All-optical modulation converter for on-off keying to duobinary and alternate-mark inversion at 42.6 Gbps

Advanced modulation formats have become increasingly important as telecoms engineers strive for improved tolerance to both linear and nonlinear fibre-based transmission impairments. Two important modulation schemes are Duobinary (DB) and Alternate-mark inversion (AMI) [1] where transmission enhancement results from auxiliary phase modulation. As advanced modulation formats displace Return-to-zero On-Off Keying (RZ-OOK), inter-modulation converters will become increasingly important. If the modulation conversion can be performed at high bitrates with a small number of operations per bit, then all-optical techniques may offer lower energy consumption compared to optical-electronic-optical approaches. In this paper we experimentally demonstrate an all-optical system incorporating a pair of hybrid-integrated semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI) gates which translate RZ-OOK to RZ-DB or RZ-AMI at 42.6 Gbps. This scheme includes a wavelength conversion to arbitrary output wavelength and has potential for high-level photonic integration, scalability to higher bitrates, and should exhibit regenerative properties [2].

Novel all-optical on-off-keyed to alternate-mark-inversion converter

We numerically investigate a novel 40 Gbps OOK to AMI all-optical modulation format converter employing an SOA-based Mach-Zehnder interferometer.  We demonstrate operation with a 27-1 PRBS and explain the phase modulation's relationship with patterning.

Vascular calcification and mineral bone disorder in chronic kidney disease

Chronic Kidney Disease (CKD), osteoporosis and mild hyponatremia are all prevalent chronic conditions that may coexist and are often under-recognized. Mineral-Bone Disorder begins early in the natural history of CKD and results in complex abnormalities of bone which ultimately confers a well-established increased risk of fragility fractures in End Stage Kidney Disease. Hyponatremia is a novel, usually renal mediated metabolic perturbation, that most commonly occurs independently of the stage of renal dysfunction but which may also predispose to increased fracture risk. The extent -if any- to which either early stages of renal dysfunction or the presence of hyponatremia contribute to fracture occurrence in the general population, independently of osteoporosis, is unclear. Renal transplantation is the treatment of choice for ESKD and although it restores endogenous renal function it typically fails to normalize either the long term cardiovascular or fracture risk. One potential mechanism contributing to these elevated long-term risks and to diminished Health Related Quality of Life is persistent, post-transplant hyperparathyroidism. In this study we retrospectively examine the association of renal function and serum sodium with Bone Mineral Density and fracture occurrence in a retrospective cohort of 1930 female members of the general population who underwent routine DXA scan. We then prospectively recruited a cohort of 90 renal transplant recipients in order to examine the association of post transplant parathyroid hormone (PTH) level with measures of CKD Mineral Bone Disorder, including, DXA Bone Mineral Density, Vascular Calcification (assessed using both abdominal radiography and CT techniques, as well as indirectly by carotid-femoral Pulse Wave Velocity) and Quality of Life (using the Short Form-12 and a PTH specific symptom score). In the retrospective DXA cohort, moderate CKD (eGFR 30-59ml/min/1.73m2) and hyponatremia (<135mmol/L) were associated with fracture occurrence, independently of BMD, with an adjusted Odds Ratio (95% Confidence Interval), of 1.37 (1.0, 1.89) and 2.25 (1.24, 4.09) respectively. In the renal transplant study, PTH was independently associated with the presence of osteoporosis, adjusted Odds Ratio (95% Confidence Interval), 1.15 (per 10ng/ml increment), (1.04, 1.26). The presence of osteoporosis but not PTH was independently associated with measures of vascular calcification, adjusted ß (95% Confidence Interval), 12.45, (1.16, 23.75). Of the eight quality-of-life domains examined, post-transplant PTH (per 10ng/ml increment), was only significantly and independently associated with reduced Physical Functioning, (95% Confidence Interval), 1.12 (1.01, 1.23). CKD and hyponatremia are both common health problems that may contribute to fracture occurrence in the general population, a major on-going public health concern. PTH and decreased Bone Mineral Density may signal sub-optimal long-term outcomes post renal transplantation, influencing bone and vascular health and to a limited extent long term Health Related Quality of Life

