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The effect of shell separation on the axial shielding with closed double-shell cylindrical shields is investigated numerically. It is found that the optimum shell separation for practical, equal-thickness shields of the above type is considerably smaller than that for transverse spherical and infinitely long cylindrical shields: in most cases, air gaps equal 5%-10% of the inner shell diameter are wide enough to bring the shielding to 90% of its maximum. This indicates that closely spaced axial shields can be used without much sacrifice in performance. Taking into account the computed optimum shell separation for double-shell shields, one can easily optimize and design a compact and effective multishell shield. Based on the numerical study, an analytical approximation is suggested for the axial shielding with narrowly spaced double-shell cylindrical shields. [ABSTRACT FROM AUTHOR]

Miniaturized atomic sensors are often fabricated using anodic bonding of silicon and borosilicate glass. Here we describe a technique for fabricating anodically bonded alkali-metal cells using GaP and Pyrex. GaP is a non-birefringent semiconductor that is transparent at alkali-metal resonance wavelengths, allowing new sensor geometries. GaP also has a higher thermal conductivity and lower He permeability than borosilicate glass and can be anodically bonded below 200 °C, which can also be advantageous in other vacuum sealing applications. [ABSTRACT FROM AUTHOR]

Scalar couplings between covalently bound nuclear spins are a ubiquitous feature in nuclear magnetic resonance (NMR) experiments, imparting valuable information to NMR spectra regarding molecular structure and conformation. Such couplings arise due to a second-order hyperfine interaction, and, in principle, the same mechanism should lead to scalar couplings between nuclear spins in unbound van der Waals complexes. Here, we report the first observation of scalar couplings between nuclei in van der Waals complexes. Our measurements are performed in a solution of hyperpolarized 129Xe and pentane, using superconducting quantum interference devices to detect NMR in 10 mG fields, and are in good agreement with calculations based on density functional theory, van der Waals forces play an important role in many physical phenomena. The techniques presented here may provide a new method for probing such interactions. [ABSTRACT FROM AUTHOR]

Some of the most sensitive methods of measuring magnetic fields use interactions of resonant light with atomic vapour. Recent developments in this vibrant field have led to improvements in sensitivity and other characteristics of atomic magnetometers, benefiting their traditional applications for measurements of geomagnetic anomalies and magnetic fields in space, and opening many new areas previously accessible only to magnetometers based on superconducting quantum interference devices. We review basic principles of modern optical magnetometers, discuss fundamental limitations on their performance, and describe recently explored applications for dynamical measurements of biomagnetic fields, detecting signals in NMR and MRI, inertial rotation sensing, magnetic microscopy with cold atoms, and tests of fundamental symmetries of nature. [ABSTRACT FROM AUTHOR]

Discusses Lorentz invariance in the framework of special relativity. Information on Lorentz symmetry and charge conjugation, parity and time-reversal symmetries; Applicability of effective-field theory expansions to the study of violations of Lorentz invariance; Link between precession frequency and magnetic field; Challenges for quantum gravity.

In this work, we have found that the key to minimizing the effect of the end-cap openings in multishell shields lies with widening the axial air-gaps between the end-caps. We have revealed that the axial air-gaps strongly influence the shielding with openings, while practically not affecting -- if the gaps are not too narrow, of course -- the shielding with no openings. As a result, widening the axial air-gaps can bring the axial shielding with large openings very close to that with no openings at all. To investigate as general case as possible we have described with the help of special charts the five-shell shields with typical 1.25, 1.5, and 1.75 aspect ratios for the innermost shell. The charts showed that while the shielding with no openings increases monotonically with either shortening the innermost shell or increasing the radial air-gaps, the shielding with openings reaches an extreme, which depends on the normalized permeability. Another important finding is that in contrast to small openings, the effect of large openings depends strongly on the radial air-gaps. Using the charts developed, a typical five-shell shield can be easily optimized in order to compensate for the effect of the openings and match the performance of the corresponding closed shield. [ABSTRACT FROM AUTHOR]

The article discusses the potential use of diamond magnetometers in single-spin nuclear magnetic resonance (NMR) detection. The atomic spin in a crystal defect in diamond nanoparticle can be manipulated with light, responding to the magnetic field generated by the spins in a sample. Also discussed are the properties of nitrogen-vacancy centers in diamond, the association of the finite magnetic moments of electrons and nuclei to their spins, magnetometry techniques and the detection of magnetic fields from single spins.

The article discusses the importance of chip-scale atomic magnetometer. The National Institute of Standards and Technology (NIST) has developed the instrument by combining tunable single-frequency laser diodes and fabrication of millimeter-scale atomic sensors to reduce the negative effects of atomic collisions. The diverse array of sensors are very useful for the geology and mineral exploration and military and medical applications.