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Power metal-oxide-semiconductor field-effect transistors (MOSFETs) experience conditions of high field during normal operation. During switching conditions, unexpected transient events may occur which force devices into avalanche or short circuit conditions. Moreover, silicon carbide devices typically experience higher fields in the gate oxide and drift regions than comparable Si devices due to channel and drift property differences. A summary of SiC MOSFET reliability and ruggedness test results are reported here. Reliability tests under high field conditions: positive-bias and negative-bias temperature instability (PBTI, NBTI) to examine threshold stability; time-dependent dielectric breakdown (TDDB) for gate oxide lifetime extrapolation; high-temperature reverse bias (HTRB); and HTRB testing under high neutron flux to determine terrestrial neutron single-event burnout (SEB) rates. High-power ruggedness evaluation is presented for SiC MOSFETs under forced avalanche conditions (unclamped inductive switching (UIS)) and under short-circuit operation to bound device safe operating areas. Overall results demonstrate the intrinsic reliability of SiC MOSFETs.

Optimization of the oscillator front-end for resonant sensors is critical to addressing key metrics such as noise floor and output stability. This paper reports a method to improve the noise floor of resonant MEMS accelerometers by avoiding aliasing of high-frequency seismic noise for long-period measurements. In particular, the optimization of a Phase Locked Loop (PLL) front-end is employed for continuous tracking of the output. A noise floor improvement of 13x is seen in comparison to the case with no anti-aliasing control. A custom PLL is designed to mitigate the impact of high-frequency noise enabling the realization of a resonant accelerometer sensor module with a noise floor of 10 ng/√Hz.

International audience; From early April 2020, wildfires raged in the highly contaminated areas around the Chernobyl nuclear power plant (CNPP), Ukraine. For about 4 weeks, the fires spread around and into the Chernobyl exclusion zone (CEZ) and came within a few kilometers of both the CNPP and radioactive waste storage facilities. Wildfires occurred on several occasions throughout the month of April. They were extinguished, but weather conditions and the spread of fires by airborne embers and smoldering fires led to new fires starting at different locations of the CEZ. The forest fires were only completely under control at the beginning of May, thanks to the tireless and incessant work of the firefighters and a period of sustained precipitation. In total, 0.7–1.2 TBq 137Cs were released into the atmosphere. Smoke plumes partly spread south and west and contributed to the detection of airborne 137Cs over the Ukrainian territory and as far away as Western Europe. The increase in airborne 137Cs ranged from several hundred μBq·m–3 in northern Ukraine to trace levels of a few μBq·m–3 or even within the usual background level in other European countries. Dispersion modeling determined the plume arrival time and was helpful in the assessment of the possible increase in airborne 137Cs concentrations in Europe. Detections of airborne 90Sr (emission estimate 345–612 GBq) and Pu (up to 75 GBq, mostly 241Pu) were reported from the CEZ. Americium-241 represented only 1.4% of the total source term corresponding to the studied anthropogenic radionuclides but would have contributed up to 80% of the inhalation dose.

Power metal-oxide-semiconductor field-effect transistors (MOSFETs) experience conditions of high field during normal operation. During switching conditions, unexpected transient events may occur which force devices into avalanche or short circuit conditions. Moreover, silicon carbide devices typically experience higher fields in the gate oxide and drift regions than comparable Si devices due to channel and drift property differences. A summary of 4H-SiC MOSFET reliability and ruggedness test results are reported here. Reliability tests under high field conditions: positive-bias and negative-bias temperature instability (PBTI, NBTI) to examine threshold stability; time-dependent dielectric breakdown (TDDB) for gate oxide lifetime extrapolation; high-temperature reverse bias (HTRB); and HTRB testing under high neutron flux to determine terrestrial neutron single-event burnout (SEB) rates. High-power ruggedness evaluation is presented for SiC MOSFETs under forced avalanche conditions (unclamped inductive switching (UIS)) and under short-circuit operation to bound device safe operating areas. Overall results demonstrate the intrinsic reliability of SiC MOSFETs.

In this paper, we present a new method to study global atmospheric processes and their changes during the last decade. A cosmogenic radionuclide measured at ground-level, beryllium-7, is utilized as a proxy to study atmospheric dynamics. Beryllium-7 has two advantages: First, this radionuclide, primarily created in the lower stratosphere, attaches to aerosols that are transported downwards to the troposphere and travel around the globe with the general atmospheric circulation. By monitoring these particles, we can provide a global, simple, and sustainable way to track processes such as multi-annual variation of the troposphere, tropopause heightening, position and speed of atmospheric interface zones, as well as the poleward movement and stalling patterns of jet streams. Second, beryllium-7 is a product of cosmic rays which are themselves directly linked to solar activity and the earth magnetic field. This study shows whether beryllium-7 observed concentration changes are correlated with such natural processes or independent of them. Our work confirms that major changes in the atmospheric circulation are currently ongoing, even though timeseries are too short to make climatological assessments. We provide solid evidence of significant and progressive changes of the global atmospheric circulation as well as modifications of tropopause heights over the past decade. As the last decade happened to be the warmest on record, this analysis also indicates that the observed changes are, at least to some extent, attributable to global warming.

This paper introduces a differential vibrating beam MEMS accelerometer demonstrating excellent long-term stability for applications in gravimetry and seismology. The MEMS gravimeter module demonstrates an output Allan deviation of 9 μGal for a 1000 s integration time, a noise floor of 100 μGal/√Hz, and measurement over the full ±1 g dynamic range (1 g = 9.81 ms−2). The sensitivity of the device is demonstrated through the tracking of Earth tides and recording of ground motion corresponding to a number of teleseismic events over several months. These results demonstrate that vibrating beam MEMS accelerometers can be employed for measurements requiring high levels of stability and resolution with wider implications for precision measurement employing other resonant-output MEMS devices such as gyroscopes and magnetometers.

This letter presents a high-performance resonant MEMS accelerometer comprising of a single force-sensitive vibrating beam element sandwiched between two inertial masses. The accelerometer demonstrates a noise floor of 98 ng/Hz1/2 and a bias stability of 56 ng under ambient conditions, corresponding to a frequency noise floor of 0.77 ppb/Hz1/2 and a frequency bias stability of 0.43 ppb. These are the best results achieved for a MEMS accelerometer employing the resonant sensing paradigm to-date. [2018-0255]

Experimental and numerical analyses have been performed to investigate the heating impact of using a thermocouple for the temperature measurement of a small volume of cold water (∼24 mm3), due to thermal conduction through the wires. Two sizes of K-type thermocouple, 80 µm and 315 µm, were used to measure the temperature of cold water inside a small, thermally regulated chamber within a Centeo TG40 cooling system. The results show that thermal conduction from the ambient environment into the cold water produces a heating effect. This effect decreases for greater submersion depth of the thermocouple junction and is eliminated when the thermocouple junction is close to the copper bottom of the chamber. The inclusion of an insert into the chamber increases the thermal resistance between the copper block and the water, raising the heating effect of the thermocouple. The cooling effect of the copper block on the water is diminished when the air gap between copper block and plastic insert is increased, consequently raising the temperature inside the small well. Moreover, increasing the water height inside the large well has a negligible effect on the temperature of the small well.

