Ramsey-type microwave spectroscopy on CO (a3Πa^3\Pi)

Using a Ramsey-type setup, the lambda-doublet transition in the $J=1,\, \Omega=1$ level of the $a^3\Pi$ state of CO was measured to be 394 064 870(10) Hz. In our molecular beam apparatus, a beam of metastable CO is prepared in a single quantum level by expanding CO into vacuum and exciting the molecules using a narrow-band UV laser system. After passing two microwave zones that are separated by 50 cm, the molecules are state-selectively deflected and detected 1 meter downstream on a position sensitive detector. In order to keep the molecules in a single $m_J^B$ level, a magnetic bias field is applied. We find the field-free transition frequency by taking the average of the $m_J^B = +1 \rightarrow m_J^B = +1$ and $m_J^B = -1 \rightarrow m_J^B = -1$ transitions, which have an almost equal but opposite Zeeman shift. The accuracy of this proof-of-principle experiment is a factor of 100 more accurate than the previous best value obtained for this transition

The effect of the front-to-rear wheel torque distribution on vehicle handling: an experimental assessment

The front-to-rear wheel torque distribution influences vehicle handling and, ulti-mately, it affects key factors such as vehicle safety and performance. At a glance, due to part of the available tire-road friction being used for traction at the driven axle, a Front-Wheel-Drive (FWD) vehicle would be expected to be more understeering than a Rear-Wheel-Drive (RWD) vehicle. However, such effect may be counterbalanced, or even reversed, mainly due to the yaw moment caused by the lateral contribution of the traction forces at the front wheels. This paper proposes an experimental assessment, carried out on a fully electric vehicle with multiple mo-tors, allowing different front-to-rear wheel torque distributions. The results confirm that the yaw moment effect discussed is considerable, especially at low vehicle speeds and high steering an-gles. In particular, the RWD vehicle resulted more understeering than the FWD one at 30 km/h

The human environmental balance

A future policy instrument for assessing the consequences of changes (already made) to the physical environment can be found in the instrument known as the human environmental balance. By taking all relevant aspects into account when using this instrument, present and future serious defects along with necessary areas of focus will become clear. In this way, the balance will fulfil an important evaluative and indicative function, serving as an integral conceptual framework to find out what investments to make and where they should be made. This report describes a survey, representing an initial step on the road to a balanced physical environment, charting further work along the way. It is also meant to stimulate a broad debate on how to audit this physical environment and what to study. The concept of the physical environment is defined as consisting of (stocks of) various objects in a certain (spatial) arrangement. These objects are evaluated from three perspectives: ecological, economic and social/psychological. The first two perspectives focus on long-term issues on sustainability. In the third perspective the central theme is the perception of the environment by humans themselves; here, we are concerned about short-term issues on the sub-national (local) level. The 1970-1995 draft balance also saw its first elaboration in this report.De leefomgevingsbalans is een door VROM voorgesteld toekomstig beleidsinstrument om gedane ingrepen in het fysieke milieu op hun integrale gevolgen voor de leefomgeving te beoordelen. De leefomgevingsbalans zou hiermee een belangrijke evaluerende en signalerende functie hebben: door beschouwing van alle relevante aspecten maakt de balans zichtbaar waar tekorten zijn of dreigen te ontstaan en waar extra inspanningen nodig zijn. Hiermee vormt de leefomgevingsbalans een integratief raamwerk dat richtinggevend kan zijn voor de aard en locatie van gewenste investeringen. Dit rapport is een verkenning van een mogelijk invulling van een dergelijke leefomgevingsbalans en dient uitsluitend als basis voor discussie. Het beschouwt de fysieke leefomgeving als een verzameling van (voorraden) van allerlei objecten in een bepaalde ruimtelijke configuratie. Deze objecten worden vanuit verschillende invalshoeken verschillend gewaardeerd. Hierbij is onderscheid gemaakt in een ecologisch, economisch en sociaal-psychologisch perspectief. De eerste twee perspectieven zijn vooral gericht op lange termijn-vraagstukken waarbij duurzaamheid voorop staat. Bij het laatste perspectief gaat om de individuele leefbaarheid van de burger, veelal handelend over korte termijn-vraagstukken op vooral lokaal niveau. Op deze wijze wordt het 'leefomgevingskapitaal' gepresenteerd als een drieluik van economische, ecologische en sociaal-psychologische waarden. In het rapport is ook een eerste uitwerking van dit concept voor de periode 1970-1995 gegeven

Nanometer control in plasmonic systems through discrete layer-by-layer macrocycle-cation deposition.

