thegoodfellas/blogset-br huggingface dataset:
ligam (ligacao intermolecular) ao revestimento de polimero dentro da coluna, denominada fase estacionaria, os quais, consequentemente, eluem em tempos diferentes. Esta abordagem funciona de forma parecida a cromatografia em papel, como muita gente conhece. Por exemplo, em sua forma mais simples, as cores das canetinhas hidrograficas se separam e ficam bem aparentes quando uma mistura de solventes lentamente encharca o papel de filtro marcado com a canetinha. Aqui, a fase estacionaria e o papel de filtro.Os compostos eludidos a partir do cromatografo de gases sao entao transformados em ions e um espectrometro de massa e utilizado para identificar cada uma dessas substancias. Cada ion pode ser identificado a partir de sua massa, localizando o pico do ion molecular no espectro; mas tambem pode ser identificado a partir dos compostos menores e mais leves fragmentados durante o procedimento.Os autores:Livia Levy, na ocasiao da escrita deste ensaio, e academica do ultimo ano de graduacao na Faculdade de Quimica da Universidade de Bristol, Reino Unido.Tim Harrison e diretor de atividades de sensibilizacao do Bristol ChemLabS, Faculdade de Quimica da Universidade de Bristol, Reino Unido.Natalie Fey e docente efetiva no Centro de Quimica Computacional da Faculdade de Quimica da Universidade de Bristol, Reino Unido.
as nacoes e facil questionar a colaboracao, alem das fronteiras nacionais, entre pessoal cientifico. Deixe-me apresentar alguns argumentos pelos quais acredito que a cooperacao cientifica internacional e mais necessaria do que nunca. Alguns desses pensamentos ja foram expressos em um editorial publicado em Angew. Chem. Int. Ed. 2011, 50, 8202-8203.Muitos problemas que a humanidade enfrenta, como a mudanca climatica, a fome, a sustentabilidade ambiental e as pandemias, sao globais por natureza. Assim, eles exigem uma abordagem global para a sua solucao. Precisamos de cientistas de todos os paises trabalhando juntos em tais problemas. As solucoes para estes problemas sao indispensaveis para nosso futuro neste planeta. Ainda mais, os avancos nas comunicacoes tornam possivel realizar colaboracoes que anteriormente eram impensaveis.Os empreendimentos cientificos se beneficiam compartilhando o que e aprendido. E verdade que se voce tem comida e um mendigo lhe pede algo, alimentar o mendigo deixa voce com menos comida. Mas por outro lado, se alguem pede que voce compartilhe seu conhecimento com eles, mais frequentemente do que nao, todos os parceiros sao enriquecidos pela intercambio. Na verdade, este e um dos beneficios secretos de ensinar o professor tambem aprende.Rejeito a ideia de que a ciencia e um jogo de soma zero. Em um jogo de soma zero, como o jogo de xadrez, que amo, deve haver um perdedor para cada vencedor. Se um pais tem talento suficiente para reconhecer um avanco cientifico, em conjunto com uma base suficientemente avancada de tecnologia, para transformar o avanco em pratica, entao, um avanco cientifico realizado em qualquer lugar do mundo, pode levar a ganhos economicos globais. Um pais nao precisa ser o primeiro em todas as disciplinas cientificas para beneficiar-se dos avancos. Muitos outros fatores, que vao do espirito empreendedor, ate uma forca de trabalho qualificada, podem transformar os avancos cientificos feitos em outros paises, em beneficios sociais.Quando dois paises pretendem reforcar suas relacoes, frequentemente convocam reunioes entre os lideres militares dos dois paises. Parece-me que e muito mais eficaz, para o estabelecimento de boas relacoes, convocar uma reuniao dos lideres cientificos. Cooperacao cientifica promove a amizade em geral, compreensao mutua, bem como valores e padroes comuns. A historia nos ensina que as relacoes entre os paises tem seus altos e baixos politicos. Ganhamos muito em suavizar os percalcos tendo pessoas, em cada pais, que se conhecem e confiam uns nos outros. Neste sentido, tendo fortes lacos cientificos entre os diversos paises e simplesmente boa diplomacia.
