Single-Particle Self-Excited Oscillator

Electronic feedback is used to self-excite the axial oscillation of a single electron in a Penning trap. Large, stable, easily detected oscillations arise even in an anharmonic potential. Amplitudes are controlled by adjusting the feedback gain, and frequencies can be made nearly independent of amplitude fluctuations. Quantum jump spectroscopy of a perpendicular cyclotron motion reveals the absolute temperature and amplitude of the self-excited oscillation. The possibility to quickly measure parts per billion frequency shifts could open the way to improved measurements of e-, e+, p, and [overline p] magnetic moments

Quantum Fluctuations of Coulomb Potential as a Source of Flicker Noise. The Influence of External Electric Field

Fluctuations of the electromagnetic field produced by quantized matter in external electric field are investigated. A general expression for the power spectrum of fluctuations is derived within the long-range expansion. It is found that in the whole measured frequency band, the power spectrum of fluctuations exhibits an inverse frequency dependence. A general argument is given showing that for all practically relevant values of the electric field, the power spectrum of induced fluctuations is proportional to the field strength squared. As an illustration, the power spectrum is calculated explicitly using the kinetic model with the relaxation-type collision term. Finally, it is shown that the magnitude of fluctuations produced by a sample generally has a Gaussian distribution around its mean value, and its dependence on the sample geometry is determined. In particular, it is demonstrated that for geometrically similar samples, the power spectrum is inversely proportional to the sample volume. Application of the obtained results to the problem of flicker noise is discussed.Comment: 14 pages, 3 figure

Lascia Ch\u27io Pianga

Recitative: [Italian] Armida, dispietata colla forza d’abisso rapimmi al caro Ciel di miei contenti, e qui con duoloeterno viva mi tiene in tormento d’inferno. Signor! Ah! Per pieta, lascia mi piangere. [German] Armida, Mitleidlose! In den Abgrund des Jammers versanken ewig mir des Lebens Freuden, und hier mit ew’gen Qualen halt mich gefesselt die grause Nacht der Holle. O Herr! Ach, hab’ Erbarmen und lass mich weinen. [English] Armida, cruel fortune with a power inhuman withdraw my heart from Heav’n and my contentment And here with grief eternal Living it holds me in torment most infernal O Lord! In pity hear me tears will relieve me. Aria: [Italian] Lascia ch’io piaga la dura sorte e che sospiri la liberta; e che sospiri, e che sospiri, la liberta! Lascia ch’io pianga la dura sorte e che sospiri la liberta. Il duol infranga queste ritorte de miei martiri sol per pieta, Si, de’ miei martiri sol per pieta. [French] Peine cruelle! Douleur mortelle!Mon Coeur t’appelle, O liberte.Par les a laremsE par le larmesCe coeur est brise! Peine cruelle!Douleur mertelle!Mon coeur t’apelle, O liberte!Quand se decahineSur moi la haineTrop inhumaineOh Dieu, brisez me chaine,Brisez me chaine,Dans votre bonte! [German] Laa mich mit Tranen mein Loos beklagen,Ketten zu tragen, welch’ hartes Geschick!Ketten zu tragen,Ketten zu tragen, welch’ hartes Geschick!Lass mit Thranen mein Loos beklagen,Ketten su tragen walch’ hartes Geschick!Ach, nut im Tode fins’ ich Erbarmen,Er giebt mir Armen die Ruh’ zuruck, ja,er giebt mir Armen die Ruh’ zuruck. [English] Here let my tears flow!Let hope my soul know,My heart is longingFor Liberty,My heart is longing,My heart is longingFor Liberty.Here let my tears flowLet hope my soul knowMy heart is longingFor Liberty!Assuage the sorrow to chains belongingO, great tomorrowThat I may be free,O, great tomorrowThat I may be free

A discrete invitation to quantum filtering and feedback control

The engineering and control of devices at the quantum-mechanical level--such as those consisting of small numbers of atoms and photons--is a delicate business. The fundamental uncertainty that is inherently present at this scale manifests itself in the unavoidable presence of noise, making this a novel field of application for stochastic estimation and control theory. In this expository paper we demonstrate estimation and feedback control of quantum mechanical systems in what is essentially a noncommutative version of the binomial model that is popular in mathematical finance. The model is extremely rich and allows a full development of the theory, while remaining completely within the setting of finite-dimensional Hilbert spaces (thus avoiding the technical complications of the continuous theory). We introduce discretized models of an atom in interaction with the electromagnetic field, obtain filtering equations for photon counting and homodyne detection, and solve a stochastic control problem using dynamic programming and Lyapunov function methods.Comment: 76 pages, 12 figures. A PDF file with high resolution figures can be found at http://minty.caltech.edu/papers.ph

