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Unsolved Problem (unsolved + problem)
Selected AbstractsUnsolved problems in observational astronomy.ASTRONOMISCHE NACHRICHTEN, Issue 6-8 2004Abstract We present the highlights of current observational programs in stellar optical spectroscopy carried out with 8-10 m class telescopes as well as with smaller telescopes. Topics discussed include: 1. light elements abundances and their cosmological implications; 2. search for Population III stars and spectroscopy of extremely metal deficient stars; 3. abundances of different stellar populations in the Galaxy; 4. spectroscopy of resolved stars in Local Group galaxies; 5. Li and Be abundances and internal mixing in stars; 6. spectroscopy of very-low mass stars and brown dwarfs; 7. radial velocity search of extrasolar planets; 8. stellar oscillations and asteroseismology; 9. stellar magnetic activity and Doppler imaging of stellar surface features. We also highlight the role that dedicated 1-2 m automatic telescopes with spectroscopic capabilities can play in several fields of stellar optical spectroscopy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Unsolved problems in observational astronomy.ASTRONOMISCHE NACHRICHTEN, Issue 6-8 2004Abstract The existence of rapidly slewing robotic telescopes and fast alert distribution via the Internet is revolutionizing our capability to study the physics of fast astrophysical transients. But the salient challenge that optical time domain surveys must conquer is mining the torrent of data to recognize important transients in a scene full of normal variations. Humans simply do not have the attention span, memory, or reaction time required to recognize fast transients and rapidly respond. Autonomous robotic instrumentation with the ability to extract pertinent information from the data stream in real time will therefore be essential for recognizing transients and commanding rapid follow-up observations while the ephemeral behavior is still present. Here we discuss how the development and integration of three technologies: (1) robotic telescope networks; (2) machine learning; and (3) advanced database technology, can enable the construction of smart robotic telescopes, which we loosely call "thinking" telescopes, capable of mining the sky in real time. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Union Citizenship,Metaphor or Source of Rights?EUROPEAN LAW JOURNAL, Issue 1 2001Norbert Reich After nearly ten years of introducing Union Citizenship as a concept into Community law it seems time to draw a preliminary evaluation of its importance in reshaping the legal and social positions of citizens living in the EU, more precisely in its Member States. The balance sheet is however mixed: On the one hand, the prevalent position in legal doctrine seems to be that Union citizenship is merely a derived condition of nationality, while on the other side certain fundamental rights are based on criteria other than citizenship/nationality alone. The European Charter on Fundamental Rights will not overcome this dilemma. This can be shown in conflictual areas which are in the centre of discusion in the paper, namely the (limited!) use of the concept of citizenship to extend existing free movement rights in the new case law of the Court of Justice, the resistance towards granting ,quasi-citizenship' rights to third country nationals lawfully resident in the Union for a longer period of time, and the yet unsolved problem of imposing ,implied duties' based on a doctrine of ,abus de droit' upon citizens paralleling the rights granted to them. As a conclusion the author is of the opinion that the question asked for in the title can be answered in the positive only to a limited extent. Citizenship appears to be a sleeping fairy princess still be be kissed awake by the direct effect of Community law. [source] Biogeochemical modelling of the rise in atmospheric oxygenGEOBIOLOGY, Issue 4 2006M. W. CLAIRE ABSTRACT Understanding the evolution of atmospheric molecular oxygen levels is a fundamental unsolved problem in Earth's history. We develop a quantitative biogeochemical model that simulates the Palaeoproterozoic transition of the Earth's atmosphere from a weakly reducing state to an O2 -rich state. The purpose is to gain an insight into factors that plausibly control the timing and rapidity of the oxic transition. The model uses a simplified atmospheric chemistry (parameterized from complex photochemical models) and evolving redox fluxes in the Earth system. We consider time-dependent fluxes that include organic carbon burial and associated oxygen production, reducing gases from metamorphic and volcanic sources, oxidative weathering, and the escape of hydrogen to space. We find that the oxic transition occurs in a geologically short time when the O2 -consuming flux of reducing gases falls below the flux of organic carbon burial that produces O2. A short timescale for the oxic transition is enhanced by a positive feedback due to decreasing destruction of O2 as stratospheric ozone