The Electronic Structures of Azaphenanthrenes and Their Dimers

Insertion of a nitrogen atom modifies the electronic structures and photochemistry of polycyclic aromatic hydrocarbons by introducing nπ* states into the molecules. To better understand the electronic structures of isolated polycyclic aromatic nitrogen-containing hydrocarbons (PANHs) and their dimers as well as the influence of the position of the nitrogen atom in the molecule, we investigate three different azaphenanthrenes, benzo[f]quinoline, benzo[h]quinoline, and phenanthridine, in a joint experimental and computational study. Experimentally, resonance-enhanced multiphoton ionization (REMPI) spectroscopy is applied to characterize the excited electronic states. The REMPI spectra of the azaphenanthrene monomers have a rather similar appearance, with origins between 3.645 and 3.670 eV for the 1ππ* ← S0 transition. In contrast to the phenanthrene parent, 2ππ* ← S0 is broad and unstructured even at the band origin. The experiments are accompanied by density functional theory computation, and vibrationally resolved spectra are simulated using a time-independent approach. The differences between phenanthrene and the azaphenanthrenes are assigned to perturbations due to the low-lying 1(nπ*) state, which accelerates nonradiative deactivation. For the dimers, it is found that two π-stacked isomers with two electronic transitions each contribute to the electronic spectrum, leading to overlapping bands that are difficult to assign.

Threshold Photoelectron Spectrum of m-Benzyne

Due to their unusual electronic structure, the biradical m-benzyne, C₆H₄, and its cation are of considerable interest in chemistry. Here, the photoion mass-selected threshold photoelectron spectrum of the m-benzyne biradical is presented. An adiabatic ionization energy of 8.65 ± 0.015 eV is derived, while a vibrational progression of 0.10 eV is assigned to the ν₉⁺ ring breathing mode, in excellent agreement with computations. The experimental spectrum was reproduced well by Franck-Condon spectral modeling of the ²A₁ ← X ¹A₁ transition, in which the cation retains a monocyclic C₆ framework. The energetically close-lying bicyclic ²A₂ cation state exhibits low Franck-Condon factors, due to the large change in geometry, and thus cannot be observed.

The MCP2 and the wrist plus two extensor compartments are the most affected and responsive joints/tendons out of the US7 score in patients with rheumatoid arthritis-an observational study

Background

There is no international consensus on an optimal ultrasound score for monitoring of rheumatoid arthritis (RA) on patient-level yet. Our aim was to reassess the US7 score for the identification of the most frequently pathologic and responsive joint/tendon regions, to optimize it and contribute to an international consensus. Furthermore, we aimed to evaluate the impact of disease duration on the performance of the score.

Methods

RA patients were assessed at baseline and after 3 and 6 months of starting/changing DMARD therapy by the US7 score in greyscale (GS) and power Doppler (PD). The frequency of pathologic joint/tendon regions and their responsiveness to therapy were analyzed by Friedman test and Cochrane-Q test respectively, including the comparison of palmar vs. dorsal regions (chi-square test). The responsiveness of different reduced scores and the amount of information retained from the original US7 score were assessed by standardized response means (SRM)/linear regression. Analyses were also performed separately for early and established RA.

Results

A total of 435 patients (N = 138 early RA) were included (56.5 (SD 13.1) years old, 8.2 (9.1) years disease duration, 80% female). The dorsal wrist, palmar MCP2, extensor digitorum communis (EDC) and carpi ulnaris (ECU) tendons were most frequently affected by GS/PD synovitis/tenosynovitis (wrist: 45%/43%; MCP2: 35%/28%; EDC: 30%/11% and ECU: 25%/11%) and significantly changed within 6 months of therapy (all p ≤0.003 by GS/PD). The dorsal vs. palmar side of the wrist by GS/PD (p < 0.001) and the palmar side of the finger joints by PD (p < 0.001) were more frequently pathologic. The reduced US7 score (GS/PD: palmar MCP2, dorsal wrist, EDC and ECU, only PD: dorsal MCP2) showed therapy response (SRM 0.433) after 6 months and retained 76% of the full US7 score’s information.

No major differences between the groups of early and established RA could be detected.

Conclusions

The wrist, MCP2, EDC, and ECU tendons were most frequently pathologic and responsive to therapy in both early and established RA and should therefore be included in a comprehensive score for monitoring RA patients on patient-level.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02874-y.

