Evidence of Local pH Changes during Ethanol Oxidation at Pt Electrodes in Alkaline Media

Local changes of the interfacial pH can significantly affect the rate and mechanism during the course of an electrodic reaction. For instance, different pH values will have a significant effect on the equilibrium properties of both solution and surface species, altering the reactions kinetics. Ethanol oxidation at platinum electrodes in alkaline media involves the fast consumption of OH− species that will change the local pH at the electrode surface, decreasing the reaction rate. In this study, the local pH change during ethanol oxidation in alkaline media is accomplished by using rotating ring-disc electrode (RRDE) experiments. The current at the ring when polarized at the onset of hydrogen evolution serves as a measure of the local pH in the vicinity of the electrode. The results show that the current at the ring at 0.1 V (vs. RHE) becomes more negative during ethanol oxidation, owing to a change in the equilibrium potential of the hydrogen evolution reaction caused by a change in the local pH.

Role of the interfacial water structure on electrocatalysis: Oxygen reduction on Pt(1 1 1) in methanesulfonic acid

Most of electrocatalytic reactions occur in an aqueous environment. Understanding the influence of water structure on reaction dynamics is fundamental in electrocatalysis. In this work, the role of liquid water structure on the oxygen reduction at Pt(1 1 1) electrode is analyzed in methanesulfonic (MTSA) and perchloric acids. This is because these different anions can exert a different influence on liquid water structure. Results reveal a lower ORR electrode activity in MTSA than in HClO4 solutions and they are discussed in light of anion's influence on water structural ordering. From them, the existence of an outer-sphere, rate determining, step in the ORR mechanism is suggested.

A proof of Jesus Christ's being the ancient promised Messiah: a sermon preached in the Chapel of Harvard College at Cambridge in New England, June 23, 1756

The hand-sewn notebook contains a 24-page manuscript draft of the second Dudleian lecture, delivered by John Barnard on June 23, 1756. The copy includes a small number of edits and struck-out words adopted in the printed version published by J. Draper of Boston in 1756. The sermon begins with the Biblical text Mark 14:61, 62. The covers are no longer with the item.

Popery a complex falsehood: or an attempt to clear and evidence, that it is so, in a lecture had at Harvard College in Cambridge, New England, on May 10th, 1769

The hand-sewn notebook contains a 30-page manuscript draft of the Dudleian lecture delivered by Samuel Mather on May 10, 1769 at Harvard College. The sermon begins with the Biblical text 2 Thess. 11:11, 12. The copy includes a small number of edits and struck-out words. The item has unattached pages and is in fragile condition. The lecture was never published.

Diocesan Episcopacy: as Founded on the supposed Episcopacy of Timothy & Titus, subverted in a sermon preached at Harvard College May 9, 1770 at the Lecture founded by Paul Dudley

Two handwritten drafts of the Dudleian lecture delivered by Amos Adams on May 9, 1770 at Harvard College written in the same hand. The sermon begins with the Biblical text Titus 1:5. The first copy (HUC 5340.70) is bound between black paper covers and includes edits and citations written on interleaved pages. The second copy (HUC 5340.70.2) appears to be a subsequent draft of the address with additional edits.

Sermon at the annual Dudleian lecture at Harvard College in Cambridge, May 14th, 1760

The hand-sewn notebook contains a 41-page manuscript draft of the Dudleian lecture delivered by Samuel Wigglesworth on May 14, 1760 at Harvard College. The sermon begins with the Biblical text I Cor. 1:21. The copy includes a small number of edits and struck-out words. The covers are no longer with the item.

Mr. Abbot's sermon at the Dudleian lecture at Harvard College in Cambridge August 29, 1764 pm: being the third in course on the important subject of Reveal'd-religion

The hand-sewn notebook contains a 27-page manuscript draft of the Dudleian lecture delivered by Hull Abbot on August 29, 1764 at Harvard College on the topic of revealed religion. The sermon begins with the Biblical text Zech. 4:6 and Rom. 10:18. The copy includes a small number of edits and struck-out words. The lecture was not printed.

Sermon at the annual Dudleian lecture, May 13th, 1772

The hand-sewn notebook contains a 108-page manuscript draft of the Dudleian lecture delivered by Benjamin Stevens on May 13, 1772 at Harvard College. The sermon begins with the Biblical text Heb. 1:1, 2. The copy includes a small number of edits and struck-out words. The cover page is no longer attached.

A discourse on natural religion: delivered in the Chapel of the University at Cambridge, September 5, 1787

The hand-sewn notebook contains a 35-page manuscript draft of the Dudleian lecture delivered by Simeon Howard on September 5, 1787 at Harvard College. The sermon begins with the Biblical text Acts 17:28. The copy includes a small number of edits and struck-out words. The covers are no longer with the item. The lecture was not printed.

A discourse on natural religion: delivered in the chapel of the University in Cambridge, September 3r, 1795, at the lecture founded by the Honourable Paul Dudley, Esqr

The hand-sewn notebook contains a manuscript draft of the Dudleian lecture delivered by Thomas Barnard on September 3, 1795 at Harvard College. The sermon begins with the Biblical text Acts 14-57. The copy includes a small number of edits and struck-out words. The covers are no longer with the item.

