Intrinsic subspace convergence in TDD MIMO communication

In numerical linear algebra, students encounter early the iterative power method, which finds eigenvectors of a matrix from an arbitrary starting point through repeated normalization and multiplications by the matrix itself. In practice, more sophisticated methods are used nowadays, threatening to make the power method a historical and pedagogic footnote. However, in the context of communication over a time-division duplex (TDD) multipleinput multiple-output (MIMO) channel, the power method takes a special position. It can be viewed as an intrinsic part of the uplink and downlink communication switching, enabling estimation of the eigenmodes of the channel without extra overhead. Generalizing the method to vector subspaces, communication in the subspaces with the best receive and transmit signal-to-noise ratio (SNR) is made possible. In exploring this intrinsic subspace convergence (ISC), we show that several published and new schemes can be cast into a common framework where all members benefit from the ISC.Peer Reviewe

Team Autonomy in Large-Scale Agile

Large-scale software development is increasingly making use of agile practices. In large-scale projects, a team needs to align with other teams and the rest of the organization. This has been shown to threaten team autonomy, which, in turn, reduces responsiveness and flexibility. Hence, agile teams face challenges in adapting to larger-scale development. We conduct a multiple case study of three large-scale projects to investigate barriers to team autonomy in large-scale agile. Two barriers are identified: overall direction and external dependencies. We found that goals are often set by management without involving the teams, that they are often equal to deliverables and deadlines, and that team members often do not know what the goals are. Consequently, teams struggle with setting and communicating goals as well as establishing a shared direction. Organizational dependencies lead to teams having to deal with additional tasks, resulting in specific members shielding the teams from external nois

A remark on the space of metrics having non-trivial harmonic spinors

Let M be a closed spin manifold of dimension congruent to 3 modulo 4. We give a simple proof of the fact that the space of metrics on M with invertible Dirac operator is either empty or it has infinitely many path components

Promises of climate engineering after neoliberalism

The apparent, if uncertain, rejection of neoliberalism manifested by the election of Donald Trump in the US (alongside the slim, but clear majority for Brexit in the UK, and a growing racist and protectionist nationalism across Europe) necessitates renewed analysis of the future of both promises of technical fixes to climate change, such as carbon capture and storage (CCS), carbon dioxide removal (CDR) and solar radiation management (SRM) (in this chapter collectively referred to as climate engineering), and the potential future hegemonic political regimes that may replace neoliberalism. Drawing on a cultural political economy analysis of the co-evolution of political regimes and promises of technical fixes to climate change (Markusson et al. 2017), we here discuss what the current moment of radical destabilisation might augur. The election of Trump indicates a potential unsettling of an established dynamic whereby promises of technical fixes to climate change co-evolved with, and imperfectly supported, the neoliberal power regime and its preferred market-based solutions to the climate change problem. We identify two key and interacting dialectics, between neoliberalism and illiberalism, and between continued neoliberal (but illiberally challenged) US hegemony and budding China-centred liberalism 2.0. Both these dialectics appear conducive to prolonged attention to the promise of climate engineering, as talk and research, or even as limited deployment

The political economy of technical fixes:the (mis)alignment of clean fossil and political regimes

This paper argues that existing critiques of technical fixes are unable to explain our simultaneous enamourment and distrust with technical fixes, and that to do so, we need a political economy analysis. We develop a critical, theoretically grounded conceptualisation of technical fixes as imagined defensive spatio-temporal fixes of specific political economic regimes, and apply it to the case of geoengineering, or ‘clean fossil’, as an attempted technical fix of the climate change problem. We map the promises of clean fossil as proposed solutions to the problem of climate change in discrete episodes since the 1960s. The paper shows that clean fossil promises have been surprisingly poorly aligned with the neoliberal regime, and explains how they have been moderately stable due to those misalignments. We also show that different liberal capitalisms could be supported by different clean fossil technologies, but also that illiberal or more egalitarian regimes remain possible alongside particular, perhaps radically re-envisioned, versions of clean fossil. Ambivalence towards clean fossil technical fix promises is intelligible, given the inherent instability of their co-evolution with neoliberalism and future political regimes

Hemodynamic changes during aortic valve surgery among patients with aortic stenosis

