Revealing the Exciton Fine Structure in PbSe Nanocrystal Quantum Dots

We measure the photoluminescence (PL) lifetime, $\tau$, of excitons in colloidal PbSe nanocrystals (NCs) at low temperatures to 270~mK and in high magnetic fields to 15~T. For all NCs (1.3-2.3~nm radii), $\tau$ increases sharply below 10~K but saturates by 500~mK. In contrast to the usual picture of well-separated ``bright" and ``dark" exciton states (found, e.g., in CdSe NCs), these dynamics fit remarkably well to a system having two exciton states with comparable - but small - oscillator strengths that are separated by only 300-900 $\mu$eV. Importantly, magnetic fields reduce $\tau$ below 10~K, consistent with field-induced mixing between the two states. Magnetic circular dichroism studies reveal exciton g-factors from 2-5, and magneto-PL shows $>$10\% circularly polarized emission.Comment: To appear in Physical Review Letter

Verletzungen und Fehlbeanspruchungen im leistungsorientierten Rudersport

Die Stellung der Breitensportart Rudern als gesundheitsfördernde Sportform ist in der Literatur gleichlautend positiv beschrieben. Im leistungsorientierten Rudersport müssen neben den Verletzungen und Fehlbeanspruchungen der eigentlichen Sportart die unabdingbaren Nebentrainingsformen berücksichtigt werden. In den neunziger Jahren vollzog sich ein trainingsmethodischer Wandel, die Einführung eines erschwinglichen Rudersimulators und eine technische Weiterentwicklung im Boots- und Ruderbau. Einhergehend kam es zu einer geänderten Belastungsphysiologie, so daß neue Untersuchungen sinnvoll erscheinen. Die vorliegende Arbeit erhebt über den retrospektiven Zeitraum von vier Jahren explorativ das Auftreten von Verletzungen und Fehlbeanspruchungen, wobei deren Qualität und Verteilung in den Trainingsformen Wasser-, Ergometer-, Kraft-, Hallen-, Rad-, Lauftraining und die unter dem Punkt "Sonstige" zusammengefaßten übrigen Trainingsformen registriert wurden. Diese Studie beschreibt trainingsformspezifische Fehlbeanspruchungen und Verletzungen sowie deren Auftreten bei den Beobachtungseinheiten Geschlecht, Leistungsgruppe und Gewichtsklasse. Im Rahmen der Diskussion werden Möglichkeiten und Ansätze zur Prävention erörtert und aufgezeigt. Erfaßt wurden bei einer Rücklaufrate von 44% anhand von auf Meisterschaften und Wettkämpfen ausgeteilten sowie an Bundes- und Landestrainer versendeten tabellarischen Fragebögen die Daten von 110 Wettkampfruderern. Als Kriterium der Aufnahme in diese Studie galt die Teilnahme an nationalen Meisterschaften oder ein der Altersklasse angepaßter wöchentlicher Trainingsumfang. Die Zuordnung der Sportler in die jeweilige Beobachtungseinheit der beiden Leistungsgruppen erfolgte aufgrund von Kaderzugehörigkeit, Teilnahme an internationalen Meisterschaften und zeitlichem Umfang des wöchentlich realisierten Trainings. Der Trainingsumfang der Ruderer beläuft sich in dieser Studie im Durchschnitt auf 12,8 Stunden reiner Belastungszeit pro Woche. Korrelierend zu den verschiedenen Jahreszeiten gestaltet sich das Training der Ruderer unterschiedlich. Im sogenannten Sommertraining, das die Wettkampfperiode beinhaltet, liegt der Schwerpunkt auf der eigentlichen Sportart, was anhand der Trainingsgewichtung von über 77% des Gesamttrainingsumfanges bestätigt wird. Einzig das Krafttraining wird in diesem Zeitraum mit 11% des Umfanges noch erwähnenswert häufig betrieben. Während des aus Übergangs- und Vorbereitungsperiode bestehenden Wintertrainings überwiegen die Nebentrainingsformen deutlich. Das Rudern selbst wird nur zu dem geringen Anteil von knapp 30% des Trainingsumfanges betrieben, wobei das für leistungsorientierte Ruderer unabdingbare Krafttraining in diesem Zeitraum mit 27% den zweitgrößten Stellenwert hat. Neben dem ebenfalls mit großen Anteilen betriebenem Ergometer- und Lauftraining ist in Anbetracht der hohen Beschwerderate beim Hallensport noch der Trainingsanteil von 7% zu erwähnen. Bei 249.480 erfaßten Belastungsstunden wurden bei 57% der Sportler Verletzungen und bei jedem Athleten Fehlbeanspruchungen erfaßt. Die dominierenden Verletzungsformen waren muskuläre Prellungen und Zerrungen sowie Schädigungen der Bandstrukturen der Sprunggelenke in Form von Bänderdehnungen und -Rupturen. Traumen größeren Schwergrades wurden, von der einen bei den sonstigen Trainingsformen aufgetretenen Lendenwirbelkörperfraktur abgesehen, in dieser Studie nicht gefunden. Als die mit Abstand verletzungsreichste Sportform mit erheblichen trainingsbegrenzenden Konsequenzen erweist sich der Hallensport, wobei eine für Ballsportarten typische Lokalisationshäufigkeit am Sprunggelenk aufzufinden war. Männliche Athleten und Hochleistungssportler wiesen jeweils höhere Verletzungsraten als ihre