Simulation of Thermal Behavior in High-Precision Measurement Instruments

In this paper, a way to modularize complex finite-element models is described. The modularization is done with temperature fields that appear in high-precision measurement instruments. There, the temperature negatively impacts the achievable uncertainty of measurement. To correct for this uncertainty, the temperature must be known at every point. This cannot be achieved just by measuring temperatures at specific locations. Therefore, a numerical treatment is necessary. As the system of interest is very complex, modularization is unavoidable to obtain good numerical results.     

Coupling of prolyl peptide bond isomerization and Ca2+ binding in a C-type mannose-binding protein

A proline residue flanked by two polar residues is a highly conserved sequence motif in the Ca2+- and carbohydrate-binding site of C-type animal lectins. Crystal structures of several C-type lectins have shown that the two flanking residues are only observed to act as Ca2+ ligands when the peptide bond preceding the proline residue is in the cis conformation. In contrast, structures of the apo- and one-ion forms of mannose-binding proteins (MBPs) reveal that, when the Ca2+-binding site is empty, the peptide bond preceding the proline can adopt either the cis or trans conformation, and distinct structures in adjacent regions are associated with the two proline isomers. In this work, measurements of Ca2+-induced changes in intrinsic tryptophan fluorescence, and fluorescence energy transfer from tryptophan to Tb3+, reveal a slow conformational change in rat liver MBP (MBP-C) accompanying the binding of either Ca2+ or Tb3+. The Ca2+-induced increase in intrinsic tryptophan fluorescence shows biphasic kinetics: a burst phase with a rate constant greater than 1 s(-1) is followed by a slow phase with a single-exponential rate constant ranging from 0.01 to 0.05 s(-1) (36 degrees C) that depends on the concentration of Ca2+. Likewise, addition of EGTA to Ca2+-bound or Tb3+-bound MBP-C causes a decrease in intrinsic tryptophan fluorescence with biphasic kinetics consisting of a burst phase with a rate constant greater than 1 s(-1), followed by a slow phase with a single-exponential rate constant of 0.065 s(-1). In contrast, Tb3+ fluorescence produced by resonant energy transfer from MBP-C decreases in a single kinetic phase with a rate constant greater than 1 s(-1), implying that the slow change in tryptophan fluorescence monitors a conformational change that is not limited in rate by ion dissociation. The rate constants of the slow phases accompanying Ca2+ binding and release are strongly affected by temperature and are weakly accelerated by the prolyl isomerase cyclophilin. These data strongly suggest that the binding of either Ca2+ or Tb3+ to MBP-C is coupled to a conformational change that involves the cis-trans isomerization of a peptide bond. Fitting of the data to kinetic models indicates that, in the absence of Ca2+, the proline in approximately 80% of the molecules is in the trans conformation. The slow kinetics associated with cis-trans proline isomerization may be exploited by endocytic receptors to facilitate sorting of carbohydrate-bearing ligands from the receptor in the endosome.     

Possible diamond-like nanoscale structures induced by slow highly-charged ions on graphite (HOPG)

The interaction between slow highly-charged ions (SHCI) of different charge states from an electron-beam ion trap and highly-oriented pyrolytic graphite (HOPG) surfaces is studied in terms of modification of electronic states at single-ion impact nanosize areas. Results are presented from AFM/STM analysis of the induced-surface topological features combined with Raman spectroscopy. I-V characteristics for a number of different impact regions were measured with STM and the results argue for possible formation of diamond-like nanoscale structures at the impact sites.     

