On the relationship between small and large signal modulation capabilities in highly nonlinear quantum dot lasers

The small signal modulation response of semiconductor lasers is commonly used to predict large signal modulation capabilities. Recent experiments suggest that this prediction may fail in some quantum dot (QD) lasers. We present a model supported by experiments, which shows that when the small signal modulation response is limited by gain compression and the gain is large, the laser can be modulated at very high bit rates. This effect is inherent to dynamics governing all semiconductor lasers but the conditions needed for high bit rate modulation in the presence of narrow small signal bandwidths are only obtainable in QD lasers

High-Frequency Electrooptic Fabry-Perot Modulators

Electrooptic modulators built from GaAs/AlxGa1-xAs Fabry-Perot cavities operating up to 6.5 GHz are reported. The measured frequency response agrees well with the one predicted using an equivalent circuit model derived from high-speed electrical measurements. The parasitic capacitances have been reduced to approximately 30 fF by fabricating the devices on semi-insulating GaAs substrates and integrating them with on-wafer bound pads which have dimensions compatible with microwave coplanar probes

Situated solidarities and the practice of scholar-activism

Drawing on an analysis of an ongoing collaboration with rural peasant movements in Bangladesh, we explore the possibility of forging solidarity through practices of scholar-activism. In so doing, we consider the practice of reflexivity, reconsider forms of solidarity, and draw on the concept of convergence spaces as a way to envision sites of possibility. We mobilize the notion of situated solidarities to propose an alternative form of reflexive practice in scholarship. We then posit that there are six ‘practices’ that provide a useful schematic for thinking through the opportunities for the construction of these solidaritie

Temperature and Resource Availability May Interactively Affect Over-Wintering Success of Juvenile Fish in a Changing Climate

The predicted global warming may affect freshwater systems at several organizational levels, from organism to ecosystem. Specifically, in temperate regions, the projected increase of winter temperatures may have important effects on the over-winter biology of a range of organisms and especially for fish and other ectothermic animals. However, temperature effects on organisms may be directed strongly by resource availability. Here, we investigated whether over-winter loss of biomass and lipid content of juvenile roach (Rutilus rutilus) was affected by the physiologically relatively small (2-5°C) changes of winter temperatures predicted by the Intergovernmental Panel on Climate Change (IPCC), under both natural and experimental conditions. This was investigated in combination with the effects of food availability. Finally, we explored the potential for a correlation between lake temperature and resource levels for planktivorous fish, i.e., zooplankton biomass, during five consecutive winters in a south Swedish lake. We show that small increases in temperature (+2°C) affected fish biomass loss in both presence and absence of food, but negatively and positively respectively. Temperature alone explained only a minor part of the variation when food availability was not taken into account. In contrast to other studies, lipid analyses of experimental fish suggest that critical somatic condition rather than critical lipid content determined starvation induced mortality. Our results illustrate the importance of considering not only changes in temperature when predicting organism response to climate change but also food-web interactions, such as resource availability and predation. However, as exemplified by our finding that zooplankton over-winter biomass in the lake was not related to over-winter temperature, this may not be a straightforward task

Genome modeling system: A knowledge management platform for genomics

In this work, we present the Genome Modeling System (GMS), an analysis information management system capable of executing automated genome analysis pipelines at a massive scale. The GMS framework provides detailed tracking of samples and data coupled with reliable and repeatable analysis pipelines. The GMS also serves as a platform for bioinformatics development, allowing a large team to collaborate on data analysis, or an individual researcher to leverage the work of others effectively within its data management system. Rather than separating ad-hoc analysis from rigorous, reproducible pipelines, the GMS promotes systematic integration between the two. As a demonstration of the GMS, we performed an integrated analysis of whole genome, exome and transcriptome sequencing data from a breast cancer cell line (HCC1395) and matched lymphoblastoid line (HCC1395BL). These data are available for users to test the software, complete tutorials and develop novel GMS pipeline configurations. The GMS is available at https://github.com/genome/gms

A 100-kHz - 22 GHz Instrumentation Photoreceiver

A photoreceiver consisting of a high-speed p-i-n photodetector and a 100-kHz to 22-GHz distributed amplifier is described. Photoreceiver calibration is accomplished by optical heterodyne techniques. The photoreceiver is used with a microwave spectrum analyzer to produce a fully amplitude-calibrated 22-GHz-bandwidth lightwave signal analyzer system for displaying intensity-modulated light with -65-dB (optical) sensitivity at 1300-nm and 1550-nm wavelengths