Sub-femtotesla scalar atomic magnetometer using multipass cells

Scalar atomic magnetometers have many attractive features but their sensitivity has been relatively poor. We describe a Rb scalar gradiometer using two multi-pass optical cells. We use a pump-probe measurement scheme to suppress spin-exchange relaxation and two probe pulses to find the spin precession zero crossing times with a resolution of 1 psec. We realize magnetic field sensitivity of 0.54 fT/Hz$^{1/2}$, which improves by an order of magnitude the best scalar magnetometer sensitivity and surpasses the quantum limit set by spin-exchange collisions for a scalar magnetometer with the same measurement volume operating in a continuous regime.Comment: 5 pages, 4 figure

Correlation function of spin noise due to atomic diffusion

We use paramagnetic Faraday rotation to study spin noise spectrum from unpolarized Rb vapor in a tightly focused probe beam in the presence of N$_2$ buffer gas. We derive an analytical form for the diffusion component of the spin noise time-correlation function in a Gaussian probe beam. We also obtain analytical forms for the frequency spectrum of the spin noise in the limit of a tightly focused or a collimated Gaussian beam in the presence of diffusion. In particular, we find that in a tightly focused probe beam the spectral lineshape can be independent of the buffer gas pressure. Experimentally, we find good agreement between the calculated and measured spin noise spectra for N$_2$ gas pressures ranging from 56 to 820 torr.Comment: 6 pages, 4 figure

Closed form Greens functions for general sources and stratified media

Cataloged from PDF version of article.The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in general, multilayer, planar media. First, the spectral domain Green's functions in an arbitrary layer are derived analytically from the Green's functions in the source layer by using a recursive algorithm. Then, the spatial domain Green's functions are obtained by adding the contributions of the direct terms, surface waves, and complex images approximated by the Generalized Pencil of Functions Method (GPOF). In the derivations, the main emphasis is to put these closed-form representations in a suitable form for the solution of the mixed potential integral equation (MPIE) by the method of moments in a general three-dimensional geometry. The contributions of this paper are: 1) providing the complete set of closed-form Green's functions in spectral and spatial domains for general stratified media; 2) using the GPOF method, which is more robust and less noise sensitive, in the derivation of the closed-form spatial domain Green's functions; and 3) casting the closed-form Green's functions in a form to provide efficient applications of the method of moments. © 1995 IEE

TRANSATLANTIC TRADE AND INVESTMENT PARTNERSHIP (TTIP): IMPACT AND CORRELATION ANALYSIS BASED ON TRADE AND INVESTMENT BETWEEN TURKEY AND EU, AND THE USA

The main objective of this study is to ascertain the importance and necessity of Turkey, based on trade and investment, in TTIP agreement as a partner country with both European Union (EU) and the USA. Here, it uses secondary data sources — Central Bank of the Republic of Turkey (CBRT) and Turkish Statistical Institute — from 2001 to 2016. To obtain vibrant findings, the study introduces two statistical analyses: correlation and regression. In addition, it elucidates descriptive analysis for comprehending the general trade and investment scenario. The results derived from correlation suggest that there is a strong positive correlation between Turkey’s total foreign trade and its export to and import from EU and the USA, Turkey’s total FDI and EU’s FDI in Turkey, as well as Turkey’s total FDI and the USA’s FDI in Turkey. In addition, a strong positive correlation has been found between Turkey’s total resident FDI in abroad and Turkey’s FDI in EU and the USA. On the other hand, the regression results indicate that Turkey’s trade and investment with EU and the USA have a significant impact on Turkey’s total foreign trade and investmen

Dipolar and scalar 3^3He and 129^{129}Xe frequency shifts in mm-sized cells

We describe a $^{3}$He-$^{129}$Xe comagnetometer operating in stemless anodically bonded cells with a 6 mm$^3$ volume and a $^{129}$Xe spin coherence time of 300 sec. We use a $^{87}$Rb pulse-train magnetometer with co-linear pump and probe beams to study the nuclear spin frequency shifts caused by spin polarization of $^{3}$He. By systematically varying the cell geometry in a batch cell fabrication process we can separately measure the cell shape dependent and independent frequency shifts. We find that a certain aspect ratio of the cylindrical cell can cancel the effects of $^3$He magnetization that limit the stability of vapor-cell comagnetometers. Using this control we also observe for the first time a scalar $^{3}$He-$^{129}$Xe collisional frequency shift characterized by an enhancement factor $\kappa_{\text{HeXe}} = -0.011\pm0.001$.Comment: 4 pages, 4 figure

Femtotesla direct magnetic gradiometer using a single multipass cell

We describe a direct gradiometer using optical pumping with opposite circular polarization in two $^{87}$Rb atomic ensembles within a single multipass cell. A far-detuned probe laser undergoes a near-zero paramagnetic Faraday rotation due to the intrinsic subtraction of two contributions exceeding 3.5 rad from the highly-polarized ensembles. We develop analysis methods for the direct gradiometer signal and measure a gradiometer sensitivity of $10.1$ fT/cm$\sqrt{\mathrm{Hz}}$. We also demonstrate that our multipass design, in addition to increasing the optical depth, provides a fundamental advantage due to the significantly reduced effect of atomic diffusion on the spin noise time-correlation, in excellent agreement with theoretical estimate.Comment: 5 pages, 4 figure

Closed-form green's functions of HED, HMD, VED, and VMD for multilayer media

The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in a general, multilayer, planar medium. The spectral domain Green's functions in a arbitrary layer are obtained through the Green's function of the source layer by using a recursive algorithm

Association of ECG characteristics with clinical and echocardiographic outcome to CRT in a non-LBBB patient population

Purpose: Effectiveness of cardiac resynchronization therapy (CRT) in patients without left bundle branch block (non-LBBB) QRS morphology is limited. Additional selection criteria are needed to identify these patients. Methods: Seven hundred ninety consecutive patients with non-LBBB morphology, who received a CRT-device in 3 university centers in the Netherlands, were selected. Pre-implantation 12-lead ECGs were evaluated on morphology, duration, and area of the QRS complex, as well as on PR interval, left ventricular activation time (LVAT), and the presence of fragmented QRS (fQRS). Association of these ECG features with the primary endpoint: a combination of left ventricular assist device (LVAD) implantation, cardiac transplantation and all-cause mortality, and secondary endpoint—echocardiographic reduction of left ventricular end-systolic volume (LVESV)—were evaluated. Results: The primary endpoint occurred more often in non-LBBB patients with with PR interval ≥ 230ms, QRS area < 109μVs, and with fQRS. Multivariable regression analysis showed independent associations of QRS area (HR 2.33 [1.44, 3.77], p = 0.001) and PR interval (HR 2.03 [1.51, 2.74], p < 0.001) only. Mean LVESV reduction was significantly lower in patients with baseline RBBB, QRS duration < 150 ms, PR interval ≥ 230 ms, and in QRS area < 109 μVs. Multivariable regression analyses only showed significant associations between QRS area ≥ 109 μVs (OR 2.00 [1.09, 3.66] p = 0.025) and probability of echocardiographic response to CRT. Conclusions: In the heterogeneous non-LBBB patient population, QRS area and PR prolongation rather than traditional QRS duration and morphology are associated to both clinical and echocardiographic outcomes of CRT