The interaction of trace environmental plutonium with dissolved natural organic matter (NOM) plays an important role on its mobility and bioavailability in freshwater environments. Here we explore the speciation and biogeochemical behavior of Pu in freshwaters of the karst system in the Swiss Jura Mountains. Chemical extraction and ultrafiltration methods were complemented by diffusive gradients in thin films technique (DGT) to measure the dissolved and bioavailable Pu fraction in water. Accelerator mass spectrometry (AMS) was used to accurately determine Pu in this pristine environment. Selective adsorption of Pu (III, IV) on silica gel showed that 88% of Pu in the mineral water is found in +V oxidation state, possibly in a highly soluble [PuO2+(CO3)n]m− form. Ultrafiltration experiments at 10 kDa yielded a similar fraction of colloid-bound Pu in the organic-rich and in mineral water (18–25%). We also found that the concentrations of Pu measured by DGT in mineral water are similar to the bulk concentration, suggesting that dissolved Pu is readily available for biouptake. Sequential elution (SE) of Pu from aquatic plants revealed important co-precipitation of potentially labile Pu (60–75%) with calcite fraction within outer compartment of the plants. Hence, we suggest that plutonium is fully available for biological uptake in both mineral and organic-rich karstic freshwaters.

Significance A massive atmospheric release of radioactive 106Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed ≤2 years after discharge, possibly for the production of a high-specific activity 144Ce source for a neutrino experiment in Italy., In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

This paper reports initial results on the implementation of a high-resolution resonant MEMS accelerometer with a noise floor of $17.8\text{ng}/\surd{}\text{Hz}$ and a bias stability of 17.5ng with a differential frequency readout configuration. The differential readout scheme provides for rejection of common mode environmental effects to first order. This prototype sensor demonstrates the best bias stability and noise floor of all MEMS resonant accelerometer configurations reported till date.

The interaction of trace metals with naturally occurring organic matter (NOM) is a key process of the speciation of trace elements in aquatic environments. The rate of dissociation of metal-NOM complexes will impact the amount of free metal available for biouptake. Assessing the bioavailability of plutonium (Pu) helps to predict its toxic effects on aquatic biota. However, the rate of dissociation of Pu-NOM complexes in natural freshwaters is currently unknown. Here, we used the technique of diffusive gradients in thin films (DGT) with several diffusive layer thicknesses to provide new insights into the dissociation kinetics of Pu-NOM complexes. Results show that Pu complexes with NOM (mainly fulvic acid) are somewhat labile (0.2 ≤ ξ ≤ 0.4), with kd = 7.5 × 10(-3) s(-1). DGT measurements of environmental Pu in organic-rich natural water confirm these findings. In addition, we determined the effective diffusion coefficients of Pu(V) in polyacrylamide (PAM) gel in the presence of humic acid using a diffusion cell (D = 1.70 ± 0.25 × 10(-6) cm(2) s(-1)). These results show that Pu(V) is a more mobile species than Pu(IV).

Early observations of the tritium (3H) activity in precipitation from Switzerland started in 1967 in Bern and a monitoring program with improved analytical techniques was carried out between 1971 and 2009. Between 2012 and 2015, we performed tritium analyses on daily precipitation samples from north-western Switzerland to better constrain the tritium variability. We also collected waters dripping inside Milandre Cave (Jura Mountains) with a 4–6 months’ resolution in order to estimate the age of the drip water, which is mandatory to interpret the high-resolution speleothem (cave carbonate deposits) records. Over the monitoring period, the mean tritium concentration in the daily precipitation samples was approximately 8.7 ± 4.7 TU with distinct seasonality showing higher values in spring and summer (from April–May to August–September). The similarity in trends with the other cosmogenic radionuclide beryllium-7 (7Be) suggests that, for the study site, tritium in precipitation essentially originates from stratospheric input in spring. In winter, precipitation dynamics with increasing moisture originating from the Atlantic and diluted during transport contribute to low values close to the Atlantic background. In cave drip water, the depleted activity level of tritium indicates a relatively long percolation time from the surface to the cave of several years. A residual superimposed short tritium variability provides evidence for the occurrence of fast flowing water paths. The contribution from both components were quantified based on a two-component lumped parameter-mixing model. Finally, we show that tritium concentrations in cave drip water are linked to the moisture origin and atmospheric transport pathways. ISSN:0265-931X ISSN:1879-1700

Uranium (U) accumulation in organic soils is a common phenomenon that can lead to high U concentration in montane wetlands. The stability of the immobilized U in natural wetlands following redox fluctuations and re-oxidation events, however, is not currently known. In this study, we investigated a saturated histosol that had accumulated up to 6000 ppm of U at 30 cm below ground level (bgl). Uranium in the waters feeding the wetland originates from the weathering of surrounding gneiss rocks, a process releasing trace amounts (

Plutonium and americium are radionuclides particularly difficult to measure in environmental samples because they are alpha-emitters and therefore necessitate a careful separation before any measurement, either using radiometric methods or ICP-SMS. Recent developments in extraction chromatography resins such as Eichrom (R) TRU and TEVA have resolved many of the analytical problems but drawbacks such as low recovery and spectral interferences still occasionally occur. Here, we report on the use of the new Eichrom (R) DGA resin in association with TEVA resin and high pressure microwave acid leaching for the sequential determination of plutonium and americium in environmental samples. The method results in average recoveries of 83 +/- 15% for plutonium and 73 +/- 22% for americium (n = 60), and a less than 10% deviation from reference values of four IAEA reference materials and three samples from intercomparisons exercises. The method is also suitable for measuring Pu-239 in water samples at the mu Bq/l level, if ICP-SMS is used for the measurement.

