3D sympathetic cooling and detection of levitated nanoparticles

Cooling the center-of-mass motion of levitated nanoparticles provides a route to quantum experiments at mesoscopic scales. Here we demonstrate three-dimensional sympathetic cooling and detection of the center-of-mass motion of a levitated silica nanoparticle. The nanoparticle is electrostatically coupled to a feedback-cooled particle while both particles are trapped in the same Paul trap. We identify two regimes, based on the strength of the cooling: in the first regime, the sympathetically cooled particle thermalizes with the directly cooled one, while in the second regime, the sympathetically cooled particle reaches a minimum temperature. This result provides a route to efficiently cool and detect particles that cannot be illuminated with strong laser light, such as absorptive particles, and paves the way for controlling the motion of arrays of several trapped nanoparticles

Ultra-high quality factor of a levitated nanomechanical oscillator

A levitated nanomechanical oscillator under ultra-high vacuum (UHV) is highly isolated from its environment, and this isolation is expected to enable very low mechanical dissipation rates. However, a gap persists between predictions and experimental data. Here, we levitate a silica nanoparticle in a linear Paul trap at room temperature, at pressures as low as $7\times 10^{-11}~\text{mbar}$. We measure a dissipation rate of $2\pi\times80(20)~\text{nHz}$, corresponding to a quality factor exceeding $10^{10}$, more than two orders of magnitude higher than previously shown. A study of the pressure dependence of the particle's damping and heating rates provides insight into the relevant dissipation mechanisms. Our results confirm that levitated nanoparticles are indeed promising candidates for ultrasensitive detectors and for tests of quantum physics at macroscopic scales

Type-specific herpes simplex virus-1 and herpes simplex virus-2 seroprevalence in Romania: comparison of prevalence and risk factors in women and men

AbstractObjectiveTo determine herpes simplex virus (HSV)-2 and HSV-1 seroprevalence in women and men in Romania.MethodsA cross-sectional seroprevalence survey was conducted between 2004 and 2005 on a total of 1058 women and men representative of the population of Bucharest. All participants were aged 15–44 years and completed a structured questionnaire. A blood sample was collected to detect IgG anti-HSV-1 and HSV-2 serum antibodies using the HerpeSelect ELISA (Focus Diagnostics).ResultsA total of 761 women (median age 29 years) and 297 men (median age 29 years) were included. Overall, HSV-2 seroprevalence (15.2%) increased with age. Among women, HSV-2 seroprevalence increased from 11.0% in 15–19-year-olds to 38.3% in 40–44-year-olds. Among men, seroprevalence increased from 4.0% in 20–24-year-olds to 27.1% in 40–44-year-olds. HSV-2 seroprevalence was significantly higher among women than men (17.0% vs. 10.8%). HSV-1 seropositivity was high (87.2%) in all age groups, with no clear trend by age or by sex. In addition to older age and female sex, risk factors for HSV-2 included greater number of lifetime sexual partners, lower educational attainment, and history of genital vesicles. Lower educational level and rural residence were associated with a higher risk of HSV-1 seropositivity.ConclusionsIn Romania, HSV-2 seroprevalence was higher in women than men, and was within European limits and lower than that in Africa and the USA. In contrast, HSV-1 seroprevalence was generally higher than that previously recorded in similarly aged populations in Western Europe

In situ photothermal response of single gold nanoparticles through hyperspectral imaging anti-stokes thermometry

Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task for both modeling and experimental measurements. Here, we present an implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual nanoparticles (NPs) from a single hyperspectral photoluminescence confocal image. The method is label-free, potentially applicable to any NP with detectable anti-Stokes emission, and does not require any prior information about the NP itself or the surrounding media. With it, we first studied the photothermal response of spherical gold NPs of different sizes on glass substrates, immersed in water, and found that heat dissipation is mainly dominated by the water for NPs larger than 50 nm. Then, the role of the substrate was studied by comparing the photothermal response of 80 nm gold NPs on glass with sapphire and graphene, two materials with high thermal conductivity. For a given irradiance level, the NPs reach temperatures 18% lower on sapphire and 24% higher on graphene than on bare glass. The fact that the presence of a highly conductive material such as graphene leads to a poorer thermal dissipation demonstrates that interfacial thermal resistances play a very significant role in nanoscopic systems and emphasize the need for in situ experimental thermometry techniques. The developed method will allow addressing several open questions about the role of temperature in plasmon-assisted applications, especially ones where NPs of arbitrary shapes are present in complex matrixes and environments