THE FORGERY OF PAINTINGS by Fredric M. Menger, Emory University, Atlanta, GA 30322 USAMy interest in paint began during a visit to the Scotland Yard crime lab in London. They were working at the time on a burglary case in which someone pried open a window, entered a house, and robbed it. A suspect was arrested and found (as occurs often in such cases) to have a small chip of paint in the corner of his shirt pocket. When I looked at the paint under a microscope, I saw four layers of paint: a thick green layer, a yellow layer, and two distinct white layers of different thickness. The paint-pattern was identical to the paint on the window of the burglarized home. It was like a paint-fingerprint, and it served later, I was told, to convict the suspect. I recall wondering at the time how paint analysis was used in art forgeries, and given below are a few things I found out.In 2011 Wolfgang Beltracchi was sentenced in Germany to several years imprisonment for forging a large collection of paintings in the style, and with the signatures, of great artists such Picasso and Monet. Paintings by the masters are worth multi-millions of dollars, so that selling well-crafted imitations can be a very profitable although highly illegal business. Beltracchi was an expert forger who took great care to make his fakes look authentic. Thus, he studied meticulously the painters he copied by going to museums where their work was displayed. He even visited the homes of the artists in order to learn their mindset. Beltracchi was able to paint with his right hand or left hand, depending upon the handedness of the artist he was copying. Brush strokes were not to betray him! Fake labels on the backs of old paintings were attached using a homemade glue of bone and other natural materials. He also was careful to use paints that were prevalent at the time of the artists life, but it is here where he made a fatal error. At one point Beltracchi was attempting to copy the style of artist Heinrich Campendouk (1889 - 1957) who used zinc oxide for a white pigment. Beltracchi also used zinc oxide in his forgery but, unknown to him, his paint had been manufactured with a trace of titanium dioxide contamination. Simple chemical analysis of a chip of paint from the forgery exposed the fraud. Released early from prison after only four years, he was asked by a reporter if he could guarantee never to do this again. He replied, laughingly, that one thing was certain, he would not again use paint with titanium.A successful forger must himself be an artist who can produce paintings good enough to fool the experts. This takes a bit of genius. The forger is also faced with the problem of selling the forgery. This usually involves creating a fake provenance (or past history) of the painting. Here is how Beltracchi did it: He collaborated with two granddaughters of Werner Yaeger, a wealthy industrialist. These women lied and claimed they
had inherited the paintings from their grandfather, who in turn had ostensibly bought them from a prominent art dealer, Alfred Flechtheim. Counterfeit Flechtheim labels were attached to the back of the paintings. A highly respected art expert, Werner Spies, was fooled by all this false information, and he issued certificates of authenticity that made it easy to sell the paintings.In another case, the forger painted a picture in 1962 that he claimed was the creation of a well-known artist earlier in the century. Upon close inspection, an art-investigator found a single polypropylene fiber embedded in the paint. The fiber had not been commercially available to the public until 1958. Case closed.Forgery goes back centuries. In 1496 Michelangelo (of St. Peters Basilica fame) sculptured a marble statue (a sleeping cupid), partially broke it, buried it to make it appear ancient, and sold it as an antiquity. In the early 1900s, art dealers would test the authenticity of a painting by rubbing alcohol on the paint, and then poking it with a hot needle. New paint can be punctured much more easily than older paint. Some forgers, aware of this test, mixed Bakelite, a hard plastic, into the paint. Other methods of deceit include using a special baking process to simulate the network of fine cracks (called craquelure) that cover paintings of the old masters. Experts, however, can tell the difference between artificial cracks, which are rather uniform in appearance, and genuine craquelure that has irregular patterns.F614 was the name given to a self-portrait of Vincent van Gogh that was brought to Marie-Claude Corbeil, a chemist at the Canadian Conservation Institute, for authentication using X-ray analysis. It was known from letters written by van Gogh that he used an asymmetrical canvas, i.e. one that had different number of horizontal and vertical threads. Although the threads do not block X-rays, the canvas was covered by a so-called priming layer (painted initially onto the canvas to make it smoother). This X-ray-visible layer is thicker in the open spaces between the threads than where the threads overlap. By this means the X-rays could detect the thread arrangement which was seen to have identical numbers in both directions. F614 was worthless. Ultraviolet and infrared spectroscopy, atomic absorption, and microscopy have all been used to track down art forgeries.The case of Ely Sakhai is worth telling. He would buy a little-known painting from a famous artist, make a copy, and then sell them both. The fake was sold in Asia, the real painting in New York or London. His operation earned him $3.5 million according to the FBI. Unfortunately for Sakhai, an owner of a fake painting in Tokyo, and an owner of the corresponding authentic painting in New York, decided to sell the paintings at the same time and at the same auction house. Because of this unlikely coincidence, the career of Mr. Sakhai ended abruptly.Marc Chagall's La Nappe Mauve. Left, original;1 Right, forged version by Ely Sakhai.2 I will close this report with one last forger, a Mark Landis. He would arrive at a museum or church