POS0106 THE MCP2 AND WRIST PLUS 2 TENDONS ARE THE MOST AFFECTED AND RESPONSIVE JOINTS/TENDONS OUT OF THE ‘US7 SCORE’ IN PATIENTS WITH RHEUMATOID ARTHRITIS – AN OBSERVATIONAL STUDY

Background

There is no international consensus on an optimal ultrasound scoring system in patients with rheumatoid arthritis (RA) yet.

Objectives

To assess the musculoskeletal ultrasound score on seven joints (‘US7 score’) (1) for the identification of the most frequently pathologic and responsive joint regions during 3 and 6 months of therapy in order to optimize the score. Furthermore, to evaluate the impact of disease duration on the performance of the score.

Methods

RA patients were recruited from 54 German rheumatology centers when starting or changing DMARD therapy. Patients were assessed by the US7 score in greyscale (GS) and power Doppler (PD) at baseline, after 3 and 6 months. The frequency of pathologic joint/tendon regions and their responsiveness to therapy were assessed including the comparison of palmar vs. dorsal regions.

Differences between the palmar and the dorsal sides were analyzed using Chi-square test, the gradings of the US-joint inflammation were compared between baseline, 3 months, and 6 months by Friedman test with Dunn test as post-hoc test.

We used standard response mean to determine the responsiveness of possible reduced scores and linear regression to assess the amount of information retained from the original score. Analyses were also performed separately for early and established RA.

Results

A total of 435 patients (n=138 early RA) were included (56.5 (SD 13.1) years old, 8.2 (9.1) years disease duration, 80% female). The dorsal wrist, palmar MCP2, extensor digitorum communis (EDC) and carpi ulnaris (ECU) tendons out of 7 joints were most frequently affected by GS/PD synovitis/tenosynovitis (wrist: 45%/43%; MCP2: 35%/28%; EDC: 30%/11% and ECU: 25%/11%) and significantly changed within 6 months of therapy (all p≤0.003 in GS/PD).

The dorsal vs. palmar side of the wrist by GS/PD (p<0.001) and the palmar vs. dorsal side of the finger joints by PD (p<0.001) were more frequently pathologic. The reduced US7 score (GS and PD: dorsal MCP2, dorsal wrist, EDC and ECU, only GS: palmar MCP2) showed therapy response (SRM 0.433) after 6 months and retained 76% of the information of the full US7 score. No major differences between the groups of early and established RA could be detected.

Conclusion

The wrist, MCP2, EDC and ECU tendons were most frequently pathologic and responsive to therapy, representing an optimized score for monitoring of RA patients for both early and established RA and should therefore be included in comprehensive scores for monitoring RA patients.

References

[1]Backhaus M, Ohrndorf S, Kellner H, Strunk J, Backhaus TM, Hartung W, et al. Evaluation of a novel 7-joint ultrasound score in daily rheumatologic practice: a pilot project. Arthritis Rheum. 2009;61(9):1194-201.

Acknowledgements

We thank Gabriela Schmittat for logistical support in the study.

Disclosure of Interests

Annika Franziska Podewski: None declared, Anne-Marie Glimm: None declared, Imma Fischer: None declared, George Bruyn: None declared, Petra Hanova: None declared, Hilde Berner Hammer Speakers bureau: Paid speaker for Lilly, Novartis and AbbVie, Employee of: Advisory board for AbbVie, Anna-Birgitte Aga Speakers bureau: AbbVie, Eli Lilly, Novartis, Pfizer and UCB, Consultant of: AbbVie, Eli Lilly, Novartis, Pfizer and UCB, Espen A Haavardsholm: None declared, Sofia Ramiro Speakers bureau: Eli Lilly, MSD, Novartis, UCB, Consultant of: AbbVie, Eli Lilly, MSD, Novartis, Pfizer, UCB, Sanofi, Grant/research support from: AbbVie, Galapagos, Novartis, Pfizer, UCB, Gerd Rüdiger Burmester: None declared, Marina Backhaus Speakers bureau: Speaker fee from AbbVie, BMS, Galapagos, UCB, Novartis, Sarah Ohrndorf: None declared

Pelvic lymphadenectomy in vulvar cancer and its impact on prognosis and outcome

BACKGROUND

The value of pelvic lymphadenectomy (LAE) has been subject of discussions since the 1980s. This is mainly due to the fact that the relation between lymph node involvement of the groin and pelvis is poorly understood and therewith the need for pelvic treatment in general.

PATIENTS AND METHODS

N = 514 patients with primary vulvar squamous cell cancer (VSCC) FIGO stage ≥ IB were treated at the University Medical Center Hamburg-Eppendorf between 1996 and 2018. In this analysis, patients with pelvic LAE (n = 21) were analyzed with regard to prognosis and the relation of groin and pelvic lymph node involvement.