The middle part of the Miocene Monterey Formation at Naples Beach, west of Santa Barbara, California, is predominantly composed of organic-rich mudstone interstratified with phosphatic laminae. Minor lithologies include volcanic ash, dolomite, porcelanite and chert, and condensed phosphatic beds. Sediments dated as 14.3–13.5 Ma have average total organic carbon (TOC) values around 8.5 wt%, and organic carbon (OC) accumulation rates are around 565 mg/cm2/k.y. Sediments dated as 13.5–13 Ma are characterized by average TOC values of 12.6 wt% and OC accumulation rates of around 1130 mg/cm2/ k.y. The interval between 13 and 10.6 Ma is marked by condensation; average TOC values are around 8.6 wt%, and OC accumulation rates diminished to around 55 mg/cm2/k.y. The last interval studied is dated as 10.6–9.4 Ma, and average TOC values are around 6 wt%, whereas OC accumulation rates rose again to 320 mg/cm2/k.y. The presence of erosional surfaces, angular unconformities, and reworked clasts and nodules suggests that bottom-current activity and gravity-flow deposition have been instrumental in sediment accumulation. The phosphatic laminae were precipitated at a very early stage of diagenesis during periods of nonsedimentation. They formed less permeable sedimentary lids and may as such have contributed to enhanced OC preservation. Between 13 and 10.6 Ma, the thus-formed phosphatic laminae were frequently subjected to subsequent sediment winnowing and reworking, resulting in the formation of condensed phosphatic beds. Calculated P:C molar ratios suggest that (1) the measured section is highly enriched in phosphorus (P) relative to OC; (2) regeneration of organic P from organic-matter decomposition was negligible; and (3) the source of P was external, likely upwelled bottom water rich in inorganic P. In spite of good preservation conditions and correspondingly high TOC contents, the overall OC accumulation rates are moderate in comparison to those of actual high productivity areas, which is mainly due to the episodic character of depositional processes and the intervening long periods of nondeposition and sediment reworking. They preclude this section, and by extrapolation, the Monterey Formation in general from being an important OC sink during the middle Miocene. Alternatively, large OC sinks were probably created on the continent (lignite deposits) and in sedimentary depocenters, which received increasing amounts of detrital sediments due to a combination of climate change, spreading of grasslands, and the increasing importance of mountain chains such as the Himalaya. The associated high nutrient fluxes may have been involved in the backstepping and drowning of carbonate platforms and in the generation of widespread phosphat-rich deposits during the late early and early middle Miocene.

The organic- and phosphate-rich interval of the Monterey Formation at El Capitan State Beach (west of Santa Barbara, California, U.S.A.; late early to early late Miocene in age) is composed of a carbonaceous marl (TOC contents between 1.2 and 23.2 wt %) with intercalated phosphate-rich laminae, lenses, and layers. Subordinate lithologies include ash layers, dolomitized horizons, and siliceous beds. We distinguished five lithological units: (1) a gray marl unit lacking major phosphate accumulations (> 16.3 Ma; average TOC content 2% by weight; average sedimentation rate 75 m/My; average TOC accumulation rate 0.19 mg/cm2/yr); (2) a black marl unit including light-colored phosphatic laminae, lenses, and discrete particles (16.3-14.5 Ma; average TOC content 7.5% by weight; average sedimentation rate 20 m/My; average TOC accumulation rate 0.19 mg/cm2/yr); (3) a red marl unit including light-colored phosphatic laminae, lenses, and commonly reworked particles (14.5-12.7 Ma; average TOC content 15% by weight; average sedimentation rate 20 m/My (14.5-13.3 Ma) and 2 m/My (13.3-12.7 Ma), respectively; average TOC accumulation rate 0.39 mg/cm2/yr (14.5-13.3 Ma) and 0.04 mg/cm2/yr (13.3-12.7 Ma), respectively); (4) a unit of complex and condensed phosphatic beds, interbedded with red marl (12.7-10.8 Ma; average sedimentation rate 3 m/My); and (5) a black marl unit with intercalated phosphatic laminae and lenses (< 10.8 Ma; average sedimentation rate 9 m/My; average TOC accumulation rate 0.09 mg/cm2/yr). Phosphogenesis and accumulation of phosphate were dynamic processes, which started with local phosphogenesis leading to the formation of phosphatized particles, as well as stratigraphically bound phosphogenesis leading to the formation of phosphate laminae and lenses. Phases of subsequent sediment reworking resulted in the concentration of phosphate particles in phosphate-rich layers, and repeated phases of sediment reworking and phosphogenesis ultimately resulted in the formation of the complex phosphate condensed horizons. Preservation of organic matter was favored by high productivity rates and by the development of dysaerobic bottom-water conditions. The dynamic sedimentary environment likely led to the formation of early diagenetic phosphatic lids (which may have sealed off subjacent organic-rich layers) as well as to the rapid deposition of entire layers in the form of mud flows, thereby eventually enhancing the potential of organic-matter preservation. Our new age data suggest that at the El Capitan State Beach section the intervals characterized by high TOC values and maximum TOC accumulation rates (red marl), as well as significant quantities of in situ phosphates appeared in the late middle Miocene, i.e., during and after the major cooling phase at around 14.5 Ma. This implies that deposition of phosphate and organic carbon continued well after this cooling phase, thereby underlining the observation that preservation of organic carbon in the Monterey Formation is not only dependent on climate change during the mid Miocene but also on regional conditions.

none 13 si The Fukushima-labeled air mass arrival, and later the cesium-134 (134Cs), cesium-137 (137Cs) and particulate iodine-131 (hereafter noted 131Ip) maximum levels were registered in Europe at different dates depending on the location. Most of those data were obtained at low-altitude sampling areas. Here, we compare the airborne levels registered at different high-altitude European locations (from 850 m to about 3500 m). The integrated 137Cs activity concentration was not uniform with regard to the altitude even after a long travel time/distance from Japan. Moreover, the relation of integrated 137Cs vs. altitude showed a linear decrease up to an altitude of about 3000 m. A similar trend was noticed for 131Ip (particulate fraction) while it increased above 3000 m. Comparison with 7Be activity concentration showed that, as far as the high altitude location is concerned, the 137Cs and 134Cs maximum concentrations corresponded to the 7Be maximum, suggesting downdraft movements from high tropospheric or stratospheric layers to be responsible for 137,134Cs increase and peak values. This was also confirmed by high potential vorticity and low relative humidity registered during the peak values. Masson, Olivier; Bieringer, Jacqueline; Brattich, Erika; Dalheimer, Axel; Estier, Sybille; Penev, Ilia; Ringer, Wolfgang; Schlosser, Clemens; Steinkopff, Thomas; Steinmann, Philipp; Tositti, Laura; Beek, Pieter Van; Vismes-Ott, Anne de Masson, Olivier; Bieringer, Jacqueline; Brattich, Erika; Dalheimer, Axel; Estier, Sybille; Penev, Ilia; Ringer, Wolfgang; Schlosser, Clemens; Steinkopff, Thomas; Steinmann, Philipp; Tositti, Laura; Beek, Pieter Van; Vismes-Ott, Anne de