Smoking and Multiple Sclerosis: An Updated Meta-Analysis

Background: Multiple sclerosis (MS) is a leading cause of disability in young adults. Susceptibility to MS is determined by environmental exposure on the background of genetic risk factors. A previous meta-analysis suggested that smoking was an important risk factor for MS but many other studies have been published since then.Methods/Principal Findings: We performed a Medline search to identify articles published that investigated MS risk following cigarette smoking. A total of 14 articles were included in this study. This represented data on 3,052 cases and 457,619 controls. We analysed these studies in both a conservative (limiting our analysis to only those where smoking behaviour was described prior to disease onset) and non-conservative manner. Our results show that smoking is associated with MS susceptibility (conservative: risk ratio (RR) 1.48, 95% confidence interval (CI) 1.35-1.63, p<10(-15); non-conservative: RR 1.52, 95% CI 1.39-1.66, p<10(-19)). We also analysed 4 studies reporting risk of secondary progression in MS and found that this fell just short of statistical significance with considerable heterogeneity (RR 1.88, 95% CI 0.98-3.61, p = 0.06).Discussion: Our results demonstrate that cigarette smoking is important in determining MS susceptibility but the effect on the progression of disease is less certain. Further work is needed to understand the mechanism behind this association and how smoking integrates with other established risk factors

On the exchange of intersection and supremum of sigma-fields in filtering theory

We construct a stationary Markov process with trivial tail sigma-field and a nondegenerate observation process such that the corresponding nonlinear filtering process is not uniquely ergodic. This settles in the negative a conjecture of the author in the ergodic theory of nonlinear filters arising from an erroneous proof in the classic paper of H. Kunita (1971), wherein an exchange of intersection and supremum of sigma-fields is taken for granted.Comment: 20 page

The Impact of Entropy on the Spatial Organization of Synaptonemal Complexes within the Cell Nucleus

We employ 4Pi-microscopy to study SC organization in mouse spermatocyte nuclei allowing for the three-dimensional reconstruction of the SC's backbone arrangement. Additionally, we model the SCs in the cell nucleus by confined, self-avoiding polymers, whose chain ends are attached to the envelope of the confining cavity and diffuse along it. This work helps to elucidate the role of entropy in shaping pachytene SC organization. The framework provided by the complex interplay between SC polymer rigidity, tethering and confinement is able to qualitatively explain features of SC organization, such as mean squared end-to-end distances, mean squared center-of-mass distances, or SC density distributions. However, it fails in correctly assessing SC entanglement within the nucleus. In fact, our analysis of the 4Pi-microscopy images reveals a higher ordering of SCs within the nuclear volume than what is expected by our numerical model. This suggests that while effects of entropy impact SC organization, the dedicated action of proteins or actin cables is required to fine-tune the spatial ordering of SCs within the cell nucleus

Epidemiology of a hybrid swarm: evidence of 11 feline infectious agents circulating in a population of sympatric European wildcat hybrids and free-living domestic cats, in Scotland:Epidemiology of a hybrid swarm

Hybridisation between wild and domestic species poses a serious challenge to conservation management and can, potentially, lead to extinction. Alongside it, disease transmission will inevitably occur. However, the link between these two phenomena has historically been neglected. In Scotland, the European wildcat is particularly threatened by hybridisation with the domestic cat, a process promoted by long-term habitat loss, human encroachment, and persecution. Between 2015 and 2019, free-living cats (n = 120) were captured in six conservation priority areas of northern Scotland. Samples were collected for infectious disease screening (feline immunodeficiency virus, feline leukaemia virus, feline calicivirus, feline herpesvirus, Chlamydia felis, Mycoplasma felis, Bordetella bronchiseptica, Mycoplasma haemofelis, Candidatus Mycoplasma haemominutum, Candidatus Mycoplasma turicensis, and Tritrichomonas foetus) and genetic analysis. Polymerase chain reaction and reverse transcriptionPCR were used to detect infectious DNA or RNA, respectively. The hybrid score (Q) for each individual cat was determined using a 35-SNP-marker test. Statistical analysis investigated the association between Q and probability of infection, accounting for spatial clustering. The results confirmed the presence of 11 infectious agents circulating in the free-living cat population of northern Scotland, which consists of a hybrid swarm between F. silvestris and F. catus. For eight of them (feline leukaemia virus, feline herpesvirus C. felis, B. bronchiseptica, M. felis, M. haemofelis, Ca. M. haemominutum, and T. foetus), there was no significant association between infection probability and Q, supporting our hypothesis that the hybrid swarm may be functioning as a single epidemiological unit. Considering the impact of infectious diseases on health, welfare, and population dynamics of domestic cats, their presence in the extremely fragile and hybridised population of F. silvestris in Scotland could be population limiting or, potentially, contribute to local extinction. Comprehensive disease surveillance, risk analysis, and domestic cat management will be essential for the European wildcat conservation, particularly where hybridisation is increasing and anthropogenic factors are prevalent