Showing 2701 - 2750 of 5831 Items
Duty and Distinction: Scientists as Intellectuals in Modern China
Date: 2020-01-01
Creator: Helen Wang
Access: Open access
- As critical players in the Chinese state’s pursuit of modernization and political legitimacy, Chinese scientists have been the recipients of state attention and scrutiny throughout modern history. This paper will analyze how Qian Xuesen (1911-2009) became a national hero as the Chinese Communist Party’s model scientist. Qian developed his scientific expertise in the United States, before Cold War political tensions forced his extradition. Upon his return to China, Qian became a key missile scientist in the state’s emerging nuclear weapons program. By analyzing Qian’s public persona as portrayed in official state media, this paper will argue that the CCP conferred distinct political duties to scientists, defining a new socio-political role for scientist-intellectuals. Beginning from the Mao era and continuing through to the present day, the CCP’s portrayal and promotion of Qian’s legacy gives insight into the state’s strategy to use science to bolster authority and legitimize policy.
Bowdoin College - Medical School of Maine Catalogue (1919-1920)
Date: 1920-01-01
Access: Open access
- Bowdoin College Bulletin no. 94
The role of adjuvant in mediating antigen structure and stability
Date: 2012-01-01
Creator: Latoya Jones Braun, Aimee M. Eldridge, Jessica Cummiskey, Kelly K. Arthur, Deborah S., Wuttke
Access: Open access
- The purpose of this study was to probe the fate of a model antigen, a cysteine-free mutant of bacteriophage T4 lysozyme, to the level of fine structural detail, as a consequence of its interaction with an aluminum (Al)-containing adjuvant. Fluorescence spectroscopy and differential scanning calorimetry were used to compare the thermal stability of the protein in solution versus adsorbed onto an Al-containing adjuvant. Differences in accessible hydrophobic surface areas were investigated using an extrinsic fluorescence probe, 8-Anilino-1-naphthalenesulfonic acid (ANS). As has been observed with other model antigens, the apparent thermal stability of the protein decreased following adsorption onto the adjuvant. ANS spectra suggested that adsorption onto the adjuvant caused an increase in exposure of hydrophobic regions of the protein. Electrostatic interactions drove the adsorption, and disruption of these interactions with high ionic strength buffers facilitated the collection of two-dimensional 15N heteronuclear single quantum coherence nuclear magnetic resonance data of protein released from the adjuvant. Although the altered stability of the adsorbed protein suggested changes to the protein's structure, the fine structure of the desorbed protein was nearly identical to the protein's structure in the adjuvant-free formulation. Thus, the adjuvant-induced changes to the protein that were responsible for the reduced thermal stability were not observed upon desorption. © 2011 Wiley Periodicals, Inc.
Determining hilbert modular forms by central values of rankin-selberg convolutions: The level aspect
Date: 2017-12-01
Creator: Alia Hamieh, Naomi Tanabe
Access: Open access
- In this paper, we prove that a primitive Hilbert cusp form g is uniquely determined by the central values of the Rankin-Selberg L-functions (formula presented), where f runs through all primitive Hilbert cusp forms of level q for infinitely many prime ideals q. This result is a generalization of the work of Luo (1999) to the setting of totally real number fields.
Assembly of the precursor and processed light-harvesting chlorophyll a/b protein of Lemna into the light-harvesting complex II of barley etiochloroplasts.
Date: 1986-01-01
Creator: P. R. Chitnis, E. Harel, B. D. Kohorn, E. M. Tobin, J. P., Thornber
Access: Open access
- When the in vitro synthesized precursor of a light-harvesting chlorophyll a/b binding protein (LHCP) from Lemna gibba is imported into barley etiochloroplasts, it is processed to a single form. Both the processed form and the precursor are found in the thylakoid membranes, assembled into the light-harvesting complex of photosystem II. Neither form can be detected in the stromal fraction. The relative amounts of precursor and processed forms observed in the thylakoids are dependent on the developmental stage of the plastids used for uptake. The precursor as well as the processed form can also be detected in thylakoids of greening maize plastids used in similar uptake experiments. This detection of a precursor in the thylakoids, which has not been previously reported, could be a result of using rapidly developing plastids and/or using an heterologous system. Our results demonstrate that the extent of processing of LHCP precursor is not a prerequisite for its inclusion in the complex. They are also consistent with the possibility that the processing step can occur after insertion of the protein into the thylakoid membrane.
