Caracterización mecánica de morteros de cemento Portland con breas de petróleo y de alquitrán de carbón

En este artículo se presentan datos experimentales de resistencia a flexión y a compresión de morteros de cemento Portland con adición y sustitución de breas de petróleo y de alquitrán de carbón, que son subproductos de la industria del carbón o del petróleo. Los materiales estudiados son breas de alquitrán de carbón A (BACA) y B (BACB), y dos breas de petróleo (BPP) y (BPT). Los datos demuestran la viabilidad del uso de estas breas en la fabricación de morteros con menores contenidos de cemento, permitiendo diseñar un nuevo material sostenible con el medio ambiente y que contribuya a reducir el impacto ambiental de los materiales de construcción, hecho que permite abrir una nueva vía de valorización de estos subproductos.

Conformational changes of dissolved humic and fulvic superstructures with progressive iron complexation

Conformational changes of a humic acid (HA) and a fulvic acid (FA) induced by iron complexation were followed by high-performance size exclusion chromatography (HPSEC) with both UV–vis and refractive index (RI) detectors. Molecular size distribution was reduced for HA and increased for FA with progressive iron complexation. Since interactions of Fe with humic components are electrostatic, it is likely that the triple-charged Fe ions formed stronger complexes with the more acidic hydrophilic and hydrated FA than with the less acidic and more hydrophobic HA. The large content of ionized carboxyl groups in FA, thus favored the formation of intra- or intermolecular bridges between the negatively charged fulvic acid molecules, and led to more compact and larger size network than for HA. Conversely, iron complexation with HA disrupted the humic conformational arrangements stabilized by only weak hydrophobic bonds into smaller-size aggregates of greater conformational stability due to formation of strong metal complexes. These results confirmed that humic molecules in solution were organized in supramolecular associations of relatively small molecules loosely bound together by dispersive interactions and hydrogen bonds, and they specifically responded to chemical changes brought about by metal additions. The present study revealed the molecular changes occurring in superstructures of natural organic matter when in metal complexes and contributed to understand and predict the environmental behavior in waters and soil of metal complexes with natural organic matter.

An approach to the application of shift-and-add algorithms on engineering and industrial processes

Different kinds of algorithms can be chosen so as to compute elementary functions. Among all of them, it is worthwhile mentioning the shift-and-add algorithms due to the fact that they have been specifically designed to be very simple and to save computer resources. In fact, almost the only operations usually involved with these methods are additions and shifts, which can be easily and efficiently performed by a digital processor. Shift-and-add algorithms allow fairly good precision with low cost iterations. The most famous algorithm belonging to this type is CORDIC. CORDIC has the capability of approximating a wide variety of functions with only the help of a slight change in their iterations. In this paper, we will analyze the requirements of some engineering and industrial problems in terms of type of operands and functions to approximate. Then, we will propose the application of shift-and-add algorithms based on CORDIC to these problems. We will make a comparison between the different methods applied in terms of the precision of the results and the number of iterations required.

Adsorption and first stages of polymerization of aniline on platinum single crystal electrodes

The present communication studies the adsorption of aniline on platinum single crystal electrodes and the electrochemical properties of the first layers of polyaniline(PANI) grown on those platinum surfaces. The adsorption process was studied in aqueous acidic solution (0.1 M HClO4) and the electrochemical properties of thin films of PANI in both aqueous (1 M HClO4) and non-aqueous media (tetrabutyl ammonium hexafluorophosphate (TBAPF6) with additions of methanesulphonic acid in acetonitrile). First of all, it was found that the adsorption of aniline on platinum single crystal surfaces is a surface sensitive process, and even more important that the adsorption features found at low concentrations (5 × 10−5 M) can be directly correlated to the electrochemical properties of thin films of PANI in the very early stages of polymerization. The Pt(1 1 0) surface was found to be more suitable to obtain polymers with more reversible redox transitions when studied in aqueous media (1 M HClO4). This is in good agreement with the higher polymerization rates found on this surface compared to Pt(1 0 0) and Pt(1 1 1). Finally the differences in ionic exchange rate were greatly enhanced when they were studied in organic media. The AC 250 Hz response in the case of the thin films synthesized on Pt(1 1 0) is about twice greater than that obtained in the other basal planes using polymer layers with the same thickness.

Analysis of the Connecting Zone between Consecutive Sections in Distillation Columns Covering Multiple Feeds, Products and Heat Transfer Stages

In the present work, we provide a systematic analysis about all tine streams involved in the zone connecting two consecutive sections for the design of distillation columns with different thermal feed conditions, product extractions and heat additions or withdrawals. This analysis allows a better understanding of what happens on a feed or side draw (of mass or energy) stage, what compositions are or are not in equilibrium, and the impact on internal liquid and vapor flows.