The Fukushima-labeled air mass arrival, and later the cesium-134 (

Peatlands are widespread and important natural archives of environmental change. Here we explore the potential of the recently introduced MBT–CBT proxy (methylation index and cyclisation ratio of branched tetraethers) to estimate past annual mean air temperature (MAT) based on the distribution of bacterially-derived branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in peat and coal. To this end, branched GDGTs in an ombrotrophic peat bog from Switzerland and three coal deposits of increasing maturity were analysed. For the surface of the bog, reconstructed annual MAT is higher than both measured annual MAT and measured in situ pore water temperature. Changes in the CBT ratio, considered a proxy for pH, with depth in the bog do not match with present day in situ pore water pH, but coincide with a peat stratigraphic boundary. This indicates that GDGTs down the bog profile are predominantly fossil and not derived from extant biomass. The MBT–CBT derived annual MAT record also shows a large drop at this stratigraphic boundary, which likely relates to past change in trophic status of the bog. Branched GDGTs are abundant in an immature lignite (vitrinite reflectance, Ro 0.25%), but occur in low amount in a slightly more mature coal (Ro 0.32%). Annual MAT could be reconstructed for the lignite alone and is higher than other proxy-based estimates from approximately the same time and location. Our results indicate potential for the application of the MBT–CBT proxy in peat and immature coals, but improved constraints on the effects of different types of peat on branched GDGT distributions as well as improved calibration of MAT estimates are needed before the method can be confidently applied.

Artificial radionuclides ( 137 Cs, 90 Sr, Pu, and 241 Am) are present in soils because of Nuclear Weapon Tests and accidents in nuclear facilities. Their distribution in soil depth varies according to soil characteristics, their own chemical properties, and their deposition history. For this project, we studied the atmospheric deposition of 137 Cs, 90 Sr, Pu, 241 Am, 210 Pb, and stable Pb. We compared the distribution of these elements in soil profiles from different soil types from an alpine Valley (Val Piora, Switzerland) with the distribution of selected major and trace elements in the same soils. Our goals were to explain the distribution of the radioisotopes as a function of soil parameters and to identify stable elements with analogous behaviors. We found that Pu and 241 Am are relatively immobile and accumulate in the topsoil. In all soils, 90 Sr is more mobile and shows some accumulations at depth into Fe–Al rich horizons. This behavior is also observed for Cu and Zn, indicating that these elements may be used as chemical analogues for the migration of 90 Sr into the soil.

The value of resistors generally changes with electrical current. For precision analog circuit layout, it is important to predict those resistance variations. For that purpose, we derive for the first time a simple analytic 3-D model to describe thermal resistance and self-heating, which we show as the dominant contribution to resistor nonlinearity for a wide range of resistors. The model shows good agreement with numerical simulations. Measured voltage coefficients of metal and polysilicon resistors can be fit to the model over a wide range of geometries. Finally, we show how thermal resistance can be reduced by placing metal bar structures underneath the resistor and apply the model to quantify the improvement.

We report the first demonstration of metal-insulator-metal (MIM) capacitors with Sm2O3/SiO2 laminated dielectrics featuring low quadratic voltage coefficient of capacitance (VCC) and high capacitance density for precision analog circuit applications. In comparison with a HfO2 MIM dielectric, the Sm2O3 MIM dielectric is found to show a smaller quadratic VCC and a similar dielectric constant. We also investigated the cancellation of the positive quadratic VCC of Sm2O3 through its combination with a SiO2 layer having a negative quadratic VCC. Thus, MIM capacitors with a Sm2O3/SiO2 laminated dielectric were fabricated with various Sm2O3 and SiO2 thickness combinations. Capacitors with the Sm2O3/SiO2 laminated dielectric exhibit tunable quadratic VCC and high capacitance density. Very low quadratic VCC at various capacitance densities were achieved. The leakage current mechanism is related to Poole-Frenkel emission at a high positive bias. A smaller quadratic VCC is obtained at higher frequencies. We also conducted an extensive physical characterization of Sm2O3 using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy.

We analysed the composition of phyllosilicate minerals in sediments deposited by the Rhone and Oberaar glaciers (Swiss Alps), in order to identify processes and rates of biogeochemical weathering in relation to glacial erosion. The investigated sediments are part of chronosequences consisting of (A) suspended, ”fresh” sediment in melt water; (B) terminal moraines from the Little Ice Age (LIA; approximately 1560–1850); and (C) tills of the Younger Dryas interval (YD; approximately 11'500y BP). Secondary weathering products associated with the suspended sediment have not been observed; we therefore exclude intermittent subglacial storage and weathering of this material and assume that the suspended sediment is directly derived from mechanically abraded bedrock. This implies that biogeochemical weathering processes started once the glacially-derived sediment was deposited in the proglacial area. The combination of a developing vegetation cover, the generally high permeability allowing the percolation of precipitation, and the chemical reactivity related to the dominance of fine-grained material ( Biotite weathering rates are calculated using the difference in the biotite content between unweathered and weathered glacial sediments within the investigated profiles. The reactive mineral surface area is estimated geometrically, both with regards to the total relative surface (WR T ) as well as to the relative edge surface (WR E ). WR T Biotite weathering rates are estimated as 10 − 13 –10 − 15 mol biotite m − 2 biotite s − 1 . WR E Biotite weathering rates are on the order of 10 − 13 –10 − 14 mol biotite m − 2 biotite s − 1 . Biotite weathering rates obtained by this study are in the order of one magnitude higher in comparison to other published field-based weathering rates. Using biotite as an indicator, we therefore suggest that glacially-derived material in the area of the Oberaar and Rhone glaciers is generally subjected to enhanced biogeochemical weathering, starting immediately after deposition in the proglacial zone and subsequently continuing for thousands of years after glacier retreat.