Animal-to-animal variability in the phasing of the crustacean cardiac motor pattern: An experimental and computational analysis
Date: 2013-01-01
Creator: Alex H. Williams, Molly A. Kwiatkowski, Adam L. Mortimer, Eve Marder, Mary Lou, Zeeman, Patsy S. Dickinson
Access: Open access
- The cardiac ganglion (CG) of Homarus americanus is a central pattern generator that consists of two oscillatory groups of neurons: "small cells" (SCs) and "large cells" (LCs). We have shown that SCs and LCs begin their bursts nearly simultaneously but end their bursts at variable phases. This variability contrasts with many other central pattern generator systems in which phase is well maintained. To determine both the consequences of this variability and how CG phasing is controlled, we modeled the CG as a pair of Morris-Lecar oscillators coupled by electrical and excitatory synapses and constructed a database of 15,000 simulated networks using random parameter sets. These simulations, like our experimental results, displayed variable phase relationships, with the bursts beginning together but ending at variable phases. The model suggests that the variable phasing of the pattern has important implications for the functional role of the excitatory synapses. In networks in which the two oscillators had similar duty cycles, the excitatory coupling functioned to increase cycle frequency. In networks with disparate duty cycles, it functioned to decrease network frequency. Overall, we suggest that the phasing of the CG may vary without compromising appropriate motor output and that this variability may critically determine how the network behaves in response to manipulations. © 2013 the American Physiological Society.
Digital Authoritarianism in China and Russia: A Comparative Study
Date: 2020-01-01
Creator: Laura H.C. Howells
Access: Open access
- Digital authoritarianism is on the rise around the world and threatens the data privacy and rights of both domestic and international Internet users. However, scholarship on digital authoritarianism remains limited in scope and case study selection. This study contributes a new, more comprehensive analytical framework for the study of Internet governance and applies it to the case studies of China and Russia. Special attention is paid to the still understudied Russian Internet governance model. After thorough literature review and novel data collection and analysis, this paper identifies relative centralization of network infrastructure and the extent and pace of change in governance as the most notable differences between the two models. These points of divergence may be explained by two theories; the varieties of authoritarianism hypothesis posits that different political systems face persistent and unique constraints to governance of the digital realm. The development trajectory theory argues that each country’s technological development path foreshadows the systems’ capacity for and extent of governance. This study is among the first to distinguish between Internet governance strategies of authoritarian regimes.
Phononic rogue waves
Date: 2018-09-13
Creator: E. G. Charalampidis, J. Lee, P. G. Kevrekidis, C. Chong
Access: Open access
- We present a theoretical study of extreme events occurring in phononic lattices. In particular, we focus on the formation of rogue or freak waves, which are characterized by their localization in both spatial and temporal domains. We consider two examples. The first one is the prototypical nonlinear mass-spring system in the form of a homogeneous Fermi-Pasta-Ulam-Tsingou (FPUT) lattice with a polynomial potential. By deriving an approximation based on the nonlinear Schrödinger (NLS) equation, we are able to initialize the FPUT model using a suitably transformed Peregrine soliton solution of the NLS equation, obtaining dynamics that resembles a rogue wave on the FPUT lattice. We also show that Gaussian initial data can lead to dynamics featuring a rogue wave for sufficiently wide Gaussians. The second example is a diatomic granular crystal exhibiting rogue-wave-like dynamics, which we also obtain through an NLS reduction and numerical simulations. The granular crystal (a chain of particles that interact elastically) is a widely studied system that lends itself to experimental studies. This study serves to illustrate the potential of such dynamical lattices towards the experimental observation of acoustic rogue waves.
