moment (SAM) index. The SAM index is the ratio of the radii of two concentric spheres based on the centre of rotation of the joint. One sphere captures the humeral head (numerator) and the other the deltoid origin of the acromion (denominator). A computational rigid body simulation was used to establish the functional link between the SAM index and a potential predisposition for pseudoparalysis. A retrospective radiological validation study based on these measures was also undertaken using two cohorts with and without pseudoparalysis and massive RC tears. RESULTS: Decreased RC activity and improved glenohumeral stability was predicted by simulations of SAM indices with larger diameters of the humeral head, being consequently beneficial for joint stability. Clinical investigation of the SAM index showed significant risk of pseudoparalysis in patients with massive tears and a SAM < 0.77 (odds ratio (OR) 11). CONCLUSION: The SAM index, which represents individual biomechanical characteristics of shoulder morphology, plays a determinant role in the presence or absence of pseudoparalysis in shoulders with massive RC tears.

Are commercially-available precontoured anatomical clavicle plating systems offering the purported superior optimum fitting to the clavicle? A cadaveric analysis and review of literature.

PURPOSE: The indication for operative treatment of displaced midshaft clavicle fractures remains controversial. However, if plate fixation is considered, implant prominence and skin irritation are the most common causes for re-operation. Low profile implants as well as closely contouring plates to the individual anatomy may reduce these complications. The aim of this study was to compare the fitting accuracy and implant prominence of 3.5mm pelvic reconstruction plates (PRP) with pre-contoured anatomical clavicle plates (PACP) for midshaft clavicle fractures. METHODS: Three-dimensional data of the largest, median and smallest male and female clavicle of an existing database of 89 cadaveric clavicles were included for analysis. A three-dimensional model of a commercially available PACP was used for digitally positioning of the plate on the segmented clavicles. Three-dimensional printouts of each clavicle were produced and the 3.5mm reconstruction plates were manually bent and positioned by the senior author. Computed tomography scans and three-dimensional reconstructions were then obtained to digitally compare the fitting accuracy and implant prominence. RESULTS: Pelvic reconstruction plates offered superior fitting accuracy and lower implant prominence compared to PACP. The largest difference in implant prominence was observed in large sized female clavicles and measured 3.6mm. CONCLUSION: Both, the less costly PRP plates and commercially available PACP for midshaft fractures of the clavicle demonstrated a clinically acceptable fitting accuracy. The manually bent pelvic-reconstruction plates demonstrated reduced implant prominence with superior fitting. Hypothetically this might contribute to a reduced rate of reoperation. LEVEL OF EVIDENCE: Level IV cadaveric study.

Anabolic steroids reduce muscle damage caused by rotator cuff tendon release in an experimental study in rabbits.

BACKGROUND: Muscles of the rotator cuff undergo retraction, atrophy, and fatty infiltration after a chronic tear, and a rabbit model has been used to investigate these changes. The purpose of this study was to test the hypothesis that the administration of anabolic steroids can diminish these muscular changes following experimental supraspinatus tendon release in the rabbit. METHODS: The supraspinatus tendon was released in twenty New Zealand White rabbits. Musculotendinous retraction was monitored over a period of six weeks. The seven animals in group I had no additional intervention, the six animals in group II had local and systemic administration of nandrolone decanoate, and the seven animals in group III had systemic administration of nandrolone decanoate during the six weeks. Two animals (group III) developed a postoperative infection and were excluded from the analysis. At the time that the animals were killed, in vivo muscle performance as well as imaging and histological muscle changes were investigated. RESULTS: The mean supraspinatus retraction was higher in group I (1.8 cm; 95% confidence interval: 1.64, 2.02 cm) than in group II (1.5 cm; 95% confidence interval: 1.29, 1.81 cm) or III (1.2 cm; 95% confidence interval: 0.86, 1.54 cm). Histologically, no fatty infiltration was measured in either treated group II (mean, 2.2%; range, 0% to 8%) or III (mean, 1%; range, 0% to 3.4%), but it was measured in the untreated group I (mean, 5.9%; range, 0% to 14.1%; p = 0.031). The radiographic cross-sectional area indicating atrophy and the work of the respective muscle during one standardized contraction with supramaximal stimulation decreased in all groups, but the work of the muscle was ultimately highest in group III. CONCLUSIONS: To our knowledge, this is the first documentation of partial prevention of important muscle alterations after retraction of the supraspinatus musculotendinous unit caused by tendon disruption. Nandrolone decanoate administration in the phase after tendon release prevented fatty infiltration of the supraspinatus muscle and reduced functional muscle impairment caused by myotendinous retraction in this rabbit rotator cuff model, but two of seven rabbits that received the drug developed infections.

Negative muscle pennation angle as a sign of massive musculotendinous retraction after tendon tear: paradoxical function of the vastus lateralis muscle.

CASE REPORT: In the presented case, an isolated vastus lateralis tendon tear resulted in a negative pennation angle of the distal muscle fibers acting paradoxical to the physiological direction of the proximal muscle fibers. This observation makes the value of an in situ repair of a far retracted tendon tear with interposition of a graft questionable and emphasizes early over late anatomic surgical restoration of the muscle architecture after tendon tears.

ELNES study of chemical solution deposited SrO(SrTiO(3))(n) Ruddlesden-Popper films: experiment and simulation.

This article analyzes electron energy-loss near-edge fine structures of the SrO(SrTiO(3))(n=1) Ruddlesden-Popper system and of the parent compounds SrTiO(3) and SrO by comparison with first principles calculations. For that, the fine structures of chemical solution deposited Ruddlesden-Popper films have been experimentally recorded by means of transmission electron microscopy. Moreover, density of states computations using an all-electron density-functional code have been performed. It is shown that the appearance and shape of the experimental O-K and Ti-L(2,3) fine structure features result from the crystallography-dependent electronic structure of the investigated oxides, which display technologically interesting dielectric as well as lattice-structural properties.

Switching Ti valence in SrTiO3 by a dc electric field.

A (001) SrTiO3 wafer has been investigated in situ at room temperature under application of a static electric field of varying polarity by fluorescence x-ray absorption near edge structure (XANES) analysis at the Sr-K and Ti-K absorption edges. The XANES spectra show a clear shift of the Ti-K absorption edge energy. The shift is attributed to a change of the Ti valence state in a volume invoked by diffusion of the oxygen ions and vacancies. No shift was observed for the Sr-K absorption edge energy. Theoretical calculations support these findings.

Materials: carbon nanotubes in an ancient Damascus sabre.

The steel of Damascus blades, which were first encountered by the Crusaders when fighting against Muslims, had features not found in European steels--a characteristic wavy banding pattern known as damask, extraordinary mechanical properties, and an exceptionally sharp cutting edge. Here we use high-resolution transmission electron microscopy to examine a sample of Damascus sabre steel from the seventeenth century and find that it contains carbon nanotubes as well as cementite nanowires. This microstructure may offer insight into the beautiful banding pattern of the ultrahigh-carbon steel created from an ancient recipe that was lost long ago.

Tendon retracts more than muscle in experimental chronic tears of the rotator cuff.

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection. The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair.

Ultrasonically implanted PLA suture anchors are stable in osteopenic bone.

We compared the in vitro pullout strengths of a metallic screw-type suture anchor (5-mm Corkscrew) and a new ultrasonically implanted absorbable pin from cadaveric humeral heads with different bone densities. They were assessed quantitatively using microcomputed tomography. Pullout tests were done at four standardized sites and then correlated with the local bone density. The mean pullout strengths for the 5-mm Corkscrew and the 3.5-mm polylactic pin were similar in weak bone (76 +/- 24 N versus 104 +/- 46 N), intermediate quality bone (194 +/- 81 N versus 218 +/- 76 N), and strong bone (349 +/- 127 N versus 325 +/- 100 N). Pullout strength correlated with bone density for both implants (r = 0.76 and r = 0.86 for the Corkscrew and polylactic pin, respectively). The ultrasonically implanted absorbable 3.5-mm polylactic pin achieved equal pullout strength in weak bone as the larger 5-mm titanium Corkscrew. Bone density is highly variable in humeral heads and influenced the pullout strength of both implants.

A new methodology for the planning of single-cut corrective osteotomies of mal-aligned long bones.