forms, which is captured in our atmospheric chemistry parameterization. We show that one numerically self-consistent solution for the rise of O2 involves a decline in flux of reducing gases driven by irreversible secular oxidation of the crust caused by time-integrated hydrogen escape to space in the preoxic atmosphere, and that this is compatible with constraints from the geological record. In this model, the timing of the oxic transition is strongly affected by buffers of reduced materials, particularly iron, in the continental crust. An alternative version of the model, where greater fluxes of reduced hydrothermal cations from the Archean seafloor consume O2, produces a similar history of O2 and CH4. When climate and biosphere feedbacks are included in our model of the oxic transition, we find that multiple ,Snowball Earth' events are simulated under certain circumstances, as methane collapses and rises repeatedly before reaching a new steady-state. [source] Contiguity Constraints for Single-Region Site Search ProblemsGEOGRAPHICAL ANALYSIS, Issue 4 2000Thomas J. Cova This paper proposes an explicit set of constraints as a general approach to the contiguity problem in site search modeling. Site search models address the challenging problem of identifying the best area in a study region for a particular land use, given that there are no candidate sites. Criteria that commonly arise in a search include a site's area, suitability, cost, shape, and proximity to surrounding geographic features. An unsolved problem in this modeling arena is the identification of a general set of mathematical programming constraints that can guarantee a contiguous solution (site) for any 0,1 integer-programming site search formulation. The constraints proposed herein address this problem, and we evaluate their efficacy and efficiency in the context of a regular and irregular tessellation of geographic space. An especially efficient constraint form is derived from a more general form and similarly evaluated. The results demonstrate that the proposed constraints represent a viable, general approach to the contiguity problem. [source] The Meissner and Pacinian sensory corpuscles revisited new data from the last decade,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2009José A. Vega Abstract This article reviews the biochemical, physiological, and experimental data cumulated during the last decade on the Meissner and Pacinian corpuscles. It includes information about (i) the localization of molecules recently detected in sensory corpuscles; (ii) the unsolved problem of the accessory fibers in sensory corpuscles and the occurrence of myelin within them; (iii) the development of sensory corpuscles, especially their neuronal and growth factor dependency; (iv) the composition and functional significance of the extracellular matrix as an essential part of the mechanisms involved in the genesis of the stimuli generated in sensory corpuscles; (v) the molecular basis of mechanotransduction; (vi) a miscellaneous section containing sparse new data on the protein composition of sensory corpuscles, as well as in the proteins involved in live,death cell decisions; (vii) the changes in sensory corpuscles as a consequence of aging, the central, or peripheral nervous system injury; and finally, (viii) the special interest of Meissner corpuscles and Pacinian corpuscles for pathologists for the diagnosis of some peripheral neuropathies nd neurodegenerative diseases. Microsc. Res. Tech., 2009. © 2008 Wiley-Liss, Inc. [source] Atrial Linear Lesions: Feasibility Using CryoablationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2006KLAUS KETTERING Background: Long linear lesions are created in the left atrium to modify the atrial substrate, thereby curing atrial fibrillation. The creation of long linear left atrial lesions using radiofrequency (RF) ablation is time consuming and difficult. Furthermore, it might result in significant complications. Cryoablation might overcome some of the disadvantages of RF ablation. Therefore, the aim of our study was to assess whether the creation of a long linear lesion is possible using cryotherapy. Methods: A right atrial septal linear lesion was created in six pigs (median weight: 50 kg; range: 40,60 kg). The ablation procedure was performed with a 7-F Freezor cryocatheter. The nonfluoroscopic mapping system LocaLisa was used as a navigation tool. At each point, freezing was maintained at the lowest attainable temperature (,75°C) for 4 minutes. The CARTO system was used for the evaluation of the linear lesions. Furthermore, all animals were sacrificed immediately after the ablation procedure and a postmortem examination of the lesions was performed. Additionally, an analysis of the amplitudes of the intracardiac electrograms registered via the ablation catheter was performed before and after the ablation procedure. Results: A right atrial septal linear lesion could be created successfully in all six pigs. For the performance of this ablation line, a median number of 16 cryoapplications (range, 11,26) was