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International audience; In this paper we explore a speleothem δ18O record from Palestina cave, northwestern Peru, at a site on the eastern side of the Andes cordillera, in the upper Amazon Basin. The δ18O record is interpreted as a proxy for South American Summer Monsoon (SASM) intensity and allows the reconstruction of its variability during the last 1600 years. Two periods of anomalous changes in the climate mean state corresponding to the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) periods identified in the Northern Hemisphere are recognized in the record, in which decreased and increased SASM activity, respectively, have been documented. Variations in SASM activity between the MCA and the LIA seem to be larger over the northern part of the continent, suggesting a latitudinal dependence of the MCA footprint. Our results, based on time series, composite and wavelet analyses, suggest that the Atlantic Multidecadal Oscillation (AMO) plays an relevant role for SASM modulation on multidecadal scales (∼65 years), especially during dry periods such as the MCA. Composite analyses, applied to evaluate the influence of the AMO on the Palestina cave δ18O and other δ18O-derived SASM reconstructions, allow insight into the spatial footprints of the AMO over tropical South America and highlight differences between records during key studied periods. This work also reveals that replicating regional climate signals from different sites, and using different proxies is absolutely essential for a comprehensive understanding of past changes in SASM activity.

Speleothem growing is closely linked to warm climates with a positive hydrological balance. Mild temperatures and hydrological availability are conditions that tend to stimulate soil CO2 production due to denser vegetation cover and higher microbial activity. In such situations, waters enriched with dissolved carbonate are common and can infiltrate in the karstic system. This study compiles 158 dates from 34 speleothems collected in nine caves in the Northeastern Iberia to distinguish the time intervals with speleothem formation. A clear connection of speleothem growth and interglacial periods is established but precesssional influence is also observed, being periods of maxima insolation those with ideal conditions to produce karstic formations such as speleothems. The Holocene is without doubt the best represented period in the available records. However, last centuries were not characterized by an important development of speleothems in the studied caves. © Universidad de La Rioja., El crecimiento de espeleotemas está estrechamente ligado a climas templados caracterizados por un balance hidrológico positivo. Las temperaturas cálidas y la disponibilidad hídrica son condiciones que estimulan la producción de CO2 en el suelo por la vegetación y por los microrganismos y facilitan, por tanto, que aguas sobresaturadas en carbonato se infiltren en el sistema kárstico. Este trabajo recopila 158 dataciones de un total de 34 espeleotemas obtenidas en nueve cuevas distintas del noreste peninsular y permite distinguir para los últimos 400 ka los periodos con crecimiento de espeleotemas. La relación de la formación de espeleotemas con los periodos interglaciares aparece clara, pero además se observa una influencia de los ciclos precesionales, siendo los periodos de máxima insolación aquellos más idóneos para el desarrollo de estas formaciones kársticas. Aunque el Holoceno es, sin duda, el periodo mejor representado con los registros disponibles, los últimos siglos no se caracterizaron por un gran desarrollo espeleotémico en las cuevas estudiadas., Este estudio se ha financiado principalmente gracias a los proyectos regionales GALC- 021/2008 y GA-LC-030/2011 y a la ayuda de investigación del Geoparque del Sobrarbe (2011). También agradecemos la financiación conseguida a través de los proyectos HIDROPAST (MEC CGL2010 1637), CGL2009-10455/BTEGRACCIE-Consolider (CSD2007-00067) y Grupo Paleoambientes del Cuaternario. No hubiera sido posible sin la ayuda y colaboración del Servicio Territorial de Mediambiente de Soria, Rubén Gallego (Gestor, Soriaventura), Lorenzo Saéz y Roberto F. García (G.E. Niphargus y Espeleofoto. com), Sergio Blanco (Gestor, Beloaventura), Ramón Queraltó y Carles Pons (Asociación Científico-Espeleológica de Cotiella), y Jaume Mas y Xavier Fuertes (Grupo de Espeleología de Badalona). Agradecemos a Ramiro Moreno y a Miguel Ángel de la Mata por los datos climáticos, a Miguel Sevilla por la figura de localización, a Aida Adsuar y Beatriz Bueno por su apoyo en el trabajo de campo y a Xianfeng Wang y Sushmita Dasgupta por su ayuda con el procedimiento analítico de las dataciones de U-Th.