and introduce himself as Father Arthur Scott. He dressed the part, wearing black clothes, a clerical collar, and a Jesuit pin on his lapel. His purpose for the visit was to donate a small expertly faked painting in memory of this mother or other relative. Who would not accept such a gift? After all, the donor looked like someone you could trust; the painting appeared authentic; and (best of all) it was free. Over forty museums were approached by Landis, and many of them displayed the paintings as authentic works. Landis obviously did not operate the scam purely for money. He was apparently satisfied just by seeing his artistry accepted as authentic. It is even unclear that he broke any laws. In any case, when the paintings were eventually discovered to be forgeries, museums were alerted, and the FBI art-crime team was put on the case. But Mark Landis suddenly disappeared and has managed to evade arrest. Like many forgers, he was a person who merely wanted a little acceptance from the public. And he delighted in the incompetency of the so-called experts who regarded his work as originating from our great masters. One rather hopes that he is never caught.1) http://www.christies.com/lotfinder/Lot/marc-chagall-1887-1985-la-nappe-mauve-5915669-details.aspx2) http://www.phaidon.com/agenda/art/articles/2015/may/20/foiling-the-forgers-with-noah-charney-gauguin/
65 anos cuando se mudo a Brasil desde Londres. Tuvo que aprender portugues y conformarse inicialmente con recursos de investigacion escasos y limitados. Entre sus intereses de investigacion, podemos citar los canales de calcio. Y es precisamente este tema el que discutiremos brevemente en honor de este gran cientifico.Richard Rodnight (in memoriam)La palabra clave aqui es "canales de calcio dependientes de voltaje" o CCDV. Como su nombre indica, estos canales, que se encuentran en las membranas celulares, son permeables a los iones calcio (aproximadamente 1000 veces mas que los iones sodio). En un potencial de membrana en reposo, los CCDV estan normalmente cerrados. Sin embargo, los canales se activan (estan abiertos) cuando la membrana esta "despolarizada", es decir, cuando se neutraliza la diferencia de carga a traves de la membrana. Este es el origen del termino "dependiente de la tension". Muchas cosas interesantes pueden suceder cuando las membranas se despolarizan electricamente. Los iones calcio, cuya concentracion fuera de la celula es generalmente miles de veces mayor que en el interior, se dirigen hacia el interior de las celulas por difusion pasiva (discutido en un ensayo anterior).La excitacion de las neuronas, la liberacion de transmisores de neuronas, y la fosforilacion de proteinas son tres de las muchas consecuencias de este movimiento de iones. Por lo tanto, la funcion de los CCDV representa una estrategia importante para la regulacion de la actividad nerviosa.Dibujo de los canales de calcio (Elaborado por Luciana Afonso)Y como funcionan los canales "cerrados"? El canal es una compleja combinacion de proteinas estiradas a traves de la membrana celular, de las cuales la mayor constituye el poro de conduccion. Diferentes segmentos de la proteina "sienten" la tension de la membrana y determinan la preferencia de la membrana al calcio sobre el sodio. Las diferentes subunidades de los complejos proteicos dentro del canal unen el sistema a diversos procesos intracelulares, incluyendo la transmision sinaptica (que depende de los iones Ca2+, entre las celulas nerviosas de varios lugares, entre ellos el talamo.Las benzodiazepinas, una clase importante de tranquilizantes (utilizados en el tratamiento de la depresion, convulsiones y ataques de panico) reducen la conductancia del calcio dependiente de voltaje, y esto puede ser un importante mecanismo por el cual los compuestos producen sus efectos sedantes. Una mayor comprension de los mecanismos de regulacion CCDV puede conducir a nuevos tratamientos de enfermedades neurologicas.Aunque el calcio parece desencadenar vias de senalizacion esenciales para ciertos tipos de memoria, el exceso de calcio puede, en realidad, causar dano cerebral. Por ejemplo, la glandula pineal puede calcificarse en condiciones tales como la enfermedad de Alzheimer y otros tipos de demencia. La biologia es, como siempre, un delicado equilibrio entre el poco y el demasiado.Referencias:Descartes Error. Emotion, Reason and the Human Brain. (A. Damasio). ISBN 978-85-359-2200-4.Shepard, M; Lader, M; Rodnight (Deposito legal Z. 719-71).
