Transform-limited single photons from a single quantum dot

A semiconductor quantum dot mimics a two-level atom. Performance as a single photon source is limited by decoherence and dephasing of the optical transition. Even with high quality material at low temperature, the optical linewidths are a factor of two larger than the transform-limit. A major contributor to the inhomogeneous linewdith is the nuclear spin noise. We show here that the nuclear spin noise depends on optical excitation, increasing (decreasing) with increasing resonant laser power for the neutral (charged) exciton. Based on this observation, we discover regimes where we demonstrate transform-limited linewidths on both neutral and charged excitons even when the measurement is performed very slowly

Cerebrospinal fluid biomarkers in Alzheimer’s disease, vascular dementia and ischemic stroke patients: a critical analysis

Vascular factors are thought to contribute to the development of disease pathology in neurodegenerative dementia such as Alzheimer’s disease (AD). Another entity, called vascular dementia (VaD), comprises a less defined group of dementia patients having various vascular diseases that especially emerge in the elderly population and require valid options for examination and differential diagnosis. In the context of a retrospective study, we analyzed the cerebrospinal fluid (CSF) biomarkers t-tau, p-tau and Aß42 of a total of 131 patients with AD (n = 47), mild cognitive impairment (MCI) (n = 22), VaD (n = 44) and stroke (n = 18). We found a remarkable alteration in CSF biomarker profile in AD, VaD and in acute ischemic events. CSF profile in AD patients was altered in a very similar way as in stroke patients, without statistical differences. In stroke, increase depend largely on size and duration after the initial event. Total tau levels were useful to differ between VaD and stroke. Aß42 decreased in a similar way in AD, VaD and stroke and had a trend to lower levels in MCI but not in controls

Differential clinical efficacy of anti-CD4 monoclonal antibodies in rat adjuvant arthritis is paralleled by differential influence on NF-κB binding activity and TNF-α secretion of T cells

The aim of this study was to analyze the differential effects of three anti-CD4 monoclonal antibodies (mAbs) (with distinct epitope specifities) in the treatment of rat adjuvant arthritis (AA) and on T-cell function and signal transduction. Rat AA was preventively treated by intraperitoneal injection of the anti-CD4 mAbs W3/25, OX35, and RIB5/2 (on days -1, 0, 3, and 6, i.e. 1 day before AA induction, on the day of induction [day 0], and thereafter). The effects on T-cell reactivity in vivo (delayed-type hypersensitivity), ex vivo (ConA-induced proliferation), and in vitro (mixed lymphocyte culture) were assessed. The in vitro effects of anti-CD4 preincubation on T-cell receptor (TCR)/CD3-induced cytokine production and signal transduction were also analyzed. While preventive treatment with OX35 and W3/25 significantly ameliorated AA from the onset, treatment with RIB5/2 even accelerated the onset of AA by approximately 2 days (day 10), and ameliorated the arthritis only in the late phase (day 27). Differential clinical effects at the onset of AA were paralleled by a differential influence of the mAbs on T-cell functions, i.e. in comparison with OX35 and W3/25, the 'accelerating' mAb RIB5/2 failed to increase the delayed-type hypersentivity (DTH) to Mycobacterium tuberculosis, increased the in vitro tumor necrosis factor (TNF)-α secretion, and more strongly induced NF-κB binding activity after anti-CD4 preincubation and subsequent TCR/CD3-stimulation. Depending on their epitope specificity, different anti-CD4 mAbs differentially influence individual proinflammatory functions of T cells. This fine regulation may explain the differential efficacy in the treatment of AA and may contribute to the understanding of such treatments in other immunopathologies