In this work, we demonstrate that coordination interactions between Fe3+ and cucurbit[7]uril (CB[7]) can be utilised to build up defined nanoscale spacing layers in metallic nanosystems. We begin by characterising the layer-by-layer deposition of CB[7] and FeCl3·6H2O coordination layers through the use of a Quartz-Crystal Microbalance (QCM) and contact angle measurements. We then apply this layered structure to accurately control the spacing, and thus optical properties, of gold nanoparticles in a Nanoparticle-on-Mirror (NPoM) structure, which is demonstrated via normalising plasmon resonance spectroscopy.European Commission for a Marie Curie Fellowship (NANOSPHERE, 658360) ERC starting investigator grant (ASPiRe 240629) RC acknowledges support from the Dr. Manmohan Singh scholarship from St. John’s College BdN acknowledges support from the Leverhulme Trust and the Isaac Newton trust ECF

Interfacial adsorption phenomena of the three-dimensional three-state Potts model

We study the interfacial adsorption phenomena of the three-state ferromagnetic Potts model on the simple cubic lattice by the Monte Carlo method. Finite-size scaling analyses of the net-adsorption yield the evidence of the phase transition being of first-order and $k_{\rm B} T_{\rm C} / J = 1.8166 (2)$.Comment: 14 page

SERS of individual nanoparticles on a mirror : size does matter, but so does shape

The authors thank Javier Aizpurua (CSIC − UPV/EHU/DIPC) for helpful discussions. We acknowledge financial support from EPSRC Grants EP/G060649/1, EP/K028510/1, EP/L027151/1, ERC Grant LINASS 320503. F.B. acknowledges support from the Winton Programme for the Physics of Sustainability. R.C. acknowledges support from the Dr. Manmohan Singh scholarship from St. John’s College.Coupling noble metal nanoparticles by a 1 nm gap to an underlying gold mirror confines light to extremely small volumes, useful for sensing on the nanoscale. Individually measuring 10 000 of such gold nanoparticles of increasing size dramatically shows the different scaling of their optical scattering (far-field) and surface-enhanced Raman emission (SERS, near-field). Linear red-shifts of the coupled plasmon modes are seen with increasing size, matching theory. The total SERS from the few hundred molecules under each nanoparticle dramatically increases with increasing size. This scaling shows that maximum SERS emission is always produced from the largest nanoparticles, irrespective of tuning to any plasmonic resonances. Changes of particle facet with nanoparticle size result in vastly weaker scaling of the near-field SERS, without much modifying the far-field, and allows simple approaches for optimizing practical sensing.Publisher PDFPeer reviewe

Correlation decay and conformal anomaly in the two-dimensional random-bond Ising ferromagnet

The two-dimensional random-bond Ising model is numerically studied on long strips by transfer-matrix methods. It is shown that the rate of decay of correlations at criticality, as derived from averages of the two largest Lyapunov exponents plus conformal invariance arguments, differs from that obtained through direct evaluation of correlation functions. The latter is found to be, within error bars, the same as in pure systems. Our results confirm field-theoretical predictions. The conformal anomaly $c$ is calculated from the leading finite-width correction to the averaged free energy on strips. Estimates thus obtained are consistent with $c=1/2$, the same as for the pure Ising model.Comment: RevTeX 3, 11 pages +2 figures, uuencoded, IF/UFF preprin

Mapping SERS in CB:Au Plasmonic Nanoaggregates

In order to optimize surface-enhanced Raman scattering (SERS) of noble metal nanostructures for enabling chemical identification of analyte molecules, careful design of nanoparticle structures must be considered. We spatially map the local SERS enhancements across individual micro-aggregates comprised of monodisperse nanoparticles separated by rigid monodisperse 0.9 nm gaps and show the influence of depositing these onto different underlying substrates. Experiments and simulations show that the gaps between neighbouring nanoparticles dominate the SERS enhancement far more than the gaps between nanoparticles and substrate

A study of SPECT/CT camera stability for quantitative imaging

BACKGROUND: The purpose of this study was twofold: to evaluate the quantitative stability of a SPECT/CT gamma camera over time and to determine if daily flood acquisitions can reliably serve as calibration factors for quantitative SPECT. Using a cylindrical water phantom filled with measured amounts of (99m)Tc, factors were calculated to convert counts/cc to activity/cps. Measurements were made over an 18-month period. System sensitivity data calculated from (57)Co daily quality assurance (DQA) flood acquisitions were then compared to the (99m)Tc calibration factors to determine the relationship of the factors. RESULTS: The coefficient of variation is 2.7 % for the (99m)Tc cylinder conversion factors and 2.6 % for the (57)Co DQA flood data. The greatest difference between the cylinder conversion factors and the flood data is less than 3 %. CONCLUSIONS: Based on the results, the camera was stable within 3 % over an 18-month time period. The daily flood source acquisitions can be a reliable source for tracking camera stability and may provide information on updating the calibration factor for quantitative imaging