Further effects of charged aerosols on summer mesospheric radar scatter

In an earlier paper, we showed that charged aerosols play a crucial role in enhancing radar echoes from the summer polar mesosphere through reduced diffusion turbulent scatter and dressed aerosol scatter (Cho et al., 1992a). Here, we explore the effects of charged aerosols on radar scatter through ‘fossil’ turbulence and electron density depletion layers. We find that the former can produce radar scatter even after the decay of neutral gas turbulence, while the latter, which are probably produced by the scavenging of free electrons by ice particles, are a candidate for causing partial reflection or Fresnel scatter. Furthermore, we examine the mutual aerosol interaction restriction on dressed aerosol scatter more closely. We find that a high ambient electron density and low aerosol number density are needed for effective dressed aerosol scatter to occur. We then show that very small (less than 1 nm radii), negatively charged aerosols enhance electron diffusivity, and thus inhibit radar scatter. Also, ice aerosol sedimentation, in the light of the reduced diffusion theory, leads us to conclude that the statistical peak in Polar Mesospheric Summer Echoes (PMSE) power should be located between the mean mesopause and the average noctilucent cloud (NLC) height, which agrees with observations. Finally, we invoke time lags in the ice particle formation cycle to account for the observed non-correlation between PMSE and NLC occurrence.     

Incoherent scatter spectral measurements of the summertime high-latitude D-region with the EISCAT UHF radar

Measurements of incoherent scatter spectra from the auroral D-region were obtained during the summer of 1985 using a sophisticated pulse-to-pulse correlation technique with the EISCAT UHF radar. The spectral width variations with altitude are interpreted in terms of ion-neutral collision frequency, neutral temperature, mean positive ion mass and negative ion number density. Close agreement with predictions of currently available atmospheric models is obtained, except for a narrow layer around 86 km altitude. This layer showed evidence of increased positive ion mass for most of the experiment, and for short intervals indicated a mean ion mass close to 200 a.m.u. It is suggested that the layer is composed of proton hydrates in the vicinity of a structured noctilucent cloud, and that the index of hydration is occasionally large.     

Short-lived bursts of plasma velocity in the auroral zone. I. Observational evidence from radar measurements

Sudden bursts of plasma velocity, including an equatorward component, are often observed by EISCAT in the evening and midnight sectors. Typically, these bursts last for about 3–7 min, and are repeated in a quasi-periodic sequence. Quasi-periodic equatorward bursts are also observed by the SABRE coherent scatter radar and these measurements confirm that the pattern can extend over several degrees of latitude and at least 10° of longitude.     

Preliminary results from a study of the F-region heating during an intense aurora observed by EISCAT

Observations of large time variations in the ionospheric F-region temperature derived from EISCAT are compared with simultaneous observations of the E- and F-region plasma densities. The observations suggest that the F-region may be heated by current driven instabilities generated during intense precipitation of auroral electrons.     

Observations of auroral E-region plasma waves and electron heating with EISCAT and a VHF radar interferometer

Two radars were used simultaneously to study naturally occurring electron heating events in the auroral E-region ionosphere. During a joint campaign in March 1986 the Cornell University Portable Radar Interferometer (CUPRI) was positioned to look perpendicular to the magnetic field to observe unstable plasma waves over Tromsø, Norway, while EISCAT measured the ambient conditions in the unstable region. On two nights EISCAT detected intense but short lived (< 1 min) electron heating events during which the temperature suddenly increased by a factor of 2–4 at altitudes near 108 km and the electron densities were less than 7 × 10⁴ cm⁻³. On the second of these nights CUPRI was operating and detected strong plasma waves with very large phase velocities at precisely the altitudes and times at which the heating was observed. The altitudes, as well as one component of the irregularity drift velocity, were determined by interferometric techniques. From the observations and our analysis, we conclude that the electron temperature increases were caused by plasma wave heating and not by either Joule heating or particle precipitation.     