A stalagmite-based isotope record (No. H82) from Nanjing Hulu Cave, spanning from 16.5 to 10.3 ka BP, provided strong evidence for a coherence relation between the East Asian summer monsoon (EASM) and the North Atlantic climates on millennial time scales. Here we extend the high-resolution δ18O time series back to 22.1 ka BP with additional 7 230Th dates and 573 stable isotope measurements on the lower part of that sample. The new record with a decadal resolution, piecing together with the previous data, provides a detailed, complete Last Glacial Maximum (LGM)/deglacial history of the EASM. Two centennial-scale weak monsoon events are detected within the analogue H1 event, and can be correlated to corresponding Greenland temperature shifts. This suggests a rapid re-organization of atmospheric and oceanic circulations during the ice-rafted debris (IRD) event in North Atlantic. A strengthened EASM event spanning from 19.9 to 17.1 ka BP, firstly reported here, reaches on average a half of the monsoon intensity of Bolling warming with its peak close to the full level. Taking all available evidence from continental and oceanic sediments into consideration, we suggest that a forcing mechanism behind the event would be a positive feedback of the tropical Pacific Super-ENSO cycles in response to precessional changes in solar irradiation.

Middle Holocene cultures have been widely studied round the E-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and E-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate–culture relation at fine time scales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from the W-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in N-Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yr BP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400–3800 yr BP blankets the onset of cave abandonment shortly after ca. 4403 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption.

Speleothem δ18O and δ13C signals have already proven to enable climate reconstructions at high resolution. However, seasonally resolved speleothem records are still scarce and often difficult to interpret in terms of climate due to the multitude of factors that can affect the proxy signals. In this paper, a fast growing (up to 2 mm yr−1) seasonally laminated speleothem from the Han-sur-Lesse cave (Belgium) is analyzed for its δ18O and δ13C values, layer thickness and changes in calcite fabric. The studied part of the speleothem covers the most recent 500 years as indicated by layer counting and confirmed by 20 U/Th-ages. Epikarst recharge occurs mainly in winter and lesser during spring and fall. a good correlation can be established between lower winter temperatures and lower winter precipitation (DJF) based on the measured data by the Belgian meteorological institute since 1833 indicating that a dry winter is also a cold winter. Colder and dryer winters cause lower winter recharge and generally drier conditions in the cave. Lower winter recharge decreases the amount of isotopically light (δ18O) winter precipitation added to the epikarst in comparison to the heavier spring and fall waters, which leads to a net increase in δ18O value of the water in the epikarst. Increased δ18O values in the Proserpine are consequently interpreted to reflect colder and dryer winters. Higher δ13C signals are interpreted to reflect increased prior calcite precipitation (PCP) due to colder and dryer winters, when recharge is lower. Thinner layers and darker calcite relate to slower growth and occur when drip rates are low and when the drip water calcium ion concentration is low due to increased PCP, both caused by lower recharge during periods with colder and dryer winters. Exceptionally cold and dry winters cause the drip discharge to decrease under a certain threshold value inducing anomalies in the measured proxy records. Such anomalies occur from 1565 to 1610, from 1770 to 1800, from 1810 to 1860 and from 1880 to 1895 and correspond with exceptionally cold periods in proxy-based, historical and instrumental records and may relate to different factors such as negative winter NAO phases, lower solar irradiance and/or volcanic eruptions. When the discharge threshold is not reached, lower amplitude variations are observed such as between 1479 and 1565 and between 1730 and 1770 with two periods of relatively warmer and wetter winters. Between 1610 and 1730 a period of relatively cooler and dryer winters occurs and may relate to a decrease in solar irradiance during the Maunder Minimum (1640–1714). Seasonal δ18O variations indicate a 2.5 °C seasonality in cave air temperature during the two periods with warmer and wetter winters (1479–1565 and 1730–1770), and correspond to the cave air temperature seasonality observed today. a smaller 1.5 °C seasonality in cave air temperature occurs during the interval with colder and wetter winters between 1610 and 1730 and suggests colder summers. The δ13C seasonal changes suggest that the seasonality in discharge was lower than the one observed today with a short interval of increased seasonality between 1600 and 1660 reflecting stronger summer PCP-effects due to decreased winter recharge.