In this study we evaluate the dynamics of the biophile element phosphorus (P) in the catchment and proglacial areas of the Rhone and Oberaar glaciers (central Switzerland). We analysed erosion and dissolution rates of P-containing minerals in the subglacial environment by sampling water and suspended sediment in glacier outlets during three ablation and two accumulation seasons. We also quantified biogeochemical weathering rates of detrital P in proglacial sedimentary deposits using two chronosequences of samples of fresh, suspended, material obtained from the Oberaar and Rhone water outlets, Little-Ice-Age (LIA) moraines and Younger Dryas (YD) tills in each catchment. Subglacial P weathering is mainly a physical process and detrital P represents more than 99% of the precipitation-corrected total P denudation flux (234 and 540 kg km−2 yr−1 for the Rhone and Oberaar catchments, respectively). The calculated detrital P flux rates are three to almost five times higher than the world average flux. The precipitation-corrected soluble reactive P (SRP) flux corresponds to 1.88–1.99 kg km−2 yr−1 (Rhone) and 2.12–2.44 kg km−2 yr−1 (Oberaar), respectively. These fluxes are comparable to those of tropical rivers draining transport-limited, tectonically inactive weathering areas. In order to evaluate the efficiency of detrital P weathering in the Rhone and Oberaar proglacial areas, we systematically graded apatite grains extracted from the chronosequence in each catchment relative to weathering-induced changes in their surface morphologies (grades 1–4). Fresh apatite grains are heavily indented and dissolution rounded (grade 1). LIA grains from two 0–10 cm deep moraine samples show extensive dissolution etching, similar to surface grains from the YD profile (mean grades 2.7, 3.5 and 3.5, respectively). In these proglacial deposits, the weathering front deepens progressively as a function of time due to biocorrosion in the evolving acidic pedosphere, with mechanical indentations on grains acting as sites of preferential dissolution. We also measured iron-bound, organic and detrital P concentrations in the chronosequence and show that organic and iron-bound P has almost completely replaced detrital P in the top layers of the YD profiles. Detrital P weathering rates are calculated as 310 and 280 kg km−2 yr−1 for LIA moraines and 10 kg km−2 yr−1 for YD tills. During the first 300 years of glacial sediment exposure P dissolution rates are shown to be approximately 70 times higher than the mean global dissolved P flux from ice-free continents. After 11.6 kyr the flux is 2.5 times the global mean. These data strengthen the argument for substantial changes in the global dissolved P flux on glacial–interglacial timescales. A crude extrapolation from the data described here suggests that the global dissolved P flux may increase by 40–45% during the first few hundred years of a deglaciation phase.

Vertical profiles of concentration and C-isotopic composition of dissolved methane and carbon dioxide were observed over 26 months in the catotelm of a deep (6.5 m) peat bog in Switzerland. The dissolved concentrations of these gases increase with depth while CO 2 predominates over CH 4 (CO 2 ca. 5 times CH 4 ). This pattern can be reproduced by a reaction–advection–ebullition model, where CO 2 and CH 4 are formed in a ratio of 1:1. The less soluble methane is preferentially lost via outgassing (bubbles). The isotopic fractionation between CO 2 and CH 4 also increases with depth, with α C values ranging from 1.045 to 1.075. The isotopic composition of the gases traces the passage of respiration-derived CO 2 (from the near surface) through a shallow zone with methanogenesis of low isotopic fractionation (splitting of fermentation-derived acetate). This solution then moves through the catotelm, where methanogenesis occurs by CO 2 reduction (large isotopic fractionation). In the upper part of the catotelm the C-13-depleted respiration-derived CO 2 pool buffers the isotopic composition of CO 2 ; the δ 13 C of CO 2 increases only slowly. At the same time strongly depleted CH 4 is formed as CO 2 reduction consumes the depleted CO 2 . In the lower part of the catotelm, the respiration-derived CO 2 and shallow CH 4 become less important and CO 2 reduction is the dominant source of CO 2 and CH 4 . Now, the δ 13 C values of both gases increase until equilibrium is reached with respect to the isotopic composition of the substrate. Thus, the δ 13 C values of methane reach a minimum at intermediate depth, and the deep methane has δ 13 C values comparable to shallow methane. A simple mixing model for the isotopic evolution is suggested. Only minor changes of the observed patterns of methanogenesis (in terms of concentration and isotopic composition) occur over the seasons. The most pronounced of these is a slightly higher rate of acetate splitting in spring.

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ13Corg isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from ~ 2.5% to ~ 10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of Preactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The Corg/Ptotal and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.

During the Hauterivian three important phases of platform drowning, phosphogenesis and mesotrophic carbonate deposition along the northern margin of the Tethys are not mirrored by positive N 13 Ccarb excursions such as during the Valanginian and Aptian, but rather by decreasing to stable trends. The aim of this study is to understand the decoupling of organic carbon and phosphorus burial during the Hauterivian. For this purpose PO4-concentrations were determined from biogenic limestones from eight sections along a platform to basin transect. Integration with a previously obtained dataset for the Valanginian leads to a biostratigraphically calibrated high resolution phosphorus accumulation rate (mg/cm 2 /kyr) curve based on 575 data points. From the Late Valanginian to Early Hauterivian phosphorus accumulation rates increased nearly threefold from 0.75 mg/cm 2 /kyr to 2.1 mg/cm 2 /kyr. The phosphorus accumulation rate increase obtained in this study correlates well with a compilation based on ODP and DSDP records, indicating that phosphorus accumulation rates along the northern margin of the Tethys reflect global changes in P in- and output. A global rise in continental P input is thought to have resulted from intensified greenhouse climate conditions leading to increased riverine runoff. Coeval sea-level rise led to re-arrangement of circulation and oxygenation of bottom waters, which meant that P was increasingly well retained by means of Fe- and Mnoxyhydroxides. Furthermore, the NW margin of the Tethys may have been especially susceptible to phosphogenesis as it was influenced by cold water exchange with the Boreal Realm and prone to coastal upwelling. The Late Hauterivian witnessed sea-level fall, more sluggish circulation along the NW Tethyan margin and also globally lower weathering and erosion rates, leading to generally lower phosphorus accumulation rates. Increased regeneration of phosphorus might have occurred as circulation stagnated and bottom water oxygen levels decreased. Increased phosphorus input into Early Hauterivian oceans did not lead to the production of organic carbon-rich rocks, but rather to increased carbonate carbon burial, also seen in a decoupling between the N 13 Ccarb record (decreasing) and phosphorus accumulation rates (increasing). Decoupling of these records reflects the ecological recovery of the carbonate system after a prolonged phase of reef destruction during the late Early and Late Valanginian. Carbonate production in the

Monsoon climate is an important component of the global climatic system. A comprehensive understanding of its variability over glacial–interglacial time scales as well as of its effects on the continent and in the ocean is required to decipher links between climate, continental weathering and productivity. A detailed multiproxy study, including bulk and clay mineralogy, grain-size analysis, phosphorus geochemistry (SEDEX extraction), organic matter characterization, and nitrogen stable isotopes, was carried out on samples from ODP Sites 1143 and 1144 (Leg 184, South China Sea), covering the past 140 000 years. We tentatively reconstruct the complex sedimentation and climatic history of the region during the last glacial–interglacial cycle, when sea-level variations, linked to the growth and melting of ice caps, interact with monsoon variability. During interglacial periods of high sea level, summer monsoon was strong, and humid and warm climate characterized the adjacent continent and islands. Clay minerals bear signals of chemical weathering during these intervals. High calcite and reactive phosphorus mass accumulation rates (MARs) indicate high productivity, especially in the southern region of the basin. During glacial intervals, strong winter monsoon provided enhanced detrital input from the continent, as indicated by high detrital MAR. Glacial low sea level resulted in erosion of sediments from the exposed Sunda shelf to the south, and clay mineral variations indicate that warm and humid conditions still prevailed in the southern tropical areas. Enhanced supply of nutrients from the continent, both by river and eolian input, maintained high primary productivity. Reduced circulation during these periods possibly induced active remobilization of nutrients, such as phosphorus, from the sediments. Intense and short cold periods recorded during glacial and interglacial stages correlate with loess records in China and marine climatic records in the North Atlantic, confirming a teleconnection between low- and high-latitude climate variability.

