Freedmen with Firearms: White Terrorism and Black Disarmament During Reconstruction

The outcome of the Civil War brought freedom to over six million slaves of African descent. These Freedmen communities remained a critical source of labor for the agrarian based economy of the southern U.S. Conflicts erupted because former slaves sought to exercise their new freedoms against the restrictions placed on them by local authorities. New laws, mob actions and acts of organized white terrorism were used to subjugate free citizens and return them to their former stations of labor. Political activities and participation in the electoral process were violently discouraged. Vocal opponents of the new system were often targeted for murder along with their families. A vital component to this oppressive movement was a concerted effort among local southern governments to disarm African American citizens. Radical Republicans attempted to intercede with new laws based on 2nd amendment protections, but Northern indifference to the plight of former slaves made this politically futile. Unconstitutional firearm restrictions in the reconstruction south ensured that the subjugation of Freedmen would continue indefinitely. Without political agency, or the means of an organized community militia to generate such power, the realization of freedom and the rights of citizenship for African Americans remained unobtainable for nearly 100 years

A case study in bigraded commutative algebra

We study the commutative algebra of three bihomogeneous polynomials p_0,p_1,p_2 of degree (2,1) in variables x,y;z,w, assuming that they never vanish simultaneously on P^1 x P^1. Unlike the situation for P^2, the Koszul complex of the p_i is never exact. The purpose of this article is to illustrate how bigraded commutative algebra differs from the classical graded case and to indicate some of the theoretical tools needed to understand the free resolution of the ideal generated by p_0,p_1,p_2.Fil: Cox, David. Amherst College. Department of Mathematics and Computer Science; Estados UnidosFil: Dickenstein, Alicia Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Schenk, Hal. Texas A&M University; Estados Unido

Optimization of the printed circuit board for power LED

Tato diplomová práce se zabývá problematikou přenosu tepla na deskách plošných spojů. První část práce se skládá z teoretického rozboru všech principů vedení tepla v různých prostředích, porovnání vlastností běžných typů základních materiálů pro desky plošných spojů z hlediska tepelných vlastností a také se věnuje odvodu tepla z čipu. V další části jsou uvedeny základní informace o programu ANSYS® Workbench™. Následně jsou představeny výchozí návrhy DPS, které jsou dále vylepšovány. Pomocí výpočtů, simulací a praktického měření jsou ověřeny tepelné vlastnosti DPS pro různé konfigurace. V poslední části je na základě srovnání výsledků původních návrhů a návrhů na vylepšení vytvořeno konstrukční doporučení pro návrh DPS.This diploma thesis deals with the problems of heat transfer on printed circuit boards. The first part consists of a theoretical analysis of the principles of conduction of heat in different environments, comparing the properties of common type’s base materials for PCBs in terms of thermal properties and focuses on heat transfer from the chip. In the following part they are general information about the program ANSYS ® Workbench ™. Next part consists of the basic designs of PCBs and their improving. PCBs thermal properties for different configurations are verified with calculations, simulations and practical measurements. In the last part there are created design recommendations for PCBs design based on the comparison of the results of initial proposals and proposals to improvements.

The design of Audio Amplifier

Cílem mé bakalářské práce je návrh konstrukce audio zesilovače pro reprodukci signálu z elektrické kytary. Rozhodl jsem se spojit výhody elektronkového předzesilovače s výhodami digitálního zesilovače. Práce popisuje princip činnosti vybraných zapojení, obsahuje simulaci filtru anodového napětí, rozbor a měření vstupních a výstupních parametrů, jakož i jejich vyhodnocení. V příloze jsou umístěny potřebné předlohy pro realizaci desek plošných spojů.The theme of my bachelor’s thesis is a design of audio amplifier for the reproduction signal from electric guitars. I decided to combine the advantages of tube preamp with the advantages of digital amplifiers. The work describesthe principle activity of selected involvement, includes the anode voltage filter simulation, analysis and measurement of input and output parameters and thein evaluation. Technical documentation for realization of the amplifier contains printed circuit board.