RESULTS

The majority had T1b/T2 tumors (n = 15, 78.9%) with a median diameter of 40 mm (11-110 mm). 17/21 patients showed positive inguinal nodes. Pelvic nodal involvement without groin metastases was not observed. 6/17 node-positive patients with positive groin nodes also had pelvic nodal metastases (35.3%; median number of affected pelvic nodes 2.5 (1-8)). These 6 patients were highly node positive with median 4.5 (2-9) affected groin nodes. With regard to the metastatic spread between groins and pelvis, no contralateral spread was observed. Five recurrences were observed after a median follow-up of 33.5 months. No pelvic recurrences were observed in the pelvic nodal positive group. Patients with pelvic metastasis at first diagnosis had a median progression-free survival of only 9.9 months and overall-survival of 31.1 months.

CONCLUSION

A relevant risk for pelvic nodal involvement only seems to be present in highly node-positive disease, therefore pelvic staging (and radiotherapy) is probably unnecessary in the majority of patients with node-positive VSCC.

MTT Heterogeneity in Perfusion CT Imaging as a Predictor of Outcome after Aneurysmal SAH

BACKGROUND AND PURPOSE

Impairment of tissue oxygenation caused by inhomogeneous microscopic blood flow distribution, the so-called capillary transit time heterogeneity, is thought to contribute to delayed cerebral ischemia after aneurysmal SAH but has so far not been systematically evaluated in patients. We hypothesized that heterogeneity of the MTT, derived from CTP parameters, would give insight into the clinical course of patients with aneurysmal SAH and may identify patients at risk of poor outcome.

MATERIALS AND METHODS

We retrospectively analyzed the heterogeneity of the MTT using the coefficient of variation in CTP scans from 132 patients. A multivariable logistic regression model was used to model the dichotomized mRS outcome. Linear regression was used to eliminate variables with high linear dependence. T tests were used to compare the means of 2 groups. Furthermore, the time of the maximum coefficient of variation for MTT after bleeding was evaluated for correlation with the mRS after 6 months.

RESULTS

On average, each patient underwent 5.3 CTP scans during his or her stay. Patients with high coefficient of variation for MTT presented more often with higher modified Fisher (P = .011) and World Federation of Neurosurgical Societies grades (P = .014). A high coefficient of variation for MTT at days 3-21 after aneurysmal SAH correlated significantly with a worse mRS score after 6 months (P = .016). We found no correlation between the time of the maximum coefficient of variation for MTT after bleeding and the patients' outcomes after 6 months (P = .203).

CONCLUSIONS

Heterogeneity of MTT in CTP after aneurysmal SAH correlates with the patients' outcomes. Because the findings are in line with the pathophysiologic concept of the capillary transit time heterogeneity, future studies should seek to verify the coefficient of variation for MTT as a potential imaging biomarker for outcome.

Plectin dysfunction in neurons leads to tau accumulation on microtubules affecting neuritogenesis, organelle trafficking, pain sensitivity and memory

AIMS

Plectin, a universally expressed multi-functional cytolinker protein, is crucial for intermediate filament networking, including crosstalk with actomyosin and microtubules. In addition to its involvement in a number of diseases affecting skin, skeletal muscle, heart, and other stress-exposed tissues, indications for a neuropathological role of plectin have emerged. Having identified P1c as the major isoform expressed in neural tissues in previous studies, our aim for the present work was to investigate whether, and by which mechanism(s), the targeted deletion of this isoform affects neuritogenesis and proper nerve cell functioning.

METHODS

For ex vivo phenotyping, we used dorsal root ganglion and hippocampal neurons derived from isoform P1c-deficient and plectin-null mice, complemented by in vitro experiments using purified proteins and cell fractions. To assess the physiological significance of the phenotypic alterations observed in P1c-deficient neurons, P1c-deficient and wild-type littermate mice were subjected to standard behavioural tests.

RESULTS

We demonstrate that P1c affects axonal microtubule dynamics by isoform-specific interaction with tubulin. P1c deficiency in neurons leads to altered dynamics of microtubules and excessive association with tau protein, affecting neuritogenesis, neurite branching, growth cone morphology, and translocation and directionality of movement of vesicles and mitochondria. On the organismal level, we found P1c deficiency manifesting as impaired pain sensitivity, diminished learning capabilities and reduced long-term memory of mice.

CONCLUSIONS

Revealing a regulatory role of plectin scaffolds in microtubule-dependent nerve cell functions, our results have potential implications for cytoskeleton-related neuropathies.

