From two-dimensional colloidal self-assembly to three-dimensional nanolithography.

A number of "top-down" lithographic and "bottom-up" self-assembly methods have been developed to fabricate three-dimensional (3D) nanostructures to support the recent advances in nanotechnology. But they are limited by a number of factors such as fabrication cost, pattern resolution, and/or flexibility of geometry. Here we present a 3D nanolithography process that utilizes self-assembled nanospheres to create a periodic array of focal spots, which are then replicated across multiple depth in a transparent medium according to the Talbot effect. The Talbot field then exposes a pattern onto the underlying photoresist, recording the 3D intensity distribution. We have demonstrated designable complex 3D periodic structures with 80 nm minimum feature size, roughly one-fourth of the operating wavelength. This approach combines 2D colloidal self-assembly and 3D phase lithography, is robust, cost-effective, and widely applicable to nanoscale research and manufacturing.

Modelling and analysis of time-variant directed interrelations between brain regions based on BOLD-signals.

Time-variant Granger Causality Index (tvGCI) was applied to simulated and measured BOLD signals to investigate the reliability of time-variant analysis approaches for the identification of directed interrelations between brain areas on the basis of fMRI data. Single-shot fMRI data of a single image slice with short repetition times (200 ms, 16000 frames/subject, 64x64 voxels) were acquired from 5 healthy subjects during an externally-driven, self-paced finger-tapping paradigm (57-59 single taps for each subject). BOLD signals were derived from the pre-supplementary motor area (preSMA), the supplementary motor area (SMA), and the primary motor cortex (M1). The simulations were carried out by means of a Dynamic Causal Modelling (DCM) approach. The tvGCI as well as time-variant Partial Directed Coherence (tvPDC) were used to identify the modelled connectivity network (connectivity structure - CS - of the DCM). Different CSs were applied by using dynamic systems (Generalized Dynamic Neural Network - GDNN) and trivariate autoregressive (AR) processes. The influence of the low-pass characteristics of the simulated hemodynamic response (Balloon model) and of the measuring noise was tested. Additionally, our modelling strategy considered "spontaneous" BOLD fluctuations before, during, and after the appearance of the event-related BOLD component. Couplings which were extracted from the simulated signals were statistically evaluated (tvGCI for shuffled data, confidence tubes for tvGCI courses). We demonstrate that connections of our CS models can be correctly identified during the event-related BOLD component and with signal-to-noise-ratios corresponding to those of the measured data. The results based on simulations can be used to examine the reliability of connectivity identification based on BOLD signals by means of time-variant as well as time-invariant connectivity measures and enable a better interpretation of the analysis results using fMRI data. A readiness-BOLD response was only detected in one subject. However, in two subjects a strong time-variant connection (tvGCI) from preSMA to SMA was observed 3 s before the tapping was executed. This connection was accompanied by a weaker rise of the tvGCI from preSMA to M1. These preceding interrelations were confirmed in the other subjects by the dynamics of tvGCI courses. Based on the results of tvGCI analysis, the time-evolution of an individual connectivity network is shown for each subject.

Visualization of flagellar interactions on bacterial carpets.

Methods for the in-depth study of the physics of microscale actuation of microfluidics environments by flagellated bacteria 'teamsters' have been developed. These methods, which include single and multi-colour fluorescent labelling and electron microscopy allow for the analysis of the effect that individual flagellar filaments have on bacterially driven microstructures, and allow for the investigation of the interaction and coordination of flagellar filaments of neighbouring bacteria on densely packed monolayers of bacteria, 'bacterial carpets'. We show that the flagella of bacteria that are immobilized on a surface often interact with each other, and that the flagella of these bacteria do not often form multi-flagella bundles that are aligned with the cell body.

Tracking the time-varying cortical connectivity patterns by adaptive multivariate estimators.

The directed transfer function (DTF) and the partial directed coherence (PDC) are frequency-domain estimators that are able to describe interactions between cortical areas in terms of the concept of Granger causality. However, the classical estimation of these methods is based on the multivariate autoregressive modelling (MVAR) of time series, which requires the stationarity of the signals. In this way, transient pathways of information transfer remains hidden. The objective of this study is to test a time-varying multivariate method for the estimation of rapidly changing connectivity relationships between cortical areas of the human brain, based on DTF/PDC and on the use of adaptive MVAR modelling (AMVAR) and to apply it to a set of real high resolution EEG data. This approach will allow the observation of rapidly changing influences between the cortical areas during the execution of a task. The simulation results indicated that time-varying DTF and PDC are able to estimate correctly the imposed connectivity patterns under reasonable operative conditions of signal-to-noise ratio (SNR) ad number of trials. An SNR of five and a number of trials of at least 20 provide a good accuracy in the estimation. After testing the method by the simulation study, we provide an application to the cortical estimations obtained from high resolution EEG data recorded from a group of healthy subject during a combined foot-lips movement and present the time-varying connectivity patterns resulting from the application of both DTF and PDC. Two different cortical networks were detected with the proposed methods, one constant across the task and the other evolving during the preparation of the joint movement.

