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Berlin Brandenburg

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  • JSTOR Archival Journals  (304)
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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 08 March 2011, Vol.108(10), pp.4035-40
    Description: A principle response of C3 plants to increasing concentrations of atmospheric CO(2) (CO(2)) is to reduce transpirational water loss by decreasing stomatal conductance (g(s)) and simultaneously increase assimilation rates. Via this adaptation, vegetation has the ability to alter hydrology and climate. Therefore, it is important to determine the adaptation of vegetation to the expected anthropogenic rise in CO(2). Short-term stomatal opening-closing responses of vegetation to increasing CO(2) are described by free-air carbon enrichments growth experiments, and evolutionary adaptations are known from the geological record. However, to date the effects of decadal to centennial CO(2) perturbations on stomatal conductance are still largely unknown. Here we reconstruct a 34% (±12%) reduction in maximum stomatal conductance (g(smax)) per 100 ppm CO(2) increase as a result of the adaptation in stomatal density (D) and pore size at maximal stomatal opening (a(max)) of nine common species from Florida over the past 150 y. The species-specific g(smax) values are determined by different evolutionary development, whereby the angiosperms sampled generally have numerous small stomata and high g(smax), and the conifers and fern have few large stomata and lower g(smax). Although angiosperms and conifers use different D and a(max) adaptation strategies, our data show a coherent response in g(smax) to CO(2) rise of the past century. Understanding these adaptations of C3 plants to rising CO(2) after decadal to centennial environmental changes is essential for quantification of plant physiological forcing at timescales relevant for global warming, and they are likely to continue until the limits of their phenotypic plasticity are reached.
    Keywords: Plant Physiological Phenomena ; Carbon Dioxide -- Analysis
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 08 March 2011, Vol.108(10), pp.4041-6
    Description: Plant physiological adaptation to the global rise in atmospheric CO(2) concentration (CO(2)) is identified as a crucial climatic forcing. To optimize functioning under rising CO(2), plants reduce the diffusive stomatal conductance of their leaves (g(s)) dynamically by closing stomata and structurally by growing leaves with altered stomatal densities and pore sizes. The structural adaptations reduce maximal stomatal conductance (g(smax)) and constrain the dynamic responses of g(s). Here, we develop and validate models that simulate structural stomatal adaptations based on diffusion of CO(2) and water vapor through stomata, photosynthesis, and optimization of carbon gain under the constraint of a plant physiological cost of water loss. We propose that the ongoing optimization of g(smax) is eventually limited by species-specific limits to phenotypic plasticity. Our model reproduces observed structural stomatal adaptations and predicts that adaptation will continue beyond double CO(2). Owing to their distinct stomatal dimensions, angiosperms reach their phenotypic response limits on average at 740 ppm and conifers on average at 1,250 ppm CO(2). Further, our simulations predict that doubling today's CO(2) will decrease the annual transpiration flux of subtropical vegetation in Florida by ≈60 W·m(-2). We conclude that plant adaptation to rising CO(2) is altering the freshwater cycle and climate and will continue to do so throughout this century.
    Keywords: Climate ; Carbon Dioxide -- Analysis ; Plant Leaves -- Physiology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    Language: English
    In: Journal of Business Ethics, 2014, Vol.123(1), pp.71-84
    Description: Studies in the behavioral ethics and moral psychology traditions have begun to reveal the important roles of self-related processes that underlie moral behavior. Unfortunately, this research has resulted in two distinct and opposing streams of findings that are usually referred to as moral consistency and moral compensation. Moral consistency research shows that a salient self-concept as a moral person promotes moral behavior. Conversely, moral compensation research reveals that a salient self-concept as an immoral person promotes moral behavior. This study’s aim was to integrate these two literatures. We argued that compensation forms a reactive, “damage control” response in social situations, whereas consistency derives from a more proactive approach to reputation building and maintenance. Two experiments supported this prediction in showing that cognitive depletion (i.e., resulting in a reactive approach) results in moral compensation whereas consistency results when cognitive resources are available (i.e., resulting in a proactive approach). Experiment 2 revealed that these processes originate from reputational (rather than moral) considerations by showing that they emerge only under conditions of accountability. It can thus be concluded that reputational concerns are important for both moral compensation and moral consistency processes, and that which of these two prevails depends on the perspective that people take: a reactive or a proactive approach.