Prehistoric demography of North America inferred from radiocarbon data

Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential sources of bias in such records are poorly understood. In this paper, we use more than 25,000 radiocarbon dates extracted from the Canadian Archaeological Radiocarbon Database (CARD) to estimate long-term population trends in North America, while critically examining biases in such records. The frequency distribution of CARD dates shows a positive curvilinear pattern, such that older dates exist in lower numbers than more recent dates, which in part reflects the removal of cultural carbon from the archaeological record through processes such as erosion and dissolution. The average annual growth rate of radiocarbon dates in CARD was calculated and used to derive estimates of the population of North America from the Paleo-Indian to the Contact Periods. While taphonomic bias has likely affected the CARD data, other factors, such as the overrepresentation of Paleo-Indian and Archaic radiocarbon dates, may have offset any bias due to taphonomy. A quantitative reconstruction of Native American population shows that population increased rapidly around 2000 cal yr BP, reaching a maximum of 2,500,000 people by ～AD 1150. From this time until European contact, the population declined, possibly due to the effects of increased sedentism and population density.     

State of preservation of polymorphic plasma proteins recovered from ancient human bones

Protected by the mineral matrix, bone proteins are capable of surviving inhumation periods of several hundreds or thousands of years in soil. While the preservation of the bone matrix protein, collagen I, is the prerequisite for a variety of archaeometric approaches, such as radiocarbon dating and the reconstruction of palaeodiet by stable isotope analysis, little is known about both the rate and state of preservation of non‐collagenous proteins. We succeeded in the isolation, electrophoretic separation (SDS‐PAGE, IEF) and immunological detection (radial immunodiffusion, IEF immunoblotting and ELISA) of plasma proteins preserved in archaeological human bones. However, sample preparation and electrophoretic methods had to be adapted to the specific demands of these aged proteins, since they are not only degraded and fragmented but also cross‐linked to other organic components, either indigenous to the bone or to contaminants from the burial environment. Complex decomposition phenomena are responsible for the altered mode of migration of aged proteins through a gel. After isoelectric focusing, the ancient proteins mainly concentrate below pH 4.45 in the pH‐gradient. Thus, highly negatively charged protein components have a better chance of preservation in bone after death. Isoelectric focusing with subsequent immunoblotting of ancient protein samples revealed protein patterns which showed marked charge‐modifications in comparison with those of modern human plasma proteins due to protein degradation (e.g. α₂‐HS‐glycoprotein and α₁‐antitrypsin). Nevertheless, in combination with different immunological analyses, previous results concerning the selective enrichment of α₂‐HS‐glycoprotein in bone compared with other plasma glycoproteins could be confirmed. Copyright © 1999 John Wiley & Sons, Ltd.     

Significance of large-scale sand injectites as long-term fluid conduits: evidence from seismic data

Sand injectites and related features that are interpreted to have formed by large‐scale, often sudden, fluid escape in the shallow (typically <500 m) crust are readily imaged on modern seismic data. Many of the features have geometrical similarity to igneous dykes and sills and cross‐cut the depositional stratigraphy. Sand injectites may be multiphase and form connected, high‐permeability networks that transect kilometre‐scale intervals of otherwise fine‐grained, low‐permeability strata. North Sea examples often form significant hydrocarbon reservoirs and typically contain degraded, low‐gravity crude oil. Fluid inclusion and stable isotope data from cements in sand injectites record a mixing of aqueous fluids of deep and shallow origin.     

Invisible cities: Geography and the disappearance of 'race' from mortgage-lending data in the USA

Recent scholarship on race and ethnicity has unpacked taken-for-granted categories of difference and the processes of social construction of racialized identities. In the USA, however, legal and policy frameworks established during the Civil Rights struggles of the 1960s and 1970s are based on problematic, reified categories of race and ethnicity. Yet these frameworks have opened limited opportunities for activist challenges, and among the most successful is the community reinvestment movement, a broad alliance of local groups using simple quantitative analysis of public data and strategic essentialist tactics to win major victories against racial discriminatory mortgage lenders. In this paper, we analyse recent trends that have undermined procedures used to collect the racial data used by reinvestment activists, regulators and housing researchers. The second-largest racial/ethnic group among US home loan applicants is now officially known as 'information not provided,' and non-reporting varies widely across different cities. We analyse the causes of this disappearance and its metropolitan contingency, using multivariate models to evaluate theories of consumer choice and lending industry segmentation. The disappearance of race stems primarily from structural changes in housing finance, including the emergence of a new breed of aggressive, high-risk subprime and predatory lenders; but distinctive contextual factors persist in the emergence of a complex urban system of racially 'invisible' homeowners and homebuyers. The erosion of racial data creates an accidental epistemology, threatening the progressive potential of strategic essentialism for activists and scholars while offering none of the emancipatory possibilities of social constructionist theories of race. Les récentes recherches académiques portant sur la race et l'ethnicité ont exploré les différentes facettes de la différence et les processus sociaux de formation d'identités raciales. Toutefois, aux Etats-Unis, les cadres politiques et légaux établis durant les luttes pour les Droits Civils des années 1960 et 1970 se fondent sur des concepts de race et ethnicité réifiés; ce sont pourtant ces cadres qui ont ouvert la voie à la critique des activistes. Parmi ces critiques, le mouvement de réinvestissement communautaire est celui qui a connu le plus grand succès. Ce mouvement était composé d'une large alliance entre divers groupes locaux utilisant une analyse simple de données publiques quantitatives ainsi que des stratégies d'essentialisme tactique. Ces moyens ont servi à remporter d'importantes victoires contre le racisme des prêteurs hypothécaires. Dans cet article, nous analysons certaines tendences récentes qui ont menacé les procédures de collecte des données raciales par les activistes du réinvestissement, régulateurs, et chercheurs. Le deuxième plus grand groupe racial/ ethnique chez les demandeurs de prêts hypothécaires aux E.U. est maintenant connu officiellement sous la rubrique 'information non-fournie' et le fait de ne pas indiquer sa race ou ethnicité varie énormément d'une ville à l'autre. Nous analysons les causes de ce manque d'information ainsi que son contexte métropolitain à l'aide de différents modèles d'évaluation du choix des consommateurs et de la segmentation de l'industrie du prêt. La disparition d'information ayant trait à la race est principalement issue de changements structuraux dans le financement immobilier, incluant l'émergence d'un nouveau groupe de prêteurs agressifs, prédateurs et à haut risque. Par contre, certains facteurs contextuels distincts persistent dans l'émergence d'un système urbain complexe de propriétaires et acheteurs dont la race demeure 'invisible'. L'érosion de données raciales crée une épistémologie accidentelle et menace le potentiel progressiste de l'essentialisme stratégique utilisé par les activistes et les chercheurs sans toutefois offrir les possibilités émancipatoires des théories raciales constructivistes. Reciente erudición sobre raza e identidad étnica ha deshecho las aceptadas categorías de diferencia y también los procesos de la construcción social de identidades basadas en raza. Sin embargo, en los Estados Unidos, los marcos legales y políticos que fueron establecidos durante la lucha por Derechos Civiles en los años 60 y 70 se fundan en categorías de raza e identidad étnica que son problemáticas y sustancializadas. Y, no obstante, estos marcos han abierto limitadas oportunidades por los desafíos de activistas, y entre los más exitosos es el movimiento de reinversión comunitaria, una extensa alianza de grupos locales que utilizan un sencillo análisis cuantitativo de datos públicos y tácticos estratégicos esencialitas para ganar victorias importantes contra los prestamistas de hipotecas que discriminan por motivos racistas. En este papel, analizamos recientes tendencias que han arruinado los procedimientos implementados para recoger datos raciales utilizados por los activistas reinversionistas, reguladores, e investigadores de viviendas. Hoy en día, el segundo grupo racial/étnica más grande de solicitantes de hipotecas en los Estados Unidos es oficialmente conocido como 'información no proporcionada' y este no revelación de información varia bastante en las varias ciudades. Analizamos las causas de esta desaparición y su contingencia metropolitana por el empleo de modelos multivarios para evaluar teorías de opciones para consumidores y la segmentación de la industria de préstamos. La desaparición de raza viene principalmente de los cambios estructurales en la financiación de viviendas, incluso la emergencia de nuevos prestamistas agresivos y predadores; pero factores contextuales distintivos persisten en la emergencia de un complejo sistema urbano de propietarios y compradores de viviendas racialmente 'invisibles'. La erosión de datos sobre raza crea una epistemología accidental que amenaza el potencial progresivo de esencialismo estratégico para activistas y eruditos y que no ofrece ninguna de las posibilidades emancipadoras de las teorías de construccionismo social sobre raza.     

Implications of hydro-political dependency for international water cooperation and conflict: Insights from new data

Hydro-political dependencies between countries are widely regarded as having important implications for international water cooperation and conflict. Quantitative ex-post empirical research on the subject so far uses very simple characterizations of international river geography to proxy for such dependencies, though. The authors developed a new geo-spatial dataset for water catchments worldwide. This dataset combines elevation models, flow accumulation approaches, hydrological data, and data on international boundaries to generate more precise and nuanced measures of hydro-political dependencies among riparian countries. The paper discusses these measurement concepts, illustrates how dependencies are distributed worldwide, and revisits three prominent quantitative studies on the issue to show how using improved data affects empirical findings. In contrast to a very popular presumption, upstream–downstream dependencies turn out to have a very small to insignificant effect on international water cooperation or conflict.     