Introduction. Patients with severe aortic stenosis (AS) undergoing surgery are at increased risk of hypotension and hypoperfusion. Although treatable with inotropic agents or fluid, little is known about how these therapies affect central hemodynamics in AS patients under general anesthesia. We measured changes in central hemodynamics after dobutamine infusion and fluid bolus among patients with severe AS and associated these changes with preoperative echocardiography. Methods. We included 33 patients with severe AS undergoing surgical AVR. After induction of general anesthesia, hemodynamic measurements were obtained with a pulmonary artery catheter, including Cardiac index (CI), stroke volume index (SVi) and pulmonary capillary wedge pressure (PCWP). Measurements were repeated during dobutamine infusion, after fluid bolus and lastly after sternotomy. Results. General anesthesia resulted in a decrease in CI and SVi compared to preoperative values. During dobutamine infusion CI increased but mean SVi did not (38 ± 12 vs 37 ± 13 ml/m², p = .90). Higher EF and SVi before surgery and a larger decrease in SVi after induction of general anesthesia were associated with an increase in SVi during dobutamine infusion. After fluid bolus both CI, SVi (48 ± 12 vs 37 ± 13 ml/min/m², p < .0001) and PCWP increased. PCWP increased mostly among patients with a larger LA volume index. Conclusion. In patients with AS, CI can be increased with both dobutamine and fluid during surgery. Dobutamine’s effect on SVI was highly variable and associated with baseline LVEF, and an increase in CI was mostly driven by an increase in heart rate. Fluid increased SVi at the cost of an increase in PCWP

Long-Term Outcome in a Phase II Study of Regional Hyperthermia Added to Preoperative Radiochemotherapy in Locally Advanced and Recurrent Rectal Adenocarcinomas

Hyperthermia was added to standard preoperative chemoradiation for rectal adenocarcinomas in a phase II study. Patients with T3-4 N0-2 M0 rectal cancer or local recurrences were included. Radiation dose was 54 Gy combined with capecitabine 825 mg/m2 × 2 daily and once weekly oxaliplatin 55 mg/m2. Regional hyperthermia aimed at 41.5–42.5 °C for 60 min combined with oxaliplatin infusion. Radical surgery with total or extended TME technique, was scheduled at 6–8 weeks after radiation. From April 2003 to April 2008, a total of 49 eligible patients were recruited. Median number of hyperthermia sessions were 5.4. A total of 47 out of 49 patients (96%) had the scheduled surgery, which was clinically radical in 44 patients. Complete tumour regression occurred in 29.8% of the patients who also exhibited statistically significantly better RFS and CSS. Rate of local recurrence alone at 10 years was 9.1%, distant metastases alone occurred in 25.6%, including local recurrences 40.4%. RFS for all patients was 54.8% after 5 years and CSS was 73.5%. Patients with T50 temperatures in tumours above median 39.9 °C had better RFS, 66.7% vs. 31.3%, p = 0.047, indicating a role of hyperthermia. Toxicity was acceptable.publishedVersio

Airborne ultra-wideband radar sounding over the shear margins and along flow lines at the onset region of the Northeast Greenland Ice Stream

We present a high-resolution airborne radar data set (EGRIP-NOR-2018) for the onset region of the Northeast Greenland Ice Stream (NEGIS). The radar data were acquired in May 2018 with the Alfred Wegener Institute's multichannel ultra-wideband (UWB) radar mounted on the Polar 6 aircraft. Radar profiles cover an area of ∼24 000 km2 and extend over the well-defined shear margins of the NEGIS. The survey area is centered at the location of the drill site of the East Greenland Ice-Core Project (EastGRIP), and several radar lines intersect at this location. The survey layout was designed to (i) map the stratigraphic signature of the shear margins with radar profiles aligned perpendicular to ice flow, (ii) trace the radar stratigraphy along several flow lines, and (iii) provide spatial coverage of ice thickness and basal properties. While we are able to resolve radar reflections in the deep stratigraphy, we cannot fully resolve the steeply inclined reflections at the tightly folded shear margins in the lower part of the ice column. The NEGIS is causing the most significant discrepancies between numerically modeled and observed ice surface velocities. Given the high likelihood of future climate and ocean warming, this extensive data set of new high-resolution radar data in combination with the EastGRIP ice core will be a key contribution to understand the past and future dynamics of the NEGIS. The EGRIP-NOR-2018 radar data products can be obtained from the PANGAEA data publisher (https://doi.pangaea.de/10.1594/PANGAEA.928569; Franke et al., 2021a)