Fine- and hyperfine-structure effects in molecular photoionization: II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations

Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine- structure effects in one-photon ionization of molecules presented in the preceding companion article. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including hyperfine structure that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ionization experiments

Forbidden Vibrational Transitions in Cold Molecular Ions: Experimental Observation and Potential Applications

A range of interesting fundamental scientific questions can be addressed by high-precision molecular spectroscopy. A promising way towards this goal is the measurement of dipole-forbidden vibrational transitions in molecular ions. We have recently reported the first such observation in a molecular ion. Here, we give an overview of our method and our results as well as an outlook on potential future applications

Langzeitergebnisse nach Entwöhnung von mechanischer Herzunterstützung im Kindesalter

Einleitung: Terminale Herzinsuffizienz kann bei pädiatrischen Patienten zur Notwendigkeit von mechanischer Herzunterstützung führen. Das Herzunterstützungssystem Berlin Heart EXCOR® kann dabei helfen, den Kreislauf so lange zu stabilisieren, dass eine Herztransplantation ermöglicht wird. In manchen Fällen erholt sich das Herz unter der entlastenden Therapie jedoch so gut, dass das EXCOR® ersatzlos explantiert werden kann (Entwöhnung). Über den langfristigen Verlauf dieser Patienten war bisher nur wenig bekannt. In dieser Studie wurde untersucht, wielange die am Deutschen Herzzentrum Berlin (DHZB) entwöhnten pädiatrischen Patienten überleben, wie sich ihre kardiale Funktion entwickelt und wie gut die körperliche Belastbarkeit sowie ihre Lebensqualität ist. Methodik: Im Zeitraum Januar 1990 bis November 2015 wurden am DHZB 20 pädiatrische Patienten vom Berlin Heart EXCOR® entwöhnt. Von diesen verstarben vier Patienten, davon einer nach vorheriger Herztransplantation. Von den 16 Überlebenden wurden 13 prospektiv mittels Follow-up im DHZB untersucht. Von zwei weiteren Überlebenden sowie zwei Verstorbenen konnten retrospektiv Follow-up-Daten eruiert werden. Je nach Altersstruktur/körperlicher Eignung wurde u. a. Folgendes durchgeführt/bestimmt: Echokardiographie, MRT, NT-proBNP, Herzinsuffizienz-Klassifikation (Ross-Klasse), Spiroergometrie, Lebensqualität, psychomotorische Entwicklung. Einige Befunde des Follow-ups wurden mit vier verschiedenen Zeitpunkten des stationären Primäraufenthalts verglichen (welcher die EXCOR®-Unterstützung beinhaltete), darunter der als Entwöhnungstest durchgeführte mehrminütige EXCOR®-Pumpenstopp. Ergebnisse: Die entwöhnten Patienten waren bei Implantation im Median 0,7 Jahre alt. Die häufigsten Diagnosen waren Myokarditis (7 x), Kardiomyopathie (7 x) und Angeborene Herzfehler (5 x). Die Rate für ereignisfreies Überleben betrug nach 5, 10 und 15 Jahren jeweils 83,7 %. Beim Follow-up lag die echokardiographische Ejektionsfraktion (EF) bei medianen 53 %. Die EF sowie der Herzdurchmesser unterschieden sich nicht signifikant von den Messungen beim Pumpenstopp sowie bei Entlassung des Primäraufenthalts. Das NT-proBNP sank nach Explantation signifikant bis zum Follow-up. 82 % der Patienten waren beim Follow-up in Ross‑Klasse I (geringe Symptome), 18 % in Ross-Klasse II. Anamnestisch bestand im Follow-up bei 73 % der Befragten keine oder eine geringe körperliche Einschränkung bei alltäglichen Belastungen. Die Spiroergometrie zeigte dagegen mehrheitlich eine leicht- bis mittelgradige Einschränkung der körperlichen Belastbarkeit. Die Lebensqualität der meisten befragten Patienten war überdurchschnittlich gut, verglichen mit der Normalbevölkerung. Die psychomotorische Entwicklung der Kleinkinder bewegte sich im Follow-up je nach erlittener neurologischer Komplikation am EXCOR® zwischen stark eingeschränkt und sehr gut. Schlussfolgerung: Die vom EXCOR® entwöhnten Patienten hatten eine gute Überlebensrate, die meisten auch eine stabile kardiale Funktion auf teilweise mäßig erniedrigtem Niveau. Darüber hinaus hatten die meisten Befragten eine überdurchschnittlich gute Lebensqualität.Background: In pediatric patients end-stage heart failure may lead to usage of mechanical circulatory support. The Berlin Heart EXCOR®, a ventricular assist device, can help stabilizing the circulatory system for longer periods of time and thus, bridging to heart transplantation. However, in some cases cardiac function is improving noticeably, allowing to wean off the assist device. Curently, long-term experience after weaning from mechanical circulatory support in pediatric patients is lacking. In this study, we examined survival time, long-term cardiac function, physical capacity and health related quality of life (HRQOL) of the weaned patients at Deutsches Herzzentrum Berlin (DHZB). Methods: Between January 1990 and November 2015, 20 pediatric patients were weaned from the Berlin Heart EXCOR® at DHZB. Of these, four died (one after heart transplantation). 13 of the 16 survivors were examined prospectively at DHZB. Of two more survivors and two deceased, follow-up data could be evaluated. Depending on age and physical eligibility, the following was conducted/determined: Echocardiography, MRI, NT‑proBNP, heart failure classification (Ross classes), cardiopulmonary exercise testing, HRQOL, mental and motor development. Some findings at follow-up were compared with four different points of time during the initial inpatient stay (which contained the EXCOR® support). One of these was the EXCOR® weaning test (pump stoppage), lasting for several minutes. Results: Median age at implantation was 0.7 years. Most frequent diagnoses were myocarditis (7), cardiomyopathy (7), congenital heart disease (5). Survival rate was 83.7 % for 5, 10 and 15 years, respectively. At follow-up, ejection fraction by echocardiography was 53 % (median). Ejection fraction and cardiac diameter did not differ significantly compared to the ones at pump stoppage as well as discharge from the initial inpatient stay. NT-proBNP decreased significantly from explantation to follow-up. At follow-up, 82 % of patients were at Ross class I (few symptoms), 18 % at Ross class II. 73 % of patients at follow-up reported little to no restrictions concerning daily routine physical capacity. Though, cardiopulmonary exercise testing revealed mild to moderate limitation of physical capacity in several patients. In most cases, HRQOL was above average. Depending on having suffered from a neurological complication during EXCOR® support, mental and motor development varied between poor and excellent. Conclusion: The weaned patients had good survival, most of them had good cardiac function, too, with some of them on a depressed level and in addition, a HRQOL above average