The Impact of Armed Conflict on Maternal Health in Colombia
Date: 2020-01-01
Creator: Madeleine Squibb
Access: Open access
- This study combines data from the 2010 Demographic and Health Survey and the Conflict Analysis Resource Center (CERAC) to examine the impact of conflict on maternal health service utilization and outcomes in Colombia. The primary results indicate a significant, negative relationship between conflict level and antenatal and postnatal care utilization. Conflict is insignificant in determining the use of professional assistance at delivery. Although rural women are, overall, less likely to access maternal health services, further analysis along rural-urban lines reveals that the negative effect of violence on prenatal and postnatal care is stronger among urban women. Secondary estimation of the occurrence of complications during or after delivery employs a Two-Stage Residuals Inclusion model to address potential endogeneity in service use. Estimated results show that conflict levels are insignificant, but that Indigenous women and women in lower wealth quintiles are significantly more likely to experience complications, even after controlling for service use. The conclusions of this paper suggest that Colombia’s universal healthcare system has been successful in reducing economic barriers to prenatal care and professional delivery, but that significant wealth-related inequalities remain in maternal health outcomes. Additionally, Indigenous and women with lower levels of education are less likely to access services and more likely to experience complications. The primary contribution of this paper is the inclusion of a conflict measure. The significant, negative impact on prenatal and postnatal care utilization, especially for urban women, warrants further study to better inform policy to increase service use and reduce maternal mortality and morbidity.
A genomewide survey argues that every zygotic gene product is dispensable for the initiation of somatic homolog pairing in Drosophila
Date: 2008-11-01
Creator: Jack R. Bateman, C. Ting Wu
Access: Open access
- Studies from diverse organisms show that distinct interchromosomal interactions are associated with many developmental events. Despite recent advances in uncovering such phenomena, our understanding of how interchromosomal interactions are initiated and regulated is incomplete. During the maternal-to-zygotic transition (MZT) of Drosophila embryogenesis, stable interchromosomal contacts form between maternal and paternal homologous chromosomes, a phenomenon known as somatic homolog pairing. To better understand the events that initiate pairing, we performed a genomewide assessment of the zygotic contribution to this process. Specifically, we took advantage of the segregational properties of compound chromosomes to generate embryos lacking entire chromosome arms and, thus, all zygotic gene products derived from those arms. Using DNA fluorescence in situ hybridization (FISH) to assess the initiation of pairing at five separate loci, this approach allowed us to survey the entire zygotic genome using just a handful of crosses. Remarkably, we found no defect in pairing in embryos lacking any chromosome arm, indicating that no zygotic gene product is essential for pairing to initiate. From these data, we conclude that the initiation of pairing can occur independently of zygotic control and may therefore be part of the developmental program encoded by the maternal genome. Copyright © 2008 by the Genetics Society of America.
Responses of central pattern generators in the American lobster STNS to multiple members of a novel neuropeptide family
Date: 2020-01-01
Creator: Benjamin Harley Wong
Access: Open access
- Neuropeptides are important modulators of neural activity, allowing neural networks, such as the central pattern generators (CPGs) that control rhythmic movements, to alter their output and thus generate behavioral flexibility. Isoforms of a neuropeptide family vary in physical structure, allowing potentially distinct functional neuromodulatory effects on CPG systems. While some familial neuropeptide isoforms can differentially affect a system, others in the same family may elicit indistinguishable effects. Here, we examined the effects elicited by members of a novel family of six peptide hormone isoforms (GSEFLamides: I-, M-, AL-, AM-, AV-, and VM-GSEFLamide) on the pyloric filter and gastric mill CPGs in the stomatogastric nervous system (STNS) of the American lobster, Homarus americanus. Recent unpublished work from the Dickinson lab found that five of the six GSEFLamides elicited similar increases in contraction amplitude when perfused through the isolated lobster heart, while one (AVGSEFLamide) had virtually no effect. Using extracellular recordings, we found the pattern of GSEFLamide effects on the STNS gastric mill to be similar to the pattern observed in the lobster cardiac system; the gastric mill circuit was fairly consistently activated by all isoforms except AVGSEFLamide. The intrinsically active pyloric pattern was also significantly enhanced by three out of five peptide isoforms, and nearly significantly enhanced by two more, but was likewise non-responsive to AVGSEFLamide. While the reason AVGSEFLamide had no effect on either pattern is unknown, the similar phenomenon noted in the isolated whole heart potentially indicates that this isoform lacks any function in the lobster.