necessary. The amplitudes of the intracardiac electrograms registered via the ablation catheter decreased significantly after ablation. The CARTO bipolar voltage map revealed very low potentials along the ablation line and showed a sharply demarcated ablation area at the septum in all pigs. Further analysis of the CARTO map revealed an incomplete conduction block in all cases. Most of the pigs had a small gap close to the fossa ovalis. The postmortem examination of 2,3,5-triphenyl-tetrazolium chloride-stained specimens showed sharply demarcated lesions without any ulcerations. There were no major complications during the procedure. Conclusions: The creation of long linear lesions using cryoablation is feasible and safe. Lesion characteristics are different and more favorable than those created by RF. However, the aim of creating a transmural lesion and a complete conduction block remains an unsolved problem even with current cryoablation techniques. Nevertheless, growing experience and technical improvements might overcome some of the current limitations of this new technique. [source] Recommendations for treatment of intermittent mild persistent asthma in children and adolescentsPEDIATRIC PULMONOLOGY, Issue 3 2009Charles K. Naspitz MD Abstract Many parents and caretakers of children and adolescents with mild persistent asthma (MPA) do not follow proposed guidelines, namely the daily and continuous administration of inhaled corticosteroids (ICS). Instead, parents and caretakers tend to use ICS and bronchodilators intermittently for short periods and restart such therapy only when symptoms reappear. It is our opinion that intermittent treatment of MPA in children and adolescents might achieve the same level of asthma control as has been achieved in adults. We propose, therefore, that after an initial period of stabilization with age-appropriate doses of oral glucocorticoids or high-dose ICS and short-acting beta-2 agonists (SABA), caretakers can stop treatment once there are no longer signs or symptoms of asthma. When asthmatic symptoms recur, treatment should be restarted with ICS and SABA, or oral corticosteroids if the exacerbation is severe. The perception of developing asthma symptoms remains an unsolved problem. Based on our clinical experience in children and adolescents with asthma, we list a number of signs and symptoms that precede an exacerbation of asthma, allowing for an early re-introduction of treatment to prevent an exacerbation. Pediatr Pulmonol. 2009; 44:205,208. © 2009 Wiley-Liss, Inc. [source] Estimating the order of a hidden markov modelTHE CANADIAN JOURNAL OF STATISTICS, Issue 4 2002Rachel J. Mackay Abstract While the estimation of the parameters of a hidden Markov model has been studied extensively, the consistent estimation of the number of hidden states is still an unsolved problem. The AIC and BIC methods are used most commonly, but their use in this context has not been justified theoretically. The author shows that for many common models, the penalized minimum-distance method yields a consistent estimate of the number of hidden states in a stationary hidden Markov model. In addition to addressing the identifiability issues, she applies her method to a multiple sclerosis data set and assesses its performance via simulation. Bien que les travaux traitant de I'estimation des paramétres d'une chatne de Markov cachéd soient nombreux, le probléme d'estimer de facon convergente le nombre détats cachés reste ouvert. Les méthodes du CIA et du CIB sont souvent utilisées a cette fin, sans toutefois que leur emploi ait été justifié théoriquement. L'auteur montre ici que, sous des conditions convenables, la méthode de distance minimum pénalisée conduit à une estimation convergente du nombre d'états cachés dans une chaine de Markov cachée stationnaire. En plus d'aborder le probléme d'identifiabilité, elle applique sa méthode à des données concernant la sclérose en plaques et en évalue la performance a taille finie par voie de simulation. [source] Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo,THE JOURNAL OF GENE MEDICINE, Issue 1 2006Gunter Kaul Abstract Background Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF-2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo. Methods Lapine articular chondrocytes overexpressing a lacZ or a human FGF-2 gene sequence were encapsulated in alginate and further characterized. The resulting lacZ or FGF-2 spheres were applied to cartilage defects in the knee joints of rabbits. In vivo, cartilage repair was assessed qualitatively and quantitatively at 3 and 14 weeks after implantation. Results In vitro, bioactive FGF-2 was secreted, leading to a significant increase in the cell numbers in FGF-2 spheres. In vivo, FGF-2 continued to be expressed for at least 3 weeks without leading to differences in FGF-2 concentrations in the synovial fluid between treatment groups. Histological analysis revealed no adverse pathologic effects on the synovial membrane at any time point. FGF-2 gene transfer enhanced type II collagen expression and individual