Governments, Informal Links to Militias and Accountability

From Syria to Sudan, governments have informal ties with militias that use violence against opposition groups and civilians. Building on research that suggests these groups offer governments logistical benefits in civil wars as well as political benefits in the form of reduced liability for violence, we provide the first systematic global analysis of the scale and patterns of these informal linkages. We find over 200 informal state–militia relationships across the globe, within but also outside of civil wars. We illustrate how informal delegation of violence to these groups can help some governments avoid accountability for violence and repression. Our empirical analysis finds that weak democracies as well as recipients of financial aid from democracies are particularly likely to form informal ties with militias. This relationship is strengthened as the monitoring costs of democratic donors increase. Out-of-sample predictions illustrate the usefulness of our approach that views informal ties to militias as deliberate government strategy to avoid accountability

The role of primary care in cancer diagnosis via emergency presentation: qualitative synthesis of significant event reports

Background: Patients diagnosed with cancer in the context of an emergency presentation (EP) have poorer outcomes. It is often assumed that such patients present to the emergency department without consulting their general practitioner (GP). Little work has been done to identify primary care involvement before hospital attendance. Methods: Participating primary care practices completed a significant event audit (SEA) report for the last patient diagnosed with cancer as a result of an EP. Accounts were synthesised and a qualitative approach to analysis undertaken. Results: SEAs for 222 patients were analysed. A range of cancers were included, the most common being lung (32.4%) and upper gastrointestinal (19.8%). In most cases, patients had contact with their practice before diagnosis, primarily in the period immediately before admission. In only eight cases had there been no input from primary care. Accounts of protracted primary care contact generally demonstrated complexity, often related to comorbidity, patient-mediated factors or reassurance provided by negative investigations. Learning points identified by practices centred on the themes of presentation and diagnosis, consultation and safety-netting, communication and system issues, patient factors and referral guidelines. Conclusions: There is extensive primary care input into patients whose diagnosis results from EP, and for the most part potential ‘delay’ in referral can be reasonably explained by the complexity of the presentation or by coexisting patient factors

Simple 60-GHz MB-OFDM ultrawideband RoF system based on remote heterodyning

A simple 60-GHz radio-over-fiber system employing a combination of uncorrelated optical heterodyning and envelope detection is proposed and experimentally demonstrated. At the central office, a multiband orthogonal frequency division multiplexing ultrawideband (MB-OFDM UWB) signal is used for the external modulation of a dual-arm Mach-Zehnder Modulator to generate an optical signal-sideband signal, which is then coupled with an unmodulated free-running continuous wave laser. Optical heterodyne mixing at the base station and envelope detection at the customer unit are utilized. The experimental results confirm that photonic millimeter-wave signal generation and detection can be achieved without the need for complex optical phase-locked loops and high-frequency microwave sources. As a proof of concept, successful transmission of a 3.84 Gb/s 16-QAM MB-OFDM UWB signal over 48-km standard single-mode fiber without chromatic dispersion compensation and a further 4-m wireless channel is experimentally demonstrated

Spectrally Efficient WDM Nyquist Pulse-Shaped Subcarrier Modulation Using a Dual-Drive Mach-Zehnder Modulator and Direct Detection

High data transmission capacity is increasingly needed in shortand medium-haul optical communication links. Cost-effective wavelength division multiplexed (WDM) transceiver architectures, achieving high information spectral densities (ISDs) (>1 b/s/Hz) and using low-complexity direct detection receivers are attractive solutions for such links. In this paper, we assess the use of dual-drive Mach-Zehnder modulators (DD-MZMs), and compare them with in-phase quadrature (IQ)-modulators for generating spectrally-efficient single sideband Nyquist pulse-shaped 16-QAM subcarrier (N-SCM) modulation format signals. The impact of the extinction ratio (ER) of a modulator on the optical sideband suppression ratio (OSSR) was investigated for the SSB signals in WDM systems, together with the resulting impact on inter-channel crosstalk penalties. First, in back-to-back operation, an IQ-modulator with an ER of 30 dB and a DD-MZM with an ER of 18 dB were experimentally compared in a 6×25 Gb/s WDM system by varying the channel spacing. Following this comparison, 16 GHz-spaced 6×25 Gb/s WDM signal transmission was experimentally demonstrated using the DD-MZM. The experiment was performed using a recirculating loop with uncompensated standard single-mode fiber (SSMF) and EDFA-only amplification. The maximum achievable transmission distances for single channel and WDM signals were found to be 565 and 242 km, respectively, at a net optical ISD of 1.5 b/s/Hz. This is the first experimental comparison of such modulator types for SSB N-SCM signal generation and the highest achieved ISD using a DD-MZM in direct-detection WDM transmission

Optical frequency tripling with improved suppression and sideband selection

A novel optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. The implementation utilises cascaded optical modulators to achieve either an optical single sideband (OSSB) or double sideband-suppressed carrier (DSB-SC) signal with high sideband suppression. Our analysis and simulation results indicate that the achievable suppression ratio of this configuration is only limited by other system factors such as optical noise and drifting of the operational conditions. The OSSB transmission system performance is assessed experimentally by the transport of 4 WiMax channels modulating a 10 GHz optical upconverted RF carrier as well as for optical frequency doubling and tripling. The 10 GHz and tripled carrier at 30 GHz are dispersion tolerant resulting both in an average relative constellation error (RCE) of −28.7 dB after 40 km of fibre

Demonstration of Photonic Integrated RAU for Millimetre-wave Gigabit Wireless Transmission

This work reports the performance of a wireless transmission link based on a radio access unit (RAU) implemented in photonic integrated circuit (PIC) form. The PIC contains a high speed photodiode for direct optical to RF conversion, monolithically integrated with a semiconductor laser, used as an optical local oscillator for up-conversion of the incoming 16-QAM-OFDM signal through heterodyning. Wireless transmission was demonstrated with a spectral efficiency as high as 3 bits/s/Hz at 60 GHz carrier and with 1.2 Gb/s transmission rate. Moreover, the RAU based on a broad bandwidth photodiode integrated with a tuneable laser allowed for a compact unit that could operate at carrier frequencies up to 100 GHz

Enhanced flow-motion complexity of skin microvascular perfusion in Sherpas and lowlanders during ascent to high altitude

An increased and more effective microvascular perfusion is postulated to play a key role in the physiological adaptation of Sherpa highlanders to the hypobaric hypoxia encountered at high altitude. To investigate this, we used Lempel-Ziv complexity (LZC) analysis to explore the spatiotemporal dynamics of the variability of the skin microvascular blood flux (BF) signals measured at the forearm and finger, in 32 lowlanders (LL) and 46 Sherpa highlanders (SH) during the Xtreme Everest 2 expedition. Measurements were made at baseline (BL) (LL: London 35 m; SH: Kathmandu 1300 m) and at Everest base camp (LL and SH: EBC 5,300 m). We found that BF signal content increased with ascent to EBC in both SH and LL. At both altitudes, LZC of the BF signals was significantly higher in SH, and was related to local slow-wave flow-motion activity over multiple spatial and temporal scales. In SH, BF LZC was also positively associated with LZC of the simultaneously measured tissue oxygenation signals. These data provide robust mechanistic information of microvascular network functionality and flexibility during hypoxic exposure on ascent to high altitude. They demonstrate the importance of a sustained heterogeneity of network perfusion, associated with local vaso-control mechanisms, to effective tissue oxygenation during hypobaric hypoxia

Distribution of airway narrowing responses across generations and at branching points, assessed in vitro by anatomical optical coherence tomography

Background: Previous histological and imaging studies have shown the presence of variability in the degree of bronchoconstriction of airways sampled at different locations in the lung (i.e., heterogeneity). Heterogeneity can occur at different airway generations and at branching points in the bronchial tree. Whilst heterogeneity has been detected by previous experimental approaches, its spatial relationship either within or between airways is unknown.Methods: In this study, distribution of airway narrowing responses across a portion of the porcine bronchial tree was determined in vitro. The portion comprised contiguous airways spanning bronchial generations (#3-11), including the associated side branches. We used a recent optical imaging technique, anatomical optical coherence tomography, to image the bronchial tree in three dimensions. Bronchoconstriction was produced by carbachol administered to either the adventitial or luminal surface of the airway. Luminal cross sectional area was measured before and at different time points after constriction to carbachol and airway narrowing calculated from the percent decrease in luminal cross sectional area.Results: When administered to the adventitial surface, the degree of airway narrowing was progressively increased from proximal to distal generations (r = 0.80 to 0.98, P < 0.05 to 0.001). This 'serial heterogeneity' was also apparent when carbachol was administered via the lumen, though it was less pronounced. In contrast, airway narrowing was not different at side branches, and was uniform both in the parent and daughter airways.Conclusions: Our findings demonstrate that the bronchial tree expresses intrinsic serial heterogeneity, such that narrowing increases from proximal to distal airways, a relationship that is influenced by the route of drug administration but not by structural variations accompanying branching sites