Valorización de cenizas de lodo de depuradora como componente de hormigones para prefabricados

Se plantea la combinación binaria y ternaria de cenizas de lodo de depuradora (CLD) con ceniza volante, polvo de mármol y ceniza de cáscara de arroz, como sustitución parcial o como adición respecto al cemento Portland en hormigones, con una dosificación similar a la utilizada en la prefabricación de bloques (consistencia muy seca). Se llevaron a cabo ensayos físico-mecánicos sobre probetas de mortero y hormigón con edades de curado de 28 y 90 días: densidad, absorción y resistencia a compresión. Se comprueba que la sustitución de cemento por CLD supone una disminución de la densidad y de la resistencia respecto a la muestra patrón, sin embargo, las combinaciones con otros residuos mejoran notablemente las características de los materiales cementantes. La adición de CLD proporcionó densidades y resistencias similares a la muestra de control y reduce significativamente la absorción de agua.

The Lawes and Orders of Harvard Colledge, 1655-1708

The 21-page handwritten copy of the College laws is laid out in two columns, and lacks a cover. In the left-hand column, in an unidentified hand, are the Laws of 1655 in English with additions dated April 9, 1660, August 24, 1663, and December 5, 1667, and an order of the General Court dated Sept. 4, 1656. In the right-hand column, in the hand of President John Leverett, are the Latin Laws of 1642-1646, with an occasional reference to the Latin Laws of 1686 and 1692, and two extracts from the Corporation records about the reading of the Scriptures dated January 26 and May 27, 1708.

The Laws of Harvard College, 1767

Handwritten soft-cover copy of the 1767 College laws includes an ornately drawn title and was marked "Corrections, Additions, etc." The volume contains many emendations, some in the hand of Edward Wigglesworth.

[Admittatur of Benjamin Merrill (Harvard AB 1804)], 1800 August 12

Published copy of the 1790 College Laws with the admittatur of undergraduate Benjamin Merrill signed by President Joseph Willard on August 12, 1800. Four pages of amendments of and additions to the Harvard Laws "enacted since the Summer of 1798, and are now in force Dec. 1, 1800" are tipped in at the beginning of the volume.

Journal of Samuel Kirkland, January 30-March 6, 1796

Folders 1 and 2 contain two manuscript copies of the same journal; these copies are not identical, but instead reveal Kirkland's revisions and additions as he rewrote some journal entries.

Journal of Samuel Kirkland, March 19, 1796-July 1796

Folders 3, 4, and 5 contain three manuscript copies of the same journal; these copies are not identical, but instead reveal Kirkland's revisions and additions as he rewrote some journal entries.

Butler's accounts for the Classes of 1789-1794, 1789-1799

The marbled-paper-covered book contains two sections written by Butlers Thomas Adams and Samuel Shapleigh: a two column debit and credit entry section for students in the Classes of 1789 through 1794, with additions made through June 1791, and at the end of the volume a two page "Account of monies paid out as Atty. to T. Adams" for 1791 with lenders' names and amounts.

Triennial Catalogue annotated by Jeremy Belknap, 1791

The collection holds a heavily interleaved 1791 Triennial Catalogue annotated, in part, by Jeremy Belknap. A note by Harvard Librarian John Langdon Sibley, on the verso of the flyleaf, indicates a second annotator: "It should be observed that this catalogue is in the handwriting of two persons, Dr. Belknap & probably interlineations & additions by Rev. Dr. [John] Eliot. The interlineing part should not be too confidently relied on for accuracy. J. L. Sibley, April 14, 1848." The volume contains biographical notes, newspaper clippings, excerpts from manuscript and printed sources such as New England's First Fruits, the manuscript memoirs of Charles Chauncey, and John Winthrop's Journal, and a 1795 letter from Isaac Mansfield. In the letter, Mansfield references an item he believed to be written by his grandfather, Ames Cheever (Harvard AB 1707), and briefly describes his grandfather. A list of election sermon orators with dates is also pasted into the inside back cover, along with an obituary of the Rev. John Wales (Harvard AB 1728) from the Boston Post-Boy, March 4, 1765.

Alphabetical catalog of Harvard College graduates through 1767, 1767

This hard-bound manuscript catalog alphabetically lists the men who graduated from Harvard College between 1642 and 1767. It is believed to be the first such list compiled. Entries contain each graduate's surname (in English), given name (in Latin), year of graduation, and occasional additional information. Francis Foxcroft (A.B. 1712) compiled the catalog. Entries for those who graduated between 1764 and 1767 have been added at the end of each alphabetical section.

Student mathematical notebook of William Tudor, 1795

Notebook containing the handwritten mathematical exercises of William Tudor, kept in 1795 while he was an undergraduate at Harvard College. The volume contains rules, definitions, problems, drawings, and tables on geometry, trigonometry, surveying, calculating distances, sailing, and dialing. Some of the exercises are illustrated with hand-drawn diagrams. The Menusration of Heights and Distances section contains color drawings of buildings and trees, and some have been altered with notes in different hands and with humorous additions. For instance, a drawing of a tower was drawn into a figure titled “Egyptian Mummy.” Some of the images are identified: “A rude sketch of the Middlesex canal,” Genl Warren’s monument on Bunker Hill,” “Noddles Island,” “the fields of Elysium,” and the “Roxbury Canal.” The annotations and additional drawings are unattributed.