Dipole-forbidden vibrational transitions in molecular ions : a novel route to precision spectroscopy and studying effects of interest to fundamental physics

Homonuclear diatomic molecules, such as H2 or N2, are usually not expected to show a vibrational spectrum. Although this is true within the electric-dipole approximation, higher-order terms in the interaction of matter and radiation give rise to very weak spectroscopic transitions. These “electric-dipole-forbidden” transitions are spectrally extremely narrow and thus of interest to precision spectroscopy and tests of fundamental physical theories by high-precision measurements. Until recently, such forbidden transitions have only been observed in neutral molecules, but not in molecular ions. In this thesis, we report the observation of electric-quadrupole rotation-vibration transitions in the molecular nitrogen cation N+2 — to our knowledge the first observation of a dipole-forbidden vibrational transition in a molecular ion. For this observation, N+2 ions produced state-selectively by photoionization of neutral N2 molecules were trapped in a radio-frequency ion trap (linear Paul trap) and cooled to millikelvin temperatures through interaction with cotrapped, laser-cooled atomic Ca+ ions (sympathetic cooling). Vibrational excitation of N+2 was achieved with high-intensity mid-infrared radiation from a frequency-stabilized quantum cascade laser. Vibrationally excited ions were detected through a state-dependent charge-transfer reaction of N+2 with Ar atoms. Addressing these extremely narrow transitions in a molecular ion enables the application of techniques developed for manipulation and control of atomic ions that exploit the long-range Coulomb interaction of charged particles, such as trapping, sympathetic cooling and non-destructive state detection through mapping of the quantum state to a cotrapped, experimentally more easily accessible ion (quantum logic spectroscopy). Besides reporting the observation of electric-quadrupole rotation-vibration transitions in a molecular ion, this thesis gives a detailed description of the mechanism underlying these transitions and a derivation of their line strengths in fine- and hyperfine-resolved spectra based on spherical tensor algebra. Moreover, a model for fine- and hyperfine-structure effects in molecular photoionization, an essential method for production of molecular ions, is presented. The model was successfully applied to analyze photoelectron spectra from the literature and is used to study future hyperfine-state-selective molecular photoionization schemes. Finally, a quantum-logic state-detection method for molecular ions is discussed. The method is based on state-dependent optical dipole forces acting on a hybrid molecular-atomic two-ion system. By inducing a geometric quantum phase, these forces map the state of the molecular ion onto the atomic one, from which it may be detected through interrogation of a closed optical cycling transition. Here, feasibility of this method for the N+2 -Ca+ system is positively assessed by estimating the relevant experimental parameters. Our observation and the theoretical framework developed here might considerably increase the precision and accuracy of molecular spectroscopy and therefore open up a new route to study fundamental scientific questions by means of high-precision molecular spectroscopy, such as a possible variation of fundamental physical constants or the search for yet unknown fundamental interactions

User-centered design of power tools: a generic process for evaluation of usability aspects [Die Nutzerzentrierte Produktentwicklung von Power-Tools: Ein generischer Prozess zur Untersuchung von Usability-Aspekten]

User-centered design focuses on the individual needs of the product users. The aim is to adjust the design of the product according to the requirements of the user and application. Existing methods for evaluation of the perceived usability are often limited to one specific aspect, and it requires a high effort to transfer the respective method to other aspects. A generic process for the evaluation of the perceived usability is missing. This paper presents the generic Usability Study Evaluation Process (USE-Process) that helps product designers to identify and evaluate usability aspects relevant to the suitability of the usage of a product. The process is divided into three sections: 1. A structured field study to identify the relevant usability aspects; 2. A generic study design for the subjective evaluation of usability aspects under objective and reproducible conditions; 3. The use of measurement tools that help to quantify the results of the subjective evaluation. The generic applicability of the process is shown by the example of the evaluation of cordless screwdrivers; several usability aspects were identified, clustered, and evaluated by using subjective evaluation methods and measurement techniques

Performance of a deep convolutional neural network for MRI-based vertebral body measurements and insufficiency fracture detection