Time-variant analysis of fast-fMRI and dynamic contrast agent MRI sequences as examples of 4-dimensional image analysis.

OBJECTIVES: Image sequences with time-varying information content need appropriate analysis strategies. The exploration of directed information transfer (interactions) between neuronal assemblies is one of the most important aims of current functional MRI (fMRI) analysis. Additionally, we examined perfusion maps in dynamic contrast agent MRI sequences of stroke patients. In this investigation, the focus centers on distinguishing between brain areas with normal and reduced perfusion on the basis of the dynamics of contrast agent inflow and washout. METHODS: Fast fMRI sequences were analyzed with time-variant Granger causality (tvGC). The tvGC is based on a time-variant autoregressive model and is used for the quantification of the directed information transfer between activated brain areas. Generalized Dynamic Neural Networks (GDNN) with time-variant weights were applied on dynamic contrast agent MRI sequences as a nonlinear operator in order to enhance differences in the signal courses of pixels of normal and injured tissues. RESULTS: A simple motor task (self-paced finger tapping) is used in an fMRI design to investigate directed interactions between defined brain areas. A significant information transfer can be determined for the direction primary motor cortex to supplementary motor area during a short time period of about five seconds after stimulus. The analysis of dynamic contrast agent MRI sequences demonstrates that the trained GDNN enables a reliable tissue classification. Three classes are of interest: normal tissue, tissue at risk for death, and dead tissue. CONCLUSIONS: The time-variant multivariate analysis of directed information transfer derived from fMRI sequences and the computation of perfusion maps by GDNN demonstrate that dynamic analysis methods are essential tools for 4D image analysis.

The neural structures involved in cross-modal recognition and tactile discrimination performance: an investigation using 2-DG.

Given the failure of the ablation method to identify the neural structures/systems that are crucial for cross-modal recognition (CMR) and for tactile discrimination performance (TDP), we injected radioactive 2-deoxy-[14C]glucose (2-DG) into monkeys trained to a high level of CMR or TDP. Nine monkeys were trained to recognize in one sense-modality, to a level greater than 80% correct, the objects experienced in the alternate modality on only a single prior trial. After injection, CMR was continued (Expt. 1a) exactly as before, except that all CMR problems were now in only one direction; or (Expt. 1b) the second--the CMR--trial of each problem was not realized (i.e. no objects were available in the second modality) so that the monkey merely 'expected' the cross-modal trial. Nine other monkeys were trained on a graded roughness discrimination task with conventional 'titration' procedures to a stable level of performance, either (Expt. 2a) without having undergone any cortical removal, or (Expt. 2b) after unilateral removal--contralateral or ipsilateral to the preferred hand--of the posterior insula or of the second somatosensory projection cortex (SII). Exactly the same training procedures were continued in Expt. 2 after injection of 2-DG. Coronal radiographs were made at 490 microns for all 18 monkeys (and also for a 19th, which served as a control in Expt. 1b). The optical densities of the autoradiographs were measured quantitatively in respect of 50 structures or part-structures (e.g. sulci, thalamic nuclei, subcortical structures); they were rated either with the aid of 'pseudo-colours' produced by the computer, or directly by judging the black/white optical densities, in respect of 29 other structures. These 79 structures were then the dependent variables in MANOVAs or ANOVAs, to determine differences between groups; or within groups with respect to the left/right and ipsilateral/contralateral hemispheres; or interaction effects. It was found that certain structures (e.g. the ventral portion of the claustrum, the insula with its extension ventrally into the fundus, nucleus Medialis dorsalis and nucleus Pulvinar oralis) repeatedly, whereas others (e.g. the amygdala) never gave rise to significant outcomes. Structures in the left cerebral hemisphere were frequently found to be more strongly labelled than those in the right hemisphere.(ABSTRACT TRUNCATED AT 400 WORDS)

[Fibrin gluing in ophthalmic surgery]. / Fibrinklebung in der Ophthalmochirurgie.

A new fibrin adhesive "Beriplast" of the Behringwerke AG Marburg was implemented for conjunctival glueing in 42 patients after intracapsular cataract extraction. The tissue adhesive was also examined in palpebral tumour surgery as to its compatibility and usefulness. Good functional and cosmetic results were obtained with regard to the conjunctiva and the eyelids, respectively. No cases of incompatibility were registered.

[Metabolism of intravenously administered prostaglandin E1 in patients with peripheral arterial occlusive disease]. / Metabolismus von intravenös appliziertem Prostaglandin E1 bei Patienten mit peripherer arterieller Verschlusskrankheit.

