Composite-type Rb-87 optical-pumping light source for the rubidium frequency standard

The light source is composed of a cylindrical Rb-87 lamp 10 mm diameter and a Rb-85 filter cell 3-7 mm long attached to the front flat face of the lamp. This composite type device is operated in an oven at about 100 C. Thus a light source for Rb-87 hyperfine optical pumping less than 4 cm long by 3 cm diameter was constructed

Global Climate Action 2022: How have international initiatives delivered, and what more is possible

Contains fulltext : 285265.pdf (Publisher’s version ) (Open Access)This report is the latest stocktake of international cooper- ative climate action. International cooperative initiatives (ICIs) have been a major feature of international climate governance ever since the UNFCCC started recording them in 2013. These partnerships engage a wide range of non- state and subnational actors, including businesses, inves- tors, civil society, national governments, and international organizations. We identified 601 ICIs launched since 2013 with more than 70,000 instances1 of participation by cities and regions, businesses, and by domestic and international NGOs. The total number of ICIs covered in this study has more than doubled compared to previous analyses as a result of examining outcomes from all major climate summits and campaigns since 2014. The growth of active initiatives (85% of all ICIs launched since 2013) has flat- tened since 2019. This is partly explained by the expiration of many initiatives that were launched prior or around the UN Climate Conference in Paris in 2015. The outbreak of the COVID 19 pandemic may also explain lower growth of new initiatives, especially in 2020. Overall productivity of initiatives is trending downwards. Through assessing the extent whether initiatives’ outputs (e.g., infrastructure, research, new installations) are consist- ent with their functions (e.g., training, norm-/standard set- ting, technical on-the-ground implementation), we observed a higher share of low or non-performing initiatives in both mitigation and adaptation since 2019. Overall productivity of initiatives is also trending downwards. ICIs have been launched without further implementation and operation- alization of commitments. This gap between commitments and implementation risks to undermine the credibility of ICIs and the campaigns and summits that convene them. The downwards trend in productivity may be explained by ICIs initially picking ‘low-hanging fruit’ and subsequently having to take more difficult measures. Moreover, the COVID-19 pandemic has likely affected the performance of ICIs. During the pandemic, ICIs’ production of outputs that are location-specific (such as in-person trainings, and new infrastructure or installations) decreased at a faster rate than those that are not location specific (such as websites, online platforms, and research publications). Conversely, we observe a rapid growth of webcasted events, which may reflect a replacement of physical activities by virtual ones. Our analysis suggests a strong and growing underrep- resentation of the Global South. Although ICIs have great potential to contribute to sustainable development in devel- oping countries, studies have consistently shown a strong underrepresentation of the Global South. Implementation disproportionately takes place in the Global North. In line with previous assessments our analysis shows the under- representation of funders, leaders, and participants of ICIs based in non-OECD countries. Moreover, since 2015 the share of outputs produced in the Global North has steadily grown. Some imbalances are to be expected as they appro- priately and reflect differentiated responsibilities and the need for a strong focus on climate mitigation. Nonetheless, the benefits of ICIs, particularly adaptation and resilience building, should also accrue to developing countries. Summit and campaign organizers should steer towards higher performance by setting requirements for ICIs, particularly among initiatives that are launched at cli- mate conferences, summits and by COP presidencies. For instance, before featuring ICIs at climate conferences, organizers should require ICIs to provide evidence that they are making progress against targets and/or have capacities and resources to deliver on pledges. Possible measures identified in the literature include the appointment of dedi- cated staff and/or a secretariat, regular reporting, credible budgets, and openness for new partners to join an initiative, while facilitating interfaces between non-state, subnational actors, policymakers and funders. The report assessed the potential contributions of 12 international sector initiatives launched around and during COP26 (hereinafter, ‘Glasgow initiatives’) on future green- house gas (GHG) emission reductions. We found that the theoretical coverage of these Glasgow initiatives is large: they cover sectors that could potentially lead to 11 GtCO2e lower emissions in 2030 compared to the aggregate of NDCs, addressing a considerable part of the ‘ambition gap’ between the NDC scenario and the benchmark 1.5°C scenario (Figure ES-1). However, not all governments have signed up and impact of signatories is quite small because many already have the action included in their NDC: There- fore, a full implementation of the initiatives’ 1.5°C-aligned goals by the current signatories would only lead to about 5 GtCO2e of emission reductions additional to the NDC scenario (Figure ES- 1). Ambition can be raised in two ways based on these results: First, the biggest potential lies in additional governments signing up to initiatives that have not yet done so (6 GtCO2e). The theory of change of the initiatives is to put non-signatories on the spot, but membership since the Glasgow COP has changed only marginally. Second, govern- ments that have signed up have not yet fully taken these actions into account in their NDCs and therefore could increase the ambition in their NDCs (5 GtCO2e). Future COPs could generate momentum in sectors not covered by the Glasgow initiatives. Although the Glasgow initiatives’ emission reduction potential is substantial, there are still sectors in which momentum for rapid transition toward decarbonisation is needed, including the buildings sector and heavy industry sectors other than steel, such as chemicals and cement. These sectors have not been well covered by ICIs, especially by those that involve large emitting countries and established international institutions. The presidencies of the next few COPs as well as the UN Climate Change High-Level Champions may take the leader- ship to generate momentum to accelerate decarbonisation in these sectors. We also compared these Glasgow initiatives to those pre- viously launched at major international conferences, which have shown mixed performance results , in terms of, for example, financing and reporting requirements. The lim- ited literature indicates that there continues to be a lack of enforcement mechanisms in some Glasgow initiatives. However, there are also noticeable improvements in other Glasgow initiatives , such as annual progress assessment mandated to international organisations and, more impor- tantly, securing finance for implementation. Continued political drive from national governments can help realize the Glasgow initiatives’ potential. The political drive as shown by the UK Presidency has been crucial for establishing the Glasgow initiatives with their launch. Continued political drive is required for the poten- tial impact of the initiatives to materialise and expand. Upcoming COP Presidencies and UN Climate Change High- Level Champions may represent this political drive and generate more leadership, particularly among large emitting countries, in order to maintain momentum and credibility after COP27 and to drive towards more signatories and implementation of global climate action.28 p