Metachronous hepatic resection for liver only pancreatic metastases

BACKGROUND

The value of liver resection (LR) for metachronous pancreatic ductal adenocarcinoma (PDAC) metastases remains controversial. However, in light of increasing safety of liver resections, surgery might be a valuable option for metastasized PDAC in selected patients.

METHODS

We performed a retrospective, multicenter study including patients undergoing hepatectomy for metachronous PDAC liver metastases between 2004 and 2015 to analyze postoperative outcome and overall survival. All patients were operated with curative intent. Patients with oligometastatic metachronous liver metastasis with definitive chemotherapy (n = 8) served as controls.

RESULTS

Overall 25 patients in seven centers were included in this study. The median age at the time of LR was 63.8 years (56.9-69.9) and the median number of metastases in the liver was 1 (IQR 1-2). There were eight non-anatomical resections (32%), 15 anatomical minor (60%) and 2 major LR (8%). Postoperative complications occurred in eleven patients (eight Clavien-Dindo grade I complications (32%) and three grade IIIa complications (12%), respectively). The 30-day mortality was 0%. The median length of stay was 8.6 days (IQR 5-11). Median overall survival following LR was 36.8 months compared to 9.2 months in patients with metachronous liver metastasis with chemotherapy (p = 0007).

DISCUSSION

Liver resection for metachronous PDAC metastasis is safe and feasible in selected patients. To address general applicability and to find factors for patient selection, larger trials are urgently warranted.

Photoelectron spectroscopy of boron-containing reactive intermediates using synchrotron radiation: BH2, BH, and BF

Mass selected slow photoelectron spectra (SPES) of three boron-containing reactive species, BH₂, BH, and BF were recorded by double imaging photoion-photoelectron coincidence spectroscopy (i²PEPICO) using synchrotron radiation. All species were generated in a flow reactor from the H-abstraction of B₂H₆ by F atoms created in a F₂ microwave discharge. The spectrum of BH₂⁺ exhibits a long bending mode progression with a 970 cm^-1 spacing due to the large geometry change from bent to linear upon ionization. Its ionization energy was determined as 8.12 ± 0.02 eV. For BH, photoionisation from both X¹Σ⁺ singlet and a³Π triplet state was observed, permitting the experimental determination of the singlet/triplet gap (ΔE_ST) from the observed IE's of 9.82 eV and 8.48 eV. In addition, a threshold photoelectron spectrum of BF was recorded, which leads to an IE of 11.11 eV and an improved value for ν_BF⁺ of 1690 cm^-1. All spectra were simulated by calculating Franck-Condon factors from optimised structures based on quantum chemical calculations.

Cross-predicting the dynamics of an optically injected single-mode semiconductor laser using reservoir computing

In real-world dynamical systems, technical limitations may prevent complete access to their dynamical variables. Such a lack of information may cause significant problems, especially when monitoring or controlling the dynamics of the system is required or when decisions need to be taken based on the dynamical state of the system. Cross-predicting the missing data is, therefore, of considerable interest. Here, we use a machine learning algorithm based on reservoir computing to perform cross-prediction of unknown variables of a chaotic dynamical laser system. In particular, we chose a realistic model of an optically injected single-mode semiconductor laser. While the intensity of the laser can often be acquired easily, measuring the phase of the electric field and the carriers in real time, although possible, requires a more demanding experimental scheme. We demonstrate that the dynamics of two of the three dynamical variables describing the state of the laser can be reconstructed accurately from the knowledge of only one variable, if our algorithm has been trained beforehand with all three variables for a limited period of time. We analyze the accuracy of the method depending on the parameters of the laser system and the reservoir. Finally, we test the robustness of the cross-prediction method when adding noise to the time series. The suggested reservoir computing state observer might be used in many applications, including reconstructing time series, recovering lost time series data and testing data encryption security in cryptography based on chaotic synchronization of lasers.

Critical evaluation of an innovative mesh for bilateral transabdominal preperitoneal (TAPP) repair of inguinal hernias

PURPOSE

Transabdominal preperitoneal hernia mesh plasty (TAPP) offers significant benefits to patients undergoing bilateral inguinal hernia repair. We evaluated a novel pre-shaped, large-pored, titanium-coated, lightweight polypropylene mesh for bilateral placement as an alternative to two separate meshes.

METHODS

Thirty-six patients underwent elective surgical repair of bilateral inguinal hernias with the new mesh at three departments of surgery in Linz and Graz, Austria, between May 1, 2015 and June 30, 2017.