Using high performance liquid chromatography and radioimmunoassay we have investigated the stability of prostaglandin (PG) E1 and its metabolite 13,14-dihydro-PGE1 in human plasma as well as the initial metabolism of PGE1 infused intravenously (80 micrograms/patient/hour) in patients with peripheral arterial occlusive disease. 13,14-dihydro-PGE1 degraded like PGE1 in human plasma at 37 degrees C with a half-life of several hours. During infusion of PGE1 higher plasma concentrations of the major metabolite 15-keto-13,14-dihydro-PGE1 and lower plasma levels of PGE1 and 13,14-dihydro-PGE1 were observed. The metabolite 13,14-dihydro-PGE1 is of interest, since in contrast to 15-keto-13,14-dihydro-PGE1 it is biologically active. The biosynthesis of 13,14-dihydro-PGE1 could contribute to the therapeutic efficacy of PGE1 administered intravenously in patients with peripheral arterial occlusive disease.

[Brief causal relations in EEG based on adaptive Granger causality]. / Untersuchung kurzzeitiger kausaler Beziehungen im EEG auf der Basis der adaptiven Granger Kausalität.

Commonly, coherence and correlation are used to describe interrelations between EEG signals. But, on this basis, the investigation of causality or direction of interrelations is not possible. The general idea of causality between two signals may be expressed in terms of upgrading the predictability of one signal bye the knowledge of the past of the other signal. The best established approach in this context is the so-called Granger causality. The study present an adaptive estimation of Granger causality, which allows to detect dynamic causal relations within time intervals of less 100 ms. The time-variant Granger causality is applied to EEG data of the Stroop task. It could be shown, that conflict situation generates a dense web of directed interactions from posterior to anterior cortical areas.

Time-varying cortical connectivity by adaptive multivariate estimators applied to a combined foot-lips movement.

In this paper we propose the use of an adaptive multivariate approach to define time-varying multivariate estimators based on the Directed Transfer Function (DTF) and the Partial Directed Coherence (PDC). DTF and PDC are frequency-domain estimators that are able to describe interactions between cortical areas in terms of the concept of Granger causality. Time-varying DTF and PDC were obtained by the adaptive recursive fit of an MVAR model with time-dependent parameters, by means of a generalized recursive least-square (RLS) algorithm, taking into consideration a set of EEG epochs. Such estimators are able to follow rapid changes in the connectivity between cortical areas during an experimental task. We provide an application to the cortical estimations obtained from high resolution EEG data, recorded from a group of healthy subject during a combined foot-lips movement, and present the time-varying connectivity patterns resulting from the application of both DTF and PDC. Two different cortical networks were detected, one constant across the task and the other evolving during the preparation of the joint movement.

Features extraction from time-varying cortical networks adopting a theoretical graph approach.

In this work, a novel approach is proposed in order to capture relevant features related to the structure and organization of the functional brain networks estimated in the time-frequency domain. To achieve this, we used a cascade of computational tools able to estimate first the electrical activity of the cortical surface by using high resolution EEG techniques. Then, on the cortical signals from different regions of interests we estimated the time-varying functional connectivity patterns by means of the adaptive Partial Directed Coherence. Such time-varying connectivity estimation returns a series of causality patterns evolving during the examined task which can be summarized and interpreted with the aid of mathematical indexes based on the graph theory. The combination of all these methods is demonstrated on a set of high resolution EEG data recorded from a healthy subject performing a simple foot movement.

Estimation of the time-varying cortical connectivity patterns by the adaptive multivariate estimators in high resolution EEG studies.

The Directed Transfer Function (DTF) and the Partial Directed Coherence (PDC) are frequency-domain estimators, based on the multivariate autoregressive modelling (MVAR) of time series, that are able to describe interactions between cortical areas in terms of the concept of Granger causality. However, the classical estimation of these methods requires the stationary of the signals. In this way, transient pathways of information transfer remains hidden. The objective of this study is to test a time-varying multivariate method for the estimation of rapidly changing connectivity relationships between cortical areas of the human brain, based on DTF/PDC and on the use of adaptive MVAR modelling (AMVAR). This approach will allow the observation of transient influences between the cortical areas during the execution of a task. Time-varying DTF and PDC were obtained by the adaptive recursive fit of an MVAR model with time-dependent parameters, by means of a generalized recursive least-square (RLS) algorithm, taking into consideration a set of EEG epochs. Simulations were performed under different levels of Signal to Noise Ratio (SNR), number of trials (TRIALS) and frequency bands (BAND), and of different values of the RLS adaptation factor adopted (factor C). The results indicated that time-varying DTF and PDC are able to estimate correctly the imposed connectivity patterns under reasonable operative conditions of SNR ad number of trials. Moreover, the capability of follow the rapid changes in connectivity is highly increased by the number of trials at disposal, and by the right choice of the value adopted for the adaptation factor C. The results of the simulation study indicate that DTF and PDC computed on adaptive MVAR can be effectively used to estimate time-varying patterns of functional connectivity between cortical activations, under general conditions met in practical EEG recordings.