Nasal cerebral heterotopic tissue (nasal glioma) in the adult: a rare cause of primary cerebrospinal fluid rhinorrhea

BACKGROUND: Nasal cerebral heterotopia is a congenital lesion that is mainly detected in early childhood. The rare cases of this disorder found in adult patients are located intranasally. A common symptom is compromised nasal air passage. Clinical findings include polypoid masses in either the nasal cavity or the paranasal sinuses. To our knowledge, primary cerebrospinal fluid (CSF) rhinorrhea has been reported only twice in these patients. PATIENT: A 64-year-old female patient presented with CSF rhinorrhea proven by beta 2-transferrin testing. Previous head injury or intranasal manipulation were excluded. Anterior rhinoscopy revealed a watery drainage from the right middle meatus. CT scan showed a defect in the lateral roof of the right ethmoid sinus, approximately 5 mm in diameter; MRI revealed a mass in the right ethmoid and frontal sinuses, penetrating the anterior skull base. The lesion was resected by an extranasal approach. It showed a fibrous connection to the frontal lobe. Histologically, the lesion consisted of neural tissue composed of gray and white matter, both with a normal structuring. Dura and skull base were reconstructed. There were no signs of a CSF leak postoperatively. RESULTS AND CONCLUSIONS: The differential diagnosis of CSF rhinorrhea includes traumatic events and neoplasms, elevated intracranial pressure, and connate lesions as encephaloceles and, in rare cases, nasal cerebral heterotopia.     

Absorption Anomalies in Ratio and Subtraction FT-IR Spectroscopy

Subtraction and ratioing of strong absorption bands in Fourier transform infrared (FT-IR) spectroscopy produces anomalous absorption errors. One source of error is the instability in the wavenumber scale of the FT-IR spectra. The possible causes of this error are explored. The thermal expansion and contraction of the cavity of the HeNe reference laser from a typical commercial instrument was found to produce changes in the laser wavenumber of ±0.034 cm(-)(1). Changes of this size are shown to introduce errors into the wavenumber scales of FT-IR spectra which are sufficient to produce the observed anomalies. The dependence of the error on instrumental and spectroscopic parameters is explored. Solutions to the problem are proposed.     

Rapid Prototyping for Pervasive Applications

VisualRDK is a high-level programming language for prototyping pervasive applications. Context is tightly integrated into the language itself, so developers can attach functionality to locations, persons, or situations instead of the device. Pervasive computing appliances range from consumer devices over embedded sensor boards to PCs and large-scale context servers. Because these devices vary tremendously in their capabilities, application developers must create different programming models for every class of device. This makes rapid prototyping infeasible as soon as more than one class of devices is involved. Rapid prototyping therefore requires a programming model that hides the environment's heterogeneity.     

Metrology and microscopic picture of the integer quantum Hall effect

Since 1990, the integer quantum Hall effect has provided the electrical resistance standard, and there has been a firm belief that the measured quantum Hall resistances are described only by fundamental physical constants--the elementary charge e and the Planck constant h. The metrological application seems not to rely on detailed knowledge of the microscopic picture of the quantum Hall effect; however, technical guidelines are recommended to confirm the quality of the sample to confirm the exactness of the measured resistance value. In this paper, we give our present understanding of the microscopic picture, derived from systematic scanning force microscopy investigations on GaAs/(AlGa)As quantum Hall samples, and relate these to the technical guidelines.     

Adaptronical compensation of geometrical machine errors

Static, quasi-static and dynamic displacements influence the accuracy of machine tool results. The low-frequency parts of these displacements can, on the one hand, be traced back to static stresses resulting from gravity as well as process loads and, on the other hand, to geometrical machine errors and the faulty positioning in the working area resulting from this. Dynamic loads, however, are characterised by the distribution of masses and stiffnesses. This paper aims to present an approach to adaptronically compensate for static and quasi-static displacements while, at the same time, showing how a component can fulfill the functions of a sensor and an actuator. In order to achieve this, an intelligent adaptronical strut was designed for which the piezoelectric transducer can fulfill actuated as well as sensoric tasks at the same time. Based on the principle of vibrating strings, a vibrating string is used to induce vibrations which allow for the static, quasi-static and dynamic machine displacements to be recorded using the developed integrated sensors and actuators. A first prototype was integrated into a machine tool to verify the concept. Static and dynamic measurements endorse the functionality of this approach. Machining trial runs show the effectiveness of this approach in a parallel kinematic machine tool with regards to adaptronically compensating for geometrical machine errors.