Libros de ciencias, página 64 de 2692

En aquest llibre es dóna un model algebraic, sustentat en el concepte d'espai vectorial, on, amb definicions adequades, es compleixen tots els axiomes de la geometria afí i euclidiana clàssica. D'aquest objecte algebraic se'n diu espai afí. S'estudien i es classifiquen les aplicacions naturals entre aquests espais: les afinitats. S'introdueix el concepte de distància i s'estudien i es classifiquen les afinitats que conserven la distància: els moviments. Finalment, s'estudien i es classifiquen les figures més elementals d'aquests espais, a part dels punts i les rectes: les quàdriques. Agustí Reventós Tarrida és professor del Departament de Matemà-tiques de la Universitat Autònoma de Barcelona i es considera, més que matemàtic, geòmetra. S'ha preocupat de la geometria clàssica i dels fonaments de la geometria i ha publicat nombrosos articles de recerca en el camp de la geometria diferencial. Ha publicat un llibre sobre geometria projectiva i un altre sobre geometria plana i àlgebra lineal, aquest últim amb Ferran Cedó. Ha traduït al català i ha comentat el Disquisitiones generales circa superficies curvas de C. F. Gauss, amb Carlos Rodríguez, i actualment està preparant la segona edició del llibre Geometria axiomàtica. Ha impartit cursos d'Història de la Geometria al Centre d'Estudis d'Història de la Ciència. També s'ha dedicat a la divulgació i ha estat invitat a fer conferències en nombroses universitats. Va ser, durant vuit anys, editor en cap de la revista Notícies de la Societat Catalana de Matemàtiques. Actualment està acabant la recopilació de les obres completes del professor L. A. Santaló.

An extraordinary companion guide to the next landmark natural history documentary series from BBC, aiming to reshape the way we think about each region of Africa by revealing never before seen impressions of the continent Sir David Attenborough CBE and the award-winning BBC Natural History Unit embark on a landmark new series, painting a breathtaking portrait of Africa as never before caught on film. This lavish and unmissable companion to the series reveals the undiscovered side of Africa's five unique regions. Inspiring photography captures unprecedented glimpses of wildlife behavior, mesmerizing creatures, and magical landscapes that will astound, captivate, and challenge what audiences think they know about Africa. This is a spectacular journey through a vast and diverse continent in all its beautiful and unexpected abundance. Readers will witness the drama of eagles catching giant bats on the wing, lizards stalking their prey on the backs of lions, antelope-hunting monkeys, and a nailbiting giraffe fight; share the discovery of the world's rarest fish species and the first-ever access to an island sanctuary for the elusive African penguin; marvel at a Congo fish that flies like a butterfly and a lovestruck beetle who thinks he's James Bond; and join a unique expedition to the most extreme parts of this vast continent.

Africa is a source of amazing bio-diversity and home to some of the planet's most spectacular landscapes. The sights of this awe-inspiring continent are captured with consummate skill and sensitivity by master lensman Michael Poliza. With extensive experience photographing the animals and terrain of Africa, Poliza's viewpoint is shaped by his concern for the fragile eco-systems he chronicles. These images embody the soul of Africa's flora and fauna with a true artist's eye for color and composition. This book will be enjoyed for years to come. Poliza started as a child actor on German TV, then founded several highly successful IT ventures in the US and Germany. His ?STARSHIP MILLENNIUM VOYAGE, around the world on a 75 ft expedition yacht, was avidly followed by millions via internet. Poliza now focuses mainly on film and photography, including work for the Discovery Channel. He spends a great deal of time based in Cape Town, and is a pioneer in the use of digital photography for illustrated books. (...)