a method to obtain them.Placental Alkaline PhosphataseThe body cannot synthesize essential amino acids, therefore we need them in our diet. The nine amino acids that the body cannot synthesize are: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine and histidine (abbreviated as: F V T W M L I K H). There are other six conditionally essential amino acids which, under certain conditions, are not synthesized in sufficient quantities by the body, for instance in premature infants or in case of catabolic problems. These amino acids are arginine, cysteine, glycine, glutamine, proline and tyrosine (abbreviated as R C G Q P Y). Also, in any situation, there are five amino acids that can be synthesized in the body: alanine, aspartic acid, asparagine, glutamic acid and serine (abbreviated as A D N E S).Thus, a daily intake of proteins is crucial to obtain the necessary amino acids and avoid self-cannibalization. There are numerous references indicating that the ideal amounts of daily proteins are 50% of animal proteins (beef, fish, eggs, dairy products) and 50% of plant proteins (cereals, legumes, peas, beans, soybeans). Obviously, children and adults have different needs, depending on size, gender, age, type of physical activity they do etc.Although there is no satisfactory system to classify proteins, they can be differentiated regarding their solubility, shape, function, physical properties and even three-dimensional structures. Proteins play a central role in terms of functions (such as enzymes) and cellular structures. According to their functions, they can be classified as structural, catalytic or transport proteins. There is a huge variety of catalytic enzymes classified according to the type of catalyzed reaction. Transport proteins are crucial. Important examples of them include: albumin (transport of bilirubin, fatty acids etc.), hemoglobin (oxygen), lipoproteins (various lipids) and transferrin (iron).So we need to be careful about protein restrictions in our daily diet. Good nutrition means keeping a constant balance between storage and elimination. If we do not ingest proteins, our body will be forced to cannibalize its own proteins (e.g. the muscles).Eating healthily is essential for a healthy body, and education is the key for everyone, future generations of researchers, administrators, politicians, students of chemical and biological sciences, public health professionals and other specialists (Jasny et al., 2014). References:Murray, R.K. (1988). Harper s Biochemistry. Twenty-first Edition. APPLETON & LANGE.Jasny, B.; Roberts, L.; Enserink, M.; Smith, O. Science. 12 September 2014. Vol 345 ISSUE 6202.Read essays T.02 (Anthony Kirby); T.13 (Faruk Nome) and T.56 (Ademir Neves) on this blog.
por tanto, se impulsa la asociacion o segregacion.Trocitos de energia, dificiles de entender. Todo el poder a las pequenitasAmbos el cabello de Esther Williams y las fibras del pincel salieron del agua todos pegados. Este es el resultado final del efecto de las pequenitas: fuerzas de dispersion, enlaces de hidrogeno, interacciones multipolares, enlaces hidrofobos son todos factores esenciales determinantes de pequenas estructuras llamadas interacciones no covalentes, para distinguirlas de los enlaces covalentes (o ionicos) que son, al menos, 10 veces mas fuertes. Las energias involucradas en las interacciones no covalentes son pequenas, con valores inferiores a 5 kcal/mol de pares de atomos.Estas pequenas energias de interaccion electrostatica pueden describirse en terminos de polarizacion mutua de dipolos (procedentes de las ecuaciones de London) o, alternativamente, como interacciones dipolo-inducido/dipolo-inducido. La contribucion de dispersion es completamente descartada. Suelo ver las cosas en terminos de orbitales. Los efectos electrostaticos deberia ser considerados en una doble vertiente, ademas d ela interaccion de dispersion, una contribucion esencial de los orbitales (no es un punto de vista popular) estabilizando la interaccion entre el par de electrones no compartidos del N o O, con un orbital molecular no cubierto y de baja energia (*) del enlace O-H o N-H con la cual esta interactuando.De igual manera, irracionalmente, son la escala humana y mis tendencias izquierdistas que me hacen dudar de mi aficion por los grandes cambios de la energia y de la propia colision. Porque me gustan las diferencias entre los seres humanos en su apariencia, su inteligencia; nuestra herencia genetica dicta tendencias e inclinaciones, pero las diferencias que valoro no estan determinadas en gran medida en el nivel molecular. Asi, aprendi a amar las pequenas diferencias de energia!BibliografiaAmerican Scientist, Volume 102, pp. 94-97 (2014) . , H.T. , , . , Inmetro, , . , , - , B, - . , , . () , . , , , . 1. . . , = 6.0223 x 1023 . () / . , , ~ 2000 . : ~ 80 . , , . , . , - . , . , ( , ) . , , . 2. : , ; . , , . , , , ... . , , ( : , ), , , ( , ). , <1 , . , . , . : . . : , , , ; , , 10 , , "" () . , 5 / . , ( ) . , - . , . , , ( ) , , : N , , ( *) O-H N-H, . , , . , , , , , , . , !BibliographyAmerican Scientist, Volume 102, pp. 94-97 (2014)
color ROJO DORADO, y su capacidad para conducir el calor y la electricidad, recordamos que el fue uno de los primeros metales usados por el hombre 5 500 anos atras. El cobre mas el estano forman parte del bronce. Ahora, no es necesario dar un gran salto para imaginar los diferentes tipos de cuerpos bronceados del CARNAVAL BRASILERO: donde todos los colores son un prodigio de la QUIMICA.Referencia: Acaster, D. Transition Elements. Cambridge University Press 2001. p.33.