Strategies for weed control in maize in water sensitive areas

Dargestellt werden seit 2014 vom Pflanzenschutzdienst Niedersachsen durchgeführten Gemeinschaftsversuche zur Unkrautbekämpfung unter besonderer Berücksichtigung von Wasserschutzaspekten. Herbizid-Wirkstoffe, deren Metabolite vermehrt in Grundwasser-Gütemessnetzen in Niedersachsen gefunden wurden (Chloracetamide, v.a. S-Metolachlor) standen dabei im Mittelpunkt der Untersuchungen. Es zeigte sich, dass bezüglich S-Metolachlor gleichwertige bodenwirksame Alternativwirkstoffe zur Verfügung stehen. Gleichwohl wird die Frage diskutiert, ob durch ein gezieltes Wirkstoffmanagement (Rotation) die Austragsgefahr für die o.a. Wirkstoffgruppe minimiert werden kann. Ziel dabei ist, eine möglichst breite Wirkstoffpalette mit Bodenherbiziden im Maisanbau zu erhalten, um dadurch zum einen einer Resistenzbildung vorzubeugen und zum anderen einer `Übernutzung` verbleibender Wirkstoffe entgegen zu wirken. Letzteres könnte dann ebenfalls zu einer stärkeren Grundwassergefährdung führen. In einem ergänzenden Versuchsprojekt in 2017 konnten Erkenntnisse zur Wirksamkeit und Umsetzbarkeit mechanischer und kombinierter Verfahren der Unkrautbekämpfung gesammelt werden. Dabei zeigte sich, dass rein mechanische Maßnahmen mit einem hohen Risiko von Ertragsverlusten verbunden sind, hauptsächlich dann, wenn die Unkrautkonkurrenz in der Maisreihe nicht ausreichend ausgeschaltet werden kann. Höhere Wirkungssicherheit bei geringeren Kosten wurde durch die Kombination aus breitflächiger Vorlage eines blattaktiven Herbizids und anschließendem Hackeinsatz erzielt. Mögliche Strategien der Unkrautbekämpfung insbesondere in Wasserschutzgebeiten werden diskutiert.Since 2014, the Crop Protection Service Niedersachsen has carried out joint experiments on weed control with special consideration of water protection aspects. The focus of the investigations was the handling of herbicidal active substances whose metabolites were increasingly found in groundwater quality measurement networks in Lower Saxony (chloroacetamides, especially S-metolachlor). It was found that s-metolachlor has equivalent soil active ingredients. Nonetheless, the question is being discussed whether a targeted active ingredient management (rotation) can reduce the risk of discharge for the active ingredient. The aim ist o obtain the widest possible range of active ingredients with soil herbicides in maize cultivation, thereby preventing the formation of resistance on the one hand, and counteracting an overuse of remaining active ingredients on the other hand. The latter could then also lead to a stronger groundwater hazard. An additional experimental project in 2017 provided insights into the effectiveness and practicability of mechanical and combined weed control methods. It showed that purely mechanical measures are associated with a high risk of yield losses, especially if the weed competition in the corn line cannot be sufficiently eliminated. Greater efficacy at lower cost was achieved through the combination of broad leafy herbicide presentation and subsequent hacking. Possible strategies for weed control, especially in water conservation areas, are discussed

Silencing of retrotransposons in Dictyostelium by DNA methylation and RNAi

We have identified a DNA methyltransferase of the Dnmt2 family in Dictyostelium that was denominated DnmA. Expression of the dnmA gene is downregulated during the developmental cycle. Overall DNA methylation in Dictyostelium is ∼0.2% of the cytosine residues, which indicates its restriction to a limited set of genomic loci. Bisulfite sequencing of specific sites revealed that DnmA is responsible for methylation of mostly asymmetric C-residues in the retrotransposons DIRS-1 and Skipper. Disruption of the gene resulted in a loss of methylation and in increased transcription and mobilization of Skipper. Skipper transcription was also upregulated in strains that had genes encoding components of the RNA interference pathway disrupted. In contrast, DIRS-1 expression was not affected by a loss of DnmA but was strongly increased in strains that had the RNA-directed RNA polymerase gene rrpC disrupted. A large number of siRNAs were found that corresponded to the DIRS-1 sequence, suggesting concerted regulation of DIRS-1 expression by RNAi and DNA modification. No siRNAs corresponding to the standard Skipper element were found. The data show that DNA methylation plays a crucial role in epigenetic gene silencing in Dictyostelium but that different, partially overlapping mechanisms control transposon silencing

Facilitating stress prevention in micro and small-sized enterprises:Protocol for a mixed method study to evaluate the effectiveness and implementation process of targeted web-based interventions

BACKGROUND: Workplace-related stress is a major risk factor for mental and physical health problems and related sickness absence and productivity loss. Despite evidence regarding the effectiveness of different workplace-based interventions, the implementation of stress prevention interventions is rare, especially in micro and small-sized enterprises (MSE) with fewer than 50 employees. The joint research project “PragmatiKK”(+) aims to identify and address the specific barriers to the implementation of stress prevention interventions in MSE. This study protocol describes a mixed method study design to evaluate the effectiveness of adapted stress prevention interventions and the implementation process via an integrated web-based platform (“System P”) specifically targeted at MSE. METHODS: First, we develop a web-based intervention, which accounts for the specific working conditions in MSE and addresses stress prevention at a structural and behavioral level. Second, we use common methods of implementation research to perform an effect and process evaluation. We analyze the effectiveness of the web-based stress prevention interventions by comparing depressive symptoms at baseline and follow-up (after 6 months and 12 months). Indicators for a successful implementation process include acceptability, adoption, feasibility, reach, dose, and fidelity, which we will measure with quantitative web-based questionnaires and qualitative interviews. We will also analyze the accumulated usage data from the web-based platform. DISCUSSION: Collecting data on the implementation process and the effectiveness of a web-based intervention will help to identify and overcome common barriers to stress prevention in MSE. This can improve the mental health of employees in MSE, which constitute more than 90% of all enterprises in Germany. (+) Full Project Name: „PragmatiKK - Pragmatische Lösungen für die Implementation von Maßnahmen zur Stressprävention in Kleinst- und Kleinbetrieben “(= Pragmatic solutions for the implementation of stress prevention interventions in micro and small-sized enterprises). TRIAL REGISTRATION: German Register of Clinical Studies (DRKS): DRKS00026154, date of registration: 2021-09-16. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-022-12921-7