Vergleichpartner auf. Beim Rudern fand sich als sportartspezifisches und zugleich geringfügiges Trauma die bei rudertechnischer Unzulänglichkeit entstehenden Hautabschürfungen der Handknöchel. Schädigungen der Bandstrukturen der Sprunggelenke fanden sich in dieser Sportform nicht. Joggen und die nicht näher erfragten "sonstigen" Sportformen zogen bevorzugt Distorsionen der Sprunggelenke nach sich, wohingegen Rad-, Kraft- und Ergometertraining vereinzelt zu Verletzungen in Form von muskulären Zerrungen führten. Im Vordergrund der Beschwerdesymptomatiken der erfaßten Fehlbeanspruchungen fand sich in allen Trainingsformen eine hohe Betroffenenrate von muskulären Verspannungen. Als ruderspezifisch zu bezeichnende Fehlbelastungen lagen bei 89% der Ruderer subepidermale Blasenbildungen im Bereich zwischen distaler Hohlhandbeugefalte, Grundgliederbeugefalten sowie auf den Grund- und Mittelphalangen vor. Weiterhin fanden sich sportartspezifisch hohe Beschwerderaten der Lendenwirbelsäule und der Kniegelenke sowie im etwas geringeren Umfang Überlastungen der Sehnenstrukturen der Handgelenke ("rower's wrist"). Neben der eigentlichen Sportform treten Fehlbeanspruchungen gleicher Symptomatik beim Ergometer- und Krafttraining auf, wobei die Betroffenenraten korrelierend mit dem geringeren Trainingsumfang niedriger liegen. Athletinnen und Schwergewichte weisen beim Ergometertraining eine deutlich erhöhte Beschwerderate auf. Das Lauftraining führte bei Athleten gehäuft zu Beschwerdesymptomatiken der Kniegelenke. Der aus Art und Umfang der Konsequenzen zugewiesene Schweregrad der erfaßten Verletzungen und Fehlbeanspruchungen zeigt zwischen Geschlecht, Leistungsklasse und Gewichtsklasse teils deutliche Differenzen. Bei ähnlicher Verteilung der Schweregrade der Verletzungen beider Geschlechter waren männliche Athleten zu höherem Anteil von Fehlbeanspruchungen leichten und zu kleineren des schweren Typs betroffen. Bei den Leistungsgruppen finden sich nur geringe Unterschiede der Schweregrade von Verletzungen. Bezüglich der Fehlbeanspruchungen fanden sich bei den Hochleistungssportlern signifikant vermehrt mittelschwere Formen, wohingegen Leistungssportler eher leichte und schwere Fehlbelastungsformen erlitten. Schwergewichte waren vermehrt von schweren Verletzungen betroffen, wohingegen Leichtgewichte zu größeren Teilen mittelschwere angaben. Bezogen auf die Fehlbeanspruchungen fanden sich bei den schwergewichtigen Sportlern charakteristisch vermehrt mittelschwere Formen und bei den Leichtgewichten geringfügig vermehrt leichte. Eine Prävention von Verletzungen ist im leistungsorientiertem Rudersport in besonderem Maße durch Überdenken der Struktur des Hallentrainings möglich. Fehlbeanspruchungen und chronische Überlastungsschäden können insbesondere durch Korrektur von Bewegungsabläufen, Reduzierung biomechanisch ungünstiger Belastungen, durchdachter Trainingsmethodik und regelmäßige sportmedizinische Überwachungen vermindert werden.Rowing as latitudinal sport is identical described as a healthy sport form in whole literature. For rowing as a serious sport in addition to nevertheless existing injuries and faulty demands of the actual sport itselfs the risks of inalienable additional training forms must be taken into account. In the nineties a training-methodical change, the introduction of an affordable rowing simulator and a technical development of boat and blade constructions happened. As a consequence thereof an altered burden physiology appeared, so that new examinations became meaningfully. The present work explorative collects the appearance of injuries and faulty demands over a retrospective time period of four years, whereby their quality and distribution were registered in coherency with the training forms water-, ergometer-, strength-, hall-, wheel-, joggingtraining and the category "miscellaneous", which summarizes all remaining trainingforms. This study describes training-form-specific faulty demands and injuries as well as their appearance with the observation units sex, accomplishment group and weight class. In the framework of the discussion possibilities and bases for the preventive measures are discussed and demonstrated. The Study grasps the data of 110 regatta rowers. Tabular questionnaires were distributed at championships and regattas as well as sent to regional trainers with a reverse piece of advice of 44 percent. The participation in championships and accordingly the old-age class adjusted weekly training scope were regarded as criterion of the reception into this study. The assignment of the athletes into the respective observation unit of the two performance - groups took place on basis of squad affiliation, participation in international master