Dropout dynamics in pulsed quantum dot lasers due to mode jumping

We examine the response of a pulse pumped quantum dot laser both experimentally and numerically. As the maximum of the pump pulse comes closer to the excited-state threshold, the output pulse shape becomes unstable and leads to dropouts. We conjecture that these instabilities result from an increase of the linewidth enhancement factor α as the pump parameter comes close to the excitated state threshold. In order to analyze the dynamical mechanism of the dropout, we consider two cases for which the laser exhibits either a jump to a different single mode or a jump to fast intensity oscillations. The origin of these two instabilities is clarified by a combined analytical and numerical bifurcation diagram of the steady state intensity modes.

An investigation of thin film magnetic recording media

Mechanical, physical and chemical changes in the surface of commercial thin film metal evaporated magnetic recording media have been correlated to recording error and signal degradation measurements. Modified and adapted commercial Hi-8 video recorders have been used for sample generation whilst analytical techniques such as SXPS,IMS and SEM have been employed in the surface characterisation. The durability of the media was assessed through stop motion (still frame) and cycling tests, where error growth and signal degradation were measured as a function of running time. The tests were performed under ambient (22°C, 40% RH) and high humidity (22°C, 80% RH) conditions. Characterisation of the lubricant layer on each tape was performed through models based on XPS and angle resolved XPS. The lubricant thickness can significantly affect the durability and signal output level of a thin film tape and thus it is important that reliable quantification can be achieved. Various models were considered for determining the lubricant thickness although ultimately, the most suitable technique was deemed to be a model that assumed a uniform layer structure. In addition to thin film metal evaporated media, equivalent durability tests and surface analysis experiments were performed using a commercial metal particle tape in order that comparisons could be made between the two types of recording media. The signal performance of the thin film metal evaporated media was found to be quite different from that for the metal particle tape since dropout errors and signal degradation increased at a much earlier stage. Extensive surface analyses enabled the mechanisms responsible for media failure and error growth to be identified in the ME and MP tapes and these were found to result from cyclic stressing and fatigue on the immediate substrate of the media.

Whither human capital? The woeful tale of transition to tertiary education in India

In this article, we examine the issue of high dropout rates in India which has adverse implications for human capital formation and hence for the country's long-term growth potential. Using the 2004–2005 National Sample Survey (NSS) employment–unemployment data, we estimate transition probabilities of moving from a number of different educational levels to higher educational levels using a sequential logit model. Our results suggest that the overall probability of reaching tertiary education is very low. Further, even by the woeful overall standards, women are significantly worse off, particularly in rural areas.

A comparison of the provision of the My Choice Weight Management Programme via general practitioner practices and community pharmacies in the United Kingdom

This study aimed to assess the effectiveness of a novel, community-based weight management programme delivered through general practitioner (GP) practices and community pharmacies in one city in the United Kingdom. This study used a non-randomized, retrospective, observational comparison of clinical data collected by participating GP practices and community pharmacies. Subjects were 451 overweight or obese men and women resident in areas of high socioeconomic deprivation (82% from black and minority ethnic groups, 86% women, mean age: 41.1 years, mean body mass index [BMI]: 34.5 kg m−2). Weight, waist circumference and BMI at baseline, after 12 weeks and after 9 months were measured. Costs of delivery were also analysed. Sixty-four per cent of participants lost weight after the first 12 weeks of the My Choice Weight Management Programme. There was considerable dropout. Mean percentage weight loss (last observation carried forward) was 1.9% at 12 weeks and 1.9% at final follow-up (9 months). There was no significant difference in weight loss between participants attending GP practices and those attending pharmacies at both 12 weeks and at final follow-up. Costs per participant were higher via community pharmacy which was attributable to better attendance at sessions among community pharmacy participants than among GP participants. The My Choice Weight Management Programme produced modest reductions in weight at 12 weeks and 9 months. Such programmes may not be sufficient to tackle the obesity epidemic.

Randomised masked clinical trial of the MGDRx eyebag for the treatment of meibomian gland dysfunction-related evaporative dry eye

Background/aims To investigate the efficacy and safety of the MGDRx EyeBag (The Eyebag Company, Halifax, UK) eyelid warming device. Methods Twenty-five patients with confirmed meibomian gland dysfunction (MGD)-related evaporative dry eye were enrolled into a randomised, single masked, contralateral clinical trial. Test eyes received a heated device; control eyes a non-heated device for 5 min twice a day for 2 weeks. Efficacy (ocular symptomology, noninvasive break-up time, lipid layer thickness, osmolarity, meibomian gland dropout and function) and safety (visual acuity, corneal topography, conjunctival hyperaemia and staining) measurements were taken at baseline and follow-up. Subsequent patient device usage and ocular comfort was ascertained at 6 months. Results Differences between test and control eyes at baseline were not statistically signi ficant for all measurements ( p>0.05). After 2 weeks, statistically significant improvements occurred in all efficacy measurements in test eyes ( p<0.05). Visual acuity and corneal topography were unaffected (p>0.05). All patients maintained higher ocular comfort after 6 months ( p<0.05), although the bene fit was greater in those who continued usage 1-8 times a month (p<0.001). Conclusions The MGDRx EyeBag is a safe and effective device for the treatment of MGD-related evaporative dry eye. Subjective benefit lasts at least 6 months, aided by occasional retreatment. Trial registration number NCT01870180.