[Motivation, volition, and ambivalence: A contribution to understanding of long-term impairments among schizophrenic patients]. / Motivation, Volition und Ambivalenz - Ein Beitrag zum Verständnis langfristiger Beeinträchtigungen bei schizophrenen Patienten.

Traditional concepts of avolition (Kraepelin) and ambivalence (Bleuler) among schizophrenic patients can be interpreted in the light of present ideas of motivation and volition. Accordingly schizophrenic patients are marked both by oppositional high hope and fear components of implicit motives and by the impairment of volitional selfregulation, which both are vulnerability factors. In an environment lacking stimuli the patients cannot surpass their ambivalence through volitional selfregulation and remain passive. In this study 61 schizophrenic patients are compared with a control group of 69 non-patients. As expected, the schizophrenic patients show significant higher fear components of the implicit affiliation, achievement, and power motives, as well as an increased hope component of the affiliation motive. The comparison of subgroups of schizophrenic patients with distinguishing symptoms reveals no differences, which supports the assumption of stable traits.

[A follow-up study of combined cataract/trabeculectomy operation]. / Nachuntersuchung bei kombinierter Katarakt-Trabekulektomieoperation.

In the past 12 years 69 combined trabeculectomy/cataract operations have been performed at Graz University Eye Clinic. Of these, 33 were examined after an average interval of three years. In 23 cases intraocular pressure was regulated without therapy, and four eyes were regulated with additional therapy. In five eyes no satisfactory pressure could be reached and one eye was lost due to late infection. In ten cases a hyphema appeared; in seven cases registered a rise in intraocular pressure was recorded and in two cases a flat chamber. In view of the great variety of indications this method seems to be especially suitable for elderly patients.

[Cartilage transplantation in the knee joint experiment - clinic - technique (author's transl)]. / Die Knorpeltransplantation am Kniegelenk Experiment - Klinik - Technik.

In the knee joints of 195 animals autologous, stored and fresh homologous osteochondral grafts were implanted. Even after 2 years the ultrastructural examination indicates that autologous and fresh homologous grafts survive. The stored grafts are absorbed. The clinical results after transplantation of 38 patients as well as the technique of transplantation are demonstrated.

[Electron microscopic studies of the healing of preserved and non preserved allogenic articular cartilage transplants]. / Elektronenmikroskopische Untersuchungen über die Einheilung konservierter und nicht konservierter allogener Gelenkknorpeltransplantate.

Preserved and fresh homologeous osteochondral grafts were implanted in the knee joints of 150 animals. The animals were sacrificed at various intervals, up to two years. Examination of the tissue was carried out by light microscopy, transmission and scanning electron microscopy. The preserved homologeous grafts become necrotic. Later a substitute tissue is seen. The ultrastructure of this tissue is not the same as that of fibrocartilage nor that of normal articular cartilage. The fresh homologeous transplants with postoperative protecting the joint from stress survive. Immediate postoperative stress leads to biomechanically caused disintegrations in the fresh homologeous grafts. Immunological factors are not important in homologeous osteochondral grafts with defined osseous portion. The most important factor for the survival of the homologeous grafts is the vitality of the transplanted tissue.

[Long-term results after cartilage transplantation]. / Langzeitergebnisse nach Knorpeltransplantation.

The authors' experimental work is concerned with the structure of articular cartilage after transplantation. In the medial condylus of the femur of the rabbit, bone-cartilage defects were produced and filled with bone-cartilage autografts and homografts preserved by different methods. At 2, 4, 6, 12, and 24 months after operation animals were sacrificed. The first phase of the healing process shows regressive processes. The second phase is marked by reactions of repair. The results of the experiment indicate that transplantation of cartilage can be regarded as a possibility of therapy in order to heal bone-cartilage lesions.

[Eye injuries in childhood]. / Augenverletzungen im Kindesalter.

A retrospective study was performed of eye injuries sustained by children up to 15 years old who had to be hospitalized for treatment. The period under review covered five years. The authors reviewed 241 cases with regard to cause of injury, type of injury, treatment, duration of hospitalization and consequences, if any. Most of the injuries were caused by other children, while playing. By far the most common injury was contusion of the bulb, seen in 107 cases. The results of the study published here contain a further breakdown of the criteria mentioned above.

[A case of strabismus concomitans convergens alternans acutus]. / Ein Fall von Strabismus concomitans convergens alternans acutus.

In the present paper the authors report on a case of acute concomitant squint in a 14-year-old girl. A study of the patient's history revealed only psychosomatic factors as possible causes.