The impact of external medium conductivity on the efficiency of the reversible permeabilisation caused by pulsed electric fields was investigated. Pulses of 12 ns, 102 ns or 100 μs were investigated. Whenever permeabilisation could be detected after the delivery of one single pulse, media of lower conductivity induced more efficient reversible permeabilisation and thus independently of the medium composition. Effect of medium conductivity can however be hidden by some saturation effects, for example when pulses are cumulated (use of trains of 8 pulses) or when the detection method is not sensitive enough. This explains the contradicting results that can be found in the literature. The new data are complementary to those of one of our previous study in which an opposite effect of the conductivity was highlighted. It stresses that the conductivity of the medium influences the reversible permeabilization by several ways. Moreover, these results clearly indicate that electropermeabilisation does not linearly depend on the energy delivered to the cells. Electropermeabilisation, also called electroporation, is one of the well documented effects of pulsed electric fields on plasma membrane12th century, conventional electropermeabilisation was obtained with pulses of a few microseconds or a few milliseconds . Several applications using such pulses have been successfully developed like electrochemotherapy4Until the end of the 20More recently light was focused on the effect of much shorter pulses in the nanosecond range. Such pulses are referred to as nanopulses, nanosecond pulses or nanosecond pulsed electric field (nsPEF). Permeabilisation of the external cellular membrane induced by such pulses of a few nanoseconds or tens of nanoseconds has been reported several times using different permeabilisation markers like propidiumSeveral groups have studied the influence of medium conductivity on membrane permeabilization by microsecond pulses13141516171813141517181413161722. We hypothesized that the longer charging time of the cell’s membrane in a low conductivity medium did not allow sufficient membrane charging in order to trigger permeabilization, as discussed in detail in referenceThe impact of extracellular conductivity on the efficiency of shorter pulses (in the nanosecond range) has been less intensively studied so far. A possible influence was suggested in a theoretical study where the authors considered that permeabilization by nanosecond pulses should be scaled with the charge densityThe experiments reported here were designed to get a more global understanding of the impact of extracellular conductivity on electropermeabilization efficacy. In contrast to our previous study, here we restricted the experimental conditions to more intense treatment parameters, where permeabilisation could be detected after one pulse or very few pulses. Both very short pulses of 12 ns and 102 ns as well as more traditional long pulses of 100 μs were used. The study was focused on reversible electropermeabilization. Cell death due to bleomycin entry was used as diagnostic approach. Indeed, experiments in which the sole pulse-induced cell death is used as a diagnostic indicator are very difficult to analyze since cell death can occur through many different pathways and, more important for this study, can be very sensitive to the composition of the external medium23In the following section we will present results on the degree of reversible membrane permeabilization as a function of the conductivity and the composition of the external medium, over a wide range of treatment parameters.The first experiments were performed in S-MEM (conductivity 1.5 S/m) and in STM (0.1 S/m) with a single pulse of 100 μs. The external electric field was varied between 85 kV/m and 145 kV/m. Under these conditions, no cell death induced by the electric pulses alone, i.e. in the absence of bleomycin, was observed (data not shown). Consequently, in the presence of bleomycin, the fraction of cells that died corresponds to the fraction of cells reversibly permeabilized by the electric pulses. Our experiments were performed with a bleomycin concentration of either 30 nM  or 5 nM At first view, this influence of the extracellular medium conductivity on cell reversible permeabilization seems to contradict a previous study of Pucihar and colleguesFor both bleomycin concentrations tested, 30 nM and 5 nM, no difference in the efficiency of the reversible permeabilization between the two extracellular media was observed, confirming previous results of Pucihar and colleagues. Apparently, the influence of the conductivity of the external medium cannot be detected under these specific experimental conditions i.e. when several pulses are applied.In order to confirm that the differences observed with one single pulse  were onl2350 corresponds to the electrical field magnitude which is necessary to obtain a survival rate of 50% and dE represents the steepness of the survival decay at E50. The quantities E50 and dE are plotted as a function of medium’s conductivity on 50 appears to depend linearly on the medium’s conductivity, confirming the fact that reversible permeabilization requires higher field strengths when extracellular conductivity is increased. No impact of the pH buffering agent or sugar type was observed. Additionally, the steepness of survival decay dE (1) was also affected by the extracellular conductivity. For external conductivities ranging between 0.1 S/m and 0.6 S/m, steepness is close to 10 kV/m. Steepness then increases to approximately 20 kV/m for the media with extracellular conductivity of 1.5 S/m. The relation of the steepness dE as a function of E50 is displayed on In order to quantify this observation, survival data were fitted by sigmoid functions according to equation In all the experiments presented above, cells were kept 10 minutes in their pulsing medium before being handled and diluted for the cloning efficiency assay. In order to check that the ionic strength of the medium did not affect the cells during this 10 minutes period rather than during the pulse delivery, an experiment was performed in which the cells were pulsed in media with different conductivities and immediately diluted in the same highly conductive medium just after the pulses delivery. Only four media were selected for this test: S-MEM , NTM , STM  and SHM . Directly after pulse delivery (10 to 20 sec), cells were all diluted in S-MEM solution also containing 30 nM bleomycin so that bleomycin would have time to diffuse in the reversibly permeabilized cells. After a delay of 10 minutes, the standard dilution procedure was performed. Results are displayed on In a recent study from our group, performed with the same cell type and the same methodology, the opposite influence of external conductivity was detected when pulses of 12 ns of duration and 3.2 MV/m field strength were used. With those pulse parameters, reversible permeabilization of the cells was obtained only in the high conductivity medium  and not in the low conductivity medium The experiment was repeated again with another set of pulse parameters. The magnitude of the pulses was set to 3.2 MV/m but the duration of the pulses was increased to 102 ns. The repetition rate was kept at 10 Hz. The pulses alone caused different drops in cell survival depending on the media . While tIn the present study, the experiments performed with one single 100 μs-pulse indicate that the efficiency of reversible electropermeabilization significantly increases when the conductivity of the external medium decreases. This result was obtained independently of the individual medium composition. In particular, a possible impact of the pH-buffering agent was excluded. Another critical aspect was that most low-conductivity media usually contain high concentration of sugars (like sucrose) which can prevent the typical cell swelling which is observed when pulses are applied in the standard saline solutionThe impact of extracellular conductivity at the time of the pulse delivery was preserved even when cells were resuspended in their culture medium a few seconds after the delivery of the electric pulses suggesting that the differences observed were not due to the post-pulse incubation conditions. A higher efficiency of low conductivity media was also observed when using a few 12-ns or 102-ns pulses , or just a single pulse of these lengths. The results presented in this study are thus overall consistent since the same tendency was obtained for many different pulse parameters.These results are in agreement with the studies from the group of Zimmermann who performed experiments with ‘exponential pulses’ in the microsecond range1718131415Some of the apparent contradictions between all the different studies can be accounted for by at least two facts. First of all, the various studies suggest that the influence of the conductivity can be different depending on whether reversible permeabilization or pulses-induced cell-death is considered. This has been reported in previous publications1417The fact that a saturation effect is able to mask the influence of the external medium conductivity was also revealed by the influence of the bleomycin concentration on the results of our experiments. Indeed, in 29The numerous factors that might influence a permeabilisation experiment also imply that the results which were obtained in this study with bleomycin might not hold when other markers of permeabilisation are used. Preliminary experiments carried in our lab indicate that our conclusions on the impact of extracellular conductivity on reversible permeabilisation hold when YO-PRO is used and at least one of the previous published study which focused specifically on reversible permeabilisation also indicate similar conclusions with PI used as a markerAmong the different papers specifically focusing on the effect of extracellular conductivity on reversible permeabilisation, the only one contradicting the conclusion of the present study, to the best of our knowledge, is therefore the one from our groupτ strongly depends on extracellular conductivity ; σiand σeintracellular and extracellular conductivities (S/m); S0membrane surface conductance (S/m2).For all the parameters tested in the present study, pulses were efficient at inducing reversible permeabilisation in the sense that uptake of bleomycin  could be detected after either a single pulse or a very low number of pulses. In that case, the linear model of the TMV cannot be used anymore since membrane conductivity increase must be accounted for. et al.35As depicted on Our first hypothesis is a purely electrical explanation. As described above, the current models of electroporation cannot account for the impact of conductivity. Their main drawback is that they consider the membrane as a continuum and cannot account for the local behavior on a nanoscopic scale. If a high TMV is assumed to create pores of a few nanometers, conductance of ion through such pores will locallyAnother hypothesis is based on electromechanical coupling. In the presence of an electric field, Maxwell stress induces a stretching force on the membrane4041817Finally, the impact of the conductivity might not be truly during the pulse but external medium conductivity might affect the initial state of the membrane before the pulse. It is known for example that ionic strength and sugar content have an impact on membrane properties such as bending rigidity and stretching coefficientAt the current state of our work, we cannot provide a unique explanation for the impact of the extracellular conductivity. Most probably, extracellular conductivity influences electropermeabilisation in more than one way. As it was detailed in our previous paperIt is currently not possible to explain precisely the influence of conductivity on electropermeabilisation. In any case the results demonstrate that electropermeabilisation efficiency cannot be predicted by the current electroporation models and also does not simply scales on macroscopic electrical parameters