International audience; In this paper we explore a speleothem δ18O record from Palestina Cave, North Eastern Peru, at a site on the eastern side of the Andes cordillera, upper Amazon Basin, interpreted as a proxy for South America Summer Monsoon (SASM) intensity. This record allows reconstructing SASM activity with 5 yr time resolution over the last 1600 yr, spanning two major periods of climate variability: the Medieval Climate Anomaly (MCA; 900-1200 AD) and Little Ice Age (LIA 1400-1850 AD) recognized as periods of decrease and increase SASM activity respectively. Time series and wavelet analyses reveal decadal to multidecadal frequencies. Our results suggest that Atlantic Multidecadal Oscillation mode (AMO) plays an important role for SASM modulation on multidecadal scale (~65 yr), especially over dry periods such as observed during MCA. Frequencies of 8 and 25 yr simultaneously with multidecadal signal (65 yr) are found over the LIA. and suggest that those modes could be related to North Atlantic Oscillation (NAO) and Interdecadal Pacific Oscillation mode (IPO). Comparison with other South American Paleoprecipitation records shows that the Atlantic and Pacific decadal to multidecadal variability and their teleconnections play an important role in the intensity and the regional patterns of rainfall distribution during the last 1600 yr.

We extend a methodology here for formalized development and validation of a component failure model in a system-modeling context. The component thermal-failure characterization problem we consider is a real one, having a rather full set of aspects and elements of model development and validation that may be encountered in practice. The interplay between modeling, experiments, and statistics illustrated here provides an interesting application example of model development and validation work.

The ferromagnetic transition temperatures of $\mathrm{Mn}{\mathrm{As}}_{x}{\mathrm{Sb}}_{1\ensuremath{-}x}$ solid solutions for $0\ensuremath{\le}x\ensuremath{\le}1$ have been measured as a function of pressure up to 4.5 kbar. Previous work has shown that for the solid solutions in the concentration range $0.9\ensuremath{\lesssim}x\ensuremath{\le}1$ the magnetic transition is first order and is accompanied by a hexagonal-to-orthorhombic structure transformation, while for $0\ensuremath{\le}x\ensuremath{\lesssim}0.9$ the magnetic transition is second order with no structural change. We have found that the initial pressure derivative of the transition temperature ($\frac{\ensuremath{\partial}{T}_{c}}{\ensuremath{\partial}P}$) changes discontinuously in the narrow concentration range $0.87\ensuremath{\lesssim}x\ensuremath{\le}0.90$, further demarcating the first- and second-order regions. We also find that substituting Sb for As in the first-order region increases the critical pressure ${P}_{c}$ which stabilizes the orthorhombic phase to the lowest temperature. This further supports Goodenough's observation of a critical molar-volume range in which the first-order transformation occurs. The solid solutions which exhibit second-order behavior are analyzed using an itinerant-electron ferromagnet model.