OBJECTIVES The aim is to validate the performance of a deep convolutional neural network (DCNN) for vertebral body measurements and insufficiency fracture detection on lumbar spine MRI. METHODS This retrospective analysis included 1000 vertebral bodies in 200 patients (age 75.2 ± 9.8 years) who underwent lumbar spine MRI at multiple institutions. 160/200 patients had ≥ one vertebral body insufficiency fracture, 40/200 had no fracture. The performance of the DCNN and that of two fellowship-trained musculoskeletal radiologists in vertebral body measurements (anterior/posterior height, extent of endplate concavity, vertebral angle) and evaluation for insufficiency fractures were compared. Statistics included (a) interobserver reliability metrics using intraclass correlation coefficient (ICC), kappa statistics, and Bland-Altman analysis, and (b) diagnostic performance metrics (sensitivity, specificity, accuracy). A statistically significant difference was accepted if the 95% confidence intervals did not overlap. RESULTS The inter-reader agreement between radiologists and the DCNN was excellent for vertebral body measurements, with ICC values of > 0.94 for anterior and posterior vertebral height and vertebral angle, and good to excellent for superior and inferior endplate concavity with ICC values of 0.79-0.85. The performance of the DCNN in fracture detection yielded a sensitivity of 0.941 (0.903-0.968), specificity of 0.969 (0.954-0.980), and accuracy of 0.962 (0.948-0.973). The diagnostic performance of the DCNN was independent of the radiological institution (accuracy 0.964 vs. 0.960), type of MRI scanner (accuracy 0.957 vs. 0.964), and magnetic field strength (accuracy 0.966 vs. 0.957). CONCLUSIONS A DCNN can achieve high diagnostic performance in vertebral body measurements and insufficiency fracture detection on heterogeneous lumbar spine MRI. KEY POINTS • A DCNN has the potential for high diagnostic performance in measuring vertebral bodies and detecting insufficiency fractures of the lumbar spine

Optical Frequency Comb Fourier Transform Spectroscopy of 14^{14}N2_216^{16}O at 7.8 {\mu}m

We use a Fourier transform spectrometer based on a compact mid-infrared difference frequency generation comb source to perform broadband high-resolution measurements of nitrous oxide, $^{14}$N$_2$$^{16}$O, and retrieve line center frequencies of the $\nu$$_1$ fundamental band and the $\nu$$_1$ + $\nu$$_2$ - $\nu$$_2$ hot band. The spectrum spans 90 cm$^{-1}$ around 1285 cm$^{-1}$ with a sample point spacing of 3 ${\times}$ 10$^{-4}$ cm$^{-1}$ (9 MHz). We report line positions of 67 lines in the $\nu$$_1$ fundamental band between P(37) and R(39), and 78 lines in the $\nu$$_1$ + $\nu$$_2$ - $\nu$$_2$ hot band (split into two components with e/f rotationless parity) between P(34) and R(33), with uncertainties in the range of 90-600 kHz. We derive upper state constants of both bands from a fit of the effective ro-vibrational Hamiltonian to the line center positions. For the fundamental band, we observe excellent agreement in the retrieved line positions and upper state constants with those reported in a recent study by AlSaif et al. using a comb-referenced quantum cascade laser [J Quant Spectrosc Radiat Transf, 2018;211:172-178]. We determine the origin of the hot band with precision one order of magnitude better than previous work based on FTIR measurements by Toth [http://mark4sun.jpl.nasa.gov/n2o.html], which is the source of the HITRAN2016 data for these bands

Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization

We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization

Angiogenesis in tissue engineering : Breathing life into constructed tissue substitutes

Long-term function of three-dimensional (3D) tissue constructs depends on adequate vascularization after implantation. Accordingly, research in tissue engineering has focused on the analysis of angiogenesis. For this purpose, 2 sophisticated in vivo models (the chorioallantoic membrane and the dorsal skinfold chamber) have recently been introduced in tissue engineering research, allowing a more detailed analysis of angiogenic dysfunction and engraftment failure. To achieve vascularization of tissue constructs, several approaches are currently under investigation. These include the modification of biomaterial properties of scaffolds and the stimulation of blood vessel development and maturation by different growth factors using slow-release devices through pre-encapsulated microspheres. Moreover, new microvascular networks in tissue substitutes can be engineered by using endothelial cells and stem cells or by creating arteriovenous shunt loops. Nonetheless, the currently used techniques are not sufficient to induce the rapid vascularization necessary for an adequate cellular oxygen supply. Thus, future directions of research should focus on the creation of microvascular networks within 3D tissue constructs in vitro before implantation or by co-stimulation of angiogenesis and parenchymal cell proliferation to engineer the vascularized tissue substitute in situ