We report the results of numerical and analytical simulations to test the hypothesis that downward vertical flow of porewater from the crests of domed alpine and kettle bogs controls vertical porewater distributions of major solutes such as Ca and Mg. The domed Etang de la Gruere bog (EGr), Switzerland, characterized by a vertical downward gradient of 0·04 and stratified layers of peat, is chosen as a field site for the model calibration and evaluation. The middle 4-m section of the 6·5 m thick bog peat is heavily humified and has a hydraulic conductivity of ∼10−5·6 cm s−1. Above and below, peat is less humified with a hydraulic conductivity of ∼10−3 cm s−1. Heuristic finite difference simulations, using Visual MODFLOW, of the bog hydraulics show that the higher conductivity peat at the bog base is critical to create the observed deep, local flow cells that substantively recharge porewater. Model results and Peclet number calculations show that before ∼7000 14C yr BP diffusion of solutes from underlying mineral soils controlled the vertical distribution of porewater chemistry. From 7000 to ∼1250 14C BP the porewater chemistry was probably controlled by both upward diffusion and downward advection, and after ∼1250 14C yr BP porewater chemistry was probably controlled by downward advection. Concentrations of conservative major solutes in the porewaters of alpine, ombrotrophic bogs are the net effect of both downward vertical porewater movement and upward vertical diffusion, the magnitudes of which are delicately poised to the configuration of the bog water table over time and subsurface peat stratigraphy. Copyright © 2002 John Wiley & Sons, Ltd.

The electrical performance of metal-insulator-metal capacitors with thicknesses from 3 to 13 nm was investigated. The magnitude of the negative quadratic voltage coefficient of capacitance (VCC) of was found to be inversely proportional to the square of its thickness. A postdeposition anneal at 400 reduced substantially. An equation based on the orientation polarization of the dipole moments in was derived, which fits the measured normalized capacitance density versus voltage across very well. This suggests that the negative quadratic VCC of is due to the orientation polarization.

The toxicity of heavy metals in natural waters is strongly dependent on the local chemical environment. Assessing the bioavailability of radionuclides predicts the toxic effects to aquatic biota. The technique of diffusive gradients in thin films (DGT) is largely exploited for bioavailability measurements of trace metals in waters. However, it has not been applied for plutonium speciation measurements yet. This study investigates the use of DGT technique for plutonium bioavailability measurements in chemically different environments. We used a diffusion cell to determine the diffusion coefficients (D) of plutonium in polyacrylamide (PAM) gel and found D in the range of 2.06-2.29 × 10(-6) cm(2) s(-1). It ranged between 1.10 and 2.03 × 10(-6) cm(2) s(-1) in the presence of fulvic acid and in natural waters with low DOM. In the presence of 20 ppm of humic acid of an organic-rich soil, plutonium diffusion was hindered by a factor of 5, with a diffusion coefficient of 0.50 × 10(-6) cm(2) s(-1). We also tested commercially available DGT devices with Chelex resin for plutonium bioavailability measurements in laboratory conditions and the diffusion coefficients agreed with those from the diffusion cell experiments. These findings show that the DGT methodology can be used to investigate the bioaccumulation of the labile plutonium fraction in aquatic biota.

In this letter, we investigate the dependence of the performance of metal-insulator-metal (MIM) capacitors with Sm2O3 dielectric on plasma treatment (PT) performed before Sm2O3 deposition, after Sm2O3 deposition, or both before and after Sm2O3 deposition. By performing PT in N2 ambient (PTN) after Sm2O3 dielectric formation, the effective quadratic voltage coefficient of capacitance (VCC) can be reduced from 498 to 234 ppm/V2 and the effective linear VCC can be reduced from 742.3 to 172 ppm/V for MIM capacitor with Sm2O3 dielectric having a capacitance density of ~ 7.5 fF/mum2. The leakage current density at +3.3 V can be reduced from 3.44 10-7 to 1.60 times 10-8 A/cm2 by performing PTN in both before and after Sm2O3 deposition. PTN after dielectric formation is an effective way to improve the performance of high-kappa dielectric MIM capacitors for RF and analog/mixed signal IC applications.

We report the first demonstration of metal-insulator-metal (MIM) capacitors with Sm2O3/SiO2 stacked dielectrics for precision analog circuit applications. By using the ldquocanceling effectrdquo of the positive quadratic voltage coefficient of capacitance (VCC) of Sm2O3 and the negative quadratic VCC of SiO2, MIM capacitors with capacitance density exceeding 7.3 fF/mum2, quadratic VCC of around -50 ppm/V2, and leakage current density of 1 times 10-7 A/cm2 at +3.3 V are successfully demonstrated. The obtained capacitance density and quadratic VCC satisfy the technical requirements specified in the International Technology Roadmap for Semiconductors through the year 2013 for MIM capacitors to be used in precision analog circuit applications.

The removal of Be-7 from lake surface waters (Lake Lugano, Switzerland/Italy) was studied from September 1995 to May 1996. During this period the atmospheric input and sedimentary flux of Be-7, as well as concentrations of dissolved (1 mm) Be-7 in the epilimnion were measured. The separation of dissolved, colloidal, and particulate fractions of Be-7 was carried out using continuous flow centrifugation (CFC) and tangential flow filtration (TFF) techniques. Lacustrine colloids (log Kc =6) were shown to be much more efficient sorbents for Be-7 than the suspended particles (log Kp 4–5). Particle concentrations Cp ranged from 0.5 to 2 mg/L. The ratio of colloid (>10 kD) to particle concentration Cc/Cp was close to 0.09 during winter months when detrital inputs are dominant, but was higher (0.16) in summer and in spring after an algal bloom. The Be-7 data were used to estimate coagulation rates of colloids. The highest coagulation rates (lambda coag = 0.4 d-1) along with the lowest Kc (log Kc = 5.2) were found after an algal bloom in spring.