parameters of chondrogenesis, such as the cell morphology and architecture of the new tissue. Overall articular cartilage repair was significantly improved at both time points in vivo. Conclusions The data suggest that localized overexpression of FGF-2 enhances the repair of cartilage defects via stimulation of chondrogenesis, without adverse effects on the synovial membrane. These results may lead to the development of safe gene-based therapies for human articular cartilage defects. Copyright © 2005 John Wiley & Sons, Ltd. [source] Gene therapy for cartilage defectsTHE JOURNAL OF GENE MEDICINE, Issue 12 2005Magali Cucchiarini Abstract Focal defects of articular cartilage are an unsolved problem in clinical orthopaedics. These lesions do not heal spontaneously and no treatment leads to complete and durable cartilage regeneration. Although the concept of gene therapy for cartilage damage appears elegant and straightforward, current research indicates that an adaptation of gene transfer techniques to the problem of a circumscribed cartilage defect is required in order to successfully implement this approach. In particular, the localised delivery into the defect of therapeutic gene constructs is desirable. Current strategies aim at inducing chondrogenic pathways in the repair tissue that fills such defects. These include the stimulation of chondrocyte proliferation, maturation, and matrix synthesis via direct or cell transplantation-mediated approaches. Among the most studied candidates, polypeptide growth factors have shown promise to enhance the structural quality of the repair tissue. A better understanding of the basic scientific aspects of cartilage defect repair, together with the identification of additional molecular targets and the development of improved gene-delivery techniques, may allow a clinical translation of gene therapy for cartilage defects. The first experimental steps provide reason for cautious optimism. Copyright © 2005 John Wiley & Sons, Ltd. [source] TIN ISOTOPY,A NEW METHOD FOR SOLVING OLD QUESTIONSARCHAEOMETRY, Issue 5 2010M. HAUSTEIN Tin was a vital commodity in times past. In central Europe, the earliest finds of tin-bronze date to about 2200 bc, while in Greece they are c. 400,500 years earlier. While there is evidence for prehistoric copper mining,for example, in the Alps or mainland Greece, among other places,the provenance of the contemporary tin is still an unsolved problem. This work deals with a new approach for tracing the ancient tin via tin isotope signatures. The tin isotope ratios of 50 tin ores from the Erzgebirge region (D) and 30 tin ores from Cornwall (GB) were measured by MC,ICP,MS. Most ore deposits were found to be quite homogeneous regarding their tin isotope composition, but significant differences were observed between several deposits. This fact may be used to distinguish different tin deposits and thus form the basis for the investigation of the provenance of ancient tin that has been sought for more than a century. Furthermore, the tin-isotope ratio of the ,Himmelsscheibe von Nebra' will be presented: the value fits well with the bulk of investigated tin ores from Cornwall. [source] Supersoft X-ray sources and the progenitors of Type Ia supernovaeASTRONOMISCHE NACHRICHTEN, Issue 2 2010Ph. Podsiadlowski Abstract Supersoft X-ray sources have been proposed as one of the major channels to produce Type Ia supernovae (SNe Ia). However, the true nature of the progenitors has remained an unsolved problem. In this review I summarize the present status of our understanding of SN Ia progenitors, the main classes of progenitor models and recent observational constraints. At present, neither the single-degenerate nor the double-degenerate model can be ruled out, and indeed more than one channel may be required to explain the observed SN Ia diversity. Finally, I discuss the origin of the lightcurve peak , lightcurve width relation (the ,Phillips relation') and show that it is expected to depend on metallicity; this needs to be taken into account in high-precision cosmological applications (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The role of air turbulence in warm rain initiationATMOSPHERIC SCIENCE LETTERS, Issue 1 2009Lian-Ping Wang Abstract Quantitative parameterization of turbulent collision of cloud droplets represents a major unsolved problem in cloud physics. Here a hybrid direct simulation tool is used specifically to quantify the turbulent enhancement of the gravitational collision-coalescence. Simulation results show that air turbulence can enhance the collision kernel by an average factor of about 2, and the observed trends are supported by scaling arguments. An impact study using the most realistic collection kernel suggests that cloud turbulence can significantly reduce the time for warm rain initiation. Areas for further development of the hybrid simulation and the impact study are indicated. Copyright © 2009 Royal Meteorological Society [source] Epithelial branching: The power of self-loathingBIOESSAYS, Issue 3 2007Wen-Chin Lee Branching