That’s DOPE: the delayed-onset, prolonged excitation response of a primary auditory interneuron in Gryllus bimaculatus This record is embargoed.
- Embargo End Date: 2025-05-13
Date: 2020-01-01
Creator: Samuel G. Brill-Weil
Access: Embargoed
Context-dependent protein stabilization by methionine-to-leucine substitution shown in T4 lysozyme
Date: 1998-01-01
Creator: Leigh Ann Lipscomb, Nadine C. Gassner, Sheila D. Snow, Aimee M. Eldridge, Walter A., Baase, Devin L. Drew, Brian W. Matthews
Access: Open access
- The substitution of methionines with leucines within the interior of a protein is expected to increase stability both because of a more favorable solvent transfer team as well as the reduced entropic cost of holding a leucine side chain in a defined position. Together, these two terms are expected to contribute about 1.4 kcal/mol to protein stability for each Met → Leu substitution when fully buried. At the same time, this expected beneficial effect may be offset by steric factors due to differences in the shape of leucine and methionine. To investigate the interplay between these factors, all methionines in T4 lysozyme except at the amino-terminus were individually replaced with leucine. Of these mutants, M106L and M120L have stabilities 0.5 kcal/mol higher than wild-type T4 lysozyme, while M6L is significantly destabilized (-2.8 kcal/mol). M102L, described previously, is also destabilized (-0.9 kcal/mol). Based on this limited sample it appears that methionine-to-leucine substitutions can increase protein stability but only in a situation where the methionine side chain is fully or partially buried, yet allows the introduction of the leucine without concomitant steric interference. The variants, together with methionine-to-lysine substitutions at the same sites, follow the general pattern that substitutions at rigid, internal sites tend to be most destabilizing, whereas replacements at more solvent-exposed sites are better tolerated.
Site-specific transformation of Drosophila via φC31 integrase-mediated cassette exchange
Date: 2006-06-30
Creator: Jack R. Bateman, Anne M. Lee, C. Ting Wu
Access: Open access
- Position effects can complicate transgene analyses. This is especially true when comparing transgenes that have inserted randomly into different genomic positions and are therefore subject to varying position effects. Here, we introduce a method for the precise targeting of transgenic constructs to predetermined genomic sites in Drosophila using the φC31 integrase system in conjunction with recombinase-mediated cassette exchange (RMCE). We demonstrate the feasibility of this system using two donor cassettes, one carrying the yellow gene and the other carrying GFP. At all four genomic sites tested, we observed exchange of donor cassettes with an integrated target cassette carrying the mini-white gene. Furthermore, because RMCE-mediated integration of the donor cassette is necessarily accompanied by loss of the target cassette, we were able to identify integrants simply by the loss of mini-white eye color. Importantly, this feature of the technology will permit integration of unmarked constructs into Drosophila, even those lacking functional genes. Thus, φC31 integrase-mediated RMCE should greatly facilitate transgene analysis as well as permit new experimental designs. Copyright © 2006 by the Genetics Society of America.