    Keywords: Accountability ; Moral compensation ; Moral consistency ; Moral licensing ; Moral self-regulation ; Prosocial behavior
    ISSN: 0167-4544
    E-ISSN: 1573-0697
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  • 4
    In: American Journal of Botany, May 2010, Vol.97(5), pp.753-759
    Description: In the present study, structural xeromorphic features in modern and subfossil leaves from southern Florida were quantified to reconstruct past precipitation changes in sensitive terrestrial settings. Absolute cell numbers/mm, quantified as epidermal cell density (ED) have been analyzed on leaves from herbarium collections as well as the leaves accumulated during the past 125 years in peat deposits. The results reveal a common principal correlation between the measured ED and winter precipitation (November through March, NDJFM: Herbarium = −0.74; peat profiles FAK98 = −0.72, FAK02 = −0.53) providing a measure of seasonal drought stress. In Florida, the amount of winter precipitation depends on El Niño–Southern Oscillation (ENSO) activity, where El Niño years produce wet and cold winters, while La Niña winters are dry and warm. The negative correlation between cell numbers and winter precipitation has the potential to record precipitation variability from subfossil leaves on near‐annual to decadal time scales. In subtropical, terrestrial environments, where traditional paleo‐proxies are limited, systematic analysis of leaf morphological characteristics can provide important information on precipitation changes through time.
    Keywords: Drought Stress ; El Niño–Southern Oscillation Activity ; Enso ; Fagaceae ; Florida ; Leaf Morphology ; Paleo‐Precipitation ; Quercus Laurifolia
    ISSN: 0002-9122
    E-ISSN: 1537-2197
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  • 5
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 02 June 2015, Vol.112(22), pp.6979-84
    Description: Fragment-based screening methods can be used to discover novel active site or allosteric inhibitors for therapeutic intervention. Using saturation transfer difference (STD) NMR and in vitro activity assays, we have identified fragment-sized inhibitors of HIV-1 reverse transcriptase (RT) with distinct chemical scaffolds and mechanisms compared to nonnucleoside RT inhibitors (NNRTIs) and nucleoside/nucleotide RT inhibitors (NRTIs). Three compounds were found to inhibit RNA- and DNA-dependent DNA polymerase activity of HIV-1 RT in the micromolar range while retaining potency against RT variants carrying one of three major NNRTI resistance mutations: K103N, Y181C, or G190A. These compounds also inhibit Moloney murine leukemia virus RT but not the Klenow fragment of Escherichia coli DNA polymerase I. Steady-state kinetic analyses demonstrate that one of these fragments is a competitive inhibitor of HIV-1 RT with respect to deoxyribonucleoside triphosphate (dNTP) substrate, whereas a second compound is a competitive inhibitor of RT polymerase activity with respect to the DNA template/primer (T/P), and consequently also inhibits RNase H activity. The dNTP competing RT inhibitor retains activity against the NRTI-resistant mutants K65R and M184V, demonstrating a drug resistance profile distinct from the nucleotide competing RT inhibitors indolopyridone-1 (INDOPY-1) and 4-dimethylamino-6-vinylpyrimidine-1 (DAVP-1). In antiviral assays, the T/P competing compound inhibits HIV-1 replication at a step consistent with an RT inhibitor. Screening of additional structurally related compounds to the three fragments led to the discovery of molecules with improved potency against HIV-1 RT. These fragment inhibitors represent previously unidentified scaffolds for development of novel drugs for HIV-1 prevention or treatment.
    Keywords: HIV ; STD-NMR ; Allosteric Inhibitors ; Fragment-Based Drug Discovery ; Reverse Transcriptase ; Drug Discovery -- Methods ; HIV-1 -- Enzymology ; Prodrugs -- Isolation & Purification ; Reverse Transcriptase Inhibitors -- Isolation & Purification
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 6
    Language: English
    In: Journal of Business Ethics, 2013, Vol.113(1), pp.133-145
    Description: We investigate how social comparison processes in leader treatment quality impact group members’ self-worth, affect, and behavior. Evidences from the field and the laboratory suggest that employees who are treated kinder and more considerate than their fellow group members experience more self-worth and positive affect. Moreover, the greater positive self-implications of preferentially treated group members motivate them more strongly to comply with norms and to engage in tasks that benefit the group. These findings suggest that leaders face an ethical trade-off between satisfying the moral standard of treating everybody equally well and satisfying individual group members’ desire to be treated better than others.