like magnitude of the electric field, current density or global energy delivered to the sample. Only microscopic parameters, electrical and mechanical, at the level of the membrane can fully describe the phenomenon. This is important for our understanding of cell membrane electroporation but has also some direct practical consequences for electroporation-based applications. Indeed, energy expenditure generated by electroporation treatment can sometimes be a hindrance to the development of certain applications. This is especially true for applications in the field of energy such as microalgae based biorefinary47In conclusion, we would like to emphasize that the effect of medium conductivity has been detected because in most of our experiments only one single electric pulse was delivered to the cells. The experiments performed with 100 μs pulses were initially performed using one single pulse in order to avoid the complex analysis of the influence of the number of the pulses as well as of their repetition rate49Chinese hamster lung cell line DC-3F [24] was grown in complete medium which consists in MEM-Minimum Essential Medium  with addition of 10% fetal bovine serum  and supplemented by antibiotics . The cells were maintained in a humidified atmosphere at 37˚C and 5% CO2 and routinely sub-cultured every two days. When they are placed in suspension, those cells have a spherical shape. The average diameter (mean ± standard deviation) was evaluated from bright light microscopy images in different extracellular medium . While t2  and osmolarities of the solutions were measured with a vapor pressure osmometer Vapro 5600 .The media containing bleomycin were prepared using 300 μM bleomycin stock solutions obtained by diluting lyophilized bleomycin in S-MEM or STM. Stock solutions were stored at −20 °C. Aliquots were taken just before the experiments and dissolved in the appropriate medium to obtain media with 30 nM bleomycin final concentration. The stock solution in S-MEM was used for all the media with a 1.5 S/m conductivity and the stock solution in STM for all the other media.6 cells/ml in the appropriate medium with or without bleomycin . Cells were immediately deposited between the two electrodes and exposed to the electric pulses. Unless otherwise specified, cells were kept for 10 min at room temperature after the delivery of the electric pulses. They were then diluted in complete medium. After dilution, cells were seeded in triplicate in complete culture medium  to measure their viability through a quantitative cloning efficacy test. After 5 days of culture at 37 °C in a humidified, 5%CO2 incubator, colonies were fixed and stained  and the number of clones N for each condition was counted. Viability was then normalized to the number of clones in the control Ncontrol and reported as a percentage of survival: N/Ncontrol.102. In experiments without bleomycin, the control condition refers to cells submitted to no treatment. In experiments with bleomycin, the control condition refers to cells, in contact with the bleomycin, that did not receive pulses. Viability of unpulsed controls was typically between 90% and 95 % after exposure to 30 nM bleomycin only.After trypsinization of exponentially growing cells and inactivation of trypsin  by the serum factors of the complete medium, cells were centrifuged for 10 min at 150 g and resuspended at a density of 4.2 × 101mm = 1.22 ± 0.02 mm for the 1 mm cuvettes and d4mm = 4.19 ± 0.02 mm for the 4 mm cuvettes. Those measured distances were the ones considered when the inter-electrode distance was needed to evaluate the field inside the cuvette. During experiments with 100 μs-pulses, the 1 mm cuvettes were used and filled with 60 μL of cell suspension.Cells were exposed in suspension in conventional electroporation cuvettes from Cell project . Depending on the experiment, 1 mm or 4 mm cuvettes were used. Precise measurements of the distance between the electrodes indicated that the distance between the electrodes was dDuring the experiments designed to test the influence of conductivity on the efficiency of nanosecond pulses, special care was taken to impose the exact same electric field in both the high and low conductivity medium. This can be difficult due to reflection phenomena that may occurPulses of 100 μs duration (micropulses) were delivered with a repetition rate of 1Hz by an electroporation power supply  able to apply high-voltage square-wave pulses. Voltage waveforms were controlled and recorded with an oscilloscope (LeCroy WaveMaster 808Zi) and a voltage probe (LeCroy PP007-WR).Pulses of 12 ns and 102 ns were delivered by a pulse-forming line generator, based on spark gap technology and designed by Europulse . Different interchanging cables were used to obtain the different pulse durations. Voltage measurements were performed using the D-dot sensor which has been described in detail in referencesHow to cite this article: Silve, A. et al. Impact of external medium conductivity on cell membrane electropermeabilization by microsecond and nanosecond electric pulses. Sci. Rep.6, 19957; doi: 10.1038/srep19957 (2016).


In this method, the parameters: the order of addition of precursors, the time of the reflux and the cooling rate should be optimized in order to obtain the desired phase and morphology of the nanostructures. The application of this method is discussed with reference to the synthesis of CZTS nanoparticles which have great potential as an absorber material in the photovoltaic devices. The highlights of this method are: There exist many methods to prepare nanostructured materials with various sizes and shapes. These methods can be broadly categorized into vacuum based and non-vacuum routes. The vacuum based methods include sputtering The aqueous based reflux method is a simple, low cost method that gives the desired product with precise control over reaction parameters. This method has been used to synthesize various nanostructured materials such as nanoparticles The order of the addition of precursors: In the case of reactions where multiple precursors are involved the order of reaction plays an important role. If the product is quaternary like CZTS then the chance of formation of secondary phases is very high. Therefore it is necessary to identify the various secondary phases that could form, find out the reactivity's and their formation energies. If one of the binary compounds is more stable than the others then such a reaction should be avoided. Thus the desired phase can be obtained by carefully choosing the order of the precursors.The time of the reflux: After the initial nucleation, grain growth takes place and simultaneously the phase formation also takes place. If the reaction is stopped early, then there will be incomplete phase formation. On the other hand the increase in the time of reaction leads to a larger grain size and hence bulk crystals will be obtained. Therefore the time of reflux should be optimized in order to obtain a pure phase nanostructure.The cooling rate: Many times this parameter is overlooked but it is an important factor. A reaction could be arrested by a rapid decrease in the temperature. At higher temperatures the kinetic energies of the molecules is high and the nucleation species are very mobile in the reaction system. As the reaction cools down, the mobility decreases and the product becomes stable. Slow cooling rate leads to defect free particles whereas rapid cooling of the solvated ions will end up in the formation of defective crystals.4 cm−1CZTS (Copper Zinc Tin Sulfide), a quaternary chalcogenide, is an upcoming material with applications in photovoltaics as an absorber. It has an optimum bandgap of about 1.5 eV, and a high absorption coefficient of the order 10In this article we report the use of reflux method for the synthesis of CZTS nanoparticles.The equilibrium equation of CZTS formation as reported in the literature The formation of the binary sulphides is favourable at higher temperatures whereas at lower temperatures the equilibrium shifts towards the right hand side. Therefore the recrystallization of CZTS depends on the cooling rate.At higher temperatures the Cu-rich phases are prone to form, leading to a greater number of defected particles. Tin sulphide is volatile and goes out of the system at temperatures above 450 °C Higher the temperature, more the defected particles and at temperatures above 550 °C, CZTS decomposes. Thus synthesis of CZTS at lower temperatures is preferable. Therefore, reflux method would be ideal as it can supply continuous energy for long time periods at a constant temperature.A typical reflux setup is shown in the schematic . The rea2, ZnCl2, SnCl2·2H2O and thio-urea. All the materials are pure and used without any further purification. Separate aqueous solutions of 1 molar Cupric Chloride, 0.5 molar zinc chloride, and 0.5 molar stannous chloride were prepared. Two molar aqueous solution of thio-urea is taken into the rbf and to it the tin chloride solution was added and stirred well till the solution turned clear. To it the Cu and Zn solutions were added simultaneously. The solution was refluxed for 8 h and was allowed to gradually cool to room temperature. Initially the solution was milky white and upon heating turned greyish-black. The products were filtered, washed with distilled water and ethanol several times. Then the obtained powder was dried under vacuum.The starting materials used are CuClThe reaction mechanism:In order to confirm the formation of CZTS and in turn validate the method, characterization of the material was carried out. Phase of the material is established by X-ray diffraction analysis and Raman spectroscopy. The bandgap of the material is determined from the UV–Vis absorption studies. The size and the morphology of the synthesized sample is seen from the scanning electron micrograph. The elemental composition is given by the EDX analysis.Phase Identification: Phase identification was done by using a Panalytical X-ray diffractometer with Cu Kα radiation λ = 1.5406 A°, step size = 2°/min. The XRD pattern of the as synthesized powder is shown in D is the average crystallite size (diameter), λ is the wavelength of the incident radiation, θ is the Bragg angle and β is the full width (in radians) of the peak at half the maximum intensity.From the XRD data the average crystallite size is calculated using the Scherrer Formula:The average crystallite size calculated from the above formula is 2.5 nm. Since the XRD patterns of CZTS and ZnS are similar, the formation of the phase needed further confirmation, which was achieved by the Raman spectroscopy.−1 and 339 cm−1 respectively, correspond to the CZTS phase For the Raman spectra, a Horiba iHR 550 Raman spectrophotometer illuminated with a 532 nm laser beam was used. The peaks at 307 cmαhν)2 is plotted as a function of incident photon energy; hν. The linear part of the curve is extrapolated and the intercept is the bandgap of the material. The optical band gap studies were performed with a Shimadzu UV 2450 uv–vis spectrophotometer. The absorbance spectrum was recorded and The electron micrographs were taken using a ZEISS scanning electron microscope fitted with an Energy dispersive X-ray detector. The elemental ratios as obtained from the EDX detector were presented in