The effect of pressure on the resistivity of Ag1−cAuc solid solutions has been measured up to 4 kbar in the temperature range 4 to 273 °K. Solid and fluid helium were used as the pressure transmitting media. The pressure derivatives of the total resistivity, ϱ−1 dϱ/dP, for the alloys in the concentration range c = 0.1 to 0.9 were observed to be negative and to increase in magnitude with increasing temperature. It is shown that the magnitude and sign of ϱ−1 dϱ/dP is primarily determined by the pressure derivative of the residual resistivity. The volume derivative of the residual resistivity, d In ϱ0/d ln V, was found to be positive and concentration dependent. It is suggested that the influence of the filled d-bands on the scattering potential is responsible for the behavior of d ln ϱ0/d ln V. Der Einflus von Druck auf den spezifischen Widerstand von Ag1−cAuc-Mischkristallen wurde bis 4 kbar im Temperaturbereich von 4 bis 273 °K gemessen. Als Druckubertragungsmittel wurde festes bzw. flussiges Helium verwendet. Es wurde festgestellt, das die Druckableitungen des Gesamtwiderstands, ϱ−1 dϱ/dP, fur die Legierungen im Konzentrationsbereich c = 0,1 bis 0,9 negativ sind und mit steigender Temperatur zunehmen. Es wird gezeigt, das Grose und Vorzeichen von ϱ−1 dϱ/dP vorwiegend durch die Druckableitung des spezifischen Restwiderstands bestimmt werden. Die Volumenableitung des spezifischen Restwiderstands d ln ϱ0/d ln V ist positiv und konzentrationsabhangig. Es wird vorgeschlagen, das der von den vollbesetzten d-Bandern auf das Streupotential ausgeubte Einflus fur das Verhalten von d ln ϱ0/d ln V verantwortlich ist.

The thermal expansion of eight Li–Mg alloys spanning the bcc solid‐solution range (100–31‐at.% Li) has been measured from 80° to 370°K using a fused silica dilatometer. The room‐temperature linear thermal‐expansion coefficients were determined for each alloy from cubic fits of the data between 250° and 370°K. It was found that the linear expansion coefficients of the alloys decreased from a value of 4.6±0.1×10−5 °K−1 for pure Li to 3.9±0.1×10−5 °K−1 for an alloy containing 31‐at.% Li. The linear expansion coefficients for Mg‐rich alloys are unusually high; the expansion coefficient decreases by only 15% over the solid‐solution range, whereas the melting point increases by 190%. The unusual behavior of the thermal‐expansion coefficients is in direct contrast with the compressibilities of the alloys which decrease rapidly with increasing Mg content. As a result, the room‐temperature Gruneisen parameter increases from a value of about 0.95 for pure Li to 1.75 for the 31‐at.% Li alloy.

The initial pressure derivative of the Curie temperature of Zr${\mathrm{Zn}}_{2}$ has been measured under hydrostatic conditions, yielding a value of - (1.95\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode^\circ\else\textdegree\fi{}K ${\mathrm{kbar}}^{\ensuremath{-}1}$ for a sample with a Curie temperature of (21.5\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode^\circ\else\textdegree\fi{}K. This is in good agreement with the values of -1.8 and -2.4\ifmmode^\circ\else\textdegree\fi{}K ${\mathrm{kbar}}^{\ensuremath{-}1}$ predicted by Wohlfarth using the model of a very weak itinerant ferromagnet and two different methods of calculation. The present measurement allows an estimate of the effective degeneracy temperature for Zr${\mathrm{Zn}}_{2}$ of 300\ifmmode^\circ\else\textdegree\fi{}K and an estimate for the initial differential susceptibility of 6.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ emu ${\mathrm{g}}^{\ensuremath{-}1}$ ${\mathrm{Oe}}^{\ensuremath{-}1}$.

Serious difficulties encountered with a vibrating sample magnetometer in an Nb3Sn ribbon wound superconducting solenoid are described. A useful sensitivity of 10−4 emu was achieved, but absolute accuracy was severely limited by unstable magnetic image effects which precluded proper calibration. It is suggested that use of large bore solenoids will overcome the basic difficulties.

The enzyme-linked immunosorbent assay (ELISA) described by Engvall and Perlmann, which uses antigen-coated tubes and enzyme-labeled anti-immunoglobulin, has been used for the detection of antibodies against streptococcal M protein. The antigen used in the assay was obtained by guanidine extraction of type M-12 streptococcal cell walls followed by hydroxyapatite chromatography. This antigen has the capacity to elicit bactericidal antibodies in rabbits. The results show that the ELISA is specific and highly sensitive for the detection of antibodies in rabbit and human antisera. Preliminary results suggest that, when M-12 antigen is used, the antibodies detected by ELISA are the same antibodies detected in the bactericidal test. The assay has been performed with human and rabbit sera. There was a 96% agreement between bactericidal and ELISA results with rabbit sera and 97.5% agreement with human sera. All bactericidal antibody-positive sera tested thus far yielded positive ELISA results.