Si Ernest Hemingway volviera al Kilimanjaro, en Tanzania, muy difícilmente se encontraría con las nieves eternas que caracterizan a este maravilloso macizo montañoso, el más elevado de Çfrica, pues se estima que se redujeron en mas de un 85% en los ultimos cincuenta años. Y esto no es un caso aislado. El ciclo del agua se ha visto gravemente alterado en el continente. En algunas partes, el agua ya no llega cuando tiene que llegar, y en otras, las inundaciones se suceden a un ritmo vertiginoso. Ya no es un secreto: a pesar de ser el continente que menos contribuye al calentamiento global en terminos absolutos, Çfrica es su primera gran victima. En el ensayo Çfrica: cambio climatico y resiliencia se exponen las evidencias del calentamiento global y los retos que supone para las sociedades africanas, desde las hambrunas hasta las migraciones o los conflictos. Tambien se resaltan nuevas amenazas vinculables con el cambio climatico (como la pandemia de la COVID-19) y las vias que existen para sobreponerse a estos escenarios dramaticos. El futuro de Çfrica depende inevitablemente de invertir en energias renovables y fortalecer un nuevo liderazgo verde.

When famine drought and malnutrition plagued their communities these farmers tried something revolutionary and managed to nourish their families and their land in the process Farmers in some of the world s oldest agricultural areas Africa s Great Rift Valley India s Indo Gangetic Plain the Highlands of Central America and the Great Plains of the U S were toiling year after year only to find that modern industrial agriculture was turning on itself The very practices that they were using to grow food yesterday were making it more difficult to grow food today Pesticides used to protect their crops were killing off beneficial biodiversity Monocropping was depleting the soil of necessary nutrients And deforestation was making the land hotter and drier Industrial agriculture s effects on our climate and environment were multiplying and worsening until the very families growing the world s food were starving But some of these farmers took a gamble and changed their practices to work with nature rather than bending nature to their will They terraced the land to catch more rainwater and prevent soil runoff they planted a diverse range of vegetables that would balance the nutrients in the soil they replaced commercial fertilizers with organic matter from their

Even in the third decade of the twenty first century it is still harder for women to make a career in science than men Two centuries ago however at the beginning of the nineteenth century when science as we know it was just getting started the situation was far worse Then the very notion of a female scientist would have been regarded as something of an oxymoron From bestselling and award winning science writers John and Mary Gribbin Against the Odds highlights the achievements of women who overcame hurdles and achieved scientific success although not always as much as they deserved in spite of male prejudice as society changed over about 150 years from the middle of the nineteenth century to the end of the twentieth century There is Eunice Newton Foote who discovered the carbon dioxide greenhouse effect Chien Shiung Wu who discovered the law which allows matter to exist in the Universe today and Barbara McClintock who discovered how genes turn on and off With a foreword from astrophysicist Jocelyn Bell Burnell this book is not only a cautionary tale about the stifling effects of prejudice against women in science but a celebration of those who achieved success against the odds and an inspiration for the next generation

Dirk Van den Abeele, experto en el campo de los agapornis, ha escrito este libro completo, detallado y maravillosamente ilustrado, que con más de trescientas páginas, trata en profundidad todas las especies de agapornis y sus subespecies.

Agapornis. Ver Y Conocer 4ª Ed. T. Halaburda Esta obra, de la colección "Ver y Conocer", nos proporciona una amplia información sobre las variedades de agapornis, su selección, mantenimiento y cuidados, alojamiento, alimentacion, salud y crianza.

Tengo un agapornis, ¿y ahora qué? Si ya vives con uno, o justo vas a empezar esta aventura, seguro que te asaltan muchas dudas: ¿Qué deberían comer? ¿Viven mejor solos o en pareja? ¿Cómo puedo ganar su confianza? ¿Son necesarios los juguetes? ¿Que es y como afecta el celo? ¿Es normal que pierda plumas? Entre las paginas de este libro encontraras respuesta a estas y a muchas otras preguntas. Ademas, descubriras consejos y trucos para que tu agapornis este sano y feliz. Queremos que tengas toda la informacion necesaria para cuidar bien de tu nuevo amigo y, por eso, han colaborado criadores, veterinarios y demas expertos en psitaciformes en la revision de este libro. ¡Adentrate con nosotros en el maravilloso mundo de los agapornis!

Guía práctica para elegir, conocer y cuidar tus agapornis, y disfrutar con ellos