Self-pulsation at 480 GHz from a two-color discrete mode laser diode

A discrete mode Fabry-Pérot laser is designed and fabricated to achieve two-color lasing. We demonstrate beating between the two laser modes and self-pulsation at 480 GHz

Optimized pulse source based on a gain-switched laser diode in conjuction with a non-linearly chirped grating for 40 Gbit/s systems

A technique based on the design of an optimized source of pico-second optical pulses, which exhibits excellent temporal and spectral purity, is presented. The procedure entails an initial complete intensity and chirp characterization of pulses, from an externally injected-gain switched laser (EI-GSL), using the technique of frequency resolved optical gating (FROG). This characterization yields the parameters that are required for the design of a non-linearly chirped fibre Bragg grating (NC FBG) with a chirp profile that is opposite to that measured across the pulse. By employing the tailor made NC FBG after the gain-switched laser, direct compression of the gain-switched pulses is achieved, to obtain pedestal-free, near transform-limited, 7 ps pulses. The system viability, characterized by simulations, portrays a 6 dB difference in performance between a pulse source with insufficient TPSR and one that exhibits adequate TPSR &(ge; 30 dB)

Inverse scattering approach to multiwavelength Fabry-Pérot laser design

A class of multiwavelength Fabry-Pérot lasers is introduced where the spectrum is tailored through a patterning of the cavity effective index. The cavity geometry is obtained using an inverse scattering approach and can be designed such that the spacing of discrete Fabry-Pérot lasing modes is limited only by the bandwidth of the inverted gain medium. A specific two-color semiconductor laser with a mode spacing in the THz region is designed, and measurements are presented demonstrating the simultaneous oscillation of the two wavelengths. The nonperiodic effective index profile of the particular two-color device considered is shown to be related to a Moiré or superstructure grating

Optimization of 40 Gbit/s transmission systems using frequency resolved optical gating characterization techniques

To achieve multiterabit/s capacities in long-haul transport networks, it is anticipated that wavelength division multiplexed (WDM) systems will be upgraded to operate at line rates of 40 Gbit/s. We have shown that by employing the FROG measurement technique to optimize the generation of optical pulses for use in a 40 Gbit/s soliton transmission link, we ensure that the performance of the overall system using the generated optical pulses is optimum

Policy Brief: How to Promote Energy Efficiency and Energy Conservation in Ethiopia

In this policy brief we investigate a research question on " Why do households use energy efficient appliances and other energy conservation methods? How can adoption be improved in Ethiopia? " We provide insights from the energy systems development pathways for Ethiopia (PATHWAYS) project, based on a survey of urban households

Democracy in authoritarian states? Political change and regime stability in Malaysia and Singapore

In Political Science literature, Malaysia and Singapore have consistently been classified as semi-democracies; combining elements of democracy such as regularly-held elections with restrictions on civil liberties more reminiscent of authoritarian regimes. Semi-democracy or competitive authoritarianism in both countries have been relatively stable with extended periods of strong economic performance. However, recent developments in the country’s political scene have cast some doubt on the resilience of such a system. In the case of Malaysia, the last two elections have shown a consistent loss in support for the ruling Barisan Nasional or National Front coalition which has been in power since independence in 1957. It also appears that restrictions on civil liberties have been lifted, albeit partially. The ‘complacency’ that existed among the middle class previously has largely given way while civil society is playing a much more prominent role in public discourse. Singapore has also experienced similar developments, though not to the extent to the extent of the ‘political tsunami’ in Malaysia. Nevertheless the ruling PAP had its lowest share of the popular vote in decades in the 2011 elections and Singaporean society is increasingly vocal about grievances regarding income inequality. Keeping in mind that there has been little structural change to the electoral system that still heavily favours the incumbent government and that key institutions of the state are still controlled by the ruling party, are both countries in a transition process to a more democratic system or will the ruling coalition retain power through these structural and institutional arrangements for the foreseeable future? In other words, will two of the world’s longest-running competitive authoritarian or semi-democratic states be resilient enough to withstand the pressures for change

Successes, challenges and needs regarding rural health medical education in continental central America: A literature review and narrative synthesis

Introduction: Central American countries, like many others, face a shortage of rural health physicians. Most medical schools in this region are located in urban areas and focus on tertiary care training rather than on community health or primary care, which are better suited for rural practice. However, many countries require young physicians to do community service in rural communities to address healthcare provider shortages. This study aimed to: (a) synthesize what is known about the current state of medical education preparing physicians for rural practice in this region, and (b) identify common needs, challenges and opportunities for improving medical education in this area. Methods: A comprehensive literature review was conducted between December 2013 and May 2014. The stepwise, reproducible search process included English and Spanish language resources from both data-based web search engines (PubMed, Web of Science/Web of Knowledge, ERIC and Google Scholar) and the grey literature. Search criteria included MeSH terms: ‘medical education’, ‘rural health’, ‘primary care’, ‘community medicine’, ‘social service’, in conjunction with ‘Central America’, ‘Latin America’, ‘Mexico’, ‘Guatemala’, ‘Belize’, ‘El Salvador’, ‘Nicaragua’, ‘Honduras’, ‘Costa Rica’ and ‘Panama’. Articles were included in the review if they (1) were published after 1984; (2) focused on medical education for rural health, primary care, community health; and (3) involved the countries of interest. A narrative synthesis of the content of resources meeting inclusion criteria was done using qualitative research methods to identify common themes pertaining to the study goals. Results: The search revealed 20 resources that met inclusion criteria. Only four of the 20 were research articles; therefore, information about this subject was primarily derived from expert opinion. Thematic analysis revealed the historical existence of several innovative programs that directly address rural medicine training needs, suggesting that expertise is present in this region. However, numerous challenges limit sustainability or expansion of successful programs. Common challenges include: (a) physicians’ exposure to rural medicine primarily takes place during social service commitment time, rather than during formal medical training; (b) innovative educational programs are often not sustainable due to financial and leadership challenges; (c) the majority of physician manpower is in urban areas, resulting in few rural physician role models and teachers; and (d) there is insufficient collaboration to establish clinical and educational systems to meet rural health needs. Recurring suggestions for curricular changes include: (a) making primary care training a core component of medical school education; and (b) expanding medical school curricula in crosscultural communication and social determinants of disease. Suggestions for health system changes include: (a) improving living and working conditions for rural physicians; and (b) establishing partnerships between educational, governmental and non-governmental organizations and rural community leadership, to promote rural health training and systems. Conclusions: Expertise in rural medicine and training exists in continental Central America. However, there are numerous challenges to improving medical education to meet the needs of rural communities. Overcoming these challenges will require creative solutions, new partnerships, and evaluation and dissemination of successful educational programs. There is a great need for further research on this topic

Increased bit rate direct modulation AMO-OFDM transmission by optical injection using monolithically integrated lasers

Experimental and simulation work, presented in this letter, demonstrates for the first time how the monolithic integration of two single-mode lasers in a master-slave configuration, can substantially increase the achievable bit rate of a direct modulation adaptively modulated optical orthogonal frequency-division multiplexing (AMO-OFDM) system. The Levin-Campello algorithm is applied to select the OFDM bit and power loading scheme used for each system configuration. Improvement in terms of data throughput due to injection is measured for several transmission distances with the improvement in performance presented in terms of error vector magnitude per OFDM subcarrier

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability