Is Twitter a Public Sphere for Online Conflicts? A Cross-Ideological and Cross-Hierarchical Look

The rise in popularity of Twitter has led to a debate on its impact on public opinions. The optimists foresee an increase in online participation and democratization due to social media's personal and interactive nature. Cyber-pessimists, on the other hand, explain how social media can lead to selective exposure and can be used as a disguise for those in power to disseminate biased information. To investigate this debate empirically, we evaluate Twitter as a public sphere using four metrics: equality, diversity, reciprocity and quality. Using these measurements, we analyze the communication patterns between individuals of different hierarchical levels and ideologies. We do this within the context of three diverse conflicts: Israel-Palestine, US Democrats-Republicans, and FC Barcelona-Real Madrid. In all cases, we collect data around a central pair of Twitter accounts representing the two main parties. Our results show in a quantitative manner that Twitter is not an ideal public sphere for democratic conversations and that hierarchical effects are part of the reason why it is not.Comment: To appear in the 6th International Conference on Social Informatics (SocInfo 2014), Barcelon

Tunable all-fibre delay line filter for residual dispersion compensation in 40 Gbit/s systems

A novel all-fibre tunable delay-line filter, with a simple structure based on two 3×3 fibre couplers and only one phase shifter is utilised for residual dispersion compensation in a 40 Gbit/s optical transmission system. In this experiment the dispersion tolerance of the receiver was successfully enhanced by 100 ps/nm

Defining Medical Futility in Ethics, Law and Clinical Practice: An Exercise in Futility?

The debate as to the meaning of medical futility and what physicians should do in clinical practice dates back to the time of the writings of Hippocrates and Plato where it was said, "To attempt futile treatment is to display an ignorance that is allied to madness". In simpler times assertions regarding the obvious were sufficient to indicate what was thought "fitting" as a medical practitioner. In recent times, however, modern technology, professional values and power, patient autonomy, limited health care resources and societal expectations, make for a much more potent and potentially explosive mixture. In this article we argue that futility is a problem that will not go away, both because of increased health expectations and emerging technologies that keep making possible what was previously impossible. The problem of definition and its ramifications in terms of institutional policies is one in which the legal profession and its process (which often represents and reflects societal values) has a key role to play by way of critical reflection and appraisal

10 Gbit/s based NRZ DWDM systems using polarisation switching in single wavelength channel

It is experimentally demonstrated that the nonlinear tolerance of 10 Gbit/s/ch NRZ based DWDM systems over 1500 km standard singlemode fibre can be significantly improved through the use of orthogonal polarisation switching between adjacent bits in a single wavelength channel

Experimental investigation of self coherent optical OFDM systems using fabry-perot filters for carrier extraction

We experimentally demonstrate self coherent optical OFDM transmission with IQ demultiplexing employing a Fabry-Perot-tunable filter for the extraction of the optical carrier. The performance is investigated and compared to a conventional CO-OFDM

Low computational complexity mode division multiplexed OFDM transmission over 130 km of few mode fiber

We demonstrate 337.5-Gb/s MDM-8QAM-OFDM transmission over 130 km of FMF. This confirms that OFDM can significantly reduce the required DSP complexity to compensate for differential mode delay, a key step towards real-time MDM transmission

11 x 224 Gb/s POLMUX-RZ-16QAM transmission over 670 km of SSMF with 50-Ghz channel spacing

We demonstrate the generation and transmission of eleven channels with 224-Gb/s polarization-multiplexed, return to zero, 16-level quadrature amplitude modulation (POLMUX-RZ-16QAM) over 670 km of standard single mode fiber (SSMF) with 50-GHz channel spacing and a spectral efficiency of 4.2 b/s/Hz. We report a penalty of around 4.3 dB in the performance at back-to-back in comparison to the theoretical limits, and a margin of 1 dB in Q-factor below the forward error correction (FEC) limit (assumed to be at a bit error rate of 3.8x10-3) after transmission over 670 km of SSMF

Optimization of five ultra-high vacuum compatible voice coil actuator topologies

In this paper, a coupled electro-thermal optimization of five ultra-high vacuum compatible voice coil actuators (VCAs) is performed. Based on the resulting force range and steady state coil temperature, a prototype VCA is manufactured. Its performance is measured on a test setup

Reduction of Gordon-Mollenauer phase noise by midlink spectral inversion

We show that spectral inversion can be employed for regeneration to reduce the effect of phase noise (Gordon-Mollenauer phase noise) in a nonreturn-to-zero differential phase-shift-keying based transmission system. Several locations of the spectral inverter in an eight-span transmission link have been investigated. We show that the best results are obtained when the spectral inverter is placed in the middle of the link. Compared to the transmission system without spectral inverter, an improvement of over four decades in bit-error-rate performance is achieved