RESULTS

All operations were completed without intraoperative complications or conversion to open procedures. The mean operation time was 74 min. There were no postoperative procedure-related complications with the exception of one hematoseroma of the spermatic cord. Two symptomatic medial recurrences (2/36 patients = 5.6%, 2/72 hernia repairs = 2.8%, respectively) after supravesical and medial hernia repair with the bilateral mesh were seen at structured follow-up examinations 6 and 12 months postoperatively.

CONCLUSION

Treatment of bilateral inguinal hernias with the newly designed bilateral mesh for TAPP theoretically brings benefits in terms of resistance to forces acting on the mesh. The larger area may decrease the risk for mesh bulging and recurrence, and one large mesh might provide more stable support than two separate meshes overlapping at the midline. The results of our study do not confirm these theoretical benefits regarding a high recurrence rate (2.8%) after treatment of medial hernia defects. We recommend re-designing the mesh with only a small central slit, which would provide a broader mesh bridge with sufficient overlap for all types of inguinal and femoral hernias, including medial and supravesical defects. After the mesh has been re-designed, a new study should evaluate its real benefits before it is marketed.

Kinetics of the a-C3H5 + O2 reaction, investigated by photoionization using synchrotron radiation

The kinetics of the combustion-relevant reaction of the allyl radical, a-C3H5, with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring, using the CRF-PEPICO (Combustion Reactions Followed by Photoelectron Photoion Coincidence Spectroscopy) setup. The ability to measure threshold photoelectron spectra enables a background-free detection of reactive species as well as an isomer-specific analysis of reaction products. Allyl was generated by direct photodissociation of allyl iodide at 266 nm and 213 nm and indirectly by the reaction of propene with Cl atoms, which were generated by photolysis from oxalyl chloride at 266 nm. Experiments were conducted at room temperature at low pressures between 0.8 and 3 mbar using Ar as the buffer gas and with excess O2 to maintain nearly pseudo-first-order reaction conditions. Whereas allyl was detected by photoionisation using synchrotron radiation, the main reaction product allyl peroxy was not observed due to dissociative ionisation of this weakly bound species. From the concentration-time profiles of the allyl signal, second-order rate constants between 1.35 × 1011 cm3 mol-1 s-1 at 0.8 mbar and 1.75 × 1011 cm3 mol-1 s-1 at 3 mbar were determined. The rates obtained for the different allyl radical generation schemes agree well with each other, but are about a factor of 2 higher than the ones reported previously using He as a buffer gas. The discrepancy is partly attributed to the higher collision efficiency of Ar causing a varying fall-off behavior. When allyl is produced by the reaction of propene with Cl atom, an unexpected product is observed at m/z = 68, which was identified as 1,3-butadienal in the threshold photoelectron spectrum. It is formed in a secondary reaction of allyl with the OCCl radical, which is generated in the 266 nm photolysis of oxalyl chloride.

Consistency properties of chaotic systems driven by time-delayed feedback

Consistency refers to the property of an externally driven dynamical system to respond in similar ways to similar inputs. In a delay system, the delayed feedback can be considered as an external drive to the undelayed subsystem. We analyze the degree of consistency in a generic chaotic system with delayed feedback by means of the auxiliary system approach. In this scheme an identical copy of the nonlinear node is driven by exactly the same signal as the original, allowing us to verify complete consistency via complete synchronization. In the past, the phenomenon of synchronization in delay-coupled chaotic systems has been widely studied using correlation functions. Here, we analytically derive relationships between characteristic signatures of the correlation functions in such systems and unequivocally relate them to the degree of consistency. The analytical framework is illustrated and supported by numerical calculations of the logistic map with delayed feedback for different replica configurations. We further apply the formalism to time series from an experiment based on a semiconductor laser with a double fiber-optical feedback loop. The experiment constitutes a high-quality replica scheme for studying consistency of the delay-driven laser and confirms the general theoretical results.

The ortho-benzyne cation is not planar

A recent review on the photoionisation of the C₆H₄ isomer ortho-benzyne suggests that bands reported in earlier photoelectron spectra might be due to side products or contaminations, while computations raise doubts, whether the cation has a planar geometry. We therefore reinvestigate the photoionisation of ortho-benzyne, generated by pyrolysis from benzocyclobutenedione, by photoion mass-selected threshold photoelectron (ms-TPE) spectroscopy using synchrotron radiation. The experiments are accompanied by a theoretical study that investigates the structure of the ortho-benzyne cation systematically as a function of the computational method, up to CASPT2(11,14) ab initio computations. Our study leads to a re-evaluation of the ionisation energy of ortho-benzyne. It reveals that the ortho-benzyne cation has indeed a twisted C₂ geometry rather than a C_2v structure. A vertical ionisation energy IE_vert of 9.77 eV and an adiabatic ionisation energy of IE_ad = 9.56 eV are computed for ortho-benzyne. A Franck-Condon simulation of the photoelectron spectrum based on the CASPT2 results and including three electronic states of the cation is in agreement with the experiment and yields IE_ad = 9.51 eV (+50 meV/-100 meV). Since this value is in contrast with previous work, the ionisation energy has to be revised based on our study. Computational methods based on density functional theory give a reasonable description of the cationic ground state, but fail for the corresponding excited electronic states that are indispensible for a proper assignment of the photoelectron spectrum.

Role of dynamical injection locking and characteristic pulse events for low frequency fluctuations in semiconductor lasers

We investigate the dynamics of semiconductor lasers subject to time-delayed optical feedback from the perspective of dynamical self-injection locking. Based on the Lang-Kobayashi model, we perform an analysis of the well-known Low Frequency Fluctuations (LFFs) in the frequency-intensity plane. Moreover, we investigate a recently found dynamical regime of fragmented LFFs by means of a locking-range analysis, spectral comparison and precursor pulse identification. We show that LFF dynamics can be explained by dynamical optical injection locking due to the delayed optical feedback. Moreover, the fragmented LFFs occur due to a re-injection locking induced by a particular optical pulse structure in the chaotic feedback dynamics. This is corroborated by experiments with a semiconductor laser experiencing delayed feedback from an optical fiber loop. The dynamical nature of the feedback injection results in an eventual loss, but also possible regaining, of the locking, explaining the recently observed phenomenon of fragmented LFFs.

Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical

We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C₇H₇, after UV excitation. Femtosecond time-resolved photoelectron imaging was applied to investigate the photodynamics of the radical. The experiments were accompanied by excited state dynamics simulations using surface hopping. Benzyl has been excited at 265 nm into the D-band (ππ*) and the dynamics was probed using probe wavelengths of 398 nm or 798 nm. At a probe wavelength of 398 nm a single time constant of around 70-80 fs was observed. When the dynamics was probed at 798 nm, a second time constant τ₂ = 1.5 ps was visible, which can be attributed to further non-radiative deactivation to the lower-lying D₁/D₂ states.

Semiconductor laser linewidth reduction by six orders of magnitude via delayed optical feedback

We demonstrate a coherence increase by six orders of magnitude of a standard quantum well semiconductor laser. Using a simple, optical-fiber-based feedback scheme, we stabilize the laser in a high-gain mode of a long external cavity. In a modified self-heterodyne measurement, we mix the high-gain mode with a strongly suppressed side mode and obtain an interference linewidth of only 12.6 Hz, corresponding to a decoherence of (3.1±2.9) Hz. In an independent characterization using an etalon, we deduce an upper limit of 300 Hz for the laser linewidth. The laser stably resides in this mode for tens of seconds. Our results agree with theoretical predictions.

Combined Effects of Neurotrophin Secreting Transplants, Exercise, and Serotonergic Drug Challenge Improve Function in Spinal Rats

Objectives. To determine the effects of neurotrophin-secreting transplants combined with exercise and serotonergic drug challenges on recovery of hindlimb function in rats with midthoracic spinal cord transection injuries. Methods. Spinalized animals received transplants of fibroblasts genetically modified to express brain-derived neurotrophic factor and neurotrophin-3 and daily cycling exercise. Hindlimb movement in an open-field test (BBB) was scored weekly. Serotonin agonists were used monthly to further stimulate motor function. Axonal growth was quantified in the transplant and at L5 using immunocytochemical markers. Weights of hindlimb muscles were used to assess muscle atrophy. Results. Neurotrophin-secreting transplants stimulated axonal growth, and cycling prevented muscle atrophy, but individual treatments did not improve motor scores. Combined treatments resulted in improvements in motor function. Serotonergic agonists further improved function in all groups, and transplant groups with exercise achieved weight-supporting levels following drug treatment. Conclusion. Combined treatments, but not individual treatments, improved hindlimb function.