Investigating the potential magnetic origin of wind variability in OB stars

In this thesis, the origin of large-scale structures in hot star winds, believed to be responsible for the presence of discrete absorption components (DACs) in the absorption troughs of ultraviolet resonance lines, is constrained using both observations and numerical simulations. These structures are understood as arising from bright regions on the stellar surface, although their physical cause remains unknown. First, we use high quality circular spectropolarimetric observations of 13 well-studied OB stars to evaluate the potential role of dipolar magnetic fields in producing DACs. We perform longitudinal field measurements and place limits on the field strength using Bayesian inference, assuming that it is dipolar. No magnetic field was detected within this sample. The derived constraints statistically refute any significant dynamical influence from a magnetic dipole on the wind for all of these stars, ruling out such fields as a cause for DACs. Second, we perform numerical simulations using bright spots constrained by broadband optical photometric observations. We calculate hydrodynamical wind models using three sets of spot sizes and strengths. Co-rotating interaction regions are yielded in each model, and radiative transfer shows that the properties of the variations in the UV resonance lines synthesized from these models are consistent with those found in observed UV spectra, establishing the first consistent link between UV spectroscopic line profile variability and photometric variations and thus supporting the bright spot paradigm (BSP). Finally, we develop and apply a phenomenological model to quantify the measurable effects co-rotating bright spots would have on broadband optical photometry and on the profiles of photopheric lines in optical spectra. This model can be used to evaluate the existence of these spots, and, in the event of their detection, characterize them. Furthermore, a tentative spot evolution model is presented. A preliminary analysis of its output, compared to the observed photometric variations of xi Persei, suggests the possible existence of “active longitudes” on the surface of this star. Future work will expand the range of observational diagnostics that can be interpreted within the BSP, and link phenomenology (bright spots) to physical processes (magnetic spots or non-radial pulsations).

Wind Shear, Gust, and Yaw-Induced Dynamic Stall on Wind-Turbine Blades

This study examined the effect of a spanwise angle of attack gradient on the growth and stability of a dynamic stall vortex in a rotating system. It was found that a spanwise angle of attack gradient induces a corresponding spanwise vorticity gradient, which, in combination with spanwise flow, results in a redistribution of circulation along the blade. Specifically, when modelling the angle of attack gradient experienced by a wind turbine at the 30% span position during a gust event, the spanwise vorticity gradient was aligned such that circulation was transported from areas of high circulation to areas of low circulation, increasing the local dynamic stall vortex growth rate, which corresponds to an increase in the lift coefficient, and a decrease in the local vortex stability at this point. Reversing the relative alignment of the spanwise vorticity gradient and spanwise flow results in circulation transport from areas of low circulation generation to areas of high circulation generation, acting to reduce local circulation and stabilise the vortex. This circulation redistribution behaviour describes a mechanism by which the fluctuating loads on a wind turbine are magnified, which is detrimental to turbine lifetime and performance. Therefore, an understanding of this phenomenon has the potential to facilitate optimised wind turbine design.

Turkey's boycott of the Cyprus EU presidency: context, meaning and its consequences. EU Centre in Singapore Working Paper No. 9, September 2012

In 2011 Turkish officials began indicating their intention to suspend all contact with Cyprus’s presidency of the Council of the European Union (EU), slated for the second half of 2012, given the issues surrounding the unresolved Cyprus conflict. This came as the latest development in a long and arduous path of Turkey’s application for EU membership that began in 1987. This paper provides the context – the Cyprus conflict, Turkey’s EU accession negotiations, and the Cyprus reunification talks – in understanding the reasons and consequences of Ankara’s boycott of the Cyprus presidency. The article also considers the evolving nature and the role of the rotating presidency of the Council of the EU, especially after the implementation of the Lisbon Treaty, and how this may have played into Turkey’s calculations in calling for the boycott.

The Cyprus Presidency: Pragmatism amid European anxiety. CEPS Commentary, 24 January 2013

Despite several daunting obstacles, the low expectations and the high level of apprehension that accompanied the start of the Cyprus Presidency, Thomas Linders and Steven Blockmans find in a new CEPS Commentary that the small, remote and politically divided island nevertheless succeeded in scoring a number of positive results, thanks in part to the country’s pragmatic approach to the job and the perpetual motion of the EU legislature. As a corrective instrument to big state politics in the EU, however, the role of the Presidency remains limited. This underscores the changed nature of the rotating Presidency of the the Council of the EU since the Lisbon Treaty entered into force. Despite several daunting obstacles, the low expectations and the high level of apprehension that accompanied the start of the Cyprus Presidency, this CEPS Commentary by Thomas Linders and Steven Blockmans expresses surprise that the small, remote and politically divided island succeeded in scoring a number of positive results at all, thanks in part to the country’s pragmatic approach to the job

(Bio)funcionalização de superfícies nanoestruturadas para eletrocatálise e desenvolvimento de biossensores eletroquímicos e óticos

Tese de doutoramento, Química (Química Física), Universidade de Lisboa, Faculdade de Ciências, 2016