Despite current technological advances, observing quantum mechanical effects outside of the nanoscopic realm is extremely challenging. For this reason, the observation of such effects on larger scale systems is currently one of the most attractive goals in quantum science. Many experimental protocols have been proposed for both the creation and observation of quantum states on macroscopic scales, in particular, in the field of optomechanics. The majority of these proposals, however, rely on performing measurements, making them probabilistic. In this work we develop a completely deterministic method of macroscopic quantum state creation. We study the prototypical optomechanical Membrane In The Middle model and show that by controlling the membrane’s opacity, and through careful choice of the optical cavity initial state, we can deterministically create and grow the spatial extent of the membrane’s position into a large cat state. It is found that by using a Bose-Einstein condensate as a membrane high fidelity cat states with spatial separations of up to ∼300 nm can be achieved. Observation of quantum mechanical effects on large scale systems has been intensively pursued since the development of quantum mechanics. This is because such observations would demonstrate the existence of quantum mechanical states which reside at the borders of the classical and quantum worlds. The creation of such ‘macroscopic’ quantum states has been a long sought after goal in quantum mechanics allowing not only for the direct study of quantum state collapse models23456pure cat, where the spatial superposition is completely disentangle from other degrees of freedom.Many approaches have been made to observe quantum mechanical effects on larger scales. In particular, extensive efforts have been direct towards up-scaling the well-known two-slit experiment in hope to observe wave like behaviour of objects much larger than electrons. To date, wave like behaviour has been reported with the use of particles ranging from single atoms all the way to organic molecules containing several hundreds of atoms8914 atoms, which acts as a mechanical oscillator. This setup can achieve spatial separations on the order of a few femtometres with demanding experimental conditionsWith the intention of creating macroscopic quantum states many researchers have directed their attention towards the field of optomechanics. Some of the more common optomechanical systems which are studied involve cavities that are comprised from two mirrors, one fixed and one moveable. The radiation pressure force due to the light confined within the cavity causes the second mirror to move, acting as a mechanical harmonic oscillator. Other types of optomechanical systems consider placing mechanical oscillators within Fabry-Pérot type optical cavities. Such systems have inherited the name “Membrane in the Middle” where the mechanical oscillator is referred to as the membrane17181202122232425There is one, yet to be mentioned, limiting factor which hinders almost all of the current cat state creation schemes: they all involve measurement and thus are probabilistic. This is a severe drawback as the overall probability for success of the protocol exponentially decreases with the size of the cat state desiredOur goal is to discover a deterministic protocol for the creation of a cat state of a mechanical object’s position. As mentioned above one approach which has been previously studied involves the introduction of mechanical oscillators into Fabry-Pérot type cavities (MITM). Here a similar approach will be used but now we also consider controlling the mechanical oscillator’s opacity. We first describe the MITM model and the light-matter interactions. Next, the effects of controlling the opacity of the membrane will be studied where two extreme cases will be considered. These cases correspond to either a reflective or a highly transmissive membrane. Finally, it will be shown that by alternating between these two opacity states the spatial displacement of the membrane can be driven.The Membrane in the Middle model describes an optomechanical system which is comprised from two degenerate modes of a cavity which interact with a physical membrane that is confined within the cavity, shown in where J is the transmission rate of the membrane. Finally, we include the interaction term describing the photon pressure force of the cavity mode photons acting on the membrane. This interaction requires that the wavelength of the optical modes satisfies l/h represent the membrane’s length/height. The photon pressure force can be expressed as L is the length of the individual cavities. The optomechanical interaction term is then expressed as,where where where the difference operator J(t), can be studied. Two extreme cases of J can be considered. The first corresponds to a reflective membrane, in particular when With the theory behind the MITM model established the effects of controlling the transmission rate, βM and the left/right cavity modes in coherent states αL/αR, the expectation value of the membrane’s position evolves as,This Hamiltonian describes a driven harmonic oscillator where the driving strength is directly proportional to not only the optomechanical coupling rate but also to the difference in the photon numbers between the optical modes. In the case where x direction. Alternatively, if the system is initialised in the state where J will now be considered. That is, the case of an almost completely transparent membrane. In this case, as In order to drive the displacement of the membrane a method of interchanging the state of the left/right cavities must next be established. As this typically requires the flow of photons through the membrane, the second limiting case of By again working in the Heisenberg picture the cavity mode operators can be evolved to give,which shows that at times satisfying We plot the dynamics of the membrane under evolution of NF times, whenever NF. Ignoring dissipative effects, the unitary evolution can be expressed by,Now that a method of interchanging, or “flipping”, the state of the two cavity modes has been established the membrane’s displacement can be driven in the manner shown in n, m. Ideally we require m = n = 0 to reduce the evolution time and hence the effects of decoherence. Numerical simulations of this evolution will be performed in later sections where the effects of decoherence will be considered . This evolution will be the basis for both the creation and ‘growth’ of a cat state.where While a possible mechanism for ‘growing’ the spatial extent of the mechanical cat state has been proposed, the cat state must first be created. One of the most common approaches to creating cat states is to first establish entanglement in the system. Once an entangled state is created there are many protocols which can be used to reduce the entangled state into a cat state. However, the majority of these protocols require that measurements are made on the system, projecting it into the cat state. This means that each of these protocols are probabilistic. In this section a similar approach to cat state creation will be made. We will first focus on establishing entanglement between the membrane’s position and the two cavity modes. This entanglement will be produced by preparing the system in specific initial states then evolving it in the manner discussed above. Several possible initial states will be considered with the intention of maximising the extent of the spatial displacement of the membrane’s position. The second half of this section will focus on disentangling the membrane from the two cavity modes to produce the desired cat state. Here, several possible disentanglement protocols which do not rely on measurement will be discussed with the use of the MITM model alone. Finally, an ensemble of atoms will be introduced into the MITM system to show that a completely deterministic and experimentally feasible disentanglement protocol is possible.N photons while the right is empty and the right cavity containing N photons while the left is empty. The initial state can be expressed as,As mentioned above, a common approach to cat state creation is to first establish entanglement. This means that a set of initial conditions must be determined which, when evolved under Eq. By evolving this state through the use of Eq. C is a normalisation constant and βM represents the coherent state amplitude of the membrane which depends on the number of ‘flips’ which have been applied as well as the number of photons in the NOON state, N. Typically NOON states are experimentally difficult to create for N > 2. From Eq. N is required to achieve large spatial displacements of the membrane. This means that, unless an ultra-small membrane is considered, an alternative set of experimentally feasible initial conditions is required.where There are two possible alternatives to initialising the cavities in a NOON state. These include (A) the coherent state analogue of the NOON state, referred to as an entangled coherent state (EC) and (B) the entangled squeezed-coherent state (ESC)29NCSS is a normalisation constant and is generated, where for arbitrary input modes For possibility (B): Entangled squeezed coherent states can also be generated using the proposed setup, 32where the squeezed state is defined as N NOON states where there is essentially no limit on the size of N. The largest ESC states which have been created correspond to high NOON states with N ≤ 9 The appeal of ESC states is that they strongly resemble high As discussed in the previous section, to produce the desired cat state entanglement must first be established between the membrane’s position and the cavity modes. This entanglement can be achieved by initialising the system in the state Eq. Disentangling is typically is a very difficult task. It is sometimes possible to find a unitary operation that will deterministically disentangle systems but such operations require the application of conditional quantum gates and these are typically extremely hard to implement physically. Rather than attempt unitary disentanglement many protocols implement probabilistic measurement based methods for disentanglement. In what follows we initially explore a naive approach to disentangle the photonic and motional systems by letting the photons escape from the optical cavities. This method fails for the reasons we outline below. We then discuss a unitary operation which achieves deterministic disentanglement by allowing the membrane’s reflectivity to change depending on the membrane’s displacement. Although formally this approach works there are currently no experiments capable of controlling transparency over pico-nano meter scales. Guided by this we note that methods to unitarily disentangle discrete (e.g. spin), systems are physically more tractable and we suggest introducing a cold atomic gas comprised of three level atomic systems and describe a protocol which converts the membrane-optical mode entanglement into membrane-atomic excitation entanglement. Once in the latter form we are then able to more easily perform the necessary conditional operations on the atomic-membrane system to unitarily disentangle them. The resulting protocol is complex but shows that deterministic unitary disentanglement is possible.As mentioned above, a naive approach to disentangle the state Eq. A second approach is a completely unitary, deterministic, method to disentangle the membrane’s position from the cavity photons. To achieve this we must posit the ability to conditionally flip the state of the cavity modes, depending on the membrane’s position. That is, performing the transformation,which can be achieved by the unitary operation,J, which is extremely experimentally challenging for pico to nano-metre displacements of the membrane. If such control over the membrane’s transmission rate were possible our disentanglement discussion would end here.where M > N three-level atomic atoms . We achieve this transfer via tagging the photons in the two optical cavities in the MITM system via separate polarizations and using this polarization degree of freedom to excite polarization dependent transitions in the atomic ensemble. Once encoded into the atomic ensemble we describe a relatively simple method to perform the disentanglement we seek by manipulating the internal states of the atomic ensemble. The entanglement transfer can be achieved if the light in the left/right cavities is left/right hand (σL/σR) circularly polarised. By quickly introducing an ensemble of M 3-level atoms into the system the photons in the left/right cavity modes are separately absorbed into the ms = ±1 excited states of the atoms. This process simultaneously removes the photons from both cavities while encoding the state of each cavity into the internal excited states of the ensemble of atoms, see σL/σR polarised photons can be considered. In this case the interaction is described by the Hamiltonian,As the two disentanglement methods discussed above either fail or are currently infeasible an alternative disentanglement protocol for Eq. gL/gR. If the interaction strengths are identical this Hamiltonian can be easily extended to account for M atoms. By incorporating M atoms into the entangled state, Eq. M-atom extension of Eq. t3, ensuring all photons are absorbed, the entanglement is essentially transferred from the two cavity modes to the M atoms,where the detuning has been set to zero and ith permutation of the N ms = ±1 magnetic states over the M atoms and the subscripts e,g the optical state, see where π pulse of linearly polarised light to the atoms. As linearly polarised light is comprised of both left and right hand circularly polarised light, application of a π pulse will simultaneously send the N ms = ±1 state atoms to the ground state. The remaining M − N atoms will be excited into the ms = 0 optically excited state. After application of this pulse Eq. This evolution requires ith permutation of the M − N ms = 0 optically excited magnetic states over the M atoms.which is a pure cat state of the membrane’s position. In this case M atoms into the system. This section will focus on illustrating the cat state creation protocol with a schematic of an optically based experiment capable of both achieving the same effective optical dynamics as modulating the transmission rate of the membrane and the introduction of an ensemble of atoms.In the previous sections it was shown that, in theory, a cat state of the membrane’s position can be deterministically created by controlling the membrane’s transmission rate and selectively introducing The first task in our cat growth protocol we address is to alter the membrane’s transparency with time. When the membrane is transparent the optical fields in the two MITM cavities interchange (flip) and this flipping is an essential component in our protocol. Controling the membrane transparency in time is experimentally challenging and so we propose an alternative method to interchange the optical fields between the two Fabry-Pérot (FP) optical cavities in the MITM setup. We will show that one can effectively rapidly switch between two setups: (A) the membrane located in a Fabry-Pérot cavity , and (B) the membrane located in a ring cavity that envelops the Fabry-Pérot arrangement in (A) . By switching the setup into (B) for a short duration and then back to (A) we can effectively provide an optical route to interchange the optical fields in setup (A) without having to control the membrane’s transparency.The second task, that of quickly inserting an atomic ensemble and allowing interaction between the ensemble and photons from both FP cavities in setup (A), is again achieved through switching the setup into a ring cavity which now contains the atomic ensemble.A and B in C and D in M atoms as well as the membrane. Provided that the atoms are each prepared in the optical ground state, Δms = ±1 transitions will be excited as the light of each mode is left/right hand polarised by two separate quarter wave plates, entangling the membrane with the atomic states.Both of the above tasks are implemented via polarization control of the optical paths taken by the photons which we now describe in more detail. The schematic experiment achieves the first task, interchanging the optical consists of a multi-cavity system where each cavity is distinguished by the polarisation of the light in the system, shown in M ground state atoms the experiment starts with an evolution in the highly reflective regime for time t1. This evolution corresponds to driving the membrane to the maximal possible displacement in the initial potential well. We predict the time at which this maximal displacement will occur. Then, at this predicted time, we switch the system into the effective transparent membrane setup to begin the dynamics that will interchange the optical fields in the cavities. At no instant are we allowed to perform any measurement of the membrane’s position or cavity field as such a measurement will cause a collapse of the cat state superposition we wish to achieve. To switch the system into the transparent membrane regime the EOPs A and B in To create a cat state with the suggested experiment a specific operational protocol must be followed. Once the system has been initialised in the state Eq. t2 will flip the state of the cavity modes, which corresponds to displacing the harmonic potential. As it was shown that after time t2 the occupation of the cavity modes will be completely interchanged, see Eq. t1, the membrane’s maximal displacement will increase in accordance with Eq. M atoms can be introduced into the system. Evolving this combined system for time t3 will transfer the entanglement between the membrane and the cavity modes to the atoms, as shown in Eq. π pulse to the atomic ensemble, a cat state of the membrane’s position can be produced.Evolution in this regime for time π pulse to the ensemble of 3-level atoms to disentangle the system is quite difficult experimentally. This difficulty stems from the short lifetimes of the optically excited states, in turn, making the disentanglement process experimentally challenging. However, the optically excited states of the 3-level atoms can be bypassed through the use of a Raman transition. To do so, we must consider atoms with triplet optical ground and excited states. Such atoms can be directly excited into the ms = ±1 levels of the optical ground state by detuning the left/right optical cavity modes from the atomic transition and introducing a similarly detuned coherent field, depicted in π pulse to the atomic ensemble. Bypassing the optically excited state requires that both the left/right optical cavity modes and the classical field are off resonance with the atomic transition such that the detuning, ΔD, satisfies g± denotes the coupling strength to the ms = ±1 transitions, shown in As optical transitions are considered in the schematic experiment, application of a the effective Hamiltonian can be expressed asIn the case of a single 3-level atom and a single, left hand circularly polarised optical mode, shown in the left half of An identical Hamiltonian can also be written to describe a right hand circularly polarised optical mode, corresponding to the ms = ±1 levels of the optical excited state and ms = ±1 levels of the optical ground state, shown in M atoms. The discussed Raman transition optically encodes the cavity information into the optical ground triplet states of the atoms. The atomic ensemble can then be disentangled from the membrane’s position by application of a microwave π pulse.with 5 Rubidium-87 atoms will be used due to its small mass and its compatibility with the MITM modelBoth the theory and a possible experimental realisation of the cat state creation protocol have now been described. Simulations of the proposed protocol can now be performed to determine the quality and size of the resulting cat states. In this section numerical simulations of the membrane’s dynamics with the consideration of dissipative effects will first be performed to show that large displacements of the membrane can be achieved. Throughout the simulations a BEC consisting of ~10The dynamics of the system can be simulated by solving the full master equation,κc and γM denote the cavity and mechanical damping rates respectively. Before continuing, it will be assumed that the mechanical damping rate, γM, is negligible with respect to the optical damping rate during the time scales that will be considered, −8), of the integrator in QOT. A more important source of numerical error arises from truncating the Hilbert spaces of the cavities and membranes. Analytically each of these are infinite dimensional but in the numerical simulation we truncate the individual cavity Hilbert spaces to n ≤ 4, while the membrane’s Hilbert space is truncated to n ≤ Ntrunc. The cavity Hilbert space truncation is found to be adequate while in Ntrunc large enough to avoid significant population in this element during our simulation and we set Ntrunc = 40. By solving Eq. N. A linear increase in the maximal displacement with N, predicted by Eq. m = 17.3 agwhere the time dependence in the Hamiltonian describes the alternation between the two different opacity regimes, Eq. N = 2. Of course, evolving this initial state results in x and −x directions. Two approaches will be made to observe the cat state produced. The first involves the calculation of the Wigner function to observe the ‘quantumness’ (negative regions of the Wigner function) of the final state while the second involves calculating the fidelity between the cat state produced and a corresponding ideal cat state. Beforehand, however, a simplification can be made to the disentanglement process to increase the efficiency of the simulations. As the time scales of the disentanglement procedure are required to be significantly shorter than that of the standard evolution which drives the membrane’s displacement, M identical atoms and two modes of light. A cat state of the membrane’s position can then be produced by application of the disentanglement unitary after the entire evolution has been made,In order to create a cat state of the membrane’s position the cavity must be initialised in a NOON state, Eq. M atoms are in the optical ground state. The resulting Wigner function of the membrane’s state after application of 5 atom BEC. This is more than double the displacement achieved in the entangled state analogue where only a single ion was usedwhere βM(t), corresponds to the membrane’s state when evolving F > 80%, the ratio between the mechanical trap frequency of the BEC and the cavity loss rate must be increased by a factor of 20 where the cat state survives all three cavity state flips.The coherent amplitude, lts show  that witIn this work a quantum system designed for the deterministic creation of macroscopic quantum states is proposed. The system consists of a BEC type membrane which is placed inside a Fabry-Pérot type optical cavity. It is shown that by controlling the opacity of the BEC its displacement from the origin can be driven at a rate proportional to the number of photons in the system. This result was then used to produce and essentially grow the spatial extent of a cat state of the BEC’s position. This required the initialisation of the two cavities in a NOON like optical state, which was shown generates entanglement between the membrane’s position and the cavity modes after the system is evolved. To reduce this entangled state to a cat state a deterministic disentanglement procedure was proposed which involved the transfer of the entanglement to an ensemble of atoms. The cat state creation protocol was then illustrated using a schematic of an experimental platform which was capable of both effectively flipping the cavity optical states and applying the deterministic disentanglement procedure.Finally, several simulations were performed showing that large spatial displacements of the BEC could be achieved using only a small number of photons in the system. Simulations of cat state creation were also performed which showed that relatively high fidelity cat states could be produced if either slightly larger mechanical frequencies or slight smaller cavity loss rates than those achieved in previous experiments could be reached. Overall the proposed cat state creation protocol provided an experimentally feasible method of deterministically creating cat states significantly larger than the majority of previous proposals. Creation of such states are essential to further the understanding of quantum decoherence and have many potential applications in a wide range of quantum technologies.How to cite this article: Lombardo, D. and Twamley, J. Deterministic Creation of Macroscopic Cat States. Sci. Rep.5, 13884; doi: 10.1038/srep13884 (2015).


In addition, time resolved electron densities are presented. There is agreement between time resolved measurements in the two reactors, in particular, the electron density in helium discharges is found to rise dramatically after the rf excitation is turned off while the electron densities in argon and nitrogen glows exhibit only slight increases.Electron density measurements with even the simplest microwave interferometry techniques can range over three to four orders of magnitude, can be responsive on time scales as fast as 50 ns, and are simple to obtain and interpret. Three groups have published electron density data taken in the Gaseous Electronics Conference (GEC) reference reactor using microwave interferometry. The agreement in the data from these groups at higher pressures is excellent especially when one considers that the GEC reactors involved have some key differences. These may have been the cause of some differences between the results obtained at low pressures, although, the manner in which the measurements were interpreted may also have contributed. The electron densities compare favorably in argon, helium, and nitrogen above 33.3 Pa (250 mTorr); but, the measurements tend to diverge some at 13.3 Pa (100 mTorr) and in 133 Pa helium above approximately 200 mA. It is speculated that the latter difference occurs as the discharges change from a bulk ionization or  A measurement of the microwave field transmission through a plasma contained in a GEC reactor can provide quick and accurate information on the spatially averaged electron concentration. This measurement can be performed using a microwave interferometer; a device which can be simple to build and operate and from which easily interpreted results may be obtained. Microwave interferometer measurements are much quicker (as fast as 20 MHz –4) and lThe purpose of this article is to review the microwave interferometry data obtained from the GEC reactor to date –6, incluMicrowave interferometers . These equations assume that there is no static magnetic field as is the case for the GEC reactor. In the event of a static magnetic field, the permittivity and conductivity become tensors and the reader is referred to one of several more comprehensive texts [The presence of free electrons lowers the dielectric permittivity and increases the conductivity of space as follows from the Langevin equation and Ampere’s Law.ve texts ,7,11. Thαp is the attenuation constant and βp is the propagation phase constant of the microwave field in the plasma. μ0 is the permeability of free space since the plasma does not greatly change this. The phase constant contains information on the plasma density and can be most easily related to the electron concentration when both the collision frequency for momentum transfer and the plasma frequency are much less than the microwave frequency. In this case, the plasma conductivity is insignificant compared to ωεp and the phase constant becomesλ0 is the free space wavelength of the microwave field.The propagation constant of a wave in a large uniform plasma (transverse dimensions ≥5× the microwave wavelength in the plasma) is derived from the permittivity and conductivity as:E and H with subscripts denoting plasma (p) and free space (0) conditions. The asterisks denote complex conjugates and the integration surface, S, is perpendicular to the beam propagation (assumed to be in the z direction). The length of the plasma is denoted as lp. Because the plasma density in the GEC reactor can vary significantly over the one inch span between the electrodes; the average microwave propagation constant is determined from a more general formula .γp+γ0*=mated by Δϕ≈∫0lp−εo is a nonzero constant only at the position of the probe. The resulting map of the induced phase shift as a function of the probe position is a direct map of the electric field intensity squared.y direction goes from one electrode to the other and the x direction is also perpendicular to the direction of travel of the beam. The value used for x0 was 5 cm and the value used for y0 was 2.54 cm. In the x direction, a Gaussian shape was chosen in order to approximate the beam-like nature of the microwave field after the focusing lens. In the y direction, a cosine shape was chosen because of the wave guiding nature of the electrodes above and below. The electric field polarization was nominally perpendicular to the electrode surfaces, however, the cosine dependence was chosen because our measurements indicated it. The electric field approximation also assumes that the beam profile does not depend strongly upon the position along the direction of travel (the z axis). The beam does have some dependence along the z axis, however, this dependence is small. At most it introduces a 20 % programmatic error.Contour plots of this phase shift were published for The University of Texas at Dallas (UTD) microwave interferometer at 8.6 GHz . In bothre is the radius of the electrodes, the reactor wall is at 12.5 cm and r = 0 is on the reactor axis. The value for L was set to 3 cm [ne0 between the electrodes of the cell of 1.3×109 electrons cm−3 per degree of phase shift. We estimate that this number is accurate to within ±30 % based upon an estimated ±20 % error in measuring and approximating the electric field intensity and a 10 % error in approximating the electron spatial distribution. The precision and repeatability of the results is much better, approximately the greater of ± 0.2° or 3 %. It should be noted that the expansion of the electrode sheaths with decreasing pressure is not accounted for in this calibration. This correction could be important for very low pressure discharges, particularly in helium where the sheath thicknesses can be large; but, is generally less than 10 % for the sheath thicknesses encountered in other gases.Once the electric field intensity is known as a function of position,  to 3 cm . The proMost of the electron density data have been obtained using the Mach-Zehnder configuration and the simplest detection techniques as shown in E and H plane arms of a matched hybrid tee on the UTD interferometer; while the Sandia group used a 90° phase shift [Φ° phase shift in Φ, the fields no longer cancel and the field at the diode detector becomes Ediode= 2Erefsin(ΔΦ/2).  The voltage on the diode detector is just the square of Ediode for a square law detector so that Vdiode becomes proportional to sin2(ΔΦ/2). Since sin(ΔΦ/2) is approximately equal to ΔΦ/2 at small phase angles, the diode signal rises as (ΔΦ)2 and the sensitivity of the instrument is very low.Both the Sandia  and UTD se shift  after thΦ if one offsets by 90° from the null field condition because sin2((ΔΦ + 90°)/2) is equal to 1/2(1−sin(ΔΦ)). The signal is now proportional to ΔΦ, but, rides on a significant dc offset voltage. This is the offset condition used by the Sandia group [E and H plane arms of the hybrid tee is then measured using a differential amplifier. The phase shift induced by the plasma causes the plasma arm fields to rotate in the phasor diagram and results in a decrease in EH-diode and an increase in EE-diode in The change in the diode voltage becomes approximately proportional to Δia group  and it i2 and CF4 plasmas are all plotted as a function of the discharge current at the fundamental rather than the voltage for two reasons. First, the peculiarities of the UTD cell did not allow both voltage magnitude and phase angle between current and voltage to be in agreement with the standard cells at the same time [J = nev applying to the body of the glow and implying that the electron density and current should have a simple relationship. This is born out somewhat in The electron densities in Ar , He, N2 ame time . It was The electron density results at different pressures and from different laboratories have been plotted for comparison in The reasons for the differences at 13.3 Pa are not nearly as clear as one could wish because there are too many possible explanations. Arguably the best explanation is that the electron densities are just not equal in these reactors at a given current because of the physical and electrical differences between them. While both the SNL and WPAFB cells have aluminum electrodes, the UTD cell has steel electrodes with the shower-head electrode powered and a pinhole welded into the grounded electrode. These differences are substantial enough to cause a 30 % reduction in the discharge current for a given electrode voltage . It may I–V curves between these cells are significantly different.) Accounting for the fraction of the plasma volume taken up by sheaths will even increase the agreement between these results. Interestingly, the plots at other pressures are not affected nearly as much so the results agree closely there as well. There are two possible reasons why the plasma current may not be the best independent variable. First, the plasma current must be calculated by accounting for the equivalent circuit between the I-V probes and the electrode surface. This is made easier using the shunt circuit [I–V curves.A final possibility is that current is not a good independent variable. This is illustrated in  circuit , but stiNe = 7.1×1010I4/3.) The similarity in the electron concentrations as a function of the rf current is surprising since the electron-neutral collision frequency in helium and argon have significantly different energy dependencies as well as magnitudes [The electron densities of helium discharges are plotted in gnitudes , the elegnitudes  and the gnitudes . These dgnitudes , 21. Thegnitudes .α-mode to the γ-mode of the discharge [γ-mode discharge is sustained by an electron avalanche in the powered electrode sheath in much the same manner as the cathode glow is sustained in a dc discharge. The electron avalanche occurs when the sheath voltage is large enough to produce significant levels of secondary electron emission from the electrode as well as electron ionization in the sheath and glow edge. The secondary electron emission coefficient of energetic helium ions is generally larger than that of argon ions [γ-mode at lower currents and voltages than the UTD reactor and consequently to have a larger electron concentration above the transition point. It could also explain why the argon discharges do not exhibit the same kind of abrupt increase; since, the secondary electron yield is expected to be smaller for argon ions in addition to the already smaller rf voltages typical of those discharges.The electron densities in helium exhibit significant differences at low pressures again, even though there is substantial agreement at higher pressures. The differences between the electron densities of the WPAFB and UTD reactors are minimized when the electron density is plotted as a function of the electrode voltage rather than the plasma current again. See . The eleischarge ,20,22. Ggon ions  and shouI–V characteristics of these cells; however, the close agreement of these results versus the rf voltage may also just be fortuitous. The LIF results have been interpreted using the excitation coefficients of Sobelman and coauthors [The Laser Induced Fluorescence (LIF) measurements of the electron density  sit belooauthors . These eoauthors . Using G4 discharges at 13.3 Pa and 40 Pa in the UTD reactor are plotted in 8 cm−3). 0.1° is the smallest phase shift which can be resolved on the UTD phase changer without using any enhanced detection techniques. Unfortunately, the electron densities of nitrogen discharges below 60 mA can be significantly smaller than 1.3×108 cm−3. As a consequence, we did not measure the electron concentrations there, and, the data points at those currents only indicate an upper limit for the electron density.The electron densities of nitrogen and CF4 indicate an electron concentration which decreased with increased pressure. An increased electron attachment rate with increased pressure is the most likely reason in the case of CF4, but, the reason for this phenomenon in the case of nitrogen is not as clear. It may be caused by a transition from a “sheath oscillation” electron heating mechanism toward an ohmic heating mechanism in the bulk of the discharge as noted by Turner for nitrogen [4 electron densities are nonlinear on the log-log scale most likely because the composition of the plasma changes with increasing current (and voltage and power.)While the UTD reactor data for the noble gases indicated an electron density which increased slightly with increased pressure or had little pressure dependence; the data in both nitrogen and CFnitrogen  and Godynitrogen . FinallyThe time dependent electron densities of pulsed discharges through argon, helium and nitrogen are plotted in 3S and 2 1S metastable electronic states. These excited state atoms can produce ionization through metastable-metastable collisions as well as superelastic electron collisions followed by electron impact ionization of a metastable state atom.The electron densities in helium discharges reach steady state within approximately 0.5 ms to 1 ms. The electron concentration increases significantly immediately after the rf excitation is turned off as was first described by Greenberg and Hebner for the GEC reactor  and by BThe electron concentration in nitrogen rises quickly to steady state at the low current, but, does not reach a good steady state within 5 ms for the discharge at 0.27 A. The electron concentration increases a small amount after the rf excitation is extinguished before decreasing in the afterglow. While the electron density decay in nitrogen is faster than in either argon or helium, it is not exponential in time. The increased loss rate for electrons in nitrogen compared to argon and helium indicates an additional loss mechanism. The most likely mechanism is electron ion gas phase recombination. This is an inefficient mechanism in low pressure atomic gases, but, can be significantly more efficient in molecular gases where energy and momentum can be more easily conserved.γ—mode at lower voltages and currents than do discharges formed between stainless steel electrodes.The electron densities of discharges through argon measured by microwave interferometry in different GEC reactors show substantial agreement at pressures above 13.3 Pa. At 13.3 Pa, there were some substantial differences in the measurements which may have been caused by differences in the reactors or the interferometers themselves. It is not clear whether one or the other or even both may be most important. The electron densities of discharges through helium show substantial agreement at low currents; but, are dissimilar at large currents. The reason for the discrepancy at large currents is postulated to be the mechanism by which the discharge is sustained. It appears that glow discharges formed using aluminum electrodes transition into


A unidirectional anisotropy appears in field cooled samples of dilute magnetic alloys at temperatures well below the cusp temperature of the zero field cooled magnetization curve. Magnetization measurements on a Cu(13.5 at% Mn) sample show that this anisotropy is essentially temperature independent and acts on a temperature dependent excess magnetization, ΔM. The anisotropy can be partially or fully transferred from being locked to the direction of the cooling field at lower fields to becoming locked to the direction of ΔM at larger fields, thus instead appearing as a uniaxial anisotropy. This introduces a deceiving division of the anisotropy into a superposition of a unidirectional and a uniaxial part. This two faced nature of the anisotropy has been empirically scrutinized and concluded to originate from one and the same exchange mechanism: the Dzyaloshinsky-Moriya interaction. Hsw2, on the other hand, starts out from a value rather close to Hsw1 and continuously increases with increasing HFC to asymptotically approach the value -Hsw1 at very high fields. The three parameters are weakly dependent on repeated hysteresis measurements (training) as long as the maximum field of the loops does not exceed the initial cooling field. However, if the maximum field, Hmax of the hysteresis measurement is increased, Hsw2 shifts to the same value as observed after field cooling in Hmax, whereas ΔM and Hsw1 remain essentially unaffected by the field increase. Using the product of ΔM and Hsw1 one can derive a measure of the anisotropy energy related to the switching of the excess magnetization ΔM. This anisotropy, EudT ∝ ΔMHsw1, is independent of the magnitude of the cooling field. Looking at the field dependence of Hsw2, one observes that at low cooling fields, the anisotropy of the sample is near unidirectional (Hsw1 ~ Hsw2), and that with increasing cooling field it attains the mentioned mixed unidirectional/uniaxial charactereb = (Hsw1 +Hsw2)/2) hysteresis loops.et al.et al.20sw1. This field remains independent of the strength of the cooling field. However, on field reversal, the switching field Hsw2 is dependent on the cooling field. This behavior requires that polarity of the chirality of parts of the local spin structure switches with the excess magnetization instead of only being confined to the original cooling field direction and that the fraction of spin chirality following the switching of the excess moment is set by the magnitude of the cooling field. Using this two-faced picture of the local spin structure (locked to the cooling field direction at low fields and locked to the switching excess magnetization at high fields), only the DMI is required to explain the observed behavior and tuning of the exchange bias. At constant low temperature, the only way to change the partition between these two fractions is to apply a higher maximum field than the employed cooling field. The magnitudes of the two fractions of the DMI can be experimentally derived using the postulation that: EudT = EudS +EudM, where EudS denotes the part of the anisotropy that remains locked to the direction of the cooling field and EudM the part of the anisotropy that is locked to the direction of the excess moment. The two parts are then be derived from the experimental parameters through:The field controlled two-faced character of the anisotropy: unidirectional and uniaxial, may be explained by the exchange mechanism giving rise to anisotropy in a Heisenberg spin system: the Dzyaloshinsky-Moriya interaction (DMI)3FC to −HFC. From these curves the detailed behavior of the field dependence of the characterizing parameters, including the low field region between 0 and 1 T where ΔM remains unsaturated, is derived. In sw1 and Hsw2 are plotted versus the cooling field strength and in 0ΔMHsw1 (EudT) and μ0ΔMHsw2 versus cooling field in udS and EudM in udT also appears temperature independent. Noteworthy is also that a larger and larger part of the anisotropy becomes locked to the excess magnetization with increasing temperature. At higher temperatures than 25 K, the collective excess moment ΔM has already relaxed to zero on the time scale of these hysteresis experiments.The temperature dependence of the hysteresis loops measured after field cooling in 1 T are shown in udT) along the direction of the applied field. The only way to alter this structure and the associated anisotropy at constant temperature is to apply a larger field (Hmax) than the original cooling field. The effect of Hmax is then to imprint a compensating unidirectional anisotropy that switches direction with ΔM and yields an anisotropy field that is controlled by Hmax. It is in this context important that in a zero field cooled sample a large field is required to establish any anisotropy and excess magnetization and that the full strength of the anisotropy is only achieved at field larger than the field where the thermoremnant magnetization (TRM) and isothermal remnant magnetization (IRM) coalesceet al.2PtGa Heusler alloy. This exchange bias is assigned to induced exchange coupling between ferromagnetic clusters dispersed in a ferrimagnetic matrix when the sample is first magnetized at low temperature. Thus, a very different mechanism from the one discussed here for Heisenberg spin glasses.Our results imply that a rigid spin structure defining the anisotropy is imprinted in the spin glass on cooling to low temperatures and that only a weak field is required to establish the full strength of the unidirectional anisotropy  of height 5 mm and diameter 2 mm with a spin glass temperature of 57 KHow to cite this article: Hudl, M. et al. Tunable exchange bias in dilute magnetic alloys – chiral spin glasses. Sci. Rep.6, 19964; doi: 10.1038/srep19964 (2016).


Feasibility of using pressurized hydraulic fluid as a source of on-demand assistive power for hybrid neuroprosthesis combining exoskeleton with functional neuromuscular stimulation was explored. Hydraulic systems were selected as an alternative to electric motors for their high torque/mass ratio and ability to be located proximally on the exoskeleton and distribute power distally to assist in moving the joints. The power assist system (PAS) was designed and constructed using off-the-shelf components to test the feasibility of using high pressure fluid from an accumulator to provide assistive torque to an exoskeletal hip joint. The PAS was able to provide 21 Nm of assistive torque at an input pressure of 3171 kPa with a response time of 93 ms resulting in 32° of hip flexion in an able-bodied test. The torque output was independent of initial position of the joint and was linearly related to pressure. Thus, accumulator pressure can be specified to provide assistive torque as needed in exoskeletal devices for walking or stair climbing beyond those possible either volitionally or with electrical stimulation alone.  Restoring walking is one of the main desires of individuals who have a spinal cord injury (SCI) . Thus, tRecently, there has been a surge in powered exoskeleton development, including commercial devices such as Rewalk and Ekso , 13. ExoTherefore, there has been an increased effort in hybrid system development that combines either surface  or implaIn this study, feasibility of a power assist system (PAS) using a hydraulic circuit with pressurized fluid to provide assistive torque for joint movement was designed and tested. We hypothesized that this PAS could be a viable alternative in providing assistive torque for joint movements.As a test bed for bench testing, the PAS  was incoWhile the PAS system can be applied to any hydraulic circuit, its operation in this design configuration  is as foOnce the power assist torque is no longer required, the DCV is deenergized shifting the valve left to the closed center position, and the system returns to its default state. To recharge PA to prepare for the next cycle, the pump is activated to transfer fluid from the tank accumulator (TA) to PA. This pressurizes PA to its initial condition (measured by the pump side pressure transducer) and at the same time reduces the pressure of TA below its original system resting pressure. The fluid volume pumped from TA to PA is equal to that displaced from PA to the blind side of the RHC during the hip flexion assist. Next, the DCV is shifted in the opposite direction and valves H1 and P1 are opened to channel the flow into TA from HA. Since TA is below the system resting pressure and the rest of the circuit is above, the excess fluid from the previous PAS injection period stored in HA will then flow back into TA bringing the entire system to its initial condition and ready for the next cycle when needed.VPA) of the hydropneumatic accumulator, PA, derived from Boyle's law, can be expressed as in , τend is the output torque at the end of the hip motion (25 Nm), prest is the system resting pressure (414 kPa), and pic is the initial pressure of PA and corresponds to the operating pressure rating of the pump. Thus, the objective is to minimize pic so that the power requirements of the pump are minimized. Equation  for PA, pic would need to be approximately 3213 kPa. In this case, when the DCV and P1 are opened to connect PA to the cylinder at 0° hip flexion, 3213 kPa of fluid pressure at the cylinder produces 35 Nm of hip flexion torque by means of the linear-to-rotary transmission. The pressure drops to 2413 kPa at 60° hip flexion to produce 25 Nm.To specify individual components of the PAS, biomechanical requirements of stair ascent in normal individuals were examined while considering the limitations of weakened muscles. A minimum of 60° hip flexion angle is necessary for a person of an average stature to clear a standard stair step riser height of 20 cm . Approxied as in  (note thed as in  and the 5 mm/deg ), Δθhipd as in  using SimMechanics, SimHydraulics, and SimScape Toolboxes of Simulink to verify the proposed PAS design. In the simulation, the PAS was connected to an anatomically realistic model of the human leg which simulated hip flexion moment on movement produced through either volitional contraction or FNS. A hip flexion torque of 20 Nm was applied to the leg model 1 second after initiating the simulation which resulted in a hip rotation of 25°. The simulated hydraulic valves of the PAS model were then opened to expose the cylinder to the high pressure accumulator to apply an external assistive hip flexion torque, which resulted in a further increase in hip flexion to the specified angle of 60° .A prototype of the hydraulic PAS was constructed from off-the-shelf components for bench testing. For simplicity, only the right hip was included for bench testing as shown schematically in Torque, angle, and angular velocity measurements were made with a Biodex System 3 robotic dynamometer . Pressure sensors  were attached to monitor pressure of accumulators PA and TA at the blind and rod side of the cylinder. Data were collected with custom circuitry integrated into the MATLAB xPC target prototyping environment which executes Simulink models in real time. A NI 6071E DAQ card  inside of the target PC acquired torque, angle, and angular velocity from the Biodex. In addition, the DAQ card delivered digital output signals from the xPC target to control the valves.The hydraulic cylinder attached to the thigh upright provided hip flexion by linear displacement of the piston through the rack and pinion transmission. The thigh upright of the brace was attached to the Biodex arm . The entTo determine passive resistance of the hydraulic circuit of the PAS, the hip was flexed through the range of motion by pulling vertically on a load cell through a rope which was attached to the brace upright for six trials. The force measured by the load cell was multiplied by the perpendicular distance from the line of force application to the hip center to calculate the moment required to flex the hip. This distance was found by attaching reflective markers at the hip center, the point of force application on the upright and on the rope using a Vicon  motion capture system to track the movement and determine the changing moment arm. This was repeated for six trials with the hydraulic cylinder detached from the rack and pinion transmission to find the difference in moment caused by the passive resistance of the hydraulic circuit.To simulate PAS operation with an SCI subject, an able-bodied volunteer  gave her informed consent and was fitted with the brace. Reflective markers were placed on the trunk corset and leg upright and the Vicon motion capture system was used to capture the marker trajectories at 120 Hz and body segments were created from the marker data to calculate joint angles. The high pressure accumulator was charged to 3172 kPa. To simulate voluntary muscle weakness or the actions of FNS, the subject was instructed to flex her right hip to approximately 45° after which the PAS was activated to complete the movement while she was instructed to provide minimal resistance or assistance. Six trials with PAS were performed and the data were averaged across the six trials.The input pressure supplied to the PA accumulator and the output isometric hip flexion torque at 0 and 60° is shown in 3/s. The average system response time was 93 ± 23 ms from the activation of the DCV to onset of hip movement. Passive resistance of the PAS circuit was found to be less than 4 Nm throughout the range of motion.The mean angular velocity of the hip was 77 ± 8°/s with a mean flow rate of 16.5 ± 1.6 cmIn the able-bodied experiments, the PAS increased hip flexion angle by a mean of 32 ± 5° across the six trials. Photographs before and after the PAS was activated are shown in A hydraulic source of assistive power was designed and tested in this study. The PAS was able to provide 21 Nm of torque to supplement hip flexion in a hybrid system combining weak voluntary muscle activity and an exoskeleton. More importantly, our results validate a linear relationship between input pressure and output torque that is independent of joint angle. For preliminary assessment, the accumulator was pressurized using a simple hand pump; however, automated pumps and motors capable of producing required pressures with reasonable weight and power consumption for portable use are available  and can The torque values measured during bench testing were lower than the values calculated from the mathematical equations and model (21 Nm as compared to the predicted 25 Nm at 60°). This difference is likely due to the passive resistance caused by friction in the hydraulic system and the linear-to-rotary transmission. The pressure drop across the cylinder was higher than predicted from the model (ending pressure of approximately 1379 kPa as compared to the predicted 2413 kPa). This is likely due to residual air in the system and suboptimal component selection. Custom fittings or a manifold designed specifically for the circuit has the potential to reduce the number of hydraulic connectors and the amount of tubing which could minimize the pressure losses and reduce passive resistance.We were able to achieve 32° of assistive hip flexion in the able-bodied testing. While it would have been beneficial to have electromyogram (EMG) recordings of the subject to ensure there was no volitional assist once the PAS was activated, the major muscles responsible for hip flexion are deep within the pelvis and not easily accessible for EMG recording. Thus, the able-bodied testing was only to approximate the results for an SCI subject using FNS and continued clinical testing with volunteers with paraplegia is necessary.From the results of the bench testing, we can extrapolate and predict pressures that would be required to produce a desired hip flexion moment. Knowing the relationship between input pressure and torque and the pressure drop across the range of motion, the pressure required to achieve desired hip flexion motion can be specified. For example, if it takes 23 Nm of hip flexion moment at 60° for a leg to clear a standard step  plus addPreliminary results show that using readily available off-the-shelf hydraulic components it is feasible to integrate a power assist system into a hybrid neuroprosthesis in order to provide additional hip flexion torque to assist in lifting and supporting the braced leg to a desired height. Controllers can be developed to combine power assist on demand with muscle stimulation  to maximAn advantage of this hydraulic design is that, with proper valve configuration , it is pThere are three major advantages of using flow discharged from an accumulator as opposed to using flow directly generated from a pump. First, pressure does not have to build from a low pressure which would result in a slow application of torque. High pressure is applied to the cylinder immediately after the DCV has opened which will enable a response time comparable to stimulated muscle. While the average system response time from valve activation to limb movement was 93 ms, isometric testing found that the time from valve activation to 90% of the maximum torque output was 159 ± 45 ms, which falls within range of stimulated muscle response times (100–300 ms) . This reSince the PAS operation is feasible, future studies need to concentrate on quantifying system performance in volunteers with SCI in conjunction with FNS. The PAS approach can also be applied without stimulation to assist physiological or household ambulators with partial paralysis or significant muscle weakness and limited voluntary movement. Future technical development should include system optimization to minimize the weight and power consumption of the system and maximize the pressure and displacement that the pump supplies to accumulator.