ships and temporal scope of the weekly realized training. The average training scope of the rowers gripped by this study amounts to 12,8 hours of pure burden time per week. Correlating to season the training of the rowers shapes differently. During the so-called summer training, that comprises the match period, the main focus lies on the actual sport which is confirmed by the training priority of over 77 percent of the total training scope. Only the strength training is still gone in for with eleven percent of the scope frequently in this time period. Additional training forms clearly prevail during the winter training consisting of passing and preparation period. Rowing itself even amounts only to the low share of barely 30 percent of the training scope, whereas for achievement-oriented rowers inalienable strength training with 27 percent has the second-biggest status in this time period. Beside the ergometer and jogging training for been also gone in with big shares, hall-sport with a training share of 7 percent is to be mentioned because of the frequent complaints. In 249.480 burden hours injuries were grasped by 57 percent of the athletes, even each athlete suffers faulty demands. The dominant injury forms were muscular contusions and strains as well as damages of the band structures of the talocalcanean joint in form of ligament extensions and rupture. Traumas of bigger heavy degree, refrained from one lumbar vertebrae fracture appeared with a miscellaneous training form, were not found in this study. As by far injury-richest sport form with considerable training-restricting consequences proves the hall-sport, with finding a typical localized maximum for ball sports at the talocalcanean joint. Male athletes and high-performance athletes showed higher injury instalments than their respective comparison partners in each case. For rowing the abrasions of the knuckles caused by rowing-technical deficiency were located as sport-specific and at the same time insignificant trauma. Damages of the band structures of the talocalcanean joint were not located in this sport form. Jogging and not more exact itemised "miscellaneous" sport forms preferentially entailed distortion of the talocalcanean, whereas wheel-, strength-, and ergometer-training sporadic led to injuries in form of muscular strains. In the foreground of the complaint symptomatic of the grasped faulty demands, a high rate of persons concerned in muscular tense was located in all training forms. As rowing specific to mark faulty burdens were with 89 percent of the rowers subepidermal blister developed in the area between distal palmar flexion crease, metacarpophalangeal crease as well as on the proximal and distal middle digital furrow. Further, sport-specifically high complaint instalments were located at the lumbar region of the vertebral column and the knee joints as well as in the some more inferior scope overloads of the sinew structures of the wrists ("rower's wrist"). Beside the actual sport form, faulty demands of same Symptomatic appeared at ergometer- and strength-training, whereby the complaint instalments is lower correlating to the more inferior training scope. Female athletes and heavyweights showed a clearly elevated complaint instalment at the ergometer training. With jogging training complaint symptomatic of the knee joints accumulated. The hardness degrees of the grasped injuries and faulty demands assigned by type and scope of the consequences partly shows significant differences between sex, accomplishment class and weight class. While distribution of the hardness degrees of the injuries is similar for both sexes, male athletes were easy to higher share of faulty demands and to smaller the heavy type concerned. Only low differences of the hardness degrees of injuries are located with the accomplishment groups. Respecting the faulty demands were located significantly with the high-performance athletes increases middle-heavy forms, whereas accomplishment athletes suffered rather easy and heavy faulty burden forms. Heavyweights were increased concerned at heavy injuries, whereas lightweights boasted middle-heavy to larger sharing. Characteristically was located covered on the faulty demands with the heavyweight athletes increased middle-heavy forms and with the lightweights negligibly increases easy forms. A prevention of injuries is possible in the achievement-oriented rowing sport to particular extent through consideration of the structure of the hall-training. Faulty demands and chronic overload damages can especially be decreased by reasoned training methods, correction of movement courses, reduction of biomechanical unfavourable loading and regular sportmedical supervisions