BACKGROUND: Corrections of combined torsional and angular deformities of long bones may be performed creating a single osteotomy which is oriented so that rotating the two fragments on the created osteotomy plane allows to correct all deformities in one step. A practical geometrical tool is presented to facilitate the difficult preoperative planning of such osteotomies. METHODS: The geometrical tool consists of two limbs connected by a mobile disk representing the osteotomy plane. This allows the two limbs to be deliberately bent and rotated against each other. Thereby, the mobile disk will change orientation in such a way that it will indicate the osteotomy plane needed in order to anatomically align the two limbs. The geometrical principle of the tool has been confirmed mathematically and compared with data from the literature. Five deformed test bones have been used to test the effectiveness of the tool. FINDING: . The geometrical principle of the tool is equivalent with the mathematical data from the literature. The maximal osteotomy angle which can be indicated by the tool is 65 degrees , with an error of +/-3 degrees compared to mathematically calculated values. The five test bones were all aligned anatomically with appropriate accuracy. INTERPRETATION: The presented tool can be easily used and facilitates largely the preoperative planning of a single cut osteotomy for complex deformities of long bones. It allows to avoid sophisticated mathematical calculations and helps to avoid the risk for errors in planning and performing correctional osteotomies.

Effect of tendon release and delayed repair on the structure of the muscles of the rotator cuff: an experimental study in sheep.

BACKGROUND: Ruptures of the tendons of the rotator cuff lead to profound and possibly irreversible changes in the structure and physiological properties of the rotator cuff muscles. Muscle atrophy and fatty infiltration are important prognostic factors that affect the natural history and outcome of treatment. The purpose of this study was to examine the amount of muscle atrophy and fatty infiltration in an animal model and to determine whether the repair of a long-standing tendon tear can reverse these changes. METHODS: The infraspinatus tendon in six sheep was released and encased in a silicone tube to prevent spontaneous healing. The musculotendinous unit was allowed to retract for forty weeks. Throughout this period, the muscular changes were studied with use of computed tomography, histological analysis, and electron microscopy. At forty weeks, the elasticity, intramuscular pressure, and perfusion were measured intraoperatively and a tendon repair was carried out. The structural changes of the muscle were studied for thirty-five weeks after the repair. The animals were then killed, and the musculotendinous units were examined macroscopically and by computed tomography, histological analysis, and electron microscopy. RESULTS: At the time of the tendon release, the infraspinatus showed no fatty changes. The force needed to cause a tendon excursion of 1 cm was a mean (and standard deviation) of 6.8 +/- 1 N. The application of tension on the tendon did not alter the perfusion and decreased the intramuscular pressure. After the tendon release, muscular atrophy developed and there was a significant increase (p < 0.001) in interfascicular and intrafascicular fat, representing fatty infiltration rather than fatty degeneration. Furthermore, there was an increase of interstitial connective tissue. At the time of the tendon repair, between forty and forty-two weeks after the release, there was a sevenfold poorer elasticity of the musculotendinous unit but preserved muscle perfusion. The structural changes increased six weeks after the repair and then recovered partially at twelve and thirty-five weeks thereafter but only to the amount demonstrated before the repair. CONCLUSIONS: Musculotendinous retraction induced by tendon release is associated with profound changes in the structure and function of the affected muscle. Vascularization, intramuscular pressure, and individual fiber composition are not markedly affected, and muscle fibers do not appear to degenerate. However, muscle atrophy, infiltration by fat cells, and an increase of interstitial connective tissue lead to impairment of the physiological properties of the muscle. These changes were irreversible under the conditions of this experiment with the repair technique used.

In vivo tendon force measurement of 2-week duration in sheep.

Tendon tension in vivo may be determined indirectly by measuring intratendinous pressure, by using a buckle transducer or by measuring the tendon strain. All of these methods require appropriate calibration, which is highly dependent on various variables. To measure the tendon load in vivo during a period of 2 weeks in sheep, a measurement technique has been developed using a force sensor interposed serially between the humeral head and the tendon end. Within a supporting frame, a flexion-sensitive force transducer is subjected to three-point bending stress. The load is transmitted by sutures from the tendon end through a hole in the sensor frame, orthogonal to the force transducer. In this configuration, the sensor measures the tensile force acting on the tendon, largely independent of the loading direction. The sensor was screwed to the humeral head and connected to the tendon end which was previously released from its insertion site along with a bone chip, using sutures. Connecting wires passed subcutaneously to a skin outlet about 30 cm away from the transducer. The sensor output was linear to the measured load up to 300 N, with maximum hysteresis of 18% full scale. All sensors worked in vivo without drift over a period of up to 14 days with no change in the calibration data. Forces up to 310 N have been recorded in vivo with daily tension measurements. This study shows that serial tendon tension measurement is feasible and allows for reliable, repeatable recording of the absolute tendon tension at the expense of tendon integrity.