The development of an assay to measure the human immune response to pneumococcal capsular polysaccharides is described.

Specific polymer dielectric materials have been identified that can be used to minimize the discharge of capacitors upon exposure to ionizing radiation. The testing procedures used to qualify the radiation-induced conductivity in capacitor dielectrics are discussed, and a comparison is made of various “radiation-hard” dielectrics that display low levels of radiation-induced conductivity.

The pressure dependences of the magnetic transition temperatures of Cr‐2.5 and 2.8 at.% Fe single crystal alloys have been determined by electrical resistance and ultrasonic measurements. The results show that the 1 bar triple point (P,I,C) in the temperature concentration plane occurs at a concentration of ∠2.5 at.% Fe in contrast to the previously published value of 4 at.% Fe. The high pressure data showed an abrupt change in the pressure dependence of the I‐C transition at 3.3 kbar, from which it is speculated that an additional magnetic phase exists.

Using an itinerant model for ferromagnetism, we have analyzed the experimental results for the pressure (P) dependence of the Curie temperature (Tc) using present and previously reported data for MnSb and present high pressure results for the Fe. 65(Ni1−xMnx).35 Invars with 0 ≤ × ≤ 0.19. Striking agreement between theory and experiment is obtained for MnSb. For the Mn‐substituted Invar alloys, on the other hand, there is a marked disagreement at high pressures between the experimental results and the predictions of the model. The data on the x = 0.19 alloy show only vestiges of the ferromagnetic state at 32 kbar (our highest pressure) and suggest that this state should vanish at pressures ≳ 36 kbar.

The effect of hydrostatic pressure (up to 3.3 kbar) on the magnetic transitions of a Cr‐2.8 at.% Fe single crystal alloy has been determined via electrical resistance and acoustic measurements. These are the first ultrasonic measurements on these alloys and the combination of the two techniques allows a clear identification of the phase boundaries. Our results show that only the paramagnetic to commensurate‐antiferromagnetic transition occurs at 1 bar and that the incommensurate‐antiferromagnetic phase does not exist below ∼ 0.5 kbar. These observations are compared to previous studies on alloys containing between 2 and 4 at.% Fe.

It is shown that in a cryostat the use of an isothermal path leading out of an applied magnetic field will ensure insensitivity of thermocouples to the magnetic field. Tests in liquid helium in such a cryostat were conducted on a number of thermocouples with the applied field ranging up to 100 kG. The results showed that Cu‐constantan, Cu–Au 0.03 at.% Fe, and Cu–Au 2.1 at.% Co thermocouples are not affected by magnetic fields. In subsequent work up to 300 K the first two thermocouples listed were still insensitive to magnetic fields. The third thermocouple was not tested at the higher temperatures.

The Seebeck coefficients of lutetium have been measured along the [10\ifmmode\bar\else\textasciimacron\fi{}10] ($b$ axis) and [0001] ($c$ axis) crystallographic directions as a function of temperature from 8 to 300 K. These results are compared with the single-crystal Seebeck coefficients of yttrium and discussed in terms of the Fermi surface.

The ferromagnetic transition temperatures of MnAsxSb1−x solid solutions for 0≤x≤1 have been measured as a function of pressure up to 4.5 kbar. Goodenough et al.1 have shown that for the alloys in the composition range 0.9≲x≤1 the magnetic transition is first order and is accompanied by a hexagonal to orthorhombic structural transformation, while for 0≤x≲0.9 the magnetic transition is second order. We find that this system exhibits a number of unusual features: (i) The change from first to second‐order behavior occurs within a narrow concentration range 0.88