Using Beatboxing for Creative Rehabilitation After Laryngectomy:Experiences From a Public Engagement Project

Laryngectomy is the surgical removal of the larynx (voice box), usually performed in patients with advanced stages of throat cancer. The psychosocial impact of losing the voice is significant, affecting a person’s professional and social life in a devastating way, and a proportion of this patient group subsequently must overcome depression (22–30%) and social isolation (40%). The profound changes to anatomical structures involved in voicing and articulation, as a result of surgery, radiotherapy or chemotherapy (separately or in combination with one another), introduce challenges faced in speech rehabilitation and voice production that complicate social reintegration and quality of life. After laryngectomy, breathing, voicing, articulation and tongue movement are major components in restoring communication. Regular exercise of the chest, neck and oropharyngeal muscles, in particular, is important in controlling these components and keeping the involved structures supple. It is, however, a difficult task for a speech therapist to keep the patient engaged and motivated to practice these exercises. We have adopted a multidisciplinary approach to explore the use of basic beatboxing techniques to create a wide variety of exercises that are seen as fun and interactive and that maximize the use of the structures important in alaryngeal phonation. We herein report on our empirical work in developing patients’ skills, particularly relating to voiced and unvoiced consonants to improve intelligibility. In collaboration with a professional beatboxing performer, we produced instructional online video materials to support patients working on their own and/or with support from speech therapists. Although the present paper is focused predominantly on introducing the structure of the conducted workshops, the rationale for their design and the final public engagement performance, we also include feedback from participants to commence the critical discourse about whether this type of activity could lead to systematic underlying research and robustly assessed interventions in the future. Based on this exploratory work, we conclude that the innovative approach that we employed was found to be engaging, useful, informative and motivating. We conclude by offering our views regarding the limitations of our work and the implications for future empirical research

Crowd:Kollaboration - Konzepte, Erkenntnisse und Fragen

Massen- beziehungsweise Crowd:Kollaboration gewinnt besonders im Kontext aktueller Informations- und Kommunikationstechnologien an Bedeutung für gesellschaftliche Transformationsprozesse und so auch an Relevanz für die pädagogisch(-didaktische) Debatte. Die Frage, wie webbasierte Großgruppenkollaboration auch im Kontext von Hochschule gefördert werden kann, bleibt jedoch weitestgehend ungeklärt. Neben einem theoretischen Verständnis entsprechender Sozialformen besteht hierbei insbesondere ein Mangel an didaktischen Methoden und Szenarien für kollaborative Prozesse der Wissensgenerierung. Hierzu wurde im Rahmen des Teilvorhabens Lernen und Forschen in der Crowd (SCoRe-LFC) eine Konzeptualisierung der Crowd sowie Gestaltungsannahmen und Designkonzepte zur Förderung kollektiver Zusammenarbeit entwickelt. Der Beitrag beschreibt den aktuellen Stand und die Erfahrungen mit den Projektergebnissen und gibt einen Ausblick über die sich anschließenden Fragen. (DIPF/Orig.

Paramagnetic, near-infrared fluorescent Mn-doped PbS colloidal nanocrystals

Mn-doped PbS colloidal nanocrystals in aqueous solution are paramagnetic and optically active in the technologically important biological window between 1.2 and 0.8 μm. Cytoxicity studies show that exposure of human cell lines to the nanoparticles at concentrations up to 0.2 mg mL−1 does not induce any adverse effect

Building a knowledge and innovation platform on diffuse and point soil contamination as base for (inter)national soil policies

This article highlights the importance of soil contamination, both from diffuse and point source pollution. It summarises a series of presentations at the Global Soil Week 2015 illustrating the current understanding of soil exposed to pollutants, including the main sources of contamination, the hazards and risks that pollutants in soil present for the environment and human health, as well as the possible ways to address the problem from both global and EU perspectives. It summarises the World Café discussions on four themes that participants identified as the key areas for further action: remediation of contaminated sites, alternatives to the use of chemicals and pollutants, harmonisation of monitoring and approaches and Knowledge and innovation platform.JRC.H.5-Land Resources Managemen

Tunable magnetic exchange interactions in manganese-doped inverted core/shell ZnSe/CdSe nanocrystals

Magnetic doping of semiconductor nanostructures is actively pursued for applications in magnetic memory and spin-based electronics. Central to these efforts is a drive to control the interaction strength between carriers (electrons and holes) and the embedded magnetic atoms. In this respect, colloidal nanocrystal heterostructures provide great flexibility via growth-controlled `engineering' of electron and hole wavefunctions within individual nanocrystals. Here we demonstrate a widely tunable magnetic sp-d exchange interaction between electron-hole excitations (excitons) and paramagnetic manganese ions using `inverted' core-shell nanocrystals composed of Mn-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe. Magnetic circular dichroism studies reveal giant Zeeman spin splittings of the band-edge exciton that, surprisingly, are tunable in both magnitude and sign. Effective exciton g-factors are controllably tuned from -200 to +30 solely by increasing the CdSe shell thickness, demonstrating that strong quantum confinement and wavefunction engineering in heterostructured nanocrystal materials can be utilized to manipulate carrier-Mn wavefunction overlap and the sp-d exchange parameters themselves.Comment: To appear in Nature Materials; 18 pages, 4 figures + Supp. Inf

Main soil contaminants and their fate in the soil environment

Soil pollution is invisible to the human eye, but it compromises the quality of the food we eat, the water we drink, and the air we breathe and puts human and environmental health at risk. Most contaminants originate from human activities such as industrial processes and mining, poor waste management, unsustainable farming practices, accidents ranging from small chemical spills to accidents at nuclear power plants, and the many effects of armed conflicts. Pollution knows no borders: contaminants are spread throughout terrestrial and aquatic ecosystems and many are distributed globally by atmospheric transport. In addition, they are redistributed through the global economy by way of food and production chains. 
 
 Soil pollution has been internationally recognized as a major threat to soil health, and it affects the soil’s ability to provide ecosystem services, including the production of safe and sufficient food, compromising global food security. Soil pollution hinders the achievement of many of the United Nations Sustainable Development Goals (SDGs), including those related to poverty elimination (SDG 1), zero hunger (SDG 2), and good health and well-being (SDG 3). Soil pollution hits the most vulnerable hardest, especially children and women (SDG 5). The supply of safe drinking water is threatened by the leaching of contaminants into groundwater and runoff (SDG 6). CO2 and N2O emissions from unsustainably managed soils accelerate climate change (SDG 13). Soil pollution contributes to land degradation and loss of terrestrial (SDG 15) and aquatic (SDG 14) biodiversity, and decreased the security and resilience of cities (SDG 11), among others