The use of acrylic bone cement for suture anchoring.

Healing of tendon or ligament sutured to bone depends among other parameters on the mechanical stability of the suture fixation in or to the bone. The authors propose a method of anchoring suture material using bone cement as a substitute for conventional suture anchors. Conditions for secure fixation of suture material in bone cement were assessed and the technique of anchoring suture material with acrylic cement in bone was developed. Mechanical testing and microcomputed tomography of the suture-cement-bone compound were done. It was found that the suture always should be knotted before embedding it at least 2 mm deep in the bone cement. The holes drilled into the bone in which the sutures are secured with cement should be at least 3.5 mm in diameter and 10 mm deep; in cortical bone a tapped thread is required. Sutures can be secured safely using cement anchors which provide higher pull-out strength of a factor two to five than conventional metallic suture anchors of comparable size. They also adapt to anatomic situations where conventional anchors cannot be used and are more favorable in osteoporotic bone. Cement anchoring of sutures seems to be a cost-effective and valuable alternative when there is poor bone quality or extraordinarily high mechanical load.

[Endoprosthesis implantation in the elbow joint]. / Endoprothetik des Ellbogens.

Previously used total elbow prostheses were mainly constrained hinged implants. Their early clinical results were favourable but they failed due to a high rate of loosening already a few years after implantation. The cause for the early loosening was the great forces across the elbow joint which were directly transmitted to the prosthesis-bone interface in these implants. Therefore, these implants were abandoned. Afterwards, unlinked, semiconstrained or non-constrained resurfacing devices were introduced. In these devices, the soft tissues constrain the joint and therefore absorb part of the transmitted forces. The rates of loosening were significantly improved and rarely the cause of early failure. But resurfacing implants require intact condyles and collateral ligaments. These implants can, therefore, only be used in a limited number of indications, and postoperative instabilities are known complications. The currently most frequently used device is the semiconstrained Coonrad-Morrey prosthesis. It is a floppy hinge which allows valgus-varus and rotational laxities. Therefore, a part of the forces across the elbow joint are absorbed by the soft tissues. The loosening rate is not a clinical problem any more, and is with 4% 10 years after implantation (rheumatoid arthritis) similar to that of total hip or knee replacement. Furthermore, this device is stabilised with a small anterior flange to the anterior cortex of the humeral shaft. Condyles and collateral ligaments are therefore not necessary neither for short nor for long-term stability. The Coonrad-Morrey total elbow prosthesis can therefore be used for almost every indication, such as severe destruction of the elbow joint and even in case of complete loss of the distal humerus. The long-term outcome with this prosthesis for the treatment of rheumatoid arthritis is favourable with 96% of very good and good results. Function is restored with an average flexion of 131 degrees, a mean loss of extension of 28 degrees, and an unrestricted pronation and supination. The rate of complications for patients with rheumatoid arthritis is 10%. Similarly, the results for Coonrad-Morrey total elbow replacement for posttraumatic arthrosis are favourable with 83% of satisfactory results. Most patients consider their elbow as improved compared to preoperatively, but pain relief is obtained only in three quarters of the patients. The rate of complications is high with 30%, indicating the total elbow replacement is contraindicated for strenuous labour and sports activities.

Software based digital signal processing and spectrum deconvolution in X-ray spectroscopy.

Approaches for software based digital signal processing and numerical deconvolution of measured signals which overcome limitations of state-of-the-art systems are described. The basic technical equipment for digital signal processing consists of an energy resolving detector with a preamplifier followed by a fast sampling analogue-to-digital converter (ADC). The main idea is the numerical decomposition of the measured signal into contributions caused by single photon absorption using standard pulses. The latter can be obtained by measurements under definite conditions. The maximum pulse rate is then limited only by the ratio of sampling time to the time between two pulses which should be attributed to single events. Thus pulse overlaps do not require pulse rejection. At sampling rates of 10(8) samples per second theoretically a comparable photon rate can be detected at throughputs of 100%. Beyond that it is outlined that in a comparable manner a numerical deconvolution of measured energy spectra (statistic distribution functions of single events) into combinations of standard spectra, which can likewise be determined by measurement, offers outstanding possibilities, too. On the one hand the energy resolution attainable for individual events for a given detector can be improved drastically by the statistical treatment of spectra. On the other hand an energy resolving work principle becomes possible for certain detectors, which do not permit this conventionally due to their poor signal to noise ratio.