    Keywords: Group value model ; Leadership ; Norm compliance ; Social comparison ; Status ; Affect
    ISSN: 0167-4544
    E-ISSN: 1573-0697
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  • 7
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 19 January 2010, Vol.107(3), pp.1201-6
    Description: After their generation and specification in periventricular regions, neuronal precursors maintain an immature and migratory state until their arrival in the respective target structures. Only here are terminal differentiation and synaptic integration induced. Although the molecular control of neuronal specification has started to be elucidated, little is known about the factors that control the latest maturation steps. We aimed at identifying factors that induce terminal differentiation during postnatal and adult neurogenesis, thereby focusing on the generation of periglomerular interneurons in the olfactory bulb. We isolated neuronal precursors and mature neurons from the periglomerular neuron lineage and analyzed their gene expression by microarray. We found that expression of the bHLH transcription factor NeuroD1 strikingly coincides with terminal differentiation. Using brain electroporation, we show that overexpression of NeuroD1 in the periventricular region in vivo leads to the rapid appearance of cells with morphological and molecular characteristics of mature neurons in the subventricular zone and rostral migratory stream. Conversely, shRNA-induced knockdown of NeuroD1 inhibits terminal neuronal differentiation. Thus, expression of a single transcription factor is sufficient to induce neuronal differentiation of neural progenitors in regions that normally do not show addition of new neurons. These results suggest a considerable potential of NeuroD1 for use in cell-therapeutic approaches in the nervous system.
    Keywords: Basic Helix-Loop-Helix Transcription Factors -- Physiology ; Cell Differentiation -- Physiology ; Interneurons -- Chemistry ; Olfactory Bulb -- Cytology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 8
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 09 November 2010, Vol.107(45), pp.19426-31
    Description: Thymic central tolerance comprehensively imprints the T-cell receptor repertoire before T cells seed the periphery. Medullary thymic epithelial cells (mTECs) play a pivotal role in this process by virtue of promiscuous expression of tissue-restricted autoantigens. The molecular regulation of this unusual gene expression, in particular the involvement of epigenetic mechanisms is only poorly understood. By studying promiscuous expression of the mouse casein locus, we report that transcription of this locus proceeds from a delimited region ("entry site") to increasingly complex patterns along with mTEC maturation. Transcription of this region is preceded by promoter demethylation in immature mTECs followed upon mTEC maturation by acquisition of active histone marks and local locus decontraction. Moreover, analysis of two additional gene loci showed that promiscuous expression is transient in single mTECs. Transient gene expression could conceivably add to the local diversity of self-antigen display thus enhancing the efficacy of central tolerance.
    Keywords: Self Tolerance ; Epigenesis, Genetic -- Immunology ; Epithelial Cells -- Metabolism ; Thymus Gland -- Cytology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 9
    Language: English
    In: Psychological Science, January 2011, Vol.22(1), pp.45-48
    Description: Apologies are commonly used to deal with transgressions in relationships. Results to date, however, indicate that the positive effects of apologies vary widely, and the match between people’s judgments of apologies and the true value of apologies has not been studied. Building on the affective and behavioral forecasting literature, we predicted that people would overestimate how much they value apologies in reality. Across three experimental studies, our results showed that after having been betrayed by another party (or after imagining this to be the case), people (a) rated the value of an apology much more highly when they imagined receiving an apology than when they actually received an apology and (b) displayed greater trusting behavior when they imagined receiving an apology than when they actually received an apology. These results suggest that people are prone to forecasting errors regarding the effectiveness of an apology and that they tend to overvalue the impact of receiving one.
    Keywords: Apologies ; Trust Game ; Forecasting Errors ; Psychology
    ISSN: 0956-7976
    E-ISSN: 1467-9280
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  • 10
    Language: English
    In: Journal of Business Ethics, 2014, Vol.121(1), pp.1-14
    Description: In the present article, we argue that the constant pressure that leaders face may limit the willpower required to behave according to ethical norms and standards and may therefore lead to unethical behavior. Drawing upon the ego depletion and moral self-regulation literatures, we examined whether self-regulatory depletion that is contingent upon the moral identity of leaders may promote unethical leadership behavior. A laboratory experiment and a multisource field study revealed that regulatory resource depletion promotes unethical leader behaviors among leaders who are low in moral identity. No such effect was found among leaders with a high moral identity. This study extends our knowledge on why organizational leaders do not always conform to organizational goals. Specifically, we argue that the hectic and fragmented workdays of leaders may increase the likelihood that they violate ethical norms. This highlights the necessity to carefully schedule tasks that may have ethical implications. Similarly, organizations should be aware that overloading their managers with work may increase the likelihood of their leaders transgressing ethical norms.
    Keywords: Unethical leadership ; Ego depletion ; Moral identity
    ISSN: 0167-4544
    E-ISSN: 1573-0697
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