Complete porewater profiles from two peat bogs in the Jura Mountains were analysed for major and trace inorganic anions and cations. At La Tourbiere des Genevez (TGe) and Etang de la Gruere (EGr), peat formation began approximately 5,000 and 10,000 years bp, respectively. The maximum depths of peat accumulation are 140 cm (TGe) and 650 cm (EGr); previous geochemical studies showed that the ombrogenic sections of the bogs extend to depths of approximately 20 cm (TGe) and 250 cm (EGr). Water samples were obtained using in situ diffusion equilibrium samplers (peepers), which allow filtered (0.2 μm) porewaters to be obtained while preventing degassing and oxidation. These samplers were found to be well suited to bog porewaters and allowed volatile (dissolved CO2, acetate) and redox-sensitive species (HS−, Fe2+) to be quantified without further sample preparation or treatment. Aqueous species concentrations were determined immediately afterwards using ion chromatography with either conductivity (acetate, HCO3−, Cl−, Br−, NO3−, HPO42−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+), amperometry (HS−), or absorbance detection (Fe(III) and Fe(II)). The comprehensive analyses of anions and cations allowed humic substances to be calculated by the difference in electrical charge balance (i.e., the anion deficit). Concentrations of total dissolved CO2 (2–12 mM) showed that carbonate equilibria play a significant role in the acid-base chemistry throughout the profiles. In near surface, ombrogenic porewaters with pH around 4, however, protons (approx. 160 μeq/L) are contributed mainly by the dissociation of humic substances (2–7 mM DOC). In the deepest, minerogenic layers H2CO3 is the predominant acid at both sites. At these depths, carbonate alkalinity (up to 3 meq/L at EGr, up to 8 meq/L at TGe) arises from reaction of the pore fluids with mineral matter in the underlying sediments. In the transition zone between the ombrogenic and minerogenic extremes, organic and inorganic acids are equal in importance. Unidentified organic S species accounted for 90–99% of total dissolved sulfur (ST) in the porewaters at TGe, with SO42− and HS− the dominant inorganic species; S species with intermediate oxidation states such as SO32− and S2O32− were always less than the detection limit of approximately 0.4 μM. At TGe the sulfate concentrations exceeded those of sulfide, with 1.25 and 0.25 μM, respectively, being typical. At EGr, ST and SO42− were comparable to the waters at TGe, but HS− at EGr was always less than the detection limit of 0.15 μM. At both sites dissimilatory sulfate reduction is limited by the low concentrations of sulfate supplied to the bog surfaces (i.e., atmospheric deposition only), and the uptake of sulfate and its conversion to organic S compounds by the living plants. Despite the anoxic condition of the waters, the ratio of Fe(III)T to Fe(II)T was always high: at EGr this ratio was generally 1:1, and even in the sulfidic waters at TGe the ratio was 1:3. PHREEQE was used to calculate the effect of complex-forming organic ligands on {Fe3+} and {Fe2+} in these porewaters. The relatively high ratios of Fe(III)T compared to Fe(II)T can be explained in terms of the much greater thermodynamic stability of the organic complexes of Fe3+ compared to those of Fe2+.

The atmospheric nuclear testing in the 1950s and early 1960s and the burn-up of the SNAP-9A satellite led to large injections of radionuclides into the stratosphere. It is generally accepted that current levels of plutonium and caesium radionuclides in the stratosphere are negligible. Here we show that those radionuclides are present in the stratosphere at higher levels than in the troposphere. The lower content in the troposphere reveals that dry and wet deposition efficiently removes radionuclides within a period of a few weeks to months. Since the stratosphere is thermally stratified and separated from the troposphere by the tropopause, radioactive aerosols remain longer. We estimate a mean residence time for plutonium and caesium radionuclides in the stratosphere of 2.5-5 years. Our results also reveal that strong volcanic eruptions like Eyjafjallajökull in 2010 have an important role in redistributing anthropogenic radionuclides from the stratosphere to the troposphere.

Equilibrium diffusion chambers ("peepers") have been constructed to collect anoxic pore waters in bogs without degassing and/or oxidizing the samples. These samplers have been constructed of Plexiglass, either as a long board with a series of sampling chambers for close interval analyses near the surface of a bog, or as single chambers inserted at greater depths (1 to 6 m). Prior to installation, the chambers have been filled with deaerated, deionized water, and have been covered by a 0.2 microm membrane filter; this membrane allows the dissolved constituents in the waters to equilibrate with the deionized water in the chamber by diffusion. The samplers have been allowed to equilibrate in the bog for 4 to 6 weeks. Thereafter, they have been withdrawn into N(2)-filled glove bags. Individual chambers have been sampled in the field by inserting a syringe through the glove bag; these syringes have been used immediately upon the arrival in the lab to analyze volatile and redox-sensitive species by ion chromatography. The effectiveness of this sampling approach has been demonstrated by measuring the concentrations of the dominant volatile acids in these waters (H(2)CO(3)) and two redox sensitive species (Fe(2+) and HS(-)). The procedure described here should be applicable also to trace metal speciation studies, provided that appropriate checks are made for all possible sources of contamination.

We report monthly averages of weekly 7 Be and 22 Na concentrations in aerosol samples collected with high volume aerosol filters at 5 sampling sites in Switzerland from 1994 to 2011 ( 7 Be) and from 2000 to 2011 ( 22 Na). Monthly average concentrations of the two cosmogenic isotopes varied between 2600 and 4600 μBq/m 3 for 7 Be and between 0.2 μBq/m 3 and 0.5 μBq/m 3 for 22 Na. The 22 Na concentration in ground level air strongly increased from March to May, while a corresponding 7 Be increase was seen from March until July. The observed variations of the 7 Be and 22 Na activities together with the changes in the 7 Be/ 22 Na ratio indicate input of stratospheric air between March and May, increased mixing of upper tropospheric air from June to August, and less exchange between the upper and lower troposphere in autumn and winter. Additionally, the 11-year solar cycle is clearly seen in the annual averages of the 7 Be concentrations.