Development of inversion-mode and junctionless Indium-Gallium-Arsenide MOSFETs

This PhD covers the development of planar inversion-mode and junctionless Al2O3/In0.53Ga0.47As metal-oxidesemiconductor field-effect transistors (MOSFETs). An implant activation anneal was developed for the formation of the source and drain (S/D) of the inversionmode MOSFET. Fabricated inversion-mode devices were used as test vehicles to investigate the impact of forming gas annealing (FGA) on device performance. Following FGA, the devices exhibited a subthreshold swing (SS) of 150mV/dec., an ION/IOFF of 104 and the transconductance, drive current and peak effective mobility increased by 29%, 25% and 15%, respectively. An alternative technique, based on the fitting of the measured full-gate capacitance vs gate voltage using a selfconsistent Poisson-Schrödinger solver, was developed to extract the trap energy profile across the full In0.53Ga0.47As bandgap and beyond. A multi-frequency inversion-charge pumping approach was proposed to (1) study the traps located at energy levels aligned with the In0.53Ga0.47As conduction band and (2) separate the trapped charge and mobile charge contributions. The analysis revealed an effective mobility (μeff) peaking at ~2850cm2/V.s for an inversion-charge density (Ninv) = 7*1011cm2 and rapidly decreasing to ~600cm2/V.s for Ninv = 1*1013 cm2, consistent with a μeff limited by surface roughness scattering. Atomic force microscopy measurements confirmed a large surface roughness of 1.95±0.28nm on the In0.53Ga0.47As channel caused by the S/D activation anneal. In order to circumvent the issue relative to S/D formation, a junctionless In0.53Ga0.47As device was developed. A digital etch was used to thin the In0.53Ga0.47As channel and investigate the impact of channel thickness (tInGaAs) on device performance. Scaling of the SS with tInGaAs was observed for tInGaAs going from 24 to 16nm, yielding a SS of 115mV/dec. for tInGaAs = 16nm. Flat-band μeff values of 2130 and 1975cm2/V.s were extracted on devices with tInGaAs of 24 and 20nm, respectively

Skin and bone: the face in the archaeological imagination

Thirteen unique archaeological countenances from Ireland were produced through the Manchester method of facial reconstruction. Their gaze prompts a space for a broad discourse regarding the face found within human and artefactual remains of Ireland. These faces are reminders of the human element which is at the core of the discipline of archaeology. These re-constructions create a voyeuristic relationship with the past. At once sating a curiosity about the past, facial reconstructions also provide a catharsis to our presently situated selves. As powerful visual documents, archaeological facial reconstructions illustrate re-presentations of the past as well as how the present can be connected to the past. Through engagment with Emmanuel Levinas’s (1906- 1995) main philosophical themes, the presence of the face is examined in a diachronic structure. The ‘starting point’ is the Neolithic period which has been associated with the notion of visuality with a reconstruction from the early Neolithic site of Annagh, Co. Limerick. The following layer of analysis appears with attention to intersubjectivity in the early medieval period with facial reconstructions from Dooey, Co. Donegal and Owenbristy, Co. Galway. Building upon the past concepts, the late medieval period is associated with the notion of alterity and paired with faces from Ballinderry, Co. Kildare and a sample of males from Gallen Priory, Co. Offaly. The final layer of examination culminates with the application of response and respons-ibility to the post-medieval Irish landscape with facial reconstructions from the prison on Spike Island, Co. Cork. These layers of investigation are similar to the stratigraphical composition of both the archaeological landscape and the skeletal/soft tissue landscape of the face. The separation of the neglected phenomenon of the face from the overwhelming embrace of the field of craniometrics is necessary. Through this detachment a new manner in which to discuss the face and its place within the (bio)archaeological record is possible. Encountering the faces seen in mortuary contexts, material culture, and archaeological facial reconstructions, inform and shape the archaeological imagination.