Fast Purcell-enhanced single photon source in 1,550-nm telecom band from a resonant quantum dot-cavity coupling

High-bit-rate nanocavity-based single photon sources in the 1,550-nm telecom band are challenges facing the development of fibre-based long-haul quantum communication networks. Here we report a very fast single photon source in the 1,550-nm telecom band, which is achieved by a large Purcell enhancement that results from the coupling of a single InAs quantum dot and an InP photonic crystal nanocavity. At a resonance, the spontaneous emission rate was enhanced by a factor of 5 resulting a record fast emission lifetime of 0.2 ns at 1,550 nm. We also demonstrate that this emission exhibits an enhanced anti-bunching dip. This is the first realization of nanocavity-enhanced single photon emitters in the 1,550-nm telecom band. This coupled quantum dot cavity system in the telecom band thus provides a bright high-bit-rate non-classical single photon source that offers appealing novel opportunities for the development of a long-haul quantum telecommunication system via optical fibres.Comment: 16 pages, 4 figure

Superresolution Full-polarimetric Imaging for Radio Interferometry with Sparse Modeling

We propose a new technique for radio interferometry to obtain superresolution full-polarization images in all four Stokes parameters using sparse modeling. The proposed technique reconstructs the image in each Stokes parameter from the corresponding full-complex Stokes visibilities by utilizing two regularization functions: the ℓ 1 norm and the total variation (TV) of the brightness distribution. As an application of this technique, we present simulated linear polarization observations of two physically motivated models of M87 with the Event Horizon Telescope. We confirm that ℓ 1+TV regularization can achieve an optimal resolution of ~25%–30% of the diffraction limit λ/D[subscript max], which is the nominal spatial resolution of a radio interferometer for both the total intensity (i.e., Stokes I) and linear polarizations (i.e., Stokes Q and U). This optimal resolution is better than that obtained from the widely used Cotton–Schwab CLEAN algorithm or from using ℓ 1 or TV regularizations alone. Furthermore, we find that ℓ 1+TV regularization can achieve much better image fidelity in linear polarization than other techniques over a wide range of spatial scales, not only in the superresolution regime, but also on scales larger than the diffraction limit. Our results clearly demonstrate that sparse reconstruction is a useful choice for high-fidelity full-polarimetric interferometric imaging

Automatic Network Fingerprinting through Single-Node Motifs

Complex networks have been characterised by their specific connectivity patterns (network motifs), but their building blocks can also be identified and described by node-motifs---a combination of local network features. One technique to identify single node-motifs has been presented by Costa et al. (L. D. F. Costa, F. A. Rodrigues, C. C. Hilgetag, and M. Kaiser, Europhys. Lett., 87, 1, 2009). Here, we first suggest improvements to the method including how its parameters can be determined automatically. Such automatic routines make high-throughput studies of many networks feasible. Second, the new routines are validated in different network-series. Third, we provide an example of how the method can be used to analyse network time-series. In conclusion, we provide a robust method for systematically discovering and classifying characteristic nodes of a network. In contrast to classical motif analysis, our approach can identify individual components (here: nodes) that are specific to a network. Such special nodes, as hubs before, might be found to play critical roles in real-world networks.Comment: 16 pages (4 figures) plus supporting information 8 pages (5 figures

Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline

The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline