Correlated fluorine diffusion and ionic conduction in the nanocrystalline F(-) solid electrolyte Ba(0.6)La(0.4)F(2.4)-(19)F T1(ρ) NMR relaxation vs. conductivity measurements.

Chemical reactions induced by mechanical treatment may give access to new compounds whose properties are governed by chemical metastability, defects introduced and the size effects present. Their interplay may lead to nanocrystalline ceramics with enhanced transport properties being useful to act as solid electrolytes. Here, the introduction of large amounts of La into the cubic structure of BaF2 served as such an example. The ion transport properties in terms of dc-conductivity values of the F(-) anion conductor Ba1-xLaxF2+x (here with x = 0.4) considerably exceed those of pure, nanocrystalline BaF2. So far, there is only little knowledge about activation energies and jump rates of the elementary hopping processes. Here, we took advantage of both impedance spectroscopy and (19)F NMR relaxometry to get to the bottom of ion jump diffusion proceeding on short-range and long-range length scales in Ba0.6La0.4F2.4. While macroscopic transport is governed by an activation energy of 0.55 to 0.59 eV, the elementary steps of hopping seen by NMR are characterised by much smaller activation energies. Fortunately, we were able to deduce an F(-) self-diffusion coefficient by the application of spin-locking NMR relaxometry.

Long-range Li+ dynamics in the lithium argyrodite Li7PSe6 as probed by rotating-frame spin-lattice relaxation NMR.

Lithium-rich argyrodites belong to a relatively new group of fast ion conducting solids. They might serve as powerful electrolytes in all-solid-state lithium-ion batteries being, from a medium-term point of view, the key technology when safe energy storage systems have to be developed. Spin-lattice relaxation (SLR) nuclear magnetic resonance (NMR) measurements carried out in the rotating frame of reference turned out to be the method of choice to study Li dynamics in argyrodites. When plotted as a function of the inverse temperature, the SLR rates log10(R1ρ) reveal an asymmetric diffusion-induced rate peak. The rate peak contains information on the Li jump rate, the activation energy of the hopping process as well as correlation effects. In particular, considering the high-temperature flank of the SLR NMR rate peak recorded in the rotating frame of reference, an activation energy of approximately 0.49 eV is found. This value represents long-range lithium jump diffusion in crystalline Li7PSe6. As an example, at 325 K the Li jump rate determined from SLR NMR is in the order of 1.4 × 10(5) s(-1). The pronounced asymmetry of the rate peak R1ρ(1/T) points to correlated Li motion. It is comparable to that which is typically found for structurally disordered materials showing a broad range of correlation times.

NMR relaxometry as a versatile tool to study Li ion dynamics in potential battery materials.

NMR spin relaxometry is known to be a powerful tool for the investigation of Li(+) dynamics in (non-paramagnetic) crystalline and amorphous solids. As long as significant structural changes are absent in a relatively wide temperature range, with NMR spin-lattice (as well as spin-spin) relaxation measurements information on Li self-diffusion parameters such as jump rates and activation energies are accessible. Diffusion-induced NMR relaxation rates are governed by a motional correlation function describing the ion dynamics present. Besides the mean correlation rate of the dynamic process, the motional correlation function (i) reflects deviations from random motion (so-called correlation effects) and (ii) gives insights into the dimensionality of the hopping process. In favorable cases, i.e., when temperature- and frequency-dependent NMR relaxation rates are available over a large dynamic range, NMR spin relaxometry is able to provide a comprehensive picture of the relevant Li dynamic processes. In the present contribution, we exemplarily present two recent variable-temperature (7)Li NMR spin-lattice relaxation studies focussing on Li(+) dynamics in crystalline ion conductors which are of relevance for battery applications, viz. Li(7) La(3)Zr(2)O(12) and Li(12)Si(7).

Radon-222 from the island of hawaii: deep soils are more important than lava fields or volcanoes.

The mean flux of radon-222 atoms from the island of Hawaii is 0.45 atom per square centimeter per second. Lava fields occupy 50 percent of the land area, but their radon flux is only 1 percent of that from deep volcanic soils. The island yields approximately 10 curies of radon-222 per hour to the air surrounding it. The radon-222 contribuition of volcanoes is negligible.

The microstructure matters: breaking down the barriers with single crystalline silicon as negative electrode in Li-ion batteries.

Silicon-based microelectronics forms a major foundation of our modern society. Small lithium-ion batteries act as the key enablers of its success and have revolutionised portable electronics used in our all everyday's life. While large-scale LIBs are expected to help establish electric vehicles, on the other end of device size chip-integrated Si-based µ-batteries may revolutionise microelectronics once more. In general, Si is regarded as one of the white hopes since it offers energy densities being ten times higher than conventional anode materials. The use of monocrystalline, wafer-grade Si, however, requires several hurdles to be overcome since it its volume largely expands during lithiation. Here, we will show how 3D patterned Si wafers, prepared by the sophisticated techniques from semiconductor industry, are to be electrochemically activated to overcome these limitations and to leverage their full potential being reflected in stable charge capacities (>1000 mAhg(-1)) and high Coulomb efficiencies (98.8%).

Li ion dynamics along the inner surfaces of layer-structured 2H-LixNbS2.

Layer-structured materials, such as graphite (LiCy) or Lix(Co,Ni,Mn)O2, are important electrode materials in current battery research that still relies on insertion materials. This is due to their excellent ability to reversibly accommodate small alkali ions such as Li(+) and Na(+). Despite of these applications, microscopic information on Li ion self-diffusion in transition metal sulfides are relatively rare. Here, we used (7)Li nuclear magnetic resonance (NMR) spectroscopy to study translational Li ion diffusion in hexagonal (2H) LixNbS2 (x = 0.3, 0.7, and 1) by means of variable-temperature NMR relaxometry. (7)Li spin-lattice relaxation rates and (7)Li NMR spectra were used to determine Li jump rates and activation barriers as a function of Li content. Hereby, NMR spin-lattice relaxation rates recorded with the spin-lock technique offered the possibility to study Li ion dynamics on both the short-range and long-range length scale. Information was extracted from complete diffusion-induced rate peaks that are obtained when the relaxation rate is plotted vs inverse temperature. The peak maximum of the three samples studied shifts toward higher temperatures with increasing Li content x in 2H-LixNbS2. Information on the dimensionality of the diffusion process was experimentally obtained by frequency dependent Rρ measurements carried out at T = 444 K, that is in the high-temperature regime of the rate peaks. A slight, but measurable frequency-dependence within this limit is found for all samples; it is in good agreement with predictions from relaxation models developed to approximate low-dimensional (2D) jump diffusion.

Are branched chain amino-acids beneficial for nutrition of severe surgical patients with sepsis?

UNLABELLED: This study investigated in severe sepsis the metabolic effects of two amino acid diets, including the same protein (0.3 gN/kg/day) and caloric intake (2g/kg/day glucose) but with different amino acid composition, 24% branched chain amino-acids (B.C.A.A.) for diet A (8 cases), 41% B.C.A.A. for diet B (11 cases). The two groups were obtained by randomisation at the operative day (D0) and were observed six days (D1-D6). During study, total nitrogen using a Kjeldhal method was measured. At D0 and D6, albumin, total hemolytic complement, transferrin, cholesterol, ammonaemia, insulin and amino acid pattern were studied in blood and skin tests were performed. The data were analysed by Mann-Whitney test. RESULTS: 1) The cumulative nitrogen balances of the six days are not significantly different, but at day 6 in diet B, patients started to be in an anabolic state (+3.7 gN) and in diet A catabolism persisted (-12 gN) (p<0.02). 2) Plasma B.C.A.A. are significantly higher and aromatic acids significantly lower in diet B. In order, Fischer ratio is also significantly different between the two regimens. All the other measured parameters are not significantly different. In this study, the B.C.A.A. enriched diet seems to be beneficial in surgical patients with severe sepsis.

Comparison of creatinine and inulin clearances in multiple trauma.

Creatinine clearance (Ccr) is a good predictor of renal dysfunction. However, numerous analytical interferences have been observed with the classical measurement of creatinine by Jaffé's procedure. This prospective study was conducted to compare 4 methods for determining creatinine; and also endogenous creatinine clearance with inulin clearance (Cin) to estimate the glomerular filtration rate. The 4 different techniques for measuring creatinine were: 1) 2 techniques using Jaffé's colorimetric reaction: one with rapid and the other with slow kinetics: 2) 2 more selective methods: enzymatic procedure and high performance liquid chromatography (HPLC). Measurements were performed in 13 multiple trauma patients after stabilization and in 5 comatose patients (control group) over a 3-day period, with strict 24-h urine collection. On the second day, inulin clearance and para-aminohippuric acid clearance (Cpah) were measured. Measurement of creatinine by Jaffé's procedure yields significantly higher levels than those obtained by the other methods. Higher levels of both plasma and urinary creatinine were observed in the multiple trauma patients with all the methods used. There were no significant differences in Ccr, Cin, Cpah between the multiple trauma patients and the control patients. The best correlations between inulin clearance and creatinine clearance were observed for Jaffé's rapid kinetics (r = 0.90) in the control group and for the enzymatic procedure in the multiple trauma group (r = 0.55). Plasma creatinine is not a useful indicator in multiple trauma. The correlation between creatinine clearance and inulin clearance is not very strong in multiple trauma, indicating that the relative evolution (not the absolute values) of creatinine clearance is of interest.

Radon transport in soil and its relation to indoor radioactivity.

The transport of radon from soil to the indoor living space involves diffusion and viscous flow in the soil coupled with transfer to the building interior of radon-rich air which accumulates in cavities and channels below and around the foundations of buildings. Radon concentrations in soil pores at depth are dependent upon the radium content of the soil, emanating power for radium, and soil moisture content. Atmospheric pressure fluctuation, thermal gradients in fractured rocks, and air instabilities due to temperature differences allow air of high radon content to reach living space in dwellings in addition to that which comes directly from building materials and other sources.

Seasonal variation of indoor Rn at a location in the southwestern United States.

Radon-222 concentrations have been measured in 12 homes typical of a small town in the southwestern United States. Nine of the houses, in which both summer and winter data are available, have an annual mean of 63 +/- 18 Bq m-3 (1.7 +/- 0.5 pCi L-1) and a range of 41 to 96 Bq m-3 (1.1 to 2.6 pCi L-1). These results were obtained with passive Rn dosimeters using polycarbonate nuclear track detector foils. The overall results fall slightly above the middle of the range of values obtained in other studies in the United States. Winter levels clearly exceed summer by a factor of from two to three. This result is attributed primarily to wide use of evaporative air conditioners for daytime cooling in the summer together with the fact that doors and windows are left open frequently during evening and nighttime hours. Both practices enhance the exchange of outdoor air with indoor air contributing to a decrease in the indoor Rn levels during the summer season. Room-to-room differences were evident during the winter season only. Bedrooms and bathrooms were generally higher in Rn than kitchens and living rooms but by only about 25%. The two adobe houses in the group showed higher Rn concentrations during the winter season than did those of frame-stucco, concrete, or cinder block construction. Dose equivalent calculations yielded a mean figure of 0.29 WLM y-1 for typical occupancy patterns in these New Mexico houses.

Radon-222 on the island of Hawaii.

The island of Hawaii, like other locations in a marine environment, has low levels of atmospheric 222Rn. The low concentrations of 222Rn and its decay products result from a low average flux density of 9.8 mBq m-2 s-1, the mixing of marine air from the Pacific having a 222Rn concentration of only 0.04 Bq m-3 with air from over the island, and the decay of 222Rn as it is transported in air masses across the Pacific primarily from the Asian continent. The overall mean concentration over the Island The overall mean concentration over the Island was found to be 0.44 Bq m-3 compared with a figure of about 8 Bq m-3 for air over continents. A consideration of the island as a source of 222Rn must take into account the relatively low average flux density associated with the lava fields and accompanying thin soils. The 222Rn formed from the U and 226Ra present in the lava cannot escape to the atmosphere. The deep agricultural soils, on the other hand, provide relatively high flux densities. When the areas of the soil types are taken into account, the exhalation for the lava fields, thin organic soils, and deep agricultural soils were 0.25, 1.7, and 32 MBq s-1, respectively. Measurements of indoor 222Rn on the island indicate levels of approximately 25 Bq m-3 which is appreciably lower than 40 Bq m-3 taken as an average for indoor levels on the mainland. Based on an assumed indoor occupancy level of 0.8, the effective dose equivalent for inhaled 222Rn and its decay products on Hawaii is 1.2 mSv y-1. This is only a little more than one-half of that for a resident of the continental United States who is estimated to receive an effective dose equivalent of 2 mSv y-1. The relatively low effective dose equivalent for the population on the island may have interesting effects in comparison with people living in areas where the inhaled dose from 222Rn is much higher.

An electrostatic precipitator for the study of airborne radioactivity.

An system has been developed to measure airborne radioactivity using electrostatic precipitation for collection and alpha-particle spectroscopy for detection. Features include good energy resolution (e.g. 170 and 300 KeV for full-width half maximum and full-width tenth maximum for 7.7-MeV alpha particles using a 7-cm2 area detector; and 52- and 122-KeV, respectively, using 1.2-cm2 area detector) and versatile computer control for collection, counting and data reduction. Aerosols bearing the radioactive atoms are deposited on a foil tape by electrostatic precipitation for a predetermined time after which the foil is moved under a solid-state detector to count the alpha-particle emissions. Activities are determined at the same frequency as samples are collected. Helium gas can be introduced at the detector to reduce energy loss and improve resolution. Although in principle certain aerosol sizes could be difficult to collect, in practice no difficulties were observed for typical environmental conditions, provided sufficiently low air-sampling rates were used. One important application is the measurement of 222Rn daughters. The sensitivity is such that detection of individual daughter concentrations less than 0.1 pCi/l. with only a 10% counting error is possible.

[Does flumazenil correct disorders of intracardiac conduction induced by accidental intravenous injection of bupivacaine?]. / Le flumazénil corrige-t-il les troubles de la conduction intracardiaque induits par l'injection intraveineuse accidentelle de bupivacaïne?

The authors report the case of a patient who experienced intracardiac conduction disturbances from accidental intravenous injection of bupivacaine, which were reversed by an intravenous injection of flumazenil. Flumazenil could act either in displacing bupivacaine from its binding site, or by an interaction involving the GABAergic system, unless a specific interaction between flumazenil and bupivacaine does exist. In case of experimental confirmation of this feature, flumazenil could be proposed as a new therapeutic tool for bupivacaine-induced cardiotoxicity.

[Acute intracranial subdural hematoma of arterial origin after spinal anesthesia]. / Hématome sous-dural aigu intracrânien d'origine artérielle après rachianesthésie.

A case of an acute intracranial subdural haematoma occurring shortly after spinal anaesthesia is reported. A 67 year old poorly controlled hypertensive man, ASA II, underwent removal of a prostatic adenoma under spinal anaesthesia. He complained of postural headache on the third day after surgery. Unresponsive to the usual analgesics, his headache became severe, persistent and non postural on the fifth day. Twenty-four hours later, he suddenly presented with a left hemiplegia and became comatose. Computed axial tomography showed a large left-sided subdural haematoma, lying over the left hemisphere. During the immediate surgical removal, a pulsatile arterial bleeding originating from a small cortical artery was discovered, and stopped. The patient slowly recovered consciousness, but the hemiplegia remained. He finally died six months later of bronchopneumonia. The link between the haematoma and the spinal anaesthetic is not proven; the possible relationship between the two is discussed.

[Severe paralysis of the upper limb after axillary brachial plexus block]. / Paralysie grave du membre supérieur après bloc plexique axillaire.

A case is reported of a severe neurological deficit occurring after axillary blockade. The 37-year-old ASA I patient underwent an axillary block for hand surgery using 20 ml of lignocaine 1% with adrenaline and 20 ml of lignocaine 2%. In order to elicit paraesthesia, several attempts were required. Injection of the local anaesthetic was not painful. The tourniquet remained at 250 mmHg for only 35 min. The following day, the patient's arm remained numb. As there was no improvement, epineurotomy was carried out on day 19, to liberate the median nerve which was severely stenosed at the axilla. The patient then started to improve slowly, so that he was able to return to part-time work 6 months later. Prevention of such an accident relies on avoiding intraneural injection and repeated punctures when searching for paraesthesia. When using axillary blockade in day-care surgery, the patient's must be informed upon the possibility of persistent paraesthesia. Should such a rare incident occur, rapid consultation with the anaesthesiologist is essential.

[Ten-year experience with heart transplantation (1987-1997)]. / Bilan de dix années de transplantation cardiaque (1987-1997).

OBJECTIVES: Analyze ten years experience with heart transplantation at the Dijon University Hospital and determine which parameters control mid and long term outcome. PATIENTS AND METHODS: One hundred thirty six heart transplantations were performed over a 10 year period (1987-1997) in 118 men and 18 women aged 51-87 years. Heart transplantation was indicated on the basis of the following criteria: ejection fraction *20%, pulmonary arteriole resistance < 6 Wood units, peak oxygen uptake < 14 l/kg/min. The Shumway or anatomic technique was used. The triple immunosuppressive protocol combined corticosteroids, azathioprine and cyclosporin. The same team conducted the post-transplantation follow-up with regular programmed consultations in addition to those requested by the general practitioner, the cardiologist or the patient. Follow-up was oriented according to the clinical situation (blood chemistry, cell counts, cyclosporinemia, search for infection, echocardiography, endomyocardial biopsy, coronarography). RESULTS: Five patients (3.6%) died when still on the waiting list. Absolute emergency transplantation was performed for patients (28.1%) including 8 (5.9%) after circulatory assist. Hospital mortality was 11.7% and late mortality was 16.1%. Actuarial survival was 78% at 1 year, 71% at 5 years and 69% at 10 years. Among the survivors, 94% were taking two, three or even four drugs for hypertension. Cyclosporin levels decreased and creatinine levels increased. Episodes of rejection were minimal: 86.57% of the biopsies were * grade 1 and 4.45% * grade 2. Cytomegalovirus infection was documented and treated in 7.55% of the cases. Incidence of graft coronary artery disease was 3.4% at 1 year, 6.5% at 2 years and 7.9% at 3 years. CONCLUSION: Our follow-up structure where the same small team conducts regular examinations together with our approach to heart transplantation appears to be the main factor leading to the quality results obtained in this series.

[Validity of cerebral angiography via venous route in the diagnosis of brain death]. / Validité de l'angiographie cérébrale par voie veineuse dans le diagnostic de la mort cérébrale.

The success of transplantations relies on uninjured organs i.e., harvested before circulatory failure. At present, french law concerning cerebral death criteria (circulaire ministérielle n. 3 du 21.01.91) requires the association of clinical patterns and 2 repeated, unreactive and flat electroencephalographic (EEG) tracings. Blood and urinary samples also need to be free from any nervous system depressant drug, the patient has not to be hypothermic. These obligations are not always compatible with patients status or local organization. The consequence might be organ loss or delay in harvesting schedule. A review of the literature points out the trap in realization and analysis of EEG in this kind of intensive care patients. Angiogram, on the opposite, is influenced neither by nervous system depressant drug nor by hypothermia. As it is in some other western countries, it should be proposed as the reference.

Evidence of low dimensional ion transport in mechanosynthesized nanocrystalline BaMgF4.

Mechanochemical milling provides a versatile method for the preparation of nano-sized, defect rich, polycrystalline materials. If ionic materials are considered, the transport parameters of the mobile ions may greatly differ from those of the microcrystalline counterparts prepared by conventional synthesis routes. Little is known about ionic conduction in nanocrystalline materials having crystal structures that offer spatially confined transport pathways. Here, we focused on mechanosynthesized BaMgF4 that combines both nanocrystallinity and anisotropic F(-) transport. The preparation of nanocrystalline BaMgF4 is presented as a facile and rapid one-pot procedure. The reaction was followed by X-ray diffraction and high-resolution (19)F nuclear magnetic resonance (NMR) spectroscopy. NMR helped prove the formation of X-ray amorphous compounds as well as the transformation of the starting materials into the final product BaMgF4. Most importantly, besides enhanced conduction properties compared to a single crystal, our broadband impedance spectra reveal characteristics pointing to anisotropic (low dimensional) ion transport processes even in the nanocrystalline form of BaMgF4.

Two-dimensional diffusion in Li0.7NbS2 as directly probed by frequency-dependent 7Li NMR.

Li ion diffusion in layer-structured Li0.7NbS2 has been complementary investigated by nuclear magnetic resonance (NMR) spectroscopy from an atomic scale point of view. In the present case, (7)Li NMR spin-lattice relaxation (SLR) rates R1ρ probed in the rotating frame of reference proved very informative in characterizing the Li self-diffusion process in the van der Waals gap between the NbS2 layers. While temperature-variable SLRρ measurements were used to determine dynamic parameters such as jump rates (τ(-1)) and the activation energy (Ea), frequency-dependent measurements were used to specify the dimensionality of the diffusion process. In particular, the effect of annealing, i.e., the distribution of Li ions between the layers, on overall Li dynamics has been studied. When plotted in an Arrhenius diagram, the R1ρ rates of an annealed sample, which were recorded at a locking frequency of 20 kHz, pass through a diffusion-induced relaxation peak whose maximum shows up at 320 K. Employing an appropriate diffusion model and appropriately accounting for a non-diffusive background relaxation, a Li jump rate τ(-1)(300 K) ≈ 1.3 × 10(5) s(-1) and an activation energy Ea of 0.43(2) eV can be deduced. Most importantly, in the high-T limit of the diffusion-induced rate peak, i.e., when ω1τ << 1 holds, the rates follow a logarithmic frequency dependence. This points to a diffusion process of low dimensionality and is in good agreement with predictions of relaxation models developed for 2D diffusion.

Spin-alignment echo NMR: probing Li+ hopping motion in the solid electrolyte Li7La3Zr2O12 with garnet-type tetragonal structure.

(7)Li spin-alignment echo (SAE) nuclear magnetic resonance (NMR) spectroscopy has been used to measure single-spin hopping correlation functions of polycrystalline Li(7)La(3)Zr(2)O(12). Damping of the echo amplitude S(2)(t(m),t(p)), recorded at variable mixing time t(m) but fixed preparation time t(p), turns out to be solely controlled by slow Li jump processes taking place in the garnet-like structure. The decay rates τ(SAE)(-1) directly obtained by parametrizing the curves S(2)(t(m),t(p)) with stretched exponential functions show Arrhenius behaviour pointing to an activation energy of approximately 0.5 eV. This value, probed by employing an atomic-scale NMR method, is in very good agreement with that deduced from impedance spectroscopy used to measure macroscopic Li transport parameters. Most likely, the two methods are sensitive to the same hopping correlation function although Li dynamics are probed in a quite different manner.