Spectroscopic and mechanistic studies of dinuclear metallohydrolases and their biomimetic complexes

An enhanced understanding of the metal ion binding and active site structural features of phosphoesterases such as the glycerophosphodiesterase from Enterobacter aerogenes (GpdQ), and the organophosphate degrading agent from Agrobacterium radiobacter (OpdA) have important consequences for potential applications. Coupled with investigations of the metalloenzymes, programs of study to synthesise and characterise model complexes based on these metalloenzymes can add to our understanding of structure and function of the enzymes themselves. This review summarises some of our work and illustrates the significance and contributions of model studies to knowledge in the area

Identification of a non-purple tartrate-resistant acid phosphatase: an evolutionary link to Ser/Thr protein phosphatases?

BACKGROUND Tartrate-resistant acid phosphatases (TRAcPs), also known as purple acid phosphatases (PAPs), are a family of binuclear metallohydrolases that have been identified in plants, animals and fungi. The human enzyme is a major histochemical marker for the diagnosis of bone-related diseases. TRAcPs can occur as a small form possessing only the ~35 kDa catalytic domain, or a larger ~55 kDa form possessing both a catalytic domain and an additional N-terminal domain of unknown function. Due to its role in bone resorption the 35 kDa TRAcP has become a promising target for the development of anti-osteoporotic chemotherapeutics. FINDINGS A new human gene product encoding a metallohydrolase distantly related to the ~55 kDa plant TRAcP was identified and characterised. The gene product is found in a number of animal species, and is present in all tissues sampled by the RIKEN mouse transcriptome project. Construction of a homology model illustrated that six of the seven metal-coordinating ligands in the active site are identical to that observed in the TRAcP family. However, the tyrosine ligand associated with the charge transfer transition and purple color of TRAcPs is replaced by a histidine. CONCLUSION The gene product identified here may represent an evolutionary link between TRAcPs and Ser/Thr protein phosphatases. Its biological function is currently unknown but is unlikely to be associated with bone metabolism.This work was funded by the Royal Society of Tropical Medicine and Hygiene through a Dennis Burkitt Fellowship to JJM. ARD is supported by the Economic and Social Research Council. JJM is supported by a Wellcome Trust Research Training Fellowship (GR074833MA)

Xylem surfactants introduce a new element to the cohesion-tension theory

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms

CONNAISSANCES ET RECONNAISSANCE DE L'EXPERT

Les experts sont des acteurs centraux de cette société de la connaissance. L'expert est supposé posséder à la fois les connaissances et le savoir faire qui devraient permettre de résoudre le problème ou nous aider à prendre les bonnes décisions. De plus sa légitimité et ses connaissances sont rassurantes. Il devient la figure emblématique de celui qui non seulement sait, mais sait aussi comment faire, sait conseiller pour les décisions à prendre... Homme de connaissance et d'action, il incarne celui qui sait agir, décider ou conseiller pour décider, en connaissance de cause, et dont la compétence est reconnue. Il a un rapport privilégié non seulement au savoir mais aussi à la décision et à l'action. Notre travail, qui se veut pluridisciplinaire2, aborde la question de l'expert sous un aspect cognitif et un aspect social. D'une part, l'expert possède des connaissances spécialisées et sait les mobiliser pour l'action, et d'autre part, son statut ne peut être dissocié de la légitimité et de la confiance dont il bénéficie. Dans notre analyse des connaissances et des modes de légitimation de l'expert, nous rappellerons d'abord quelques distinctions clefs touchant la question des connaissances pour spécifier, ensuite, celles de l'expert. Dans une troisième partie, nous abordons la question de la légitimité de l'expert. Une typologie illustrée de recours à l'expert nous permettra de préciser et d'affiner notre approche.Expert, connaissance, légitimé, institutions, communautés