*e-mail: faruk.nome@ufsc.brINTRODUCAOApesar da notavel importancia biologica, agregados dipolares ionicos tem sido menos estudados que os demais. Tais agregados apresentam a caracteristica unica de alterar diferencialmente suas propriedades atraves da incorporacao de anions e cations em sua interface, fenomeno conhecido como efeito camaleao.(1) Neste sentido, busca-se utilizar as potencialidades de liquidos ionicos para modular as propriedades de agregados dipolares ionicos, explorando racionalmente o efeito camaleao. Pretende-se desenvolver interfaces com propriedades diferenciadas para utilizacao em catalise ou como modelos de membranas biologicas.EXPERIMENTALO liquido ionico BMIMBr foi sintetizado e caracterizado por RMN de 1H e ESI-MS e, empregado juntamente com o surfactante dipolar ionico ImS3-14 para formar agregados nanoestruturados.Os agregados foram caracterizados por espalhamento de luz ressonante, tensao superficial (determinacao da CMC), diametro hidrodinamico e potencial zeta. Ainda, utilizou-se o pireno como sonda fluorescente de polaridade e o 6-nitro-benzisoxazol-3-carboxilato (6-NBIC) como sonda cinetica de polaridade (reacao de descarboxilacao que forma os produtos 4-nitro-salicilonitrila e CO2).RESULTADOS E DISCUSSAOO liquido ionico BMIMBr permite a solubilizacao do ImS3-14 a partir de [BMIMBr]=0,0175 mol L-1, possibilitando a formacao de agregados de diametro hidrodinamico de 7,7 nm. A concentracao micelar critica determinada para ImS3-14 na presenca de BMIMBr foi 1,12x10-4 mol L-1.As medidas de potencial zeta apresentadas na Figura 1, possibilitaram evidenciar que inicialmente ocorre a ligacao preferencial do anion Br ate uma concentracao critica (Cc) e posteriormente a ligacao do BMIM+. Os resultados sao confirmados pelo espectro de fluorescencia do pireno, os quais mostram que a polaridade e praticamente constante ate a concentracao critica (Cc), apos a qual ha uma substancial diminuicao da polaridade.Figura 1 Efeito camaleao dos agregados estudados.Experimentos com 6-NBIC na Figura 1 mostram que a reacao de descarboxilacao segue perfis de mudanca de kobs que sao divididos pela mesma Cc obtida nos estudos de potencial zeta e da sonda pireno, mostrando que o liquido ionico permite mudar as propriedades da interface.Assim, o decaimento inicial do valor de kobs corresponde a diminuicao do potencial zeta, sendo que o segundo perfil, bem mais acentuado, esta relacionado com o aumento da polaridade interfacial.CONCLUSOESOs resultados obtidos evidenciaram a ligacao diferencial e sequencial de Br e BMIM+, em funcao da concentracao do liquido ionico no agregado dipolar ionico estudado. O efeito observado mostra que e possivel modular as propriedades interfaciais dos agregados e controlar de forma fina um conjunto de propriedades como: potencial zeta, polaridade e composicao interfacial. Dessa forma, os dados experimentais permitem o desenvolvimento racional de interfaces com propriedades especificamente moduladas, o que possibilita as mais diversas aplicacoes, entre elas a catalise.AGRADECIMENTOS