Transplantation of neural progenitor cells in chronic spinal cord injury

Previous studies demonstrated that neural progenitor cells (NPCs) transplanted into a subacute contusion injury improve motor, sensory, and bladder function. In this study we tested whether transplanted NPCs can also improve functional recovery after chronic spinal cord injury (SCI) alone or in combination with the reduction of glial scar and neurotrophic support. Adult rats received a T10 moderate contusion. Thirteen weeks after the injury they were divided into four groups and received either: 1. Medium (control), 2. NPC transplants, 3. NPC+lentivirus vector expressing chondroitinase, or 4. NPC+lentivirus vectors expressing chondroitinase and neurotrophic factors. During the 8 weeks post-transplantation the animals were tested for functional recovery and eventually analyzed by anatomical and immunohistochemical assays. The behavioral tests for motor and sensory function were performed before and after injury, and weekly after transplantation, with some animals also tested for bladder function at the end of the experiment. Transplant survival in the chronic injury model was variable and showed NPCs at the injury site in 60% of the animals in all transplantation groups. The NPC transplants comprised less than 40% of the injury site, without significant anatomical or histological differences among the groups. All groups also showed similar patterns of functional deficits and recovery in the 12 weeks after injury and in the 8 weeks after transplantation using the Basso, Beattie, and Bresnahan rating score, the grid test, and the Von Frey test for mechanical allodynia. A notable exception was group 4 (NPC together with chondroitinase and neurotrophins), which showed a significant improvement in bladder function. This study underscores the therapeutic challenges facing transplantation strategies in a chronic SCI in which even the inclusion of treatments designed to reduce scarring and increase neurotrophic support produce only modest functional improvements. Further studies will have to identify the combination of acute and chronic interventions that will augment the survival and efficacy of neural cell transplants.

Experimental Phase-Space Tomography of Semiconductor Laser Dynamics

We perform phase-space tomography of semiconductor laser dynamics by simultaneous experimental determination of optical intensity, frequency, and population inversion with high temporal resolution. We apply this technique to a laser with delayed feedback, serving as prominent example for high-dimensional chaotic dynamics and as model system for fundamental investigations of complex systems. Our approach allows us to explore so far unidentified trajectories in phase space and identify the underlying physical mechanism.

Assignment of high-lying bending mode levels in the threshold photoelectron spectrum of NH2: a comparison between pyrolysis and fluorine-atom abstraction radical sources

The bending mode progression in the photoelectron spectrum of NH₂ was observed and assigned up to υ₂⁺ ≤ 5 and K_a⁺ ≤ 3.

Formation of polycyclic aromatic hydrocarbons from bimolecular reactions of phenyl radicals at high temperatures

The self-reaction of the phenyl radical is one of the key reactions in combustion chemistry.

Molecular-like hierarchical self-assembly of monolayers of mixtures of particles

We present a technique that uses an externally applied electric field to self-assemble monolayers of mixtures of particles into molecular-like hierarchical arrangements on fluid-liquid interfaces. The arrangements consist of composite particles (analogous to molecules) which are arranged in a pattern. The structure of a composite particle depends on factors such as the relative sizes of the particles and their polarizabilities, and the electric field intensity. If the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles form a ring around it. The number of particles in the ring and the spacing between the composite particles depend on their polarizabilities and the electric field intensity. Approximately same sized particles form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate.

17β-Estradiol reduces nitric oxide production in the Guinea pig cochlea

Intense noise exposure and the application of ototoxic substances result in increased levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as nitric oxide (NO). In order to reduce the free NO concentration in the inner ear under pathological conditions, the use of natural cytoprotective substances such as 17β-estradiol is a promising therapeutic concept. In male guinea pigs the organ of Corti and the lateral wall were isolated from the cochlea and afterwards incubated for 6 h in cell-culture medium. 17β-Estradiol was adjusted in 2 concentrations to organ cultures of the right ears (12 animals per concentration). The left ears were used as controls. The NO production was quantified in the supernatant by chemiluminescence after incubation. Depending on the concentration, 17β-estradiol reduced NO in the organ of Corti by 43% (p=0.015) and 46% (p=0.026), respectively. In the lateral wall, the NO concentration was reduced by 24%, but without statistical significance (p=0.86). However, when analyzing the association between the 2 cochlear regions for each animal separately, the NO concentrations were lower in nearly all 17β-estradiol-treated ears compared to controls. In order to demonstrate the flexibility of the organ culture system, the NO donor DETA NONOate and the nitric oxide synthase inhibitors L-NAME and L-NMMA were applied. The electron microscopic analysis revealed a well-preserved cochlear cell morphology after incubation. The ability of 17β-estradiol to influence the NO production preferentially in the organ of Corti might offer new therapeutic perspectives for inner ear protection.

