100,832 research outputs found
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Stratosphere-troposphere exchange: An angular momentum perspective
No full textThe exchange of axial angular momentum (AM) between stratosphere and troposphere forms an important part of stratosphere–troposphere exchange (STE). Data are used to quantify the related fluxes through an idealized tropopause for specific flux events both for the global tropopause and regional segments. Time mean fluxes are considered as well. These are largest in the tropics and closely tied to mass fluxes. The data accuracy is found to be insufficient for a closure of the momentum budget of the Brewer–Dobson circulation. Positive regional flux events at the tropical tropopause are partly due to a short lived intensification of the Hadley circulation, but are also embedded in a rather long lived circulation anomaly which leads to a gain of positive AM in the lower tropical stratosphere. Moreover, there are large fluxes through the ‘tropopause breaks’. Flux events at midlatitude segments involve also strong horizontal fluxes through the ‘tropopause breaks’, which override an otherwise downward flux from the stratosphere. These events are closely linked to tropical anomalies of AM, so that all ‘regional’ events turn out to be of global character. Data accuracy becomes a problem when fluxes through a global tropopause are investigated where substantial uncertainties are encountered near the ‘tropopause breaks’.
All cases discussed exhibit a distinct similarity with deep anomalies of AM in the tropics sandwiched between anomalous AM columns of opposite sign to the north and south. There is always a center of flux convergence or divergence in the lower stratosphere. This suggests that all the events of large scale-angular momentum exchange between stratosphere and troposphere as analysed here follow a distinct dynamic pattern, which appears not to have been described before
Iberian thermal lows in a changed climate
No full textRecent results from enhanced greenhouse-gas scenarios over southern Europe suggest that climate change implies a summertime mean surface warming of up to 4 K over the Iberian Peninsula. It is suggested that thermal lows, the most prominent Iberian summer weather, will undergo significant modifications in a changed climate. This is studied in the present paper by determining statistical features of the Iberian thermal low, at first for today's climate using data provided by ERA-40 and by the regional climate model PROMES. In general the analysed and simulated climatic structures compare well. However, the ERA-40 data provide conditions more favourable for thermal lows than simulated with the model. Statistics in a changed climate are obtained by performing two 30-year model simulations for 1961-1990 and 2071-2100. It is found that thermal lows strengthen by decreasing the central Iberian surface pressure from 1012.2 to 1010.5 hPa and increasing its daily variation by about 7% in magnitude. Associated with this is an increase in the number of thermal low days by more than 60%. A second finding is an enhancement of the sea breezes over the Iberian westerly and easterly coasts and a particularly significant strengthening of the sea breeze between Cadiz and Huelva. The westerly flow over the Strait of Gibraltar, observed during thermal low events, decreases. The increase in occurrence of the thermal low is associated with a significant increase in the number of dry spells of longer period, and could involve considerable impact on desertification, water resources and wildfire hazards around the Mediterranean basin. The results suggest that there is some evidence that the subtropical character of the Mediterranean climate strengthens
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
Downward Control from Lower Stratosphere?
No full textThe concept of downward control proposes a mechanism for the impact of the stratospheric circulation on the troposphere. Momentum forcing at upper-stratospheric levels induces a meridional circulation that eventually reaches the surface. So far, a lack of sufficiently accurate data hindered an observational test of this downward propagation. The concept is extended in this paper by looking at the effect of angular momentum forcing in prescribed regions in the lower stratosphere on the tropospheric circulation. In that
case, the European Centre for Medium-Range Weather Forecasts Reanalysis Project (ERA) data can be used to investigate the atmospheric response to forcing in a prescribed domain. It is found that these forcing events are quite short lived and that angular momentum flux convergence in the prescribed domain is highly correlated with convergence outside this forcing area. Typically, these fields of convergence and also divergence extend to the surface in a quasibarotropic manner outside the Tropics. This structure of the forcing is not compatible with the assumptions of the downward control concept. The observed related meridional circulation therefore differs widely from that predicted. In particular, there is no obvious descent of the circulation to the ground. Even so, such forcing events are accompanied by an intensive exchange of angular momentum between stratosphere and troposphere. The confinement of the forcing to the selected forcing domain is reasonably strict in the Tropics. A relatively narrow tongue of angular momentum is growing at the equator underneath the forcing area. Frictional torques play a role in this development.
Altogether, the forcing events as selected involve a strong angular momentum exchange between stratosphere and troposphere but are not suited for a test of the downward control concept. Alternatives are discussed
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
Wave turbulence of a rotating array of quantized vortices in the T → 0 temperature limit
No full textThe dynamics of quantized vortices in the zero temperature limit is currently of great interest, particularly in the case of the Fermi superfluid He-B. Here we study wave turbulence, generated by the librating motion of a rotating cylindrical container filled with He-B, in the limit of vanishing viscous forces at temperatures . The polarization of the quantized vortices with respect to the axis of rotation is measured using non-invasive NMR techniques. We observe a decrease of the polarization when the librating motion is started, and a two-stage relaxation process when the modulation of the rotation velocity is stopped. The first relaxation process is associated with the dissipation of large-scale flow stored in inertial waves and the solid body rotation of the vortex array. From the decay of these energy reservoirs we determine the rate of energy dissipation of large-scale flow. The later second process is related to the relaxation of Kelvin waves on individual vortices. This process is monitored by the recovery of the polarization. The existence of a Kelvin wave cascade at the lowest temperatures is currently a central open question. We supply some evidence for the cascade
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