Accurate transcription of truncated ribosomal DNA templates in a Drosophila cell-free system
Date: 1982-01-01
Creator: B. D. Kohorn, P. M.M. Rae
Access: Open access
- An extract of Drosophila melanogaster Kc cells is shown to give specific and accurate transcription of truncated segments of cloned D. melanogaster ribosomal DNA (rDNA). When clones are digested with restriction enzymes so that the initiation site is flanked by 0.3 kilobase (kb) of nontranscribed spacer and >0.4 kb of external transcribed spacer, RNA polymerase I activity in the extract parallels in vivo rRNA synthesis in selection of the coding strand of template and the site of transcription initiation. When >0.3 kb of the nontranscribed spacer is contiguous with transcribed spacer, in vitro initiations evidently also occur in repeated sequences adjacent to the site of in vivo initiation; when ≤0.4 kb of the external transcribed spacer is present in a segment, expected transcripts are heterogeneous in length or not detectable. Transcription in the cell-free system requires the specific addition of D. melanogaster rDNA: neither D. virilis rDNA, vector plasmid, nor clones of D. melanogaster genes that are transcribed in vivo by RNA polymerases II and III serve as templates in the system. Drosophila rDNA units that have an interruption in the 28S rRNA coding region are not transcribed in vivo, but restriction digests of a recombinant phage DNA that contains such a unit are active as template for in vitro rDNA transcription.
Transient phenomena in ecology
Date: 2018-09-07
Creator: Alan Hastings, Karen C. Abbott, Kim Cuddington, Tessa Francis, Gabriel, Gellner, Ying Cheng Lai
Access: Open access
- The importance of transient dynamics in ecological systems and in the models that describe them has become increasingly recognized. However, previous work has typically treated each instance of these dynamics separately. We review both empirical examples and model systems, and outline a classification of transient dynamics based on ideas and concepts from dynamical systems theory. This classification provides ways to understand the likelihood of transients for particular systems, and to guide investigations to determine the timing of sudden switches in dynamics and other characteristics of transients. Implications for both management and underlying ecological theories emerge.
Bowdoin College - Medical School of Maine Catalogue (1910-1911)
Date: 1911-01-01
Access: Open access
- Bowdoin College Bulletin no. 31
Survival Strategies: Historic Preservation, Jewish Community, and the German Democratic Republic
Date: 2020-01-01
Creator: Emily Ann Cohen
Access: Open access
- Following the Second World War, as German Communists worked to establish a new socialist East German state, Jews who survived persecution and imprisonment by the Nazis worked to reestablish a Jewish community at the same time. Though many scholars dismiss the relationship between Jews and the Socialist Unity Party, the ruling party of the German Democratic Republic, as one characterized only by neglect and occasional political exploitation, it was much more nuanced, shaped in large part by the Cold War. Both the party and the Jewish community relied on the other to accomplish their goals, namely, survival in a new world order: The Socialist Unity Party relied on the Jewish community to maintain the German Democratic Republic's claim to legitimacy, and the Jews, few in number, relied on the party for financial support. Despite mutual benefits, however, the state and party nearly always had the upper hand. The power imbalance led Jews to find creative ways to fulfill their needs and, at several points, even prompted protest of the party’s treatment of its Jewish citizens. This paper follows the course of this relationship by focusing on the German Democratic Republic's management of sites of historical significance—which vacillated between outright destruction and dedicated protection—returning particularly to the Jewish cemetery in Berlin-Weissensee, one of the largest Jewish cemeteries in Europe. With this particular lens, this project addresses questions about memory, mythology, and agency in a socialist dictatorship and challenges assumptions about Jewish life in East Germany.
Environmental issues in russia
Date: 2008-12-01
Creator: Laura A. Henry, Vladimir Douhovnikoff
Access: Open access
- This review examines the literature available on the state of the environment and environmental protection in the Russian Federation. As the largest country on Earth, rich in natural resources and biodiversity, Russia's problems and policies have global consequences. Environmental quality and management are influenced by the legacy of Soviet economic planning and authoritarian governance, as well as by Russia's post-Soviet economic recession and current strategies of economic development. Russia achieved a reduction in some pollutants owing to the collapse of industrial production in the 1990s, but many environmental indicators suggest growing degradation. Russia has signed on to a number of international environmental agreements, but its record on implementation is mixed, and it discourages environmental activism. Scholarship on the Russian environment is a limited, but growing, field, constrained by challenges of data availability, yet it offers great potential for testing scientific and social scientific hypotheses. ©2008 by Annual Reviews.
Food Comes First: Growing Up at my Family’s Table This record is embargoed.
- Embargo End Date: 2025-05-14
Date: 2020-01-01
Creator: Eleanor Sapat
Access: Embargoed