Characterizing the deterministic nature of individual power dropouts in semiconductor lasers subject to delayed feedback

We implement a method to identify the deterministic nature of specific events in the dynamics of a semiconductor laser subject to time-delayed optical feedback. Specifically, we study the power dropouts in the low-frequency fluctuations regime on an individual event basis and identify whether the underlying dominant mechanism is deterministic. Our approach is based on sychronization with a twin system in a symmetric relay configuration. We investigate the dependence of the fraction of deterministically driven (i.e., synchronized) dropouts on the laser's pump current as a key parameter. Our experimental results are corroborated by numerical modeling based on rate equations. Our numerical findings also provide insights into the influence of spontaneous emission noise.

Optoelectronic reservoir computing: tackling noise-induced performance degradation

We present improved strategies to perform photonic information processing using an optoelectronic oscillator with delayed feedback. In particular, we study, via numerical simulations and experiments, the influence of a finite signal-to-noise ratio on the computing performance. We illustrate that the performance degradation induced by noise can be compensated for via multi-level pre-processing masks.

Unilateral evisceration of an eye following cornea and lens perforation in a sulfur-crested cockatoo (Cacatua galerita)

A 24-year old male sulfur-crested Cockatoo (Cacatua galerita) was presented with a subacute perforation of the cornea without involvement of the lens. The bird was treated conservatively and the eye remained quiescent up to a second traumatic corneal perforation associated with a lens capsule rupture 15 months later. Due to the second perforating trauma of an already blind eye involving the lens, evisceration of the eye was performed. Two months after surgery the cosmetic result was excellent. Treatment options for perforating ocular traumas in captive birds are discussed in detail.

Association of microtubule-associated protein (MAP1B) with growing axons in cultured hippocampal neurons

Microtubule-associated protein 1B (MAP1B) is a major constituent of the neuronal cytoskeleton early in development. This protein is present in embryonic brain and is composed of two isoforms that are the result of differential phosphorylation. We examined the distribution of MAP1B during the differentiation of cultured hippocampal neurons and compared it to that of MAP2 and tubulin. We demonstrated by immunofluorescent doublestaining that MAP1B and MAP2 are colocalized in cell bodies and the minor processes of hippocampal neurons during the early stages of development, before the establishment of neuronal polarity. Later, when neurons acquire axonal and dendritic characteristics, MAP1B is sorted into growing axons, including the growth cone, whereas MAP2 is restricted to dendrites and cell bodies. Unlike tubulin, the localization of MAP1B in growing axons is not uniform. Rather, the protein is found concentrated in the distal portion. During later stages of development, the neurons extend a network of fasciculating axonal and dendritic neurites in which the segregation of MAP1B and MAP2 is maintained. However, the staining of MAP1B in mature neuronal cultures decreases in a pattern that resembles the decline of this protein during brain development. These results support the association of MAP1B with growing axons and its correct developmental regulation in the hippocampal culture system.

Spectral and correlation properties of rings of delay-coupled elements: comparing linear and nonlinear systems

The dynamical properties of delay-coupled systems are currently of great interest. So far the analysis has concentrated primarily on identical synchronization properties. Here we study the dynamics of rings of delay-coupled nodes, a topology that cannot show identical synchronization, and compare its properties to those of linear stochastic maps. We find that, in the long delay limit, the correlation functions and spectra of delay-coupled rings of nonlinear systems obey the same scaling laws as linear systems, indicating that important properties of the emerging solution result from network topology.

Zero-lag synchronization and bubbling in delay-coupled lasers

We show experimentally that two semiconductor lasers mutually coupled via a passive relay fiber loop exhibit chaos synchronization at zero lag, and study how this synchronized regime is lost as the lasers' pump currents are increased. We characterize the synchronization properties of the system with high temporal resolution in two different chaotic regimes, namely, low-frequency fluctuations and coherence collapse, identifying significant differences between them. In particular, a marked decrease in synchronization quality develops as the lasers enter the coherence collapse regime. Our high-resolution measurements allow us to establish that synchronization loss is associated with bubbling events, the frequency of which increases with increasing pump current.

Photonic information processing beyond Turing: an optoelectronic implementation of reservoir computing

Many information processing challenges are difficult to solve with traditional Turing or von Neumann approaches. Implementing unconventional computational methods is therefore essential and optics provides promising opportunities. Here we experimentally demonstrate optical information processing using a nonlinear optoelectronic oscillator subject to delayed feedback. We implement a neuro-inspired concept, called Reservoir Computing, proven to possess universal computational capabilities. We particularly exploit the transient response of a complex dynamical system to an input data stream. We employ spoken digit recognition and time series prediction tasks as benchmarks, achieving competitive processing figures of merit.