Spatial Distribution of Jack Pine Cones and Those Attacked by Insects

The middle crown and south quadrant of 6-m-tall jack pines, Pinus banksiana Lamb., produced significantly more cones than the rest of the tree. The number of cones attacked by Eucosma monitorana Heinrich was also highest in the middle crown and south quadrant. Laspeyresia toreuta (Grote) attacked the most cones in the middle crown. A positive, linear correlation existed between the number of cones attacked by inseets and cone abundanee per tree, indicating a response of the insect population to inereased food supply

Absolute frequency measurement of an 171Yb lattice clock and optical clock comparisons

The measurement of time and frequency is at the heart of many technological applications and scientific measurements alike. In fact, the SI-unit the second is by quite a margin the SI-unit with the best relative uncertainty (ca. 10^{-16}), given by the accuracies of Cs fountain clocks probing the F = 3 - F = 4 ground-state transition in 133Cs. Still, demands for even higher accuracy and especially stability (a Cs fountain needs up to two weeks for the statistics to reach its declared uncertainty) are uttered in support of technological advancements (e.g. geodesy and GNSS systems) as well as fundamental science (physics beyond the standard model, tests of relativity). Nowadays optical lattice clocks confining a large number of neutral atoms in Stark shift free optical traps (the Stark shift free condition is characterised by a so-called magic wavelength of the trap) propose good candidates for a future redefinition of the SI-second in terms of an optical transition. Their accuracy and stability already surpass the Cs-fountains by two and three orders of magnitude, respectively. With further improvements to be expected in the near future, the application of optical lattice clocks to relativistic gravimetry, quantum computing, quantum simulation and fundamental physics keeps evolving. This thesis describes the development and characterisation of an 171Yb lattice clock at INRIM as well as its first frequency measurement campaigns and technolo- gies towards improved optical frequency measurements. The lattice clock confines cold atoms in a 1D optical dipole trap at the magic wavelength, which also cancels any Doppler- and recoil-related effects on the ultra-narrow clock transition. The first chapter offers a general overview of the physics behind lattice clocks and opti- cal frequency measurements. In the second chapter the 171Yb lattice clock developed during this work is expounded, including the trapping, state-preparation and state-probing of ultracold atoms inside the optical lattice. An exhaustive uncertainty budget for the clock transition is given and discussed showing already a performance beyond state-of- the-art Cs fountain clocks. An absolute frequency measurement obtained during this work is laid out. The result represents the lowest uncertainty achieved in a measurement of this transition against a primary frequency standard so far and is in agreement with previous values obtained by other groups around the world. A proof-of-principle experiment demonstrating for the first time the feasibility of transportable optical lattice clocks for geodesy and metrology applications outside of laboratory environments is described in chapter three. This experiment was conducted in collaboration with PTB and NPL and included a geodetic measurement with a transportable optical lattice clock that agreed with conventional methods as well as an optical 171Yb-87Sr frequency ratio measurement, enlarging the database on this particular ratio and thereby contributing to a possible redefinition of the SI-unit the second in terms of an optical transition or frequency-ratio matrix in the future. The fourth chapter discusses improvements added to the Yb lattice clock after the aforementioned measurements, in particular the stabilisation of the cooling and trapping lasers on a single stable low-drift cavity using mirrors coated for three disparate wavelengths across the optical spectrum. The simultaneous offset sideband locking and a throughout characterisation of the cavity are discussed. The last chapter is about the characterisation and optimisation of the NPL universal oscillator, which was conducted during my secondment at the NPL research facilities in the UK. The universal oscillator consists out of a femtosecond frequency comb, an ultra stable master laser and six slave oscillators. The femtosecond comb is transferring the stability of the superior master oscillator cavity to all six slave oscillators, which includes five lasers ranging from the infrared to the visible region. The principle of operation is explained and the obtained high performance of the spectral purity transfer set forth and discussed. This experiment demonstrated an unprecedented spectral purity transfer performance in a multi-branch configuration, opening the way for the interrogation of whole clock ensembles by just one master oscillator

Absolute frequency measurement of the 1S0 - 3P0 transition of 171Yb

We report the absolute frequency measurement of the unperturbed transition 1S0 - 3P0 at 578 nm in 171Yb realized in an optical lattice frequency standard. The absolute frequency is measured 518 295 836 590 863.55(28) Hz relative to a cryogenic caesium fountain with a fractional uncertainty of 5.4x10-16 . This value is in agreement with the ytterbium frequency recommended as a secondary representation of the second in the International System of Units.Comment: This is an author-created, un-copyedited version of an article accepted for publication/published in Metrologia. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/1681-7575/aa4e62. It is published under a CC BY licenc

