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Structural, magnetic and electromechanical changes resulting from spin crossover between the spin quintet and spin triplet forms of a mononuclear Mn3+ complex embedded in six lattices with different charge balancing counterions are reported. Isostructural ClO4- and BF4- salts (1) and (2) each have two unique Mn3+ sites which follow different thermal evolution pathways resulting in a crossover from the spin quintet form at room temperature to a 1:1 spin triplet:quintet ratio below 150 K. The PF6- (3) and NO3- (4) salts which each have one unique Mn3+ site show a complete conversion from spin quintet to spin triplet over the same temperature range. A complete two step spin crossover is observed in the CF3SO3- lattice (5) with a 1:1 ratio of spin quintet and spin triplet forms at intermediate temperature, while the BPh4- lattice (6) stabilizes the spin triplet form over most of the temperature range with gradual and incomplete spin state switching above 250 K. An electromechanical piezoresponse was detected in NO3- complex 4 despite crystallization in a centrosymmetric space group. The role of defomations associated with strain-induced spin triplet-spin quintet switching in breaking the local symmetry are discussed and computational analysis is used to estimate the energy gap between the two spin states.

Transdermal amplitude modulated signal (TAMS) is a novel electrical stimulus which has been recently introduced for the treatment of overactive bladder (OAB) syndrome. It has been suggested that it has advantages over conventional waveforms by providing more effective penetration of the skin to enhance the efficacy of therapy. As there is no literature which supports this, we performed this study to evaluate potential advantages of the TAMS signal for electrical stimulation of subcutaneous nerves as compared to conventional stimuli. The stimuli were applied on forearms of ten healthy volunteers and electrical parameters of stimuli and sensation measurements were recorded. None of the recorded electrical parameters showed significant differences (paired t-test p ≥ 0.250) between the TAMS and conventional waveforms. Similarly, the mean sensation recorded at motor threshold level and at 50% of maximal motor response level showed no differences (paired t-test p = 0.242 and p = 0.687 respectively). It is unlikely, based on the results of this study, that TAMS provides any enhancement of the efficacy of conventional stimuli. We would recommend that further studies are carried out to clearly demonstrate in man what, if any, advantages the TAMS waveform has over conventional stimulation before it is widely deployed into clinical practice.

There are a number of claims in the literature that specific combinations of low-level DC and AC magnetic fields can cause biologically significant effects. The combinations of fields required to elicit these responses fulfil the theoretical conditions for classical cyclotron resonance of the selected ion. Because of the biological importance of calcium ions any effects on them are of particular interest, for instance the claimed increase in calcium uptake by electromagnetically exposed lymphocytes. We have measured the intracellular calcium concentration, by means of a sensitive fluorescent probe, during a 60 min exposure of mouse lymphocytes to 'cyclotron resonance' conditions for calcium ions. 'Resonance' conditions at two frequencies (16 Hz and 50 Hz) were tested, with a range of DC field amplitudes used to shift the frequency up to 25% either side of the calculated optimum. Treatment of the lymphocytes with concanavalin A was used as a positive control and caused a significant increase in intracellular calcium concentration. No change in intracellular calcium concentration could be detected when lymphocytes were exposed to 'cyclotron resonance' conditions or to the other magnetic field combinations used.

There are many claims made for biological effects of low-frequency pulsed magnetic fields ranging from beneficial to harmful, but few have been independently verified. The ubiquitous nature of both natural and man-made magnetic fields makes the possibility of biological interaction a potentially important subject. We have investigated the claimed stimulatory action of low-frequency pulsed magnetic fields, of a type used clinically, on the growth of embryonic chicks. Four day old embryos were exposed to a magnetic field, peak field strength 2.1 mT pulsed in 5 ms bursts repeated at 15 Hz, for 100 h. Embryo weights and long-bone lengths were compared to sham-exposed controls. Particular care was taken to reduce temperature differences between the test and control groups because this model has a known sensitivity to small temperature changes. We found no increase in embryonic growth due to this low-frequency pulsed magnetic field and hence have been unable to confirm earlier findings by other workers using the same model. We conclude that rigorous design of experimental protocol and a full description of the physical parameters are essential in studies purporting to show effects of electromagnetic fields if the results are to be confirmed by other workers.

People have been fascinated by magnetism and its effects since the discovery of lodestone, and the biological effects of currents from natural sources, such as electric eels, have been observed – if not understood – for thousands of years. Galvani and Volta started to place the interaction of electric currents and biological systems on a scientific footing in the 18th century and today the stimulation of nerves and muscles by electricity is well understood and widely used in medicine for diagnostic purposes.

Describes experiments on normal rats and on rats treated with digitalis to reduce the cardiac threshold to electrical stimulation. The possible implications for NMR imaging are discussed. It is concluded that the fields investigated are unlikely to constitute a direct hazard to the electrical activity of the heart.

Measurements were made on 10 children who had finger tip amputations. They were made at 1 to 7 day intervals until 2 successive zero readings were obtained. The injured finger was immersed in physiologically normal saline for approximately 2/3 of its length, and the probe was moved across the surface of the wound. The currents recorded a remarkable similarity to those obtained by Borgens et al. (1977) on salamanders, rising to a peak average current density of 22 mu A cm-2 after an average of 8 days.

The electromagnetic spectrum is traditionally divided into ionising and nonionising radiation, based on the frequency or energy of that radiation. Frequencies above approximately 3 × 1015 HZ (energies greater than 10 eV) cause ionisation, and their biological effects have been extensively studied.