morphogenesis of epithelia is an important mechanism in mammalian development. The last decade has seen the identification of many signalling pathways and intracellular mechanisms that control epithelial branching. Tissue-level mechanisms that space new branches out have, however, remained an unsolved problem. A recent publication by Nelson et al.1 suggests,if extrapolation from their novel and abstract culture system is valid,that branches may be spaced out by a system of mutual inhibition based on diffusion of TGF,. Such a system would allow a developing tree to arrange itself, without detailed genetic specification, by adaptive self-organization. BioEssays 29: 205,207, 2007. © 2007 Wiley Periodicals, Inc. [source] String and supergravity motivated cosmologyFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005Article first published online: 30 JUN 200, R. Kallosh In this pedagogical lecture we explain some basic part of the standard cosmological model which is most relevant for the fundamental theoretical physics. We stress the common features and differences between early universe inflation and late-time acceleration. We than proceed with some recent attempts to address the issues of cosmology in string theory and higher dimensional supergravity with the emphasis on successes and still unsolved problems. [source] A Resurgent Phoenix--A Hypothesis for the Origin of MeiosisIUBMB LIFE, Issue 1 2002Wei Li Abstract The origin and evolution of sex is a great puzzle in biology, and meiosis is the core of sex. Here, we propose a new hypothesis that meiosis may have evolved by blending features of two responses that cells have to deal with double-strand-DNA breaks, recombinational repair and apoptosis. This hypothesis can explain some unsolved problems and is in agreement with some known molecular mechanisms, cytological phenomena, and the fossil records. Furthermore, it can predict some testable features of meiosis. [source] Factors affecting the formation of fingering in water-assisted injection-molded thermoplasticsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2006Shih-Jung Liu Abstract Water-assisted injection-molding technology has received extensive attention in recent years, due to the lightweight of plastic parts, relatively low-resin cost per part, faster cycle time, and flexibility in the design and manufacture. However, there are still some unsolved problems that confound the overall success of this technology. One of these is the water "fingering" phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. This study has investigated the effects of various processing parameters on the formation of fingering in water-assisted injection-molded thermoplastic parts. Both amorphous and semicrystalline polymers were used to mold the parts. The influence of water channel geometry, including aspect ratio and fillet geometry, on the fingering was also investigated. It was found that water-assisted injection-molded amorphous materials gave less fingering, while molded semicrystalline parts gave more fingering when compared to those molded by gas-assisted injection molding. For the water channels used in this study, the channels with a rib on the top produced parts with the least water fingering. Water fingering in molded parts decreases with the height-to-thickness ratio of the channels. The water pressure, water injection delay time and short-shot size were found to be the principal parameters affecting the formation of water fingering. In addition, a numerical simulation based on the transient heat conduction model was also carried out to help better explain the mechanism for the formation of fingering in water-assisted injection-molded thermoplastics. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 98,108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20062 [source] Progress in the Study of Molecular Genetic Improvements of Poplar in ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2006Shan-Zhi Lin Abstract The poplar is one of the most economically important and intensively studied tree species owing to its wide application in the timber industry and as a model material for the study of woody plants. The natural resource of poplars in China is replete. Over the past 10 years, the application of molecular biological techniques to genetic improvements in poplar species has been widely studied in China. Recent advances in molecular genetic improvements of poplar, including cDNA library construction, gene cloning and identification, genetic engineering, gene expression, genetic linkage map construction, mapping of quantitative trait loci (QTL) and molecular-assisted selection, are reviewed in the present paper. In addition, the application of modern biotechnology to molecular improvements in the genetic traits of the poplar and some unsolved problems are discussed. (Managing editor: Li-Hui Zhao) [source] A COMPLETE THEORY OF COMPARATIVE STATICS FOR DIFFERENTIABLE OPTIMIZATION PROBLEMSMETROECONOMICA, Issue 1 2006M. Hossein Partovi ABSTRACT A new comparative statics formalism using