Absolute frequency measurement of the 1S0 – 3P0 transition of 171-Yb with a link to International Atomic Time

Dataset of the INRIM Yb clock measured respect to TAI collected between October 2018 to February 2019. YbvsSIm-viaEAL.dat: montly data with columns MJDstart: start date in MJD MJDstop: stop date in MJD MJDmed: mid point date in MJD MJDbaro: baricenter date in MJD Ybduty: Yb clock duty time y0=Yb/HM3: ratio between Yb clock and H Maser 03 u0: statistical uncertainty of y0 uB0: systematic uncertainty of y0 y1=extrap.: extrapolation over HM3 udead1: uncertainty of y1 from dead times udrift1: uncertainty of y1 from HM3 drift HM3drift/d: HM3 drift per day udrift/d: uncertainty of HM3 drift y2=HM3/UTCit: ratio between HM3 and UTC(IT) u2: uncertainty of y2 y3=UTCit/TAI: ratio between UTC(IT) and TAI u3: uncertainty of y3 y4=EALext.: extrapolation over EAL udead4: uncertainty of y4 from dead times udrift4: uncertainty of y4 from EAL drift y5=-d: ratio between TAI and the SI second from Circular T u5: uncertainty of y5 uA5: statistical uncertainty of y5 uB5: systematic uncertainty of y5 y=Yb/SI: final ratio beween the Yb clock and the Si second uA: not used uB: not used u: uncertainty of y YbvsTAId.dat: data every 5 days with columns: MJDstart: start date in MJD MJDstop: stop date in MJD MJDmed: mid point date in MJD MJDbaro: baricenter date in MJD Ybduty: Yb clock duty time y0=Yb/HM3: ratio between Yb clock and H Maser 03 u0: statistical uncertainty of y0 uB0: systematic uncertainty of y0 y1=extrap.: extrapolation over HM3 udead1: uncertainty of y1 from dead times udrift1: uncertainty of y1 from HM3 drift HM3drift/d: HM3 drift per day udrift/d: uncertainty of HM3 drift y2=HM3/UTCit: ratio between HM3 and UTC(IT) u2: uncertainty of y2 y3=UTCit/TAI: ratio between UTC(IT) and TAI u3: uncertainty of y3 y=Yb/TAI: final ratio beween the Yb clock and TAI uA: not used uB: not used u: uncertainty of yWe acknowledge funding from the European Metrology Program for Innovation and Research (EMPIR) project 15SIB03 OC18, from the Horizon 2020 Marie Skłodowska-Curie Research and Innovation Staff Exchange (MSCA-RISE) project Q-SENSE (Grant Agreement Number 691156), from the Italian Space Agency (ASI) funding DTF-Matera, from the EMPIR project 18SIB05 ROCIT. The EMPIR initiative is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States

Phase noise cancellation in polarisation-maintaining fibre links

The distribution of ultra-narrow linewidth laser radiation is an integral part of many challenging metrological applications. Changes in the optical pathlength induced by environmental disturbances compromise the stability and accuracy of optical fibre networks distributing the laser light and call for active phase noise cancellation. Here we present a laboratory scale optical (at 578 nm) fibre network featuring all polarisation maintaining fibres in a setup with low optical powers available and tracking voltage-controlled oscillators implemented. The stability and accuracy of this system reach performance levels below 1 * 10^(-19) after 10 000 s of averagingComment: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in "Phase noise cancellation in polarisation-maintaining fibre links", Rauf et al., Review of Scientific Instruments, 89, 033103 (2018) and may be found at https://doi.org/10.1063/1.501651

Figurations of displacement in and beyond Pakistan: empirical findings and reflections on protracted displacement and translocal connections of Afghans