Organic-rich, anaerobic pore waters from peatlands have been sampled using peepers which filter the waters in situ. Pore waters collected using these devices are neither oxidized nor degassed. Anions (F - , acetate, formate, Cl - , HCO 3 - , NO 2 - , Br - , NO 3 - , PO 4 3- , SO 4 2- and S 2 O 3 2- ) and cations (Na + , K + , Mg 2+ and Ca 2+ ) were analyzed using ion chromatography (IC). With a Na borate gradient increasing from 4.9 to 24.5 mM, F - , acetate, formate, Cl - , HCO 3 - , NO 3 - , PO 4 3- and SO 4 2- can be quantified in one run (12 min). The high concentrations of dissolved CO 2 in the pore waters are manifested as a broad HCO 3 - peak in the chromatograms. This allows HCO 3 - to be quantified (with a linear calibration curve from 40 to 800 μg/g), but interferes with the Br - and NO 2 - peaks. Measurement of these two species requires sample degassing to remove dissolved CO 2 . While S 2 O 3 2- can also be determined using a modified borate gradient (7 to 35 mM), its concentration in the pore water samples is below the detection limit of approximately 30 ng/g. In an earlier report, IC measurements of Na + , K + , Mg 2+ , and Ca 2+ in peat bog pore waters were found to yield significantly lower concentrations compared to inductively coupled plasma analyses of the same samples. Here, 20 mM methanesulfonic acid was used to acidify the pore waters to pH 2 prior to injection. Following this sample pretreatment, the measured concentrations of Na + , K + , Mg 2+ , and Ca 2+ obtained by IC were significantly higher than in the unacidified samples and were in good agreement with the concentrations determined independently using inductively coupled plasma mass spectrometry.

Pore waters from two peat bogs in the Jura mountains, Switzerland, were analyzed for Fe 2+ and Fe 3+ using ion chromatography (IC). In order to prevent oxidation, the samples were collected under N 2 using in situ diffusion-equilibrium pore water samplers (peepers). The metals were separated on a Dionex CS-5 analytical column and detected by visible absorbance at 520 nm after post-column mixing of the pyridine-2,6-dicarboxylic acid eluent with 4-(2-pyridylazo)resorcinol. The concentrations of total Fe determined by IC ranged from 0.1 to 2 μg/g and agreed well with total Fe measured in the same samples with inductively coupled plasma spectroscopy. However, a problem is caused by humic substances present in the samples because they gradually contaminate the column. Contaminated columns show reduced precision, peak tailings and reduction of Fe 3+ to Fe 2+ on the column. The relatively high Fe 3+ concentrations measured in the pore waters are not an oxidation artefact, but instead reflect the stabilization of the trivalent oxidation state by complexation with humic substances.

Organic-rich, acidic, anaerobic pore waters from two peat bogs in Switzerland were analyzed for sulfide using ion chromatography (IC) with electrochemical detection. With one Dionex CarboPac PA1-Guard as separator column and another one in front of the 100-μl injection loop, it was possible to separate sulfide and cyanide with detection limits as low as 1 ng/g sulfide. Pore water samples were obtained using in situ diffusion-equilibrium pore water samplers (peepers). Samples were collected under N2 to prevent sample oxidation. Instead of preserving the dissolved sulfide with zinc acetate, sulfide was preserved by collecting the samples into 5-ml syringes containing 1 ml of concentrated eluent. In this way, the pH of the sample increased to 12 and no volatile H2S was lost. Measured sulfide concentrations in the pore waters were all below 20 ng/g. Some samples were spiked in the field to contain 5 ng/g sulfide. This amount could be detected using IC, whereas unspiked aliquots of the same samples yielded no sulfide peak. Based on the measurements of total dissolved sulfur, sulfate and sulfide, almost all of the sulfur in the pore waters is organically bound. The IC method presented here is well suited for the measurement of acid-volatile sulfur (AVS), and was applied to AVS measurements of some pore water samples. Trapping the volatilized H2S in eluent gave low detection limits and allowed rapid analyses without further treatment of the solution. The measured concentrations of AVS were not significantly different from the concentrations of free dissolved sulfide, suggesting that metal-sulfide complexes are relatively unimportant sulfur species in these waters.

In this study, electromigration (EM) reliability of TSV-microbump (μ-bump) joints was investigated. Sn-based μ-bumps with three different schemes of metallization were tested under current stressing at elevated temperatures. EM-stressed μ-bumps, together with thermal anneal-only μ-bumps and as-received controls, were cross-sectioned and characterized using scanning electron microscope (SEM), energy dispersed x-ray (EDX) and focused ion beam (FIB). Intermetallic compound (IMC) growth kinetics under EM for the three types of metallization were obtained, and compared with those subjected to thermal annealing only. Results showed good EM performance of the TSV μ-bump joints, indicating that IMC formation plays an important role in improving the EM reliability of μ-bump joints. However, non-EM related voids were observed in the μ-bumps, and the voiding mechanisms were discussed.

To enable the miniaturization, electrical performance and heterogeneous functionality needs for emerging Analog applications, a stacked Wafer-level Chip Scale Package (WCSP) package platform has been developed using Through-Silicon Via (TSV) technology. This allows stacking of ICs, MEMS, passives and other components in the vertical direction onto active or passive TSV wafers, to create innovative System-in-Package (SiP) product solutions. Since Analog devices are small in size and cost is a key care about, a careful selection of the integration flow is required to achieve a low cost packaging solution. In this work, an integration flow for the stacked WCSP package is presented, along with development details for the Chip-on-Wafer (CoW) bonding and wafer overmolding unit processes. The test vehicle was 3mm × 3mm in size and used 25u diameter Cu TSVs in a 200mm diameter wafer. Interconnect reliability evaluations were done with different micro-bump Under Bump Metallurgy (UBM) and TSV tip surface finish metallization combinations. Wafer ovemolding development included warpage, saw and adhesion evaluations with multiple mold materials. A back-end assembly flow was established with a mass reflow bonding process and an overmold material with low CTE and intermediate T g and modulus. Samples were prepared with mold-on-die and exposed die package structures. Excellent time-zero yields were obtained, with an average TSV micro-bump interconnect resistance of 25 mohms. Results and failures modes from preliminary reliability testing are included.

Background and aims: Uptake of 90Sr and 137Cs in plants varies widely between soil types and between plant species. It is now recognized that the radionuclide uptake in plants is more influenced by site-specific and plant-specific parameters rather than the bulk radionuclide concentration in soil. We hypothesized that the stress which Alpine plants experience because of the short growing season may enhance the phylogenetic effect on the 137Cs and 90Sr transfer factors as well as the dependency of the uptake by plant to the concentrations of exchangeable Ca and K of soils. Methods: We carried out a field study on the 90Sr and 137Cs uptake by 11 species of Alpine plants growing on 6 undisturbed and geochemically different soils in the Alpine valley of Piora, Switzerland. Results: Results show that a strong correlation exists between the log TF and the log of exchangeable Ca or K of the soils. Conclusions: Cs uptake by Phleum rhaeticum (Poales) and Alchemilla xanthochlora (Rosales) is more sensitive to the amount of exchangeable K in the soil than the corresponding uptake by other orders. Moreover, the 90Sr results indicate a phylogenetic effect between Non-Eudicot and Eudicots: the order Poales (Phleum rhaeticum) concentrating much less 90Sr than Eudicots do