Chronic kidney disease (CKD) is associated with an increased mortality rate, risk of cardiovascular events and morbidity. Impaired renal function is common in elderly patients, and their glomerular filtration rate (GFR) should be taken into account when prescribing renally excreted drugs. In a hospital care setting the GFR may fluctuate substantially, so that the renal function group and therefore the recommended dose, can change within a few days. The magnitude and prevalence of the fluctuation of renal function in daily clinical practice and its potential effects on appropriateness of drug prescriptions after discharge from the hospital is unknown.2) admitted to a geriatric ward are eligible to participate. Participants undergo blood sample collection to measure serum creatinine level at three time points: at discharge from hospital, 14 days, and 2 months after discharge. At these time points the actual medication of the participants is assessed and the number of incorrect prescriptions according to the Dutch guidelines in relation to their estimated renal function is measured. In addition, for a hypothetical selection of drugs, the need for drug dose adaptation in relation to renal function is measured. The outcome of interest is the percentage of patients that changes from renal function group after discharge from hospital compared to the renal function at discharge. In addition, the percentages of patients whose actual medications are incorrectly prescribed and for the hypothetical selection of drugs that would have required dose adaptation will be determined at discharge, 14 days and 2 months after discharge. For each outcome, risk factors which may lead to increased risk for fluctuation of renal function and/or incorrect drug prescribing will also be identified and analysed.This is a prospective observational study. Patients ≥ 70 years with renal impairment (eGFR <60 ml/min/1.73 mThis study will provide data on changes in renal function in elderly patients after discharge from the hospital with a focus on the medications used. The benefits for healthcare professionals comprise of the creation, adjustment or confirmation of recommendations for the monitoring of the renal function after discharge from hospital of elderly patients. Chronic kidney disease (CKD) is associated with an increased mortality rate, as well as with an increased risk of cardiovascular events and morbidity –3. BecauUp to one-third of the adverse drug reactions (ADRs) leading to hospital admission of elderly patients receiving outpatient care, may be related to impaired renal function , 6. The The estimated glomerular filtration rate (eGFR) is important in the clinical management of patients . It is uIn a hospital care setting a patient is closely observed and (repeated) creatinine measurements are easy to perform. Informal clinical observations suggest that the renal function may fluctuate so much that the renal function group and therefore the recommended dose, can change within a few days. A frequent scenario is that the patient is dehydrated at hospital admission with impaired renal function and during hospital admission the fluid balance is optimized and the eGFR increases.The prevalence and the magnitude of fluctuations of the renal function after discharge from the hospital are still unknown. Since measurement of renal function is not routinely performed in the ambulatory care setting changes in renal function may remain unnoticed. It is possible that the eGFR may decrease, because of comprised fluid intake, or may increase because of the patient’s further recovery. Changes of renal function may lead to a shift to another renal function group for drug dosing . The Jeroen Bosch Hospital in ‘s-Hertogenbosch has provided local feasibility approval.This study is a prospective observational study and will be performed at the geriatric ward of the Jeroen Bosch hospital (JBZ), which is a teaching top-clinical hospital in The Netherlands serving 800 beds.2 calculated with the MDRD formula (eGFR)) at admission to the geriatric ward will be asked to participate in the study. Furthermore, patients must remain community dwelling after discharge from hospital for at least 2 months. Exclusion criteria are patients with an eGFR < 10 ml/min/1.73 m2 and patients discharged for end-of-life care.All consecutive patients ≥ 70 years with renal impairment . Serum creatinine level will be measured at 3 different time points, at discharge, 14 days and 2 months after discharge. The eGFR(MDRD) will automatically be calculated as follows:iffemale .The estimated renal function will be classified according to the categories, which are commonly applied in relation to DTM  that require dose adaptation in patients with renal impairment are selected from the database of the Dutch foundation for pharmaceutical statistics see  .Prior to discharge (max. 2 days) a blood sample will be taken to measure serum creatinine. At discharge the patients are given two laboratory forms to collect blood samples 14 days and 2 months after discharge to measure creatinine. The patient will be reminded to go to the nearest general practitioners laboratory for blood sample collection 14 days and 2 months after discharge. Initially the blood samples were taken at the patient’s nearest general practitioners laboratory. This was changed to blood sample collection at home because patients often did not show up at the laboratory.At admission the following variables are collected as part of usual care: age, gender, weight, length, use of NSAIDs in the two weeks prior to admission, nutritional status and hydration status. The nutritional status will be defined with the Simplified Nutritional Appetite Questionnaire (SNAQ)  and the The following parameters will be collected retrospectively per patient: all creatinine values measured during admission, admission via emergency department or a planned admission, reason for admission (diagnosis), duration of admission, co-morbidities, and medication orders during admission.After two months the researcher will obtain the medication history (from at least 6 months prior to discharge to 2 months after discharge) of the patient from the community pharmacy.All blood samples (heparinized plasma) will be analyzed at the Clinical Chemistry and Hematology department of JBZ. Serum creatinine levels will be measured in blood samples with the isotope dilution mass spectrometry (IDMS)-traceable Jaffe method on a Dimension Vista 1500 system  .The results of the creatinine measurements will be reported to the general practitioner and/or the geriatrician as soon as the creatinine value is available. If necessary, adjustment of the medication can be made according to the Dutch guidelines by the general practitioner and/or the geriatrician. Reporting the creatinine value will not have an influence on the results. We will carefully examine the medication histories and identify changes made after reporting the creatinine value.This study focuses on the fluctuation of renal function in elderly patients within two months after discharge from hospital. We are both interested in the percentage patients that change from one to another renal function group, but also in the direction of these changes (improvement or deterioration).http://www.raosoft.com/samplesize.html) was used to estimate the number of subjects required to detect a change in renal function group in 15 % of the population with a 95 % confidence level and a 5 % margin of error. The recommended sample size is 195 subjects.Raosoft sample size calculator (https://www.statstodo.com/SSizMcNemar_Pgm.phpPgm.php). Assuming that 5 % of the patients improve and 15 % of the patients deteriorate after discharge from hospital, power (1-beta) is 0.8 and probability of type I error  is 0.05, the sample size calculated is 155.In order to detect a difference in percentage of patients in whom the change in renal function group improved or deteriorated the sample size is calculated based on the McNemar test  and then finalised and locked. This file will be the basis for all further data analyses.To analyse if the percentages of patients in which the renal function group improves, deteriorates and remains unchanged 14 days and 2 months after discharge from hospital compared to the renal function group at discharge are statistically significant, the McNemar-Bowker test will be used .The secondary outcome is the percentage of patients in whom the prescribed drugs are not in accordance with the Dutch guidelines. To test the differences of the concordance of the medication to Dutch guidelines at the different time points, the McNemar test will be used (binary data with repeated measurements within one patient). The same test will be used to analyse the percentage of patients in whom a change in the medication would be needed if they had been using the top 10 most frequently prescribed drugs in elderly outpatients (>70 years) that require dose adaptation in patients with renal impairment.In further explorative analyses, we use various analytical methods  to identify potential determinants of outcomes.DTM in patients with renal impairment is an important issue. Efforts are being taken to reduce drug therapy errors in these patients, for example by introducing clinical decision support systems , 16. An Guidelines, such as KDIGO, do not offer advice about monitoring of the renal function after hospital discharge , 21. In