Pakistan currently hosts up to three million Afghans, a number that is likely to increase due to the Taliban's recent return to power in Afghanistan. This working paper is based on empirical research on the experience of Afghan displacement in Pakistan from 2019 until early 2021 as part of the European Union funded TRAFIG project. Findings show that Afghans' protracted displacement is classed. Many low-skilled, low-income and largely non-educated Afghans experience barriers to upward social mobility, particularly leading the Afghan youth to consider migrating to Europe. First-generation Afghan refugees who migrated mainly in the 1980s and 1990s prefer to stay in Pakistan; only few would return if the conditions allowed it. While aiming to incentivise return, Pakistani government policies hamper the opportunity for Afghans to move around within and beyond Pakistan and remain connected to their translocal and transnational networks. Many Afghan refugees have family members who live in other parts of Pakistan or in other countries, but the potential of these networks to lift those in Pakistan out of protracted displacement is limited. We also found that social cohesion between Afghan refugees and the Pakistani host society has been decreasing. Local networks are highly significant in day-to-day life, but intergroup relations do not yield any emancipatory potential for Afghans. Afghans' presence in Pakistan needs to be reconsidered by all actors, namely the country of origin, host and donor countries. The current approach of 'administering Afghans' keeps them in protracted displacement without the opportunity to integrate legally or sustainably. It needs to be replaced with a new narrative and operational approach - one that acknowledges Afghans' contributions to Pakistan's economy, society and culture, and that secures their right to remain in Pakistan. Such an approach is particularly important today given the looming prospect of more Afghans entering Pakistan to escape from living under a government headed by the Taliban

Inhibitory and excitatory responses in the dorso-medial prefrontal cortex during threat processing

Objective: To evaluate cortical excitability during instructed threat processing. Methods: Single and paired transcranial magnetic stimulation (TMS) pulses were applied to the right dorsomedial prefrontal cortex (dmPFC) during high-density electroencephalography (EEG) recording in young healthy participants (n = 17) performing an instructed threat paradigm in which one of two conditioned stimuli (CS+ but not CS-) was paired with an electric shock (unconditioned stimulus [US]). We assessed TMS-induced EEG responses with spectral power (both at electrode and source level) and information flow (effective connectivity) using Time-resolved Partial Directed Coherence (TPDC). Support vector regression (SVR) was used to predict behavioral fear ratings for CS+ based on TMS impact on excitability. Results: During intracortical facilitation (ICF), frontal lobe theta power was enhanced for CS+ compared to single pulse TMS for the time window 0–0.5 s after TMS pulse onset (t(16) = 3.9, p < 0.05). At source level, ICF led to an increase and short intracortical inhibition (SICI) to a decrease of theta power in the bilateral dmPFC, relative to single pulse TMS during 0–0.5 s. Compared to single pulse TMS, ICF increased information flows, whereas SICI reduced the information flows in theta band between dmPFC, amygdala, and hippocampus (all at p < 0.05). The magnitude of information flows between dmPFC to amygdala and dmPFC to hippocampus during ICF (0–0.5 s), predicted individual behavioral fear ratings (CS+; coefficient above 0.75). Conclusion: Distinct excitatory and inhibitory mechanisms take place in the dmPFC. These findings may facilitate future research attempting to investigate inhibitory/facilitatory mechanisms alterations in psychiatric disorders and their behavioral correlates

Guidelines for developing optical clocks with 10−1810^{-18} fractional frequency uncertainty

There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the $10^{-18}$ range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with $1 imes 10^{-18}$ uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects

Geodesy and metrology with a transportable optical clock

partially_open24openGrotti, Jacopo; Koller, Silvio; Vogt, Stefan; Häfner, Sebastian; Sterr, Uwe; Lisdat, Christian; Denker, Heiner; Voigt, Christian; Timmen, Ludger; Rolland, Antoine; Baynes, Fred N.; Margolis, Helen S.; Zampaolo, Michel; Thoumany, Pierre; Pizzocaro, Marco; Rauf, Benjamin; Bregolin, Filippo; Tampellini, Anna; Barbieri, Piero; Zucco, Massimo; Costanzo, Giovanni A.; Clivati, Cecilia; Levi, Filippo; Calonico, DavideGrotti, Jacopo; Koller, Silvio; Vogt, Stefan; Häfner, Sebastian; Sterr, Uwe; Lisdat, Christian; Denker, Heiner; Voigt, Christian; Timmen, Ludger; Rolland, Antoine; Baynes, Fred N.; Margolis, Helen S.; Zampaolo, Michel; Thoumany, Pierre; Pizzocaro, Marco; Rauf, Benjamin; Bregolin, Filippo; Tampellini, Anna; Barbieri, Piero; Zucco, Massimo; Costanzo, Giovanni A.; Clivati, Cecilia; Levi, Filippo; Calonico, David