3D modelling of magnetic data from an archaeological site in north-western Tlaxcala state,Mexico

In Archaeology, geophysical methods had been applied usually in a qualitative form, limited only to the use of filters that enhance the data display. The main objective in this work is the implementation of a modelling technique that allows us to reconstruct the geometry of buried bodies and the determination of their depths. This is done by means of the estimation of the magnetic moments of archaeological objects using a three-dimensional mesh of individual magnetic dipoles using the least squares method and the singular value decomposition of a weighted matrix to solve the linear problem. The distribution and shape of the underlying archaeological remains can be inferred. This methodology was applied to an archaeological site called Los Teteles de Ocotitla, in the state of Tlaxcala, Mexico. A high-resolution magnetic prospection was carried out in three selected areas (terraces). The most important total field anomalies found on each area were inverted, obtaining results that were corroborated by archaeological excavations. This investigation demonstrates the potential of quantitative geophysical methods for the characterization of archaeological structures, in extension and in depth.     

Analysis of faunal remains from the Kretuonas lake settlement

The Middle (Kretuonas 1B), Late Neolithic (Zemaitiške 1 and Zemaitiške 2) and Old Bronze Age (Kretuonas 1C) settlements near Kretuonas Lake (Svencioneliai district, Reskutenai village) yielded many artefacts of bone, antler, horn and teeth (750 in total). In the Kretuonas 1B assemblage, deer bones accounted for 50.5 per cent, elk bones 19.7 per cent and boar bones for 27.7 per cent of the total. In the Zemaitiške 1 and 2 settlements the respective portions were 27.7 and 62.0 per cent deer, 6.8 and 20.0 per cent elk and 10.1 per cent boar. In Kretuonas 1C the proportions were 10.9, 36.0 and 7.5 per cent respectively. In the Kretuonas 1B settlement 32 artefacts were identified, 16 from deer bone, four from elk and four from boar. In the Zemaitiške 2 settlement there were 114 artefacts of which 57 were identified to species. Of these, 39 were from deer, eight from elk and four from boar. Finally, in the Kretuonas 1C settlement, of the 531 artefacts found, 120 were identified to species and of these 49 were from deer, 44 from elk, nine from boar and nine from bear.     

台湾出土部分古代玻璃珠的科学分析

使用北京大学科技考古实验室的激光剥蚀电感耦合等离子体发射光谱分析了台湾省出土的18件古代玻璃珠子标本．结果表明这些珠子主要属于钙镁玻璃系统、钾玻璃系统、铅玻璃系统以及钠钙玻璃系统．除钠钙玻璃以外其它玻璃的制作技术均和同时期在大陆流行的玻璃制作技术同源。而成分分析结果显示钠钙玻璃可能来自印度或者东南亚,说明中古时期台湾岛是“海上丝绸之路”的重要中转站。     

危机管理视角下的绥靖行为论析

20世纪30年代英法等西方国家对纳粹德国实施的绥靖政策,一般被认为是鼓励希特勒侵略胆量和野心、最终导致二战爆发的一个重要原因,它在日后甚至发展成了国际政治中软弱无能、胆怯和丧失原则的无益让步的代名词,即所谓"慕尼黑类比"。在"慕尼黑类比"的阴影下,"绥靖"一词被严重污名化,沦为政治攻击的工具,用以反对任何正常和必要的国家间谈判、妥协和友好交往,为强硬外交乃至战争铺路,产生了严重的国际政治后果。但从危机管理的角度来看,绥靖可以是一种通过向对方做出不对等的利益让步来化解危机、避免战争的理性手段,它是一国在面临他国直接威胁挑战或危机情形下,当相互妥协、威慑与强制外交等其他手段都失败或不可行,从而使危机发展到一定阶段时,国家基于成本收益计算和利害权衡,为了避免战争而做出的最后努力。未来研究中应摒弃政治与意识形态上的偏见,发掘更多绥靖案例,对诸如绥靖政策何以成败等问题进行深入分析,以丰富和加深我们对于国际政治中的绥靖现象的理解。