generalized compensated derivatives is presented that, in contrast to existing methodologies, directly yields constraint-free semidefiniteness results for any differentiable, constrained optimization problem. The formalism provides a natural and powerful method of constructing comparative statics results, free of constraints and unrestricted in scope. New results on envelope relations, invariance conditions, rank inequalities and non-uniqueness are derived that greatly extend their utility and reach. The methodology is illustrated by deriving the comparative statics of multiple linear constraint utility maximization models and the principal-agent problem with hidden actions, both highly nontrivial and hitherto unsolved problems. [source] The occurrence of surface roughness in gas assist injection molded nylon compositesPOLYMER COMPOSITES, Issue 2 2000Shih-Jung Liu Gas assist injection molding has increasingly become an important industrial process because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that limit the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composities. The materials used were 15 % and 35% glass-fiber filled nylon-6 composites. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. Two "float-shape" axisymmetric cavities were used. After molding, the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature, mold temperature, melt filling speed, short-shot size, gas pressure, and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness results mainly from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure. [source] Nutritional Effect of Dialysis TherapyARTIFICIAL ORGANS, Issue 3 2003Tsutomu Sanaka Abstract: The prognosis of patients with end-stage renal disease has been improved by the recent remarkable advances in medical and engineering technology. However, there are still many unsolved problems in the clinical field. One of the problems is an intractable malnutrition characterized by clinical manifestations including hypoproteinemia and decrease in muscular volume, which is associated with deterioration in the quality of the patient's life. Malnutrition in hemodialysis patients involves abnormal energy metabolism and aberrant amino acid metabolism. In the most malnourished patients, immunodefense mechanisms and homeostasis are disrupted, greatly influencing the prognosis. Moreover, when the performance of dialyzer used is too high, the dialysis treatment might remove a necessary nutrient for the patient. There is also a possibility that the protein catabolism is accelerated when the biocompatibility is inferior. On the other hand, in malnutri-tion, the circulating level of insulin-like growth factor-1 (IGF-1) falls while the level of insulin-like growth factor binding protein-1 (IGFBP-1) is remarkably increased. It has been recognized that IGF-1 and IGFBP-1 are indicators reflecting the initiation of a malnutritional state in patients with chronic renal failure, although there are many indicators such as albumin, prealbumin, and anthropometric measurement for nutritional assessment. We have suggested that r-hGH and IGF-1 improve the malnutritional state by alleviating hypoproteinemia and abnormality of serum amino acid profile in uremic patients on hemodialysis. The serum IGF-1/IGFBP-1 ratio is useful not only as a nutritional parameter but also as a predicting index of responsiveness to r-hGH. It is necessary to examine the problem from various angles to improve malnutrition in the dialysis patient, while considering the above mentioned. [source] The outbursts of classical and recurrent novaeASTRONOMISCHE NACHRICHTEN, Issue 2 2010M.F. Bode Abstract In this review, I present our current state of knowledge regarding both Classical Nova and Recurrent Nova systems. Two particular objects (V1974 Cyg and RS Oph) are chosen to illustrate the range of phenomena that may be associated with their outbursts. The wider importance of nova research is emphasised and some of the most pressing unsolved problems are summarised (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Supersoft X-ray sourcesASTRONOMISCHE NACHRICHTEN, Issue 2 2010F. Haberl Abstract The workshop "Supersoft X-ray Sources , New Developments" brought together observers and theoretician to discuss the present status and unsolved problems of supersoft source research. A large part of the workshop was devoted to optical novae and their supersoft state. Large samples of supersoft X-ray sources were presented from nearby galaxies, as well as extensive monitoring campaigns ofbright individual sources. The theoretical modelling oflight curves and high-resolution X-ray spectra are well underway, but details are often not yet understood (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Missing pieces of the solar jigsaw puzzleASTRONOMY & GEOPHYSICS, Issue 5 2009David Tsiklauri David Tsiklauri reviews the role of small-scale, kinetic effects in the solar corona, throwing new light on unsolved problems of solar physics, such as coronal heating and solar flare particle acceleration. [source] | |||||||||||||||||||||||||